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Review
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Engineering Handbook for Hazardous Waste Incineration
Summary ot Directive
Technical description of incineration design, operation, sampling
and some aspects of permitting relating to combustion.
Key Words:
Typt o< Directive iMtnutl. Policy Oirtctive. Announcement, etc.!
Status
1 D Draft
!_1 Final
O New
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Signature of Lead Office Directives Officer
Date
Signature of OSWER Directives Officer
| Date
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IPA
United States
Environmental Protection
Agency
Office of Water and
Vvaste Management
Washington DC 20460
SW-889
September 1981
Engineering
Handbook for
Hazardous Waste
Incineration
OSWER POUCY DIRECTiYE S&
9 4 '-
-------
-------
SW-889
September 1981
ENGINEERING HANDBOOK
FOR HAZARDOUS WASTE INCINERATION
U.S.
Offi
rlease return to:
Pat Wheeler
Incineration Research Branch
IPCD, IESL
26 W. St. Clair St.
Cincinnati, Ohio 45268
-------
ENGINEERING HANDBOOK FOR HAZARDOUS WASTE INCINERATION
by
T. A. Bonner, C. 1. Cornett, B. 0. Desai, J. M. Fullenkamp, T. W. Hughes
M. L. Johnson, E. D. Kennedy, R. J. McCoraick, J. A. Peters and D. L. Zanders
I
Monsanto Research Corporation
1515 Nicholas Road
Dayton, Ohio 45407
—i ^B
EPA Contract No. 68-03-3025; Work Directive SDM02
Project Officer: Mr. Donald A. Oberacker {
I
(
Industrial Environmental Research Laboratory
Office of Environmental Engineering and Technology '
Cincinnati, Ohio 45208 _^
Prepared for
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Washington, DC 20460
-------
PREFACE
The Resource Conservation and Recovery Act (RCRA) authorizes the United States
Environmental Protection Agency (EPA) to regulate owners/operators of facili-
ties that treat hazardous waste in incinerators. Pursuant to the legislative
mandates specified in RCRA, the EPA has proposed regulations to ensure that
hazardous waste incinerators are operated in an environmentally responsible
manner. Specifically, the proposed regulations include an operational per-
formance standard, general design and construction requirements, combustion
and destruction criteria, waste analysis, trial burns, monitoring and inspec-
tions, recordkeeping and reporting, emission control criteria, control of
fugitive emissions, and closure.
The proposed regulations rely upon the technical advisory information con-
tained in this document - Engineering Handbook for Hazardous Waste
Incineration. The proposed regulations provide very little specificity per-
taining to actual hazardous waste incineration performance requirements.
Permitting officials will develop best engineering judgments for each site
based primarily on suggested minimums or acceptable ranges for performance
parameters-contained in this report. As a result, each permitting official
will set a "standard" for each hazardous waste incineration facility based on
the application of the criteria or factors contained in the proposed regula-
tions and this document. In turn, each owner/operator, in preparing a permit
application, can determine what may be acceptable to the permitting official
by utilization of the Permit Writers Guidelines for Hazardous Waste
Incineration.
no.
-------
CONTENTS
Page
1. INTRODUCTION 1-1
2. CURRENT PRACTICES 2-1
2.1 Introduction 2-1
2.2 Generic Incineration Processes 2-11
2.2.1 Incineration of Gaseous or Liquid Waste with no Appre-
ciable SO or NO Production 2-11
2.2.2 Incineration of Gaseous Liquid Waste to Control SO or
C12/HC1 . . 2-13
2.2.3 Incineration of Gaseous or Liquid Wastes to Control
NO 2-14
2.2.4 Incineration of Gaseous or Liquid Waste to Control NO
and C12/HC1 7 2-15
2.2.5 Incineration of Gaseous or Liquid Waste to Control
Particulates 2-15
2.2.6 Incineration of Solid Waste with No Appreciable SO
or NO Production . 2-17
2.2.7 Incineration of Fine Solids in Gaseous Waste to Control
Particulates 2-18
2.2.8 Incineration of Fine Solid Waste to Control NO .... 2-19
2.2.9 Incineration of Solid Waste to Control Particulates. . 2-19
2.2.10 Incineration of High Nitrogen Crude to Control NO . . 2-20
A
2.3 Incinerator System Components 2-21
2.3.1 Incinerator Technology 2-21
2.3.1.1 Rotary Kiln 2-21
2.3.1.2 Liquid Injection 2-23
2.3.1.3 Fluidized Bed 2-27
2.3.1.4 Multiple Hearth 2-29
2.3.1.5 Coincineration 2-31
2.3.2 Emerging Incineration Technology 2-32
2.3.2.1 Starved Air Combustion/Pyrolysis 2-33
2.3.3 Air Pollution Control Devices 2-34
2.3.3.1 Afterburner 2-35
2.3.3.2 Gas-Atomized Spray Scrubber (Venturi) .... 2-37
-------
CONTENTS (continued)
2.3.3.3 Packed Bed Scrubber 2-40
2.3.3.4 Spray Tower 2-43
2.3.3.5 Plate Scrubber 2-44
2.3.3.6 Electrostatic Precipitator (ESP) 2-46
2.3.3.7 Wet Electrostatic Precipitator (WEP) 2-48
2.3.4 Heat Recovery Technology 2-50
2.4 Foreign Technologies 2-51
2.4.1 Introduction 2-51
2.4.2 Cement Kilns 2-56
2.4.3 Japan 2-57
2.4.4 West Germany 2-57
2.5 Incinerator Manufacturers 2-60
2.6 References 2-67
WASTE CHARACTERIZATION 3-
3.1 Introduction 3
.t
3.2 Waste Characterization Background Information 3-1
3.2.1 Information Available from Waste Generators 3-1
3.2.2 Information Available from Transporters 3-1
3.2.3 Additional Information Sources 3-2
3.3 Waste Sampling 3-22
3.4 Basic Analysis of Waste 3-24
3.5 Supplemental Analysis of Waste 3-28
3.6 Analysis Test Methods 3-29
3.7 Thermal Decomposition Unit Analysis. ... 3-30
3.8 Work Sheet 3-32
3.9 References 3-36
4. INCINERATOR AND AIR POLLUTION CONTROL SYSTEM DESIGN
EVALUATION 4-1
4.1 Introduction 4-1
VI
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CONTENTS (continued)
Page
4.2 Destruction and Removal Efficiency 4-2
4.2.1 Definition 4-2
4.2.2 Sample Calculation 4-3
4.3 Incinerator Evaluation 4-4
4.3.1 Basic Design Considerations 4-6
4.3.1.1 Liquid Injection Incinerators 4-6
4.3.1.2 Rotary Kiln Incinerators 4-7
4.3.2 Physical, Chemical, and Thermodynamic Waste
Property Considerations 4-8
4.3.2.1 Liquid Injection Incinerators 4-8
4.3.2.2 Rotary Kiln Incinerators 4-20
4.3.3 Temperature, Excess Air, Residence Time, and
Mixing Evaluation 4-22
4.3.3.1 Liquid Injection Incinerators 4-23
4.3.3.2 Rotary Kiln Incinerators 4-37
4.3.4 Auxiliary Fuel Capacity Evaluation 4-44
4.3.4.1 Liquid Injection Incinerators 4-44
4.3.4.2 Rotary Kiln Incinerators 4-46
4.3.5 Combustion Process Control and Safety Shutdown
System Evaluation 4-46
4.3.5.1 Liquid Injection Incinerators 4-46
4.3.5.2 Rotary Kiln Incinerators 4-48
4.3.6 Construction Material Evaluation 4-50
4.4 Air Pollution Control and Gas Handling System Design
Evaluation 4-50
4.4.1 Emission/Air Pollution Control Device Matching
Criteria 4-53
4.4.1.1 Particulate Removal 4-54
4.4.1.2 Gaseous Pollutant Removal 4-56
4.4.2 Air Pollution Control Device Design and Operating
Criteria Evaluation 4-57
4.4.2.1 Venturi Scrubbers 4-57
4.4.2.2 Packed Bed Scrubbers . 4-61
4.4.2.3 Plate Tower Scrubbers 4-67
vii
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CONTENTS (continued)
4.4.3 Quenching and Mist Elimination Considerations 4-69
4.4.4 Prime Mover Capacity Evaluation 4-71
4.4.5 Process Control and Automatic Shutdown System
Evaluation 4-76
4.4.6 Material of Construction Considerations 4-77
4.5 Worksheets 4-79
4.6 References . 4-116
5. OVERALL FACILITY DESIGN, OPERATION, AND MONITORING 5-1
5.1 Introduction 5-1
5.1.1 Purpose 5-1
5.1.2 Hazardous Waste Incinerator Facility Design 5-2
5.2 Incinerator Facility Site Selection and Operation 5-2
5.2.1 Site Selection Concerns 5-2
5.2.2 Operation of the Facility 5|$
5.2.2.1 Operations Plan 5»5
5.2.2.2 Operations Manual 5-6
5.2.2.3 Emergency Manual or Handbook 5-6
5.2.2.4 Leak Detection and Repair Plan 5-13
5.2.2.5 Hazardous Chemical Spill Handling Plan .... 5-13
5.2.2.6 Facility Security 5-15
5.2.2.7 Operator Practices and Training 5-15
5.2.2.8 Loss Prevention Program 5-16
5.3 Waste Receiving Area . . . 5-16
5.3.1 Typical Operations and Layouts 5-17
5.3.2 Laboratory for Waste Verification and/or
Characterization ' 5-18
5.3.3 Liquids Unloading 5-20
5.3.3.1 Safety/Emergency Provisions 5-26
5.3.3.2 Spill and Runoff Containment 5-28
5.3.3.3 Static Electricity Prevention 5-28
5.3.4 Container Unloading. 5-30
5.3.5 Bulk Solids Unloading 5-32
5.3.5.1 Mechanical Conveyors ... 5-32
5.3.5.2 Pneumatic Conveyors 5-33
Vlll
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CONTENTS (continued)
5,4 Waste Storage Area 5-34
5,4.1 Types of Storage 5-35
5,4.1.1 Liquid Storage 5-35
5.4.1.2 Bulk Solids Storage 5-38
5.4.1.3 Container Storage 5-41
5.4.1.4 Tank Cars 5-42
5.4.2 Segregation of Wastes During Storage 5-42
5.4.3 Safety Provisions for Storage Areas 5-43
5.4.3.1 Fire Safety 5-43
5.4.3.2 Spill/Toxicity Safety 5-44
5.5 Waste Blending and/or Processing Before Incineration 5-49
5.5.1 Waste Compatibilities 5-49
5.5.2 Liquid Feed and Blending Equipment 5-50
5.5.3 Pumps and Piping 5-53
5.5.3.1 Positive-Displacement Pumps 5-55
5.5.3.2 Centrifugal Pumps 5-55
5.5.3.3 Pump Emission Control 5-56
5.5.3.4 Pump and Piping Safety 5-59
5.5.4 Valving and Controls 5-62
5.5.5 Valving and Control Safety Consideration 5-63
5.5.5.1 Safety Shutoffs 5-63
5.5.5.2 Gages, Meters, and Gage Glasses 5-66
5.5.5.3 Operating Controls 5-66
5.5.6 Solids Feeding Equipment 5-68
5.5.6.1 Shredders 5-68
5.5.6.2 Explosion Suppression and Safety Considera-
tions for Shredders 5-69
5.5.6.3 Feeders 5-70
5.5.6.4 Container Feeding Equipment 5-72
5.5.7 Backup/Redundancy Provisions 5-73
5.5.8 Waste Processing Instrumentation 5-75
5.6 Combustion Process Monitoring 5-75
5.6.1 Temperature Monitoring 5-76
5.6.1.1 Metal Tubes 5-81
5.6.1.2 Ceramic Tubes 5-82
5.6.1.3 Metal-Ceramic Tubes 5-82
ix
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CONTENTS (continued) 4
Page
5.6.2 Oxygen Monitoring 5-82
5.6.3 Gas Flow Measurement 5-83
5.6.3.1 Orifice Plates 5-84
5.6.3.2 Ventura Tubes 5-84
5.6.3.3 Pitot Tubes 5-85
5.6.4 Solid Waste Retention Time and Mixing Characteristics
Information 5-85
5.7 Air Pollution Control Device Inspection and Monitoring .... 5-86
5.7.1 Wet Scrubbers 5-86
5.7.1.1 Temperature 5-86
5.7.1.2 Liquid and Gas Flows 5-86
5.7.1.3 pH 5-87
5.7.1.4 Pressure Drop 5-87
5.7.1.5 Residue Generation ... 5-89
5.7.2 Fabric Filters |-89
5.7.2.1 Temperature 5-89
5.7.2.2 Gas Flow and Pressure Drop 5-93
5.7.2.3 Residue Generation 5-93
5.7.3 Electrostatic Precipitators 5-94
5.7.3.1 Rapping Cycle Practice 5-94
5.7.3.2 Temperature, Resistivity, and Gas Moisture
Effects 5-95
5.7.3.3 Applied Voltage (Power Supply Control) .... 5-96
5.7.3.4 Gas Flow 5-97
5.7.3.5 Residue Generation Rate and Dust Removal
Capacity 5-98
5.7.3.6 Internal System Pressure 5-98
5.7.4 Mist Eliminators 5-98
5.7.4.1 Temperature 5-98
5.7.4.2 Gas Flow and Pressure Drop 5-99
5.7.4.3 pH Level 5-99
5.7.4.4 Maintenance 5-99
5.8 Scrubber Waste Stream Treatment Inspection and Monitoring. . . 5-99
5.8.1 Flow Measurement and Monitoring 5-99
5.8.2 Flow Control 5-99
5.8.3 pH Monitoring 5-99
-------
CONTENTS (continued)
5.8.4 pH Control Systems. . , 5-100
5.8.4.1 On-Off Controller, . . 5-101
5.8.4.2 Proportional Controller 5-101
5.8.4.3 Resetting Derivative Controller 5-101
5.8.4.4 Flow Proportional Controller 5-101
5.8.5 Scrubber Solution pH Control 5-101
5.9 Continuous Monitoring Instrumentation for Gaseous Components . 5-102
5.9.1 Available Systems 5-103
5.9.1.1 Extractive Systems 5-105
5.9.1.2 In-Situ Monitoring Systems 5-109
5.9.2 Analyzers 5-110
5.9.2.1 NDIR Analyzers 5-110
5.9.2.2 Nondispersive Ultriviolet Analyzers (NDUV) . . 5-110
5.9.2.3 Polarographic Analyzers 5-111
5.9.2.4 Electrocatalytic Oxygen Analyzers 5-112
5.9.2.5 Paramagnetic Oxygen Analyzers 5-112
5.10 Manual Stack Sampling and Analysis Approaches 5-113
5.10.1 Hydrochloric Acid Emissions 5-116
5.10.2 Principal Organic Hazardous Constituents 5-116
5.10.3 Calculation of Sample Volume Required to Show 99.99%
DRE 5-123
5.11 Plant Condition Monitoring Systems 5-125
5.11.1 Machine Vibratory Signature Analysis 5-126
5.11.2 High Frequency Acoustic Emission Analysis 5-126
5.12 Scrubber/Quench Water and Ash Handling 5-126
5.12.1 Description of Potential Incinerator Wastes 5-127
5.12.1.1 Quench Water 5-131
5.12.1.2 Scrubber Effluents 5-136
5.12.1.3 Ash 5-136
5.12.2 Sampling and Analysis of Quench/Scrubber Water and
Ash 5-137
5.12.3 Handling of Quench/Scrubber Wastewater 5-139
5.12.4 Handling of Ash 5-139
XI
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CONTENTS (continued)
5.13 Fugitive Emissions 5-139
5.13.1 Significance of Observed Emissions 5-139
5.13.2 Fugitive Emission Control 5-143
5.13.3 Fugitive Emission Measurement Devices and Methodology 5-143
5.13.3.1 Area Monitoring 5-143
5.13.3.2 Fixed-Point Monitoring 5-143
5.13.3.3 Source Monitoring , . . . . 5-143
5.13.3.4 Current Instrumentation 5-143
5.14 Materials of Construction .' 5-144
5.14.1 Metals . 5-145
5.14.2 Nonnetallics 5-148
5.15 Miscellaneous Concerns 5-152
5.15.1 Personnel Health and Safety 5-152
5.15.2 Facility Housekeeping 5-153
5.15.3 Maintenance 5-lfc4
5.15.4 Firefighting/Emergency Personnel and Equipment. . . . 5-1E6
5.15.5 Stonnwater Diversion 5-lo7
5.15.6 Flue Gas Plume Aesthetics 5-158
5.16 Technical Assistance 5-158
5.17 References 5-159
6. ESTIMATING INCINERATION COSTS 6-1
6.1 Introduction 6-1
6.2 General Principles of Cost Estimation 6-2
6.2.1 Capital Costs 6-2
6.2.1.1 Purchased Equipment Costs 6-2
6.2.1.2 Installation Costs 6-3
6.2.2 Annualized Costs. 6-3
6.2.2.1 Direct Operating Costs 6-3
6.2.2.2 Indirect Operating Costs 6-4
6.3 Capital and Operating Costs for Hazardous Waste Incineration
Facilities and Air Pollution Control Devices 6-5
6.3.1 Hazardous Waste Incinerators 6-5
6.3.1.1 Capital Investment for Hazardous Waste
Incinerators 6-5
xii
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CONTENTS (continued)
6.3.1.2 Operating Costs of Hazardous Waste
Incinerators . . . . ' 6-8
6.3.2 Air Pollution Control Devices 6-8
6.3.2.1 Air Pollution Control Device Capital Installed
Costs 6-8
6.3.2.2 Electrostatic Precipitator 6-20
6.3.2.3 Fabric Filter 6-20
6.3.2.4 Mechanical Collectors 6-20
6.3.2.5 Incinerators 6-20
6.3.2.6 Venturi Scrubbers 6-21
6.3.2.7 Example Calculation 6-21
6.4 Cost of Particulate Fugitive Emission Control 6-22
6.5 Cost Effects of Hazardous Waste Incineration Facility
Modifications 6-24
6.5.1 Cost Effects on Material of Construction 6-24
6.5.2 Cost Effects Using Equipment Modules 6-24
6.6 Trial Burns 6-28
6.6.1 Normal Operations 6-30
6.6.2 Trial Burn Activities 6-30
6.6.2.1 Site Survey 6-30
6.6.2.2 Equipment Preparation 6-30
6.6.2.3 Equipment Set-Up and Takedown 6-30
6.6.2.4 Stack Sampling 6-30
6.6.2.5 Sample Analysis . 6-30
6.6.2.6 Equipment Cleanup 6-31
6.6.2.7 Report Preparation 6-31
6.7 References 6-31
APPENDICES
A. Subject Index A-l
B. Glossary of Terns B-l
C. Conversion Factors C-l
D. Bibliography D-l
E. Laboratory-Scale Thermal Decomposition Analytical Data E-l
F. Trial Burn Summaries F-l
xiii
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LIST OF FIGURES
Number
2-1 Incineration process configurations for disposal of gaseous
or liquid waste with no appreciable SO or NO production. 2-13
X X
2-2 Incineration process configuration for disposal of gaseous
or liquid waste with control of excessive SO or C12/HC1 . 2-14
X
2-3 Two stage combustion process for disposal of gaseous or
liquid waste with control of excessive NO 2-15
2-4 Incineration process for disposal of gaseous or liquid waste
with control of excessive NO and C12/HC1. 2-16
X
2-5 Incineration process configurations for disposal of gaseous
or liquid waste with control of excessive particulate
matter 2-3
2-6 Incineration process configurations for disposal of fine
combustible solid waste with no appreciable SO or NO
production 2-17
2-7 Incineration process configurations for disposal of gaseous
waste containing fine solid particles with control of
particulates 2-18
2-3 Incineration process for disposal of fine solid waste with-
out control of NO 2-19
X
2-9 Incineration process for disposal of solid plastic waste
containing catalyst with control of particulates 2-20
2-10 Two-stage combustion process for disposal of high nitrogen
crude with control of NO 2-20
X
2-11 Rotary kiln incinerator schematic 2-21
2-12 Horizontally-fired liquid injection incinerator schematic . 2-24
2-13 Vertically-fired liquid injection incinerator schematic . . 2-24
2-14 Tangentially-fired vortex combustor liquid injection
incinerator schematic 2-25
xiv
-------
FIGURES (continued)
Number
2-15
2-16
2-17
2-18
2-19
2-20
2-21
2-22
2-23
2-24
2-25
2-26
3-1
3-2
3-3
3-4
4-1
4-2
4-3
4-4
4-5
4-6
Typical fluidized bed incinerator schematic
Typical multiple hearth incinerator schematic
Starved air combustion/pyrolysis schematic
Basic afterburner flow scheme
Venturi scrubber schematic
Packed bed scrubber schematic
Packed tower pressure drop as function of gas rate and
liquid rate
Spray tower schematic
Plate tower schematic
Electrostatic precipitator schematic
Wet electrostatic precipitator schematic
Heat recovery/ gas-to-water
Field sampling chain of custody form
Decomposition of hexachlorobiphenyl . .
Decomposition of pentachlorobiphenyl in different gaseous
atmospheres
Relative concentration of hexachlorobenzene in "Hex" wastes
after different thermal exposures
Incinerator design evaluation criteria
High heat release burner for combustion of liquid waste . .
Internal mix nozzle
External mix nozzle
Sonic atomizing nozzle
Equilibrium constant versus temperature
Page
2-27
2-29
2-33
2-35
2-28
2-40
2-42
2-43
2-45
2-47
2-49
2-50
3-24
3-30
3-30
3-31
4-5
4-6
4-9
4-9
4-10
4-15
XV
-------
FIGURES (continued)
Number Page
4-7 Relationship between activation energy and heat of
combustion 4-16
4-3 Adiabatic temperature of combustion gases from typical
liquid wastes 4-17
4-9 Adiabatic temperature of combustion gases from typical
gaseous wastes ' 4-18
4-10 Heat of combustion of chlorinated hydrocarbons 4-19
4-11 Nomograph for checking the internal consistency of proposed
excess air rate and combustion temperature in hazardous
waste incinerators 4-24
4-12 Energy balance for combustion chamber 4-26
4-13 Enthalpy balance for combustion processes 4-27
4-14 Logic diagram for air pollution control and gas handling
system design 4
.1
4-15 Pressure drop versus cut diameter for gas-atomized scrubber .
systems (experimental data from large Venturis, other
gas-atomizers, scrubbers, and mathematical model) .... 4-60
4-16 Pipe flow chart 4-73
4-17 Total frictional pressure drops in 90° bends 4-74
4-18 90° Bends (a) smooth bend, (b) segmental bend 4-74
5-1 Typical incinerator facility layout 5-3
5-2 Typical incinerator facility flow diagram, solid and liquid
wastes 5-4
5-3 Spill-response diagram illustrating the interrelating
information available, decisions to be taken, and
improvements needed 5-14
5-4 Flow diagram showing handling procedures for incineration
of hazardous wastes 5-17
5-5 Layout for liquid receiving area 5-18
5-6 Typical tank trailer (car) with parts identified 5-21
xvi
-------
FIGURES (continued)
Number Page
5-7 Typical tank car with parts identified 5-22
5-8 Tank car unloading station 5-22
5-9 Bonding and grounding of a flammable liquid tank truck
and loading rack 5-23
5-10 Compressed inert gas transfer method . 5-25
5-11 Fail-safe transfer line for hazardous fluids 5-25
5-12 Fail-safe transfer line inlet and outlet assemblies .... 5-26
5-13 Containment curb type spill catchment system, depressed
area form 5-29
5-14 A tank car unloading siding showing rail joint bonding,
insulated track joint, detail, and track grounding. . . . 5-29
5-15 Fluidizing outlets for hopper cars 5-32
5-16 Diagram of pneumatic railcar unloading 5-34
5-17 Typical shapes for storage vessels 5-36
5-18 Typical tank condenser vent system 5-37
5-19 Dike drain detail Type "A" diversion box 5-47
5-20 Compatibility matrix for neutralized hazardous wastes . . . 5-51
5-21 Compatibility matrix when wastes cannot be neutralized. . . 5-51
5-22 Example of a baffled mixing vessel 5-51
5-23 Slurry injection and monitoring system 5-53
5-24 Liquid feed 5ystem with redundant recirculation 5-54
5-25 Pump classification chart 5-55
5-26 Reciporacting pumps: (a) Principle of reciprocating pump,
(b) principle of fluid-operated diaphragm pump, (c) direct-
acting steam pump, (d) principle of mechanical diaphragm
pump, (e) piston-type power pump, (f) plunger-type power
pump with adjustable stroke, (g) inverted, vertical,
triplex power pump 5-56
xvii
-------
FIGURES (continued)
Number page
5-27 Rotary pumps: (a) External-gear pump, (b) internal-gear
pump, (c) three-lobe pump, (d) four-lobe pump,
(e) sliding-vane pump, (f) single-screw pump,
(g) swinging-vane pump, (h) cam or roller pump, (i) cam-
and-piston pump, (j) three-screw pump, (k) shuttle-block
pump, (1) squeegee pump, (m) neoprene vane pump 5-57
5-28 Centrifugal pumps: (a) Principle of centrifugal-type pump,
(b) radial section through volute-type pump, (c) radial
section through diffuser-type pump, (d) open impeller,
(e) semi-enclosed impeller, (f) closed impeller, (g)
nonclog impeller 5-58
5-29 Two safeguards for piping of highly toxic liquids 5-61
5-30 Three areas of a typical gate valve that can leak and
result in fugitive emissions 5-64
5-31 Cross-section through a nonreversible horizontal shredder . 5-19
5-32 Continuous feeding of sludge to fluid bed incinerator . . . 5-72
5-33 Continuous type containerized toxic material thermal
disposal process 5-74
5-34 Example of a waste-charging door 5-74
5-35 Liquid waste incinerator schematic 5-75
5-36 Schematic diagram showing typical monitoring locations for
a liquid injection incinerator 5-78
5-37 Schematic diagram showing typical monitoring locations for
a rotary kiln incinerator 5-79
5-38 Recommended measurement and inspection locations 5-93
5-39 Typical vibratory rapper 5-95
5-40 Recommended measurement location 5-96
5-41 Power supply system for modern precipitators 5-97
5-42 Elements of a typical pH control system 5-102
5-43 Two-step neutralization flow schematic 5-103
5-44 Elements of pollutant monitoring system 5-104
XVlll
-------
FIGURES (continued)
Number Page
5-45 Schematic diagram of hydrogen chloride sampling train . . . 5-117
5-46 Modified EPA Method 5 sample train for POHC collection. . . 5-118
5-47 Adsorbent sampling system 5-119
5-48 Temperature controlled cooled probe 5-120
5-49 SASS schematic 5-122
5-50 Various quenching devices 5-128
5-51 Generalized schematic of incinerator facility 5-130
5-52 Schematic of rotary kiln facility with quench spray chamber
and venturi scrubber 5-130
5-53 Single-pass scrubber system 5-133
5-54 Recirculating scrubber system 5-133
5-55 Incineration system with two-stage scrubber 5-135
5-56 Incineration system with three-stage scrubber 5-135
5-57 Incineration process with emissions treatment and disposal
options 5-138
5-58 Possible process leakage areas 5-141
6-1 Total capital investment for a rotary kiln incinerator. . . 6-6
6-2 Total capital investment for a liquid injection
incinerator 6-7
6-3 Total annual operating cost for a rotary kiln incinerator . 6-9
6-4 Total annual operating cost for a liquid injection
incinerator 6-10
6-5 Capital and annualized costs of fans and 30.5 length of duct 6-11
6-6 Capital and annualized costs of fan driver for various head
pressures 6-12
6-7 Capital and annualized costs of electrostatic precipitator
carbon steel construction 6-13
xix
-------
FIGURES (continued)
Number Page
6-8 Capital and annualized costs of fabric filters, carbon
steel construction 6-14
• 6-9 Capital and annualized costs of fabric filters, stainless
steel construction 6-15
6-10 Capital arid annualized costs of mechanical collectors,
carbon and steel construction 6-16
6-11 Capital and annualized costs of incinerators 6-17
6-12 Capital and annualized costs of venturi scrubbers, carbon
steel construction 6-18
6-13 Capital and annualized costs of venturi scrubbers, stainless
steel construction 6-19
6-14a Capacity vs. installed cost for a fan 6-27
6-14b Capacity vs. installed cost for a steam boiler 6-E7
6-14c Capacity vs. installed cost for an incinerator 6-28
-------
LIST OF TABLES
Number Page
1-1 ENGINEERING HANDBOOK FOR HAZARDOUS WASTE INCINERATION -
CHAPTERS AND THEIR CONTENT 1-2
2-1 PERTINENT INCINERATION PROCESSES AND THEIR TYPICAL
OPERATING RANGES 2-2
2-2 APPLICABILITY OF AVAILABLE INCINERATION PROCESSES TO
INCINERATION OF HAZARDOUS WASTE BY TYPE 2-3
2-3 WASTE CHEMICAL STREAM CONSTITUENTS WHICH MAY BE SUBJECTED
TO ULTIMATE DISPOSAL BY CONTROLLED INCINERATION 2-4
2-4 INDUSTRIAL WASTE AND POLLUTION PROCESS 2-12
2-5 TECHNOLOGIES APPROPRIATE FOR HAZARDOUS WASTE INCINERATION . 2-52
2-6 - SELECTED INDUSTRIAL WASTE INCINERATION FACILITIES IN EUROPE
AND JAPAN 2-61
2-7 HAZARDOUS WASTE INCINERATOR VENDORS 2-62
3-1 HAZARDOUS WASTES RATED AS GOOD, POTENTIAL, OR POOR CANDI-
DATES FOR INCINERATION BY APPROPRIATE TECHNOLOGIES. ... 3-4
4-1 KINEMATIC VISCOSITY AND SOLIDS HANDLING LIMITATIONS OF
VARIOUS ATOMIZATION TECHNIQUES 4-11
4-2 EVALUATION PROCEDURE FOR PHYSICAL WASTE PROPERTY/
ATOMIZATION TECHNIQUE COMPATIBILITY 4-12
4-3 STOICHIOMETRIC OXYGEN REQUIREMENTS AND COMBUSTION PRODUCTS
YIELDS 4-13
4-4 CHEMICAL AND THERMODYNAMIC WASTE PROPERTY EVALUATION
PROCEDURE 4-21
4-5 TEMPERATURE/EXCESS AIR EVALUATION PROCEDURE 4-34
4-6 GAS RESIDENCE TIME EVALUATION PROCEDURE 4-35
4-7 MIXING EVALUATION PROCEDURE 4-36
XXI
-------
TABLES (continued)
Number Paqe
4-8 TEMPERATURE/EXCESS AIR EVALUATION PROCEDURE FOR ROTARY
KILN/AFTERBURNER INCINERATORS 4-42
4-9 KILN RETENTION TIME EVALUATION PROCEDURE 4-44
4-10 COMBUSTION PROCESS CONTROL EVALUATION PROCEDURE 4-48
4-11 COMBUSTION PROCESS CONTROL EVALUATION PROCEDURE ....... 4-49
4-12 GENERAL CHARACTERISTICS OF SILICA AND ALUMINO-SILICATE
REFRACTORY BRICK 4-51
4-13 PROCEDURE TO COMPARE PARTICULATE REMOVAL REQUIREMENTS WITH
PROPOSED CONTROL STRATEGIES „ . 4-55
4-14 PROCEDURE TO COMPARE GASEOUS POLLUTANT REMOVAL REQUIREMENTS
WITH PROPOSED CONTROL STRATEGIES 4-58
4-15 VENTURI SCRUBBER DESIGN EVALUATION PROCEDURE,
4-16 TYPICAL VALUES OF K a
g
<-n.
4-61
4-17 PACKING DEPTH REQUIRED TO ACHIEVE SPECIFIED REMOVAL
EFFICIENCY 4-64
4-18 PACKED BED SCRUBBER EVALUATION PROCEDURE 4-66
4-19 MURPHREE VAPOR PHASE EFFICIENCY FOR PLATE TOWERS 4-67
4-20 PLATE TOWER SCRUBBER EVALUATION PROCEDURE 4-69
4-21 SUDDEN CONTRACTION-LOSS COEFFICIENT FOR TURBULENT FLOW. . . 4-76
5-1 HAZARDOUS WASTE INCINERATOR MALFUNCTIONS AND REMEDIAL OR
EMERGENCY RESPONSES 5-7
5-2 TYPICAL STEEL DRUM SPECIFICATION FOR HAZARDOUS MATERIALS. . 5-31
5-3 TYPES AND CHARACTERISTICS OF DRY BULK STORAGE 5-39
5-4 MATERIALS OF CONSTRUCTION FOR POSITIVE DISPLACEMENT PUMPS . 5-54
5-5 FEEDERS FOR BULK MATERIALS 5-71
5-6 LIMITS OF ERROR FOR THERMOCOUPLES 5-80
5-7 DEVICES FOR LIQUID FLOW MEASUREMENT 5-88
JOEll
-------
TABLES (continued)
Number
5-8
5-9
5-10
5-11
5-12
5-13
5-14
5-15
5-16
5-17
5-18
5-19
5-20
5-21
6-1
6-2
6-3
6-4
6-5
6-6
6-7
A GUIDE TO PRESSURE SENSING ELEMENT SELECTION
ANALYZERS CAPABLE OF MEASURING GASEOUS COMPONENTS
INFRARED BAND CENTERS OF SOME COMMON GASES
EXTRACTIVE MONITOR SUMMARY
IN-SITU MONITOR SUMMARY
OXYGEN ANALYZER SUMMARY
POTENTIAL AIR POLLUTANTS FROM HAZARDOUS WASTE INCINERATION.
SCRUBBER WATER AND WASTE PARAMETERS FOR TWO LAND-BASED
LIQUID INJECTION INCINERATORS
SCRUBBER WATER QUALITY
POSSIBLE SOURCES OF FUGITIVE EMISSIONS FROM HAZARDOUS WASTE
INCINERATOR SYSTEMS
CONTROL ALTERNATIVES FOR FUGITIVE DUST
BRAND NAMES OF POLYMERIC MATERIALS
PROPERTY COMPARISONS - NATURAL AND SYNTHETIC RUBBERS. . . .
PROPERTIES OF COMMERCIALLY AVAILABLE PLASTICS
ESTIMATES OF LIFE OF MATERIALS, PARTS, AND EQUIPMENT FOR
AIR POLLUTION CONTROL SYSTEMS
TYPICAL COST OF WET SUPPRESSION OF INDUSTRIAL PROCESS
FUGITIVE PARTICULATE EMISSIONS
COST ESTIMATES FOR WET SUPPRESSION OF FUGITIVE DUST ....
COST ESTIMATES FOR STABILIZATION OF FUGITIVE DUST
COST ESTIMATES FOR SWEEPING AND FLUSHING OF FUGITIVE DUST
SOURCES
MATERIAL COST FACTORS
TRIAL BURN COST COMPONENTS (DOLLARS)
Page
5-90
5-104
5-111
5-114
5-115
5-115
5-131
5-134
5-134
5-140
5-142
5-149
5-150
5-151
6-5
6-23
6-24
6-25
6-26
6-26
6-29
tiii
-------
TABLES (continued)
Number Pace
._ i .1 ml ._ i -* —
6-8 HOURLY FUEL COSTS 6-31
6-9 MATERIAL COST FACTORS 6-33
6-10 TRIAL BURN COST ASSUMPTIONS 6-36
XXIV
-------
CHAPTER 1
INTRODUCTION
Millions of tons of industrial waste materials are generated each year in the
United States. A sizable fraction of this waste is considered hazardous (an
estimated 57 million metric tons in 1980). In recent years, incineration has
emerged as an attractive potential alternative to hazardous waste disposal
methods such as landfill, ocean dumping, and deep-well injection.
Incineration possesses several advantages as a hazardous waste disposal
technology:
- Toxic components of hazardous wastes can be converted to harmless
compounds or, at least, to less harmful compounds.
- Incineration provides for the ultimate disposal of hazardous wastes,
eliminating the possibility of problems resurfacing in the future.
- The volume of hazardous waste is greatly reduced by incineration.
- Heat recovery makes it possible to recover some of the energy
produced by the combustion process.
It is likely that incineration will be a principal technology for the dis-
posal of hazardous waste in the future because of the above advantages.
This engineering handbook is a compilation of information available in the
literature and describes current state-of-the-art technology for the incin-
eration of hazardous waste. The handbook is designed to serve as a technical
resource document in the evaluation of hazardous waste incineration operations.
This document is intended to serve as a useful technical resource for Federal,
regional, and state EPA officials; designers of hazardous waste incineration
facilities, owners and operators of hazardous waste incineration facilities,
and the general technical community.
Each chapter in the handbook addresses a separate topic involved in hazardous
waste incineration. A brief abstract for each chapter is presented in
Table 1-1.
The user is encouraged to make use of the references cited in each chapter
if additional information is required.
1-1
-------
TABLE 1-1. ENGINEERING HANDBOOK FOR HAZARDOUS WASTE
INCINERATION - CHAPTERS AND THEIR CONTENT
Chapter Abstract
1 Introduction
Describes the utility of the handbook and its structure, specifying
where various types of information are available.
2 Current Practices
Provides an overview of incineration systems for various types of
waste. Commercially available technology, emerging technology, and
foreign technology are included. The components of these systems
are described in detail, including air pollution control devices and
heat recovery systems. A matrix of the types of components appli-
cable to different generic types of waste is provided, along with a
list of U.S. incinerator manufacturers.
Waste Characterization »
Describes the basic types of analysis required to characterize
wastes, and discusses how the resulting data are used to match a
waste to an appropriate type of incinerator. Hazardous wastes
listed under Section 3001 of the RCRA regulations are evaluated for
their suitability for incineration.
Incinerator and Air Pollution Control System Design Evaluation
Provides detailed information and procedures for evaluation of in-
cinerator and air pollution control device design and operating con-
ditions. Basically, this involves a series of internal consistency
checks designed to determine whether (1) acceptable temperatures,
residence times, oxygen concentrations, and mixing can be achieved
and maintained in the incinerator, (2) the various components of the
system have sufficient capacity to accommodate the quantities of
waste to be burned, (3) appropriate air pollution control device
operating conditions can be maintained, (4) the design includes
process control and automatic shutdown safeguards to minimize re-
lease of hazardous materials in the event of equipment malfunction,
and (5) proper materials of construction are used. Individual eval-
uation procedures are provided for liquid injection and rotary kiln
incinerators, and for several types of wet scrubbers.
(continued)
1-2
-------
TABLE 1-1 (continued)
Chapter Abstract
Overall Facility Design, Operation, and Monitoring
Provides engineering background information on the technical capa-
bilities necessary for the incineration facility to process hazard-
ous waste safely and effectively. The chapter discusses overall
facility layouts; equipment requirements common to all facilities,-
waste receiving equipment, procedures, and storage,- personnel
safety,- emergency procedures and provisions; monitoring procedures
and instrumentation; sampling and analysis equipment and methodolo-
gies,- sources of fugitive emissions and their control; scrubber/
quench water handling and disposal; and ash collection systems.
Estimating Incineration Costs
Examines the economic factors involved in the construction of new
facilities and the operation of existing facilities. Capital costs
for incinerators and air pollution control devices are discussed.
The costs involved in changing incinerator operating conditions
(temperature, percent excess air, residence time) and the removal
efficiency of air pollution control devices are examined. The
costs involved in performing trial burns are also addressed in this
chapter.
Appendices
Provide a subject index, glossary of terms, tables of conversion
factors, bibliography, and descriptions of equipment used for
laboratory-scale thermal chemical waste decomposition experiments.
The results of laboratory experiments and trial burn studies are
also summarized.
1-3
-------
CHAPTER 2
CURRENT PRACTICES
2.1 INTRODUCTION
Incineration has developed over a number of years as a means for disposal of a
wide variety of waste materials. Recently, applying incineration to hazardous
waste disposal has been given an increasing amount of attention as an alterna-
tive to more expensive and controversial treatment and disposal technologies.
Besides the economics involved, another advantage of incineration is that it
does not necessarily need to be carried out at land-based facilities. Ship-
board incineration is currently being studied and utilized in destruction of
dangerous chlorinated hydrocarbon wastes [1, 2].
The U.S. Environmental Protection Agency estimates that in 1979 only 5% of the
country's total hazardous waste stream was managed by incineration, yet 60% of
the total wastes could have been successfully destroyed using current incin-
erator technology [1, 2].
The EPA estimates further that in 1979 about 39 million short tons (35 million
metric tons) of hazardous wastes were generated in this country by some
270,000 industrial plants and other facilities. The majority of these wastes
(65%) were produced in ten states.- Texas, Ohio, Pennsylvania, Louisiana,
Michigan, Indiana, Illinois, Tennessee, West Virginia, and California. It is
expected that the quantities of hazardous waste generated will increase annu-
ally by 3%. Based on these figures, incineration is becoming an increasingly
more important option in solving hazardous waste disposal problems [3, 4].
Incineration is an engineered process using thermal oxidation of a waste
materiel to produce a less bulky, toxic, or noxious material. A waste must be
combustible to some extent in order for incineration to be a viable disposal
method [5]. The 3 T's of combustion, temperature, residence time, and turb-
ulence, are crucial in controlling operating conditions. Table 2-1 summarizes
the typical ranges for temperature and residence time in six incineration
processes. Chapter 4 deals with turbulence and oxygen availability.
The waste characteristics are likewise important parameters, including chemi-
cal structure and physical form. Table 2-2 presents a summary of those phy-
sical forms suitable for each of the six types of incinerators. Table 2-3
lists candidate compounds for destruction by incineration.
This chapter outlines the basic variations of incinerator processes and illu-
strates the individual components and their applications. Included are six
types of incinerator technologies, along with pertinent air pollution control
2-1
-------
TABLE 2-1. PERTINENT INCINERATION PROCESSES ANC THEIR TYPICAL
OPERATING RANGES [6]
Process
Temperature
range, °F (°C)
Residence time
Rotary kilne
Liquid injection
Fluidized bed
Multiple hearth
Coincineration
Starved air combustion/pyrolysis
1,500 to 2,900
(820 to 1,600)
1,200 to 2,900
(650 to 1,600)
840 to 1,800
(450 to 980)
Drying zone
600 to 1,000
(320 to 540)
Incineration
1,400 to 1,800
(760 to 980)
300 to 2,900
(150 to 1,600)
900 to 1,500
(480 to 820)
Liquids and gases, seconds;
solids, hours
0.1 to 2 seconds
Liquids and gases, second!;
solids, longer
0.25 to 1.5 hours
Seconds to hours
Tenth of a second to
several hours
aA highly developed hazardous waste incineration technology; covered in detail
in Chapter 4.
2-2
-------
J3
X
x x
X X
X X
«» ^
V «M
a
ope
- s rs -a
•8 "S0 BS
•H *J y h, k.
2. C -H o o
O1 o *J o
•^ u 0 o w
^ I fM 3
•^ V O .Q
W -W V. N «
2 § «~g,
•g* <
(0
y «o
2-3
-------
TABLE 2-3. WASTE CHEMICAL STREAM CONSTITUENTS WHICH MAY BE SUBJECTED
TO ULTIMATE DISPOSAL BY CONTROLLED INCINERATION [7]
ORGANIC
Acetaldehyde
Acetic acid
Acetic anhydride
Acetone
Acetone cyanohydrin-. oxides of nitrogen are removed from the effluent gas by
scrubbers and/or thermal devices.
Acetonitrile.- oxides of nitrogen are removed from the effluent gas by scrub-
bers and/or thermal devices.
Acetyl chloride
Acetylene
Acridine: oxides of nitrogen are removed from the effluent gas by scrubber,
catalytic, or thermal device.
Acrolein: 1500°F, 0.5 sec minimum for primary combustion,- 2000°F, 1.0 sec for
secondary combustion, combustion products C02 and H20.
Acrylic acid
Acrylonitrile: NO removed from effluent gas by scrubbers and/or thermal
devices. |-
Adipic acid I
Allyl alcohol *
Allyl chloride: 1800°F, 2 sec minimum.
Aminoethylethanolamine: incinerator is equipped with a scrubber or thermal
unit to reduce NO emissions.
Amyl acetate
Amyl alcohol
Aniline: oxides of nitrogen are removed from the effluent gas by scrubber,
catalytic, or thermal device.
Anthracene
Benzene
Benzene sulfonic acid: incineration followed by scrubbing to remove the S02
gas.
Benzoic acid
Benzyl chloride: 1500°F, 0.5 sec minimum for primary combustion; 2200°F,
1.0 sec for secondary combustion; elemental chlorine formation may be alle-
viated through injection of steam or methane into the combustion process.
Butadiene
Butane
Butanols
1-Butene
Butyl acrylate
n-Butylamine: incinerator is equipped with a scrubber or thermal unit to re-
duce NO emissions.
Butylenesx
Butyl phenol
Butyraldehyde
(continued)
2-4
-------
TABLE 2-3 (continued)
Camphor
Carbolic acid (phenol)
Carbon disulfide: a sulfur dioxide scrubber is necessary when combusting sig-
nificant quantities of carbon disulfide.
Carbon monoxide
Carbon tetrachloride: preferably after mixing with another combustible fuel;
care must be exercised to assure complete combustion to prevent the forma-
tion of phosgene; an acid scrubber is necessary to remove the halo acids
produced.
Chloral hydrate: same as carbon tetrachloride.
Chlorobenzene: same as carbon tetrachloride.
Chloroform: same as carbon tetrachloride.
Creosote
Cresol
Crotonaldehyde
Cumene
Cyanoacetic acid: oxides of nitrogen are removed from the effluent gas by
scrubbers and/or thermal devices.
Cyclohexane
Cyclohexanol
Cyclohexanone
Cyclohexylamine: incinerator is equipped with a scrubber or thermal unit to
reduce NO emissions.
Decyl alcohol
Di-n-butyl phthalate
Dichlorobenzene: incineration, preferably after mixing with another combusti-
ble fuel; care must be exercised to assure complete combustion to prevent
the formation of phosgene. An acid scrubber is necessary to remove the halo
acids produced.
Dichlorodifluoromethane (freon): same as dichlorobenzene.
Dichloroethyl ether: same as dichlorobenzene.
Dichloromethane: (methylene chloride) same as dichlorobenzene.
1,2-Dichloropropane: same as dichlorobenzene.
Dichlorotetrafluoro*thane: same as dichlorobenzene.
Dicyclopentadiene
Diethnolamine: incinerator is equipped with a scrubber or thermal unit to re-
duce NO emissions.
Diethylamine: sane as diethanolamine.
Diethylene glycol
Diethyl ether: concentrated waste containing no peroxides; discharge liquid
at a controlled rate near a pilot flame. Concentrated waste containing
peroxides; perforation of a container of the waste from a safe distance fol-
lowed by open burning.
Diethyl phthalate
Diethylstilbestrol
Diisobutylene
Diisobutyl ketone
(continued)
2-5
-------
TABLE 2-3 (continued)
i
Diisopropanolamine: incinerator is equipped with a scrubber or thermal unit
to reduce NO emissions.
Dimethylamine: same as diisopropanolamine.
Dimethyl sulfate: incineration (1800°F, 1.5 sec minimum) of dilute, neutral-
ized dimethyl sulfate waste is recommended. The incinerator must be equip-
ped with efficient scrubbing devices for oxides of sulfur.
2,4-Dinitroaniline: controlled incineration whereby oxides of nitrogen are
removed from the effluent gas by scrubber, catalytic, or thermal device.
Dinitrobenzol: incineration (1800°F, 2.0 sec minimum) followed by removal of
the oxides of nitrogen that are formed using scrubbers and/or catalytic or
thermal devices. The dilute wastes should be concentrated before incin-
eration.
Dinitrocresol: incineration (1100°F minimum) with adequate scrubbing and ash
disposal facilities.
Dinitrophenol: incinerated (1800°F, 2.0 sec minimum) with adequate scrubbing
equipment for the removal of NO .
Dinitrotoluene: pretreatment involves contact of the dinitrotoluene contami-
nated waste with NaHC03 and solid combustibles followed by incineration in
an alkaline scrubber equipped incinerator unit.
Dioxane: concentrated waste containing no peroxides; discharge liquid at
controlled rate near a pilot flame. Concentrated waste containing
peroxides: perforation of a container of the waste from a safe distance
followed by open burning.
Dipropylene glycol
Dodecylbenzene
Epichlorohydrin: incineration, preferably after mixing with another combus-
tible fuel. Care must be exercised to assure complete combustion to prevent
the formation of phosgene. An acid scrubber is necessary to remove the halo
acids produced.
Ethane
Ethanol
Etahnolamine: controlled incineration; incinerator is equipped with a scrub-
ber of thermal unit to reduce N0x emissions.
Ethyl acetate
Ethyl acrylate
Ethylamine: controlled incineration; incinerator is equipped with a scrubber
or thermal unit to reduce N0x emissions.
Ethylbenzene
Ethyl chloride: incineration, preferably after mixing with another combusti-
ble fuel. Care must be exercised to assure complete combustion to prevent
the formation of phosgene. An acid scrubber is necessary to remove the halo
acids produced.
Ethylene
Ethylene cyanohydrin: controlled incineration (oxides of nitrogen are removed
from the effluent gas by scrubbers and/or thermal devices).
Ethylenediamine: same as ethylene cyanohydrin.
(continued)
2-6
-------
TABLE 2-3 (continued)
Ethylene dibromide: controlled incineration with adequate scrubbing and ash
disposal facilities.
Ethylene dichloride: incineration, preferably after mixing with another com-
bustible fuel; care must be exercised to assure complete combustion to pre-
vent the formation of phosgene. An acid scrubber is necessary to remove the
halo acids produced.
Ethylene glycol
Ethylene glycol monoethyl ether: concentrated waste containing no peroxides,-
discharge liquid at a controlled rate near a pilot flame. Concentrated
waste containing peroxides; perforation of a container of the waste from a
safe distance followed by open burning.
Ethyl mercaptan: incineration (2000°F) followed by scrubbing with a caustic
solution.
Fatty acids
Formaldehyde
Formic acid
Furfural
Glycerin
n-Heptane
Hexamethylenediamine: incinerator is equipped with a scrubber or thermal unit
to reduce NO emissions.
Hexane x
Hydroquinone: incineration (1800°F, 2.0 sec minimum) then scrub to remove
harmful combustion products.
Isobutyl acetate
Isopentane
Isophorone
Isoprene
Isopropanol
Isopropyl acetate
Isopropylamine: controlled incineration (incinerator is equipped with a
scrubber or thermal unit to reduce NO emissions).
Isopropyl ether: concentrated waste containing no peroxides; discharge liquid
at a controlled rate near a pilot flame. Concentrated waste containing
peroxides; perforation of « container of the waste from a safe distance fol-
lowed by open burning.
Maleic anhydride: controlled incineration; care must be taken that complete
oxidation to nontoxic products occurs.
Mercury compounds (organic): incineration followed by recovery/removal of
mercury from the gas stream.
Hesityl oxide
Methanol
Methyl acetate
Methyl acrylate
Methylamine: controlled incineration (incinerator is equipped with a scrubber
or thermal unit to reduce NO emissions).
Methyl amyl alcohol x
(continued)
2-7
-------
TABLE 2-3 (continued)
n-Methylaniline.- controlled incineration whereby oxides of nitrogen are
removed from the effluent gas by scrubber, catalytic or thermal device.
Methyl bromide: controlled incineration with adequate scrubbing and ash dis-
posal facilities.
Methyl chloride: same as methyl bromide.
Methyl chloroformate: incineration, preferably after mixing with another com-
bustible fuel; care must be exercised to assure complete combustion to pre-
vent the formation of phosgene. An acid scrubber is necessary to remove the
halo acids produced.
Methyl ethyl ketone
Methyl formate
Methyl isobutyl ketone
Methyl mercaptan: incineration followed by effective scrubbing of the efflu-
ent gas.
Methyl methacrylate monomer
Morpholine: controlled incineration (incinerator is equipped with a scrubber
or thermal unit to reduce NO emissions).
Naphtha
Naphthalene i
B-Naphthylamine: controlled incineration whereby oxides of nitrogen are I*
removed from the effluent gas by scrubber, catalyst or thermal device. I
Nitroaniline: incineration (1800°F, 2.0 sec minimum) with scrubbing for
NO abatement.
Nitrobenzene: same as nitroaniline
Nitrocellulose: incinerator is equipped with scrubber for NO abatement.
Nitrochlorobenzene: incineration (1500°F, 0.5 sec for primary combustion;
2200°F, 1.0 sec for secondary combustion). The formation of elemental
chlorine can be prevented through injection of steam or methane into the
combustion process. NO may be abated through the use of thermal or cataly-
tic devices.
Nitroethane: incineration, large quantities of material may require N0x
removal by catalytic or scrubbing processes.
Nitromethane: same as nitroe thane.
Nitrophenol: controlled incineration; care must be taken to maintain complete
combustion at all times. Incineration of large quantities may require
scrubbers to control the emission of NO .
Nitropropane: same as nitroethane.
4-Nitrotoluene: same as nitrophenol.
Nonyl phenol
Octyl alcohol
Oleic acid
Oxalic acid: pretreatment involves chemical reaction with limestone or calci-
um oxide forming calcium oxalate. This may then be incinerated utilizing
particulate collection equipment to collect calcium oxide for recycling.
Paraformaldehyde
Pentachlorophenol: incineration (600° to 900°C) coupled with adequate scrub-
bing and ash disposal facilities.
(continued)
2-8
-------
TABLE 2-3 (continued)
n-Pentane
Perchloroethylene: incineration, preferably after mixing with another combus-
tible fuel; care must be exercised to assure complete combustion to prevent
the formation of phosgene. An acid scrubber is necessary to remove the halo
acids produced.
Phenylhydrazine hydrochloride: controlled incineration whereby oxides of ni-
trogen are removed from the effluent gas by scrubber, catalytic, or thermal
device.
Phthalic anhydride
Polychlorinated biphenyls (PCB's): incineration (3000°F) with scrubbing to
remove any chlorine containing products.
Polypropylene glycol methyl ether: concentrated waste containing no perox-
ides; discharge liquid at a controlled rate near a pilot flame. Concentra-
ted waste containing peroxides; perforation of a container of the waste from
a safe distance followed by open burning.
Polyvinyl chloride: incineration, preferably after mixing with another com-
bustible fuel; care must be exercised to assure complete combustion to pre-
vent the formation of phosgene. An acid scrubber is necessary to remove the
halo acids produced.
Propane
Propionaldehyde
Propionic acid
Propyl acetate
Propyl alcohol
Propylamine: controlled incineration (incinerator is equipped with a scrubber
or thermal unit to reduce NO emissions).
Propylene
Propylene oxide: concentrated waste containing no peroxides; discharge liquid
at a controlled rate near a pilot flame: Concentrated waste containing
peroxides; perforation of a container of the waste from a safe distance fol-
lowed by open burning.
Pyridine: controlled incineration whereby oxides of nitrogen are removed from
the effluent gas by scrubber, catalytic, or thermal devices.
Quinone: controlled incineration (1800°F, 2.0 sec minimum).
Salicylic acid
Sorbitol
Styrene
Tetrachloroethane.- incineration, preferably after mixig with another combus-
tible fuel; care must be exercised to assure complete combustion to prevent
the formation of phosgene. An acid scrubber is necessary to remove the halo
acids produced.
Tetraethyllead: controlled incineration with scrubbing for collection of lead
oxides which may be recycled or landfilled.
Tetrahydrofuran: concentrated waste containing peroxides; perforation of a
container of the waste from a safe distance followed by open burning.
Tetrapropylene
Toluene
(continued)
2-9
-------
TABLE 2-3 (continued)
Toluene diisocyanate.- controlled incineration (oxides of nitrogen are re-
moved from the effluent gas by scrubbers and/or thermal devices).
Toluidine.- same as toluene diisocyanate.
Trichlorobenzene: incineration, preferably after mixing with another com-
bustible fuel; care must be exercised to assure complete combustion to pre-
vent the formation of phosgene. An acid scrubber is necessary to remove the
halo acids produced.
Trichloroethane: same as trichlorobenzene.
Trichloroethylene: same as trichlorobenzene.
Trichlorofluoromethane: same as trichlorobenzene.
Triethanolamine: controlled incineration (incinerator is equipped with a
scrubber or thermal unit to reduce NO emissions).
Triethylamine.- same as triethanolamine?
Triethylene glycol
Triethylene tetramine: same as triethanolamine.
Turpentine
Urea: same as triethanolamine.
Vinyl acetate
Vinyl chloride: incineration, preferably after mixing with another combusti-
ble fuel; care must be taken to assure complete combustion to prevent tha-
formation of phosgene. An acid scrubber is necessary to remove the halo I
acids produced.
Xylene
INORGANIC
Inorganic chemicals which may be disposed of (after indicated pretreatment in
some cases) by controlled incineration are:
Boron hydrides: with aqueous scrubbing of exhaust gases to remove B203 par-
ticulates.
Fluorine: pretreatment involves reaction with a charcoal bed. The product
of the reaction is carbon tetrafluoride which is usually vented. Residual
fluorine can be combusted by means of a fluorine-hydrocarbon air burner fol-
lowed by a caustic scrubber and stack.
Hydrazine: controlled incineration with facilities for effluent scrubbing to
abate any ammonia formed in the combustion process.
Hydrazine/hydrazine azide: the blends should be diluted with water and
sprayed into an incinerator equipped with a scrubber.
Mercuric chloride: incineration followed by recovery/removal of mercury from
the gas stream.
Mercuric nitrate: same as mercuric chloride.
Mercuric sulfate: same as mercuric chloride.
Phosphorus (white or yellow): controlled incineration followed by alkaline
scrubbing and particulate removal equipment.
(continued)
2-10
-------
TABLE 2-3 (continued)
Sodium azide: Disposal may be accomplished by reaction with sulfuric acid
solution and sodium nitrate in a hard rubber vessel. Nitrogen dioxide is
generated by this reaction and the gas is run through a scrubber before it
is released to the atmosphere. Controlled incineration is also acceptable
(after mixing with other combustible wastes) with adequate scrubbing and ash
disposal facilities.
Sodium formate: pretreatment involves conversion to formic acid followed by
controlled incineration.
Sodium oxalate: pretreatment involves conversion to oxalic acid followed by
controlled incineration.
Sodium-potassium alloy: controlled incineration with subsequent effluent
scrubbing.
devices, and heat recovery techniques. Foreign technological advances are
studied, followed by a listing of manufacturers of incinerator systems and
components.
2.2 GENERIC INCINERATION PROCESSES
Incineration of hazardous wastes is an engineered process, with waste destruc-
tion being the ultimate goal. As previously stated, a waste's chemical makeup
and physical form are important parameters, particularly in selecting the
proper incineration process. A system has been devised to classify industrial
wastes into five physical forms/combinations as shown in Table 2-4. The
system also takes into account the waste's chemical makeup by noting pollu-
tants in the resulting off-gases. This section includes ten processes,
corresponding to the numbers in the last column, which are appropriate for
thermal destruction of the listed wastes. These wastes are not characteristic
of all possible hazardous waste combinations, but the intent of this section
is only to present process options. Section 2.3 will look at each process
component in more detail and include more complete waste applications [8].
2.2.1 Incineration of Gaseous or Liquid Waste With No Appreciable SO or NO
Production K*
Figure 2-1 contains four diagrams, one for each of the four configurations of
a process to dispose of either a gaseous or liquid waste which produces a flue
gas containing acceptable amounts of SO and/or NO . Configuration 2-1.1 is
simply an incinerator which is supplied^with waste, fuel, and combustion air.
Fuel is required when the waste's combustion energy is insufficient (endo-
thermic) to produce a design operating temperature. An exothermic waste only
requires fuel for pilot start-up. A highly exothermic waste requires a cool-
ing medium such as excess air, steam, or water for temperature control.
Configuration 2-1.2 is an incinerator fitted with a heat recovery boiler. The
boiler, with economizer, can recover approximately 70% of the heat energy
supplied to the incinerator by the waste and fuel.
2-11
-------
TABLE 2-4. INDUSTRIAL WASTE AND POLLUTION PROCESS [8J
Classification
Gas
Gas/solid
Liquid
Liquid/solid
Solids
Industrial waste
Asphalt fumes
Chloroform
Hydrocarbon fume
HCN H2
H2S vents
Methyl chloride
NH3
M0x
Phosgene
Tail gas
VCM vents
Air/maleic anhydride
Air/phthalic anhydride
Air/polyethylene
CO H2/C
CO H2/C ash
Hydrocarbon/C ash
Propehe/Al203
Acrylonitrile
Carbon tetrachloride
Chloroamine
Herbicides
Hexachlorobenzene
Hydrazine
HjO creosote
H20 isocynates
Nitrosamine
Organic acids
Pesticides
PCS
Pyridine
VCM
High N2 crude
APPA solvent/catalyst
Biosludge
Dye solution
Melanine slurry
Phosphorous sludge
Salt solution
TPA /catalyst
Polypropylene/catalyst
APPAb/ catalyst
Coal fines
Coke fines
DNT cellulose
Polyethylene
Sodium organic salts
Wood chips
Pollutant
C12/HC1
Conf
2-1.
2-2.
•I:
• 1 ,
2-1.1,
*°x
S0x
CLjT/HCl
"°x
NO*
C1J/HC1
C12/HC1
Particulate
Particulate
Particulate
N0x
C12/HC1
C12/HC1, NO
C12/HC1
C12/HC1
N0x
A
NOV
X
C12/HC1
C12/HC1
^x
C12/HC1
N0x
Particulate
Particulate
Particulate
NO
H3P04
Particulate
Particulate
Particulate
Particulate
Particulate
Particulate
NO,,
X
Particulate
Particulate
2-3
0
2-2.1,
2-2.
2-3
.1,
.0
:iguration number
2-1
2-2
2-1
2-2
2-2
.2,
.2
.2,
.2
.2
2-1
2-1.
3,
3,
2-1.4
2-1 4
2-3.0
2-2
2-1
2-2
2-1
2-1
2-6
2-6
2-7
2-7
2-5
2-3
2-2
2-4
2-2
2-2
2-3
2-1
2-1
2-3
2-1
2-2
2-2
2-3
2-2
.1.
.1,
.1,
.1,
.1,
.1,
.1,
.1,
.1,
.1,
.0
.1,
.0
.1,
.1,
.0
.1,
.1,
.0
.1,
.1,
.1,
.0
.1,
2-2
2-1
2-2
2-1
2-1
2-6
2-6
2-7
2-7
2-5
2-2
2-2
2-2
2-1
2-1
2-1
2-2
2-2
2-2
.2
.2,
.2
.2,
.2,
.2,
.2,
.2
.2
.2,
.2
.2
.2
.2,
.2,
.2,
.2
.2
.2
2-1.
2-1
2-1
2-6
2-6
2-5
2-1
2-1
2-1
.3,
.4
.4
.3
.3
.3
.4
.4
.4
2-1.4
1.
2-10.0
2-5
2-5
2-5
2-8
2-5
2-5
2-5
2-5
2-9
2-7
2-7
2-8
2-6
2-7
2-7
.1,
.1,
.1,
.0
.1
.1,
.1,
.1,
.0
.1,
.1,
.0
.1,
.1,
.1,
2-5
2-5
2-5
2-5
2-5
2-5
2-7
2-7
2-6
2-7
2-7
.2,
.2,
.2,
.2,
.2,
.2,
.2
.2
.2,
.2
.2
2-5
2-5
2-5
2-5
2-5
2-5
2-6
.3
.3
.3
.3
.3
.3
.3
*Vinyl chloride monomer.
0,0-Dunethyl-phthalimidiomethyl-dithiophosphate.
cPhorbol acetate, rayristate.
2-12
-------
WASTE
GAS
LKXJIO
EXAMPLE
TAIL GAS
ORGANIC ACID
PBOOUCTS OF OXIDATION
FLUE GAS, NOX. SOX
FLUE GAS, NOX
FLUE GAS
WASTE •*
AIR-*
iSC'N
!«»TO«
t
FUEL
?
A
K
CONFIGURATION 2-1.1
WASTE — *
AW— »
INON
f»»TO»
T
FUEL
STEAM
4
i
c
GL
-*
FLUE CAS
CONFIGURATION 2-1.2
}
FLUE GAS
FUEL WASTE (GAS)
CONFIGURATION 2-1.3
WASTE-
STEAM
t
r-»Fu* GAS
i«T1 m^
nott^ami^ BUILe
T^ t~
FUEL AIM
CONFIGURAnON 2-1.4
Figure 2-1. Incineration process configurations for disposal of gaseous
or liquid waste with no appreciable SO or NO production.
2-13
-------
Configuration 2-1.3 is an incinerator fitted with a gas-to-gas heat exchanger.
In the heat exchanger the flue gas is cooled and the waste gas heated.
Configuration 2-1.4 is an incinerator fitted with a gas-to-gas heat exchanger
and a heat recovery boiler. The preheater heats the incoming combustion air
and the boiler extracts the heat available in the flue gas from exchanger
outlet temperature. This configuration offers flexibility in the amount of
steam produced versus fuel usage.
2.2.2 Incineration of Gaseous Liquid Waste to Control SO or C12/HC1
X"""
Figure 2-2 contains two block diagrams, one for each of the two configurations
of a process to dispose of either a gas or liquid waste which produces flue
gas containing excessive amounts of SO or C12/HC1.
O»*
LIQUID
nrnoou
mooucn o* omxme*
*G NO. Cl.'Nd
re NO, ci.'MQ
KL NO.. a,/Ma
CONFIGURATION 2-2.1
GAS
LIQUID
VCM
FG NO, CI..HCI
TO NO i CI./HO
FG NO,. a,/MCI
•tin
CONFIGURATION 2-2.2
Figure 2-2. Incineration process configuration for disposal of gaseous
or liquid waste with control of excessive SO or C12/HC1.
X
2-14
-------
Configuration 2-2.1 consists of an incinerator, a quench section which cools
the flue gas to its saturation temperature by directly contacting it with
water, two adiabatic absorbers which remove inorganic acids and chlorine and
an unlined (no refractory) vent stack.
Water is used in the first absorber to remove a majority of the HC1 from the
flue gas. The remaining HC1 and virtually all the entering C12 leaves the
absorber with the flue gas. A second absorber with caustic is used when
either the C12 or HC1 in this stream exceed allowable levels. This occurs
when excessive C12 is formed in the incinerator, or when the first absorber is
used to make strong HC1.
Configuration 2-2.1 consists of an incinerator, a heat recovery boiler which
produces steam in cooling the flue gas, two adiabatic absorbers, the first
being fitted with a lower section of ceramic packing which cools the flue gas
to saturation temperature prior to its entry into the acid absorption section.
A second absorber for residual HCl and C12 removal and an unlined vent stack
follow.
Note that cool flue gas (recycle gas) is recycled to the incinerator for
control of operating temperature when the waste is highly exothermic.
2.2.3 Incineration of Gaseous or Liquid Wastes to Control NO
Figure 2-3 is a block diagram of a two stage combustion process to dispose of
either a gas or liquid that, when oxidized (one stage process), produces a
flue gas containing excessive amounts of NO . It consists of a reduction
furnace in which a high temperature reducing environment (less than stoichio-
metric air) converts the fuel into H2, H20, C02, and CO which converts the NO
present into N2, quench section which cools the water gas by directly contact-
ing it with cool recycle gas, an incinerator which converts the H2 to H20 and
CO to C02, heat recovery boiler which produces steam in cooling the flue gas,
and an unlined vent stack. Recycle gas cooling in lieu of air, steam, or water
is an integral part of this process to minimize NO formation and maximize
heat recovery. X
2.2.4 Incineration of Gaseous or Liquid Waste to Control NO and C12/HC1
Figure 2-4 is a block diagram of a process to dispose of either a gas or
liquid that produces a flue gas containing C12/HC1 and excessive amounts of
NO . It consists of a reduction furnace in which a high temperature reducing
environment converts NO into N2, the C12 into HCl, and fuel into water gas; a
quench station which cools the water gas by directly contacting it with recycle
gas,- an incinerator which converts the H2 to H20, CO to C02 and allows the HCl
to come to equilibrium producing C12/HC1; a heat recovery boiler which produces
steam in cooling the flue gas,- an adiabatic absorber, fitted with a lower
section of ceramic packing which cools flue gas to saturation temperature
prior to its entry into the acid absorption section which removes the inorganic
acids; and an unlined vent stack. Recycle gas cooling is an integral part of
this process to minimize NO formation and maximize heat recovery.
A
2-15
-------
WASTE CATEGORY
GAS
LIQUID
WASTE
AIM
EXAMPLE
NH,
NITROSAMINE
MOWCTIO* .
•41 'UMNACf I
j'
*U«L
OUfMCM
CO.
M,
CO
N,0
Ni
INON
PRODUCTS OP OXIDATION
RIJE GAS NO,
FUIE GAS . NO,
»I.U€ CAS
•OH.EM
MCCTCLi CAS
f
I
Figure 2-3. Two stage combustion process for disposal of gaseous
or liquid waste with control of excessive NO .
X
QfOMMTIOH
MLT
THERMAL OXIDIZCT
Figure 2-4. Incineration process for disposal of gaseous or liquid
waste with control of excessive N0x and
2-16
-------
2.2.5 Incineration of Gaseous or Liquid Waste to Control Particulates
Figure 2-5 is three block diagrams, one for each of three configurations of a
process to dispose of either a gaseous or liquid waste which produces flue gas
containing excessive amounts of particulate matter.
Configuration 2-5.1 consists of an incinerator, a quench section which cools
the flue gas to its saturation temperature by directly contacting it with
water, a venturi scrubber which removes the particulate matter, and a vent
stack.
Configuration 2-5.2 consists of an incinerator; a conditioning tower which
cools the flue gas to either 600°F or 350°F depending upon the dry particulate
removal system selected, by directly contacting it with water; either an
electrostatic precipitator or bag house for particulate removal; and an unlined
vent stack.
Configuration 2-5.3 consists of an incinerator; a conditioning tower, fitted
with a Salt Master, which lowers the flue gas to below salt fusion temperature
by directly contacting it with recycle gas,- a heat recovery boiler which
produces steam in cooling the flue gas; either an electrostatic precipitator
or bag house for particulate removal; and an unlined vent stack. The Salt
Master removes salt from the bottom of the conditioning tower before it can
build up to the level sealing the inlet duct to the boiler. This would cause -
high system pressure drop causing system shutdown. Note, recycle gas may be
used for cooling to maximize heat recovery.
2.2.6 Incineration of Solid Waste with no Appreciable SO or N0_ Production
X""1"~~~' ~* X ~~ —i —
Figure 2-6 is three block diagrams, one for each of three configurations of a
process to dispose of a waste containing combustible fine solids (less than
500 u) which produces flue gas containing acceptable amounts of SO and/or
NO . *
X
Configuration 2-6.1 consists of a cyclonic incinerator in which a high radial
gas velocity causes the denser solid particles to be preferentially "slung" to
the wall, thus markedly increasing their retention time, and a refractory
lined stack.
Configuration 2-6.2 consists of a cyclonic incinerator fitted with a heat
recovery boiler which produces steam in lowering the flue gas temperature, and
an unlined vent stack.
Configuration 2-6.3 consists of a cyclonic incinerator, fitted with a gas-to-
gas heat exchanger, which heats the incoming combustion air, and a heat recov-
ery boiler which recovers the heat available in the flue gas, and an unlined
vent stack. This configuration offers flexibility in the amount of steam
produced versus fuel usage.
2-17
-------
LIOUIO/SOUO
P.IMEIE
NAO
E*OOUCTS O* O»IOATi(X
FG. NO, »»*T1CUL»TE
K. MO.
IMC >K
CONFIGURATION 2-5.1
uou«/souo
moeucrt QN
., MMTKULATE
SJmcuuf!
CONFIGURATION 2-5.2
msri
CONFIGURATION 2-5.3
Figure 2-5.
Incineration process configurations for disposal of gaseous or
liquid waste with control of excessive particulate matter.
2-18
-------
/M
>
WASTE » / " l
AIR - «
CYCLONIC J C
. TWrTMCDATno M K 1
1
FUEL
CONFIGURATION 2-6.1
STEAM
t
WASTE
AIR
"* CYCLONIC nm .- J
^INCINERATOR °OIIIR 1
FUEL
CONFIGURATION 2-6.2
T
CYCLONIC ft HEAT
INCINERATOR EXCHANGER *
T T
FUEL AIR
• » FLUE GAS
^
C
K 1
STEAM J-i
X m
FLUE GAS
CONFIGURATION 2-6.3
Figure 2-6.
Incineration process configurations for disposal of fine
combustible solid waste with no appreciable SO or NO
production. • x x
2-19
-------
2.2.7 Incineration of Fine Solids in Gaseous Waste_to Control Particulates
Figure 2-7 consists of two block diagrams, one for each of two configurations
of a process to dispose of a gaseous waste containing a combustible fine solid
(less than 500 u), which produces flue gas containing acceptable amounts of
SO and/or NO and excessive amounts of particulate.
X X
WASTE »
AIR »
CYCLONIC
INCINERATOR
f OR
FUEL
H20
^
CONDITION-
~* ING T-*
TOWER !
1
OR1
1
350°F
VtWUKl
*
ESP
i
BAG-
HOUSE
1
DRY ASH
— »
-
r
FLUE CAS
CONFIGURATION 2-7.1
ii i i
CYCLONIC '
INCINERATOR
FUEL
r :
_» HOT
CYCLONE
i
1
1 ,
CONDITION -
TOW^B
i
i
STEAM
t
— J
OR'
ESP
DRY ASH
8AG-
HOUSE
^
i
RECYCLE GAS i
FLUE GAS
V
I
DRY ASH
CONFIGURATION 2-7.2
Figure 2-7. Incineration process configurations for disposal of gaseous waste
containing fine solid particles with control of particulates.
2-20
-------
Configuration 2-7.1 consists of a cyclonic incinerator and either a quench
column, which by directly contacting the flue gas with water, cools it to its
saturation temperature, and a venturi scrubber which removes the particulate
matter, or a conditioning tower which by directly contacting the flue gas with
recycle gas cools it, depending on the dry particulate removal system selected,
and either an electrostatic precipitator or bag house for particulate removal,
and an unlined vent stack.
Configuration 2-7.2 consists of a cyclonic incinerator, a hot cyclone for
large particulate removal and/or conditioning tower which by directly
contacting the flue gas with recycle gas cools it to below ash fusion tempera-
ture, a heat recovery boiler which produces steam in cooling the flue gas,
either an electrostatic precipitator or bag house for particulate removal, and
an unlined vent stack. Recycle gas may be used for cooling to maximize heat
recovery.
2.2.8 Incineration of Fine Solid Waste to Control NO
A
Figure 2-8 is a block diagram of a process to dispose of a waste that contains
combustible solids in the size range of 10 to 500 M that produces a flue gas
containing excessive amount of NO . It consists of a cyclonic reduction
furnace in which a high radial velocity, high temperature reducing environment
(less than stoichiometric air) converts the bound nitrogen into N2 and the
fuel into water gas, a quench section which cools the water gas, and an incin-
erator which coverts the H2 to H20 and CO to C02, a heat recovery boiler which
produces steam in cooling the flue gas and an unlined vent stack. Recycle gas
cooling, (not air, steam, or water) is an integral part of the process to
minimize NO formation and maximize heat recovery.
A
WASTE1
AIR —
>
-»
+
CYCLONIC
REDUaiON
FURNACE
FUEL
CONDITION-
ING
TOWER
t
INCIN-
ERATOR
f
BOILER
1
RECYCLE GAS
I
C02
CO
HjO
Figure 2-8. Incineration process for disposal of fine solid waste
without control of NO .
2-21
-------
2.2.9 Incineration of Solid Waste to Control Particulates
Figure 2-9 is a block diagram of a process to dispose of plastic chunks con-
taining catalyst which produces flue gas containing excessive amounts of
particulate. It consists of a reduction furnace which burns the waste in a
pool on the furnace floor in a reducing environment producing a moderate Btu
gas; an incinerator; a conditioning tower which, by directly contacting the
flue 'gas with recycle gas, cools it to below salt fusion temperature; a heat
recovery boiler which produces steam in cooling the flue gas,- either an elec-
trostatic precipitator or bag house for particulate removal; and an unlined
vent stack. Recycle gas may be used for cooling to maximize heat recovery.
<
POOL
REDUCTION » INCINE
FURNACE
t ;
/ r
FUEL
<
CONDITION-
TOWER
k ' '
STEAM
t
35C
M
ES?
*
5RY SALT
BAG-
HOUSE
1
3RY SALT
— ^
4
i
/
Figure 2-9. Incineration process for disposal of solid plastic waste
containing catalyst with control of participates.
2.2.10 Incineration of High Nitrogen Crude to Control NO
x
Figure 2-10 is a block diagram of a two stage combustion process to burn a
high nitrogen crude that, when oxidized (one stage), produces a flue gas
containing excessive amounts of NO .
X
WASTE-
AIR —
FLUE GAS
i
-*
CYCLONIC
REDUCTION
FURNACE
T
FUEL
i •
1 I
r
^
TOR —-** BOILEN "" *]
/
RECYCLE GAS
CC,
H2
CO
H20
"2
Figure 2-10. Two-stage combustion process for disposal of high
nitrogen crude with control of NO .
2-22
-------
This process is similar in concept to process three. It consists of a reduc-
tion boiler, substituting for process three's reduction furnace, in which a
high temperature reducing (less than stoichiometric air) converts the high
nitrogen crude into H2, H20, C02, and CO which limits the formation of NO and
reduces any formed NO into N2, a smaller quench section than process three
which cools the waterxgas by directly contacting it with cool recycle gas, an
incinerator which converts the H2 to H20 and CO to C02, convection boiler
which produces steam in cooling the flue gas, and an unlined vent stack.
Recycle gas cooling (in lieu af air, steam, or water) is an integral part of
this process to minimize NO formation and maximize heat recovery.
2.3 INCINERATOR SYSTEM COMPONENTS
This section deals with the individual components introduced in the previous
sections. Commercially available and emerging incineration technologies are
examined, as well as pertinent air pollution control devices and heat recovery
techniques. An accompanying matrix (Table 2-5) integrating particular waste
types with these various components is presented at the end of Section 2.3.
2.3.1 Commercially Available Incineration Technologies
Five technologies will be studied in this subsection, with emphasis given to
two major hazardous waste destruction techniques, rotary kiln and liquid
injection incineration. The less frequently used techniques are fluidized bed*
and multiple hearth incinerators, along with the fifth technique, coincinera-
tion, usually involving a variation of rotary kiln or multiple hearth
applications. Each technology is described, illustrated, and discussed as to
its advantages, disadvantages, and applications.
2.3.1.1 Rotary Kiln [6, 7, 9-14] —
Operation -
Rotary kiln incinerators are generally refractory-lined cylindrical shells
mounted at a slight incline from the horizontal plane. The speed of rotation
may be used to control the residence time and mixing with combustion air.
They are generally used by industry, the military, and municipalities to
degrade solid and liquid combustible wastes, but combustible gases may also be
oxidized. Recently, rotary kiln incinerators have been used to successfully
dispose of obsolete chemical warfare agents and munitions. Figure 2-11 is a
schematic of what a general rotary kiln system involves [7, 9]. This sche-
matic is typical of most rotary kilns, including small portable units cur-
rently being used in hazardous waste disposal site restoration and demilitari-
zation projects.
Two types of rotary kilns are currently being manufactured in the U.S. today,
cocurrent (burner at the front end with waste feed) and countercurrent (burner
at the back end). For a waste which easily sustains combustion, the position-
ing of the burner is arbitrary from an incineration standpoint; both types
will destroy a waste. However, for a waste having low combustibility (such as
2-23
-------
RJEl
TO *?C3
AND STACK
ASH
Figure 2-11. Rotary kiln incinerator schematic.
a high water volume sludge), the countercurrent design offers the advantage of
controlling temperature at both ends, which all but eliminates problems such
as overheating the refractory lining. The countercurrent flow technique has
been reputed to carry excessive ash over into the air pollution control system
due to the associated higher velocities involved, however, this condition also
increases the turbulence during combustion which is generally a desirable
factor*.
Optimal length to diameter (L/D) ratios have ranged from 2 to 10, and rota-
tional speeds of 1 to 5 FPH at the kiln periphery are common,, depending on the
nature of the waste. Residence times vary from a few seconds; for a highly
combustible gas, to a few hours for a low combustible solid waste. A typical
feed capacity range is 600 kg/hr to 2,000 kg/hr for solids, and 630 L/hr to
2250 L/hr for liquids at temperatures ranging from 800°C to 1600°C. Since
rotary kilns are normally totally refractory-lined and have no exposed metal-
lic parts, they may operate at high incineration temperatures while experienc-
ing minimal corrosion effects. Solid wastes, sometimes packed in fiber drums,
are generally fed to the kiln by conveyor. Liquids and sludges are pumped in,
with liquids usually being strained, then atomized with steam or air. The
kiln and liquid burner are equipped with natural gas ignitors and gas burners
for initial refractory heating, flame stability, and supplemental heat if
necessary [7, 9].
Afterburners are commonly used to ensure complete combustion of flue gases
prior to treatment for air pollutants. Resource recovery (depending on the
waste) and heat recovery are also common practices as initial steps to treat-
ment of flue gases.
Types of Wastes -
Numerous hazardous wastes which previously were disposed of in potentially
harmful manners (ocean dumping, landfilling and deep-well injection) are cur-
rently being safely and economically destroyed using rotary kiln incinerators
*Per phone call to Will Kepner of Bartlett-Snow, Chicago, Illinois
2-24
-------
combined with proper flue gas handling. Included in this list of primarily
toxic wastes are polyvinyl chloride wastes, PCB wastes from capacitors, obso-
lete munitions, and obsolete chemical warfare agents such as GB, VX, and
mustard. Beyond these specific wastes, the rotary kiln incinerator is gen-
erally applicable to the destruction and ultimate disposal of any form of
hazardous waste material which is combustible at all. Table 2-5, at the end
of this section, helps illustrate this fact. Unlikely candidates are non-
combustibles such as heavy metals, high moisture content wastes, inert mater-
ials, inorganic salts, and the general group of materials having a high
inorganic content.
Advantages -
(1) will incinerate a wide variety of liquid and solid hazardous wastes.
(2) Will incinerate materials passing through a melt phase.
(3) Capable of receiving liquids and solids independently or in combination.
(4) Feed capability for drums and bulk containers.
(5) Adaptable to wide variety of feed mechanism designs.
(6) Characterized by high turbulence and air exposure of solid wastes.
(7) Continuous ash removal which does not interfere with the waste oxidation.
(8) No moving parts inside the kiln (except when chains are added).
(9) Adaptable for use with a wet gas scrubbing system.
(10) The retention or residence time of the nonvolatile component can be con-
trolled by adjusting the rotational speed.
(11) The waste can be fed directly into the kiln without any preparation such
as preheating, mixing, etc.
(12) Rotary kilns can be operated at temperatures in excess of 2,500°F (1,400°C),
making them well suited for the destruction of toxic compounds that are
difficult to thermally degrade.
(13) The rotational speed control of the kiln also allows a turndown ratio
(maximum to minimum operating range) of about 50%.
Disadvantages -
(1) High capital cost for installation.
(2) Operating care necessary to prevent refractory damage; thermal shock is a
particularly damaging event.
(3) Airborne particles may be carried out of kiln before complete combustion.
(4) Spherical or cylindrical items may roll through kiln before complete
combustion.
(5) The rotary kiln frequently requires additional makeup air due to air
leakage via the kiln end seals.
(6) Drying or ignition grates, if used prior to the rotary kiln, can cause
problems with melt plugging of grates and grate mechanisms.
(7) High particulate loadings.
(8) Relatively low thermal efficiency.
(9) Problems in maintaining seals at either end of the kiln are a significant
operating difficulty.
(10) Drying of aqueous sludge wastes or melting of some solid wastes can
result in clinker or ring formation on refractory walls.
2-25
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2.3.1.2 Liquid Injection [3, 5, 6, 10, 11, 13-15]--
Operation -
Liquid injection incinerators are currently the roost commonly used incinerator
for hazardous waste disposal. A wide variety of units is marketed today, with
the 2 major types being horizontally- and vertically-fired units. A less
common unit is the tangentially-fired vortex combustor; all three of these
units are schematically represented in Figures 2-12 through 2-14. As the name
implies, the liquid injection incinerator is confined to hazardous liquids,
slurries and sludges with a viscosity value of 10,000 SSU* or less [7]. The
reason for this limitation being that a liquid waste must be converted to a
gas prior to combustion. This change is brought about in the combustion
chamber, and is generally expedited by increasing the waste surface area
through atomization. An ideal size droplet is about 40 p or less, and is
attainable mechanically using rotary cup or pressure atomization, or via
gas-fluid nozzles and high pressure air or steam.
The key to efficient destruction of liquid hazardous wastes lies in minimizing
unevaporated droplets and unreacted vapors. Just as for the rotary kiln,
temperature, residence tine, and turbulence may be optimized to increase
destruction efficiencies. Typical combustion chamber residence tine and
temperature ranges are 0.5 to 2 seconds and 700°C to 1650°C, respectively. ,
Liquid injection incinerators are variable dinensionally, and have feed rates
up to 5,600 L/hr.
The combustion chamber is a refractory-lined cylinder. Burners are normally
located in the chamber in such a manner that the flames do not inpinge on the
refractory walls. The combustion chamber wall can be actively cooled by
process air prior to its entry into the combustion zone, thus preheating the
air to between 150°C and 370°C .
Liquid waste fuel is transferred from drums into a feed tank. The tank is
pressurized with nitrogen, and waste is fed to the incinerator using a remote
control valve and a compatible flowmeter. The fuel line is purged with N2
after use. A recirculation system is used to mix the tank contents [17].
Normally a gas (for example, propane) preheats the incinerator system to an
equilibrium temperature of approximately S15°C before introduction of the
waste liquid.
Of the three types of units discussed earlier, the horizontal and vertical are
basically similar in operating conditions. The tangentially-fired unit is
known to have a much higher heat release and generally superior mixing than
the previous two units, making it more attractive for disposal of high water
content wastes and less combustible materials. However, these conditions lend
to increased deterioration of the refractory lining from thermal effects and
erosion [7].
*To obtain the Saybolt universal viscosity equivalent to a kinematic viscosity
determined at t°F, multiply the equivalent Saybolt universal viscosity at
100°F by 1 + (t - 100) 0.000064; e.g., 10 centistokes at 210°F are equivalent
to 58.8 x 1.0070, or 59.2 SSU at 210°F. (Handbook of Chemistry and Physics,
45th edition).
2-26
-------
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2-27
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FREE STANDING
INTERLOCKING REFRACTORY
MODULES
TEMPERATURE MEASURING
INSTRUMENTS
TURBO-BLOWER
IGNITION CHAMBER
HIGH VELOCITY
AIR SUPPLY
AIR-WASTE ENTRAPMENT
COMPARTMENT
WASTE UNF
EFFLUENT DIRECTLY TO ATMOSPHERE
OR TO SCRUBBERS AND STACK FRESH AIR INTAKE
'FOR TURBO-BLOWER
AND AFTERBURNER FAN
AIR CONE
UPPER NACELLE
DECOMPOSITION CHAMBER
DECOMPOSITION STREAM
AFTER-BURNER FAN
FLAMES ENS HIZER
TURBULENCE COMPARTMENT
LOWER NACELLE
AUXILIARY FUEL LINE
ELECTRICAL POWER LIME
Figure 2-13. Vertically-fired liquid injection incinerator schematic [7]
2-28
-------
ANNUL*! S'ACf flUfO
WIIH All UNOtl
rot iur»(S
tfHUINt TO SCIUMiK
ANO SlACK
«FIAC1O*Y WAU
— COMBUSTION AII
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Mf*ACTO*Y
COOlINC All
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All
B
OH SHAY
COOLING AH
CAST IN If FIACTOIV SLU
M»U SMI U
Figure 2-14.
Tangentially-fired vortex combustor liquid
injection incinerator schematic [7].
Types of Wastes -
Liquid injection incinerators are capable of handling any combustible liquid
hazardous waste with the viscosity constraints previously mentioned. They have
been widely used in industry for a broad range of liquid wastes, as shown in
Table 2-5 (at the end of Section 2.3). In the case of the rotary kiln inciner-
ator, wastes which are unlikely candidates for destruction are noncoobustibles
such as heavy metals, high moisture content wastes, inert materials, inorganic
salts, and the general group of materials having high inorganic content.
Advantages -
(1) Capable of incinerating a wide range of liquid hazardous wastes.
(2) No continuous ash removal system is required other than for air pollution
control.
(3) Capable of a fairly high turndown ratio.
(4) Fast temperature response to changes in the waste fuel flowrate.
(5) Virtually no moving parts.
(6) Low maintenance costs.
Disadvantages -
(1) Only wastes which can be atomized through a burner nozzle can be
incinerated.
(2) Heat content of waste burned must maintain adequate ignition and incin-
eration temperatures or a supplemental fuel must be provided.
(3) Burners susceptible to pluggage (burners are designed to accept a certain
particle size; therefore, particle size is a critical parameter for
successful operation).
(4) Burner may or may not be able to accept a material which dries and cakes
as it passes through the nozzles.
2-29
-------
2.3.1.3 Fluidized Bed [6, 10, 11, 13-15, 17, 18]--
Operation -
Fluidized bed incinerators are vessels containing a bed of inert granular
material, usually sand, which is kept at temperatures in a range from 450 to
850°C. Fluidizing air is passed through a distributor plate below the bed and
agitates the heated granular material. Hazardous waste material and auxil-
liary fuel are injected radially in proportionately small amounts and mixed
with the bed material which transfers heat to the waste. The waste in turn
combusts and returns energy to the bed [7].
This process is pictured in Figure 2-15, which represents a typical fluidized
bed incinerator. The reactor vessel is commonly about 7-8 meters in diameter
and 10 meters high. Bed depths are typically*1 meter while at rest, and
2 meters during operation. Variations in the depth affect both residence time
and pressure drop, resulting in a compromised depth which optimizes residence
time and excess air to ensure complete combustion [18].
FLUE GAS -^
MAKEUP SAND
ACCESS DOOR
AUXILIARY BURNER
/ (OIL OR GAS)
;— WASTE INJECTION
r- FUJIDIZINC AIR
ASH REMOVAL
Figure 2*15. Typical fluidized bed incinerator schematic.
Bed temperatures are restricted by the softening point of the bed medium,
which is about 900°C for sand. These high temperatures allow for reaction of
gaseous wastes and combustion gases above the bed as well. Gas velocities in
the bed are generally maintained near 2 meters per second. The gas velocity
is constrained by the terminal velocity,, and thus particle size. Too high a
velocity results in bed attrition and heavy particulate loading of the flue
gas, while a lower velocity reduces pressure drop and results in lower power
requirements. The residence tine is generally around 12 to 14 seconds for a
liquid hazardous waste [7, 18].
2-30
-------
Types of Wastes -
Most fluidized bed applications to hazardous waste in the literature involve
incineration of sludges and slurries. The type and composition of the waste
are key design parameters determining feed mechanisms, processing, and bed
specifics. A homogeneous combustible liquid may be immediately injected, but
a nonhomogeneous sludge having moderate combustion potential and interspersed
with large solid matter will require sorting, drying, shredding, and special
feed considerations prior to entering the reactor. Despite the need for pre-
treatment, the fluidized bed is capable of handling most any waste that the
rotary kiln can, depending on the heat limitations of the bed material.
Advantages -
(1) General applicability for the disposal of combustible hazardous solids,
liquids, and gaseous wastes.
(2) Simple design concept, requiring no moving parts in the combustion zone.
(3) Compact design due to high heating rate per unit volume (100,000 to
200,000 Btu/hr-ft3 (900,000 to 1,800,000 kg-cal/hr-m3) which results in
relatively low capital costs.
(4) Relatively low gas temperatures and excess air requirements which tend to
minimize nitrogen oxide formation and contribute to smaller, lower cost
emission control systems.
(5) Long incinerator life and low maintenance costs.
(6) Large active surface area resulting from fluidizing action enhances the
combustion efficiency.
(7) Fluctuation in the feed rate and composition are easily tolerated due to
the large quantities of heat stored in the bed.
(8) Provides for rapid drying of high-moisture-content material, and combus-
tion can take place in the bed.
(9) Proper bed material selection suppresses acid gas formation; hence,
reduced emission control requirements.
i (10) Provides considerable flexibility for shockload of waste; i.e., large
f quantities of waste being dumped in the bed at a single time.
I Disadvantages -
(1) Difficult to remove residual materials from the bed.
(2) Requires fluid bed preparation and maintenance.
(3) Feed selection must avoid bed degradation caused by corrosion or
reactions.
(4) Hay require special operating procedures to avoid bed damage.
(5) Operating costs are relatively high, particularly power costs.
(6) Possible operating difficulties with materials high in moisture content.
(7) Formation of eutectics is a serious problem.
(8) Hazardous waste incineration practices have not been fully developed.
(9) Not well suited for irregular, bulky wastes, tarry solids, or wastes with
* a fusible ash content.
2-31
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2.3.1.4 Multiple Hearth [1, 3, 5, 6, 10, 13 - 15]--
Operation -
A typical multiple hearth furnace includes a refractory-lined steel shell, a
central shaft that rotates, a series of solid flat hearths, a series of rabble
arms with teeth for each hearth, an air blower, fuel burners mounted on the
walls, an ash removal system, and a waste feeding system. Side ports for tar
injection, liquid waste burners, and an afterburner may also be included.
Figure 2-16 illustrates the incinerator and its typical flow scheme.
RETURN AIR
SOLID
WASTE FEED
BUCKET ELEVATOR
ASH BIN
ASH
CONDITIONER
HAULING
— "1 APCD
\
^
FUEL
BURNERS
ill00ID AND
GASEOUS
WASTE)
COOLING AIR FOR RABBLE
ARMS AND DRIVE SHAFTS
Figure 2-16. Typical multiple hearth incinerator schematic.
Sludge and/or granulated solid combustible waste is fed through the furnace
roof by a screw feeder or belt and flapgate. The rotating air-cooled central
shaft with air-cooled rabble arms and teeth distributes the waste material
across the top hearth to drop holes. The waste falls to the next hearth and
then the next until discharged as ash at the bottom. The waste is agitated as
it moves across the hearths to make sure fresh surface is exposed to hot
gases.
Units range from 1.8 m to 7.6 m in diameter and from 3.6 m to 23 m in height.
The diameter and number of hearths are dependent on the waste feed, the
required processing time, and the type of thermal processing employed. Gen-
erally, the uppermost hearth is used as an afterburner. Normal incineration
usually requires a minimum of six hearths, while pyrolysis applications require
a greater number [6].
2-32
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The rabble arms and teeth located on the central shaft all rotate in the same
direction; additional agitation of the waste (back rabbling) is accomplished
by reversing the angles of the rabble teeth. Waste retention time is con-
trolled by the design of the rabble tooth pattern and the rotational speed of
the central shaft [3].
Liquid and/or gaseous combustible wastes may be injected into the unit through
auxiliary burner nozzles. This utilization of liquid and gaseous waste repre-
sents an economic advantage because it reduces secondary fuel requirements,
thus lowering operating costs [3].
A multiple hearth unit generally has three operating zones, the uppermost
hearths where feed is dried ( 350° to 550°C), the incineration zone (800° to
1000°C), and the cooling zone (200° to 350°C). Exit gases have good potential
for heat recovery, being around 300° to 600°C. Temperatures on each hearth can
be maintained using supplemental fuel [7].
Types of Waste -
Multiple hearth units are best suited for hazardous sludge disposal. As in
the case of fluidized bed incinerators, solid wastes generally have to be
pretreated prior to successful incineration. Allowing for this, multiple
hearths are capable of handling the sane hazardous wastes as rotary kilns.
Unlikely candidates are heavy metals, inert materials, inorganic salts, and
the general group of materials having high inorganic content.
Advantages -
(1) The retention or residence time in multiple hearth incinerators is usu-
ally higher for hazardous materials having low volatility than in other
incinerator configurations.
(2) Large quantities of water can be evaporated.
(3) A wide variety of wastes with different chemical and physical properties
can be handled.
(4) Multiple hearth incinerators are able to utilize many fuels including
natural gas, reformer gas, propane, butane, oil, coal dust, waste oils,
and solvents.
(5) Because of its multizone configuration, fuel efficiency is high and
typically improves with the number of hearths used.
(6) Fuel burners can be added to any of the hearths to maintain a desired
temperature profile.
(7) Multiple hearth incinerators are capable of a turndown ratio of 35%.
(8) High fuel efficiency is allowed by the multizone configuration.
Disadvantages -
(1) Due to the longer residence times of the waste materials, temperature
response throughout the incinerator when the burners are adjusted is
usually very slow.
(2) It is difficult to control the firing of supplementary fuels as a result
of this slow response.
2-33
-------
(3) Maintenance costs are high because of the moving parts (rabble arms, main
shaft, etc.) subjected to combustion conditions.
(4) Multiple hearth incinerators are susceptible to thermal shock resulting
from frequent feed interruptions and excessive-amounts of water in the
feed. These conditions can lead to early refractory and hearth failures.
(5) If used to dispose of hazardous wastes, a secondary combustion chamber
probably will be necessary and different operating temperatures might be
necessary.
(6) Not well suited for wastes containing fusible ash, wastes which require
extremely high temperature for destruction, or irregular bulky solids.
2.3.1.5 Coincineration—
Operation -
Hazardous waste coincineration has been performed in a rotary kiln pyrolyzer
and a multiple hearth incinerator on a test basis. This technique is used to
supply needed Btu's when the principal waste to be burned possesses insuffi-
cient heat content to be autogenic. Coincineration generally refers to the
joint incineration of hazardous waste, in any form, with refuse and/or sludge.
This is not a unique technology; any existing incineration process can be used
for this special case of mixing waste streams to obtain better destruction of
a particularly intractable waste material.
The rotary kiln pyrolyzer test unit used for Kepone incineration contained the
following components [21]:
• Waste feed system • Afterburner
• Rotary kiln pyrolyzer • Air pollution control device system
Kepone-contarainated sludge was simulated by the mechanical mixing of appro-
priate amounts of Kepone solution in acetic acid into sludge in the feed tank.
The latter was a cylindrical vessel, 86 cm in diameter and 60 cm high fitted
with a pneumatic stirrer. The 10 on outlet port in the conical bottom of the
feed tank was fitted with a screen and connected to a two-stage, variable
speed pump. The discharge line was fitted with a pressure relief valve and
with provisions to inject sludge from the feed tank or water from the mains.
The feed line, which entered the kiln within the kiln discharge line, was
water-jacketed to prevent caking within the feed line. At the end of a run,
the feed line was flushed with water [20].
The rotary kiln pyrolyzer 1.5 m in diameter and 3.0 m in length, was fitted
with rotary seal charge and discharge connections so as to minimize the leak-
age of gases into or out of the kiln. It was heated directly by the hot gases
from a 0.923-J/s burner to maintain a nominal temperature of 500°C. Normally
this kiln was batch fed through cover doors on the side, but for the purposes
of the coincineration experiments the sludge feed was accomplished through a
water-cooled feed line which entered the kiln through the discharge pipe. The
maximum feed rate was a nominal 45 kg/hr. Cake buildup within the kiln was
prevented by 10 rows of link chain within the kiln [20].
2-34
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The afterburner, with a residence chamber volume of 2.4 m3, was fired by two
0.147-J/s throat mix burners and an auxiliary gas supply. The incinerator was
equipped with a temperature controller and a high limit safety shutoff
instrument. In this configuration, the maximum temperature that could be
sustained was 1,260°C with residence times on the order of several seconds [20]
The multiple hearth test unit used for pesticide and PCS incineration con-
tained the following components [15]:
Waste feed system • Air pollution control device system
Multiple hearth incinerator
The PCB's in the form of a solution in kerosene were fed from a burette into
the sludge cake feed screw at a rate of 22.5 g/hr. The test PCS was a prep-
aration Aroclor 1254 which is a combination of some 14 to 16 PCB's [15].
The DDT feed was accomplished by a hopper arrangement placed over the screw-
feed mechanism used to conduct the dewatered sludge from the centrifuge to the
top hearth of the furnace. The mechanical properties of the powdered DDT
preparation used were such that the simple gravity feed device was not partic-
ularly satisfactory; one might elect to go to a more elaborate vibratory feed
system in practice. The feed device used did not effect a constant feed rate,
a factor which was less serious than might be supposed [15].
The furnace was equipped with a scum line feeding into the third hearth. The
injection of 2,4,5-T solution was accomplished by gravity feeding the netered
solution into the scum flow, incinerating temperature was 635°C and after-
burner temperature was 650°C [15].
Types of Wastes -
The type of incinerator used in coincineration dictates the limitations on
types of hazardous wastes which may be disposed.
Advantages -
(1) Will potentially incinerate any thermally destructible hazardous waste.
(2) Incorporates the advantages of the type of incinerator used.
(3) Provides for the incineration of two different wastes simultaneously in
the same facility, thus increasing return on investment.
(4) Provides potential for hazardous waste incineration in existing incinera-
tion facilities.
Disadvantages -
(1) Incorporates the disadvantages of the type of incineration used.
2.3.2 Emerging Incineration Technology
This section deals with a technology that is in a research and development
stage. It is not currently a recommended technique for hazardous waste
disposal.
2-35
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2.3.2.1 Starved Air Combustion/Pyrolysis [3, 6, 8, 10, 19, 25]--
Qperation -
The terms "starved air combustion" and "pyrolysis," while often used inter-
changeably, are not one and the same. Starved air combustion uses less than
the stoichiometric amount of oxygen required for complete combustion. Pyroly-
sis is defined as the thermal decomposition of a compound in the absence of
oxygen. Figure 2-17 shows a schematic for a device utilizing starved air
corabustion/pyrolysis.
APCO OR
RECOVERY UNIT
FEED
PYROLYTIC REACTOR
• SUPPLEMENTAL FUEL
•COMBUSTION AIR
ASH
Figure 2-17. Starved air combustion/pyrolysis schematic.
Pyrolytic conversion processes are generally custom engineered according to
input volumes and types of waste being treated. With respect to waste car-
bonaceous material, pyrolysis represents a means of converting the unwanted
waste into a usable commodity with economic value. Modifications to the
pyrolysis process involve treatment of converter effluents. The pyrolysis
oils may be sent through a hydrotreating unit and converted to industrial fuel
oil. The pyrolysis effluent gas may be cooled and the resultant condensate
separated into its components (namely, acetic acid, methanol, furfural, ace-
tone, butyric acid, propionic acid, methyl ethyl ketone, light fuel oil, and
other water soluble volatile organics) through the use of conventional separa-
tion techniques. The cooled wet gas may be dried and utilized as fuel gas.
The charlike pyrolysis residue can be further treated and converted into
activated carbon [1].
Other variations include the pyrolyzer itself, which may be incorporated into
a specific incinerator unit (i.e., rotary kiln, molten salt, etc.). A typical
rotary kiln pyrolyzer, for instance, is a sealed, airtight retort cylinder
with an insulated shell. The retort is mounted on a slight incline and rotates.
Without oxygen, the wastes in the retort chamber cannot burn; they are broken
down (pyrolyzed) into steam, carbon oxides, volatile vapors, and charcoal.
Gases formed during pyrolysis are combusted in an afterburner..
Operational temperatures will vary with waste type, incinerator type, and
desired products. Operating temperatures are usually in the 650°C ± 150°C
2-36
-------
range, with the lower operating temperature generally resulting in greater
residue (coke), tar, and light oil yields, and lower gas yields. Residence
times will range from a fraction of a second (for flash pyrolysis) to hours
(for solids) [1].
Types of Wastes -
The general types of hazardous waste which are potential candidates for this
technology are all physical forms of compounds having carbon, hydrogen, and/or
oxygen. Wastes containing nitrogen, sulfur, sodium, silicon, phosphorous,
fluorine, bromine, chlorine, or iodine aren't acceptable.
Advantages -
(1) Potential for byproduct recovery.
(2) Reduction of sludge volume without large amount of supplementary fuel.
(3) Thermal efficiency is higher than for normal incineration due to the
lover quantity of air required for this process.
(4) Reduced air emissions are sometimes possible.
(5) Converts carbonaceous solids into a gas which is more easily combustible.
(6) Allows for the suppression of particulate emissions.
(7) Allows for some treatment of the hot fuel gas stream prior to combustion
to suppress the formation of acid gases.
Disadvantages - I
(1) Potential source of carcinogenic decomposition product formation.
(2) Not capable of functioning very well on sludge-like or caking material
alone unless cake-breaking capabilities are included in the design.
2.3.3 Air Pollution Control Devices
The products of combustion in any well-designed and operated incinerator are
primarily carbon dioxide and water (vapor), but trace amounts of undesirable
additional products (pollutants) are also formed, depending upon the composi-
tion of the incinerated waste. Among these, CO, SO , NO , HXj, x£, and par-
ticulate are most commonly encountered and oust be Minimized to the point of
emission standards outlined in Part 264 of RCRA [7].
An optimum pollution control process serves to minimize fuel usage, and/or
maximize energy recovery, while converting an industrial waste into an envi-
ronmentally acceptable form. This section looks at how such emission control
processes are selected for various incineration technologies.
Application of air pollution control processes depends on operating character-
istics of the components or devices, the physical/chemical characteristics of
the waste to be treated, and the emission standards iaposed by government
regulations. In addition to the use of standard treatment devices of both the
dry control and wet control methods (Table 2), the control of air pollutants
with off-gas cleaning systems is the subject of rapidly developing technologies.
2-37
-------
As each new generation process or device is introduced, it is evaluated and
employed where warranted by the fast-developing state of the art [7].
Organic pollutants emitted as a result of incomplete combustion of waste
material are often present in effluents from the primary combustion chamber at
low concentration levels well under the lower flammability limit. The control
of the emission of these organic pollutants can be handled by continued com-
bustion at high temperatures using afterburners (also termed secondary com-
bustion chambers).
Scrubbers are also used to control pollutant emissions. They operate by
removing pollutants from the gas stream instead of changing the pollutants, as
afterburners do. Afterburners and four types of scrubbers are covered in this
section, as are electrostatic precipitators (ESP) and wet electrostatic pre-
cipitators (WEP). The subsections presented for each control device include
operating principles, status with hazardous waste incinerators, suitable waste
streams, advantages, and disadvantages.
2.3.3.1 Afterburner--
Afterburners are simple combustion chambers (incinerators) designed to improve
destruction efficiencies. As a first step to an air pollution control process,
the afterburner acts to continue the combustion process and greatly decrease
pollutants in the flue gas. This in turn creates less pollutant loading on I
downstream emission control devices which require less servicing and main- I
tenance, and produce less residue as a result. Figure 2-18 shows a basic
afterburner flow scheme.
INCINERATOR ^ AFTERBURNER ^ EiFFLUENT TO STACK
EFFLUENT CHAMBER OR APCD
AUXILIARY
BURNER AND FUEL
Figure 2-18. Basic afterburner flow scheme.
Three types of afterburners are discussed here: direct flame, thermal, and
catalytic. Direct flame and thermal use a similar principle in thermally
destroying combustible material. Direct flame afterburners pass the flue gas
directly through a burning fuel stream, while thermal afterburners involve the
flue gas flowing through a high temperature zone. Catalytic units incorporate
a catalytic surface to accelerate the oxidation of uncombusted gas constituents.
2-38
-------
Thermal afterburners are used more predominantly than direct flame incinerators.
Temperatures ranging from 650°C to 1,300°C are generally required for success-
ful operation of these devices. Hydrocarbon levels can usually be satisfac-
torily reduced at temperatures below about 760°C, but higher temperatures may
be required to simultaneously oxidize the CO. The following temperatures are
often used as guidelines [5]-.
To oxidize hydrocarbons.- 500 - 700°C
To oxidize carbon monoxide: 700° - 800°C
Depending on the type of pollutant in the gas stream, residence times ranging
from 0.2 s to 6.0 s are required for complete combustion. The residence time
in most practical afterburner systems is dictated primarily by chemical kinet-
ic considerations. To ensure good mixing, afterburners are operated at high
velocity gas flows. Gas velocities in afterburners range from S to 15 m/s. A
typical afterburner will be 10 m long, 4m high, and 4 m wide [5].
From a chemical viewpoint, two main types of reactions occur in afterburner
systems: oxidation and pyrolysis reactions. In general, the detailed mecha-
nisms for the oxidation and pyrolysis of even the simplest organic compounds
are not completely understood, but it is well established that the reactions
occur in many complicated sequential and concurrent steps involving a multi-
tude of chemical intermediates [5].
An auxiliary fuel is fired to supply the heat to warm the gases to a temper-I
ature that will promote oxidation of the organic vapors. Usually a portion
the gas stream supplied the oxygen necessary for organic vapor oxidation.
Both gaseous and liquid fuels are used to fire afterburners. Gaseous fuels
have the advantage of permitting firing in multiple jet (or distributed)
burners. Oil firing has the disadvantage of producing sulfur oxides (from
sulfur in the oil) and normally produces higher nitrogen oxides emissions [5].
Catalytic afterburners are applied to gaseous wastes containing low concentra-
tions of combustible materials and air. Usually noble metals such as platinum
and palladium are the catalytic agents. A catalyst is defined as a material
which promotes a chemical reaction without taking a part in it. The catalyst
does not change nor is it used up. However, it may become contaminated and
lose its effectiveness [1].
The catalyst must be supported in the hot waste gas stream in a manner that
will expose the greatest surface area to the waste gas so that the combustion
reaction can occur on the surface, producing nontoxic effluent gases of carbon
dioxide, nitrogen, and water vapor. Most of the combustion occurs during flow
through the catalyst bed which operates at maximum temperatures of 810°C to
870°C. The ability to carry out combustion at relatively low temperatures
while achieving high destruction efficiencies is a major advantage of the
catalytic incinerator for gaseous wastes [1].
Residence time for catalytic oxidation is about 1 second [1].
2-39
-------
Due to the form of the waste material to be treated (dilute and in the gaseous
state), the catalytic afterburner is best suited for use at the processing
site where the waste material is generated [1].
Generally, catalytic afterburners are considered for operation with waste con-
taining hydrocarbon levels that are less than 25% of the lower explosice
limit. When the waste gas contains sufficient heating value to cause concern
about catalyst burnout, the gas may be diluted by atmospheric air to ensure
operating temperatures within the operating limits of the catalyst. Burned
gases are discharged through a stack to the atmosphere if they are not sent to
a waste heat recovery unit [6].
Applicable Waste Streams - Thermal afterburners are suitable for any gaseous
material that is also suitable for incineration or which has been produced by
auxiliary equipment; i.e., a rotary kiln. Catalytic afterburners are appli-
cable to the destruction of combustible materials in low concentrations (they
are not applicable to chlorinated hydrocarbons due to the HCl formation).
Advantages -
Thermal or Direct Flame
(1) Destroys those pollutants that were not destroyed in the primary
incineration.
(2) Allows more flexibility in incinerator operation.
Catalytic
(I) Carries out combustion at relatively low temperatures (more economical to
operate than other afterburners).
(2) Clean heated gas produced is well suited for waste heat recovery units.
Disadvantages -
Thermal or Direct Flame
(1) Auxiliary fuel requirements.
(2) Afterburner costs.
Catalytic
(1) Burnout of th« catalyst occurs at temperatures exceeding 815°C.
(2) Catalyst system* are susceptible to poisoning agents, activity suppres-
sants, and fouling agents.
(3) Occasional cleaning and eventual replacement of catalyst is required.
(4) Maintenance costs are high.
2.3.3.2 Gas-Atomized Spray Scrubber (Venturi)—
One of the most predominant air pollution control devices for hazardous waste
incinerators is a venturi scrubber (Figure 2-19). A typical venturi scrubber
is a duct with a constricted area (throat). Generally, liquid is introduced
into the venturi at the throat. Incinerator exhaust gas enters the venturi at
2-40
-------
LIQUID
Figure-2-19. Venturi scrubber schematic.
a velocity of approximately 30 to 120 m/s. The moving gas atomizes the liquid
into fine filaments and droplets which allow a large surface area for mass
transfer. It is the gas/liquid contact that permits removal of gaseous con- t
taminants. I*
Prior to passage of the incinerator exhaust gas into the venturi, the gas is
quenched to reduce the temperature. While it is recognized that the quench
systems when utilized will effect some degree of particle removal, the primary
function of these units is to reduce flue gas volume and downstream materials
and operating problems through gas cooling. As a result of quenching, inlet
temperatures for venturi scrubbers range from 60°C to 150°C.
Some hazardous waste incineration facilities employ sequential venturi and
plate type or packed bed scrubbers. For these systems, a gas quench is op-
tional since the venturi may be utilized to effect gas cooling by the mecha-
nism of adiabatic expansion of the gases. Such systems are capable of han-
dling a variety of incineration gas compositions and dust loadings. Plate
towers or packed beds, when used in conjunction with gas-atomized spray scrub-
bers, serve the dual function of eliminating the entrainment of liquid drop-
lets from upstream and further reducing the emission levels of gaseous con-
taminants .
Incinerating hazardous waste may produce effluent gases with corrosive con-
taminants, such as HC1. It is possible to neutralize the acid with a caustic
solution. The scrubbing solution is determined by the waste burned and its
exhaust gas. In addition to corrosion, erosion is a particular problem in
venturi scrubbers. This is due to the high gas velocities and particulate
loadings encountered during normal duty. Throat and elbow areas are generally
subject to the most wear. Acid-resistant tile liners, polymeric liners, and
Inconel 625 are often used for scrubber construction.
2-41
-------
Venturi scrubbers have been used to control emissions of S02, HF, and HC1. fj
Several of the primary operating parameters that will affect the removal of
these gaseous contaminants are pressure drop, liquid-to-gas ratio, contact
time, and gas flow rate. Pressure drops in venturi scrubbers for controlling
gaseous emissions from incineration of hazardous wastes are typically in the
7.5 to 12.5-kPa water gage (WG) range [21J. It is necessary to use the cor- ,
rect pressure drop to ensure efficient removal. A higher than needed pressure
drop will result in wasted energy,- a lower than needed pressure drop will
result in a lower removal efficiency. As a prime operating parameter, the
pressure drop should be as low as possible yet yield the needed removal
efficiency.
The liquid-to-gas ratio is a design and operating parameter of prime impor-
tance. It is needed in the determination of the scrubber diameter, and has an
effect on the unit dimensions. Normal liquid-to-gas ratios for venturi
scrubbers are 0.7 to 2.7 L/m3 [21].
Higher efficiencies are attained by allowing the gas and liquid phases to be '
in contact for a longer period of time. The contact time required for gas
absorption is a function of the rate of mass transfer. The mass transfer I
rate, in general, is dependent upon four separate resistances: gas-phase \
resistance, liquid-phase resistance, chemical reaction resistance, and a
solids dissolution resistance for scrubbing liquids containing solid . •,
reactants. For absorption of gaseous contaminants that are highly soluble or I*
chemically reactive with the scrubbing liquid, such as the absorption of HC1 |
by caustic solution, the contact tine required for 99% removal is extremely ' (
short (of the order of 0.4 to 0.6 s). The less reactive and less soluble
pollutants require a longer contact tine [21].
The rate at which a flue gas from waste incineration must be processed by a
particle control device depends primarily on the waste composition, the quan-
tity of excess combustion air used, the initial gas temperature, and the
method(s) by which the gas has been cooled, if cooling is used. Hence these
parameters, in conjunction with control device size or geometry, will dictate
the velocity at which the gas will pass the particle collection elements [21]. '
It has been shown that the pressure drop across a venturi is proportional to I
the square of gas velocity and directly proportional to the liquid-to-gas I
ratio. Therefore, within limits, increasing gas velocity will result in
increasing pressure drop, other parameters being equal [21].. Typical gas
velocities employed commercially are 30 to 120 m/s. The low end of this
range, 30 to 45 m/s, is typical of power plant applications, while the upper
end of the range has been applied to lime kilns and blast furnaces [21].
Particle cut diameter (diameter of particles in which there is a 50% collec- k
tion) is a frequently used parameter for describing the particle collection
performance of venturi scrubbers. One reason for this is because plots of
collection efficiency versus particle diameter tend to be rather steep in the (
region where inertial impaction is the predominant collection mechanism. High
energy venturi scrubbers provide the highest wet scrubber efficiency with cut
diameters in the 0.3 to 0.5 Mm range [21].
2-42
-------
Applicable Waste Streams - Suitable for particles, and fairly effective in
removing noxious gases that are highly soluble (HCl, HF) or reactive with the
scrubber solution (S02, NO , HCN).
A
Advantages -
(1) Simultaneous gas absorption and dust removal.
(2) Suitable for high temperature, high moisture.
(3) Particulate removal efficiency is high.
(4) Scaling not usually a problem.
Disadvantages -
(1) Corrosion and erosion problems.
(2) Dust is collected wet and the wastewater will have to be treated.
(3) Moderate to high pressure drop; large amount of energy needed.
(4) Requires downstream mist eliminator.
2.3.3.3 Packed Bed Scrubber—
Packed bed scrubbers are used in hazardous waste incineration facilities
because of their high removal efficiency for gaseous emissions. Designed
properly, a packed bed scrubber will remove >99% of the halogens from inciner-
ator exhaust gases. The inherent nature of the design does not, however,
allow for removal of particulates from exhaust gases with high particulate I-
loadings. Unless prior treatment is used, this type of waste stream will I
cause clogging in the packed bed scrubber [21].
The packed bed scrubber is a vessel filled with packing material as shown in
Figure 2-20. The scrubbing liquid is fed into the top of the vessel, with gas
flowing in either a cocurrent, countercurrent, or crosscurrent node. As the
liquid flows through the bed, it wets the packing material and provides inter-
facial surface area for mass transfer with the gas phase [21].
GAS FROM
INCINERATOR
4 LIQUID IN
PACKING
EUMCNTS
GAS DISTRIBUTOR
AMD
PACKING SUPPORT
LIQUID OUT
Figure 2-20. Packed bed scrubber schematic.
2-43
-------
Differences between packed bed scrubbers include the flow mode, the packing
material, and the depth of packing. The choice of flow mode is dependent upon
the particular application. Crossflow scrubbing is generally applied to
situations where the bed depth is less than 2 meters, and countercurrent
design is applied at bed depths of 2 meters or more [21].
Packing material varies in shape and type. Shapes used include rings, spiral
rings, and saddles. Packing materials are usually made of ceramic or some
other material that will withstand corrosion from acids [21].
The primary parameters that affect scrubber design and the removal of gaseous
emissions are discussed below. These include pressure drop, liquid-to-gas
ratio, contact time, and gas flow rate [21].
Packed beds used for gaseous emission control in hazardous waste incineration
facilities usually have a pressure drop range from 0.5 to 1.8 kPa. The total
pressure drop across the packed bed is directly proportional to the depth of
packing and affects the gaseous removal efficiency in the packed bed scrubber.
Normal liquid-to-gas ratios in packed beds vary from 0.8 to 10 L/m3, with most
units operating between 3 and 7 L/m3 [21].
In gas absorption devices, higher efficiencies are attained by allowing the
gas and liquid phases to be in contact for a longer period of time. Removal
efficiencies for gaseous contaminants in packed beds are directly related to
the depth of packing, which in turn determines the contact time [21].
The contact time required for gas absorption is a function of the rate of mass
transfer. The mass transfer rate, in general, is dependent upon four separate
resistances: gas-phase resistance, liquid-phase resistance, chemical reaction
resistance, and a solids dissolution resistance for scrubbing liquids contain-
ing solid reactants [21].
In the design of gas absorption devices, the cross-sectional area for gas-
liquid contact is determined by the superficial gas velocity selected. The
greater the gas velocity selected, the smaller will be the scrubber diameter
but the larger will be the pressure drop [21].
There are two additional factors to be considered in the selection of gas
velocity. First, the gas velocity through the scrubber should allow suffi-
cient residence time for gas-liquid contact. Second, in a countercurrent
packed bed, the gas velocity should not exceed the flooding velocity. At the
flooding point, the pressure-drop-versus-gas-rate curve becomes almost verti-
cal, and a liquid layer starts to build up on top of the packing. The flood-
ing poing represents the upper limiting conditions of pressure drop and fluid
rates for practical tower operation (Figure 2-21). A margin of 30% to 40% of
the flooding velocity should be allowed in designing these scrubber types.
The most common gas velocities in packed beds range from 2.1 to 3.0 m/s [21].
As in the case with other wet scrubbers, mist eliminators are often used down-
stream of the packed bed scrubber for proper pollution control.. When a wet
scrubber follows or precedes a packed scrubber, mist eliminators are often not
2-44
-------
1 2
o
a.
5
I
1
0.8
* 0.6
a."
O
ac
& 0.4
t/l
«
0.2
0.1
-3/4 -m. RINGS
WATCR-AIR-SYSTEM
I-SUPERFICIAL LIQUID
RATt. MhrXsq «>
PRESSURE • 1 «m
FLOOOINC
REGION
LOADINC
L - _
13.000 7-50D"
z
T500
L
L
100
200 400 600 1,000 2,000 3,000
G, SUPERFICIAL GAS RATE, lb/(hrMsq ft)
"From PLANT DESIGN AND ECONOMICS FOR CHEMICAL ENGINEERS.
by Peters & Tinmerhaus. Copyright 1968, McGraw-Hill
Used with the permission of McGraw-Hill Book Company".
Figure 2-21. Packed tower pressure drop as function
of gas rate and liquid rate.
used. A packed bed scrubber is often sequential to a venturi in a hazardous
waste incineration facility.
Most commonly, packed scrubbers are used with liquid injection incinerators
because of the low particulate loading in the exhaust gas. The particulates
in gas streams tend to clog up the bed and decrease removal efficiency. When
packed beds are used to control gaseous emissions from rotary kilns and fluid-
ized bed incinerators, venturi scrubbers are usually incorporated upstream as
the primary APCD.
2-45
-------
Applicable Waste Streams - Most suitable for the removal of noxious gases in
streams containing low or no particulate loading.
Advantages -
(1) High removal efficiency for gaseous and aerosol pollutants.
(2) Low to moderate pressure drop.
(3) Engineering principles controlling the performance of packed bed scrub-
bers are well developed and understood.
(4) Availability of corrosion-resistant packings to withstand corrosive
materials.
Disadvantages -
(1) Low efficiency for fine particles.
(2) Not suitable for high temperature or high dust loading applications.
(3) Requires downstream mist eliminator.
(4) Potential scaling and fouling problems.
(5) Possible damage to the scrubber if scrubber solution pumps fail.
2.3.3.4 Spray Tower—
Preformed spray towers are chambers in which a liquid is atomized by high
pressure spray nozzle. The gas stream usually enters the bottom of the cham-
ber and flows countercurrent to the liquid, although both cocurrent and cross-
current modes have been used. The gas may travel in a single path (as in
Figure 2-22) or may be directed by a series of baffles. The atomized liquid
forms droplets and mass transfer occurs at the droplet surface. The finer the
droplets, the more gas absorption is enhanced. Impurities which are soluble
in the scrubbing liquid are removed by the gas absorption process.
CAS OUT
S«AYS
CAS FROM ft
INCINEBATO*
LIQUID IN
Figure 2-22.
LIQUID OUT
Spray tower schematic.
Several of the primary operating parameters that will affect, the removal of
gaseous contaminants in preformed towers are discussed here. These include
the pressure drop, liquid-to-gas ratio, contact time, and gas flow rate. A
normal pressure drop for a preformed spray tower is 0.125 to 0.996 kPa WG [21]
2-46
-------
Liquid-to-gas ratios are strongly dependent upon the control device and the
specific application. Under normal operating conditions, preformed spray
towers employ liquid-to-gas ratios in the range of 4 to 14 L/ra3 [22].
In gas absorption devices, higher efficiencies are attained by allowing the
gas and liquid phases to be in contact for a longer period of time. The
contact time required for gas absorption is a function of the rate of mass
transfer. The mass transfer rate, in general, is dependent upon four separate
resistances: gas-phase resistance, liquid-phase resistance, chemical reaction
resistance, and a solids dissolution resistance for scrubbing liquids contain-
ing solid reactants. For absorption of gaseous contaminants that are highly
soluble or chemically reactive with the scrubbing liquid, such as the absorp-
tion of HC1 by caustic solution, the contact time required for 99% removal is
extremely short (of the order of 0.4 to 0.6 s). The rate at which flue gas
from a waste incinerator must be processed by a particle control device de-
pends primarily on the waste composition, the quantity of excess combustion
air used, the initial gas temperature, and the method(s) by which the gas has
been cooled, if cooling is used. Hence these parameters, in conjunction with
the control device size or geometry, will dictate the velocity at which the
gas will pass the particle collection elements. Because inertial impaction is
the principal particle collection mechanism it is beneficial to operate with a
high relative velocity between the gas and the collection element. Practical
relative velocity limitations occur as a result of the increased operating
costs associated with high pressure drops, flooding, or other considerations.
The most common gas velocities in spray towers range from 2.1 to 3.0 m/s [21]*
Applicable Waste Streams - Spray towers are suitable for gas streams with
particles and gaseous pollutants.
Advantages -
(1) Simultaneous gas absorption and dust removal.
(2) Suitable for high temperature, high moisture, and high dust loading
applications.
(3) Simple design.
(4) Rarely have problems with scaling.
Disadvantages -
(1) High efficiency may require high pump discharge pressures.
(2) Dust is collected wet.
(3) Nozzles are susceptible to plugging.
(4) Requires downstream mist eliainator.
(5) Structure is large and bulky.
(6) Lower particulate collection efficiency than a high pressure venturi.
(7) Lower absorption efficiency than a packed tower.
2.3.3.5 Plate Scrubber—
Plate scrubbers, like all wet scrubbers, remove gaseous contaminants in a gas
absorption process that depends on intimate gas/liquid contact. The basic
design of a plate scrubber is a vertical cylindrical column with a number of
plates or trays inside as in Figure 2-23. Each plate has openings which can
2-47
-------
GAS OUT
tl LIQUID IN
LIQUID
DOWNCOMER
PUTE5
CAS FROM
INCINERATOR
LIQUID OUT
Figure 2-23. Plate tower schematic.
be in the form of perforations or slots. The scrubbing liquid is introduced
at the top plate and flows across it, then down to the next plate. A down-
comer, located on alternate sides of each successive plate, permits the down-
ward movement of the liquid. The scrubbing liquid exits along with the
pollutants at the liquid outlet located at the tower bottom.
Incinerator gas enters the bottom of the tower and passes up through the plate
openings before exiting at the top. The gas has enough velocity to prevent
the liquid from flowing through the holes in the plates. Gas absorption is
promoted by the breaking up of the gas phase into little bubbles which pass
through the volume of liquid in each plate.
At hazardous waste incineration facilities, plate towers with two sieve trays
are typically used as an absorber/mist eliminator in conjunction with a high
energy venturi scrubber.
The primary operating parameters that will affect the removal of gaseous con-
taminants such as S02 are discussed here. These include the pressure drop,
liquid-ta-gas ratio, contact time, and gas flow rate.
Total pressure drop across the plate towers is similar to that of packed beds
and in the 0.5 to 1.8 kPa WG range. In plate towers pressure drop is not used
as an operating parameter to estimate removal efficiency. Rather, the number
of plates is the primary parameter that determines removal efficiency [21].
The liquid-to-gas ratio is a design and operating parameter of prime impor-
tance. It is needed in the determination of the scrubber diameter, and has an
effect on the height of a transfer unit. A high liquid-to-gas ratio will lead
to the requirement of a larger diameter, but at the same time will also reduce
the height of a transfer unit. Normal liquid-to-gas ratios in plate towers
vary from 0.8 to 10 L/m3 with most units operating at between 3 and 7 L/m3 [21]
t
i
2-48
-------
Higher efficiencies are attained by allowing the gas and liquid phases to be
in contact for a longer period of time. Greater depths of liquid on the trays
lead to higher tray efficiency through longer contact time. An increase in
the number of plates and the column height also improves removal efficiency.
In the design of gas absorption devices, the cross-sectional area for gas-
liquid contact is determined by the superficial gas velocity selected. The
greater the gas velocity selected, the smaller will be the scrubber diameter
but the larger will be the pressure drop.
There are two additional factors that must be considered in the selection of
gas velocity. First, the gas velocity through the scrubber should allow
sufficient residence time for gas-liquid contact. Second, in countercurrent
plate towers, the gas velocity should not exceed the flooding velocity (the
upper limiting conditions of pressure drop and fluid rates for practical
operation). A margin of 30% to 40% of the flooding velocity should be allowed
in designing these scrubber types. The most common gas velocities in plate
towers, range from 2.1 to 3.0 m/s.
Parameters that affect the particle collection performance of a plate scrubber
include pressure drop, liquid-to-gas ratio, gas velocity, dust loading, and
particle size distribution. High particulate loadings and fine particles are
unfavorable conditions.
I
Plate towers are appropriate when particle size is not less than 1pm. Unlike
absorption efficiency, particle collection efficiency will not necessarily
improve with an increased number of plates, but decreased perforation diameter
does increase particle collection efficiency. The other parameters have been
. discussed previously and will not be addressed [22].
1 Applicable Waste Streams - Most suitable for the removal of noxious gases with
low particulate loadings.
\
I Advantages -
/ (1) Simultaneous gas absorption and dust removal.
, (2) High removal efficiency for gaseous and aerosol pollutants.
(3) Low to moderate pressure drop.
(4) Mass transfer increases with multiple plates.
(5) Handles high liquid rates.
Disadvantages -
(1) Low efficiency for fine particles.
(2) Not suitable for high temperature or high dust loading applications.
(3) Requires downstream mist eliminator.
(4) Limestone scrubbing solution causes scaling.
(5) Not suitable for foamy scrubbing liquid.
2-49
-------
2.3.3.6 Electrostatic Precipitator (ESP)—
Electrostatic precipitation is a process by which particles suspended in a gas
are electrically charged and separated from the gas stream. In this process,
shown in Figure 2-24, negatively charged gas ions are formed between emitting
and collecting electrodes by applying a sufficiently high voltage to the
emitting electrodes to produce a corona discharge. Suspended particulate
matter is charged as a result of bombardment by the gaseous ions and migrates
toward the grounded collecting plates due to electrostatic forces. Particle
charge is neutralized at the collecting electrode where subsequent removal is
effected by periodically rapping or rinsing. A majority of industrial EPS's
used today are the single-stage, wire and plate type; charging and collection
take place in the same section of the ESP. Two-stage ESP;s, often called
electrostatic filters, utilize separate sections for particle charging and
collecting, and are not generally employed for controlling particulate emis-
sions from combustion sources.
O£AM CAS OUT
NEGATIVE ELECTRODE CONNECTED TO
EUCTUICAL POWER SOURCE
NEGATIVELY CHARGED WIRE
OROUNDED COUfCTING PLATE
WITH POSITIVE CHARGE
DIRTY CAS IN
HOPPER TO
DISCHARGE
Reprinted by permission
Electrostatic precipitator schematic.
Figure 2-24.
charge is neutralized at the collecting electrode where subsequent removal is
effected by periodically rapping or rinsing. A majority of industrial EPS's
used today are the single-stage, wire and plate type; charging and collection
take place in the same section of the ESP. Two-stage ESP,-s, often called
electrostatic filters, utilize separate sections for particle charging and
collecting, and are not generally employed for controlling particulate emis-
sions from combustion sources.
Electrostatic precipitators have been widely used in conjunction with utility
boilers and with municipal and industrial incinerators. ESP's have been
employed by European facilities where hazardous wastes are incinerated, al-
though the wastes generally do not contain highly chlorinated compounds. When
halogenated wastes are incinerated, careful waste blending is employed to
protect ESP's from corrosion, so that HCl concentrations do not exceed 1,000
ppm and usually average 300 ppm [23]. Dry ESP's are not capable of removing
acid gases and, therefore, facilities burning halogenated wastes must employ
two-stage gas cleaning if ESP's are used for particulate emission control.
2-50
-------
ESP components that are in direct contact with the process gas stream include
the shell, electrodes, high voltage frames, rapper rods and gas distribution
plates. On the basis of mild steel construction, such components constitute
approximately 68% of the total precipitator weight and account for 45% of the
total unit cost [23]. Hence, the applications requiring exposure to corrosive
gas streams have substantial impact on ESP design and ultimate cost. Lead
linings, used in acid mist ESP's, are not generally suitable for use in incin-
erator gas treatment due to poor resistance to attack by gaseous halogens.
Fiber glass reinforced plastic (FRF) has been successfully utilized for inlet
and outlet plenums as well as collecting electrodes; however, the latter
application requires provision of adequate conductivity to permit current flow
to ground.
ESP's are carefully designed and constructed for maximum electrical safety;
however, normal high voltage precautions must be observed. Design features
such as interlocks between access doors and electrical elements should be
employed. Also, access after deenergizing should be delayed to allow for
static charge drainage.
Compared to those of wet scrubbers, pressure and temperature drops across
ESP's are very small. The pressure drop across an ESP is typically below
0.25 kPa WG as compared with wet scrubbers which may operate with pressure
drops up to 15 kPa WG. Additionally, ESP's provide generally higher removal,
efficiencies for particles smaller than 1 \m in diameter than do wet scrubbers.
A standard gas temperature range is up to 370°C and the voltage normally |
applied ranges from 30 kV to 75 kV.
Applicable Waste Streams - Effective for the collection of fine particles
(less than 1 urn in diameter), but unable to capture noxious gases. Performs
poorly on particles with high electrical resistivity.
Advantages -
(1) Dry dust collection.
(2) Low pressure drop and operating cost.
(3) Efficient removal of fine particles.
(4) Collection efficiency can be improved when stream is treated (i.e.,
highly conducting dust treated with S02).
Disadvantages -
(1) Relatively high capital cost.
(2) Sensitive to changes in flow rate.
(3) Particle resistivity affects removal and economics.
(4) Not capable of removing gaseous pollutants.
(5) Fouling potential with tacky particles.
2.3.3.7 Wet Electrostatic Precipitator (WKP)—
The wet electrostatic precipitator (Figure 2-25) is a variation of the dry
electrostatic precipitator design. The two major added features in a WE?
system are: (1) a preconditioning step, where inlet sprays in the entry
section are provided for cooling, gas absorption, and removal of coarse
2-51
-------
particles, and (2) a wetted collection surface, where liquid is used to con-
tinuously flush away collected materials. Particle collection is achieved by
introduction of evenly distributed liquid droplets to the gas stream through
sprays located above the electrostatic field sections, and migration of the
charged particles and liquid droplets to the collection plates. The collected
liquid droplets from a continuous downward-flowing film over the collection
plates, and keep them clean by removing the collected particles. To control
the carryover of liquid droplets and mists, the last section of the WEP is
often designed so that mists can be collected on baffles [24] .
CAS aow IN
CAS FLOW OUT
HIGH VOLTAGE
UADS
- WATER PI PES
Figure 2-25. Wet electrostatic precipitator schematic.
The WEP overcomes some of the limitations of the dry electrostatic precipita-
tor. The operation of the WEP is not influenced by the resistivity of the
particles. Further, since the internal components are continuously being
washed with liquid, buildup of tacky particles is controlled and there is some
capacity for removal of gaseous pollutants. In general, applications of the
WEP fall into two areas: removal of fine particles, and removal of condensed
organic fumes. Outlet particulate concentrations are typically in the 2 to
24 mg/m3 range. [24].
Data on capability of the WEP to remove acid gases are very limited. WEP's
have been installed to control HF emissions from Soderberg aluminum reduction
cells [23]. With a liquid-to-gas ratio of 0.67 L/m3 and a liquid pH between 8
and 9, fluoride removal efficiencies higher than 98% have been measured.
Outlet concentration of HF was found to be less than 1 ppm.
There are no WEP installations at hazardous waste incineration facilities. A
potential application is to consider use of the WEP in conjunction with a low
pressure drop venturi scrubber upstream, where a major portion of the gaseous
contaminants and heavy particles will be removed. The WEP will then serve as
2-52
-------
a second stage control device for removal of the submicron particles and
remaining gaseous pollutants. Because of its limited application history,
extensive pilot testing prior to design and installation may be necessary [24]
Applicable Waste Stream - Effective in removal of fine particles and of con-
densed organic fumes.
Advantages -
(1) Simultaneous gas absorption and dust removal.
(2) Low energy consumption.
(3) No dust resistivity problems.
(4) Efficient removal of fine particles.
Disadvantages -
(1) Low gas absorption efficiency.
(2) Sensitive to changes in flow rate.
(3) Oust collecton is wet.
2.3.4 Heat Recovery Technology
As Section 2.3.1 on incinerator technology in hazardous waste incineration
pointed out, temperatures during incineration may range up to 1600°C. The
flue gas from such a process has a substantially high heating value, especi
ally if the volumetric flow rate is great. Some form of waste heat recovery
is beneficial at any rate.
:l
Three basic types of waste heat recovery are possible in any incineration
process. These include gas-to-water, gas-to-air, and gas-to-organic fluid [7].
Since steam has a tremendous heat energy per unit weight, gas-to-water systems
producing steam are the most commonly used heat recovery systems. This steam
in turn is generally used as a power source in other site processes. Steam
generation is usually accomplished by directing flue gases immediately from
the last incineration step into a heat recovery boiler. A simple version of
this heat exchange process is included in Figure 2-26. Gas flow may be regu-
lated, usually by a damper, to control the amount of heat recovery. This
system, depending on the volume and temperature of the flue gas, can act as
the primary or secondary source of process steam when combined with a conven-
tional boiler system.
Gas-to-air systems are also commonly used heat recovery systems, usually using
heated air as combustion air in the incineration process. The same heat
exchange principle as in gas-to-water is practiced in heating air. Heating of
combustion air lessens the need for auxilliary combustion fuel, as the temper-
ature of the air-waste-fuel mixture is much closer to the waste's oxidation
point. Research is also being done to determine the value of heating air for
use in power generation.
2-53
-------
SHAM OUT
T-«T
PL
FLUE GAS FROM
INCINERATOR *~
(-*-
h
EXCHANGER TUBES
i >•' ::
EXCHANGER TUBES |
u
^ *
I ;;*•.-:•; -:•<-.,. ,-«»,: :,,^:,^
l^>
EXCHANGER TUBES
\
~~ KUt GAb !0 tMlbblON
CONTROL SYSTEM
^^'
I
WATER IN
Figure 2-26. Heat recovery/gas-to-water
Gas-to-organic fluid heat exchange also uses a heat exchange principle out-
lined in Figure 2-26. This process can be used in heating mineral oil or
ethylene glycol, which is in turn used in controlling temperatures of addi-
tional processes [7].
2.4 FOREIGN TECHNOLOGIES
2.4.1 Introduction
Foreign incinerators are basically the sane as found in the United States.
The rotary kiln is widely used for the simultaneous incineration of solid,
liquid, and semisolid wastes of all calorific values. In addition, the fixed
firebox/muffle furnace is used for liquid and/or gaseous wastes,- fluidized bed,
multiple chamber, and liquid injection incinerators are utilized less frequently.
Heat recovery is incorporated into hazardous waste incineration systems more
frequently than in the United States.
In nearly all waste-to-energy combustion units, energy is recovered through
production of sttam, either with classic fire-tube boilers or newer waterwall
boilers. Some combustion units do without a boiler and use the hot combustion
gases directly. Coincineration of municipal wastes and selected hazardous
wastes is a common practice in a number of foreign countries, particularly the
Netherlands. Countries with strict environmental legislation are more likely
to segregate hazardous wastes for treatment in separate facilities. Selected
hazardous waste incineration technologies of Canada, Japan, and Germany are
discussed in the following three sections. Table 2-6 presents a partial list-
ing of industrial waste facilities outside the United States.
2-54
-------
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2-57
-------
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TABLE 2-6. SELECTED INDUSTRIAL WASTE INCINERATION
FACILITIES IN EUROPE AND JAPAN.
1
I
Plant
BASF
Ladvigshafen
Boehnnqer Pharma
Ingeir.em
Bocnuin
BASF
Ludvigshafet
Continental
Hannover
Ope.
Russelsneim
Chemical Works Huls
Marl
Explosives factory
Dottikon
Alfa Sud
Pomigliano (Naples)
Kobe Steel
Kobe
Komnune Kemi
Nyborg
Gelsenberg-Hannesmann
Unveltschutz
Bochum
Kobe Steel
Kakogawa
Oenki Kagaku
Ohni
Entsorgungsbetriebe
Sinner ing
Vienna
Hessische Industnemull
Biebesheu»
Svensk Avfallskonvertering
Norrtorp
Explanation of symbols:
0 »
K >
H *
r -
M *
Country
Germany
Germany
Germany
Germany
Germany
Germany
Germany
Switzerland
Italy
Japan
Denmark
Germany
Japan
Japan
Austria
Germany
Sweden
Start-up
1960
1962
1963
1964
1964
1966
1966
1969
1973
1974
1975
1976
1976
1977
1980
1980
1981
Type of furnace
Srate furnace
Rotary kiln
Hearth- type furnace
fluidized bed furnace
Halting chamber
waste to be treated
solid industrial waste
solid chemical waste, timber
waste paper, garbage
waste paper, timber, plastic,
garbage, waste paint
solid, scan-solid and liquid
chemical waste, waste oil,
waste paint, solvents
carbon black, waste paper,
rubber, grease, waste oil
waste paper, timber, plastic
garbage, waste paint
solid, seai-solid and liquid
chemical waste, carbon black,
rubber, timber
acid sludge, distillation re-
sidues, waste oil. activated
carbon, waste paper, timber
waste paper, timber, plastic.
garbage, waste paint
waste oil, grease, plastic,
timber, rubber, waate paint
solid, saai-solid and liquid
industrial waste
waste oil, solvents, slurries,
puapable chemical waste
waste oil, grease, plastic,
timber, rubber, waste paper
tar, plastic, rubber, vasts
oil , slurries
sewage sludge
solid, seal-solid and liquid
industrial waste
solid, seau-solid and liquid
industrial waste
solid, seai-solid and liquid
industrial waste
Kind of heat recovery
s Steam for internal use)
S Steaa for sale
h Hot water for internal use
H Hot water for sale
e Electric potter for internal v
E Electric power for sale
Capacity
Gcal/h
15
2
4
7 2
7.5
6.2
12
3.2
4
4
20
30
1.8
1.1
14. S
2S.8
IS
17.4
ue
furnace recover".
G s
G none
G none
K s
G s
G s
K s
H none
G none
K none
K s h H I'
H s e E
X none
K none
t ' s h e H
K s h e H
K He
K s h e E
2-59
-------
2.4.2
T
There are two t-eaionai incineration facilities with a possible third in the
planning stag* . All are privately owned and financed. Licensing of these
facilities is the responsibility of the government of the provinces in which
the incinerators are locate. Conventional methods for treatment and disposal
of hazardous wastes generated by the petroleum and organic chemical industries
have proven inadequate for the volume of such wastes. Experimental programs
to determine the feasibility of utilizing a cement kiln for destruction of
hazardous wastes have been conducted by the Environmental Protection Service
of Canada under partial sponsorship of the U.S. Environmental Protection
Agency.
The use of cement kilns for the disposal of waste liquids was recommended in
Canada at first in 1974 in a report issued by Environment Canada. It was
suggested to use cement kilns for the disposal of waste oil, thereby recover-
ing the heat value of the oil and as well as retaining the inorganic constitu-
ents of the oil in cement clinker.
An extensive series of experimental waste oil burns was conducted in the
spring of 1974. The result verified that the emissions of toxic substances to
the atmosphere were negligible, and there were no adverse effects on cement
quality. Heavy metal contaminants were chemically combined into the lattice
structure of the cement in a manner similar to the glazing of pottery. j
Severe temperature conditions required for the thermal destruction of other
hazardous wastes, such as chlorinated hydrocarbons, are customarily maintained
in the cement kiln. In addition, hydrochloric acid and calcium chloride are
added to the cement kiln feed for purposes of alkali reduction.
The use of kilns for the destruction of chlorinated hydrocarbon wastes con-
taining up to 46% (by weight) chlorine was investigated in joint U.S. - Canada
incineration tests. The waste used included a variety of chlorinated hydro-
carbons in the series of program phases designed to progress from easily
combusted chlorinated hydrocarbons (chlorinated aliphatics) to those which are
combusted with difficulties (chlorinated aromatics and alicyclics). The last
phase consisted of 50-100 percent polychlorinated biphenyl wastes.
The results of the stack gas sampling analyses indicated a minimum combustion
efficiency of the waste feed to be 99.986%, and although traces of volatile
low molecular weight hydrocarbons were found (approximately 50 ppb), there was
no evidence of the existence of polychlorinated biphenyls at the limits of
detection of the methods and procedures, 3 micrograms per cubic meter.
It was concluded in early 1976 that cement kilns could be a viable alternative
for the destruction of liquid hazardous wastes and in fact an approval or
license was issued to a Canadian cement works. But it may be added that the
public was totally and completely unaware of these investigations, and speci-
fically of the positive results. When it became generally known that this
company was handling PCB's, the public reaction was swift and intensive, and
2-60
-------
finally so effective that the company voluntarily surrendered back to the
provincial agency, its license for PCS disposal. Therefore at present no
PCB's are burned.
The Canadian experience with the use of cement kilns has spanned five years.
It has proven that cement kilns represent an environmentally secure system for
the destruction of liquid chlorinated hydrocarbons if they are properly equip-
ped, operated, and regulated. But it has also shown that introducing a new
waste disposal method for hazardous wastes means involving the public at an
early stage of the development, such that their concerns could be recognized,
and the appropriate answers developed in a rational and scientific manner.
2.4.3 Japan [24, 26, 31]
The rotary kiln is the incinerator most commonly used in Japan. Takuma Boiler
Manufacturing Company designed a continuous synthetic polymer waste disposal
plant for destruction of PVC products. A rotary kiln is used in this system
for pretreatnent of PVC products under dry distillation conditions. PVC
products are dry distilled at about 300°C; when air is excluded this produces
HC1. After HCl is vaporized from the resin material, the carbonized resin
materials are burned in the incinerators (the same way as other techniques).
The HCl gas from the rotary kiln passes through a multi-cyclone and a gas
cooler. It is then reacted with ammonia gas to produce ammonium chloride, i
separated, collected by a dust collector, and finally carried away by a con- I"
veyor to a storage point. |
Kawasaki Heavy Industries utilize fluidized bed incinerators for the burning
of liquid plastic wastes. Recently, this type of incinerator has been used
for drying various kinds of chemicals in many industries. For further infor-
mation on the operation of fluidized beds consult Section 2.3.3.3.
The FLK process has been developed by Ebara Infilco Company incorporating
equipment invented by Dr. Johannes Wotchke and currently in use at Volkswagen-
werk of West Germany for destruction of defective automobile tires (at the
rate of 250 per hour). The Ebara FLK process incorporates the small flame
chamber (FLK) incinerator for complete high temperature incineration (up to
1500°C). The process can be used to burn either solid wastes (such as tires
or high-polymer plastics) or liquids (such as waste oils or solvents).
Emission control technologies utilized in Japan and other countries are those
in use in the United States - the spray tower, centrifugal spray scrubber,
venturi scrubber, electrostatic precipitator, and cyclone.
2.4.4 West Germany [25, 28, 29, 32]
West Germany has the most stringent environmental emission standards in West-
ern Europe, yet incineration is the preferred method for disposal of certain
hazardous industrial wastes. Co-incineration is seldom conducted since the
method of disposal of industrial waste is determined by government regulation.
Waste oil, plastics, solvents, and other wastes of organic origin can be
incinerated with or without chemical or physical pretreataent. Five incin-
erator technologies are used for the destruction of most hazardous wastes:
2-61
-------
(1) rotary kilns and burn-out chambers
(2) fluidized bed kiln
(3) combustion chamber kiln
(4) turbulator action kiln
(5) grate kiln
The general rules for the application of these kiln types are:
(1) Rotary kiln: the most versatile kiln for all kinds of waste in solid,
pasty, or liquid condition. Very flexible by distribution of the liquid
waste feed between rotary kiln head and secondary combustion chamber.
(2) Fluidized bed kiln: for pasty and liquid wastes like sludges and efflu-
ents from refineries, petrochemical plants, and water purification plants,-
flexible for fluctuating throughput rates and wastes of varying
composition. Wastes with low calorific value need a support firing.
(3) Combustion chamber with special nozzles: for effluents with low calori-
fic value to be used where the expensive fluidized-bed kiln is not
necessary.
1
(4) Turbulator: a high-temeprature combustion chamber with turbulent gas
flow for liquid wastes with high calorific value. Due to' special refrac
tory lining it can stand great thermal loads.
Suitable for pyrolysis and breaking-up of metal chlorides. Due to high
gas velocities, solids and dust are carried over. Therefore the off-gas
cleaning is very important.
(5) Grate: types utilized in incinerators with longitudinal over thrust
grates and rotating basket grates, mostly in combination with steam
boiler systems.
A description of the operation of the Bavarian regional hazardous waste dis-
posal plant follows*:
The central plant has a laboratory to check all incoming wastes and to dis-
tribute then to the proper storage and treatment areas.
The annual capacity is approximately 100,000 t/year of solid, pasty, and
liquid residues with a mean calorific value of 3,300 kcal/kg. The thermal
capacity is 25 Gcal/h. It is processed in two parallel rotary kilns having
one common after-burner chamber. The plant is designed for adding a third
kiln some tine in the future.
Bunkers for the solids have a capacity of 900 m3. They are controlled by a
crane operator from a stationary location.
For pasty residues 4 steam-heated bunkers of 100 m3 capacity each are provided.
*Reference 28.
2-62
-------
The tank yard for liquid wastes has a total storage capacity of 200 m3.
Beside it is located the barrel melting cabinet.
Each rotary kiln can handle either 5 t/h solids with a net calorific value of
2500 Kcal/kg, or 3.1 t/h pasty wastes with a net calorific value of 4000 Kcal/Jcg
or any combination which does not exceed 12.5 Gcal/h.
The afterburner chamber handles the off-gases from:
(1) 2 rotary kilns without burning additional liquids, or
(2) 1 rotary kiln and in addition 2.4 t/h liquid wastes with a net calorific
value of 5200. These liquids are burned in the side walls.
The vertical gas velocity is 3.5 m/s in the afterburner chamber at a thermal
load of 25 Gcal/h.
The off-gas at a rate of 66,000 Nm3/h leaves the afterburner chamber at a
temperature of 1000°C.
Heat is recovered in a steam boiler. The gases leave the boiler at 270°C.
Steam is generated at 25 atm and superheated to 250°C at a rate of 34 t/h.
A steam turbine generates electric power at the rate of 1320 kv/h consuming |-
22 t/h steam. The remainder is condensed in an air condenser. This electric
energy is sufficient to supply the entire plant's demand requirements. The
steam from the turbine - 3 atm - is utilized for heating the building and for
process heat in the central plant.
The off-gas is cleaned with high efficiency by an electrostatic precipitator
followed by a two-stage radial flow scrubber. Oust, HCl, and HF are nearly
completely removed; S02 removal is on the order of 70 percent. The scrubbing
liquid is circulated at a rate of 150 m3/h. Since 2 m3/h are discharged to
< keep the concentration at a constant value, and 10 m3/h are vaporized in the
1 two scrubber stages, some 12 m3/h fresh water is supplied to the system. The
discharged water carries sludge from the neutralizing agents and is further
; processed in the central plant. The saturated off-gases are reheated before
leaving the stack to avoid condensation of the gas stream. This is accom-
plished in a heat exchanger and by addition of preheated air before the gases
are exited to the stack.
The gases leaving the stack are almost completely free from toxic ingredients.
They consist of nitrogen, oxygen, C02, and H20 as they normally exist in the
atmosphere.
Slag and ashes are deposited at a selected sanitary landfill and constitute
approximately l/10th of the original volume of the materials charged.
J The Bavarian incineration facility was designed to comply with stringent West
German environmental regulations. Ownership of the plant is shared by indus-
try and municipal and state governments.
2-63
-------
2.5 INCINERATOR MANUFACTURERS fl
This section lists vendors of various types of hazardous waste incinerators.
The listing does not necessarily include all manufacturers of hazardous waste
incineration equipment. It should also be noted that inclusion in this list
does not guarantee that the organization listed is currently a supplier of
hazardous waste incineration equipment, nor does it represent an endorsement
of any such equipment manufacturer by EPA.
The following list (Table 2-7) of vendors was taken from an EPA-sponsored
report and represents only manufacturers who were willing to provide the
additional information shown. For the most part, names, addresses, and some
phone numbers were obtained from one or more listings in four current vendor
directories. These directories include;
(1) 1981 Chemical Engineering Catalog.
(2) February 1981 Buyers' Guide, Solid Waste Management Magazine. f
(3) 1981 Catalog and Buyers' Guide, Pollution Equipment News (Nov. 1980,
Vol. 13, #6).
(4) 1980-81 Directory and Resource Book, Air Pollution Control Association. P
A later report [33] estimated that, of the 340 hazardous waste incinerators in
service, 219 are liquid injection, 57 are fixed hearth (controlled air), 42 i I
are rotary kiln (primarily cocurrent), and the remaining 22 are of several I* (.
modified and other types of designs. J
f
I
2-64
-------
TABLE 2-7. HAZARDOUS WASTE INCINERATOR VENDORS
Air Resources
600 N. First Bank Dr.
Palatine, IL 60067
(312) 359-7810
Basic Environmental Engineering, Inc.
21 W. 161 Hill Avenue
Glen Ellyn, IL 60137
(312) 469-5340
Baumco, Inc.
Pittsburgh, PA 15219
(412) 216-3555
Bayco Industries of California
2108 Davis Street
San Leandro, CA 94577
(415) 562-6700
Bigelow-Liptak Corp.
21201 Civic Center Drive
Southfield, MI 48076
(313) 353-5400
Brule C.E.&E., Inc.
13920 Southwestern Avenue
Blue Island, IL 60406
(312) 388-7900
C. E. Raymond Co.
Bartlett-Snow Division
200 West Monroe Street
Chicago, IL 60606
(312) 236-4044
CICO, Inc.
1600 W. Haskell
Appleton, WI 54911
(414) 734-9861
Coen Company
Burlingane, CA
(415) 697-0440
Commercial Fabrication & Machine Co., Inc.
P.O. Box 472
Mount Airy, NC 27030
(919) 786-8374
(continued)
2-65
-------
TABLE 2-7 (continued)
Copeland Associates, Inc.
125 Windsor Dr.
Oak Brook, IL 60521
(312) 986-8564
Dorr Oliver, Inc.
Stamford, CT 06904
(203) 358-3676
Ecologenics Corp.
P.O. Box 348
Red Lion, PA 17356
(717) 244-8549
Econo-Thera Energy Systems Corp.
11535 K-Tel Drive |
Minnetonka, HN 55343 ;
(612) 938-3100
Enercon Systems, Inc. I-
16115 Puritas Avenue I
Cleveland, OH 44135
(216) 267-0555 .
Energy, Inc.
Idaho Falls, ID 83401
(208) 529-1000
Entech Industrial Systems, Inc.
The Woodlands, TX 77380 '
(713) 353-2319 '
Environmental Control Products, Inc. i
11100 Nations Ford Road ft
P.O. Box 15753
Charlotte, NC 28210 (
(704) 586-1620
Environmental Elements Corp.
(Sub. of Koppers Co., Inc.)
Baltimore, MD 21203
(301) 796-7334
Fuller Co.
Bethlehem, PA
(215) 264-6011
(continued)
2-66
-------
TABLE 2-7 (continued)
Fuller Co.
Bethlehem, PA
(215) 264-6011
HPD, Inc.
Glen Ellyn, IL 60137
(312) 357-7330
Hirt Combustion Engineers
931 South Maple Avenue
Hontebello, CA 90640
(213) 728-9164
Industronics, Inc.
489 Sullivan Ave.
P.O. Drawer G
S. Windsor, CT 06074
(203) 289-1551
International Incinerators, Inc.
P.O. Box 19
Columbus, GA 31902
(404) 327-5475
John Zink Co.
Tulsa, OK 74105
(918) 747-1371
Kelley Co., Inc.
6720 N. Teutonia Avenue
Milwaukee, WI 53207
(414) 352-1000
Met-Pro Corporation, Sys. Div.
160 Cassell Rd.
P.O. Box 144
Harleysville, PA 19438
(215) 723-6751
Midland-Ross Corp.
2275 Dorr Street
Toledo, OH 43691
(419) 698-4341
Morse Boulger, Inc.
53-09 97th PI.
Corona, NT 11368
(continued)
2-67
-------
TABLE 2-7 (continued)
Peabody International Corp.
4 Landmark Sq.
Stamford, CT 06901
(202) 327-7000
Plibrico
1300 N. Kingsbury Avenue
Chicago, IL 60614
(312) 549-7014
Prenco, Inc.
29SOO Stephenson Hwy.
Madison Heights, MI 48071
(313) 399-6262
Pyro Magnetics Corp.
200 Essex Street
P.O. Box 288
Whitman, MA 02382
(617) 447-0448
Shirco, Inc.
2451 Stemmons Hwy.
Dallas, TX 75207
(214) 630-7511
Sunbeam Equipment Corp.
Comtro Division
180 Mercer Street
Meadville, PA 16335
(814) 724-1456
Sure-Lite Corp.
Santa Fe Springs, CA 90670
(213) 693-0796
TR Systems, Inc.
239 Connerce Street
So. Windsor, CT 06033
(203) 528-3728
Tailor & Co., Inc.
P.O. Box 587
Davenport, IA 52805
(319) 355-2621
(continued)
I
2-68
-------
TABLE 2-7 (continued)
Thermal Processes, Inc.
507 Willow Springs Road
La Grange, IL 60525
(312) 747-6600
Trane Thermal Co.
Conshohocken, PA 19428
(215) 828-5400 (x45)
Trofe, Inc.
Pike Road .
Mt. Laurel, NJ 08054
(609) 235-3036
United Corporation
1947 N. Topeka Blvd.
Topeka, KS 66608
(913) 232-2349
U.S. Smelting Furnace Co.
C.E. Industries Corp.
Belleville, IL
(618) 233-0129
Vulcan Iron Works, Inc.
• United Penn Bank Bldg., Roon 1050
Wilkes Barre, PA 18701
(717) 822-2161
The Washburn & Granger, Inc.
1 85 5th Avenue
P.O. Box 304
Patterson, NJ 07524
(211) 278-1965
2-69
-------
2.6 REFERENCES
1. Ottinger, R.; Blumenthal, J.; Dalporto, D.; Gruber, G. ; Santy, M.; and
Shih, C. Recommended methods of reduction, neutralization, recovery, or
disposal of hazardous waste. Volume III. Disposal processes descrip-
tions, ultimate disposal, incineration, and pyrolysis processes. Cin-
cinnati, OH; U.S. Environmental Protection Agency,- 1973 August. 251 p.
PB 224 582.
2. Stevens, J. ,- Crumpler, S.,- and Shih, C. Thermal destruction of chemical
wastes. -Presented at the 71st annual meeting of the American Institute
of Chemical Engineers; 1978 November 16. 45 p.
3. Dawson, R. Hazardous sludge criteria procedures. Sludge Magazine. '
2(1) .-12-21, 1979 January-February.
4. Chementator. Chemical Engineering. 87(5):72, 1980 March 10.
5. Barnes, R. H.; Barrett, R. E.; Levy, A.,- and Saxton, M. J. Chemical
aspects of afterburner systems. Research Triangle Park, NC; U.S. Envi-
ronmental Protection Agency; 1979 April. 117 p. PB 298 465.
6. Hitchcock, 0. Solid-waste disposal: incineration. Chemical Engineering.!
86(11):185-194, 1979 May 21. I
7. Sittig, M. Incineration of industrial hazardous wastes and sludges.
Noyes Data Corporation, 1979.
8. Cegielski, J. M. Waste disposal by thermal oxidation. 1981.
9. Ackerman, D.; et al. Destroying chemical waste in commercial-scale
incinerators, facility report No. 6, Rollins Environmental Services.
Washington, DC; U.S. Environmental Protection Agency; 1977 June. 162 p.
PB 270 897.
10. Destructing chemical wastes in commercial-scale incinerators; technical
summary, Volume I (preliminary draft). Washington, DC; U.S. Environmental
Protection Agency; 197S March. PB 257 709.
11. Farb, D.; and Ward, S. Information about hazardous waste management
facilities. Cincinnati, OH; U.S. Environmental Protection Agency,-
1975 July. 130 p. EPA-530/SW-145.
12. Genser, J.; Zipperstein, A.; Klosky, S.; and Farber, P. Alternatives for
hazardous waste Management in the organic chemical pesticides, and explo-
sives industries. Washington, DC; U.S. Environmental Protection Agency,-
1977 September 2. 286 p. PB 278 059.
13. Technical briefing report: optmizing the energy efficiency of incin-
erators for the disposal of industrial waste (second draft). Argonne,
IL; Argonne National Laboratory; 1972 June 20. Contract 31-109-38-4223.
2-70
-------
14. Scurlock, A.; Lindsay. \. ; Fields, T., Jr.; andHuber, D. Incineration
in hazardous waste m^n^gement. Washington, DC; U.S. Environmental Pro-
tection Agency; 1975. 110 p. PB 261 049.
15. Wilkinson, R.; Kelso, G.; and Hopkins, F. State-of-the-art-report:
pesticide disposal research. Cincinnati, OH; U.S. Environmental Protec-
tion Agency; 1978 September. 247 p. PB 284 716.
16. Clausen, J.,- Johnson, R.; and Zee, C. Destroying chemical wastes in
commercial-scale incinerators, facility report No. 1, Marquardt Company.
Washington, DC; U.S. Environmental Protection Agency; 1976 October.
116 p. PB 265 541.
17. Hanson, L.; and Unger, S. Hazardous material incinerator design criteria.
Cincinnati, OH; U.S. Environmental Protection Agency; 1979 October.
100 p. PB 80-131 964.
18. Ackerman, D.; Clausen, J.; Johnson, R.; and Zee, C. Destroying chemical
wastes in commercial-scale incinerators, facility report No. 3, Systems
Technology, Inc. Washington, DC; U.S. Environmental Protection Agency,-
1 1976 November. PB 265 540.
19. Ferguston, T.; Bergman, F.; et al. Determination of incineration operat-4
ing conditions necessary for safe disposal of pesticides. Cincinnati, I
OH; U.S. Environmental Protection Agency; 1975 July. 400 p. PB 251 131J
20. Bell, B. A.; and Whitmore, F. C. Kepone incineration test program.
Cincinnati, OH; U.S. Environmental Protection Agency,- 1978 Hay. 148 p.
PB 285 000.
21. Calvert, S.; Goldschmid, J.; Leith, D.; and Mehta, D. Wet scrubber
system study, Volume I - scrubber handbook. Report prepared by A.P.T.,
Inc., for the U.S. Environmental Protection Agency, 1972 August. EPA-R2-
72-118a.
22. Peters, H. S.; and Tiamerhaus, K. D. Plant design and economics for
chemical engineers. New York, McGraw-Hill Book Company, 1968, 641-642.
23. Novak, R. G.; and Clark, J. N. Impact of RCRA on hazardous waste incin-
eration design. Presented at the CMA Seminars on Disposal of Hazardous
Wastes; Newark, NJ; 1979-80.
24. Bakke, E. Wet electrostatic precipitators for control of submicron
particles. Journal of the Air Pollution Control Association. 25(2):
163-167. 1975 February.
25. Disposal of hazardous wastes: thermal treatment. NATO CCMS pilot study,
phase II. Draft report. Federal Republic of Germany, 1979. 72 p.
26. Berry, R. Cement: building a new future. Chemical Engineering. 86(10):
33-35, 1979 Hay 7.
2-71
-------
27. Neff, W.; Skinner, D.; and McDonald, L. The destruction of chlorinated
hydrocarbons including PCB's in a cement kiln. Proceedings of the 32nd
Industrial Waste Conference, Purdue University, Lafayette, IN. 1977 May
10-12. pp. 507-517.
28. Sinning, B. Technologies and equipment for removal of industrial resi-
dues and wastes. Proceedings of the 1976 National Waste Processing
Conference, American Society of Mechanical Engineers, New York, 1976.
pp 329-358.
29. Sundberg, A; and DeBorms, C. Solid waste treatment arid resource recovery
in the european economic community (EEC): a status report. .Proceedings
of the 1976 National Waste Processing Conference, American Society of Me-
chanical Engineers, New York, 1976. pp. 447-451.
30. Enelco-VonRoll thermal systems for waste and refuse disposal. Baltimore,
HD; Environmental Elements Corporation; 1980. 20 p.
31. McDonald, L.; Skinner, 0.; Hopton, F.; and Thomas, G. Burning waste
chlorinated hydrocarbons in a cement kiln. Washington, DC; U.S. Envi-
ronmental Protection Agency; 1978. 240 p. PB 280 118 (EPA-530/SW-147C).
32. European waste-to-energy systems, an overview. Washington, DC; U.S.
Energy Resource and Development Administration,- 1977 June. Report CONS -
2103-6. 62 p.
33. Frankel, Irwin. Draft report. Vendor information on rotary kiln and
liquid injection incinerators. Draft report: Mitre Corporation, EPA
Contract 68-03-3021, 1981 August.
2-72
-------
CHAPTER 3
WASTE CHARACTERIZATION
3 . 1 INTRODUCTION
Waste characterization is a major factor in assessing the feasibility of
destroying a hazardous waste material by incineration. It affects the design
of the incinerator and its emissions control system and helps determine the
compatibility of a waste with a proposed or available facility. It also plays
a part in determining incinerator operating conditions for complete destruction
of a specific waste.
This chapter discusses the importance of the physical, chemical, and thermo-
dynamic properties of hazardous wastes in evaluating them for incineration and
in selecting a compatible incineration technology type. It also classifies
RCRA Section 3001 hazardous wastes and other hazardous wastes as good, poten-l-
tial, or poor candidates for incineration, based on technical considerations,!
and identifies compatible incineration technology types for these wastes. In
addition, it presents information on sampling and analysis of hazardous wastes
for characterization, and it provides a work sheet to help in evaluating a
waste for incineration.
3.2 WASTE CHARACTERIZATION BACKGROUND INFORMATION
Background information about the hazardous waste(s) is generally available.
Such information may have been generated under Section 3001 (Identification
and Listing of Hazardous Waste), Section 3002 (Standards Applicable to Gener-
ators of Hazardous Waste), or Section 3003 (Standards Applicable to Transporters
of Hazardous Waste) of the RCRA regulations. Additional information can usu-
ally be obtained from studies of the process(es) generating the waste(s).
This background information is helpful in evaluating waste for incineration.
3.2.1 Information Available from Waste Generators
A generator of hazardous waste should be able to provide the Standard Industrial
Classification (SIC) code of the industry from which the waste originates, the
EPA hazardous waste number, and a short description of the waste. The generator
may also provide a detailed description of the process that generates the
waste.
3.2.2 Information Available from Transporters
Federal or state regulations regarding transportation of the waste may give
additional waste characterization information. The manifest that accompanied
3-1
-------
a waste shipment will identify the waste hazard class according to DOT regula-
tions. Also, waste data sheets (forms) that are used prior to discharge of any-
waste at a disposal operation may be available. These types of information
are helpful in evaluating a waste or planning provisions for personnel and
environmental safety during storage and handling of the waste at the facility.
3.2.3 Additional Information Sources
Additional information relevant to hazardous waste incineration can be obtained
by contacting the following sources.-
A. EPA regional offices.-
Region I
John F. Kennedy Federal Building
Room 2203
Boston, MA 02203 ,
Telephone: (617) 223-7210
Region II F
26 Federal Plaza, Room 1009
New York, NY 10007
Telephone: (212) 264-2525 j f
I l
Region III 1
Curtis Building M
6th & Walnut Streets ^
Philadelphia, PA 19106
Telephone: (215) 597-9814
Region IV
345 Courtland Street, NE
Atlanta, GA 30308 I
Telephone: (404) 881-4727 fc
Region V t
230 S. Dearborn Street J
Chicago, IL 60604
Telephone: (312) 353-2000
Region VI »
First International Building
1201 Elm Street
Dallas, TX 75270
Telephone: (214) 767-2600
Region VII
1735 Baltimore Street '
Kansas City, MO 64108
Telephone: (816) 374-5493
3-2
-------
Region VIII
1860 Lincoln Street
Denver, CO 80203
Telephone: (303) 837-3895
Region IX
215 Fremont Street
San Francisco, CA 94105
Telephone: (415) 556-2320
Region X
1200 6th Avenue
Seattle, WA 98101
Telephone: (206) 442-1220
B. Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
5555 Ridge Avenue
Cincinnati, OH 45268
Telephone: (513) 684-4303
C. Office of Solid Waste
U.S. Environmental Protection Agency i
401 M Street, SW j'
Washington, DC 20460 |
Telephone: (202) 755-9206 .
D. State Environmental Protection Departments
Table 3-1 can also be consulted relative to RCRA Section 3001 hazardous wastes
and other hazardous wastes which are good, potential, or poor candidates for
incineration with appropriate incineration technologies, based on technical
considerations. This table was prepared using available background documents
for some of the listed waste, trial burn data, and engineering judgment based
on chemical fonnula(s) of compound(s) present in the waste. The following
criteria were used to structure engineering judgment:
Waste containing Incineration category
• Carbon, hydrogen, and/or oxygen Good
• Carbon, hydrogen, <30% by weight chlorine and/or
oxygen Good
• Carbon, hydrogen, and/or oxygen, >30% by weight
chlorine, phosphorus, sulfur, bromine, iodine,
or nitrogen Potential
• Unknown percent of chlorine Potential
• Inorganic compounds Poor
• Compounds containing metals Poor
Other factors to be considered in evaluating waste for incineration are:
3-3
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3-15
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3-18
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i
3-19
-------
• Moisture content
• Potential pollutants present in incinerator effluents
• Inert content
• Heating value and auxiliary fuel requirements
• Potential health and environmental effects
• Physical form
• Corrosiveness
• Quality
• Known carcinogenic content
• PCB content.
Table 3-1 should be used with caution. The information is indicative rather
than conclusive. Conclusive decisions can be made only after studying the
actual physical, chemical, and thermodynamic characteristics of the material(s)
along with trial burn data (if available), and comparing expected behavior with
the known behavior of a similar material (similar composition or physical,
chemical, and thermodynamic characteristics) undergoing thermal destruction.
The incineration technology ratings in Table 3-1 are influenced by the physi-
cal form of the waste. In general, liquid wastes can be incinerated by a
liquid injection incinerator, rotary kiln, or fluidized bed incinerator.
Waste in gas, liquid, solid, and mixture forms can be incinerated by either
a rotary or fluidized bed incinerator. The kinematic viscosity of the liquid
waste has to be considered in determining its suitability for incineration
by liquid injection incinerators.
I
Liquid injection, and rotary kiln incinerators are widely used to dispose of
hazardous wastes. There is substantial research going on fluidized bed inciner-
ators and they appear to be promising in disposing of hazardous wastes.
Multiple hearths and multiple chambers incinerators have moderate applicability
for incineration of hazardous wastes. They are widely used for the destruction
of solids (municipal refuse) and sludges (sewage sludges). If the ash resulting
from incineration of a waste is fusible, multiple hearths incinerators are
not well suited for its disposal. Multiple hearth incinerators are not capable
of operating at elevated temperatures - so that if a temperature over 2000°F
is needed for destruction, multiple hearths incinerators are not applicable.
Multiple hearths and multiple chambers incinerators have limited applicability
to hazardous wastes, so they are not included in Table 3-1.
It may be possible to blend different wastes or wastes and fuel oils to change
poor or potential candidates into good candidates for incineration. Such
blending may also change the characteristics of a waste, making it incinerable
in a different incineration type than is identified in Table 3-1. It is also
possible that soae wastes identified in Table 3-1 as good or potential candi-
dates may turn out to be poor candidates for incineration if mixed with or
contaminated by poor incineration candidates like metals (arsenic, chromium,
etc.). Therefore, such factors as blending and waste contamination should
be considered on a case-by-case basis in making decisions. As mentioned
earlier, Table 3-1 should be used with caution for indicative guidance rather
than conclusive decisions.
3-20
-------
3.3 WASTE SAMPLING [9]
It is important that a representative sample of the waste be collected and
properly handled in determining waste characteristics. Sampling situations
vary widely and therefore no universal sampling procedure can be recommended.
However, it is important to incorporate quality assurance procedures as necessary
components in any waste sampling plan.
Sampling procedures require a plan of action to maximize safety of sampling
personnel, minimize sampling time and cost, reduce errors in sampling, and
protect the integrity of the samples after sampling. The following steps are
essential in this plan of action:
1. Prior to collecting a sample, check the manifest to see whether dangerous
emissions can be expected and to make sure that what is sampled resembles
what is described in the manifest.
2. Ask the generator for background information on the waste.
3. Determine what should be sampled (truck, barrel, pond, etc.).
4. Select the proper sampler (Coliwasa, scoop, bucket, etc.).
5. Select the proper sample container and closure (glass, plastic, etc.). I
6. Design an adequate sampling plan that includes the following:
(a) Choice of the proper sampling point, (b) Determination of the number
of samples to be taken, (c) Determination of the volumes of samples to be
taken.
7. Observe proper sampling precautions (safety of personnel, protective
gear).
8. Handle samples properly (sample preservation).
9. Identify samples and protect then from tampering.
10. Record all sample information in a field notebook.
11. Fill out chain of custody record.
12. Fill out sample analysis request sheet.
13. Deliver or ship the samples to the laboratory for analysis.
Various samplers and their applicabilities; sample containers and their com-
patibility with wastes; sampling points, number of samples and sample volume
requirements,- personnel protective gear and other safety precautions; sample
preservation requirements; sampling procedures for various situations; and
sample handling (labeling, field logging, chain of custody, analysis request
form and sample shipping) are discussed in detail in "Samplers and Sampling
3-21
-------
Procedures for Hazardous Waste Streams" (EPA-600/2-80-018, January 1930).
This source can be consulted prior to sampling.
Chain of custody procedures recommended by EPA's National Field Investigation
Center are described below:
1. The laboratory director designates one full-time employee (usually the
laboratory supervisor) as a sample custodian and one other person as an
alternate. In addition, the laboratory sets aside a "sample storage
security area." This is a clean, dry, isolated room which can be
securely locked.
2. All samples are handled by the minimum number of persons.
3. All incoming samples are received only by the custodian or, in his absence,
the alternate, who indicates receipt by signing the sample transmittal
sheets and, as appropriate, sample tags, accompanying the samples and re-
taining the sheets as permanent records.
I
4. Immediately upon receipt, the custodian places the sample in the sample
room, which is locked at all times except when the samples are removed or
replaced by the custodian. To the maximum extent possible, only the
custodian is permitted in the sample room.
5. The custodian ensures that heat-sensitive or light-sensitive samples, or
other sample materials having unusual physical characteristics, or
requiring special handling, are properly stored and maintained.
6. Only the custodian, or in his absence, the alternate, distributes samples
to, or divides them among, personnel performing tests. The custodian
enters into a permanent log book the laboratory sample number, tine and
date, and the name of the person receiving the sample. The receiver also
signs the entry.
7. Laboratory personnel are then responsible for the care and custody of the
sample until analytical tests are completed. Upon completion of tests un-
used portion of the sample together with all identifying tags and labora-
tory records are returned to the custodian, who records; the appropriate
entries in the log book. These, and other records are retained as
appropriate.
8. The analyst records in his laboratory notebook or worksheet the name of
the person from whom the sample was received, whether it was sealed, iden-
tifying information describing the sample (by origin and sample identifi-
cation number), the procedures performed, and the results of the testing.
If deviations from approved analytical procedures occur, the analyst is
prepared to justify this decision under cross-examination. The notes are
signed and dated by the person performing the tests. If that person is not
available as a witness at time of trial the government may be able to
introduce the notes in evidence under the Federal Business Records Act.
3-22
-------
Samples, tags, and laboratory records of tests may be destroyed only upon the
written order of the laboratory director, who ensures that this information is
no longer required.
The Field Sampling Chain of Custody Form should be completed by the field
sampling team and included with the shipping container when sent to the con-
tractor's laboratory. A separate form should be included with each box of
samples, listing the samples contained in that box. A sample of a completed
form is included for reference (Figure 3-1).
A copy of chain of custody procedures can be obtained by contacting:
National Field Investigation Center
U.S. Environmental Protection Agency
Denver Federal Center
Building #53, Box 25227
Denver, Colorado 80225
Telephone: (303) 234-4650
Other reference materials that can be consulted before developing a sampling
plan are listed below.
1. Sampling petroleum and petroleum products; Method ASTM D270. j.
2. Sampling industrial chemicals; Method ASTM E300. »
3. Benedetti-Pichler, A. A. Theory and principles of sampling for chemical
analysis. In: Walfer, E. J.; and Bell, G., eds. Physical methods in
chemical analysis, Vol. 3. New York, Academic Press, Inc., 1956.
4. Preparing coal samples for analysis; Method ASTM 02013.
5. Sampling coke for analysis,- Method ASTM D345.
6. Guidelines establishing test procedures for the analysis of pollutants,
proposed regulations. Federal Register. 44(233).-69464-69575, 1979
December 3.
7. Procedures for level 2 sampling and analysis of organic materials.
Research Triangle Park, NC; U.S. Environmental Protection Agency;
1979 February. 164 p. EPA-600/7-79-033.
8. Test Methods for Evaluating Solid Waste - Physical/Chemical Methods,- SW-
646-1980.
9. Hazardous Waste and Consolidated Permit Regulations, Federal Register.
45(98):33063-33285. 1980 May 19.
3.4 BASIC ANALYSIS OF WASTE [10, 12]
This section discusses the basic physical and chemical information about a
waste that may be required in determining its feasibility for incineration and
3-23
-------
FIELD SAMPLING CHAIN CT CUSTODY FORM
LEADER HAMZ OF SURVEY OH ACTIVITY DATE OF COLLECTION SHEET
Melvin Priority Pollutant Survty 523.10 9/12/84 1 of 1
DESCRIPTION OF SHIPMENT
TYPE OF SAMPLE Mater S«^l««
TOTAL NUMBER SAMPLE CONTAINERS 10 _
COK7EKTS OF SHIPMENT |
FIELD NO. OF CONTAINERS/TIELD NO. AMALYSE5 REQUIRED - CHECK WHERE APPROPRIATE
SAMPLE NO. PLASTIC GLASS VOA CYANIDE PHENOLS ASBESTOS PESTICIDES METALS VOA SEMI-
0876 1 /
0895 2 /
1992 1 /
3862 1 • /
3812 3 /
6413 1 /
6863 1
PERSONNEL CUSTODY RECORD
RELINQUISHED BY (SAMPLER) HECZrVZD BY DATE TIME REASON
H. Mclvin H»rpy Aitlin.i 10/1/84 1600 DcUvvry to l«b
DNSEALEP X SEALED UMSEALED _
_
RELINQUISHED BY RECEIVED BY DATE TIME REASON
AirUn« _ V«ndor _ 10/3/84 _ 900
Figure 3-1. Field sampling chain of custody form.
3-24
-------
its compatibility for a given incineration facility and in designing an
incineration facility. Basic hazardous waste data helpful in selecting an
incineration system are as follows:
• Type(s) of waste: Physical form - liquid, gas, solid, or
mixture
• Ultimate analysis: C, H, 0, N, S, P, Cl, F, Br, I, ash,
moisture
• Heating value: Btu/lb
• Solids.- Size, form, and quantity
• Liquids: Viscosity as a function of temperature, specific gravity
• Sludges: Density, viscosity, and percent solids
• Slurries: Density, viscosity, and percent solids
• Gases: Density
• Special characteristics: Toxicity, corrosiveness, and |.
other unusual features I
• Disposal rate: Peak, average, and minimum (present and
future)
* Trace metals: As, Ba, Cd, Cr, Pb, Hg, Se, Ag
• Major organic compound groups.- e.g., aroma tics, aliphatics, etc.
It may not be necessary to follow the complete, elaborate analysis protocol
for each shipment of waste from the same source, unless the material is entire-
ly different from earlier shipments. How often the shipments should be sampled,
and for what parameters samples should be analyzed, should be determined on a
case-by-case basis using best engineering judgment by the user of this
handbook.
In matching different wastes with commercial incineration facilities, the
physical form (solid, liquid, etc.) of the wastes is very important. The
criteria used for matching different wastes to the various incineration
facilities are:
(1) Physical form:
Gas, liquid, slurry, sludge, or solid
(2) Temperature range required for destruction:
(a) >2,000°F (>1,087°C)
(b) 1,400-2,000°F (757-1,087°C)
(c) 700-1,400°F (367-757°C)
(d) <700°F (<367°C)
3-25
-------
(3) Off-gases:
(a) Essentially oxides of carbon and nitrogen, and
water vapor
(b) Halogen, sulfur, phosphorus or volatile metal
species
(4) Ash:
Nonfusible, fusible, or metallic
(5) Heating value:
(a) 10,000 Btu/lb (>23 MJ/kg)
(b) 5,000-10,000 Btu/lb (12-23 MJ/kg)
(c) 5,000 Btu/lb.(<12 MJ/kg)
Liquid injection, fluidized bed, and rotary kiln incinerators are widely used
to dispose of hazardous waste. A particular incinerator may be better suited
for incineration of a particular type of waste based on the physical character-
istics of the waste. Solids, sludges, and slurries of high viscosity liquids
can be disposed in rotary kiln or fluidized bed incinerators, but not in a
liquid injection incinerator. If the ash resulting from the incineration of a
waste is fusible, fluidized bed incinerators are not well suited for its
disposal. Furthermore, fluidized bed incinerators are not capable of opera- f-
ting at elevated temperatures, so if a temperature over 2,000°F (1,087°C) is I
needed for destruction, rotary kilns or liquid injection incinerators are
applicable. Fluidized bed incinerators are generally not operated at temperatures
above 1,500°F.
The percentages of carbon, hydrogen, oxygen, nitrogen, sulfur, halogens, and
phosphorus in the waste, as well as its moisture content, need to be known to
calculate stoichiometric combustion air requirements and to predict combustion
gas flow and composition. The presence of halogenated and sulfur-bearing
waste can result in the formation of HC1, HF, H2S, and SOa in the incinerator
gases. These must be removed with suitable scrubbing equipment before dis-
charge to the atmosphere. Also, in the incineration of organic wastes contain-
ing chlorine, sufficient hydrogen should be provided by either the waste or
auxiliary fuel for the chlorine to form HC1 and not C12. Nitrogen oxides are
produced during high temperature combustion by reaction between nitrogen and
oxygen in the air. Their formation can be reduced by reducing combustion
temperature or excess air, but such controls may cause the formation of other
pollutants. Nitrogen content of waste material is generally low, but the
presence of nitrogen-containing materials (nitrates, ammonium compounds, etc.)
can greatly increase the NO emissions.
A
Trace metals (arsenic, barium, cadmium, chromium, mercury, lead, selenium, and
silver) are a potential cause for concern in incinerator emissions. Analyses
for them should be performed unless it is known that they are or are not
present in the waste. Wastes containing significant amounts of metals will
generally be poor candidates for incineration. Such wastes will require
postcombustion emission control of a special type, and the effluent or solid
waste from the emission control device must in turn be treated as a hazardous
3-26
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waste, although considerably reduced in volume and weight from the original
hazardous waste.
Ash content of the waste should be determined to evaluate the potential for
excessive slag formation as well as potential particulate emissions from the
incinerators. Kinematic viscosity and the size and concentration of solids in
a liquid waste are the most important physical properties to consider in
evaluating a liquid waste incinerator design. The physical handling system
and burner atomization techniques are dependent on viscosity and solid content
of the waste. Chemically complex .sludges may contain such elements as Na, K,
Mg, P, S, Fe, Al, Ca, Si, 02, N2, C and H2. Several chemical reactions can be
expected to take place in the high temperature oxidizing atmosphere of an
incineration operation of chemically complex sludges. Resulting ash may
contain Na2S04, Na2C03/ NaCl, etc. Pure Na2S04 has a melting point of
1,623°F. Pure Na2C03 has a melting point of 1,564°F. However, mixtures of
these two compounds have melting points lover than either one of the two by
themselves. At 47% Na2S04 - 53% Na2C03, the melting point is 1,552°F. Sodium
chloride has a melting point of 1,472°F. In combination with Na2C03, sodium
chloride will lover the melting point of the mixture. At 62 mole % Na2C03,
the eutectic melting point is 1,172°F. Likewise, mixtures of NaCl and Na2S04
form low melting mixture with the eutectic melting point of 1,154°F for a 65
mole % Na2S04 mixture. When all three of these compounds are present, a
mixture melting point as lov as 1,134°F is possible. So sludges containing j.
substantial amounts of sodium can cause defluidization of fluidized bed by |
forming lov melting eutectic mixtures. Furthermore, if the particles of the.*
fluidized bed are silica-sand,- Na2S04 vill react with the silica to form a
viscous sodium-silicate glass, vhich vill cause rapid defluidization.
The heating value of a vaste corresponds to the quantity of heat released when
the vaste is burned, commonly expressed as Btu/lb. It should be considered in
1 establishing an energy balance for the combustion chamber and in assessing the
need for auxiliary fuel firing. As a rule of thumb, a minimum heating value
| of about 8,000 Btu/lb is required to sustain combustion.
t
Special characteristics of the vaste such as extreme toxicity, mutagenicity or
( carcinogenicity, corrosiveness, fuming, odor, pyrophoric properties, thermal
instability, shock sensitivity, and chemical instability should also be con-
sidered in incinerator facility design. Thermal or shock instability are of
particular concern from a combustion standpoint, since vastes with these
properties pose an explosion hazard. Other special properties relate more
directly to the selection of vaste handling procedures and air pollution
control requirements.
Chapter 4 discusses detailed procedures for evaluating the design and compati-
bility of incinerators vith the basic physical, chemical, and thermodynamic
properties of the vaste.
1 3.5 SUPPLEMENTAL ANALYSIS OF WASTE
In addition to its basic analysis, supplemental analysis of vaste to identify
and quantify its major chemical components vill be helpful in evaluating vaste
for incineration. This information vill help to determine whether or not the
3-27
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waste is similar to others that have been successfully incinerated previously,
in a similar facility or in the existing facility. The necessary supplemental
information may be available from sources described in Section 3.2. For
example, the waste generator may have previously analyzed the waste stream or
may have a sufficiently thorough understanding of the process generating the
waste to adequately characterize it.
The supplemental analyses that may be necessary to determine whether a waste
can be effectively incinerated and/or whether a trial burn is required are the
following:
• Level 1 organic analysis
• Specific organic analysis
• Trace metal scan
• Thermal decomposition unit analysis
3.6 ANALYSIS TEST METHODS
All the physical, chemical, and thermodynamic analyses of the waste should be
conducted following ASTM, EPA, or EPA-sponsored equivalent methods. The Hay
19, 1980 Federal Register (pages 33130 and 33131) identifies approved measure-
ment techniques for each organic chemical and inorganic species (heavy metals)
listed in Section 3001 of RCRA (May 19, 1980 Federal Register). Additional
reference materials that can be consulted for analytical guidance are listed
below:
1. ASTM books.
2. Test methods for evaluating solid waste. Washington, DC; U.S. Environ-
mental Protection Agency; 1980 May. EPA SW-846.
3. Lentzen, D. E.; Wagoner, D. E.,- Estes, E. D.; and Gutfcnecht, W. F.
IERL-RTP procedures manual: level 1 environmental assessment, second
edition. Research Triangle Park, NC; U.S. Environmental Protection Agency;
1978 October. 279 p. EPA 600/7-78-201.
4. Guidelines establishing test procedures for the analysis of pollutants,
proposed regulations. Federal Register. 44(233):69464-69575, 1979
December 3.
5. Procedures for level 2 sampling and analysis of organic materials.
Research Triangle Park, NC; U.S. Environmental Protection Agency;
1979 February. 164 p. EPA-600/7-79-033.
6. Standard methods for the examination of water and wastewater, 14th ed.
Washington, American Public Health Association, 1976. 1193 p.
7. Methods for chemical analysis of water and wastes. Cincinnati, OH;
U.S. Environmental Protection Agency; 1979 March. 463 p.
EPA-600/4-79-020.
I
3»28
-------
8. Hauser, R.,- and Cummins, R. L. Increasing sensitivity of 3-methyl-2-
benzothiazolone hydrazone test for analyses of aliphatic aldehydes in
air. Analytical Chemistry. 56:679, 1964.
9. Kraak, J. C.,- and Huber, J. F. K. Separation of acidic compounds by
high-pressure liquid-liquid chromatography involving ion-pair formation.
Journal of Chromatography. 102:331-351, 1974.
10. Smythe, L. E. Analytical chemistry of pollutants. In: Bockris, J.
O'M., ed. Environmental chemistry. New York, Plenum, 1977.
Thermal decomposition unit analysis is briefly discussed in Section 3.7.
3.7 THERMAL DECOMPOSITION UNIT ANALYSIS [11]
In the interest of safety, it may be necessary that knowledge of the thermal
decomposition properites of a toxic organic substance be obtained before
large-scale incineration is conducted.
In response to this need, a laboratory system has been designed and assembled
by the University of Dayton Research Institute (UDRI) under EPA sponsorship.
This thermal decomposition analytical system (TDAS) is a closed, continuous
system which consists of a versatile thermal decomposition unit followed by |
in-line dedicated gas chromatograph-mass spectrometer-data handling computer I*
(GC-MS-COMP). The objective of this laboratory system is to provide fundamen-
tal thermal decomposition data on a wide variety of organic materials - gases,
liquids, and solids (including polymers).
Thermal decomposition tests were conducted with the TDAS on polychlorinated
biphenyls (PCB's) and on "Hex" wastes. The PCB's were found to have high
thermal stability in air. Furthermore, in oxygen-deficient atmospheres their
thermal stability is increased by at least 390°F (200°C) over that experienced
in air. Several chlorinated, aromatic compounds were still present after
exposure to 1,470°F (800°C). Further increases in temperature to 1,830°F
(1,000°C) decomposed all compounds except for low levels of hexachlorobenzene.
Figures 3-2, and 3-3, illustrate decomposition of hexachlorobiphenyl in air,
decomposition of pentachlorobiphenyl in different gaseous atmospheres, respec-
tively. Figure 3-4 shows the relative concentration of hexachlorobenzene in
"Hex" wastes after different thermal exposures.
The UDRI thermal decomposition analytical system, decomposition experiments,
resulting test data and their interpretation are discussed in detail in Appen-
dix E. Also, the following articles can be consulted for more information on
TDAS .-
1. Rubey, W. A. Design consideration associated with the development of a
thermal decomposition analytical system (TDAS). Dayton, OH; University
of Dayton Research Institute; 1979 May. Technical Report UDR-TR-79-34
(EPA Grant No. R805 117-01-0).
3-29
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LO
0.1
INI
TETtAOUmOtiBC
LOGO
OPOSUft 1WWAJWK. *C
Figure 3-2. Decomposition of hexachlorobiphenyl [11]
uo
LI
Oil
o so
SOD JM too ao m BO
Figure 3-3. Decomposition of pentachlorobiphenyl in
different gaseous atmospheres [1.1].
3-30
-------
200
2 150
M
3*
5"
UJ
oc
100
50
100 200 300
400
500 600 700 800 900
Figure 3-4.
EXPOSURE TEMPERATURE, °C
Relative concentration of hexachlorobenzene in
"Hex" wastes after different thermal exposures.
J
2. Duvall, D. 5.; Rubey, W. A.,- and Mescher, J. A. High temperature decom-
position of organic hazardous waste. Treatment of hazardous waste, pro-
ceedings of the sixth annual research symposium. Cincinnati, OH; U.S.
Environmental Protection Agency; 1980 March, p. 121-131. EPA-600/9-80-011.
The temperature, residence time, and oxygen required to destroy a given waste
by incineration can be determined by thermal decomposition unit analysis or by
a pilot- or full-scale trial burn. It is not necessary to generate tempera-
ture, residence time, and oxygen requirement data for wastes for which such
data already exist. Trial burn data for some wastes are presented in Appendices F
and G.
3.8 WORK SHEET
The work sheet presented in this section is designed to help evaluate a waste
for incineration in light of the information presented in this chapter for
waste characterization.
WORK SHEET
1. Background Information
• Is background information available and known?
• Is the SIC code of the waste generating source
known?
Yes No*
3-31
-------
Yes No*
• Does the waste fall into an EPA hazardous
waste classification?
• If the waste falls into an EPA hazardous waste
classification, is the EPA hazardous waste
number known?
• Any special characteristics of the waste known?
• Are principal waste components and their per-
centages known?
• Is the detail of the process generating the
waste known?
• Is the waste hazard class according to DOT
regulations known?
2. Waste Sampling
• Is the waste sampled with a compatible sampling
device?
• Is the waste collected in a compatible sample
container?
• Was sampling plan adequate to collect repre-
sentative samples (determination of sampling
points, number of samples, and samples'
volumes)?
• Were the samples properly handled (preserva-
tion, labeling, and shipping)?
• Was pertinent information adequately recorded
in the field log book?
• Were the chain of custody procedures recom-
mended by EPA's National Field Investigation
Centers followed?
3. Basic Analysis Information
• Are data for specific basic analysis known?
- Physical state of waste at 25°C
- Single phase
- Multiphase
- Vapor pressure
- Viscosity
- Specific gravity
- Melting point
- Boiling point
- Flash point
- Solids (size, form, and quantity)
3-32
_ _|
-------
Yes No*
- pH
- Trace metals (As, Ba, Cd, Cr, Hg, Pb, Se, Ag)
- Net heating value
- Elemental analysis (C, H, 0, N, S, P, Cl, F, Br, I)
- Ash content
- Moisture content
- PCB's
- Presence of
Carcinogen
Pesticide
Odor
- Toxicity
Ingestion
Inhalation
Dermal
Eyes
- Reactivity
- Fire hazard
- Radioactivity
4. Supplemental Analysis Information I.
• Are the major chemical components of the waste and their J
percentages known? .
• If waste is known or suspected to contain potentially
hazardous metals other than those listed in basic analysis
information, are their percentages known?
• Has the waste been tested for thermal decomposition analysis?
• Are the temperature and residence time necessary for destruc-
tion as determined by IDAS known?
• Are any principal hazardous particle decomposition products
identified by IDAS?
• Has the waste been incinerated before and, if so, in what
type of incineration technology?
5. Other Information
• Are past disposal practices for the waste known?
• Are any other wastes similar to the one under consideration
known for good or potential incineration?
• Has the proposed facility and/or technology been used before
to destroy a similar or like waste?
• Are waste generation rates (i.e., peak, average, and niniaua)
known (present and future)?
• Are there any trial burn data available for the waste?
3-33
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Yes No'
• Are any potential health and environmental effects of the
waste known?
6. Waste Incineration Decision
• Can a decision be made about waste incineration with the
available information about the waste and information
available from this chapter and Chapter 4?
• If answer is no to the above question, will any additional
waste characterization information help to make a decision
about waste incineration?
• If answer is no to the above question, will a trial burn
be necessary?
*Any response in the "No" column may indicate the possibility that the informa-
tion provided is not sufficient for a decision, and additional information
may be required.
3-34
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3.9 REFERENCES
1. Hazardous waste and consolidated permit regulations. Federal Register.
45(98):33121-33133; 1980 May 19.
2. Assessment of industrial hazardous waste practices: leather tanning and
finishing industry. Washington, DC; U.S. Environmental Protection Agency,-
1976 November. 233 p. EPA SW-131C.
3. Assessment of hazardous waste practices in the petroleum refining industry.
Washington, DC; U.S. Environmental Protection Agency,- 1976 June. 353 p.
EPA SW-129C.
4. Assessment of industrial hazardous waste practices: paint and allied
products industry, contract solvent reclaiming operations, and factory
application of coatings. U.S. Environmental Protection Agency; 1976.
EPA SW-119C.
5. Alternatives for hazardous waste management in the organic chemical,
pesticides and explosives industries. Cincinnati, OH; U.S. Environmental
Protection Agency; 1977. EPA SW-151C.
6. Assessment of industrial hazardous waste practices: electronic components
manufacturing industry. Washington, DC; U.S. Environmental Protection I
Agency; 1977 January. 207 p. EPA SW-140C. '
7. Assessment of industrial hazardous waste practices: special machinery
manufacturing industries. Washington, DC; U.S. Environmental Protection
Agency; 1977 March. 328 p. EPA SW-141C.
8. Background document, Resource Conservation and Recovery Act; Subtitle C
-Identification and listing of hazardous waste; Section 261.31 and 261.32 -
Listing of hazardous wastes. Washington, DC; U.S. Environmental Protec-
tion Agency; 1980 May 2.
9. Sampling and sampling procedures for hazardous waste streams. Cincin-
nati, OH; U.S. Environmental Protection Agency; 1980 January. 78 p.
EPA-600/2-80-018.
10. Hazardous material incineration design criteria. Cincinnati, OH; U.S.
Environmental Protection Agency; 1979 October. 110 p. EPA-600/2-79-198.
11. Duvall, D. S.; Rubey, W. A.,- and Mescher, J. A. High temperature decom-
position of organic hazardous waste. Treatment of hazardous waste, pro-
ceedings of the sixth annual research symposium. Cincinnati, OH; U.S.
Environmental Protection Agency; 1980 March, p. 121-131. EPA-600/9-80-011
12. Becker, K. P.; and C. J. Wall. Waste treatment advances: Fluid bed
incineration of wastes. Chemical Engineering Progress. 72:61-68, 1976
October.
3-35
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CHAPTER 4
INCINERATOR AND AIR POLLUTION CONTROL
SYSTEM DESIGN EVALUATION
4.1 INTRODUCTION
This chapter presents engineering calculations and general "rules of thumb"
that can be used to determine whether or not incinerator and air pollution
control system design and operating criteria are consistent with good industry
practice and sufficient to meet current emission standards. The evaluation
procedures are intended to determine if (1) the physical, chemical, and thenno-
dynamic properties of the waste have been properly considered in the incinera-
tor and air pollution control device design,- (2) the basic design considera-
tions for these units have been addressed; (3) acceptable temperatures,
residence times, oxygen concentrations, and mixing can be achieved and main-
tained in the incinerator,- (4) air pollution control system design and operat-
ing criteria are in line with current industry practice and the desired degree
of pollutant removal; (5) various components of the incinerator, air pollution
control, and gas handling systems have sufficient capacity to handle the
quantities of waste to be burned; (6) the design incorporates process control
and automatic shutdown capability to minimize the release of hazardous material
in the event of equipment malfunction,- and (7) appropriate materials of con-
struction are used.
Evaluation procedures are presented for two generic types of incinerators and
three generic types of air pollution control devices: liquid injection incin-
erators, rotary kiln/afterburner incinerators, venturi scrubbers, packed bed
scrubbers, and plate (or tray) tower scrubbers. While liquid injection incin-
erators are used only for disposal of liquid organic wastes, rotary kilns
are used to dispose of both liquid and solid wastes. Venturi scrubbers are
primarily used for particulate control, while packed bed and plate tower
scrubbers are used for acid gas removal. It is believed that more than 90% of
the hazardous waste incineration facilities in the United States employ these
generic incinerator and air pollution control device designs. Electrostatic
precipitators may be used for particulate removal at large incineration
facilities. However, these devices are extremely difficult to evaluate from a
theoretical standpoint; a compliance test is usually needed to ensure accept-
able performance. If other types of incinerators and/or air pollution control
devices are being evaluated technical assistance can be requested.
Incinerator and air pollution control system evaluation procedures are pre-
sented in Sections 4.3 and 4.4, respectively. Section 4.5 presents worksheets
to simplify some of the calculations shown in 4.3 and 4.4.
4-1
-------
The following section, 4.2, describes how the destruction and removal effi- ™
ciency (DRE) of an incinerator/air pollution control system can be calculated
for the principal organic hazardous constituent(s) (POHC) of a waste. The
determination of how to designate POHC's is given in Section 2 of the Guidance
Manual for Evaluating Permit Applications for the Operation of Incinerator
Units. The current state-of-the-art in combustion modeling does not allow a
purely theoretical prediction of destruction and removal efficiency based on
design and operating parameters for the incinerator/air pollution control
system. Therefore, the DRE calculations presented in Section 4.2 cannot be
applied in preliminary design evaluation unless sampling and analysis data are
available. However, destruction and removal efficiency calculations are an
integral part of the final design evaluation process.
4.2 DESTRUCTION AND REMOVAL EFFICIENCY CALCULATIONS
4.2.1 Definition
Destruction and removal efficiency for an incinerator/air pollution control
system is defined by the following formula:
DRE = -*^ ~ (100) I-
in I
where DRE = destruction and removal efficiency, % ^
W. = mass feed rate of the principal organic hazardous constituent(s)
to the incinerator.
W = mass emission rate of the principal organic hazardous constit-
ou uent(s) to the atmosphere (as measured in the stack prior to
discharge.
Thus, DRE calculations are based on the combined efficiencies of destruction
in the incinerator and removal from the gas stream in the air pollution con-
trol system. The (potential) presence of principal organic hazardous
constituents in incinerator bottom ash or solid/liquid discharges from air
pollution control devices is not accounted for in the DRE calculation as
currently defined by EPA. Many previous trial burn tests determined only the
"destruction efficiency". These tests ignored the contribution of the pollu-
tion control devices.
Part 264, Subpart 0 regulations for hazardous waste incineration require a DRE
of 99.99% for all principal organic hazardous components of a waste unless it
can be demonstrated that a higher or lower DRE is more appropriate based on
human health criteria. Specification of the principal organic hazardous con-
stituents in a waste is subject to best engineering judgment, considering the
toxicity, thermal stability, and quantity of each organic waste constituent.
DRE requirements in the Subpart 0 regulations do not apply to metals or other
noncombustible materials.
4-2
-------
Destruction and removal efficiencies are normally measured only during trial
burns and occasional compliance tests, and are used as a basis for determining
whether or not the incinerator/air pollution control system operating condi-
tions are adequate. Sections 4.3 and 4.4 present design evaluation procedures
for incinerators and air pollution control devices that are based on state-of-
the-art engineering practice. However, any conclusions reached through these
evaluation procedures should be supported by trial burn data demonstrating
acceptable destruction and removal efficiency.
4.2.2 Sample Calculation
A liquid injection incinerator equipped with a quench tower, venturi scrubber,
and packed bed caustic scrubber has been constructed to burn a mixture of
waste oils and chlorinated solvents with the following empirical composition:
73.0 wt % carbon
16.5 wt % chlorine
10.5 wt % hydrogen
The principal organic hazardous components are trichloroethylene, 1,1,1-tri-
chloroethane, raethylene chloride, and perchloroethylene. Each of these com-
pounds constitutes about 5% of the total waste feed to the incinerator.
During a trial burn, the incinerator was operated at a waste feed rate of
5,000 Ib/hr and 50% excess air. The gas flow rate measured in the stack
19,200 dscfm. Under these conditions, the measured concentrations of the
principle organic hazardous components were:
Trichloroethylene - 4.9 ug/dscf
1,1,1-Trichloroethane - 1.0 pg/dscf
Methylene chloride - 49 ug/dscf
Perchloroethylene - 490 ug/dscf
In order to calculate destruction and removal efficiency for each of these
compounds using the equation,
•JL
DR£ = w (100)
in
it is necessary to calculate the mass flow of each component entering and
exiting the system. Because each hazardous component constitutes about 5% of
the waste and the total waste feed rate was 5,000 Ib/hr, W. for each compo-
nent is: in
Win ~ °-05 <5'000 l*/hr) = 250 Ib/hr
The mass flow rate of each component exiting the stack is then calculated by
the following equation:
4-3
-------
W . = C. X
out i
(19,200 dscfm) (60 min/hr)
4.54 x 10* pg/lb
where W = mass flow rate of component i exiting the stack, Ib/hr
C. = concentration of component i in the stack, gas, pg/dscf
Using this equation to calculate W for each component and the previously
cited equation for destruction and removal efficiency, the following results
are obtained:
Component
Trichloroethylene
1 , 1 , 1-Trichloroe thane
Methylene chloride
Perchloroethylene
Vf lb/hr
out ,
0.0124
0.00254
0.124
1.24
ORE, %
99.995
99 . 999
99.95
99.5
These results indicate that the required 99.99% destruction and removal effi-
ciency was achieved in the trial burn for trichloroethylenc and 1,1,1-tri- i
chloroethane, but not for methylene chloride and perchloroethylene. I
Worksheet #1 in Section 4.5 presents a generalized procedure for destruction
and removal efficiency calculations.
4.3 INCINERATOR EVALUATION
A logic diagram for evaluating both liquid injection and rotary kiln incinera-
tor designs and operating criteria is shown in Figure 4-1. It consists of six
separate evaluation procedures intended to answer the following questions:
• Are the basic incinerator components properly incorporated in the design?
• Have the physical, chemical, and thennodynamic properties of the waste
been properly considered in the incinerator design and proposed operating
conditions?
• Are the proposed temperature/excess air/residence time combinations
internally consistent and achievable? Can adequate turbulence and mixing
be achieved under these conditions?
• Is the auxiliary fuel firing capacity acceptable?
• Does the design incorporate suitable combustion process control and
safety shutdown interlocks?
• Are appropriate materials of construction employed?
Subsections 4.3.1 through 4.3.6 present background information and procedures
for answering questions.
4-4
-------
BASIC DESIGN
CONSIDERATIONS
SECTION 4.3.1
PHYSICAL, CHEMICAL, AND
THERMODYNAMIC WASTE
PROPERTY CONSIDERATIONS
SECTION 4.3.2
I
TEMPERATURE/EXCESS AIR7
RESIDENCE TIME/MIXING
EVALUATION
SECTION 4.3.3
I
AUXILIARY FUEL FIR ING
CAPACITY EVALUATION
SECTION 4.3.4
i
COMBUSTION PROCESS
CONTROL EVALUATION
SECTION 4.3.5
1
MATERIAL Of CONSTRUCTION
CONSIDERATIONS
SECTION 4.3.6
Figure 4-1. Incinerator design evaluation criteria.
4-5
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4.3.1 Basic Design Considerations
4.3.1.1 Liquid Injection Incinerators--
Liquid injection incinerators are usually simple, refractory-lined cylinders
(either horizontally or vertically aligned) equipped with one or more waste
burners. Liquid wastes are injected through the burner(s), atomized to fine
droplets, and burned in suspension. To heat the unit to operating temperature
before waste is introduced, however, all liquid injection incinerator designs
should also include an auxiliary fuel firing system. This may consist of
separate burners for auxiliary fuel, dual-liquid burners, or single-liquid
burners equipped with a premix system whereby fuel flow is gradually turned
down and waste flow is increased after the desired operating temperature is
attained. If auxiliary fuel firing is needed during routine operation the
same types of systems are needed: fuel/waste premix, dual-liquid burners, or
separate auxiliary fuel burners.
Each burner, regardless of type, is generally mounted in a refractory block or
ignition tile (see Figure 4-2 for an illustration). This is necessary to
confine the primary combustion air introduced through the burner, to ensure
proper air/waste mixing, and to maintain ignition. The shape of the ignition
tile cavity also affects the shape of the flame and the quantity of primary
air which must be introduced at the burner. Some burners and tiles are ar- t
ranged to aspirate hot combustion gases back into the tile, which aids in I*
vaporizing the liquid and increasing flame temperature more rapidly. J
* . BURNER BLOCK
SCANNED ru '
"Reproduced courtesy of Trane Thermal Company, Conshohocken, Pa."
Figure 4-2. High heat release burner for
combustion of liquid waste [1].
The dimensions of the burner block, or ignition tile, vary depending on the
burner design. Each manufacturer has his own geometrical specifications,
which have been developed through past experience. Therefore, it is not pos-
sible to specify a single burner block geometry for design evaluation purposes.
However, this aspect of the design can be checked to eliminate systems that do
not provide for any flame retention.
4-6
-------
The location of each burner in the incinerator and its firing angle, relative
to the combustion chamber, should also be checked. In axial or side-fired
nonswirling units, the burner is mounted either on the end firing down the
length of the chamber or in a sidewall firing along a radius. Such designs,
while simple and easy to construct, are relatively inefficient in their use of
combustion volume. Improved utilization of combustion space and higher heat
release rates can be achieved with the utilization of swirl or vortex burners
or designs involving tangential entry. Regardless of the burner location
and/or gas flow pattern, however,' the burner is placed so that the flame does
not impinge on refractory walls. Impingement results in flame quenching, and
can lead to smoke formation or otherwise incomplete combustion. In multiple
burner systems, each burner should be aligned so that its flame does not
impact on other burners.
Engineering judgment is used in predicting whether or not these undesirable
phenomena will occur with a specific incinerator design.
4.3.1.2 Rotary Kiln Incinerators--
To insure complete waste combustion rotary kiln incinerator designs normally
include an afterburner. The primary function of the kiln is to convert solid
wastes to gases, which occurs through a series of volatilization, destructive
distillation, and partial combustion reactions. However, an afterburner is
almost always required to complete the gas-phase combustion reactions. Tie
afterburner is connected directly to the discharge end of the kiln, wherejjy
the gases exiting the kiln turn from a horizontal flow path to a vertical-flow
path upwards to the afterburner chamber. The afterburner itself may be hori-
zontally or vertically aligned.
Both the afterburner and kiln are usually equipped with an auxiliary fuel
firing system to bring the units up to the desired operating temperatures. As
explained in Section 4.3.1.1 for liquid injection incinerators, the auxiliary
fuel system may consist of separate burners for auxiliary fuel, dual-liquid
burners designed for combined waste/fuel firing, or single-liquid burners
equipped with a premix system, whereby fuel flow is gradually turned down and
liquid waste flow is increased after the desired operating temperature is
attained.
If liquid wastes are to be burned in the kiln and/or afterburner, additional
considerations are:
• flame retention characteristics of the burners,
• burner alignment to avoid flame impingement on refractory walls, and
in multiple burner systems, burner alignment to avoid interference with
the operation of other burners.
These topics are discussed in Section 4.3.1.1 under liquid injection incinera-
tor evaluation.
One difference between liquid injection incinerators and rotary kilns burning
liquid wastes in conjunction with solids is that in the kiln liquid wastes may
4-7
-------
be fired either at the feed or discharge end of the unit. Cocurrent and
countercurrent firing designs are both widely used.
4.3.2 Physical, Chemical, and Thermodynamic Waste Property Considerations
4.3.2.1 Liquid Injection Incinerators--
Before a liquid waste can be combusted, it must be converted to the gaseous
state. This change from a liquid to a gas occurs inside the combustion cham-
ber and requires heat transfer from the hot combustion gases to the injected
liquid. To cause a rapid vaporization (i.e., increase heat transfer), it is
necessary to increase the exposed liquid surface area. Most commonly the
amount of surface exposed to heat is increased by finely atomizing the liquid
to small droplets, usually to a 40 pM size or smaller. Good atomization is
particularly important when high aqueous wastes or other low heating value
wastes are being burned. It is usually achieved in the liquid burner directly
at the point of air/fuel mixing.
The degree of atomization achieved in any burner depends on the kinematic
viscosity of the liquid and the amount of solid impurities present. Liquids
should generally have a kinematic viscosity of 10,000 SSU or less to be satis-
factorily pumped and handled in pipes. For atomization, they should have a
maximum kinematic viscosity of about 750 SSU. If the kinematic viscosity .
exceeds this value the atomization may not be fine enough. This may cause I*
smoke or other unburned particles to leave the unit. However, this is only |
rule of thumb. Some burners can handle more viscous fluids, while others
cannot handle liquids approaching this kinematic viscosity.
Viscosity can be reduced by heating with tank coils or in-line heaters. How-
ever, 400-500°F (200-260°C) is normally the limit for heating to reduce viscos-
ity, since pumping a hot tar or similar material becomes difficult above these
temperatures. Should gases be evolved in any quantity before the desired
viscosity is reached, they may cause unstable fuel feed and burning. If this
occurs, the gases should be trapped and vented safely, either to the incinera-
tor or elsewhere. Prior to heating a liquid waste stream, a check should also
be made to insure that undesirable preliminary reactions such as polymerization,
nitration, oxidation, etc., will not occur. If preheating is not feasible,
based on these considerations, a lower viscosity and miscible liquid may be
added to reduce the viscosity of the mixture; fuel oil for example.
Solid impurities in the waste can interfere with burner operation via plug-
gage, erosion, and ash buildup. Both the concentration and size of the solids,
relative to the diameter of the nozzle, need to be considered. As discussed
in Chapter 5, filtration may be employed to remove solids from the waste prior
to injection through the burner.
Liquid waste atomization can be achieved by any of the following means:
rotary cup atomization
• single-fluid pressure atomization
two-fluid, low pressure air atomization
two-fluid, high pressure air atomization
two-fluid, high pressure steam atomization
4-8
-------
In air or steam atomizing burners, atomization can be accomplished internally,
by impinging the gas and liquid stream inside the nozzle before spraying;
externally, by impinging jets of gas and liquid outside the nozzle; or by
sonic means (see Figures 4-3 through 4-5). Sonic atomizers use compressed gas
to create high frequency sound waves which are directed on the liquid stream.
The liquid nozzle diameter is relatively large, and little waste pressuriza-
tion is required. Some slurries and liquids with relatively large particles
can be handled,without plugging problems.
AIR OR
STEAM
MECHANICAL Ria TIP BODY , CONE FUME TIP
FINAL
SPRAY
STEAM MIXING
ORIFICES CHAMBER
"Reprinted by permission of Chemical Engineering Progress."
Figure 4-3. Internal mix nozzle [2J.
ATCM2ED
VV\\\\\\
\ \ \ \ \ N N \ I — »
uouc
"Reproduced courtesy of Trane Thermal Company, Conshohocken, Pa."
Figure 4-4. External mix nozzles [1].
The rotary cup consists of an open cup mounted on a hollow shaft. The cup is
spun rapidly and liquid is admitted through the hollow shaft. A thin film of
the liquid to be atomized is centrifugally torn from the lip of the cup and
surface tension reforms it into droplets. To achieve conically shaped flames
an annular high velocity jet of air (primary air) must be directed axially
around the cup. If too little primary air is admitted the fuel will impinge on
the sides of the incinerator. If too much primary air is admitted the flame
will not be stable and will be blown off the cup. For fixed firing rates, the
proper adjustment can be found and the unit operated for long periods of time
without cleaning. This requires little liquid pressurization and is ideal for
4-9
-------
onnuum
'o uouu
• MHC
Reprinted by permission of Fluid Kinetics, Inc.
Figure 4-5. Sonic atomizing nozzle [3].
atomizing liquids with relatively high solids content. Burner turndown is
about 5:1 and capacities from 1 to 265 gal/hr, (1-280 cm3/S) are available.
In single-fluid pressure atomizing nozzle burners, the liquid is given a swirl
as it passes through an orifice with internal tangential guide slots. Moder-
ate liquid pressures of 100-150 psi provide good atomization with low to
moderate liquid viscosity. In the simplest form, the waste is fed directly to
the nozzle but turndown is limited to 2.5 to 3:1 since the degree of atomizah
tion drops rapidly with decrease in pressure. In a modified form, involving a
return flow of liquid, turndown up to 10:1 can be achieved. .1
When this type of atomization is used, secondary combustion air is generally
introduced around the conical spray of droplets. Flames tend to be short,
bushy, and of low velocity. Combustion tends to be slower as only secondary
air is supplied and a larger combustion chamber is usually required.
Typical burner capacities are in the range of 10 to 105 gal/hr. Disadvantages
of single-fluid pressure atomization are erosion of the burner orifice and a
tendency toward pluggage with solids or liquid pyrolysis products, particu-
larly in smaller sizes.
Two-fluid atomizing nozzles may be of the low pressure or high pressure vari-
ety, the latter being more common with high viscosity materials. In low
pressure atomizers, air from blowers at pressures from 0.5 to 5 psig is used
to aid atomization of the liquid. A viscous tar, heated to a viscosity of
15-18 centistokes, requires air at a pressure of somewhat more than 1.5 psig,
while a low viscosity or aqueous waste can be atomized with 0.5 psig air. The
waste liquid is supplied at a pressure of 4.5-17.5 psig.. Burner turndown
ranges from 3:1 up to 6:1. Atomization air required varies from 370 to
1,000 ft3/gal of waste liquid. Less air is required as atomizing pressure is
increased. The flame is relatively short as up to 40% of the stoichiometric
air may be admixed with the liquid in atomization.
High pressure two-fluid burners require compressed air or steam at pressures
from 30 to 150 psig. Air consumption is from 80 to 210 ft3/gal of waste, and
steam requirements may be 2.1 to 4.2 Ib/gal with careful control of the oper-
ation. Turndown is relatively poor (3:1 or 4:1) and considerable energy is
4-10
-------
employed for atomization. Since only a small fraction of stoichiometric air
is used for atomization, flames tend to be relatively long. The major ad-
vantage of such burners is the ability to burn barely pumpable liquids without
further viscosity reduction. Steam atomization also tends to reduce soot
formation with wastes that would normally burn with a smoky flame.
Table 4-1 identifies typical kinematic viscosity and solids handling limita-
tions for the various atomization techniques. These data are based on a
survey of 14 burner manufacturers. In evaluating a specific incinerator
design, however, the viscosity and solids content of the wastes should be
compared with manufacturer specifications for the particular burner employed.
TABLE 4-1. KINEMATIC VISCOSITY AND SOLIDS HANDLING LIMITATIONS
OF VARIOUS ATOMIZATION TECHNIQUES
Atomization type
Rotary cup
Single-fluid pressure
Internal low pressure
air (<30 psi)
External low pressure air
Maximum
kinematic
viscosity,
SSU
175 to 300
150
100
200 to 1,500
Maximum solids
mesh size
35 to 100
200 (depends on
Maximum solids
concentration
20%
Essentially zero
Essentially zero
30% (depends on
nozzle ID) nozzle ID)
External high pressure 150 to 5,000 100 to 200 (depends 70%
air on nozzle ID)
External high pressure 150 to 5,000 100 to 200 (depends 70%
steam on nozzle ID)
A procedure for evaluating whether or not a given burner atomization technique
is suitable for the waste under consideration is presented in Table 4*2.
Chemical and thermodynamic properties of the waste that need to be considered
in incinerator design evaluation are its elemental composition, its net heat-
ing value, and any special properties (e.g., explosive properties) that may
interfere with incinerator operation or require special design considerations.
The percentages of carbon, hydrogen, oxygen, nitrogen, sulfur, halogens, and
phosphorus in the waste, as well as its moisture content, need to be known to
calculate stoichiometric combustion air requirements and to predict combustion
gas flow and composition . In these calculations, the following reactions are
assumed:
Air requirements, combustion gas flow, and gas composition form the basis
for many subsequent evaluation procedures.
4-11
-------
C + 02 " C02
H2 + 1/202 •* H20
H20 -» H20
N2 - N2
C12 + H20 - 2HC1 + 1/202
F2 + H20 •* 2HF + 1/202
Br2 •» Br2
I2 - I2
S + 02 •* S02
2P + 2.502 •» P205
TABLE 4-2. EVALUATION PROCEDURE FOR PHYSICAL WASTE
PROPERTY/ATOMIZATION TECHNIQUE COMPATIBILITY |.
1. Identify the atomization technique employed.
2. Identify the kinematic viscosity of the waste at the proposed injection
temperature.
3. Check Table 4-1 and/or burner manufacturer specifications to determine if
the waste viscosity and atomization technique are compatible.
4. Identify the solids content of the waste and the maximum size of the
particles (after pretreatment, if any).
5. Check Table 4-1 and/or burner manufacturer specifications to determine if
the solids content of the waste and the atomization technique are
compatible.
Table 4-3 shows the stoichiometric or theoretical oxygen requirements and com-
bustion product yields for each of these reactions. Once the weight fraction
of each element in the waste has been determined, the stoichiometric oxygen
requirements and combustion product yields can be calculated on a Ib/lb waste
basis. The stoichiometric air requirement is determined directly from the
stoichiometric oxygen requirement via the weight fraction of oxygen in air.
Of course, the reactions listed above are not the only ones that occur in com-
bustion processes. Carbon, carbon monoxide, free hydrogen, nitrogen oxides,
free chlorine and fluorine, hydrogen bromide and iodide, sulfur trioxide, and
4-12
-------
TABLE 4-3. STOICHIOMETRIC OXYGEN REQUIREMENTS
AND COMBUSTION PRODUCTS YIELDS
Elemental
waste
component
Stoichiometric
oxygen requirement
Combustion
product yield
C
H2
02
N2
H20
C12
Br2
S
P
Air N2
2.67 Ib/lb C
8.0 Ib/lb H2
-1.0 Ib/lb 02
-0.23 Ib/lb C12
-0.42 Ib/lb F2
1.0 Ib/lb S
1.29 Ib/lb P
3.67 Ib C02/lb C
9.0 Lb H20/Ib H2
1.0 Ib N2/lb N2
1.0 Ib H20/lb H20
1.03 Ib HCl/lb C12
-0.25 Ib H20/lb C12
1.05 Ib HF/lb F2
-0.47 Ib H20/lb F2
1.0 Ib Br2/lb Br2
1.0 Ib I2/lb I2
2.0 Ib S02/lb S
2.29 Ib P205/lb P
3.31 Ib N2/lb
Stoichiometric air requirement = 4.31 x (02)
stoich
hydrogen sulfide, among other'compounds, are also formed to some extent when
the corresponding elements are present in the waste or fuel being burned.
However, these combustion product yields are usually small in comparison to
the yields of the primary combustion products identified above, and need not
be considered in gas flow scoping calculations. (They do, however, need to be
considered to determine the potential products of incomplete combustion). For
most organic wastes and fuels, nitrogen, carbon dioxide, and water vapor are
the major combustion products. When excess air is factored into the combus-
tion gas flow, oxygen also becomes a significant component of the gas. Excess
air requirements are discussed in Section 4.3.3. Worksheet 4-2 can be used
to calculate the stack gas composition for major components, e.g., N2/ 02,
C02, HC1. S02.
Exceptions to the aforementioned combustion stoichioraetry can occur when
highly chlorinated or fluorinated wastes are being burned and insufficient
hydrogen is present for equilibrium conversion to the halide form. Since
hydrogen halides are much more readily scrubbed from combustion gases than
halogens themselves, sufficient hydrogen should be provided for this equili-
brium conversion to take place. If the waste itself contains insufficient
hydrogen, auxiliary fuel or steam injection is needed to supply the necessary
hydrogen equivalents. The Stoichiometric (absolute minimum) requirements are
1 Ib H2/ 35.5 Ib Clg and 1 Ib Hg/l9 Ib Fg in the waste.
Equilibrium between halogens and hydrogen halides in incinerator gases is
given by:
X2 + H20 = 2HX + 1/2 02
4-13
-------
where %2 represents any free halogen.
For chlorine, this expression becomes:
C12 + H20 = 2HC1 + 1/2 02
At equilibrium, the concentrations of C12, H20, HC1, and 02 in the combustion
gas (at essentially atmospheric pressure) is given by:
P "• (PC12)
where K = equilibrium constant
P. = partial pressure of ith component, atm
Figure 4-6 presents a plot of the equilibrium constant, K , vs. temperature
for the conversion of Clj to HCl. If the combustion temperature is known, K
can be identified from Figure 4-6 and the following equation can be used to P
predict the extent of conversion of C12 to HCl. 4
,i
-------
100
10
8
CO
1.0
0.1
1832°F
2732°F
3632°F
•180°F-
i i
tiii
1,000
1,500
2,000
TEMPERATURE ( C)
(P ) (P )l/2
th ^ ^
p (P ) (P )
ir Ir
Figure 4-6. Equilibrium constant versus temperature.
4-15
-------
is the quantity of heat needed to destabilize molecular bonds and create
reactive intermediates so that the exothermic reaction with oxygen will pro-
ceed. Figure 4-7 shows the general relationship between activation energy and
heating value.
u
OE
z
T
ACTIVATION
ENERGY
T
MEAT OF
COMBUSTION
1
KCACTION
Figure 4-7. Relationship between activation energy and heat of combustion.
Note.- The diagram is simplified in the sense that it shows a single activa-T
tion energy for the reaction. Reactions with more than one intermediate
have correspondingly more activation energy levels.
Waste heating values needed to sustain combustion without auxiliary fuel
firing depend on the following criteria:
• physical form of the waste (i.e., gaseous vs. liquid vs solid),
temperature required for refractory waste component destruction,
• excess air rate, and
• heat transfer characteristics of the incinerator.
In general, higher heating values are required for solids vs liquids vs gases,
for higher operating temperatures, and for higher excess air rates, if combus-
tion is to be sustained without auxiliary fuel consumption. Gases can sustain
combustion at heating values as low as 3,000 Btu/lb, while 4,500 to 5,500 Btu/lb
may be considered minimum heating value requirements for combustion of liquid
wastes in high efficiency burners [1]. Figures 4-8 and 4-9 illustrate the
relationship of adiabatic temperature to heating value for several levels of
excess air for liquid wastes and gaseous wastes, respectively. Higher heating
values are needed for solid wastes, but the requirements depend on particle
size, and thus, the area available for heat and mass transfer. In the hazard-
ous waste incineration industry, it is common practice to blend wastes (and
fuel oil, if necessary) to an overall heating value of 8,000 Btu/lb.
4-16
-------
o
UJ*
QC
ae.
UJ
a.
o
?
OD
O
PARAMETERS: % EX CESS AIR
2000 6000 10,000 14,000
HIGHER HEATING VALUE, Btu/lb
18,000
Figure 4-8. Adiabatic teapcrature of combustion gases
from typical liquid wastes [1].
4-17
-------
ac.
PARAMETERS: % EXCESS AIR
i i i i i t i i
200 400 600 800
HIGHER HEATING VALUE, Btu/lb
1000
Figure 4-9. Adiabatic temperature of combustion gases
from typical gaseous wastes [1].
4-18
-------
When an organic waste exhibits a low heating value, it is usually due to high
concentrations of moisture or halogenated compounds. Since water is an ulti-
mate oxidation product, it has no heating value. In fact, a portion of the
heat generated by combustion of the organic waste fraction is consumed in
vaporizing and heating the moisture up to incinerator temperature. Therefore,
an increase in the moisture content of an organic waste proportionately de-
creases the overall heating value on a Btu/lb waste basis.
The heating value of a waste also decreases as the chlorine (or other halogen)
content increases, although there is no simple mathematical relationship.
Figure 4-10 shows an empirical relationship between heating value and chlorine
content for pure substances. At chlorine contents of 70% or greater, auxil-
iary fuel is needed to maintain combustion. Auxiliary fuel may also be re-
quired for less highly chlorinated waste unless high efficiency burners are
used.
x araunca HSW.TS
f
W.ODO
1.000
"Reproduced courtesey of Trane Thermal Company, Conshohockon, Pa."
Figure 4-10.
Heat of combustion of chlo-
rinated hydrocarbons [4].
In hazardous waste incineration, it is common practice to blend wastes so that
the chlorine content does not exceed 30%. This is done to maintain sufficient
heating value for sustained combustion and to limit free chlorine
concentration in the combustion gas.
When heating value data are reported for a given waste, it is desirable to know
whether they are "higher heating values," "lower heating values," or "net heating
values." The difference between the higher heating value and lower heating value
of a material is that the higher value includes the heat of condensation of water
formed in the combustion reaction. The higher heating value of a material is
sometimes called its "gross heating value." In the combustion of methane, for
example, the higher heating value is based on the following stoichiometry:
where the subscripts g and i represent gaseous and liquid states, respectively.
The lower heating value is based on:
4-19
-------
CH<(g) + 2°2(g) * C°2(g) + 2H2°(g)
The net heating value of a waste is determined by subtracting from its lower
heating value the energy necessary to vaporize any moisture present in the
waste initially. Thus, high aqueous wastes may exhibit: a negative net heating
value. Since this quantity represents the true energy input to the combustion
process, only net heating values should be used in developing energy balances
for incinerators.
The heating value of a complex waste mixture is difficult to predict a priori.
Therefore, these values should be measured experimentally. Since healing
values measured using oxygen bomb calorimeters are higher heating values,
conversion to the net heating value is required for energy balance calcula-
tions. Worksheet 4-3 in Section 4.5 shows how this conversion is performed.
Approximate net heating values for common auxiliary fuels are:
Residual fuel oil (e.g., No. 6) - 17,500 Btu/lb
Distillate fuel oil (e.g., No. 2) - 18,300 Btu/lb
Natural gas - 19,700 Btu/lb (1,000 Btu/scf)
Special characteristics of a waste such as extreme toxicity, mutagenicity or
carcinogenicity, corrosiveness, fuming, odor, pyrophoric properties, thermali
instability, shock sensitivity, and chemical instability should also be con-r
sidered in incinerator facility design. Thermal or shock instability is of.}
particular concern from a combustion standpoint, since wastes with these '
properties pose an explosion hazard. Other special properties relate more
directly to the selection of waste handling procedures and air pollution
control requirements. If potentially explosive wastes are encountered, technical
assistance is advised.
Table 4-4 presents a procedure for chemical and thermodynamics waste property
evaluation.
4.3.2.2 Rotary Kiln Incinerators—
When liquid wastes are to be burned in the kiln or afterburner, the kinematic
viscosity of the liquid and its solids concentration and solids particle size
must be considered to determine whether or not good atomization can be achieved
with the proposed burner design. This subject is addressed in subsection 4.3.2.1
under liquid injection incinerator evaluation. The procedure outlined in
Table 4-2, along with the discussion preceding this table, can be used to
check physical waste property/burner compatibility for rotary kiln
incinerators burning liquid wastes.
Although liquid wastes are frequently incinerated in rotary kilns, kilns are
primarily designed for combustion of solid wastes. They are exceedingly
versatile in this regard, capable of handling slurries, sludges, bulk solids
of varying size, and containerized wastes. The only wastes that create prob-
lems in rotary kilns are (1) aqueous organic sludges that become sticky on
drying and form a ring around the kiln's inner periphery, and (2) solids
(e.g., drums) that tend to roll down the kiln and are not retained as long as '
the bulk of solids. To reduce this problem, drums and other cylindrical
4-20
-------
TABLE 4-4. CHEMICAL AND THERMODYNAMIC WASTE
PROPERTY EVALUATION PROCEDURE
1. Identify the elemental composition and moisture content of the waste and
record this information on Worksheet 4-2 for future reference.
2. Does the waste contain chlorinated or fluorinated materials? (If YES,
proceed to checkpoint #3. If NO, proceed to checkpoint #5.)
3. Is sufficient hydrogen present in the waste for equilibrium conversion of
chlorine and fluorine to hydrogen chloride and hydrogen fluoride, respec-
tively? See aforementioned evaluation criteria in Section 4.3.2.1. (If
YES, proceed to checkpoint #5. If NO, proceed to checkpoint #4.)
4. Is auxiliary fuel firing or steam injection employed to provide the
necessary hydrogen equivalents?
5. Identify the major components of the combustion gas, based on the ele-
mental composition of the waste, that need to be considered in subsequent
material and energy balance calculations. See Worksheet 4-2 for the
recommended procedure. This procedure also determines the stoichiometric
air requirement and combustion gas flow, which will be needed for subs^r
quent evaluation procedures. |
6. Determine the net heating value of the waste. Worksheet 4-3 shows how
the net heating value can be calculated when higher heating values are
known.
7. Does it appear likely that the waste will sustain combustion, based on
its net heating value? (If YES, proceed to checkpoint #9. If NO, pro-
ceed to the following checkpoint.)
8. Is auxiliary fuel to be burned in conjunction with the waste?
9. Is the waste potentially explosive when exposed to high temperature or
shock?
containers are usually not introduced to the kiln when it is empty. Other
solids in the kiln help to impede the rolling action.
The major design checkpoint for rotary kiln/physical waste property
compatibility is the type(s) of solid waste feed systems employed. These feed
systems are discussed in Chapter 5.
Chemical and thermodynamic properties of the waste that need to be considered
in rotary kiln design evaluation are its elemental composition, its net heat-
ing value, and any special properties (e.g., explosive properties, extreme
toxicity) that may interfere with incinerator operation or require special
design considerations. These are essentially the sane properties that must be
4-21
-------
considered in liquid injection incinerator evaluation. Therefore, the back- ™
ground discussion in Section 4.3.2.1 and the evaluation procedure presented in
Table 4-4 can be used for rotary kilns as well as liquid injection
incinerators with some modifications.
The first modification relates to the calculation procedures for stoichio-
metric air requirement, combustion gas flow and composition. These calcula-
tions are more complex for rotary kiln incinerators because (a) liquid and
solid wastes may be fed simultaneously to the kiln, and (b) liquid wastes and
auxiliary fuel may be fed to the kiln,afterburner, or both. Therefore, Work-
sheet 4-4 (See Section 4-5) should be used instead of Worksheet 4-2 for com-
bustion gas flow calculations. Worksheet 4-3 can still be used to calculate
net heating values.
The second modification relates to the consideration of special waste proper-
ties. As discussed in Section 4.3.2.1 for liquid injection incinerators,
technical assistance may be required if wastes with explosive properties are
encountered. For rotary-kilns, technical assistance is also advised if ex-
tremely toxic, mutagenic, or carcinogenic wastes are to be burned. This
recommendation is based on the fact, that kilns are much more prone to release
of fugitive emissions than are liquid injection incinerators.
Unlike liquid injection incinerators which have no moving parts, rotary kilif-
designs incorporate high temperature seals between the stationary end plates!
and rotating section. These seals are inherently difficult to maintain air* ^
tight, which creates the potential for release of unburned wastes. Rotary ^
kilns burning hazardous wastes are almost always operated at negative pressure
to circumvent this problem, however, difficulties can still arise when batches
of waste are fed send-continuously. When drums containing relatively volatile
wastes are fed to the kiln, for example, extremely rapid gas expansion occurs.
This results in a positive pressure surge at the feed end of the kiln (even
though the discharge end may still be under negative pressure), which forces
unburned waste out through the end plates seals. This phenomenon is known as
"puffing", and can pose a major problem if extremely toxic or otherwise
hazardous materials are being burned.
Fugitive emissions can also exit the kiln through the feed chute if improperly
designed. Therefore, the design of the solid waste feed system is an extreme-
ly important consideration in evaluating rotary kiln incinerators. This topic
is addressed in Chapter 5.
4.3.3 Temperature, Excess Air, Residence Time, and Mixing Evaluation
Temperature, residence time, oxygen concentration, and the degree of air/waste
mixing achieved are the primary variables affecting combustion efficiency in
any incinerator design. The theoretical significance of these interrelated
variables is discussed in the following subsection under "Liquid Injection
Incinerators." Subsection 4.3.3.2 addresses additional temperature, time,
excess air, and mixing considerations for rotary kilns.
In general, two major factors are involved in evaluating these variables as '
they relate to incinerator design. The first factor is whether or not the
temperature, residence time, and excess air level, along with the degree of
4-22
-------
mixing achieved in the incinerator, are adequate for waste destruction. The
second factor is whether or not the proposed operating conditions are
achievable, since temperature, excess air, residence time, and mixing are all
interrelated.
At the current state of the art, the adequacy of incinerator operating condi-
tions can only be determined by past experience with the waste or by actual
testing. Therefore, this factor is not addressed per se in the following
subsections. The major focus of the following evaluation procedures is on
whether or not a proposed set(s) of operating conditions is achievable.
Basically, this involves a series of internal consistency checks.
4.3.3.1 Liquid Injection Incincerators--
The most basic requirement of any combustion system is a sufficient supply of
air to completely oxidize the feed material. The stoichiometric, or theoreti-
cal air requirement is calculated from the chemical composition of the feed
material, as shown in Section 4.3.2. If perfect mixing could be achieved and
liquid waste burnout occurred instantaneously, then only the stoichiometric
requirement of air would be needed. Neither of these phenomena occur in
real-world applications, however, so some excess air is always required to
ensure adequate waste/air contact. Excess air is usually expressed as a
percentage of the stoichiometric air requirement. For example, 50% excess air
implies that the total air supplied to the incinerator is 50% greater than
stoichiometric requirement.
r
The amount of excess air used- or needed in a given application depends on the
degree of air/waste mixing achieved in the primary combustion zone, process-
dependent secondary combustion requirements, and the desired degree of combus-
tion gas cooling. Since excess air acts as a diluent in the combustion pro-
cess, it reduces the temperature in the incinerator (e.g., maximum theoretical
temperatures are achieved at zero percent excess air). This temperature
reduction is desirable when readily combustible, high heating value wastes are
being burned in order to limit refractory degradation. When high aqueous or
other low heating value waste is being burned, however, excess air should be
minimized to keep the system temperature as high as possible. Even with
highly combustible waste, it is desirable to limit excess air to some extent
so that combustion chamber volume and downstream air pollution control system
capacities can be limited.
Figure 4-11 maybe used to check the internal consistency of the proposed
excess air rate and temperature, as long as the amount of carbon, hydrogen,
and oxygen in the stream and its net heating value are known. To use the
figure, first find the weight fraction of carbon on the scale marked C (on the
far left) and the weight fraction of hydrogen on scale H. Connect these two
points with a ruler and read the value at its intersection with arbitrary
scale 1 . Subtract the weight fraction of oxygen in the feed stream from this
number. Plot this value on the middle graph, using arbitrary scale 1 as the
vertical axis and the excess air scale as the horizontal axis. Interolate
between the set of curves to find a value for arbitrary scale 2, which is then
plotted on the vertical axis of the right-hand graph, with the net heating
value of the feed plotted on the horizontal axis to determine the combustion
gas temperature.
4-23
-------
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4-24
-------
For example, suppose methane (CH4-75% carbon, 25% hydrogen; net heating value
of 19,700 Btu/lb) is burned with 50% excess air. Connecting 0.75 on the C
scale with 0.25 on the H gives 4.9 at the intersection with arbitrary scale 1.
Using this value and 50% excess air gives 7.25 on the middle graph. Plotting
7.25 vertically and 19.7 KBtu/lb horizontally on the right-hand graph shows a
temperature of 2,700°F. If a temperature of 2,000°F is desired and excess air
is to be calculated, plotting 19.7 JcBtu/lb and 2,000°F gives 9.8 on arbitrary
scale 2. Then using the middle graph, 9.8 on arbitrary scale 2 and 4.9 on
arbitrary 1 shows an excess air rate of 100%. Figure 4-11 is accurate so long
as the combustion gases consist of air, 003 and H20, i.e., the wastes consist
mainly of carbon, hydrogen, and oxygen. The latter part of this section
describes the procedures for more accurate calculations.
In liquid injection incinerators, two excess air rates must be considered:
(1) the excess air present in the primary combustion air introduced through
the burner, and (2) the total excess air, which includes secondary combustion
air. Normally, 10% to 20% excess air (i.e., 1.1 to 1.2 times the stoichio-
metric requirement) is supplied to the burner to prevent smoke formation in
the flame zone. When relatively homogeneous wastes are being burned in high
efficiency burners, 5% excess air may be adequate. Too much excess air
through the burner is also undesirable, since this can blow the flame away
from its retention cone. Burner manufacturer specifications are the best
source of information for analysis. I-
In general, the total excess air rate should exceed 20% to 25% to insure ade-
quate waste/air contact in the secondary combustion zone. However, the mini-
mum requirement for a given incinerator depends on the degree of mixing
achieved and waste specific factors.
Four basic questions should be considered in evaluating whether or not a
proposed operating temperature is sufficient for waste destruction:
(1) Is the temperature high enough to heat all waste components (and combus-
tion intermediates) above their respective ignition temperatures and to
maintain combustion?
(2) Is the temperature high enough for complete reaction to occur at the
proposed residence time?
(3) Is this temperature within normal limits for the generic design and/or
attainable under the other proposed operating conditions?
(4) At what point in the combustion chamber is the proposed temperature to be
measured?
Complete waste combustion requires a temperature, and heat release rate, in
the incinerator high enough to raise the temperature of the incoming waste
constituents above their respective ignition temperatures (i.e., to provide
energy input in excess of their respective activation energies). In cases
where combustion intermediates are more stable than the original waste con-
stituents, higher temperatures are required for complete combustion of the
intermediates than for parent compound destruction.
4-25
-------
Since heat transfer, mass transfer, and oxidation all require a finite length
of time, temperature requirements must also be evaluated in relation to the
proposed residence time in the combustion chamber. Heat transfer, mass trans-
fer, and kinetic reaction rates all increase with increasing temperature,
lowering the residence time requirements. For extremely short residence
times, however, temperatures higher than those needed for ignition may be
required to complete the combustion process.
The current state of the art in combustion modeling does not allow a purely
theoretical determination of temperature and residence time requirements for
waste and combustion intermediate destruction. Therefore, the only reasonable
alternative is an examination of temperature/residence time combinations used
to destroy the same or similar waste in a similar or identical incinerator.
After addressing the temperature requirements for waste destruction, it is
reasonable to determine whether or not the proposed temperature is within
normal limits for the generic incinerator design and whether or not this tem-
perature can be attained under the proposed firing conditions. Generally,
liquid injection incinerator temperatures range from 1,400°F to 3,000°F depend-
ing on the generic design, type of waste being burned, and location within the
combustion chamber. Usually 1,400°F is the minimum temperature needed to
avoid smoke formation. A more typical hazardous waste incineration tempera-
ture is 1,800°F, although temperatures of 2,000°F to 2,200°F or higher are I.
usually employed for halogenated aromatic wastes. . I
The question of whether or not the proposed temperature and excess air rate
are attainable can be resolved by approximate calculations based on a heat
balance around the combustion chamber. Figure 4-12 shows the heat inputs and
outputs for the combustion chamber.
ENTHALPY OF
INCOMING WASTE,
AIR. AUXILIARY
FUEL
HEAT LOSS THROUGH
REFRACTORY
ENTHALPY OF
COMBUSTION GASES
HEAT OF WASTE/
AUXILIARY FUEL
COMBUSTION
Figure 4-12. Energy balance for combustion chamber.
Since liquid waste incineration is a steady state (or quasi-steady state)
process, the enthalpy of the waste/auxiliary fuel/combustion air feed plus the
heat released by combustion must equal the enthalpy of the combustion gases
4-26
-------
leaving the unit plus the heat loss through the refractory walls.
the general relationship:
This yields
Heat loss
i through refractory/
\.
/ Enthalpy of
I incoming feed
Heat released by
combustion
/ Enthalpy
1 of combus-
\ tion gases
or
where
Q = AH
Q = heat loss through refractory, Btu/lb waste
AH = overall enthalpy change in the combustion chamber, Btu/lb waste
Since enthalpy is a thermodynamic state function, the overall enthalpy change
can be represented by any series of incremental enthalpy changes, so long as
the initial state and final state correspond to the incinerator inlet and
outlet conditions, respectively. The key is to select an enthalpy change
pathway that simplifies the calculations involved, such as that shown in
Figure 4-13.
Using this approach, the overall energy balance equation becomes:
Q = AH = AHa_2 + AH2_3 + AH3_4
where AH. . = incremental enthalpy changes, Btu/lb waste
*
In Figure 4-13, the first enthalpy change, AH^. represents the difference in
feed enthalpy between injection temperature and standard conditions of 77°F
(25°C) . This term is seldom significant unless the combustion air is
preheated to high temperature.
WASTE AND AIR
AT INJECTION
TEMPERATURE
COMBUSTION PRODUCTS,
UNREACTED WASTE, AND
EX CESS AIR AT COMBUSTION
TEMPERATURE
WASTE AND AIR
AT 77°F(25°C)
COMBUSTION PRODUCTS,
UNREACTED WASTE. AND
EXCESS AIR AT
77°F (25°C)
Figure 4-13.
Enthalpy balance for combustion processes.
4-27
-------
The term AH2_3 represents the heat released by combustion at isothermal condi-
tions of 25°C. This corresponds to the way in which heats of combustion are
measured and presented in the literature. The third term, AH3 4/ represents
the difference in combustion product enthalpy between 25°C and'the temperature
at the combustion chamber outlet.
In mathematical terms, these incremental enthalpy changes are expressed as:
k
.2 =
n. C .(77
i piv
T. )
in/
waste
components
p air
<77 -
177°F
and
AH3_4 = <
reactive
waste
components
- V
(reaction
products
reactive
waste
components
remaining
+ 4.31 C . (02) .. . . (EA)
p airv zystoichv
* z
"icpi
inert
waste
components
i%
- E
reactive
components
4-28
-------
where n. = Ib ith component/Ib waste
C . = mean heat capacity of ith component over the temperature
pl range involved, Btu/lb °F
T. = waste injection temperature, °F
T . = air inlet temperature, °F
31 r
X. = fractional conversion of ith component (X. = 1.0 at 100%
combustion of ith component)
(AH ). = heat of combustion of ith component at 77°F (25°C), Btu/L
c 177°F
T = temperature at the combustion chamber outlet, °F
(02) . . = stoichiometric oxygen requirement, Ib 02/lb waste
EA = excess air, %/lOO
To determine whether or not the proposed temperature/excess air combination is
achievable, it is necessary to specify the desired temperature and calculate
the corresponding excess air rate for comparison with the proposed value.
However, there are far too many unknowns in these equations to solve for EA..
These equations can be simplified considerably by assuming that the combusti
_ a'
reactions go to essentially 100% completion. With this assumption, the
overall energy balance reduces to:
2 = ~p waste'77 - Tin> + 4'31 ~p air'77 ' T.ir><0*>.toich(1 + EA)
1
:i|>n
NHV)77oF + (T - 77)
n. C . + 4.31 C
i=1 i Pi P air
combustion
products
where NHV = net heating value of the waste, Btu/lb
From the empirical waste composition (carbon content, hydrogen content, etc.),
proposed excess air rate, and combustion stoichiometry discussed in Section
4.3.2, all the variables in this equation are fixed except the outlet temper-
ature or excess air rate, mean heat capacities of the combustion gases, and
the heat loss through the walls of the combustion chamber. To avoid rigorous
heat transfer calculations, this heat loss can be assumed to be about 5% of
the heat released in the combustion chamber, based on operating experience
with hazardous waste incinerators. With this assumption, the energy balance
reduces to.-
Acceptance of the proposed temperature/residence combination should ensure
combustion efficiencies close enough to 100% for this value to be used in
heat balance calculations.
4-29
-------
C/ T *7
( ' 7
p waste
4'31 Cp air(7? ' Tair)(°2>stoich(1 + EA)
4'31 <°2>
1=1
combustion
products
air2stoich
EA
(TQut - 77) * 0
from which the first two terms can be deleted if neither waste nor air pre-
heating is employed. (The waste enthalpy term can almost always be deleted
anyway.) This yields:
0.95 (-NHV) +
r *
S •*
combustion
. products
Si
"31 Cp air<°2>stoichEA
The mean heat capacities of the combustion gases will vary to a small degree""
depending on the incinerator outlet temperature. For this purposes of approxi-
mate calculations, however, the following values can be assumed:
Gas component C , Btu/lb °F
c
Excess air
N2
C02
H20
HC1
S02
0.26
0.26
0.26
0.49
0.20
0.18
This yields the expression3:
0.95 (-NHV) + J0.26 (n^^ + n
0.49
20
- 77) =
e term n.. in this equation refers to the nitrogen present in the combustion
gases under2stoichiometric conditions. It does not include excess air
nitrogen.
4-30
-------
for wastes containing only carbon, hydrogen, oxygen, and nitrogen. If other
gas components, constitute more than a few percent of the total flow, additional
heat capacity terms must be added.
If auxiliary fuel is to be burned in conjunction with the waste, a modification
of the previous equation is needed. This is as follows:
0.95
n
fuel
k
Z
n. C .
i pi
waste
combustion
products
(n.
i fuel pi'
:p air<°2>stoichEA
fuel
combustion
products
out
- 77) = 0
where
= Ib ith combustion gas component/Ib fuel j
- mean heat capacity of fuel over the applicable temperature
range, Btu/lb °F
= heating value of fuel, Btu/lb
- Ib fuel/lb waste
If only carbon, hydrogen, oxygen, and nitrogen are present, the equation can
be simplified to :
C
NHV
r i
0.95
[
°'26
nfuel <-NHV)fuel]
O^ f °'49 "H.,0 + »-
(TQut - 77) = 0
In this equation, n^ , UCQ , HH Q, (°2)stoich- and EA apply to the combined
waste/auxiliary fuel mix, and r^ accounts refers to the nitrogen present in
the combustion gases under stoichiometric conditions.
4-31
-------
By fixing the outlet temperature at the proposed value, the equations shown
above can be used to estimate the maximum achievable excess air rate for
comparison with that proposed. Thus, the equations provide an internal consis-
tency check for proposed temperature/excess air combinations. Worksheet 4-5
in Section 4-5 shows how the calculation can be performed in a step-by-step
manner .
When identifying a minimum temperature acceptable for waste destruction, it is
also important to identify the location in the combustion chamber at which
this temperature should be measured. Temperature varies tremendously from one
point to another in the combustion chamber, being highest in the flame and
lowest at the refractory wall or at a point of significant air infiltration
(e.g., in the vicinity of secondary air ports). Ideally, temperature should
be measured in the bulk gas flow at a point after which the gas has traversed
the combustion chamber volume that provides the specified residence time for
the unit. It should not be measured at a point of flames impingement or at a
point directly in sight of radiation from the flame. Chapter 5 discusses
temperature measurement in more detail.
A comprehensive evaluation procedure for temperature/excess air considerations
is shown in Table 4-5.
In addition to temperature and excess air, residence time is a key factor I-
affecting the extent of combustion. This variable, also referred to as reterj-
tion time or dwell time, is the mean length of time that the waste is exposecr
to the high temperatures in the incinerator. It is important in designing and
evaluating incinerators because a finite amount of tine is required for each
step in the heat transfer/mass transfer/reaction pathway to occur.
In liquid waste combustion, discrete (although short) time intervals are re-
quired for heat transfer from the gas to the surface of the atomized droplets,
liquid evaporation, mixing with oxygen in the gas stream, and reaction, which
itself involves a series of individual steps depending on the complexity of
the waste's molecular structure. The total tine required for these processes
to occur depends on the temperature in the combustion zone, the degree of
mixing achieved, and the size of the liquid droplets. Residence tine require-
ments increase as combustion temperature is decreased, as mixing is reduced,
and/or as the size of discrete waste particles is increased. Typical
residence times in liquid injection incinerators range from 0.5 s to 2.0 s.
Gas residence times are defined by the following formula.-
where 8 = mean residence time, s
V = combustion chamber volume, ft3
q = gas flow rate, ft3/s within the differential volume, dv
and gas flow rate is given by:
4-32
-------
q
= /Q-79 W T + 460
528
4'31 <°2>stoich 68'F
-------
In the preceding discussion, all equations apply to the nominal, or mean,
residence time in the combustion chamber. A thoroughly rigorous approach
would require tracer studies to determine residence time distributions in the
incinerator. However, nominal residence times are sufficient for evaluation
purposes, so long as the incinerator design is such that significant channel-
ing (analogous to dead space in the combustion chamber) does not occur. Chan-
neling is usually prevented by creating abrupt changes in flow direction or by
establishing a definite flow pattern in the combustion chamber (e.g., cyclonic
flow).
TABLE 4-5. TEMPERATURE/EXCESS AIR EVALUATION PROCEDURE.
1. Identify the proposed operating temperature.
2. Is this temperature sufficient to convert all waste components to their
ultimate oxidation products, assuming that adequate residence time,
oxygen, and mixing are provided? See the preceding discussion (Section
4.3.3.1) for general guidelines. Outside sources of information can be
consulted for waste-specific data.
3. Identify the excess primary combustion air rate proposed in the permit *
application. I
*
4. Does this excess air rate meet, or exceed the general requirements identi-
fied in the preceding discussion and/or burner manufacturer
specifications?
5. Identify the total excess air rate proposed.
6. Is this excess air rate acceptable? General guidelines are presented in
Section 4.3.3.1.
7. Independently calculate the total excess air rate needed to maintain the
proposed operating temperature (see Worksheet 4-5).
8. Is this calculated excess air rate greater than or comparable to the
proposed total excess air rate? (If YES, proceed to checkpoint til. If
NO, proceed to the following checkpoint).
9. Is this excess air rate acceptable, even though it is less than the pro-
posed excess air rate? See the preceding discussion for general guide-
lines. (If YES, proceed to checkpoint #11. If NO, proceed to the
following checkpoint.)
10. Are there any mechanical restraints in the system that would prevent
increasing the auxiliary fuel-to-waste firing ratio (which would be
needed to maintain both an acceptable temperature and excess air rate)?
If necessary, repeat the calculations shown in Worksheet 4-5 for the
maximum achievable fuel-to-waste ratio.
(continued)
4-34
-------
TABLE 4-5 (continued)
11. Identify the location at which temperature is to be measured in the
incinerator.
12. Is this location (a) suitable based on the considerations in the preced-
ing discussion or (b) comparable to the location at which temperature was
measured during an appropriate prior test?
Table 4-6 presents a gas residence time evaluation procedure which can be used
in conjunction with the evaluation procedure for temperature and excess air
shown in Table 4-5, since all three variables are interrelated.
TABLE 4-6. GAS RESIDENCE TIME EVALUATION PROCEDURE
1. Identify the proposed gas residence tine.
L
2. Does this residence time appear adequate, considering the proposed operat
ing temperature and excess air rate, and assuming that good mixing is
achieved? See the preceding discussion for general guidelines and the
appendices for specific information.
3. Does the proposed residence time appear to be achievable? See
Worksheet 4-6.
Temperature, oxygen, and residence time requirements for waste destruction all
depend to some extent on the degree of mixing achieved in the combustion
chamber. This parameter is difficult to express in absolute terms, however.
Many of the problems involved in interpreting burn data relate to the diffi-
culty involved in quantifying the degree of mixing achieved in the incinerator,
as opposed to the degree of mixing achieved in another incinerator of
different design.
In liquid waste incinerators' the degree of nixing is determined by the spe-
cific burner design (i.e., how the primary air and waste/fuel are mixed),
combustion product gas and secondary air flow patterns in the combustion cham-
ber, and turbulence. Turbulence is related to the Reynolds number for the
combustion gases, expressed as.:
4-35
-------
where D = combustion chamber diameter, ft
v = gas velocity, ft/s
p = gas density, lb/ft3
^i = gas viscosity, lb/ft s
Turbulent flow conditions exist at Reynold's numbers of approximately 2,300
and greater. Below this Reynold's number laminar or transition flow prevails
and mixing occurs only by diffusion.
In conventional liquid injection incinerators or afterburners, it is possible
to simplify the Reynold's number to consideration of superficial gas velocity
only. Adequate turbulence is usually achieved at superficial gas velocities
of 10 to 15 ft/s. Superficial gas velocities are determined by
where q = gas flow rate at operating temperature, ft3/s
A = cross-sectional area of the incinerator chamber, ft2
When primary combustion air is introduced tangentially to the burner (e.g.,
vortex burners), secondary air is introduced tangentially, or burner alignment
is such that cyclonic flow prevails in the incinerator, actual gas velocitie^-
exceed the superficial velocity. Thus, adequate turbulence may be achieved *t
superficial velocities less than 10 ft/s in cyclonic flow systems. However, *
the tradeoff is difficult to quantify. Turbulence can also be increased by
installing baffles in the secondary combustion zone of the incinerator, which
abruptly change the direction of gas flow. However, this also increases
pressure drop across the system and is not a common practice in liquid injec-
tion incinerator design. Steam jets can als.o be used to promote turbulence.
Table 4-7 presents a procedure for evaluating the mixing characteristics of
liquid injection incinerators. Since mixing is related to the gas flow rate
through the incinerator; this evaluation procedure can be used in conjunction
with that for temperature and excess air, which affect gas flow independent of
the waste feed rate.
TABLE 4-7. MIXING EVALUATION PROCEDURE
1. Calculate the superficial gas velocity in the incinerator chamber at
operating temperature (see Worksheet 4-7).
2. Does this velocity meet or exceed the general guidelines provided above
(i.e., 10-15 ft/s)?
3. If not, is cyclonic flow or some mechanical means of enhancing turbulence
designed into the system? If 7ES, somewhat lower superficial velocities
than those listed above may still provide suitable mixing.
4-36
-------
4.3.3.2 Rotary Kiln Incinerators--
In rotary kiln/afterburner incineration systems, three excess air rates must
be considered: (1) excess air present in the primary combustion air intro-
duced through liquid waste burners in the kiln or afterburner section,
(2) total excess air fed to the kiln, and (3) the excess air percentage main-
tained in the afterburner.
Normally, 10% to 20% excess air (i.e., 1.1 to 1.2 times the stoichiometric
requirement) must be supplied to liquid waste burners to prevent smoke forma-
tion in the flame zone. When relatively homogeneous wastes are being burned
in high efficiency burners, 5% excess air may be adequate. Too much excess
air through the burner is also undesirable, since this can blow the flame away
from its retention cone. Burner manufacturer specifications are the best
source of information for case-by-case analysis.
As stated in Section 4.3.3.1, 20% to 25% total excess air is a practical
minimum for liquid injection incinerators to achieve adequate air/waste con-
tact. Higher excess air rates are needed in rotary kilns, however, because
the efficacy of air/solids contact is less than that for air and atomized
liquid droplets. Typical excess air rates range from 140% to 210% or greater,
depending on the desired operating temperature and the heating value of the
waste. When high aqueous wastes are being burned, lower excess air rates may
be needed to maintain adequate temperature. However, less than 100% excess!
air in the kiln may not provide adequate air/solids contact. I
Since it is usually desirable to maintain the afterburner at a higher tempera-
ture than the kiln, and because only liquid wastes or auxiliary fuel is fired
in the afterburner, the excess air rate in the afterburner is usually less
than that in the kiln. In a typical system operating at 1,500°F in the kiln
and 1,800°F in the afterburner, approximately 160% to 170% excess air would be
maintained in the afterburner compared to ^210% in the kiln. Considering 100%
excess air in the kiln as a practical minimum, approximately 80% excess air or
more should be maintained in the afterburner. This includes air contained in
the kiln exit gases as well as air introduced in the afterburner itself, and
is based on the total stoichiometric oxygen requirement for all wastes and
fuels burned in the system.
In evaluating temperature requirements for a rotary kiln/afterburner system,
seven basic questions should be considered:
(1) Is the temperature in the kiln high enough to volatilize, partially
oxidize, or otherwise convert all organic components of the waste to a
gaseous state?
(2) Is this temperature high enough for the aforementioned processes to occur
within the proposed solids retention time?
(3) Is the afterburner temperature high enough to heat all volatilized wastes
(and combustion intermediates) above their respective ignition tempera-
tures and maintain combustion?
4-37
-------
(4) Is the temperature high enough for complete reaction to occur within the
proposed afterburner residence time?
(5) Is the kiln operating temperature within normal limits and/or attainable
under the other proposed operating conditions?
(6) Is the afterburner temperature within normal limits and/or attainable
under the other proposed operating conditions?
(7) At what points in the system are the temperatures to be measured?
The current state-of-the-art in combustion modeling does not allow a purely
theoretical determination of time and temperature requirements for solid waste
burnout or combustion in the gas phase. Therefore, the only reasonable alter-
native is an examination of temperature/time combinations used to destroy the
same or similar waste in a similar or identical rotary kiln/afterburner system.
This information is needed to address questions 1 through 4 above. The latter
three questions are addressed in the following paragraphs.
Temperatures in rotary kiln incinerators usually range from about 1,400°F to
3,000°F, depending on the types of waste being burned and the location in the
kiln. Common operating temperatures, measured outside of the flame zone, are
1,500°F to 1,600°F. The question of whether or not these or other proposed I"
temperatures are attainable at the proposed excess air rate can be resolved fy
approximate calculations based on a heat balance around the kiln (see Sec-
tion 4.3.3.1 for a discussion of how heat balances are formulated).
The difficulty that arises in this calculation is that the extent of combus-
tion, or actual heat release compared to the maximum attainable heat release,
is unknown. However, the maximum achievable excess air rate in the kiln at
the specified operating temperature can still be estimated by assuming com-
plete combustion. This corresponds to a worst case analysis. The maximum
calculated excess air rate must exceed the proposed excess air rate, or the
specified'operating temperature will not be attainable.
The applicable heat balance equation for the kiln, assuming complete
combustion is shown on the following page.
This equation is also based on the assumptions that (a) heat loss through the
kiln walls is about 5% of the heat released on combustion, and (b) waste
preheating, if employed, will result in negligible heat input compared to the
heat released on combustion (which is almost always the case). This equation
can be solved directly for EA, the maximum attainable excess air rate in the
kiln, once the desired operating temperature is specified. Mean heat capaci-
ties for common combustion gas components, applicable over temperature ranges
normally encontered, are shown in Section 4.3.3.1.
Worksheet 4-8 in Section 4-5 presents a step-by-step calculation procedure.
4-38
-------
4.31 C
•pair <77-Tair><°*Wch(k)(1+EV
/ni>fHV1 + n2NHV2 + n,
- 0.95 (
k
1 + n
fK
i Cpi
Cp air(°2)stoichEAk
combustion
products
Jfrom kiln
(T
out
- 77) = 0
where
C . = mean heat capacity of ith component over the temperature
pi range involved, Btu/lb °F
T . = air preheat temperature, °F
(°2) • >. = total stoichiometric oxygen requirement for wastes and
31 lcn auxiliary fuel fed to the kiln, Ib 02/lb feed ,
EA, = percent excess air/100(in kiln) I
I
r\i - Ib liquid waste/lb waste
n2 = Ib solid waste/lb waste
n^ = Ib fuel/lb waste
NHV: = net heating value of liquid waste, Btu/lb
NHV2 = net heating value of solid waste, Btu/lb
HV.^ = net heating value of fuel, Btu/lb
n, = Ib ith combustion product/Ib feed
T = desired temperature at the kiln outlet, °F
When no combustion air preheating is employed, this equation simplifies to.-
/n1NHV1 + n2NHV2 + n
-0.95 —. ;
\ 1 + n
fK
k
r
i=l
combustion
products
from kiln
/
4'31 Cp air^^stoich^k
dout - 77) = 0
4-39
-------
Using the heat capacities presented in Section 4.3.3.1, and assuming that C02,
H20, No, and 02 are the only significant components of the combustion gas, the
equation further simplifies to3:
-0.95
I
n2NHV2
n
fK
i.26 n
co
0.49
(*out - 77) = 0
Excess air in the afterburner can be estimated in similar fashion, after the
desired operating temperature is specified. In this calculation, heat inputs
to and from the entire system (kiln and afterburner) are considered. The
resulting heat balance equation is shown below.
This equation is also based on assumptions of 5% heat loss from the system and
negligible energy input due to waste/auxiliary fuel or air preheating. Work-
sheet 4-9 presents a step-by-step calculation procedure.
-0.95
+ n2NHV2 +
I +
+ n.
n
fA
n
AK
combustion
products
from kiln
niK Cpi
niA Cpi
where
combustion
products
afterburner
feed
n
+ 4.31 C_
[<°2>
AK
stoich(K)
-------
n, = Ib fuel/lb waste in afterburner
fA
HVf = heating value of auxiliary fuel burned in the after-
A burner, Btu/lb
n... = Ib ith combustion product from kiln/lb kiln feed
IK
n. = Ib ith combustion product from afterburner feed/lb
afterburner feed
T = desired afterburner outlet temperature, °F
Once the major components of the combustion gas have been identified (C02,
H20, N2, and 02 in most cases), the latter two terms in this equation can be
simplified by substituting in the heat capacities reported in Section 4.3.3.1.
A similar substitution is shown on the preceding page for the rotary Kiln heat
balance equation.
When quantifying the desired temperatures in the kiln and afterburner, it is
also important to fix the locations at which these temperatures should be
measured. Temperature varies tremendously from one point to another in each
unit, being highest in the flame and lowest at the refractory wall or at a
point of significant air infiltration (e.g., in the vicinity of secondary air
ports, end plate seals, and feed chute). Ideally, temperatures should be
measured in the bulk gas flow at a point after which the gas has traversed
volume of each chamber that provides its specified residence tine. Tempera
tures should not be measured at a point of flame impingement or at a point
directly in sight of radiation- from the flame. Temperature measurement is
discussed in more detail in Chapter 5.
•t
An evaluation procedure for temperature/excess air considerations is shown in
Table 4-8.
i
In rotary kiln incineration systems, both the solids retention time in the
' kiln and the gas residence time in the afterburner must be considered. After-
I burner residence time considerations are essentially the same as those for
liquid injection incinerators, a topic which is addressed in Section 4.3.3.1.
Therefore, the following discussion focuses primarily on solids retention time
estimates. For a discussion of gas residence time estimates and corresponding
evaluation procedures, see Section 4.3.3.1.
Solids retention times in rotary kilns are a function of the length-to-diam-
eter ratio of the kiln, the slope of the kiln, and its rotational velocity.
The functional relationship between these variables is [5]:
6 = 0.19 (L/D)/SN
where 9 = retention time, min
L = kiln length, ft
D « kiln diameter, ft
S = kiln slope, ft/ft
N ~ rotational velocity, rpm
4-41
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TABLE 4-8. TEMPERATURE/EXCESS AIR EVALUATION PROCEDURE FOR
ROTARY KILN/AFTERBURNER INCINERATORS
1. Identify the proposed kiln and afterburner operating temperatures.
2. Is the kiln temperature sufficient for complete solid waste burnout,
assuming that adequate retention time, excess air, and mixing are pro-
vided? This determination must be based on operating experience and/or
other burn data.
3. Is the afterburner temperature sufficient to complete the combustion
reactions, assuming that adequate residence tune, excess air, and mixing
are provided? See the preceding discussion (Section 4.3.3.2) for general
guidelines.
4. Identify the excess primary air rates for each liquid waste burner in the
kiln or afterburner.
5. Does this excess air rate meet or exceed the general requirements
identified in the preceding discussion and/or burner manufacturer
specifications? I-
6. Identify the total excess air rate for the kiln.
7. Is this excess air rate acceptable? See the preceding discussion
guidelines .
8. Independently calculate the maximum total excess air rate needed to main-
tain the proposed operating temperature in the kiln (see Worksheet 4-8).
9. Is this calculated excess air rate greater than the proposed total excess
air rate? (If YES, proceed to checkpoint #12. If NO, proceed to the
following checkpoint.)
10. Is this excess air rate acceptable, even though it is less than or compa-
rable to the proposed excess air rate? See the preceding discussion for
general guidelines. (If YES, proceed to checkpoint #12. If NO, proceed
to the following checkpoint.)
11. Are there any mechanical restraints in the system that would prevent
increasing the auxiliary fuel-to-waste firing ratio in the kiln (which
would be needed to maintain both an acceptable temperature and excess air
rate). In other words, is the maximum achievable fuel-to-waste firing
ratio insufficient to maintain an acceptable excess air rate? Repeat the
calculations shown in Worksheet 4-8 at this fuel- to-waste ratio, if
necessary.
12. Identify the total excess air rate for the system (i.e., in afterburner).
(continued)
4-42
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TABLE 4-8 (continued)
13. Is this excess air rate acceptable? See the preceding discussion for
general guidelines.
14. Independently calculate the total excess air rate needed to maintain the
proposed operating temperature in the afterburner (see Worksheet 4-9).
Is the calculated excess air rate greater than or comparable to the
proposed total excess air rate? (If YES, proceed to checkpoint #17. If
NO, proceed to the following checkpoint.)
15. Is this excess air rate acceptable, even though it is less than the pro-
posed excess air rate? See the preceding discussion for general guide-
lines. (If YES, proceed to checkpoint #17. If NO, proceed to the
following checkpoint.)
16. Are there any mechanical restraints in the system that would prevent
increasing the auxiliary fuel-to-waste firing ratio in the afterburner
(which would be needed to maintain both an acceptable temperature and
excess air rate)? If necessary repeat the calculations shown in
Worksheet 4-9 at the maximum achievable fuel-to-waste ratio.
17. Identify the locations at which temperature is to be measured in the
and afterburner.
t
IS. Are these locations (a) suitable based on the general guidelines given in
the preceding discussion, or (b) comparable to the location at which
temperature was measured during a prior similar burn?
This equation can be used for a rough approximation of the retention time.
Typical ranges for the parameters are L/D = 2-10, 0.03-0.09 ft/ft slope, and
1-5 ft/min rotational speed measured at the kiln periphery (which can be
converted to rpm by dividing by the kiln circumference measured in ft). Some
examples of retention tine requirements are 0.5 s for fine propellants, 5 rain
for wooden boxes, 15 min for refuse, and 60 rain for railroad ties [5]. How-
ever, the retention tine requirements for burnout of any particular solid
waste should be determined experimentally or extrapolated from operating
experience with similar wastes.
Table 4-9 presents an evaluation procedure for kiln retention time.
In rotary kiln incineration systems, both the degree of air/solids contact in
the kiln and gas mixing in the afterburner must be considered. Afterburner
mixing considerations are essentially the same as for liquid injection incin-
erators, a topic which is addressed in Section 4.3.3.1. See Table 4-7 for the
afterburner mixing evaluation procedure.
4-43
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TABLE 4-9. KILN RETENTION TIME EVALUATION PROCEDURE
1. Identify the estimated solids retention time in the kiln.
2. Is this retention time acceptable, based on past experience and/or prior
burn data?
3. Independently estimate solids retention time in the kiln (see
Worksheet 4-10).
4. Does the proposed retention time appear to be achievable?
Air/solids mixing in the kiln is primarily a function of the kiln's rotational
velocity, assuming a relatively constant gas flow rate. As rotational veloc-
ity is increased, the solids are carried up higher along the kiln wall and
showered down through the air/combustion gas mixture. Typical rotational
velocities are in the range of 1-5 ft/min, measured at the kiln periphery.
Since solids retention time is also affected by rotational velocity, there
a tradeoff between retention time and air/solids mixing. Mixing is improve*
to a point by increased rotational velocity, but the solids retention time
reduced. Mixing is also improved by increasing the excess air rate, but this
reduces the kiln operating temperature. Thus, there is a distinct interplay
between all four operating variables.
4.3.4 Auxiliary Fuel Capacity Evaluation
4.3.4.1 Liquid Injection Incinerators--
As discussed in Section 4.3.1, liquid injection incinerators should be
equipped with an auxiliary fuel firing system to heat the; unit to operating
temperature before waste is introduced. Although not essential from an engi-
neering standpoint, it is desirable for the auxiliary fuel system to have
sufficient capacity to attain this temperature at the design air flow rate for
waste combustion. This capacity requirement can be approximated by the
following heat balance equation :
0.95 mf NHVf
'if Cpi (I»ut - 77>
aSee Section 4.3.3.1 for a discussion of how heat balances are formulated.
4-44
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4-31 mw (02)stoich(w) (1 * EA) Cp aif (T^ - 77
- 4.31 mf (02)stoich(f) Cp air (Tout - 77)
where m, = required auxiliary capacity, Ib/hr
NHVf = net heating value of auxiliary fuel, Btu/lb
N.- = Ib combustion ith product Ib fuel
C~ = heat capacity of ith component, Btu/lb °F
T = proposed operating temperature, measured at the
• incinerator outlet, °F
4.31(02) . , / x - stoichiometric air requirement for waste combustion,
stoicn(.w; ., • yjL ,,_..*.-.
m = proposed waste feed rate (average), Ib/hr
EA = proposed excess air rate, %/100
4.31(02) ,. • h/r\ = stoichiometric air requirement for fuel combustioft,
stoicnir; -Q, air/lb fuel j
This equation is based on these assumptions: (a) air is not preheated,
(b) there is a 5% heat loss through the refractory walls, and (c) the air flow
rate for normal waste burning operation exceeds the air requirements for fuel
combustion during startup.
Since C02, H20, and N2 are the only major components of fuel combustion gases
at stoichiometric firing conditions, this equation can be further simplified
using the heat capacities presented in Section 4.3.3.1 The simplified form
is:
0.95 mfNHVf = mf [0.26 (n^ + n^ + 0.49 n^j (T^ - 77)
> 1.12 mtf (02)stoich(w) (1 * EA)
-------
If this rating is reported in Btu/hr rather than Lb/hr, the capacity require- ^
ment calculated in Worksheet 4-11 can be converted to equivalent units by.-
Qf = mf NHVf
where Q, = required auxiliary fuel capacity, Btu/hr
4.3.4.2 Rotary Kiln Incinerators--
In rotary kiln incinerators, both the kiln and afterburner need to be heated
to operating temperature before waste is introduced. Since the afterburner
temperature is usually higher than the kiln temperature and more critical in
terms of emissions, it should be sufficient to limit the auxiliary fuel capac-
ity evaluation to the afterburner section. Th« evaluation procedure described
for liquid injection incinerators can be modified for this purpose in the
following manner:
• The proposed average waste feed rate (mw) and stoichioraetric air require-
ment for waste combustion should be based on the combined kiln and after-
burner waste feed.
• Temperature (T t) should be specified at the afterburner outlet.
• The excess air rate (EA) used in the calculation should be the proposed!"
excess air level for the afterburner section. J
With these modifications, Worksheet 4-11 can be used to estimate the auxiliary ™
fuel startup requirements for rotary kiln incinerators as well as liquid
injection units.
4.3.5 Combustion Process Control and Safety Shutdown System Evaluation
All incinerators should be equipped with combustion process control systems to
maintain the desired conditions of temperature and excess air. Incinerators
burning hazardous wastes should also be equipped with automatic shutdown
systems in order to prevent the release of hazardous materials to the environ-
ment in the event of flameout, other combustion process upsets, or air pollu-
tion control device failure. The following subsections discuss combustion
process control and automatic shutdown procedures related to upsets in liquid
injection and rotary kiln incinerators. Process control procedures for air
pollution control devices are discussed in Section 4.4.5.
4.3.5.1 Liquid Injection Incinerators—
In most liquid injection incinerator designs, the desired temperature at the
chamber outlet is preset by the operator, and secondary air is fed to the
system at a constant rate. Fluctuations in temperature are controlled by
increasing or reducing the waste or auxiliary fuel feed rate to the burner
within the design turndown ratio. This turndown ratio is fixed, in part, by
the limited range of liquid waste injection velocities required to prevent
flame liftoff or flashback. If waste is injected through the burner nozzle at
too high a velocity, the flame will separate from the burner and be extin- A
guished. If the injection velocity is too low, the waste will burn in the ~
nozzle and damage it. The range of injection velocities needed to prevent
4-46
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these occurrences is determined by the flame propagation rate for the wastes
and the flame retention characteristics of the burner.
Since the burner turndown ratio is also limited by the atomization technique
employed (see Section 4.3.1) and the need to maintain air/fuel stoichiometry
in the burner on turndown, the burner must be equipped with a primary air feed
control system. There are a number of ways to control burner stoichiometry,
depending on whether aspirator burners or forced-draft burners are used and on
manufacturer preference. For evaluation purposes, a package burner/primary
air control system provided by the same manufacturer can be considered
sufficient.
Problems with the automatic temperature control system described above occur
on loss of ignition, or flameout. When flameout occurs, the temperature in
the incinerator drops and more waste is automatically fed to the burner.
Without a heat source for ignition, this waste passes through the incinerator
partially or completely unreacted. Thus, temperature continues to drop, more
waste is automatically injected, and the problem of incomplete combustion is
magnified.
To prevent this phenomenon from occurring, burners are usually equipped with
flame scanners. These devices sense ultraviolet radiation from the flame.
When used in conjunction with an automatic waste feed cutoff, flame scannerL
immediately terminate the feed to the burner on loss of ignition. I
Flame scanners are usually designed to sense ultraviolet radiation from gas or
fuel oil flames. These flames tend to be more stable than the flames from
burning wastes which are usually much more heterogeneous than fuels. For
example, organic wastes containing a significant amount of moisture burn with
a sputtering flame, particularly when a slug of water passes through the
burner. Although combustion may continue despite such occurrences, flame
scanners often sense loss of ignition. This leads to unnecessary waste feed
cutoff.
To prevent unnecessary shutdown, flame scanners can be used in conjunction
with temperature sensors at the outlet of the incinerator. With this sys-
tem, feed is only cut off by a combination of flameout, as sensed by the flame
scanner, and low temperature at the combustion chamber. This considerably
reduces operator problems when relatively heterogeneous wastes are being
burned. If the low temperature cutoff is preset to the minimum temperature
needed for waste destruction, release of hazardous substances to the environ-
ment is also prevented.
The other automatic shutdown parameter related to the combustion process is
high temperature at the incinerator outlet. This can signal loss of secondary
In aspirator burners, primary air is supplied by an induced-draft fan down-
stream from the incinerator. In forced-draft burners, primary air is sup-
plied by a separate blower, although an induced-draft fan may still be
employed to pull the combustion gases through the air pollution control system.
4-47
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combustion air or other control system malfunctions. The high temperature
cutoff point should be well above the tolerance level associated with normal
operating temperature fluctuations to prevent shutdown in the event of routine
variations, and should be low enough to prevent damage to downstream air
pollution control equipment.
Table 4-10 lists three checkpoints for liguid injection incinerator combustion
process control evaluation.
4.3.5.2 Rotary Kiln Incinerators--
In rotary kiln incinerators, temperature is controlled within a specified
range by automatically varying the liquid waste or auxiliary fuel firing rate
within the design turndown ratio and/or manually or automatically controlling
the solid waste feed. Regardless of which technique is employed, provisions
should be included for the following:
• Termination of liquid waste feed on loss of ignition in the burner. If
more than one liquid waste burner is employed, feed only needs to be
terminated in the burner where flameout occurs. See Section 4.3.5.1 for
a discussion of flame supervision systems.
• Termination of solid waste feed to the kiln when low temperatures are
sensed at the kiln outlet. If the feed to the kiln is automatic or »
semiautomatic, then the low temperature cutoff system should also be J*
automatic. If manual feeding is employed, an alarm system is needed to|-
warn the operator. The low temperature cutoff point should be such that
solid waste burnout can be maintained, but at lower than the normal
operating temperature to avoid shutdown due to routine temperature
fluctuations. Engineering judgment must be used to determine an
acceptable minimum temperature.
• Termination of solid waste feed on loss of negative pressure at the kiln
outlet.
TABLE 4-10. COMBUSTION PROCESS CONTROL EVALUATION PROCEDURE
Is each burner equipped with an automatic flame supervision system, as
discussed in the preceding subsection, (Section 4.3.5.1)?
Is the system equipped with an automatic high temperature/low temperature
control system, employing variable flow of either waste or auxiliary
fuel?
Is each burner equipped with an air supply control system so that air:
fuel stoichiometry is maintained on turndown?
4-48
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Afterburner burner temperature can be controlled by varying the liquid or
auxiliary fuel feed or by varying the secondary air flow rate. Regardless of
which technique is employed, provisions should be included for the following:
• Termination of liquid waste or auxiliary fuel feed on loss of ignition
(see Section 4.3.5.1 for a discussion of flame supervision). This cutoff
is necessary to prevent the release of unburned waste contaminants (if
liquid waste is being burned) and to prevent potential explosion on
release of unburned fuel. However, it also eliminates the function of
the afterburner. Therefore, solid waste feed to the kiln should also be
terminated on loss of ignition in the afterburner. To minimize the
occurrence of flameout in the afterburner, only "clean," homogeneous
liquid wastes (or fuel) should be burned.
• Termination of solid waste feed to the kiln if low temperatures are
sensed at the afterburner outlet. The afterburner feed should be main-
tained, however, to minimize potential release of unburned contaminants.
As previously stated, the low temperature cutoff point should be such
that combustion is maintained, but at lower than normal operating
temperatures to avoid shutdown due to routine fluctuations.
• Termination of solid waste feed to the kiln if high temperatures are j
sensed at the afterburner outlet. This is necessary to prevent damage to
the refractory lining and to downstream air pollution control devices. )
The high temperature cutoff point should be well above normal operating -.
temperatures, but low enough to avoid damage to the system. In the event
of this cutoff, some liquid waste or fuel feed to the afterburner should
be maintained to complete combustion of off-gases from solid wastes
remaining in the kiln.
In addition to these criteria, all liquid waste burners in the kiln and after-
burner should be equipped with manufacturer specified primary air control
systems so that air/fuel stoichiometry is maintained on turndown.
Table 4-11 presents a five-point checklist for rotary kiln incinerator combus-
tion process control evaluation.
TABLE 4-11. COMBUSTION PROCESS CONTROL EVALUATION PROCEDURE
1. Is each burner in the kiln and afterburner equipped with an automatic
flame supervision system for waste feed shutdown?
2. Is the afterburner equipped with an automatic high temperature/low tem-
perature control system employing variable flow of waste, auxiliary fuel,
or secondary combustion air?
3. Is the kiln equipped with an automatic temperature control system
employing variable feed of either waste or auxiliary fuel?
(continued)
4-49
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TABLE 4-11 (continued)
4. Is the kiln equipped with a pressure monitoring system which alerts the
operator or automatically terminates waste feed if negative pressure is
lost?
5. Is each burner equipped with an air supply control system so that
air .-fuel stoichiometry is maintained on turndown?
4.3.6 Construction Material Evaluation
Since hazardous waste incinerators usually operate at temperatures of 1,800°F
or higher (sometimes hundreds of degrees higher for halogenated wastes),
refractory linings are virtually always employed to prevent damage to the
structural steel shell and to reduce heat loss. Aluminosilicate refractories
backed up by insulating brick are most commonly used, although refractories
made predominantly of silica or specialty refractories may be used in certain
applications. Table 4-12 lists various types of aluminosilicate and silica j
refractories along with their approximate chemical compositions, fusion I*
temperatures, and resistances to degradation by different chemical species- |
that may be encountered in incinerator combustion gases.
Table 4-12, along with the operating temperature range and the chemical compo-
sition of the waste, can be used to evaluate the suitability of a refractory
for a given application.
In addition to refractory composition, the physical form of the material
should also be considered in evaluating liquid injection vs. rotary kiln
incinerator designs. Suspended refractory brick is normally used in station-
ary liquid injection units and afterburners. In kilns, however, castable
refractories are normally used to better withstand the physical abrasion and
vibration imparted by rotation and contact with solid wastes. Castable
refractories are made of the same clays as those used in aluminosilicate
firebrick, but bonding agents are added to impart strength until the
temperature in the incinerator during initial startup is raised sufficiently
high to "cure" the material and develop ceramic bonds. Castable refractories
are easily installed in much the same manner as cement; thus, they are also
used for quick repairs and spot patching.
4.4 AIR POLLUTION CONTROL AND GAS HANDLING SYSTEM DESIGN EVALUATION
Figure 4-11 presents a logic diagram for air pollution control and gas han-
dling system design evaluation. It consists of six separate evaluation
procedures intended to answer the following questions:
aSee references listed in Table 4-12 for information on specialty refractions
4-50
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TABLE 4-12. GENERAL CHARACTERISTICS OF SILICA AND ALUMINO-
SILICATE REFRACTORY BRICK (6, 7, 8, 9, 10]
Type
Silica
High- duty
fireclay
Super-duty
fireclay
Typical
composition
95% Si02
5 -% Si02,
40% A1203
52% Si02,
42% A1203
Fusion
temperature, °Fa
3,100
3,125
3,170
Resistant
to
HC1, NH3, acid
slags
Most acids,
slag condi-
tions
HC1, NH3, S02,
most acids
Degraded
bv
Basic slags,
Al, Na, Mg,
F2 , C12 , H2 ,
(>2,550°F)
High- lime
slags, other
bases at high
temperature
Basic slagsj.
Na, Mg, F2,|
Acid-resistant 59% Si02
(type H)
High-Alumina 50-85%
A1203
3,040
3,200-3,400
Extra-High-
Alumina
Mullite
90-99%
A1203
71% A1203
3,000-3,650
3,290
Excellent for
most acids,-
bases in mod-
erate concen-
tration
HC1, NH3, S02
HC1, HF, NH3,
S02, S2/ HN03,
H2S04, C12
HC1, S02, NH3
C12, H2,
(>2,550°F)
HF, H3P04
Basic slags,
Na, Mg, F2,
C12, H2
(>2,550°F)
Na, F2
(>1,800°F)
Na, F2, C12/
H2 (>2,550°F)
A safety factor of at least several hundred degrees between refractory fusion
temperature and incinerator operating temperature is advisable.
4-51
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EMISSION SPECIES/AIR POLLUTION
CONTROL DEVICE MATCHING CONSIDERATIONS
SECTION 4.4.1
AIR POLLUTION CONTROL DEVICE DESIGN
AND OPERATING CRITERIA EVALUATION
SECTION 4.4.2
1
QUENCHING AND MIST ELIMINATION
EVALUATION
SECTION 4.4.3
I
PRIME MOVER CAPACITY EVALUATION
SECTION 4.4.4
I
PROCESS CONTROL AND AUTOMATIC
SHUTDOWN SYSTEM EVALUATION
SECTION 4.4.5
I
MATERIAL OF CONSTRUCTION
CONSIDERATIONS
SECTION 4.4.6
Figure 4-14.
Logic diagram for air pollution control and
gas handling system design.
4-52
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(1) Are the generic air pollution control device designs appropriate for
removal of the pollutants present in the combustion gases?
(2) Are the air pollution control device designs and operating criteria
consistent with current industry practice and capable of achieving the
necessary pollutant removal efficiencies?
(3) Have combustion gas quenching and mist elimination been properly con-
sidered in the system design?
(4) Does the prime mover have sufficient capacity to handle the combustion
gas flow and overcome pressure drops across the air pollution control
system?
(5) Are appropriate process control and safety shutdown interlocks
incorporated?
(6) Are appropriate materials of construction employed?
These topics are addressed in Sections 4.4.1 through 4.4.6
4.4.1 Emission/Air Pollution Control Device Matching Criteria
When incinerating hazardous wastes, air pollutants may arise from two sources:
incomplete combustion of organic waste constituents and conversion of certaf
inorganic constituents present in the waste and/or combustion air to ultimate
oxidation products. The products of incomplete combustion include carbon
monoxide, carbon, hydrocarbons, aldehydes, amines, organic acids, polycyclic
organic matter (POM), and any other waste constituents or their partially
degraded products that escape thermal destruction in the incinerator. In well
designed and operated incinerators, however, these incomplete combustion
products are only emitted in insignificant amounts. The primary end products
of combustion are, in most cases, carbon dioxide (002) and water vapor (H20).
When wastes containing elements other than carbon, hydrogen, and oxygen are
burned, however, ultimate combustion products other than C02 and water vapor
are formed. These include:
• Hydrogen chloride (HC1) and small amounts of chlorine (C12) from the
incineration of chlorinated hydrocarbons,
• Hydrogen fluoride (HF) from the incineration of organic fluorides,
• Bromine (Br2) and lesser quantities of hydrogen bromide (HBr) when
organic bromides are burned,
• Iodine (I2) from organic iodide compound incineration,
• Sulfur oxides, mostly as sulfur dioxide (S02), but also including 1% to
5% sulfur trioxide (S03), formed from sulfur present in the waste
material and auxiliary fuel,
4-53
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• Phosphorus pentoxide (P205), formed from the incineration of
organophosphorus compounds,
• Nitrogen oxides (NO ) from thermal fixation of nitrogen in the combustion
air or from organic nitrogen compounds present in tne waste, and
• Particulates, including metal salts from the waste, metal oxides formed by
combustion, and fragments of incompletely burned material (primarily
carbon).
Gaseous pollutant concentrations in the combustion gases leaving an incinerator
can be estimated by the methods described in Section 4.3.2 . Step-by-step pro-
cedures for calculating these concentrations are presented in Worksheets 4-2
and 4-4. Particulate emissions from liquid injection incinerators can also be
estimated from the ash content of the waste, the combustion gas flow rate cor-
rected to standard conditions of temperature and pressure (see Worksheets 4-2
and 4-12), and the oxygen content of the combustion gas. Oxygen concentration
is important because particulate loadings are often expressed as gr/scf (mg/m3)
corrected to zero percent excess air. A procedure to estimate particulate
concentrations in combustion gases from liquid injection incinerators is
presented in Worksheet 4-12. Particulate emissions from rotary kilns are more
difficult to estimate because sizable fractions of incombustible material art
removed as bottom ash, and the fly ash:bottom ash ratio is usually unknown
prior to actual testing. In general, particulate emissions from rotary kill
burning solid wastes are greater than particulate emissions from liquid injec-
tion incinerators. This is due to the fact that solid wastes frequently have
a higher ash content than liquid wastes.
1
Lr*
As indicated in Section 4.1, venturi scrubbers, packed bed scrubbers, and
plate tower scrubbers are used for air pollution control at the majority of
hazardous waste incineration facilities. In selecting from among these ge-
neric scrubber designs, the factors most frequently considered are the need
for particulate emission control, particulate loading in the combustion gas
(assuming that control is required to meet emission standards), the types of
gaseous pollutants to be removed, and the desired removal efficiencies.
Particulate loading governs the choice between venturi and packed bed or plate
tower scrubbers for a given application, and the characteristics of the gas-
eous emission species govern the choice of scrubber medium (e.g., water vs.
caustic solution, lime solution, etc.) as well as generic scrubber design.
These factors are discussed in the following subsections.
4.4.1.1 Particulate Removal—
Particulate removal is required when the ash content of the waste is such that
emissions will exceed applicable state, local, or Federal standards. Particu-
late removal is nearly always required at rotary kiln incineration facilities,
and may or may not be required for liquid injection incinerators depending on
the ash content of the waste. (See Worksheet 4-12 for a method to estimate
particulate emissions from liquid incinerators.) Venturi, packed bed, and
aThese procedures are not applicable for products of incomplete combustion.
4-54
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plate tower scrubbers can all be used to control particulate emissions from
hazardous waste incinerators, depending on the particulate loading in the gas.
Packed bed or plate tower scrubbers are commonly used at liquid injection
incinerator facilities where particulate control is considered secondary to
gaseous emission control. These devices are superior to venturi scrubbers for
removal of gaseous pollutants and they operate at lower pressure drops; thus
they are more economical to operate. Both the plate tower and the packed bed
scrubber have some capacity for particle collection, and they are considered
applicable for streams containing low particulate loadings with particles
generally >5 ym in diameter [11]. Cut diameters as low as 1 M"» can be at-
tained with plate scrubbers or packed bed scrubbers employing 1-inch berl
saddles or Raschig rings [12]. However, packed bed and plate tower scrubbers
are not primarily designed for particulate control. Both devices, particular-
ly packed bed scrubbers, are susceptible to pluggage by solids. Therefore,
they are seldom, if ever, used as the primary particulate collection devices
at rotary kiln incineration facilities or liquid injecton incineration facili-
ties where high ash content wastes are burned. Venturi scrubbers are the most
popular devices for these applications.
High energy venturi scrubbers are capable of 99% removal of particulate in the
1- to 2-pm size range and above, 90-99% removal of particulate in the 0.5 - to
1-um size range, and 50% removal of particulate in the 0.3- to 0.5-um size
range [13]. By comparison, particulates emitted from liquid and solid waste!.
incinerators have mean diameters in the 0.5- to 3-um and 5- to 100-um range*,
respectively. Therefore, venturi scrubbers are capable of efficient particxA-.
late removal for most hazardous waste incineration applications.
Table 4-13 presents a checklist procedure that can be used to compare par-
ticulate removal requirements with proposed control strategies.
TABLE 4-13. PROCEDURE TO COMPARE PARTICULATE REMOVAL
REQUIREMENTS WITH PROPOSED CONTROL STRATEGIES
1. If a rotary kiln incinerator facility is being evaluated, is a venturi
scrubber provided for particulate control?
2. If a liquid injection incinerator facility is being evaluated, does the
estimated particulate emission rate exceed applicable standards? See
Worksheet 4-12 for a procedure to estimate particulate emissions.
3. If particulate emissions do exceed standards, is a venturi scrubber
provided for particulate removal (upstream from other gaseous emission
control devices)?
4. If not, are packed bed or plate tower scrubbers to be used for
simultaneous particulate and gaseous pollutant removal?
5. If so, can the selected control device function properly in its dual
role? (Technical assistance may be needed to make this determination).
4-55
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4.4.1.2 Gaseous Pollutant Removal-- •
Gaseous pollutants generated by hazardous waste incineration include HC1, C12,
SO , Br2,, HBr, HF, P205 and NO^, of which NO^ and HC1 are most commonly encoun-
tered. ' ' These compounds are usually removed from the combustion gases by
packed bed or plate tower scrubbers, although venturi scrubbers are used in
some applications for simultaneous particulate and gaseous pollutant removal.
For highly soluble gases such as HC1 and HF, water can be used in packed bed
or plate tower scrubbers to control emissions. When water is used as the
scrubbing liquor, an acidic blowdown stream is produced that must be neutral-
ized prior to discharge. HC1 concentration in the scrubbing liquor is normal-
ly limited to 1-2% by adjusting the makeup water and blowdown rates. The
scrubber must also be lined with an acid-resistant material, as discussed in
Section 4.4.6.
Caustic solution (typically 18-20 wt % caustic soda in water) is also commonly
used in packed bed and plate tower scrubbers to control HC1 and HF emissions.
Because these compounds react with caustic, the driving force for mass trans-
fer is increased and more efficient removal is achieved at the same liquid-to-
gas ratio and packing depth (or number of trays). Neutralization is also
achieved "in situ" if sufficient caustic is supplied for complete conversion I
of HC1 to NaCl. Unlike water scrubbing, caustic scrubbing can also achieve ;
high removal efficiencies for S02, Pa^s, and HBr, which are less soluble in
water than HC1 or HF. When gases such as S02 are being scrubbed, the caustic ,
addition rate is adjusted to maintain an alkaline scrubbing media. Alter- I*
natively, the caustic addition rate can be adjusted to sub-stoichiometric |
levels. This reduces the scrubber water makeup and blowdown rates needed to* •
maintain a specified acid concentration in the scrubber liquor.
Lime slurry, typically 10-32 wt % Ca(OH)2 in water, can also be used to con-
trol emissions of HCl, HF, S02, and PaOj. However, lime slurries are not
often used as the scrubbing liquid in packed bed designs because of plugging
problems. Also, the use of lime slurries can lead to plugging of the spray
nozzles and cause scale formation on the surfaces of the scrubber equipment,
particularly scrubber internals and mist eliminator surfaces.. The magnitude
of the scaling problem will depend on the levels of HCl, HF, P20$» and SO in '
the incinerator exhaust gases. Lime solutions are used in plate tower scrub-
bers, however, because lime is less expensive than caustic. At several haz- '
ardous waste incineration facilities, venturi scrubbers with lime slurry i
injection are used to control emissions of HCl, HF, and
NO emissions are not economically amenable to control by scrubbing or other
post-generation removal techniques. NO emissions can be minimized by con-
trolled temperature combustion, but this is seldom possible in hazardous
waste incineration due to the requirements for efficient, high temperature
waste destruction.
1 2 and HI emissions may be an occasional problem as veil.
is present in conjuncton with HCl, but equilibrium favors HCl formation
at the high temperatures employed in chlorinated waste incinerators. C12 and
the other free halogens are not readily removed by scrubbing.
4-56
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When organic bromine and iodine wastes are incinerated, the exhaust gases from
the incinerator will contain bromine and iodine both as hydrogen halides and
as free halogens. Hydrogen bromide can be readily removed by scrubbing with
caustic soda. The technology for controlling emissions of bromine, hydrogen
iodide, and iodine, however, is not well developed. Some of the methods that
could be considered to control bromine emissions include: (1) absorption in
ammonia solution with the formation of ammonia bromide; (2) absorption in
caustic soda or soda ash solution in which bromine reacts to form sodium
bromate, sodium bromide, and either water or carbon dioxide,- and (3) absorp-
tion in lime slurry in which bromine reacts to form calcium bromide and cal-
cium bromate. It is also conceivable that bromine can be reduced by the
sulfur dioxide present in the flue gas, giving rise to the formation of a
spray of fine droplets of hydrobromic and sulfuric acids, which could
subsequently be removed by absorption in caustic solutions or lime slurries.
when combustion gases contain a high particulate loading as well as one or
more of the gaseous pollutants discussed above, venturi scrubbers are often
used in conjunction with packed bed or plate tower scrubbers. Venturi scrub-
bers remove the particulate from the stream to prevent fouling of the packed
bed or plate tower absorber, and may also remove a significant fraction of
gases highly soluble in water. However, venturi scrubbers alone are not
considered suitable for removal of low solubility gases,- when water is used
the scrubbing medium, estimated efficiencies are less than 50-75% [11].
Venturi scrubbers using water are not suitable for highly efficient (>99%)
removal of HCl or HF either.
Table 4-14 presents a checklist procedure that can be used to compare gaseous
pollutant removal requirements with proposed control strategies. The
following rules of thumb are generally applicable:
• Water, caustic, or lime in packed bed or plate tower scrubbers for
removal of HCl and/or HF,
• Caustic or lime in packed bed or plate tower scrubbers for removal of
other acid gases discussed above, and
Specialized scrubbing techniques for HBr, Br2, HI, and I2- Technical
assistance is advised in evaluating these systems.
4.4.2 Air Pollution Control Device Design and Operating Criteria Evaluation
4.4.2.1 Venturi Scrubbers--
Venturi scrubbers utilize the kinetic energy of a moving gas stream to atomize
the scrubbing liquid into droplets. Liquid is injected into the high velocity
gas stream either at the inlet to the converging section or at the venturi
throat. In the process, the liquid is atomized by the formation and subse-
quent shattering of attenuated, twisted filaments and thin, cuplike films.
These initial filaments and films have extremely large surface areas available
for mass transfer [14].
Venturi scrubbers are usually designed for particulate collection, but they
can be used for simultaneous gas absorption as well. However, the design of
4-57
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TABLE 4-14. PROCEDURE TO COMPARE GASEOUS POLLUTANT REMOVAL
REQUIREMENTS WITH PROPOSED CONTROL STRATEGIES
From Worksheet 4-2 or 4-4, identify the gaseous pollutants present in the
combustion gases in excess of desired emission levels.
Is removal of Brg , HBr, Iz, or HI required? If YES, technical assistance
may be required.
3. Is removal of SO or P20s required? If YES, proceed to checkpoint #4.
If NO, proceed to checkpoint #5.
4. Is caustic or lijne slurry scrubbing to be used for SO ./P205 removal, as
described in the preceding pages? (Water scrubbing afone is usually not
sufficient to remove these compounds). *
5. Is removal of HC1 or HF required?
6. Is alkali or aqueous scrubbing in a packed bed or plate tower scrubber, F
or alkali scrubbing in a venturi scrubber, to be used for HCl/HF removal?
I '
7. If not, are other methods for HCl/HF removal provided? I
8. If so, are these methods acceptable? (Technical assistance may be needed 4
to make this determination) .
venturi scrubbers for removal of gaseous contaminants is dependent on the '
availability of applicable experimental data. There is no satisfactory gener-
alized design correlation for these types of scrubbers, especially when I
absorption with chemical reaction is involved. Reliable design must be based I
on full-scale data or at least laboratory- or pilot-scale data.
Correlations are available to design venturi scrubbers for particulate removal. ^
The important design parameters are particulate loading and desired removal
efficiency, particle size distribution, pressure drop, liquid-to-gas ratio,
and gas velocity.
Particulate loading, size distribution, and removal efficiency-If the partic-
ulate size distribution and desired removal efficiency are known, several
correlations can be used to predict the required cut diameter for design .
purposes. Calvert et al. [15] have developed parametric plots of overall
penetration versus the ratio of cut diameter to mass median diameter with
geometric standard deviation as the third parameter. These plots can be used
to determine the required cut diameter if the desired removal efficiency and *
particle size distribution are known. Cut diameter can then be related to
pressure drop, liquid-to-gas ratio, and gas velocity for design purposes as
described in the following subsection. »
4-58
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Hesketh [16] has also developed an empirical relationship between penetration
of all particles 5 |jra or less in diameter and the pressure drop across
Venturis based on data from the collection of a variety of industrial dusts.
Assuming that particles larger than 5 |jm are collected with 100% efficiency,
this relationship may be utilized with size distribution data to estimate
overall penetration:
Pt = 0.065W(AP)"1-43
where Pt = fractional penetration
W = the weight fraction of inlet particles 5 urn or less in diameter
AP = pressure drop, in. WG
The major drawback in applying these correlations to venturi scrubber design
evaluation is that the particle size distribution will rarely be known until
testing is performed after startup. The size distribution of particles emit-
ted from an incinerator depends upon the relative number of particles genera-
ted by several factors responsible for the formation of particulate emissions:
(1) mechanical entrainment of combustible and noncombustible particles in the
furnace gases, (2) pyrolysis of hydrocarbons and subsequent condensation, and
(3) volatilization of metallic salts and oxides present in the wastes and
auxiliary fuels. Further, particle growth due to agglomeration and
condensation of moisture between the incinerator and the control device will |-
affect the particle size distribution. There is no method for the a priori I
prediction of particle size distributions resulting from waste incineration. •*
While incineration of liquid wastes may result in mean particle diameters in
the 0.5-.-to 3-um range, mean particle diameters resulting from incineration of
solid waste could range from 5 to 100 urn, depending upon the size distribution
of feed solids, their combustion characteristics, and the incinerator design.
If particle size distribution data is available, methods described in refer-
ences 15 or 16 can be used to determine the required cut diameter.
Pressure drop, liquid-to-gas ratio, and gas velocity—As described above,
particle cut diameter is a frequently used parameter for expressing and deter-
mining the particle collection performance of wet scrubbers. One reason for
this is because plots of collection efficiency versus particle diameter tend
to be rather steep in the region where inertial impaction is the predominant
collection mechanism. Because the cut is fairly sharp for venturi scrubbers,
a rough approximation of scrubber performance may be made by assuming that
particles larger than the cut diameter are collected with 100% efficiency
while those saaller will not be collected. A plot of cut diameter versus
pressure drop for gas-atomized scrubbers is presented in Figure 4-15 [12].
The plot is based on industrial and experimental data as well as mathematical
models, and can be used in conjunction with the methods developed by Calvert
et al. [15] to estimate penetration as a function of pressure drop.
Available data indicate that Venturis at hazardous waste incineration facili-
ties operate with pressure drops in the 30- to 50-in. WG range. Based on
Figure 4-15, this indicates that venturi scrubbers at these facilities are
designed for 0.3- to 0.4-(jm cut diameters.
4-59
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E
a
as
0.4
0.3
0.2
0.1
Figure 4-15.
2
(0.50)
3 4 5
I0.73MLOM1.2)
10
(2.51
20
(5.0)
30 40 50
(7.51 (101(12)
100
(25)
CAS PHASC PRESSURE DROP. in-. HjO <*P»)
Pressure drop versus cut diameter for gas-atomized scrubber
systems (Experimental data from large Venturis, other gas-
atomizers, scrubbers, and mathematical model.) [12].
Pressure drop in venturi scrubbers is theoretically related to gas velocity
and liquid-to-gas ratio, as shown in the following relation developed by
Calvert [15]. This relationship assumes that all energy is used to accelerate
the liquid droplets to the throat velocity of the gas.
where
AP * 2.12 x 10~5(UG)2 ~
pressure drop, in. WG
«_ = gas velocity, ft/s
Q./Q- =* liquid-to-gas ratio, gal/1,000 ft3
I* G
A?
U.
An alternative empirical approach by Hesketh [16] indicates that the pressure
drop for Venturis is proportional to U* and (0./QG)0*78, as well as to the
gas density p_ (measured downstream from the venturi throat) and to A0*133,
where A is the cross-sectional area of the venturi throat:
4-60
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10.78
AP = (U )*P_/
1270
Pressure drop will be relatively unsensitive to changes in A because of the
small exponent, but density will be inversely proportional to the gas tempera-
ture. These relationships can be used as internal consistency checks for the
proposed conditions of gas velocity, liquid-to-gas ratio, and pressure drop.
Liquid-to-gas ratios for venturi scrubbers are usually in the range of 5 to 20
gal/1,000 ft3 of gas. At existing hazardous waste incineration- facilities,
liquid-to-gas ratios ranging from 7 to 45 gal/1,000 ft3 of gas have been
reported. : In many cases, a minimum ratio of 7.5 gal/1,000 ft3 is needed to
ensure that adequate liquid is supplied to provide good gas sweeping. Gas
velocity data are not available at this time for venturi scrubbers operating
at hazardous waste incineration facilities. Typical venturi throat velocities
for other applications, however, are in the 100- to 400-ft/s range. The low
end of this range, 100-150 ft/s, is typical of power plant applications, while
the upper end of the range has been applied to lime kilns and blast furnaces.
Table 4-15 presents a procedure that can be used to evaluate proposed design
and operating criteria for venturi scrubbers. |-
TABLE 4-15. VENTURI SCRUBBER DESIGN EVALUATION PROCEDURE
Is the design pressure drop comparable to current industry practice
(i.e., 30-50 in. «G)?
Are the proposed gas velocity and liquid-to-gas ratio comparable to
current industry practice?
Are the design pressure drop, gas velocity, and liquid-to-gas ratio
internally consistent? (see Worksheet 4-13.)
4.4.2.2 Packed Bed Scrubbers--
As described in Chapter 2, packed bed scrubbers are vessels filled with ran-
domly oriented packing material such as saddles and rings. The scrubbing
liquid is fed to the top of the vessel, with the gas flowing in either cocur-
rent, countercurrent, or crossflow modes. As the liquid flows through the
bed, it wets the packing material and thus provides interfacial surface area
for mass transfer with the gas phase. Water and caustic solution are both
commonly used as the liquid absorbent.
In the absorption of gaseous contaminants, the rate of mass transfer is direc-
tly proportional to the concentration gradient driving force, and restricted
by both gas and liquid film resistances. The primary design variables for gas
absorption are the depth of packing, liquid-to-gas ratio, superficial gas
4-61
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velocity, and contact time. Pressure drop across the bed is also an important
design consideration, but does not directly affect absorption efficiency.
Packed bed scrubbers can be used for limited particulate collection as well as
gas absorption, but, as explained in Section 4.4.1, they are not primarily
designed for this purpose.
Packing depth--The depth of packing required is best calculated from the
following expression [6]:
2 = NOG X HOG
where Z is the packing depth, N is the number of overall transfer units, and
H _ is the height of a transfer unit.
The number of transfer units depends on the removal efficiency requirement.
In gaseous emission control for hazardous waste incineration, the gaseous
contaminants to be removed usually constitute less than 10% of the total gas
stream because of the presence of nitrogen, oxygen, carbon dioxide, and water
vapor as the major gaseous components. Under these circumstances, the number
of transfer units can be calculated from the expression [6]:
where Y is the actual gas concentration of the contaminant, Yj is the con-
centration at the scrubber outlet, Yj is the concentration at the inlet,
and Y is the gas concentration of the contaminant in equilibrium with the
scrubBing liquid. In industrial applications, the gaseous contaminant is
often very soluble in the scrubbing liquid, as is the case of hydrogen
chloride in water, or reacts very rapidly with the scrubbing liquid, as is the (
case of hydrogen chloride with caustic solution. For both of these cases, the
equilibrium gas concentration is negligible and the number of transfer units .
can be calculated as:
/„ \
NOG =
where Y! and 7% are the inlet and outlet concentrations of the gaseous
contaminant.
The height of a transfer unit is a characteristic of the particular system,
and is influenced by the type and size of packing, gas and liquid flow rates,
and gas and liquid physical and chemical properties. It is often taken as a
constant over fixed ranges of operation and is given by the expression [6]:
HOG
4-62
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where G is the total gas flow rate per unit cross section of bed, K is the
overall gas mass transfer coefficient, a is the interfacial surfacegarea per
unit volume of packing, and P is the total pressure. Values of K a for many
of the more commonly used gas absorption processes have been published in the
literature [17,18]. Typical values of K a are given in Table 4-16. For
gaseous contaminants that are highly solible or chemically reactive with the
scrubbing liquid, the height of a transfer unit H is typically in the 1 to
1.7-ft range.
TABLE 4-16. TYPICAL VALUES OF K a [18]
Reprinted with permission from Industrial and Engineering
Chemistry, 59(2) Copyright 1967 American Chemical Society
Gas
C12
HC1
S02
C02
S02
C12
Scrubbing
solution
NaOH
H20
NaOH
NaOH
H20
H20
Ib mole
in. H20'ffi-s
.5
1.4 X 10 5
1.1 X 10 6
4.8 x 10 6
1.6 x 10 7
2.2 x 10 8
9.5 x 10
The transfer unit concept can be used to calculate packing depth requirements
if overall gas mass transfer coefficients are available. For quicker esti-
mates, however, other methods can be used. In Table 4-17, the estimated
depths of packing beds required are given for various removal efficiencies of
gaseous contaminants that are highly soluble or chemically reactive with the
scrubbing liquid. These estimated packing depth requirements are based on the
general rule that 1 in. size packings yield an HQ_ (height of a transfer unit)
equal to 1 ft, 1-1/2 in. size packings yield an H equal to 1.3 ft, and 2 in.
size packings yield an HQ equal to 1.5 ft [11].
The depth of packed beds for gaseous emission control typically ranges from
4.0 to 9.3 ft. The depth of packing can also be changed if removal efficiency
is lower than anticipated or if the carrier gas flow rate or waste streams
incinerated change. However, an evaluation of the packing depth requirement
is still desirable to assure that a packed tower design has sufficient
capacity.
Liquid-to-gas ratio--The liquid-to-gas ratio is a design and operating param-
eter of prime importance. It is needed in the determination of the scrubber
diameter, and it has an effect on the height of a transfer unit. A high
liquid-to-gas ratio will lead to the requirement of a larger diameter, but at
the same time will also reduce the height of a transfer unit.
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TABLE 4-17. PACKING DEPTH REQUIRED TO ACHIEVE
SPECIFIED REMOVAL EFFICIENCY3 [11]
Reprinted by permission of Chemical Engineering Progress
Removal
efficiency,
percent
90
95
98
99
99.5
99.9
99.99
Packing size
1 in.
2.5
3.0
4.00
4.59
5.24
6.99
9.25
1-1/2 in.
3.2
3.74
4.99
5.74
6.50
8.76
11.5
2 in.
Depth, ft
3.74
4.49
6.00
6.99
8.01
10.5
14.0
3 in.
5.74
6.76
8.99 .
10.2
12.0
15.7
21.0
3.5 in .
6.99
8.50
11.3
13.0
14.8
19.8
26.0
Applicable only to gaseous contaminants that are highly soluble
or chemically reactive with the scrubbing liquid. Also, there are
variations in packing depths vs. the type of packing used (approx-
imately ±25% to 30%) which have not been taken into account.
For each set of design conditions, there is a minimum liquid-to-gas ratio that
is required to achieve the desired removal efficiency. This minimum ratio can
be computed from equilibrium relationships. For gas contaminants that are
highly soluble or chemically reactive with the scrubbing liquid, the equili-
brium vapor pressure approaches zero. Theoretically, there is no minimum
liquid-to-gas ratio for the removal of these gas contaminants, based on vapor-
liquid equilibrium considerations. In practice, of course, sufficient scrubb-
ing liquid must be provided to assure that it is not saturated with the gas
contaminants removed, and to keep the packing surfaces thoroughly wet. When
scrubbing HCl, for example, acid concentration in the scrubber liquor is
normally limited to 1-2%.
The chemical requirement for acid gas neutralization iri a scrubber is directly
proportional to the halogen content, sulfur content, arid phosphorus content of
the hazardous waste streams incinerated. If caustic soda is used, at 60% in
excess of the stoichiometric amount, the requirement is given as:
Caustic soda requirement = 0.0176 x wt % Cl in waste + 0.0328
(Ib/lb waste) x wt % F in waste + 0.0604 x wt % P
in waste + 0.0389 x wt % S in waste
If the caustic content of the scrubbing solution is known, the minimum liquid
flow rate for neutralization can then be calculated in terms of gallons of
60% excess is typical for single pass scrubbing. When scrubber liquid is
recycled, 5-30% excess can be acceptable for neutralization.
4-64
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solution per pound of waste incinerated. The combustion gas yield per pound
of waste (previously calculated in Section 4.3.2) can then be used in conjunc-
tion with this value to determine the minimum liquid-to-gas ratio in units of
gallons per standard cubic foot of combustion gas.
Such methods can be used to determine the chemical requirements and minimum
liquid-to-gas ratio for scrubber water neutralization. However, complete
neutralization is not required for efficient acid gas scrubbing, as evidenced
by the fact that water is often used as the scrubbing liquor. When water is
used, acid gas solubilities as functions of temperature must be known to
accurately determine equilibrium relationships and minimum liquid-to-gas
ratios. A more complex situation is encountered in caustic scrubbing since
absorption in water and reaction occur simultaneously.
A simpler approach to evaluating minimum liquid-to-gas ratio requirements is
to examine current industry practices and/or to rely on actual test data.
Normal liquid-to-gas ratios in packed beds vary from 6 to 75 gal/1000 acf,
with most units operating at between 22 and 52 gal/1000 acf. In general,
lower liquid-to-gas ratios are needed for once-through scrubbing systems than
for recycle systems to achieve the same removal efficiency because the driving
force for mass transfer is greater for once-through scrubbing. Likewise,
increasing the caustic addition rate will lower the minimum required
liquid-to-gas ratio, all other factors being equal.
The upper limit for liquid-to-gas ratio in packed towers is set by the flood-
ing condition. Generalized correlations of flooding velocities are available
and can be used to estimate the maximum liquid-to-gas ratio [6]. In practice,
however, flooding can be readily detected by sharply increased pressure drop
across the packed bed, and it can be eliminated by adjustment of the liquid
flow rate during operation. A quick check for proper column diameter sizing
can be accomplished by calculating the superficial gas velocity through the
tower. For packed beds with countercurrent flow, superficial gas velocities
are normally in the range of 7 to 10 ft/s, corresponding to approximately 60%
of the flooding velocity. The 40% safety factor allows for fluctuating gas
flows from the incinerator caused by changing waste composition and feed rate.
Contact time—In gas absorption devices, higher efficiencies are attained by
allowing the gas and liquid phases to be in contact for a longer period of
time. Removal efficiencies for gaseous contaminants in packed beds are di-
rectly related to the depth of packing, which in turn determines the contact
time.
The contact time required for gas absorption is a function of the rate of mass
transfer. The mass transfer rate, in general, is dependent upon four separate
resistances: gas phase resistance, liquid phase resistance, chemical reaction
resistance, and a solids dissolution resistance for scrubbing liquids contain-
ing solid reactants. For absorption of gaseous contaminants that are highly
soluble or chemically reactive with the scrubbing liquid, such as the absorp-
tion of HCl by caustic solution, the contact time required for 99% removal is
extremely short (on the order of 0.4 to 0.6 s).
4-65
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Pressure drop — For gas flow through packed beds, the pressure drop may be
calculated using the approximate correlation developed by Leva [6]:
AP/Z = C2 10
where AP/2 is the pressure drop in in. WG/ft of packing, U is the liquid
superficial velocity in ft/s, p_ is the gas density in Lb/rt3, U is the
'superficial gas velocity in ft/s, and C2 and C3 are constants. Pressure drops
for the common commercial packings can also be obtained from plots of pressure
drop versus gas and liquid flow rates. These plots are available from the
packing manufacturers and should be used for more accurate estimation of
pressure drop in the design evaluation process. For packed beds used for
gaseous emission control in hazardous waste incineration facilities, the
pressure drop usually ranges from 2.0 to 7.2 in. WG. Since the total pressure
drop across the packed bed is directly proportional to the depth of packing,
it indirectly affects the removal efficiency of gaseous contaminants. Higher
pressure drops also result in more efficient particulate collection.
Table 4-18 presents a procedure that can be used to evaluate packed bed scrub-
ber design, based on the foregoing considerations of packing depth, liquid-to-
gas ratio, superficial gas velocities, contact time, and pressure drop.
TABLE 4-18. PACKED BED SCRUBBER EVALUATION PROCEDURE
1. Is the proposed packing depth sufficient to attain the desired gas (
absorption efficiency? See Table 4-17a.
2. Is the proposed liquid-to-gas ratio within normal limits, as described in
the preceding discussion?
3. Is the superficial gas velocity through the scrubber reasonable, based on
the preceding discussion? (Worksheet 4-7 shows how superficial gas
velocities may be calculated for incinerators. The same procedure may be
used for scrubber velocity calculation.)
4. Are the contact tunes and pressure drops through the scrubber reasonable,
based on the preceding discussion? (Contact time can be estimated using
the methods shown in Worksheet 4-6 for incinerator gas residence time,
replacing the incinerator volume term with the total volume occupied by
the packed section of the scrubber:
where Z = bed depth and D = column diameter.)
Table 4-17 is only applicable for highly soluble gases such as HCl and HF. If
other gaseous pollutants are to be removed, technical assistance may be
requested. I
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4.4.2.3 Plate Tower Scrubbers--
Plate towers are vertical cylindrical columns with a number of plates or trays
inside. The scrubbing liquid is introduced at the top plate and flows succes-
sively across each plate as it moves downward to the liquid outlet at the
tower bottom. Gas comes in at the bottom of the tower and passes through
openings in each plate before leaving through the top. Gas absorption is
promoted by the breaking up of the gas phase into small bubbles which pass
through the volume of liquid on each plate. Water, caustic solution, and lime
solution can all be used as the scrubbing liquid.
The primary design variables for gas absorption in plate tower scrubbers are
the number of plates or trays, the liquid-to-gas ratio, and the contact time.
Pressure drop is also an important design criteria although it does not direc-
tly affect absorption efficiency. Like packed bed scrubbers, plate tower
scrubbers can be used for limited particulate collection as well as gas
absorption, but they are not primarily designed for this purpose.
Number of plates--In the design of plate towers for absorption of gaseous
contaminants that are highly soluble or chemically reactive with the scrubbing
liquid, the -umber of actual plates, N_, may be calculated from the
equation [6J:
M _
Np - '
where y: and 72 are the inlet and outlet concentrations of the gaseous contam-
inant and £._. is the Murphree vapor phase efficiency. In developing the above
equation, the assumption is made that £._. is the same for each plate in the
tower. The Murphree vapor phase efficiencies for the various plate designs may
be obtained from published data for selected gas-liquid systems [6,17]. These
would normally be in the 25% to 80% range. A rigorous estimation of the
Murphree vapor phase efficiency is extremely complex. For the case of absorp-
tion towers operating with low viscosity liquids and without excessive weepage
(liquid dripping) or entrainment, the figures in Table 4-19 can be used.
TABLE 4-19. MURPHREE VAPOR PHASE EFFICIENCY
FOR PLATE TOWERS [19]
"Reprinted by special permission from CHEMICAL ENGINEERING November 13
Copyright 1972 by McGraw-Hill, Inc., New York, N.Y. 10020."
Perforation
diameter,
in.
1/16
1/16 to 1/8
1/8 to 3/16
1/4 to 3/8
Murphree vapor phase
efficiency,
percent
80
75
70
65
4-67
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Liquid-to-gas ratio--For plate towers, the selection of the optimum liquid-
to-gas ratio depends largely on operating experience. Experience has indi-
cated that for single-pass crossflow bubble cap trays, the liquid flow should
not exceed 0.72d ft3/s, where d is the diameter of the tower in feet. Since
the gas flow rate in the tower can be estimated from the Souders-Brown
equation, the maximum liquid-to-gas ratio is given as follows:
(Liquid ] = 630 / PG \Q-5,gal/1,000 ft3
V Gas /max Kd I PL - PG/
where K is an empirical constant in the Souders-Browri equation, and p_ and p
are the gas and liquid densities, respectively. Values of K are available
from Chemical Engineers' Handbook [6] or any other standard chemical engineer-
ing reference on mass transfer, distillation, or unit operations. For towers
with a tray spacing of 24 in., K is typically 0.17.
Contact time—As in packed bed scrubbers, gas/liquid contact time is an impor-
tant factor affecting removal efficiency. In tray towers, greater depths of
liquid on the plates lead to greater plate efficiency through longer contact
time with the gas. Typical gas residence times in tray towers are comparable
to those for packed bed scrubbers; for example, 0.4 s to 0.6 s for 99+% ab-
sorption of HC1 in caustic solution. For absorption of S02 by lime solution,
longer contact times (in the range of 3-9 s) are needed to overcome the ajddi-
tional mass transfer resistance due to solids dissolution.
r
Pressure drop — For plate towers, the pressure drop across a perforated plate
is the sum of the gas resistance in passing through the perforations plus the
head required to overcome the equivalent liquid depth on the plate:
P, , the pressure drop due to gas resistance in in. WG, can be calculated from
tne equation [20] :
where p.. and p. are the gas and liquid densities, respectively; U is the
linear velocity of the gas through perforations in ft/s; and C»Q Is the ori-
fice coefficient. Values of C^. are 0.7-0.8 for sieve trays ana 0.6-0.7 for
bubble cap trays. The pressure drop due to liquid head in in. WG, h_ , can be
calculated from a knowledge of weir dimensions:
^ - 1.5 « 10"7 PL (htf +
where p is the liquid density in lb/ft3, hw is height of weir on the tray in
mm, ano; h is height of weir crest in mm.
4-63
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Total pressure drop can be roughly estimated by:
AP = AP x N
T P P
where AP_ = total pressure drop
AP = pressure drop per plate
N = number of plates
Table 4-20 presents a procedure that can be used for plate tower scrubber
design evaluation, based on consideraton of the number of plates required,
liquid-to-gas ratio, contact time, and pressure drop. The equa~ions presented
above can be used to estimate pressure drop if this information is not
available from the vendor. However, vendor data are preferable.
TABLE 4-20. PLATE TOWER SCRUBBER EVALUATION PROCEDURE
1. Are the proposed number of plates comparable to or greater than the f
required number of plates, as estimated by the procedures shown in I
Worksheet 4-14 . -I
2. Are the proposed liquid flow and liquid-to-gas ratio reasonable and less
than the maximum acceptable values calculated by the methods shown in
Worksheet 4-15?
3. Are the contact time and pressure drop within reason?
This procedure is only valid for gases highly soluble in the scrubber liquor.
4.4.3 Quenching and Mist Elimination Considerations
In addition to scrubbers used for particulate and gaseous emission control,
air pollution control systems for hazardous waste incinerators frequently
include quench towers and mist eliminators. Located upstream from the scrub-
bers, quench towers are designed to reduce the temperature of the combustion
gases leaving the incinerator. This temperature reduction reduces the volu-
metric gas flow rate, and thus the scrubber capacity requirement. Quenching
also reduces evaporative water losses in the scrubber, and allows the use of
low temperature materials of construction such as fiber-reinforced plastic
(FRP) rather than more expensive, high temperature alloys or refractory.
Since venturi scrubbers provide evaporative gas cooling by the very nature of
their design, quenching may be considered optional when these devices are used
for primary particulate and/or gaseous emission control. Packed bed and plate
tower scrubbers, however, are not designed for evaporated cooling. When these
devices are used without upstream venturi scrubbing, quenching is nearly
4-69
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always required. Without quenching, evaporative water loss from caustic or
lime solution can lead to particulate emissions of sodium or calcium salts .
At existing hazardous waste incineration facilities, combustion gases are
normally quenched to temperatures of 120-300°F, and below 200°F for FRP scrub-
ber construction. Typical water consumption rates for quenching are in the
range of 0.75 to 3.75 gal/1000 ft3 (0.1 to 0.5 L/m3) of gas.
Mist eliminators are widely used to reduce emissions of liquid droplets from
scrubbers. Mist eliminators are normally installed downstream from, or as an
integral part of, the scrubbing system. In general, only one mist eliminator
is needed. Where two or more scrubbers are used in series, intermediate mist
elimination may be provided, but it is not considered necessary to prevent the
release of liquid droplets to the environment.
The types of mist eliminators most commonly used in hazardous waste incinera-
tion facilities are cyclone collectors, simple inertial separators such as
baffles, wire mesh mist eliminators, and fiber bed mist eliminators. Cyclones
are used for collecting very heavy liquid loadings of droplets over 10 urn,
such as those emitted from venturi scrubbers. The design of cyclone mist
eliminators follows the principles of cyclone design for particles. For this
type of mist eliminator, therefore, the collection efficiencies for liquid
droplets and solid particles are about the same. Collection efficiencies of
nearly 100% are possible for droplets in the 10- to 50-um range, which is t
consistent with the liquid droplet sizes emitted from venturi scrubbers. I"
In the simple inertial separators, the primary collection mechanism is iner- (
tial impaction, and to a lesser extent interception. Devices such as louvers,
zigzag baffles, tube banks, and chevrons are simple inertial separators. The
cut diameter for liquid droplet collection in these devices is typically
10 urn. Pressure drops are in the 0.02- to 0,12-in. WG (50-to 300-Pa range)
depending on the gas velocity and closeness in spacing of the collection
surfaces.
Wire mesh eliminators are formed from meshes of wire knitted into a cylindri-
cal open weave which is then crimped to give a stable wire configuration. As
rising mist droplets contact the wire surface, they flow down the wire to a
wire junction, coalesce, run off, and flow freely to the bottom of the bed.
The depth of the wire pad varies from 2 to 12 in. (50 to 300 mm) with 4-6 in.
pads being the most common. Pressure drops usually range from 0.02 to
4.0 in. WG, depending on the gas velocity, the wire density, and the depth of
the pad. In normal operation, the pressure drop is not likely to be more than
1 in. WG. Th« cut diameter for liquid droplet collection is a strong function
of the gas velocity, and can range from 1 to 10 urn. Sizing of the wire mesh
mist eliminator is based on the allowable gas velocity, calculated using the
Souders-Brown equation:
u = 0.107
4-70
-------
where u is the gas velocity in m/s, p is the density of the scrubbing liquid,
and p. is the gas density.
u
For collection of fine acid mists, fiber bed mist eliminators are most appro-
priate. In this type of device, large mist particles are collected on the
fibers by inertial impaction and direct interception, whereas smaller parti-
cles are collected by Brownian diffusion. Since fiber bed mist eliminators
are designed so that Brownian diffusion is the predominant mechanism for mist
collection, extremely small particles of less than 1 M"i are recovered with
high efficiency. Typical gas velocities through fiber bed mist eliminators
range from 5 to 10.0 ft/s (1.5 to 30 m/s), with corresponding pressure drops
of 5 to 15 in. WG. Collection efficiencies are 100% for droplets larger than
3 Mm< and 90% to 99.5% for droplets less than 3 urn.
In wire mesh and fiber bed mist eliminators, plugging by solid deposition is a
potential problem. This problem can be partially overcome by intermittent
washing with sprays, by selection of a less densely packed design, and by the
use of sieve plate towers or cyclone separators upstream as an additional mist
and particle collection device. At hazardous waste incineration facilities,
the most common configuration used for gas cleanup is a high energy venturi
scrubber followed by two sieve trays for additional gas absorption, and then
another sieve tray and an inertial separator or a wire mesh eliminator to |
reduce emissions of liquid droplets. Operating experience has indicated that I
this is a most effective combination.
In general, three "rules of thumb" can be followed in evaluating provisions
for quenching and mist elimination at hazardous waste incineration facilities.
• Quenching should be provided upstream from packed bed or plate tower
scrubbers unless these devices are preceded by a venturi scrubber.
• Quenching is optional when venturi scrubbers are used, although high
temperature materials of construction may be required if quenching is not
employed.
• A mist eliminator should be provided downstream or as an integral part of
the last scrubber in the air pollution control system.
4.4.4 Prime Mover Capacity Evaluation
Prime movers in rotary kiln incineration systems are always induced draft
fans, located downstream from the air pollution control devices, while either
induced draft or forced draft systems may be used with liquid injection incin-
erators. For the overall system to function properly, the prime mover must be
capable of moving the combustion gases through each air pollution control
device while overcoming the corresponding pressure drops. As the total pres-
sure drop through the system increases, the volumetric flow capacity of the
fan decreases. The functional relationship between these two variables,
pressure and flow capacity at a specific temperature, should be specified by
the manufacturer.
4-71
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Therefore, it is necessary to (a) determine the combustion gas flow rate at
the fan inlet temperature, (b) estimate the total pressure drop across the
system, and (c) compare the fan capacity at the calculated pressure drop with
the predetermined combustion gas flow rate in order to evaluate whether or not
the fan has sufficient gas handling capacity. If this capacity is insuffi-
cient the burning rate must be decreased, the fan capacity must be increased,
or the ductwork must be modified to reduce pressure drop. The following
discussion focuses on Step (b) above, estimation of the total system pressure
droo. Combustion gas flow rate calculations are discussed in Section 4.3.2.
The major pressure drops to be considered are the pressure drops across the
various air pollution control devices. These pressure drops can be determined
from manufacturer specifications once the gas flow rates at the inlets to
these devices are known. Flow, rates can be calculated c[uite simply as
follows:
q =
where q = combustion gas flow rate, acfm
q , = combustion gas flow rate, at standard conditions of 63°F and
1 atm, scfm (from Worksheet 4-2 or 4-4)
T = inlet temperature, °F
P = combustion gas static pressure, atm I
Other pressure drops that need to be considered are frictional losses due £o
flow through the ductwork connecting each air pollution control device, for
any given duct, the total pressure drop may consist of three component pres-
sure drops: (1) frictional losses due to flow through straight lengths of
ductwork, (2) frictional losses due to flow through bends in the ductwork, and
(3) losses due to sudden constriction of flow at the inlet to the duct.
Pressure drop through a straight length of duct can be estimated using Fig-
ure 4-16, reproduced from Reference 6. This figure can be used in the fol-
lowing manner-.
(1) Identify the temperature and average molecular weight of the gas.
(2) Draw a line through these two points on the temperature and molecular
weight scales, and extrapolate this line to a point on the viscosity
scale.
(3) Identify the inside diameter of the duct and the mass flow of combustion
gases.
(4) Draw a line through these two points on the diameter and weight flow
scales, and extrapolate this line to the arbitrary reference scale.
(5) Connect the point on the arbitrary reference scale with the predetermined
point on the viscosity scale.
(6) Identify the pressure drop per foot of duct on the AP scale at the inter-
section of the line between the reference and viscosity scales.
4-72
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FLOW IN TIT** AMD CBANNEL*
Ttrtuttm
Permission from McGraw-Hill encyclopedia of scence and technology,
Vol. XI. Copyright 1960, by McGraw-Hill Book Company.
Figure 4-16. Pipe flow chart [6].
(7) Calculate the total pressure drop across the length of straight duct as
follows:
*vr w
where AP = total pressure drop, in. H20
LS = length of straight duct, ft
PQ = absolute gas pressure, ata
For a reasonable approximation, assume
P,, = 1 atm
From Figure 4-13.
4-73
-------
If the duct is square or rectangular the following quantities should be used
as equivalent diameters:
Square duct: D = length of a side
Rectangular duct: D = —^-r-
' eq a + D
where a, b = width and depth of the duct
Pressure drops across bends in "a duct can be estimated using Figure 4-17.
Here, L /D, the equivalent straight-length-to-diameter ratio, is expressed as
a function of the ratio of the radius of curvature of the elbow, R, to the
diameter of the duct. Figure 4-18 shows the relationship between R and D.
Figure 4-17. Total frictional pressure drops in 90° bends [6].
Permission for Figures 4-17 and 4-18 from Chemical Engineers' Handbook,
fifth edition. Copyright 1973 by McGraw-Hill Book Company.
Figure 4-18. 90° bends (a) smooth bend, (b) segmental bend [6].
The procedure for estimating pressure drops from Figure 4-14 is as follows:
(1) Determine R/D and read the corresponding Lft/D value from Figure 4-14.
4-74
-------
(2) Identify the pressure drop across the length of straight duct upstream
and downstream from the bend and the corresponding length of straight
duct.
(3) Convert the L /D value to a pressure drop estimate:
where AP' = pressure drop across the bend, in.
AP = pressure drop across the straight segment of duct, in. H20
D = diameter of the duct, in.
L = length of straight duct, ft
If 45° or 180° angle bends are encountered, the corrected pressure drops are:
= 0.65 AP'
and AP'O =1.4AP'O
9Q
18QO .'9Q
Additional pressure drops occur at the inlet to a duct because of the sudden
contraction of the gases. These pressure drops can be estimated by the
following equation:
„. . 6 X (
where AP" = pressure drop, in.
V = gas velocity, ft/s
gc = gravitational constant, 32.2 Ib-m ft/lb-f s2
= gas density, lb/ft3
pu n - density of liquid water, 62.4 lb/ft3
K = sudden contraction-loss coefficient for turbulent flow
Table 4-21 presents K values for various ratios of duct cross-sectional area,
A,, to the cross-sectional area of the unit upstream from the duct, A .
When the pressure drops through each air pollution control device and segment
of ductwork are calculated and summed, this should provide a rough estimate of
the total pressure drop through the system.
Table 4-22 presents a procedure for evaluating the prime gas mover capacity.
A step-by-step method for performing the necessary calculations is shown in
Worksheet 4-16.
4-75
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TABLE 4-21. SUDDEN CONTRACTION-LOSS COEFFICIENT
FOR TURBULENT FLOW [6]
Permission from Chemical engineers' handbook, fifth
edition. Copyright 1973 by McGraw-Hill Book Company.
A./A 0 0.2 0.4 0.6 0.8 1.0
d p
K 0.5 0.45 0.36 0.21 0.0? 0
TABLE 4-22. PRIME MOVER CAPACITY EVALUATION PROCEDURE
Identify the approximate combustion gas flow rate in scfm (see Work-
sheet 4-2 or 4-4).
Identify the temperatures at (a) the incinerator outlet, (b) the inlet to
each air pollution control device, and (c) the fan inlet. Record this
information on Worksheet 4-16.
1
-
3. Identify the pressure drops across each air pollution control device, -as
specified by the manufacturer, and record this information on
Worksheet 4-16.
4. Estimate the pressure drops across each segment of ductwork between the
incinerator and the fan, and add these pressure drops to those determined
in checkpoint #3 to estimate the total pressure drop across the system.
S. Identify the manufacturer specifications for fan capacity at the calcu-
lated pressure drop and fan inlet temperature.
6. Does this capacity meet or exceed the approximate combustion gas flow
rate?
4.4.5 Process Control and Automatic Shutdown System Evaluation
In the design of the incinerator and scrubber systems, a number of safety
features should be provided to allow for equipment failures and operational
errors. Process control systems and safety interlocks for incinerators are
discussed in Section 4.3.5. The following safety interlocks relating to the
scrubber operation are recommended:
(1) Shutdown of the waste and auxiliary fuel feed systems on loss of scrubber
water flow.
4-76
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(2) Shutdown of the waste and auxiliary fuel feed systems if the incinerator
effluent gas temperature exceeds the maximum design temperature for the
quench section.
(3) Shutdown of the waste and auxiliary fuel feed systems if the quenched gas
temperature exceeds the maximum design temperature for the scrubber.
(4) Shutdown of the waste and auxiliary fuel feed systems, followed by shut-
down of the scrubber systems, on failure of forced or induced draft fan.
(5) Shutdown of the waste and auxiliary fuel feed systems followed by shut-
down of the scrubber systems, if the pH of the scrubbing liquid does not
meet specified values.
(6) Shutdown of the waste and auxiliary fuel feed systems, followed by shut-
down of the scrubber systems, if the pressure drop across the scrubber
becomes excessive, indicating unsteady-state operation or clogging
problems.
When possible, it is desirable to have a time delay between shutting off the
waste to be incinerated and shutting off the auxiliary fuel. This will help
to ensure an adequate burnout of the waste and minimize emissions of I
incomplete products of waste combustion and unreacted waste.
In situations when the incinerator effluent gas temperature or the quenched
gas temperature exceeds the maximum design temperature for the next piece of
equipment, it is desirable to have provisions for emergency stack bypass
designed into the system. An indication of excess temperature should lead to
shutdown of the incinerator through the safety interlock system. It is recog-
nized, however, that any of the interlock devices can and will malfunction
some o'f the time. To protect the scrubber system from damage by excess tem-
perature, switches for stack bypass can be provided. These switches should
only be operated as an emergency measure, and under strict supervision. To a
limited extent, the additional thermal lift caused by the excess temperature
will raise the effective stack height and alleviate the impact on plant
personnel.
At power plants, chemical plants, and refineries, stack bypass switches are
often provided to enable maintenace to be done on scrubber systems while
process operation continues. Stack bypass for maintenance purposes is not
recommended for hazardous waste incineration facilities.
4.4.6 Material of Construction Considerations
Effluent gases from incineration of hazardous wastes contain a number of
corrosive contaminants, including HCl, S02, S03, HF, and possibly C12, HBr,
Br2, P2°5' and organic acids. The presence of HCl, the principal gaseous
contaminant, is of particular concern because it accelerates pitting and
crevice corrosion of most materials. The careful selection of the materials
of construction for the quench tower and scrubber system is therefore
extremely important.
4-77
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In the quench section where temperatures of approximately 130G°F are commonly
encountered, Hastelloy C and Inconel 625 have found wide acceptance. Other
possibilities are the use of carbon graphite or acid resistant refractories as
lining material for carbon steel or stainless steel construction, but the
quench spray nozzles should still be made of Hastelloy C or Inconel 625.
For the scrubber, Hastelloy C or Inconel 625 can again be used as materials of
construction. At more moderate temperatures, however, FRP is recommended
because it is economical, easily fabricated, and lightweight. It also has
good resistance in both acid and alkaline environments, up to a service tem-
perature of around 200°F. Polyvinyl chloride (PVC) can also be considered as
a material for wet scrubber construction, but its use is limited to tempera-
tures of less than 160°F.
If structural strength becomes a prime consideration because of the size and
weight of the scrubber, carbon steel or stainless steel can be used with a
suitable lining material to provide the required corrosion protection. Field
corrosion studies have shown that carbon steel and stainless steel both expe-
rienced severe corrosion problems and are not recommended as materials of con-
struction for scrubber systems treating acid gases unless linings are used.
Rubber, carbon graphite, FRP, Teflon, Kynar (polyvinylidene fluoride), acid
resistant bricks, and refractories are examples of suitable lining materials.
Teflon, however, cannot be bonded to a metal surface and requires multiple
flanges to stay in place. Kynar is similar to Teflon in most of its proper-
ties, but it is available in sheet form bonded to a glass backing. In packed
beds, the packing material should be made of ceramic, carbon, or plastics fo
withstand attack by corrosive acids.
A special concern is the potential presence of HF in the incinerator exhaust
gases. It is veil known that glass and any ceramic material containing silica
are attacked by HF or H2SiF6. Many grades of rubber linings also contain
silica as a filler, which could be leached out by HF or H2SiF6- Common mate-
rials of construction of HF scrubbers include FRF (with, special shielding
material to prevent attack of the glass fibers), rubber-lined steel, Kynar,
and graphite-lined steel. Among the metals, monel has shown good resistance
over wide concentration and temperature ranges. At one hazardous waste incin-
eration facility, a Monel-lined stainless steel packed tower with polypropyl-
ene Intalox saddles is used to control HF emissions from the incinerator. In
addition, both Hastelloy C and Inconel 625 have been used as lining material
in hydrofluoric acid service and have demonstrated outstanding corrosion
resistance to HF.
Although the corrosion and temperature aspects of materials selection are of
primary importance, erosion must also be considered in scrubbers designed for
particulate control. Venturi scrubbers are particularly susceptible to ero-
sion due to the high gas velocities and particulate loadings encountered
during normal duty. Throat and elbow areas are generally subject to the most
wear. FRP does not stand up well in these regions and harder, corrosion
resistant, materials are required for long.service life.
All the foregoing factors should be considered in evaluating materials selec-
tion for the quench tower and scrubber system. If materials of construction
4-78
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" th!n th°Se dlscussed above are proposed, the adequacy of these mat
the temperature/gas environment under consideration should be evaluated
4 . 5 WORKSHEETS
4-79
-------
WORKSHEET 4-1. PROCEDURE TO CALCULATE DESTRUCTION
AND REMOVAL EFFICIENCY
1. From trial burn data, identify the following parameters:
Total waste feed rate, (win)TOTAL = __ Lb/hr
Mass fraction of each puncysal
organic hazardous constituent in
the waste, n: = __ Lb/lb waste
n2 = __ Lb/lb waste
1*3 = __ Lb/lb waste
n4 = __ Lb/lb waste
n5 = __ Lb/lb waste
Gas flow rate in the stack, q = __ scfm
Concentration of each prin-
cipal organic hazardous
constituent in the stack gas, Ci . ,
* l = __ Mg/scf
C2 = __ Mg/scf
Mg/scf
Mg/scf
2. Calculate the mass feed rate of each hazardous constituent to the inc
erator, using the following equation: .
in
T
ni (Win>TOTAL
lb/hr
Lb/hr
lb/hr
Lb/hr
lb/hr
3. Calculate the mass flow rate of each hazardous constituent in the stack
using the following equation:
/u \ = 3 c-i
7.57 a
3 " Lb/hr
'"out\ = Lb/hr
5 = Lb/hr
4. Calculate the destruction and removal efficiency for each hazardous
constituent using the following equation:
4-80
-------
(W ). - (W )
™>- ln?» ),°Utl <™>
in i
DRE2 =
DRE3 =
DRE4 =
DRE5 =
4-81
-------
WORKSHEET 4-2. PROCEDURE TO CALCULATE STOICHIOMETRIC AIR REQUIREMENTS
COMBUSTION GAS FLOW, AND COMPOSITION (LIQUID"
INJECTION INCINERATION)
1. Identify the elemental composition and moisture content of the waste or
waste mixture.
Carbon, C^-. Ib/lb waste
Fuel hydrogen, HW: Ib/lb waste
Moisture, H20w: Ib/lb waste
Oxygen, 0^-. Ib/lb waste
Nitrogen, N • Ib/lb waste
Chlorine, Cl*: Ib/lb waste
Fluorine, FW: Ib/lb waste
Bromine, Br^-. Ib/lb waste
Iodine, I • Ib/lb waste
Sulfur, SjJ: Ib/lb waste
Phosphorus, PW= Ib/lb waste
2. If auxiliary fuel is to be burned in conjunction with the waste, identify
the fuel type and approximate, proposed fuel-to-waste ratio from the per-
mit application. (If auxiliary fuel is to be used only for startup,
proceed to Step #5.) .
Fuel type:
Fuel:waste ratio, nf = Ib fuel/lb waste
3. Determine the approximate elemental composition of the fuel from the
following table.
Component
£
S* 0.03 0.005
4. Calculate the composition of the combined waste,/auxiliary fuel feed.
Cw * nfCf
C: -T— — =
Ib Component /Ib fuel [211
Residual fuel Distillate fuel
oil (e.g., No. 6) oil (e.g.. No. 2)
0.866 0.872
0.102 0.123
Natural
gas
0.693
0.227
0.08
H: -— i-i = Ib/lb feed
H2o; rr-r- = _ u*/u> feed
4-82
-------
1 •*• n.
lb/lb feed
0: . " = _ lb/lb feed
1 + n, -
Clw
Cl: T— r— = _ lb/lb feed
J. i £ ^^^^— ^^^^— ^™.
F-. . " = _ lb/lb feed
1 + n, ^—— __
Brw
Br: . * = _ lb/lb feed
1 + n^ — — — — — ^
feed
Sw + n
S: = lb/lb feed
P: •?— - = lb/lb feed
5. Calculate the stoichiometric oxygen requirement based on the combustion
reactions described in Section 4.3.2.1.
C x 2.67 ~2 = _ ^ 02/lb feed
- ) x 8.0 ~ = ib 02/lb feed
s x i.o _| = _ it 02/lb feed
P x 1.29 ~2i = ^ 02/lb fee(J
-0(in feed) = - _ lb 02/lb feed
stoich = Z • * °2/ * feed
4-83
-------
6. Calculate the combustion cas mass flows, based on the stoichiometric
oxygen requirement.
C02: C x 3.67
lb CO;
Ib C
= lb C02/lb feed
H20:
N2:
H -
Cl F_
35.5 " 19
(02)
x 9.0
lb
H20(in feed) = lb H20/lb feed
stoich x 3'31 lb
']•
HC1: Cl x 1.03
HF: F x 1.05
Br2: Br
I2: I
lb HC1
lb Cl
lb HF
lb F
S02:
lb H20
lb H
(in air)'| + N(in feed) - lb N2/lb feed
= lb HCl/lb feed
= lb HF/lb feed
= lb Br2/lb feed
= lb I2/lb feed
= lb S02/lb feed
P20S: P x 2.29
lb P20s
lb P
lb P205/lb feed m
J
fe<
Combustion products = CP =
Ib/lb feed
7. Identify the total excess air rate.
EA = %/lOO
8. Calculate the additional nitrogen and oxygen present in the combustion
gases due to excess air feed.
(02)£A = EA X (02)stQich
(N2)
EA
3.31
air)
lb 02/lb waste
= lb N2/lb waste
9. Calculate the total combustion gas flow.
Combustion gases = CG = CP + (02)_. + (N2)-. s
HA C.A
Ib/lb waste
10. Calculate the mass fraction of each combustion gas component.
C02:
H20:
CG
CG
Ib/lb gas
Ib/lb gas
4-84
-------
N2(from #6) + (N2)
,-a
- -
CG
0,:
HCl:
CG
HCl
CG
HF- ^
HF- CG
Br2:
Br
CG
- Li
•' CG
S02:
P205:
S0
CG
CG
Ib/lb gas
Ib/lb gas
Ib/lb gas
Ib/lb gas
Ib/lb gas
Ib/lb gas
Ib/lb gas
Ib/lb gas
11. Identify those components that constitute less than 1-2% of the combus-
tion gas. These components can be eliminated from further consideration
in heat and material balance calculations. In most cases, C02, ^0, N2,
and 02 will be the only combustion gas components that need to be considered
12. Calculate the volumetric flow of the major combustion products at stand-
ard conditions of 68°F and 1 atm.
C02: * x CG T 0.114 ~
H20:
N2:
02:
x CG -f 0.0467
x CG T 0.0727
~
+ 0.083
Other: ~ x CG T (0.00259 M)~
CG SCI
where M = molecular weight
scf
scf/lb feed
scf/lb feed
scf/lb feed
scf/lb feed
scf/lb feed
Total flow, q =
q x
Ib feed
(lb/hr) f 60
4-85
scfm
-------
WORKSHEET 4-3. PROCEDURE TO CALCULATE THE NET HEATING VALUE3 OF THE WASTE (
Basis: Heating value is reported as a higher heating value (HHV) determined
at standard 77°F (25°C).
Identify the following:
HHV =
H =
Cl =
F =
H20 =
Btu/lb waste
IbH/lb waste
IbCl/lb waste
IbF/lb waste
Ib/moisture/'lb waste
Calculate the net heating value (NHV):
NHV = HHV - 1,050 I H20' + 9(H - -rf^r - fj
Btu/lb waste
Seating value: The quantity of heat released when waste is burned, commonly
expressed as Btu/lb. The higher heating value includes the heat of condensa
tion of the water present in the waste and the heat formed in the combustion
reaction,- the lower heating vfalue represents the heat formed in the combus-
tion reaction; and the net heating value is the lower heating value minus th
energy necessary to vaporize any moisture present.
4-86
-------
WORKSHEET 4-4. PROCEDURE TO CALCULATE STOICKIOMETRIC AIR REQUIREMENTS,
APPROXIMATE COMBUSTION GAS FLOWS, AND APPROXIMATE GAS
COMPOSITIONS (ROTARY KILNS)
1. Identify the elemental composition and moisture content of the wastes fed
to the kiln.
1. Solids (kiln) 2. Liquids (kiln)
Carbon, C
Fuel hydrogen, H
Moisture, H20
Oxygen, 0,
Nitrogen, N
Chlorine, Cl
Fluorine, F,
Bromine, Br
Iodine, I
Sulfur, 5
Phosphorus, P.
Lb/lb waste
Lb/lb waste
Lb/lb waste
Lb/lb waste
Lb/lb waste
Lb/lb waste
Lb/lb waste
Lb/lb waste
Lb/lb waste
Lb/lb waste
Lb/lb waste
2. Identify the approximate liquid and solid waste feed rates to the kiln, I-
and calculate the liquid/solid feed fractions. I
Liquid feed rate, mj = Lb/hr
Solid feed rate, m2 = Lb/hr
Total feed, m12 = mj + m2 = Lb/hr
Liquid fraction, nj = mj/m^ = Lb liquid/Ib waste
Solid fraction, n2 = 1-nj = Lb solid/Lb waste
3. If auxiliary fuel is to be burned in conjunction with the wastes, identify
the fuel type and approximate, proposed fuel-to-waste ratio.
Fuel type:
Fuel:waste ratio in kiln: n^.. = Lb fuel/lb waste
4. Determine the approximate elemental composition of the fuel from the
following table.
Lb component/Lb fuel [21]
Component
S£ 0.03 0.005
4-87
Residual
fuel oil
(e.g. No. 6)
0.866
0.102
Distillate
fuel oil
(e.g. No. 2)
0.872
0.123
Natural
gas
0.693
0.227
0.08
-------
5. Calculate the composition of the combined waste/auxiliary fuel feed to
the kiln.
Ck: TTl^ = U>/lb feed
nlHl + n2H2 + n<
H. : r—— — = Ib/lb feed
\ ± T Jj £ ~~ - - ~ —" ~ —
"lH2Ol + „, = lb/lb fefid
x T n _ ""^""^""- ^- —^~i™-" -
Ib/lb feed
nf
nf
) "IT*. "^2 = lb/lb feed
K j» * n^ ~ " --._--.— __ .._- __
L. : nlc^l/ n2cl2 = ib/ib feed
K i ••• nf
F. : "1*1 + "Z'-z = lb/lb feed
X 1 ' A^ '" ""'"'"' ™"""" ~ -~ ~"—-"~
»i° i - "2ot2 = lb/lb feed
K i. • n^ ~~~ : "L^r- : ~ •• ~"
T: -1*1 - "2*2 = ib/ib feed
K A * r*^ ^™i^w««^^««^»
-------
x 1
x "'
-
Ib P
Ib 02/lb feed
-Ok (in feed)
lb/02/lb feed
(02)
stoich(k)
Ib o2/lb feed
7. Calculate the combustion gas mass flows, based on the stoichiometric
oxygen requirement (assume complete combustion is achieved for purposes
of gas flow estimation).
S..7
Ib C02/lb feed
clk Fk
H -
"k 35.5 19
3'31
Ib H
H20k (in feed)
(in feed)
Ib H20/lb feed
Ib N2/lb feed
Ib HCl/lb feed
HIV
Ib HF/lb feed
: Br
Ib Br2/lb feed
Ib I2/lb feed
Ib S02/lb feed
•) ?Q
2.29
P2°S
Kiln combustion products = CP,
Ib P205/lb feed
Ib/lb feed
4-89
-------
8. Identify the elemental composition and moisture content of the liquid '
wastes to be burned in the afterburner (if any).
C3: Ib/lb waste
H3: Ib/lb waste
H203: Ib/lb waste
03: Ib/lb waste
N3: Ib/lb waste
C13: Ib/lb waste
F3: Ib/lb waste
Br3: Ib/lb waste
I3: Ib/lb waste
S3: Ib/lb waste
P3 = I Ib/lb waste
9. Identify the fuel type and approximate, proposed fuel-to-waste ratio for
the afterburner.
Fuel type:
Fuel: waste ratio, n-A = __ Ib fuel/lb waste
10. Determine the approximate elemental composition of the fuel from the!
table shown in Step 4.
Cf_ = _ Ib/lb fuel
H" * _ Ib/lb fuel
N" * _ Ib/lb fuel
s = Ib/lb fuel
11. Calculate the composition of the combined waste/ auxiliary fuel feed to
the afterburner.
Ca * nf, CfA
C_: . ** IA = _ Ib/lb feed
A 1 + nfA -
t
H3 * nfAHfA
H IA tA = _ Ib/lb feed
H20.: .23 = _ Ib/lb feed
A 1 + nfA -
4-90
-------
0.: - = _ Ib/lb feed
A 1 + nfA -
lb/lbfeed
lb/lhfeed
lb/lbfeed
V FV • - lb/lbfeed
$3 * nfASfa
V 1 + n
feed
12. Calculate the stoichiometric oxygen requirement for the afterburner feed,
based on the combustion reactions described in Section 4.3.2.1.
CA x 2.67 ~-2* = _ ib Q2/lb feed
HA - ITS - rtx 8-° =^ °/lb fced
SA x 1.0 jg-jp = Ib 02/lb feed
PA x 1.29 ^ °2 = Ib 02/lb feed
-0A (in feed) = - Ib 02/lb feed
°2/lb feed
4-91
-------
13. Calculate the combustion gas mass flows, based on the stoichiometric
oxygen requirement.
Ib C02/lb feed
H
5L
1A 35.5
HoO
Ib H
+ H20A (in feed) =
Ib H20/lb feed
: (02)
StOich(A)
(in feed)
Ib M2/lb feed
HCl.: Cl, X 1.03
A A
HC1
HFA:
05
'05
HF
: Br.
Ib HCl/lb feed
Ib HF/lbjfeed
i
Ib Br2/lb feed
Ib I2/lb feed
Ib SO?
Ib S
Ib S02/lb feed
B
: P
A
Ib P
Ib P205/lb feed
Afterburner combustion products * Cf. * Tj- __ Ib/lb feed
14. Calculate the ratio of total afterburner feed to total kiln feed.
Liquid waste to kiln: mi
Solid waste to kiln: m2
Auxiliary fuel to kiln: (mi •«• na)11
Ib/hr
Ib/hr
Ib/hr
4-92
-------
Liquid waste to afterburner: m3 = Ib/hr
Auxiliary fuel to afterburner: m3nfa = Ib/hr
(in] + m2) (1 * nfK)
n.v = — = lb afterburner feed/lb kiln feed
AK m3 nfA
15. Calculate the total combustion gas mass flows, based on stoichiometric
oxygen requirements.
C02 + C02A n
C02: -1:— ^—^ = Ib/lb feed
1 nAK
H2Q: " "" = Ib/lb feed
1 nAK
, +
AK
4. n
nAK
AK
feed
HC1 * n HC1
V * n * = ^/^ feed
1 nAK
HF + n HF
, + = Ib/lb feed
Ib/lb feed
feCd
so2K + n
S02: T 4. „ £ = ^/^ feed
1 nAK
n P205
- -
Combustion products = CP = = Ib/lb feed
4-93
-------
16. Identify the total excess air rate for the system (i.e., to be maintained
in the afterburner). (I
EA = %
17. Calculate the additional nitrogen and oxygen present in th« combustion
gases due to excess air feed.
= EA X . _ ^
-
(N2)EA = 3.31 - (in air) x (02)£A = __ Ib N2/lb waste
13. Calculate the total combustion gas flow.
Combustion gas flow = CG = CP + (02)£A + (N2)EA = _ Ib/lb feed
19. Calculate the mass fraction of each combustion gas component.
C02: §§* = Ib/lb gas
H^O: •£- = Ib/lb gas
* QQ • • i— i in-, i —i —
N2(from 15) + (^2)5-1
N2: pg == = Ib/lb gas
(02)EA
02: —sp— * Ib/lb gas
HC1: = Ib/lb gas
CG -
HF: ^ « Ib/lb gas
CG "
Br2: 5|Z s ib/lb gas
I2: = Ib/lb gas
4-94
-------
S02.- gp = lb/lb gas
gas
20. Identify those components that constitute less than 1-2% of the combustion
gas. These components can be eliminated from further consideration in
heat and material balance calculations. In most cases, C02, H20, N2,
and 02 will be the only combustion gas components that need to be considered.
21. Calculate the volumetric flow of the major combustion products from the
kiln at standard conditions of 68°F and 1 a tin.
/ \
C02: f £22 x CG T 0.114 Ib/scf = scf/lb
H20: ( | x CG ? 0.0467 Ib/scf = scf/lb
N2: x CG r 0.0727 Ib/scf = scf/lb
02: x CG r 0.083 Ib/scf = ' scf/lb
Other: (^T-p-yx CG T (0.00259 M) Ib/scf = scf/lb
where M = molecular weight
Total flow, q = = _ scf/lb feed
q x (mj + m2) (1 + n) (1 + n) T 60 = _ scfm
4-95
-------
WORKSHEET 4-5. PROCEDURE TO CALCULATE EXCESS AIR RATE FOR A I
SPECIFIED TEMPERATURE AND FEED COMPOSITION
Identify the following input variables:
From Worksheet 4-2, Step #5
<02)stoich= - Ib/lbfeed
From Worksheet 4-2, Step #6
C02 = _ lb/lb feed
H20 = _ lb/lb feed
N2 = _ lb/lb feed
Other major component(s) = _ lb/lb feed
From Worksheet 4-3
NHVtfastfi = _ _ Btu/lb waste
From proposed operating conditions
Operating temperature, T = _ °F t
Air preheat temperature, T . = _ °F {
(if applicable) air --1
If auxiliary fuel is to be burned in conjunction with the waste, also
identify the following from Worksheet 4-2.
n- = _ Ib fuel/lb waste
HVf = _ Btu/lb fuel
If air preheating is employed, calculate the corresponding enthalpy
input to the incinerator. If the combustion air is not to be preheated,
proceed to Step #3.
Btu/lb feed
EA)
3. Calculate the heat generated by combustion of the waste or waste/
auxiliary fuel mix.
* nf HVf
Btu/lb feed
4. Calculate the heat loss through the walls of the incinerator, assuming
5% loss.
4-96
-------
Q = 0.05 AH2
= Btu/lb feed
5. Calculate the enthalpy of the combustion products leaving the incinerator.
0.26(C02 + N2)(T - 77) = Btu/lb feed
0.49 H20(T - 77) = Btu/lb feed
Other x C~ Qther (T - 77) = Btu/lb feed
AH3 == _ Btu/lb feed
6. Calculate the enthalpy of excess air leaving the incinerator.
AH4' = 1
Btu/lb feed
AH4 = AH4' x EA
7. Calculate the excess air percentage as follows:
EA = 100 (X'
4-97
-------
WORKSHEET 4-6. PROCEDURE TO ESTIMATE THE MAXIMUM ACHIEVABLE GAS RESIDENCE T
AFTER THE DESIRED OPERATING TEMPERATURE HAS BEEN ACHIEVED
1. Identify the following input variables:
Volume of the incinerator chamber, V = ft3
Combustion gas flow rate, q = scfm
Operating temperature, T = °F
Combustion gas static pressure, P = atm
2. Calculate the gas flow in actual cubic feet per second at operating
temperature.
3. Calculate the maximum achievable gas residence time in the incinerator
after the desired operating temperature has been achieved.
A - v I
9max ' o '
4-98
-------
WORKSHEET 4-7. PROCEDURE TO CALCULATE SUPERFICIAL GAS
VELOCITY AT OPERATING TEMPERATURE
Identify the following input variables:
Gas flow rate at operating temperature, q' = acf/s
(See Worksheet 4-6)
Cross-sectional area of the incinerator chamber, A"= ft2
Calculate:
Superficial gas velocity, v = q'/A
= ft/s
4-99
-------
WORKSHEET 4-8. PROCEDURE TO CALCULATE THE MAXIMUM ACHIEVABLE EXCESS AIR RA
FOR A ROTARY KILN OPERATING AT A SPECIFIED TEMPERATURE WITH
SPECIFIED FEED COMPOSITION
1. Identify the following input variables:
From Worksheet 4-4, Step 6
(0*>
Stoich
-------
2. If air preheating is employed, calculate the corresponding enthalpy input
to the kiln. If the combustion air is not preheated, proceed to Step 3:
= i'06 (Tair ' 77><°*>stoich(K) = - BtU/li> feed
3. Calculate the maximum heat generated in the kiln by combustion of the
wastes or waste/auxiliary fuel mix:
+ n2NHV2 +
AH2 = - r— - = _ Btu/lb feed
4. Estimate the heat loss through the walls of the kiln, assuming 5% loss:
Q(K) =0.05 AH2(K) = _ Btu/lb feed
5. Calculate the enthalpy of the combustion products leaving the kiln:
0.26 (C02(K) + N2(K)\ (TR - 77) = Btu/lb feed
0.49 H20(K) ' Btu/lb feed
Btu/lb feed
6. Calculate the enthalpy of excess air levaing the kiln:
'1 (TK ' 77> <°2) = - BtU/lb
7. Calculate the excess air percentage as follows:
= 100
j
4-101
-------
WORKSHEET 4-9. PROCEDURE TO CALCULATE EXCESS AIR IN h ROTARY KILN AFTERBURNER.
FOR A SPECIFIED AFTERBURNER TEMPERATURE AND OVERALL FEED (
COMPOSITION
1. Identify the following input, variables:
From Worksheet 4-4, Steps 6 and 12
<°2>Stoich(K) = --
°2/li3 afterburner feed
From Worksheet 4-4, Step 15
C02 = __ Ib/Lb feed
H20 * __ Ib/lb feed
N2 = __ Ib/Lb feed
Other major combustion product(s) = __ Ib/lb feed
From Worksheet 4-4, Step 14 j
Afterburner/kiln feed ratio, n... = _ Ib afterburner feed/lb kiln feed
Afi. -
From Worksheet 4-3
Afterburner waste heating value, NHVj = __ Btu/lb
From proposed operating conditions
Afterburner temperature, T. = _ °F
Air preheat temperature, T . = _ °F
(if applicable) aar
If auxiliary fuel is to be burned in the afterburner along with liquid
wastes during normal operation, identify the following from Worksheet 4-4:
n.. * _ Ib fuel/Ub afterburner waste feed
HVfA = _ Btu/lb fuel
From Worksheet 4-8,
AH2/.,v = _ Btu/lb kiln feed
(K.) — ^— — —• -—
4-102
-------
2. If air preheating is employed, calculate the corresponding enthalpy input
to the kiln and afterburner combined. If the combustion air is not pre-
heated, proceed to Step 3:
= 1.06 (Tair - 77)
= AHj' (1 + EA)
(°2)
stoich(K)
(°2)
stoich(A)
Btu/lb feed
3. Calculate the heat generated in the kiln and afterburner by combustion
of the total waste/auxiliary fuel feed:
AH2
NHV3
(A)
*fA
Btu/lb afterburner feed
Btu/lb feed
4. Estimate the heat loss through the walls of the kiln and afterburner,
assuming 5% loss:
Q = 0.05 AH2 =
Btu/lb feed
5.
Calculate the enthalpy of the combustion products leaving the afterburner:
= Btu/lb feed
0.49 H20 (TA -77) = Btu/lb feed
Ib
0.26 (C02 + N2) (T. - 77)
A
Other
Ib feedj x Cp other (TA " 77> *
Btu/lb feed
Btu/lb feed
7.
Calculate the enthalpy of excess air leaving the afterburner:
AH-. ' = 1 1 (7 - 11) (On) + (Oo^
4 v A ' v 2/stoich(K) v 2'stoich(A)
AH4 = AH4' EA
Calculate the excess air percentage in the afterburner:
ra - inn / AHi ' + AH;? - Q -
" " 10° I AH4- - AH,'
Btu/lb feed
4-103
-------
WORKSHEET 4-10. PROCEDURE TO ESTIMATE SOLID WASTE
RETENTION TIMES IN ROTARY KILNS
Identify the following input variables-.
Kiln length, L = ft
Kiln diameter, D = ft
Slope of kiln, S = ft/ft
Rotation velocity, N = rpm
Calculation:
9 = 0.19 (L/D)/SN = min
4-104
-------
WORKSHEET 4-11. PROCEDURE TO CALCULATE AUXILIARY FUEL CAPACITY REQUIREMENTS
FOR STARTUP AT DESIGN AIR FLOW FOR WASTE COMBUSTION
1. Identify the following input data from the proposed operating conditions,
Section 4.3.2, and/or Section 4.3.3.
Auxiliary fuel type:
Fuel heating value, NHV = Btu/lb
Desired operating temperature, T = °F
Average proposed waste feed rate, ra = Ib/hr
Stoichiometric oxygen requirement for waste,
<°*>StOich
[0.26(C02 + N2) + 0.49 H2oJ (T - 77)
out
Btu/lb fuel
4. Calculate the heat output from the unit associated with design air flow
for waste combustion.
Ql * 1.12 mtf (02)sto.ch(w) (1 + EA) (TQut - 77)
= Btu/hr
4-105
-------
5. Calculate "enthalpy" of air consumed in fuel combustion.
h2 = 1.12 (02)stoich(f) (TQUt - 77)
= Btu/lb fuel
6. Calculate the heat of fuel combustion, less 5% heat loss through the
refractory walls.
h3 = 0.95 NHVf = Btu/lb fuel
7. Calculate the required auxiliary fuel capacity.
mf " h3 * hi - hl = * fuel/hr
8. If necessary for comparison with the reported auxiliary fuel rating,
calculate the required auxiliary fuel capacity in Btu/hr.
Qf = mf NHVf = Btu/hr
4-106
-------
WORKSHEET 4-12. PROCEDURE TO ESTIMATE PARTICULATE CONCENTRATION AND
EMISSION RATE FROM LIQUID INJECTION INCINERATORS
1. Identify the following input data:
Ash content of waste, ASH = wt%
Average waste feed rate, m = Ib/hr
Volumetric combustion gas flow rate, q = scfm
Volumetric fraction of oxygen in the gas, (Og) =
2. Calculate the particulate emission rate, based on the ash content of the
waste
m = ASH x m = Ib/hr
p w
3. Correct the volumetric combustion gas flow rate to zero percent excess
air.
qa = q [l - 4.77(02)v J = scfm j
4. Calculate the particulate loading in the gas at zero percent excess
air.
m
c = 117 -£ = _ gr/scf
4-107
-------
WORKSHEET 4-13. INTERNAL CONSISTENCY CHECK FOR PROPOSED CONDITIONS
OF GAS VELOCITY, LIQUID TO GAS RATIO, AND PRESSURE
DROP FOR VENTURI SCRUBBERS
1. Identify the following input data:
QL
Proposed liquid to gas ratio, — = gal/1,000 ft-
yG
Proposed gas velocity (at the throat), U_ = ft/s
Cross-sectional throat area, A = ft2
Gas density (downstream of throat), p = lb/ft3
p may be estimated from the ideal gas law:
3
M P
pa " RT
where M = average molecular weight of gas (normally about 30)
P = absolute pressure (atm)
R = gas constant =0.73 atm ft3/°R Ib mol
T = absolute temperature (°R) J.
2. Calculate the pressure drop, AP
2 0.133 / \ 0.78
(U ) p A /Q
4-108
-------
WORKSHEET 4-14. PROCEDURE TO CALCULATE THE NUMBER OF PLATES
REQUIRED FOR A SPECIFIED GASEOUS POLLUTANT
REMOVAL EFFICIENCY3
1. Identify the desired removal efficiency for pollutant i.
E = %/ioo
2. From Table 4-19 or other sources, identify the average Murphree vapor
phase efficiency for the plate tower
E = Vioo
3. Calculate the required number of plates
In (1 - E.)
N = -
p In (1 -
This procedure is only applicable for gaseous pollutants that are highly
soluble or chemically reactive with the scrubbing liquid.
4-109
-------
WORKSHEET 4-15. PROCEDURE TO CALCULAT'I THE IVIIMUM i:;'Ji:
TO GAS RATIO FOR PLATI TOWERS *
1. Identify the inlet temperature to the tcwar and the tower diameter.
°F + 460 =
d = _ ft
2. Identify the volumetric fraction of each major component in the gas
YC02 = -
Yother
3. Calculate the average molecular weight of the gas
Ib/lb mol
4. Calculate the gas density
PG = 1'3? T(°R)
5. Determine the scrubber liquor density
PL = lb/ft3
4-110
-------
6. Determine the Souders-Brown constant, K, from Reference 6 or other
sources. (For 24-in. tray spacing, use K = 0.17)
7. Calculate the maximum liquid-to-gas ratio
4-111
-------
WORKSHEET 4-16. PROCEDURE TO CALCULATE PRESSURE DROP BETWEEN
THE INCINERATOR AND INDUCED DRAFT FAN
1. Identify and/or calculate the following input data relevant to the
combustion gas:
a) From Section 4.3.2,
Approximate waste feed rate, m = __ Ib/hr
Combustion gas mass flow, CG = __ Ib/lb waste
CG x m = __ Ib/hr
Combustion gas volumetric flow, q , = __ scfm
Volumetric fraction of each major component in the gas
yC02
YH20
other *
b) Calculate the average molecular weight of the gas
M = 44 + 18 yH2Q + 28 y^ + 32 y^ +
Ib/lb mol
2. Calculate the actual gas flow rate and gas density at the entrance to
each gas conditioning or air pollution control device and the fan using
the following equations:
/ T°F + 460 \
528 '
4-112
-------
Location (inlet) q, acfm gas, Ib/ft3
Quench tower
Scrubber
Demister
Fan
Other (specify)
Approximate gas temperatures at these locations need to be determined.
3. From manufacturer specifications, estimate the pressure drop across each
gas conditioning device for the gas flow rates calculated in the preceding
step.
Location AP, in. H20
Quench tower
Scrubber
Demister
Other (specify)
TOTAL
For the segments of ductwork entering the aforementioned devices, detemjine
the inner diameter (D), the cross-sectional area of the duct (A,), the."
cross-sectional area of the device preceding the duct (A ), the length of
straight duct (L), the radius of curvature of any bends^in the duct
(R), and the gas velocity through the duct.
If the duct is square, use the length of a side as the equivalent diameter.
If the duct is rectangular, calculate an equivalent diameter by the follow-
ing equation:
D = a + b' wnere a ^d b are width and depth of the duct.
Figure 4-15 in Section 4.4.4 shows how radii of curvature can be estimated.
Gas velocities can be calculated by the following equation:
, ft/s
Location
(inlet duct) D, in. Ad' ft* V ft* VAp Ls' ft R, in. V, ft/s
Quench tower
Scrubber
Demister
Fan
Other (specify)
4-113
-------
5. Calculate the pressure drop across each straight length of ductwork
using Figure 4-13 in Section 4.4.4. and the known diameters of the
combustion gas mass flow rate, average molecular weight of the gas, and
temperatures at the specified locations.
Figure 4-13 yields pressure drop values per length of straight duct.
These can be converted to total pressure drops by the following
calculation:
AP = (£.} L in H20
Location
(inlet duct) AP, in. H?0
Quench tower
Scrubber
Demister
Fan
Other (specify)
6. Estimate the pressure drop across any bends in the ductwork. t
Figure 4-14 in Section 4.4.4 shows L /D values as a function of R/D Jfor
90° bends, e
where L = equivalent length, in.
D = diameter, in.
R = radius of curvature, in.
L /D values can be converted to pressure drops by the following calculatio
. in. H20
where AP' = pressure drop across the bend in the duct, in. H20
For 45° bends, AP1 is afcout 65% of that calculated for a 90° bend. For
180° bends, AP1 is about 140% of that calculated for a 90° bend. Thus,
' =0.65AP'(900)
^'(180°)
4-114
-------
Location
;inlet duct AP' , in. H20
Quench tower
Scrubber
Demister
Fan
Other (specify)
TOTAL
7. Estimate the additional pressure drops due to sudden contraction of flow
at the entrance to each duct.
AP1 = .003 KC p V2, in. H20
where AP" = pressure drop due to contraction, in H2Q
p = gas density, lb/ft3
<^«S
V = gas velocity, ft/s
K = sudden contraction-loss coefficient
|
KC is a function of the ratio of the duct cross-sectional to the cross-l
sectional area of the preceding vessel, A./A . Table 4-21 in Section 4.4.4
shows this relationship. "
Location
(inlet duet) AP", in. H?0
Quench tower
Scrubber
Demister
Fan
Other (specify)
TOTAL
8. Calculate the total pressure drop across the system by sunning the totals
from Steps 3, 5, 6, and 7
4-115
-------
4.6 REFERENCES M
1. Kiang, Yen-Hsuing. Total hazardous waste disposal through combustion.
Conshohocken, PA; Trane Thermal Co. Reprinted from Industrial Heating,
December 1977.
2. Santoleri, J. J. Spray nozzle selection. Conshohocken, PA; Trane Ther-
mal Co. Reprinted from Chemical Engineering Progress, 1974 September.
3. FloSonics) supersonic atomization, high efficiency twin fluid atomizers
and systems (manufacturer's brochure). Fairfield, OH; Fluid Kinetics,
Inc. Form No. DX1277-2.
4. Trane thermal waste disposal and recovery (manufacturer's brochure).
Conshohocken, PA; Trane Thermal Co. Bulletin No. 143-A.
5. Manson, L.; and Unger, S. Hazardous material incinerator design criteria.
Cincinnati, OH; U.S. Environmental Protection Agency; 1979 October. 100
p. EPA-600/2-79-198.
6. Perry, R. H. Chemical engineers' handbook, fifth edition. New York,
McGraw-Hill Book Company, 1973.
7. McGraw-Hill encyclopedia of science and technology, Vol. XI. New York,
McGraw-Hill Book Company, 1960. 409-411. " I"
8. Ross, R. D., ed. Industrial waste disposal. New York, Van Nostrand I
Reinhold, 1968. 190-239.
9. Brown, R. W. High-temperature non-metallics. Chemical Engineering.
65(8) .-135-150, 1958 April 21.
10. Sittig, M. Incineration of industrial hazardous wastes and sludges. Park
Ridge, NJ; Noyes Data Corp.; 1979. p. 68.
11. Hanf, E. W.; and MacDonald, J. W. Economic evaluation of wet scrubbers.
Chemical Engineering Progress. 71(83):43-52, 1975 March.
12. Calvert, S. How to choose a particulate scrubber. Chemical Engineering.
84(18):54-68, 1977 August 29.
13. Shannon, L. J.; Gorman, P. G.; and Reichel, H. Particulate pollutant
system study, Vol. II - fine particle emissions. Durham, NC; U.S. Envi-
ronmental Protection Agency; 1971. PB 203 521 (APTD-0744).
14. Wen, C. Y.; and Uchida, S. Gas absorption by alkaline solutions in a
venturi scrubber. Industrial and Engineering Chemistry, Process Design
and Development. 12(4):437-443. 1973 April.
15. Calvert, S.,- Goldschmid, J.; Leith, D.; and Mehta, D. Wet scrubber
system study, Vol. I - scrubbber handbook. Research Triangle Park, NC;
U.S. Environmental Protection Agency,- 1972 August. PB 213 016
(EPA-R2-72-118a).
4-116
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16. Hesketh, H. E. Fine particle collection efficiency related to pressure
drop, scrubbant and particle properties, and contact mechanism. Journal
of the Air Pollution Control Association. 24(10):939-942, 1974 October.
17. Shervood, T. K.; and Pigford, R. L. Absorption and extraction, 2nd ed.
New York, McGraw-Hill Book Company, 1952. 278 p.
18. Eckert, J. S.; Foote, E. H.; Rollinson, L. R.; and Waller, L. F. Absorp-
tion process utilizing packed towers. Industrial and Engineering Chemistry.
59(2):41-47. 1967 February.
19. Zenz, F. A. Designing gas-absorption towers. Chemical Engineering.
79(25):120-138, 1972 November 13.
20. Fair, J. R. Sorption processes for gas separation. Chemical Engineering.
75(15) :90-110, 1969 July 14.
21. Devitt, T.; Spaile, P.; and Gibbs, L. Population and characteristics of
industrial/commercial boilers in the U.S. Research Triangle Park, NC;
U.S. Environmental Protection Agency; 1979 August. 431 p.
EPA-600/7-79-178a.
4-117
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CHAPTER 5
OVERALL FACILITY DESIGN, OPERATION, AND MONITORING
5.1 INTRODUCTION
Incineration is one controlled combustion process used in the ultimate dispos-
al of unusable hazardous wastes that result from industrial and chemical
manufacture. Careful selection of equipment and processes for the incinera-
tion of chemical wastes is essential to ensure that the basic obligations of
safe handling and proper ultimate disposal are met in a satisfactory manner.
In addition to fulfilling social obligations, an effective system will satisfy
regulatory needs with minimum, adverse community reaction.
Prior to incineration, the handling, storage, and feeding of hazardous wastes t
require special care to ensure safety and reduce exposure. During incinera- I
tion and while the facility operates, certain parameters must be monitored by J
the operators to assure that proper conditions are maintained in day-to-day
operation.
Although the problems are substantially reduced, incineration of hazardous
waste materials alone does not eliminate all of the disposal problems associ-
ated with hazardous waste. Most incinerators produce combustion products that
must be properly removed prior to discharging gas products to the environment.
These products include ash or inert residues from such things as silica oxides
and/or metals. Captured gas products, such as HCl, when reacted with caustic
solutions in the scrubber, can also produce dissolved and suspended solids.
These solutions from the quench process and scrubber reactions oust be care-
fully disposed of to ensure the entire sequence of combustion is safe. When-
ever these wastes are of a nonhazardous nature, standard procedures can be
used for their treatment and ultimate disposal. However, in some cases the
secondary wastes can be hazardous themselves and require special handling.
5.1.1 Purpose
The purpose of this chapter is to provide the permit writer with engineering
back-up information to supplement the guidance criteria necessary to judge the
capability of the overall incineration facility to technically and practically
process and monitor hazardous wastes safely and effectively.
This chapter discusses overall facility layouts, requirements common to all
facilities, site and combustor specific requirements, material and process
flows, waste receiving procedures, waste and other storage, material handling
equipment, emergency and safety procedures and provisions, personnel safety,
monitoring for the incineration process itself, monitoring of the air
5-1
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pollution control system, monitoring of waste handling and treatment systems,
monitoring and controlling parts of the overall facility that may become
fugitive emission sources, proper handling and disposal of quench/scrubber
water and ash, and sampling and analysis of wastewaters and ash.
5.1.2 Hazardous Waste Incinerator Facility Design
The overall facility design of hazardous waste incinerators is significantly
influenced by the category of waste involved; i.e., solids, liquids, or sludges.
The systematic approach to facility design, therefore, requires investigation
of the composition of each class of waste to define the equipment and operating
procedures for each of the following elements:
1. Safety (toxicity, fire explosion)
2. Transportation and unloading
3. Segregation of wastes during storage
4. Storage
5. Handling and feeding
6. Monitoring
7. Fugitive emission control
8. Scrubber/quench water treatment
9. Residue handling and disposal
10. Secondary problems (e.g., stream pollution, runoff, ground-water
contamination). j-
The overall success of an incinerator facility depends upon the successful "•
integration of storage, feeding, and firing equipment; often these are areas
which do not receive as much attention as is necessary. In the case of hazard-
ous waste incineration it is crucial that these areas require special attention.
Figure 5-1 is a block diagram of a typical incinerator facility layout. In an
overall facility evaluation, the key areas are the facilities and equipment before
and after the combustor; i.e., waste receiving, waste storage, waste blending,
transfer between these areas, equipment feeding waste to the incinerator, han-
dling and treatment of quench and scrubber waters, and ash disposal. Figure 5-2
is a schematic diagram of an incinerator facility handling both solid and liquid
wastes; illustrating the interrelationships between the key facility areas.
5.2 INCINERATOR FACILITY SITE SELECTION AND OPERATION
5.2.1 Site Selection Concerns
The Guidance Manual for Location Standards contains guidance for complying
with general (i.e., applicable to all facilities) location standards 11264.18.
Flood plains, holocene faults, and endangered and threatened species are
discussed.
The selection of a site for a hazardous waste incineration facility is a
phased decision process which has occurred prior to making a permit applica-
tion. Site screening is the process of identifying and evaluating a parcel of
land for its suitability as a hazardous waste disposal site. Specific site- M
screening criteria which the permit applicant has addressed include geologic, ™
5-2
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INCCMING
RAIL TANK CA9
TRUCK TRAIlfR-HOPPER
• til HOPPER CAR
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MET At DRUMS
FIIER DRUMS
TON CONTAINERS
PIPELINE iRARE'
BARGE (RARE
| SECURITV
ACCESS
STACK
EXHAUST
SECURE FENCE
Figure 5-1. Typical incinerator facility layout. r
hydrogeologic, topographic, economic, social, and political aspects. While many
sites may exist which meet technical, economic, and ecological criteria, public
acceptance or rejection may ultimately decide the fate of the facility [1].
The main geological constraints that can render a site unsuitable for a hazard-
ous waste incinerator facility are historical or predicted seismic activity,
landslide potential, soil slump of solifluction, and volcanic or hot spring
activities.
The main topographic constraints are susceptibility to flooding, erosion, and
offsite drainage runoff. The site will need sufficient area for the construc-
tion of a runoff-holding pond (or diversion to an existing holding pond) to
retain surface runoff which may contain hazardous substances in solution. Be-
cause of the holding pond and flood protection criteria, siting in flood
plains is not normally acceptable.
The primary climatic features which can adversely affect an incineration site
are the amount of annual or seasonal precipitation and incidence of severe
storms. Copious precipitation will cause surface runoff and water infiltra-
tion through the soil. Runoff, that amount of rainfall that does not infil-
trate the soil, depends on such factors as the intensity and duration of the
precipitation, the soil moisture content, vegetation cover, permeability of
the soil, and slope of the site. Normally, the runoff from a 10-year storm
(recurrence interval of only once in 10 years) or annual spring thaw, which-
ever is greater, is containable by the site's natural topography. If not,
berms, dikes, and other runoff control measures must be constructed to modify
the site.
5-3
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Ecological site features are those elements determined through earlier studies
and environmental impact statements (EIS) which determine whether ecosystems at
the site are in a delicate balance. Whether a site is a habitat for rare and
endangered species,- or used seasonally by migratory wildlife is also a factor
determined for final site selection.
Cultural site features are those elements that are a direct result of human
activities which modify and affect the site's desirability as a hazardous
waste incineration facility—access, land-use, and aesthetics. Land areas
zoned for nonresidential uses and adequate buffer zones are generally preferred
for siting a hazardous waste management facility. The site ideally needs to
contain sufficient land area to provide a concentric ring of unoccupied space
as a buffer zone between active storage, treatment, and disposal areas, and
the nearest area of human activity. Vegetation, topography, distance, and
artificial barriers are all potential means to screen facility activities
from line-of-sight observations from commercial, residential, or recreational
areas.
One of the most difficult problems faced by a hazardous waste incineration
facility applicant has been that of gaining public approval from a community
for construction of the facility. No matter how thoroughly the above
parameters have been examined in the facility site selection, public accept-
ance or rejection probably decides the fate of the facility. Public aware-
ness of the planned facility, early planning input, and active participation
by political leaders, public officials, environmental groups, as well as
other public interest groups and adjacent industry have led to successful
facility sitings in 'the past.
5.2.2 Operation of the Facility
Preplanning of the proper operation of a hazardous waste incineration facility
is necessary to protect and prevent adverse effects of the facility on the
public health or to the environment. Proper facility operation, on a day-to-
day basis, includes plans and manuals of operation for handling wastes, safety
at the site, monitoring of operating parameters, monitoring to assure protec-
tion of the environment, and operator training. These plans are developed
within the operating company (and corporate structure) and are done in cooper-
ation with other neighboring or similar organizations and with governmental
agencies. It may not always be possible for all of them to fully cooperate or
participate, but through planned action each organization is made aware of
certain available assistances.
5.2.2.1 Operations Plan—
An operations plan includes the following:
(1) Classification of wastes to be handled and estimated quantities
(2) Methods and processes utilized
(a) Facility capacity
(b) Detailed description of each process
5-5
-------
(3) Storage and disposal procedures
(a) Plans for receipt, checking, processing, segregating
incompatible wastes, and odor control
(b) Life of facility based on projected use
(4) Monitoring Procedures
(a) Monitoring of incinerator operating parameters
(b) Monitoring and recording of incoming wastes
(c) Leachate control and groundwater monitoring
(d) Security system
(e) System for monitoring water and air pollution affecting area
outside the site
(f) Air pollution control device monitoring
(5) Administrative Procedures
(a) Hours of operation/day and days/week
(b) Security procedures including entry control, hours manned,
lighting, and other procedures to prevent unauthorized entry
(c) Procedures planned and equipment available in case of break-
downs, inclement weather, or other abnormal conditions.
(d) Description of recordkeeping procedures, types of records to
kept, and use of records by management to control the
operation.
(e) List of general qualifications of key operating personnel
(f) Maintenance and inspection schedules
r
5.2.2.2 Operations Manual—
Once in operation, the incinerator facility will maintain operation guides or
manuals, covering the routine workings of the plant. An operations guide can
include .-
(1) A scaled engineering drawing, pictorial flow diagram, or scale model
of the plant, shoving all major components by name and function.
(2) A set of formal drawings at the plant for reference by operational
and maintenance personnel
(3) Equipment manuals
(4) Equipment catalogs
(5) Spare parts lists
(6) Job or task functions for each assignment during a typical shift
5.2.2.3 Emergency Manual or Handbook—
An emergency manual or handbook is prepared which specifies the plan-of-action
for any type of emergency the incinerator facility may reasonably expect to
encounter. These include weather extremes (severe cold, heavy snowfall, hail
damage, hurricances, tornadoes, high winds, or lightning damage), floods,
earthquakes, power outages, bomb scares, fires and explosion, and spills (See
Section 5.2.2.5). The typical remedial actions for emergency situations
presented in Table 5-1 cover many of the items that can be included in the
5-6
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emergency handbook, but other items may be needed as dictated by the anticipated
emergencies and the available resources.
5.2.2.4 Leak Detection and Repair Plan--
Any facility that processes hazardous air pollutants as described under Section
112 of the Clean Air Act must develop a Leak Detection and Repair Plan (LDRP)
to aid in reducing fugitive emissions [2]. The LDRP must be certified by the
owner of the facility as meeting the fugitive emission criteria established by
the EPA under the Clean Air Act. The plan is to be reviewed and updated, as
required, once every three years, or within 90 days of a major modification at
the facility. At the minimum, the LDRP:
(1) Develops a schedule and recordkeeping program for routine
surveillance and/or monitoring of fugitive emissions.
(2) Establishs a written plan for detection and repair of leaks, and a
reasonable schedule for repair.
(3) Provides a written plan for sampling procedures, housekeeping (e.g.,
small spill cleanup) and onsite waste handling.
(4) Develops recordkeeping procedures for all aspects of the LDRP and |.
saves these records for one year. I
(5) Establishes a written plan for specifying sufficient personnel to
fulfill the LDRP, and provides a training program with a written
manual.
5.2.2.5 Hazardous Chemical Spill Handling Plan—
Most plants' safety, disaster or operating plans and manuals do not fulfill
the requirement for a spill-handling plan. The key to adequate spill-handling
is decision-making. None of the above manuals or procedures supply the infor-
mation required to make the decisions necessary to cope with the spill of a
hazardous material. Thus, a chemical-spill-handling plan will fill an information
need, but will not program decisions.
In a spill-handling plan, the decisions that must be made in a spill incident
are defined. First, the plant or plant superintendent must accept the fact
that a spill has occurred, based on information from his monitoring systems.
The most immediate steps are those aimed at the protection of human life. If
the information obtained about the location and nature of the leak/spill shows
that the threat to life is "immediate and great," the decision should be to
"shut down - all persons immediately take cover." Otherwise, the decision
should be to "cleanup the area."
The "immediate cover" for persons is a spill response usually described by the
plant disaster/emergency plan, whereas the protection of employees during the
"cleanup the area" procedure is ordinarily contained in a safety plan. It is
the lack of information between these two extremes that the spill-response
plan fills.
5-13
-------
Once a spill-response leader has been chosen, the decision-making process
continues toward containment actions and disposition procedures. Figure 5-3
diagrams the decision-making process and information needed in a spill-
handling situation, as well as the requirements for improving the spill
response.
A spill-handling plan is written as an easy-to-consult document for decision-
making, and includes:
(1) Monitoring all possible spills of materials
INFORMATION REQUIREMENTS
SPILL-MONITORING
INFORMATION
PLANT-EQUIPMENT CONTENTS
ANO MATERIAL-HAZARD
INFORMATION
SPILL-RES PONSECHAIN-
OF-COMMAND INFORMATION
EQUIPMENT AVAILASUUTY
AND MATERIAL-HAZARD
INFORMATION
DECISION PROCESS
IS IT AN
IMMEDIATE
THREAT TO LIFE ?
WHAT CONTAINMENT\
ACTION SHOULD BE >
TAKEN? J
NONE
AVAILABLE
WHAT DEPOSnON
ACTION SHOULD BE
TAKEN?
NONE
IMPROVEMENTS
REQUIREMENTS
REVIEW AND/OR
IMPROVE SPILL
MONITORING
REVIEW AND/OR USE
DISASTER PLAN
REVIEW SPILL RESPONSE
CHAIN OF COMMAND
IMPROVE
CONTAINMENT
DEVICES
AVAILABLE
IMPROVE
DEPOSITION
CAPABILITY
ACTION
Figure 5-3.
Spill'response diagram illustrating the interrelating information
available, decisions to be taken, and improvements needed [3].
5-14
-------
(2) Identifying of all plant equipment and other contents it may
have (can be separated into convenient process groupings or modules)
(3) Describing hazards of materials that would comprise potential spills
(4) Designating the chain of command during a spill incident
(5) Specifying equipment available for containment, and disposition
alternatives in response to a spill.
Every spill-handling plan has seven relatively independent parts that fulfill
the five needs mentioned above. These parts are kept as autonomous as
possible to facilitate the upgrading of each one. The seven parts are:
(1) List of contacts for spill emergencies, including plant/shift
individuals, safety personnel, environmental control personnel, and
government agency contacts, with home and office telephone numbers.
(2) Process flowsheets, showing primarily those pieces of equipment
containing sufficient volume of material to constitute a potential
spill problem.
(3) Site map.
(4) Chemical-effects list for all hazardous materials located within
the boundaries of the plant.
(5) Monitoring checklist, consisting of a matrix indicating how equipment
is monitored for potential spills.
(6) Containment alternatives matrix, describing the series of contain-
ments that occur in sequential order for various process equipment.
(7) Chemical-disposition alternatives, including a listing of equipment
that are considered alternative places of material disposition for
recovery, treatment, ultimate disposal.
5.2.2.6 Facility Security
Incineration facility security is management's responsibility. Basic security
problems are protection of property and controlling access to the facility.
Security procedures for hazardous waste disposal-facilities are described in
the Federal Register, Vol. 45, No. 98, Part 265 - Interim Status Standards for
Owners and Operators of Hazardous Waste Treatment, Storage, and Disposal
Facilities, Subpart B - General Facility Standards, 265.14 Security, pg.
33235, May 19, 1980.
5.2.2.7 Operator Practices and Training
Operator practices and training of personnel ensure the smooth, efficient
running of a hazardous waste incineration facility. Some of the areas covered
under practice and training include:
5-15
-------
(1) Selection of personnel, pre-employment physicals, periodic
examinations
(2) Training; e.g., supervisory, operator, emergency
(3) Operating manual use; e.g., development of the manual, process
description, material specifications, safety considerations
(4) Instruction of personnel
(5) Start-up and shut-down procedures; e.g., problems of start-up,
normal shut-down, emergency shut-down
(6) Maintenance and inspection
(7) Preparation for emergencies; e.g., recognition, alarms, simulated
emergencies, disaster drills
Operator training procedures and rules are described in the Federal Register
(as cited in Section 5.2.2.6), 265.16 - Personnel Training.
5.2.2.8 Loss Prevention Program
A loss prevention program embodies many of the facets of an emergency handbook,
operations manual, and personnel training. Usually, loss prevention
encompasses a whole facility concept and can include other concerns such as:
(1) Accident prevention
(2) Industrial Health and Hygiene I
(3) Environmental Control I*
(4) Fires and explosions I
(5) Fire prevention measures
(6) Explosion prevention measures
5.3 WASTE RECEIVING AREA
The type and nature of hazardous waste received at an incinerator facility
will dictate the design and equipment of the waste receiving area. The
physical types of hazardous waste which may be received are:
(1) Liquid
(2) Containerized materials, liquid and solids
(3) Dry solid materials
(4) Wet solid materials
(a) Pumpable
(b) Nonpunpable.
The types of receiving equipment for unloading can be divided into three
general areas:
(1) Pumpable liquid transfer
(2) Container transfer
(3) Bulk solids transfer.
Figure 5-4 shows a generalized flow diagram of handling procedures for incin-
eration of hazardous wastes. Careful consideration must be given to the
layout, safety, and recordkeeping arrangements of the waste receiving area.
Unloading material offers one of the greatest spill or toxic exposure
5-16
-------
IN =>l«K'
INSPICTIOX
c*c«
I
INSTCIIWI
cua
futi
Figure 5-4.
Flow diagram showing handling procedures
for incineration of hazardous wastes.
potentials at a hazardous waste facility. For recordkeeping, the waste
receiving area poses the first interface with the transporter and manifest
system.
5.3.1 Typical Operations and Layouts
A detailed flow sheet is a useful guide in laying out receiving areas, partic-
ularly those handling hazardous materials. The nature of the materials and
handling procedures can be studied and provisions made to eliminate or control
hazards.
Access to the incinerator facility will most likely be by truck or rail. (An
inspection procedure will be required for all incoming waste.) Figure 5-5
illustrates a receiving area layout of a facility designed to accommodate both
forms of transport. Most receiving areas for liquids will consist of a dock-
ing area, pumphouse, and storage facilities. For solid materials the pump-
house is replaced with mechanical or pneumatic conveyor devices. For receipt
of containers, a suitable docking area with conveyors and inspection appropri-
ate to the hazardous nature of the containers is necessary. Later sections
describe
in greater detail some of the equipment, handling procedures, and safety re-
quirements for each form of hazardous waste received.
5-17
-------
ft.*. SIDING
111
TANK CAR
UNLOADING STATIONS
CONCRETE DIKE
TRUQC TANKER
UNLOADING STATIONS
./X.
o
Oi
O
0 0
0 0
GRACE
WAS
D
D
D
PUMP
HOUSE
Q D
D D
D D
ROADWAY
Figure 5-5. Layout for liquid receiving area.
5.3.2 Laboratory for Waste Verification and/or Characterization
Analytical data should be made available for all wastes to be incinerated.
The physical and chemical properties and the combustion characteristics of i
each chemical waste or general classification of wastes, will be determined J"
before incineration. Only after such analysis can successful waste disposal!
be carried out safely and without violation of air or water pollution
regulations as set forth by state and federal agencies.
A minimal but complete laboratory facility requires a working area, including
office facilities, of about 2,400 sq ft. Provisions are made for air, water,
gas, and electricity, preferably both AC and DC. The laboratory furniture in-
cludes benches, sinks, fume hood, shelving, glassware racks and a refrigerator.
Good lighting and air-conditioning are also important. Identification of
laboratory equipment needed for analyses of chemical wastes follows. Specific
requirements depend on the types of wastes to be processed and type of inciner-
ator used. If the equipment for sophisticated analytical methods is not
available in-house, the analyses can be performed by commercial analytical
laboratories.
(1) Typical laboratory equipment to determine physical properties:
(a) Specific gravity balance - specific gravity of liquids.
(b) Brookfield viscosimeter - viscosity measurement of liquids and
sludges.
(c) Imhoff cones and centrifuge with graduated tubes -measurement
of percent solids by volume.
(d) Sieving machine for screen analysis (to 100 micron) and HIAC
particle counter (100-5 micron) - particle size measurement.
5-18
-------
(e) Cleveland open cup flash point tester - flash and fire point
determinations.
(f) Oven and balances - percent solids and moisture by weight.
(g) Gas chromatograph-mass spectrometry and infrared apparatus to
identify organic substances which may be toxic.
(h) Differential thermal analyzer - explosion characteristics and
fusion temperature.
(i) Juno meter or equivalent - sensitive to alpha, beta and gamma
rays for radioactivity.
(2) Laboratory equipment to determine chemical properties.
(a) Muffle furnace, oven, balances - for percent ash by weight.
{b) Orsat, fyrite techniques for flue gas analyses to provide data
for excess air calculations.
(c) pH meter and automatic titrator - acidity and alkalinity
measurement.
(d) Emission spectrograph for concentration and presence of metals.
(e) Atomic absorption spectrometer for concentration of metals and
elements.
(f) Optical microscope for particulate characterization down to the
sub-micron size. Electron microscope may be required for some
sub-micron determinations.
(3) Laboratory equipment to determine combustion properties:
(a) Calorimeter for heating value and combustibility.
(b) Orsat (previously listed ) for COj, CO, 0%, Ha and N2 analysis.
(c) Flue gas analyzer (previously listed) for analysis at various
excess air rates.
(d) Mass spectrometer (previously listed) for hazardous products of
combustion.
Reliable, bench-scale, chemical incineration equipment is generally unavail-
able. The present practice appears to follow the line of waste characteriza-
tion, physical, chemical and combustibility analysis followed by a test burn
in pilot or plant scale equipment.
5-19
-------
5.3.3 Liquids Unloading
Liquids will arrive in bulk in tank cars or tank trucks by either truck or
rail. Standard rail tank cars vary in capacity from 6,000 to 26,000 gallons
and tank trucks carry up to 10,000 gallons. Figures 5-6 and 5-7 illustrate
typical tank cars with parts and nomenclature identified.
The unloading stations are not normally located near important buildings or
facilities. The site is arranged so that escaping liquid will flow to a safe
location by utilizing the natural grade or by providing diversionary dikes or
drains. (For more information, see Section 5.3.3.1). When possible, 50 feet
or more of clear space is provided between unloading stations and buildings.
Hazardous liquids and "pumpable" materials are transferred through piping by
pump, gravity flow, or compressed-gas displacement. Pumping systems are most
commonly used and have an inherent safety advantage in that they can easily be
arranged so that the flow of liquid ceases when the pump is stopped. Either
direct-displacement or centrifugal pumps can be purchased in a wide variety of
capacities suitable for a wide range of liquids.
The safest method of unloading tank cars or trucks is through the top by means
of a pump, as shown in Figures 5-8 and 5-9, which also illustrate provisions
for grounding and bonding to prevent static electricity discharges. Many tihk
cars are equipped with permanent unloading connections in the dome. For ca|s
not so equipped, special covers are available to replace the dome cover during
unloading. Bottom unloading, unloading by siphoning, or unloading by air
pressure is undesirable, since accidental movement of the tank car during
unloading may result in the escape of the entire contents of the car. Bottom
unloading may be tolerated under favorable conditions if a remote control or a
heat-actuated automatic shutoff is provided at the tank car connection.
Tank trucks are usually unloaded from the bottom by gravity or by pumps
mounted on the vehicle. These methods are considered acceptable.
For the best methods when transferring liquid wastes:
(1) Positive-displacement pumps are preferred
(2) Centrifugal pumps are suitable for flammable-liquid service but
cannot be used as shutoffs.
Positive-displacement pumps are preferred because, unlike centrifugal pumps,
they afford a reasonably tight shutoff and prevent siphoning when not in
operation. A relief valve is provided downstream of positive-displacement
pumps, of sufficient capacity to prevent excess pressure in the system. The
relief-valve discharge is then piped back to the supply source or to the
suction side of the pump. With liquids having closed-cup flash points of 0°F
or lower, the relief valve should be piped to the storage tank; otherwise the
churning action of the pump might cause dangerous overheating.
Centrifugal pumps are suitable for flammable-liquid service but cannot be used
as shutoffs, since they usually must take suction under a head. Submerged or
5-20
-------
I
Ul
a
JS
u
u
u
V
n>
&
H
vO
I
&
•H
te.
5-21
-------
T
/
•<
-^
IITIJC
4IX3O
r
\ J
A. CAR BRAKE
B. WHEEL BLOCK
C. IDENTIFICATION NUMBER
0. CAR SEAL
E. SAFETY VALVE
F. DOME COVER
G. OUTLET LEG VALVE
H. OUTLET LEG CAP
J. DRAIN PAN
K. OUTLET NOZZa
L "FLAMMABLE" CARD
Figure 5-7. Typical tank car with parts identified [5].
1. BONDING WIRE ATTACHCO WITH GROUND OAMP
2. RELIEF-VALVE BYPASS
3. EXPlOSIONPROOf MOTOR
4. INSULATED FLEXIBLE GROUNDING CABLE ATTACHED
TO TANK CAR WITH GROUND OAMP; NOT SMALLER
THAN NUMBER 4
5. NO. 4 STRANDED CABLE SECURED TO PLATFORM
COLUMN
6. NONFERROUS TUBE
7. SAFETY-DOME COVER
L GROUND SLOPING AWAY FRON IMPORTANT FACILITIES
9. BARE-COPPER CONDUCTOR
10. GROUND ROD DRIVEN TO PERMANENT MOISTURE
LEVEL
11. WATER MAIN. IFAVAILABlf
Figure 5-8. Tank car unloading station [6].
5-22
-------
DOWNSPOUT SHOULD onoio
TO «/t« (OTTOM Or TAME
HMiN IOAOIMC.
PLACE PI« CLAMP ON
tvt«r nn 4 CONNECT
TO COMMON MOUND
*.J
\^ J
\^ ^J
\
^ _J
«T
rr
Li f
M
>•)
CONNECTION IS TO |{ MAK
ICWtt MAMHOU IS OftWO
j. N fW USE ON TUCKS MOT EQUIPKO
A\ KITH CMUNOINC PiOC
f M"Xr-r'6MUNO MO WITH OAMT
Figure 5-9.
Bonding and grounding of a flammable liquid
tank truck and loading rack [5].
deep-well (vertical-shaft) centrifugal pumps mounted on tanks are satisfactory
if the pump and bearings are cooled by the liquid being pumped. This is to
prevent dry rotating parts from operating in the vapor space of the tank.
A gravity feed system has the disadvantage of being more difficult to arrange
for prompt automatic or manual shutoff than unloading by pumping. Another
disadvantage is that gravity usually maintains constant pressure on the system,
whereas pumps can be easily arranged to permit pressurizing only during demand.
If very volatile liquids cause vapor lock when pumped by conventional methods,
gravity transfer may be necessary,- it is required for many processing
operations.
Some of the safety precautions for a gravity feed system are:
(1) Installation of emergency shutoff valves in all gravity transfer
systems.
(2) Location of such valves as close to the source as possible.
Inert gas transfer methods, owing to the compressible nature of the transfer
medium, have the same disadvantage as the gravity system. In the event of
5-23
-------
breakage or leakage, flow from the system will be continuous. Such systems
also introduce the complication of pressure storage tanks.
Among the disadvantages of the inert gas transfer methods are these:
. (1) A considerable amount of liquid may be discharged in the event of
pipe failure or careless valve operation.
(2) Because vapor-air explosions are extremely violent at high pressure,
transfer by compressed air should be avoided.
(3) Tanks for inert gas transfer systems have to be constructed,
installed, and tested in accordance with ASME or other recognized
codes for unfired pressure vessels.
(4) The gas pressure is regulated at the minimum needed to force the
liquid through the transfer system, and a relief valve with a
slightly higher setting downstream must normally be installed.
(5) Provisions need to be made for automatically shutting off the supply
of inert gas and for bleeding the gas pressure from the flammable-
liquid system in event of fire.
Transfer can be made by nitrogen, carbon dioxide, or other inert gases. Thl*
system is under constant pressure, and the compressibility of the transfer I
medium results in discharge of considerable liquid if there is pipe failure or
careless valve operation.
A schematic diagram illustrating the inert gas transfer method is shown in
Figure 5-10.
Fail-safe transfer lines primarily intended for use in transferring hazardous
liquids between a mobile transporter and storage facility have been developed
[7]. The operating principle is based on measurement of flow rate at the
inlet and outlet of the transfer line, and detection of a leak through
comparison of the two rates.
The system consists of four items: an inlet assembly, at flexible hose, an
outlet assembly, and a control module. It is designed to transfer hazardous
fluids, and to automatically close both the inlet and outlet valves upon
detection of a leak. It will also cause the inlet and outlet valves to close
if electrical power is lost, the valve operating air pressure is out of toler-
ance, or if any cable is severed. Figure 5-11 shows a simplified diagram of
the system.
The inlet and outlet assemblies are shown in Figure 5-12. They are identical,
except that a strainer is included on the inlet assembly only. The transfer
hose is a 2-inch diameter, 50 ft. length of steel-reinforced steam hose,
designed to carry about 100 gpm. The control module is housed in an explosion
proof junction box, consisting primarily of a simple hardwired computing
device [7].
5-24
-------
HEAT-RESPONSIVE
DEVICE
PUSH-BUTTON
SWITCH
>-
ORAIM
1. INERT CAS SUPPLY LINE
2. MANUAL CONTROL VALVE
3. GAS COMPRESSOR
4. PRESSURE-REGULATOR VALVE
5. SOLINOID-OPERATtO THREE-WAY TWO-PORT
VALVE. WHEN CIRCUIT TO SOLINOID IS COM-
PLETED. VALVE INLET IS CONNECTED TO OUT-
LET TO SUPPLY INERT GAS TO TANK. SHOWN
WITH CIRCUIT TO SOLENOID BROKEN. VALVE
DISCHARGE IS CONNECTED TO DRAIN TO
RELIEVE PRESSURE ON TANK.
6. RELIEF VALVE
COMPRESSED
INERT GAS
FIAMMABU
LIQUID
7 LIQUID-LEVEL DIAL INDICATOR
t FILL CONNECTION
9. STRAINER
10. SOLINOIO VALVE. INTERLOCKED SO THAT IT
WILL BE OPEN ONLY WHEN VALVE 5 ON INERT
GAS SUPPLY LINE IS IN THE POSITION SHOWN
AND VALVE 11 ON DELIVERY LINE IS CLOSED.
11. SOLINOID VALVE. ARRANGED FOR MANUAL
CONTROL AND FOR AUTOMATIC SHUTOFF IN
EVENT OF FIRE AT PROCESS.
Figure 5-10. Compressed inert gas transfer method.[6].
AIR SUPPLY
AIR
RESERVOIR
FROM
TANK CAR
TODISCHAICE
PUMP
Figure 5-11. Fail safe transfer line for hazardous fluids [7].
5-25
-------
WDcc RESERVOIR
PNEUMATIC VALVE ,
ACTUATOR r-A-f
PILOT VALVE
PORTABLE CA8l£
TO CONTROL MODULE
CHECK VALVE
1/4" AIR LINE
PORTABLE CABLE
TO CONTROL MODULE
STRAINER
(INLET ONLY)
Figure 5-12. Fail safe transfer line inlet and outlet assemblies [7].
The device will reliably detect leaks of 0.5% or greater. Average fluid loss
before valve actuation (closing at 85 gpm and 0.5% leak rate setting) was 25C
ml. It should be noted that the extremely low fluid loss before shutdown is|
only a measure of the device reaction time and not of the total fluid loss I
that may be experienced in the event of a leak. , Fifty feet of 2-inch hose
holds about 8 gal of fluid; all of which could be lost through the leak after
shutdown.
5.3.3.1 Safety/Emergency Provisions—
Hazardous fluid unloading and transfer operations offer one of the highest
likelihoods of accidents; i.e., fire, spills, or worker exposure. Technical
bulletins of the Chemical Manufacturers Association (CMA) and the American
Petroleum Institute (API) provide excellent guidance for the unloading of tank
cars and tank trucks [8-11].
Some of the design provisions and procedures for safely unloading hazardous
liquids include:
(1) The condition of the cars is examined, and any leaks are to be
reported immediately.
(2) Before unloading starts the area is checked to be sure it has no
exposed lights, fires, or other sources of ignition.
(3) Vents on tank cars are protected by flame arresters.
(4) In all cases, personnel should be thoroughly trained and have been
given written instructions suitable for each material they will
handle.
5-26
-------
(5) Adequate personal, protective equipment have been furnished for
those involved in the loading and unloading of tank cars. For
materials that are corrosive to the skin or that may be absorbed
through it, full protective clothing with face masks, rubber gloves,
rubber shoes, etc., is required. When materials that have toxic
vapor or gas are unloaded, personnel should be equipped with airline
respirators or self-contained breathing equipment. Protective equip-
ment not available at the site should be obtained even though this
may mean some delay in making the transfer.
(6) First aid and medical procedures are worked out in advance and
posted in the unloading area. Where unusually toxic substances are
handled, medical personnel will have information on the character-
istics of the material and on the medical management needed for
any material they may encounter.
(7) Fire extinguishers-of adequate type for the material handled are
distributed throughout the area.
(8) Personnel responsible for unloading stay in the immediate vicinity
of the operation at all times, and ascertain that all conditions
are normal.
(9) An emergency shower and an eyewash device is available at each
loading location. Preferably, these devices are tied to an alarm
system that would bring help to any man making use of them.
(10) Safe access to the top of the vehicle is one general safety
requirement for liquid unloading. This is particularly important
for top unloading, but it may also be necessary for operations such
as gauging or sampling. Thus, loading racks with suitable ladders,
platforms, gangways, or even railings permanently affixed to the
vehicle are usually required.
(11) Keeping liquid-unloading facilities usable in adverse weather
conditions, such as icing, may be difficult, but every effort
must be made to keep them safe. Good general illumination,
especially at night, is far preferable to providing the operator
with an extension light, which he might drop.
(12) Steel pipe and swing joints or flexible hose of the standard metal
type are usually used for connections to tank cars or tank trucks.
Metal-reinforced rubber hose of a type resistant to the material
being handled is acceptable but less desirable. See Section 5.13
on materials compatibility.
(13) Each .line and connection should be clearly identified to avoid
intermixing materials.
(14) Liquids that require heat within the tank car for pumping purposes
should be received only in cars equipped with heater coils. The
minimum steam pressure necessary to being the liquid to a fluid
5-27
-------
state is used. A regulator adjusted to this pressure is installed
in the steam line, and a relief valve with a slightly higher setting
is provided downstream.
(15) Some tank cars and tank trucks have interior linings of rubber
or plastic of various kinds. When such cars are being unloaded,
special care must be taken to prevent damage to the lining.
(16) Pumps are preferably-located outdoors so that fire at the pump will
not expose property of appreciable value. They should not be located
inside diked areas. Pumps are sometimes located in small detached
noncombustible pump houses or in cutoff rooms of main buildings.
When they are located indoors and handle flammable liquids with
flash points below 110°F, positive low-level exhaust ventilation
of 1.0 ft3/min-ft2 of pumproom floor area is recommended.
Natural ventilation is acceptable for less hazardous liquids.
(17) Where flammable liquids are handled in a pump house, motors can be
partitioned and sealed off from the rest of the pump house, or
can be of a type approved for use in flammable atmospheres. It is
a good operating and safety practice to have a well-marked master
cutoff switch outside the building. However, consideration is
normally given to locating flammable liquid pumps outside of I-
buildings whenever feasible. I
(18) As a fail-safe precaution, an interlocked warning light or physical
barrier system is often provided in unloading areas to prevent
vehicular departure before complete disconnect of flexible or
fixed transfer lines.
5.3.3.2 Spill and Runoff Containment—
Drainage from the unloading area is collected or diverted to allow runoff of
any spills or runoff from rainfall to permit recovery or at least proper
disposal. The basic objective of secondary containment is to prevent the
discharge of hazardous materials to waterways, sewer systems, or groundwaters.
Containment systems which fail under rainstorm conditions are considered
inadequate. To the extent feasible, such containment is designed to hold 110%
of the largest unit handled (or largest unit contents plus the maximum
24-hr/10-yr rainfall event, if greater).
For tank trucks a system of containment curbs are used for unloading areas,
•sing ramps to provide truck access into the confines of the containment curb.
led trenching system encompasses the railroad tank car unloading area.
rench is designed to carry away any spill or runoff to a catchment basin
ding pond for later treatment. Figure 5-13 illustrates a containment
•pe spill catchment system, depressed area form.
Static Electricity Prevention—
ectricity is generated when fluid flows through a pipe or from an
to a tank. The principal hazards created by static electricity are
' 're and explosion, which are caused by spark discharges containing
5-28
-------
SIOPC
KSCKITION
OPWATION/WtlP.
ITEM
1
2
3
«. >
i
T
of PtoncriON
DUE
(AISID DRAIN
TRttCH DRAIN
SUMP PUMP
OILUTCSUMP
COM. SUMP
PROTECTED
TANKS
OVERFLOW, MIPS
TAMCCM
ptoass Siwa
TANK MAT
pRoasssmu
SPIOS. MASHING
CONC. SPILLS
UNLOAD. SPILLS
SLUG DISCHARGE
SPILLS
DISCHUBE
Figure 5-13.
Containment curb type spill catchment
system, depressed area form [12].
sufficient energy to ignite any flammable or explosive vapors or dust present.
A point of great danger from a static spark is the place where a flammable
vapor may be present in the air, such as a delivery hose nozzle.
The terms "bonding" and "grounding" often have been used interchangeably
because the terms are poorly understood. Bonding is done to eliminate a
difference in potential between objects. Grounding is done to eliminate a
difference in potential between an object and ground. Figures 5-3 and 5-9
(Section 5.3.3) illustrate bonding and grounding of tank cars during unloading
operations. Figure 5-14 shows rail joint bonding and track grounding.
QfVATION
CROUM MO WIRE TO If FASTDK9
rouas,
Figure 5-14. A tank car unloading siding showing rail joint bonding,
insulated track joint, detail, and track grounding [5].
When unloading tank cars through open domes, it is best to use a downspout
long enough to reach the tank bottom. Generally, tank cars need not be
5-29
-------
separately grounded because the resistance of the natural ground through the
tank car wheels and rails, and the resistance of piping, flexible metallic
joints, or metallic swivel joints, are considered sufficiently low to protect
against static electricity. For detailed information and exceptions to this
generality, consult NFPA Standard No. 77, "Recommended Practice on Static
Electricity."
5.3.4 Container Unloading
For hazardous wastes, the choice of container will usually be made from among
various types of drums, barrels, and special bulk units. As is true in any
bulk handling problem, the first step is to obtain information on the type of
container which will be received with respect to its handling properties.
Since it contains a hazardous waste, the container must then meet the regula-
tions for its transportation set forth by the Department of Transportation and
RCRA.
Containerized hazardous waste is most likely to arrive for unloading via rail
boxcar or truck semitrailer. Due to economics of transportation, the carrying
capacity of a trailer or boxcar will most likely be near the maximum. A
55-gal drum is the most popular form of container; a boxcar can carry 360
55-gal drums per carload.
In addition to liquid waste, certain dry materials require the strength, wattr
tightness, weatherability, and general ruggedness of a steel drum. Standard;
specifications for steel drums have been established by the Department of
Transportation; a typical specification is shown in Table 5-2. The heavier
gage drums find use in transporting liquids.
The process for unloading trailers or cars differs by the waste and hauler.
Drummed material may be placed on pallets or may rest on the bed of the trail-
er. In the latter case, the hauler may be involved with unloading and may
manually handle the cargo. A common delivery condition for cargo touching the
truck bed is "tail gate delivery", whereby the truck driver moves the packaged
cargo to the tailgate of the trailer, and the recipient removes it.
Alternative methods include industrial trucks with drum-loading attachments,
or fork-lifts for containers on pallets. Type EE battery-powered industrial
trucks have the additional safeguards (electrical equipment enclosed to pre-
vent emission of sparks) needed to work in hazardous locations; Type EX trucks,
which are of explosion-proof or of dust tight construction, are also
recommended.
After removal steel drums can be handled by gravity conveyors. However, steel
drums should not be transported on wheel conveyors., because the chime, or lip,
at the drum bottom gets hung up on the wheels. If roller conveyors are used,
the rolls need to extend at least 2 in. beyond the outside surface of the
chime, unless the drums are centered by guard rails. Drum loads up to 250 Ib
can be handled on a conventional 1.9-in. roller conveyor having rollers spaced
at 3 in. and positioned at a 1-1/2 in. pitch.
5-30
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TABLE 5-2. TYPICAL STEEL DRUM SPECIFICATION FOR HAZARDOUS MATERIALS [13]'
Steel
Capacity, Inside Inside Outside Overall gage,
gal diameter height diameter height body
30
22 1/2
22 1/3
18 1/4
32 11/16
32 11/16
27 5/16
23 27/32
23 27/32
19 19/32
34 13/16
34 13/16
29
16
18
18
55C
55d
30d
Steel
gage,
cover
16
16
18
Steel
gage,
bottom
16
18
18
Steel
gage,
ring
12
12
12
Tare
weight . DOT
(approx.) spec.
64.5
55.5
37.5
17C
17H
17C &
17H
All dimensions given in inches. Dimensions are within
normal manufacturing tolerances of ± 1/16 in. (± 1/8 in.
on height).
Container weights shown are approximate and may vary
within the allowable limits for manufacturers standard
gage.
On the 55-gal drum, a third rolling hoop, directly
below the top rim, gives strength and rigidity to meet
specifications.
These drums meet Department of Transportation Specifi-
cations DOE 17H and DOT 17C for storage and shipment of
hazardous materials. They also meet Rule 40 of the
Uniform Freight Classification, and Rule 26C of the
National Motor Freight Classification; DOT 17H drums
also comply with ANSI standards.
Because of the difference in weights between empty and full drums, a roller
pitch as high as 5 in. can be specified for empties, while a pitch of 3 in.
may be sufficient for full drums. Both live-roller conveyors and belt-on-
roller conveyors can also be used to convey drums.
A host of other special containers have been made for storing, shipping, and
handling hazardous materials. Some of these units are designed to hold
2,000 Lb or more; some designs include metal-walled containers equipped with
specialized filling and discharge openings and rubberized containers. A major
factor to be looked at when a facility receives these types of units is the
total system concept of handling, with appropriate machinery and design taken
into account.
5-31
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Once a container has been unloaded, three possible options exist for
distributing the contents:
(1) Place the container in storage.
(2) Pump the contents (liquid) into another storage tank.
(3) Dump the contents (bulk solids) into another receiver.
5.3.5 Bulk Solids Unloading
Hazardous waste bulk solids for incineration will arrive for unloading in
hopper cars - both truck and rail. Due to the hazardous nature of the materi-
al transported, the hopper cars must be the covered type, typically with
bottom unloading ports. Three types of unloading systems are used:
(1) gravity,
(2) pressure differential, and
(3) fluidized.
Figure 5-15 shows examples of fluidized unloading ports. Fluidized unloading
is preferable for hazardous wastes when possible, because gravity unloading
necessitates having a pit located under the rail spur.
WOING SLIDES TO
DISCHARGE OPENING
ONPAOOMJR
DISCHARGE
OPENING
AIR INJECTED IN TO AREA
AROUND DISCHARGE
OKNINC
OPERATING
HANOU
LOCKING WIT
SANITARY 5HHLO
PfXMEAm STAINUS
STEEL SUJPt SHEETS
RJJIOniNG AIR Of.
CONTROL VALVE
Figure 5-15. Fluidizing outlets for hopper cars [14].
5.3.5.1 Mechanical Conveyors—
When a discharge pit is used for unloading, the material is then conveyed to
storage via one or more of three methods:
5-32
-------
(1) screw conveyor,
(2) belt conveyor, and
(3) bucket elevator.
The screw conveyor is one of the oldest and most versatile conveyor types. It
consists of a long pitch, steel helix flight mounted on a shaft, supported by
bearings within a U-shaped trough. Screw conveyors are generally easy to
maintain and inexpensive to replace.
Belt conveyors consist of an endless belt moving horizontally or on an incline.
ALr->t all belt conveyors for bulk solids use rubber-covered belts whose inner
car-ass provides the strength to pull and support the load. Belt conveyor
slopes are limited to a maximum of about 30° with those in the 18-20° range
more common. In an evaluation of a materials-handling system involving belt
conveyors, the number of belt transfer points should be reduced to a minimum
to cut degradation, dust, and cost. Elevation of all belt lines a few feet
above ground will ease inspection, maintenance, and cleanup. Belt conveyors
emit dust almost exclusively at the transfer points. Placing enclosures
around transfer points can give effective dust control. A few simple rules
are normally followed for dust control:
(1) Reduce the number of belt transfers point to a minimum
(2) Be generous in sizing enclosures
(3) Arrange enclosures in easily removable sections
(4) Provide access doors on enclosures
(5) Install skirting and curtains at openings.
Bucket elevators are the simplest and most dependable units for making
vertical lifts. They can be totally enclosed to reduce fugitive dust
emissions.
5.3.5.2 Pneumatic Conveyors—
Pneumatic conveyors are commonly used to transfer dry granular or powdered
materials, both vertically and horizontally, to plant areas hard to reach
economically with mechanical conveyors. The properties of a material deter-
mine whether or not it can be successfully conveyed pneumatically. The materi-
al must pass through piping and auxiliary equipment without clogging,
degradation, or segregation, and be readily disengaged from the conveying air.
Materials from fine powders through 1/4-in. pellets can be handled.
Pneumatic systems can be completely enclosed to prevent contamination, materi-
al loss, and dust emissions. Furthermore, some materials are better protected
from adverse reactions when they are conveyed using an inert gas or dried air.
Pneumatic conveying systems can provide smooth, controlled, hands-off unload-
ing of bulk rail cars. The unloading procedure begins with the insertion of a
material pickup probe into the rail car's discharge port. The probe controls
the material-to-air ratio, and probe kits are designed to fit all rail cars.
5-33
-------
They consist of housing with slotted probes of varying lengths, designed to
reach different areas or compartments across the rail car. An air intake
filter is clamped to the car's discharge port opposite the material pickup
connection, and a car hatch filter attaches to the top of the rail car to
relieve vacuum created in the car by the material flow. Figure 5-16 illus-
trates pneumatic unloading of a railcar.
MATWIALUNt
CAR HATCH
FILTER
VACUUM
LINE
SILO
SILO
IN-PUNT IN-PIANT CONVEYING
DISTRIBUTION VACUUM POWER UNIT
MANIFOLD
BULK UNLOAD INC
VACUUM POWER UNIT
MATERIAL
UNCS
Figure 5-16. Diagram of pneumatic railcar unloading.
5.4 WASTE STORAGE AREA
The manner in which a waste is handled on-site is dependent on the nature of
the waste (corrosivity, explosivity, etc.), plant storage facilities, and heat
content of the fuel. Wastes received for incineration at a disposal facility
are either incinerated directly (in some cases via pumping directly from the
tank truck), or stored until they can be handled more conveniently. A plant
operator may want to store some of the incoming wastes with higher heating
values to possibly blend with other wastes which have heating values too low
to support combustion alone. At some plants, waste blending occurs prior to
storage. For a discussion on waste blending, see Section 5.5.
For further information on storage of hazardous waste in tanks, piles or con*
tainers, see The Permit Writer's Manual on each of those topics (prepared by
Fred C. Hart Assoc., Inc.)
Storage capacity is based on:
• Seasonal inventory buildup
• Redundancy or excess incinerator capacity
• Maintenance schedules and downtime
5-34
-------
Operating schedules (i.e., number of shifts vs. inshipment rates)
Amounts and nature of waste blending to be done.
Depending on the type of incinerator installation, storage facilities may be
required to hold both liquid and solid hazardous wastes. If an incinerator
cannot burn solids, facilities for solid storage are obviously not necessary.
A hazardous waste storage area is designed to address three problem areas.-
(1) Segregation of incompatible corrosive and reactive waste types;
(2) Fire hazards due to flammable liquids and solids; and
(3) Toxic hazards to prevent human exposure during storage, transfer,
and spill possibilities.
The safety and emergency design provisions for storing hazardous liquid wastes
are described in Section 5.4.3.
5.4.1 Types of Storage
5.4.1.1 Liquid storage—
Liquid/fluid waste storage includes temporary holding tanks, batching tanks, i
main storage tanks, and transfer pumps (pumps and valving are discussed in I
Section 5.5). Holding tanks provide initial storage of wastes prior to final ]
deposition of the material. Other tanks can store specific waste categories
which have been analyzed, require segregation, and are ready for incineration.
Batching tanks are used to prepare an 8-hr shift waste feed for the incinera-
tor. Also, tanks may be needed to store fuel oil (or bottled gas) for
incinerator ignition and auxiliary burners.
The storage tank farm facility is designed for liquids which may have high
vapor pressure, will be corrosive, will contain suspended solids, and may be
prone to polymerize. Tanks should be provided with nitrogen blanketing. Before
storing, the suspended solids are largely removed to minimize equipment erosion/
corrosion and valve sticking. Tank access is designed to facilitate ease-of-
entry for cleaning in the event that solidification does occur, and it most
certainly will at some tine [15].
Container nomenclature is vague but, ordinarily, "tank" means a container
designed to withstand pressures from atmospheric up to about 15 psig, whereas
"vessel" refers to a container which can withstand external or internal pres-
sures exceeding 15 psig. Tank pressure design of 15 psig is recommended [15].
Vapor pressures of 10 psig are not uncommon.
There are several basic types of storage tanks, as shown in Figure 5-17. The
aids to design of tanks takes the form of specifications, rules, standards,
and codes.
5-35
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3 DOME ROOF 4 ROAriNG WOF
S ROAT1NC ROOF. 6 EXPANSION ROOF
7 CDK-SOTTOM.
UNSKIRTU
I SWCM
HORtZONTAL MUM
Figure 5-17. Typical shapes for storage vessels [16].
Any of the vessels noted above can be lined or coated with corrosion-resistant
materials. All weld spatter is removed, and welds ground smooth or flush,
depending on the type of coating to be applied. Tank nozzles must be large
enough so a coating can be applied. Corrosion is an unavoidable problem. Grit
scouring destroys surface passivation, and promotes corrosion, another reason
for screening the incoming waste [15].
Both vertical and horizontal tanks are available for storing liquids. Verti-
cal tanks are acre economical to install, and occupy less space, while horizon-
tal tanks are easier to maintain and repair. Usually the lower maintenance
generally required by horizontal tanks does not offset their higher cost and
greater space requirements,- hence, vertical tanks are normally recommended.
If, however, it appears that future compartmentation of the tank will be
likely (as with segregated waste storage), it is easier to modify a horizontal
tank.
Installation and maintenance of aboveground tanks are less troublesome than
for underground tanks. With underground storage, the functions of gaging,
pumping, and leak detection become more difficult. With storage of hazardous
5-36
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wastes and liquids, underground tanks and their possibility of leakage is dis-
couraged. Underground tanks lend themselves to accelerated corrosion and often
require cathodic protection. Also, a means of containing leaked or spilled
materials is necessary for most underground tanks. However, when very volatile
materials are stored, underground storage is the only practical alternative.
Depending upon the liquid waste contained, tank storage can also require many
accessory equipment features such as:
(1) Flash arrester fill pipes.
(2) Flame arrester rodding and sampling units.
(3) Conservation breather vents with pipe-away construction—used where
pressure or vacuum relief is required and vapors must be piped away
rather than released into the atmosphere.
(4) Tank vent condensers—designed to condense and return to the tank vapors
that could escape, as shown in Figure 5-18. Due to potential unanticipated
reactions between physically or chemically incompatible wastes, large
volumes of organic vapor can be generated and must be vented to some con-
trol device. Venting the tanks into the incinerator combustion air intake ,
has the potential of creating an explosive condition, even with nitrogen I
blanketing. Chilled water condensers, coupled with knockout tanks, are J
best utilized to control emissions from the liquid transfer and storage
facilities [17].
IIQUID LEVEL
CONDENSING Oft
CHILLING SYSTEM
Figure 5-18. Typical tank condenser vent system.
5-37
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(5) Steam-heated conservation, pressure, or vacuum relief vents — designed
for use on tanks containing liquids whose vapors tend to crystallize
at ambient temperatures (also with pipe-away construction).
(6) Mushroom vent with flame arrester—used where it is not necessary to con-
serve vapor losses, but where low flash point solvent materials must be
protected against fire and explosion from exterior sources of ignition.
(7) Steam-jacketed flame arrester vents—designed for use on tanks containing
hazardous liquids whose characteristics require steam heating to prevent
crystallization of interior vapors; e.g., naphthalene.
(8) Manhole and emergency pressure relief vent covers—to provide emergency
pressure relief as well as access for tank cleaning..
(9) Internal safety valve—intended for use where tanks are required to be
equipped with valves that close automatically when subjected to fire.
(10) Integral internal heating coils—usually steam, designed to prevent
freezing of tank contents.
(11) Overflow piping—usually connected to an adjacent tank to mitigate spill
possibilities. I-
5.4.1.2 Bulk Solids Storage— " '
Material received as bulk solids at a hazardous waste incineration facility
can be stored in three ways:
(1) Enclosed bins or silos
(2) Concrete pits or below-grade concrete hoppers
(3) Stockpiles
Generally, solid hazardous waste materials which present a toxicity problem to
plant personnel are stored in totally-enclosed storage, such as single-outlet
bins, multiple-outlet silos, and portable bins. These enclosures protect the
hazardous material from exposure to the elements, or guard against dangers
represented by explosive, flammable, ignitable, or corrosive properties.
Table 5-3 gives a rough rating of the major types of bulk storage units in
terms of their capacities and method of reclamation or discharge.
Multiple-Outlet Silos--Multiple-outlet silos are useful for storing small or
medium quantities of material. Because they generally rely on gravity flow to
discharge the solids, hopper slopes and outlet dimensions must satisfy the
minimum requirements for uninhibited flow.
One of the most common problems with multiple-outlet silos is structural
failure caused by nonsymmetric flow patterns. Side discharge is typically
used with free-flowing materials such as grain. With this arrangement, bin
failures, especially in steel structures, manifest themselves as dents in the
region of the localized flow channel.
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TABLE 5-3. TYPES AND CHARACTERISTICS OF DRY BULK STORAGE [13]
Storage technique
and method of
reclaim or discharge
Storage capacity
Small, Large,
under over
20,000 700,000
ft3 Med. ft3
Stockpiles
Bottom tunnel X X
Bucket wheel X
Scraper truck X
Front-end loader X X
Multiple-outlet silos
Mass flow X X
Expanded flow X X
Funnel flow X X
Single-outlet bins
Mass flow X
Expanded flow X X
Funnel flow X X
Portable bins
Funnel flow X
Mass flow X
Concrete pits
Grapple X X
Single-Outlet Bins--Single-outlet bins are the most common type of storage
units in industry. Most of them are funnel-flow type, in which the sidewalls
of the hopper are sufficiently steep to maintain continuous flow. Most
pyramidal hoppers and conical hoppers with slopes of 60° or less from the
horizontal will display funnel flov.
Portable Bins—These special bulk units, generally limited to volumes less
than 200 ft-*, are often thought of simply as large buckets used to transport
homogenous material of a specified size and composition. Typically, these
bins are cube-shaped, with a flat hopper leading to a central outlet about 10
in. or less in diameter.
Some of the solid material characteristics considered when designing a solids
storage and retrieval system include:
(1) Bulk density
(2) Moisture content
(3) Particle size
(4) Angle of repose
5-39
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(5) Angle of slide
(6) Temperature
(7) Pressure differentials
(8) Abrasiveness
(9) Cohesiveness
(10) Material melting point
(11) Hygroscopicity
Many different types of bin hopper discharging devices have been developed,
primarily because solid material retrieval is difficult to achieve reliably
and consistently. Some of the bin hopper discharging devices are:
(1) Manual prodding through poke holes to eliminate material "bridging"
(definitely not useful for hazardous wastes)
(2) Chain or cable elements suspended to reduce bridging
(3) Agitators or "rotating fingers"
(4) Sweep arms or rotary vanes
(5) Rotary plows
(6) Multiple screw bottoms
(7) Bin activators or vibratory sections
(8) Electromechanical devices, such as side vibrators
(9) Pneumatic and hydraulic vibrators
(10) Air pads, cushions, and slides, wherein air is injected to fluidize the|-
material.
t
If one word could describe the basis of all solids retrieval problems, it
would be "friction." Any hopper surface which can reduce friction can mini-
mize bridging or arching. Fortunately, for a corrosive-type hazardous solid
material, the material of construction or lining of the hopper bin can solve a
dual problem. Materials to be given consideration are:
(1) Stainless steel, full thickness or dad-polished
(2) Teflon sheets bonded to steel containers.
Items of safety in bin design considerations include:
(1) Access doors for inspection, routine maintenance, and firefighting
(2) Fire detection—sensors; alarming; automatic suppression systems such as
C02, foam, or water; standpipes for connection to a water source and
availability of fire hoses
(3) Detection of level and pluggage
(4) Provisions for dust control
(5) Provisions for maintenance removal of bin discharge mechanisms which are
normally buried under waste.
Concrete Waste Pits—Concrete solid waste pits are in wide use in municipal
and industrial waste disposal plants which handle nonhazardous wastes. Bulk
solid refuse is dumped into the storage pit by packer truck, load lugger
bucket, or other collection vehicles.
5-40
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The storage pits are normally under an enclosure to prevent precipitation from
entering, and there is an approximately 10 ft wide vestibule which trucks back
into. Refuse is picked out of the pit by a bridge crane with a bucket or
grapple, and the crane delivers the solid waste to an infeed system. Control
of the crane and grapple is usually :rom an air-conditioned pulpit in which
the operator sits. Control is a saturable reactor type which provides cush-
ioned starting and acceleration. Protective zones are provided preventing the
operator from drawing the grapple into a wall, pulpit, etc. Automatic control
can be provided.
For fugitive dust control at each truck dumping point, there can be a down
blast heater. The vestibule and pit area are designed for complete sprinkler
protection of fire. Sprays in both the front and rear wall of the pit can be
included to suppress dust clouds that arise when a load is dumped.
The entire pit is usually watertight and sloped to troughs and drains for
dewatering. When a pit is constructed below grade, it is usually necessary to
have a sump. Screening devices to prevent material from entering the sump are
also used [18].
Stockpiles--Hazardous wastes are occasionally stored in piles, generally small
in size. Many are in buldings or maintained outside, under cover, on concrete
or other pads. They are most frequently used to accumulate waste composed of
a single, dry material.
Wind dispersal is controlled, by a cover or windscreen; piles inside a building
are adequately protected from dispersal.
5.4.1.3 Container Storage—
Hazardous materials for incineration will often arrive in small container form
(e.g., 55 gallon drums), and can be stored until used, provided the containers
are in good condition and are not leaking.
Metal and fiber containers are loaded, stored, and unloaded so as to minimize
the possibility of container damage. The containers are stored in a covered
area, off the ground, in a manner which will preclude damage, weathering, and
subsequent leakage. Storage pads of concrete or other impervious materials
are used as a base to prevent ground water leaching and percolation. The area
itself is provided for drainage to a treatment facility in an analogous manner
to diked storage tank areas.
If some containers contain corrosive substances, these are stored so that,
should leakage develop during storage, these substances will not corrode
through adjacent containers. Waste segregation practices of bulk storage
(liquid and solid) also prevail with indoor container storage.
All containers in storage are inspected to insure physical and mechanical
integrity, and the drainage and containment systems are also inspected.
Nonstationary containers can proliferate in a storage area; hence, all con-
tainers are clearly labeled and records maintained. In this way the operator
is able to quickly locate any hazardous waste.
5-41
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Waste containers are sealed to prevent the escape of vapors. Gasketed clo-
sures of containers and containers themselves are normally of a material that
will not be deteriorated by the waste inside the container. The container
storage enclosure area is vented to allow for collection and control of any
released vapors.
5.4.1.4 Tank Cars--
Hazardous waste storage can also occur in parked tank cars — both truck and
rail. Usually, the wastes are then pumped directly to the incinerator or
blending tanks. As with bulk storage, the area is designed to prevent ground
contamination and percolation, and diked or drained to collect spills and
surface runoff. As with container storage, each tank car is clearly labeled
and records maintained to quickly locate each hazardous waste.
5.4.2 Segregation of Wastes During Storage
Hazardous wastes may be segregated at an incineration facility due to waste
categories for fuel value and are certain to be segregated when incompatible
waste types are received. The type of incinerator and nature of wastes which
can be burned will greatly influence the extent of waste segregation during
storage.
Incompatible wastes are normally segregated due to corrosive and reactive |-
effects. Examples of segregation during storage are reactive chemicals whicl
should be stored in air or water tight containers, oxidizers which should be-
isolated from flammable materials, and materials which may polymerize in the
presence of accelerators. Section 5.5 on waste blending contains a ready and
quick reference for determining the compatibility reactions of most binary
combinations of hazardous wastes.
Wastes may also be segregated and stored to allow for fuel blending for maxi-
mal incinerator performance. Examples of the categorization of wastes which
could occur and the storage requirements necessary are as follows [19]:
(1) Light hydrocarbons and nonaqueous solvents — includes low flash
point wastes such as paint thinners, aromatics (toluene, benzene,
xylene, etc.) which reduce viscosity of heavier wastes and assist
fuel oil in initial heating prior to firing heavy blends.
(2) Medium to heavyweight hydrocarbons — includes still bottom
residues, crankcase oils, and discarded transformer oils. Most have
high flash points but relatively low ignition temperatures and
moisture is generally under 10 percent. Handling these wastes may
require use of insulated storage tanks and auxiliary heat to
maintain proper fluidity, particularly during cold weather.
(3) Low-water-content aqueous wastes -- sludges from fatty acids
production, starches, reject fatty acids, waste soluble oils, and
clabberstock. These wastes may be blended in limited proportions
with the heavier wastes in group 2 but require storage in insulated
and heated tanks to avoid congealing and freezing of contained water
during winter.
5-42
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(4; Dirty solvents -- includes kerosene, soluble inks, oil-solvent
residues, organic pigments. Storage tanks do not require insulation
or heating.
(5) High-water-content aqueous wastes, semisolids, sludges, and low
heating value liquids -- includes aqueous mixture of paint, enamel
and lacquer oversprays, liquid polymers in water, paint sludges.
(6) Skimmings from wastewater treatment plants -- floatable material
skimmed from settling tanks and thickeners such as spent grease.
(7) Spent earth -- from filters and contaminated areas. Due to high
water content this waste can require insulated storage, auxiliary
heat, and continuous agitation to maintain fluidity and prevent
freezing in cold weather.
5.4.3 Safety Provisions for Storage Areas
For safe facility design in the storage area, provisions are made to protect
personnel and the immediate environment from catastrophe—particularly fire
hazards and material spills. Liquid and container storage are most likely to
occur at a hazardous waste incineration facility, and are discussed below.
5.4.3.1 Fire Safety—
Volume 1 of National Fire Codes (National Fire Protection Association (NFPA),
Boston) contains recommendations and standards in NFPA 30, "Flammable and
Combustible Liquids Code," for venting, drainage, and dike construction of
tanks for flammable liquids. Also possibly applicable are NFPA 327, "Standard
Procedures for Cleaning or Safeguarding Small Tanks and Containers", and NFPA
43A, "Liquid and Solid Oxidizing Materials."
Many of the devices and equipment utilized to prevent fire hazards in the
liquid storage area were discussed in Section 5.4.1.1. Some other considera-
tions which apply to storage of large quantities of flammable liquids include:
(1) Instrumentation or remotely-operated valves to minimize flow of
flammables.
(2) Combustible gas monitors in the storage area which have an alarm
set below the lower flammable limit.
(3) Combustible gas monitors'that automatically actuate a deluge system
or safely shut down systems below lower flammable limit.
(4) Drainage and collection ponds (equalization basin) to carry away
liquid spills resulting from a fire incident.
For the storage of drums, many safety precautions can be used for the protec-
tion of the operators who open and inspect drums prior to incineration.
Safety features include.-
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(1) explosion-proof electrical equipment
(2) automatic fire doors
(3) a "light water" system
(4) dry chemical and C02 fire extinguishers
(5) special safety fork trucks with nonsparking forks
(6) air-operated pumps
(7) nonsparking tools
(8) safety showers and eyewashes
(9) safety glasses and face shields
(10) a ventilation system which makes a minimum of three air volume
changes per hour in all areas and thirteen (13) air volume changes
per hour in the drum pumping room or area.
For storage of bulk-solids, evidence of spontaneous heating is closely moni-
tored. Heat-sensitive devices in silos and bins are installed, connected to a
continuous temperature recorder at a central control board and arranged to
sound an alarm if unsafe temperatures are produced. Excessively wet materials
are not placed or permitted in storage silos or bins.
5.4.3.2 Spill/Toxicity Safety—
The most effective way of addressing a bulk liquid storage area's vulnerabili-
ty to spill incidents is to prevent them from happening. Assuming that all 4
storage tanks are properly designed, equipped with overflow alarms, and usea
only for intended or compatible purposes, the possibility of spills can be-I
substantially reduced by:
• Assuring the continual physical integrity of the vessels and their
fittings (inspection and testing).
• Establishing strong administrative controls covering all loading/unload-
ing and in-plant transfer operations (plans and procedures).
• Providing adequate secondary containment facilities (dikes, diversion
ditches, equalization basins)..
Physical Testing and Inspections—Spark testing (of lined storage tanks),
wall-thickness testing, or other appropriate means of nondestructive physical
testing or inspection are conducted on storage vessels which hold hazardous
liquids.
The exterior of each bulk storage tank is also visually examined at regular
intervals. Each inspection includes an examination of seams, rivets, nozzle
connections, valves, and pipelines directly connected to the tank. Visible
leaks of waste from tank seams and rivets are then promptly corrected.
Foundations and/or tank supports are also subject to inspection.
New and old tank installations are, as far as practical, fail-safe engineered
or updated to a fail-safe engineered installation. Design considerations are
given to providing the following devices.-
5-44
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(a) High liquid-level bell or horn alarms with an audio signal at a
constantly manned operating or listening station; in smaller plants
an audible air vent may suffice.
(b) Low liquid-level alarms with an audio signal at a constantly manned
operation or listening station; such alarms can also have a non-
bypassing reset device that can be readjusted to a given operating
level following tank fill or liquid removal.
(c) High liquid-level pump cutoff devices set to stop flow at a predeter-
mined tank content level.
(d) Direct audible or code signal communication between the tank gauger
and the pumping station.
(e) At least one fast response system for determining the liquid level
of each bulk storage tank such as digital computers, telepulse, or
direct vision gauges.
Tanks are then not knowingly used if the "head" or "top" is in a corroded-
through condition. Action is taken to drain such tanks and repair the defec-
tive member as promptly as possible.
Partially buried tanks for the storage of oil or hazardous materials are
normally avoided, unless the buried section of the shell is adequately coated
to prevent rapid corrosion of metallic surfaces buried in damp earth,
especially at the earth/air interface.
Buried storage tanks represent a potential for undetected spills. A buried
installation, when required, is wrapped and coated to retard corrosive action.
In addition, the earth is subjected to electrolytic testing to determine if
the tank should be further shielded by a cathodic protection system. Such
buried tanks are also subjected to regular hydrostatic testing. In lieu of the
above, arrangements can be made to expose the outer shell of the tank for
external examination at least every five years. Alternatively, a means of
conducting examinations of the tank at regular intervals can be provided,
e.g., down-hole television.
Tank Overfill—A variety of engineering practices suited to the nature of any
hazardous material stored are used to prevent tank overfilling, a major source
of spill incidents. The following general principles can be used in designing
a system of protection against tank overfill:
(1) Tanks are gauged before filling.
(2) Overflow pipes are connected to adjacent, compatable waste storage
tanks, or to secondary containment.
(3) Fail-safe devices and level alarms have been tested and insured in
place.
(4) Provisions to prevent static electricity discharge have been
implemented.
5-45
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Protection of Integral Heating Coils—Many liquids in storage require auxili-
ary heating to remain in a fluid state. This is normally accomplished econo-
mically by integral steam coils inside the storage tank and, often, agitation.
To control leakage through integral heating coils which may become defective
through prolonged use, the following design factors are considered and applied:
(1) The past life span of internal steam coils is determined, and a
regular system of maintenance and replacement that does not exceed
the anticipated life span is established.
(2) The temperature and environment is carefully considered when
selecting heating coil materials to reduce failure from corrosive
action, prolong life, and reduce replacement costs.
(3) The steam return of exhaust lines from integral heating coils which
discharge into an open watercourse is monitored for contamin-
ation, or passed through a settling tank, or skimmer, etc.
(4) The nature of the wastes is carefully considered to prevent wastes
from caking on the heating coils, which reduces their efficiency as
well as causing waste materials to be contained in a tank thought.
to be empty. r
(5) The feasibility of installing an external heating system is also
considered, and, if feasible, often is recommended to solve
problems which may arise from implementation of (1) through (4).
Secondary Containment--All bulk storage tank installations at a hazardous
waste incineration facility are planned so that a secondary means of contain-
ment is provided for the entire contents of the largest single tank. Dikes,
containment curbs, and pits are commonly employed for this purpose, but they
may not always be appropriate. An alternative system would consist of a
complete drainage trench enclosure arranged so that a spill could collect and
be safely confined in an in-plant catchment basin or holding pond.
Dikes are generally constructed of concrete, cinder blocks, and/or earth.
However, dike materials are designed to be chemially resistant and essentially
impervious (e.g., permeability rate no greater than 10 7 on/s when subjected
to a head of 1 ft of water) to the substances contained. Acceptable engineer-
ing design criteria for a dike will enable it to withstand a sudden massive
release.
Some of the important design guidelines for dike construction include [20]:
(1) Single storage tank — The capacity of diked area is at least ade-
quate to hold the entire tank contents plus a reasonable allowance
for precipitation. Local regulations may contain more stringent
requirements. An alternative design goal is for the diked area to
contain the volume of the tank plus 1 ft of freeboard.
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(2) Clustered storage tanks -- The capacity of the diked area is adequate
to hold the entire contents of the largest tank plus a reasonable
allowance for precipitation. Again, local regulations may be more
stringent.
(3) To the extent feasible, dike walls generally do not exceed a height
of 6 ft above interior grade. A greater height might require the
observance of tank entry procedures including safety harnesses,
oxygen deficiency checks, standby observers, and other precautions
each time it is necessary to enter the diked area.
(4) For earthen dikes, a slop of 2.5:1 is preferred. Earthen dike walls
3 ft or more in height are generally designed with a flat walkway
section at the top not less than 2 ft wide.
(5) Dikes may also need to be constructed to provide necessary ramps for
vehicles needing access to the storage areas.
(6) The disposal of rainwater and other liquids from within diked areas is
normally accomplished by a manually activated pump or siphon system.
Such accumulated stormwater must be removed in order to maintain
adequate volume for a maximum spill. Figure 5-19 shows a diversion |
structure which serves this purpose. Of course, retained drawoff wata
and the rainfall accumulated are checked (analyzed) before release. J
STOftM WATER
SUMP
BL 3
OILY WATER
SEWER
SEALED
MANHOLE
STORM WATER _
PAIN f=.
PLAN
Figure 5-19. Dike drain detail Type "A" diversion box [21]
5-47
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(7) For hazardous and toxic liquids, the ground area within the dike
and curbing are designed to be essentially impermeable. This can be
achieved by use of concrete, asphalt, or suitable clays. Neutraliz-
ing materials for the stored chemical waste such as limestone or
clam shells for acidic wastes are sometimes used as a ground cover,
although neutralizing ground covers need to be replaced promptly
after a spill or incident.
(8) Generally, it is recommended that there be no discharge or loading
pipes through the dike wall. However, construction design has to
conform to state and local regulation, and some local fire regula-
tions (applicable to flammable liquids) require a valved pipe through
the dike wall, while others prohibit this installation. If a drain-
age valve through the dike wall is required, it is kept locked in
the closed position when not in use and a chemically resistant seal
is installed around the pipe passing through the wall.
(9) The storage tanks located immediately adjacent to the dike itself
are oriented so that no manholes face the dike. This is considered
desirable, so that, if a manhole fails, the resulting discharge
from a full tank will not be aimed over or at the dike. Where
this design is not feasible, appropriate baffles are installed 4
to deflect potential leaks and cause them to drop within the I
contained area. I
(10) If storage tanks located immediately adjacent to the dike are
equipped with fill lines which enter the tank near the bottom, and
if the fluid pumped has suspended abrasive material, the discharge
into the tank should be on the dike side, discharging against the
tank side away from the dike. Alternatively, a baffle plate located
inside the tank opposite the pump discharge in the area apt to be
abraded, may be provided.
The final defense in the prevention and containment of liquid and solid spills
is at the end of the plant storm-drain system. Here, an automatic system mon-
itors the storm drain for acidity or alkalinity (pH), turbidity, total oxygen
demand (TOD), and flow (variance from normal).
If any of the parameters are sensed beyond normal limits, a diversion gate
automatically move into position to divert the discharge to a holding pond.
Such a system provides protection against a spill that goes beyond the process
area, dikes, and into the storm drains. Discharges diverted to the holding
pond are removed to a process area for recycle, treatment, or disposal.
Container Storage—Containers with a capacity of less than 45 gallons are
stored out-of-doors, when possible, in rows no more than 30 feet in length,
five feet in width, and six feet in height. Containers which have a capacity
of 45 gallons or more are stored in rows no more than 30 feet in length and
two containers in width and should not be stacked. A minimum of five feet
between rows of containers of hazardous wastes is usually maintained.
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If exposure of the containers to moisture or direct sunlight (see Section 5.5)
will create a hazardous condition or adversely affect the containers' ability
to hold the hazardous waste, the containers are then stored in an area with
overhead roofing or other covering that does not obstruct the visibility of
the container labels.
The area under or around the container storage area is built to be able to
collect or hold any spilled material; e.g., collection drains, trenches, or
dikes.
5.5 WASTE BLENDING AND/OR PROCESSING BEFORE INCINERATION
The methods by which hazardous wastes are removed from storage, prepared for
incineration, and fed to the incinerator are dependent on the nature of the
waste and type of incinerator. Figure 5-4 in Section 5.3 illustrates the
various pathways from storage to final feed into the incinerator. Careful
design consideration is given:
(a) To the layout for liquid waste blending, pumping and associated
pipework, and
(b) To the handling and feeding arrangements for nonpumpable sludges, I-
solids, and containerized wastes, where applicable. [
Operating experience has shown that these are areas that do not receive as
much attention as is necessary,- the overall success of an incineration
facility depends upon the successful integration of storage, feeding, and
firing equipment.
5.5.1 Waste Compatibilities
The "combination of wastes" often presents many problems for the management of
hazardous wastes. In some instances, the combination or mixture of two or
more types of the wastes produces undesirable or uncontrolled reactions
resulting in adverse consequences. These reactions may cause any one or more
of the following:
(1) Heat generation, fire, and/or explosions,
(2) Formation of toxic fumes,
(3) Formation of flammable gases,
(4) Volatilization of toxic or flammable substances,
(5) Formation of substances of greater toxicity,
(6) Formation of shock and friction sensitive compounds,
(7) Pressurization in closed vessels,
(8) Solubilization of toxic substances,
(9) Dispersal of toxic dusts, mists, and particles, and
(10) Violent polymerization.
Available data indicate that hazardous wastes are ill-defined, complex mixtures
generated by a great variety of sources. No two types of wastes appear to be
identical, for even a single process appears to produce different types of wastes.
Characterization of the wastes by the analysis of the processes and the materials
5-49
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used appear to give inaccurate descriptions of the resulting wastes. The data '
indicate that each waste is unique and that individual reactivities may be best
assessed by identifying respective chemical constituents.
For further information on compatability of hazardous waste refer to the
Guidance Manual entitled, "Treatment Trial Tests and Hazardous Waste
Compatability". Another commonly used laboratory test for waste compatibility
is ASTM £476-73, "Thermal Instability of Confined Condensed Phase Systems,"
which measures the temperature at which exothermic reactions begin and amount of
pressure release.
While empirical data exist concerning the consequences of reactions between
pure substances under laboratory conditions (mostly binary combinations), very
little work has been done in the field of waste combination reactions. Very
seldom are wastes pure substances. They are usually sludges, emulsions,
suspensions, or slurries containing many different compounds.
The chance of combining noncompatible wastes within a specific category can be
minimized in several ways. First, the problem is restricted to puntpable
wastes since nonpumpable scrap is often handled in individual drums or bin
containers and is not mixed prior to incineration. Secondly, a single manu-
facturing location normally uses compatible solvents. Thus, with knowledge of
the generator in hand (manifest system), the greatest chance that noncompat-i-
ible wastes will be combined occurs at the incineration facility. Basically,!
proper labelling at the waste generation source and the experience and know- -
ledge in liquid segregation of the incinerator operators will greatly minimize 4
the problem. The primary concern in waste blending is minimizing the reactivity
of combined wastes. Other secondary concerns in waste blending are precipitate
formation, increases in viscosity, and blends which could generate acid gas
combustion products.
It is evident from the existing data that the largest and most common dangers
inherent from incompatible reactions involve strong acids or bases. For this
reason, it is desirable that acids and bases be neutralized to within a pH
range of 4.5 to 9 before being mixed with other wastes (sometimes acidic and
basic wastes are mixed in a controlled manner to achieve pH neutrality).
Even within this restricted pH range, acids should be segregated from acid-
soluble sulfide and cyanide salts.
With the above inclusions, an example of a compatibility mcitrix is depicted
in Figures 5-20 and 5-21. If it is not feasible to neutralize acid wastes
and/or caustics to within the prescribed pH range, then the matrix in Figure
5-21 is used.
5.5.2 Liquid Feed and Blending Equipment
Liquid blending or mixing of hazardous wastes is done as part of an overall
liquid feed system, which includes a feed pump, usually some recirculation to
the mix vessel, and associated piping to the incinerator.
An example of a mixing vessel is shown in Figure 5-22. For hazardous waste ,
blending, the vessel is always closed-top rather than open-top to prevent
5-50
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AMINES &
ALKANOL AMINES
MAtOGESiATED CMPDS
PEROXIOES& ETHERS
ALDEHYDES fc
KETONES
MONOMERS &
POLYMERI.ZA81.E ESTERS
ALKYLENE OXIOES,
NITRIIES fcAClD ANHYDRIDES
OXIDIZING AGENTS
1
X
X1
X
X
2
x
X
3
x
4
X)
6
X
«
ACIOS
CAUSTICS
AMINEl 4
ALKAMOl AWINf S
MALOGCNATED OM*OS
KXOIIOft li ETHERS
ALDIMYOSS 4
XE TOMES
MOMOMC«S A
POLYMf KIZAtLt tfTIMS
ALKVLIMt OXIDES
MITDII.ES « ACID ANMYOKIOES
OXIDI2INC ACCNTS
1
V
X
x
^
R
8
x
i
>3
X
x
X
x
i
x
X
X
X
4
x
X
s
X
1
r
X •
DENOTES INCOMPATIBILITY
DEMOTES INCOM*ATHILITV
Figure 5-20.
Compatibility matrix
for neutralized
hazardous wastes [1].
Figure 5-21.
Compatibility matrix
when wastes cannot be
neutralized [1].
Figure 5-22. Example of a baffled mixing vessel [14].
splashing and vapor escape. Impeller mixer drives, both direct drive and gear
drive, are available. The shaft length and number or configuration of impel-
lers must be based on the geometry of the tank and viscosities of the waste.
Generally, fuel blending requires a mild agitation or intensity of blending,
and the use of baffles increases the turbulence and mixing characteristics.
Where conditions warrant extreme safety, the blending and feeding process can
be augmented by the use of a pneumatic compressed air (or gas mixer) motor
and pneumatically-driven diaphram feed pump. The pumps used to transfer the
wastes from storage to blending can also be pneumatic diaphram pumps. Inert
5-51
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gas blanketing with nitrogen of the mixing vessel is almost aways used. The '
blending tanks are also equipped with a pH recorder, an in-tank viscometer, and
a sampling port and/or valve.
A typical sequence of activities prior to the injection of a liquid waste blend
to the incinerator is as follows: a waste batch arrives at the plant; a grab
sample is taken to confirm that the shipment is within the contracted specif-
ications between the generator and the incinerator operator; the waste batch
is then unloaded and received in an agitated tank to homogenize the batch;
an integrated sample is taken and analyzed for Btu content, ash content, chlorine
content, etc., and the batch is then piped to the blending tank(s). If longer-
term storage is necessary, the batches received are typically stored according
to Btu content, ash content, or acid gas generating potential, as well as
constraints dictated by waste compatibilities.
Waste blending goals are based on stack emissions limitations and loadings
on the pollution control system. Worksheets 4-2 and 4-12 in Chapter 4 describe
procedures for calculating the pollutant loadings of SOz, acid gas components,
and particulate matter. Ash contents of a waste blend are typically targeted
at 1-1 1/2% in order to meet particulate emission limitations; if a chlorinated
feed can be handled, the waste is blended to 15-30% chlorine,- and a final Btu
content of 7,000-9,000 Btu/lb is desirable (personal communication with Jerry
Jordan, Rollins Environmental Services, Inc., Bridgeport, NJ, June 1981). L
The DRE requirement of 99.99% for the POHC's in the waste blend will have I
already been demonstrated in a trial burn or met through similarity criteria?.
The amount of waste blended is usually enough for one day's operation of the
incinerator.
If the type of incinerator can handle a slurry feed, the piping system should
be designed to handle slurries. A slurry piping system has a minimum diameter
of 4-6 times the particle size being pumped. All piping is recirculated to
prevent settling, and possibly, mechanically comminuted to destroy any
agglomerations which would cause plugging problems. A careful monitoring of
the pump discharge pressure allows the operator to determine whether the feed
pump is being influenced by the mixer (entrained air), as a check of slurry
density, and to point to plugging problems. Figure 5-23 shows a slurry
injection and monitoring system.
When slurries cannot be fed to an incinerator, the feed lines to the mixing tanks
are filtered to prevent solids from reaching the burner nozzles. If slurries can
be fed to the incinerator, sometimes an in-line grinder/chopper or grinder pump
is used to reduce the size of the solids in the liquid waste.
Several stages of waste line filtering are advisable in order that control
valves and measuring devices on the route to the burner nozzle do not stick or
clog. In a waste mixture, solid particulate may form as precipitates or polymer
seeds in situ. Frequently, the small beads may be elastomeric as behave in the
same way as synthetic rubber by extruding through the screens. To minimize
these conditions, stategically placed filters in sequence are very helpful
in maintaining onstream time [15]. M
5-52
-------
SLURRY
CONTROL
PANEL
| SLURRY GUN
I PRESSURE
| GAGE
M/
FUJID BED
CHAMBER
SLURRY GUN
PRESSURE
TRANSMITTER
WATER COOLED
SLURRY NOZZEL
HEADER
PRESSURE
TRANSMITTER
2-1/?" SLURRY HEADER
SLURRY
aow
Figure 5-23. Slurry injection and monitoring system.
Liquid streams can carry impurities of every sort. Furthermore, they may be
highly viscous, which makes handling and atomizing difficult. Liquids should
generally have a viscosity of 10,000 SSU or less to be satisfactorily pumped
and handled in pipes. For atomization, a viscosity of 750 SSU is the maximum.
Table 4-1 in Section 4.3.2 presents the viscosity and impurity limitations
for various atomization techniques. Viscosity can usually be controlled by
steam heating with tank coils or in-line heaters, but careful notice of the
flash points must be taken. If preheating is not feasible, a lower viscosity
and miscible liquid may be added to reduce the viscosity of the mixture. Line
heat tracing is a must, taking into account worst case material .freezing points
and local winter design temperatures [15].
A feed system may have two or more recirculating loops installed, chiefly to
keep any solids remaining in the liquid mixture from settling and plugging
pipelines. Figure 5-24 illustrates an example of multiple recirculation.
5.5.3 Pumps and Piping
Pump and piping materials of construction are designed to be suitable for the
liquids encountered (See Section 5.14). While centrifugal pumps can be used
to feed liquids and/or slurries, positive displacement-type (PD) pumps are
preferred. Unlike centrifugal pumps, they afford a reasonably tight shut-off
and prevent siphoning when not in operation. Table 5-4 displays the materials
of construction for positive displacement pumps. Figure 5-25 provides a pump
classification chart.
5-53
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TO 1NCINESATC*
TANK ~
MOYNO
PUMP
SV- GATE VALVE CK» SIO« VALVE
P»V-P«ESSURE «UEF VALVE HEARTH
Figure 5-24. Liquid feed system with redundant recirculation.
TABLE 5-4. MATERIALS OF CONSTRUCTION FOR POSITIVE DISPLACEMENT PUMPS
Pump body
Plunger pump
Plunger
Lantern ring
Diaphragm pump
Diaphragm
or bellows
Steel
Iron
Stainless steel
PVC
Alloy 20
Monel
Carpenter 20
Stainless steel
Ceramic
Monel
Stainless steel
Allow 20
Hastelloy "C"
PVC
Alumina-ceramic
Elastometer
Teflon
Polyethylene
Buna N
Neoprene
Viton
Resistant steels
Check valves
Valve body
Steel
Stainless steel
PVC
Alloy 20
Hastelloy "C"
Monel
Ball
Stainless steel
PVC
Hastelloy "C" to "D"
Alumina-ceramic
Ball seat
Stainless steel
PVC
Alloy 20
Monel
Hastelloy "C"
5-54
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CENTRIFUGAL
HORIZONTAL
GENERAL SERVICE
CHEMICAL (ANSI)
HIGH TEMP. (API)
MULTISTAGE
SLURRY
SELF-PRIMING
MIXED FLOW
PROPELLER
VERTICAL
GENERAL SERVICE
TURBINE TYPE
VOLUTE TYPE
SUMP TYPE
CHEMICAL TYPE IN-LINE
HIGH-SPEED IN-LINE
CAN TYPE (LOW NPSH)
POSITIVE
DIS PLACEMENT
ROTARY
GEAR
SCREW
PROGRESSING CAVITY
LOBE
VANE
RECIPROCATING
DIRECT ACTING TYPE
POWER FRAME TYPE
PLUNGER OR PISTON
HORIZONTAL OR VERTICAL
CONTROLLED VOLUME
PLUNGER TYPE
DIAPHRAGM TYPE
NUMBER OF FEEDS
TYPE OF STROKE
ADJUSTMENT
Figure 5-25. Pump classification chart.
A relief valve is usually provided downstream of PD pumps, of sufficient
capacity to prevent excess pressure in the system. The relief valve discharge
is then piped back to the supply source or to the suction side of the pump.
5.5.3.1 Positive-Displacement Pumpg—
Positive-displacement pumps have as their principle of operation the displacement
of the liquid from the pump case by reciprocating action of a piston or diaphragm,
or rotating action of a gear, cam, vane, or screw. The type of action may be used
to classify positive-displacement pumps as reciprocating or rotary. Figures 5-26
and 5-27 depict some typical pumps of each type. When a positive-displacement
pump is stopped, it serves as a check valve to prevent backflow.
5.5.3.2 Centrifugal Pumps--
Centrifugal pumps operate by the principle of converting velocity pressure
generated by centrifugal force to static pressure. Velocity is imparted to
the fluid by an impeller that is rotated at high speeds. The fluid enters at
the center of the impeller and is discharged from its periphery. Unlike
positive-displacement pumps, when the centrifugal type of pump is stopped
there is a tendency for the fluid to backflow. Figure 5-28 depicts some
centrifugal pumps.
5-55
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SUCT)ON 'Oil T I OH
ItSCmMC 9 I JC"ilH >l »f
C » I 11 tl^i.mna^a » it t C I I » »
SCHitii
COmtCCT ill
IOOS
ClmiCCT HI
Figure 5-26. Reciprocating pumps: (a) Principle of reciprocating pump,
(b) principle of fluid-operated diaphragm pump, (c) direct-
acting steam pump, (d) principle of mechanical diaphragm pump,
(e) piston-type power pump, (f) plunger-type power pump with
adjustable stroke, (g) inverted, vertical, triplex power pump
[22].
Power for driving the various types of pumps is usually derived from electric
motors or pneumatic drives. Most rotary pumps are driven by electric motor.
5.5.3.3 Pump Emission Control--
Operation of various pumps in the handling of fluids can result in the release
of air contaminants. Both reciprocating and centrifugal pumps can be sources
of emissions.
5-56
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C ' S C « » • G £ 0•! V iN S til*
10 T0»
i OLE»OTO
I U C T I 0 M
HOILEI ECCENTKIC
h
f LEI I HE DUIlEi
t TUII
r-i
j^S-S^ST? '^'^r^V^—r
r^b^* x" ^^— ~/ • / >• j • // "v,^L \\~^r™™i
Figure 5-27. Rotary pumps: (a) External-gear pump, (b) internal-gear pump,
(c) three-lobe pump, (d) four-lobe pump, (e) sliding-vane pump,
(f) single-screw pump, (g) swinging-vane pump, (h) cam or
roller pump, (i) cam-and-piston pump, (j) three-screw pump,
(k) shuttle-block pump, (1) squeegee pump, (m) neoprene vane
pump [22].
The opening in the cylinder or fluid end through which the connecting rod
actuates the piston is the major potential source of containants from a recip-
rocating pump. In centrifugal pumps, normally the only potential source of
leakage occurs where the drive shaft passes through the impeller casing.
Several means have been devised for sealing the annular clearance between pump
shafts and fluid casings to retard leakage. For most applications, packed
seals and mechanical seals are widely used.
Packed seals can be used on both positive displacement and centrifugal type
pumps. Typical packed seals generally consist of a stuffing box filled with
sealing material that encases the moving shaft. The stuffing box is fitted
with a takeup ring that is made to compress the packing and cause it to tight-
en around the shaft. Materials used for packing vary with the fluid's tempera-
ture, physical and chemical properties, pressure, and pump type. Some
commonly used materials are metal, rubber, leather, and plastics.
5-57
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0 I SCMMU
VOLUTE B1MU|IO
IM'ELLE' yANCS »*"CJ I ' '
Figure 5-28. Centrifugal pumps: (a) Principle of centrifugal-type pump,
(b) radial section through volute-type pump, (c) radial section
through diffuser-type pump, (d) open impeller, (e) semi-
enclosed impeller, (f) closed impeller, (g) nonclog impeller
[22].
Lubrication of the contact surfaces of the packing and shaft is effected by a
controlled amount of product leakage to the atmosphere. This feature makes
packing seals undesirable in applications where the liquid can cause a pollu-
tion problem. The packing itself may also be saturated with some material
such as graphite or oil that acts as a lubricant. In some cases cooling or
quench water is used to cool the impeller shaft and the bearings.
The second commonly used means of sealing is the mechanical seal, which was
developed over a period of years as a means of reducing leakage from pump
glands. This type of seal can be used only in pumps that have a rotary shaft
motion. A simple mechanical seal consists of two rings with wearing surfaces
at right angles to the shaft. One ring is stationary while the other is
attached to the shaft and rotates with it. A spring and the action of fluid
pressure keep the two faces in contact. Lubrication of the wearing faces is
accomplished by a thin film of the material being pumped. The wearing faces
are precisely finished to ensure perfectly flat surfaces. Materials used in
the manufacture of the sealing rings are many and varied. Choice of materials
depends primarily upon properties of fluid being pumped, pressure, temperature,
and speed of rotation. The vast majority of rotating faces in commercial use
are made of carbon.
5-58
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Emissions to the atmosphere from centrifugal pumps may be controlled in some
cases by use of the described mechanical-type seals instead of packing glands.
For cases not feasible to control with mechanical seals, specialized types of
pumps, such as canned, diaphragm, or electromagnetic, are required.
Another specialty category is the sealed pump, which has no external seal or
potential leakage. The two major types are the canned-rotor and the magnetic.
Sealed pumps are used where no leakage can be tolerated, or where pump seal
failure might cause major trouble. Such pumps are available in a limited
range of sizes, most are low-flows, and all are of single- or two-stage con-
struction. They have been used for both high-temperature and very low-tempera-
ture liquids. High-suction-pressure applications avoid the need for a trou-
blesome high-pressure stuffing box. The centrifugal-type pumps follow the
same hydraulic performance rules as conventional centrifugal pumps. Because
of their small size, these pumps show a rather low efficiency but, in
dangerous applications, efficiency must often be sacrificed for safety.
5.5.3.4 Pump and Piping Safety—
The primary objectives of pumping and piping systems are to prevent escape of
liquid and to keep to a minimum the quantity lost if the liquid does escape.
Inherent safety and freedom from human failure can, to a considerable extent,
be built into a hazardous/flammable liquid system. Some design
recommendations which help to attain the above objectives are listed below:
(1) Complete automatic sprinkler protection is provided in indoor areas
where pumps, piping, tanks, and other parts of hazardous liquid
transfer systems are located. In well-drained areas, sprinkler
discharge of 0.30 gpm/sq ft of floor area is usually recommended to
prevent structural and equipment damage.
(2) Indoor piping is located either overhead or in trenches in the
floor. Overhead piping is normally installed close to ceilings or
beams or along walls at least 6 ft above floor level. If piping is
located in a trench in the floor, the trench is covered with remov-
able steel plates and a trapped drain installed to a point of safe
discharge. Positive-exhaust ventilation is provided in the trench,
or the trench is backfilled with sand for liquids having closed-cup
flash points below 110°F.
(3) Provisions are made to clean out the piping and equipment when long
or scheduled shutdowns occur. This is usually done by purging with
steam. The condensate is then collected and treated as a wastewater.
(4) Pipe materials are used which are chemically resistant to the liquid
handled, which have adequate design strength to withstand the maxi-
mum service pressure and temperature, and which, when possible, are
resistant to mechanical damage or thermal shock. Cast-iron, soft-
rubber, or thermoplastic pipe or fittings of low melting point are
never used.
5-59
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(5) If corrosive liquids or high standards of purity make special pipe
necessary, the use of stainless steel, nickel alloys, or other
materials having high resistance to heat and mechanical damage or
steel pipe with tin, glass, plastic, rubber, lead, or other lining
is preferred to more fragile piping. If problems of corrosion,
contaminations, or sanitation are the controlling factor, the use of
carbon, graphite, glass, porcelain, thermosetting-plastic, or hard-
rubber pipe is acceptable. Where specifically needed for the liquid
being handled, aluminum alloy, aluminum bronze, or lead pipe is
acceptable. Extra care is then used in locating, guarding, and
supporting specialty piping against mechanical injury.
(6) Each waste material pipeline is clearly marked by lettering (coded
or otherwise), color banding, or complete color coding to indicate
the product transferred therein. The coding normally conforms with
company policy or standard plant practice which, in turn, should
conform with state or federal requirements.
(7) Each oil or hazardous material product-fill line which enters a tank
below the liquid level has a one-way flow check valve located as
closely as possible to the bulk storage tank. In addition to confin-
ing the product to the tank, in the event of valve or pipeline
failure, the check valve permits overhaul of the main shut-off va^ve
and should aid in preventing shock loading of the pipeline and
valves from a "slug" of the tank content caused by backflow into
empty fill line. The waste feed flow in suction lines is controlled
by use of a positive displacement pump.
t
(8) Buried pipelines are generally avoided. When they do occur however,
buried installations have a protective wrapping and coating and are
cathodically protected if soil conditions warrant. A section of the
line is then exposed and inspected regularly. This action is normal-
ly recycled until the entire line has been exposed and examined on a
regularly established frequency. An alternative would be the use of
exposable pipe corridors or galleries.
(9) When a pipeline is not in service, the terminal connection at the
transfer point is capped or blank-flanged, and marked as to origin.
(10) Wood-to-metal is normally avoided as a pipeline support since it is
apt to retain moisture and cause pipeline corrosion which, when
coupled with the abrasive action caused by the pulsating action of
the line, could cause line failure with resulting leakage. Supports
are generally designed with only a minimum point of surface contact
that allows for the pulsating movement (expansion and contraction)
inspections at which time the general condition, of items, such as
flange joints, valve glands and bodies, catch trays, pipeline
supports, locking of valves, and metal surfaces, are assessed.
(12) Elevated pipelines are also subjected to constant review to insure
that the height of vehicular traffic granted plant entry does not
exceed the lowermost height of the elevated line; gate check-in and
in-plant travel are routes which warrant attention in this respect.
5-60
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(13) Double-walled piping and/or flange shielding may be necessary for
some above-ground pipelines carrying an especially hazardous or
toxic waste stream if the pipeline intersects critical locations
such as highways, driveways, railroads, or small watercourses. An
example is illustrated in Figure 5-29.
(14) As far as practical, all pumps feeding the blender are located as
close as possible to the storage tank.
1. A SHIELD PREVENTS SPLASHING IF THE FLANGE FAILS.
2. OUTER CONCENTRTIC PIPE PREVENTS ESCAPE (AND
k INDICATES THE FAILURE) IF INNER, LI QUID-CARRY ING
PIPE FAILS.
Figure 5-29. Two safeguards for piping of highly toxic liquids [23].
Many liquid wastes are solids at room temperature or become highly viscous at
lower temperatures, and require heated piping to keep them in a fluid state
suitable for transfer through the system. Liquids from heated tanks can
usually be handled by providing adequate insulation on the pipe and fittings.
The following methods of applying heat to piping systems are considered
acceptable:
(1) Flammable-liquid lines are often steam-traced. The minimum steam
pressure needed is used to make the liquid fluid, and a regulator is
provided in the steam line with a relief valve downstream of the
regulator set somewhat higher. The pipe and tracing are enclosed
with noncombustible insulation.
(2) Electric heating cable is usually fastened along the pipe or wound
spirally around it and the whole covered with noncombustible insula-
tion. No splices in the cable should be made, and all connections are
located outside the insulation-covered pipe. Individual thermostatic
5-61
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controls for each cable section should be provided and protected
with a fuse or fused disconnect switches of as low a rating as
practical. Outdoors, weather-proof enclosures are provided for
thermostats, plug assemblies, and switches, and in all installations
are located safely away from the pipelines and out of the flammable-
liquid area. Accessories will introduce a hazard unless located so
that the make-and-break contacts will function in a nonexplosive
atmosphere.
(3) Thermal-electric conduction may be utilized by passing a low-voltage
alternating current though the pipe. This method is commonly used
to maintain a constant temperature in a system of piping when materi-
al in the storage tank has been previously wanned. Sufficient heat
is supplied to the piping to compensate for normal heat loss in the
system without raising the temperature of the liquid in transfer.
Thermal-electric conduction systems is normally installed and tested
as complete units by the manufacturer or his qualified agent.
Sections of the piping to be heated are insulated by electrically
nonconductive fittings from unheated sections to confine the current
paths and to eliminate any current leakage at hazardous locations.
For thermal-electric conduction systems the following i
recommendations usually apply: J"
(a) An automatic high-temperature-limit safety cutoff switch is
provided in each circuit of each system to prevent overheating
of liquid in event of failure of the operating temperature-
control thermostat.
(b) Each circuit is protected with fuses or fused disconnect
switches of the lowest practical rating.
(c) All parts of the piping and fittings are enclosed in electri- i
cal- and thermal-insulating covering to prevent accidental
grounding of the system.
(d) All switches, transformers, contactors, or other sparking units \
are located in a safe area away from any flammable liquid or
vapor.
(e) The system is inspected and tested periodically to .insure its
continued safe operation. Maintenance of the installation is
the responsibility of trained employees.
5.5.4 Valving and Controls
Valve functions can be defined as follows: »
(1) On/off service
(2) Throttling service
(3) Prevention of reverse flow, or backflow
(4) Pressure control
5-62
-------
(5) Special functions:
(a) Directing flow
(b) Sampling service
(c) Limiting flows
(d) Sealing vessel or tank outlets
(e) Other.
Valve selection requires consideration of three basic and critical details:
(1) The flow control element
(2) The regulating mechanism
(3) The seal to contain the fluid within the valve.
In addition to these three important design aspects, features such as mechani-
cal strength, materials of construction, dimensional arrangement, and types of
end-connections are considered.
Valves are weak links in fluid transfer systems as regards leaks and fugitive
emissions. There are three types of leakage:
(1) Process fluid escapes downstream, past flow-control element in
closed position. Identified as "flow seal" leakage. i
(2) Process fluid escapes to the outside of the valve, from around the |
stem and from the joints (bonnet) with the body. Identified as
either stem-seal or bonnet-seal leakage.
(3) Air leaks into the valve body and to the process medium under
vacuum.
Figure 5-30 shows a gate valve with the possible leakage areas around the stem
packing, the bonnet assembly, and between the valve stem and packing gland.
5.5.5 Valving and Control Safety Consideration
5.5.5.1 Safety Shutoffs—
Hazardous and flammable-liquid pumping and piping systems are equipped with
emergency shutoffs to stop the flow of liquid in event of fire or accidental
escape of liquid or vapor. This can usually be done by safety shutoff valves
and/or positive-displacement pumps. In general, these devices are arranged
for automatic operation in event of fire and for manual or automatic operation
in event of accidental escape of liquid. If the location of a possible fire
can be accurately determined, as would be the case at dispensing locations,
remote actuation is not necessary. If a fire could occur anywhere at an
extensive installation, provision for remote actuation of the main safety
shutoff valve will be needed.
(1) Safety shutoff valves are needed in flammable-liquid systems in the
following locations.-
5-63
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« POSSI8U
LEAK AREAS
Figure 5-30.
Three areas of a typical gate valve that can
leak and result in fugitive emissions [2].
(a) At connections on supply and feed tanks where transfer is by
gravity, centrifugal pump, inert-gas pressure, or other means
that permits the maintenance of continuous pressure in the
system. The possibility of siphon action through a centrifugal
pump requires installation of a safety shutoff valve on the
pump inlet.
(b) On feed lines where they enter important buildings or struc-
tures or on branch lines where they take off from main-supply
headers. The valve is located out of doors or immediately
adjacent to an exterior wall, accessible from outdoors.
(c) On feed lines at dispensing locations.
(2) Safety shutoff valves may be of the diaphragm, solenoid, or weight-
or spring-operated fusible-element types. They generally
incorporate some of the following design features:
(a) Have bodies with the appropriate service rating for the maximum
pressure and temperature to be encountered. Bodies should be of
cast steel, except that bronze is acceptable in sizes of 2 in.
and less if under sprinkler protection.
."(b) Close on failure of the operating electrical or air supply.
(c) Close in the direction of the liquid flow so that system
pressure tends to hold the valve in the dossed position.
5-64
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(d) Close against a pressure of at least 150 per cent of design
rating.
(e) Close within 5 seconds after actuation.
(f) Valve should not readily be bypassed, blocked, or otherwise
made ineffective.
(g) Have an indicator to show when the valve is open or shut,
except on packless solenoid types.
(h) Be manually reset, except where the valve-control circuit is
arranged for manual resetting.
(i) Have no direct connections between the liquid and air section
of diaphragm valves that might permit leakage of the liquid
past the packing into the air lines.
(j) Have packing and lubrication, if any, resistant to the liquid
being handled.
(3) Automatic operation of safety shutoff valves and/or direct- '
displacement pumps is normally accomplished by one of the followingl-
methods: I
(a) Actuation by thermal devices located at the ceiling and above
the point, of flammable-liquid use where spills may be expected.
(b) Release of a dead-man control.
(c) Operation of the fire-protection system. With automatic sprin-
kler systems, actuation may be by waterflow indicators, alarm
valves, or dry-pipe valves with hydraulic-pressure switches.
With special fixed extinguishing systems, actuation is by
pressure switches. Drain and alarm tests of sprinkler system
are made during idle periods or arranged that they can be made
without operating the safety shutoff.
(d) If the piping contains fragile components such as rotameters
and sight glasses, the safety shutoff is actuated automatically
by excessive pressure drop downstream from such components.
(4) Arrange safety shutoff valves and/or positive-displacement pumps for
manual shutdown by use of one or more stop buttons or switches at
safe and accessible locations throughout the flammable-liquid
system. In general, such stop buttons or switches are located near
points of egress from the building or structure.
(5) Self-closing manual valves and dead-man controls of a type not
readily blocked open are recommended as emergency safety shutoffs on
small systems, where liquid transfer is intermittent, and on larger
5-65
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systems that lend themselves economically to such an arrangement.
They require constant attendance by the operator and close auto-
matically if he leaves.
(6) If normal flow in piping is in one direction only and the piping
discharges to feed tanks, receivers, or other vessels so located
that a leak in the piping upstream of these vessels could be fed by
reverse flow through the piping, check valves are installed in the
piping as close to the vessel as possible to prevent the reverse
flow.
5.5.5.2 Gages, Meters, and Gage Glasses--
(1) Accessories on flammable-liquid piping systems, such as gages,
meters, gage glasses, hydrometers, and sight glasses are designed to
have strength equal to that of the piping system.
(2) Gage glasses are particularly susceptible to breakage. Their use is
generally discouraged.
(3) Restricted orifices are used in piping to gages and instruments to
reduce the amount of leakage in event of failure.
(4) Armored rotameters or instruments that read indirectly or sample a I
proportion of the flow in preference to those that enclose the •'
entire stream or have the full flow directed to the glass reading
chamber are also used. Vents on air releases used in conjunction
with some metering devices are then piped to outdoors in order to
dispose safely of flammable liquid that may be discharged if the
float is inoperative.
5.5.5.3 Operating Controls—
(1) Operating control valves are located in hazardous and flammable-
liquid piping systems so as to regulate the control and flow of
liquids to connected equipment and to isolate equipment for mainten-
ance purposes. Conventional types of valves are suitable for most
liquids. Valves are used having the appropriate service rating for
the maximum pressure and temperature to be encountered and packing
or lubrication resistant to the liquid being handled. Valve bodies
are normally of cast steel, except that bronze is acceptable on
piping 2 in. or less in size in sprinklered locations. Cast-iron
bodies are usually not used. If corrosive conditions or product
purity require the use of special materials of construction, stain-
less-steel, Monel, or lined-steel valves are preferred to those made
of more fragile materials.
(2) Valving is arranged to minimize the likelihood of improper operation.
Rising-stem or other valves that indicate whether open or closed are
preferred. The following recommendations for valve arrangements are
generally followed where applicable:
5-66
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(a) Three-way two-port valves are used at all branch lines so that
flow can only proceed through one line.
(b) Plug-cock valves are used with a slotted guard arranged so that
the handle can be removed only when the valve is in the closed
position. This arrangement will prevent discharge through
valves accidentally left open. One handle can serve all valves
on the system,
(c) Electrical or mechanical interlocks are provided between valves
so that the position of one valve with respect to another will
be automatically determined.
(3) Where the correct sequence of additions of waste materials to a
blending tank is of importance, sequence locks are used on valves in
pipelines.
(4) Hydraulic accumulators or safety relief valves are provided on
pipelines that can be valved off with liquid trapped between valves.
This prevents damage or overpressure from thermal expansion. The
discharge is piped from safety relief valves to a collection point.
(5) Tanks, mixers, and other equipment to which hazardous liquid waste
is transferred are arranged so as to prevent accidental overflow. I
The best arrangement is a trapped overflow drain leading back to the I
source of supply or to- a point of safe collection. The capacity of -
the overflow drain should be at least equal to that of the fill
pipe.
(6) If the equipment normally operates under pressure so that an over-
flow drain is not practical but overflow is possible during filling
because of open manholes or sampling connections, a liquid-level
control is provided to stop the liquid flow by closing a valve or
stopping the pump or to sound an alarm if the maximum safe level is
approached or exceeded. Float valves or switches, pressure switches,
and various other liquid-level indicators are available and may be
used. Mechanical interlocking of valves on overflow drain and fill
pipe can sometimes be arranged so that the overflow drain will be
open when the fill-pipe valve is open.
(7) The use of accurate measuring devices, such as dispensing meters,
measuring tanks, or weight tanks will assist greatly in the preven-
tion of overflows. Dispensing meters permit a predetermined amount
of liquid to pass and then automatically stop the delivery. Such
meters control a spring-loaded quick-action valve that should be
designed for manual starting with a hand-trip emergency shutoff.
(8) If control valves are to be remotely actuated, valves are chosen
having characteristics described in recommendation 2 of Safety
Shutoffs and arranged for operation in an emergency situation.
5-67
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5.5.6 Solids Feeding Equipment
Waste material is pneumatically, mechanically, or gravity fed into an inciner-
ator capable of burning solids. Normally, heterogeneous waste material must
be reduced in size (shredded, pulverized, etc.) to facilitate the feed system
operation and allow injection, distribution, and combustion within the
incinerator.
In addition to reducing moisture content and waste material size, separation
of noncombustible material such as ferrous and nonferrous metals may often be
required. The former is removed using magnetic separators. Nonferrous metals
are commonly removed using ballistic-type separators.
5.5.6.1 Shredders —
To reduce the size of waste materials for easier handling and feeding, shred-
ders are used. Also, to expose all surfaces of hazardous waste containers
(metal and fiber drums), it may be necessary to shred the cc5ntainers. Usually,
due to industrial hygiene, safety, and materials handling considerations, drums
or packs of solidified residues cannot be shredded and must be charged directly
into the incinerator [17]. Thus, it would be rare that a shredder would be
used in conjunction with hazardous waste incineration, although in some applica-
tions, e.g., in-plant dedicated incinerators, shredders may be useful. I
A shredder capable of consuming 55-gallon steel drums has to be a rugged unit, I
capable of containing dusts and mists of toxic materials as well as particles
of steel thrown around at high velocity. This type of potential danger
indicates a need for a hopper feed system to enclose flying debris, with
mechanical feed from a conveyor so that plant personnel need, never be in the
vicinity of the hopper opening during operation. The hopper is elevated for
gravity feed into the shredder, which also may be above ground level and well
ventilated. A suction fan can then draw fumes and dust from the shredder into
the incinerator or an alternate collection device.
A shredder capable of consuming 55-gallon drums would probably have a capacity
for handling material several times as fast as the incinerator. Thus, some
silo storage is necessary to safely contain the shredded material. The
material discharged from the silo would go directly into the incinerator.
A shredding operation normally consists of a shredding unit and a transfer
network including a variety of conveyors and feeders. Several types of shred-
ding devices exist: vertical and horizontal axis hammer mills, vertical axis
grinders, and horizontal axis impactors,- horizontal hammer type shredders are
the most common.
Unlike most other rotating equipment (pumps, fans, turbines, etc.), there is
very little design criteria for predictable performance of mixed solid waste
shredders. Size, style, and power selection is on an empirical basis, and
this is not likely to change in view of the infinite types and combinations of
input material.
5-68
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There are three basic types of horizontal shaft swing hammer type shredders:
vi) Topfeed, single direction rotor rotation
(2) Topfeed, reversible rotor rotation
(3) Controlled feed, single direction rotor rotation.
Figure 5-31 illustrates a cross-sectional view of a horizontal axis shredder.
EED
VEYO
V
FEED
CONVEYOR
fEED MATERIAL
FEED CHUTE
HAMMER
REJECT
POCKET
LINERS
MAIN FRAME
BREAKER PLATE
FOUNDATION
DISCHARGE
CHUTE
DISCHARGE
GRATE
DISCHARGE
CONVfYOR
Figure 5-31.
Cross-section through a nonreversible
horizontal shredder [24].
I 5.5.6.2 Explosion Suppression and Safety Considerations for Shredders—
The primary explosion in a shredding system is a gas explosion caused by a fric-
I tion spark and sometimes followed by a more violent dust explosion. Explosive
dust mixtures of the type most likely to form in a solid waste shredder require
a higher energy level for ignition than available from a friction spark.
Explosion suppression systems have proved effective for gas and dust explosions
on municipal solid waste shredders and are used on most installations. Today,
most systems use a demand-inerting suppression system, whereby metal hemispher-
ical containers release a suppressant in advance of a flame front. Such con-
tainers are connected to the shredding chamber by piping to channel the
suppressant toward the interior of the chamber to provide blanket coverage.
The most popular suppressant is Halon (short for halogenated hydrocarbon), a
family of chemicals which possess unique properties with regard to fire
extinguishing.
Also, sufficient pressure relief area is provided in the shredder and connecting
superstructures such as hoods, ducts, or any connected enclosure. Excepting the
shredder, this can be by means of hinged flaps, tethered blowout panels, and
flexible flaps.
5-69
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In addition, other means for minimizing personal injury and building damage
are [25] :
(1) Rigid enforcement of off-limits areas for roving personnel.
(2) Complete enclosure protection for the shredder operator.
(3) Separate or detached shredder building enclosures with blow-out
sidewall and roof panels.
(4) Partially open walls and/or roof.
5.5.6.3 Feeders--
Critical components in any system handling bulk solids are the feeders, which,
in conjunction with conveyors and other handling equipment, transfer solids at
a controlled rate from storage into the process, or from point-to-point within
a process. Feeders may be called upon to transfer materials from railcar to
storage bin, from storage bin to conveyor, or from conveyor to the incinerator.
There are four major types of solids feeders:
(1) Rotary
(2) Screw
(3) Vibrating
(4) Belt *
Many specialized feeders are also available. Table 5-5 relates feeder types J
to material characteristics. The most common types of feeders which will be
encountered in handling hazardous solid wastes are belt feeders and screw
feeders.
Both belt feeders and screw feeders have their own limitations. Steps must be
taken to alleviate dusting during operation of belt feeders. Total dust con-
trol can be assured only by enclosing the feeder with the proper dust entrain-
ment hoods. Most manufacturers furnish enclosures for belts up to about 36
inches wide. These housings can be made gas-tight for inert-gas purging.
However, if the user does not monitor feeder operation, or if a poor hopper
design allows powder to avalanche onto the feeder belt, or if a dust collec-
tion system has not been provided to remove particles as they become airborne,
the enclosure will serve only to contain the dust so that it eventually buries
the feeder.
Caution is advised when using screw feeders with sticky or very cohesive mate-
rials. Such materials can build up in short pitch sections, and conveying
will cease. For these services, longer-pitch, smoothly surfaced flights,
multiple screws with overlapping flights, or ribbons instead of solid flights
are normally specified.
Oust leakage around covers and along shaft seals is a common problem with
screw feeders. "Dust tight" means little in a specification. Because this is
an important requirement, "gas tight" to about one inch w.c. (water column)
pressure is a term used. To ensure continued dust control, followup is normal-
ly needed during operation to make sure operators maintain seals, gaskets, and
covers. Shaft seals are difficult to keep dust tight, especially if the
5-70
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TABLE 5-5. FEEDERS FOR BULK MATERIALS
Material characteristics
Feeder type
Fine, free-flowing materials
Nonabrasive and granular materials,
materials with some lumps
Materials difficult to handle
because of being hot, abrasive,
lumpy, or stringy
Heavy, lumpy, or abrasive materials
similar to pit-run stone and ore
Bar flight, belt, oscillating or vibrat-
ing, rotary vane, screw
Apron, bar flight, belt, oscillating or
vibrating, reciprocating, rotary
plate, screw
Apron, bar flight, belt, oscillating or
vibrating, reciprocating
Apron, oscillating or vibrating,
reciprocating
trough is gas-purged. Even with the variety of seals offered, most will leak
dust within a few hours unless shaft runout at the seal area is minimized.
There is no standard industry specification covering runout; as much as 1/32 j
in. runout is not unusual. Manufacturers will furnish special construction
for tight sealing, if this requirement is spelled out clearly in the J
specification.
Solid Waste Charging To Combustion Zone—The methods of feed to the combusion
zone can be broken down as follows:
(1) Batch
(a) open charging
(b) air lock feeders
(2) Continuous
Batch open charging can be as simple as gravity feeding solid waste into a
chute leading to the combustion zone, as in a rotary kiln incinerator.
An example of a batch air-lock feeder can be a charging hopper located above a
rotary kiln inlet, charged by a grapple which is controlled from a fully
air-conditioned operator cab, sealed against the bin space, using TV cameras
and TV screen in a partially automatic, partially manual operation. The
rotary kiln inlet is sealed from the bin space by a lock fitted with two
sliding gates. When the inclined sliding gate in the drop chute of the rotary
kiln inlet is closed, a horizontal sliding gate located in the charging hopper
will open.
An example of a continuous solids feed is given in Figure 5-32, which illus-
trates a screw conveyor carrying sludge to a rotary feeder which is then
pneumatically conveyed to a spin air nozzle within a fluidized bed incinerator.
5-71
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TO SCRUBBER
SCREW CONVEYOR
FILTER
ROTARY
FEEDER
HI
FLUID I2ED
BED
BURNER
PI LOT GAS
PNEUMATIC
SLUDGE FEED
AIR BLOWER
Figure 5-32. Continuous feeding of sludge to fluid bed incinerator.
5.5.6.4 Container Feeding Equipment—
For the most part, disposal technology for filled containers is appropriate
for toxic materials and for materials which are not readily removable from the
container. When opening the container might be harmful to operations personnel,
the container should preferably be processed within a closed system. Further-
more, if the material cannot be easily poured, co-disposal of both the chemical
and the container is preferable. Batch feeding of containerized solid wastes
results in a cyclic waste loading that can contribute to reduced destruction
and removal efficiencies [17].
In order to prevent the possibility of explosion or rapid temperature excursions,
drummed material should not contain free-standing combustible liquids or even
combustible liquids of high vapor pressure that are bound within solids or
sludges. A series of holes are typically punched in the drums or other contain-
ers or their covers are removed to provide adequate venting. Small quantities
I
I
I
5-72
-------
of the material should be tested for thermal stability and exothermic decomposi-
tion at elevated temperatures before significant quantities are charged into the
high-temperature environment of the rotary-kiln primary combustion chamber. It
is often necessary to regulate the charge size of various containerized solids
depending upon heat release characteristics [17].
There are three basic types of automated container feeding equipment to
incinerators:
(1) Conveyor to air-lock charging to rotary kilns.
(2) Hydraulic drum and pack-feeding mechanisms.
(3) Conveyor to air-lock vestibule with puncturing apparatus to thermal
treatment chamber.
Figure 5-33 illustrates a schematic diagram of a rotary kiln incineration
system using air-lock charging of containers. A more detailed example of an
air-lock waste charging system is given in Figure 5-34. The general practice
of dropping small containers into a rotary kiln without emptying them has
process disadvantages. Occasionally, there will be deflagrations with strong
soot generation and excessive thermal and mechanical loading of the kiln refrac-
tories resulting from this practice. A separate explosion vent for the charging
system is required to handle possible explosions.
A different type of container handling, feeding, and thermal treatment system I
is illustrated in Figure 5-35. The process includes a remote handling opera- I
tion and a completely enclosed cannister punching operation. Containers are
then thermally cleaned in the first thermal stage with the controlled
volatilization of toxic chemicals.
The process described is excellent in the protection afforded to the operators
by the remote automated handling, punching, and thermal disposal approaches.
A wide range of containers or cannisters can be processed, including 55-gallon
drums, chemical ton containers, munition cannisters, projectiles, and cans.
Contaminated filter media have also been detoxified using the same technique.
The thermal furnace uses a containerized conveyor to transport the cannisters
through the thermal process chamber, which is equipped with entry and exit
vestibules with gas-tight doors at either end to facilitate the total contain-
ment of vapors which might escape from opened containers. Mechanized punching
of the cannisters takes place within the entry vestibule.
5.5.7 Backup/Redundancy Provisions
The functional diagram of an incineration facility indicates that most compon-
ents of the system are in a "series" configuration; each series component must
be adequately functioning to avoid degraded performance. A few process com-
ponents may be in a "parallel" configuration allowing a switchover to another
component when problems are detected with an on-stream component. Examples
are waste feed line filters which will usually have two or more units in
parallel. Critical thermocouples for temperature measurement related to control
functions and automatic shutoff must be redundant. Feed pumps are typically
redundant; if plant processing rates are determined to be especially critical,
5-73
-------
Figure 5-33. Continuous type containerized toxic
material thermal disposal process [26].
TO STACK
r
t
Figure 5-34. Example of a waste-charging door [27]
5-74
-------
WASTE IN
DRUMS
PUNCHING
O O OO O
FUME INCINERATOR
STACK
SCRUBBER
THERMAL TREATMENT
COOLING
OOOOOOOOOOOOOOOOO O O OOOOOOOO
u
Figure 5-35. Liquid waste incinerator schematic [26].
redundant level monitors or extra gaging in critical storage tanks and silos, and
flow monitoring cells may need backup devices to assure safety. A detailed failure
mode analysis of each particular incinerator facility will identify the roost i-
likely potential malfunctions of each process element and point toward which I
safety systems cannot afford to fail for pointing out redundancy needs at a -
particular facility.
5.5.8 Waste Processing Instrumentation
An automated instrumentation system is used to transfer hazardous wastes from
storage to the incinerator. Electrical and/or pneumatic systems permit obser-
vation of control, for all material handling, from a graphically illustrated
control panel which shows such things as discharge valve positions, pump motor
operation, storage tank and bin levels (high and low), storage tank agitator
operation, and liquid or solid waste flow. The control instrument technology
has been well developed. Instrumentation used in oil-burning utility systems
is excellent. The difficulty encountered in the hazardous waste liquid applica-
tion is caused by the nature of the product. It is invariably corrosive, con-
tains particulate, and has a nasty tendency to foul the surfaces it contacts.
The flow-sensing system is the heart of the control problem [15]. Equipment
operation including belt conveyors, shredder, bucket elevator, or screw con-
veyors to the incinerator can also be displayed.
5.6 COMBUSTION PROCESS MONITORING
Before incineration process conditions can be controlled automatically they
must be measured with precision and reliability. Instrumentation for an
incineration process is essential because of the variability of the many
factors involved in attaining good combustion. For example, as the heat
.content of the solid waste rises, changes in the combustion process become
necessary. Instrumentation indicates these variations so that automatic or
manual control adjustments can be made.
5-75
-------
f
The uses of instrumentation and controls include means of process control,
protection of the environment, protection of the equipment, and data collec-
tion. A control system must have four basic elements:
(1) the standard of desired performance•
(2) the sensor (instrument) to determine actual performance;
(3) the capability to compare actual versus desired performance (error),
and
(4) the control device to effect a corrective change.
The four major factors governing incineration efficiency for a given waste feed
are temperature, residence time, oxygen concentration, and the turbulence
achieved. Chapter 4 discusses the significance of these factors in incinerator
design and operation. Methods to determine appropriate conditions of temper-
ature, residence time, etc., for a given waste/incinerator combination are also
described in Chapter 4.
To comply with RCRA and EPA regulations, monitoring is required for combustion
temperature, waste feed rate, air feed rate, carbon monoxide, carbon dioxide,
excess oxygen, particulate matter, hydrogen chloride, and nitrogen oxides.
Temperature in the incinerator can be directly measured. Instrumentation is
also available to directly monitor CO, C02, and oxygen concentration in the
combustion gas to insure that excess air levels are maintained. Residence timeJ
and mixing efficiency cannot be directly measured, however, so other parameters
indicative of these conditions need to be measured instead.
Gas residence time in the combustion zone depends upon the volume of the
combustion chamber and the volume flow rate. Since the volume of the chamber
is fixed for a given unit, residence time is directly related to combustion
gas volume flow rate. Therefore, measuring this flow rate is equivalent to
residence time measurement for a given incinerator.
Mixing in liquid waste incinerators or afterburners is a function of burner con-
figuration, gas flow patterns, and turbulence. Burner configuration and gas
flow pattern are a function of the incinerator design and will not vary from
baseline conditions. Turbulence is determined by gas velocity in the combustion
chamber, which is proportional to gas volume flow rate. Therefore, combustion
gas flow rate is an indicator of mixing as well as residence time in liquid
injection incinerators.
In incinerators burning solid hazardous wastes, other factors need to be consid-
ered to determine solids retention time and degree of agitation. These factors,
which vary from one type of incinerator to another, are discussed in Section
5.6.4. Sections 5.6.1 through 5.6.3 discuss where and how temperature, oxygen
concentration, and gas flow rate can be measured.
5.6.1 Temperature Monitoring
Incinerator temperature is monitored on a continuous basis to assure that
the minimum acceptable temperature for waste destruction is maintained.
5-76
-------
This requires one or more temperature sensors in the hot zone and a strip
chart recorder or equivalent recording device.
Generally, wall temperatures and/or gas stream temperatures are determined
using shielded thermocouples as sensors. Thermocouples are the most commonly
used contact sensors for measuring temperatures above 1,000°F. Specifically,
thermocouples can measure the following thermal parameters:
a. Average gas temperature - accomplished using a shielded thermocouple with
relatively large thermal capacity anchored to a relatively large mass.
The metering circuit is provided with a 30-second time constant to
further smooth and average the readings.
b. Instantaneous gas temperature - accomplished using a shielded thermo-
couple with very small thermal capacity with the output metered by a
circuit with a 1-second time constant. (Nominally, the reaction rates
within the hot gas stream should be strongly temperature dependent; they
thus should depend on the highest temperature to which the constituents
are exposed.)
c. Open flame temperature - obtained using an unshielded low thermal mass
thermocouple with the output metered by an amplifier with a 30-second
time constant. |.
d. Average wall temperature - obtained using a shielded thermocouple -
imbedded in the refractory wall. (Here, the averaging is accomplished by
the thermal inertia of the refractory material.)
Optical pyrometers are not recommended for these measurements due to spectral
bias factors present in the combustion area which can cause unacceptable meas-
urement error.
The location at which temperature measurements are taken is important, due to
possible variations from one point to another in the combustion chamber.
Temperatures are highest in the flame and lowest in the refractory wall or at
a point of significant air infiltration. Ideally, temperatures are measured
in the bulk gas flow at a point after which the gas has traversed the combus-
tion chamber volume that provides the specified residence time for the unit.
Generally, temperature measurement at a point of flame impingement or at a
point directly in sight of radiation from the flame is not recommended. Figures
5-36 and 5-37 show typical monitoring locations for liquid injection and rotary
kiln incinerators, respectively.
The types of thermocouples used include J, K, E, R, S, and B. The letter
symbols identifying the thermocouple types are those defined in ANSI Standard
C96.1. These symbols are in common use throughout industry:
Type J - Iron versus constantan (modified 1913 calibration)
Type K - Originally Chromel-P versus Alumel
Type R - Platinum 13% rhodium versus platinum
5-77
-------
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Type S - Platinum 10% rhodium versus platinum
Type T - Copper versus constantan
Type E - Originally Chromel-P versus constantan
Type B - Platinum 30% rhodium versus platinum 6% rhodium
Table 5-6 lists the limits of error for the common thermocouple types; most
manufacturers supply thermocouples and thermocouple wire to these limits of
error or better.
TABLE 5-6. LIMITS OF ERROR FOR THERMOCOUPLES [28]
Type
J
K
R, S
Temperature
range, °F
32 to 530
530 to 1,400
32 to 530
520 to 2,300
32 to 1,000
1,000 to 2,700
Limits
Standard
±4°F
±3/4%
±4°F
±3/4%
±5°F
±1/2%
of error
Special
±2°F
±3/8%
±2°F
±3/8%
±2-l/2°F
±1/4%
-300 to -75
-150 to -75
-75 to +200
200 to 700
32 to 600
600 to 1,600
±2%
±1-1/2°F
±3/4%
±3°F
±1/2%
±1%
±1%
±3/4°F
±3/8%
±2-l/4°F
±3/8%
B
1,600 to 3,100 ±1/2%
Since the thermocouple element in a thermocouple assembly is usually expend-
able, conformance to established emf-temperature relationships is necessary to
permit interchangeability. Calibration of a thermocouple consists of the
determination of its emf at a sufficient number of known temperatures such
that with some accepted means of interpolation its emf will be known over the
entire range in which it is to be used. The process requires a standard
thermometer with a high-level calibration to indicate temperatures on a stand-
ard scale, a means for measuring the emf of the thermocouple, and a controlled
environment in which the thermocouple and standard can be brought to the same
temperature [28].
Thermocouples use one of three different types of measuring junctions—grounded,
ungrounded, and exposed. The grounded junction is the most popular. The
ungrounded junction is the most rugged, but its speed of response is slower than
that of the grounded type. The unprotected exposed junction responds the fastest
but is more vulnerable to corrosion and mechanical damage.
5-80
-------
A complete thermocouple assembly consists of the following:
1. A sensing element assembly, including in its most basic form two
dissimilar wires joined at one end and separated by an electrical
insulator
2. A protection tube, either ceramic or metal, or a thermowell. In some
cases, both primary and secondary protection tubes are used
3. A thermocouple head or connector
4. Miscellaneous type hardware such as pipe nipples or adaptors to join the
protection tube to the head and thermocouple glands for mounting and
pressure sealing
Protection tubes and thermowells serve the double purpose of guarding the
thermocouple against mechanical damage and shielding it from corrosive atmos-
pheres. The choice of the proper material for the protection tube or thermo-
well is governed by the conditions of use and by the tolerable life of the
thermocouple. There may be times when the strength of the protection tube is
more important that the long term stability of the thermocouple. On the other
hand, gas tightness, resistance to thermal shock, or chemical compatibility of
the protection tube with the process may be the deciding factors [28]. |-
The most common forms of protection tubes and thermowells and their applica- •
tions are covered in the following subsections [28].
5.6.1.1 Metal Tubes--
Metal tubes offer adequate mechanical protection for base metal thermocouples
at temperatures to 1,423 K (1,100°F; 1,150°C). It must be remembered that all
metallic tubes are somewhat porous at temperatures exceeding 1,088 K (1,500°F;
815°C) so that, in some cases, it may be necessary to provide an inner tube of
ceramic material [28].
(a) Carbon steels can be used to 973 K (1,300°F; 700°C) usually in oxidizing
atmospheres.
(b) Austenitic stainless steels (300 series) can be used to 1,143 K (1,600°F;
870°C), mostly oxidizing although Types 316, 317, and 318 can be used in
some reducing atmospheres.
(c) Ferritic stainless steels (400 series) can be used from 1,248 K to
1,423 K (1,800°F to 2,100°F; 975°C to 1,150°C) in both oxidizing and
reducing atmospheres.
(d) High nickel alloys, Nichrome, Inconel, etc., can be used to 2,100°F
(1,150°C) in oxidizing atmospheres [28].
Where the protection tube is subject to high pressure or flow-induced stresses
or both, a drilled thermowell often is recommended. Although less expensive
metal tubes, fabricated by plugging the end of the protection tube, may satisfy
5-81
-------
application requirements, more stringent specifications usually dictate the ^
choice of gun-drilled bar stock, polished and hydrostatically tested as a
precaution against failures [28].
5.6.1.2 Ceramic Tubes--
Ceramic tubes are usually at temperatures beyond the ranges of metal tubes
although they are sometimes used at lower temperatures in atmospheres harmful
to metal tubes [28].
I
The ceramic tube most widely used has a Mullite base with certain additives to
give the best combination of mechanical and thermal shock properties [upper
temperature limit 1,923 K (3,000°F; 1,650°C)] [28].
Silicon carbide tubes are used as secondary protection tubes. This material
resists the cutting action of flames. It is not impermeable to gases and,
where a dense tube is required, a nitride-bonded type material can be obtained
so that the permeability is greatly reduced [28].
Fused alumina tubes can be used as primary or secondary protection tubes or I
both where temperatures to 2,253 K (3,600°F; 1,980°C) are expected and when a f
gas-tight tube is essential. Fused alumina tubes and insulators should be
used with platinum-rhodium, platinum thermocouples above 2,200°F (1,200°C) in •
order to ensure long life and attain maximum accuracy. [The Mullite types I- L
contain impurities which can contaminate platinum above 2,200°F (1,220°C). I
The alumina tubes are more expensive than the Mullite base tubes, but types
impervious to most gases to 2,088 K (3,300°F; 1,815°C) can be obtained] [28]. fl
5.6.1.3 Metal-Ceramic Tubes--
"Cermets" are combinations of metals and metallic oxides which, after proper
treatment, form dense, high-strength, corrosion-resistant tubes usable to
about 1,698 K (2,600°F; 1,425°C) in most atmospheres [28].
5.6.2 Oxygen Monitoring
— t
Oxygen concentration in the combustion gas is usually measured at a point of
high turbulence, after the gas has traversed the full length of the combustion t
chamber. A good location for measurement is at the inlet to the duct leading I
from the combustion chamber to the quench zone, immediately after the gas has
gone through a 90° turn. Figures 5-36 and 5-37 show this location. I
Oxygen measurements are made on a continuous basis. Commercially available
instruments are discussed in Section 5.9. Whichever type of sensor is used,
it is typically equipped with a gas conditioning system specified by the
manufacturer for the gas environment in which the instrument is used.
When measuring oxygen concentration directly in the high-temperature flow, some
difficulty can be experienced because of molten slag impingement on the probe. ,
Trial-and-error solutions of location and probe length have minimized this
problem. A redundant system for scheduled maintenance is desirable [15].
5-82
-------
5.6.3 Gas Flow Measurement
Gas flow rates can be measured or approximated in several ways: by insertion
in the flue gas duct of an air pressure measuring element (e.g., pitot tube)
or by measuring the drop in pressure across a restriction to the gas flow
(e.g., baffle plate, venturi section, or orifice) downstream of the combustor.
Exhaust gas flow, however, is the most difficult flow measurement application
on the incinerator for many reasons:
(1) Because the gas is dusty, moist, and corrosive, pressure taps will tend
to plug. For this reason it is extremely important that the connection
to the duct be made sufficiently large and with cleanout provision.
(2) If the two pressure sensing points are at widely different temperatures,
the resulting difference in density of the gas in the connecting lines to
the instrument will create an error in measurement. For this reason,
avoid measurement across spray chambers or other locations where gas
temperature changes radically [29].
(3) If taken across a restriction to gas flow, the fouling tendencies of the
dirty gas will cause the restriction to increase with time, thereby
changing the differential measurement for a given rate of flow [29J.
For the reasons stated above, the usefulness of this measurement as an indication
of quantitative flow is limited and care should be taken in this application [19].
Flow measurements are performed at either of two locations: (1) in the duct
between the combustion chamber and quench zone, or (2) in the stack (Figures
5-36 and 5-37). Both locations have their advantages and disadvantages. In
the combustion chamber outlet duct, a sufficiently long length of duct may not
be available for flow pattern development. Access to this location can also be
a problem when the incinerator is vertically oriented and because of the neces-
sity to breech the duct at a high temperature point. High temperatures at this
location may require special materials of construction (e.g., inconel) for
measurement elements.
The advantages of flow rate measurement in the stack are relief of the prob-
lems associated with high temperature gas flow measurement, increased access-
ibility to the gas flow, and increased likelihood of having a proper section
of duct for the flow measurement. One minor disadvantage associated with this
position is the increased possibility that ambient air leaks into the system
upstream of the draft fan could bias the flow measurement. This is not a
common occurrence, however, and good facility management practice will
normally detect such leaks quickly.
Of the instruments available to measure gas flow in closed conduits, pressure
or velocity head meters are among the oldest and most common. The principal
shortcomings are the need for elements to be inserted directly into the flow
paths (in contact with th gas stream), making then susceptible to corrosion,
erosion, and fouling; the requirement for seals; the likelihood that the,con-
duit may have to be opened for inspection or service; and permanent pressure
losses caused by restrictions placed in the channels.
5-83
-------
Head-type flowmeters incorporate primary elements, which interact directly
with the streams to induce velocity changes, and secondary elements, which
sense the resulting pressure perturbations. The flow rate of interest is a
function of the differential pressures which can be detected.
5.6.3.1 Orifice Plates--
Orifice plates, the predominant primary flow elements, can yield accuracy and
repeatability of ±0.25 to 2% full scale at Reynolds numbers from 8,000 to
500,000 [29]. Units are offered in a variety of designs, with flow area
shapes which can be.-
(1) Concentric
(2) Eccentric
(3) Segmental,
and profile cross sections which can be-.
(a) Square-edged
(b) Sharp-edged
(c) Quadrant-edged
(d) Double bevel
(e) Conical inlet.
i
Principal advantages include low cost, interchangeability, and installation '
with minimal modification of piping systems. The greatest disadvantages are
high unrecoverable pressure loss, requirement for skill in installation and
making pressure connections, need for long runs of unobstructed piping or use
of straightening vanes upstream and downstream of the primary element to
achieve accuracy, and sensitivity of measurement reliability to orifice geom-
etry and surface conditions which can vary as a result of normal use or
handling [29].
Orifice plates can be specified in corrosion-resistant materials appropriate
for many operating conditions. For fluids above 600°F, plate materials should
be specified that have thermal expansion coefficients matched with those of
the mounting flanges, and effort should be made to moderate the rate of tem-
perature change on the complete primary assembly to avoid thermal stresses
[29].
The most common orifices have sharp, square, or rounded upstream edges. Cir-
cular concentric designs are particularly popular since accuracy is highly
predictable and extensive performance data are available for broad ranges of
flow rates, duct sizes, pressure differentials, and other application factors.
Eccentric and segmental orifice designs may be considered when the measured
fluid contains suspended materials since these may lead to accumulations
behind concentric plates and cause erratic or false readings [29].
5.6.3.2 Venturi Tubes--
Venturi tube configurations can be standard, eccentric, or rectangular. In
standard designs, cylindrical barrel sections having inner diameters close to
those of the main pipes connect to the throat sections through cones of fixed
5-84
-------
angular convergence; the throats terminate in diverging exit cones which again
match the inner pipe diameters. Eccentric venturi elements are available to
handle flows with mixed phases, and rectangular units can be specified for use
in noncircular ducts [29].
Venturis handle 25% to 50% more flow than orifices for comparable line size
and head loss The flow range for satisfactory measurement is usually con-
sidered to extend upward from Reynolds numbers of about 200,000. Advantages,
in addition to capacity, include high pressure recovery, good accuracy with
beta ratios greater than 0.75, integral pressure connections, minimal require-
ments for straight runs of upstream piping, and suitability for dirty applica-
tions because the streamlined inner surfaces resist erosion and particle
accumulation. Purchase cost is high compared with most other primary elements,
but the greater pressure recovery can result in significant energy savings in
large ducts. A more significant problem is that large sizes make the tubes
awkward to install [29].
5.6.3.3 Pitot Tubes--
Pitot tubes are the simplest velocity head sensors. Models can be specified
for a variety of difficult fluid services, including high temperature, high
pressure, and corrosive, dirty gases. Moreover, the sensors are formed as
probes, which often are designed to be inserted in conduits without system
shutdown [29]. I-
Numerous special as well as standard configurations are available; for in-
stance, models can be ordered to measure velocity direction as well as magni-
tude. Limitations include tendency to plug when fluids contain suspended
solid particles unless provision is made for purging or flushing, narrow
velocity ranges with standard secondary elements, and sensitivity to local
distrubances in the flow pattern [29].
Another fundamental problem is that measurement indicates velocity at one
point in the stream, rather than providing integrated volumetric flows. The
probes must be traversed across the pipes or the velocity profiles known in
advance to calculate average flow. Moreover, to avoid uncertainty about local
perturbations, at least 8 diameters of straight smooth pipe are recommended
upstream of typical devices [29].
5.6.4 Solid Waste Retention Tijne and Mixing Characteristics Information
Retention time for nonvolatile or solid wastes in an incinerator is different
from that for volatiles. When solid wastes are being incinerated using incin-
erators which have mechanical means for agitating and moving solids through
the combustion zone such as is possible with rotary kilns and multiple hearth
incinerators, residence time of nonvolatiles will become a function of these
variables. Mixing will also become a variable when rabble arms or other
mechanical devices are used to tumble or otherwise break up chunks of solid
material. Residue analysis is typically performed to ascertain the condition
of the ash produced at these conditions. If analysis shows that insufficient
agitation or residence time is being achieved in exposing the solids to com-
bustion zone conditions, a change of those conditions is normally requested to
eliminate the problem.
5-85
-------
5.7 AIR POLLUTION CONTROL DEVICE INSPECTION AND MONITORING
5.7.1 Wet Scrubbers
Five parameters are routinely checked on wet scrubbers to monitor their opera-
tional effectiveness. These are discussed below. Gas and liquid flow rates
are discussed together in Section 5.7.1.2
5.7.1.1 Temperature--
Deviations from the design temperature can have serious effects on the removal
efficiency of a wet scrubber, particularly when the scrubber is being used to
remove gaseous components. Since incineration inherently produces high tem-
perature gas to be scrubbed, pre-cooling of the gas stream is necessary.
Units used for this are commonly called quench towers, and they normally bring
the gas temperature down to around 150°F prior to entry into the scrubber.
This scrubber inlet temperature is continuously monitored to assure that
proper scrubbing conditions are maintained in accordance with the design inlet
temperature value or range. Deviations can cause several effects, including
rapid loss of scrubbing liquid, compromise of absorption efficiency, undue
corrosion, and structural damage to the unit. One or more of these occur-
rences can increase emissions from the unit. Figures 5-36 and 5-37 show the
approximate position for temperature measurement. Emergency shut down j.
features regarding this temperature measurement are discussed in Chapter 4. I
5.7.1.2 Liquid and Gas Flows— ^
A wet scrubber must provide good gas-liquid turbulence and optimum contacting ^|
surfaces for proper absorption of contaminant gases or removal of particles
[30]. This provision is typically specified by the vendor and normally ex-
pressed as the liquid-to-gas ratio (e.g., 5 gpm/1,000 cfm [L/G]). A certain
L/G will be necessary to achieve design removal efficiency. The vendor also ,
supplies the sensitivity of the L/G ratio to removal efficiency because each
design has a somewhat different sensitivity to the L/G ratio. With this data >
in hand, a range of acceptable L/G ratios can be established, consistent with £
removal efficiency requirements. This range serves as the parametric limits
for acceptable L/G ratio operation. System gas flow will have been measured
as part of the incinerator operating requirement covered previously. There- r
fore, scrubber liquid flow rate measurement will provide the remaining neces- fc
sary parameter measurement to define the L/G ratio. This parameter is moni-
tored often and remedial actions taken by the operator, should the ratio '
exceed the parametric limits. Operator action will normally be a minor
adjustment of the scrubber liquid flow rate.
A measurement of the moisture content of the gas leaving the scrubber is made
in cases where some other device is in the system which can contribute addi- '
tional moisture to the total gas flow such as a mist eliminator. This also
covers the situation where the gas flow measurement may be made upstream of '
the quench zone in the hot gas area. In the case of the hot zone measurement, ft
the sum of hot zone gas flow plus moisture content corrected to scrubber
pressure and temperature conditions represent scrubber gas flow. Obviously, a >}
direct measurement of the gas flow exiting the scrubber may also be used, but ^
this will necessitate another measurement system set-up. ^
5-86
-------
Measurement of the liquid flow rate is accomplished by using any of several
types of flowmeters, including venturi, orifice, flow tube, pitot tube, mag-
netic, or acoustic varieties. Device acceptability considerations are sum-
marized in Table 5-7. Figures 5-36 and 5-37 show the appropriate measurement
location.
5.7.1.3 p_H--
Ano'ther important parameter in wet scrubber operation is pH. Materials of
construction are selected in part based upon the degree of acidity or alka-
linity provided by the scrubbing liquid during operation. Deviation from the
design pH condition or range may result in deterioration of the scrubber
structure in contact with the liquid. Furthermore, maintenance of the pH
design condition is important to scrubber liquid absorption efficiency when
removing gaseous contaminants.
The liquid composition and its attendant pH will be determined during the
design phase. Absorption efficiency can change drastically as a function of
pH, thereby altering the scrubber removal efficiency, so an acceptable pH
variation range is designed for the equipment. The pH is monitored continu-
ously and either manual (operator) or automatic adjustment made to keep the pH
within proper operating specifications. A number of commercially available pH
monitoring systems can adequately serve this purpose. These systems normally
include a direct readout device which can be conveniently located on a control!
panel for continuous monitoring accessibility. Figure 5-42, Section 5.8, I
shows the measurement location and arrangement for scrubber liquid pH. I
5.7.1.4 Pressure Drop—
Pressure drop is an important indicator parameter in monitoring the opera-
tional condition of a wet scrubber. It is sensitive to changes in the gas
flow rate, liquid flow rate, and clogging phenomena in the system. During the
design phase, a proper pressure drop value or range to maintain design removal
efficiency is specified. Monitoring this parameter provides a continuous,
additional check on the normal operation of the scrubber. A change in the
pressure drop is an indication that other measured parameters in the system
need to be observed immediately to find the cause of the disturbance and
corrective action should be taken. It is also an indicator which covers the
time span between other routine parameter checks. If, after checking the pH,
temperature, and gas and liquid flow rates, all appears in order, then the
pressure drop measuring system is checked for correct operation and a visual
inspection of the scrubber conducted to identify possible clogging problems.
A check of the control efficiency is also routinely made to see if removal
efficiency is being maintained.
Many kinds of pressure measurement devices are commercially available to meas-
ure pressure drop across a device; however, a differential pressure gage cali-
brated in inches of water is usually recommended for this purpose. The read-
out device is located in a convenient place for the operator to observe at any
time. Figures 5-36 and 5-37 show the location of the pressure taps relative to
the device.
5-87
-------
TABLE 5-7. DEVICES FOR LIQUID FLOW MEASUREMENT
Flow
measurement
device
Ventun meter
Advantages
Low permanent
pressure drop.
Applicable to
streams with ap-
preciable solids
content. Accurate.
Disadvantages
Flow disrupted and
plumbing modifica-
tions required for
installation.
Expensive.
Flow range, gpm
(applicable
pipe
diameter)
0-750
(1-18 in.)
Orifice meter Inexpensive.
Flow tube
Pitot tube
Flow disrupted and
plumbing modifica-
tions required for
installation. Large
permanent pressure
drop. Solids may
deposit behind device.
Moderately accurate.
Flow disrupted and
plumbing modifica-
tions required for
installation. Inter-
mediate permanent
pressure drop. Mod-
erately expensive.
Moderately accurate.
Low permanent pres- Flow disrupted and
0-750
(0.5-30 in.)
Applicable to
streams with
appreciable solids
content.
0-750
(1-18 in.)
250-50,000
Magnetic meter
cure drop. Inez*
pensive method for
pipes of large
diameter.
Minimum permanent
pressure drop.
Applicable to
streams with ap-
preciable solids
content. Accurate.
Acoustic meter
Installation without
flow disruption.
Relatively accu-
rate. No head
loss or pressure
drop. Applicable
to streams with
appreciable solids
content. Portable.
plumbing modifica-
tions required for
installation. Solids
may cause plugging.
High flow velocities
may cause instability.
Moderately accurate.
Flow disrupted and
plumbing modifica-
tions required for
installation. Expen-
sive. Electrodes may
be fouled by waste-
waters containing oil
and grease. Suscep-
tible to electromag-
netic interference fro
nearby equipment.
Expens ive. Mode ra tely
accurate.
250-20,000
(0.1-100 in.)
250-20,000
(pipes of all
diameters)
5-88
-------
In selecting a pressure measuring device, the following items are considered:
Pressure range
Temperature sensitivity
Corrosivity of the fluid
Durability
Frequency response
A guide to pressure sensing device selection is summarized in Table 5-8.
5.7.1.5 Residue Generation--
Generation of residue from wet scrubbers results from operational requirements
of the scrubber liquid in the specific system used. Vaporization losses in
the contacting area create the need for make-up liquid to be provided, and
changes in liquid pH create the need for adjustment. Collected material (such
as solid particles) also creates abrasion, contamination, and corrosion prob-
lems in the scrubbing liquid and/or transport system. In addition, when
hazardous materials are collected, a need for further treatment may be created
prior to disposal. Sometimes a designer will choose to accommodate these
problems in an integrated system design approach. Monitoring requirements
relative to generation of residue from a wet scrubber are those required for
observation of waste stream treatment systems and are covered in Section 5.8.
Control of pH is also discussed. I
5.7.2 Fabric Filters '
Fabric filters basically consist of a porous layer of flexible, textile mater-
ial through which a contaminated gas is passed to separate entrained material
from the gas stream [32]. As collected material accumulates, resistance to
the gas flow increases. The collected material is removed periodically by
vigorously cleaning the filter to maintain proper pressure drop across the
system.
Certain fabric filter parameters are monitored on a regular basis to evaluate
operational effectiveness. These are detailed below.
5.7.2.1 Temperature—
A limiting factor in filtering hot gases with a fabric filter is the temper-
ature resistance of the fibrous materials from which the filter cloth is made.
Therefore, the manufacturers temperature specifications regarding appropriate
filter material are important for efficient operation. Continuous recording
of the temperature of the gas coming into contact with the filter media is
made to assure that extended excursions above the recommended value are not
occurring. Appropriate corrections are then made immediately, either automa-
tically or by the operator, to maintain inlet temperature within design cri-
teria. This helps minimize the occurrence of extraordinary material breakdown
with resultant increased emissions. It also aids in keeping maintenance of
the filter in good order and extending the life of the filter material.
Measurement technique is similar to that depicted in Section 5.7.1. Figure
5-38 shows the appropriate measurement location.
5-89
-------
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5-92
-------
LIQUID
INCINERATOR
KILN
INLET GAS
TEMPERATURE
MEASUREMENT
DIFFERENTIAL PRESSURE
GAUGE FOR PRESSURE
DROP MEASUREMENT
TO ATMOSPHERE
UPSTREAM PRESSURE
TAP LOCATION
ROTARY AIR
LOCK VALVES
DOWNSTREAM
PRESSURE TAP
LOCATION
FABRIC FILTER
vw-
CONVEYOR
SIGHT PORT
PARTI CULATE TO
TREATMENT
AND DISPOSAL
Figure 5-38. Recommended measurement and inspection locations.
5.7.2.2 Gas Flov and Pressure Drop—
Fabric filter collectors are commercially available to handle total gas flows
from 100 cfm to greater than a million cfm. The quantity of gas processed and
the contaminant concentration in conjunction with specific flow resistance
properties of the particulate deposit on the fabric determine the amount of
filtration area required for a selected value of operating pressure drop. A
design pressure drop is generally chosen around 3 or 4 inches of water for
economic reasons, but some units are designed to operate higher than 10 inches
of water pressure drop. Variation in the pressure drop over a specified range
is normal in fabric filter operation. The operational cycle consists of a
gradual buildup of material on the surface of the filter which is periodically
cleaned off. The development of this deposition increases the pressure drop
with time.* This cycle usually remains within specified limits. Continuous
recording of the operating pressure drop is maintained by the operator. The
pressure drop is maintained within the manufacturer's specified range so that
undue disturbance of the design filtration efficiency does not occur. Chapter
4 provides further information regarding fabric filters. The pressure drop
measurement device is essentially the same as described in Section 5.7.1.4.
Measurement location is shown in Figure 5-38.
5.7.2.3 Residue Generation--
Accumulated particulate matter is removed and transported to a central point
for reprocessing or disposal depending on the hazardous nature of the collec-
ted material. Means of preventing gas leakage at the hopper discharge is an
5-93
-------
important design factor. This is normally accomplished through the use of
double flap valves or rotary air-lock valves, although the rotary air lock
valve will give the most positive seal.
A means of preventing bridging in the hoppers is also important. Common types
are .mechanical, spring loaded rappers, electric vibrators, and compressed air
vibrators. Helicoid screw conveyors are commonly employed for horizontal
transport of the collected material to a central point.
Residue analysis is needed to ascertain the hazardous nature of the collected
material and to select appropriate disposal options. The type of such
analyses is covered in Chapter 3.
5.7.3 Electrostatic Precipitators
Precipitators are theoretically complex control devices which are almost
always specifically designed for a given application. Many technical consid-
erations are evaluated initially to aid the applicability determination [33].
In each case, however, a set of operating conditions and checkpoints are
defined by the vendor as proper and necessary to maintain the design removal
efficiency. Compliance with these and other conditions pertinent to
maintaining the quality of the environment are evaluated; the following
information serves as a checklist for such items.
5.7.3.1 Rapping Cycle Practice--
Precipitators use a "rapping" or force impact sequence to remove buildup of
collected material on the internal surfaces of the equipment. This causes
re-entrainment of collected material in the exhaust gas stream which affects
precipitator removal efficiency. Three variables are involved; the rapping
interval, the rapping intensity, and the duration of the rapping cycle.
(1) Rapping interval - It is desirable to know the time interval of rapping
for each electrode in the precipitator field, because the upstream fields
are normally rapped more frequently than the downstream fields as a
result of the relatively high material buildup in the initial stages.
(2) Rapping intensity - How hard an electrode is rapped will affect the
amount of material removed each rap.
(3) Cycle duration - How long a time the rap covers affects the degree of
"cleanliness" achieved.
The intervals for these three variables are designed to be appropriate for the
application. This choice is normally based on the experience of the company
with their product. Common practice ranges from very frequent rapping (every
few minutes) to intervals as long as an hour. The intensity may range from
low to high with frequent intervals, but is normally high at longer intervals.
The ability to change the values is normally a part of the precipitator con-
trols. A check of the proper settings is made at least once a day by the
operator and records kept for examination by the EPA upon request. A typical
rapping mechanism is shown in Figure 5-39.
5-94
-------
a
{NO.OSUK
maosutt
VIMATOt
MOUNHNC
STUFFING (OX 4NO GUIOC
CONDUIT
CONOUn FITTWS
HOIK INC
— OJUM1C INSUIATINC SHAFT
run
— HICK VOLTA6I mSMNB
T HIGH TENSION FMMI
oncHAnamios
Figure 5-39. Typical vibratory rapper.
5.7.3.2 Temperature, Resistivity, and Gas Moisture Effects—
The resistivity of the material collected can have an influence on the collec-
tion efficiency. If the resistivity is greater than about 5 x 1010 ohm-cm,
the electrical field developed in the collected particle layer can exceed the
breakdown field strength. Excessive spark rates and back corona can occur
which will cause operation at lower than normal current densities with result-
ing degraded performance. If the particle resistivity is less than about 107
ohm-cm, the electrical forces holding the material to the collection plates
may be low. Excessive re-entrainment can occur yielding lower performance.
A resistivity range showing the allowable span for maintenance of removal
efficiency is normally supplied with an ESP along with a measurement of the
resistivity of the material collected. As long as the feed material does not
change, no further check on the resistivity is usually necessary, unless
removal efficiency changes for no apparent cause.
Increasing moisture content will also lower the resistivity. A change in
moisture content will normally only occur with a change in the feed material
moisture or a change in steam injection conditions if such a technique is used
to increase hydrogen ion availability in the combustion zone.
5-95
-------
Temperature affects precipitator removal efficiency although not as much as it
affects baghouses and wet scrubbers. Temperature considerations are normally
evaluated during the design phase of the precipitator by the vendor.
Specifications are provided by the owner/operator showing the allowable temper-
ature range for design removal efficiency. Continuous recording of the in-
coming gas temperature is made by the owner/operator to assure that extended
excursions above or below the recommended range are not occurring. Appropri-
ate corrections are then made to maintain inlet temperature within design
criteria. The measurement technique must be similar to that discussed in
Section 5.7.1. Figure 5-40 shows the appropriate measurement location.
LIQUID
INCINERATOR
TO
ATMOSPHERE
ELECTROSTATIC
PRECIPCTATOR
INLET GAS
TEMPERATURE
TO
DISPOSAL
Figure 5-40. Recommended measurement location.
5.7.3.3 Applied Voltage (Power Supply Control)—
The overall objective of precipitator design is to combine the component parts
into an effective arrangement that results in optimum collection efficiency.
A very important aspect toward this objective is the design, of the
precipitator power supply.
The power supply normally consists of four components as shown in Figure 5-41;
a step-up transformer, a high voltage rectifier, a control element, and a
sensor for the control system. A step-up transformer is required because the
operating voltages (applied voltage) range from about 20 to 100 KV. This
system is used to maintain the applied voltage at an optimum value even when
the material characteristics and concentration exhibit temporal fluctuations.
5-96
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AC VOLTAGE
INPUT
CONTROL
ELEMENT
STEP-UP
TRANSFORMER
MANUAL
HIGH VOLTAGE
RECTIFIER
AUTOMATIC
CONTROL
FEEDBACK
ELECTROSTATIC
PRECIPITATOR
Figure 5-41. Power supply system for modern precipitators. |.
Once normal operating conditions have been established, continuous monitoring •
of the power supply system is typically maintained. The necessary indicators
(meters) for this are normally provided as part of the precipitator control
panel. Deviations will likely be caused by excessive buildup of collected
material in the precipitator or breakdown of the electrical supply circuitry.
Investigation should begin immediately to locate the cause, and correction
made, including shut off of feed material and/or shut down for repair if
removal efficiency drops below specifications.
5.7.3.4 Gas Flow--
Changes in the gas flow rate can affect removal efficiency. This becomes more
critical as the particles get smaller. The precipitator is designed so that
the combination of the forces applied on the particles and the time that the
forces remain on the particle (dwell time) result in the movement of the
particles to a collection surface. The smaller the particle, the longer it
takes under fixed conditions to do this.
If the gas flow rate increases beyond design capacity, this combination
becomes compromised and a degradation of removal efficiency will occur.
The gas flow measurement requirement discussed in Section 5.7.3 is appropriate
for checking the precipitator flow parameter also. Sustained increase in the
gas flow is usually checked immediately for effect on the design removal
efficiency, and correction made to remain within design conditions. This may
require reduction in input feed material flow or some other modification(s).
5-97
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5.7.3.5 Residue Generation Rate and Dust Removal Capacity--
It is important to determine that the dust removal system remains working
properly according to specifications. Hoppers are used to collect material
removed from the collecting surfaces by the rapping sequence. If the residue
generation rate exceeds the material removal capacity, re-entrainment of
collected material will occur, greatly reducing precipitator efficiency.
Historically, automatic removal of collected material is one of the major
causes of precipitator failure, and daily inspection for proper operation is
typically required.
5.7.3.6 Internal System Pressure--
If the precipitator system is operated with internal pressures less than
ambi-ent, leakage of air through the hopper can also cause a re-entrainment of
mate-rial from the hoppers. A design check to make sure the hopper area is
properly sealed is made to prevent such occurrence. Section 5.7.2.3 discusses
appropriate seal techniques. Further details regarding electrostatic
precipitators is found in Chapter 4.
5.7.4 Mist Eliminators
Mist eliminators are extensively employed to reduce emissions of entrained
liquid droplets from wet scrubbers. The most commonly used types include
cyclone collectors, simple inertial separators such as baffles, wire mesh mist
eliminators, and fiber bed elminators. In use, the latter three devices work
by the same principle. Rising mist droplets strike the mist eliminator,
coalesce due to inertial impaction and direct interception, and form larger
droplets which fall back into the scrubber.
Cyclones differ from the other types of mist eliminators because centrifugal
force is used to remove the droplets. The particulates, because of their
inertia, tend to move toward the outside wall from which they are led to a
receiver [22].
The choice of mist eliminator equipment is dependent on droplet size, gas flow
pressure drop, and cost considerations. Cyclone collectors are used to remove
larger droplets (10 to 100 urn range), and are used commonly in conjunction
with venturi scrubbers. Simple inertial mist eliminators (baffle, louvre, and
vane-type among others) are effective with droplets about 10 un in size.
Fiber bed mist eliminators have the highest efficiency of any of the types of
eliminators for trapping very fine droplets (as small as 0.5 urn).
Although the different types of mist eliminators vary in design, they have
common parameters which must be monitored to evaluate operational effective-
ness. These are detailed below.
5.7.4.1 Temperature—
Excessive temperatures can adversely effect the performance of a mist elimi-
nator. Higher temperatures could result in a heavier loading and increased
corrosion. Since the mist eliminator is located downstream from the wet
scrubber, monitoring the temperature of the scrubber is sufficient to ensure
the mist eliminator is operating at a suitable temperature.
5-98
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5.7.4.2 Gas Flow and Pressure Drop--
For maximum efficiency, flow of gases through the mist eliminator should be
high enough to be practical while allowing a reasonable retention time.
Re-entrainment of the liquid droplets can result if the gas flow is too high.
The optimum gas flow varies according to the particulate mist eliminator used,
and is normally supplied by the manufacturer. Pressure drop may vary from 2
to 12 in. of water gage, in accordance with manufacturers' specifications.
Continuous recording of the operating pressure drop is typically maintained by
the owner/operator and such records made available for inspection. A change
in the pressure drop would indicate a change in the gas flow rate or, more
importantly, the accumulation of solids in the equipment, decreasing its
efficiency.
5.7.4.3 pH Level--
To prevent excessive corrosion, the mist eliminator is normally constructed of '
material that is resistant to the pH level of the mist. pH is monitored in
the wet scrubber to ensure the mist eliminator is operating within the manu-
facturer 's recommended pH range.
5.7.4.4 Maintenance—
Proper maintenance of mist elimination equipment is essential in order to
maintain optimal efficiency, for collection of solid material in the equipment
can decrease efficiency. The equipment can be cleaned by backwashing or by |.
automatic spray devices. Often, daily inspection is required to assure that I
the backwash system is operating properly. *
5.8 SCRUBBER WASTE STREAM TREATMENT INSPECTION AND MONITORING
5.8.1 Flow Measurement and Monitoring
In any treatment system unit operation, the measurement and/or control of flow
is a critical parameter. In this case, flow is a factor in determining the
rate of caustic solution addition in the neutralization system. Flow measur-
ing and recording devices are described in detail in Section 5.7.1.2.
5.8.2 Flow Control
Automatic monitoring systems are employed to provide advanced warning when the
water level in the neutralization system has increased above a set operating
limit. This enables operators to institute immediate process alterations to
allow the neutralization system to equilibrate back to normal operations.
5.8.3 pH Monitoring
Sensors for automatic monitoring, recording, and control of pH are especially
sensitive to process interferences. It is necessary, therefore, that care is
taken in the selection of automatic equipment in order to ensure that it will
function satisfactorily in the treatment scheme.
5-99
-------
Automatic monitoring of pH has the following advantages.-
(1) pH is recorded on a continuous basis, producing a clear picture of
variation with time.
(2) Time lag between sampling and analysis is much shorter than in manual
sampling. Problems resulting from the storage cf sampling equipment are
also eliminated.
(3) The rate of neutralizing chemical addition can be continuously
controlled.
(4) Automatic monitoring can be combined with an alarm system to provide
warning if the neutralized effluent is of insufficient quality. When
this occurs, a by-pass valve could be opened to direct the effluent to a
storage basin for gradual addition to the treatment system once normal
operations have been resumed.
Automatic monitoring is not without disadvantages, however. Among them are:
(1) The sensor may not be capable of registering unusual circumstances due to
probe location.
(2) The wastewater characteristics, at least in general, must be known in
advance of monitoring equipment selection.
(3) The initial cost of automatic equipment is relatively high.
Problems which can be anticipated and need to be addressed in system design
and operation are.-
(1) Loss of calibration. Regular maintenance is necessary to prevent errors.
(2) Bacterial growth may inhibit sensor operation. Regular cleaning is
necessary unless self-cleaning sensors are used.
(3) Mechanical damage may occur if the probe is unprotected by a screen,
similar device, or design.
(4) Miscellaneous problems resulting from power failures, mishandling of
equipment, pump difficulties, etc.
(5) Interferences should be analyzed and addressed before equipment selection
and installation.
5.8.4 pH Control Systems
A pH control system consists of a pH electrode probe, located in the flow
scheme, connected to a controller which reports to a recorder. The controller
regulates the rate of neutralization chemical addition.
5-100
-------
In the monitoring/control system, several types of valves may be used, depend-
ing on the consistency of the influent quality and the treatment chemicals
used. The types of controllers likely to be employed are on-off, proportional,
resetting derivative, and flow-proportional.
5.8.4.1 On-Off Controller--
The on-off controller is the least expensive of the above devices. If the pH
exceeds, in either direction, a certain limiting value, the valve opens and
neutralizing agent is added until an established corrected value is achieved.
This system has limited application here due to the potential for large
chemical overdose.
5.8.4.2 Proportional Controller—
Proportional controllers are more advanced than on-off controllers and are
used where a more constant effluent quality is desired. In its simplest
application, the proportional controller regulates the amount of neutralizing
solution in proportion to a deviation from a set point as a means of control-
ling pH within an acceptable range.
5.8.4.3 Resetting Derivative Controller—
A resetting derivative controller regulates the speed with which the valve
opens to add neutralizing agent. The valve speed is based on the rate of
derivation from a set point. This system does not typically operate well with
high suspended .solids effluent, however. |-
5.8.4.4 Flow Proportional Controller— .•
If the influent water quality is constant, but flow varies, the neutralization
control valve may be connected to a flow meter rather than the pH probe.
Neutralizing agent will be added proportional to the flow.
A schematic of the general elements in a pH control system using lime is given
in Figure 5-42.
5.8.5 Scrubber Solution pH Control
The particulate removal efficiency of a venturi scrubber and the acid gas
scrubbing efficiency of a packed tower is affected by maintenance of the pH of
the incoming scrubbing solution.
If a recirculating mode is utilized, the incoming stream must be neutralized
after contact with the gas. Neutralization is necessary to prevent corrosion
of metal surfaces, construction'materials, and tower packing.
The process of neutralization is the interaction of an acid with a base. The
typical properties exhibited^by an acid in solution are due to the concentra-
tion of the hydrogen ion, (H ). Alkaline (basic) properties are the result of
the concentration of hydroxyl ion (OH~). In an aqueous solution, acidity and
alkalinity are defined with respect to pH, where pH = -log [H ], or as
pH = 14+ log [OH"]. Neutralization is typically the adjustment of pH from one
extreme to a range of pH 6.0 to 8.5.
5-101
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LIVE
CONTROL
ELEMENT
INFLUENT
CONTROLLER
F
5
^
MIX TANK
SENSING
ELECTRODES
NOTES
pH ANALYZER
FINAL CONTROL ELEMENT MAY
•E CONTROL VALVE PUMP OR
DRY FEEDER.
pM CONTROLLER MAY BE CASCADED
WITH INFLUENT FLOW.
Figure 5-42. Elements of a typical pH control system.
The scrubber and absorber solutions will, after contact with acid gases, be
acidic in nature, (pH <7). Neutralization is accomplished by the addition of
an alkaline material, such as caustic soda (NaOH). An example of the
neutralization process is the reaction between hydrochloric acid and sodium
hydroxide:
HC1 + NaOH •* H20 + NaCl
The product, sodium chloride in aqueous solution, is neutral with pH = 7.0.
Neutralization is usually accomplished by contacting the incoming feed with
concentrated caustic or acid solution in a well mixed chamber.
Lagoons, concrete basins, chemically resistant tanks, and in-line static
mixers are all used for this purpose.
Neutralized water can be piped to storage ponds for subsequent process reuse,
solar evaporation, or further treatment, if necessary for NPDES discharge.
A simple schematic of a two-step neutralization system is given in Figure 5-43.
5.9 CONTINUOUS MONITORING INSTRUMENTATION FOR GASEOUS COMPONENTS
Continuous monitoring of at least 02, CO, and C02 gases in the exhaust stream
of hazardous waste incineration are proposed. A number of continuous monitor-
ing systems are available for this general purpose. These monitors are automa-
ted, and are capable of unattended operation for days or weeks. While such
instruments have been successfully applied to measuring CO, C02, and 02 in
combustion gases, their accuracy remains somewhat controversial within both
the technical community and users.
A
5-102
-------
|H WTO CDWTKOUlt
ru*n
INCOMING *»Tt»
WUT1AIIZIW QCMJCAJ.
s
J*
9
0
t
I
-/^
f
e»
\
\
s
B
1
a
NomuuziowAi
Figure 5-43. Two-step neutralization flow schematic. j
The following text provides a summary of aspects pertinent to the evaluation.
Should greater detail be desired, the permit writer is encouraged to consult
the EPA Handbook of Continuous Air Pollution Source Monitoring Systems,
EPA-625/6-79-005, from which most of the following information is derived [34].
The basic elements of a pollutant monitoring system are shown in Figure 5-44.
5.9.1 Available Systems
Proposed continuous monitoring systems will likely fall into one or more of
the following types:
• Nondispersive infrared analyzers (NDIR)
• Polarographic analyzers
• Paramagnetic analyzers
• Nondispersive ultraviolet analyzers (NDUV)
• Electrocatalytic analyzers
Table 5-9 summarizes what component each type of analyzer is capable of
measuring.
In addition to being categorized according to detection type, a broader classi-
fication of monitoring systems exists which distinguishes between extraction
and in-stack or in-situ type systems. All five of these instruments with the
exception of the pola.rographic monitor, are available in both extractive and
in situ types.
5-103
-------
EXHAUST
Figure 5-44. Elements of pollutant monitoring system.
TABLE 5-9. ANALYZERS CAPABLE OF MEASURING GASEOUS COMPONENTS
Component
Detection device
NDIR
NDUV
Paramagnetic
Polarographic
Electrocatalytic
0^ CO,
xa
X
X
xa x
xa
CO
xa
X
X
typically used.
5-104
-------
Discussions of the components, advantages and disadvantages, and limitations
of both extractive and in-situ versions follow. The general principles of
operation discussed for the analyzers themselves may be applied to either
version, as the differences in the detector mechanics are subtle.
5.9.1.1 Extractive Systems--
The ability of an extractive, or remote monitoring system, to provide reliable
data depends upon a properly designed sampling interface. The total
extractive system must perform several functions:
Remove a representative gas sample from the source on a continuous basis.
• Maintain the integrity of the sample during transport to the. analyzer
(within specified limits).
Condition the sample to make it compatible with the monitor analytical
method.
Allow a means for a reliable calibration of the system at the sampling
interface.
The design of the sampling interface, including the components used in its
construction, will depend on the characteristics of both the source gas stream
and the monitoring instrument.
The design of a sampling interface requires that the system deliver a condi- j
tioned, continuous gas sample to the gas analyzer. A number of different I
interface designs may be able to perform this task at a given source. The .'
actual system designed for a specific source generally incorporates a variety
of trade-offs based on source/analyzer requirements and financial restraints.
A system typically will include the following components:
In-stack sampling probe
• Coarse in-stack filter
Gas transport tubing
• Sampling pump
• Moisture removal system
• Fine filter
Analyzer
• Calibration system
• Data recorder
Sampling Probe—Representative gas sampling requires samples that will demon-
strate the total pollutant gas emissions from a source. The temperature and
velocity traverse across the duct may indicate a necessity for a multipoint
probe to extract samples from numerous points across the entire duct. Several
research studies have shown that, although gas concentration cannot be assumed
to correspond directly to temperature and velocity gradients in a duct, these
measurements are excellent indications for positioning gas sampling probes.
This research has shown that a representative gas sample may be extracted from
a grid of equal areas laid out in the duct. A temperature and velocity trav-
erse is then performed in each row of the grid. The multipoint gas sampling
probe is then positioned across the row that indicated temperature and
velocity readings closest to the average reading in the duct.
5-105
-------
Gas sampling requires that particulate matter, which can harm the analyzer and
shorten the operating life of the sample pump, be removed from the gas stream.
Directing the probe inlet countercurrent to the gas flow helps prevent many
large particulates from entering the system. Particulates that enter the
probe can be removed by coarse and fine filters.
Coarse Filters—The coarse filter is usually located at the probe tip in the
stack, where it then can prevent particulate matter from plugging the sampling
probe and will not require heat tracing to prevent moisture condensation.
There are two general types of coarse in-stack filters: external or internal.
The external coarse filter is a porous cylinder, typically constructed of
sintered 316 stainless steel, though it may also be glass, ceramic, or quartz.
It is essential that the porous cylinder be protected by a baffle to prevent
excessive particulate buildup on the leading edges. These porous cylinders
have an expected utility of approximately 2 to 3 months before they become
clogged with particulate, depending on the sampling rate. Although they can
be regenerated by back flushing, they eventually need replacing. The nominal
cost (^525) suggests that it may be easier to replace the filter on a routine
basis than to install costly automatic backflushing equipment.
Filter material is available from a number of manufacturers. Glass wool
filters have been used in some experiments; however, .they have a higher
pressure drop than the Alundum thimble.
Fine Filters--The majority of extractive stack gas analyzers require almost
complete removal of all particles larger than 1 micron from the gas stream.
This is best accomplished by including a fine filter near the analyzer inlet.
Fine filters are divided into two broad categories: surface filters and depth
filters.
Surface filters remove particulates from the gas stream using a porous matrix.
The pores prevent penetration of particulates through the filter, collecting
them on the surface of the filter element. Surface filters can remove particu-
lates smaller than the actual filter pore size with particulate cake buildup
and electrostatic forces acting to trap smaller particles. These filters
perform well on dry, solid particulates without excessive pressure drop. A
surface filter will foul quickly if it becomes wet or if the particulate is
gummy.
Depth filters collect particulates within the bulk of the filter material. A
depth filter may consist of loosely packed fibers or relatively large diameter
granules. These filters perform veil for gunny solids or moist gas streams
and dry solids. In the case of malfunction, their flexibility can protect the
analyzer from damage. Glass wool packed to a density of 0.1 gm/cm3 and a bed
depth of at least 2 inches can act as an inexpensive depth filter for normal
gas flowrates. These filters must be carefully packed to avoid channeling.
Gas Transport Tubing--The gas tubing or sample lines transport the extracted
gas sample from the stack through the interface system and into the analyzer.
When evaluating sampling lines, it is important to consider:
5-106
-------
Tube interior-exterior diameter
may contain significant quantities of water and
water ^gfl£c^5 rlliifiRc'S biases ieinVlimMd3*530^10" ultraviolet instfu-
ment).^0X^ese analyzers do, however, require that gases be kept above the dew
point to protect against condensation and corrosion within the analyzer.
ressure drop is . quite acceptable for most sampling pumps. ,The response
ae or most sampng pumps. ,Te response
in
t. The calibration gases enter .. the continu-
1"3*6" as a unit. The calibration gases
ous gas monitoring system as near as possible to the same entrance point for
the «t.ck gjs.VTyj^igjsggtuljo^g^J^ S^^sv^^The analyzer is
then calibratedfat the same gas flowrate, pressure, temperature, and operating
procedure used in monitoring the stack gas. Flooding the coarse filter with
any
leaks, blockage, or sorption of gases taking place in the system will be
in
e of stainless steel is enhanced by keeping gases above the dew
point. These materials are commercially available in heat traced form.
f«
ctff&?aitOQ ?9d e«90$0ieiii0ftfl)fiiiBOb^oe «ys$p|ioprobably would incorporate
stainless steel, Teflon®, and plastic.
EPA is currently studying the option of using National Bureau of Standards
sfitfile but are more expensive than commercial gases.
System — The best, system does not
iuUt*Cit*tohfift$B*C?d.The necessary controls are easily
personnel. The suggested controls
includAd«.fl«afolJBw$AO,8 and discharge pressures are developed at flowrates well
above those needed for gas sampling systems.
Temperature control at the cold end of the heated sample line. This is
tM«r&fegayf$ea?ei'ia#opia{fet*fn9u«p
tor pttflfleHilho^ fliatwaiaa[fiJ$stuP6ep6MC«aalrtffiei»hCyanalyzer would be higher,
but for some analyzers with built-in pressure regulators, this may be prefer-
of
, _._ .__ v'er system function (most analyzers are
sensitive to pressure changes).
5-W
-------
Gas flowrate control is installed to make certain the analyzer receives
the correct gas flow. This is not critical, since most analyzers are
relatively insensitive to minor flowrate change.
Calibration gas valving automatically injects calibration gases once
every 24 hr. This can be accomplished with a simple electric solenoid
valve. The calibration ,gases should flow through the sampling system at
the same condition of temperature, pressure, and flow as does the stack
gas.
5.9.1.2 In-Situ Monitoring Systems—
The problems and expense associated with extractive monitoring systems have
led to the development of instrumentation that can directly measure source-
level gas concentrations in the stack. The so-called in-situ systems, do not
modify the flue gas composition and are designed to detect gas concentrations
in the presence of particulate matter. Since particulate matter causes a
reduction in light transmission, in-situ monitors utilize advanced
electro-optical techniques to eliminate this effect when detecting gases.
Cross-stack in-situ monitors measure a pollutant level across the complete
diameter or a major portion of the diameter of a stack or duct. Stratifica-
tion effects are lessened by the use of cross-stack instruments, since an
average reading is taken over a relatively long sample path. There are tw
-------
One of the principal marketing features of cross-stack analyzers is that a
single instrument can monitor a number of gases and even opacity. The cost of
such a monitor can be comparable to the purchase price of three or four
separate instruments combined in an extractive system.
There are, however, a number of disadvantages associated with the cross-stack
monitors. An in-situ cross-stack monitor can monitor only one flue or stack
at a time. Costs might be prohibitive if a number of stacks must be monitored.
In such a case, multiple probes and sampling lines leading into a single
extractive system might be the better choice. Problems with optical misalign-
ment, vibration affecting the optical systems, and the failure of electronic
components also can occur. It is common among vendors of these instruments to
offer service packages whereby the systems are periodically checked by a
company serviceman. A service package generally will ensure that a system
will continue to function, but the cost involved may bring the operating
expenses to a level comparable to that of an extractive system.
5.9.2 Analyzers
5.9.2.1 NPIR Analyzers--
Nondispersive infrared (NDIR) analyzers have been developed to monitor SOj,
NO , CO, C02, and other gases that absorb in the infrared, including hydro-
carbons. NIDR instruments utilize a broad band of light that is centered at
an absorption peak of the pollutant molecule.
This broad band is usually selected from all the light frequencies emitted by
the infrared source by using a bandpass filter. Table 5-10 gives the band
centers for several of the gases found in source emissions.
In a typical NDIR analyzer, infrared light from a lamp or glower passes
through two gas cells—a reference cell and a sample cell. The reference cell
generally contains dry nitrogen gas, which does not absorb light at the wave-
length used in the instrument. As the light passes through the sample cell,
pollutant molecules will absorb some of the infrared light. As a result, when
the light emerges from the end of the sample cell, it will have less energy
than when it entered. It also will have less energy than the light emerging
from the reference cell. The energy difference is then sensed by some type of
detector, such as a thermistor, a thermocouple, or microphone arrangement.
The advantages of the NDIR-type analyzers are their relatively low cost and
the ability to apply the method to many types of gases. Generally, a separate
instrument is required for each gas, although several instruments have inter-
changeable cells and filters to provide more versatility. Problems associated
with the method are those that arise from interferring species, the degrada-
tion of the optical system caused by corrosive atmospheres, and in some cases,
limited sensitivity. The microphone type detectors are sensitive to vibration
and often require both electronic and mechanical damping, for example, by
placing the instrument on a foam insulation pad.
5.9.2.2 Nondispersive Ultraviolet Analyzers (NDUV)--
Several available nondispersive systems use light in the ultraviolet and
visible regions of the spectrum rather than in the infrared. Essentially, the
5-110
-------
TABLE 5-10. INFRARED BAND CINTIRf
Gas
NO
MO 2
S02
H20
CO
C02
NH3
CH<
Aldehydes
Location of
band centers, v-3v» ?.un±
5.: -
55-
3 -
3.
5.0 -
7.1 -
2.
4.
2.
5 .
3 -
10.
3.
7.
3 m ~"! ™
- -
20
14
1
5 . 5
10
3
6
7
2
12
5
3
7
3.9
7 - -
5CO
700
1,000
1,300
2
2
4
850
1
3
1
3
2,550
_ ""*
•~ J.
- 1
- 1
- 2
,200
,200
,300
- 1
,900
,700
950
,300
,000
- 2
•a r"
,3CC
,250
,400
,000
,250
,950
analyzers measure the degree of absorption at a wavelength in the absorption
band of the molecule of interest. This is similar to the NDIR method, but the"
major different is that a reference cell is not used. Instead, a reference
wavelength, in a region where the pollutant has minimal absorption, is
utilized.
This method of analysis is often differential absorption, since measurements
are performed at two different frequencies. This method is not limited to
extractive monitoring systems, but it also is used in both in-situ analyzers
and remote sensors. As with all extractive monitoring systems, particulate
matter is removed before entering the analyzer. It is not necessary, however,
to remove water vapor in some of these systems. A heated sample line and
heated cell prevent condensation in the analyzer. Since water does not absorb
light in this region of the ultraviolet spectrum, no interference occurs.
5.9.2.3 Polarographic Analyzers—
Polarographic analyzers have been called voltanmetric analyzers or electro-
chemical transducers. With the proper choice of electrodes and electrolytes,
instruments have been developed utilizing the principles of polarography to
monitor S02, N02, CO, 02, H2S, and other gases.
The transducer in these instruments is generally a self-contained electro-
chemical cell in which a chemical reaction taxes place involving the pollutant
molecule. Tvo basic techniques are used in the transducer: (1) the utiliza-
tion of a selective semipenneable membrane that allows the pollutant molecule
to diffuse to an electrolytic solution, and (2) the aeasuraaent of the current
change produced at an electrode by the oxidation or reduction of the dissolved
gas at the electrode.
5-111
-------
The electrolyte of the cell generally will be used up in 3 to 6 months of
continuous use. The cells can be sent back to the company and recharged, or
new ones can be purchased. It is extremely important that the sample gas be
conditioned before entering these analyzers. The stack gas will come to
ambient temperature, and the particulate matter and water vapor are removed to
avoid fouling the cell membrane.
5.9.2.4 Electrocatalytic Oxygen Analyzers--
A new method for the determination of oxygen has developed over the past
several years as an outgrowth of fuel-cell technology. These so-called fuel-
cell oxygen analyzers are not actually fuel cells, but simple electrolytic
concentration cells that use a special solid catalytic electrolyte to aid the
flow of electrons. These analyzers are available in both extractive and
in-situ (in-stack) configurations. This versatility of design is making them
popular for monitoring diluent oxygen concentrations in combustion sources.
In basic electrochemistry, one of the common phenomena studied is the flow of
electrons that can result when two solutions of different concentrations are
connected together. The electron flow results from the fact that the chemical
potential is different on each side and that equilibrium needs to be reached.
There are two half-reactions that take place in this example.
The instruments designed to continuously monitor oxygen concentrations utilize
different concentrations of oxygen gas expressed in terns of partial pres-
sures. A special porous material, zirconium oxide, serves both as an
electrolyte and as a high temperature catalyst to produce oxygen ions.
If the temperature is well stabilized and the partial pressure of the oxygen
on the reference side is known, the percentage of oxygen in the sample can be
easily obtained.
One problem with the method is that carbon monoxide, hydrocarbons, and other
combustible materials will burn at the operating temperature of the device.
This will result in a lowering oxygen concentration in the sample cell, which,
however, would be insignificant for concentrations of the combustible
materials on the ppm level.
5.9.2.5 Paramagnetic Oxygen Analyzers—
Molecules will behave in different ways when placed in a magnetic field. This
magnetic behavior will be either diamagnetic or paramagnetic. Most materials
are diamagnetic and when placed in a magnetic field will be repelled by it. A
few materials are paramagnetic; they are attracted by a magnetic field. Para-
magnetism arises when a molecule has one or more electrons spinning in the
same direction. Most materials will have paired electrons; the same number of
electrons spinning counterclocJcwise as spinning clockwise. Oxygen, however,
has two unpaired electrons that spin in the same direction. These two elec-
trons give the oxygen molecule a permanent magnetic moment. When an oxygen
molecule is placed near a magnetic field, the molecule is drawn to the field
and the magnetic moments of the electrons become aligned with it. This strik-
ing phenomenon was first discovered by Faraday and forms the basis of the
paramagnetic method for measuring oxygen concentrations.
5-112
-------
There are two methods of applying the paramagnetic properties of oxygen in the
commercial analyzers. These are the magnetic wind or thermomagnetic methods
and the magnetodynamic methods:
• Magnetic Wind Instruments (Thermomagnetic)—The magnetic wind instruments
are based on the principle that paramagnetic attraction of the oxygen
molecule decreases as the temperature increases.
Several problems can arise in the thermomagnetic method. The cross-tube
filament temperature can be affected by changes in the thermal conduct-
ivity of the carrier gas. The gas composition should be relatively
stable if consistent results are desired. Also, unburned hydrocarbons or
other combustible materials may react on the heated filaments and change
their resistance.
• Magneto-dynamic Instruments—The magneto-dynamic method utilizes the
paramagnetic property of the oxygen molecule by suspending a specially
constructed torsion balance in a magnetic field. When a sample contain-
ing oxygen is added, the magnet attracts the oxygen and the balance
swings to realign itself with the new field. Light reflected from a
small mirror then can be used to indicate that degree of swing and hence,
the oxygen concentration.
Water and particulate matter have to be removed before the sample enters this I
monitoring systems. It should be noted that NO and N02 are also paramagnetic »
and may cause some interference in the monitoring method if high concentra-
tions are present. - .• • •
Tables 5-11, 5-12, and 5-13 summarize information on extractives and in-situ
monitoring instrumentations, including range capabilities, approximate cost,
and ability to measure specific effluent gas components.
5.10 MANUAL STACK SAMPLING AND ANALYSIS APPROACHES
Incinerators burning hazardous waste are required to achieve a destruction and
removal efficiency (DRE) of 99.99% for each principal organic hazardous con-
stituent (POHC) in the waste feed as required under RCRA, as well as meeting
emissions limitations for HC1 and particulate matter. These pollutants are
sampled and analyzed by manual extractive techniques at the exhaust stack.
Stack gas sample volume, stack moisture content, stack gas volume flow rate, and
particulate emissions are typically determined by EPA Methods 2, 4, and 5 or,
alternatively, ASTM Method D2928. Hydrochloric acid emissions are determined by
midget impinger collection and subsequent titration. Stack emissions of POHC's
may be determined using a modified EPA Method 5 apparatus and includes collection
and analysis of particulate matter, gas phase organics and water present in the
stack gas, with subsequent analysis done typically on a gas chromatograph/mass
spectrometer (GC/MS) system. The following discussions describe in more detail
each of these manual stack sampling approaches.
5-113
-------
TABLE 5-11. EXTRACTIVE MONITOR SUMHARY'
Approximate
Instrument
vendor
Beckman
Bendix
Esterline
Angus
Honba
Infrared Ind.
Leeds and
Northrop
MSA
Teledyne
Gases measured
S02 NO NOo CO, CO 02
Nondispersive infrared
XX XX
XX XX
XX XX
X X X X X
XX XX
X X
XX XX
X X
Measurement
range
instruments
Various ranges
in ppm or %
0 . 5 ppm - 50%
2 ppm - 100%
10 - 2 , 000 ppm
200 ppm - 10%
0 • 1,000 ppm
0 - 2,000 ppm
0 - 1,000 ppm
cost in
thousands
of dollars
3 - 5.4
1 - 4
5
3-5
1-2
5.5
3-4
11 - 13
Extract differential absorption instruments
CEA
DuPont
Esterline
Angus
Teledyne
Western
XX X
XXX
X X
X
,»• X XX X
2 - 50,000 ppm
1 ppm - 100%
2 ppm • 100%
75 - 5,000 ppm
3-6
13 - 23
12 - 14
12 - 22
Polarographic instruments
Beckman
IBC/Berkeley
Dynasciences
InterScan
Corp.
Teledyne
Theta Sensors
(MR!)
Western
Precipitator
(Joy)
X
XXX
XXX XX
XXX
X
XX X
X X X X X
0 - 25%
0 - 1,000 ppm
0.01 - 200,000
ppm
0 - 25%
1 - 20.000 ppm
0 - 1,000 ppm
1 - 1.5
2 - 5.5
2-8
1
1.5
1-4
1.5
Electrocatalytic instruments
CEA
Dynatron
Lear Siegler
MSA
Teledyne
Thennox
X
X
X
X
X
X
0 • 25%
0 - 25%
0 - 25%
0.1 - 20.8%
0 - 25%
0 - 25%
4.5 - 5.8
2
1.5
2
Paramagnetic instruments
Beckman
MSA
CEA
SCOTT
Ledds and
Northrop
Taylor-
Servomex
X
X
X
X
X
X
0 - 25%
0 - 25%
0 - 100%
0 - 100%
3
1 - 1.5
1 - 1.5
This is a representative listing of known vendors. It is not intended
to be a complete listing of all suppliers of such equipment.
5-114
-------
TABLE 5-12. IN-SITU MONITOR SUMMARY'
Gases aeasured
Vendor SO, NO CO, C0_ 02
Approximate
Method Measure- cost in
Opac- In- Cross- «ent thousands
stack stack
range
of dollars
CEA
Contraves X X
Goerz
Dynatron
Environmental X X
Data Corp.
Lear Siegler X X
Westinghouse
X X
X X
0 - 25\
0 - 5,000
PP»
30
20-40
0 - 500; 4.5 - 17
0 - 1.000;
0 - 1,500
PP»
*This is • representative listing of known vendors. It is not intended to be «
complete listing of all suppliers of such equipment.
TABLE 5-13. OXYGEN ANALYZER SUMMARY5
X
X
X
Electro-
irographic catalytic
X
X
X
X
X
X
X
X
X
X
x
X
x
X
X
Sampling typ*
In-Situ Extractive
x X
X
X v
A X
X
X
X
X
X
x x
x
X
X
X
X
X
X
X
X
x
X
Vendor
Astro
Beckman
Cleveland
Controls
Corning
Dynasciences
uynatron
Esterline Angus
Gas Tech
Hays-Republic
Joy
Lear Siegler
Leeds and
Northrop
Lynn
MSA
Scott
Taylor-
Servomex
Teledyne
The rmox
Theta Sensors
westinghouse
This is a representative listing of known vendors. It is not intended to
be a complete listing of all suppliers of such equipment.
5-115
-------
5.10.1 Hydrochloric Acid Emissions
The sampling procedure developed for the determination of hydrogen chloride
emissions from stationary sources is basically a modification of the standard
procedure for S02 determination (EPA Reference Method 6): The HC1 method utili-
zes the same sampling equipment (i.e., probe, glassware, pump, dry gas meter,
etc.) with the exception that a regular midget impinger is used for the first
impinger in place of the midget bubbler used in Method 6. Dilute NaOH is used
as the absorbing solution for HC1. After pretreatment of the impinger catches
to remove possible interfering species, samples are analyzed for chloride ion
by titration with a standard solution of mercuric nitrate [Hg(N03)2].
A heated glass lined probe is used with the temperature maintained at 300 F or
at stack temperature, whichever is greater. A pyrex wool plug is inserted in
the inlet end of the probe in the same manner as required by Method 6. The
impinger train, illustrated in Figure 5-45, which should be immersed in an ice
bath during the sampling, consists of four midget impingers connected by glass
U tubes and clamps. Impinger Nos. 1 and 2 should'contain 15 mL of the absorbing
solution (0.1N NaOH). Impinger No. 3 should contain 15 mL of 3% H^OZ solution,
which will remove S02 from the sample stream. Impinger No. 4 is a dry impinger
which functions to remove moisture from the sample stream. The impinger train
is interfaced with the probe by using a short, right angle bend glass adaptor
with the appropriate standard taper ground glass joints at either end. A
standard Method 6 control box with umbilical cord is used to complete the samp14.
train. A sampling rate of 2.0 liters per min is recommended with a total sample
volume of 2.0 to 10.0 scf per sample, depending on the expected concentrations I
of HCl to be measured.
The Mercuric Nitrate Method involves titration of Cl" with standard Hg(NOs)2
solution using bromophenol blue diphenylcarbazone mixed indicator. Diphenyl-
carbazone forms an intensely violet colored complex with the first slight excess
of Hg beyond the equivalence point. The bromophenol blue performs two func-
tions, the first being that it allows for a very accurate adjustment of the
pH of the solution to be titrated to the range of 3.2 to 3.4 which is necessary
for accurate results; and, secondly, its yellow color in the acid range serves
as an excellent background color for detection of the violet colored complex
formed at the endpoint.
Additional details on the sampling and analysis procedures can be found by
consulting the Guidance Manual for Evaluating Permit Applications for the
Operation of Incinerator Units.
5.10.2 Principal Organic Hazardous Constituents (POHC)
The sampling system used to obtain gaseous emission samples from the stack
gas will be a modified version of that normally employed to perform EPA
Reference Method 5 procedures. The system will consist of a quartz-lined,
water-cooled sampling probe, a cyclone (optional), a high efficiency glass or
quartz fiber filter, an XAD-2 sorbent resin module to allow for the collection
of volatile organic vapors, four impingers and a control module. The sorbent
module will be located between the filter assembly and the impinger train. A
diagram of the sampling system is shown in Figure 5-46, and the sorbent module
5-116
-------
GLASS WOOL
FILTER
REVERSE-TYPE
PITOTTU8E
SILICA GEL
DRYING TUBE
1 _!£!!*!!!__
CD * @ MIOGH IMPINGER (15 mC Of a 1 N NjOH)
(3) MIOGH IMPINGW (15 mL Of 3 *
0 MIDGET IMPINGER (DRY)
Figure 5-45. Schematic diagram of hydrogen chloride sampling train.
is shown in Figure 5-47. Sampling probe cooling is required to prevent severe
probe damage that would occur if an unjacketed probe was placed in a zone where
temperatures exceed 600°C (1100°F). Furthermore, the water cooling also
assists in cooling the sample gas stream so that existing probe gas temperatures
may be regulated to 205°C (400°F) as the gas passes through the filter. A
schematic of the water cooled probe assembly is shown in Figure 5-48. The
probe is constructed of stainless steel with a quartz liner. If the stack
gas temperature is low, then a probe which meets the requirements of EPA Method 5
sampling may be used instead.
The ball or spherical joint of the probe connects to a glass cyclone with a
collection flask attached. The use of the glass cyclone is optional. The
purpose of the cyclone is to remove large quantities of particulates to prevent
plugging of the filter. In gas streams where the particulate loading is expected
to be light, the cyclone may be replaced with a glass tube connecting the probe
to a glass filter holder. If used, the cyclone outlet is connected to the glass
filter holder. The cyclone, flask, and filter holder are contained in an
5-117
-------
c
o
u
4)
O
u
u
§
fiu
c
•H
«J
V
,— I
Q.
w
IO
T3
O
4)
CL,
b]
•o
o
I
5-118
-------
FLOW DIRECTION
/ 28/12 BALL JOINT
GLASS WATER JACKET I
GLASS FRITTED DISC
GLASS WOOL PLUG
N^
15 mm SOLV-SEAL JOINT
(OR 28/12 SOCKET JOINT)
FLOW DIRECTION
8 mm-GLASS
COOLING COIL
ADSORBENT
FRITTED
STAINLESS STEEL DISC
RETAINING SPRING
Figure 5-47. Adsorbent sampling system.
5-119
-------
V
•§
u
a
T3
o
o
u
o
*J
o
u
01
IM
4)
H
CO
*
I
in
v
I
•H
bb
5-120
-------
electrically heated enclosed box, which is thermostatically maintained at a
temperature"of [120°C ± 12°C (250°F ± 25°F)] which is sufficient to prevent
water condensation in the portion of the train contained in this box.
Downstream of the heated filter, the sampled gas passes through a module that is
filled with roughly 20 gms of XAD-2 resin. The XAD-2 sorbent is a porous polymer
resin with the capability of absorbing a broad range of organic species. Before
reaching the sorbent resin, the sampled gas should be cooled to a temperature
of 15°C (60°F). "his cooling operation may cause some of the water vapor
contained within the sampled stream to condense, which, in turn, may result
in some of the organic vapor becoming entrained in the condensate. For this
reason, the condensate must be allowed to percolate through the resin bed prior
to it being discharged into the impinger located below the sorbent module.
At the downstream side of the sorbent module, four ijnpingers are connected
in series and immersed in an ice bath. The first impinger, connected to the
outlet of the sorbent module, is of the Greenberg-Smith design, modified by
replacing the tip with a 0.3 cm (0.5 in.) inside diameter glass tube extending
to within 1.3 cm of the bottom of the flask. This iapinger is initially filled
with 100 ml of scrubbing solution. The selection of scrubbing solution is con-
tingent upon the type of inorganic vapors that are suspected of being contained
in the stack gas. A caustic solution such as sodium hydroxide or sodium
acetate is used to collect acid gases such as HCl. (The sodium acetate is j.
used to prevent depletion of scrubbing reagent by carbon dioxide.) For collec-
tion of volatile metals (mercury, arsenic, selenium) a strongly oxidizing solu-
tion (such as silver catalyzed ammonium persulfate) must be used. The second
and third .impinger are Greenberg-Smith types modified like the first. They
may be filled with an organic liquid with a high boiling point, such as iso-
octane, in order to trap organics not adsorbed on the resin. The fourth
impinger is also a modified Greenberg-Smith and contains approximately 175
grams of accurately weighed silica gel. If volatile metals collection is not
desired, then the impinger section may set up as an EPA Method 5 backhalf, as
shown in Figure 5-46.
In connecting the sampling train together, no stopcock grease should be used
on any joint upstream of the sorbent module as it may flow into the sampled
stream and contaminate the particulate and organic vapor portion of the sample.
This requirement means that some extra effort is required to achieve a leak
check. Nevertheless, it is essential to avoid stopcock grease since its
presence would make organic analysis virtually impossible.
Alternatively, a source assessment sampling system (SASS) train may be used for
stack gas sampling when a large sample is required and the stack gas temperature
is less than 500°F. The SASS train operates at a 5 cfm flow rate and collects
a 25.5 m3 sample in a three-hour period. The SASS train consists of a stainless
steel probe that connects to three cyclones and a filter in an oven module, a
gas treatment section, and an impinger series, as shown in Figure 5-49. Size
fractionation is accomplished in the cyclone portion of the SASS train, which
incorporates the three cyclones in series to provide large collection capacities
for particulate matter nominally size-classified into three ranges.- (a) 10 urn,
(b) 3 urn to 10 pm, and (c) 1 um to 3 um. By means of a standard 142-mm or
230-mm filter, a fourth cut,
-------
V
u
M
en
in
v
I
•i-4
Cb
5-122
-------
I
follows the oven unit and is composed of four primary components.- the gas
cooler, the sorbent trap, the aqueous condensate collector, and a temperature
controller. Volatile organic material is collected in a cartridge or "trap"
containing sorbent, which is designated to be XAD-2, a microreticular resin
with the capability of absorbing a broad range of organic species. Volatile
inorganic elements are collected in a series of impingers that follow the con-
denser and sorbent system. The last ixnpinger in the series contains silica
gel for moisture removal. Trapping of some inorganic species also may occur
in the sorbent module. The pumping capacity is supplied by two 10-ft^/min,
high-volume vacuum pumps, while required pressure, temperature, power, and flow
conditions are regulated through a main controller. At least 60 A of power at
100 V is needed for operating the sampling equipment.
The organic "trap" packings may be extracted using a Soxhlet extractor. This
extract and organic liquids in the impingers may be analyzed for POHCs using
the methods in "Test Methods for Evaluating Solid Wastes," EPA SW-846, 1980.
Methods presented in EPA SW-S46 may be used to analyze scrubber water and ash
samples as necessary to compute a mass balance on POCH's. In addition, particu-
lates collected on the filters and cyclones must be extracted and analyzed in
order to compute the mass balance. A full mass balance on the POHC's in the
waste require monitoring at the following locations:
• Stack gas *
• Particulates collected from the stack gas I
• Ash
• Scrubber liquid
• Other residues
• Waste feed composition
5.10.3 Calculation of Sample Volume Required to Show 99.99% ORE
1 Incinerators burning hazardous waste must achieve a destruction and removal
efficiency (DRE) of 99.99% for each principal organic hazardous constituent
(POHC) in the waste feed. The DRE is determined from the following equation:
W. - W
DR£ =
in
where W^ - Mass feed rate of the principal organic hazardous constituent
(POHC) in the waste stream feeding the incinerator, Ib/hr
W = Mass emission rate of the principal organic hazardous constituent
(POHC) present in exhaust emissions prior to release to the
atmosphere , Ib/hr
Win *s ca^cu^ated using the following formula:
(Concentration of POHC in waste) (Waste feed rate)
5-123
-------
POHC concentrations must be expressed in percentages when applying this formula.
The waste feed rate is expressed in mass per unit time and must be consistent
with the units used to express W If a waste is co-fired with auxiliary
fuel, the auxiliary fuel feed ra?e does not affect the calculation of W. .
w is calculated from stack sampling data and involves three steps:
• Computation of stack gas sample volume
• Computation of POHC concentration in stack sample
• Computation of stack gas volume flow rate
Stack gas sample volume and stack gas volume flow rate may be determined by
EPA Methods 2 and 5 or ASTM Method D2928. Stack emissions of POHCs may be
determined using a modified EPA Method 5 apparatus and includes collection and
analysis of particulate matter, gas phase organics and water present in the
stack gas.
The following sample calculation will identify the minimum volume necessary to
demonstrate a 99.99% ORE:
Step 1 - Computation of maximum W to satisfy 99.99% DRE
Given: POHC designated by the permit writer: hexachlorobenzene I
Concentration of POHC in waste feed: 1.0%
Waste Feed Rate:. 1,000 Ibs/hr
W. = (Concentration of POHC in waste) (Waste feed rate)
in = (0.01)(1,000 Ib/hr)
= 10 Ib/hr
DRE = w x 100
in
W = W. (1-DRE)
°Ut = <}9 Ib/hr) (1-0. 9999)
= 0.001 Ib/hr
Note: The expression of the DRE to 5 or 6 decimal places is justified because
an error by as much as 25% in the W would affect only the fifth
decimal place.
Step 2 - Computation of minimum weight of POHC sample that can be collected
Given: Detection limit of hexachlorobenzene in analytical sample extract
as injected in the GC/MS: 1 ng/uL, or 1 vq/mL [35].
Average Extraction Efficiency: 60%
Because the extracted sample is concentrated via evaporation before
injection into the GC/MS, then the minimum weight of collected
hexachlorobenzene is independent of extract liquid volume.
5-124
-------
The minimum detectable total weight of POHC collected as obtained
from laboratory analysis
W , = (Detection limit)/(Extraction efficiency)
sample
= (1 uL/mL)/(0.60)
= 1.667 ug
Step 3 - Computation of the POHC stack gas loading
Given: Stack gas volume flow rate at standard conditions, Q: 85,382 scf/min
Total weight of POHC in sample
' Volume of sample at standard conditions
out hr
9 = Q x 60 min
_ 0.001 lb/hr hr
~ 85,382 scf/min 60 min
= 1.95 x 10"10 Ib/scf = 8.85 x 10"7 grams/scf
Note: This computation assumes 100% collection of the POHC on the filter, resij
module, and impingers.
Step 4 - Computation of minimum stack gas sample volume
W
V = saj"Ple
m(std) ~ Cg
_ 1.667 x 10"6 grans
8.85 x 10"7 grams/scf
= 1.884 scf
5.11 PLANT CONDITION MONITORING SYSTEMS
The presence of defects in machinery and mechanical structures can lead to
catastrophic failure. Plant facilities which are super-designed for safety
and minimal downtime (e.g., nuclear power plants and oil refineries) utilize
large fixed-base condition monitoring systems for lowered repair costs, lower
production losses, and decreased accident and fire risks.
Defects present are characterized by corresponding abnormalities and changes
in acoustic and vibratory emission patterns. By the use of sensors small
defects in bearings and gears, growing cracks in shafts and weld joints, loose
parts, and operating deficiencies such as pump cavitation can be detected
early enough to either allow correction of the problem or provide time for
predictive maintenance planning. These plant-wide incipient failure detection
(IFD) systems can sequentially examine more than 800 channels and quantize
their vibratory or acoustic energy levels. The signal is compared with the
5-125
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previously obtained energy level retrieved from the memory bank of a dedicated
minicomputer. Significant deviations are programmed to cause an alarm
annunciation [36].
5.11.1 Machine Vibratory Signature Analysis
Traditional machinery vibration signature analysis (MVSA) is a method of
determining the mechanical condition of an operating machine by monitoring and
analyzing frequency characteristics produced by internal elements using narrow
band spectrum analysis techniques.
Vibration signature analysis makes use of the fact that vibration produced by
a machine contains a great number of discrete frequencies, some of which can
be tied directly to the operating dynamics of particular elements within the
machine. When the amplitude of a specific frequency or pattern of frequencies
changes, it represents a change within the machine and possibly a
deteriorating condition.
Vibration measuring equipment is often used to detect solids build-up on fan
blades, e.g., ID fans. If the vibration exceeds a preset level, the fans are
shutdown, clean and repaired, if necessary [15].
5.11.2 High Frequency Acoustic Emission Analysis
The basic premise of high frequency acoustic IFD monitoring is that the pres-
ence of defects in machinery and mechanical structures is characterized by
corresponding abnormalities and changes in the acoustic signature and that
machinery vibration is inevitably accompanied or even preceded by metal defor-
mation. Metal deformation generates "acoustic emissions," i.e., noise
resulting from the propagation of intergranular dislocations in material
subjected to stress.
For early identification of failure these defects must be detected when they
first develop and are quite small. However, the amount of detectable energy
released from a small defect is usually negligible in comparison to normal
machinery operating noise. Fortunately, operating noise tends to be concen-
trated in the low frequency range of vibration while defect-originated energy
extends to much higher frequencies. It is this frequency separation that
accounts for the success of IFD technology.
High frequency acoustic techniques have been shown to be more effective in
detecting mechanical failures at a very early stage then the popularly used
low frequency vibration and sound techniques. Furthermore, high frequency
acoustics have very often picked up fluid flow deviations such as pump
cavitation and mechanical seal leakage.
5.12 SCRUBBER/QUENCH WATER AND ASH HANDLING
5.12.1 Description of Potential Incinerator Wastes
Operation of a hazardous waste incinerator typically produces a number of
secondary products, namely quench water, scrubber effluent, and ash. The
5-126
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following subsections describe each of these possible secondary wastes and
provide information on their potential composition.
5,12.1.1 Quench Water--
Following the afterburner section, a quench section is usually installed to
reduce the combustion gas temperature prior to entering the scrubber. Enter-
ing temperatures are approximately 1,800°F to 2,000°F and the exit temperature
may be below 250°F. The inclusion of the quench section becomes necessary
when nonmetallic materials are used for. scrubber construction and packing.
The upper temperature -limit for sustained operation is about 300°F for poly-
ester and epoxy fiberglass and 150°F for PVC [37]. The gases are commonly
quenched with a water spray at a rate capable of reducing the gas temperature
to a desired level. Besides lowering the flue gas temperature, this quench
water functions as a scrubber by removing some particulate matter and certain
gaseous pollutants from the exhaust stream.
I Four basic designs are used to generate the water spray in quench towers:
f (1) Air and water nozzle (2) High pressure sequenced spray nozzles (3)
Orifice plate (4) Low pressure venturi or variable throat venturi
The type of device used depends upon the composition of the quench water, the .
composition of the exhaust gas, the type of air pollution control equipment I
being used, the initial investment, and maintenance considerations. Various j
quenching devices are illustrated in Figure 5-50.
The air and water nozzle system is the most sophisticated device and requires
a fresh water feed, free from particles which might clog the spray nozzles.
It also requires the least amount of water because it produces small, uniform
droplets which efficiently cover an exhaust area.
High pressure sequenced spray nozzles operate on a demand basis. Initially,
certain banks of spray are activated and as the gas temperature rises, addi-
tional banks come on to maintain a constant temperature. This system, like
the air and water nozzle system, cannot operate on clarified recycle water due
to dissolved and suspended solids; however, where fabric filters or
electrostatic precipitators follow, these types of systems are necessary to
prevent damage to these units from excessive heat.
An orifice plate is an effective precleaner capable of removing particulates
down to 5-10 microns [38]. It is simply a perforated plate through which
water is forced. It is very effective preceding a high energy scrubber be-
cause it removes the larger particles which would create an erosion problem in
the high velocity throat.
Another device which is essentially maintenance free and works well when used
ahead of a scrubber is a low pressure venturi. Water nozzles, located just
upstream of the venturi throat, saturate the flow and knock out the larger
particles. In a variable throat venturi, gas velocities and corresponding
pressure drop can be varied by adjusting throat diameter. For any particle
size, the collection efficiency increases with increased energy consumption.
Increased energy can be obtained by increasing gas velocities through the
5-127
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QUENCH SPRAY
THROAT -
ADJUSTMENT
COLD GAS OUT
VARIABLE THROAT VENTURI
COLD GAS OUT
HOT GAS IN
QUENCH
SPRAY
THROAT
A A A A A
HOT GAS IN-
SPRAY
NOZZLES
.QUENCH
SPRAY
COLO GAS OUT
VENTURI
SPRAY TOWER
ORIFICE
PLATE
COLD GAS OUT
ORIFICE
PLATE *
HOT GAS IN-
J
« QUENCH SPRAY
ORIFICE QUENCH TOWER
Figure 5-50. Various quenching devices [38]
5-128
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variable throat. Due to their larger and less restrictive water nozzle sys-
tems, both the orifice plate and low pressure venturi or variable throat
venturi quenching devices may be operated using recycled quench water, after
passing through a reduction and clarification process.
A generalized schematic of incinerator facilities and schematic of a rotary
kiln facility with quench spray chamber and venturi scrubber are illustrated
in Figures 5-51 and 5-52, respectively.
Material selection of the nozzles is very important because the cooling effect
of the spray nozzle can cause condensation of the hot acidic gases along the
wall of the spray nozzle, and these gases will react with the metal at or
below the dewpoint of the acid. Also, the water will immediately react with
the acid gas to form, for example, hydrochloric acid mist in the fine spray
droplets, if an organochlorine waste is being destroyed. These are recycled
and result in direct contact with the nozzle body.
The main body of the quench chamber is in contact with the highly acidic
solution formed by the partial scrubbing of the combustion gases. Material
selection is also important for this section. Hastelloy alloy B is a material
1 generally recommended for the quench section, spray nozzles, and the duct work
leading into the quench chamber. This material is a nickel-molybdenum alloy
developed primarily for resistance to the corrosive effects of hydrochloric
acid. This alloy also possesses useful high-temperature properties. In oxi
dizing atmospheres, the alloy may be used at temperatures up to 1,400°F. In
reducing atmospheres, the alloy may be used at substantially higher
temperatures.
•\
f Hastelloy alloy B is particularly well suited for equipment handling hydro-
chloric acid at all concentrations and temperatures including the boiling
1 points. Hastelloy alloy B is easily fabricated, and can be forged and cold-
formed by a variety of methods. Most of the common welding methods can be
\ used to weld it, although the oxy-acetylene process is not recommended when
|j the alloy is to be used in corrosion service.
, Inconel alloy 625 and Incoloy alloy 825 are two other materials which show
good resistance to hydrochloric acid and could thus be used in the quench
section.
The composition of the quench water depends directly on the wastes being
incinerated. Table 5-14 summarizes the possible air pollutants that nay be
produced and captured by the quench tower and by other air pollution control
devices. Because chlorinated organic compounds constitute the most common
type of hazardous waste disposed of by incineration, quench waters are gener-
ally acidic and must be neutralized before discharge. Although hazardous
species would not typically be present in quench water, this is typically
verified before the effluent is disposed. Quench water is normally combined
1 with the scrubber effluent for treatment and disposal.
5-129
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GAS
OIL'
AIR
AUX.
REACTION
CHAMBER
WASH FEED
WATER FLOW
QUENCH
SCRUBBER
STACK
ASH
Figure 5-51. Generalized schematic of incinerator facility.
SECONDARY
AIR
LIQUID
PUMPA1U
DRUMMED NON-fUMf
PLENUM AIR
,*HJ v™, L_twuca^fut
WUEI/ASM t SIEVE TOMDOBNISTU)
NATOUASM
ASH/DRUMS
Figure 5-52.
Schematic of rotary kiln facility with quench
spray chamber and venturi scrubber.
5-130
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TABLE 5-14. POTENTIAL AIR POLLUTANTS FROM HAZARDOUS WASTE INCINERATION
Likely removal
Hazardous waste
Air pollutants
Quench
tower
Scrubber
sites
Baghouse
or ESP
Organic materials containing:
1.
2.
3.'
4.
5.
6.
7.
8.
C, H, 0 only
Cl
Br
F
S
P
N
C, N
b
Thermal NOx
HC1
HBr
HF
SOx
PaOs
NOx
CH~ compounds
-
X
X
X
-
-
-
X
c
X
X
X,
A
1C
xe
c
X
-
-
-
_
_
_
-
-
Materials containing some
morgana c components: *
1. Nontoxic minerals only,
e.g., Al, Ca, Na
2. Toxic elements including
metals, eg., PS, As, Sb
Particulate matter X
Particulate matter X
Volatile species^
X
X
Based on complete destruction (i.e., oxidation) of hazardous waste.
NOx produced from atmospheric nitrogen at high temperatures (about 1,100*C) in the
incinerator.
'NOx is not normally controlled. Special scrubbers have been developed for NOx con-
trol in special circumstances.
Alkaline scrubbers are required for efficient SOx control.
3
'Special high efficiency scrubbers are needed to collect phosphoric acid mist.
A portion of the inorganic components may be removed as bottom ash from the
incinerator.
Certain elements from volatile species (e.g., ASaOj) that condense out in the
exhaust gas as the temperature falls. They can be collected in the gas phase by
special scrubbers or as particulate matter at low temperatures by normal particulate
control equipment.
5.12.1.2 Scrubber Effluents—
Characterization of scrubber effluents varies considerably from that of the
quench water. Quench towers are primarily used to reduce the combustion gas
temperatures prior to entering the scrubber, whereas scrubbers are primarily
used to reduce noxious gases from the combustion gas prior to discharge to
atmosphere. Commonly used scrubber types, design, material of construction,
scrubber selection for specific applications, advantages, and disadvantages,
etc., are covered in detail in Chapter 4.
5-131
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In an incinerator burning chlorinated organic compounds, if water is the
scrubbing fluid, the wastewater effluent will contain suspended particulates ,
dissolved HCl (i.e., hydrochloric acid), and other soluble constituents which
may be present (e.g., trace quantities of organics and waste constituents that
may be soluble). If alkaline scrubbing solutions are used, the HCl will
undergo neutralization reactions to produce additional water and salts (either
NaCl or CaCl2 depending on whether NaOH or Ca(OH)2 was used in the scrubbing
solution). Because alkaline materials are often used in excess, residual
amounts of these substances will be present. The wastewater will also contain
suspended particulates and any soluble combustion products.
The venturi scrubbing process involves either a single pass of the scrubbing
fluid or recirculation of the scrubbing fluid. If recirculation is used,
scrubber fluid is recirculated through the venturi scrubber until the total
dissolved solids (TDS) content reaches approximately 3% [39]. When this
occurs, a portion of the scrubbing fluid is removed (blowdowri) and new scrub-
bing fluid is added to make up for the fluid lost as blowdowri. The blowdown
from the single pass or recirculation scrubbing systems is neutralized (as
needed) before delivery to on-site wastewater treatment processes, on-site
storage facilities (e.g., evaporation ponds), or dispensing to the municipal
sewer or a receiving water body. Single pass and recirculating scrubber
systems are illustrated in Figure 5-53 and 5-54, respectively.
Alternative types of scrubber systems have been designed to recover HCl pro-
duced during organochlorine incineration. Such systems can produce commercial
grade hydrochloric acid streams with concentrations ranging between 20% and
60% HCl [39]. These systems utilize aqueous solutions to absorb HCl from the
combustion chamber effluent gas stream, and the resulting solution is concen
trated via water extraction procedures. Residual HCl that may be left in the
remaining combustion gas stream can be removed by passing this stream through
an alkaline neutralization tower, or by using conventional gas scrubbing
procedures.
Characteristics of Slowdown from Recirculating Scrubbers—Blowdown from recir-
cu lation systems occurs when the salinity reaches approximately 3 percent.
This relates to a TDS value of 30,000 milligrams per liter [39]. The blowdown
rate is variable, depending on the amount of chlorine in the liquid
incinerated and on the liquid feed rate.
Characteristics of Single-Pass Scrubber Effluent--The characteristics of
single-pass scrubber effluents are highly variable, depending on the chlorine
content of the liquid incinerated, the liquid feed rates, the scrubber
solution feed rates, and the efficiency of the scrubber, Because single-pass
systems have so many variables, it is not possible to obtain a normal or aver-
age TDS concentration. However, it is possible to estimate the magnitude of
TDS concentration. This has been done by using two sets of data shown in
Tables 5-15 and 5-16. The data were picked because their operating parameters
produced two extremes in scrubber water quality, as shown in Table 5-15.
Generally, scrubber wastewaters will contain TDS concentrations less than
40,000 milligrams per liter.
5-132
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TO STACK AMO
ATMOSPKK
t
;*k
SCIUSKU SOLUTION
(NOMINAL lOtMAMI
PACKING
ANONlOH
$
auiicn SOLUTION
HOLOIWTAMC
PUMP
i
tBBBB
A ff
t*»* -:1-
^,->-
fe
\
1
/
— otMisru
~ SPtAYS
"- PACMD ICO
SCDUIKi)
|
WASTE FOT
Cl TV — "~ — —
WATCH
"^P^l-
Hdl OUOCH I
l?l «-«•
^•^ • rn^-
mAnn
UOUIO SCJHJIICt
ffRUCNT
-.
i '
NEUTRALIZATION
TANK
kfiO NCUTRALIZ1NS MOH OR
ACID AM DILUENT VATER
PRIOR TO DIS
MKll
KILN
WUTtALIZCD SOLUTION TO STVKI SYSTW (M
CVAmiATION/STOIACt MMO
Figure 5-53. Single-pass scrubber system [37]
TO STACK AND
ATMOSPHERE
SCRU8IER SOLUTION
(NOMINAL 10 *N«OH)
PACXINC
ADO WATER
ANOMOH
OEMISTER
SPRAYS
&— PACKED IED
WASTE RED
scautia SOLUTION
HOLOINB TANK
^Q-J
PUN*
UQUIOSCWIKX
EFRUENT
WUTRAUZAnON
TANK
-AOO NEUTRAL! ZINC HMH OR
ACID AND DILUENT HATER
PRIOR TO DISPOSAL
KILN
NEUTRALIZED SOLUTION TO SEWER SYSTEM OR
EVAPORATION/STORAGE PONO
Figure 5-54. Recirculating scrubber system [37]
5-133
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TABLE 5-15. SCRUBBER WATER AND WASTE PARAMETERS FOR TWO
LAND-BASED LIQUID INJECTION INCINERATORS [39
Waste incinerated
Hexachlorocyclo-
pentadiene
Nitrochloro-
benzene
Fresh scrubber water feed rate
(liters/min)
Caustic solution feed rate
(laters/min)
Type of solution used
Liquid waste feed rate
(kg/hr)
Elemental chlorine content of
the waste
60
23.8
12% NaOH
52.8
77%
3,200
8.5
32% Ca(OH).
1,893
10%
Source: Reference 34.
Source: Reference 37.
TABLE 5-16. SCRUBBER WATER QUALITY [39]
Waste incinerated
Hexachlorocyclo-
pentadiene
Nitrochloro-
benzene
Chlorides (mg/L)
Calcium (mg/L)
Sodium (mg/L)
Total dissolved solids (mg/L)
11,000
—
25,670
36,670
1,300
530
—
1,830
It can be expected that the HC1 recovery processes will have much lower TDS
concentrations than systems which do not recover HCl because a large propor-
tion of the dissolved ions would be removed during recovery of the acid.
Scrubber effluents generally contain very little organic material due to high
waste destruction efficiencies required.
The particular gaseous pollutant of interest may require scrubbing with a medium
specific for the pollutant. Water is adequate for a gas such as HCl, but other
scrubber media may be required for S02, NO , etc. In some cases, multiple stages
are required to efficiently remove a combination of gaseous pollutants, with each
stage specific for given pollutant. Two-stage and three-stage scrubber systems
are illustrated in Figures 5-55 and 5-56, respectively. The type of technology
illustrated in Figure 5-55 is not normally utilized for a hazardous waste incin-
erator. It is presented here for scrubber review. The three stage scrubber
system illustrated in Figure 5-56 was implemented for a research project in an
attempt to very carefully scrub effluent from a pesticide incineration program.
5-134
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FEEDERS
SCRUBBER
WATER IN
2- STAGE
SCRUBBER
ASH
SCRU8IER
WATER OUT
Figure 5-55. Incineration system with two-stage scrubber
[40].
EXHAUST
INCINERATOR
FEED
INCINERATOR
, . N
SCJHJ1BEB CLYC6L
5CRUBBER SCRUBBE
SCRUBBER!
J
Figure 5-56. Incineration system with three-stage
scrubber [41].
5-135
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5.12.1.3 Ash--
Ash denotes the solid residue that remains after a material is incinerated.
Ash produced during incineration is primarily inorganic and falls into two '
basic categories. Fly ash consists of the ash that is entrained in exhaust
gases leaving the incinerator and which is usually captured in air pollution
control equipment. Bottom ash refers to the ash remaining in the combustion 1
chamber after incineration and is normally associated with inerts. The com-
position of the ash depends on the composition of the waste being incinerated
and can therefore Vary greatly. Because hazardous waste incinerators are
designed for complete destruction of toxic organic compounds, the ash normally
contains very little carbonaceous material. Solid materials not susceptible
to oxidation (e.g., glass or ceramic) consitute the major ash species. Amount
of ash produced is very small in relation to total mass of waste incinerated.
The relative proportion of fly ash to bottom ash is influenced by the waste
composition and the incinerator design and operation. As expected, no bottom ,
ash and relatively little fly ash result when liquid (except when liquids are *
from a complex chemical process that has inert materials in it or from a
blending procedure that creates incompatible reactions that produce inerts) or
gaseous wastes are incinerated.
5.12.2 Sampling and Analysis of Quench/Scrubber Water and Ash
t 1
Samples collected must be a representative sample of the whole water or ash.
A .-epresentative sample for water can be collected by using various techniques
and devices such as a coliwasa, automatic composite samplers like Isco,
Manning, pond sampler, weighted bottle sampler, etc. Representative samples
for ash can be collected by using devices such as a grain sampler, sampler
corer, trowel or scoop, etc. Sampling devices and strategies are covered in
detail in Chapter 3. Water samples are usually preserved because of any
unstable species with the addition of appropriate preservatives. Where pos-
sible, samples are stored in a cool (4°C) and dark area prior to shipment to
the laboratory for analysis. I
The analysis of samples is directed primarily at determining the concentration
f
• Principal chemical species known to be present in the waste incinerated •
and believed to be hazardous. In some cases these will represent dis-
crete chemical species such as nitrochlorobenzene and HCB. In other
cases, such as those involving the incineration of tarry wastes from ,
captan, rubber manufacturing and TDI, the analyses may have to be
restricted to a general class of chemical species such as total organic
chloride, total aromatic amine, etc.
• Primary decomposition products of waste such as chlorides, phosphates,
sulfates, nitrates.
i
Solids can be analyzed via soxhlet extraction and water via liquid-liquid
extraction. ^
5-136
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5.12.3 Handling of Quench/Scrubber Wastewater
Quench water and scrubber effluents are normally combined for treatment and
ultimate disposal. Depending on the scrubbing liquids used and the gaseous
contaminants removed, wastewater may contain chlorides, fluorides, sulfites,
sulfates, phosphates, bromides, and bromates, as well as particulate matter.
Liquid waste streams containing sodium fluoride can be treated with lime or
limestone slurry to yield the insoluble calcium fluoride. Sulfates, phos-
phates, and fluorides can be readily removed from the wastewater stream be-
cause of the low solubility of their calcium salts. Therefore, treatment
normally includes clarification (to remove particulates), neutralization (to
take care of any residual acid or base that may still be present), and dilu-
tion (to help control IDS levels). Particulates which are insoluble in the
scrubber fluid become suspended solids in the scrubber wastewater. If the
particulates dissolve in the scrubber fluid, they contribute to the waste-
water's IDS level. Suspended solids in scrubber wastewater generally present
little, if any, problems because their concentrations are usually less than 5
mg/L [39]. Suspended solids are usually removed by on-site settling ponds.
Overflow from settling ponds can be recycled to scrubber.
Wastewater with either high or low pH levels is neutralized prior to final
discharge (to a municipal sewer, or receiving stream). This is usually accom-
plished by adding either acid or base.
The high concentration of total dissolved solids (due to NaCl, CaCl2 and in I
some cases the excess NaOH not used to neutralize HCl) is also reduced. This--
is usually accomplished by piping scrubber effluents to in-plant treatment
systems or by diluting with other plant process streams and storing in a hold-
ing pond or lagoon.
In geographical locations with high evapotranspiration rates, solar evapora-
tion could be used as a method for disposing of scrubber vastewater. For such
a method to be considered environmentally acceptable, the scrubber wastewater
would have to be devoid of potentially volatile materials which are hazardous.
The ponds used for evaporation are periodically drained, and the accumulated
sludge removed. Quench/scrubber effluents, evaporation sludge and ash treat-
ment, and disposal options are illustrated in Figure 5-57.
For a discharge to a municipal sever (publicly-owned treatment works - POTW),
discharge must meet national general pretreatment standards and local POTW
requirements, and must have approval from local POTW authority for such a
discharge. By national pretreatment standards, pollutants introduced into
POTW by any source of a nondomestic discharge are not to inhibit or interfere
with the operation or performance of the works. The following pollutants may
not be introduced into a POTW:
1. Pollutants which create a fire or explosion hazard in the POTW
2. Pollutants which will cause corrosive structural damage to the
POTW, but in no case discharges with pH lower than 5.0, unless
the works is specifically designed to accommodate such discharges.
5-137
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AUXI
FU
(IF ME
LIQUID WAST!
.IARY
a
EDED)
»•)
AIR ^{_
BURNER
COMBUSTION
CHAMBER
i
WA
i
BURNER
RESIDUAL
LANDFILL
fER
_ CAUSTIC SOLUTION
""^ (OPTIONAL)
_ VENTURI
SCRUBBER
S
EPARAT
w/DEMI!
PACKED
NEUTRALIZATION »•
1
SOLIDS ON-S.TE
TREATMENT
OR TANK
>TER OR —
TOWER
LIQUID
EFFLUENT
ON-SITE
STORAGE
(EVAPORATION)
'LIQUID
SOLIDS
*" STACK
I GASEC
* EFFLU
ATMOSPHERE
(IFNE
SEWER SYSTEM
OR OTHER
WATER BODY
J
US
:NT
TION
EDED)
Figure 5-57.
Incineration process with emissions
treatment and disposal options [40].
3. Solid or viscous pollutants in amounts which will cause obstruc-
tion to the flow in sewers, or other interference with the opera-
tion of the POTW
4. Any pollutant, including oxygen demanding pollutants (BOD, etc.),
released in a discharge of such volume or strength as to cause
interference in the POTW.
5. Heat in amount which will inhibit biological activity in the POTW
resulting in interference but in no case heat in such quantities
that the temperature at the treatment works influent exceeds 40°C
(104°F) unless the works is designed to accommodate such heat.
Compliance with Prohibited Discharge Standards was required beginning August
25, 1978, except for the heat Standard which must be compiled with within 3
years, or August 25, 1981.
For a discharge to a receiving body, an NPDES permit will be required. Such a
discharge has to meet with the limitations set in the permit. Wastewater may
require costly treatments to meet the limitations set in the NPDES permit.
5-138
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The sludges or other sediments collected from settling ponds, evaporation
ponds, or other types of lagoons may contain unburned wastes or toxic trace
elements (abstracted from the combustion gases as particulates, or formed as
precipitates following chemical reactions occurring in the pond). Sludges
from scrubber processes are chemical sludges,- these are handled and treated
carefully and possibly differently from municipal sludges. In order to insure
the fewest adverse effects, they sometimes can be properly disposed of in an
approved hazardous waste landfill in accordance with federal guidelines
mandated by RCRA.
5.12.4 Handling of Ash
Bottom ash will contain primarily inorganic and carbonaceous compounds. Less
than 3% of the total weight of carbonaceous compounds will be trace compounds,
including heavy metals. These solids can be disposed of in landfills approved
for hazardous wastes.
5.13 FUGITIVE EMISSIONS
Fugitive emissions are those which result from occurrences such as leaks in
valves and piping, entrainment from open vents or piles of material, and
transfer operations [2]. Such emissions must be minimized and/or eliminated
at hazardous waste incineration facilities. This section discusses monitoring4
and techniques which may be used to control such emissions. Table 5-17 I*
illustrates areas having fugitive emission potential. I
The most likely areas of process oriented fugitive emissions are around rotat-
ing seals on kilns, piping joints and valves, ductwork leaks on the positive
pressure side of induced draft systems, ash handling system leaks, and quench
water scrubber liquid handling and treatment system leaks. For illustration
purposes, these areas are indicated in Figure 5-58. In the preprocess area,
handling, storage, and preparation of the waste for feeding into the inciner-
ator are critical operations to watch for fugitive emissions. Post-process
operations also can pose a problem, such as those which transport and treat
residue streams emanating from quenching, scrubbing, and post-treatment of
residue.
5.13.1 Significance of Observed Emissions
The two primary concerns regarding inspection and monitoring of fugitive emis-
sions are protection of the personnel around the operation itself and the
health and welfare of those residing outside the fence limits of the facility.
Working conditions within the facility must be in accordance with the exposure
constraints defined by OSHA regulations. Such emissions outside the facility
area are governed by applicable ambient air regulatory constraints.
5.13.2 Fugitive Emission Control
Control of fugitive emissions is best accomplished through implementation of
good engineering management practice. Initially, for a new facility a careful
leak check is performed without hazardous components being treated in the sys-
tem. Then during normal operation, visual inspection of all areas is performed
5-139
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TABLE 5-17. POSSIBLE SOURCES OF FUGITIVE EMISSIONS FROM
HAZARDOUS WASTE INCINERATOR SYSTEMS
WASTE PROCESSING AND FEED
Waste shipping
Waste unloading
Waste loading to preparation/processing plant
Waste processing
Crushing
Sizing
Washing
• Drying
Fine particulate removal or preparation for recycle
Material transfer in waste processing plant
Fugitives from loading/unloading storage bins
Waste feed hopper backflow
WASTE INCINERATION AND POLLUTION CONTROL
• Waste feed
• Waste incineration/feed
• Air flow leaks in the incinerator furnace and associated systems
• Ash collection
• Stack flue gas particulate removal and disposal systems
Ancillary equipment
Scrubber wastes/neutralization water
• Dust collectors
• Secondary combustion units (afterburners)
• Gas/steam storage lines and transport lines
Water treatment units
• Air coolers
• Mixing chambers
• Ancillary equipment leaks
REMOVAL OR DISPOSAL METHODS
Solids removal
• Ash transfer and storage
• Recycling systems
• Transfer lines for scrubber and cooler water
• Ash transport vehicles
• Ash transport
• Ash unloading
• Ash disposal
5-140
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I **** I "^*
1^-25—H T
-------
to minimize the occurrence of undetected leaks. These visual inspections
are then conducted regularly for any leaks, spills, odors, or other fugitive
emissions. All automatic control system alarms and emergency shutdown fea-
tures are also checked during the inspection to assure proper operation.
Any leak detected is recorded in a log. Immediate repair is accomplished if
feasible. If immediate repair is not feasible, as judged by the owner/operator,
a sample of the leak is then taken. If analysis shows that a hazardous component
is leaking at a concentration above 10 ppm, immediate temporary or permanent
repair should be affected. Maintenance data is recorded on the leak detection
and repair survey log. This includes a recheck to make sure the repair was
effective after maintenance.
For sources of fugitive dust emissions, several control alternatives are
possible. Table 5-18 illustrates the types of activities which can generate
dust (primarily around storage and ash handling), and the traditional tech-
niques or types of equipment used for air pollution control. Two decisions
need to be made initially for the control of particulate matter at a facility--
the degree of control required, and whether the system will handle dust, wet
or dry.
A wet-type particulate control system has limitations in that the wastewater
created must be collected and treated for discharge and/or recycle. Recycle I
systems are preferred because of compliance with the NPDES permit program. I
TABLE 5-18. CONTROL ALTERNATIVES FOR FUGITIVE DUST [42]
Control techniques
Wind breaks
Baghouses/ Covers and Spray Encrusting and physical Paving or
Type of activity
Transfer points
Conveyor belts
Hoppers, dumpers
Reclaimer*
scrubbers
X
X
enclosures
X
X
X
systems agents
X
X
X
X
arrangements spray vehicle
Stockpiling equipment
(bandwagons) X
Roads X
Piles X
Bins, silos, bunkers X X
5-142
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5.13.3 Fugitive Emission Measurement Devices and Methodology
Source monitoring, area monitoring, and fixed-point monitoring are methods
that can be used to detect fugitive emissions. Each of these is discussed
below.
5.13,3.1 Area Monitoring--
To perform area monitoring, a path through the area to be monitored is pre-
determined so that one following the path will pass within a given distance
(~3 ft) from all equipment within the area to be monitored. An instrument
operator with a portable analyzer follows the predetermined path through the
area and makes a complete survey around each piece of equipment. The operator
must be careful that both the upwind and downwind sides of the equipment are
sampled. If a concentration peak is observed, the location is recorded and a
subsequent, more detailed survey made to pinpoint the exact source.
This is the same general procedure used for the regular visual inspection, but
with a portable measuring instrument. An advantage of this method is that
leaks can be detected quickly. Disadvantages include the possible detection
of other emissions from outside the process area or improper readings due to
wind gusts and wind direction variability. One outstanding disadvantage cur-
rently is that continuous portable monitoring equipment for measuring specific
hazardous air pollutants are in the developmental stage and use would need to t
be examined carefully for appropriateness and utility. I
5.13.3.2 Fixed-point Monitoring—
In the fixed-point methodology, analyzers are placed at specific points in the
process area to monitor automatically for fugitive emissions. Individual sam-
plers are placed either near specific pieces of equipment or in a grid pattern
throughout the process area. If a concentration peak is observed, the
operator then performs an individual component survey to detect the leak.
5.13.3.3 Source Monitoring—
In this methodology, leaks are detected by examining each individual component.
Again, a portable detector is used. The instrument sample probe is moved
along the component surface with care that both upwind and downwind areas are
sampled. For sources such as drains, residue treatment tanks, and pressure
relief valves, the probe is placed in the center and then along the periphery.
When no portable instrument is available, individual components can be en
closed in a plastic bag (where practical). Any leaks accumulate in the bag
and are exhausted through a sampling train designed to measure flow and
prepare the sample for subsequent analysis by applicable laboratory techniques.
5.13.3.4 Current Instrumentation—
Particulate Measurements—Particulate sampling downwind of potential sources
can be accomplished using high volume samplers. These devices consist of a
pump and filter holder assembly encased in a weatherproof container. Ambient
air is drawn across a preweighed filter membrane by a calibrated/feedback pump
system. Filters are then weighed to obtain total mass particulate dust levels
and analyzed for appropriate components.
5-143
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Generally, a weather station is used to record wind speed, direction, tempera-
ture, atmospheric stability and barometric pressure over the sampling period.
Short-term ambient particulate levels can also be obtained by using either
piezoelectric or beta attenuation monotors. These devices provide quick
read-outs of ambient dust levels around a source. A number of readings can be
obtained over a long period of time. Analysis of the collections on the sub-
strate can be achieved as with the Hi-vol filter.
A particle size distribution of fugitive dust levels can be accomplished by
attaching size - selective units (impactors) to the inlet of a high volume
sampler. Particles are then collected on a substrate in each stage, depending
upon the aerodynamic diameter of the incoming particles.
Particles less than 15 urn (EPA's definition of inhalable particulates) can be
measured using dichotomous samplers. These devices consist of an elutriator
in series with an impactor. The elutriator collects particles less than 15 |jm
and the impactor divides them into two fractions (<2.5 fjm and >2.5 urn to
15 urn) which are collected on preweighed filters. Filters are then weighed
and analyzed as necessary.
Particles can also be classified using a beta attenuation device by employing
a small cyclone (inertial separator) in series with the pump. The cyclone
collects the >10 urn particles, which then allows an attenuation readout of the
<10 urn levels.
Measurement of Gases--Certain techniques for quantifying the fugitive gaseous
emission levels from sources are available, which "can obtain either (1) hydro-
carbon-less-methane values or (2) if high enough concentrations exist, detec-
tion of individual components. In the latter case, a tandem-coupled gas
chromatograph/mass spectrometer unit or GC alone would be employed for analy-
sis with samples obtained by capture in a plastic bag for subsequent analysis.
Charcoal and porous polymer tubes connected to air pumps to draw ambient air
across the median can be employed. The collection median is then solvent
eluted for laboratory analysis.
Direct reading of ppm levels can be accomplished using Drager® tubes which are
reactant impregnated substances. Ambient air is hand pumped through the col-
lection median and the ppm levels read according to a color change.
Ambient total hydrocarbon levels can be measured using portable field gas
chromatographs or hand-held flame ionization detectors. These devices operate
on the same principle as the laboratory GC's except they have field use
capabilities.
5.14 MATERIALS OF CONSTRUCTION
Materials of construction have been discussed for specific equipment through-
out this chapter. This section is a repository of general information on
various materials which may be encountered at a hazardous waste incineration
5-144
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facility. Included is information regarding trade names, corrosion
resistances, and typical uses of both ferrous and nonferrous metals and other
nonmetallic materials.
The general corrosion resistance properties are discussed. In most inciner-
ator, receiving, storage, feed situations, and residue handling, the flow
stream will contain contaminants, so corrosion problems will be maximal. This
section will allow the permit writer to augment his knowledge of the materials
involved and check the recommended application.
5.14.1 Metals
(1) Cast Iron - This material is found in many cast process components
such as pump bodies, impellers, valve parts, etc. Cast iron is a
general term applied to high carbon-iron alloys containing silicon.
Common varieties are: gray, white, malleable, ductile, and nodular.
The material is quite susceptible to oxidation or "rust".
Increasing the silicon content to over 14% produces an extremely
corrosion resistant material; e.g., Duriron, which is very hard and
resists erosion-corrosion (notable exception: hydrofluoric acid).
The alloy is sometimes modified by the addition of 3% molybdenum;
e.g., Durichlor or Durichlor 51, for increased resistance to hydro-
chloric acid and chlorides.
\
•. In addition to alloys.using silicon and molybdenum, other alloys
using nickel, chromium and copper also produce improved corrosion
resistance. Copper addition causes the metal to better withstand
attack from sulfuric acid. High nickel-chromium cast irons with and
without copper; e.g., Ni-Resist and Ni-Hard, produce very tough
castings to resist erosion-corrosion in near-neutral and alkaline
solutions or slurries.
(2) Carbon Steel - Carbon steel is alloyed, in various combinations,
with chromium, nickel, copper, molybdenum, phosphorous, and vanadium.
Low-alloy steels (2% total maximum alloying elements or less) are
generally the more corrosion resistant. However, like cast iron, it
is very susceptible to rusting.
Steel products are cast and also readily available in sheet, plate,
and structural forms, as well as in a variety of products. Steels
can be easily field cut and welded.
(3) Stainless Steel - Stainless steel has the same versatility of usage
as carbon steel, with greatly improved corrosion resistance. De-
sired corrosion resistant properties are produced by alloying at
least 11 percent of chromium. The chromium is reactive, but sets up
a passive film to inhibit further corrosion. The following is a
brief description of the five types of corrosion resistant alloys
most commonly used in chemical applications:
5-145
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Type 304 The basic 18% Cr-8% Ni type for relatively mild corrosion
resistance.
Type 316 The "18-8" type with 2.0/3.0% Mo for superior resistance
to pitting and to most types of corrosion, particularly in
reducing and neutral solutions.
Type 317 The "18-8" type with 3.0/4.0% Mo, which has moderately
better resistance than type 316 in some conditions, such
as high concentrations of acetic anhydride and hot acetic
acid.
"20" A 29% Ni-20% Cr steel with copper and molybdenum,
developed specifically for resistance to sulfuric acid.
Ni-o-nel A 42% Ni-21.5% Cr alloy with copper and molybdenum, devel-
oped to meet more severe corrosion and stress-corrosion
conditions than can be handled by the stainless steels but
where nickel-base alloys are not needed.
A popular fallacy is that stainless steels are generally resistant to all
environments. Stainless steels do have widespread application in resisting
corrosion, but also have limitations. In fact, under conditions involving
chloride-bearing solutions and stressed members, stainless steels are subject
to chloride stress corrosion cracking and thus are much less suitable than
alloyed steels. Stainless steels are also more susceptible than regular
steels to localized corrosion such as intergranular, crevice, and pitting
attack.
Consequently, many corrosion failures have resulted from the indiscriminate
use of stainless steels on the assumption that they were the "best." In
practice, stainless steels represent a class of highly corrosion-resisting
materials of moderate strength and cost that are the bulwark of the chemical
process industries when used with discretion.
(4) Aluminum and Alloys - Next to carbon steel and stainless steel,
aluminum represents a versatile metal for construction, available in
cast form and sheet, plate, and structural forms and in a variety of
commercially available process components.
Aluminum is reactive but develops a passive oxide film which pro-
tects it from further corrosion in many environments. This film
remains stable in neutral and many acid solutions, but is attacked
by alkalies. The passive film is produced after contact with the
chemical environment, unless the film has been artificially produced
through anodizing. Structural members are typically produced from
high-copper alloys, whereas process components are usually con-
structed of the low-copper or copper-free alloys, which have better
corrosion resistance.
(5) Magnesium and Alloys - A lightweight material often found on port-
able devices and vehicles, however one of the least corrosion
5-146
I
-------
resistant. It must generally be physically separated from other
metals or it will become a sacrificial anode for them. It is cap-
able of forming a good passive film,- however, the film breaks down
in salty air conditions, necessitating special coatings or other
surface preparations. Magnesium is susceptible to erosion-corrosion.
It is much more resistant to alkalies than is aluminum. It is
attacked by most acids except chromic and hydrofluoric. The
corrosion product in HF acts as a protective film.
(6) Lead and Alloys - Used often on corrosion resistant applications in
such forms as: sheet linings, solder, cable sheath, bearings, and
piping. Lead forms protective films consisting of corrosion prod-
ucts such as sulfates, oxides, and phosphates. It is subject to
erosion-corrosion because of its softness. Chemical-resistant lead,
containing about 0.06% copper, is resistant to sulfuric, chromic,
hydrofluoric, and phosphoric acids, neutral solutions, and seawater.
It is rapidly attacked by acetic acid and generally not used in
nitric, hydrochloric, and organic acids.
(7) Copper and Alloys - Copper alloys are found in pump bodies and
impellers, process component bodies and parts, and in pipe tubing
and fittings, tanks, bearings, wire and screen.
A good chemically resistant material, copper is not corroded by
acids unless oxygen or other oxidizing agents (e.g., HN03) are
present. Copper-base alloys are resistant to neutral and slightly
alkaline solutions (exception: ammonia). Common alloys are:
brass, bronze, and cupernickel. Bronze, aluminum brass, and cupra-
nickel are stronger and harder than copper and brass and less
subject to erosion-corrosion.
(8) Nickel and Alloys - A workhorse in severe corrosion applications,
nickel and its alloys are found in many commercially available
process components, expecially pumps, valve parts, and other criti-
cal process parts. Nickel is resistant to many corrosives and is a
natural for alkaline solutions, found in many tough applications on
caustics. It shows good resistance to neutral and slightly acid
solutions. It is not resistant to strongly oxidizing solutions;
e.g., nitric acid, ammonia. Among the common varieties.-
Monel - natural for hydrofluoric acid
Chlorlmet 3 and Hastelloy C - two of the most generally
corrosion-resistant materials commercially available
Chlorlmet 2 and Hastelloy B - very good in cases where
oxidizing conditions do not exist
(9) Zinc and Alloys - Not a corrosion-resistant metal, chiefly used in
galvanized steel.
f
5-147
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(10) Tin and Tin Plate - Usually found as a coating and used in solder
and babbit bearings, it is corrosion resistant, easily formed and
soldered; and provides a good base for organic coatings. Tin has
good resistance to dilute mineral acids in the absence of air, and
many organic acids, but is corroded by strong organic acids;
generally not used for handling alkalies.
(11) Titanium and Alloys - A newcomer tc corrosion resistant construction,
is available as castings in pumps, valves, and other process com-
ponents. Titanium is a reactive metal which depends on a passive
oxide film for corrosion resistance. Titanium has resistance to
seawater and other chloride salt solution; hypochlorites and wet
chlorine; and nitric acid. Salts such as FeCl3 and CuCl2/ which
tend to pit other metals do not corrode titanium. It is not
resistant to relatively pure sulfuric and hydrochloric acids.
5.14.2 Nonmetallics
(1) Natural and Synthetic Rubbers - Rubber is an important process mate-
rial with an extensive range of uses: hoses, tanks, tubing, gas-
kets, pump diaphrams and impellers, sheets, liners, etc. Rubber has
excellent chemical resistance, and has been a standard for handling
of hydrochloric acid containers. Generally, the synthetic rubbers
have better chemical resistance than the natural rubbers. Vulcaniza
tion, the process of hardening rubber by adding sulfur and heating,
can produce a wide range of hardnesses from soft gaskets to hard
pump impellers. Corrosion resistance generally increases with
hardness.
-\
A wide variety of synthetic rubbers is available, including combina-
tions with plastics. In developing the various products, plasticiz-
er fillers and hardeners are compounded to obtain a large range of
properties, including chemical resistance. Table 5-19 presents a
list of brand names of plastic materials and the corresponding
generic type of plastic.
Table 5-20 shows chemical resistance and other properties of commer-
cially available rubber products. One of the newer elastomers which
should be added to the list is Hypalon, which has excellent resist-
ance to oxidizing environments such as 90% sulfuric acid and 40%
nitric acid at room temperature.
(2) Plastics - Used extensively in chemical process applications as
process component bodies and parts, tanks and tank liners, pipe,
valves, tubing, and fittings, sheets, structurals, etc., plastics
are high-molecular weight organic materials that can be shaped into
a variety of useful forms.
When comparing plastics to metals, the former are softer and weaker,
more resistant to chloride ions and hydrochloric acid, less resist-
ant to concentrated sulfuric ad oxidizing acids such as nitric, less
5-148
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TABLE 5-19. BRAND NAMES OF POLYMERIC MATERIALS
Material
Aeroflex
Alathon
Araldite
Avisco
Bakelite
Beelte
Dacron
Durcon
Durez
Dypol
Epon
Excon
Kel F
Lauxite
Lucite
Lustrex
Moplen
Chart classification
Polyethylene
Polyethylene
Epoxy
Urea
Phenolic
Urea
Polyester
Epoxy
Phenolic
Polyester
Epoxy
Polypropylene
Fluorocarbon
Urea
Methyl methacrylate
Polystryene
Polypropylene
Material
Mylar
Nylon
Penton
Plexiglas
Plioflex
Polythene
Pro-Fax
PVC
Resinox
Saran
Styron
Teflon
Tygon
Vibrin
Vinylite
Viton
Chart classification
Polyester
Nylon
Polyether
Methyl methacrylate
Vinyl
Polyethylene
Polypropylene
Polyvinyl chloride
Phenolic
Vinyl
Polystyrene
Fluorocarbon
Vinyl
Polyester
Vinyl
Fluorocarbon
.1
resistant to solvents, and have .definitely lover temperature limitations.
Plastics, when subjected to corrosive environments do not fail as
metals do. Rather than dissolving, they are degraded or corroded
because of swelling, loss in mechanical properties, softening,
hardening, spalling, and discoloration. Table 5-21 lists the
properties of some commercially available plastics.
For ease of using this table, commonly used tradenames and other
designations are listed here alphabetically in reference to the
chart classification to which they belong:
(3) Other Nonmetallics - Used as materials of construction and lining of
process systems:
Ceramics - compounds of metallic and nonmetallic elements,- include
magnesia, brick, stone, fused silica, stoneware, glass,
clay tile, procelain, concrete, abrasives, mortar, high
temperature refractories. Most ceramics exhibit good
chemical resistance, with the exception of hydrofluoric
acid and caustic.
Carbon and Graphite - often used for shaft seals; inert to many
chemical environments,- good resistance to alkalies and
most acids; attacked by oxidizing acids such as nitric,
concentrated sulfuric, and chromic; also attacked by
fluorine, iodine, bromine, chlorine, and chlorine dioxide.
5-149
-------
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Wood - Typical chemically resistant woods are cypress, pine,
oak, and redwood; generally limited to dilute chemicals;
strong acids, oxidizing cards, and dilute alkalies attack
wood.
5.15 MISCELLANEOUS CONCERNS
5.15.1 Personnel Health and Safety
The health and" safety of the public and of plant employees should be consid-
ered of major importance in any industrial installation design or operation.
Although the greater part of this manual deals with possible injury to public
health and property, the effect of plant emissions on the plant employees is
also a primary-concern. Often, plant employees in direct contact with the
industrial processes for extensive periods of time are in the greatest imme-
diate danger. This section will not attempt to define the multitude of work-
related hazards facing hazardous waste incinerator workers., but will concen-
ntrate on these areas of concern: equipment for worker protection and
procedures for worker protection [43].
• Synthetic Gloves - These provide skin protection for the hand and arm, as
required. Synthetic means rubber, polyethylene, or other impervious
materials. Full-arm-length gauntlets or sleeve protectors can also be
used.
• Synthetic Aprons - Materials specified for synthetic gloves also apply to
aprons. Disposable-type coveralls or laboratory coats may be preferred
for many tasks at an incinerator facility.
• Respiratory Protective Devices - There are three types of these devices.-
(1) air-purifying respirators, (2) supplied-air respirators, and (3)
self-contained breathing apparatuses.
The air-purifying respirators utilize an aerosol filter for protection
against particulate matter and/or a chemical cartridge for protection
against certain known gases of vapors. The choice of cartridge is
dictated by the hazard involved.
The supplied-air respirators are supplied with air remote from the hazard-
ous location, usually through a breathing-air manifold and hoses. The
self-contained breathing apparatus is normally used only in emergency
situations. Use only devices that are certified by NIOSH.
• Adequate Ventilation - Ventilation in an area must be sufficient to
prevent harmful exposure to toxic materials. The threshold-limit value
(TLV) for an individual chemical vapor or type of dust refers to the
time-weighed concentration for a normal workday, under which
it is believed that nearly all workers may be repeatedly exposed, day
after day, without harmful effect. If this value is exceeded, then a
"ceiling" value applies. This ceiling value should not be exceeded
(emergency situations such as spills require the use of protective
equipment). Exposure to concentrations above the TLV
5-152
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up to the ceiling value are not desirable, but are permitted as long as
the overall eight-hour time-weighted average (TWA) does not exceed the
TLV.
If inadequate ventilation is indicated (TLV is exceeded) for any opera-
tion or area, immediate use of a personal air-supply system is engaged.
A permanent solution involving good engineering practices is then
desirable and should be implemented as soon as possible.
• Full Suit - This is a suit that provides head-to-toe protection for the
hazard involved.
Line Breaks - Line breaks include broken flanges on lines not previously
exposed to the atmosphere, and drained and repacking of valves and pumps,
where there exists a potential for hazardous streams in concentrated form
or under pressure. In this type of operation, the following protective
equipment is usually required: full-rubber acid-suit consisting of
rubber coat, rubber pants, acid gloves, rubber boots under the pants, and
rubber hood.
• Repairs - Repairs apply to work performed on equipment or lines that
handled hazardous waste streams, which had previously been opened to the
atmosphere, and which have been drained and proven to be under no pressures.
Since the hazardous potential still exists, goggles or an approved hood j
and gloves are typically required. After flushing with water—or a . I
neutralizer agent where feasible—and the danger potential no longer
exists, as determined by supervision, hazardous-material protection is no
longer required. If the underfoot area is still puddled or vet from
flushing and draining, rubber overshoes are usually required.
If a pump is not delivering, and troubleshooting or priming is necessary,
goggles and gloves with coat or apron are worn even though no breaks in
the line have occurred.
5.15.2 Facility Housekeeping
Good housekeeping plays a key role in occupational health protection. Basic-
ally, it is another tool in addition to those other facility safeguards listed
for preventing dispersion of dangerous contaminants. Housekeeping is always
important; where there are toxic materials, it is paramount.
Immediate cleanup of any small spills of toxic material is a very important
control measure. A regular cleanup schedule using vacuum cleaners or lines is
the only truly effective method of removing dust from a work area, an air
hose for blowing away dust is never used.
A high standard of housekeeping is the most important single factor in the
prevention of fire. Many types of waste and rubbish are susceptible to spon-
taneous ignition. Practically all organic materials have a tendency to heat
spontaneously. This tendency is greater for those containing oil, solids when
pulverized, and vegetable or animal fibers, especially when wet. Many materi-
als which are safe at room temperature will heat spontaneously after prolonged
5-153
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exposure to high temperatures, such as accumulations occurring in ducts or on
heated pipes.
Accumulations of all types of dust are cleaned at regular intervals from
overhead pipes, beams, and machines, particularly from bearings and other
heated surfaces. It must be understood that all organic as well as many
inorganic materials, if ground finely enough will burn and propagate flame.
Roofs also are kept free from combustible refuse. Such cleaning perferably is
done by vacuum removal, because blowing down with air may disperse dusts into
dangerous clouds.
5.15.3 Maintenance
Testing is a prime activity in a maintenance program, particularly for a
hazardous waste incineration facility. While alarm systems, spill-alert sys-
tems, and fail-safe devices are available, a testing program usually peri-
odically creates situations which require fail-safe devices to demonstrate
their operation. For instance, pressure testing of pipe, valves, and fittings
along with hydrostatic testing of storage tanks will do this. Other tasks
such as visual and electronic inspections will make up the remainder of a
maintenance program and are included on prepared forms. These forms state the
optimum timing for each inspection as well as the required frequency.
Incidences of excess emissions can be reduced by good operation and mainten-
ance (O&M) practices and a comprehensive preventative maintenance program.
With these practices, control equipment can provide maximum benefit.
while maintenance activities are not repetitive in-the same manner as operat-
ing tasks, the maintenance function can be formalized. Available to facility
management are maintenance management information systems, inventory and mate-
rials control systems, scheduling algorithms, work standards, indirect work
measurement, and replacement theory.
A mechanism which is becoming more prevalent as equipment and technologies
increase in sophistication is contract maintenance. Air pollution control
equipment lends itself particularly well to this concept and appears attrac-
tive to new facilities which own several pieces of control equipment [44].
From the vendor's perspective, the advantages of providing a maintenance
contract are:
(1) Close surveillance of the system's performance, especially during
the warranty period.
(2) Immediate identification and troubleshooting of malfunctioning
components.
(3) Avoidance of customer complaints.
(4) Operational experience that facilitates product improvement.
(5) Quick handling of emergency situations.
5-154
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(6) A well functioning system that is the best recommendation for sales
of additional systems.
From the user's point of view, the benefits of contract maintenance are:
(1) Plant personnel do not have to be thoroughly trained in equipment
maintenance, thus allowing them to devote their time to process
equipment.
(2) Technological troubleshooting and problem diagnosis are not usually
in-house resources.
(3) Plant personnel do not necessarily have the knowledge to improve
equipment performance.
(4' Plant personnel may lack awareness of alternative supplies and
suppliers.
(5) Expenditures for larger crews, repair facilities, tools, and
measurement instruments are reduced.
(6) Previous experience on similar equipment and applications can be
used.
(7) Intrepretations of causes of component failure can be provided.
(8) Contract maintenance programs are more effectively regulated and
administered than are in-house programs.
(9) Dirty and hazardous jobs do not have to be performed by plant
» personnal.
j (10) Fluctuating workloads due to startup and seasonal variations can
g be handled easily.
, An in-house regular maintenance/repairs program entails:
' (1) Establishing a record system wherein periodic maintenance of each
incinerator component is scheduled for completion by a qualified
person.
(2) Cleaning, lubricating, and adjusting equipment by operating
personnel as part of their daily or weekly task.
(3) Certifying that maintenance has been performed.
(4) Recording major repairs separately and completely.
i
(5) Thoroughly reporting each inspection, including condition of
furnace, repairs performed, and expectation of future repairs
or major overhaul.
5-155
\
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(6) Inspecting components subject to rapid wear or damage weekly, at
a time when such components are not being operated.
5.15.4 Firefighting/Emergency Personnel and Equipment
In addition to automatic sprinkler and extinguisher equipment, an incident
confined to a limited area and that can be safely handled by a select emergen-
cy squad does not directly involve the overall emergency control program. If,
however, such an incident should escalate beyond the capability of these
forces, they have the authority to request the activation of the emergency
program.
A fire emergency plan includes:
(1) An emergency squad composed of personnel from operations, mainten-
ance, front office supervision, and guard force--specifically
selected and trained in emergency control techniques and equipment.
(2) Emergency planning taking into account the plant's alarm system,
communications, organization responsibilities, evacuation possi-
bilites, available emergency equipment, mutual aid arrangements, and
traffic control.
(3) Emergency crews engaged in continual training.
(4) Emergency squad members thoroughly trained in comprehensive
first-aid treatment.
(5) Emergency squad members familiar with firefighting equipment.
The emergency squad composed of personnel from operations, maintenance, front
office supervision, and guard force -- specifically selected, and trained in
emergency control techniques and equipment. The exact number of employees on
an emergency squad will vary depending on the potential hazard and size. Only
if an emergency cannot be handled by this select squad, should the emergency
control organization be activated.
Emergency planning also take into account the plant's alarm system, communica
tions, organizational responsibilities, evacuation possibilities, available
emergency equipment (and where it is located), dangers and emergency situa-
tions both inside and outside the plant (such as bomb threats), mutual-aid
arrangements and traffic control. A manual containing the relevant informa-
tion is prepared and distributed to those responsible for executing the plan.
This is reviewed at least annually, and updated as needed.
Emergency crews must undergo continual training because the time available to
respond to an actual emergency is usually quite limited. Furthermore, the
infrequency of calls to action can, with time, erode the ability of crews to
respond with the speed usually required. Crews are typically provided for all
shifts, and be trained to handle all types of emergencies: fire, toxic-gas
releases, chemical spills, serious injury, and personnel rescue.
5-156
-------
Emergency-squad members are usually thoroughly trained in comprehensive first-
aid treatment, including cardiopulmonary resuscitation, handling of breathing
apparatus, and emergency rescue procedures, and are familiar with station and
ambulance first-aid equipment. In addition, they learn the different types of
fires, extinguishing agents, the proper protective clothing for firefighting,
and become familiar with firefighting equipment, including hoses, nozzles,
portable extinguishers, wheel units, fire trucks, and with the plant's fire-
protection systems. Finally, field training in firefighting with protective
clothing includes experience extinguishing "Christmas-tree," impingement, pan
and spill, and other types of fires.
At a sprinklered property, the most important function of men assigned to the
emergency organization is to assure at all times that the automatic sprinkler
protection will operate as intended. At the start of the fire it must be made
certain that sprinkler valves are open and fire pumps operating as needed;
during the fire, that valves are not closed too soon; and after the fire, that
opened sprinklers are replaced and protection restored promptly.
An emergency squad is designed to be capable of containing small fires, pre-
venting them from developing into large, uncontrollable ones that can cause
loss of life and property.
5.15.5 Stormvater Diversion
Stormwater drainage and other innocuous discharges are segregated and handled
within the battery limits of the incinerator facility. These streams are
normally collected and directed by pipe, drainage ditches, or area grading
through one outlet from the area to a local feeder ditch. The single outlet
or outfall also contain a spill control structure and gate which can be closed
to contain contaminated drainage that may occur due to leaks or spills in the
facility area. Feeder ditches generally border the plant sites along roadways
and eventually drain outside the plant [45].
Facility process areas are usually paved and curbed or diked to contain leaks,
spills, and washdowns, and these directed to a process sump area. The process
sumps are pumped to the appropriate waste treatment facility.
Outlying facility storage tanks, pumps, and unloading facilities are curbed,
diked, or paved for leak and spill control to prevent contamination of area
drainage. The contained areas are then drained and valved to allow normal
storm water drainage. These valves, which are normally closed, are opened for
storm water drainage. In the event a contamination occurs, it is contained
for subsequent treatment and appropriate disposal.
Other general features relative to plant drainage are:
(1) Valves used for the drainage of diked areas are normally manual,
open-and-close design. The condition of the retained stonowater is
determined before drainage, especially if such drainage of impounded
waters goes into water courses and not into wastewater treatment
plants.
5-157
\
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(2) All plant drainage systems, if possible, flow into ponds, lagoons,
or catchment basins designed to retain materials less dense than
water. Consideration is also given to possible chemical reactions,
if spilled chemicals are commingled.
(3) If plant drainage is not engineered as above, the final discharge of
all in-plant drainage ditches is equipped with a diversion system
that could, in the event of an uncontrolled spill, be returned to
the plant for treatment, the objective being to work toward a
closed-cycle system.
(4) Where drainage waters are chemically treated in more than one treat-
ment unit, natural hydraulic flow is usually used. If pump transfer
is needed, two pumps are typically provided, and at least one of the
pumps is permanently installed.
5.15.6 Flue Gas Plume Aesthetics
Finally, the aesthetics of the flue gas plume should be considered. In a com-
bustion gas which has been quenched with water, but from which no heat has been
removed, the moisture content can be on the order of 0.5 Ib of water vapor per
Ib of dry gas. This creates a moisture plume which can persist for a consider-
able distance depending upon ambient conditions. A water vapor plume does not I.
violate any code but may be undesirable because of its visibility. A heavy I
moist plume falling on a non-plant area may be interpreted as a nuisance. This.*
could be an important aesthetic consideration which must be specifically
considered for each case. A stack gas moisture plume can be reduced by:
(1) installing a cooling system for cooling recycled scrubbing water or by the
use of cold once-through water for water cooling of the gases, or (2) installing
a gas dehumidification and reheating system to reduce the relative humidity of
the stack gas [17].
5.16 TECHNICAL ASSISTANCE
Other books and manuals which have applicability to overall facility design,
operation, and monitoring for hazardous waste incinerators are:
Peterson, D. The OSHA compliance manual. New York, McGraw-Hill, 1980.
241 p.
Budinski, K. Engineering materials: properties and selection. Engle-
wood Cliffs, NJ; Reston Publishing; 1980. 436 p.
Conway, R. A.; and Ross, R. D. Handbook of industrial waste disposal.
New York, Van Nostrand Reinhold, 1980. 565 p.
Metry, A. A. The handbook of hazardous waste management. Westport, CT;
Technomic Publishing Co.; 1980. 446 p.
Scott, R. A., ed. Toxic chemical and explosives facilities: safety and
engineering design. Symposium proceedings; 1978 September,- Miami Beach.
Washington, American Chemical Society, 1979. 352 p.
5-158
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5-17 REFERENCES
1. Kovalick, W. W., Jr. State decision-makers guide for hazardous waste
management. Washington, DC,- U.S. Environmental Protection Agency,- 1977.
103 p. EPA-SW-612.
2. Wallace, M. J. Controlling fugitive emissions. Chemical Engineering.
86(18):78-92, 1979 August.
3. Wirth, G. F. Preventing and dealing with in-plant hazardous spills.
Chemical Engineering. 82(17)=82-96, 1975 August.
4. Development of an emergency response program for transportation of
hazardous waste. Washington, DC; U.S. Environmental Protection Agency,-
1979 March. 333 p. EPA-SW-171C.
5. Accident prevention manual for industrial operations, seventh edition.
Chicago, National Safety Council, 1974. 1523 p.
6. Handbook of industrial loss prevention, second edition. New York,
McGraw-Hill Book Company, 1967.
7. Houghton, A. J.; Simmons, J. A.; and Gonso, W. E. A fail-safe transfer .
line for hazardous fluids. Proceedings of the 1976 national conference r
on control of hazardous material spills,- 1976 April 25-28; New Orleans, j
Rockville, MD; Information Transfer, Inc.; 29-32.
8. Recommended good practices for bulk liquid loss control at terminals and
depots. Washington, DC; American Petroleum Institute; 1971. API tech-
nical bulletin No. 1623.
9. Recommended practices for bulk loading and unloading of flammable liquid
chemicals to and from tank trucks. Washington, DC; Chemical
Manufacturers Association,- 1975. CMA technical bulletin No. TC-8.
10. Loading and unloading flammable chemicals, tank cars. Washington, DC;
Chemical Manufacturers Association,- 1975. CMA technical bulletin No.
TC-29.
11. Loading and unloading corrosive liquids, tank cars. Washington, DC;
Chemical Manufacturers Association; 1975. CMA technical bulletin No.
TC-27.
12. Huibregtse, K. R.; Sholz, R. C.,- Wullschleger, R. E.; Moser, J. M.;
BoHinge, E. R.; and Hansen, C. A. Manual for the control of hazardous
material spills. Volume one - spill assessment and water treatment
techniques. Cincinnati, OH; U.S. Environmental Protection Agency,- 1977
November. 490 p. EPA-600/2-77-227.
13. Materials handling. Chemical engineering deskbook. Chemical Engineering.
85(24), 1978 October. 152 p.
5-159
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14. Perry, R. J.; and Chilton, C. J. Chemical engineers' handbook, fifth
edition. New York, McGraw-Hill Book Company, 1973.
15. Gregory, R. C. Design of hazardous waste incinerators. Chemical
Engineering Progress. 77(4):43-47, 1981 April.
16. Liquids handling. Chemical engineering deskbook. Chemical Engineering.
85(8) , 1978 April. 220 p.
17. Novak, R. G.; and Clark, J. N. Impact of RCRA on hazardous waste incinera-
tion system design. Paper presented at the Chemical Manufacturer's
Association seminars on disposal of hazardous wastes. Newark, NJ; Chicago,
IL; Atlanta, GA; Kansas City, MO; Houston, TX; and San Francisco, CA;
1979-1980.
18. DeMarco, J.; Keller, D. J.; Leckman, J.; and Newton, J. L.
Municipal-scale incinerator design and operation. U.S. Department of
Health, Education, and Welfare, 1969. Public Health Service Publication
No. 2012. 98 p.
19. Bonner, R. F.; and Petura, R. C. Disposing of liquid/fluid industrial
wastes. Pollution Engineering. 11(10) :46-48, 1979 October.
20. Shields, E. F. Prevention and control of chemical spill incidents.
Pollution Engineering. 12(4):52-55, 1980 April.
21. D'Alessandro, P. L.; and Cobb, C. B. Hazardous material control for bulk
storage facilities. Proceedings of the 1976 national conference on
control of hazardous material spills; 1976 April 25-28; New Orleans.
Rockville, MD; Information Transfer, Inc.; 39-43.
22. Danielson, J. A., ed. Air pollution engineering manual, second edition.
Research Triangle Park, NC; U.S. Environmental Protection Agency; 1973
May. 987 p. AP-40.
23. Payne, W. R. Toxicology and process design. Chemical Engineering.
85(10):83-85, 1978 April.
24. Franconeri, P. Selection factors in evaluating large solid waste
shredders. Proceedings of 1976 national waste processing conference,-
1976 May 23-26; Boston. New York, The American Society of Mechanical
Engineers, 233-247.
25. Robinson, W. D. Shredding systems for mixed municipal and industrial
solid wastes. Proceedings of 1976 national waste processing conference,-
1976 May 23-26; Boston. New York, The American Society of Mechanical
Engineers, 249-260.
26. Rinker, F. G. Controlled disposal of containerized toxic materials.
1979 national conference on hazardous material risk assessment, disposal
and management; 1979 April 25-27; Miami Beach. Silver Spring, MD; Infor-
mation Transfer, Inc.; 107-111.
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27. Corey, R. C., ed. Principles and practices of incineration. Wiley-
Interscience, New York, NY; 1969. p. 250.
28. Gable, L. W. Installation and calibration of thermocouples. ISA Trans-
actions. 13(l):35-39, 1974 January-March.
29. Slomiana, M. Selecting pressure and velocity head primary elements for
flow measurement. Instrumentation Technology. 26(11):40-49, 1979
November.
30. The Mcllvane scrubber manual, Vol. I. Northbrook, IL; The Mcllvane
Company,- 1976.
31. Hall, J. A guide to pressure monitoring devices. Instruments and
Control Systems. 51(4):19-26, 1978 April.
32. The fabric filter manual, Vol. 1. Northbrook, IL; The Mcllvane Company;
1976.
33. Smith, W. B.; Gushing, K. M.,- and McCain, J. D. Procedures manual for
electrostatic precipitator evaluation. Research Triangle Park, NC; U.S.
Environmental Protection Agency; 1977 June. 421 p. EPA-600/7-77-059.
|
34. Continuous air pollution source monitoring systems, U.S. Environmental I
Protection Agency handbook. Cincinnati, OH,- U.S. Environmental Protec- I
tion Agency; 1979 June. 262 p. EPA-625/6-79-005.
35. Draft final report: sampling and analysis procedures for screening of
industrial effluents for priority pollutants. Cincinnati, OH; U.S.
Environmental Protection Agency,- 1977 April. 145 p.
36. Block, H. P. Predict problems with acoustic incipient failure detection
systems. Hydrocarbon Processing. 56(10):191-198, 1977 October.
37. Shih, C. C.; Tobias, R. F.,- Clausen, J. F.; and Johnson, R. J. Thermal
degradation of military standard pesticide formulations. Washington, DC;
U.S. Army Medical Research and Development Command; 1975 March. 287 p.
38. The Mcllvane scrubber manual, Vol. II. Northbrook, IL; The Mcllvane
Company; 1976.
39. Paige, S. F.; Babodal, L. B.; Fisher, H. J.,- Schcyer, K. H.,- Shaug, A.
M.; Tan, R. L.; and Thorne, C. F. Environmental assessment: at-sea and
land-based incineration of organochlorine wastes. Research Triangle
Park, NC; U.S. Environmental Protection Agency; 1978 June. 116 p.
EPA-600/2-78-087.
40. Whitmore, F. C. A study of pesticide disposal in a sewage sludge
incinerator. Washington, DC; U.S. Environmental Protection Agency,- 1975.
193 p. EPA-SW-116C.
5-161
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41. Ferguson, T. L.; Bergman, F. J.; Cooper, G. R.; Li, R. T.; and Honea, F
I. Determination of incinerator operating conditions necessary for sa:^
disposal of pesticides. Cincinnati; OH; U.S. Environmental Protection
Agency; 1975 December. 417 p. E.PA-600/2-75-041.
42. Cross, F. L. Control of fugitive dust from bulk loading facilities.
Pollution Engineering. 12(3):52-53, 1980 March.
43. Morton, W. I. Safety techniques for workers handling hazardous materials.
Chemical Engineering. 83(21):127-132, 1976 October.
44. Rimberg, D. B. Minimizing maintenance makes money. Pollution
Engineering. 12(3) .-46-48, 1980 March.
45. Elton, R. L. Designing stormwater handling systems. Chemical
Engineering. 86(11):64-68, 1980 May.
5-162
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CHAPTER 6
ESTIMATING INCINERATION COSTS
6.1 INTRODUCTION
This chapter provides the user with tools for assessing the costs associated
with: (1) hazardous waste incineration facilities, (2) the most likely modi-
fications to the equipment and/or operations of such facilities, and (3) trial
burns. The modifications may be necessary for a facility to comply with appli-
cable environmental regulations, and they are closely related to the hazardous
waste incineration design and operating criteria defined in Chapter 4. The
trial burn may be necessary when uncertainties are present relative to the
ability of a given facility to burn a given waste while preventing hazards to
the environment and public health.
The cost data presented in this chapter are intended to be used only for first-
cut estimating purposes and are believed to be accurate to no more than ±50fc.
It is impossible to present more accurate data in this chapter for three
reasons.
1. All incinerators are not alike. Differences in design, operation,
and in the waste burned in a given incinerator have a significant
effect on costs.
2. There is a lack of agreement about exactly what costs should be
considered in determining the capital and operating costs of
hazardous waste incineration facilities.
3. Industry has had only limited experience with incinerating bulk
quantities of hazardous waste.
Work in this area is continuing at EPA and, with the cooperation of industry,
EPA will hopefully be able to provide more accurate and comprehensive data in
the future. The user is encouraged to develop and use estimates which repre-
sent the conditions of a given facility more accurately and to consult refer-
ences cited in this chapter and other resources for additional data on costs
related to hazardous waste incineration.
The chapter contains five more sections. Section 6.2 is a generalized dis-
cussion of techniques for estimating capital and operating costs. Section
6.3 presents capital and operating cost estimates for liquid injection and
rotary kiln hazardous waste incinerators, and air pollution control devices.
Sections 6.4 and 6.5 discuss those costs associated with incineration facility
6-1
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modifications and trial burns, respectively. Finally, Section 6.6 provides fl
references for further assistance.
6.2 GENERAL PRINCIPLES OF COST ESTIMATION [1]
Several methods of varying degrees of accuracy are available for estimating
the capital and operating costs of incineration and air pollution control
systems. These methods range from presenting overall installed costs on a per
unit basis, to detailed cost estimates based on preliminary designs, schematics,
and contractor quotes. The least accurate method is the equating of overall
capital costs to a basic operating parameter such as tons per hour or cfm. An
example is a typical installed cost for a fabric filtration system of approxi-
mately $7/cfm. This figure is developed from average costs of many installations
which may range from $3/cfm to $12/cfm. The low end of the range might represent
an installation using standard equipment installed by plant personnel. The high
end of the cost range may represent a system designed for: 1) the inclusion of
standby equipment and redundant systems, 2) provisions for safety, 3) fully
automated operation with complex controls, and 4) expensive materials of con-
struction or other custom features. These factors affect both equipment and
installation costs, and therefore the degree of accuracy produced using such
an estimating method would, at best, provide accuracies in the "order of
magnitude" category (probable accuracy of +50%, -30%) [1]. The cost informa-
tion in this chapter is presented in terms of Btu/hr and acfm and is intended
only for first-cut estimating purposes. I*
The detailed cost estimate, in turn, can produce accuracies of ±5 percent tf
depending on the amount of preliminary engineering involved. These estimates ^
take many months of engineering effort and require process and engineering flow
sheets, material and energy balances, plot plans, and equipment arrangement
drawings before a cost estimate can be developed [1].
6.2.1 Capital Costs
Capital costs consist of the delivered equipment costs for major equipment items
and all the auxiliary equipment and appurtenances plus the direct and indirect
costs of installation. The delivered equipment costs represent a firm cost,
since these are obtainable from the supplier's quoted prices or from curves
compiled from average costs for the specific type of equipment. The cost of
installation can vary substantially from one pollution control system to
another depending on such features as: 1) the degree of assembly of the con-
trol device; 2) the geographic location of the installation,- 3) the topography
of the land site; and 4) the availability of utilities [1].
6.2.1.1 Purchased Equipment Costs—
The purchased equipment costs represent the delivered costs of the control
device, auxiliary equipment, and instrumentation. These costs are developed
by first establishing the design and operating characteristics of the equipment
that will satisfy the process requirements and then using graphs and/or tables
of historical cost data for the various items. The typical cost factor for
instrumentation can be considered as 10% of the equipment costs. Freight costs
within the U.S. are generally 5% of the equipment cost although a cost adjust- M
ment must also be included for unusually remote or distant sites. The purchased
6-2
-------
equipment costs, which include the F.O.B. equipment cost, instrumentation,
freight and taxes, then become the basis for determining the direct and
indirect installation costs. This is done by multiplying the appropriate
factor for each element by the purchased equipment cost [1].
6.2.1 2 Installation Costs--
Installation costs consist of the direct expenses of material and labor for
foundations, structural supports, handling and erection, electrical, insulatior
painting, site preparation, and facilities,- plus the indirect expenses for
engineering and supervision, construction and field expenses, construction
fees, start up, performance tests, model studies, and contingencies. In
considering the direct costs, site preparation, buildings, and facilities are
items that have little or no relationship to the cost of the purchased equip-
ment. Therefore, some cost adjustment, must be used. Although handling and
erection are related to equipment costs, some adjustment must also be made
for either field erection or factory assembly as well as the type of instal-
lation, that is, new or retrofit of an existing process [Ij.
Variations in the indirect expenses can be substantial since items such as
engineering, construction fees, and contingencies are related to contracting
methods and the overall magnitude of the project rather than the equipment
costs. These items all require some adjustment based on system size and con-
tracting arrangement. Other cost items such as model studies may appear
unusual circumstances such as large electrostatic precipitator systems or
other systems where the level of previous experience may be limited [1].
6.2.2 Annualized Costs
Typical annualized costs consist of the direct expenses of labor and materials
for operation and maintenance, the cost of replacement parts, utility costs, anc
waste disposal; plus the indirect costs of overhead, taxes, insurance, general
administration, and capital recovery charges. Unit costs can vary significantly
from installation to installation. In the case of pollution control systems,
waste disposal costs are only applicable to those systems where the collected
pollutant has no value and must be removed to a disposal site [1].
The indirect operating costs are basically related to the capital investment
with the possible exception of overhead. Overhead expenses include, for example
the cost of employee fringe benefits, medical and property protection, and
cafeteria expenses and are accounted for as a percentage of direct salaries or
payroll [1].
The operating costs must be adjusted for any credits that are obtained from
the reuse or sale of recovered products or from the recovery of heat and energy
from the process. Credits such as solvent recovery can significantly offset
control expenses and must be considered as an important factor in an accurate
cost analysis [1].
6.2.2.1 Direct Operating Costs—
Labor and material costs for operation and maintenance vary substantially
between plants due to the degree of automation, equipment age, and operating
schedule. Some generalizations must be made to develop a reasonable method of
6-3
-------
estimating these costs. Normally these costs represent fro.t 2 to 8 percent of™
the total annualized costs with the remainder reflecting the cost of utilities
and capital charges. In general, operating labor and supervision will be
reduced with increased system automation. Small systems which operate inter-
mittently or on demand may require a full-time operator for start-up, control,
and shutdown while the system is in operation. In contrast, larger automated
systems operating continuously may only require a short period per shift for
monitoring purposes. The total annual labor cost is also a function of the
number of 8-hour operating shifts per year. Small plants may be expected to
operate one shift per day, five days per week, and fifty weeks per year while
large plants, such as those in the basic metals, petroleum, and chemical indus-
tries, would be expected to operate three shifts per day for 365 days. The
operator labor, therefore, should be estimated on a man-hours per shift basis
for the particular types of system. For large, automated, continuously operated
pollution control systems, the operating labor can be estimated.
When periodic replacement of major parts is required, such as the replacement
of filter bags in a fabric filter, the labor cost for replacement should be
equal to the material cost of the replacement parts. For small- to medium-size
systems where the installed cost is approximately $100,000, or less, the total
cost of maintenance is assumed to be 5 percent of the installed capital cost [1] .
The annual cost of replacement parts represents the cost of the parts or corar
ponents divided by their expected life. Replacement parts are those components
and materials such as filter bags and catalyst which have a limited life and|
are expected to be replaced on a periodic schedule. Estimates of the life o'f
pollution control equipment and related replacement parts, such as are shown
in Table 6-1, are based on qualitative judgement of the type of application,
maintenance service, and duty cycle. The guideline for average life represents
a process operating continuously with 3 shifts per day, 5 to 7 days per week,
handling moderate concentrations of non-abrasive dusts or non-corrosive gases.
The guideline for low-life applications is based on a continuous process handling
moderate- to high-temperature gas streams with high concentrations of corrosive
gases or abrasive dusts, .applications having high life expectancies for parts
and equipment would be those operating intermittently or approximately one shift
per day with gas streams with low concentrations and at ambient gas stream
temperatures [1].
6.2.2.2 Indirect Operating Costs—
The indirect operating costs include the cost of taxes, insurance, administration
expenses, overhead, and capital charges. Taxes, insurance and administration
can collectively be estimated at 4 percent of the capital cost while overhead
charges can be considered as 80 percent of the labor charges for operation and
maintenance of the system. The annualized capital charges reflect the costs
associated with capital recovery over the depreciable life of the system and
can be determined as follows [1]:
6-4
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TABLE 6-1. ESTIMATES OF LIFE OF MATERIALS, PARTS, AND EQUIPMENT
FOR AIR POLLUTION CONTROL SYSTEMS [1]
Length of service, years
Item Low Average High
Materials and Parts
Filter bags 0.3 1.5 S
Catalyst 25 8
Refractories 15 10
Equipment
Electrostatic precipitators
Venturi scrubbers
Fabric filters
Thermal fume incinerators
Catalytic fume incinerators
5
5
5
5
5
20
10
20
10
10
40
20
40
20
20
I
I
Capital recovery cost = (capital costs) x ,j 't" - i I"
where i = annual interest rate
n = capital recovery period.
6.3 CAPITAL AND OPERATING COSTS FOR HAZARDOUS WASTE INCINERATION FACILITIES
AND AIR POLLUTION CONTROL DEVICES [2-4]
i
6.3.1 Hazardous Waste Incinerators
i
1 Information presented in this subsection aids in determining whether capital
and operating costs of the hazardous waste incinerator are in the expected
j range compared to similar incinerators. All costs are shown as a function of
incinerator heat load and are grouped as follows: (1) rotary kiln incinerator
with and without energy recovery, and (2) liquid injection incinerator with
and without energy recovery.
6.3.1.1 Capital Investment for Hazardous Waste Incinerators—
Figures 6-1 and 6-2 show the total capital investment for a rotary kiln incin-
erator and for a liquid injection incinerator, respectively. These costs are
based on references 2 through 4, representing incineration of rubber wastes,
polyvinyl chloride waste, and ethylene. The estimated capital investments
represent costs for "grass roots" plant installation excluding land costs.
Chart accuracy is anticipated to be ±50% of mid-1980 costs. The incinerator
1 capacity in Btu/hour includes the heat release rate from the auxiliary fuel
as well as that of the waste being burned.
The rotary kiln incineration system costs include those for the material
handling building, the rotary kiln primary combustion chamber, an afterburner,
6-5
-------
•s
1C
Q.
U
<
O
0 1
NO ENERGY RECOVERY
WITH ENERGY RECOVERY
0.01
0.1 1.0
INCINERATOR CAPACITY. 107 8tu/hr
10
100
Figure 6-1. Total capital investment* for a
rotary kiln incinerator [2-4].
*Expressed in June 1980 dollars, actual costs expected
to be within ±50% of values from curve.
6-6
-------
100
10
2 1.0
S
o.i
I
WITH ENERGY RECOVERY
NO ENERGY RECOVERY
i i i i
0.01
0.1 1.0
INCINERATOR CAPACITY. 107 Btu/hr
100
Figure 6-2. Total capital investment* for a
liquid injection incinerator [2-4].
*Expressed in June 1980 dollars, actual costs expected
to be within ±50% of values from curve.
6-7
-------
a water quench chamber, a high energy venturi scrubber, a demister, a fan,
stack, a scrubber water neutralization system (for HC1 from the combustion
of vinyl chloride waste), and associated equipment. The; capital costs for
rotary kiln incinerator systems were calculated by adding the costs for
Purchased Equipment Items (PEI) (rotary kiln incinerator and afterburner
equal 50 to 70% of PEI); adding 15 percent to get Installed Equipment Cost
(IEC); adding costs for piping (40% IEC), building, structures, and founda-
tions (35% IEC), and electrical and instruments ($50,000) to get Total
Physical Plant Cost (TPPC); and then adding 50% of TPPC for engineering,
construction, and contingencies. All costs were adjusted to June 1980
dollars. In sizing equipment, on-stream factors of 0.8 to 0.9 were used
(7000-7900 hours/year).
The liquid injection incineration system costs include those for the building,
waste storage tank, automated feed system, fuel oil storage tank, liquid
injection incinerator, high energy venturi scrubber, scrubber water supply
system, and pH control system. The capital costs for the liquid injection
incinerator system were calculated by adding the costs for the Purchased
Equipment Items (PEI), (liquid injection incinerator and venturi scrubber
equal 40 to 60% PEI); adding 10% PEI for labor to get Installed Equipment
Cost (IEC),- adding costs for piping (90% IEC), buildings, structures and
foundations (30% of IEC), and electrical (50% IEC) to get Total Plant
Cost (TPC); and then adding 30% of TPC for overhead to get Total Erected h
Cost (TEC) and then adding 20% of TEC for engineering and contingencies I
to get Total Capital Investment. All costs were adjusted to 1980 dollars, I
and an on-stream factor of 0.8 to 0.9 was used.
While the useful life of these facilities was not specifically discussed in
literature cited, a general rule of thumb of 20 years seems appropriate. This
is the life experienced by most petroleum and petrochemical facilities.
6.3.1.2 Operating Costs of Hazardous Waste Incinerators--
Figures 6-3 and 6-4 exhibit annual operating costs for rotary kiln and liquid
injection incinerators, with and without energy recovery. Due to savings
realized by making steam on site, total annual operating costs are generally
lower when an energy recovery unit is employed.
The term "fuel" is used in sources cited to indicate auxiliary or supple-
mental fuel (usually No. 2 fuel oil) used to raise combustion zone tempera-
tures. The need for supplemental fuel is determined by the heating value
and/or water content of the waste.
6.3.2 Air Pollution Control Devices [5]
An important cost-related item that should not be overlooked in using inciner-
ators for hazardous waste disposal is air pollution control to meet Federal,
state, and local regulations. The combustion of the waste in the incinerator
may not end the pollution problem, since dust, fumes, smoke, and particulate
emissions may be combustion byproducts requiring removal hardware. Many of
the air cleanup devices use recirculating water, which in turn may require wa-
ter pollution control devices or ultimate chemical treatment. These steps can
6-8
-------
INCINERATOR CAPACITY, 107Btu/hr
Figure 6-3. Total annual operating cost for
a rotary kiln incinerator [2-4].
0.01
6-9
-------
_2
"o
00
O
CL
O
10
100
01
INCINERATOR CAPACITY, 10' Btu/hr
Figure 6-4. Total annual operating cost for a
liquid injection incinerator [2-4].
6-10
-------
add significant investment and operating costs to the overall cost of the
incineration process.
Pollutants that are likely to show up in the exhaust gases include: flyash
and other noncombustible particulates, sulfur and nitrogen oxides, acidic gas-
es, odors, and smoke. Figures 6-5 through 6-13 give capital and annualized
costs for fans, electrostatic precipitators, fabric filters, mechanical collec-
tors, incinerators, and venturi scrubbers.
6.3.2.1 Air Pollution Control Device Capital Installed Costs--
A number of cost curves (Figs. 6-5 through 6-13) have been developed that pro-
vide conceptual or study estimates of the capital and annualized costs of
complete air pollution control systems. These curves presented provide costs
for grass-roots installations. A retrofitted installation generally costs
10 to 30 percent more than a grass-roots installation and, depending on specific
difficulties at a given site, the costs can be calculated on the basis of the
latter percentage.
Figures present these costs based upon gas volume through the major air pol-
lution control device types. The gas volume generated under a given set of
waste and combustion conditions can be determined through the methods des-
cribed in Chapter 4. For reference purposes, as a rough approximation, the
following relationship may be used:
scf of SA _ Gross heating value of fuel (Btu/lb)
Ib of feed = 100
\
where SA = stoichiometric air.
6.3.2.2 Electrostatic Precipitator—
Figure 6-7 presents cost curves for systems utilizing an electrostatic pre-
cipitator housed in an insulated, carbon steel shell. The assumption is made
that the uncontrolled gas stream is normally vented to a stack. Thus, the
necessary fan and ductwork are considered part of the process. Costs are pre-
sented for three levels of control efficiency based on medium- and high-
reactivity dust. For a given collection efficiency, high-resistivity dust
requires a greater SCA (specific collection area) and the cost of the ESP is
thus increased. For purposes of estimating equipment costs, plate area was
calculated according to the Deutsch equation with partical drift velocities of
0.036 m/s for high-resistivity dusts and 0.086 ra/s for low-resistivity dusts.
Ousts such as fly ash from low-sulfur coal combustion and cement kiln dust
have high resistivity.
6.3.2.3 Fabric Filters—
Fabric filters are commonly used across a broad range of exhaust gas volumes.
Low-temperature and low-volume exhaust streams from conveyor transfer points are
normally vented to a fabric filter. On the other hand, high-temperature and
high-volume exhausts from electric arc furnaces are also often vented to a
fabric filter. Figures 6-8 and 6-9 present cost curves for a variety of fabric
filter applications. Costs are presented for filters utilizing each type of
6-11
-------
1,0001
ioo
o
o
o*
>-
OS
<
^
<
•^
o
to
O
10
10.000
CAPITAL COST
ANNUALJZED COST
NOTE - COST OF DUCT
INCLUDES ONE ELBOW
100,000 1,000,000
EXHAUST GAS RATE, acfm
Figure 6-5. Capital and annualized costs of
fans and 30.5 length of duct.
10,000,000
6-12
-------
iO.OOOr
i.ooo U
OS
CAPITAL COST
ANMJAUZED COST BASED ON
8700 h/yr OPERATION
100,000
EXHAUST GAS RATE, acfm
1,000.000
Figure 6-6. Capital and annual12cd cost of fan
driver for various head pressures.
6-13
-------
lO.OOOr
or
s
1,000
<
m
o
100
10.000
NOTES A & C
SCA • SPECIFIC COU£CTION AREA
NOTE A • FOR DUST HAVING HIGH RESISTIVITY
NOTE B - FOR OUST HAVING MODERATE TO LOW RESISTIVITY
NOTE C • CAPITAL COSTS
NOTE 0 • ANNUAUZED COSTS
i. i i i I i i i I i i i i
100,000
EXHAUST GAS RATE, acfm
1,000,000
Figure 6-7. Capital and annualized costs of electrostatic
precipitators, carbon steel construction.
6-14
-------
lO.OOOr
h
L
L
1,000
<
CO
O
CAPITAL COST
ANNUALIZED COST
TYPE OF CLEANING MECHANISM
CURVE 1 - REVERSE AIR
CURVE 2 - SHAKER
CURVE 3 - PULSE JET
AIR-TO-CLOTH RATIO
CURVE 1 0.46 TO 1
CURVE 2 - 0.61 TO 1
CURVE 3 - 2.12 TO I
100
10,000
BAG MATERIAL
CURVE 3 - NYLON
CURVE 2 - NYLON
CURVE 3 - NOMEX
Figure 6-8.
100,000
EXHAUST GAS RATE, acfm
Capital and annualazed cost of fabric
filters, carbon steel construction.
1,000.000
6-15
-------
10,000 r
>•
OS
<
1,000
BAG
CAPITAL COST
ANNUAUZED COST
CLEANING MECHANISM
CURVE 1 - REVERSE AIR
CURVE 2 - SHAKER
CURVE 3 - PULSE JET
CLOTH RATIO
CURVE 1 OM TO 1
CURVE 2 - 0.61 TO 1
CURVE 3 - 2.12 TO 1
MATERIAL
CURVE 3 - NYLON
CURVE 2 - NYLON
CURVE 3 - NOMEX
1 i I i j I i_
10,000
100,000
EXHAUST GAS RATE, acfm
1,000,000
Figure 6-9. Capital and annualized costs of fabric
filters, stainless steel construction.
6-16
-------
1,000
2
100
8
o
10
1.000
I I . , I I
10,000
EXHAUST GAS RATE, acfm
100,000
Figure 6-10. Capital and annualized cost of mechanical
collectors, carbon steel construction.
6-17
-------
10.000
1.000-
f
1009
CAPITAL COST
ANNUAUZED COST
CURVE 1 -CATALYTIC UNIT. 35% HEAT RECOVERY
CURVE 2 - CATALYTIC UNIT. NO HEAT RECOVERY
CURVE 3 -THERMAL UNIT, 35% HEAT RECOVERY
CURVE 4 - THERMAL UNIT, NO HEAT RECOVERY
10,000
EXHAUST GAS RATE, acfm
100,000
Figure 6-11. Capital and annualized costs of fume incinerators.
6-18
-------
10,000
as
CAPITAL COST
ANNUAUZED COST
PRESSURE DROP. Pa
CURVE 1 - 14,928
CURVE 2- 9,952
CURVE 3- 4,976
100
10.000
i I
I I I I l
100,000
EXHAUST GAS RATE, acfm
1,000,000
Figure 6-12. Capital and annualized costs of venturi
scrubbers, stainless steel construction.
6-19
-------
10,000
1,000 -
o
o
<
ff\
CAPITAL COST
ANNUALIZED COST
PRESSURE DROP, Pa
CURVE 1 - 14.928
CURVE 2- 9.952
CURVE 3 - 4,976
10
10,000
100,000
EXHAUST GAS RATE, acfm
1,000,000
Figure 6-13. Capital and annualized cost of venturi scrubber,
carbon steel construction.
6-20
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bag-cleaning mechanism. The cost curves assume that the fan and drive are
process equipment. The control costs include tie-in ductwork, a dust handling
conveyor, and a dust storage bin. The costs of thermal insulation and heaters
(necessary to prevent condensation in some applications) are not reflected in
the cost curves. Separate curves are presented for stainless construction.
6.3.2.4 Mechanical Collectors--
Capital and annualized cost curves for mechanical collector systems are shown
in Figure 6-10. System costs include hooding to capture the exhaust at the
emission point, ducting, a fan and drive, and a dust storage bin. The system
cost is based on carbon steel construction. Collection efficiency for this
type of system generally ranges from 80 to 90 percent, depending on the particl<
size distribution and inlet grain loading.
6.3.2.5 Fume Incinerators--
Fume incinerators are included in this handbook because it is believed that
they are sometimes used to cofire hazardous combustible liquid waste as a fuel
supplement. Fume incinerators are of two basic types, thermal and catalytic.
Although thermal incinerators are less costly from a capital cost standpoint,
the fuel savings associated with catalytic units make them attractive for
compatible exhaust streams. Both types of units may recover heat and thereby
reduce the fuel requirements. The additional cost of the heat exchangers must
be compared with the fuel savings on a case-by-case basis. Additionally, the
use of catalytic incinerators for control of particulate matter is limited po
substances that will not blind or poison the catalytic mesh. Figure 6-11 p|*e-
sents cost curves for both types of units, based on an exhaust stream at 2?
percent of the lower explosive limit (LEL). The costs of units having a heat
exchanger are based on a 25 percent heat recovery rate. Exhaust streams that
are amenable to incineration are normally exhausted to the atmosphere. Thus
for purposes of the cost curves presented herein, *he fan and drive are con-
sidered process equipment. The cost curves include the cost of ductwork to tie
the incinerator into the process vent system.
6.3.2.6 Venturi Scrubbers—
Venturi scrubber use ranges from control of small process fugitive exhaust
streams to control of hi$h-volume point sources such as basic oxygen furnaces.
Figures 6-12 and 6-13 present cost curves for a variety of pressure drops. The
costs include a clarifier and circulating pump for the scrubber liquor, a fan
and drive, and ductwork sufficient to tie the scrubber into the process exhaust
stream.
Note: Direct-fired incinerators are considered as thermal incinerators for
purposes of this analysis.
6-21
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6.3.2.7 Example Calculation--
The following example is presented to illustrate the use of the cost curves
presented in this chapter.
Example: (a) Determine the capital and operating costs of a rotary
kiln incineration system with a high energy venturi scrubber
having a throughput of 10 million Btu/hour, processing a
waste with a heating value of 5000 Btu/pound, and operating
with 20% excess air. Assume no heat recovery,
b) Determine the differences in capital and operating costs
which might be expected if an electrostatic precipitator were
used instead of the high-energy venturi scrubber to collect
high resistivity dust with 99.5% efficiency.
a) Using Figure 6-1 the 1980 capital cost of the rotary kiln incineration
system with a 10 million Btu/hour throughput is estimated to be 3.5
million dollars. Using Figure 6-3 the 1980 operating cost of this
type of system is estimated to be 1,500,000 dollars per year.
b) First, the exhaust gas rate needs to be determined.
From the relationship given on page 6-11,
scf of SA _ H.V. _ 5000 Btu/lb _ 50 scf SA |-
Ib of feed " 100 ~ 100 ~ Ib/feed J
Assume stack gas temperature = 2000°F or 2460°R
- _ scf (T °R) _ 50(2460) _
»« - 4g20R - 492 - «u
at 20% excess air
acf = 1.20 x 250 = 300 acf/lb of feed
Therefore the exhaust gas rate is
. _ 10M Btu 1 hr 1 Ib 300 acf
OT ~ hr 60 min * 5000 Btu * Ib
exhaust gas rate = 10000 acfm
For a carbon steel venturi scrubber with an exhaust gas rate of 10,000 actual
cfm at a 5 kPa pressure drop, Figure 6-13 shows a capital cost of 185,000
dollars for a carbon steel unit, and its annual operating cost is 72,000
dollars.
For a carbon steel electrostatic precipitator to handle 10,000 actual cfm.
Figure 6-7 shows a capital cost of 450,000 dollars and an operating cost of
140,000 dollars.
The change from a venturi scrubber to an electrostatic precipitator would,
therefore, be estimated to result in an increased capital cost of 265,000
dollars and an operating cost of 68,000 dollars per year.
6-22
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6.4 COST EFFECTS OF HAZARDOUS WASTE INCINERATION FACILITY MODIFICATIONS
The purpose of this section is to provide the user with the costs associated
with facility modifications. Costs presented herein are based on the prime
operating parameter of the facility component relative to the component's cost.
6.4.1 Cost Effects on Material of Construction
Table 6-2 provides material cost factors which permit determination of a modi-
fication cost where materials of construction have been changed. While carbon
steel is a widely used construction material, higher alloys are often required.
The cost of a new material may be determined using the cost of the original
material and factoring up or down using the material cost factors.
TABLE 6-2. MATERIAL COST FACTORS [6]
Construction Material
material factor
Carbon steel 1.0
FRP 0.95
304 Stainless steel 1.55
316 Stainless steel 1.85
Hastelloy C 5.90
Kynar lined FRP 1.55
Teflon lined steel 2.95
Carbon lined steel 4.05
Rubber lined steel 2.30
PVC 1.38
Carpenter 20 4.0 (est.)
6.4.2 Cost Effects Using Euipment Modules
Equipment modifications needed to fit the conditions for a specific inciner-
ator or a specific waste can vary greatly. Reference 7 provides the installed
costs of commonly used equipment nodules. Where modifications change the ca-
pacity of a module, the cost of the modifications can be determined by the
difference in installed costs at the two capacities. Figures 6-14a through
6-14c are provided for selected incineration modules.
6.5 TRIAL BURNS
A trial burn is defined as any attempt to incinerate the waste in question for
a limited period, and it is designed to establish the conditions at which in-
cineration of waste in a given facility must be carried out to assure protec-
tion to public health and the environment. A trial burn aay be requested when
the EPA believes (1) the information is insufficient to assure protection to
public health and the environment, and (2) a trial burn can provide informa-
tion necessary to assure such protection (i.e., to verify 99.99% destruction
6-23
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100 000 I
10.000
1.000
100
1.000
CAPACITY, cfm
10,000
Figure 6-l4a. Capacity vs. installed cost for a fan [7a].
Updated using Marshall and Stevens process machinery indexes for 1972 and 1980.
1,000,000
3 100.000
10'°8ooo
1 '—L-LJ.ii
100,000
CAPACITY. Ib STEAM/h
1,000,000
Figure 6-14b. Capacity vs. installed cost for a steam boiler [7a]
6-24
-------
1,000,000
~ 100.000
o
(J
10, (
100
1,000
CAPACITY, IWh
10,000
Figure 6-l4c. Capacity vs. installed cost for an incinerator [7a]
Updated using Marshall and Stevens process machinery indexes for 1972 and 1980
efficiency). A trial burn may comprise either a single burn or a sequence of
burns conducted at constant or varied incineration parameters.
A trial burn will be typically conducted at a given facility which is applying
for a permit to incinerate the waste in question on a more permanent schedule.
The facility could be a commercial (full-sized) incinerator, a pilot-scale
unit operated by an incinerator vendor, or a pilot-scale unit operated by a
vendor specializing in trial burns.
A trial burn requires a temporary permit from the EPA and may be conducted in
the presence of an EPA official. A trial burn itself should not present any
serious threat to public or operators' health and the environment. To prevent
any serious hazard to public and operators' health and the environment, a
trial burn should provide for (a) rapid detection in the incinerator effluents
of hazardous materials in quantities potentially threatening health and safety
of the public and/or the operators, and (b) rapid incinerator shutdown upon
detection of such quantities.
Table 6-3 presents estimated average costs for various of the trial burn
activity. Costs contained in Table 6-3 are for trial burns at an existing,
full-scale incinerator. It is assumed that the incinerator is already
permitted to burn hazardous wastes and that the trial burn is being conducted
for the plant to obtain a permit to burn an additional hazardous waste. These
6-25
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TABLE 6-3. TRIAL BURN COST COMPONENTS (DOLLARS)3'b
Site survey
Equipment preparation
Equipment setup and takedown
Stack sampling
Sample analysis
Equipment cleanup
Report preparation
Average
200°
i,oooc
i,oooc
i,oood
3,000d
500°
i,oooc
Range
$ 100 -
500 -
500 -
500 -
1,000 -
300 -
500 -
500
2,000
2,000
2,000
5,000
800
3,000
aCosts included in this table are estimated averages
obtained by questioning selected consultants experienced
in trial burn situations. Additional costs may be
incurred under specific conditions.
Mid-1980 estimated costs.
One-time costs. j*
Costs during trial burn period. (Dollars per day of •
testing.)
costs are based principally on information furnished by privately-owned environ-
mental laboratory and consulting firms. The trial burn period is assumed to
require a minimum of 4 hours but may extend to several days or weeks, depending
upon facility operations and management decisions concerning the number of
replicative samples to be taken. Facility operators may choose to conduct
parallel tests or implement procedures for permit applications simultaneous
with conducting trial burns. Any costs incurred through normal operations and
those related to obtaining a permit under Subtitle C of RCRA are not included
in the trial burn activity costs.
Specific situations could arise which would increase costs above those repre-
sented in Table 6-3. These include costs for incinerating new and unfamiliar
wastes, new construction, and retrofitting of existing facilities.
6.5.1 Normal Operations
Previously constructed and existing commercial-sized facilities are assumed,
with normal operating costs (fixed and variable) expected to be recovered
through established charges for incinerating customers' wastes. These costs
include amortized engineering design and capital investment costs, costs for
analyzing incoming wastes, burn adjustments, supplementary fuel, and expendi-
tures associated with installing and operating pollution control devices.
Wastes for the trial burns and related storage facilities,, including use of
supplementary fuel, are assumed as part of the facilities normal operations
for which the usual charges offset operating costs. All costs related to
6-26
-------
obtaining a permit under Subtitle C of RCRA are excluded from consideration
as trial burn costs.
6.5.2 Trial Burn Activities
6.5.2.1 Site Survey--
Costs include professional services and travel to a local site for inspection
of the facility to be tested and discussion of plans for trial burns. Specific
characteristics of wastes to be incinerated are assumed known or provided by
waste generators and listed on manifest records or analyzed previously.
Information on the compatibility of these wastes with the specific facility
characteristics is assumed available.
6.5.2.2 Equipment Preparation—
Sampling equipment may be leased by the facility or provided by a consulting
firm. Certain costs are incurred in calibrating and loading of instruments and
transport to facility site; estimates of these average costs are shown in
Table 6-3.
6.5.2.3 Equipment Setup and Takedown—
Installation of equipment includes any scaffolding and securing of ports and
proper sampling instruments at facility stack(s) to ensure the necessary monitor-
ing and procurement of trial burn samples.
\
6.5.2.4 Stack Sampling—
A minimum of three tests involving 1 to 1 1/2 hours per test is assumed. Costs
for testing, instrumentation, and adjustments associated with a permit applica-
tion are considered separate costs not attributable to the trial burn activity.
Development of sampling procedures and verification of test methods are presumed
available and accomplished prior to the trial burns.
6.5.2.5 Sample Analysis—
Laboratory analysis costs include preservation and transporting of samples to
an off-site laboratory and makeup of fractional samples. Compounds to be
analyzed include those potential air pollutants listed in the previous section
(Table 5-13). GCMS testing is conducted for the chlorinated hydrocarbons and
EPA test methods Nos. 5, 6, and 7 for various other potential pollutants,
including particulate matter. GCMS testing at the site is excluded.
Daily testing assumes one EPA Method No. 5, two Method No. 6, and four Method
No. 7 tests for analyzing single waste trial burns. Blending of incoming
wastes could complicate analytical procedures and increase the laboratory
analysis costs.
6.5.2.6 Equipment Cleanup—
These costs are the routine costs incurred for cleaning and storing various
sampling and analysis equipment.
6.5.2.7 Report Preparation—
The written report displays and interprets the trial burn results. Preparation
of this report and the information contained therein is considered independent
from any information produced for permit negotiations.
6-27
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6.6 REFERENCES
1. Neveril, R. B. Capital and operating costs of selected air pollution con-
trol systems. EPA-450/5-80-002. Research Triangle Park, North Carolina;
U.S. Environmental Protection Agency; 1978 December. PB 80-157282.
2. Adams, J. W. ; Harris, J. C. ; Levins, P. L. ; Stauffer, J. L. ; Thrun, K. E.;
and Woodland, L. Destroying chemical wastes in commercial scale inciner-
ators, facility report No. 2. Washington, DC; U.S. Environmental Protec-
tion Agency; 1976 November. 150 p. PB 268 232.
3. Ackerman, D.,- Clausen, J. ; Grant, A.; Johnson, R. ,- Shih, C. ,- Tobias, R. ;
Zee, C.,- Adams, J. ; Cunningham, N. ,• Dohnert, E.; Harris, J. ; Levins, P.;
Stauffer, J.'; Thrun, K.; and Woodland, L. Destroying chemical wastes in
commercial scale incinerators; final report - phase II. Washington, DC;
U.S. Environmental Protection Agency; 1978. 130 p. PB 278 816.
*»
4. Ackerman, D.; Clausen, J.; Johnson, R.; Tobias, R.; Zee, C.; Adams, J.;
Harris, J.; Levins, P.; Stauffer, J.; Thrun, K.; and Woodland, L.
Destroying chemical wastes in commercial scale incinerators, facility
report No. 6. Washington, DC; U.S. Environmental Protection Agency•
1977. 173 p. PB 270 897.
Alpert, L. D.; et al. Control techniques for particulate air pollutants
Washington, DC; U.S. Department of Health, Education, and Welfare; 1969 '
January. 241 p. .PB 190 253.
Gilbert, W. Selecting materials for wet scrubbing systems. Westfield,
NJ; Caroll-Reynolds Co., Inc.
Capital and operating costs of pollution control equipment modules, data
manual, volume II. U.S. Environmental Protection Agency,- 1973 July.
183 p. EPA-R5-73-023b.
\
6-28
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APPENDIX A
SUBJECT INDEX
Abrasion (see erosion)
Absorption, 2.2.2
Acoustic analysis, 5.11.2
Activation energy, 4.3.2. Appendix E
(Section 6)
Afterburner, 2.3.3.1, 4.3, 6.4.2.5
catalytic, 2.3.3.1
cost, 6.4.2.5
direct flame, 2.3.3.1
general, 2.3.1.1, 2.3.1.4-5
thermal, 2.3.3.1
Air pollution
emissions (see emissions)
fugitive, 5.1.4.1-2
nonitonng. 5.7, 5.9, 5.10
Air pollution control device
absorption (see absorption)
applicability, 2.3.3, 4.4.1
baghouse (see baghouse)
cost, 6.4
design. 2.3.3, 4.4.1
electrostatic precipitator
(see electrostatic precipitator)
evaluation, 5.3.1-3
scrubber (see scrubber)
Air requirements
excess air, 4.3.3
(worksheets. 4-5. 4-8. 4-9)
stoichiometnc, 4.3.3
(worksheets. 4-2, 4-4)
Ash. 5.12.1.3, 5.12.4
Atomization
evaluation, 4.3.2.1
general. 2.3.1.2
rotary cup, 2.3.1.2. 4.3.2.1
single fluid. 4.3.2.1
sonic, 4.3.2.1
two fluid, high pressure air, 2.3.1.2,
4.3.2.1
two fluid, high pressure steam, 2.3.1.2.
4.3.2.1
Auto ignition temperature, 5.2.2.3. 5.2.2.8
Automatic sprinkler systesi, 5.5.5.1
Baghouse. 2.2.S
Baghouse monitoring, 5.7.2
Bibliography. Appendix 0
Bonding, 5.3.3.2
Bottom ash, 5.7.2.3
Burner
atosuzation (see atomixation)
evaluation, 4.3.2
general design, 4.3.1
placement, 4.3.1
suspension, 4.3.1
Catalytic afterburner (see afterburner)
Chain of custody, 3.3
Co-incineration, 2.3.1.5, 2.4
Coding, pipe, 5.5.3.4
Combustible organic*, 2.1
Combustible inorganics, 2.1
Combustion gases, 2.2, 2.3.4
Compatibility matrix, 5.5.1
Construction materials (see corrosion), 5.14, 6.5.1
Container (see storage)
Contract maintenance, 5.15.3
Control system, 5.6
Conversion tables, Appendix C
Conveyors
mechanical, 5.3.5.1
pneumatic, 5.3.5.2
Corrosion, 4.4.6
Cost
air pollution control device, 6.4
capital, 6.2.1, 6.3.1
facility modification. 6.5
operating, 6.3.2
trial burn, 6.6
Current practices, 2.2, 2.3
Cyclone, 5.7.4
Destruction and removal efficiency (see
efficiency)
Dichotomous sampler, 5.13.3.4
Differential absorption. 5.9.2.2
Dikes, 5.4.3.1
Drager tubes, 5.13.3.4
Duct design, 4.4.4
Dust tight, 5.5.6.3
Ifficiency
destruction aad removal, 4.2.
4.5 (worksheet 4.1). 5.10.3
removal, 2.3.3. 4.4.1
Effluent (see water pollution)
Electric heating cable. 5.5.3.4
Electrostatic precipitator
cost. 6.4.2.4
dry, 2.3.3.6
The references are to section numbers in the Handbook.
A-l
-------
Electrostatic pr-cipitator (continued)
dweK time 5 ~ 3 4
removal efficiency . 5 7 3 2
step-up transformer, 5733
two stage. 2.4 6
wet 2337
Emergency handbook, 5.2.2.3
Emergency squad, 5 IS 4
Emissions
air pollution 22 233 432,
441 4.5 lworKSheet 4-12)
fugitive, 5 13
Erosion, 2 3 1.2
Evaluation
air pollution control 4 4
incinerator. 4 3
safety systems. 4.3 5, 4.4.5
Fan selection. 444
Foreign technology. 2.4
Feeder ditch 5.15.5
Feeders 5 5 6.3
Filters
depth, 5911
surface, 5.9.1 1
Flame scanner, 4.3.5
Flyash. 5 12.1.2
Fuel, 4.3.4, 4.5 (worksheet 4-11)
Fugitive emissions
blowdown. 5 12.1.2
control, 5.13.2
monitoring, 5.13.3
significance. 5.13.1
Gauges, 5.5.5.2
Glossary. Appendix B
Grounding, 5.3.3 3
Hand-held FID, 5.13.3.4
Hazard Class (DOT). 3.3.2
Hazardous waste generation, 2.1
Heat capacity, 4.2.3
Heat input capacity, 4.3.3-4
Heat recovery
economizer, 2.2.1
general, 2.2
heat exchanger, 2.2.1
heat recovery boiler, 2.2
Heating value
higher, 4.3.2.1
lower, 4.3.2.1
net. 4.3.2.1, 4.5 (worksheet 4-3)
Housekeeping (facility), 5.15.2
Hydraulic accuaulator, 5.5.5.3
Incinerator
applicability, 2.1, 2.2, 2.3
coincineration, 2.3.1.5, 2/4
evaluation, 4.3
facility design, 5.1.2
fluidized bed, 2.3.1.3. 2.4
general discussion, 2.1-3, S.I
liquid injection (see liquid injection)
Multiple hearth. 2.3.1.4, 2.4
operation, 5.2.2
overall layout, 2.2. S.I.2
Incinerator (continued)
process control, 4.3.5
rotary kiln, 4.3
site selection, 5.2.1
Inspections (see monitoring)
Interlock (see safety)
Leak detection and repair plan, 5.2.2.4
Liquid to gas ratio (see scrubber)
Liquid injection
general, 2312 24 43
horizontally-fired. 2.3.1 2
tangentially-fired, 2312
vertically-fired, 2312
Loss prevention program, 5228
Maintenance, 5.15.3
Manufacturers, 2 S
Mist eliminator, 4.4 3,574
Mixing, 2.1, 4 3 3
Mixing vessel. 5.5.2
Monitoring
air pollution control system, 4.3.5, 5 7, 5.10
air pollution emissions, 5 10
ash, 5.3.3.1, 5.12.2
continuous, 5.9
general, 5.2.2.1
incinerator process, 4.3.5, 5.2.2, 5.6
interface, 5.9.1.1
liquid*, 5.7.1.2, 5.8. 5.12.2
oxygen, 5.6.2
pH, 5.7.1.3, 5.8.3, 5.8.4
plant condition, 5.11
pressure drop, 5.7.1.4
slurry, 5.7.1.2. S.S.2
solid waste, 3.6, 5.12.2
tanks, 5.4.3.2
temperature, 4.3.3. 5.6.1, 5.7.1.1
vaste handling, 5.3.3.1
waste. 5.3.2, 5.5, 5.6.2-3
Multicyclone (see cyclone)
Hurphee vapor phase efficiency, 4.4.2 j
Neutralization. 5.8.5 !
Nozzle (see atosuzation, burner)
Operations Manual, 5.2.2.2
Operation* plan, 5.2.2.1
Packing, 4.4.2
Particle size, 2.3.3.2. 4.4.1. 4.4.2
Penetration, 4.4.2
Piping, 5.5.3
Plant disaster emergency plan, 5.2.2.3, 5.2.2.5, 5.2.2.8
Polymer tube, 5.13.3.4
POTW disposal restrictions, 5.12.3
Pressure drop
calculation (also see fan selection), 4.4.4
(worksheet 4-16)
masure»ent, 5.7.1.4
Process control (see incinerator, safety)
Products of combustion (see waste)
Protection of human health (see safety)
Pump house. 5.3.3.1
Pumps. 5.5.3
Punching, 5.5.6.4
Purpose of handbook, 1.1
Pyrolysis. 2.3.1
Quench, 4.4.3
Quench water, 5.12.1.1
ROtt regulations, 3.2
Relief valves, 5.3.3
Residence time
delivered by incineration process, 2.1
evaluation, 4.3.3
•UUMB, 4.3.3
requirements, 4.3.3, 4.5 (worksheets 4-6, 4-10)
Rotary kiln (see incinerator)
Run off, 5.2.1, 5.15.5
Safety
emergency handbook, 5.2.2.3
fire, 5.4.3.1, 5.15
general. 5.1S.1
shutdown equipment, 4.3.5, 4.4.5
k
t
A-2
-------
Safety (continued)
spills. 5.2.2.5. 5.3.3, 5.4.3
static electricity prevention, 5.3.3.3
storage, 5.4.3
training, 5.2.2.7
unloading hazardous liquids, 5.3.3.1
valves, 5.5.5
weather extremes, 5.2.2.3
Sampling (see monitoring}
Scrubber
applicability, 4.4.1-2
cost, 6.4.2.2
flooding velocity, 4.4.2
gas atomized spray, 4.4.1-2
ionizing (see electrostatically augmented)
liquid to gas ratio, 4.4.2, 4.5
(worksheet 4-15), 5.7.1.2
monitoring, 4.4.5, 5.7.1
orifice, 5.12.1.1
packed bed, 2.3.3.3, 4.4.1-2
plate tower. 2.3.3.3, 4.4.1-2, 4.5
(worksheet 4-14)
selection (see applicability)
sieve tray, 4.4.1-2
spray tower, 2.3.3.4
transfer unit, 4.4.2
venturi, 2.2.5, 2.3.3.2, 2.3.3.5, 4.4.1,
4.4.2, 4.5 (worksheet 4-13)
water handling, 5.12
Seals
packed, 5.5.3.3
mechanical. 5.S.3.3
Security (of facility), 5.2.2.6
Shipping and receiving, 5.3. 5.3.3-4, 5.4.3.2
Shredders, 5.5.6.1-2
Site selection, 5.2.1
Sludge, 5.12.3
Slurry, 5.5.2
Spill and runoff contai
Spill handling plan, 5.2.2.5
Spills (see safety)
Stack, bypass, 4.4.5
Starved air combustion. 2.3.2,
Static electricity prevention, 5.3.3.3
Steam
injection, 4.3.2
production, 2.3.4
requirements, 4.3.2
tracing, 5.5.3.4
Stock piles. 5.4.1.2
Storage
bulk solids, 5.4.1.2
containers, 5.4.1.3
liquid, 5.4.1.1, 5.4.3.2
safety, 5.4.2-3
tank cars, 5.4.1.4
Storm water diversion, 5.15.5
Tanks (see storage)
Temperature
incinerator, 2.3.1, 2.3.3.1, 4.3.3
measurement. 5.6.1, 5.7.1
Test burn (see trial burn)
Testing (see monitoring)
Thermal afterburner (see afterburner)
nt. 5.3.3.2, 5.4.3.2
Thermal decomposition unit,
Training. 5.2.2.7
Transducer, 5.9.2.3
Transfer lines (fail safe),
Trenching system. 5.3.3.2
3.7, appendix I
5.3.3
5.12.4
4.3.3, 4.4.2, 4.5
.13.2
3.8
3.2.1,
3.4, 4.3.2
5.1, 4.5 (worksheet 4-2)
Trial burn
results, Appendix F
use, 4.3.3
Turbulence (see mixing)
Unloading
bulk solids, 53.5
containers, 5.3.4
liquids, 5.3.3
Valves, 5.5.4, 5.12.2,
Velocity, superficial,
(worksheet 4-7)
Vents, 5.4.1.1
Viscosity
absolute, 4.3.2
kinematic, 4.3.2
Visual inspection, 5.
Haste (solid)
blending (see waste preparation)
characterization, 3.4, 3.5, 3.6,
compatability with incinerator,
composition, 3.4. 4.3.2
monitoring. 5.3.2
physical properties, 3.4, 4.3.2
pit, 5.4.1.2
preparation, 4.3.2, 5.5
products of combustion, 4.3.2,
receiving, 5.3
sampling, 3.3
segregation, 5.4.2, 5.5.1
shipping and receiving (see shipping and receiving)
sources , 5.1
transport , 5.3
Hater pollution
emissions (see emissions)
monitoring, 5.8, 5.12-2
Worksheet
auxiliary fuel capacity requirements, 4.5
(worksheet 4-11)
combustion gas flow and composition. 4.5
(worksheets 4-2, 4-4)
destruction and removal efficiency, U.S.
(worksheet 4-1)
excess air rate at specified afterburner
temperature and overall feed composition , 4.5
(worksheet 4-9)
excess air rate at specified temperature and
feed composition, 4.5 (worksheets 4-5)
gas residence time. 4.5 (worksheet 4-6)
internal consistency in venturi scrubber for
proposed gas velocity, liquid to gas ratio
and pressure drop, 4.5 (worksheet 4-13)
maximum achievable excess air rate at
specified temperature and feed composition,
4.5 (worksheet 4-6)
maximum liquid-to-gas ratio for plate tower
scrubber, 4.5 (worksheet 4-15)
act heatiag value of waste, 4.5 (worksheet 4-3)
particle concentration and emission rste in
liquid injection incinerator, 4.5
(worksheet 4-12)
plate requirement in plate tower scrubber,
4.5 (worksheet 4-14)
pressure drop, 4.5 (worksheet 4-16)
solid waste retention time for rotary kiln
incinerator, 4.5 (worksheet 4-10)
stoichiometric air requirements , 4.5
(worksheets 4-2. 4-4)
superficial gas velocity, 4.5 (worksheet 4-7)
waste characterisation evaluation for
incineration, 3.4
A-3
-------
I
t
i
i
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APPENDIX B
GLOSSARY
This appendix is a glossary of terms used throughout this Handbook.
activation energy: The quantity of heat needed to destabilize molecular bonds
and form reactive intermediates so that the reaction will proceed
afterburner (or combustor): A pollution control device that uses combustion to
reduce the emission levels of organic gaseous and particulate matter.
ambient concentration (ac): The appropriately time-averaged concentration of a
substance at a location to which the general public has access.
analyzer: A device used to monitor emissions, such as: (1) a nondispersive
infrared analyzer (monitors S02> NO , CO, C02, and other gases that abfcorb
. light in the infrared region of th« spectrum, including hydrocarbons I,
(2) a nondispersive ultraviolet analyzer (monitors gases that absorb light
in the ultraviolet and visible regions of the spectrum), (3) a polarographii
analyzer (monitors S02/ N02, CO, 02, and H2S), (4) an electrocatalytic
oxygen analyzer, and (5) a paramagnetic oxygen analyzer.
angle of repose: The angle at which matter will lie or stack in a stationary
configuration.
ANSI: American National Standards Institute.
APCD: Air pollution control device.
ash: The solid residue that remains after a material is incinerated. There
are two types: (1) bottom ash remains in the combustion chamber after
incineration, and (2) fly ash is entrained in exhaust gases leaving the
incinerator.
ash fusion temperature (or melting temperature of ash): The temperature at
which ash has the potential to melt.
ASME: American Society of Mechanical Engineers.
baghouse: An air pollution abatement device used to trap particulates by
filtering gas streams through large fabric bags.
BaP: benzo(a)pyrene.
B-l
-------
beta attenuation monitor: An instrument that measures the absorption of
^-radiation as it traverses a small area onto which aerosol particles are
collected by means of inertial impaction.
blowdown: The portion of scrubbing fluid that is purged in order to prevent
buildup of dissolved solids.
BOD: Biological oxygen demand.
catalytic combustion: A type of combustion employing a catalyst bed.
coburning: The burning of waste and a fuel.
coincineration.- The joint incineration of hazardous waste and refuse and/or
sludge.
combustor (or afterburner): A pollution control device that uses combustion
to reduce the emission levels of organic gaseous and particulate matter.
dedicated incinerator: A privately owned incinerator used to burn only the
owner's wastes.
deflagration: The act of burning very suddenly and violently, but without*
a resultant shock wave (detonation). I*
destruction and removal efficiency (DRE): This term is defined
by the following equation:
W. - W „
DRE = ln °Ut
W .
in
where:
DRE = Destruction and removal efficiency
W. = Mass feed rate of principal organic hazardous constituent(s)
in the waste stream feeding the incinerator (kg/min)
W = Mass emission rate of principal organic hazardous
ou constituent (s) present in exhaust emissions (kg/min)
[downstream of all air pollution control equipment] .
destruction efficiency (DE): Same as destruction and removal efficiency
except W - mass emission rate of principal organic hazardous
constituent (s) leaving combustion zone of incinerator (upstream of
all air pollution control equipment).
dry sorption process: A process that involves contacting the gas stream with
a solid phase that can remove one or more of the gaseous contaminants.
dwell time: See residence time.
effluent: A discharge of pollutants (either gases, liquids, or solids) into
the environment.
B-2
-------
electrostatically augmented scrubbers: Control devices that couple the
mechanisms of electrostatic attraction and inertial separation by
charging particles prior to entry into a wet collector.
electrostatic precipitator (ESP): An air pollution control device that
removes particulate matter by imparting an electrical charge to particles
in a gas stream, causing their collection on an electrode.
excess air: The air flow rate above that required to achieve theoretically
complete combustion.
fabric filter: A device for removing dust and particulate matter from industria
emissions by filtration through cloth or other porous materials.
flash point: The lowest temperature at which a material will volatilize to yiel
sufficient vapor to form a flammable
gaseous mixture with air.
flooding velocity: The gas velocity or narrow range of gas velocities in a
packed bed or plate tower scrubber at which (for a given packing or plate
design and liquid flow rate) the liquid flow down the column is impeded,
and a liquid layer is formed at the tip of the column. Eventually, liquid
is blown out the top of the column. I
fluid: Any substance (for example, a liquid or slurry) that tends to flowjor
conform to the outline of its container.
fluidized bed incinerator: An incinerator consisting of a refractory-lined
vessel containing inert granular material through which gases are blown
at a rate sufficiently high to cause the bed to expand and act as a
theoretical fluid. The gases are injected through nozzles that permit
upward flow the bed but restrict downward flow of the material.
fugitive emissions: Pollutants arising from sources other than stacks and
effluent pipes.
GC: Gas chromatograph
general purpose incinerator: An incinerator that burns miscellaneous types of
wastes, usually from numerous sources and customers.
HCB: Hexachlorobenzene
heating value: The quantity of heat released when waste is burned, commonly
expressed as Btu/lb. The higher heating value includes the heat of
condensation of the water present in the waste and the heat formed in the
combustion reaction; the lower heating value represents the heat formed
in the combustion reaction; and the net heating value is the lower heating
value minus the energy necessary to vaporize any moisture present.
heat of combustion: The heat evolved from the union of combustible elements
with oxygen.
B-3
-------
hygroscopicity: Act of attracting moisture from the air.
incinerator: An engineered apparatus used to burn waste substances in which all
the combustion factors (temperature, retention time, turbulence, and
combustion air) can be controlled.
incinerator, similar.- Incinerator A is similar to incinerator B if, based on
the best engineering judgement, while incinerating identical waste as
incinerator B, the stream leaving the combustion chamber of incinerator A
contains equal or lower amounts of each, but no additional, potentially
hazardous components as the stream leaving the combustion chamber
of incinerator B.
kinematic viscosity: The ratio of absolute viscosity to density.
liquid injection incinerator: An incinerator that uses an atomization device
or nozzle to feed liquid waste.
mass spectrometer: An instrument that analyzes samples by sorting molecular
or atomic ions according to their masses and electrical charges.
MEG: See multimedia environmental goals.
microwave plasma destruction (or plasma destruction): A method of destructid
that uses microwave energy to excite the molecules of a carrier gas (sud
as helium or air), thus raising electron energy levels and forming high]
reactive free radicals.
mist eliminator: A control device used to reduce emissions of liquid droplets,
usually from scrubbers. There are three types: (1) cyclone mist
eliminators (2) fiber bed mist eliminators and (3) wire mesh eliminators.
molten salt incinerator: An incinerator in which waste is injected below the
surface of a molten salt bath.
multimedia environmental goals (MEG's): The levels of contaminants (in ambient
air, water, or land, or in emissions or effluents conveyed to ambient media)
that (1) will not produce negative effects in the surrounding populations
or ecosystems, or (2) represent control limits demonstrated to be achievable
through technology.
multiple chamber incinerator: An incinerator in which wastes are thermally
decomposed in the presence of oxygen in the primary chamber, and decompo-
sition products are oxidized in the secondary chamber(s).
multiple hearth incinerator: An incinerator containing multiple refractory-
lined hearths, vertically aligned, designed for staged drying and com-
bustion of wastes.
NFPA: National Fire Protection Association.
B-4
-------
nitrogen oxides (NO ): The collective term used for the gaseous oxides of
nitrogen, primarily nitric oxide (NO) and nitrogen dioxide (N02).
NPDES: National pollutant discharge elimination system.
packed tower.- An air pollution control device in which polluted air is forced
upward through a tower packed with materials (such as raschig rings, cerami
saddles, tiles, marbles, crushed rock, or wood chips) while a liquid is
sprayed downward on the packing material. The pollutants in the air
stream dissolve and/or chemically react with the liquid.
PAH.- Polycyclic aromatic hydrocarbons
particulates.- Minute solid or liquid particles in the air or in an emission.
Particulates include dust, smoke, fumes, mist, spray and fog.
PCS: Polychlorinated biphenyls.
piezoelectric monitor.- A type of particle monitor which measures mass
concentration by utilization of a vibrating piezoelectric crystal driven
by a standard oscillation circuit.
f
PNA: Polynuclear aromatic compounds.
POHC: Principal organic hazardous constituent.
POM: Polycyclic organic matter.
pyrolysis: The thermal decomposition of a compound in the absence of oxygen.
pyrophoric: Capable of igniting spontaneously.
, quench: To cool rapidly.
removal efficiency: The ratio of the mass rate of flow of the contaminants
going into a control device minus the mass rate of the contaminants going
out of the control device to the mass rate of flow of the contaminants
going into the control device.
residence time: The period of time that the waste is exposed to the reported
temperature in the incinerator.
retention time: See residence time.
rotary kiln incinerator: An incinerator with a cylindrical, horizontal, refrac
tory-lined shell that is mounted at a slight incline. Rotation of the
shell causes mixing of the waste with the combustion air.
i
scrubber: An air pollution control device that uses a liquid to remove
pollutants from a gas stream by absorption and/or chemical reaction.
(Scrubbers also reduce the temperature of the emission.)
B-5
-------
similar waste: Waste A is similar to waste B if, based on best engineering
judgement, the incineration of waste A in the same facility and under the
same operating conditions as those used for waste B would yield a stream
leaving the combustion chamber that contains equal or lower amounts of each,
(but no additional) potentially hazardous pollutants compared to the
amounts yielded by waste B incineration.
sludge: A nonpumpable mixture of solids and liquids.
slurry: A pumpable mixture of solids and liquids.
solifluction: Liquid seepage.
SSU (standard saybolt universal): A unit for measuring kinematic viscosity.
starved air combustion (or thermal gasification): A process that utilizes
equipment and process flows similar to those for incineration; but, in
this process, less than the theoretical amount of air for complete
combustion is supplied.
TCDD: Tetrachlorodibenzo-p-dioxin.
TDAS: Thermal decomposition analytical system.
TDD: Thermal decomposition device I
TDI: Toluene diisocyanate.
temperature: A measure of the level of thermal energy in molecules to which
a waste is exposed during the incineration process.
TLV (threshold limit value): Exposure levels representing conditions under
which it is believed that nearly all workers may be repeatedly exposed
day after day without adverse effects. For airborne substances, the
exposure levels are stated as airborne concentrations and durations of
exposure, including:
• Time-weighted average concentrations for a normal 3-hour
workday or 40-hour workweek (threshold limit value - time-weighted
average).
Maximal concentrations to which workers can be exposed for a period
up to 15 minutes (threshold limit value - short-term exposure
limit).
• Concentrations that should not be exceeded even instantaneously
(threshold limit value - ceiling).
These values are published annually by the American Conference of
Governmental Industrial Hygienists.
TOD: Total oxygen demand.
B-6
-------
trial burn: Any attempt to incinerate the waste in question for a limited
period. A trial burn is designated to establish the conditions at vhic.
incineration of waste in a given facility must be carried out to assurs
protection to public health and environment.
trial burn proposal: A detailed plan which describes the procedure that wil]
be used and the precautions that will be ta
-------
TABLE C-l. CONVERSION FACTORS
To convert fro
acre
Btu (Britnh thenul unit)
Btu/ainute (8tu/«in)
Btu/pound (Btu/ Us)
Stu/ (pound- 'F) (Btu/ (lb-"F)j
Btu/ second (Btu/*)
calorie (cal)
square kilo»et«r (la2)
iquarc meter (m2)
square Bile (mi*)
caloric (cal)
joule (J)
kilocalone (kcal)
joulc/aecond (J/i)
calorie/gram (cal/g)
calorie/ (gram-'C) (cal/(g-*C)]
Kilocalone/hour (kcal/h)
kilocalone/minute
Btu
kilocalorie (kcal)
joule (J)
0 00404047
4,046 36
0.0015625
251.99576
1 054 35
0.251996
17.5725
0.555S5S
l-.O
970.185
15.1197
0.00396*3207
0.001
4.1*4
calorie/gram (cal/g)
calorie/hour (cal/h)
centigrade CO
centimetar (cm)
centipoise (cP)
centutokee (cSt)
cubic centimeter (em3)
cubic foot (ft4)
cubic meter (a4)
dyne/aquare centimeter
Fahrenheit CF)
foot (ft)
Btu/pound (Btu/tt)
Btu/hour (Btu/h)
(erg/a)
Fahrenheit CF)
Kelvin CK)
inch (in.)
gram/(centimetar-second)
•aybolt teconda (SSO)
cubic foot (ft4)
cubic inch (in.4)
cubic yard (yd4)
cubic centimeter (cm*)
cubic meter (m4)
gallon (U.S. liquid)
liter (L)
cubic foot (ft4)
cubic yard (yd4)
liter (L)
atmoephere (eta)
bar
centimeter of mercury • o*C (em Kg f 0*C)
centimeter of water • 4*C (cm M«0 • 4*C)
inch of mercury • 32»F (in. Hq • 32"P)
inch of water 9 4*C (in. MfO * 4«C)
paacal (Pa)
pound/square inch (lb/in.2)
Centigrade CC)
RanJun (•»
centimeter (cm)
inch (in.)
meter (•)
millimeter (mm)
1.8
0.0039683207
11,622.222
•P " (1.8 i «C) *32
•H « »C * 273.17
0.39370079
0.01
See Table C-2
3.5314*67 s 10~*
0.061023744
1.3079506 * 10~«
28.316.847
0.02*316*47
7.4*05195
28.316*47
35.314667
1.3079506
1,000
9.8*923 x 10-'
1 < 10 •
7.50062 s 10-*
0.00109745
2.95300 x 10-*
0.000401474
0.1
1.450377 > 10~*
•C - 0.5556 CF - 32*
•»«•?* 459.7*
30.4*
12
0.304*
304.8
(continued)
I
C-l
-------
TABLE C-l (continued;
To convert frc
gallon (L1 K liquid)
(gal 1
gallon :c 3 lisuid) [gal'
grains 'standard cubic foot
igr/$cf 1
grasi (g>
graa/ (centiaeter-second)
graa/cubic centiaeter (g/ca3)
graa/cubic aeter (g/a3)
graa/ liter (g/li
graa/ailliliter (g/al)
inch of water 9 4°C
'in H20 9 4°C)
joule (J)
joule 'second (J/s)
kilocalone (kcal)
kilograa (kg)
liter (L;
aeter (a)
pascal (Pa)
gallon (L1 S liquid [gal]
liter (L;
cubic centimeter ics3)
cubic foot (ftj)
cubic inch (in J)
cubic swter (m1)
liter (L)
•illigri«/ standard cubic steter
kilograa (kg)
pound 'Ib)
poise (P)
grain/ailliliter (gr/aL)
graa/Billiliter (g/at)
pound/ cubic foot (Ib/ft3)
pound/cubic inch (lb/m.3)
pound/ gallon (U.S. liquid) (Ib/gal)
grain/cubic foot (gr/ft3)
part/aillion (ppa)
pound/cubic foot (lb/ft3)
graa/cubic centiaeter g/ca3)
pound/ cubic foot (Ib/ft3)
pound/gallon (U.S.) (Ib/gal)
•taosphert (ata)
inch of aercury 9 32*T (in. Hg 9 32°F)
kilopascal (kPa)
pascal (Pa)
pound/ square inch (psi)
Btu
Btu/ainute (Btu/ain)
Btu/ hour (Btu/h)
Btu
erg
joule (J)
pound (avoirdupois) [Ib (avdp)J
ton (short, 2,000 Ib aaas)
cubic foot (ft4)
quart (U.S. liquid) (qt)
foot (ft)
inch (in. )
aile (statute) (ai)
•illoaicrons (ap)
y«rd (yd)
.taosphere (standard) (ata)
dyne/square centiaeter (dyne/caz)
inch of water 9 39.2«F (in. H,0 9 39.2«F)
inch of water 9 60°F (in. HZ0 9 60«F)
pound-force/square inch ( Ib- force/ in. *) (psi)
: 20095
0 00668932
3.785 4118
0 133630335
231
0 0037854118
3 7854118
2286 . 3
0.001
0.0022046226
1
15.43279
1
32.427961
0 . 036127292
8.3454044
0.43699572
1.000
0.06242621
1
62.4261
8.34S171
0.0024582
O.C73553?
249,082
249 . 082
0.03612628
0.000948451
0.0569071
3.414426
3 . 9683207
4.1«4 x 10'
4,184
2.2046226
0.0011023113
0.03S314667
1.0566M2
3.2808399
39.370079
0.00062137119
1 x 10*
1.0936133
9.869233 x 10~*
10
0.004014742
0.004018647
0.0001450377
\
(continued)
C-2
-------
To convert
Pascal -seconds (?t-s)
'»)
pound ; ib •
pound/ (foot -second)
fib/ (ft -$i j
pound cubic foot
pound/ cubic inch (Ib/in
<„.,. Uquid)
(u s- Uquid)
pound/ square inch (p»i)
saybolt second* (ssu)
square foot (ft2)
square kiloB,t»r
square aeter (•*,
stoke (St>
ton (at
TABLE C-l (continued;
centipose
-------
:ABLE c-2. KINEMATIC VISCOSITY CONVERSION FACTORS
FOR CENTISTOKES TO SSU UNITS3
Centi-
stokes
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
12.0
14.0
16.0
18.0
20.0
22.0
24.0
26.0
Saybolt
1CC°F
32.6
36.0
39.1
42.3
45.5
48.7
52.0
55.4
58.8
62.3
65.9
73.4
81.1
89.2
97.5
106.0
114.6
123.3
seconds
(SSU)
13C°F
32.7
36.1
39.2
42.4
45.6
48.8
52.1
55.5
58.9
62.4
66.0 '
73.5
81.3
89.4
97.7
106.2
114.8
123.5
at
210°F
32.8
36.3
30.4
42.6
45.8
49.0
52.4
55.8
59.2
62.7
66.4
73.9
81.7
89.8
98.2
106.7
115.4
124.2
Centi-
stokes
28.0
30.0
32.0
34.0
36.0
38.0
40.0
42.0
44.0
46.0
48.0
50.0
60.0
70.0
80.0
90.0
100.0
Saybolt
100° F
132.1
140.9
149 . 7
158.7
167 . 7
176.7
185.7
194.7
203.8
213.0
222.2
231.4
277.4
323.4
369.6
415.8
462.0
seconds
(SSU)
130°F
132.4
141.2
150.0
159.0
168.0
177.0
186.0
195.1
204 . 2
213.4
222.6
231.8
277 . 9
324 . 0
370.3
416.6
462.9
at
2 1 0 ° F
133.0
141.9
150.8
159.8
16?. 9
177.9
187.0
196.1
205.2
214.5
223. 8
233.0
279.3
325.7
372,2
418.7
465.2
For kinematic viscosity levels above 100 centistokes, use the
same ratio as the ratio in the table above for 100 centistokes
(at the temperature of the fluid); e.g., 120 centistokes
(9 130°F) = 120 x 4.629 = 555.5.
To obtain the saybolt universal viscosity at a temperature not
shown in te table above, multiply the saybolt universal viscosity
Q 100°F by [1 + (t - 100) 0.000064], where "t" is the temperature
in degrees fahrenheit, e.g., 10 centistokes 9 220°F = 58.8 x
[1 + (220-100) 0.000064]; = 58.8 x 1.00768 = 59.25
\
C-4
-------
Accident prevention manual for industrial operations, seventh edition
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D-l
-------
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t
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D-3
-------
Danielson, J. A., ed. Air pollution engineering manual, second edition
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D-10
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APPENDIX E
LABORATORY-SCALE THERMAL DECOMPOSITION ANALYTICAL DATA
1. INTRODUCTION
Labo-itory-scale thermal decomposition data for hazardous wastes can be help-
ful ror establishing sampling and analytical protocols for incinerator per-
formance monitoring, and for determining potential operating conditions for
incinerator trial burns. Such data can be generated using laboratory-scale
thermal decomposition systems such as the Thermal Decomposition Analytical
System (TDAS) employed at the U.S Environmental Protection Agency research
program at the University of Dayton Research Institute (UDRI). The objectives
of this appendix are to describe how the data are collected and to provide
guidance for their use.
2. THERMAL DECOMPOSITION ANALYTICAL SYSTEM (TDAS) f
2-1 General Description
This system is designed to evaluate the thermochemical behavior of volatile
materials under controlled conditions. As indicated in Figure E-l, it con-
sists of a modular control panel (where the operating parameters for tests are
established), several gas cylinders (that supply reaction atmospheres with
known compositions), a sample insertion and vaporization chamber, a special
quartz tube reactor in a furnace (for the decomposition of samples), a product
collection trap, a gas chromatograph, a mass spectrometer, and a minicomputer.
Figure E-2 is a block diagram shoving a simplified representation of the
operational relationships of the various components.
2.2 Operation
In operation, several micrograms of a solid, liquid, or gaseous sample are
introduced into a sample insertion chamber (location K in Figure E-l). The
chamber is then sealed and flushed with the controlled atmosphere to be used
for the experiment. Solid and liquid samples are heated, vaporized at tem-
peratures up to 300°C (over a controlled time interval), and mixed with a
continuous stream of the reaction atmosphere. Samples can be flash pyrolyzed
or gradually vaporized, depending on the desired reaction conditions. The
mixture then passes through a reactor (location M) consisting of an 98-cm
long, 0.097-mm inside diameter, thin walled, folded quartz tube enclosed in an
electric furnace. The furnace and tube can be operated at temperatures up to
1,150°C. The temperature of the reactor is monitored by a thermocouple lo-
cated at a point representing the mean temperature for the reactor furnace [1]
E-l
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IN-LINE
GC/MS/DS
A HELIUM GAS
B COMPRESSED AIR
C INERTCARRIETR
D PRESSURE REGUALTOR
E OXYGEN SCRUBBER
F DIRECTIONAL VALVE
G FILTER
H FLOW CONTROL VALVE
I FLOW TRANSDUCER
j PRESSURE TRANSDUCER
K INSERTION CHAMBER
L TEMPERATURE PROGRAMMER
M REACTOR IN FURNACE
N PRODUCT COLLECTION TRAP
0 MODULAR CONTROL PANa
'THE MODULAR CONTROL PANa DID NOT APPEAR IN nc
ORIGINAL PUBLICATION
Figure E-l. Simplified schematic of IDAS [1]
E-2
-------
B-3
-------
f
It is estimated that a typical reaction mixture entering the TDA5 reactor
heats to the reactor temperature within 0.005 second. Ninety-five percent of
the molecules are estimated to be exposed to the reported temperature over
time intervals with a maximum deviation of 4% to 10% from the reported mean
residence time, depending on the conditions of the test. The percent devia-
tion increases as the mean residence time decreases. The temperature is
controlled to within ±2°C across the operating range of the device. Mean
residence times between 0.23 and 5.0 seconds may be selected [1], It is
possible to operate the reactor at pressures up to two atmospheres.
The effluent from the TDAS reactor enters a sorbent trap (Location N) that can
be maintained at -110°C. In the trap, reactions are quenched and reaction
products and unreacted sample are collected with a sorbent (usually Tenax-GC,
although other materials, such as quartz wool, have also been used). The
chemicals collected are then thermally desorbed directly into a capillary
column gas chromatograph/mass spectrometer for identification and quantifi-
cation of reaction products and unreacted sample.
The chromatograph has been used with glass and fused silica capillaries coated
with selected materials (such as a 0.1-um layer of Supelco SP 2100) [2]. The
mass spectrometer contains an ion detector upstream of the magnetic sector.
This detector may be calibrated and used to measure quantities of pure sub-
stances leaving the gas chromatograph at different times. A photomultiplier
tube downstream of the magnetic sector of the mass spectrometer responds to
the ionic fragments of molecules emerging from the magnetic field. The iden-
tity of chemicals and mixtures of chemicals emerging from the gas chroma-
tograph can be determined by comparing the observed ion fragment patterns with
those of known compounds. The NIK/EPA Chemical Information Mass Spectral Data
Base is routinely used to help identify compounds and mixtures.
Samples of effluent from the reactor may be collected on activated carbon (or
other sorbents) simultaneously with the samples collected in the cold sorbent
trap described above. These samples could be desorbed with solvents and
injected into laboratory gas chromatographs or other analytical devices not
directly connected to the TDAS.
3. THERMAL DECOMPOSITION DEVICE (TDD)
3.1 General Description
Figure E-3 is a schematic diagram of the thermal decomposition device (TDD).
This device is the predecessor to the TDAS. It consists of a compressed air
cylinder (to supply the reaction atmosphere), pressure regulators, flow regu-
lators (to adjust the residence time), a sample insertion and vaporization
chamber, a quartz tube reactor in an electrically heated furnace (for the
decomposition of samples), a product collection trap, and a flow meter.
3.2 Operation
The TDD is operated in the following manner. Compressed air is filtered (at
location C in Figure E-3) and its flow rate is adjusted (location D) to pro-
vide the desired residence time. The gas enters the inlet chamber (location G)
E-4
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DO*
I I J
HIGH TEMPERATURE REGION
VENT
A COMPRESSED AIR, BREATHING QUALITY GRADE
B TWO STAGE PRESSURE REGULATOR
C "HYOROPURGE" FILTER
D FLOW CONTROL VALVE
E PRESSURE TRANSDUCER
F SAMPLE HOLDER, PYREX
G HEATED INLET CHAMBER
H QUARTZ TUBE
I HEATED OUTLET CHAMBER
J EFFLUENT TRAP, TENAX-GC OR CHARCC
K FLOW METER
Figure E-3. Schematic of thermal decomposition device [3].
which surrounds a sample holder containing several micrograms of sample (loca-
tion F). The chamber is gradually heated to a maximum temperature of about
300°C to vaporize the sample [3]. As material from the sample vaporizes, it
is swept into the reactor chamber (location H) by the compressed air flow. In
the reactor chamber, the reaction mixture is thermally stressed at a con-
trolled temperature (up to 1,000°C). An 84-c» by 0.8-ma ID quartz reaction
chamber and an 84-cm by 2.14-mm ID quartz reaction chamber are available. The
average temperature of the reactor furnace is controlled to ±5°C; but there
are temperature gradients in the furnace of up to 50°C, compared to the
reported average temperature. In most experiments, the residence times in the
reactor were approximately one second (±0.04 s), but residence times between
0.5 s and 3.0 s are possible [3].
After the mixture passes through the reactor, it is cooled to approximately
300°C [3]. The partially cooled mixture then enters the effluent trap (loca-
tion J), where it rapidly cools to ambient temperature. The effluent trap and
sorbent (Tenax GC or charcoal) collect unreacted sample and the products of
decomposition of the waste. The sorbents used at room temperature are gener-
ally suitable for materials with molecular weights between 78 and 800.
E-5
-------
At the end of a run, the effluent trap is removed from the TDD. If Tenax is
the sorbent, the trap is inserted directly into an adapter on a separate
laboratory gas chromatograph (GC). The trap is then heated to desorb the
products, which are flushed into the GC by a carrier gas. If activated carbon
is used as the sorbent, the products are desorbed with a suitable solvent. A
sample of the solvent/product mix is then injected directly into the GC for
analysis.
4. DIFFERENCES BETWEEN THE TDAS AND TDD
Both of these devices were designed for the purpose of studying the thermal
chemical decomposition of various materials, and their basic designs and
methods of operation are quite similar. However, important specifications,
summarized in Table E-l, are different.
5. DIFFERENCES BETWEEN INCINERATORS AND LABORATORY DEVICES
While the results obtained with the previously described laboratory devices may
resemble the performance of an incinerator, there are differences. The labora-
tory devices are not designed to simulate incinerator behavior. They are de-
signed to generate basic thermal decomposition data at the molecular level.
The operating conditions in most incinerators are not as simple as those in
the laboratory devices. Among the potential complications associated with
real incinerators (compared to the TDAS and TDD systems) are the following:
• Wastes may enter the combustion chamber of an incinerator as liquids or
solids, while only gases enter the reaction zones in the TDAS and TDD.
\
Direct combustion of fuel and/or waste supplies the heat required for. the
reactions in incinerators, and the waste in an incinerator may pass
directly through a distinct flame or flame front. The TDAS and TDD are
indirectly heated. I
There may be a significant lack of homogeneity in the temperature pro-
files of incinerators, and the temperature is often not as closely con-
trolled as in the laboratory devices. Furthermore, the maximum '
temperature in an incinerator may be higher than the highest temperature *
at which laboratory devices can be operated. '
The residence times reported for incinerators often does not really ,
represent the exposure times of wastes at the reported operating
temperatures. An "upper bound" residence time is the only value reported
for many incinerators. This represents the total volume of the incin-
erator combustion chamber (whether or not it is all at the reported
temperature) divided by the volume rate of flow of flue gas out of the
chamber. All of the waste passing through an incinerator does not have
the same residence time. Some waste passes through faster than other >
portions of the same charge, resulting in a residence tine distribution.
The mean residence times in the previously described laboratory devices
are well controlled and represent true residence times for all of the '
E-6
-------
TABLE E-l. COMPARISON OF THE TDD AND TDAS
Parameter
TDD [3]
TDAS
Sample type
Reactor construction
Regulation of mean
reactor temperature
Maximum operating
temperatures
Range of tempera-
tures in reactor
Residence time range
Effluent traps
Sampling and
analysis
Liquid or soluble solids
with low volatility
and molecular weights
between 78 and 800.
Heavy-wall folded quartz
84 cm long, 0.8-mm ID
(an 84. cm long, 2.14-mm
10 tube is also available)
±5°C
l,000°Ca
+25°C
-50°C
0.5 - 3.0 sc
Ambient temperature trap
Sample must be manually
removed from unit for
analysis on a nearby GC
Gas, liquid or solid
samples with molecular
weights less than
about 800.
Thin-wall folded quartz
(98 cm long, 0.97 mm ID)
±2°C
1,
±2°C
0.25 - 5.0 s • '
Cryogenically cooled trap
Sample normally thermally
desorbed in-situ and
carried directly to
GC/MS by the carrier
gas.
aLimited by the heating unit.
Limited by the properties of quartz.
°Personal communication with W. A. Rubey, 8 August 1980.
waste passing through the devices at the reported temperatures with a
degree of accuracy seldom (if ever) achieved for incinerators.
Physical and chemical interactions between components of mixtures of
wastes and reaction products (such as adsorption on particulates and
catalysis) might inhibit or accelerate the rate of waste decomposition
and combustion product formation. Furthermore, interaction of the com-
bustion products with the walls of the incinerator might affect the
degree of combustion and the products. Possible wall effects include
heat transfer, flame quenching, the adsorption of reactive components on
E-7
-------
surfaces, and catalysis. Some of these effects cannot oe studied in the
TDAS and TDD laboratory units, since solids and liquids cannot enter the
reaction chambers of those devices and the wails are not the same as in
incinerators.
Mixing in an incinerator will be different from mixing in laboratory
devices This can result in changes in the relative proportions of
uncomousted, partially combusted, and completely combusted waste.
In an incinerator, the conditions to which various molecules are exposed
can vary greatly in terms of temperature, oxyger. concentration, and con-
centrations of free radicals.
The laboratory devices were usually operated in such a manner that waste
concentrations were very low, and the amounts of oxygen leaving the
reactors were not significantly different from the amounts going into the
reactors. Furthermore, most experiments were performed with 21% oxygen
(although 0% to 40% oxygen have also been used). The oxygen concentra-
tions found in incinerator'flue gas are often much lower than the oxygen
concentrations used in laboratory experiments.
The feed rate of incinerators may be constant, allowing steady state
conditions to occur. The laboratory devices are batch fed. I
6. POSSIBLE APPLICATIONS OF LABORATORY EXPERIMENTS J
The previously described laboratory devices were not designed to simulate
incinerators, and no systematic studies of the performance of the TDAS or TDD
compared to incinerators of different sizes, designs, and operating conditions
have been reported. Furthermore, no systematic studies of the quantitative
limitations of scaleup methods are available. As a result, great caution must
be exercised when using data from the laboratory device when designing trial
burn studies, since the applicability of the data to predicting the behavior
of hazardous waste incinerators has not been demonstrated. However, some
potential uses for laboratory experiments exist:
The rate constant for the decomposition of a waste and its temperature
dependence can be identified with the TDAS and the TDD [4].
• The TDAS and TDD devices can be used to identify byproducts of decomposi-
tion of hazardous materials and the conditions under which they are
formed.
• Experienced combustion chemists and engineers can obtain evidence that
can aid in understanding the detailed operating conditions within an
incinerator by comparing the results of laboratory decomposition experi-
ments to the results of full-scale test burn experiments under similar
conditions.
• Various thermochemical modeling techniques used to predict the behavior
of full-scale incinerators can be tested using data from laboratory
experiments. Once their accuracy for predicting the behavior of waste in
E-8
-------
relatively well controlled circumstances is determined, the models can be
tested in experiments on incinerators. Most of these models use an
activatio-n energy for the reactive species. An apparent activation energy
for the reaction of a dilute waste with oxygen can be derived with IDAS
or TDD laboratory data [4].
Data from laboratory experiments can be compiled and used to help develop
empirical modeling techniques for full-scale incinerators by simulating
(insofar s possible) various microscale regions within an incinerator in
laboratory experiments and then using the data to help predict what
happens to waste after it passes through such regions in incinerators.
Data from the device can be used to help determine researcn priorities
for hazardous waste incineration (when pilot or full-scale trial burn
data are unavailable) by considering the types, amounts, and potencies of
the reaction products observed.
Data from laboratory waste decomposition experiments can help to deter-
mine operating conditions at the beginning of trial burns. Temperature,
retention time, turbulence, and excess air levels at the beginning of
trial burns should be far enough above those associated with unacceptable
emissions (based on laboratory data) to give a reasonable confidence of
having acceptable emissions. The margins of safety for this purpose ha
not been systematically studied.
r
• Data from laboratory tests can be used to help determine which compounds
to monitor during trial burns and at full-scale industrial installations.
Figure E-4 shows the effects of oxygen concentrations on the thermal decom-
position of a PCB in the thermal decomposition device. The high sensitivity
to oxygen is clearly shown. This suggests that operating laboratory devices
(or modifying them to operate) with amounts of excess air similar to those
found in an incinerator may significantly improve the utility of the data
generated. If the percent oxygen used in a laboratory experiment is equiva-
lent to the percent oxygen in incinerator flue gas, the probability of a
laboratory experiment yielding a lover destruction and removal efficiency than
that achieved in an incinerator will be increased (compared to operation of a
laboratory device at 21% oxygen). This can increase the utility of laboratory
data for quickly making conservative estimates of acceptable operating condi-
tions at the beginning of trial burns.
7. RESULTS OF LABORATORY-SCALE DECOMPOSITION EXPERIMENTS
7.1 Kepone Results
Kepone decomposition experiments were performed in the thermal decomposition
device. As can be seen from Table E-2, the destruction of Kepone increases
rapidly with increasing temperature above 400°C (at a relatively constant
retention time). It is also apparent that there are several byproducts.-
hexachlorobenzene, hexachlorocyclopentadiene [3] and hexachloroindenone. The
amounts of byproducts formed are dependent upon the reactor temperature. This
information is graphically represented in Figure E-5.
E-9
-------
100
I
5
o
s
10 :
1 I-":
0.
Cn
*- 0.1 :
0.01
2.5* OXYGEN
IM NITROGEN
THERMAL DECOMPOSITION
OF
2,2', 4,5, y- PENTACHLOROBIPHENYL
IN
DIFFERENT GASEOUS ATMOSPHERES
50 500 550 600 650 700 750 800 850 900
EXPOSURE TEMPERATURE, °C
Figure E-4. Effect of oxygen concentration [5].
950 1,000
E-10
-------
TABLE E-2. KEPONE THERMAL DESTRUCTION SUMMARY
Waste: kepone; sample size.- 40 pg;
laboratory device: thermal decomposition device.
Unit
temperature, Input
9C ataosphere
302
397
435
463
495
603
708
807
910
433
433
433
Air,
*ir,
Air,
Air,
Air,
Air,
Air,
Air,
Air,
Air,
Air,
Air,
21%
21%
21%
21%
21%
21%
21%
21%
21%
21%
21%
21%
02
02
°2
°2
02
02
02
02
02
02
02
02
Destruction
Retention and removal
tine, efficiency,
• %
0.
0.
0.
0.
1.
0".
0.
0.
0.
0.
1.
1.
93
99
94
93
10
99
91
92
94
23
04
79
0
12
46
96
299.55
299.55
299.55
299.55
299.999655
6
53
68
Relative
Byproducts, quantity of
identified^ byproducts
None
Hexachlorocyclopentadiene
Hexachloroindenone*
He*achlorocyclopentadiene
Hexachloroindenone
Hexachlorocyclopentadiene
Hexacnloroindenone
Hexachlorocyc lopentadiene
Hexachloroindenone
Hexachlorobenzene
Hexachlorobenzene
Hfxich 1 9T9 irvdtnont
HMULChlorocyclop«nt*di«iM
H*sachlorob«nztn*
Hcxachloroindinon*
Itesachlorob«iucn«
H*sachlorob«&z«n«
Mot reported
Not rtporttd
Mot rtporttd
None
0
0
0
0
0
0
0
1
0
.05
.05
.5
.75
.85
.65
.65
•2d
U
.04
1-75
0
1
0
0
0
.05
.10
.05
.45
.15f |
MA1
MA j
MA
iteuchloroind*none identified in a personal eoMwnication with Don Duvall and
Wayne Rubey, 4 August 1980.
Byproducts collected on Tenas GC and detected in quantifiable amounts unless otherwise
specified.
Reported as relative peak heights on a flaae ionization detector.
Detected, but below aeasureable levels.
'Collected on activated carbon, desorbed with mixed solvent (acetone, benzene, CS2) and
quantified with an electron capture detector (residual Kepone 138 pg; hexachlorobenzene
••200 nanograsu).
fNot applicable.
E-ll
-------
100
30
10
S x
<•» O
I §3.0
11 1.0
z 2
°- LU
<< 0.3 h
ce =
z ^
O 3
0.1 r
K -HEXACHrROCYCLOPENTADIENE
K. -HEXACHLOROINOENONE
D
- HEXACHLOROBENZENE
KEPONE
0.01 I 1 1 1 1 1 1 1 1 1—
0 200 400 600 800 1,000
TEMPERATURE, QC
Figure E-5. Thermal destruction plot for Kepone [3].
t
E-12
-------
8. REFERENCES
1. Rubey, W. A.
cal system.
August. 143
2.
3.
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Ferguson, T. L. ; Bergman, r. -.; Cooper j- 3.; '-- , ?. 7.; ar.
I. ; Determination zf ir. c_;.-,er3tcr opera: .r.~ tc-r.ditic.-.5 -ecessary f;r
jafe disposal c: pesticides. -i.-.ci.-.r.ar.i, ~H, 'JSEPA, 13 "3 J
Contract 63--J-^-35.
2. Jcsim, s. J. ; K. M. Barclay, s. ;,. Gay, ,a,-d L. F. Grantham. "Disposal of
hazardous wastes by molten salt comiusticn," Presented at the American
Cheirucal Society (ACS) symposium on 'The -Itimate Disposal of Hazardous
Wastes', April 1979.
3. Shin, C. c.; Tobias, H. F.; Clausen, J. F.; and Johnson, R. I. Thermal
degradation of military standard pesticide formulations. Washington, D. C.;
U.S. Army Medical Research and Development Command; 1975 Mary 20, 287 p.
Contract DAOA 17-73-C-3132.
4. Ahling, Sengt, "Destruction of chlorinated hydrocarbons in a cement kiln."
environmental Science and Technology. 13(11), 1979 pp. 1377-1379.
5. A study of pesti-ride disposal in a sewage sludge incinerator. Whitnore
and Durfee, Vesar, Inc. Contract 68-01-1587. 1975. i-
6. Feldoan, John B.; Leighton, Ira W.; Denenstration teat burn of DDT in -
General Electric's liquid injection incinerator. USEPA, Region I.
7. Destroying chemical wastes in eoianereia.JL scale incinerators, phase II.
Final Report. Washington, D.C., USEPA; 197V, 121 p. Contract No.
68-01-2966.
«
8. Ac German, P. G.; H. J. Fisher, R. J. Johnson, R. F. Maddalone,
I 3. J. Matthews, S. L. Moon, K. H. Scheyer, C. C. Shah; and R. F. Tobias.
1 At-se-a incineration of herbicide orange on-board the n/t Vuleanus.
EPA, 1978 April, 263 p.
I
9. Bell, Bruce A.; Whitnore, Franfc C.; Kapone incineration test program.
' USEPA, 1978, May, Grant No. R-805112.
10. The PCS Incineration Test Burn made by Rollins Environmental Services at
Deer'Par*, Texas. November 12-16, 1979. A report to the United States
Environmental Protection Agency, Region VI, Dallas, Texas.
11. TRW Systeou Group 6 Arthur D. Little, Inc., Destroying chemical wastes
in coaaBereial scale incinerators, USEPA, 1977 June, 120 p. Contract
No. 68-01-2966.
12. Destroying chemical wastes in commercial-scale incinerators-facility
report 5. USEPA, 1977. Contract No. 68-01-2966.
F-7
-------
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