APTD-1101
FIELD OPERATIONS
AND ENFORCEMENT
MANUAL FOR
AIR POLLUTION
CONTROL
VOLUME II:
CONTROL TECHNOLOGY AND
GENERAL SOURCE INSPECTION
US. ENVIRONMENTAL PROTECTION AGENCY
Office of Air Programs
Stationary Source Pollution Control Programs
Research Triangle Park, North Carolina 27711
-------
APTD-1101
FIELD OPERATIONS
AND ENFORCEMENT MANUAL
FOR AIR POLLUTION CONTROL
VOLUME II: CONTROL TECHNOLOGY
AND GENERAL SOURCE INSPECTION
Prepared by
Melvin I. Weisburd
Pacific Environmental Services, Inc.
2932 Wilshire Boulevard
Santa Monica, California 90403
for
System Development Corporation
2500 Colorado Avenue
Santa Monica, California 90406
Contract No. CPA 70-122
Prepared for
ENVIRONMENTAL PROTECTION AGENCY
Office of Air Programs
Stationary Source Pollution Control Programs
Research Triangle Park, North Carolina 27711
August 1972
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ii
The APTD (Air Pollution Technical Data) series of reports is issued by the
Office of Air Programs, Environmental Protection Agency, to report technical
data of interest to a limited number of readers. Copies of APTD reports are
available free of charge to Federal employees, current contractors and
grantees, and non-profit organizations - as supplies permit - from the Air
Pollution Technical Information Center, Environmental Protection Agency,
Research Triangle Park, North Carolina 27711 or may be obtained, for a
nominal cost, from the National Technical Information Service, 5285 Port
Royal Road, Springfield, Virginia 22151.
This report was furnished to the Environmental Protection Agency by Pacific
Environmental Services, Inc. of Santa Monica, California (pursuant to a
subcontract with System Development Corporation) in fulfillment of prime
Contract No. CPA 70-122. The contents of this report are reproduced herein
as received from Pacific Environmental Services, Inc. The opinions,
findings, and conclusions expressed are those of the author and not neces-
sarily those of the Environmental Protection Agency.
Office of Air Programs Publication No. APTD-1101
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iii
The Field Operations and Enforcement Manual for Air Pollution Control is
divided into three separate volumes.
Volume I, Organization and Basic Procedures, contains Chapters 1 through 4
Volume II, Control Technology and General Source Inspection, contains
Chapters 5 and 6.
Volume III, Inspection Procedures for Specific Industries, contains
Chapter 7.
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ABSTRACT
The Field Operations and Enforcement Manual for Air Pollution Control,
Volume II explains in detail the following: technology of source control,
modification of operations, particulate control equipment, sulfur dioxide
removal systems, and control equipment for gases; inspection procedures
for general sources, fuel burning equipment, incinerators, open burning,
odor detection, and motor vehicle visible emissions.
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TABLE OF CONTENTS FOR VOLUME II
LIST OF FIGURES ix
LIST OF TABLES xiii
CHAPTER 5. THE TECHNOLOGY OF SOURCE CONTROL 5.1
I. INTRODUCTION 5.1
II. ELIMINATION OF AIR POLLUTION OPERATIONS 5.2
III. REGULATION OF LOCATION OF OPERATIONS 5.3
IV. MODIFICATIONS OF OPERATIONS 5.4
A. Change in Fuels or Process Materials 5.4
B. Process and Facility Changes 5.7
C. Improvements in Operational Practices 5.9
V. SPECIFIC TYPES OF AIR POLLUTION CONTROL EQUIPMENT 5.11
A. Introduction 5.11
B. Gravitational Settling Chambers 5.27
C. Cyclone Separators 5.31
1. Inspection Points 5.38
D. Scrubbers (Wet Collectors) 5.38
1. Inspection Points 5.56
E. Fabric Filters 5.61
1. Inspection Points 5.66
a. Pressure Drop 5.66
b. Operation 5.66
c. Maintenance 5.73
d. Temperature and Dew Point 5.78
e. General 5.78
F. Electrostatic Precipitators 5.78
1. High Voltage Precipitators 5.79
a. Inspection Points 5.89
2. Two-Stage Precipitators 5.90
3. Maintenance 5.93
VI. SULFUR DIOXIDE REMOVAL SYSTEMS FOR POWER PLANTS 5.93
A. Limestone/Dolomite Injection-Dry Process 5.93
B. Limes tone/Dolomite Injection-Wet Process 5.97
C. Catalytic Oxidation 5.97
D. Inspection Points 5.101
1. Lime Injection, Dry and Wet Processes 5.101
2. Catalytic Oxidation Process 5.101
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vi
VII. CONTROL EQUIPMENT FOR GASES AND VAPORS 5.102
A. Afterburners 5.102
1. Direct-Fired Afterburners 5.102
2. Catalytic Afterburners 5.104
3. Boilers Used as Afterburners 5.106
B. Absorption Equipment 5.106
1. Packed Towers 5.107
2. Plate Towers 5.108
3. Spray Towers and Chambers 5.111
4. Spargers 5.111
5. Venturi Absorbers 5.112
C. Adsorption Equipment 5.112
1. Fixed-Bed Adsorber 5.115
2. Continuous Adsorber 5.117
3. Operational Problems 5.117
D. Condensers Used in Vapor Recovery Systems 5.117
1. Surface Condensers 5.118
2. Contact Condensers 5.118
3. Typical Installations 5.121
REFERENCES 5.125
CHAPTER 6. INSPECTION PROCEDURES FOR GENERAL SOURCES 6.1
I. INTRODUCTION 6.1
II. FUEL-BURNING EQUIPMENT 6.2.1
A. Introduction 6.2.1
B. Elements of the Combustion System 6.2.3
C. Fuels 6.2.16
1. Coal 6.2.20
2. Fuel Oil 6.2.24
3. Gaseous Fuels 6.2.26
4. Fuel Sampling 6.2.26
D. Types of Fuel-Burning Functions 6.2.27
E. Size of Fuel-Burning Functions 6.2.30
F. Inspection Points 6.2.37
1. Solid Fuel-Burning Systems—Inspection Points and
Operating Guides 6.2.43
a. Stokers 6.2.43
b. Pulverized Fuel-Burning Equipment 6.2.53
c. Cyclone Furnaces 6.2.61
2. Oil-Burning Equipment 6.2.65
3. Gas-Burning Equipment 6.2.74
REFERENCES 6.2.76
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vii
III. INCINERATORS 6.3.1
A. Introduction 6.3.1
B. Incinerator Definitions and Terminology 6.3.3
C. Multiple-Chamber Incinerators 6.3.8
1. General Principles 6.3.8
2. General Inspection Points—Multiple Chamber
Incinerators 6.3.13
a. Composition of Refuse 6.3.14
b. Refractories 6.3.16
c. Insulation Requirements 6.3.17
d. Charging Doors 6.3.19
e. Air Inlets 6.3.19
f. Clearance 6.3.19
g. Stack Viewer 6.3.20
h. Sampling Ports 6.3.20
i. Auxiliary Gas Burners 6.3.20
j. Scrubbers 6.3.24
3. General Refuse Incinerators 6.3.25
a. General Operating Procedures 6.3.26
4. Multiple-Chamber Incinerators, Woodworking Industries . . 6.3.28
a. General Operating Procedures 6.3.30
5. Multiple-Chamber Flue-Fed Incinerators 6.3.32
a. General Operating Procedures 6.3.32
D. Single-Chamber Incinerators 6.3.35
1. General Residential and Commercial 6.3.36
2. Flue-Fed Incinerators 6.3.36
3. Wood Waste-Burning Incinerators 6.3.38
4. General Operating Procedures and Inspection Points . . . . 6.3.45
E. Municipal Incinerators 6.3.46
REFERENCES 6.3.63
IV. OPEN BURNING 6.4.1
A. Description of Source 6.4.1
B. Types of Open Burning 6.4.1
1. Household Wastes 6.4.2
2. Construction and Demolition Wastes 6.4.2
3. Salvaging Operations 6.4.3
4. Open Dump Burning 6.4.4
5. Agricultural Burning 6.4.5
6. Coal Refuse Piles 6.4.7
7. Other Sources 6.4.7
C. Control of Open Burning 6.4.8
D. Inspection Points 6.4.10
REFERENCES 6.4.13
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viii
V. ODOR DETECTION AND EVALUATION 6.5.1
A. Introduction 6.5.1
B. Characteristics of Odors and Odorants 6.5.3
1. Odor Perception 6.5.A
2. Odorants 6.5.5
3. Odor Parameters 6.5.6
a. Quality 6.5.7
b. Intensity 6.5.9
c. Acceptability 6.5.10
d. Pervasiveness 6.5.11
C. Determinants of Odor Perception 6.5.11
1. Identity of Odorant 6.5.11
2. Concentration of Odorant 6.5.13
3. Ambient Conditions 6.5.15
4. Status of Observer 6.5.15
a. Sensitivity 6.5.15
b. Expertise and Training 6.5.15
c. Physiological and Psychological Condition 6.5.16
D. Measurement of Odor Intensity or Odorant Concentration .... 6.5.17
1. Sampling for Later Evaluation 6.5.18
2. Dilution Techniques 6.5.20
E. Determining Sources Responsible for Odors 6.5.23
1. Odor Patrol 6.5.23
2. Field Investigations of Odor Incidents 6.5.25
a. Determining Air Flow from Source 6.5.26
b. Tracking Odors 6.5.28
(1) Point Observations 6.5.30
(2) Micrometeorological Problems 6.5.32
(3) Approaching the Plant 6.5.33
F. Investigation of Odor Potentials of Sources 6.5.35
1. Plant Inspection and Source Testing 6.5.35
a. Interrogation 6.5.36
b. Equipment Data 6.5.36
2. Evaluating Odor Concentrations 6.5.37
G. Relating Source Strength to Control Requirements 6.5.37
H. Odor Control 6.5.40
REFERENCES 6.5.41
VI. MOTOR VEHICLE VISIBLE EMISSIONS 6.6.1
A. Introduction 6.6.1
B. Gasoline-Powered Vehicles 6.6.2
1. Vehicle Emission Control Systems 6.6.3
a. Crankcase Control Devices 6.6.3
b. Exhaust Control Systems 6.6.3
c. Fuel-Evaporative Control Systems 6.6.8
2. Types of Visible Vehicle Emission Violations 6.6.13
a. Nuisance Type Violations 6.6.13
b. Opacity Type Violation 6.6.15
3. Following and Halting of Vehicles 6.6.16
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C. Emissions from Diesel-Powered Vehicles 6.6.18
1. Cause of Diesel Emissions 6.6.18
2. Reading Visible Emissions, Halting and Inspection of
Vehicles 6.6.20
REFERENCES 6.6.22
GLOSSARY G.I
LIST OF FIGURES
Figure 5.1. Composite Grade (Fractional) Efficiency Curves Based
on Test Silica Dust 5.30
Figure 5.2. Double-Vortex Path of the Gas Stream in a Cyclone 5.34
Figure 5.3. Cyclones Arranged in Parallel 5.34
Figure 5.4. Cyclones Arranged in Parallel 5.34
Figure 5.5. High Efficiency Cyclone 5.35
Figure 5.6. High Throughput Cyclone 5.35
Figure 5.7. Typical Layout for Gravity Spray Tower 5.40
Figure 5.8. Centrifugal Spray Scrubbers 5.41
Figure 5.9. Impingement Plate Scrubber 5.42
Figure 5.10. Venturi Scrubber May Feed Liquid Through Jets (a),
Over a Weir (b), or Swirl Them on a Shelf (c) 5.43
Figure 5.11. Multiple-Venturi Jet Scrubber 5.44
Figure 5.12. Vertical Venturi Scrubber 5.45
Figure 5.13. Packed-Bed Scrubbers 5.46
Figure 5.14. Flooded-Bed Scrubber 5.47
Figure 5.15. Floating-Ball (Fluid-Bed) Packed Scrubber 5.48
Figure 5.16. Self-Induced Spray Scrubbers 5.49
Figure 5.17. Mechanically Induced Spray Scrubbers 5.50
Figure 5.18. Centrifugal Fan Wet Scrubber 5.51
Figure 5.19. Inline Wet Scrubber 5.52
Figure 5.20. Wetted and Impingement Plate Filters 5.53
Figure 5.21. Collection Efficiency vs. Pressure Drop in Venturi
Scrubbers 5.55
Figure 5.22. Low-Velocity Filtering Elements 5.57
Figure 5.23. Wire Mesh Mist Eliminator 5.58
Figure 5.24. Coke Quench Mist Elimination Baffle System 5.58
Figure 5.25. Bed of Berl Saddles Added to Discharge Stack 5.59
Figure 5.26. Typical Flat or Envelope Dust Collector Bag 5.63
Figure 5.27 Typical Round or Tubular Dust Collector Bag 5.63
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Figure 5.28. Open Pressure Baghouse 5.65
Figure 5.29. Closed Pressure Baghouse 5.65
Figure 5.30. Closed Suction Baghouse 5.65
Figure 5.31. Mechanical Shaking of Bottom Entry Design Uni-Bag
Dust Collector 5.67
Figure 5.32. Air Shaking Wind-Whip Cleans Dust Collector Bags 5.67
Figure 5.33. Bubble Cleaning of Dust Collector Bags 5.67
Figure 5.34. Jet Pulse Dust Collector Bag Cleaning 5.67
Figure 5.35. Reverse Air Flexing to Clean Dust Collector Bags by
Repressuring 5.68
Figure 5.36. Sonic Cleaning of Dust Collector Bags 5.68
Figure 5.37. Repressuring Cleaning of Dust Collector Bags 5.68
Figure 5.38. Cloth Cleaning by Reverse Flow of Ambient Air 5.69
Figure 5.39. Reverse Jet Cleaning of Dust Collector Bags 5.69
Typical Parallel Flow System for a Conventional
Multicompartment Baghouse 5.74
Schematic View of a Flat Surface-Type Electrostatic
Precipitator 5.80
Schematic View of Tubular Surface-Type Electrostatic
Precipitator 5.81
Cutaway View of a Flat Surface-Type Electrostatic
Precipitator 5.82
Cross-Sectional View of Irrigated Tubular Blast
Furnace Precipitator 5.83
Size-Efficiency Curves for Electrostatic Precipitator 5.85
Variation of Precipitator Efficiency with Sparking
Rate for a Representative Fly-Ash Precipitator 5.87
Effect of Moisture Content on Apparent Resistivity of
Precipitated Cement Dust 5.87
Components of Standard Two-Stage Precipitator 5.91
Limestone Injection - Dry Process 5.98
Limestone Injection - Wet Scrubbing Process 5.99
Catalytic Oxidation Process 5.100
Typical Direct-Fired Afterburner with Tangential
Entries for Both the Fuel and Contaminated Gases 5.103
Typical Catalytic Afterburner Utilizing Direct Heat
Recovery
Figure 5.54. Schematic Diagram of a Packed Tower
Figure 5.55. Common Tower Packing Materials
Figure 5.56. Schematic Diagram of a Bubble-Cap Tray Tower
Figure 5.57. Adsorption Efficiency, Single Solvent
Figure 5.58. Diagrammatic Sketch of a Two-Unit, Fixed-Bed Adsorber 5.116
Figure 5.59. Left: Diagrammatic Sketch of a Rotating Fixed-Bed
Continuous Adsorber Showing the Path of the Vapor-Laden
Air to the Carbon Bed
Right: Cut of Continuous Adsorber Showing Path of Steam
During Regeneration 5.116
Figure 5.60. Types of Condensers. Surface Condensers: Shell and
Tube 5.119
Figure 5.40.
Figure 5.41.
Figure 5.42.
Figure 5.43.
Figure 5.44.
Figure 5.45.
Figure 5.46.
Figure 5.47.
Figure 5.48.
Figure 5.49.
Figure 5.50.
Figure 5.51.
Figure 5.52.
Figure 5.53.
105
,109
,109
,110
,114
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xi
Figure 5.61. Types of Condensers. Surface Condensers: Integral
Finned Section, Calumet & Hecla Inc. 5.120
Figure 5.62. Types of Condensers. Surface Condensers: Tubular,
Hudson Engineering Corp. 5.120
Figure 5.63. Types of Condensers. Contact Condensers: Spray,
Schutte and Koerting Co. 5.120
Figure 5.64. Types of Condensers. Contact Condensers: Spray,
Schutte and Koerting Co. 5.120
Figure 5.65. A Condenser-Afterburner Air Pollution Control System
in Which a Vacuum Pump is Used to Remove Uncondensed
Gases from Condensate 5.122
Figure 5.66. A Contact Condenser-Afterburner Air Pollution Control
System in Which Malodorous, Uncondensed Gases are
Separated from Condensate in a Closed Hot Well 5.122
Figure 5.67. A Surface Condenser Used to Prevent Surge Losses from
an Accumulator Tank Handling Warm, Volatile,
Organic Liquid 5.122
Figure 6.2.1. Simplified Schematic of Combustion Heat Exchange System
Elements. Broken Blocks are Additional Components
Usually Found in Large Steam Generation Installations 6.2.4
Figure 6.2.2. Oxides of Nitrogen Concentrations in Gases from Various
Gas-Fired, Oil-Fired, and Coal-Fired Steam Generators 6.2.18
Figure 6.2.3. A Typical Fuel Survey Form 6.2.28
Figure 6.2.4. Summary of Characteristics of Coal Firing Equipment 6.2.29
Figure 6.2.5. Fire-Tube Boiler 6.2.34
Figure 6.2.6. Scotch-Marine Boiler 6.2.35
Figure 6.2.7. Cast-iron Sectional Boiler 6.2.36
Figure 6.2.8. Relation of Major Pollutants to Principal Design and
Operational Variables 6.2.40
Figure 6.2.9. Residential Underfeed Stoker 6.2.47
Figure 6.2.10. Multiple-Retort Underfeed Stoker 6.2.47
Figure 6.2.11. Spreader Stoker-Fired Furnace 6.2.47
Figure 6.2.12. B&W Jet-Ignition Stoker 6.2.48
Figure 6.2.13. Vibrating-Grate Stoker 6.2.48
Figure 6.2.14. Pulverized-Coal Bin System 6.2.54
Figure 6.2.15. Stirling Two-Drum Boiler (B&W) 6.2.55
Figure 6.2.16. Direct-Fired Copper Reverberatory-Furnace and Waste-
Heat-Boiler Arrangement 6.2.57
Figure 6.2.17. B&W Circular Burners for Pulverized Coal 6.2.59
Figure 6.2.18. B&W Multiple-Intertube Multitip Pulverized-
Coal Burners 6.2.59
Figure 6.2.19. B&W Cross-Tube Pulverized-Coal Burners 6.2.60
Figure 6.2.20. 700,000-KW-Capacity Universal Pressure Boiler 6.2.62
Figure 6.2.21. Types of Boiler Furnaces Used with Cyclone Furnaces 6.2.63
Figure 6.2.22. Bin-Firing and Direct-Firing Systems for Coal
Preparation and Feeding 6.2.64
Figure 6.2.23. Oil and Gas Burners for the Cyclone Furnace 6.2.66
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xii
Figure 6.2.
Figure 6.2.
Figure 6.2.
Figure 6.2.
Figure
Figure
.24.
.25.
.26.
.27.
6.2.28.
6.3.1.
Figure 6.3.2.
Figure 6.3.3.
Figure 6.3.4.
Figure 6.3.5.
Figure 6.3.6.
Figure 6.3.7.
Figure 6.3.8.
Figure 6.3.9.
Figure 6.3.10.
Figure 6.3.11.
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
Figure
.3.12.
. 3.13.
.14.
6.
6.
6.3.
6.3.15.
6.3.16.
6.3.17.
,3.18.
.19.
.20.
,5.1.
,5.2.
6.
6.3,
6.3
6,
6,
.5.3.
.5.4.
6.
6.
6.5.5.
6.6.1.
Figure 6.6.2.
Figure 6.6.3.
Figure 6.6.4.
6.6.5.
6.6.6.
6.6.7.
Figure 6.6.8.
Figure 6.6.9.
Figure
Figure
Figure
Figure 6.6.10.
Low-Pressure, Air Atomizing Oil Burner
High Pressure, Steam- or Air-Atomizing Oil Burner
Rotary Cup Oil Burner
Typical Atmospheric Gas Burner
A Multiple-Port Burner
Cutaway of a Retort Multiple-Chamber Incinerator
Cutaway of an In-Line Multiple-Chamber Incinerator
Multiple-Chamber Incinerator with Single Pass Flue
Multiple-Chamber Incinerator with Double Pass Flue
Flue-Fed Incinerator Modified by a Roof Afterburner
and a Draft Control Damper
Flue-Fed Incinerator Modified by a Roof Afterburner
and a Draft Control Damper
Flue-Fed Incinerator Modified by an Afterburner at
the Base of the Flue
Modified Single-Chamber Flue-Fed Incinerator
Fuel-Feed System of a Wigwam Burner
Fuel Feed and Dryer System of a Wigwam Burner
Diagram of the Inplant Systems Based Upon Dry Fly Ash
Collection and Conveying from Cooling and Collection
Operations
Plan of Tipping Area and Storage Pits with Crane
Rectangular Furnace
Vertical Circular Furnace
Multicell Rectangular Furnace
Rotary Kiln Furnace
Traveling Grates
Reciprocating Grates
Rocking Grates
Circular Grates
Odor Chart
Schematic Diagrams of Odor Sampling Apparatus
Schematic of Scentometer
Equipment Used for Transferring and Diluting Odor Samples
Odor Survey
Crankcase Ventilation System Using Variable Orifice
Control Valve
Valve Controlled by Crankcase Vacuum
Crankcase Ventilation System Using a Vent Tube to the
Air Cleaner
Schematic View of Completely Closed Type Crankcase
Ventilating System
6-Cylinder Engine Air Injection System
V-8 Engine Air Injection System
Vacuum Advance Control Valve
Carburetor/Control Valve/Distributor Relationship
Evaporative Loss Control System—Vapor Storage Case
Used by Toyota
Halting of Diesel Cab and Trailer on the Highway
6.2.68
6.2.68
6.2.70
6.2
6.2
6.3
6.3
75
75
11
12
6.3.33
6.3.34
6.3.39
6.3.40
6.3.41
6.3.42
6.3.43
6.3.44
6.3.48
6.3.50
6.3.52
6.3.53
6.3.54
6.3.55
.3.
.56
.56
.3.57
.3.57
.8
.19
.21
6.5.22
6.5.29
6.
6.3.
6.
6.
6.5.
6.5.
6.5.
6.6.4
6.6.5
6.6.6
6.6.7
6.6.9
6.6.10
6.6.11
6.6.12
6.6.14
6.6.22
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xiii
LIST OF TABLES
Table 5.1. Control Techniques Applicable to Unit Processes at
Important Emission Sources 5.12
Table 5.1. Continued thru page 5.26 5.26
Table 5.2. Use of Particulate Collectors by Industry 5.28
Table 5.2. Continued 5.29
Table 5.3. Settling Velocities of Spherical Particles of Unit
Density in Air 5.32
Table 5.4. Applications of Centrifugal Collectors 5.36
Table 5.5. Representative Performance of Centrifugal Collectors 5.37
Table 5.6. Collection Efficiency Relative to Partical Size 5.37
Table 5.7. Wet Scrubber Operational Characteristics 5.54
Table 5.8. Typical Industrial Application of Wet Scrubbers 5.60
Table 5.9. Typical Performance Data for Venturi Scrubber 5.62
Table 5.10. Recommended Maximum Filtering Ratios and Dust Conveying
Velocities for Various Dusts and Fumes in Conventional
Baghouses with Woven Fabrics 5.70
Table 5.11. Recommended Maximum Filtering Ratios and Fabric for
Dust and Fume Collection in Reverse-Jet Baghouses 5.71
Table 5.12. Filter Fabric Characteristics 5.72
Table 5.13. Troubleshooting Checklist for Fabric Filters 5.75
Table 5.13. Continued 5.76
Table 5.13. Continued 5.77
Table 5.14. Typical Values of Some Design Variables Used in
Commercial Electrical Precipitator Practice 5.88
Table 5.15. Typical Maintenance Schedule for Electrostatic
Precipitators 5.94
Table 5.15. Continued 5.96
Table 5.16. Types of Processes or Equipment for Which Condensers
Have Been Applied in Controlling Contaminant Emissions 5.123
Table 6.2.1. Common Chemical Reactions of Combustion 6.2.2
Table 6.2.2. Usual Amount Excess Air Supplied to Fuel-Burning
Equipment 6.2.6
Table 6.2.3. Emission of Nitrogen Oxides 6.2.11
Table 6.2.4. Examples of Principal Types of Air Pollution Control
Rules/Codes Affecting Fuel-Burning Installations 6.2.13
Table 6.2.5. Optimum Expected Performance of Various Types of Gas
Cleaning Systems for Stationary Combustion Sources 7.2.17
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xiv
Table 6.2.6. Sulfur Content Limitations in Coal 6.2.19
Table 6.2.7. New Jersey Sulfur Content Limitations by Fuel Oil
and Viscosity 6.2.19
Table 6.2.8. Overview of Fuel Types, Properties and Specifications
Pertinent to Air Pollution 6.2.21
Table 6.2.9. Fuel Analysis, Standards and Procedures References 6.2.22
Table 6.2.10. Classification of Coals by Rank 6.2.23
Table 6.2.11. Variations in Sulfur Content and Fuel Properties
Likely to be Encountered 6.2.25
Table 6.2.12. Conversion of Fuel to Heat Equivalency, Average Values 6.2.32
Table 6.2.13. Examples of Fuel-Burning Equipment Inspection Points
as Related to Type of Inspection 6.2.41
Table 6.2.14. Coal Characteristics Relative to Method of Firing 6.2.44
Table 6.2.15. General Uses of Several Bituminous Coal Sizes 6.2.45
Table 6.2.16. Classifications of Oil Burners According to
Application and List of Possible Pollutants 6.2.72
Table 6.2.17. Common Causes and Results of Poor Combustion 6.2.73
Table 6.3.1. Classification of Waste to be Incinerated 6.3.4
Table 6.3.2. Comparison Between Amounts of Emissions from Single-
and Multiple-Chamber General Refuse Incinerators 6.3.10
Table 6.3.3. Determinations of Incinerator Capacity 6.3.15
Table 6.3.4. Recommended Types of Multiple-Chamber Incinerator
Refractories 6.3.18
Table 6.3.5. Gas Burner Recommendations for General-Refuse Incinerators 6.3.23
Table 6.5.1. Miscellaneous Tests: Rendering Plant; Coffee Roaster;
Rubber Processing Plant 6.5.39
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5.1
CHAPTER 5
THE TECHNOLOGY OF SOURCE CONTROL
I. INTRODUCTION
The technology of source control consists of all of the sciences and
techniques that can be brought to bear on the problem of controlling air
pollution. These include the analysis and research that enter into
determinations of technological and economic feasibility, planning and
standard-setting as well as the application of specific hardware, fuels
and materials with low emission potentials. Technology also includes
the process of evaluating and upgrading the effectiveness of air
pollution control practices. In this sense, the enforcement techniques
described in this manual are an important part of the technology of
source control.
At the heart of the control strategy process (see Chapter 1, Section IV)
is the selection of the best air pollution control measures from among
those available. To eliminate or reduce emissions from a polluting
operation, four major courses of action are open:
• Eliminate the operation.
• Regulate the location of the operation.
• Modify the operation.
• Reduce or eliminate discharges from the operation by applying
control devices and systems.
To achieve an acceptable atmosphere in a community requires a combination
of these measures aimed at all or a major fraction of the contaminant
sources within any control jurisdiction.
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5.2
Control technology is self-defeating if it creates undesirable side-
effects in meeting limited air pollution control objectives. Air
pollution control should be considered in terms of both total technolo-
gical systems and ecological consequences. The former considers the
technology that can be brought to bear on controlling not only individual
pieces of equipment, but whole technological systems. Consideration of
ecological side-effects must take into account, for example, the problem
of disposal by other means of possibly unmanageable accumulations of
contaminants which are concentrated in the collection process, such as
ground water pollution resulting from landfill practices or pollution
of streams from the discharges of air pollution control systems.
II. ELIMINATION OF AIR POLLUTION OPERATIONS
An operation or activity can be eliminated only if it is unnecessary to
those engaged in it or to the public, or if a reasonably satisfactory
alternate exists. Thus, the prohibition of open burning and of single-
chamber incinerators may depend on the availability of land for sanitary
landfill, or the availability of approved multiple-chamber incinerators
(see Chapter 6, Sections III and IV). Certain operations can be
prohibited when they can be replaced by improved methods. For example,
hand-firing of coal-burning installations can be prohibited in favor
of automatic fuel-feeding systems; existing by-product core ovens can be
prohibited in favor of systems or equipment using modified feed and
product removal systems. Air pollution from motor vehicles could be
drastically reduced by limiting their use if alternate, low-emission
means of transportation were available. Thus, all control strategies
which involve elimination of activities of a certain type must also
provide for the institution of feasible alternate means of accomplishing
the ends presently served by those activities.
Sources of air pollution can be eliminated by legislative fiat, i.e., by
passage of a rule or regulation prohibiting a specific operation or type
-------
5.3
or design of equipment. These regulations are comparatively easy to
enforce.
III. REGULATION OF LOCATION OF OPERATIONS
Alternative or supplementary approaches to air pollution control include:
(1) applying zoning ordinances which cause the sources of air pollution
to be located or distributed to minimize the effects of air pollution on
receptors downwind and/or (2) imposing areal limits on emission rates
that have been derived from air quality standard requirements. Both
approaches may be implemented by regulatory standards, land-use planning
and zoning controls and through the special handling of individual zone
exception and land use permit cases. They can be useful in preventing
potential public nuisance problems, reducing emission source densities
and locating air pollution sources to make maximum use of the prevailing
air flows of an area. The cooperation of urban planning, transportation
and zoning agencies is required.
Zoning through legal sanctions is within the concept of the police power
of the state, when sufficient evidence established through objective
zoning studies can be presented. Air pollution zoning can be legally
applied to prohibit new industries, limit expansion of existing industries,
liquidate nonconforming industries after amortizing their existing
investments, or eliminating existing harmful industries.
For many years planning commissions have recognized that smoke and other
emissions from industrial sources would create less of a pollution
potential for urban receptor areas if the emitting industries were
located "downwind" of the metropolitan area. To take advantage of this
possibility, the commission would select a location in one of the
directions of most frequent air movement away from the city and designate
land in that vicinity for an industrial district, where incentives to
industrial development would be provided.
-------
5.4
Another principle which is sometimes applied is that of buffer zoning,
or isolation of a source of air pollution from potential effect areas
by the creation of uninhabited areas around the source. Actual imple-
mentation of such plans will, of course, require close coordination
between planning for public open land and planning for industrial
development.
Enforcement officers can play a role in some phases of planning,
particularly in the handling of zone exception cases. Enforcement
personnel generally have intensive experience and knowledge of the
nuisance potentials of specific types of industries, the community
problems that are created and the economic and ecological relationships
of an industry to its community and environment. In some agencies,
enforcement officers are part of an inter-agency team that investigates
zone exception cases (see Section VI E, Chapter 1).
IV. MODIFICATIONS OF OPERATIONS
The main thrust of current control technology is directed at hardware,
fuels and materials. These are applied at appropriate points in the
operational cycles of processes—from the preparation and charge of the
feed (fuel, material and air) to the discharge of contaminated air
and other waste products at the completion of the process cycle. This
section describes examples of the many modifications that can be made
to existing equipment and processes to help lessen emissions. Specific
operational changes are further described in Chapters 6 and 7 in
connection with specific equipment and processes of interest. Sections
V and VI of this chapter describe the specific control devices that can
be applied.
A. Change in Fuels or Process Materials
Frequently it is possible to reduce or eliminate certain contaminants
from a particular process simply by substituting for the fuel or
-------
5.5
material customarily used another fuel or material having less con-
taminant emission potential.
The most obvious example is the use of low-sulfur fuels to replace
high-sulfur coal or oil, much used in space-heating and in the
generation of electric power. In the absence of equipment for
removing the oxides of sulfur from stack gases, the emissions of
sulfur oxides are proportional to the sulfur content of the fuels
used.
According to the Environmental Protection Agency, it is technically
feasible to produce or desulfurize fuels to meet the following
specifications: Distillate oil—0.1 percent sulfur (though it should
be noted that distillate oil containing less than 0.2 percent sulfur
is not generally available at this time); residual oil—0.3 percent
sulfur; bituminous coal—0.7 percent sulfur.
Availability of significant quantities of such low-sulfur fuels in
any region where they do not naturally occur or have not been imported
from other domestic or foreign sources will require planning for the
timely development of new sources of such fuels. Because residual
oil generally is obtained from overseas sources, its use ordinarily
is restricted to areas accessible to waterborne transportation.
There are limited tonnages of 0.7 percent sulfur coal produced at the
present time, primarily in the western United States. Large reserves
of such coal exist but are not currently being mined.
In some cases, the sulfur content of coal may be substantially reduced
by washing and pulverizing it. As much as 40 percent reduction in
sulfur content in some coals may be obtained in this way, but this is
not true of most types of coal. Methods for optimizing the use of
limited supplies of low sulfur fuels include: (1) blending high and
-------
5.6
low sulfur grades, (2) storing low sulfur fuel and issuing it for
use as a substitute for a high sulfur fuel when unfavorable weather
conditions reduce the natural processes of atmospheric dilution and
dispersion, (3) requiring high efficiency flue gas cleaning systems
for large fuel users so they may burn high sulfur fuels safely, and
then allocating the limited supply of low sulfur fuel to the large
numbers of small users who discharge flue gases close to ground
(2)
level and cannot operate flue gas cleaning systems economically.
To reduce the emission of hydrocarbons from automobiles, one feasible
measure is conversion to gaseous fuels—liquid natural gas (LNG) or
liquid petroleum gas (LPG). To reduce the emission of particulate
lead compounds from automobiles, the use of unleaded gasoline can be
an effective measure.
To reduce emissions of organic solvents which have a high degree of
reactivity in the development of oxidant-type smog, Los Angeles
County devised a regulation (Rule 66) limiting the use of such
solvents in large-scale operations. The regulation has been largely
met by reformulation of industrial and architectural coatings.
Another example concerns the manufacture of paint brushes. When the
bristles were bonded in rubber, the vulcanization process caused severe
odor nuisances. The substitution of cold-setting resins for rubber
completely eliminated such emissions.
In die casting, some molds are coated with mold release compounds
containing oils or other volatile material. The heat from the molten
metal vaporizes the oils, creating air contaminants. Recently mold
release compounds have been developed that do not contain oils, and
this source of air pollution is thereby eliminated.
-------
5.7
B. Process and Facility Changes
In many operations, contaminant emissions can be eliminated or sub-
stantially reduced by changes in processes or facilities used to
accomplish the operation.
Sometimes relatively small changes in the conditions under which a
process is carried out may greatly reduce the quantity of contaminants
the process usually produces. For example, in the control of fugitive
dust, the liberal use of water to prevent dust emissions due to the
action of the wind is a simple measure that can be employed in con-
struction operations, grading of roads, land clearing, and the like.
For dirt roads, asphalt or other materials may be applied to the
same purpose. Again, in combustion of fossil fuels which contain
sulfur, a substantial proportion of sulfur trioxide may occur in
the stack gas when excess air of the order of 15 to 20 percent is
used. This contaminant may be essentially eliminated by reducing
(2)
excess air to less than 1 percent.
Where it is not feasible to prevent mixing of contaminants with air,
changes in process or facilities may reduce emission by restricting
access of atmospheric air to the contaminant-producing operation.
For example, open-bodied trucks may be covered when carrying dirt
or other materials which can give rise to airborne dusts. Storage
of volatile organic compounds, as in the petroleum industry, may be
done in pressure tanks, or in tanks equipped with floating roofs.
The chemical and petroleum refining industries have, in recent years,
undergone radical changes in processing methods which emphasize
continuous automatic operations, often computer-controlled, and
completely enclosed systems that minimize release of materials to
the atmosphere. Vapor recovery systems for transfer of gasoline at
loading docks and filling stations and for prevention of evaporation
losses from automobile fuel tanks belong in this category.
-------
5.8
Where closed or covered systems for confining contaminants are
impractical, it may be possible to collect the contaminated air or
stack gas and to remove the contaminants from it while they are in
a relatively concentrated form, before dispersion into the general
atmosphere. It has been found possible, and often profitable, to
control the loss of volatile materials by condensation and reuse of
vapors, as by condensation units on tanks storing volatile petroleum
products. For the handling of dusty materials, for sandblasting and
spraying of materials that produce a dry particulate residue,
installation and use of hoods, fans and fabric filters to enclose
the process and prevent the escape of contaminated air may be
effective. Hydrogen sulfide and mercaptans generated in petro-
chemical operations, if discharged through flares, are converted to
oxides of sulfur. They may be absorbed from the gas stream and
converted to elemental sulfur or sulfuric acid in a sulfur recovery
plant. Emissions of carbon monoxide can be limited by requiring
complete secondary combustion of waste gas generated in such
operations as a grey iron cupola, blast furnace, regeneration of
petroleum cracking catalysts, and others. In some instances,
particularly in the petroleum industry, it is possible to utilize
the heat produced by this secondary combustion, as in waste heat
boilers.
To reduce or eliminate the pollution potential of a very objectionable
operation, it may be to advantage to use an entirely different process
to accomplish similar ends. Such changes, of course, are likely to
require corresponding changes in facilities. As an example, the use
of liquid and gaseous fertilizer chemicals (such as anhydrous ammonia),
applied by injection into the earth, reduces pollution by eliminating
the process of spreading fertilizers as finely divided powders,
subject to entrainment by wind. For the disposal of solid waste,
an adequate sanitary landfill system can replace the use of burning
-------
5.9
dumps or municipal incinerators, both of which may be prolific
sources of combustion contaminants.
C. Improvements in Operational Practices
Even after control techniques have been applied to a process or
system, emissions may be greater than necessary if the details of
operation are not scrupulously observed. Careful evaluation of the
sources of contaminants may in various cases reveal methods of
operation which can alleviate persistent problems.
In food processing plants, odor problems can often be appreciably
alleviated by housekeeping measures akin to those required for good
(2)
sanitation. First has reviewed some of the desirable procedures
for use in the traditional "offensive trades," slaughtering,
rendering, leather tanning, and pig farming, as well as in processes
that handle food or inedible putrescible material. Processing steps
such as storage of raw materials, grinding and other preparation of
raw materials, cooking, oil extraction, drying of residues or products,
are typical odor sources. Quick and adequate refrigeration of
stored material is desirable. Plant design and maintenance should
be conducive to good sanitation: all floors, walls and fixtures
should be smooth, hard, and impervious to water so that they may be
hosed down. Water for cleansing should contain residual chlorine to
discourage microbiological activity. Surfaces should be pitched to
drain the cleaning water to sumps for treatment. In heating vessels
for cooking and drying, steam heating is preferred to direct flame
units, in order to minimize local overheating and scorching of the
organic material. (See Rendering Plants, Chapter 7, Section III.)
Such practices minimize the emissions from processing vessels,
reducing the load and therefore the efficiency demanded of the
terminal odor incinerators or other control devices.
-------
5.10
The effectiveness of any operational improvement depends upon con-
tinuing scrupulous attention to the procedures necessary to implement
them. Thus, the use of water for the control of fugitive dust may
represent a change in process for a given operation, but each appli-
cation has a temporary effect. The change therefore must become a
part of a continuous procedure. In other cases, frequent maintenance
of process equipment or of control equipment is essential. As a
general principle, it should be assumed that a control system is fully
effective only when its operation and maintenance conforms to good
practice. Field enforcement is primarily concerned with determining
to what extent such good practice is being observed.
If the emissions from a given operation are observed to be sub-
stantially higher than those attainable (see Table 1.2) for any
given operation, then improvements could be expected from the source,
either by modernizing processes and equipment or by improving
maintenance and operating practices.
Abnormally large emissions to the atmosphere may result from operating
production equipment at excessive rates. For example, the output
of the rotary sand and stone drier controls the production rate of
hot mix asphalt plants. (See Asphaltic Batching Concrete Operations,
Chapter 7, Section 8.) When the hot gas velocity through the drier
is increased above the design rate, the quantity of dust emitted
increases in greater proportion than the increase in gas flow. In
the same industry, many air pollution problems stem from a customary
practice of postponing maintenance procedures pending an annual
shutdown. Machinery progressively declines in effectiveness during
the operating season, resulting in cumulative unrepaired damage to
dust collectors, exhaust systems, and equipment enclosures. For
plants operating in this manner, intensive surveillance of emissions
would be indicated, with increased frequency of maintenance measures
required when control performance deteriorates.
-------
5.11
Modification of unsatisfactory incinerators is usually practicable
only if the changes required are relatively minor. Multiple-chamber
incinerators may usually be operated satisfactorily, although this
depends to some degree on the type of material charged. Use of the
secondary burners is required occasionally to maintain the combustion
efficiency of the secondary chamber. (See Incinerators, Chapter 6,
Section III.)
In some operations, smoke abatement may be substantially a matter of
adequate pre-processing of the material being burned. As noted pre-
viously, washing of coal may substantially reduce the emissions of
ash, as well as oxides of sulfur in combustion operations. In
reclaiming scrap metal from automobile bodies, great quantities of
black smoke are sometimes generated by incineration. This can be
avoided by first stripping the bodies of all fabric and upholstery,
as well as rubber and plastic accessories. In the melting of scrap
metal in steel manufacturing or foundry practice, much unnecessary
smoke may be produced when oily scrap is charged into a melt. Such
processes may be hooded and the effluent treated by incineration, or
the oil and grease may be removed in a degreasing step, before the
scrap enters the furnace.
SPECIFIC TYPES OF AIR POLLUTION CONTROL EQUIPMENT
A. Introduction
A major responsibility of field enforcement personnel is the inspection
of the operation of air pollution control systems. The systems
include hoods, ductwork, fans, compressors, gas conditioners and
other auxiliary equipment needed for effective capture and conveying
of the contaminant laden gases to the air pollution control equip-
ment. Examples of specific types of air pollution control equipment
applied to control specified contaminants are shown in Table 5.1.
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Aluminum
Reduction
Plants
Materials
Handling
Buckets & Belt
Conveyor or
Pneumatic
Conveyor
Anode & Cathode
Electrode Prep.
Cathode
Baking
Anodes
Grinding &
Blending
Baking
Pot Charging
Metal Casting
Particulates (dust)
Hydrocarbon Emissions from
Binder
Particulates (dust)
Particulates (dust), CO, SO ,
Hydrocarbons & Fluorides
Particulates (dust), CO, HF,
SO,, CF & Hydrocarbons
C1-, HC1, CO & Particulates
(dust)
Exhaust Systems & Baghouse
Exhaust Systems & Mechanical
Collectors
Hi-ef£ Cyclone, Elect. Free.,
Scrubbers, Catalytic Combustion or
Incinerators , Flares , Baghouse
Hi-eff. Cyclone, Baghouse, Spray
Towers, Floating Bed Scrubber,
Elect. Prec., Chemisorption, Wet
Elect. Prec.
Exhaust Systems & Scrubbers
Ul
I-1
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Asphalt Batch
Plants
Materials
Handling, Storage
& Classifiers
Elevators
Chutes
Vibrating
Screens
Drying
Rotary Oil or
Gas Fired
Truck Traffic
Particulates (dust)
Particulates & Smoke
Dust
Local Exhaust Systems with a
Cyclone Precleaner & a Scrubber
or Baghouse
Proper Combustion Controls, Fuel
Oil Preheating where Required;
Local Exhaust System, Cyclone & a
Scrubber or Baghouse
Wetting down Truck Routes
ement Plants
Quarrying
Primary
Crusher,
Secondary
Crusher,
Conveying,
Storage
Wetting, Exhaust Systems with
Mechanical Collectors
Particulates (dust)
Dry Processes
Materials
Handling,
Air Separator
(Hot Air
Furnace)
Particulates (dust)
Particulates (dust)
Local Exhaust System & Mechanical
Collectors & Baghouse
-------
INDUSTRY
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Cement Plants
(continued)
Grinding
Pneumatic, Con-
veying & Storage
Wet Process
Materials
Handling
Grinding
Storage
Kiln Operations
Rotary Kiln
Clinker Cooling
Materials
Handling
Grinding &
Packaging
Air Separator
Grinding
Pneumatic
Conveying
Materials
Handling
Packaging
Particulates (dust)
Particulates (dust)
Wet Materials, No Dust
Particulates (dust), CO,
SO , NO , Hydrocarbons,
Alaehydes, Ketones
Particulates (dust)
Particulates (dust)
Local Exhaust System with
Cyclones & Baghouse
Elect. Prec. & Baghouses, Scrubber,
Flare
Local Exhaust System & Mechanical
Collectors
Local Exhaust Systems & Mechanical
Collectors
Ln
i--
-P-
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Coal Preparation
Plants
Materials
Handling
Conveyors
Elevators
Chutes
Sizing
Crushing
Screening
Classifying
De-Dusting
Storing Coal in
Piles
Refuse Piles
Coal Drying
Rotary, Screen,
Suspension,
Fluid Bed,
Cascade
Particulates (dust)
Particulates (dust)
Particulates (dust)
Blowing Particulates (dust)
H S, Particulates and Smoke
from Burning Storage Piles
Dust, Smoke, Particulates,
Sulfur Oxides, H S
Local Exhaust Systems & Cyclones
Local Exhaust Systems & Cyclones
Local Exhaust System, Cyclone
Precleaners & Baghouse
Wetting, Plastic Spray Covering
Digging out Fire, Pumping Water
onto Fire Area, Blanket with
Incombustible Material
Exhaust Systems with Cyclones &
Packed Towers on Venturi Scrubbers
-------
INDUSTRY
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Coke Plants
Fertilizer
Industry
(Chemical)
By-Product Ovens
Charging
Pushing
Quenching
By-Product
Processing
Material
Storage
(coal & coke)
Phosphate
Fertilizers
Crushing ,
Grinding &
Calcining
Hydrolysis of
P2°5
Smoke, Particulates (dust)
Smoke, Particulates (dust)
so2
Smoke, Particulates (dust &
mists) , Phenols & Ammonia
CO, H S, Methane, Ammonia,
H , PEenols , Hydrogen Cya-
nide, N , Benzene, Xylene,
etc.
Particulates (dust)
Particulates (dust)
PH3, P205, H3P04 mist
Pipeline Charging, Careful Charging
Techniques; Portable Hooding &
Scrubber or Baghouses
Minimize Green Coke Pushing -
Need for Collection Techniques
Baffles & Spray Tower
Klect. Free., Scrubber, Flaring
Wetting, Plastic Spray, Fire
Prevention Techniques
Exhaust System, Scrubber, Cyclone
Baghouse
Scrubbers, flare
-------
INDUSTRY
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Fertilizer
Industry
(Chemical)
(continued)
Acidulation
& Curing
Granulation
Ammoniation
Nitric Acid
Acidulation
Superphosphate
Storage &
Shipping
Ammonium Nitrate
Reactor
Prilling
Tower
HF, SiF.
4
Particulates (dust)
(product recovery)
NH3, NH4C1, SiF4, HF
NO Gaseous Fluoride
X
Compounds
Particulates (dust)
NH3, N0x
NH4> N03
Scrubbers
Exhaust System, Scrubber or
Baghouse
Cyclone, Elect. Free., Baghouse,
High Energy Scrubber
Scrubber, Addition of Urea
Exhaust System, Cyclone or
Baghouse
Scrubber
Proper Operation Control
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Foundries
Iron
Brass Bronze
Melting (cupola)
Charging
Melting
Pouring
Bottom Drop
Melting
Charging
Melting
Pouring
Smoke & Particulates
Smoke & Particulates, Fume,
Oil, Mist, CO
Smoke & Particulates
Smoke, Particulates, Oil Mist
Zinc Oxide Fume, Particu-
lates, Smoke, Zinc Oxide
Fume, Lead Oxide Fume
Closed Top with Exhaust System, CO
Afterburner, Gas-cooling Device &
Baghouse or Elect. Free., Wetting
to Extinguish Fire
Low Zinc Content Red Brass: Use
Good Combustion Controls & Slag
Cover. High Zinc Content Brass:
Use Good Combustion Controls,
Local Exhaust System & Baghouse
Ol
M
oo
Aluminum
Melting
Charging
Melting
Pouring
Smoke & Particulates
Charge Clean Material (no paint or
grease) Proper Operation should be
Required. No Air Pollution Con-
trol Equipment if no Fluxes are
Used & Degassing is not required.
Dirty Charge Requires Exhaust
System with Scrubbers & Baghouses
Zinc
Melting
Charging
Melting
Pouring
Smoke & Particulates
Zinc Oxide Fume
Oil Mist & Hydrocarbons
from Die Casting Machines
Exhaust System with Cyclone and
Baghouse. Charge Clean Material
(no paint or grease)
Careful Skimming of Dross
Use Low Smoking Die Casting
Lubricants
-------
INDUSTRY
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Foundries
(continued)
Sand Handling
Shakeout
Magnetic
Fully
Conveyors &
Elevators
Rotary Cooler
Screening
Crusher
Mixer
Core Making
Ovens
Particulate (dust), Smoke
Organic Vapors
Particulates (dust)
Organic Acids, Aldehydes,
Smoke, Hydrocarbons
Exhaust System, Cyclone & Baghouse
Use of Binders that will Allow
Ovens to Operate at Less than
400°F or Exhaust Systems & After-
burners
Galvanizing
Operations
Hot Dip Gal-
vanizing Tank
Kettle
Dipping
Material into
the Molten
Zinc. Dusting
Flux onto the
Surface of the
Molten Zinc.
Fumes, Particulates (liquid),
Vapors - NH.C1, ZnO, ZnCl?,
Zn, NH Oil, & C
Close Fitting Hoods with High In-
draft Velocities (in some cases
the hood may not be able to be
close to the kettle so that the
indraft velocity must be very
high) Baghouses, Elect. Free.
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Kraft Pulp Mills
Digesters
Batch &
Continuous
Multiple Effect
Evaporators
Recovery Furnace
Weak & Strong
Black Liquor
Oxidation
Smelt Tanks
Lime Kiln
Mercaptans, Methanol (odors)
H S, Other Odors
H S, Mercaptans, Organic
Sulfides & Disulfides
Particulates (mist or dust)
Particulates (dust), H S
Condensers & Use of Lime Kiln, Hog
Fuel Boiler or Furnaces as After-
burners
Caustic-Scrubbing & Thermal
Oxidation of Non-Condensibles
Paper Combustion Controls for
Fluctuating Load & Unrestricted
Primary & Secondary Air Flow to
Furnace & Elect. Prec.
Packed Tower & Cyclone
Demlsters, Venturi, Packed Tower
or Impingement Type Scrubbers
Venturi Scrubbers
Oi
o
Municipal &
Industrial
Incinerators
Single Chamber
Incinerators
Flue Fed
Particulates, Smoke,
Volatiles, CO, SO , Ammonia,
Organic Acids, Aldehydes,
NO , Hydrocarbons, Odors, HC1
Settling Chambers, Scrubbers,
Afterburner, By-pass Flue, Ash
Cleanout
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Municipal &
Industrial
Incinerators
(continued)
Multiple Chamber
Incinerators
Retort, Inline
Flue Fed
Wood Waste
Municipal
Incinerators
50-100 tons/day
Pathological
Incinerators
Wood Waste &
Industrial Waste
Box Type
Particulates, Smoke and
Combustion Contaminants
Particulates, Smoke and
Combustion Contaminants
Particulates, Smoke and
Combustion Contaminants
Particulates, Smoke,
Volatiles, CO, Ammonia,
Organic Acids , Aldehydes ,
NO , Hydrocarbons , SO ,
Hydrogen Chloride, Odors
Odors, Hydrocarbons
Particulates, Smoke and
Combustion Contaminants
Particulates, Smoke and
Combustion Contaminants
Operating at Rated Capacity, Using
Auxiliary Fuel as Specified & Good
Maintenance including Timely Clean-
out of Ash
Use of Charging Gates & Automatic
Controls for Draft
Continuous Feed Systems, Operate at
Design Load & Excess Air, Limit
Charging of Oily Material
Preparation of Materials Including
Weighing, Grinding, Shredding;
Control of Tipping Area, Furnace
Design with Proper Automatic Con-
trols; Proper Startup Techniques;
Maintenance of Design Operating
Temperatures; use of Scrubbers &
Baghouses; Proper Ash Cleanout
Proper Charging
Modified Fuel Feed, Auxiliary Fuel
& Dryer Systems
Allow Proper Startup, Charge
Material Slowly, Don't Overload
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Non-Ferrous
Smelters, Primary
Copper
Roasting
Reverberatory
Furnace
Converters
Charging
Slag Skim
Pouring
Air or Oxygen
Blow
SO , Particulates, Fume
Smoke, Particulate, Fume,
SO,,
Smoke, Fume, SO,.
Exhaust System, Settling Chambers,
Cyclones or Scrubbers & Elect.
Free, for Dust & Fumes & Sulfuric
Acid Plant for SO .
Exhaust System, Settling Chambers,
Cyclones or Scrubbers & Elect.
Free, for Dust & Fumes & Sulfuric
Acid Plant for SO^
Exhaust System, Settling Chambers,
Cyclones or Scrubbers, Elect.
Free, for Dust & Fumes & Sulfuric
Acid Plant for SO,,
Lead
Sintering
SO , Particulates, Smoke
Exhaust System, Cyclones & Bag-
house or Precipitators for Dust &
Fumes, Sulfuric Acid Plant for SO,
Blast Furnace
SO CO, Particulates
Lead Oxide, Zinc Oxide
Exhaust System, Settling Chambers,
Afterburner & Cooling Device,
Cyclone & Baghouse
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Lead
(continued)
Cadmium
Zinc
Non-Ferrous
Smelters,
Secondary
Dross Rever-
beratory Furnace
Refining
Kettles
Roasters, Slag,
Fuming Furnaces ,
Deleading Kilns
Roasting
Sintering
Calcining
Retorts
Electric Arc
Blast Furnaces &
Cupolas -
Recover Metal
from Scrap &
Slag
SO Particulates, Fume
SO , Particulates
Particulates
Particulates (dust) & SO
Particulates (dust) & SO
Zinc Oxide Fume, Particu-
lates, SO , CO
Dust, Fumes, Particulates,
Oil Vapor, Smoke, CO
Exhaust System, Settling Chambers,
Cyclone & Cooling Device, Baghouse
Local Exhaust System, Cooling
Device Baghouse or Precipitator
Local Exhaust System, Baghouse or
Precipitator
Exhaust System, Humidifier, Cyclone
Scrubber, Elect. Prec. & Acid Plant
Exhaust System, Humidifier, Elect.
Prec. & Acid Plant
Exhaust System, Baghouse
Exhaust Systems, Cooling Devices,
CO Burners & Baghouses or
Precipitator s
t-n
U>
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Non-Ferrous
Smelters,
Secondary
(continued
Reverberatory
Furnaces
Crucible Furnaces
Sweat Furnaces
Wire Reclamation
& Autobody
Burning
Dust, Fumes, Particulates,
Smoke, Gaseous Fluxing
Materials
See Non-Ferrous Foundries
Smoke, Particulates
Fumes
Smoke, Particulates
Exhaust Systems & Baghouses,
or Precipitators or Venturi
Scrubbers
Precleaning Metal & Exhaust
Systems with Afterburner & Baghouse
Scrubbers & Afterburners
Paint
Mfg.
& Varnish
Resin Mfg.
Closed
Reaction
Vessel
Acrolein, Other Aldehydes
& Fatty Acids (odors)
Phthalic Anhydride (subl.)
Exhaust System with Scrubbers &
Fume Burners
Varnish
Cooking
Open or
Closed
Vessels
Ketones, Fatty Acids,
Formic Acids, Acetic
Acid, Glycerine, Acrolein,
Other Aldehydes, Phenols
& Terpenes; From Tall Oils,
Hydrogen Sulfide, Alkyl
Sulfide, Butyl Mercaptan
& Thiofene (odors)
Exhaust System with Scrubbers &
Fume Burners - Close Fitting Hoods
are Required for Open Kettles
Solvent
Thinning
Olefins, Branches Chain
Aromatics & Ketones (odors),
Solvents
Exhaust System with Fume Burners
-------
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
INDUSTRY
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Rendering
Plants
Feed Stock
Storage &
Housekeeping
Cookers &
Percolators
Grinding
Odors
SO,,, Mercaptans , Ammonia,
Odors
Particulates (dust)
Quick Processing, Washdown of All
Concrete Surfaces, Pave Dirt
Roads, Proper Sewer Maintenance
Exhaust System, Condenser, Scrubber
or Incinerator
Exhaust System & Scrubber
Roofing Plants
(Asphalt
Saturators)
Felt or Paper
Saturators
Spray Section
Asphalt Tank
Wet Looper
Asphalt Vapors & Particulates
(liquid)
Exhaust System with High Inlet
Velocity at Hoods (> 200 ft/min)
with Either Spray Scrubbers,
Baghouses or Two Stage Low Voltage
Elect. Free.
L/l
Ul
Crushed Rock
or Other
Minerals
Handling
Particulates (dust)
Local Exhaust System, Cyclone or
Multiple Cyclones
Steel Mills
Blast Furnaces
Charging,
Pouring
CO, Fumes, Smoke
Particulates (dust)
Good Maintenance, Seal Leaks;
Use of Higher Ratio of Pelletized
or Sintered Ore; CO Burned in Waste
Heat Boilers, Stoves or Coke Ovens;
Cyclone, Scrubber, Elect. Free.
or Venturi Scrubber
-------
INDUSTRY
Table 5.1. CONTROL TECHNIQUES APPLICABLE TO UNIT
PROCESSES AT IMPORTANT EMISSION SOURCES (continued)
PROCESS
OF
OPERATION
AIR CONTAMINANTS EMITTED
CONTROL TECHNIQUES
Steel Mills
(continued)
Electric Steel
Furnaces
Charging,
Pouring,
Oxygen Blow
Open Hearth
Furnaces
Oxygen Blow,
Pouring
Basic Oxygen
Furnaces
Oxygen Blowing
Raw Material
Storage
Pelletizing
Sintering
Fumes, Smoke, Particulates
(dust), CO
Fumes, Smoke, SO , Particu-
lates, (dust), c5, NO
Fumes, Smoke, CO,
Particulates, (dust)
Particulates (dust)
Particulates (dust)
Smoke, Particulates (dust),
S0_, NO
2' x
Segregate Dirty Scrap; Proper
Hooding, Baghouses, Venturi
Scrubbers, or Elect. Prec.
Proper Hooding, Settling Chambers,
Waste Heat Boiler, Baghouse, Elect.
Prec. or Venturi Scrubber
Proper Hooding (capture emissions
& dilute CO) Scrubbers or Elect.
Prec.
Wetting or Application of Plastic
Spray
Proper Hooding, Cyclone, Baghouse
Proper Hooding, Cyclones, Venturi
Scrubbers, Baghouse or
Precipitator
Ul
N)
-------
5.27
These include all industries dealt with in this manual with the excep-
tion of petroleum refineries, chemical plants, construction and
demolition activities, and mining which are treated more fully in
Chapters 6 and 7.
This section of the document describes air pollution control devices
in use by industry to reduce particulates where they are produced in
quantities sufficient to come under the provisions of most air
pollution control agencies. Part E of this section, fabric systems,
in particular, describes inspection points common to most air
pollution control systems. Section VII of this chapter describes
sulfur dioxide removal systems for power plants and Section VIII
describes control systems for gases and vapors.
Equipment used to reduce the emission of air contaminants is selected
on the basis of collection efficiency. The factors which affect the
design of the equipment are:
• Particle size range.
• Concentration of particles in the gas stream.
• Physical and chemical characteristics of the contaminants.
Table 5.2 represents an overview of particulate collectors in common
use by industry. Figure 5.1 shows theoretical collection efficiencies
vs. particle sizes for families of collectors.
B. Gravitational Settling Chambers
Gravitational settling chambers, commonly known as settling chambers
or balloon ducts are the simplest devices used to collect dust of
large particle sizes. This is accomplished by reducing the velocity
of the carrier gas and allowing the dust to "settle" by gravity. As
the horizontal velocity of the particle decreases due to an increase
-------
5.28
Table 5.2. USE OF PARTICULATE COLLECTORS BY INDUSTRY
Industrial classification
Steel
Process
Coal
Oil
Wood and bark . _ -
Bagasse
Kraft
Soda
Chemical
Dissolver tank vents
Cement _ - _
Phosphate
Alumina
Bauxite
Blastfurnace „ - -_ _.
Open hearth
Basic oxygen furnace
Electric furnace _ ._
Sintering __
Coke ovens __
Ore roasters
Cupola
Pyrites roaster
Taconite
Hot scarfing _
Zinc roaster.
Zinc smelter
Copper roaster
Copper reverb
Copper converter _
Lead furnace
Aluminum
Elemental phos
Ilmenite
Titanium dioxide
Molybdenum
Sulf uric acid
Phosphoric acid.
Nitric acid
Ore beneficiation .. _
EP
0
0
0
+
o
0
0
0
0
0
0
0
0
-f
0
0
0
+
0
0
0
-)-
0
+
0
0
0
0
0
0
0
0
0
+
+
0
+
MC
0
0
0
0
0
-f
0
0
0
0
0
0
0
-1-
0
0
0
0
0
0
0
+
FF WS
+
0
0
0
0
0 +
0 0
0 0
0 +
+
0
-f
0
0 0
+
+ 0
0
+
0 0
0
0
0
0
0
H- +
Other
+
+
+
+
•f
+
0
0
0
+
-------
5.29
Table 5.2. USE OF PARTICULATE COLLECTORS BY INDUSTRY (continued)
Industrial classification
Miscellaneous
Process
Refinery catalyst
Coal drying
Coal mill vents
Municipal incinerators
Carbon black
Apartment incinerators
Spray drying
Machining operation
Hot coating
Precious metal
Wood working
EP MC
0 0
0
+ 0
0
0
0
0
0
0
FF
0
_J_
0
0
0
0
0
WS Other
0 +
0
+ -f
0 0
Key:
0 = Most common
-f- =Not normally used
EP = Electrostatic Precipitator
MC = Mechanical Collector
FF = Fabric Filter
WS = Wet Scrubber
Other = Packed towers
Mist pads
Slag filter
Centrifugal exhausters
Flame incineration
Settling chamber
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.30
BAG FILTERHOUSE
VENTURI SCRUBBER (6-INCH THROAT, 30-INCH WATER GAUGE)
SPRAY TOWER (22-FOOT DIAMETER}
DRY ELECTROSTATIC PRECIPITATOR (3-SECOND CONTACT TIME)
MULTIPLE CYCLONES (12-INCH DIAMETER TUBES)
< SIMPLE CYCLONE (4-FOOT DIAMETER)
UNERTIAL COLLECTOR
30 40 50
PARTICLE SIZE, microns
Figure 5.1. COMPOSITE GRADE (FRACTIONAL) EFFICIENCY CURVES
BASED ON TEST SILICA DUST (SOURCE: CONTROL
TECHNIQUES DOCUMENTS, Reference 3)
-------
5.31
in the cross-sectional area of the chamber (1 to 10 feet per second)
the larger particles, >43 microns, will tend to settle to the
bottom of the chamber (Table 5.3). These devices are usually
used as precleaners and may form a part of a gas cleaning and cooling
train upstream of higher efficiency collectors.
Since settling chambers are usually precleaners and serve to remove
large particles and sometimes cool gases, the enforcement officer
may not be able to determine the effectiveness of the device until
the more efficient collectors downstream begin to show loss of
efficiency by a change in the opacity or color of the effluent.
Removal of captured material from the bottom of the chamber is
essential to its effectiveness. Where chain or screw conveyors are
used to remove the particulates it is easy to find out if they are in
operation. During an inspection, the operator of the equipment can
be requested to open the door of the hopper to see if it has been
recently cleaned. Maintenance is also important since air leaks
can alter the pickup of the dust collection points.
C. Cyclone Separators
Cyclone is a common name for the centrifugal separator. The cyclone
is a closed device consisting of a cylinder on top of an inverted
cone. Dust-laden air enters through a tangential duct at the top of
the cylinder. The velocity of the air, as governed by a blower motor
in the ductwork causes the particles to be separated from the air
stream by centrifugal deflection. This is accomplished by means of
the double vortex principle (Figure 5.2) in which the dust-laden
gases spiral down the walls of the cyclone and then move up the inside
of the spiral after losing particles due to centrifugal force. The
particles slide down the walls of the cyclone into a hopper while the
cleaned gases escape through a tube at the top of the cylinder.
-------
5.32
Table 5.3. SETTLING VELOCITIES OF SPHERICAL
PARTICLES OF UNIT DENSITY IN AIR
Temperature: 20°C(68°F): Pressure 760mm Hg.
Particle diameter
microns
O'l
0-2
0-4
1-0
2
4
10
20
40
100
400
1000
Experimental
cm/sec
8-7 x 10-
2-3 x 10-"
6-8 x 10-"
3-5 x 10~3
1-19 x 10-2
5-0 x 10-2
3-06 x 10-'
1-2
4-8
24-6
157
382
Calculated
from Stokes1 law
cm/sec
8-71 x 10-5
2-27 x 10-"
6-85 x 10-"
3-49 x 10-3
1-19 x 10-2
5-00 x 10-2
3-06 x 10-'
1-2
5
25
483
3050
(SOURCE: OFFICE OF MANPOWER DEVELOPMENT, Reference 4)
-------
5.33
This device ranges from a simple cyclone to a mechanically driven
device such as the American Air Filter dynamic cyclone. Depending
on the gas condition, particle size range and dust loading (also
liquid particles) cyclones can be used singly (Figure 5.2) or in
parallel (Figures 5.3 and 5.4). They can be designed with either
tangential inlets or straight flow-through passages.
High efficiency tangential inlet cyclones are characterized by a
narrow inlet opening to attain a high inlet velocity, long body
length relative to body diameter, and a small outlet diameter relative
to the body diameter. Higher collection efficiencies result from the
increased energy expended due to the high inlet velocities. High
throughput cyclones have larger inlet openings and larger gas exits.
Figures 5.5 and 5.6 show the geometrical relationships for these
types of cyclones.
All of the dimensions of a cyclone are related to its largest inside
diameter. These ratios were derived from experimental dimensional
analysis for optimum collection of particulates based upon particle
size and grain loading. High efficiency cyclones therefore are
long and thin (sometimes called pencil cyclones) while the high
throughput and lower efficiency cyclones have a squat appearance.
Cyclones are in common use in many industrial operations as both
primary gas cleaners and precleaners. Many pneumatic conveying
systems use some form of centrifugal separator to remove the product
from the conveying medium. Food and grain handling processes, hot
asphalt plants, cement plants, chemical plants and petroleum
refineries use some configuration of centrifugal separators.
Table 5.4 shows applications of cyclone collectors. Table 5.5
describes representative performances of these collectors. Table 5.6
describes collection efficiencies relative to particle size.
-------
5.34
Figure 5.2. DOUBLE-VORTEX PATH
OF THE GAS STREAM
IN A CYCLONE.
(SOURCE: AIR POLLUTION ENGINEERING
MANUAL, Reference 5)
Figure 5.3. CYCLONES ARRANGED IN
PARALLEL, COURTESY OF
BUELL ENGINEERING
COMPANY, INC.
(SOURCE: CONTROL TECHNIQUES DOCUMENTS,
Reference 3)
Figure 5.4. CYCLONES ARRANGED IN
PARALLEL, COURTESY
OF WESTERN PRECIPITA-
TION DIVISION
(SOURCE: CONTROL TECHNIQUES DOCUMENTS,
Reference 3)
-------
5.35
CoUectin,
Hopper
0.2D
Figure 5.5. HIGH EFFICIENCY CYCLONE (SOURCE: OFFICE
OF MANPOWER DEVELOPMENT, Reference 4)
0. 375D
Figure 5.6.
Collecting
Hopper
HIGH THROUGHPUT CYCLONE (SOURCE: OFFICE
OF MANPOWER DEVELOPMENT, Reference 4)
-------
5.36
Table 5.4. APPLICATIONS OF CENTRIFUGAL COLLECTORS
Type of air Collector
Operation or process Air contaminant cleaning efficiency,
equipment wt percent
Crushing, pulverizing, mixing, screening:
Alfalfa feed mill Alfalfa dust Cyclone, settling 85
chamber.
Barley feed mill Barley flour dust Cyclone 85
Wheat air cleaner Chaff Cyclone 85
Drying, baking:
Catalyst regenerator (petroleum),. Catalyst dust Cyclone, ESP 95
Detergent powder spray drier Detergent powder Cyclone 85
Orange pulp feed drier Pulp dust ,__.,_ Cyclone 85
Sand drying kiln Silica dust Cyclone 78
Sand and gravel drying Silica dust Inertia! collector 50
Stone drying kiln_ Silica dust Cyclone 86
Mixing fluids:
Asphalt mixing _ Sand and gravel dust Cyclone 60-86
Bituminous concrete mixing Sand and stone dust Cyclone, scrubber. _ 95
Polishing, buffing, grinding, chipping:
Grinding (aluminum) Aluminum dust Cyclone 89
Grinding (iron).. Iron scale and sand Cyclone 66
Grinding (machine shop). Dust Impeller collector 91
Surface coating rubber dusting Fluffy zinc stearate Impeller collector 78-88
Surface treatment—physical:
Abrasive cleaning Talc dust.. Cyclone 93
Abrasive stick trimming and Silicon carbide and 2 parallel cyclones.. 51
shaping. alumina dust.
Casting cleaning with metal shot, Metallic and silica dust.. Impeller collector... 97-99+
sandblasting and tumbling.
Foundry tumbling _ Dust Impeller collector... 99
Truing and shaping abrasive Silicon carbide and Cyclone 68
products. alumina dust.
Woodworking, including plastics rub- Wood dust and chips Cyclone 97
bcr, paper board: mill planing.
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.37
Table 5.5. REPRESENTATIVE PERFORMANCE OF CENTRIFUGAL COLLECTORS
Collector
type
Process
Series cyclone. Fluid-catalvtic
Cyclone
Cyclone
Cyclone
Cyclone
Impeller
collectors.
Impeller
collectors.
cracking.
Abrasive cleaning
Drying
Grinding
Planing mill
Grinding
Rubber dusting
Pressure
Material Airflow, drop, Efficiency,
ft3/min in. H.O wt percent
Catalyst
Talc
Wood
Iron scale _
. Zinc stearate „
40,000
2 300
12 300
2 400
3 100
11,800
3,300
High
0.33
1 9
1.2
3 7
4.7
9.0
99.98
93 0
86 9
89 0
97 0
56.3
88.0
Inlet Inlet
load, mass
gr/(t3 median
size, M
2800 37.0
2 2
38.0 8 2»
0.7
0.1
0.15 3.2b
0.6 0.7
* Outlet mass median size = 3.2 microns.
k Outlet mass median size = 2.5 microns.
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
Table 5.6. COLLECTION EFFICIENCY RELATIVE TO PARTICLE SIZE
Particle
size(p)
Less than 5
5-20
15 - 50
40
Efficiency
Conventional
cyclone
—
50 - 80
80 - 95
95 - 99
(% by wt.)
High efficiency
cyclone
50 - 80
80 - 90
95 - 99
95 - 99
(SOURCE: OFFICE OF MANPOWER DEVELOPMENT, Reference 4)
-------
5.38
1. Inspection Points
Problems that affect the collection efficiency of cyclones which
an enforcement officer must recognize are:
• Buildup of dust on the cyclone walls and at the bottom
of the cone resulting in clearly visible dust emissions
in the exhaust gas.
• Plugging of the inlet duct which causes sufficient back
pressure to decrease dust pickup or dust conveying
upstream of the cyclone.
• Increase in the humidity of the conveying gas which will
cause particle agglomeration and plugging.
• Air leaks caused by holes will change the pressure drop
across the cyclone adversely affecting its efficiency.
• An increase in dust loading or a decrease in particle size
or density will adversely affect the collection efficiency.
• Improper application of cyclones as dust collectors.
The efficiency of these types of collectors drops rapidly for
particle sizes below 5|j.. They are most effective for particle
(3)
sizes ranging from 10 to 200|j..
D. Scrubbers (Wet Collectors)
The mechanisms for wet collection of particulates are:
(1) Wetting the particle by contact with a liquid droplet. This
occurs by impingement of fine droplets (100 p optimum) on
dust particles, deposition of the dust particles on collector
plates and by diffusion and condensation of the carrier gas
by cooling it below its dew point.
(2) Impingement of the wet particles on a collecting surface
and removal by flushing.
-------
5.39
As with all collection equipment, particle size distribution and
operating conditions will be the determining factors in the selection
of a particular wet collector for a specific air pollution control
application. The scrubber efficiency is a function of the power
input. As an example, venturi scrubbers can have pressure drops
exceeding 70" W.G. (inches of water) where small particle sizes and
high grain loadings are involved.
(3)
Wet collectors are classified as:
(1) Gravity spray towers (Figure 5.7).
(2) Centrifugal spray scrubbers (Figure 5.8).
(3) Impingement plate scrubbers (Figure 5.9).
(4) Venturi scrubbers (Figures 5.10, 5.11, 5.12).
(5) Packed bed scrubbers (Figures 5.13, 5.14, 5.15).
(a) cross flow
(b) countercurrent flow
(c) parallel flow
(d) flooded-bed
(e) fluid-bed
(6) Self-induced spray scrubbers (Figure 5.16).
(7) Mechanically induced spray scrubbers (Figure 5.17).
(8) Disintegrator scrubbers.
(9) Centrifugal fan wet scrubbers (Figure 5.18).
(10) Inline wet scrubbers (Figure 5.19).
(11) Irrigated wet filters (Figure 5.20).
Due to the almost endless variety of scrubbers it is difficult to
generalize relationships among such operating parameters as pressure
drop and liquid flow rate. Manufacturer's data covering the specific
piece of equipment of interest is the best source of this data.
Table 5.7 gives ranges of water-to-gas ratios and pressure drops for
the most common types of scrubbers in use. The efficiency of Venturi
scrubbers depends on the pressure drop and can be improved by
increasing the gas velocity or the water injection rate. Venturi
scrubbers as a class of wet collectors are effective for collecting
particles smaller than 2 (j.. Figure 5.21 shows a set of curves
relating the percentage of contaminant collection efficiency to
-------
5.40
GAS IN
MIST ELIMINATOR
GAS DISTRIBUTOR PLATE
Figure 5.7. TYPICAL LAYOUT FOR GRAVITY SPRAY TOWER, COURTESY OF SPRAYING
SYSTEMS COMPANY (SOURCE: CONTROL TECHNIQUES DOCUMENTS,
Reference 3)
-------
5.41
CLEANED GAS
CLEAN GAS OUT
ANTI-CARRYOVER BAFFLE
SPRAY RING
"WATER SUPPLY
CORE BUSTER DISK
LARGE DIAMETER IRRIGATED CYCLONE
GAS IN
SPRAY MANIFOLD
WATER WATER
OUT IN
b. PEASE ANTHONY CYCLONIC SCRUBBER
(Courtesy of Chemical Construction Corporation)
CLEAN GAS
OUT
TOWER NOZZLES,
DIRECTED
CROSS-FLOW
RECTANGULAR
-INLET
FRESH WATER
SUPPLY
FLUSHING JETS,
DIRECTED
DOWNWARD
SEPARATOR
IMPINGEMENT
PLATES
CLEAN GAS
OUT
WASTE OUT
WATER OUT
c. CYCLONIC SPRAY SCRUBBER.
(Courtesy of Buffalo Forge Company}
d. MULTI-WASH SCRUBBER.
(Courtesy of Claude B. Schneible Company)
Figure 5.8. CENTRIFUGAL SPRAY SCRUBBERS (SOURCE: CONTROL
TECHNIQUES DOCUMENTS, Reference 3)
-------
5.42
IMPINGEMENT
BAFFLE STAGE
AGGLOMERATING
SLOT STAGE
TARGET
PLATE \
GAS FLOW
ARRANGEMENT OF "TARGET PLATES"
IN IMPINGEMENT SCRUBBER
WATER DROPLETS ATOMIZED
AT EDGES OF ORIFICES
a. IMPINGEMENT SCRUBBER
DOWNSPOUT TO
LOWER STAGE "
b. IMPINGEMENT PLATE DETAILS
Figure 5.9. IMPINGEMENT PLATE SCRUBBER (SOURCE: CONTROL
TECHNIQUES DOCUMENTS, Reference 3)
-------
5.43
Figure 5.10. VENTURI SCRUBBER MAY FEED LIQUID THROUGH JETS (a),
OVER A WEIR (b), OR SWIRL THEM ON A SHELF (c),
COURTESY OF UOP AIR CORRECTION DIVISION (SOURCE:
CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.44
Figure 5.11. MULTIPLE-VENTURI JET SCRUBBER, COURTESY OF BUELL CORPORA-
TION (SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.45
Figure 5.12. VERTICAL VENTURI SCRUBBER, COURTESY OF UOP
AIR CORRECTION DIVISION (SOURCE: CONTROL
TECHNIQUES DOCUMENTS, Reference 3)
-------
5.46
GAS OUTLET
LIQUID
DISTRIBUTION
HEADERS
UNWETTED
SECTION FOR
MIST ELIMINATION
- PACKING SUPPORT
GRID
CLEAN GAS
OUT
GAS INLET —
VSUMP
MIST
ELIMINATOR
SECTION
'V WEIR
DISTRIBUTOR
PACKED
•SCRUBBING
SECTION
a. CROSS-FLOW SCRUBBER
b. COUNTERCURRENT-FLOW SCRUBBER
Figure 5.13. PACKED-BED SCRUBBERS, COURTESY OF
CHEMICAL ENGINEERING MAGAZINE (SOURCE:
CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.47
GLASS SPHERES
SPRAY
WATER INLET
MIST
ELIMINATOR
TURBULENT
LAYER
Figure 5.14. FLOODED-BED SCRUBBER, COURTESY OF NATIONAL
DUST COLLECTOR CORPORATION (SOURCE: CONTROL
TECHNIQUES DOCUMENTS, Reference 3)
-------
5.48
CLEAN GAS
MIST ELIMINATOR
FROM
RECIRCULATION •
PUMP
SCRUBBING LIQUOR
RETAINING GRID
FLOATING BED OF LOW-
DENSITY SPHERES
RETAINING GRID
MAKEUP LIQUOR
TO . . ,
RECIRCULATION < ' P=
PUMP
^^lil^^^^l'^J^
ooioo.ooooo qi:ir£
o, olto'^o bx o o o p p
TO DRAIN
OR RECOVE
Figure 5.15. FLOATING-BALL (FLUID-BED) PACKED SCRUBBER,
COURTESY OF UOP AIR CORRECTION DIVISION
(SOURCE:CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.49
GAS OUTLET
SEPARATOR
-' PLATES
PRIMARY
-"SEPARATOR
GAS
, CONTACTING
TUBE
SCHMIEG SWIRL-ORIFICE DUST COLLECTOR
k. LIQUID VORTEX CONTRACTOR
(Courtesy of Blow Kno* Co.)
RECYCLE TO
PROCESS
c. DOYLE SCRUBBER
(Court.iy of W.it.rn P,.
Figure 5.16. SELF-INDUCED SPRAY SCRUBBERS (SOURCE;
CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
g
a. SCHMIEG VERTICAL-ROTOR DUST COLLECTOR
(Courtesy of United Sheet Metal Co., Inc.)
b. CENTER SPRAY HIGH-VELOCITY SCRUBBER
(Courtesy of Air Engineering Magazine)
Figure 5.17. MECHANICALLY INDUCED SPRAY SCRUBBERS (SOURCE:
CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.51
DIRT AND WATER
DISCHARGED AT
BLADE TIPS
DIRTY GAS
INLET
CLEAN GAS
OUTLET
WATER AND
SLUDGE OUTLET
Figure 5.18. CENTRIFUGAL FAN WET SCRUBBER, COURTESY OF AMERICAN AIR FILTER
COMPANY (SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.52
GAS OUTLET
Figure 5.19. INLINE WET SCRUBBER, COURTESY OF JOY MANUFACTURING COMPANY
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.53
SPRAY HEADER CONNECTION
/ FLOAT VALVE
- QUICK FILL
OVERFLOW
LIQUIDLEVELINDICATORS
SUCTION CONNECTION
u. WETTED FILTER
IMPACTION
DUST-LADEN GAS
WATER FILM
VENA CONTRACTA
WATER DROPLETS
b. IMPINGEMENT PLATE FILTER
WATER FILM
Figure 5.20. WETTED AND IMPINGEMENT PLATE FILTERS, COURTESY OF BUFFALO
FORGE COMPANY (SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
Table 5.7. WET SCRUBBER OPERATIONAL CHARACTERISTICS
(Compiled from References 3 and 6.)
Scrubber Type
Gravity Spray Towers
Centrifugal Spray
Scrubber
Impingement Plate
Scrubber
Venturi Scrubbers
Packed Bed Scrubbers
a. Cross Flow
b. Countercurrent
Flow
c. Parallel Flow
d. Flooded-Bed
e. Fluid-Bed
Self-Induced Spray
Scrubbers
Mechanically Induced
Spray Scrubbers
Disintegrating
Scrubbers
Centrifugal Fan Wet
Scrubbers
Inline Wet Scrubbers
Irrigated Wet
Filters
Gas
Velocity
Range
Ft/Sec
2 to 5
UP to 200
75 to 100
200 to 600
9 to 17
9 to 17
9 to 17
9 to 17
9 to 17
50 to 180
33 to 66
33 to 66
33 to 66
33 to 50
3.3 to 5.0
Water to
Gas Ratio
Gal/1000 CFM
5 to 20
5 to 15
3 to 5
5 to 7
1 to 4
10 to 20
7 to 15
2 to 2-1/2
3 to 5
No pumping
4 to 5
4 to 9
.75 to 1.5
1
8 to 10
Gas Flow
Counter-
Current
V
V
V
V
V
vs. Spray Direction
Right
Concurrent Angle
V
J
V
^
V
V
V
V
V
V
Pressure
Drop
in W.G.
< 1.0
1.5 to 3.5
1.0 to 8.0
6.0 to 70.0
0.2 to 0.5/
ft bed
0.5 to l.O/
ft bed
1.0 to 4.0/
ft bed
4.0 to 6.0
4.0 to 8.0
2.0 to 15.0
[3 to 10 HP]
[7 to 11 HP]
6.5 to 9.0
5.0
0.2 to 3.0
01
.p-
-------
5.55
g100-!
I
*JH
H
| 95
I
10
20
30
40
Venturi Pressure Drop (in. w. g. )
Curve A: Rotary iron powder kiln
B: Lime kiln, asphalt plant
C: Iron cupola
D: Phosphoric acid plant (acid mist)
E: Incinerator (sodium oxide fumes)
Figure 5.21. COLLECTION EFFICIENCY VS. PRESSURE DROP IN
VENTURI SCRUBBERS (PAGE 3, SECTION ON VENTURI
SCRUBBERS, INSTITUTE FOR A.P. TRAINING, CONTROL
OF PART). (SOURCE: Reference 4)
-------
5.56
pressure drop. Other types of scrubbers lose efficiency rapidly
when particle sizes drop below 3 microns.
Another critical area in the selection of a scrubber for a specific
application of dust control is the concentration of particulates in
the gas stream. Effluent streams with heavy concentrations of dust
and relatively large particle size should first be treated in a pre-
cleaner such as a cyclone or settling chamber. The dust-laden gas
then can be cleaned by a scrubber with the proper design character-
istics for the types of particulates, grain loading and particle
sizes to be collected.
Demisters while not generally classified as primary collectors are
used in conjunction with scrubbers for the capture of large diameter
liquid and solid particulates. The types of demisters are:
Fiber filters Figure 5.22
Wire Mesh Figure 5.23
Baffles Figure 5.24
Packed Beds Figure 5.25
These devices depend on inertial impaction for control of large size
particles (>10 u). Table 5.8 shows the typical applications for
the various types of mist eliminators. Pressure drops on fiber
filter demisters range from 5 to 15 inches of water. Pressure drops
on other types of demisters tend to be lower and range from 1 to 5
inches of water.
1. Inspection Points
In addition to observing the color, opacity and carryover after
the dissipation of water vapor from the scrubber, the enforcement
officer must be aware of its operating characteristics and
-------
5.57
SUPPORT PLATE
SCREENS
FIBER PACKING
CLEAN
GAS OUT
LIQUID DRAINAGE
LIQUID
SEAL
POT
LIQUID BACK TO PROCESS
u. LOW-VELOCITY FILTERING ELEMENT
CLEAN GASES
'' TO STACK
TT
6
t b
•«
v \
ACID-LADEN
GASES
TUBE SHEET
BRINK MIST
ELIMINATOR
ELEMENTS
RECOVERED
H2S04
b. MULTIPLE MOUNTING OF LOW-VELOCITY FILTER-
ING ELEMENTS
Figure 5.22. LOW-VELOCITY FILTERING ELEMENTS
(SOURCE: CONTROL TECHNIQUES
DOCUMENTS, Reference 3)
-------
5.58
EFFLUENT FROM
ABSORBER
V/IRE MESH
WIRE MESH
ACID DRAIN
MIST ELIMINATOR ARRANGEMENT IN VESSEL
ABOVE ACID PLANT ABSORBER
(Courtesy of Chemical Engineering Progress Magazine)
Figure 5.23. WIRE MESH MIST ELIMINATOR
WATER SPRAY
MANIFOLD
HANGER-
BAFFLES-
SECTION A-A-
TOP VIEW
TOP OF
-QUENCH
TOWER
SPRAY
NOZZLES
SIDE VIEW
b. MIST ELIMINATOR BAFFLES
a. DIAGRAM OF BAFFLE SYSTEM SHOWING CLEAN-
ING WATER SPRAYS AND BAFFLE ARRANGEMENT
Figure 5.24. COKE QUENCH MIST ELIMINATION BAFFLE SYSTEM
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.59
BERL SADDLES
Figure 5.25. BED OF BERL SADDLES ADDED TO DISCHARGE STACK
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.60
Table 5.8. TYPICAL INDUSTRIAL APPLICATION OF WET SCRUBBERS
Scrubber type
Spray chambers
Spray tower
Centrifugal
Impingement plate
Venturi:
Venturi throat
Flooded disk
Multiple jet
Venturi jet
Vertical venturi
Packed bed:
Fixed
Flooded
Fluid (floating) ball .
Self-induced spray
Mechanically-induced spray
Disintegrator
Centrifugal fan Inline fan
Wetted filters
Dust, mist eliminators:
Fiber filters
Wire mesh .
Baffles
Packed beds
Typical application
Dust cleaning, electroplating, phosphate fertilizer, kraft paper,
smoke abatement
Precooler, blast furnace gas
Spray dryers, calciners, crushers, classifiers, fluid bed processes,
kraft paper, fly ash
Cupolas, driers, kilns, fertilizer, flue gas
Pulverized coal, abrasives, rotary kilns, foundries, flue gas, cupola
gas, fertilizers, lime kilns, roasting, titanium dioxide processing,
odor control, oxygen steel making, coke oven gas, fly ash
Fertilizer manufacture, odor control, smoke control
Pulverized coal, abrasive manufacture
Fertilizer manufacturing, plating, acid pickling
Acid vapors, aluminum inoculation, foundries, asphalt plants,
atomic wastes, carbon black, ceramic frit, chlorine tail gas, pig-
ment manufacture, cupola gas, driers, ferrite, fertilizer
Kraft paper, basic oxygen steel, fertilizer, aluminum ore reduction,
aluminum foundries, fly ash, asphalt manufacturing
Coal mining, ore mining, explosive dusts, air conditioning, incin-
erators
Iron foundry, cupolas, smoke, chemical fume control, paint spray
Blast furnace gas
Metal mining, coal processing, foundry, food, Pharmaceuticals
Electroplating, acid pickling, air conditioning, light dust
Sulfuric, phosphoric, and nitric acid mists; moisture separators;
household ventilation; radioactive and toxic dusts, oil mists
Sulfuric, phosphoric, and nitric acid mists; distillation and absorp-
tion
Coke quenching, kraft paper manufacture, plating
Sulfuric and phosphoric acid manufacture, electroplating spray
towers
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.61
physical characteristics. Inspection points include:
(1) A check for structural wear from corrosion.
(2) Recording the water pressure to the scrubber to compare
it with the design pressure.
(3) An inspection of the interior of the scrubber to see if
there are deposits of material which could disturb the
flow pattern.
(4) Noting impairment in efficiency due to freezing.
(5) Establishing the maintenance schedule for cleaning and
replacing nozzles.
(6) Noting the operation of fans and pumps and fraying or
excessively worn drive belts.
(7) Noting if the bypass system has been opened and the
duration of the time of bypass.
(8) Recording temperature and pressure of gases entering
the scrubber to check against design parameters.
Table 5.8 describes applications of scrubbers by industrial
process. Since venturi scrubbers are among the high efficiency
collectors, additional descriptive performance data is included
in Table 5.9.
E. Fabric Filters
Most often referred to as baghouses, fabric filters remain among the
most efficient air pollution control equipment for small size particu-
(3)
lates (< 0.01 [j.). Dust-laden gases are forced through a fabric
bag which may be tubular or flat (Figures 5.26 and 5.27) where the
particulates are retained by direct interception, inertial impaction,
diffusion, electrostatic attraction and gravitational settling.
Gases to be cleaned can either be "pushed" through or "pulled"
through the baghouse. In the pressure system (push through) the
-------
5.62
Table 5.9. TYPICAL PERFORMANCE DATA FOR VENTURI SCRUBBER*
Source of Gas
IRON i STEEL INDUSTRY
Cray Iron Cupola
Oxygen Steel Converter
Steel Upen HiMilh lurnai-e iStrdpl
Sleet Open Kedrtli Fjtnacr
(Oxygen lancedl
Blast Furnace (Iron)
Electric Furnace
Electric Furnace
Rotary Kiln — Iron Reduction
Crushing & Screening
CHEMICAL INDUSTRY
Acid— Humidified SO,
la) Scrub with Water
0>) Scrub with 40% Acid
Acid Concentrator
Copperas Roasting Kiln
Chlorosulfonic Acid Plant
Dry Ice Plant
Wood Distillation Plant
TiCI. Plant, TiO, Dryer
Spray Dryers
Flash Dryer
Phosphoric Acid Plant
NON-fERROUS METALS INDUSTRY
Blast Furnace (Sec. Lead)
Reverberatory Lead Furnace
Ajai Furnace — Aluminum Alloy
Zinc Sintering
Reverberatory Brass Furnace
MINERAL PRODUCTS INDUSTRY
Lime Kiln
lime Kiln
Asphalt Stone Dryer
Cement Kiln
PETROLEUM INDUSTRY
Catalytic Reformer
Acid Concentrator
TCC Catalyst Regenerator
FERTILIZER INDUSTRY
Fertilizer Dryer
Superphosphate Den & Mixer
PUIP t PAPER INDUSTRY
lime Kiln
lime Kiln
Black Liquor Recovery Boiler
MISCELLANEOUS
Pickling Tanks
Boiler Flue Gas
Sodium Disposal Incinerator
A
Contaminants
Iron, Coke. Silica DuM
Iron Onde
1 on ( /(in 0>ide
1 on Oxide
1 on Ore £ Coke Oust
F rro-Manganese Fume
F iro-Silicon Dust
Iron, Carbon
Taconite Iron Ore Dust
H.SO, Mist
H.SO. Mist
H.SO. Mist
H,SO, Mist
Amine Fog
Tar t Acetic Acid
TiO.-HCI Fumes
Detergents, Fume t Odor
Furfural Dust
H,PO, Mist
Lead Compounds
Lead i Tin Compounds
Aluminum Chloride
Zinc 1 Lead Oxide Dusts
Zinc Oxide Fume
Lime Oust
Soda Fume
Limestone I Rock Dust
Cement Dust
Catalyst Dust
H.SO, Mist
Oil Fumes
Ammonium Chloride Fumes
Fluorine Compounds
Lime Dust
Soda Fume
Salt Cake
NCI Fumes
Fly Ash
Sodium Oxide fumes
3proximat«
ize Range
iMicrons)
110
5?
.081
M
.520
.1-1
.1-1
.5-50
.5-100
—
_
.5-1
.1-1
—
.1-1
,1-J
.1-.9
.1-1
.05-.5
1-50
.3-1
1-50
.5-55
.5-50
_
—
.05-1
.1-50
.1-2
.1-3
3-.1
; Load
(Grain
Inlet
1-2
8-10
.5-1.5
1-6
3-24
10-12
1-5
3-10
5-25
303'
406"
136'
198'
756'
25'
1080"
1-5
1-1.5
192*
2-6
1-2
3-5
1-5
1-8
5-10
.2-5
5-15
1-2
.09
136'
756'
.1-.5
309*
5-10
2-5
«
25'
1-2
3-1
ing
s/ cf)
Exit
.05-. 15
.05- .08
03-.W
.01-.07
.008- .05
.04-.08
.1-.3
.1-.3
.005-.01
1.7'
2J'
3.3*
2.0*
7.8"
2.0'
58.0*
.05-.!
.05-.08
3.8'
.05-.15
.12
.02-.05
.05-.!
.1-5
.05-.15
.01-.05
.05-.15
.05-.!
.005
3.3'
8.0'
.05
5V
.05-.15
.01-.05
.4-.6
2.3'
.05-.08
.02
Average
Removal
Efficiency (%)
95
98.5
95
99
99
99
92
99
99.9
99.4
99.3
97.5
99
98.9
9°+
93
95
95
95+
98+
99
91
95
98
95
99-+
99
98+
97+
95+
97.5
98+
85+
98+
99+
99
90
90+
98
98
• Milligrams pir cubic (t
ffott': The efficiencies ekovm above are average valuet for a particular
plant or group of inetallationt operating under a tpecific tet of condition*.
*Figure 5.21 shows relationship of efficiency to pressure drop.
(SOURCE: OFFICE OF MANPOWER DEVELOPMENT, Reference 4)
-------
5.63
TOP VIEW
SIDE VIEW
Figure 5.26. TYPICAL FLAT OR ENVELOPE DUST COLLECTOR BAG
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
TOP VIEW
\
— 1
\
'
\
t
/
<
H
1
\
^
H
/
f
^
,
H
'
(
,>
^
1—
SIDE VIEW
Figure 5.27 TYPICAL ROUND OR TUBULAR DUST COLLECTOR BAG
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.64
gases may enter through the cleanout hopper in the bottom or through
the top of the bags. (In the suction type [pullthrough] the dirty
gases are forced through the inside of the bag and exit through the
outside of the bag.) Figures 5.28 through 5.30 depict these flows.
Other design variables are the type of fabric used (either woven for
dust cake sieving or felted fabrics), bag cleaning mechanisms, equip-
ment geometry and mode of operation.
Fabric filters are usually rated by the ratio of gas (CFM) to the
area of the filter (square feet) which is the velocity of the gas through
the filter cloth. A rule of thumb is a ratio of 1.5 to 3.0 CFM per
square foot of cloth for dust and 1 to 2 CFM per square foot of cloth
for fumes.
General operating characteristics of baghouses which the enforcement
officer must understand are the following:
• The temperature and moisture content of the gases to be
cleaned are important factors in the operation of baghouses.
"Wet" gases will cause blinding (plugging) of the bags
resulting in extremely high pressure drops which in turn
will reduce the effectiveness of the entire collection system
by reducing the volume of gases handled. The baghouse
therefore should operate at a temperature above the dewpoint
of the incoming gas. The closed suction type baghouse is
used for gases with dewpoints between 165°F and 180°F. In
this design, blower maintenance is less because it sees only
clean gases. Open pressure type baghouses can handle hotter
gases; however, this design will cause excessive wear on the
fan, since it will handle the entire dust load.
• Physical shape and structural design are important to assure
properly proportioned air flow through the bags, corrosion
resistance and removal of the captured materials.
• Precooling equipment is a necessary part of most dust control
systems using baghouses. Three cooling methods are usually
employed:
(a) Radiation and convection.
-------
5.65
(nc\)
CLEANED GAS
OUTLET
/ J
V
1
ll.
S1
7
V
/
y
^
»
f
jL
•
'1
?1
t
Y
r
\
t
jL \
v'
\
/
*
'
it
CORRUGATED
HOUSING
OPEN
"GRATING
/ OUTSIDE AIR
SIDE VIEW
Figure 5.28. OPEN PRESSURE BAGHOUSE
DIRTY
GAS
FROM
FAN
J CLEANED GAS
' —OUTLET
A
,
»
h
V.
.'
V:
'1
FT
,--
> :•
\.
,v
V
/J>
V
, :/
j.
V-
\?-:.-j>t-.-'-:JI
t4
u
:•
I
,.•
\
v
><
X
i
'•/,
if.
'-(
^
fv
'
^
'•'-.••"*:/
CORRUGATED
HOUSING
^CLOSED
SIDE VIEW
CLEAN GAS AA
TO FAN [rTj
^-^L
/I
y
r*
y
\
\
n
\
n
^
A
•
/
.
\
A
f
\
\i
*
^
n
\
/
\
\
^
CLOSED
ALL WELDED
HOUSING
SIDE VIEW
Figure 5.29. CLOSED PRESSURE BAGHOUSE Figure 5.3". CLOSED SUCTION BAGHOUSE
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.66
(b) Dilution air.
(c) Spray cooling.
Radiation and convection cooling systems need large cooling
surfaces resulting in considerable space requirements. A
longer term penalty in additional motor horsepower needs will
result from increasing the system pressure drop. Spray
cooling is not advised for gases with high moisture content.
Where dilution air is used, it is necessary to increase the
filter area to comply with good practice thus making the
installation costlier. Where spray cooling can be used,
controls must be included to keep the temperature of the
gases 50°F to 75°F above the
Bag cleaning techniques vary. Figures 5.31 through 5.39
describe the most common cleaning mechanisms. Bags may be
mechanically shaken, fibrated by air jets or vibrated by sonic
waves to remove the agglomerated dust and fumes on the cloth
surface. The shaking reduces the pressure drop across the
baghouse to ensure optimum resistance for high collection
efficiency. It is therefore necessary that the enforcement
officer become familiar with the various cleaning methods in
common use.
The properties of fabrics used and recommendations for operating
temperatures, types of fabric vs. duct to be collected and
filtering ratios are found in Tables 5.10 through 5.12. These
are important guides to the enforcement officer. They assist
him in determining whether or not the proper fabric is being
used for any given application.
1. Inspection Points
a. Pressure Drop
Pressure drop across the baghouse can range from 0.5" W.G. to
8" W.G. The enforcement officer should determine from design
information the operating range of the baghouse after shaking
and when shaking is required. Many baghouses operate on a
present time schedule, independent of pressure drop. In these
cases there is a gas bypass system which is activated when the
bags are to be cleaned.
Operation
The field enforcement officer should observe emissions during
regular operations and during the cleaning cycle. The
-------
5.67
PRESSURE BLOWER
INSIDE OUT
FILTERING
SIDE VIEW
oooJ
0001 rooo
oooJ Looo
0001 rooo
ooo J Looo'
oooi rooo
oooJ Looo
ooo1 rooo
*J
;'
TOP VIEW
AIR JETS
FOR SHAKING
SIDE VIEW
Figure 5.31. MECHANICAL SHAKING OF
BOTTOM ENTRY DESIGN
UNI-BAG DUST COLLECTOR.
Figure 5.32. AIR SHAKING WIND-WHIP
CLEANS DUST COLLECTOR
BAGS.
UNI-BAG
INSIDE OUT,
FILTERING
rih
JET
SIDE VIEW
COMPRESSED AIR
OUTSIDE IN
FILTERING
SIDE VIEW
Figure 5.33. BUBBLE CLEANING OF
DUST COLLECTOR BAGS.
Figure 5.34. JET PULSE DUST COLLECTOR
BAG CLEANING.
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.68
\
\
n
'
-
i
* s^>
*
EXHAUST
REPRESSURING
VALVE
SIDE VIEW
FILTERING
SIDE VIEW
COLLAPSING
INLET
VALVE
SIDE VIEW
CLEANING
Figure 5.35. REVERSE AIR FLEXING TO CLEAN DUST
COLLECTOR BAGS BY REPRESSURING.
AIR HORN
FILTER BAG
1 <::••;-*•>*
1 .'• •"•••• '•''j • —
'.'V.^-Vtl SOUND WAVES
SIDE VIEW
INSIDE OUT
FILTERING
SIDE VIEW
Figure 5.36. SONIC CLEANING OF
DUST COLLECTOR BAGS.
Figure 5.37. REPRESSURING CLEANING OF
DUST COLLECTOR BAGS.
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.69
TO FAN
VENT OPEN
TO NEXT
COMPARTMENT
SIDE VIEW \ / SIDE VIEW
OPERATING CLEANING
Figure 5.38. CLOTH CLEANING BY REVERSE FLOW OF AMBIENT AIR.
EXHAUST CLOSED
TOP ENTRY
\
HIGH PRESSURE
•*-AIR BLOW
RING
INSIDE OUT
"FILTERING
CROSS-SECTION
Figure 5.39. REVERSE JET CLEANING OF
DUST COLLECTOR BAGS.
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.70
Table 5.10. RECOMMENDED MAXIMUM FILTERING RATIOS AND DUST
CONVEYING VELOCITIES FOR VARIOUS DUSTS AND FUMES
IN CONVENTIONAL BAGHOUSES WITH WOVEN FABRICS.
Dust or fumes
Abrasives
Alumina ...
Aluminum oxide
Asbestos ..
Baking powder
Batch spouts for grains
Bauxite
Bronze powder
Brunswick clay
Buffing wheel operations
Carbon
Cement crushing and
grinding
Cement kiln
(wet process) . .
Ceramics
Charcoal
Chocolate
Chrome ore
Clay
Cleanser
Cocoa
Coke
Conveying
Cork
Cosmetics
Cotton
Feeds and grain
Feldspar
Fertilizer (bagging)
Fertilizer (cooler, dryer)
Flint
Maximum
filtering
ratios,
cfm/fts
cloth area
3.0
2.25
2.0
2.75
2.25-2.50
3.0
2.5
2.0
2.25
3.0-3.25
2.0
1.5
1.5
2.5
2.25
2.25
2.5
2.25
2.25
2.25
2.25
2.5
3.0
2.0
3.5
3.25
2.5
2.4
2.0
2.5
Branch
pipe
velocity,
fpm
4500
4500
4500
3500-4000
4000-4500
4000
4500
5000
4000-4500
3500-4000
4000-4500
4500
4000-4500
4000-4500
4500
4000
5000
4000-1500
4000
4000
4000-4500
4000
3000-3500
4000
3500
3500
4000-4500
4000
4500
4500
Dust or fumes
Flour .. .
Glass . .
Granite
Graphite
Grinding and separating
Gypsum
Iron ore
Iron oxide . ....
Lampblack
Lead oxide
Leather .. .
Lime
Limestone .
Manganese
Marble
Mica
Oyster shell . . . ..
Packing machines
Paint pigments
Paper
Plastics .. .
Quartz
Eock . .
Sanding Machines
Silica
Soap
Soapstone
Starch
Sugar
Talc
Tobacco
Wood
Maximum
filtering
ratios,
cfm/ft5
cloth area
2.5
2.5
2.5
2.0
2.25
2.5
2.0
2.0
2.0
2.25
3.5
2.0
2.75
2.25
3.0
2.25
3.0
2.75
2.0
3.5
2.5
2.75
3.25
3.25
2.75
2.25
2.25
2.25
2.25
2.25
3.5
3.5
Branch
pipe
velocity,
fpm
3500
4000-4500
4500
4500
4000
4000
4500-5000
4500
4500
4500
3500
4000
4500
5000
4500
4000
4500
4000
4000
3500
4500
4500
4500
4500
4500
3500
4000
3500
4000
4000
3500
3500
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.71
Table 5.11. RECOMMENDED MAXIMUM FILTERING RATIOS AND FABRIC FOR
DUST AND FUME COLLECTION IN REVERSE-JET BAGHOUSES.
Material
or operation
Bauxite
Carbon, green
Carbon, banbury
Cement, raw
Cement, milling.. ..
Chrome, (ferro)
silicious.
Flour
Gypsum
Lead oxide fume
Limestone (crushing) .
Metallurgical fumes __
Paint piements .
1
Fabric
i
Napped cotton
Cotton sateen . _ . .
wool felt.
Orion felt
Wool felt
Cotton sateen
Cotton sateen .
Cotton sateen
Napped cotton
Cotton sateen
Wool felt,
cotton sateen.
Wool felt
Cotton sateen,
orlon felt.
Orion felt,
wool felt.
Napped cotton
Cotton sateen —
Orion felt,
wool felt.
Napped cotton.
Cotton sateen. _
filtering
ratios,
efm/ft'
11
10
8 •
7
8
9
10
8
10
10
12
12
14 "
16
7 *
10
8"
10
10
10 •
11
10
Material
or operation
Phenolic molding
powders.
Polyvinyl chloride
(PVC).
Refractory brick
sizing (after firing).
Silicon carbide
Soap and detergent
powder.
Soy bean
Starch
Sugar
Talc
Tantalum fluoride
Tobacco
Wood flour
Wood sawing
operations.
Zinc, metallic .
Zinc oxide
Zirconium oxide ..
" Decrease 1 cfm/ft2
particle size is small.
Fabric
Cotton sateen
Wool felt . .
Napped cotton
wool felt.
Cotton sateen
Dacron felt.
orlon felt.
Cotton sateen ..
Cotton sateen
Cotton sateen,
wool felt.
Cotton sateen
Orion felt...
Cotton sateen
Cotton sateen
Cotton sateen
Orion felt,
dacron felt.
Orion felt
Orion felt
if dust concentration
Filtering
ration,
cfm/ft'
10
10 •
12
6 8 •
9-11
12 •
14
10
10 •
11
6-
12
10
12
11
is high or
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.72
Table 5.12. FILTER FABRIC CHARACTERISTICS
Fiber
Operating
exposure S
°F.
i
Long
Cotton
Wool
Nylon d
Orion d
Dacron d
Polypropylene
Nomex d
Fiberglass, . .
Teflon d
180
200
200
240
276
200
425
550
450
Short
225
260
250
275
325
260
500
600
500
upporta
com-
bustion
yes
no
yes
yes
yes
yes
no
yes
no
Air
perme-
ability •
cfm/ft'
10-20
20-60
16-30
20-45
10-60
7-30
25-54
10-70
15-65
Resistance b
Composition
Abrasion
Cellulose
Protein
Polyamide
Polyacrylonitrile
Polyester
Olefin
Polyamide
Glass
Polyfluoroethylene
G
G
E
G
E
E
E
P-F
F
Mineral
acids
P
F
P
G
G
E
F
E
E
Organic
acids
G
F
F
G
G
E
E
E
E
Alkali
G
P
G
F
G
E
G
P
E
Cost*
rank
1
7
2
3
4
6
8
5
9
• cfm/ft' at 0.5 in. W.G.
» P = Poor, F = Fair, G = Good, E = Excellent.
« Cost rank, 1 = lowest cost, 9 = highest cost.
d Dupont registered trademark.
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.73
observation during bag shaking (Figure 5.40) may detect a time
and opacity violation. In baghouses using reverse jet action,
cleaning is continuous, allowing much higher air-to-cloth
ratios. Some designs employ an air actuated ring which rides
along the vertical axis of the bag. In this instance, the
enforcement officer must also become familiar with the oper-
ation of the system to be certain that the cleaning mechanism
is operating properly and not binding at any point.
As a general rule, it is often necessary to know the maintenance
schedule for closed baghouses in order to be able to inspect
the inside of the equipment when it is offstream.
Maintenance
It is always necessary to consider the entire system and not
only the air cleaning device. The enforcement officer,
therefore, must determine the state of repair and operation
of the hooding, ductwork, gas cooling equipment and fan, as
well as the baghouse. Maintenance of the system is vital
to its operation in order to avoid reduction in dust and fume
pickup at the basic equipment caused by leaks in the system,
fan deterioration due to handling high grain loading in a
pressure system, or corrosion.
In systems where the material collected can be returned to
the process or sold, the maintenance effort will more than
likely be satisfactory. Where the material collected poses
the additional problem of disposal, the enforcement officer
should know what means are used to dispose of the collected
material. Dumping the finely divided particulates onto the
ground can result in a fugitive dust problem. In this regard,
it is necessary to make sure that the collection hoppers are
emptied on a regular basis and that the material is disposed
of in a manner that will create the least problem, i.e.,
closed barrels, carts, trucks, etc.
A schedule of bag inspection leading to repair or replacement
should be made available to the enforcement officer. This
will be a very important tool in the determination of problems
relating to baghouse system malfunctions. A well-defined
program for bag replacement based upon expected baglife for
the particular fabric used will help insure proper operation
and minimal downtime (see Table 5.13).
-------
5.74
Incoming gases
Filtering
Filtering
1
3L
Filtering
to fan
All compartments filtering, dampers open
incoming gases
Filtering
JJ
Shaking
Filtering
to fan
Incoming gases
Shaking
/N
Filtering
Filtering
^
-------
5.75
Table 5.13. TROUBLESHOOTING CHECKLIST FOR FABRIC FILTERS*
"Condition: High differential pressure (Note: Most installations are de-
signed for differential pressure of 3 to A in. A differential pressure of
1 in. to 6 in. can be considered normal).
1. Improper compressed air supply (80 to 100 psig is required. More
effective cleaning is possible with pressures up to 110 psig) .
2. Improper timer operation. Make sure all valves are being activated.
Check for sticking timer relay.
3. Improper solenoid valve operation. A leaking diaphragm will reduce
cleaning energy by slowing or preventing valve opening.
4. Leaky airlock or dust discharge valve can overload collector by
preventing dust discharge.
5. Moisture blinded bags. Recovery is often possible by running the
cleaning mechanism without moving air through the collector from one to 30
hours.
6. Considerable dust in the clean air plenum (from a previously leaky
bag, etc ) can reduce cleaning effectiveness by impregnating the bags in the.
reverse direction.
7. Static electricity can cause a high differential pressure. Increase
humidity if possible.
8. Make sure blow tubes are installed correctly_(field assembly units).
9. Collector overloaded by too much air. Check fan speed. Check
damper adjustment and system design.
" Condition: Seepage - Visible discharge
Points to check and remedy:
1. Improperly installed bags.
2. Loose bag clamps.
3. Torn bags or holes in bags.
4. Improper sealing of tube sheet joints (field assembled units).
5. Missing or loose venturi rivets.
* Primarily for pulse cleaned equipment; from Mikro-pulsaire Instruction
Manual, Pulverizing Machinery Corp.
(SOURCE: APPENDIX OF HANDBOOK OF FABRIC FILTER TECHNOLOGY,
Reference 9.)
-------
5.76
Table 5.13. TROUBLESHOOTING CHECKLIST FOR FABRIC FILTERS (continued)
"Condition: Insufficient suction on exhaust hood or system
Points to check and remedy:
1. Fan direction of rotation incorrect. Fan will pump air ineffi-
ciently if wrong direction.
2. Check for high differential pressure (see above).
3. Slippage on fan belts?
4. Leaking duct work? Access doors? Explosion doors? Discharge
valve on air lock?
5. Clogged duct, or closed gate, or damper.
6. Duct size or run other than original design.
7 Poor system design?
"Condition: Unable to maintain compressed air pressure
Points to check and remedy:
1. Dirty solenoid valve sticking open Clean and check pilot plunger.
2. Short circuit in wiring keeping one or more valves open.
3. SLickiug i_imer reiay, or pulse longer than 0.15 seconds.
4. Faulty or too small a compressor, and/or pipe leaks.
5. Solenoid valves require a minimum of 5 psig to close. A long com-
pressed air run after the shut-off valve can prevent the required 5 psig
from developing. Solution to this would be provision of reservoir and
shut-off valve near the collector.
"Condition: Filter cylinder problems (blinding, poor life, etc.)
Points to check and remedy:
1. Check operating temperature (e.g. 180 deg. for wool).
2. Check operating humidity, free moisture, etc. (relative humidity
is too low if static electricity occurs).
3. Check for shrinkage, free moisture, etc.
-------
5.77
Table 5.13. TROUBLESHOOTING CHECKLIST FOR FABRIC FILTERS (continued)
4. Review physical and chemical characteristics of material and gas
stream.
5. Check for hopper bridging. Material buildup into the bag area can
overstress elements.
6. Incorrect bag retainer installation can cause bag wear by allowing
friction between adjacent elements or between outside elements and housing.
Make sure tubes are installed vertically. "
-------
5.78
d. Temperature and Dew Point
The enforcement officer must determine the nominal operating
conditions for baghouses. Good operating procedures dictate
that the gas temperature should be 50°F to 75°F above the
dew point. This temperature will then determine the fabric
to be used for the given operating condition. Table 5.12
will be helpful in making this determination. In baghouses
using reverse jet action for cleaning, the compressed air
used to blow the dust from the inside of the bag may have
to be heated to avoid blinding the bags from condensed
moisture. In some baghouses, it may be necessary to maintain
the temperature significantly above ambient by the use of
heaters when it is down, to preclude blinding from moisture
at startup.
e. General
Mechanical devices need to be tended and maintained, including
painting to retard corrosion and lubrication of moving parts
and repairs. Mechanical shakers, screw conveyors and other
materials handling equipment must be kept in good working order
to prevent equipment downtime.
Electrostatic Precipitators
Electrostatic precipitators employ the principle of attraction of
opposite charges. The particles in the contaminated exhaust stream
are charged in a high voltage electric field and are then attracted
to a plate of the opposite charge where they are collected. When
the plate is shaken or rapped, the contaminants drop into a hopper.
There are 2 basic types of electrostatic precipitators. Single-
stage precipitators operating at high voltage, 30 to 100 KV peak
voltage, and 2-stage, low-voltage precipitators operating at 12 to 13
KV. The higher voltage precipitator is commonly used in large
installations such as coal-burning central power stations and Portland
cement plants. The low-voltage, 2-stage precipitators are used to
control mists and other particulates from smokehouses, asphalt paper
-------
5.79
(3)
saturators, pipe-coating machines and high-speed grinders.
1. High Voltage Precipitators
(4)
High voltage precipitators operate in four basic steps:
• Electrically charging the particles to be collected from
the gas stream by ionization.
• Transporting the charged particles by means of the force
exerted upon them by the electric field to a collecting
surface.
• Neutralizing the electrically charged particle precipitated
on the collecting surface.
• Removing the precipitated particles from the collecting
surface.
There are 2 designs of the 1-stage precipitator in general use
which combines ionization and collection in a single stage. They
are:
• Wire-in-plate (Figure 5.41)
• Wire-in-tube (Figure 5.42).
The wire-in-plate design uses grounded parallel plates 6 to 12
inches apart with the wire equidistant between the plates
(Figure 5.43). The wire-in-tube design uses cylinders as
grounded collectors with the wire suspended on the centerline of
the tube (Figures 5.42 and 5.44). The high voltage current is
provided by transformers (usually oil cooled) with rectifiers
for converting the alternating current to direct current.
After the charged particles have been collected on the plates
or tubes, effective removal is the next step in the operation.
Liquid particulates flow down the grounded collector to the bin
by gravity. Solid particulates must be dislodged by mechanical
-------
5.80
CHARGING FIELD
Charged (-) PARTICLES
PARTICLE PATH
HIGH-VOLTAGE DISCHARGE ELECTRODE ( - )
COLLECTING BAFFLE
GROUNDED (+) COLLECTING SURFACE
DISCHARGE ELECTRODE TENSION WEIGHT
Figure 5.41. SCHEMATIC VIEW OF A FLAT SURFACE-TYPE
ELECTROSTATIC PRECIPITATOR (SOURCE:
CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.81
GROUNDED
COLLECTING SURFACE
CHARGED PARTICLES
HIGH-VOLTAGE
DISCHARGE ELECTRODE
(NEGATIVE'- )
GROUNDED COLLECTING SURFACE
Figure 5.42. SCHEMATIC VIEW OF TUBULAR SURFACE-TYPE
ELECTROSTATIC PRECIPITATOR (SOURCE:
CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
I
SAFETY RAILING
HIGH VOLTAGE TRANSFORMER/RECTIFIER
RAPPER - H. V. ELECTRODE
RAPPER - COLLECTING SURFACE
PENTHOUSE ENCLOSING INSULATORS AND GAS SEALS
ACCESS PANEL
INSULATOR
H. V. WIRE SUPPORT
H. V. DISCHARGE ELECTRODE
PERFORATED DISTRIBUTION BAFFLE
GROUNDED COLLECTING SURFACE
Ln
00
SUPPORT COLUMNS
QUICK OPENING DOOR
(INSPECTION PASSAGE BETWEEN STAGES)
WIRE WEIGHTS
HOPPERS
Figure 5.43. CUTAWAY VIEW OF A FLAT SURFACE-TYPE ELECTROSTATIC PRECIPITATOR
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.83
GAS INLET
GAS OUTLET
HIGH-VOLTAGE
CONDUCTOR
INSULATOR COMPARTMENT
HIGH-VOLTAGE SYSTEM
SUPPORT INSULATOR
ELECTRIC HEATER
WATER SPRAYS
DISCHARGE ELECTRODE
SUPPORT FRAME
WEIR PONDS
DISCHARGE ELECTRODES
TUBULAR COLLECTING
SURFACES
CASING
WEIGHTS
DISCHARGE SEAL
Figure 5.44. CROSS-SECTIONAL VIEW OF IRRIGATED TUBULAR BLAST FURNACE PRECIPITATOR
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.84
means such as rapping or vibration. Collection of the solid
particles and removal from the collection hoppers is a design
problem usually solved by using screw or pneumatic conveyors.
Hopper bottoms can be fitted with swing valves, slide gates or
rotary vane type valves. Some precipitators use a water spray
to clean the plates which may result in the need for drag chains
or other devices to preclude bridging of the collected material
in the hoppers.
(4)
Design parameters for electrostatic precipitators include:
• Peak effective electrical charging field.
• Average electrical field at collecting electrode.
• Particle radius
• Gas velocity
• Precipitator collecting electrode area
• Precipitator gas flow rate
• Efficiency of collection of particulate size.
Figure 5.45 indicates collection efficiency vs. particle size.
Practical aspects of high voltage electrostatic precipitator design
include:
• Modification of the condition of the gases upstream of the
precipitator to cool, humidify, dilute or introduce
additives to the gases.
• Sectionalization of single-stage precipitators is usually
required since large volumes of gases are handled and
conditions within the precipitator may vary requiring
adjustments in current and voltage to compensate for the
variation. Each section should have its own power controls
and supply to ensure peak efficiency and to prevent power
fluctuations. Power controls regulate current, voltage
and sparking.
-------
5.85
o
o
-\
f- -Prac ical Cur
,Theoret
4 8 12 16 20 24
PARTICLE SIZE, MICRONS
Figure 5.45. SIZE-EFFICIENCY CURVES FOR ELECTROSTATIC PRECIPITATOR
(SOURCE: OFFICE OF MANPOWER DEVELOPMENT, Reference 4)
-------
5.86
• Sparking control is necessary because in some designs
sparking is desirable to obtain optimum collection
efficiency.(5) Other designs dictate no sparking.
Optimum sparking is dependent upon such factors as preci-
pitator size, fume characteristics and fume concentration.
Figure 5.46 illustrates this point.
e Gas velocity, treatment time in the precipitator and flow
distribution are vital factors in the collection efficiency
of precipitators. Uniform gas velocity through all
sections of the precipitator is the optimum case.
Velocities range from 3 to 15 feet per second. Table 5.14
shows values used by precipitator manufacturers gained
through years of experience in the field.
• Electrical resistivity is the resistance of certain
particles to maintaining a negative charge which negates
the attraction of the positively charged collector. The
resistivity varies with temperature and moisture content.
Figure 5.47 illustrates this point. These deficiencies
are overcome by the addition of water vapor, acid or other
conducting material to increase the surface conductivity
of highly resistive particulates.(5)
Conditioning agents include:
(1) Ammonia.
(2) Triethylamine for acid particles not readily
wetted with moisture.
(3) Acid salts, sulfuric acid and 803 for basic
particles. The 803 that may be found in stacks
carrying cool combustion effluents may be an aid
in precipitating fly ash.
In addition to observing the precipitator discharge, the enforce-
ment officer must learn the operating limits for good collection
as indicated by the following:
• Individual (sectional) electrical set controls and
instruments.
• Spark rate indicators.
• Rapping, cycle, frequency, intensity and duration controls
and indicators.
-------
5.87
KS PEH MINUTE
Figure 5.46. VARIATION OF PRECIPITATOR EFFICIENCY WITH SPARKING RATE
FOR A REPRESENTATIVE FLY-ASH PRECIPITATOR, WHITE, 1953
CSOURCE: AIR POLLUTION ENGINEERING MANUAL, Reference 5)
K>0 IOO 100 400 *OO
TCUPCIUTURe IN OtO. FAHRENHEIT
Figure 5.47. EFFECT OF MOISTURE CONTENT ON APPARENT RESIS-
TIVITY OF PRECIPITATED CEMENT DUST (SOURCE:
OFFICE OF MANPOWER DEVELOPMENT, Reference 4)
-------
5.88
Table 5.14. TYPICAL VALUES OF SOME DESIGN VARIABLES USED
IN COMMERCIAL ELECTRICAL PRECIPITATOR PRACTICE.
Design variable
Plate spacing
Velocity through precipitator
Vertical height of plates
Horizontal length of plates
Applied voltage
Drift velocity w
Gas temperature
Treatment time
Draft loss
Efficiency
Corona current
Field strength
Normal range of values
8 to 11 in.
2 to 8 ft/sec
12 to 24 ft
0. 5 to 1. 0 x height
30 to 75 kv
0. 1 to 0. 7 ft/sec
up to 700°F standard
1, 000°F high tempera-
ture 1,300°F special
2 to 10 sec
0. 1 to 0. 5 in. WC
up to 99. 9 + % usually
90% to 98%
0. 01 to 1. 0 ma/ft wire
7 to 15 kv/in.
(SOURCE: CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
• Outlet opacity indicators.
• Line voltage indicators.
a. Inspection Points
The enforcement officer must determine from the operator of
the equipment the design characteristics which may be checked
during operation from the instruments and controls cited
above. These include:
• Power supply
(1) Direct current at potential close to that required
for arcing.
(2) Input source of power.
(3) Regulation of voltage during arcing.
(4) Output power:
(a) Voltage 30 to 100 KV.
(b) Current 20 to 100 MA.
(The use of automatic voltage controls will result in
increased collection efficiency.)
• Operation - general
(1) Changes in particulate loading.
(a) Process changes.
(b) Raw material change.
(c) Fuel rate or grade change.
(d) Gas stream conditioning change.
(2) Alarms for signaling control variable deviation.
(3) Malfunction of control valves, gates or conveyors.
(4) Mechanical maintenance of conveyors, required to
prevent corrosion, etc.
• Operation of wet precipitators.
(1) Collection of grease on the inside of tube
electrodes.
(2) Check water sprayed for mineral content to reduce
deposition of solids.
(3) Recirculated water should be treated for removal
of solids.
-------
5.90
• Operation of dry-type precipitators
(1) Prevention of re-entrainment of dust in the gas
stream.
(2) Rapping mechanism must operate properly, i.e.,
proper maintenance is required. Some types are:
(a) Mechanical.
(b) Compressed air actuated.
(c) Magnetic impulse actuated.
(3) Some particulates require the application of an
adhesive to the collection electrodes. This can
be removed only by washing. After washing is
complete, the adhesive must be reapplied. Exten-
sive problems can be caused if a rigid cleaning
schedule is not followed.
2. Two-Stage Precipitators
Low-voltage, 2-stage electrostatic precipitators have come into
use to control emissions from operations "smaller" than cement
kilns or coal-fired power plants and for particulate removal from
air conditioning systems. Their effectiveness falls off rapidly
if the grain loading of the inlet gases exceeds 0.4 grains per
standard cubic feet or if the material to be collected is solid
(4)
or sticky. Thus the equipment is recommended only with low
grain loading.
The two stages of the equipment are:
a. lonization, which is accomplished by a series of fine wires 1
to 2 inches apart, positively charged, placed parallel to
grounded tubes (Figure 5.48). There is a high voltage corona
discharge which ionizes gas molecules that cause charging of
particles passing through the field. The direct current
potential applied to the wires is 12 to 13 KV.
-------
5.91
COLLECTOR CELL
(TO COLLECT PARTICLES)
BAFFLE
(TO DISTRIBUTE
AIR UNIFORMLY)
w^
IONIZER
(TO CHARGE PARTICLES)
Figure 5.48. COMPONENTS OF STANDARD TWO-STAGE PRECIPITATOR,
WESTINGHOUSE ELECTRIC CORPORATION, HYDE PARK,
BOSTON, MASSACHUSETTS (SOURCE: AIR POLLUTION
ENGINEERING MANUAL, Reference 5)
-------
5.92
b. The second stage is a series of grounded plates usually less
than 1 inch apart which attract the positively charged
particles and act as the collector. Liquid particles drain by
gravity to collection pans. Rapping is not used because the
plates are too closely spaced. Materials which tend to be
viscous can be collected in a 2-stage precipitator if adequate
washing is provided.
Two-stage precipitators often require the use of gas conditioning
or precleaning equipment. Mist eliminators, precleaners, heaters
and humidifiers may be required to attain design collection
efficiencies.
Low-voltage, 2-stage precipitator efficiencies are calculated
according to the Penny (1937) equation:
F .
vd
where
F = efficiency as a decimal
w = drift velocity, feet per second
L = collector length, feet
v = gas velocity through the collector, feet per second
d = distance between collector plates, feet.
In air-conditioning applications of the 2-stage precipitator, the
dust grain loading is lighter so that the velocity range is from 5
to 10 feet per second. Heavier grain loading in air pollution
control applications for this type of precipitator requires reduced
velocities on the order of 1.7 feet per second.
-------
5.93
c. Inspection Points
The inspection points for 2-stage precipitators are the same
as those described for single-stage precipitators. The
enforcement officer should know the maintenance schedule since
this is the only way that the collected material will be
removed from the plates (unless oils are collected which will
run off the plates). The maintenance schedule can be from 1
to 6 weeks depending on the material collected in the preci-
pitator. During this period, the ionizing wires should also
be inspected for corrosion damage to determine replacement
requirements.
3. Maintenance
Schedules should be established to inspect, service and repair
critical precipitator components. Table 5.15 shows a typical
maintenance schedule for a fly ash precipitator. The major
components are rappers, transformers, electrodes, particulate
removal equipment and electrical controls.
VI. SULFUR DIOXIDE REMOVAL SYSTEMS FOR POWER PLANTS
The removal of S0~ from the exhaust gases of power plants remains a major
air pollution control problem. Extensive research and development work
is in progress to determine effective and economical processes for S0_
removal. The processes now in use which reflect the state-of-the-art
are limestone-dolomite injection (wet and dry) and catalytic oxidation.
In addition to these processes limits on the sulfur content of fuels are
also a significant step towards the reduction of SO. from power plants.
A. Limestone/Dolomite Injection-Dry Process
Pulverized limestone or dolomite is injected into the combustion zone
of large steam generators where it is calcined into lime. The lime
-------
5.94
Table 5.15. TYPICAL MAINTENANCE SCHEDULE FOR ELECTROSTATIC PRECIPITATORS
A. Annual Inspection
1. Internal inspection
a. Observe dust deposits on collecting plates and wire before
cleaning a j" deposit is normal. If metal plates are clean,
there is a possibility that a section is shorting out. If more
than y of dust is on plates, rappers are not cleaning.
b. Observe dust buildup on wires.
c. Interior corrosion corrosion could indicate air leak through
shell, or could indicate moisture carryover from air heater
washer.
d. Plate corrosion adjacent to door or near bottom of plate could
indicate inleakage through doors.
e. Check plates for alignment and equal spacing between plates.
f. Measure to see that discharge wires hang midway between
plates.
g. Check for and replace broken wires.
2. Hopper inspection
a. Check for dust buildup in upper corners of hoppers.
b. Check anti-sway insulators to see that they are cleaned and
not cracked.
c. Check high tension weights - if one has dropped 3", this
indicates broken wire.
d. Check hopper bottom and valve for debris.
(SOURCE: Reference 10)
-------
5.95
Table 5.15. TYPICAL MAINTENANCE SCHEDULE FOR ELECTROSTATIC PRECIPITATORS (continued)
3. Penthouse inspection
a. Check for corrosion due to condensation and/or leakage of
flue gas into housing.
b. Excessive dust in penthouse indicates air sealing pressure too
low.
c. Clean all high tension insulators.
d. Check that all high tension connections are secure.
e. Check that collars on high tension vibrator insulators are
secure.
4. Transformer inspection
a. Check liquid level.
b. Clean high tension line, insulators, bushings, and terminals.
c. Check surge arrestors, spark gap should be-^".
5. Control cabinet inspection
a. Clean and dress relay contacts.
B. Rappers and Vibrators Checked Quarterly
1. Rappers
a. Check distributor switch contacts for wear and lubricate.
b. Clean dust, dirt, and moisture from cabinet.
c. Check rapper assembly for binding at plunger or misalignment.
-------
5.96
Table 5.15. TYPICAL MAINTENANCE SCHEDULE FOR ELECTROSTATIC PRECIPITATORS (continued)
2. Vibrators
a. Check contacts on load cams to see that they are clean.
b. Clean dirt, dust, and moisture from cabinet.
c. Check vibrators to see that they operate at proper intervals.
C. Checks to Be Made Each Shift
1. Electrical reading for each control unit should be recorded and
checked for abnormal readings.
2. Rapper controls should be checked to see that they operate.
3. Vibrator controls should be checked.
(SOURCE: OGLESBY, JR. ET AL, Reference 10)
-------
5.97
reacts with the oxides of sulfur from the combustion of the fuel (at
temperatures over 1200°F) to form gypsum (CaSO,). The sulfate
particulates formed as a result of this reaction, unreacted lime and
fly ash are then removed from the stack gases by an electrostatic
precipitator, or combination of high efficiency mechanical collector
and a precipitator. Figure 5.49 is a flow chart of a prototype
system using lime/dolomite injection with "dry" collection. The
efficiency range for removal of SO. by this process is 40-60 percent.
(4)
B . Limestone/Dolomite Injection-Wet Process
Ground limestone or dolomite is injected into the furnace combustion
zone in a manner similar to the "dry" process. In the wet process,
the boiler exhaust gases containing the particulates formed are
scrubbed in a lime slurry. The lime slurry is recycled from a
settling tank to the scrubber. Disposal of the sediment may be a
problem if adequate facilities are not available. Figure 5.50 is a
schematic drawing of a wet system. Collection efficiencies expected
from the wet process range between 80-90 percent.
C. Catalytic Oxidation
Catalytic oxidation of SO. to SO is a variation of the contact cata-
lytic process used in the manufacture of sulfuric acid, described in
Chapter 7, Section VII. As an air pollution control measure, the
mechanism forms SO- from SO. by action of a vanadium pentoxide cata-
lyst which then combines with the moisture in the products of
combustion to form sulfuric acid. The gas thus treated must first
be subjected to highly efficient particulate removal since very small
amounts of selenium, arsenic or chlorides can deactivate the vanadium
pentoxide catalyst. Figure 5.51 is a schematic drawing of this
process. Collection efficiencies of 90 percent should be expected
from this system. The drawbacks to this system may overshadow its
effectiveness. These are:
-------
5.98
STEAM SUPERHEATERS
AND REHEATERS
LIMESTONE
INJECTION PORT
COAL-FIRED
BURNERS
Figure 5.49. LIMESTONE INJECTION - DRY PROCESS (SOURCE:
CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.99
COAL
SUPPLY
I , J
|
MIL
LIMESTONE
SUPPLY
1 <
L
FURNACE
TO STACK
GAS
STACK
3EHEATER
-AIR
SCRUBBER
SETTLING
TANK
RECYCLE
AND
MAKE-UP
WATER
TO DISPOSAL
Figure 5.50. LIMESTONE INJECTION - WET SCRUBBING PROCESS (SOURCE:
CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.100
CATALYST BED
AIR PREHEATER
HIGH-EFFICIENCY
PARTICIPATE
SEPARATOR
HOT FLUE
GAS FROM-
BOILER
DUST
AIR
ECONOMIZER/
CONDENSER
FLUE GAS
CLEANED GAS
TO STACK
H20
FLUE GAS
ABSORBER/MIST
ELIMINATOR
H2S04
FLUE GAS
H2S04
Figure 5.51. CATALYTIC OXIDATION PROCESS (SOURCE:
CONTROL TECHNIQUES DOCUMENTS, Reference 3)
-------
5.101
• The requirement for the use of costly corrosion-resistant
construction materials.
• Boiler redesign to supply the converter with high temperature
(850°F) flue gas.
• Lack of a market for the 75-80 percent acid captured.
D. Inspection Points
1. Lime Injection, Dry and Wet Processes
In addition to the inspection points for boilers described in
Chapter 7, the enforcement officer must determine the optimum
rate of lime injection into the furnace. Maintenance of this
rate is essential for the formation of the particulates which
will be captured by the precipitator or scrubber. Inspection of
the equipment and operation will provide a qualitative estimate
of emissions but stack sampling is the only way that the actual
effectiveness of the system can be determined.
2. Catalytic Oxidation Process
Before oxidation of S0« to SO. can take place as a result of flue
gases going through the catalyst bed, the gases must be virtually
free of particulates. This means that the enforcement officer
must be sure that the dust collector upstream of the catalyst
bed is operating properly. The enforcement officer should check
for corrosion to make sure that the scrubber and mist eliminator
are not damaged to the point where the effectiveness is reduced.
Only stack testing will provide quantitative data regarding the
effectiveness of the system.
-------
5.102
VII. CONTROL EQUIPMENT FOR GASES AND VAPORS
A. Afterburners
Combustible material in the gas phase—typically organic gases and
vapors—may be eliminated by complete oxidation to give carbon
dioxide and water vapor. Equipment designed for this purpose is
generally known as an afterburner (or fume and vapor incinerator).
1. Direct-Fired Afterburners
Direct-fired afterburners are the most common type. They have
been successfully applied to control effluents from aluminum
chip driers, animal blood driers, asphalt-blowing stills, brake
shoe debonding ovens, foundry core ovens, smokehouses, paint-
baking ovens, rendering cookers and similar sources.
Principal components are a combustion chamber, a gas burner with
appropriate controls, and a temperature indicator. Figure 5.52
illustrates a typical direct-fired afterburner in sectional view.
The combustion chamber must provide complete mixing of the con-
taminated gases with the burning fuel-air mixture in the flame zone.
A blower may be needed to deliver the contaminated gases to the
afterburner when natural draft is inadequate.
Burners having long, luminous flames appear to incinerate con-
taminants more effectively than others. Where the load of
contaminants to be incinerated varies appreciably during the
process cycle, modulating burner controls may be used to effect
fuel s-avings.
A temperature indicator, ordinarily a bare-wire thermocouple,
should be installed near the top of the chamber in such a position
-------
5.103
^REFRACTORY RING BAFFLE
INLET FOR CONTAMINATED
AIRSTREAM
Figure 5.52. TYPICAL DIRECT-FIRED AFTERBURNER WITH
TANGENTIAL ENTRIES FOR BOTH THE FUEL
AND CONTAMINATED GASES. (SOURCE: AIR
POLLUTION ENGINEERING MANUAL, Reference 5)
-------
5.104
as to measure gas temperature while avoiding direct flame radiation.
A safety pilot is usually provided. To shut off the fuel supply
when the contaminated gas stream is interrupted, a high-temperature
limiting control may be incorporated.
2. Catalytic Afterburners
The use of a catalyst promotes many combustion reactions at lower
temperatures than those required for direct-flame incineration.
In some cases this may accomplish satisfactory combustion at less
fuel cost than a direct-flame device. Incomplete combustion,
however, must be carefully avoided, as odor potentials of the
contaminated gases may sometimes be increased by passage through a
catalytic afterburner operated at too low a temperature (or with
insufficient air) .
A typical catalytic afterburner consists of a housing comprising a
preheater section and a catalyst section. Arrangements for the
recovery of heat from the afterburner gases may be incorporated,
as shown in Figure 5.53.
The contaminated gases are preheated to reaction temperature by a
gas burner. Operating temperatures are usually between 650°F and
1000°F. The catalyst is most commonly platinum, but other formu-
lations utilize copper chromite or oxides of various metals.
Catalyst activity declines with use, raising the necessity for
occasional regeneration and eventual replacement of the catalyst.
Where the contaminant load is variable, burner controls may be
regulated by the temperature of the gas discharged from the catalyst
The amount of fuel used to preheat the contaminated gas is thus
reduced when the contaminant concentration increases, releasing
-------
5.105
RETURN TO OVEN-*
Figure 5.53. TYPICAL CATALYTIC AFTERBURNER UTILIZING
DIRECT HEAT RECOVERY. (SOURCE: AIR
POLLUTION ENGINEERING MANUAL, Reference 5)
-------
5.106
more heat within the catalyst bed. With a preheat burner which
operates at fixed input, a high-temperature limiting control may
be needed to prevent overheating of the catalyst.
The contaminated gas stream must be free of substances which might
act as poisons for the particular catalyst in use. Particularly
troublesome are fumes or vapors of certain metals, including
mercury, arsenic, zinc and lead. For optimum efficiency in
combustion, air should be provided in excess of the amount
theoretically necessary for complete combustion.
3. Boilers Used as Afterburners
Boiler firebox conditions are, in some cases, similar to those
required of contaminant incinerators. Under certain conditions
such equipment may be adapted for contaminant incineration. For
a successful adaptation, the contaminated gas must be essentially
free of non-combustible dust or fumes, its volume must be moderate
and its oxygen content near that of air, and the minimum firing
rate of the boiler must be great enough to incinerate the maximum
volume of effluent to be expected.
Installations of this type have been successful in application to
control of effluents from smokehouses, rendering cookers and
various process units in oil refineries.
B. Absorption Equipment
Absorption is the process of removing contaminants from a gas stream
by causing them to dissolve in a liquid. Both gaseous and vapor
contaminants may be separated by absorption methods. The effectiveness
of the method for a particular contaminant depends upon the use of a
liquid which is a specific solvent for that contaminant, i.e., the
-------
5.107
contaminant must be very much more soluble than the air or other non-
contaminant gases which carry the contaminant.
The gaseous air contaminants most commonly controlled by absorption
include sulfur dioxide, hydrogen sulfide, hydrogen chloride, chlorine,
ammonia, oxides of nitrogen and light hydrocarbons. Vaporous con-
taminants may be recovered from the solution after absorption, when
their value warrants such a procedure. The most useful absorbents are
ordinarily of low volatility, non-corrosive, inexpensive, of low
viscosity, non-toxic, non-flammable, chemically stable and not subject
to freezing at ordinary temperatures.
Absorption equipment is designed to provide thorough contact between
the gas and liquid phases, as the rate of removal is largely dependent
upon the amount of surface exposed. The necessary contact can be
accomplished by dispersing gas in liquid (bubbling) or liquid in gas
(spraying). In packed towers, on the other hand, both gas and liquid
phases are continuous
1. Packed Towers
A packed tower is filled with small solid objects (packing)
designed to expose a large surface area, which is kept wet by a
continuous flow of the absorbent, as shown in Figure 5.54.
Usually the flow through a packed column is countercurrent, with
the liquid introduced at the top to trickle down through the
packing, while gas is introduced at the bottom to pass upward
through the packing. This results in high efficiency, since, as
the solute concentration in the gas stream decreases as it rises
through the tower, there is constantly fresher solvent available
for contact.
-------
5.108
In concurrent flow, the gas stream and the absorbent both enter at
the top of the column. This is seldom used, except for the solution
of special design problems.
Packing materials are readily available as ceramic objects of
various standard shapes, such as those illustrated in Figure 5.55.
Most common are Raschig rings, consisting of hollow cylinders
having external diameters equal to their length. Packing may be
dumped into the column for randomness or may be manually stacked
in an orderly pattern. Dumped packing ordinarily has a higher
specific surface contact area, but causes a higher gas pressure
drop across the bed.
To ensure complete wetting, liquid must be introduced into the
tower at not less than 5 pints per square foot of cross
section. The liquid flow rate must be sufficient to wet the
packing, but not enough to flood the tower, as this causes bubbling
and drastically increases the pressure drop.
2. Plate Towers
Plate towers employ stepwise gas-liquid contact by means of a
number of trays or plates arranged to disperse gas^ through a liquid
layer on each plate. Most common is the bubble-cap plate tower,
illustrated in Figure 5.56. Each plate is equipped with openings
(vapor risers) surmounted with bubble caps. Gas rises through
the tower, passing through the openings in the plates and through
slots in the periphery of the bubble caps, which are submerged in
liquid. The liquid enters at the top of the tower, flows across
each plate and downward from plate to plate through downspouts.
Depth of the liquid and patterns of flow across the plates are
controlled by weirs.
-------
5.109
| GAS OUT
LIO.UID-
IN
-LIQUID DISTRIBUTOR
LIQUID
RE-DISTRIBUTOR
PACKING SUPPORT
GAS IN
Figure 5.54. SCHEMATIC DIAGRAM OF A
PACKED TOWER, TREYBAL,
1955, p. 134 (SOURCE:
AIR POLLUTION ENGINEERING
MANUAL, Reference 5)
RASCHIG RING
INTALOX SADDLE
TELLERETTE
Figure 5.55. COMMON TOWER PACKING
MATERIALS, TELLER, 1960,
p. 122 (SOURCE: AIR
POLLUTION ENGINEERING
MANUAL, Reference 5)
-------
5.110
• GAS OUT
SHELL
TRAY - --
DOWNSPOUT
TRAY
SUPPORT RING
TRAY
STIFFENER-
VAPOR
RISER
^-LIQUID IN
— BUBBLE CAP
n:
SIDESTREAM
~»ITHDRA«AL
INTERMEDIATE
FEED
-LIQUID OUT
Figure 3.56. SCHEMATIC DIAGRAM OF A BUBBLE-CAP TRAY TOWER,
TREYBAL. 1955, p. Ill (SOURCE: AIR
POLLUTION ENGINEERING MANUAL, Reference 5)
-------
5.111
In perforated plates or sieve trays, the gas passes upward through
a pattern of holes in the trays. Such towers are less costly to
fabricate, but are more subject to channeling than bubble-cap
towers and may be less efficient in prolonged operation. Various
other designs have also been promoted on a proprietary basis.
3. Spray Towers and Chambers
Contact between a gas stream and a liquid absorbent in droplet
form is achieved in spray towers or spray chambers. For greatest
efficiency of absorption, droplets must be very small, with
diameter about 1 millimeter or less. Such fine droplets require
a high pressure drop across spray nozzles, and gas velocities must
be kept low to avoid liquid entrainment. In one design, spray
droplets are forced to the chamber walls by the centrifugal action
of tangentially entering gas to avoid entrainment loss from the
top of the chamber. Application of such devices in air pollution
control is uncommon.
4. Spargers
Probably the simplest method of dispersing a gas in a liquid for
absorption is by injecting the gas through a perforated pipe, or
sparger, into a vessel filled with the liquid. For best efficiency
of absorption, the bubbles must be very fine; this requires a high
pressure drop in the gas stream. However, increased dispersion
can also be achieved by injecting the gas below a rotating propeller,
where the blade breaks up larger bubbles.
Absorption in a single vessel is usually not very effective, but
substantial separations can be achieved with a series of vessels
in a countercurrent arrangement.
-------
5.112
Such vessels have been used to remove odorous products in the
manufacture of specialty lubricants, with a caustic soda solution
as the absorber. Acid gases may be similarly controlled with
adequate efficiency by alkaline solutions.
5. Venturi Absorbers
In a venturi scrubber, gases are cleaned by passage through a
venturi tube to which low-pressure water is added at the throat.
For fine dusts, very high collection efficiencies have been
reported, and gases which are highly water-soluble may also be
removed in this way. High power requirements for operation of such
a device constitute a disadvantage which is usually decisive, unless
the dust problem is an important consideration.
C. Adsorption Equipment
Adsorption is the process of removing contaminants from a gas stream by
passing it through a bed of granules of a highly porous solid, called
an adsorbent. In the general case, an adsorption process is usually
followed by a regeneration process, in which the activity of the
adsorbent is restored by driving the adsorbate (the contaminant) out
of the bed, with or without recovery of the adsorbate.
Activated charcoal is the adsorbent most suitable for removing organic
vapors, as it affords practical control for all vapors of compounds
having boiling temperatures above the temperature of melting ice. Even
more volatile contaminants can be effectively adsorbed if the tempera-
ture of the adsorbent is lowered.
A number of processes in food technology are associated with odorous
effluents which can be readily controlled by adsorption. In this
category are meat processing, food canning, dehydration, cooking,
-------
5.113
baking and roasting, processing of spent mash, fat rendering and waste
digestion. Odorous materials used or produced in many chemical manu-
facturing and commercial uses may be similarly controlled.
Activated charcoal impregnated with a suitable alkaline material is an
excellent adsorbent for acid gases, such as sulfur dioxide, hydrogen
chloride and hydrogen fluoride. Other commercially important adsorbents
are silicas, aluminosilicates, metal oxides, etc. These substances show
considerably greater selectivity than does activated charcoal and are,
therefore, far less useful than charcoal for over-all decontamination
of air. They are essentially ineffective for direct decontamination
of any gas stream containing appreciable water vapor.
When air containing a contaminant vapor is passed over a bed of charcoal,
adsorption is initially complete. As the retentive capacity of the
carbon is reached, traces of vapor appear in the exit air. This stage
of adsorption is called the breakpoint, beyond which the efficiency of
removal decreases rapidly. As the flow of air is continued, additional
vapor is adsorbed, but the concentration of vapor in the exit air
(Figure 5.57) increases until it eventually equals that in the inlet.
In this condition, the adsorbent is said to be saturated and is of no
further use until regenerated.
If pure air is passed through a charcoal bed initially saturated with
a vaporous contaminant, a large part of the adsorbed substance may be
readily removed, but another fraction will remain. The ratio of the
weight of adsorbate retained to the weight of the adsorbent is known
as the retentivity, or retentive capacity.
During adsorption of a vapor, heat is liberated, which can increase
the temperature of the adsorbent bed. Vapor concentrations encountered
-------
5.114
3 20
Figure 5.57. ADSORPTION EFFICIENCY, SINGLE SOLVENT, REPORT NO. 8. EXPERIMENTAL
PROGRAM FOR THE CONTROL OF ORGANIC EMISSIONS FROM PROTECTIVE
COATING OPERATIONS, LOS ANGELES COUNTY. AIR POLLUTION CONTROL
DISTRICT, LOS ANGELES, CALIF.. 1961 (SOURCE: AIR POLLUTION
ENGINEERING MANUAL, Reference 5)
-------
5.115
in paint spraying or coating operations result in a temperature rise of
(81
about 15°F and do not seriously affect the capacity of the adsorbent.
On the other hand, the use of activated carbon to capture vaporized
organic compounds at relatively large concentrations, such as the
discharge from the filling of gasoline tanks, can result in a tempera-
ture rise that can reach dangerous levels.
Regeneration is accomplished by passing a hot gas through the carbon
bed. Saturated steam at low pressure, up to 5 psig, is the usual
medium. Steam superheated to as high as 650°F, however, may be
necessary to reactivate carbon to its original condition, especially
when the adsorbate contains high-boiling constituents such as are found
in mineral spirits. Normally, the flow of steam passes in a direction
opposite to the flow of gases during adsorption.
1. Fixed-Bed Adsorber
The enclosure for a simple fixed-bed adsorber may be a vertical or
a horizontal cylindrical vessel. For more than one bed in a single
housing, a vertical arrangement is usual.
For the capture of vapors in a continuous operation, it is customary
to use 2 or more fixed-bed units, so that one may be adsorbing on
stream while the other is being stripped of adsorbate and
regenerated. A schematic diagram of such a unit is shown in
Figure 5.58.
Regeneration and cooling of the adsorbent determines the cycle time
for this type of system. Regeneration releases the bulk of the
adsorbed vapor rapidly; usually, no attempt is made to remove all
the adsorbate. Normally 2 absorbing units are sufficient, but
with 3 units it is possible to have 1 adsorbing, 1 cooling and
1 regenerating. Vapor-free air from the adsorbing unit can
then be used to cool the unit just regenerated.
-------
5.116
Figure 5 58 DIAGRAMMATIC SKETCH OF A TWO-UNIT, FIXED-BED
ADSORBER. (SOURCE: AIR POLLUTION ENGINEERING
MANUAL, Reference 5)
ROTATING ADSORBER
HOTOR
FAN
-FILTER
COOLER
AIR AND SOLVENT
VAPOR :N
ACTIVE CARBON
STRIPPED AIR OUT
STEAM IN
ACTIVE CARBON
Figure 5.59. LEFT: DIAGRAMMATIC SKETCH OF A ROTATING FIXED-BED CONTINUOUS
ADSORBER SHOWING THE PATH OF THE VAPOR-LADEN AIR TO THE CARBON
BED. RIGHT: CUT OF CONTINUOUS ADSORBER SHOWING PATH OF STEAM
DURING REGENERATION, SUTCLIFFE. SPEAKMAN CANADA. LTD., HAMILTON,
ONTARIO (SOURCE: AIR POLLUTION ENGINEERING MANUAL,
Reference 5)
-------
5.117
2. Continuous Adsorber
A continuous, activated-carbon, solvent recovery unit is available.
Figure 5.59 shows the cutaway view of the unit. Filtered air
containing the solvent is delivered into the enclosure and enters
ports to the carbon section. It then passes through the cylindrical
bed to the inside space. Vapor-free air travels axially to the
drum and is discharged. In regeneration, the steam enters through
a row of ports by means of a slide valve as the cylinder rotates.
Solvent and steam leave through a second row of ports and are
separated continuously by decantation.
3. Operational Problems
The adsorbent should be protected by filtration of the gas stream
from accumulation of partlculate matter, which can interfere with
adsorption and reduce the life of the carbon.
Corrosion of adsorbers may also be a problem, due to the steam used
in regeneration; this is intensified when superheated steam is used.
Corrosion can be reduced or controlled by the use of stainless steel
in construction or by application of a protective coating of a
baked phenolic resin.
D. Condensers Used in Vapor Recovery Systems
Condensation is the process of removing a vaporous material from a gas
stream by cooling it, thereby converting it into a liquid phase. In
some instances, control of volatile contaminants can be satisfactorily
achieved entirely by condensation. However, most applications require
additional control methods. In such cases, the use of a condenser as
part of the control system, or vapor recovery system, can confer such
benefits as reducing the load on a more expensive control device, or
-------
5.118
reducing the concentration of corrosive or otherwise troublesome
constituents in the gas stream entering the control device.
1. Surface Condensers
Condensers used in air pollution control systems operate through
removal of heat from the gas stream and they differ principally
in the means of cooling. In surface condensers, the coolant does
not contact the vapors or condensate.
Most surface condensers are of the tube and shell type shown in
Figure 5.60. Water flows inside the tubes, and vapors condense on
the shell side. Cooling water is normally chilled, as in a cooling
tower, and reused. Air-cooled surface condensers provide for
condensation within the tubes; these are usually constructed with
extended surface fins to facilitate heat transfer. A typical fin-
tube design is shown in Figure 5.61.
A section of an atmospheric condenser is shown in Figure 5.62.
Here, vapors condense inside tubes cooled by a curtain of falling
water, which is cooled by air circulating through the tube bundle.
2. Contact Condensers
Contact condensers employ liquid coolants, usually water, which
come in direct contact with condensing vapors. These devices are
relatively uncomplicated, as shown by the typical designs of
Figure 5.63 and Figure 5.64. Some are simple spray chambers,
usually with baffles to ensure adequate contact; others are high-
velocity jets designed to produce a vacuum.
In comparison with surface condensers, contact condensers are more
flexible, simpler and considerably_less expensive. On the other
-------
5.119
Figure 5.60. TYPES OF CONDENSERS. SURFACE CONDENSERS:
SHELL AND TUBE, SCHUTTE AND KOERTING CO.,
CORNWELL HEIGHTS, PENN. (SOURCE: AIR
POLLUTION ENGINEERING MANUAL, Reference 5)
-------
5.120
Figure 5.61. TYPES OF CONDENSERS. SURFACE
CONDENSERS: INTEGRAL FINNED
SECTION, CALUMET & HECLA INC.,
ALLEN PARK, MICH. (SOURCE:
AIR POLLUTION ENGINEERING
MANUAL, Reference 5 )
Figure 5.62.
TYPES OF CONDENSERS. SURFACE
CONDENSERS: TUBULAR, HUDSON
ENGINEERING CORP., HOUSTON,
TEXAS. (SOURCE: AIR POLLUTION
ENGINEERING MANUAL, Reference 5)
Figure 5.63. TYPES OF CONDENSERS.
CONTACT CONDENSERS:
SPRAY, SCHUTTE AND
KOERTING CO., CORNWELL
HEIGHTS, PENN. (SOURCE:
AIR POLLUTION ENGINEERING
MANUAL, Reference 5)
Figure 5.64. TYPES OF CONDENSERS. CONTACT
CONDENSERS: SPRAY, SCHUTTE
AND KOERTING, CO., CORNWELL
HEIGHTS, PENN. (SOURCE: AIR
POLLUTION ENGINEERING MANUAL,
Reference 5)
-------
5.121
hand, surface condensers require far less water and produce a far
smaller volume of condensate. Condensate from contact units,
diluted with water as it is, cannot be reused and may constitute
a waste disposal problem. Surface condensers can be used to
recover a valuable condensate, but they must be equipped with more
auxiliary equipment and they usually require a greater degree of
maintenance.
Contact condensers normally afford a greater degree of air pollution
control because of condensate dilution. With contact units, about
15 pounds of water at 60°F is required to condense 1 pound of
steam and cool the condensate to 140°F. The resultant 15 to 1
dilution greatly reduces the concentration and vapor pressure of
the volatile materials, provided they are miscible with water.
3. Typical Installations
Besides collecting condensable contaminants, condensers may materially
reduce the volume of the contaminated gas streams. To a degree,
contact condensers are also scrubbers. Probably their most common
application is as auxiliary units in systems containing afterburners,
absorbers, baghouses, or other control devices. A number of
possible combinations are diagrammed in Figures 5.65, 5.66, and
5.67.
Installations incorporating condensers have been used successfully
for many operations in petroleum refineries, petrochemical plants
and chemical manufacturing in general (see Table 5.16). In all
such installations, precautions must be taken to ensure that there
is no major evolution of vapors from the condensate discharged.
In most instances, the condensate is merely cooled to a temperature
at which the vapor pressure of the contaminants is satisfactorily
low. Most condensed aqueous solutions must be cooled to 140°F or
-------
5.122
ID 1TMOSPHEBE
CONDENStTE
J RECEIVER
CONOENSftTE
10 SEIER
Figure 5.65, A CONDENSER-AFTERBURNER AIR
POLLUTION CONTROL SYSTEM IN
WHICH A VACUUM PUMP IS USED
TO REMOVE UNCONDENSED GASES
FROM CONDENSATE. (SOURCE:
AIR POLLUTION ENGINEERING
MANUAL, Reference 5)
Figure 5.66. A CONTACT CONDENSER-AFTERBURNER
AIR POLLUTION CONTROL SYSTEM IN
WHICH MALODOROUS, UNCONDENSED
GASES ARE SEPARATED FROM CONDEN-
SATE IN A CLOSED HOT WELL.
(SOURCE: AIR POLLUTION
ENGINEERING MANUAL, Reference 5)
»ARM ORGANIC
LIQUID STREAM
Figure 5.67. A SURFACE CONDENSER USED TO PREVENT SURGE LOSSES FROM
AN ACCUMULATOR TANK HANDLING WARM, VOLATILE, ORGANIC
LIQUID. (SOURCE: AIR POLLUTION ENGINEERING MANUAL,
Reference 5)
-------
5.123
Table 5.16. TYPES OF PROCESSES OR EQUIPMENT FOR WHICH CONDENSERS
HAVE BEEN APPLIED IN CONTROLLING CONTAMINANT EMISSIONS.
REFINERY AND PETROCHEMICAL
Alkylation unit accumulator vents Polyethylene gas preparation accumulator vents
Amine stripper units Residuum stripper unit accumulator vents
Butadiene accumulator vents Storage equipment
Coker blowdown Styrene-processing units
Ketone accumulator vents Toluene recovery accumulator vents
Lubricating oil refining Udex extraction unit
CHEMICAL MANUFACTURING
Manufacture and storage of ammonia Manufacture of nitric acid
Manufacture of Cooper naphthenates Manufacture of phthalic anhydride
Chlorine solution preparation Resin reactors
Manufacture of ethylene dibromide Soil conditioner formulators
Manufacture of detergents Solvent recovery
Manufacture of insecticides Thinning tanks
Manufacture of latex
MISCELLANEOUS
Aluminum fluxing Dry cleaning units
Asphalt manufacturing Esterification processes
Blood meal driers Pectin preparation
Coal tar dipping operations Rendering cookers
Degreasers Vitamin formulation
-------
5.12A
less before venting to the atmosphere; for volatile organics, even
lower temperatures are necessary. Uncondensable contaminants are
normally vented to further control equipment, as in Figures 5.65
and 5.66.
-------
5.125
REFERENCES
1. Requirements for Preparation, Adoption, and Submittal of Implementation
Plans. Federal Register. Vol. 36, No. 158. August 14, 1971.
2. First, M. W. Process and System Control. In: Air Pollution, Vol. Ill,
A. C. Stern (ed.). New York City, Academic Press, 1968.
3. Control Techniques for Particulate Pollutants. DHEW, PHS, National Air
Pollution Control Administration. Washington, B.C. January 1969.
4. Control of Particulate Emissions. DHEW, PHS, Office of Manpower Develop-
ment, Institute for Air Pollution Training, Research Triangle, N. C.
(No date).
5. Danielson, J. A. (ed.). Air Pollution Engineering Manual. Cincinnati,
DHEW, PHS, National Center for Air Pollution Control and the Los Angeles
County Air Pollution Control District. P.H.S. No. 999-AP-40, 1967.
6. Fan Engineering. 7th Edition. Buffalo Forge Co. (No date).
7. McGraw, M. J. and R. L. Duprey. Compilation of Air Pollution Emission
Factors. Preliminary Document. Environmental Protection Agency,
Research Triangle Park, N.C. April 1971.
8. Elliot, J., N. Kayne, and M. Leduc. Experimental Program for the Control
of Organic Emissions from Protective Coating Operations. Los Angeles
County Air Pollution Control District. Report No. 8. 1961.
9. Billings, C. E., and J. Wilder. Handbook of Fabric Filter Technology.
GCA Corporation. CPA-22-69-38. December, 1970.
10. Oglesby, Jr., S., and G. B. Nichols. A Manual of Electrostatic Precipitator
Technology - Part I Fundamentals. Southern Research Institute.
CPA-22-69-73. August 25, 1970.
-------
6.1.1
CHAPTER 6
INSPECTION PROCEDURES FOR GENERAL SOURCES
I. INTRODUCTION
General inspection procedures apply to emission sources which are common
to many air quality regions, are large in number, and tend to be distributed
throughout any given air quality control region. These are sources which
are most subject to general surveillance, observation of visible emissions,
source testing and nuisance complaints. The sources may constitute indepen-
dent or captive operations and possess a wide range of design characteristics,
capacities, applications and emission potentials. Emission sources of this
type which are treated in this chapter include fuel-burning equipment,
incinerators, open burning activities, odor nuisance sources, and motor
vehicles.
With the exception of certain aspects of odor nuisances, combustion of fuels
and refuse is the central process to be considered. Inspection procedures
described in this chapter, therefore, are mostly oriented to fuel properties;
preparation and distribution of fuels; type, design and capacities of firing
systems; firebox and combustion conditions; management of combustion air,
and use of air pollution control equipment and techniques.
-------
6.2.1
II. FUEL-BURNING EQUIPMENT
A. INTRODUCTION
Fuel-burning equipment, as treated in this chapter, consist of equipment
designed for the purposes of steam generation, electric power generation,
space heating, service water heating and other thermal processes. Liquid,
solid or gaseous fuel is burned in the firebox of a boiler to generate
heat. The heat, in turn, is transferred through heat absorbing furnaces,
or heat exchangers, to a fluid such as air, water or liquid chemicals. In
this form of indirect heating, the products of combustion cannot contact
the fluid to be heated and are exhausted through a stack to the ambient
air.
Fuel-burning encompasses the combustion of conventional fuels such as
coal, fuel oil and natural gas, but also includes waste wood products,
refuse and other liquid or solid materials if these are used to provide
space or process heat and a heat exchanger or other method of indirect
heating is employed. Combustion systems in which a material is burned for
the primary purpose of reducing the material to ash are known as incinerators
and are treated in Section III of this chapter.
Most air pollutants emitted from fuel-burning installations result from
the incomplete combustion of fuel. When complete combustion occurs only
carbon dioxide, water vapor and small amounts of ash are emitted. (Common
chemical reactions occurring during combustion are shown in Table 6.2.1.)
Conditions approaching complete combustion can be maintained throughout
the fuel burning cycle—ignition, burning and burndown—provided that:
• Temperature is high enough to ignite and burn all of the fuel.
• Sufficient time is allowed to complete burning of all of the fuel.
• Sufficient turbulence is permitted to allow thorough mixing of
fuel particles with combustion air.
• Sufficient oxygen is provided for a proper air fuel ratio.
-------
6.2.2
Table 6.2.1. COMMON CHEMICAL REACTIONS OF COMBUSTION
COMBUSTIBLE REACTION
Carbon (to CO) 2C + 02 = 2CO + Q
Carbon (to CO ) C + 0_ = CO + Q
Carbon monoxide 2CO + 0 = 2CO_ + Q
Hydrogen 2H2 + 02 = 2H20 + Q
Sulfur (to S02) S + 0 = SO. + Q
Sulfur (to S03) 2S + 302 = 2SO + Q
Methane CH. + 20. = CO + 2H 0 + Q
Acetylene ^C.H. + -^9 = AGO. + 2H 0 + Q
Ethylene C9H, + 3®j = 2C09 + 2H 0 + Q
Ethane 2C_H. + 70_ = 4CO + 6H 0 + 0
26 2 2 2 v
Hydrogen sufide 2H-S + 309 = 2SO + 2H 0 + Q
Where Q = the heat of reaction
Source: Babcock and Wilcox Company, Reference 1.
-------
6.2.3
B. ELEMENTS OF THE COMBUSTION SYSTEM
A combustion system feeds fuel, mixes fuel with air and ignites and burns
the fuel in a firebox at rates necessary to generate the amount of thermal
energy required. Several types of systems are in common use. Gas, oil,
pulverized coal or crushed coal burners are affixed to a furnace opening
and fired under fuel or pneumatic pressure directly into the furnace.
Stoker systems mix, classify and transport solid fuels into and through
the boiler firebox and provide for continuous dumping and removal of ash
residue. Specific firing systems are described in greater detail in
part F of this section.
Common elements of fuel-burning systems are shown in Figure 6.2.1. The
combustion system in actuality is a control or feedback system intended to
maximize combustion efficiency and production of thermal energy and to
minimize air pollution emissions. Principal options as between manual
and automatic process control systems, and additional heat exchange and
air heating units used in large central power stations are shown in
Figure 6.2.1. Systems may be fully automatic (operated from a central
control panel) or semi-automatic or manual. The latter are found in
medium-sized or small installations where trained operators make the
necessary combustion system adjustments.
The following terms define the principal features and aspects of the fuel-
burning system.
1. FUEL—this consists of liquid, gaseous and solid fuels treated in
part C of this section,
2. FUEL PREPARATION AND FEED—these include preheating liquid fuels, or
crushing, grinding, classifying, washing or otherwise conditioning
solid fuels prior to combustion. Washing includes purifying, cleaning
or removing impurities from coal by mechanical processes, regardless
of the cleaning medium used. (See also Coal Preparation Plants,
Chapter 7. Section XIII.)
3. FEEDWATER—the water supplied to the heat exchanger units for heating
or steam production.
-------
GASEOUS
CONTAMINANTS SMOKE FLY ASH
Figure 6.2.1. SIMPLIFIED SCHEMATIC OF COMBUSTION HEAT EXCHANGE SYSTEM ELEMENTS. BROKEN BLOCKS
ARE ADDITIONAL COMPONENTS USUALLY FOUND IN LARGE STEAM GENERATING INSTALLATIONS.
SI = Smoke Indicator; SB = Soot Blower; OAC = Overfire Air Control (Used in
Stoker Installations).
-------
6.2.5
4. COMBUSTION AIR—several types of combustion air are of interest.
Primary air is air which is introduced with the fuel at the burner,
or over the fuel bed. Secondary air or draft is air which is intro-
duced to the furnace through ports or tuyeres. Secondary air may be
supplied by means of forced draft, induced draft, or natural draft.
Forced draft is air injected into the furnace by means of fans. In-
duced draft is air drawn through the furnace by means of a fan located
on the flue side of the boiler. Dampers (barometric butterfly,
guillotine, sliding etc.) regulate the flow of combustion air into
and through the various compartments of the furnace as well as the
flow of flue gases out of the furnace, Overfire air control (OAC
in Figure 6.2.1), used in stoker equipment, releases air from jets
over the fuel beds. These are usually controlled by manual means,
electric timer, or by activation of a smoke indicator (SI in Figure
6,2.1). Excess air is air for effective combustion and the amount of
excess air over that theoretically required for complete combustion
is a factor in the emission of all air contaminants. Excess air can
be determined from oxygen analyzers located in the power plant.
Optimum excess air requirements should be established for each in-
stallation. Table 6,2,2 is a guide to recommended amounts of excess
air for various types of fuel-burning installations,
5. FIREBOX—this is usually of refractory cement, water wall, water
tube or firebrick construction. Type and condition of firebox and
flame clearance in feet should be noted.
6. HEAT EXCHANGERS—these are basic boiler or steam generating units
which transfer heat through surfaces to the feedwater to produce
steam. Heat transfer may be by convection or radiation. Superheaters
found in large installations are tubular elements which produce high
pressure steam (potential pressure) from the initial heating of the
water. They are an integral part of the boiler system. Radiant ex-
changers are located in the furnace. Convection exchangers are located
in flue gases where comparatively low gas temperatures occur.
7, REHEATERS--reheaters heat steam which has been used to do work as in
turbines.
8, ECONOMIZERS—economizers preheat feedwater from the low-temperature
flue gases leaving the steam generating unit.
9. SOOT BLOWERS—sootblowers (SB in Figure 6.2,1) are lances which release
jets of steam or air to remove soot deposited on heat exchanger
surfaces. These are usually of a retractable type in large installations.
The lances move across tube surfaces to remove particulates, Usually
8 to 15 blowers are used in large installations. Soot blowing may be
conducted at least once every 24 hours or may be operated automatically
at 2-4 hour intervals. Soot blowing schedules should be checked.
-------
Table 6.2.2. USUAL AMOUNT EXCESS AIR SUPPLIED TO FUEL-BURNING EQUIPMENT
Fuel
Pulverized coal
Crushed coal
Coal
Fuel oil
Acid sludge
Natural, Coke-oven, &
Refinery gas
Blast-furnace gas
Wood
Bagasse
Black liquor
Type of Furnace or Burners
Completely water-cooled furnace for slag-tap or dry-ash-removal
Partially water-cooled furnace for dry-ash-removal
Cyclone Furnace—pressure or suction
Stoker-fired, forced-draft, B&W chain-grate
Stoker-fired, forced-draft, underfeed
Stoker-fired, natural-draft
Oil burners, register-type
Multifuel burners and Hat-flame
Cone- and flat-flame-type burners, steam-atomized
Register-type burners
Multifuel burners
Intertube nozzle-type burners
Dutch-oven (10-23% through grates) and Hofft-type
All furnaces
Recovery furnaces for kraft and soda-pulping processes
Excess Air, % by Wt
15-20
15-40
10-15
15-50
20-50
50-65
5-10
10-20
10-15
20-90
7-12
15-18
20-25
25-35
5-7
Source: Babcock and Wilcox Company, Reference 1.
(Modified)
-------
6.2.7
10. LOAD—this is the demand for steam or energy imposed on the combustion
system. It is measured in pounds steam, electrical energy or resistance
or pressure drop. Load may be varied by altering firing rates, or by
tilting burners in various positions which modulate the heat released
to heat exchanger surfaces. Load may be measured in inches of water
gage or other devices, and is the principal feedback regulator of
the combustion system, as shown in Figure 6.2.1. The inspector should
note peak, fluctuating or other abnormal conditions which may affect
emissions.
11. AIR HEATERS—these recover heat from the flue gases and recycle them
as combustion air to the furnace. Air heaters and economizers help
to reduce fuel requirements and improve combustion efficiency and are
found in all boilers and heaters of 100 million Btu/hr. and greater
gross input. Combustion air temperatures augmented by air heaters
may contribute to the formation of NO emissions.
' x
12. STACK—stacks may run 25 to 1,000 feet in height and are of brick,
steel or transite construction. Stack height is usually the vertical
distance measured in feet between the point of discharge from the stack
or chimney into the outdoor atmosphere and the elevation of the land
thereunder. Effective Stack Height is the sum of the stack height and
the plume rise. Plume rise is the calculated distance in feet of the
vertical ascent of the air contaminants above the stack or chimney.
13, BOILER CONTROLS—these are essentially dampers, valves and orifices
which control fuel flow, combustion air flow, feedwater flow, furnace
draft or pressure and steam temperature. Instruments used to monitor
steam boilers are similar to those described in part E of Section III,
Incinerators. Conditions monitored include:
steam pressure
steam temperature (if other than saturated)
water level
feedwater pressure
*furnace draft or pressure
For units producing more than 10,000 Ibs. steam per hour, instruments
monitor:
steam flow
feedwater flow
*combustion-air flow
^component drafts or pressures
feedwater temperature
**flue gas temperature
-------
6.2.8
**fuel flow (if possible)
**fuel pressure (if involved)
*fuel temperatures (if involved)
**speed and amperage indicators for fans, pumps, feeders, and
other power consuming auxiliaries
*flame detector or flame temperature measurement if available
*continuous stack analyzers (if performed)
**flue gas analysis (may be manual)
*smoke-density control systems or alarms
*oxygen and combustion analyzers
The single asterisks designate instruments or conditions that should
be routinely checked, particularly in connection with violations and
nuisance complaints. Double asterisks are items that may be involved
in emission inventories, source registration, source testing, or other
intensive investigations. Items without asterisks provide low
priority information that may be of interest to enforcement personnel.
14. CONTAMINANTS EMITTED—the principal types of air contaminants resulting
from incomplete combustion include:
a. Smoke—incompletely burned solid and gaseous material which forms
a visible plume, usually dark or black in color. Visible emissions
from the stacks of fuel-burning equipment may vary from a light
haze (less than #1 Ringelmann) indicating an efficient combustion
rate to #5 Ringelmann.
b, Particulates—these are solid particles which are incombustible or
incompletely burned liquid or solid particles. The various forms
of particulates emitted from fuel-burning equipment include:
(1) Soot—small, fine, carbon particles resulting from soot blowing.
(2) Coarse Solid Particles—particles generally equal to or
greater than 44 microns; they may also consist of solid
particles contained in liquid particles.
(3) Fly Ash—a noncombustible mineral material, usually grey,
flakey or powdery in form. The term is sometimes used to
refer to all particulates.
(4) Cenospheres—large particles consisting of "skeletons'1 of
burned-out fuel particles that have hollow, black, coke-like
spherical properties. Cenosphere emissions are usually
associated with atomization in oil burning operations.
-------
6.2.9
(5) Acidic Smut—large particles, 1/4" in diameter, containing
metallic sulfate and carbonaceous material. SO-, condensed
with water on furnace surfaces maintained below the temperature
of the dew point of the flue gas, acidifies the soot particles.
Acidified particles are usually discharged during soot blow-
ing and may spot painted or metallic particles or damage
vegetation. Smuts may be prevented by maintaining temperatures
of the furnace surfaces above the dew point of the flue gases.
(6) Combustible Particulates—particles of unburned or incompletely
burned fuel due to poor maintenance, operation or incorrect
selection of burner or fuel.
(7) Trace Metals—trace metals found in coal that have possible
health effects include nickel (as nickel carbonyl), beryllium,
boron (as boran), germanium, arsenic, selenium, yttrium,
mercury and cadmium. As a group these have potential for
carcinogenises, acute and chronic system poisoning, cardio-
vascular disease, hypertension and nerve disease.(2)
c. Gaseous cont am i n an t s— these include;
(1) Carbon Monoxide—product of incomplete combustion.
(2) Sulfur Dioxide (SO.)—a principal oxide of sulfur formed from
the oxidation of the sulfur contained in the fuel burned.
(3) Sulfur Trioxide (SO.—oxidation product of SO ) . A
characteristic "white to brown" detached plume which is believed
to consist of finely divided sulfuric acid aerosol. Sulfur
trioxide, hydrated in the atmosphere to sulfuric acid aerosol,
can cause acid damage downwind from the source. Approximately
2-3% of the sulfur content of the fuel is converted to S0_.
S0_ is associated with large fuel-burning installations. For
example in oil-burning installations(3) that consist of:
• units up to 60,000 Ibs. steam/hr,, visible emissions due
to sulfur compounds are not likely to occur when fuels
containing 0.3 to 0.5% sulfur are burned.
• units ranging from 50,000 to 500,000 Ibs. steam/hr.,
opacities may not exceed 30%, with 1.4 to 2.0% sulfur
in the fuel.
• steam generating units at 750,000 Ibs./hr. and greater may
emit gases greater than 40% opacity when fired with oil
of more than 1.0% sulfur.
-------
6.2.10
(4) Oxides of Nitrogen (NO )—includes NO, NO , NO, NO and NO .
NO is usually reportea as N0_, which is oxidized from the
initial emission, NO. NO emissions are due primarily to
"fixation" of atmospheric oxygen and nitrogen at high com-
bustion temperatures. Concentrations are a function of
flame temperature, firebox oxygen concentration, and firebox
and burner design. NO stack concentrations may range up
to over 2,000 lbs.hr. in large steam generating installations
and are associated with firebox temperatures approaching or
exceeding 3,000°F (at about 2% oxygen with air preheated to
600°F) . *• ' NO emissions from large plants may produce a
brownish haze Sr cloud in the vicinity of the plant. NO
emissions from fuel-oil burning average about 9 Ibs./NO
per 1,000 pounds oil fired.(^' Emissions from coal-fired
equipment are shown in Table 6.2.3,
15. EMISSION FACTORS—emission rates for individual boilers are so
variable that only stack tests can provide reliable data. However,
the following emission factors can be useful in determining gross
emissions,
,a
SO,,—38 times the percent of sulfur by weight in the coal = pounds of
(7)
(8)
SO^/ton of coal burned (assumes 5% of sulfur remains in ash).
NO —20 pounds/ton of coal burned.
X
CO—0.5 pounds/ton of coal burned.
(9)
Particulates
Combustion of coal
Pulverized:
General (anthracite and bituminous) 16A Ib/ton of coal burned
Dry bottom (anthracite and
bituminous) 17A Ib/ton of coal burned
Wet bottom (anthracite and
bituminous):
Without fly ash reinjection 13A Ib/ton of coal burned
With fly ash reinjection 24A° Ib/ton of coal burned
Cyclone (anthracite and bituminous) 2A Ib/ton of coal burned
-------
6.2.11
Table 6.2.3. EMISSION OF NITROGEN OXIDES*
Pounds per
million
Type of unit Btu input
Pulvcri/.ed coal
Vertical firing 0.38
Corner firirig 0.95
Front wall firing 0.68
Horizontal opposed
firing 0.65
Cyclone 2.5
Stoker:
Spreader stoker 0.65
Commercial underfeed 0.30
Residential underfeed 0.36
Hand-fired 0.11
*From Hangebrauk, R. P., et al, J. Air Pollution Control Association. 267-278
1964; Cuffe, S. T. and Gerstle, R. W. , "Summary of Emissions from Coal-Fired
Power Plants," A.I.H.A., Houston, Texas, 1965.
Source: Engdahl, R. B., Reference 5.
-------
6.2.12
Spreader stoker (anthracite
and bituminous):
Without fly ash reinjection 13A Ib/ton of coal burned
With fly ash reinjection 20A° Ib/ton of coal burned
16. RULES—typical types of rules and regulations enforced in the field
are shown in Table 6.2.4.
17. STANDARD CONDITIONS AND UNITS—for sampling and analysis of gaseous
and particulate pollutants from stack gases to establish compliance
with maximum allowable emission standards, units and conditions for
testing are usually specified in ordinances. For example, with respect
to dusts and fumes, standard conditions may be in terms of 60 -70 F
at one atmosphere pressure, 14.7 psia or 760 mm Hg. Conditions may be
stated in terms of volume of source gas as standard cubic feet of dry
exhaust gas (SCFD) or standard cubic feet per minute (SCFM) which may
be calculated as if 50% excess air had been used in fuel burning
equipment. Concentrations may be specified in grains per standard
cubic foot (Gr/SCF). Combustion contaminants are also calculated at
12% carbon dioxide (C0_) at standard conditions.
18. AIR POLLUTION CONTROL TECHNIQUES—air pollution control techniques
may be applied to reductions of both gross emissions and to specific
contaminants. The former will depend on such techniques as improved
design of the combustion system, fuel substitution, (e.g., gas for
oil, utilization of low ash and low sulfur fuels), reduction of
electricity or steam load demand, diversion of electric power generation
to facilities outside of the air quality control region, good operational
practice, tall stacks and source shutdowns.
Positive control of continuously operating coal and oil-fired
facilities will depend on the application of a specific technique for
Emission rates are those from uncontrolled sources, unless otherwise noted.
Where letter A is shown, multiply number given by percent ash in the coal.
°Value should not be used as emission factor. Values represent the loading
reaching the control equipment always used on this type of furnace.
Revised from 5A.
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6.2.13
Table 6.2.4. EXAMPLES OF PRINCIPAL TYPES OF AIR POLLUTION CONTROL
RULES/CODES AFFECTING FUEL-BURNING INSTALLATIONS
1. EMISSION LIMITATIONS BY VOLUME/WEIGHT OF STACK GAS
Maximum sulfur compound concentrations expressed as percent
by volume or parts per million; combustion compounds expressed
as maximum grains per cubic foot of gas calculated at 12 per-
cent carbon dioxide at standard conditions.
2. EMISSION LIMITATIONS IN RELATION TO BTU OF HEAT INPUT
Maximum particulate concentrations in pounds per million
Btu of heat input; or grains per SCFD in relation to units
of specified heat inputs; for example, prohibitions of
particulate matter in excess of 0.10 pounds per million
Btu per hour emitted from solid fuel-burning equipment;
particulate matter in excess of 0.025 pounds per million
Btu per hour from equipment rated greater than or equal
to 250 million Btu per hour heat input.
3. EMISSION LIMITATION IN RELATION TO FUEL-USE
Particulates, pounds per 1,000 gallons of oil burned or
grains per SCFD at 50 percent excess air; sulfur content
by fuel oil grade and viscosity.
4. EMISSION LIMITATION IN RELATION TO TIME PERIOD AND STACK HEIGHT
Coarse solid particles and fine solid particles computed in
relation to stack height and distance in stack height from
stack to nearest property line. Allowable emissions of
sulfur compounds, expressed in pounds per hour, calculated
on the basis of stack height, stack exit velocity, exit gas
temperature, and stack height adjustment factor using pre-
calculated tables.
5. EMISSION LIMITATIONS BASED ON RINGELMANN AND OPACITY
Emissions of shade or density equal to or darker than (#1, #2,
#3) Ringelmann or equivalent opacity for periods totaling
more than (0, 2, 3) minutes in any one hour.
-------
6.2.14
Table 6.2.4. EXAMPLES OF PRINCIPAL TYPES OF AIR POLLUTION CONTROL
RULES/CODES AFFECTING FUEL-BURNING INSTALLATIONS (Continued)
6. LIMITATION OF SULFUR CONTENT IN FUELS
All fuels, maximum percent of sulfur by weight, with separate
specifications for distillate fuels, residual fuel oils, and
solid fuels. Gaseous fuels containing sulfur compounds in
excess of specified grains per 100 cubic feet of gaseous fuel
(calculated as hydrogen sulfide at standard conditions).
7. LIMITATION OF ASH, VOLATILE CONTENT AND OTHER FUEL PROPERTIES
Example: solid fuel equipment must remove about 99 percent
of particulate matter generated by combustion of the average
10 percent ash coal. Removal may be required of about 80
percent of particulate generated from combustion of high-
ash residual fuel oil in large boilers.
8. SOOT EMISSION LIMITATION
Bachrach smoke spot test.
9. FUEL SUBSTITUTION REQUIREMENTS
New installations below heat input rate of specified Btu/hr.
capacity are prohibited from using residual oils. Distillate
oil or natural gas may be substituted.
10. REQUIREMENTS FOR WASHING OR PREPARING COAL
Coal with specified volatile content in excess of a specified
percent of ash or sulfur (dry basis) must be washed and used
in approved mechanical fuel-burning equipment.
11. PROHIBITION OF FUEL SALES, IMPORTATIONS, TRANSPORTATION OR USE
Coal containing excess volatile matter, except sizes which
pass through 2-inch circular opening or equivalent.
-------
6.2.15
Table 6.2.4. EXAMPLES OF PRINCIPAL TYPES OF AIR POLLUTION CONTROL
RULES/CODES AFFECTING FUEL-BURNING INSTALLATIONS (Continued)
12. SOURCE REGISTRATION REQUIREMENTS
All coal, oil and gas burning, except;
- Natural gas and other types,of gas, #1 and #2 fuel oil with
heat input less than 1 x 10 Btu/hr.; or approximately 1,000
cubic feet of gas or 7 gallons of oil per hour equivalent
fuel use.
- Coal or wood having a heat input of less than 250,000 Btu/hr.
13. PERMIT SYSTEM
All structures with combustion equipment, except four-family
dwelling units or less. All fuel-burning equipment greater
than specified Btu input.
14. EQUIPMENT PROHIBITIONS
New coal burning installations smaller than specified
Btu/hr. input capacity prohibited. All hand-fired and surface
burning equipment prohibited.
15. AIR POLLUTION CONTROL EQUIPMENT REQUIREMENT
Particulate control equipment effective at removing specified
percent of particulate matter smaller than specified microns
in diameter. Allowance for equivalent desulfurization of
stack gases. Authorizes operation of sulfur scavenger or
recovery plant to reclaim sulfur compounds capable of re-
ducing sulfur compounds at least 95 percent compared to emissions
when plant is not operating.
-------
6.2.16
the control of a specific contaminant or class of contaminants.
Separate gas cleaning techniques usually will be required for
each of the following: particulates, oxides of sulfur and oxides
of nitrogen, with the exception of alkaline scrubbers (see below)
which are capable of controlling both particulates and oxides of
sulfur.
Particulate control techniques applicable to coal and oil fired
equipment include settling chambers, large diameter cyclones,
multiple-small-diameter cyclones, wet scrubbers, electrostatic
precipitators and fabric filters. The expected performances of
various types of gas cleaning devices are shown in Table 6.2.5.
The control of oxides of sulfur depends on the conversion of SO-
to a particulate that can be collected by fly ash collection
equipment. Principles of control include reactions of SO with
calcined limestone (limestone-dolomite injection, wet and dry
processes), alkalized alumina sorption (removal of SO by
sorption on solid metal oxides), catalytic oxidation ^conversion
of SO- to SO- using vanadium, nickel or platinum catalysts and
collection as sulfuric acid, and caustic scrubbing). Control of
NO depends on design of the combustion equipment, especially
with respect to flue gas recirculation, variations in air flow to
burners and steam injection at the burners. Control techniques
are further treated in other parts of this section and
in Chapter 5, The Technology of Source Control.
C. FUELS
Assuming that fuel-burning equipment is adequately designed and operated,
emissions of sulfur dioxide and particulates are most related to the
tyPe> grade and properties of the fuel used. Emissions of carbon monoxide
and smoke are primarily due to burner and boiler operation and
maintenance.
Sulfur trioxide and oxides of nitrogen emissions tend to be significant
in fuel-burning installations, and are related to the design of the
combustion equipment and arrangement of the burners. In these
installations 303 is formed from approximately 2-3% of the total fuel's
sulfur.^
-------
Table 6.2.5. OPTIMUM EXPECTED PERFORMANCE OF VARIOUS TYPES OF GAS CLEANING
SYSTEMS FOR STATIONARY COMBUSTION SOURCES
Removal of uncontrolled particulate emissions, percent
Sources
Coal-fired:
Spreader, chain grate, and
vibrating stokers.
Other stokers
Cyclone furnaces
Other pulverized coal units
Oil-fired
Systems in operation
Settling
chambers
60 «
60 »
10 "
20 "
5 '•
Large
diameter
cyclones
GO »
65"
15"
30"
10 h
Small
diameter
cyclones
85 -
90 •
70 »
80"
30 ''
Electro-
static
precip-
itators
99.5 '
99.5 «
99.5 °
99.5 '
75. Od
Systems under
development
8-in.
Stack pressure Fabric
sprays drop filters
scrubbers
GO « 99+ ' 99.5 "
80 ' 99+ « 99.5 ^
(') 99+ ' 99.5 h
" Estimate based on references 17 and 18.
b Efficiency estimated—not commonly used.
c Estimate based on reference 15.
d Estimate based on private reports of field ex-
perience.
1 Reference 19.
' Insufficient data for estimate.
* Estimate based on reference 20.
h Estimate based on reference, 21.
K3
M
~-J
Source: Control Techniques for Particulate Pollutants, Reference 9.
-------
6.2.18
NO^ emissions tend to increase with the flame temperatures of fuels which
X
in turn vary with the carbon/hydrogen ratios of the fuel contents. Coal
burns hotter than oil and oil hotter than gas, as shown in Figure 6.2.2.
Excessive smoke and particulate emissions may be due, in many instances,
to the firing of fuels which are improper for a given design and function
of combustion equipment. Also, even within a given fuel type, grade and
specification the quality of the fuel, in terms of ash and sulfur content
and the presence of water, sediment and other impurities may change
thus necessitating constant surveillance of fuel properties. The
objective is to employ fuels which are low in sulfur and ash content and
low in moisture and other undesirable impurities.
1.400
1.200
1.000
OIL FIRING
| | - GAS FIRING
FUEL FIRING
400
200
Figure 6.2.2,
OXIDES OF NITROGEN CONCENTRATIONS IN GASES FROM VARIOUS
GAS-FIRED, OIL-FIRED, AND COAL-FIRED STEAM GENERATORS
SOURCE; WALSH, Reference 3.
-------
6.2.19
Regulations prohibiting sulfur content in fuels will depend on the enforce-
ment agency, available fuels and economic feasibility. Sulfur content re-
strictions, on a dry weight basis, vary from .2% to 2%. For example, regu-
lations in effect in New Jersey
(10)
are shown in Tables 6.2.6 and 6.2.7.
Table 6.2.6.
TYPE COAL
Bituminous
Anthracite
SULFUR CONTENT LIMITATIONS FOR COAL
PERCENT SULFUR BY WEIGHT (DRY BASIS), COAL
Effective
5/6/68
1.0%
0.7%
Effective
10/1/71
0.2%
0.2%
SOURCE: State of New Jersey, Reference 10.
Table 6.2.7. NEW JERSEY SULFUR CONTENT LIMITATIONS
BY FUEL OIL AND VISCOSITY
GRADES OF
COMMERCIAL
FUEL OIL
No. 2 and
lighter
No. 4
No. 5, No. €
and heavier
CLASSIFICATION BY
SSU VISCOSITY @
100°F
EFFECTIVE
5/1/68
Less than or equal to 45 0.3%
Greater than 45 but less
than 145
Equal to or greater
than 145
0.7%
1.0%
EFFECTIVE
10/1/70
0.3%
0.4%
0.5%
EFFECTIVE
10/1/71
0.2%
0.3%
0.3%
SOURCE: State of New Jersey, Reference 10.
-------
6.2.20
Table 6.2.8 presents an overview of inspection points for fuel types and
properties. Many of the properties shown should be subject to analysis by
the laboratory of the enforcement agency. In doubtful or suspicious cases
samples should be taken to the laboratory for analysis. Fuel properties will
vary considerably among regions.
Enforcement officers should become familiar with the specific requirements in
their regions. In regions where high sulfur, high ash fuels are the only
economical fuels available, emphasis is usually given to air pollution control
equipment, desulfurization of stack gases, boiler operation and design. In
regions where lower sulfur and ash fuels are available, enforcement officers
may participate in a program to promote and enforce fuel substitution. In
cases of emission violations, they may be required to establish that the fuel
used played a role in the violation. They should also become familiar with
ASTM standards and procedures listed in Table 6.2.9.
1. COAL
Coal usually is classified by "rank," the degree of change from
lignite to anthracite, as shown in Table 6.2.10. In addition to
the chemical composition of coal, the physical property of caking
(coking) is an important consideration in the ultimate use of
stokers or other methods of firing. Caking refers to the remaining
fixed carbon and ash melts after the volatiles have been distilled
from the coal. To some degree caking takes place with all coal.
The degree is variously described as strong caking, weak caking, or
noncaking. Bituminous coal usually is caking coal and anthracite
and most sub-bituminous coals are free burning or noncaking.
-------
Table 6.2.8. OVERVIEW OF FUEL TYPES AND PROPERTIES AND
SPECIFICATIONS PERTINENT TO AIR POLLUTION
COAL
Type
Bituminous
Subbituminous
Anthracite
Semi anthracite
Lignite
Properties
Sulfur content
pyritic, organic,
sulfate
Ash softening temperature
Moisture content
Fixed carbon
Heating value
Chlorine content
Coal Sizing and Form
Run-o f- the-mine
Slack coal
Double screen
Pulverized
Caking coal
Free burning coal
OIL
Type
Distillate
Grades #1 and #2
residential; commercial
heating
Grades #4 and #5
Blended
Commercial and
industrial
Residual
Grade #6, Bunker C,
PS 400
Heavy oil-large
boilers, public
utility, industrial,
commercial, diesel,
marine
Specifications
Sulfur content
Ash content
Viscosity
Flash point
Gravity, API
Pour point
Water and sediment
Heating value
GAS
TyjDe
Natural
Coke oven
Liquified
Make-gas
Waste-gas
Constituents
Methane, Ethane,
etc .
specific
gravity (relative
to air)
Heat value
OTHER
Wood
Refuse
Oil shale
Bagasse
(sugar
cane or
beet residue)
Coke breeze
(coke fines)
Char (fluidized
bed) carbonized
coal
Petroleum coke
Black liquor
(paper pulp wastes)
-------
6.2.22
Table 6.2.9. FUEL ANALYSIS, STANDARDS AND PROCEDURES REFERENCES
Specifications for Fuel Oils
Moisture of Oil Determination ASTM Standard
Coal Classification by Grade Standard
Sampling and Analysis of Coal (percent
of sulfur in coal) and Heat Content
Sampling of Volatile Matter
Gross Calorific Value of Solid Fuels
by the Adiabatic Bomb Calorimeter
Particulate Matter Emitted;
Power Test Codes
Heat Content of Liquid Fuels
Sampling Coal for Ash Content
Preparing Coal Sample for Analysis
Mechanical Sampling of Coal
Grindability of Coal, for Pulverizing
Equipment
Test Code for Coal Pulverizers
Classification of Coals by Rank
Sieve Analysis Size Distribution
Technical Manual on Single Retort
Underfeed Stokers
Application of Over-Fire Jets to Prevent
Smoke from Stationary Plants
Recommended Guide for the Control
of Dust Emission - Combustion
for Indirect Heat Exchangers
Document
ASTM D396
ASTM D271, D1412-565
ASTM D389
ASTM D271-64
ASTM D271-6A, Appendix A
ASTM D2015-62T
ASME PTC27
ASTM D240-64
ASTM D129-62
ASTM D270-65
ASTM D492-48
ASTM D2013-65
ASTM 02234-65^
ASTM D409
ASTM D197
ASTM D388-38
Bureau of Mines, Information
Circular 7346 (1446)
JAPCA 9(3):145-146,
November, 1959
Aid to Industry, 500-300.
Bituminous Coal Research, Inc.,
Monroeville, Pa., 1957
ASME Standard No. APS-1; 1966,
Appendix B
-------
6.2.23
Table 6.2.10. CLASSIFICATION OF COALS BY RANK
3. High
4. High-volatiW B
5. High-volatile C
98% (dry VM 9To or less and
th.tn 15, 500 i
Source: W. S. Smith and C. W. Gruber, Reference 11.
-------
6.2.24
Factors that are of particular importance In the emissions of air
contaminants from the combustion of coal and fuel oil are sulfur
content, volatile matter and ash content. The sulfur content includes
organic sulfur, distributed in coal, and pyritic sulfur. Only the
latter can be removed by washing or mechanical means. The ash content
of fuels contributes to the emission of fly ash and other particulate
emissions, and consists of inorganic materials such as metals and
minerals including silica, iron, aluminum, calcium, vanadium,
alkalies, calcium oxides, magnesium oxides and titanium oxide. The
volatile matter consists of essentially the combustible material,
exclusive of fixed carbon, including complex mixtures of hydrocarbons
and organic materials which decompose to form smoke and organics
during combustion. Variations in sulfur content and fuel properties
in bituminous and anthracite coals are shown in Table 6.2.11. Other
coal properties are described in Coal Preparation Plants, Chapter 7,
Section 13.
2. FUEL OIL
Fuel oils of #1 and #2 grades, the distillate fuels, are usually used
to heat homes and domestic hot water. #2 fuel oil is used in small
apartment houses and industrial processes. The firing rate is usually
not more than 20-25 gallons per hour.
Fuel oil of #4 grade, residual fuel oil, is fired in large apartments,
small industrial plants and other commercial establishments up to 50
gallons per hour. Fuel oils #5, light and heavy, are used in
installations burning more than 50 to 100 gallons per hour respectively,
Fuel oil #5 possesses greater heating value. Fuel oil grade #6 is
used in power generating stations, marine vessels and other large
installations, and is fired at rates greater than 50 gallons per hour.
-------
6.2.25
Table 6.2.11. VARIATIONS IN SULFUR CONTENT AND FUEL
PROPERTIES LIKELY TO BE ENCOUNTERED
BITUMINOUS ANTHRACITE
Moisture, weight % 2-15 4-10
Volatile matter, weight % 14-40 4-8.5
Ash, weight % 4-15 7-20
Sulfur, weight % 0.5-4.5 0.4-0.8
Heating Valve, Btu/lb. 11,000-14,000 11,000-13,500
SOURCE: Smith and Gruber, Reference 11.
Important fuel oil specifications of interest to the enforcement
officer include:
Pour Point; The lowest temperature at which oil will barely flow.
Pour point is measured by chilling a sample of fuel oil in a glass
jar at a constant rate. It is specified as 5°F above the exact
temperature at which the oil will not move when the test jar is held
horizontally for five seconds. The pour point may be important in
frigid climates as an indicator of whether or not fuel preheating is required.
Cloud Point: The temperature at which a cloud or haze of wax crystals
appears in the cooled sample, applied only to transparent oils. The
cloud point indicates whether filters and lines will be clogged due
to crystal accumulation at lower temperatures.
Saybolt Viscosity: The source of the resistance of the fuel oil to flow
or shear. Viscosity is a function of temperature. SSU (Saybolt
Seconds Universal) is the number of seconds it takes 60 cubic
centimeters of an oil to flow through the standard orifice of a
Saybolt Universal Viscometer at 100°F.
Gravity: Gravity is an indirect measure of heat content, and is
measured by means of a hydrometer, in relation to the density of
water. Heat content is related to degrees of API gravity, which can
be established from standard API tables. For example, a fuel of API
gravity of 33 possesses a heat content of 140,000 Btu per gallon.
-------
6.2.26
The sulfur content of No. 1 distillate will vary from .04-.124, and
of No. 2 distillate from .104-.307. The sulfur content in Grade 6,
residual oils will range from 0.9 to 3.2% by weight.
3. GASEOUS FUELS
Natural gas consists of primarily methane and ethane, although small
amounts of sulfur compounds are usually added to distribution lines
(about .15 grain calculated as sulfur per 100 SCF) to impart a
detectable odor to the fuel. The primary problem from natural gas
burning is CO and NO emissions.
4. FUEL SAMPLING
Determinations of emission rates, as well as compliance with fuel
limitations, are based on the sampling and analysis of fuels (see
Table 6.2.9). The inspector obtains a sample of the fuel which is
representative of the fuel stored or fired, seasonal or other cyclic
operations, or of operations related to an actual or suspected
violation of visible emissions. Also, samples may be taken from the
consumer, supplier, distributor or the mine. The inspector may:
1. Conduct fuel inventories of all suppliers in a region,
2. Determine the source of the fuel, including the producing district,
3. Establish the representative fuel properties and fuel preparation
methods for each producing district by coal rank and type.
4. Take samples and forward them for laboratory analysis to establish
or verify fuel properties.
5. Match fuel properties with commercial names.
-------
6.2.27
Coal can be sampled in 10 pound containers, and oil in pint, quart or
gallon plastic or tin containers. A sample coal shovel is used, for
example, to sample coal from a chute feeding a stoker. Samples are
taken at regular intervals and placed on a tarp (usually 4' x 61)
until approximately 100 pounds of coal are collected. The tarp is folded
over the coal and the coal shaken. From this sample, approximately
ten pounds of coal are taken in a 10 pound bucket to the laboratory
for analysis. Samples of fuel oil can be taken from the fuel or
service line, or the storage tank with an "oil thief." A typical fuel
survey form is shown in Figure 6.2.3.
D. TYPES OF FUEL-BURNING FUNCTIONS
The fuel-burning function relates to the purpose of the fuel-burning and is
important from the standpoint of the number and types of users, and
degree of control the user can exercise as an individual and as a class
over his operation to control emission rates.
Each fuel user class presents different problems which must be appro-
priately treated from an inspection and enforcement standpoint. Residential
space-heating usually will be treated as an area source, handled primarily
through region-wide fuel substitution and special equipment prohibitions or
as single code violations. A large single-point source, such as a power
plant, may be attacked from the standpoint of fuel supply, burner design,
power plant design and air pollution control equipment. The specificity
and breakdown of fuel-burning functions may differ among enforcement
agencies according to the emphasis with which any class of fuel-burning
source is to be controlled. A general scheme for fuel-burning operations,
given by building or plant categories is shown in Figure 6.2.4.
-------
6.2.28
DATE
STATE HEALTH DISTRICT.
..TIME OF SAMPLING .
a.m.
_p.m.
a.m.
_p.m.
_COUNTY.
Parti
z
o
FULL BUSINESS NAME.
MAILING ADDRESS
Zip Cod.
LOCATION ADDRESS.
Book Plate.
-Lot.
.Block.
TYPE OF OWNERSHIP- NAME OF OWNER, PARTNER, OFFICERS, OFFICIALS
TITLE
o
u
Individual
Partnership .
Corporation
Municipal (type)
Petson(s) interviewed & title(s).
Remarks
Part 2
NAMEOFSUPPLIER(S)_
ADDRESS OF SUPPLIER ,
GRADE OF OIL:.
SAMPLED BY: _
_DATE OF LAST DELIVERY .
Zip Cod.
. TEMP. OF Oil
_TITLE .
_TRUCK»_
-OTHER.
_GAL. TOTAL TANK CAPACITY:.
SAMPLE TAKEN FROM: TANKo
QUANTITY OF OIL fN TANK:
TYPE OF SAMPLING:
A. DIP SAMPLE: TRAVERSE - TANK AVERAGE Q TOP Q MIDDLED BOTTOM Q
B. SAMPLING VALVE ON TANK:
C. CIRCULATION SAMPLE:
-GAL.
.D. SAMPLE AT BURNER.
BLENDING FACILITIES: NOQ YES Q DESCRIPTION:.
FIELD SAMPLE c
DATE SUBMITTED FOR ANALYSIS: .
DATE ANALYZED:
-DUPLICATE SAMPLE LEFT WITH .
-SUBMITTED TO.
_LAB. SAMPLE .v_
_BY:_
Par! 3
ANALYSIS:
% SULFUR:
POUR POINT:
RECOMMENDATIONS: .
-VISCOSITY:.
-API GRAVITY:
_BTU VALUE:.
COMMENTS:
Figure 6.2.3. A TYPICAL FUEL SURVEY FORM
SOURCE: STATE OF NEW JERSEY, REFERENCE 13.
-------
Of
PLANT
FIRING METHODS
EFFLUENT.
COAL-TO-SUAK
EICESS US, *
GENEflATION. H
HE*T i>^1
1 GROUP ' S - A
HAKO-FIBED EQ^JIP*
i !
&
I |
"5 .0
I MM1
s.oco
1 1
II 1
10
iil 1
i > .000
j 1 1
0
tc.
I.
JSP
II
5',
II
0.
1
1
1
is. !K.
of IRiYF.
SPR
ilG GFiK
a° vi B . Sfu
Lf RElbR
0
60
:
»0
1 III
1 II
50
1 1 1
5.000
1 t II
50
Wl TH ?^DCr"if, •; 'UH J
KG GFU.TE1 J
GRATE
fn
LKO-HfEEO SK'-KER |
I 1 I
500 4iO 100
1
as
I
5 30
1 1 1 i 1 III
50.000 1 00.000
! 1 TT'T 1 1 1
iO 50
II 1 ! 1 Ml!
100 500
! EH ' 1 I - M
1C. 000 50. KO
\ \ I 1 N 1 IF
500 '.
1"
|
i
i
r "
i
i
i
i
i
i
i
i
1 1
350 300
1
I
(
[
! i
25
!
1 1 (I ! 1 II 1 1 M 1 III
500 . 000 1 . 000 . 000 | 5. 000 . 000 i 0 . CCO. CM
!
1 I I M Mill 1 1 MINI
00 500 1 .000 5 000
;
! 1 1 ! 1 Mill 1 1 1 M II
.000 5.000 ,10.000
1
111 1 • • 1 1 1 Mill 1 Mil!
i 00. 000 530.000 j 1,000, CCO 5,000.000
!
1 1 1 1 M Illl 1 1 1 1 M 11
100 5.000 10.000 50.000
SPI'- SPIEADEI ITOICI.
Figure 6.2.4. SUMMARY OF CHARACTERISTICS OF COAL FIRING EQUIPMENT
SOURCE: SMITH AND GRUBER, REFERENCEH.
-------
6.2.30
The fuel-burning operation may be independent (stand alone) or on-line
with other processes. Generally speaking, when the fuel-burning operation
is used to provide space heating or electrical power, the inspector is
not directly concerned with steam distribution or electrical power
generation and distribution equipment, except possibly to establish load
conditions and peaks imposed upon the combustion equipment. When the
fuel-burning equipment is used to provide steam or heat to other processes
which may emit important contaminants, or if emissions from other
processes are vented to the firebox or to the stack of the boiler, then the
inspector must inventory or note this equipment and evaluate its air
pollution potential. The inspector should show the flow of fuel, air, and
process material to the system, together with a description of the
ventilation system, including blower size and horsepower, ash removal rate,
points of air pollution emission, air pollution control equipment, and
stack characteristics.
E. SIZE OF FUEL-BURNING FUNCTIONS
The size of the fuel-burning operation is important from the standpoint of
the fuel firing rates, the size of the combustion chamber, and the rate of
thermal energy produced since these parameters are related to emission
rates. Small fuel-burning operations tend to be less efficient than larger
installations per pound of fuel burned. State and local air pollution
control regulations tend to define fuel-burning equipment by size, and
inspection programs are designed accordingly. Permit fees are also
related to size of equipment.
-------
6.2.31
The size of the operation may be rated by Btu per hour of heat input, fuel
firing rates, pounds of steam per hour produced, boiler horsepower, or
electrical energy. Most legislation deals with Btu per hour heat input
which can be related to fuel firing rates, as noted in Table 6.2.12, and to
contaminant emissions. The horsepower rating is commonly found on the
combustion equipment and is related to the pounds of steam produced per
hour. A 1,000 HP boiler is equivalent to about 34,500 pounds of steam
production per hour or 2,500 pounds of oil fired per hour. The Btu value
may be computed from knowledge of the heat content of the fuel. The
average heat content of oil, for example, may be 18,300 Btu per pound
burned. A 1,000 HP boiler installation may produce about 45-46 million
C46 x 106) Btu/hour.
The Btu input rating obtained from the fuel firing rates is more increas-
ingly relied upon as a function of "size," than is boiler horsepower or
pounds of steam. The Btu rating tends to be most related to the total
pollutants emitted. The boiler horsepower rating, stamped on boilers, is
often unreliable as an indicator of capacity. For permit applications,
emission inventories or source registration, the Btu/hour input estimate
is usually taken as the larger of either the boiler rating or the operation-
al practice.
Figure 6.2.4 relates size of operation and fuel-burning function to Btu
heat input, steam output and other combustion ratings. Equipment subject
to inspection is likely to be in the 1 x 10 Btu/hour and greater
classifications, depending on the air pollution problems and regulations
in effect in the air quality region.
The heat input value is used in a number of ways of interest to the
inspector. For example, emission factors may be related on a graduated
-------
6.2.32
Table 6.2.12. CONVERSION OF FUEL TO HEAT EQUIVALENCY,
AVERAGE VALUES
26 x 10 Btu in 1 ton coal
3
1 x 10 Btu in 1 cu. ft. natural gas
136 x 103 Btu in 1 gal. No. 1 oil
139 x 10 Btu in 1 gal. No. 2 oil
144 x 10 Btu in 1 gal. No. 4 oil
148 x 10 Btu in 1 gal. No. 5 oil
151 x 103 Btu in 1 gal. No. 6 oil
-------
6.2.33
basis to the heat in the fuel burned. Proposed regulations may prohibit
the use of certain fuels such as coal or residual oils in units with less
than a specific heat input, e.g., 5 million Btu/hr.
The heat input value may also be used as a criteria for source
registration, e.g., all units burning coal or wood with heat input values
of 350,000 Btu/hour or greater (approximately 28 pounds of coal per hour
fuel use rate) must be registered. Permit or other fees may also be
assessed on the basis of heat input.
The type of equipment the inspector will physically inspect is also
related to size. Factors include the type and construction of the firebox,
heat exchanger and method of firing. In general, small boilers or heaters
(residential and some institutional) are likely to be of the water-tube
type in which the water flows through tubes which are heated by combustion
air. Intermediate types of boilers may be of fire-tube, scotch marine,
or cast-iron sectional construction as shown in Figures 6.2.5, 6.2.6 and
6.2.7. Large steam generating stations or recovery furnaces (see Kraft
Mills, Chapter 7) are based on water tube or water wall construction.
Fireboxes may be of refractory construction in intermediate units, whereas
small and large-scale units are of metal construction.
The size of the fuel-burning operation also involves considerations of
scale and design which affect the types and rates at which contaminants
are emitted. Emissions of oxides of nitrogen and sulfur trloxide are a
function of size as well as other considerations treated in this
section.
-------
6.2.34
Figure 6.2.5. A FIRE-TUBE BOILER WITH A REFRACTORY-LINED FIREBOX
(ERIE, CITY IRON WORKS, ERIE, PA.)
SOURCE: WALSH, REFERENCE 3.
-------
6.2.35
/
Figure 6.2.6. A THREE-PASS, SCOTCH-MARINE BOILER (RAY
BURNER CO., BOILER DIVISION, SAN FRANCISCO, CA.)
SOURCE: WALSH, REFERENCE 3,
-------
6.2.36
Figure 6.2.7. A CAST IRON SECTIONAL BOILER (CRANE CO.,
JOHNSTOWN, PA.)
SOURCE: WALSH, REFERENCE 3.
-------
6.2.37
F. INSPECTION POINTS
Many of the inspections to be conducted in the field will involve fuel-
burning installations. Field operations functions will include:
1. Enforcement of all regulations affecting the use of fuels and the
installation and operation of fuel-burning equipment. Typical
enforceable regulations are shown in Table 6.2.4.
2. Establishing the causes of excessive emissions and public nuisances.
3. Inventorying fuel-burning equipment in buildings and plants.
4. Assistance in source testing and emission inventories.
5. Collection or verification of information for source registration
purposes.
6. Assistance in the administration of a permit system.
7. Checking progress in meeting compliance plan schedules.
8. Participation in fuel-use or fuel marketing surveys,
9. Responding to questions concerning the completion of source registration
questionnaires and application forms by respondents.
*Attainable emission limits are listed in Table 1.2, Chapter 1. Rules
recommended under the Clean Air Act are described in Reference 14.
-------
6.2.38
The inspection points and the type of information the inspector collects
will depend on the type and purpose of his investigation. An inspection
involving equipment or emission inventories, permit system checks, or
source registration follow-ups will require:
1. Identification Data. The identification and listing of all equipment
and principal equipment components at the facility capable of
emitting air pollutants.
2. Descriptive Data. The acquisition of descriptive information on the
equipment to establish or verify the principal design features, such
that gross alteration to the equipment above that found on previous
inspection reports and applications can be determined. Descriptive
information includes, for example, the number and type of boilers,
type and capacity of air pollution control equipment, the number,
types and placement of burners, the type and horsepower of combustion
air blowers, the breeching of boilers in series, etc.
3. Operational Practices Data.. These include established, i.e. , ongoing
practices relating to the type and grade of fuels normally used,
standby equipment utilization, method of ignition and control, ash
handling and soot blowing, quantities of fuel and materials processed,
operating schedules, and operating conditions as may be noted from
process control monitors.
Incident investigations concern inspections-that are made pursuant to a
visible violation or a public nuisance. This type of investigation re-
quires that the enforcement officer have knowledge of the installation,
as may be gained from previous inventory inspections, and intensive inspection
of operational practices as close to the time of the incident or the violation
as possible.
-------
6.2.39
Figure 6.2.8 is a simple correlation of the fuel burning-parameters which
have the greatest impact on the quantities of contaminants emitted by
class. In practice, the enforcement officer will be most concerned with
visible emissions—smoke, SO. and particulate fall-out nuisances. He
should also be prepared to report on the parameters which produce non-
visible emissions such as CO, NO „ organics and submicron particulates,
X
even though he may not always be able to quantitatively estimate actual
emission rates. Such information may lead to a source test request.
Table 6.2.13 correlates the likely inspection points of interest with
types of inspections and required information. Specific inspection points
relating to specific types and components of fuel-burning equipment are
treated in the following parts of this section.
In conducting the physical inspection of fuel-burning installations, the
field enforcement officer should be aware that the emissions of a variety
of air contaminants are sensitively related to the specific characteristics
of fuel firing systems in several ways. First, the firing system comprises
the most variable feature of boiler operations. Excessive emissions of
smoke, particulates and carbon monoxide are related to burner or stoker
feed rates, adjustment, wear and level of maintenance. The variability
of the operation further increases with the number of burners employed
and with fuel properties. Second, the design of the firebox and placement
of burners affect SO. and NO emissions.
-J X
SO,, emissions, for example, depend largely on the size and temperature of
(15)
the firebox. Crumley and Fletcher found that:
• SO formation increases as flame temperatures are increased up
to about 3150°F.
• Above 3150°F SO formation does not increase, that is, the SO /SO
rate remains constant.
• When flame temperatures are held constant, SO formation decreases
as the excess air rate is reduced.
• SO- formation decreases with coarser atomization, possibly due to
lower resultant flame temperatures.
-------
6.2.40
CONTAMINANT
so2
Ash (particulates)
Smoke, particulates
CO
Aldehydes
Organic Acids
FUEL-BURNING FACTOR
Fuel Type, Grade, Size, Rank,
Composition
Fuel Burner Design and Operation
Air Fuel ratio
Atomizing
Mixing and Turbulence
Time Interval
SO - Visible Plume
3
NO
Power Plant Size
Firebox Temperature
Excess Oxygen
Oxygen Concentration
Oxidation Catalysts in Tube Deposits
and Particulates
Power Plant Size
Boiler/Furnace/Firebox Design
Firing Rates
Firing System Design
Flame Temperature
Residence Time of Combustion gases
in High Temperature Zone
Excess Oxygen
Figure 6.2.8.
RELATION OF MAJOR POLLUTANTS TO PRINCIPAL
DESIGN AND OPERATIONAL VARIABLES
-------
Table 6.2.13 EXAMPLES OF FUEL-BURNING EQUIPMENT INSPECTION POINTS
AS RELATED TO TYPE OF INSPECTION
COMBUSTION SYSTEM
Boiler &
Supporting
Equipment .
Fuel used.
Stoker and/or
Burner.
Firebox.
Ash and
Soot
Handling
INVENTORY INSPECTION POINTS
IDENTIFICATION DATA
Boiler type, (fire
tube, water tube,
etc.).
Boiler H.P., Btu
rating.
Make and model and
serial number .
Fuel Type.
Burner type .
Combination/
standby equipment .
DESCRIPTIVE DATA
Instruments/
controls employed '•
air/steam, fuel/
steam, combustion
recorders, smoke
indicators,
alarms etc. Stack
height & diameter.
Fuel Type.
Placement of
front, vertical) .
Single vs. dual
stage. Clearance
of burners in
firebox (feet) ,
Overfire air
controls . Pro-
vision for fuel
oil preheaters
Smoke Reading
Equipment .
Firebox
dimensions . Type
of refractory .
Combustion air
provision (natural,
forced, induced) .
Location of ash
pit and provisions
for ash removal.
Soot blowing
method . Number ,
type (air/steam) .
OPERATIONAL PRACTICES DATA
Extent of equipment
supervision & operation.
Operation & use of smoke
alarm equipment,
Grade, rank, analysis, size;
average and peak firing
rates .
Conditions of burners and/or
standby and combination
equipment. Ignition method
and conditions . Coal & ash
Distribution of coal sizes
tion procedure .
Refractory repair. Firebox
temperatures . Flame
temperatures.
Ash handling, removal rate
and disposal. Ash analysis.
Soot blowing schedule. Tube
washing procedures.
INCIDENT INVESTIGATION
VIOLATION & NUISANCE INVESTIGATION: SMOKE
PARTICULATES, SPECIFIC CONTAMINANTS
Ringelmann/Opacity from stack or other
source. Readings of oxygen, C02, fuel &
other instruments. Particulate, soiling,
fallout indications .
Grade, rank, analysis, firing rates, fuel
Appearance of flame . Flame clearance (same
Condition of refractory. Primary and
compartment pressure.
Ash accumulation in. pits. Ash quenching
and watering. Dirt In fire tubes or vent
system.
-------
6.2.42
NO concentrations vary with flame temperature, firebox oxygen concentration
and firebox and burner design, for example:
• At 3,000°F firebox temperature concentrations are well over 1,000
ppm at 1% oxygen.
• Calculated flame temperatures are in excess of 4,000 F at 10% excess
air (2% oxygen) for both oil and gas firing when air is preheated
at 600°F.
• NO emissions tend to be 35 to 50% higher during oil firing than
gas firing.
(3)
NO emissions can be reduced by employment of a two stage combustion
X
design in which
• Only 90 to 95% of theoretical combustion air is injected at the
burner.
• Remaining air is introduced a few feet downstream of the burner
to complete combustion over a somewhat larger zone.
• Normal excess air rate is maintained.
In some installations NO emissions may be reduced by modifying the
X
combustion control system to give a more precise method for proportioning
fuel and air. One method is supplying all of the fuel through the bottom
of a number of rows of burners while maintaining normal air flow to all
burners. The delayed introduction of excess air tends to
reduce NO concentrations in flue gases by 40 to 50%. Also, tangential,
(corner fired) burners can result in substantially less NO emissions
than front-fired units.
Other approaches used are aimed at reducing flame temperature or the
time the combustion gases are exposed to high temperature. These
include increased flue gas circulation, varying air flow to various
burner levels and injecting steam at the burners.
-------
6.2.43
The relationship of fuel properties to combustion equipment is further
illustrated in the following tables: Coal Characteristics Relative to
Method of Firing, Table 6.2.14; and General Uses of Bituminous Coal Sizes
in Relation to Type of Coal Burning Equipment, Table 6.2.15.
The text below summarizes background information on the operation and in-
spection of the principal types of fuel firing systems that are likely to
be encountered in the field. Actual inspection points will depend on the
inspection and the type of equipment involved. Some of the first-hand
information the field enforcement officer collects such as the appearance
of the flame, condition of refractories, type of coal and apparent thickness
of the fuel bed may relate directly to an air pollution incident. Other
information such as type of slag tap furnace, fineness of coal, or excess
air may be needed for inventory or source registration follow-up inspections,
and may be collected by the field enforcement officer to permit subsequent
retrieval and evaluation by the engineering staff of the enforcement agency.
This information may be acquired by direct observation, reading of instru-
ment gauges and interviews with the air pollution or technical staff of
the plant. Specific inspection procedures will depend on the policies of
the enforcement agency involved.
1. Solid Fuel-Burning Systems—Inspection Points and Operating Guides
In general coal-firing systems provide for the feeding of raw fuel, the
ignition of the fuel and the removal of ash. Systems generally vary in
the direction and method by which raw coal reaches the fuel bed, and
the flow of primary air in relation to the movement of the bed. The
firing method will depend on the type of coal available and used.
a. Stokers (Commercial, Institutional and Industrial)
(1) Function and Types
Stokers are designed to produce steam in small and moderate
size boilers, and are generally limited to 400,000 Ibs. steam/
hour. They fall into the following classifications:
-------
Table 6.2.14. COAL CHARACTERISTICS RELATIVE TO METHOD OF FIRING
METHOD OF FIRING
Max Total Moisture *
Min Volatile Matter (dry basis), %
Max Total Ash (dry basis), %
Max Sulfur (as fired), %
Max Ash-Softening Temp, F
STOKER
15-20
15
20
5
PULVERIZED COAL
15
15
CYCLONE FURNACE
20
15
25
2400
* These limits may be exceeded for lower rank, higher inherent-moisture-content coals,
i.e., subbituminous and lignite.
Source: Babcock and Wilcox Company, Reference 1.
-------
6,2.45
Table 6.2.15. GENERAL USES OF SEVERAL BITUMINOUS COAL SIZES
Type
Most common use
5 lump
5x2 egg
2 x 1-1/4 nut
1-1/4 x 3/4 stoker
1-1/4 x 5/16 stoker
3/4 x 3/8 stoker
3/4 x 0 slack
5/8 x 0 slack
1/2x0 slack
1/4x0 slack
1-1/4 x 0 nut and slack
2x0 nut and slack.
Hand-firing, domestic and industrial
Domestic hand-firing and gas producers
Domestic hand-firing, industrial stokers,
and gas producers
Domestic and small industrial stokers
Domestic and small industrial stokers
Domestic and small industrial stokers
Industrial stokers and pulverizers
Particularly suited to pulverizers
Particularly suited to pulverizers
Particularly suited to pulverizers
Industrial stokers
Industrial stokers
Source: W. S. Smith and C. W. Gruber, Reference 11.
-------
6.2.46
Overfeed—In this equipment burning gases rise through
fresh fuel resulting in rapid devolatization of the new
fuel in a zone deficient in oxygen. These designs
together with hand-fired equipment inherently smoke
and are disappearing from use.
Underfeed—These units include single retort, multiple
retort; screw fed or ram fed. Air and fresh fuel flow
concurrently, usually upward. The zone of ignition is
near the point of maximum evolution of combustible gases,
and is supplied with ample air and adequate mixing to
promote complete combustion. These designs tend to be
smoke-free, but substantial quantities of fly ash may be
emitted because of the high velocity jets of escaping
gas. Dust collectors may be required. This type of
design is better suited for caking coals. Screw fed
units burn 60-1200 Ibs. coal/hour; ram fed, 400-3500 Ibs.
coal/hour. Multiple retort boilers produce 20,000 to
500,000 Ibs. steam/hour with burning rates up to
600,000 Btu/sq. ft. of grate area (see Figures 6.2.9 and
6.2.10).
Spreader Stokers—Employ a mechanical spreader or jets
of steam or air to throw solid fuel into furnaces where
it falls on a stationary or traveling grate (suspension
firing, see Figure 6.2.11). Control of smoke is good,
but overfire jets are essential, and high efficiency
collectors for particulates are required. A rotating
flipper mechanism throws the fuel onto the furnace grate.
The fuel thus burns partly in suspension and partly on ,
grates. Spreader stokers have a capacity of 6-500 X 10
Btu/hour.
Traveling Grate and Chain Grate (Figure 6.2.12) and
Vibrating Grate (Figure 6.2.13). The stoker carries fuel
from a hopper by a moving, endless grate system, through a
gate into and to the rear of the furnace. Ash is
continuously discharged. The vibrating grate includes a
high speed vibrating mechanism on a time cycle control
for homogenous distribution of coal sizes. Traveling and
chain grates have capacities of 20 to 300 x 10 Btu/hour;
vibrating grate, 350,000 - 500,000 Btu/sq. ft. hour.
-------
6.2.47
Figure 6.2.9. RESIDENTIAL UNDERFEED STOKER
SOURCE: NAPCA, REFERENCE 16.
COAL HOPPER
COAL RAMS
(DEL
DISCHARGE PLATE DISTRIBUTORS
Figure 6.2.10. MULTIPLE-RETORT UNDERFEED STOKER
SOURCE: NAPCA, REFERENCE 16.
Figure 6.2.11. SPREADER STOKER-FIRED FURNACE
SOURCE: NAPCA, REFERENCE 16.
-------
6.2.48
OVtRH RE-All||,
NO«IES
^_^ir— -lAZTii /
STOKER DRIVE HYDRAULIC
PLATE CHAIN SPROCKET OBI VE
Figure 6.2.12. B & W JET-IGNITION CHAIN-GRATE STOKER
SOURCE: NAPCA, REFERENCE 16.
COAL HOPPER
COAL GATE
OVE8FIHE-AIR HOZZLES
Figure 6.2.13. VIBRATING-GRATE STOKER FURNACE
SOURCE: NAPCA, REFERENCE 16.
-------
6.2.49
(2) Factors affecting Emissions. Spreader stokers tend to have
high fly ash carryover with high burning rates, and tend
to smoke at low burning rates. Otherwise, overall factors
affecting emissions from stoker equipment are similar and
include:
• Overall fuel properties, discussed in Part C
• Distribution of coal sizes on grate.
• Fuel bed thickness on grates.
• Grate speed.
• Air distribution and compartment pressure.
• Ash discharge and removal procedures.
These factors are discussed below.
(3) Fuels and Fuel Preparation:
• Almost any coal—including anthracite, coke breeze,
lignite—can be fired. Hogged wood, bark, and bagasse
can also be fired.
• Caking coals should be avoided. Coal can be preconditioned
by adding moisture for improved burnout of carbon and
removal of 1/4" fines for better air flow through grate,
but moisture in high sulfur fuels can cause corrosion of
equipment. Caking coals may be dried or weathered to
achieve the swelling or thickening desired.
• Bituminous coal should pass through 1" ring, and 60%
through 1/4" screen. Anthracite #2 coal should pass
through 5/16" - 3/16" screen; #5 through 3/64". Coke
breeze should pass through 3/8", less than 20% through
1/32" screen.
• Auxiliary gas and oil firing systems are frequently used
with chain grate stokers.
-------
6.2.50
• Underfeed stokers can fire a wide range of coal.
Note:
- Horizontal feed type is good for free-burning coal
sizes—1 1/4", zero nut, pea or slack in equal
proportions are most desirable.
- Anthracite can be burned separately or mixed with
bituminous coal.
- Stationary grates can burn coal with low ash fusion
temperatures without clinker problems. Agitating
type grates can burn coal with high caking tendencies.
• Coal hoppers should not be allowed to run empty,
particularly with spreader stokers.
(4) Stoker Conditions:
Traveling, Chain Grate, Vibrating Grate, Spreader
• Coal sizing should be distributed across width of -stoker
to prevent overheating of grates. Use of traversing
coal spout is desirable. Strips or areas of coarse
coal tend to mat.
• Coal gate opening controls fuel-bed thickness, and is
usually adjusted by hand.
• Fuel bed thickness for bituminous coal should be about
5" to 7"; for anthracite, 3 1/2" to 5".
• Grate speed should be maintained so. that ignition is
maintained at front end of stoker; the fuel should not
burn back to the raw coal gate.
• In spreader stokers, the thickness of the ash on the
grate at point of dumping governs speed of grate travel.
Bituminous ash thickness should be about 3" to 5".
Spreader controls are used to maintain proper fuel
distribution over active grate area.
• Grates should be maintained in good condition: broken
grates should be replaced.
-------
6.2.51
• Traveling and chain grate equipment may be able to
operate smokelessly from 10% to full load.
• With rapidly fluctuating loads, fuel bed is carried
longer; the rate of burning is reduced in second and
third compartments by lowering blast pressure and
increasing pressure slightly in rear compartments.
• If oil or gas is used, flame should not impinge on
furnace walls or grate surfaces. 4" - 5" layer of ash
should be maintained on chain grates. Firebricks or
false refractory floors should be used if changeover is
for a long period of time.
Underfeed
• Mechanical ram feeds coal to pusher blocks that distribute
coal in firebox. Note:
Separate overfire air systems.
- Grates must be kept cool. Hot spots can be noted
through wind box doors.
(5) Combustion Air and Firebox:
• All overfeed units have zoned controlled forced draft
undergrate provisions with automatic combustion control
systems, including individual sectionalized zone dampers.
• Responsive combustion control systems are particularly
required with spreader stokers.
• Overfire air is frequently used on all systems to burn
volatiles.
• Water cooling may be found in newer furnaces.
• Settings and seals on doors and ports should be used and
kept in good condition to prevent furnace air infiltration.
• Forced draft air pressure and grate speed are regulated
by steam pressure when automatic combustion controls are
used. Distribution of air in compartments under stoker
grate is adjusted manually. Boiler meters (C02 recorders)
will indicate pressures in various compartments by weight
of air. Highest air pressures are maintained in middle
-------
6.2.52
compartments, for most furnaces. Settings of pressure in
compartments are related to type of coal burned, e.g.,
- Bituminous coal—highest pressure in second compartment
1" - 3" water, depending on load and fuel bed thickness;
pressure in first compartment, 30 percent; pressure in
third, 60%. Pressure tapers to zero in last compartment.
- Small anthracite or coke breeze—air pressure in first
compartment is blanked off with dead plate and should
not exceed .1" of water. Pressures in succeeding
compartments are gradually increased with the highest
in the next to the last compartment.
• Spreader stokers should not be operated for long periods
with one section clean and another dirty. This impairs
the uniformity of air distribution. Excess air should be
in range of 25 to 40% (see Table 6.2.3).
• Combustion control system—air flow steam-flow proportions
air and fuel more accurately than does simple positioning
type of system (coal feed and air flow rates reduce with
drop in load).
• Multiple retort underfeed stoker—consists of several
indirect retorts side by side; tuyeres are located between
each retort
Forced air system is zoned beneath grates by air dampers.
- Combustion controls are fully modulating.
- Water cooled walls are used in larger systems.
- Air ports may be blocked by slag and should be checked.
(6) Ash Handling:
• Ash may be raked by hand or removed by a water sluice,
drag conveyor or jump pump, or dumped into a disposal
car and quenched.
• Ashes should be wet down when removed.
-------
C..2.53
Underfeed Units—ash is continuously discharged to pit
by side-dump grates
Water sprays in ash pit are sometimes used to cool
refuse immediately after burning.
Frequency of ash cleanings should be geared to
prevention of clinkering.
Uniform air fuel relation must be maintained over
entire stoker area.
- Air leaks through setting should be prevented.
- Ash should be kept on stoker grates as insulation
and protection against overheating.
Excess sittings should not be permitted to build-up
in stoker wind boxes.
b. Pulverized Fuel-Burning Equipment
(,1) Function and Types
Pulverised Coal-Firing Equipment—Coal is dried and
ground into powder and fed to burners in a manner similar
to oil-burning equipment. Pulverized coal-firing and
cyclone furnaces represent the principal firing methods
for large coal-firing steam generating stations.
Pulverized coal-firing equipment is used in steam
generation, cement, metallurgical processes including
copper and nickel ore smelting. Capacities run from
200,000 to several million pounds steam/hour.
Various types of pulverized coal-firing equipment are
important from the standpoints of gathering identifying
and descriptive information for inventory and registration
inspections and emission potentials. These include the bin
system in which coal is ground and then conveyed to storage
by a pneumatic transport system to the burners of the
furnace (.Figure 0.2.14) and the Direct-Firing system
where the pulverizer is integral to the combustion
system (Figure 6.2.151.
-------
6.2.54
ELECTROPNEUMATIC
CONTROL MECHANISM-
ft ff
=
I PRESSURE-REGULATING
PULVERIZED.COAL VALVE
FEE° H°PPER ' AIR L,NE FROM
-1
— HIGH-PRESSURE
AIR LilNE
Figure 6.2.14. PULVERIZED-COAL BIN SYSTEM. PNEUMATIC
TRANSPORT SYSTEM FOR CONVEYING PULVERIZED
COAL. CAPACITY 1 to 100 TONS PER HOUR
SOURCE: BABCOCK AND WILCOX, REFERENCE 1.
-------
6.2.55
Figure 6.2.15.
STIRLING TWO-DRUM BOILER (B&W).
INDIRECT-FIRED WITH PULVERIZED COAL
COMPONENTS OF THE DIRECT-FIRING
SYSTEM, IN GENERAL, ARE AS FOLLOWS:
1. Steam or gas air heater to supply hot air to the pulverizer for
drying the coal as pulverized.
2. Pulverizer fan, known as the primary-air fan, arranged either as an
exhauster or as a blower.
3. Pulverizer arranged to operate under suction or pressure.
4. Automatically controlled raw-coal feeder.
5. Coal-and-air conveying lines.
6. Burners.
SOURCE: BABCOCK AND WILCOX, REFERENCE 1.
-------
6.2.56
Furnaces may also be classified with respect to handling
of ash as wet bottom and dry bottom.
Wet bottom (slag tap)—molten ash accumulates on
lower walls and floor of furnace and flows through
slag tap; 50% may be entrained in the flue gases as
fly ash. Units may or may not be equipped with slag
screens which are water tubes set perpendicular to the
gas flow, the purpose of which is to reduce the
temperature of the ash particles in suspension below
their sticky or tacky temperature to avoid build-up
of slag in closely spaced tube banks.
Dry bottom—residual particles are cooled below
melting point before contact with heat absorption
surfaces—60 to 80% of residuals leave as fly ash.
Other types—these include applications in the
metallurgical industry, shown in Figure 6.2.16.
(2) Factors Affecting Fjnissions
• Principal emission problems include fly ash, particulates,
fines, SOX and NOX. Tall stacks are employed, usually
400 to 1,000 feet in height. Coal fines may be emitted
from the stacks, as well as from vents on coal storage
bins and the pulverizer system. Emissions from the
combustion system are primarily related to coal-air
ratios in the transport system and burners, finess of coal
and excess air. Values for these variables must be
determined in each situation.
• Typical particulate emissions: a 200 megawatt station
burning 1800 tons coal/day will produce 360 tons ash and
emit 290 tons particulates/day, uncontrolled; 30 tons/day,
controlled. Dust collectors (e.g., baghouses) should be
required on stacks and pulverizer system vents.
(3) Fuels, Fuel-Preparation and Transport
• In conducting inventory and other inspections where
inspectors must describe equipment, the inspector should
gather information sufficient to complete his understanding
of the combustion system and to establish normal and
abnormal practices with regard to fuel properties, and
fuel preparation and transport. This information should
-------
6.2.57
AUXILIARY PULVERIZED-
COAL BURNERS
A
BALLOON FLUE
BY-PASS
STEAM COIL
AIR HEATER
ULVERIZERS
Figure 6.2.16. DIRECT-FIRED COPPER REVERBERATORY-FURNACE
AND WASTE-HEAT-BOILER ARRANGEMENT
SOURCE: BABCOCK AND WILCOX, REFERENCE 1,
-------
6.2.58
include: grindability, rank, moisture, volatile matter
and ash content of coals used in firing. Fuels with
moisture content as high as 20% (surface, 15%) can be
fired if dried in the pulverizer at 600°F. At least 70%
of the pulverized fines should pass through a 200 mesh.
In checking the pulverizer equipment, the inspector
should report the apparent condition of grinding elements,
extent of rejection of oversize fuel, and extent of the
production and handling of superfines. The inspector
should also determine the grindability of coal which is
based on a hardness index. Coals <100 are harder than
coals >100.
• The inspector should check the transport system and type
of pulverizer used: impact, tube-mill, roll and race,
ball and race. He should inquire as to the capacity of
the air transport system, and moisture and fineness in
bin systems. In general, a high velocity, uniform coal/
air mixture is desirable. Air/coal ratios are increased
at lower loads and decreased at higher loads. Pitot tube
and orifices are frequently used by furnace operators
to meter the air in the transport system. This information
should be available to the inspector.
• Direct firing-coal feed is adjusted to load demand;
primary air supply is regulated to coal feed, or primary
air through the pulverizer is controlled proportional to
the load demand, and coal feed is automatically adjusted
to the rate of the air flow.
• The pulverizer may grind only or may grind, feed, dry,
classify, circulate and transport, or these functions may
be conducted in separate equipment.
• Dust cleaning devices should be used on bin systems.
(4) Burner
In conducting routine, incident or inventory inspections,
the inspector should record the following:
Burner type: horizontal, vertical, tangential,
circular, multiple-intertube multitip, cross-tube
(see Figures 6.2.17, 6.2.18, and 6.2.19).
-------
6.2.59
Figures 6.2.17 and 6.2.18 not available for this publication.
-------
6.2.60
Figure 6.2.19 not available for this publication.
-------
6.2.61
Adjustment of coal/air distributors and nozzles.
- Number bends in coal pipe.
Use of correcting distributors.
Dispersion of fuel stream from the piping
over the burner area.
(5) Firebox and Firing Conditions;
• Complete combustion with minimum excess air is desirable
to maintain fuel stream ignition stability and to reduce
particulate emissions.
• Usual excess air is 15 to 40% by weight; excess air of
15 to 22% may help to keep the combustible content of
the particulate emission under 10%.
• The inspector should establish burner clearance to
confining furnace walls. Fire should show a uniform and
symmetrical pattern, predominantly bright with some short
dark streaks. Burner flames should not blast against
furnace walls. The inspector should check the condition
of refractory walls for evidence of flame impingement, and
external surface of furnace tubes for corrosion. Tube
wastage may be due to high heat release, high sulfur and
alkaline coals, and areas deficient in oxygen.
c. Cyclone Furnaces
(1) Function and Types
• Fires crushed coal nearly as fine as pulverized coal into
refractory lined cylindrical chamber. The furnace is used
for cooling. Combustion air tangentially enters burner and
imparts whirling motion to incoming coal, hence cyclone
furnace. These furnaces are designed to burn low grades and
ranks of high ash, low fusion temperature coal and are used
to generate steam, similar to pulverized coal burning
equipment. The size range of cyclone units is generally
comparable to pulverized fuel units. The allowable range
of maximum heat input is 100 to 500 million Btu/hour. The
principal types of furnaces are screened and open, as shown
in Figure 6.2.21. Coal preparation and feeding systems
include bin and storage, Figure 6.2.22.
-------
6.2.62
Figure 6.2.20. A 700,000-kw-CAPACITY B&W UNIVERSAL-PRESSURE
BOILER, ONE OF THE LARGEST IN THE WORLD
SOURCE: BABCOCK AND WILCOX, REFERENCE 1.
-------
6.2.63
(1)
SCREENED-FURNACE
ARRANGEMENT
«,, *
OPEN-FURNACE
ARRANGEMENT
I2b)
OPEN-FURNACE
ARRANGEMENT
Figure 6.2.21. TYPES OF BOILER FURNACES USED WITH CYCLONE FURNACES
SOURCE: BABCOCK AND WILCOX, REFERENCE 1.
-------
BIN FIRING SYSTEM
CONVEYOR
DIRECT.FIRING SYSTEM
Figure 6.2.22. BIN-FIRING AND DIRECT-FIRING SYSTEMS FOR COAL
PREPARATION AND FEEDING TO THE CYCLONE FURNACE
(SCHEMATIC)
SOURCE: BABCOCK AND WILCOX, REFERENCE 1.
-------
6.2.65
(2) Emissions
15 percent ash is emitted as extremely fine particles; 85%
retained as molten slag. Particulates are difficult to
collect and high efficiency collectors are required. NOX
emissions are likely to be greater than for other comparable
coal fired equipment. Fly ash rate is lower than for
pulverized units. A 200 megawatt station, uncontrolled,
may emit 30 tons/day fly ash.
(3) Fuel and Fuel Preparation
• Suitability of solid fuel is based primarily on viscosity
of slag formed from molten ash. At 2600°F viscosities
exceeding 250 poises cause difficulty in tapping slag.
• Petroleum by-products and waste fuels such as bark can
be burned. Petroleum products may range in volatile
matter from as low as 5% for petroleum coke to as high
as 60% for pitch. Coal chars may also be burned. Oil
or gas can also be fired in cyclone furnaces (see
Figure 6.2.23). Coal is crushed so that 95% passes
through 4 mesh screen.
(4) Burners
• The fuel is burned quickly and completely in a small
cyclone chamber; the boiler furnace is used only for
cooling of flue gases. The coal is ignited by a
permanently installed gas lighting or retractable oil
lighting torch. Fuel is fired and heat is released at
extremely high rate—500,000 to 900,000 Btu/cu. ft./hr.
Gas temperatures exceeding 3,000°F are developed. 20
percent of the combustion air enters the cyclone burner.
Excess air required is less than 10 percent; 10 to 15
percent with automatic controls.
2. Oil-Burning Equipment
To burn oil in combustion equipment, fuel oil must be atomized into
finely divided liquid droplets. This is accomplished by forcing oil
under pressure through a nozzle, use of steam or air under pressure
(which can range from 1/2 to 1,000 psig), or by mechanical means, as
in the rotary cup type of burner.
-------
6.2.66
SAS BURNER.
Figure 6.2.23. OIL AND GAS BURNERS FOR THE CYCLONE FURNACE
SOURCE: BABCOCK AND WILCOX, REFERENCE 1.
-------
6.2.67
Atomizing burners are used primarily in heating, stationary power,
locomotive and marine installations. Mechanical atomizing burners
of the spray nozzle type are usually used with power plant steam
generating units. The rotary cup burner is usually used in low
pressure installations.
In the low pressure, air atomizing burner (Figure 6.2.24) most of the
combustion air is supplied near the oil orifice at 1/2 to 5 psig.
Secondary combustion air flows around the periphery of the mixture.
Since most of the combustion air supplied to the burner is close to
the burner tip, this type of burner produces a short flame.
In high pressure steam or air atomizing burners, steam or air at
pressures ranging from 30 to 150 psig is applied to atomize the oil
steam at the burner tip (see Figure 6.2.25). These burners are
often used on an oil standby basis. Steam atomizing burners appear to
perform well at oil viscosities of 150 to 200 saybolt seconds
universal (SSU). Air atomizing burners can operate at 80 to 100 SSU.
Oil pressure atomizing burners. Oil is mechanically atomized by the
force of high fuel pressure (75 to 150 psig) through small fixed
orifices. The burner performs satisfactorially only over a fairly
narrow pressure range.
In the wide range mechanical atomizing burner a strong whirling
action is imparted to the oil which is then released through the
orifice, while excess oil is drawn off through the central oil line.
Proper atomization is dependent upon centrifugal velocities, which
require high pressures, e.g., 100 to 200 psig.
-------
6.2.1
Figure 6.2.24. LOW-PRESSURE, AIR-ATOMIZING OIL BURNER (HAUCK
MANUFACTURING CO., 1953)
SOURCE: WALSH, REFERENCE 3.
CLEAN-OUT PLUG
OIL VALVE / PACKING
HOLE FOR PILOT TIP .fl. TILE
ALLOY
NOZZLE'
STEAM OH COMPRESSED
OIL INLET AIR INLET
Figure 6.2.25. HIGH PRESSURE, STEAM- OR AIR-ATOMIZING OIL BURNER
(NORTH AMERICAN MANUFACTURING CO, 1952)
SOURCE: WALSH, REFERENCE 3.
-------
6.2.69
In the rotary cup burner (Figure 6.2.26) the oil is fed through a hollow
rotating shaft. A hollow cup on the end of the shaft throws the oil
from its edges in the form of fine liquid droplets. Air is not mixed
with the oil before atomization, and combustion air is admitted
through an annular port around the rotary cup. Rotary cup burners can
be used to burn oils of widely varying viscosity, ranging from
distillate to residuals greater than 300 SSU.
Strainers and filters which remove sludge are essential to good
combustion. The removal of sludge reduces burner wear and increases
burner efficiency. Also, viscosity must be controlled. Fuel oils with
viscosities less than 100 SSU can be burned efficiently in almost any
burner. Most burners optimally perform at 150 SSU or lower. Distillate
oils and some blends are rated at less than 100 SSU.
When oil viscosity is not satisfactory, preheaters must be used,
particularly with grades 5 and 6 oil. Oil preheaters are used to
improve viscosity, and may be mounted directly on the burner, at the
supply tank or any place in between. Preheaters operate with either
electricity or steam. Typical oil preheat temperatures necessary
to obtain a suitable viscosity for atomization is usually between
150 and 200°F.
The principal air contaminants affected by burner design and operation
are oxidizable materials: carbon, carbon monoxide, aldehydes, organic
acids, unburned hydrocarbons, and soot and other particulates. The
principal causes of smoke and incomplete combustion are:
• Burner and fuel not compatible.
• Burner not properly adjusted or operated.
• Burner improperly maintained.
-------
6.2.70
MOUNTING
HINGE —*(P
Figure 6.2.26. ROTARY CUP OIL BURNER (HAUCK
MANUFACTURING COMPANY, 1953)
SOURCE: WALSH, REFERENCE 3.
-------
6.2.71
Burner adjustment can be critical. A well adjusted air atomizing
unit is capable of producing as little as 12 to 14 lbs./l,000 gallons
of heavy oil burned. This would equal .034 to .04 gr./SCFD at 50%
excess air during normal operation. Oil burner servicemen should
adjust burners, particularly light oil burning installations, to
achieve a specified Bachrach limitation, for example #1, with
allowance for degradation of performance with operating time. Some
burners may need more efficient replacement burners. Some agencies
include Bachrach limitations in their legislation. Proper adjustment
of burners can result in a 30% decrease in particulate (soot) emissions.
Smaller furnaces using residual oil may have a greater tendency to burn
fuel inefficiently, thus causing substantial soot emissions and
resulting in relatively higher operating costs.
Table 6.2.16 classifies oil-burners according to application and
possible pollutants emitted. Common causes of poor combustion in
boilers are shown in Table 6.2.17. ' When lighting off a cold boiler,
the operator should
1. Open stack damper and air registers (allow sufficient time
for any accumulated gases to be dissipated).
2. Recirculate fuel oil until proper temperature is reached
at the burners.
3. Insure sufficient oil pressure on the burner header line.
4. Thoroughly blow out all condensate in the atomizing steam
line (make sure atomizing steam to burner is dry).
5. Be sure that burner to be used in "lighting off" is clean.
6. Use small orifice tips (pressure burner).
7. Only one burner (on boilers fitted with multiple burners)
should be used until refractory is relatively hot.
-------
6.2.72
Table 6.2.16. CLASSIFICATION OF OIL BURNERS ACCORDING TO APPLICATION
AND LIST OF POSSIBLE POLLUTANTS
Burner type
Domestic"
Pressure atomizing
Rotary
Vaporising
Commercial, Industrial
Pressure atomizing
Applications
Residential
furnaces,
water heaters
Residential
furnaces,
water heaters
Residential
furnaces,
water heaters
Steam boilers,
process
furnaces
Oil type Defects which may cause
usually used odors and smoke
No. 1 or 2 Increased viscosity of oil;
no//.le wear; clogged Hue,
gas passes, or chimney; dirt
clogging air inlet; oil rate
in excess of design
No. 1 or 2 Increased viscosity of oil;
clogged noi/le or air sup-
ply; oil rate in excess of
design
No. 1 Fuel variations; clogged Hue
gas passages, or chimney;
clogged air supply
No. 4, 5 Oil preheat loo low or too
high; nozzle wear; nozzle
partly clogged; impaired air
supply; clogged flue gas pas-
sages; poor draft; over-
loading
Horizontal rotary Steam hollers, No. 4, 5, 6 Oil preheat too low or too
cup process high; burner partly clogged
furnaces or dirty; impaired air sup-
ply; clogged due gas pas-
sages; poor draft; over-
loading
Steam atomizing Steam boilers, No. 5, 6 Oil preheat too low or too
process high; burner partly clogged
furnaces or dirty; impaired air supply;
clogged Hue gas passages;
pooi draft; overloading; in-
sulhcient alomi/.mg pressure
Air atomizing Steam boilers, No. 5 Oil preheat too low or too
process high; humor pan!) dogged
furnaces or diri\, impaired air sup-
ply; clogged Hue gas pas-
sages; poor draft; overload-
ing; insufficient atomizing
pressure
" Commercial M.ind.ml CS-75 established by U.S. Dc-pl. ol Commerce requires that all
oil burners labeled as complying with the standard shall ha\e smoke-free combuslion.
Source: Engdahl, Reference 5.
-------
6.2.73
Table 6.2,17- COMMON CAUSES AND RESULTS OF POOR COMBUSTION
Cause
Insufficient air or too
much oil (improper air-
fuel ratio)
Poor draft
Excess air (causing white
smoke
Dirty or carbonized burner
tip (caused by improper
location, insufficient
cleaning at regular inter-
vals)
Carbonized or damaged
atomizing cup (rotarv cup)
Worn or damaged orifice
hole
Improper burner adjustment
(diffuser plate protruding
improper distance)
Oil pressure to burner tno
hisrh or too low
Oil viscositv too high
Oil viscosity too low (too
high fuel oil temperature)
Forcing burner (especially
after initial light-off or
when combustion space is
relatively cold)
Insufficient atomizing steam
Water in fuel oil
Dirty fuel oil
Fluctuating oil pressure
Incorrect furnace con-
struction causing flame
and oil impingement
Carbon clinker on furnace
floor or walls
Incorrect atomizer tip size
Condensate in atomizing
steam
Atomizing steam pressure
too high
Furnace cone angle too
wide
Furnace cone angle too
narrow (making it neces-
sary to have atomizer in
maximum position)
Atomizer not immediately
removed from burner
being secured
Result
Smoking Carbon formation
fire in the boiler
X X
X Sometimes
Pulsating
fire
X
X
X
X X
X X
X X
X X
Sometimes
X X
X Sometimes
X
X X
X
X
X X
X
X X
Intermittent
X
X
X
X
X X
X
X
X
X
X
X
X
X
Source: Parmelee and Elliot, Reference 17.
-------
6.2.74
8. Use most centrally located burner during the initial period.
9. Allow sufficient time to bring cold boiler up very gradually
to operating temperature and pressure. (2 to 3 hours for
water tube boilers and 8 to 10 hours for fire-tube boilers.
This time may be less for smaller boilers.)
3. Gas-Burning Equipment
Gas fired burners are of three types: atmospheric, multiple port,
and forced draft, as shown in Figures 6.2.27 and 6.2.28.^ ' in gas fired
equipment, the jet of raw gas draws with it atmospheric or primary
air which mixes with the gas in the burner. Secondary air is drawn
into the combustion chamber by action of draft or thermal head.
Industrial gas burners are usually of the atmospheric or power
driven type in which intense mixing is provided by a blower.
Emissions from gas burning equipment are generally lower than for
other operations. Smoke from this equipment is rare, although units
have been known to smoke when dampers or secondary air regulators are
severely out of adjustment. The generally smokeless condition of this
equipment can cause complacency especially with regard to CO and NO
emissions, which can be considerable. Multiple port burners are, in
general, associated with comparatively larger NO emissions.
X
Combustion efficiency may be generally lower than for coal and oil
fired operations for similar reasons. Air/fuel ratios can vary
widely and should be periodically checked. Excess air in gas fired
equipment should be maintained below 25%.
-------
6.2.75
Figure 6.2.27. TYPICAL ATMOSPHERIC GAS BURNER
SOURCE: WALSH, REFERENCE
ZERO-PRESSURE
REGULATOR
Figure 6.2.28. A MULTIPLE-PORT BURNER (NONPRIMARY AERATED)
INSTALLED IN A VAPOR INCINERATOR
SOURCE: WALSH, REFERENCE
-------
6.2.76
REFERENCES
1. Steam, Its Generation and Use. Babcock and Wilcox Co. 37th Edition.
2. Chemical and Engineering News. Staff Article. July 19, 1971. pp. 29-33.
3. Walsh, R. T. Combustion Equipment. In: Air Pollution Engineering Manual,
J. A. Danielson (ed.). Cincinnati, DHEW, PHS, National Center for Air
Pollution Control and the Los Angeles County Air Pollution Control District.
PHS No. 999-AP-40. 1967.
4. Smith, W. S. Atmospheric Emissions from Fuel Oil Combustion. DHEW, PHS,
DAP. Cincinnati, Ohio. November 1962.
5. Engdahl, R. B. Stationary Combustion Sources. In: Air Pollution,
Vol. Ill, A. C. Stern (ed.). New York City, Academic Press, 1968.
6. Control Techniques for Sulfur Oxide Pollutants. Washington, D.C.,
DHEW, PHS, NAPCA, January 1969.
7. Control Techniques for Nitrogen Oxide Emissions from Stationary Sources.
Washington, D.C., DHEW, PHS, NAPCA, March 1970.
8. Control Techniques for Carbon Monoxide Emissions from Stationary Sources.
Washington, D.C., DHEW, PHS, NAPCA, March 1970.
9. Control Techniques for Particulate Air Pollutants. Washington, D.C.,
DHEW, PHS, NAPCA, January 1969.
10. State of New Jersey. Air Pollution Control Code. Chapter 10, Sulfur in
Fuels. Chapter lOa, Sulfur in Coal. Air D4 1, Apr 70. Air D-30-A,
May 1968.
11. Smith, W. S., and C. W. Gruber. Atmospheric Emissions from Coal
Combustion—An Inventory Guide. DHEW, PHS, DAP. Cincinnati, Ohio.
April 1966.
12. Bunkie's Guide to Fuel Oil Specifications. National Oil Fuel Institute,
Inc. NOFI Technical Bulletin No. 68-101.
13. State of New Jersey. Fuel Survey Form. Department of Health.
14. Federal Register. Vol. 36, Nos. 158 and 159. August 14 and 17. 1971.
15. Crumley, P. H., and A. W. Fletcher. The Formation of Sulfur Trioxide in
Flue Gases. J. Inst. Fuel. 29:322-27, August 1956.
-------
6.2.77
16. Visible Emissions Evaluation. DHEW, PHS, NAPCA. (No date).
17. Parmelee, W. H., and J. H. Elliott. Operation of Oil Burners on Steam
Boilers. Los Angeles County Air Pollution Control District. #18.
-------
6.3.1
III. INCINERATORS
A. INTRODUCTION
Incineration is the disposal of waste materials by burning in an enclosed
structure especially designed for this purpose. The boxlike or cylindrical
structure serves to confine the fuel pile, regulate the air supply and pro-
vide some control over the rate and degree of combustion.
Incinerators are a major source of smoke, particulates and a wide variety
of gaseous contaminants, particularly in communities that rely on them as
a principal means of waste disposal. Proper combustion in incinerators is
a science and skill beyond the capability and patience of most operators.
Provided that acceptable methods of waste disposal are available—such as
sanitary land fills—the use of small incinerators by the residential and
much of the commercial and industrial sectors of the economy should be
prohibited, as has been done in several communities. Many urban areas are
establishing new regulations limiting emissions from incinerators to
0.1 grains per standard cubic foot or .20 Ibs per 100 Ibs charged and more
stringent opacity requirements. Specific requirements for incinerator
design, auxiliary combustion equipment and particulate control systems are
also being established. This legislation will thus prevent the installation
of incinerators that cannot meet emission standards.
The principles of incinerator combustion are similar to those described in
the fuel-burning section of this chapter. In the burning of solid wastes,
three stages are involved: (1) water evaporation, (2) distillation and
combustion of volatile matter and (3) reaction of fixed carbon with oxygen.
Effective incinerator design depends on the satisfaction of requirements
for time, temperature, turbulence and oxygen. This is best achieved by
the multiple-chamber type of incinerator design. Single-chamber incinera-
tors, as a class, cannot meet new emission standards and their use should
not be permitted.
-------
6.3.2
The variability of the composition, moisture, volatility and weight of waste
materials and charging rates and methods presents problems which differ from
those of fuel-burning in which fuels, burners and other factors are maintained
on a comparatively steady-state basis and are subject to a greater degree of
control on the part of operators. Particular attention must be paid, with
incinerators, to assure the following:
• Air and fuel must be in proper proportion. Adequate provision
should be 'given for underfire and overfire air (where required).
Admission of air due to infiltration through cracks and doors
should be prevented-
• Air and fuel, especially combustible gases, must be mixed
adequately.
• Temperature must be sufficient for ignition of both the solid refuse
and the gaseous components. Low temperatures will cause incomplete
oxidation reactions and consequent air pollution emissions;
excessive high temperatures will cause equipment and structural
damage, refractory failure, slag build-up in the furnace linings
(in large installations) and increases in oxides of nitrogen
emissions•
• Furnace volumes must be large enough to provide the retention time
needed for complete combustion.
• The incinerator should have provisions to dry the refuse in order
to facilitate ignition. This can be accomplished through design,
operation, moving grates or the use of auxiliary burners.
• Furnace proportions must be such that ignition temperatures are
maintained and fly ash entrainment is minimized.
Enforcement personnel will be primarily concerned with the identification
of incinerators by design and type, identification of incinerator appurte-
nances, construction materials and the condition and operation of incin-
erators. The inspector should be familiar with the operating instructions
-------
6.3.3
for specific incinerators and equipment, such as auxiliary fuel burners,
afterburners, methods of priming and light-off of cold incinerators and
burning of highly combustible materials, air port adjustments and refuse
charging and burndown procedures.
B. INCINERATOR DEFINITIONS AND TERMINOLOGY
The definitions given below apply to incinerators as typically defined in
ordinances and give commonly used nomenclature.
INCINERATOR TYPES ^
1. INCINERATOR: Any device, apparatus, equipment or structure used for
destroying, reducing or salvaging by fire any material or substance in-
cluding but not limited to refuse, rubbish, garbage, trade waste, debris
or scrap or a facility for cremating human or animal remains.
2. COMMON INCINERATOR: An incinerator designed and used to burn waste
materials of Types 0, 1, 2, and 3 only, in all capacities not exceeding
2,000 pounds per hour of waste material input. (See Table 6.3.1.)
3. SINGLE-CHAMBER INCINERATOR: Incinerator in which one chamber serves for
ignition, combustion and ash removal.
A. SPECIAL INCINERATOR: Municipal, pathological waste, or trade waste
incinerator of any burning capacity, or any incinerator with a burning
capacity in excess of 2,000 pounds per hour.
5. MUNICIPAL INCINERATOR: An incinerator owned or operated by government
or by a person who provides incinerator service to government or others,
and designed and used to burn waste materials of any and all types,
0 to 6 inclusive.
6. PATHOLOGICAL WASTE INCINERATOR: An incinerator designed and used to
burn Type 4 waste materials, primarily human and animal remains, in all
burning capacities. Crematoriums are included in this category.
7. TRADE WASTE INCINERATOR: An incinerator designed and used to burn waste
material primarily of Types 5 and 6, either separately or together with
waste materials of Types 0, 1, and 3.
8. FLUE-FED APARTMENT INCINERATORS: Either a single-chamber or multiple-
chamber type of incinerator in which the chimney also serves as a chute
for refuse charging. Some incinerators may have exhaust flues separate
from the charging chutes.
-------
Table 6.3.1 CLASSIFICATION OF WASTE TO BE INCINERATED
Classification of Wastes
Type Description
*0 Trash
*1 Rubbish
*2 Refuse
*3 Garbage
4 Animal
solids and
organic
wastes
Principal Components
Highly combustible
waste, paper, wood,
cardboard cartons.
including up to 10%
treated papers.
plastic or rubber
scraps; commercial
and industrial
sources
Combustible waste,
paper, cartons, rags.
wood scraps, combus-
tible floor sweepings;
domestic commercial,
and industrial sources
Rubbish and garbage;
residential sources
Animal and vegetable
wastes, restaurants.
hotels, markets;
institutional.
commercial, and
club sources
Carcasses, organs,
solid organic wastes;
hospital, laboratory,
abattoirs, animal
pounds, and similar
sources
5 Gaseous, Industrial
liquid or 'process wastes
semi- liquid
wastes
6 Semi- solid
and solid
wastes
Combustibles requiring
hearth, retort, or grate
burning equipment
Approximate
Composition
% by Weight
Trash 100%
Rubbish 80%
Garbage 20%
Rubbish 50%
Garbage 50%
Garbage 65%
Rubbish 35%
100% Animal
and H im,v.:
Tissue
Variable
Variable
Moisture
Content
%
10%
25%
50%
70%
85%
Dependent
on pre-
dominant
components
Dependent
on pre-
dominant
components
B.T.U.
Incombus- Value /lb.
tible |Of Refuse
Solids % |as fired
5% 8500
i
i
i
i
10% 6500
7%
4300
5% J2500
i
5%
Variable
accord-
ing to
wastes
survey
Variable
accord-
ing to
wastes
survey
1000
B.T.U.
of Aux. Fuel
Per lb.
of Waste
to be
included in
Combustion
Calculations
0
Recommended
Min. B.T.U. /hr,
Burner Input
per lb.
Waste
0
0
0
1500
3000
Variable
accord-
Variable
according
ing to i to wastes
wastes • survey
survey
Variable
according
to wastes
survey
Variable
according
to wastes
survey
0
1500
3000
8000
(5000 Primary)
(3000 Secondary)
Variable
according
to wastes
survey
Variable
according
to wastes
survey
*The above figures on moisture content, ash, and B. T. U. as fired have been determined by analysis of many samples. They are
recommended for use in computing heat release, burning rate, velocity, and other details of incinerator designs. Any design based on
these calculations can accommodate minor variations.
U)
-P-
SOURCE: Kaiser, Reference 2.
-------
6.3.5
9. WOOD-WASTE BURNING INCINERATORS: These include wigwam, silo type or
multiple-chamber incinerators designed to burn wood waste produced from
lumber mills and wood working industries. These incinerators are usually
continuously fed from pneumatic and mechanical feed systems.
10. MULTIPLE CHAMBER INCINERATOR: An incinerator with two or more refractory-
lined combustion chambers in series physically separated by refractory
walls, interconnected by gas passages, and employing adequate design
parameters necessary for maximum combustion of the waste materials.
Multiple-chamber incinerators are of two types: Retort, in which the flow
of gases is returned through a "U" arrangement and, the In-line type, in
which the flow of gases is through each of three successive chambers. The
former is intended for smaller operations, the latter for larger operations.
Multiple-chamber incinerator design principles and standards can be
applied to all incinerator functions listed here, including apartment
flue-fed incinerators.
11. MOBILE MULTIPLE CHAMBER: Specially designed and constructed multiple-
chamber incinerators mounted on wheels, constructed of light-weight
materials and limited in size to comply with state vehicle codes. These
incinerators are intended for use in land-clearing operations as a
substitute for open burning.
12. RECLAMATION INCINERATORS: A special incinerator designed to reclaim
electrical equipment windings or to debond brake shoes.
INCINERATOR NOMENCLATURE
1. AUXILIARY-FUEL FIRING EQUIPMENT: Equipment to supply additional heat,
by the combustion of an auxiliary fuel, for the purpose of attaining
temperatures sufficiently high (a) to dry and ignite the waste material,
(b) to maintain ignition thereof, and (c) to effect complete combustion
of combustible solids, vapors, and gases.
2. BAFFLE: A refractory construction intended to change the direction of
flow of the products of combustion.
3. BREECHING: The connection between the incinerator and the stack.
4. BREECHING BY-PASS: An arrangement of breeching and dampers to permit
the intermittent use of two or more passages for products of combustion
to the stack or chimney.
5. BRIDGE-WALL: A partition wall between chambers over which pass the
products of combustion.
-------
6.3.6
6. BTU (BRITISH THERMAL UNIT): The quantity of heat required to increase
the temperature of one pound of water from 60 to 61 F.
7. BURNERS: Primary—A burner installed in the primary combustion chamber
to dry out and ignite the material to be burned.
Secondary—A burner installed in the secondary combustion chamber to
maintain a minimum temperature of about 1400 F. It may also be considered
as an after-burner.
After-burner—A burner located so that the combustion gases are made to
pass through its flame in order to remove smoke and odors. It may be
attached to, or be separated from the incinerator proper.
8. BURNING AREA: The horizontal projected area of grate, hearth, or
combination thereof on which burning takes place.
9. BURNING RATE: The amount of waste consumed, usually expressed as
pounds per hour per square foot of burning area. Occasionally expressed
as BTU per hour per square foot of burning area, which refers to the
heat liberated by combustion of the waste.
10. CAPACITY: The amount of a specified type or types of waste consumed
in pounds per hour. Also may be expressed as heat liberated, BTU
per hour, based upon the heat of combustion of the waste.
11. CHECKER-WORK: Multiple openings above the bridge-wall, and/or below
the drop arch, to promote turbulent mixing of the products of combustion.
12. CHUTE, CHARGING: A pipe or duct through which wastes are conveyed from
above to the primary chamber, or to storage facilities preparatory to
burning.
13. COMBUSTION AIR: Primary—Air introduced to the primary chamber through
the fuel bed by natural, induced, or forced draft.
Secondary—Air supplied in the secondary combustion chamber usually
through the bridge wall (see Figure 6.3.1 in part C).
Theoretical—Air, calculated from the chemical composition of waste,
required to burn the waste completely without excess air. Also
designated as Stoichiometric air.
Excess—Air supplied in excess of theoretical air, usually expressed
as a percentage of the theoretical air.
14. COMBUSTION CHAMBER: Primary—Chamber where ignition and burning of
the waste occur.
-------
0.3.7
Secondary—Chamber where combustible solids, vapors, and gases from the
primary chamber are burned and settling of fly ash takes place.
15. CURTAIN WALL OR DROP ARCH: A refractory construction or baffle which
serves to deflect gases in a downward direction.
16. DAMPER: A manual or automatic device used to regulate the rate of flow
of gases through the incinerator.
Barometric—A pivoted, balanced plate, normally installed in the breeching,
and actuated by the draft.
Guillotine—An adjustable plate normally installed vertically in the
breeching, counterbalanced for easier operation, and operated manually
or automatically.
Butterfly—An adjustable, pivoted, plate normally installed in the breeching.
Sliding—An adjustable plate normally installed horizontally or vertically
in the breeching.
17. DRAFT: The pressure difference between the incinerator, or an}'
component part, and the atmosphere, which causes the products of combustion
to flow from the incinerator to the atmosphere.
Natural—The negative pressure created by the difference in density
between the hot flue gases and the atmosphere.
Induced—The negative pressure created by the action of a. fan, blower,
or ejector, which is located between the incinerator and the stack.
Forced—The positive pressure created by the action of a fan or blower,
which supplies the primary or secondary air.
IS. FLU! GAS WASHER OR SCRUBBER: Equipment for removing fly ash and other
objectionable materials from the products of combustion by means of
sprays, wet baffles, etc. Also reduces excessive temperatures of effluent.
19. FLY ASH: All solids including ash, charred paper, cinders, dust, soot, or
other partially incinerated solid matter, carried in the products of combustion
20. FLY ASH COLLECTOR: Equipment for removing fly ash from the products of
combustion.
21. GRATE: A surface with suitable openings, to support the fuel bed and
permit passage of air through the fuel. It is located in the primary
combustion chamber and is designed to permit the removal of the unburned
residue. It may be horizontal or inclined, stationary or movable, and
operated manually or automatically.
-------
6.3.8
22. HEARTH: Cold drying—A surface upon which wet waste material is placed
to dry prior to burning by the actual hot combustion gases passing only
over the wet material.
Hot drying—A surface upon which wet material is placed to dry by the action
of hot combustion gases that pass successively over the wet material
and under the hearth.
23. HEAT OF COMBUSTION: The amount of heat, usually expressed as BTU per
pound of as-fired or dry waste, liberated by combustion at a reference
temperature of 68°F. With reference to auxiliary gas it is expressed as
BTU per standard cubic foot, and to auxiliary oil as BTU per pound or
gallon.
24. HEAT RELEASE RATE: The amount of heat liberated in the primary
combustion chamber, usually expressed as BTU per hour per cubic foot.
25. HEATING VALUE: Same as heat of combustion.
26. INCINERATOR: Equipment in which solid, semi-solid, liquid or gaseous
combustible wastes are ignited and burned, the solid residues of which
contain little or no combustible material.
27. MIXING CHAMBER: A chamber usually placed between the primary combustion
chamber and an expansion chamber wherein thorough mixing of the products
of combustion is accomplished by turbulence created by increased velocities
of gases, checkerwork, and/or changes in direction of the gas flow.
28. SETTLING CHAMBER: Chamber designed to reduce the velocity of the gases
in order to permit the settling out of fly ash. It may be either part
of, adjacent to, or external to the incinerator.
29. SPARK ARRESTER: A screen-like device located on top of the stack or
chimney, to prevent incandescent material above a given size from being
expelled to the atmosphere.
30. STACK OR CHIMNEY: A vertical passage whether of refractory, brick, tile,
concrete, metal or other material or a combination of any of these
materials for conducting products of combustion to the atmosphere.
MULTIPLE-CHAMBER INCINERATORS
1. General Principles
Multiple-chamber incinerators are constructed of two or more combustion
chambers and are specifically designed to improve combustion and to
minimize the emissions of air pollutants. The design features provide
time, temperature and turbulence sufficient to maximize the speed and
completeness of the combustion reaction.
-------
6.3.9
Multiple-chamber incinerators have found widespread use in Air Quality
Control Regions where stringent emission regulations are in effect or
where the use of single-chamber incinerators is prohibited. These
incinerators are used for a wide variety of purposes, including general
refuse disposal, flue-fed apartment house incinerators, waste wood
incineration, pathological waste, wire reclamation and municipal
incinerators. Comparison of emissions between single chamber and
multiple-chamber general refuse incinerators is shown in
Table 6.3.2.^
Multiple-chamber incinerators provide a two-stage combustion process.
Primary combustion includes drying, volatilization and ignition of
the solid wastes. Secondary combustion includes oxidation of gases
and particulate matter released by primary combustion with consequent
combustion of unburned gases, elimination of odors and combustion
of the carbon suspended in the gases. The chambers are interconnected
by fire and curtain wall ports which by their position and design
effect turbulent mixing of the gaseous flow, in a mixing chamber, and
expansion and final oxidation in the secondary combustion chamber, as
shown in Figures 6.3.1 and 6.3.2. Fly ash and particulate matter
are collected in the combustion chamber by wall impingement, and
settling due to centrifugal and gravitational action. The gases finally
discharge through a stack or a combination of gas cooler, such as a
water spray chamber and induced draft system.
Multiple-chamber incinerators comprise two basic types: retort and in-
line as shown in Figures 6.3.1 and 6.3.2. The retort type offers
advantages of compactness and structural economy due to its cubic shape
and reduction in exterior well length and is applicable to burning
rates ranging from 50 to 750 pounds per hour. The basic features of
this type of incinerator are as follows:
-------
6.3.10
Table 6.3.2. COMPARISON BETWEEN AMOUNTS OF EMISSIONS FROM SINGLE-
AND MULTIPLE-CHAMBER GENERAL REFUSE INCINERATORS
Item
Particulate matter, gr/scf at 12% CO
Volatile matter, gr/scf at 12% CO
Total, gr/scf at 12% CO
Total, Ib/ton refuse burned
Carbon monoxide, Ib/ton of refuse burned
Ammonia, Ib/ton of refuse burned
Organic acid (acetic), Ib/ton of refuse burned
Aldehydes (formaldehyde), Ib/ton of refuse burned
Nitrogen oxides, Ib/ton of refuse burned
Hydrocarbons (hexane) , Ib/ton of refuse burned
Multiple
Chamber
0.11
0.07
0.19
3.50
2.90
0
0.22
0.22
2.50
<1
Single
Chamber
0.9
0.5
1.4
23.8
197 to 991
0.9 to 4
<3
5 to 64
<0.1
SOURCE: AIR POLLUTION ENGINEERING MANUAL,
Reference 4.
-------
6.3.11
MIXING CHAMBER
BURNER PORT
CURTAIN WALL PGRT
Figure 6.3.1. CUTAWAY OF A RETORT MULTIPLE-CHAMBER INCINERATOR
(SOURCE: AIR POLLUTION ENGINEERING MANUAL,
Reference A)
-------
6.3.12
Figure 6.3.2. CUTAWAY OF AN IN-LINE MULTIPLE-CHAMBER INCINERATOR
(SOURCE: AIR POLLUTION ENGINEERING MANUAL,
Reference 4)
-------
6.3.13
• The arrangement of the chambers causes the combustion gases to
flow through 90-degree turns In both lateral and vertical
directions.
• The return flow of the gases permits the use of a common wall
between the primary and both secondary combustion chambers.
• Bridge wall thickness under the flame port is a function of di-
mensional requirements in the mixing and combustion chambers.
The resulting bridge wall construction is unwieldy in incin-
erators in the size range above 500 pounds per hour.
In-line types of incinerators are generally applicable for burning
rates in excess of 750 to more than 1000 pounds per hour. Basic
features include:
• Flow of the combustion gases straight through the incinerator
with 90-degree turns only in the vertical direction.
• The in-line arrangement of the component chambers giving a
rectangular plan to the incinerator. This style is readily
adaptable to installations that require separated spacing of
the chambers for operating, maintenance or other reasons.
• All ports and chambers extending across the full width of the
incinerator.
2. General Inspection Points—Multiple Chamber Incinerators
Emission control is built into the design of multiple-chamber incin-
erators, provided that the incinerator is used for the purpose for
which it is designed and is properly operated and maintained. Even
properly designed incinerators can emit excessive emissions through
neglect or through exceeding design parameters. Permit or licensing
systems should assure that the correct application is made for any
given design; enforcement operations should assure that the incin-
erator is properly operated and maintained.
-------
6.3.14
The design and construction of multiple-chamber incinerators vary
considerably with the types of waste to be burned, charging rates and
methods and space requirements. The inspector should be able to recog-
nize types of incinerator designs and differences in construction in
relation to a given use. The common types of applications that will be
of interest to the inspector include the following:
(1) General refuse incinerators.
(2) Flue-fed incinerators (apartment houses)
(3) Wood-burning incinerators.
(4) Pathological waste incinerators.
(5) Reclamation and debonding incinerators.
Operating practices with respect to some of these incinerators are
described in other parts of this section, below. This section is
concerned with inspection points that generally apply to all incin-
erator types.
a. Composition of Refuse
An important inspection point is the volume and composition of the
refuse being charged to the incinerator. The type of refuse
available increasingly presents problems in incinerator design and
operation. Both the volume of solid waste*being generated and the
average Btu content of municipal refuse are rapidly increasing.
Refuse currently contains substances such as plastics, which burn
with great difficulty or tend to emit large volumes of dense smoke,
organics, particulates and other contaminants. Table 6.3.1 gives
a commonly used classification of incinerator wastes and
Table 6.3.3 can be used as a guide for estimating incinerator
capacities, quantities of refuse charged, burning rates and the
heat value of refuse.
-------
6.3.15
Table 6.3.3. DETERMINATION OF INCINERATOR CAPACITY
GENERAL DATA:
A. To help determine capacities of Industrial Incinerators, the cubic foot
unit measurement may be the simplest. The following information may be used:
1. 15 Gallon Garbage Can 16" dia. x 22" high
2. 26 Gallon Garbage Can 18" dia. x 24" high
3. 31 Gallon Garbage Can 21" dia. x 25-1/2" high
4. Oil Drum (50 gallon)
5. Bushel (U.S. Standard)
6. Gallon (U.S. Standard)
7. One Cubic Yard
8. 7.5 Gallons
2.0 cubic feet
3.6 "
4.1 "
6.0 "
1.25 "
.134 "
27.0
1.0 " "
TRANSLATING CUBIC FEET INTO POUNDS
B. 1. Dry rubbish, waste paper variety
2. Wood Waste
3. Average Mixed Refuse
App. 4 to 7 Ibs. per cubic foot
App. 8 to 10 Ibs. per cubic foot
App. 6 to 8 Ibs. per cubic foot
GARBAGE DENSITY
C. 1. Garbage, 75% moisture content
2. The variable in garbage is the
moisture content. MORE MOISTURE,
MORE WEIGHT
3. Water
App. 40 Ibs per cubic foot
62.4 Ibs per cubic foot
B.T.U. VALUES
D. 1. Ordinary waste paper
2. Wood Waste
3. Waxed coated paper waste
5-7m BTU per pound
8m BTU per pound
8-9m BTU per pound
GRATE BURNING RATE
E. 1. Ordinary Waste Paper
2. Wood Waste
3. Waxed and coated paper
25 Ibs. per hr. per sq. ft. grate area
30 Ibs. per hr. per sq. ft. grate area
40 Ibs. per hr. per sq. ft. grate area
SOURCE: McNavlin, Reference 6.
-------
6.3.16
Refuse usually consists of dry combustibles, non-combustibles and
moisture. The major source of the dry combustible portion originates
in plant life and includes such items as paper, wool, natural
textiles, vegetable wastes, brush and leaves. Cellulose, the basic
ingredient found in all of these materials, has a calorific value
of 7526 Btu per pound.
A second major source of dry combustibles includes hydrocarbons,
fats, oils, waxes, resins, synthetics (plastics and textiles),
rubber, linoleum and similar materials with calorific values
ranging up to 19,000 Btu per pound.
The moisture content varies with any particular source of refuse.
Food waste and greens, for example, are high in moisture—about
75% when fresh. Paper products, wood, and natural textiles readily
absorb moisture. Metals are not combustibles, but will oxidize in
the fire to varying degrees and thus produce heat as well as consume
(2)
oxygen.
The ash remaining after the combustibles have been burned, together
with the dry mineral oxides in the incinerator charge, present in
crockery, bricks, glass, and dirt, may be considered to be inert.
Trade magazines and junk mail will have a high ash content due to
the clay fillers and sizing used in producing smooth printing papers.
b. Refractories
Refractories are materials used to line the interior surfaces of
incinerators and other combustion equipment for the purpose of
reflecting and maintaining heat. The interior surfaces include
combustion chambers, mixing chambers, arches, subsidence chambers,
breechings and stacks.
-------
6.3.17
Refractories are classified according to their physical and chemical
properties, which may vary considerably. These include heat con-
ductivity, chemical resistivity, thermal expansion characteristics,
hardness and strength. Most refractories are composed wholly or in
part of alumina, magnesia and silica although chromite and zircon
are common synthetic or artificial refractories. Many of these
materials are interground with kaolin, the oldest and most widely
(1 R^
used natural refractory. '
Since the combustion efficiency of the incinerator depends on its
ability to maintain heat, the type and condition of the refractory
should be checked. Spalling is the breaking away of the
refractory, usually of the outer surface. Slagging is the destruc-
tion that occurs from the buildup of flux on the refractory surface.
Softening and erosion of refractories will also occur as a result
of temperatures exceeding 2000°F. Refractories may also be damaged
from abrasion due to tools, materials, or gases.
Refractory specifications depend upon the specific incinerator
application, particularly with respect to refuse type and Btu
content. Mineralogically stable, high melting point refractories
that are dense, of low porosity and most resistant to slagging and
spalling should be used where comparatively high combustion
temperatures occur particularly with respect to wood burning
incinerators, municipal incinerators and pathological waste
burning incinerators. Recommended refractories are shown in
Table 6.3.4.
(8)
c. Insulation Requirements
Where the incinerator is constructed with a steel plate exterior
wall, insulation must be used between the refractory wall and the
steel plate. A high-temperature insulating block should be used.
-------
6.3.18
Table 6.3.4. RECOMMENDED TYPES OF MULTIPLE-
CHAMBER INCINERATOR REFRACTORIES
1. High Temperature Block Insulation, service temperature up to 1800°F
(ASTM C-392-63 Class 2).
2. High-Heat-Duty Firebrick, spall resistant, 10 percent panel spalling loss
at 2910°F (ASTM C-106-67).
3. Super-Duty Firebrick, spall resistant, 4 percent maximum spalling loss at
3000°F (ASTM C-106-67).
4. Class C, Hydraulic Castable Refractory, service temperature rated at
2600°F maximum (ASTM C-213-66 Class C).
5. Class D, Hydraulic Castable Refractory, applicable to high heat flux areas
of incinerators, such as the arches of pathological incinerators; service
temperature at 2800°F maximum (ASTM C-312-66 Class D).
6. Class Q, Insulating Castable, for direct flame radiation (ASTM C-401-60
for Class Q Insulating Castables).
7. Class 0, Insulating Castable, where direct flame radiation is not involved,
as in a stack (ASTM C-401-60 for Class 0 Insulating Castables).
8. High-Duty Plastic Refractory, high-duty air setting plastic refractory,
15 percent panel spalling loss at 2910°F; minimum type of recommended air-
setting plastic refractory (ASTM C-176-67).
9. Super-Duty Plastic Refractory, recommended for use in areas of high heat
flux, such as arches of pathological incinerators, 5 percent panel spalling
loss at 3000°F (ASTM C-176-67).
-------
6.3.19
Minimum thickness for insulation is 2 inches. Units larger than
500 pounds per hour should have 2-1/2 inches. Loose-fill insulation
is not satisfactory because of its packing into the lower portion of
the unit over long periods of time. When the exterior wall is of
regular clay brick construction, a minimum of 1 inch air space
between the exterior brick and the refractory brick, with adequate
venting of the insulating air space should be provided.
/ON
d. Charging Doors
Guillotine charging doors used in recommended designs should be
lined with refractory material with a minimum service temperature
of 2600°F. Units of less than 100 pounds per hour capacity should
have door linings at least 2 inches thick. In the size range of 100
to 350 pounds per hour, lining thickness should be increased to 3
inches. From 350 pounds per hour to 1000 pounds per hour, the
doors should be lined with 4 inches of refractory. On units of
1000 pounds per hour and larger, linings should be 6 inches thick.
/ Q \
e. Air Inlets
All combustion air inlets should provide positive control. While
round "spinner" controls with rotating shutters should be used
for both underfire and overfire air openings in retort incinerators,
they should only be used for underfire air openings in the in-line
incinerator. Rectangular ports with butterfly or hinged dampers
should be provided for all secondary air openings and overfire air
openings of in-line incinerators. All air inlet structures should
be of cast iron. Sliding rectangular dampers become inoperative and
should not be used.
(8)
f. Clearance
Incinerators should be installed to provide a clearance to combustible
material of not less than 36 inches at the sides and rear, and not
-------
6.3.20
less than 48 inches above, and not less than 8 feet at the front
of the incinerator; except in the case where an incinerator is
encased in brick, then the clearance may be 36 inches at the front
and 18 inches at the sides and rear. A clearance of not less than
1 inch should be provided between incinerators and walls or ceilings
of noncombustible construction. Walls of the incinerator should
never be used as part of the structural walls of the building.
(8)
g. Stack Viewer
When possible, it is advisable to arrange a system of mirrors to
allow an incinerator operator, who would otherwise be unable to see
the top of the stack because of his location, to view the stack
outlet.
/o \
h. Sampling Ports
Each new incinerator stack should have two sampling ports 3-1/2
inches in diameter. Each port should be positioned in the stack
at right angles to each other. They should be located, when
possible, eight to ten stack diameters downstream from any bend or
disturbance of gas flow, and two stack diameters upstream of the
exit of the stack. The ports should be provided with suitable
removable, replacement caps.
/Q\
i. Auxiliary Gas Burners
(1) Incinerators Requiring Burners
Secondary burners alone need be installed on incinerators that
are to be used solely to burn Type 0 waste. If the incinerator
is to burn wastes of Types 1, 2, 3 or 4, both primary and
secondary burners should be installed. The need for burners in
incinerating other types of waste is dictated by the nature of
the waste itself.
-------
6.3.21
/ Q\
(2) Types of Natural Gas Burners Recommended
Incinerators having a capacity of less than 200 pounds per hour
that use burners rated at less than 400,000 Btu per hour may
be of either the atmospheric or power-burner type. In either
case, a continuously or intermittently burning stable pilot
adequate to ensure safe, reliable ignition should be installed.
A flame safeguard should be used so that no gas can flow to the
main burner unless satisfactory ignition is assured. The
response time of this flame safeguard to de-energize the gas
shutoff device on flame failure should not exceed 180 seconds.
Auxiliary burners on incinerators with ratings of 200 pounds per
hour or more, i.e., those equipped with a fan and scrubber,
should be of the power-burner type, because this type of burner
usually retains its flame better when a fan is used to induce
draft. For burners with ratings of more than 400,000 Btu per
hour input, the burner equipment shall be of the power type that
utilizes a forced-draft blower to supply air needed for combustion
under controlled conditions. A continuously or intermittently
burning pilot should be used to ensure safe and reliable igni-
tion. Automatic spark ignition should be used on pilots for
burners with input of more than 1,000,000 Btu per hour. A
suitable flame safeguard should be used so that no gas can flow
to the main burner unless satisfactory ignition is assured. On
burners with inputs of from 400,000 to 1,000,000 Btu per hour,
the response time of the flame safeguard to de-energize the gas
shutoff device on flame failure should not exceed 180 seconds.
In capacities of more than 1,000,000 Btu per hour, the response
time of the aforementioned flame safeguard should not exceed
4 seconds.
-------
6.3.22
The burner assembly should consist of the main burner, pilot
burner, automatic valve, the necessary manual valves, and
accessory equipment, plus interconnecting pipes and fittings
with provision for rigid mounting. The burner should be con-
structed so that parts cannot be incorrectly located or
incorrectly fitted together. Power burners sealed to the walls
of incinerators with capacities of more than 100,000 Btu per
hour must be supplied with a means of proving air supply before
the main gas valve can be energized.
Electrical motors of more than 1/12 horsepower on power burner
equipment should be designed for continuous duty and should be
provided with thermal overload protection or current-sensitive
devices.
When a complete automatic pilot shutoff system is utilized, the
controls should be readily accessible and arranged so that the
main burner gas can be manually shut off during lighting of the
pilot. When a complete automatic pilot system is not utilized,
a readily accessible, manually operated, quarter-turn, lever-
handle, plug-type valve should be provided to shut off or
turn on the gas supply to the main burner manifold. This valve
should be upstream from all controls except the pilot control
valve.
Clearly defined and complete instructions for lighting and
shutting down the burner should be provided in durable, weather-
proof material for posting in a position where they can be read
easily.
(3) Sizes of Burners Recommended
Where auxiliary burners are used, their capacity range should
/•OS
include the values shown in Table 6.3.5.
-------
6.3.23
Table 6.3.5. GAS BURNER RECOMMENDATIONS FOR
GENERAL-REFUSE INCINERATORS
Capacity of
incinerator,
Ib/hr
50
100
150
250
500
750
1000
1500
2000
Size of burners, 10 Btu/hr
Primary Burners Secondary Burners
Type 1
refuse
150
200
250
300
550
750
900
1100
1600
Type 2
refuse
250
550
650
750
1100
1500
1700
2200
3300
All refuse
200
300
AOO
650
1000
1300
1700
2100
2700
SOURCE: INTERIM GUIDE, Reference 8.
-------
6.3.24
(4) Other Fuels
If natural gas is not available, equivalent amounts of liquid
fuels may be used. Fuel oils of grades higher than Number 2,
however, should not be used. The National Fire Protection
Association Standard No. 31, Installation of Oil Burning Equip-
ment (1965), should be adhered to where oil burners are used.
If liquified petroleum gas is used, burners should be equipped
with a device that will automatically shut off the main gas
supply in the event the means of ignition becomes inoperative.
The arrangement should be such as to shut off the fuel supply
to the pilot burner also.
j . Scrubbers
Effluents from general refuse incinerators burning more than 200
pounds per hour should be cleaned in scrubbers to meet particulate
limits. Alternate scrubber designs or gas washers should include,
as a minimum, the following features:
(1) The scrubber or gas washer should contain sprays, wetted
baffles, or orifices arranged singly or in combination
so as not to permit the discharge of particulate matter in
violation of the Code of Federal Regulations.
(2) Unlined gas washers or scrubbers should have welded or
gasketed seams and be corrosion resistant. Lined gas
washers or scrubber casings should be made of at least
12-gauge steel and be welded or gasketed. The density of
refractory lining should be no less than 120 pounds per
cubic foot. The refractory should never be less than 2
inches thick and must be adequately anchored to the casing.
(3) Scrubbers requiring an induced-draft fan should have a motor
capable of cold startup (70°F). When the impeller of an
induced-draft fan is in the gas stream, the fan must be
equipped with a cleanout door and drain.
(4) Where spray nozzles are employed, an optimum spray pattern
must be provided to cover all the area of the gases as they
-------
6.3.25
pass through the gas washer or scrubber. Nozzles and
valves should be arranged for Independent removal by
means of unions or flanges. When water is recirculated,
a pressure regulator and a strainer should be provided.
(5) An access door for cleanout should be provided on all
scribbers.
(6) Interlocks should be provided when induced-draft fans and
sprays are used.
(7) When the outside skin temperature of a gas washer or
scrubber exceeds 260°F, protection should be provided.
(8) For inside installations, a by-pass arrangement of
breeching, or flue connections with dampers, to by-pass
the scrubber and induced-draft fan is recommended.
Provision should also be made to supply scrubbing water and a means
of disposing of contaminated water from the scrubber. In some areas
it will also be necessary to adjust the pH and process the con-
taminated water through a clarifier to remove fly ash and other
collected solids before the water is sewered.
The inspector should check for corrosion caused by the acidic water
continuously flowing through the scrubber.
Water-gas mixtures should be retained within the scrubber from 1 to
1-1/2 seconds at gas velocities not exceeding 15 feet per second.
The residence time in the scrubber should also be sufficient to
vaporize all the water droplets within the effluent gas stream.
Complete vaporization is important since nuisance complaints may
result from the carryover of water droplets deposited on the
surrounding area.
3. General Refuse Incinerators
General refuse incinerators are designed to handle wide ranges of fuel
composition (types 0, 1, 2, 3, and 4 wastes), moisture, volatility,
-------
6.3.26
diversity in ash content, bulk density, heat of combustion, burning
rates and component particle size. General refuse incinerators should
be equipped with secondary burners for combustion of Type 0 waste and
primary and secondary burners for Types 1, 2, 3, and 4 wastes (See
Table 6.3.2). Incinerators with capacities greater than 200 pounds
per hour should be equipped with scrubbers.
a. General Operating Procedures
The most important single aspect of operation of a multiple-chamber
incinerator is the method of charging the refuse into the ignition
(4)
chamber. A multiple-chamber incinerator must be charged pro-
perly at all times in order to reduce the formation of fly ash and
maintain adequate flame coverage of the burning rubbish pile and
the flame port. A recommended charging cycle starts with the
placing of the initial charge of refuse in the incinerator. The
ignition chamber should be filled to a depth approximately two-
thirds to three-fourths of the distance between the grates and the
arch before lightoff. After approximately half of the refuse has
been burned, the remaining refuse should be carefully stoked and
pushed as far as possible to the rear of the ignition chamber. New
refuse should be charged over the front section of the grates,
which have been emptied by the moving of the burning refuse. To
prevent smothering the fire, no material should be charged on top
of the burning refuse at the rear of the chamber. With this charging
method, live flames cover the rear half of the chamber, fill the
flame port, and provide nearly complete flame coverage in the mixing
chamber. The fire propagates over the surface of the newly charged
material, spreading evenly and minimizing the possibility of smoke
emissions. Since the refuse pile need not be disturbed unduly,
little or no fly ash is emitted.
-------
6.3.27
Characteristic of the multiple-chamber incinerator is that control
of air-polluting emissions is built in, if the incinerator is
operated with reasonable care. The discharge of combustion
contaminants is almost entirely a function of ignition chamber
design and the actions of the operator. Control of smoke is
attained by proper admission of combustion air and by use of
secondary burners in cases of incineration of refuse with a low
heating value or high moisture content. The use of secondary
burners is required at times since the efficiency of the mixing
chamber depends upon both luminous flame and adequate temperatures
for vapor phase combustion. The need for supplementary burners
may be determined readily by observing the nature of the flame
travel and coverage at both the flame port and the curtain wall
port.
The overfire and underfire air ports are usually half-open at
lightoff and are opened gradually to a full open position as the
incinerator reaches its rated burning capacity. If black smoke is
emitted, the admission of more secondary air and reduction of the
capacity of other air ports are advisible. On the other hand,
white smoke is usually the result of a too cold furnace and may be
eliminated by reducing or closing all air ports. After the final
charge or refuse, the air ports are closed gradually so that during
the burndown period the only air introduced into the furnace is
provided through leaks around door and port openings.
When ignition and mixing chamber burners are necessary, the mixing
chamber or secondary burner is lighted before the incinerator
is placed into operation. The burner should remain in operation
for the first 15 to 20 minutes of operation and should be used
thereafter as needed. Under normal conditions, the ignition
-------
6.3.28
chamber or primary burner is used only when wet refuse is charged.
At other times, its use, too, may be required when refuse to be
burned contains high percentages of inorganic compounds such as
clay fillers used in quality paper.
Multiple-Chamber Incinerators, Woodworking Industries
Multiple-chamber incinerators used in the woodworking industries are
similar in overall design to those used for general refuse purposes,
but differ in some important respects. These incinerators must employ
super duty plastic or super duty fire clay firebrick refractories and
include design factors with respect to secondary chamber cross-sectional
areas, inlet air port sizes and other values and proportions which
permit higher combustion temperatures arising from the charging of
wood products. The gross heating value of kiln dried wood, for example,
is about 9000 BTU per pound, and continuous charging of sander dusts
and chips from hoggers by mechanical feed systems, further increases
combustion temperatures as compared to hand fed general refuse in-
cinerators.
As a consequence, these incinerators must be designed for greater
stresses and strains. Adjustment of primary air and the design and
operation of the mechanical feeder systems are also important
variables in the effectiveness of the incinerator and in the control
of emissions. Primary air ports for continuously fed incinerators are
sized for induction of theoretical plus 100 percent excess air. Ten
percent of the air is admitted through ports located below the grates
and 90 percent above the grates. Additional primary air can be
admitted by opening the charging door when necessary. If excessively
wet refuse is charged in quantity or products such as rubber, oily
rags and plastics are significantly charged, secondary burners with
automatic controls may be required to maintain high temperatures
during all phases of the operation.
-------
6.3.29
Hand charging or intermittent delivery of sawdust (from local exhaust
systems serving woodworking) may smother the flames in the ignition
chamber and cause smoke. For this reason, continuous feed systems are
desirable.
In inspecting woodworking facilities, the inspector should:
• Inventory all local exhaust systems discharging into mechanical
feed systems, including the woodworking machines served such as
saws, tenoners, sanders, jointers, etc., as well as the diameter
of the ducts and number and horsepowers of blowers.
• Establish types of woods employed such as softwoods and hardwoods
(e.g., pine wood shavings do not flow as easily as hardwood
shavings due to resin content and adhesive properties).
• Check type of surge or feed bins employed in the mechanical
feed system. These should be appropriately designed to handle
the type and volume of wood wastes. Wood wastes that exhibit
poor flow characteristics should be handled in bins constructed
with vertical sides and screw or drag conveyors covering the
entire flat bottom of the bin. Bins with sloping bottoms may
require mechanical agitators or vibrators to prevent bridging.
• Check conveyor systems: Screw conveyors with variable pitch
are recommended over screws with uniform pitch because they
permit more even loading of the screw along the entire length
and thus minimize the compressing of sawdust and shavings
causing bridging above the discharge end of the screw. Brag
conveyors should be used where long, tough, fibrous shavings are
to be conveyed.
• Check pneumatic conveyor system: These should be designed and
operated to prevent sawdust from being aspirated into the
system faster than the normal delivery rate of the screw.
-------
6.3.30
Conveyors should extend at least three screw diameters beyond
the end of the bin and shrouds should be installed over the
extended section.
• Check the discharge of wood waste from the pneumatic conveying
system to assure that particles are being spread evenly over
the entire grate area and to maintain active flame over the
surface of the burning pile. The amount of conveying air
entering the ignition chamber can be regulated by means of a
butterfly damper in the top outlet duct of the cyclone separator,
or spiral vanes within the cone of the cyclone.
• Check the cyclone separators: These are usually of the small
diameter, high efficiency type. A flap-type damper equipped
with a counter balance weight should be installed at the bottom
outlet of the cyclone. This damper prevents smoke from being
emitted from the cyclone and damage from occurring to the
sheet metal construction.
(9)
General Operating Procedures
Certain differences exist between the operation of wood-burning
incinerators and general-refuse incinerators. The operator of a
general-refuse incinerator generally relies on auxiliary burners
to maintain temperatures for maximum combustion in the secondary
chamber. The operator of a woodburning incinerator, without
provisions for auxiliary burners, is able to maintain adequate
secondary chamber temperatures by proper charging and control of
combustion air.
Generous amounts of clean dry paper are mixed with the wood for
the initial charge. After the ignition chamber is one-half to
two-thirds full, additional paper is placed on top of the pile to
-------
6.3.31
ensure quick flame coverage at the surface. It is important,
in keeping smoke to a minimum, that only clean dry paper and dry
scrap wood comprise the initial charge. After charging is completed,
the paper is ignited near the front of the chamber and the charge
door is closed. All combustion air ports are almost completely
closed to restrict combustion air.
As burning proceeds, the incinerator passes through the most
critical period of its operation. By observing the emissions
from the stack, the necessary adjustments can be made promptly
to reduce or eliminate smoke. Gray or white smoke emitted
after lightoff indicates that the incinerator is cold. This smoke
can be minimized or eliminated by closing all air ports. Smoke of
this color usually ceases within a few minutes after lightoff when
flames completely cover the refuse pile and fill the flame port.
A few minutes later, black smoke may appear, resulting from a
lack of adequate combustion air. These emissions can usually
be eliminated by opening primary air ports and then the secondary
air ports. If additional combusion air is required, it may be
supplied by opening the charge door.
Although each incinerator has its own operating characteristics,
the overfire and underfire air ports can usually be opened to 10
minutes after lightoff, and the secondary port, 20 to 30 minutes
later. If opening of the secondary ports results in gray or
white smoke emissions, the ports should be closed immediately since
the incinerator has not yet reached its normal operating temperature.
After attaining normal operating temperatures, maximum combustion
is maintained by placing the mechanical feed system in operation
or by hand charging at regular intervals.
-------
6.3.32
The refuse is then ignited and, if the refuse is moist, the grate
burners are also lighted. The refuse may be stoked frequently
to uncover fresh material without fear of creating excessive fly
ash emissions because of the draft-limiting action of the damper.
When the refuse has been destroyed, the grate burners are turned
off and the grates are cleaned by dumping the ashes into the ash
pit. After a brief period of time is allowed to permit smoke
from the smoldering ashes to clear, the afterburner is turned
off and the draft control damper opened.
The final step, that of unlocking the chute doors, should not be
performed until about 10 minutes after the grates have been
cleaned. This delay allows the incinerator to cool so that newly
charged refuse is not ignited by the residual heat in the incinerator.
The sequence of operation in using a flue-fed incinerator modified
with a basement afterburner is the same as that described above.
5. Multiple-Chamber Flue-Fed Incinerators
Examples of single and double by-pass flue multiple-chamber incin-
erators for apartment houses are shown in Figures 6.3.3 and 6.3.4.
These incinerators have the potential for complying with new emission
limitations and are far superior to single-chamber incinerators, but
improvements in combustion efficiencies are still needed. Consideration
also may need to be given to seasonal variations in building pressure
of high rise buildings in terms of their effect on gas flow in charging
chutes and exhaust flues.
a. General Operating Procedures
Before burning is begun, the solenoid locks on the charging chute
doors are actuated and the damper below the breeching is closed.
-------
/Sampling point
Primary• ,—
burner
Charging
door
Primary chamber
Incinerator
Draft
control
damper
Entrainment
separator
Impingement plate
~-.:-<~?~-?~^:--~*~\tlater level
r
Washer
Figure 6.3.3.
MULTIPLE-CHAMBER INCINERATOR WITH SINGLE PASS FLUE
(SOURCE: Sableski, Deference 10)
-------
Charging
door
\ \ \ \ \ \ \ \ \ \ \ \
Charging
/ gate
/ \\M.
/Sampling point
Fl ame
port
CO
-p-
-Water
level
SIDE VIEW
FRONT VIEW
Draft control
damper
Incinerator
Washer
Figure 6.3.4 MULTIPLE-CHAMBER INCINERATOR WITH DOUBLE PASS FLUE
(SOURCE: Sableski, Reference 10).
-------
6.3.35
The mixing chamber burners of the incinerator are then ignited. The
ignition chamber burners are also ignited if the refuse is of low
heating value or high moisture content. The charging and operation
of the incinerator are similar to General Refuse Incinerators
described above. Burning is usually carried out once a day, since
the bin does not normally provide storage for much more than that
length of time. When burning is completed, the incinerator burners
are turned off, the doors to the bin are closed, the flue damper is
opened, and the chute doors unlocked.
The sequence of operations performed in using a flue-fed incinerator,
modified with afterburners, starts with the locking of the chute
doors from the main switch in the basement. The draft control
damper is closed and the afterburner ignited by remote control from
another switch also located in the basement.
D. SINGLE-CHAMBER INCINERATORS
Single chamber incinerators are devices in which one chamber serves ignition,
combustion and ash removal, partitioned only by a fixed or movable grate.
Since this type of incinerator fails to provide the conditions necessary for
complete combustion—it is quite often nothing more than an enclosed open
fire—the control of smoke, volatilized gases and fly ash in its operation
is uncertain. Single-chamber incinerators inherently do not meet current
or proposed particulate, opacity or other emission limitations and should
be prohibited. While they can be improved by means of auxiliary equipment,
design modifications and control devices (such as afterburners), the results
are frequently questionable. The cost of modifying a single-chamber incin-
erator may be equivalent to the cost of installing a multiple-chamber
incinerator in many cases.
While the use of single-chamber incinerators is declining, field officers
in some communities will be inspecting these incinerators. Their primary
-------
6.3.36
objective will be to (1) seek abandonment of single-chamber incineration
in favor of disposal in cut-and-cover dumps or multiple chamber incinerators
or (2) to assure that such incinerators are being properly operated and
maintained to meet all emission standards. Inspectors should be familiar
with the following types of single-chamber incinerators:
1. General Residential and Commercial
Small residential concrete slab or brick construction, box-type or
Dutch oven types, or improvised or homemade equipment made from drums,
etc., in which provisions are made for charging and clean-out
doors, stacks and air supply. Operation of these incinerators should
not be prohibited.
2. Flue-Fed Incinerators
The operation of flue-fed incinerators may be additionally complicated
by (1) the method of charging; (2) the number of users; and (3) exces-
sive draft conditions due to tall flues, particularly in high buildings.
Since the charging method consists of depositing of rubbish into the
flue through chute doors located at the various floors of the dwelling
unit, rubbish material can block flues causing excessive smoke from
the stack and leakage of smoke through chute doors, or smothering of
the fire. Random charging by residents results in poor control of
burning conditions.
In these types of incinerators the type of refuse burned is related to
the number and types of apartments rented. If food is prepared on the
premises, the.refuse will contain a high quantity of plastics, waxed
cartons and non-combustibles.
Excessive draft conditions in tall flues also result in cooling the
fire, causing incomplete burning particularly of combustible gases,
-------
6.3.37
oils, tars and fats usually contained in the refuse pile. Draft, and
the incinerator conditions it causes, increase with stack height. Fly
ash emissions are also increased by stoking refuse piles. Operation of
this type of incinerator can be improved by the following types of
modifications:
• Installation of solenoid locks on each of the chute charging
doors. Locks can be actuated from a single switch in the
basement before the stack damper is closed and the burning
cycle begins.
• An air tight unit is essential if combustion air is to be con-
trolled. Particular attention should be paid to cracks which
occur with age and use, and to relatively large openings around
chute doors.
• Installation, where none exists, of dampers in the stack to
control stack drafts and to achieve desired combustion tempera-
tures. Swinging, counter-weighted dampers are effective and
are usually located in the flue beneath the first floor chute
door to ensure a negative pressure at each door and thus prevent
smoke and sparks from blowing by the chute doors into the
buildings. Automatic draft control dampers are preferred in
most installations.
• Installation of double flues; one for charging refuse and one
for exhaust of products of combustion are desirable.
• Auxiliary gas burners under grates to further promote drying of
refuse is desired.
• Installation of a gas washer for particulate collection or
afterburner for elimination of smoke, odors and fly ash is
desirable. Afterburners may be either direct-fired or cataly-
tically fired, usually the former. Afterburners can be located
either in the stack on the roof of the apartment house or at
-------
6.3.38
the base of the flue in the basement. Figures 6.3.5 through
6.3.7 are examples of modified afterburner installations.
Figure 6.3.8 is a schematic of a modified single-chamber flue-
fed incinerator that includes a separate exhaust flue, gas
(10)
washer, moving grates and other control and automatic features.
The effectiveness of any modifications in any given installation,
however, may be of questionable value since constant observa-
tion and frequent source testing will be required to assure
compliance with incinerator regulations.
3. Wood Waste-Burning Incinerators
Wood waste-burning incinerators include wigwam burners and silo
incinerators used in connection with the lumber and woodworking in-
dustries. These are usually of metal construction, refractory lined
or unlined, are fed continuously or intermittently by cyclone, hogger,
moving grates, or by hand. Many enforcement agencies are prohibiting
the construction of these types of incinerators.
Silo incinerators are large cylindrical incinerators used mostly in
connection with woodworking and furniture manufacturing industries.
Wigwam incinerators are of round construction and taper towards the
top, and are used primarily for the disposal of wood and bark residue
from the lumbering industry. Generally, these incinerators do not
employ grates and tend to have an underfire air problem. Overfire
air can be regulated by port openings located around the base of the
burner. Because of the large capacities of these incinerators and the
commitment to them on the part of industry, most efforts to control
emissions from this source are concentrated in the modification of
fuel feed systems. Figures 6.3.9 and 6.3.10 illustrate typical wigwam
burners with various fuel feed and dryer systems.
-------
6.3.39
CUANOUT DOOR
Figure 6.3.5. FLUE-FED INCINERATOR MODIFIED BY A ROOF AFTER-
BURNER AND A DRAFT CONTROL DAMPER
(SOURCE: AIR POLLUTION ENGINEERING MANUAL,
Reference 11.)
-------
6.3.40
BIOHER
Figure 6.3.6. FLUE-FED INCINERATOR MODIFIED BY A ROOF AFTER-
BURNER, AND A DRAFT CONTROL DAMPER
(SOURCE: AIR POLLUTION ENGINEERING MANUAL,
Reference 11.)
-------
6.3.41
ELECTRIC LOCK IN OPEN
POSITION FOR CHARGING
CHUTE DOOR
COOLING AIR DUCT
FIRST-FLOOR LEVEL
BAROMETRIC DAMPER
PORTS FOR VENTURI
GAS BURNERS
DAMPER «ITH ORIFICES
SHOWN IN POSITION FOR
CHARGING OF REFUSE i
NOTE DURING THE BURNING
CVCLE THE CHUTE DOORS ARE
LOCKED AND THE DAMPER WITH
ORIFICES IS PLACED IN A
HORIZONTAL POSITION
Figure 6.3.7. FLUE-FED INCINERATOR MODIFIED BY AN AFTER-
BURNER AT THE BASE OF THE FLUE
(SOURCE: AIR POLLUTION ENGINEERING MANUAL,
Reference 11.)
-------
6.3.42
Motorized
damper -
Hopper
door
^iv- '
>
L_
\
\
\
\
\
\
\
\
\
\
\
\
i_
c
>
>
,
ai
:3
r-
4
4
J
LO
^3
rO
.cr
X
LU
— -^
2r-
-Sampling paint
/Roof
^-Spray
Hydraulic J
cylinders
Secondary
temperature
^Water
level
Cleanout-
door
Incinerator
Washer
Figure 6.3.8- MODIFIED SINGLE-CHAMBER FLUE-FED INCINERATOR,
360 POUNDS PER HOUR CAPACITY (SOURCE:
SABLESKI, et al., Reference 10.)
-------
Figure 6.3.9. FUEL FEED SYSTEM OF A WIGWAM BURNER
(SOURCE: CORDER, et al., Reference 12.)
-------
CO
-p-
Figure 6.3.10. FUEL FEED AND DRYER SYSTEM OF A WIGWAM BURNER
(SOURCE: CORNER, et al., Reference 12.)
-------
6.3.45
General Operating Procedures and Inspection Points - Single-Chamber
Incinerators
It is difficult to generalize good operating guides for all classes of
single chambers, for all designs, refuse types and uses. These must
be established in each case by:
• Control over moisture, constituents and mixtures of refuse
charged.
• Adjusting ignition procedures with respect to air supply
(opening of charging doors, underfire air ports or supply,
setting dampers, etc.), size of refuse pile, positioning of
refuse pile and use of kindling materials.
• Closing or adjusting charging and ash pit doors, or underfire
and overfire spinners, for appropriate air supply throughout
the burning cycle.
• Stoking of burning pile, particularly near the end of the
burning period, by grate manipulation and use of stoking
implement. Stoking action should be gentle to avoid fly ash
emissions.
• Use of underfire or overfire gas firing system.
• Maintaining free draft passages, e.g., regular removal of ash
from ash chambers and avoidance of blockages of chutes and grates.
Single-chamber incinerators should be in frequent or constant attendance
and appropriate adjustments to the combustion system should be made
whenever smoke or fly ash occurs. The color of the smoke is generally
an indicator of the type of problem that must be remedied. Black smoke
suggests a deficiency of air in relation to the volume and composition
of the material being burned. Material with high organic or carbon
content may tend to burn black. White smoke indicates that combustion
temperatures are too low. This is usually due to too much excess air
or moisture in the refuse. A fly ash problem may result from
-------
6.3.46
excessive air supply—particularly underfire air—and uneven mixtures
of light and heavy materials (e.g., paper products and saw dusts),
defective spark arrestor, excessively short stack and poor damper
control. In general, low excess air is preferred in lessening smoke
and particulate emissions.
E. MUNICIPAL INCINERATORS
Municipal incinerators are designed to dispose of combustible wastes
collected from residential, commercial and industrial sources that have
been transported to the incinerator site. The principles of combustion
of solid waste—especially primary and secondary combustion treated in
the previous parts of this section—also apply to municipal incinerators.
However, the operation of these incinerators involves a number of additional
considerations associated with the scale and complexity of the operation
that the inspector should take into account.
• Combustion of an equivalent amount of refuse in municipal incin-
erators is more efficient and results in less air pollution, than
burning of refuse by individuals in open fires and small incin-
erators, particularly single-chamber incinerators.
• The municipal incinerator, like a large steam-generating station,
constitutes a large concentrated source of air pollution, which
may not only fail to comply with local particulate and Ringelmann
regulations, but may create a public nuisance in terms of odors,
dust, noise and unsightliness. The stacks from such incinerators
are usually visible from many miles away.
• Other air pollution and environmental problems are presented by
municipal incinerators in addition to stack effluents. These
include odors from putrefaction of organic material present in
the effluent and stored refuse, dusts from truck traffic and
material handling, water and land pollution problems from residue
-------
6.3.47
quenching and water treatment procedures and insect and rodent
problems, as summarized in Figure 6.3.11. '
Small municipal incinerators are those which range in size from 50-100
tons per day (TPD) capacity. Large incinerators may exceed 1000 TPD
in capacity. Fly ash emissions from municipal incinerators may vary
from 8 to 70 Ib. per ton of solid waste burned, without control equip-
ment. Sulfur oxide emissions run approximately 1.5 Ibs. per ton of
waste as fired. Most of the sulfur is further retained in the ash.
Oxides of nitrogen emissions are on the order of 2 Ibs. per ton of
waste, which is approximately ten times less than from fuel combustion
due to the generally lower Btu value of solid waste fuel, although,
the heat value of solid waste fuel appears to be increasing. Hydrogen
chloride (HCL) emissions may be of concern because of the toxicity of
this contaminant to the eyes and respiratory system. HCL emissions
result from plastic polyvinyl chloride found in increasing amounts in
municipal solid waste. The gas is highly soluble in water and can
probably be effectively removed with water scrubbers.
The design of municipal incinerators should be based on the waste
characteristics and current and projected waste volumes of the community
being served. The composition, moisture, heating value and specific
materials contained in the solid waste will vary by community. Household
wastes will differ from food wastes from stores and restaurants and from
the relatively dry high-heat-value waste generated from industry. Factors
that must be considered in the design of the incinerator system include
furnace chamber, grates, feed mechanisms and refractories. Procedures for
sampling and analysis of solid waste have been published by the American
Public Works Association. *-13^Oxygen bomb calorimetry for determining the
amount of heat liberated from solid materials and liquids are also
(14)
described.
-------
PLANTS WITHOUT
AIR POLLUTION CONTROL
GASES
AND
ENTRAINED
SOLIDS
01
U)
FLY ASH
LAND SEWER
DISPOSAL
Figure 6.3.11.
DIAGRAM OF THE INPLANT SYSTEMS BASED UPON DRY FLY ASH COLLECTION AND CONVEYING
FROM COOLING AND COLLECTION OPERATIONS. ALTERNATIVES FOR WET COLLECTION AND
CONVEYING SHOWN IN PARENTHESES (SOURCE: DEMARCO, et al., Reference 7.)
-------
6.3.49
Bulky combustible items, such as furniture and fixtures, as well as flammable,
toxic, radioactive, organic, pathological or putrescible residues may present
special prouleuis.
A flow chart of the overall operation of municipal incinerators is shown
in Figure 6.3.11. Municipal incinerators operations that may be of
concern to the inspector include:
• Delivery and Weighing of Solid Waste and Residue. Trucks trans-
porting solid wastes are weighed at the plant to establish the
weight of solid wastes being handled by the incinerator, and the
weight of ash residue removed from the incinerator. These data
are used to improve operation, to assist management control, to
facilitate planning and to provide an equitable basis for assessing
fees. From an air pollution standpoint, this information is useful
in rating the effective capacity of the incinerator, and to test air
pollution control devices. A number of different types of scales
varying from simple beam scales to electronic relay scales are in
use. These have varying degrees of accuracy, depending on plant size
and age. Incinerators with a capacity of 100 or more tons per day
will generally require two or more scales. The most accurate and
most secure system of establishing net weights is through a two-scale
system with fully controlled access. One scale weighs in the loaded
vehicles, the other weighs out the empty vehicles.
• Shredders and Grinders. The use of shredders and grinders in the
handling of bulky wastes should be noted.
• Tipping Area and Storage Pits. (Figure 6.3.12) After being weighed,
trucks move on to the tipping area which is adjacent to the storage pits
or charging hoppers. At large installations trucks unload into a
storage pit, whereas in small incinerators the waste is dumped directly
into the furnace charging hopper or onto the tipping floor. If the
-------
6.3.50
tipping floor is not enclosed, this area can be a major source of
dusts, odor and noise, particularly during periods of peak traffic.
Accidental fires also can be started in the storage pit, thus providing
TIPPING
AREA
GROUND LEVEL
-TIPPING AREA WIDTH-
CRANE
OVERRIDE
AREA
X
CRANE
- BRIDGE -
RAILS
LOADING
,SHAFT
CHARGING
FLOOR
Figure 6.3.12. PLAN OF TIPPING AREA AND STORAGE PITS WITH CRANE
(SOURCE: DEMARCO, et al., Reference 7.)
a source of uncontrolled combustion emissions. The inspector should
check to assure that dewatering facilities are available for quantities
of water that may be necessary in fire fighting. Portable pumps should
also be available for removal of excess water.
Storage pits are usually rectangularly shaped. Some pits are divided
into separate rectangular units with charging hoppers between units.
The storage pit is usually designed to contain about 15 times the
24-hour capacity of the incinerator.
Scattering of dust and litter from dumping, recasting and charging
operations is a common problem at municipal incinerators and provision
should be made for cleaning the tipping area. Vacuum cleaning
facilities and compressed air system for cleaning electrical contacts,
powered mobile sweepers and flushers can be used in controlling dust
and litter.
-------
6.3.51
An adequate drainage system should also be available to accommodate
the wash waters. The inspector should check the size of the receiving
sewer.
• Charging Methods. Front-end loaders, vibrating hoppers, conveyors and
other mechanical means are used in small installations to transfer and
charge the solid waste, where the storage area is on the same elevation
as the charging hoppers. At larger installations, cranes are employed.
Waste is charged to the furnace under gravity or with the assistance
of reciprocating or vibrating feed mechanisms through charging chutes.
In batch-feed furnaces a gate separates the charging hopper from the
furnace and supports the solid waste while the furnace is burning the
previous charge. Generally, one hopper is provided for each furnace
cell. In a continuous-feed furnace, the waste filled hopper and chute
assist in maintaining an air seal to the furnace as well as to provide
a continuous supply of solid waste. The inspector should note
whether arching of oversized material occurs across the hopper bottom,
or whether clogging occurs in the chutes, as these conditions can
effect furnace operation and hence emissions. Chutes constructed of
smooth surfaces, corrosion-resistant materials and vertical or nearly
verticle and increasing cross section design are preferred.
• Furnace Categories. Municipal incinerator furnaces fall into the
following categories:
a. Rectangular. (Figure 6.3.13) In this furnace two or more grates
are arranged in tiers so that the moving solid waste is agitated
as it drops from one level to the next.
-------
CHARGING
CHUTE
HORIZONTAL
BURNING GRATE
CJ
Ul
Figure 6.3.13.
RECTANGULAR FURNACE
(SOURCE: DEMARCO, et al.. Reference 7.)
-------
6.3.53
Vertical Circular Furnace. (Figure 6.3.14) In this furnace waste
drops onto a central cone grate and surrounding circular grate.
The fuel bed is agitated by means of a slowly rotating cone with
arms. Underfire forced air is the primary combustion air, which
also serves to cool the grates. Manual agitation and assistance
in residue dumping is required, and stoking doors are provided
for this purpose. Overfire air is usually introduced to the
upper portion of the circular chamber.
CHARGING HOPPER
Figure 6.3.14.
VERTICAL CIRCULAR FURNACE
(SOURCE: DEMARCO, et al.,
Reference 7.)
-------
6.3.54
c. Multicell Rectangular Type (Mutual Assistance Furnace). (Figure
6.3.15) This type of furnace, which may be refractory-lined or
water cooled, is constructed of two or more cells set side-by-side.
The cells of the furnace usually have a common secondary combustion
chamber and share a residue disposal hopper.
CHARGING CHUTE
TO
SECONDARY
COMBUSTION
CHAMBER
STOKING
DOOR
RESIDUE
HOPPER
RESIDUE
HOPPER
Figure 6.3.15. MULTICELL RECTANGULAR FURNACE
(SOURCE: DEMARCO, et al.. Reference 7.)
-------
6.3.55
Rotary Kiln Furnace. This consists of a slowly revolving inclined
kiln following a rectangular furnace where drying and partial
burning occurs (Figure 6.3.16). The partially burned waste is fed
by the grates into the kiln where cascading action exposes combined
material for combustion. Final combustion of the combustible gases
and suspended combustible particulates occurs in the mixing chamber
beyond the kiln discharge. The residue falls from the end of the
kiln into a quenching tank.
TO EXPANSION CHAMBER
AND GAS SCRUBBER
RESIDUE CONVEYORS
Figure 6.3.16. ROTARY KILN FURNACE
(SOURCE: DEMARCO, et al.,
Reference 7.)
-------
6.3.56
systems are used in municipal incinerators to
6.3.17 through 6.3.20.
C7ID DID DID DID DI°)
Figure 6.3.17. TRAVELING GRATES
8 (SOURCE: DEMARCO,
etal. , Reference 7.)
Fieure 6.3.18. RECIPROCATING GRATES
iigure o.j (SOURCE: DEMARCO,
et al., Reference 7.)
-------
6.3.57
NORMAL POSITION
Figure 6.3.19. ROCKING GRATES
(SOURCE: DEMARCO,
etal., Reference 7.)
A Rototing Cone
B Extended Stoking
Arm (Robbie Arm)
C Stationary Circular
Grate
D Peripheral Dumping
Grate
Figure 6.3.20. CIRCULAR GRATES
(SOURCE: DEMARCO,
et al., Reference 7.)
-------
6.3.58
The grate systems perform two essential functions: (1) agitation of
the refuse to promote combustion by means of tumbling and dropping of
the refuse from one grate tier to the next; and (2) passage for underfire
air. The inspector should note whether abrupt or excessive tumbling
occurs and if excessive amounts of partieulates are being emitted.
Inert materials, such as glass bottles and metal cans will aid com-
bustion by enhancing porosity of the fuel bed, although they may
inhibit combustion by clogging the grate openings. The mechanical
condition of the grate system should be checked, where possible, for
misalignment of moving parts, bearing wear and warping or cracking of
castings due to high temperatures, thermal shock, abrasion, wedging
clogging and heavy loads.
The inspector should attempt to determine if sittings are burning
beneath the grates. These are fine materials which fall through the
fuel bed and may consist of combustible materials such as oil,
plastics and grease.
The inspector should note the residue removal operation and method of
disposal. Residue usually consists of ash, clinkers, tin cans, glass,
rock and unburned organic substances. The residue is dumped from the
residue hoppers into trucks or other containers and quenched. Wet,
dripping trucks can create a nuisance. In many continuous-feed operations
the residue is discharged into water filled troughs, and a slow moving
drag conveyor discharges the residue to a holding hopper or directly
into a truck. The quench water is allowed to drain from the system
before discharge to truck or hopper. This water may be highly
abrasive and corrosive.
The following operational guides and inspection points should be noted
during inspections of municipal incinerators.
-------
6.3.59
For most municipal incinerator designs, underfire air is from 40 to 60
percent of total air (underfire, overfire, infiltration).
A minimum of 50 percent excess air is usually necessary to complete
combustion and to promote turbulence: In general, refractory furnaces
require 150 to 200 percent excess air, whereas water tube wall furnaces
require only 50 to 100 percent excess air.
Temperatures of burning gases generally range from 2,100 to 2,500 F
and for short periods of time may reach 2,800 F in localized areas
Combustion air may be preheated to 200 to 300 F. Gas temperatures are
between 1,400 and 1,800°F exiting the combustion chamber, and 1000°F
or less entering the stack. Gases should be cooled to 500 to 700 F be-
fore entering the air pollution control equipment. If heat exchangers
are used, gas volumes are reduced, thus reducing requirements for
collection devices, fans and gas passages. Excessively high temperatures
will increase NO emission rate, and cause refractories to fail and
X
slag to buildup on furnace linings.
When starting a municipal incinerator, operation temperatures of
1,400 to 1,800 F should be reached quickly, consistent with good
practice. Incinerators with induced draft fans usually reach operating
temperatures in less than one hour. Natural draft plants may require
more than four hours. Plants with suspended wall construction require
as little as half an hour for heating refractories.
Auxiliary fuels are desirable to warm the furnace, dry solid waste
that is wet or has low BTU content, complete secondary combustion—
for odor and smoke control—and to supplement heat for heat recovery
units.
Height and diameter of incinerator stacks depend upon the amount of
draft required and topographic and climatic conditions. Induced draft
fans should be used to supplement the natural draft in moving gases
-------
6.3.60
through the incinerator. Dampers are generally used in both natural
draft stacks and in stacks employing induced draft fans of constant
speed. Adjustable speed, induced draft fans are also used to control
draft.
Instrumentation and controls are used in municipal incinerators to
assess performance, safety, and to prevent pollution. Instruments
and automatic controls which monitor and regulate performance are
important in the actual control of air pollution from the incinerator.
For example, gas temperatures in the furnace are often controlled by
increasing or decreasing the amount of underfire and overfire air.
Some automatic control systems not only adjust the amount of overfire
air, but also adjust the amount of underfire air needed to maintain
a specific ratio with the overfire air. Instruments and controls
can be used to maintain a steady, high temperature in the secondary
combustion zone to assure that odor-producing organic matter in the
gas stream is completely oxidized to innocuous compounds. Furnace
draft necessary to maintain proper negative pressure in the furnace can
be controlled manually or automatically by adjustment of the induced
fan and the chimney draft. Draft pressures should be measured at
the (1) underfire air duct; (2) overfire air duct; (3) stoker compart-
ments; (A) sidewall air duct; (5) sidewall low furnace outlet; (6)
dust collector inlet and outlet (pressure differential); and (7)
induced draft fan inlet. Many instruments need frequent calibration
to ensure accurate and reliable readings.
Types of parameters and instruments that can be used to assist in
the operation of an incinerator include the following:
1. Temperatures
-Optical pyrometers for flame and wall temperatures in the range
of 2,200 to 2,500F
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6.3.61
-Shielded thermocouples (Chrome-Alumel) for furnace temperatures
in the 1,400 to 1,800F range, and iron-constantan in duct
temperatures down to 100F Gas- or liquid-filled bulb thermometers
for duct temperatures below 1,OOOF and for ambient temperatures
and water temperatures
2. Draft Pressures
-Manometers and inclined water gauges for accurate readout close
to the point of measurement
-Diaphragm-actuated sensors where remote readouts are desired
3. Gas or Liquid Pressures from 1 to 100 psi
-Bourdon-tube pressure gauges for direct readout
-Diaphragm-actuated sensors for remote readout
4. Gas Flows
-Orifice or venturi meters with differential pressures measured
by draft gauges
-Pitot tubes and draft gauges
5. Liquid Flows
-Orifices with differential pressure measurement
-Propeller-type dynamic flowmeters
-Weirs
6. Electrical Characteristics
-Voltmeters, ammeters, and wattmeters
7. Smoke Density
-Photoelectric pickup of a light beam across the gas duct
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6.3.62
8. Motion
-Tachometers for speeds of fan, stoker, or conveyor drives
-Counters for reciprocating stokers and conveyors
9. Visual Observation
-Vidicon closed-circuit television cameras for viewing furnace
interiors, furnace loading operations, or stack effluents
-Peep holes in furnace doors
-Mirror systems
10. Weight
-Motor truck platform scales for measuring the quantity of in-
coming solid waste and outgoing residue, fly ash, and siftings
-Load cells for automatically weighing crane bucket contents
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6.3.63
REFERENCES
1. State of New Jersey. Chapter 11—Incinerators. Control and Prohibition
of Air Pollution from Incinerators. Department of Health, June 12, 1968
(applies to items 1-7 and 9).
2. Kaiser, E. R. Chemical Analysis of Refuse Components. Proceedings of the
1966 National Incinerator Conference.
3. Terminology Used in Incinerator Technology. Journal of the Air Pollution
Control Association, pp. 125-26. Vol. 15, No. 3. March 1965.
4. MacKnight, R. J. and J. E. Williamson. General Refuse Incinerators.
In: Air Pollution Engineering Manual, J. A. Danielson (ed.). Cincinnati,
DREW, PHS, National Center for Air Pollution Control and the Los Angeles
County Air Pollution Control District. PHS No. 999-AP-40. 1967.
5. Williamson, J. E. Design Principles for Multiple Chamber Incinerators.
In: Air Pollution Engineering Manual, J. A. Danielson (ed.). Cincinnati,
DHEW, PHS, National Center for Air Pollution Control and the Los Angeles
County Air Pollution Control District. PHS No. 999-AP-40. 1967.
6. Compiled by McNavlin, Inc., 3100 West Walnut Street, Milwaukee, Wisconsin.
7. DeMarco, J., D. J. Keller, J. Leckman, and J. C. Newton. Incinerator
Guidelines—1969. DHEW, PHS, Bureau of Solid Waste Management. 1969.
8. Interim Guide of Good Practice for Incineration at Federal Facilities.
DHEW, PHS, National Air Pollution Control Administration, November 1969.
9. Netzley, A. B., and J. E. Williamson. Multiple-Chamber Incinerators for
Burning Wood Waste. In: Air Pollution Engineering Manual,
J. A. Danielson (ed.). Cincinnati, DHEW, PHS, National Center for Air
Pollution Control and the Los Angeles County Air Pollution Control District.
PHS No. 999-AP-40. 1967.
10. Sableski, J. A., and W. A. Cote. Air Pollutant Emissions from Apartment
House Incinerators. DHEW, PHS, National Air Pollution Control Administra-
tion (MS, undated).
11. Sableski, J. J., and J. E. Williamson. Flue-Fed Apartment Incinerators.
In: Air Pollution Engineering Manual, J. A. Danielson (ed.). Cincinnati,
DHEW, PHS, National Center for Air Pollution Control and the Los Angeles
County Air Pollution Control District. PHS No. 999-AP-40. 1967.
12. Corder, S. E., G. H. Atherton, P. E. Hyde, and R. W. Bonlie. Wood and
Bark Residue Disposal in Wigwam Burners. Bulletin 11, Forest Research
Laboratory. Oregon State University, March 1970.
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6.3.64
13. American Public Works Association. Municipal Refuse Disposal, 2nd ed.
Chicago, Public Administration Service, 1966.
14. Par Instrument Company. Oxygen Bomb Calorimetry and Combustion Methods.
Technical Manual, No. 130, Moline, Illinois, 1960.
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6.4.1
IV. OPEN BUENING
A. DESCRIPTION OF SOURCE
Open-burning is the practice of burning waste materials on-site and out-of-
doors in which the burning pile is directly exposed to the atmosphere.
The waste materials are usually generated from a nearby process or activity,
collected into piles and set on fire; or they may consist of natural vege-
tation such as weeds or agricultural, forestry or other natural products
which are burned standing or are cut down and collected into piles and then
burned. Whole structures such as automobile bodies and houses may also
be set on fire either deliberately or accidentally. Burning in pits, in
open containers such as oil drums or bins not designed as incinerators
is another form of open burning. Food preparation in the out-of-doors,
such as barbecueing, bonfires and open drum fires for heating purposes
are sometimes defined as open burning practices, depending on local
regulations.
Open burning is a virtually uncontrollable source of air pollution and
should be prohibited. The type and amount of material being burned,
the location of the burning, frequency of burning, the purpose of the
burning, and the rates of contaminants emitted complicate any attempt
to control this practice. Smoke, particulates and fly ash are the principal
emissions as well as partial products of combustion such as carbon
monoxide, oxides of nitrogen, hydrocarbons, aldehydes, and ketones. In
addition, wastes containing ammonia, nitrogenous, sulfurous materials,
animal matter or other material may produce odors.
B. TYPES OF OPEN BURNING
The handling of open-burning and control of emissions (where open
burning is permitted) varies with the type of operation or activity with
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6.4.2
which the burning is connected. The following types of open burning may
be noted:
1. Household Wastes
These may consist principally of paper and wood products, particularly
sulfide treated materials, and organic matter (fats oils, vegetable
matter, plastics and a variety of other materials). Open burning
of garbage, rubber products, green vegetation, plastics and other
highly organic or carbonaceous materials should never be permitted.
The burning of fallen leaves in the autumn in piles , in gutters, and
containers with screened curtains is widely condoned although many
communities are banning this practice. The collective contribution
to community smoke levels by many householders burning leaves,
particularly in the fall, can be substantial. Besides presenting an
important air pollution problem, the smoke may contain allergenic
materials, such as oils and pollens which may affect susceptible
individuals with respiratory disorders. Any class of open burning
which is dispersed among the general population should be eliminated.
Open-burning by householders should be prohibited, particularly in
large cities. Even in rural or semi-rural areas, open-burning by
householders should be prohibited or regulated by fire department
and air pollution control agencies.
2. Construction and Demolition Wastes
These usually consist of waste wood materials, including bark,
chips and saw dust. Wood that is kiln dried and uncontaminated,
e.g., furniture manufacturing wastes can be stacked to provide
"underfire" air and ignited to quickly produce a hot fire and
comparatively little smoke, although organic pollutants such
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6.4.3
as pyroligneous acids, and aldehydes are emitted. Creosoted lumber,
oily woods, oil rig timbers, rubber or plastic coated wires or other
materials which produce dense black smoke should never be burned. Wood
coated with oil and lead-based paints should not be burned or if burned,
included in relatively small quantities with largely clean woods and
cardboard. Contaminated non-combustible substances such as paint
cans or oil drums should not be charged to the burning pile.
Where burning is permitted in construction and demolition activities,
attempts should be made to segregate combustibles from noncombustibles,
and highly carbonaceous and oil soaked, stained or coated wastes should
be segregated from the clean wastes and hauled away. Wet material
should be dried before burning or hauled to a dump or to an approved
municipal incinerator.
Undesirable material, if permitted by local ordinances, should be
carefully fed to an existing hot fire in small quantities. Refuse
piles should be carefully stacked to "sandwich" wastes so that the
material used to kindle the fire, such as paper and cardboard, is
at the bottom of the fire, and the heavier materials are near the top.
The material should be stacked to allow for circulation of air, but
should not be too loosely packed as fly ash may result. Fires
should be constantly attended. The operator should periodically
stir the contents when smoke occurs or extinguish the fire if the
smoke gets out of hand, or a dangerous situation occurs.
3. Salvaging Operations
These usually consist of the burning off of rubber, plastics, textiles,
upholstery stuffings and other materials from junked or waste products
to recover metals which have economic value. Major sources of this
type of interest to the inspector are the preparation of motor vehicle
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6.4.4
hulks for the scrap market and salvaging of metal wires. These
operations when burned in the open are a major source of large volumes
of dense black smoke. Burning of this type should be one of the first
forms of open burning to be prohibited. Where it is not, the opera-
tions should be cited under smoke and opacity violations. Reclamation
activities of this type can be conducted in approved multiple-chamber
incinerators (see Section III, Incinerators).
Automobile bodies can be manually stripped. Blow torches are
frequently used to facilitate this operation. Automobile bodies
are prone to catch on fire either deliberately or accidentally, with
the latter frequently used as an excuse for the burning. Wrecking
yards should be kept under frequent surveillance and normal practices
observed, including the prevention and handling of runaway fires.
Wrecking yards generally erect tall fences which interfere with the
inspector's observation of the premises. The inspector should frequently
enter the yard.
4. Open Dump Burning
Dump burning consists of the burning of large accumulations of mixed
refuse which are transported to and deposited at the surface
of the dump site. Although this practice continues in some
communities, it is rapidly disappearing.
In view of the volume and range of materials burned, enormous
quantities of smoke and other contaminants are emitted. Control is
usually achieved by injunctive action, inter-agency cooperation, or
by special legislation prohibiting the practice. However, elimination
of the practice will require development of alternative means of
final disposal such as sanitary land fill, in which the rubbish is
compacted and buried, the use of specially designed municipal
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6.4.5
incinerators, removal of rubbish at sea, or use of rubbish in
special land fill projects. Sanitary land fill operations,
however, must be closely observed to prevent the admission and
circulation of underground air which promote underground fires.
Dump odors can also be released causing nuisances to neighbor-
hoods situated nearby. The inspector should check the dump
site to assure that no openings and fissures are permitted in
the ground. Under proper conditions, spontaneous combustion and
smouldering materials can occur for many days. These can be
extinguished by recompacting the earth.
5. Agricultural Burning
Agricultural burning consists of burning of standing vegetation
or crop stubble, cuttings, trimmings and prunings, dead fruit trees,
dried grasses, swamp grasses, sugar cane, straw stacks, potatoe and
peanut vines, citrus groves, cotton ginning burrs, and animal wastes,
including manure piles.
The greatest amount of open-burning tends to be performed during and
after the harvest season. Burning is also often performed during
cleaning of agricultural lands for conversion to residential,
commercial or other property.
Emissions include blue, brown or white smoke. The burning of
forestry products etc., can result in black smoke. Forest fires
due to slash burning or to accident will produce large quantities of
soot and fly ash, in addition to smoke. Plumes from all burning can
be voluminous and travel long distances.
Agricultural burning, when associated with the raising of crops and
animals for human consumption, is often permitted, although the
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6.4.6
practice has been banned when alternative disposal methods are found.
Agricultural wastes, including uprooted trees and tree stumps,
can be cut up into small pieces and disposed of in cut and cover
dumps. Forest scraps can be processed by chipping or crushing and
can be used as raw materials for Kraft Pulp Mills or processes
producing fibreboard, charcoal briquettes or synthetic firewood.
Agricultural waste material can be disposed of in approved stationary
or mobile multiple-chamber incinerators, and air curtain destructors,
although methods of disposal other than combustion—such as composting
and cut-and-cover dumps—are preferred.
The burning of trees, brush and lumber wastes in land clearing opera-
tions can be effectively performed in an open pit with a portable Air
Curtain Destructor or equivalent device. The pit may be approxi-
mately 8' across, 15' wide and 12' deep, unlined or lined with
refractory material (e.g., firebrick and reinforced concrete). The
destructor consists of an air blower, driven by an industrial engine
(approximately 50 h.p.), a plenum chamber and a nozzle. The blower
delivers approximately 800 scfm of air for each foot of length of the
pit, against a static pressure in the plenum of 10 inches of water.
This arrangement provides an air velocity of 150' per second or about
100 mph in a flat sheet or curtain of air blowing diagonally downward
across the pit. The air is deflected by the back wall to the bottom
of the pit and is directed across the pit against the material to be
destroyed, and finally upward at the front wall until it reaches the
under side of the curtain. This sets up ideal conditions for combus-
tion. The gases that finally escape through the air curtain have been
stripped of any solid waste material that has not completely burned.
The destructor can burn about 5 tons of trees and brush per hour, or
about an acre of refuse material per day.
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6.4.7
Agricultural burning, when permitted, can be confined to days on
which air pollution potentials are minimal. Care should be taken
not to burn materials that are wet or contaminated. Vegetation con-
taining large amounts of pesticides or which include possibly poisonous
or allergenic materials should not be disposed in a manner which
exposes individuals to the emissions.
6. Coal Refuse Piles
Coal refuse from mine tailings should be kept under constant
surveillance. These may consist of millions of tons of refuse
which can ignite due to accident or deliberate action. Coal refuse
piles should be allowed to cool before fresh waste material is added,
or they should be replied. The piles should also be compacted or
sealed with impervious material, or injected with slurries of non-
combustible material where holes or fissures appear. As in land
fill dumps, compaction and sealing of the piles prevent air circulation
and the chance of spontaneous combustion. Also such potential kindling
materials as mine timbers, paper, vegetation and other combustibles
should be segregated and disposed of separately. (See Coal Preparation
Plants, Chapter 7, Section XIII and Mining, Chapter 7, Section XII.)
7. Other Sources
Open-burning from industrial and commercial sources can consist of
materials which are involved in activities conducted at the source.
The burning of industrial wastes is likely to result in undesirable
emissions particularly where chemicals, packing materials, or oily
or carbonaceous materials are involved. The actual or potential
practice of open-burning at industrial sites should be looked upon
as a possible operation in the overall industrial activity and should
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6.4.8
be reported by the inspector. Since private disposal facilities
and approved multiple chamber incinerators are usually available
to industry, the practice should be prohibited.
C. CONTROL OF OPEN BURNING
The extent of open-burning conducted is largely a function of the type,
quality and coverage of the waste-pickup and disposal practices of the
community. Factors that may affect the extent of open-burning conducted
include:
1. Type of refuse pick-up service available to householders, and
commercial and industrial institutions.
2. Provision for separate or combined refuse collection for different
materials.
3. Provision for recovering or recycling of salvageable materials.
4. Waste storage and materials handling practices at the source.
5. Collection method, frequency and schedule.
6. Transport routes and transfer points.
7. Availability and location of disposal sites and capacities.
8. Attitude of public towards both waste disposal and air pollution.
9. Availability of other waste disposal methods, e.g., incineration.
10. Extent of public and private services available, fees and other
assessments.
11. Method of final disposal: incineration, sanitary land fill, open
dumping, composting, other.
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6.4.9
The extent or coverage, access to facilities, and costs to users are some
of the principal factors which determine the types of open-burning prohibi-
tions and regulations that can be applied. Where pickup services and dis-
posal facilities are inadequate or incomplete, open-burning is permitted
under controlled conditions in some communities.
Where service is adequate and comprehensive, almost all forms of open-
burning can be prohibited. In between these two situations, a combination
of disposal service, open-burning regulation, and specific prohibitions
may be applied, until such time as it is feasible to ban the practice
all together. The types of regulations that can be applied include:
1. Restriction on excessive emissions by use of Ringelmann and opacity
regulations.
2. Prohibition of open burning.
3. Specification of approved method of incineration.
4. Limitation on substances that can be burned, e.g., garbage and
smoky material such as rubber products, wet materials and hazardous
substances.
5. Restriction of burning to prescribed burning hours.
6. Restriction of burning to certain locations.
7. Restriction of burning days according to official air pollution
forecasts.
8. Application of public nuisance, where complaints have been made.
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6.4.10
9. Requirement of burning permit by fire department and/or air pollution
control or other agency.
10. Fire tending requirements, including minimum distance to habitable
structures.
11. Use of tree and brush shredders; mobile multiple-chamber incinerators
or air curtain destructors; use of oil or gas fired salamanders
to replace burning in drums for the purpose of outdoor heating.
While most open-burning can be prohibited, some burning may still be per-
mitted for health, safety, and conservation reasons either by official
agencies or under their control. Examples are prevention of a fire hazard
by burning off dry weeds and vegetation, slash burning, and emergency
measures required to dispose of contaminated materials to prevent
the spread of possible disease.
Control programs should proceed in a direction which leads to eventual
elimination of open-burning altogether. This must be accomplished by
institution, expansion and coordination of pickup services, recycling of
waste materials, sanitary land fills, composting, waste heat incineration,
and rail or boat hauling (where necessary). Often such programs must be
accompanied by an intensive local public education program that will result
in an awareness of the waste disposal problem and support for improved
disposal methods. The inspector can play an important role in informing
the public.
D. INSPECTION POINTS
Open-burning differs from other stationary source problems in that it is
not conducted at a fixed location, nor are the persons responsible for
setting fires always easily located. Fires may be set and abandoned, and
the individuals responsible may have to be determined from the business
licensing division, the owners of the land, or from others residing or
working nearby.
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6.4.11
The inspector should note the following in his reports or violation
notices:
1. Size, diameter and height of fire.
2. Location—distance from any near structure, corner of lot and other
re fe ren ce p oint.
3. Materials being burned; describe whether green or wet.
4. Possession of permit by operators from local fire department or
other agency; expiration date, conditions.
5. Is fire being conducted on a day when high air pollution conditions
have been forecasted?
6. Means available to extinguish the fire.
7. Individuals in attendance at the fire. Was the individual adding
material to the fire, stirring the fire, raking or controlling the
fire in any manner?
8. Name of individual in attendance, name of firm, organization or
individual he works for or represents.
9. Attempts being made to extinguish the fire on arrival, during visit
of inspector, or later.
10. Did the operator attempt to segregate heavy material, contaminated
material, heavies or other material which is capable of emitting
heavy quantities of smoke?
11. Was the fire in view at the time of the observation. Position of
Inspector relative to reading of emissions.
12. Record of Ringelmann and opacity on smoke observation sheet. Show
continuous time interval for each opacity and density, color change
and total violation time in minutes.
13. Comments of operator and/or owner.
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6.4.12
14. Weather conditions during observations including wind direction.
15. Status of plume at end of recorded observation.
16. Source of the materials.
17. Reason for the fire.
18. How often fires are set.
19. Availability of pick-up services in the area.
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6.4.13
REFERENCE
1. Geyer, 0. W., and E. A. Rudulph. Minimizing Air Pollution from Open
Burning with an Air Curtain Destructor. Air Pollution Control Association,
paper 70-143.
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6.5.1
V. ODOR DETECTION AND EVALUATION
A. INTRODUCTION
All air pollutant emissions of concern from the standpoint of field
operations divide into those which are perceptible to the human observer
(e.g., enforcement officers, complainants), and those which are imper-
ceptible. Imperceptible contaminants cannot be consciously perceived
through the senses (seeing, hearing, smelling, feeling, touching) at
normal ambient concentrations and can include such contaminants as carbon
monoxide, hydrocarbons, and oxides of nitrogen. They are primarily de-
tected and measured through ambient air sampling and source sampling and
analysis, or are indirectly inferred through the determination of design,
operational and process parameters associated with equipment and systems
capable of emitting air contaminants. These factors are dealt with
principally in Chapters 6 and 7 of this manual.
The perceptible emissions are those, like dust, smoke, and fumes, which can
be seen, or leaking gases which can be heard, or gases and vapors which
can be detected through the sense of smell. The field enforcement officer's
stock-in trade are these forms of emissions. Indeed, he should be trained
to be an expert in detecting, describing, quantifying these emissions and
in establishing their sources and causes.
The field enforcement officer will be concerned with odors from a number of
standpoints:
1. To identify odors that are the cause of a public nuisance and to
establish the extent and frequency of the public nuisance.
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6.5.2
2. To identify the contaminants (the odorants) and sources responsible
for odors and to collect evidence to establish the extent and cause
of the public nuisance or violations of emission regulations.
3. To assess odors as a means of identifying emissions in general and
of evaluating the effectiveness of air pollution control practices.
The problem in the evaluation of odors is essentially that there are no
reliable objective methods for field identification of specific compounds
and conditions causing the odors, or for quantifying the concentration of
odorants in the ambient environment. These aspects of odor evaluation
must be treated as scientific investigations. Nevertheless, a trained
enforcement officer should be sufficiently expert in odor evaluation so
that:
1. He can objectively evaluate the perception and his own level of odor
sensitivity in relation to complainants and the general population.
2. He has thorough knowledge of the sources which produce odors and the
physical conditions that affect odor potentials.
3. He can identify odors in the field.
4. He has knowledge of the conditions which affect odor perception and
of scientific techniques used in odor evaluation.
Thus, to be an expert, the enforcement officer should have knowledge of
both the perceptual and the scientific aspects of odor investigation.
These are treated in this section.
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6.5.3
B. CHARACTERISTICS OF ODORS AND ODORANTS
A major difficulty in dealing with odors as an air pollution problem arises
from the fact that an odor is not an air contaminant but is a property of
air contaminants which can only be detected or measured through its
effects on the human organism. Briefly, an odor is that property of a
substance which affects the sense of smell. A contaminant which has an
odor is called an odorant.
The capacity in humans to perceive odors varies considerably among
individuals, and in one individual from time to time. Some persons
("anosmiacs") are very insensitive to odors, while others may be acutely
sensitive to odors unnoticed by most people. This variability of
individual sensitivity complicates the problem of estimating the
prevalence of an odor nuisance.
The air pollution inspector is primarily interested in establishing the
existence of an odor problem according to legal criteria: i.e., a
problem which constitutes a nuisance to a considerable number of persons
over a continuing or significant period of time. Both of these elements
are important from a practical standpoint, since there is little value
in devoting substantial effort to the solution of a nonrecurrent problem
or one not affecting an appreciable number of persona in the community.
In such problems, the inspector is concerned with (1) identifying the
odor, (2) rating the odor's intensity, (3) identifying the odorant, (4)
establishing the frequency of the nuisance, (5) locating the "odor
route," (6) locating the source of the odorant, and (7) influencing some
operational or engineering control over the odorant.
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6.5.4
1. Odor Perception
There are a few characteristics about odor perception which the
enforcement officer should be familiar with in estimating whether an
odor problem exists. These are as follows:
a. The olfactory sense becomes fatigued after continuous perception
of an odor.
b. An odor is usually detected whenever there has been a significant
change in odor quality or intensity. A pleasant odor can become
objectionable to one who has become used to it under continuous
exposure, when it increases in intensity.
c. Odors do not, in themselves, cause physical disease. The odor
of many toxic materials (e.g., chlorine, sulfur dioxide, hydrogen
sulfide) may serve as a warning agent, however. Odors, also, may
bring on nausea and have an adverse effect on asthmatics.
d. A person's ability to perceive odors varies from day to day.
e. Compounds of different constitution may yield similar odors,
whereas compounds of very similar constitution may yield different
odors.
f. An unfamiliar odor is more likely to cause complaints than a
familiar one.
g. The perception level of odors decreases with increasing humidity.
High humidity tends, however, to concentrate odors in a given
locality.
h. Odor quality may change upon dilution.
i. Some persons can detect certain odor qualities but not others.
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6.5.5
2. Odorants
It is not necessary for enforcement purposes to consider all of the
odorants. Nearly all substances known, excepting those to which one
is accustomed such as oxygen, have an odor. According to Moncrieff,
potent odorants generally possess a significant degree of volatility
and chemical reactivity such as are exhibited by the aldehydes and
various classes of hydrocarbons. Also, materials of high vapor
pressure tend to yield odors more readily than those of low vapor
pressure.
The average person would find all familiar environmental odors
objectionable were they strong enough. There is no problem about
identifying these through mental association. Such familiar odors
as coffee, gasoline, moth balls, roses, tobacco, wood smoke, jasmine,
paint, skunk do not need further definition to most people and can be
termed characteristic odors.
However, there are many odors whose qualities are familiar though the
odorants themselves are not. These are the so-called chemical odors,
as complainants might call them, associated with chemical and
petrochemical processes. The odors of skunk, garlic, onions and
cabbage, for example, may arise from various sulfur compounds (ethyl,
methyl, propyl and butyl mercaptans, respectively) generated from
oil-refining processes. These are good examples of the fact that
compounds of similar constitution have different odors.
We may further distinguish between strong, pungent "chemical" odors,
which offend primarily because of intensity, and those which are
obnoxious or malodorous because of their quality. The latter are odors
originating from the handling and processing of organic compounds containing
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6.5.6
nitrogen and sulfur. The odors arising from nitrogenous compounds
may be associated with animal odors and decomposition and putrefractlon
of animal tissue. The odors arising from sulfur are characterized
by "rotten egg," "skunk," and "decayed cabbage." They also include the
acrid, bitter sulfide odors found in metallurgical operations.
3. Odor Parameters
In investigating odor complaints to establish the existence of a
nuisance, the enforcement officer should attempt to identify the odorant,
describe the odor and establish its objectionability, and provide
(2)
some indication as to its severity. Nader in describing perceptual
measurements of odors in the laboratory, defines the following set
of parameters pertinent to such an evaluation.
• Quality
• Intensity
• Acceptability
• Pervasiveness
Although developed primarily for experimental use, these parameters
are also useful for characterizing odors in the field. Skill in
evaluating odors lies in the ability to distinguish the separate
characteristics of the odor, and in isolating the smell from other
senses (taste, feel, sight and hearing). Normally sensitive persons
can develop such skill through training.
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6.5.7
a. Quality
The quality of an odor may be described either in terms of
association with a familiar odorant, such as coffee, onions, etc.
(characteristic odors) or by associating a familiar odor with an
unfamiliar odorant. Aside from such direct descriptive
terms, the observer, in an attempt to be complete and accurate,
may add modifiers to his description to indicate shades or
overtones of an odor. These may actually include subjective
reactions such as "fragrant," "foul" and "nauseating,"
or characteristics of odor which may be associated with the
sense of taste such as "bitter," "sweet," "sour," "burnt," or
even partially with the sense of touch as far as contaminants
which are irritating are concerned, such as "pungent," "acrid,"
"acidic," and "stinging." As a matter of fact, a contaminant may
sometimes affect more than one sense. An irritant can be smelled,
cause eye-irritation and be tasted.
Odor terminology is meaningless without actual exposure through
odor training. Therefore, the inspector should be exposed to
samples of typical odorants found in the local industry, so
that he can be prepared to make quick and accurate identifications.
There is no substitute for this kind of training. Verbal
descriptions of odors do not implant as vivid an imagery in the
mind as do descriptions of visual or auditory phenomena.
A few of the well-known odor classification systems are indicated
here. They are useful in training inspectors in making associations
and analyzing the various component sensations which odors may
produce. For field purposes, one system is as good as another.
The advantage of all systems is that they yield a usable odor
vocabulary, as shown in Figure 6.5.1 and below.
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6.5.8
Figure 6.5.1. ODOR CHART. This chart attempts to
present a complete range of odor terms
which can be used to construct phrases
of odor description. Each of these
terms, moreover, can be numerically
fixed from a "clock" chart for map
notations, tabulations, or general
reporting. Reported by Gruber, and
attributed to Dean Foster, Head of the
Psychophysical Laboratory at the Joseph
E. Seagram Co., Louisville, Kentucky.
(SOURCE: Weisburd, Reference 14.)
-------
6.5.9
(3 4)
Henning's Odor Classification '
Based on Six Types of Odor Classification
1. Spicy: Conspicuous in cloves, cinnamon, nutmeg, etc.
2. Flowery: Conspicuous in heliotrope, jasmine, etc.
3. Fruity: Conspicuous in apple, orange oil, vinegar, etc.
4. Resinous: Conspicuous in coniferous oils and turpentine.
5. Foul: Conspicuous in hydrogen sulfide and products of decay.
6. Burnt: Conspicuous in tarry and scorched substances.
(3 4)
Crocker-Henderson Classification '
A Condensation of the Henning Arrangement
1. Fragrant or sweet.
2. Acid or sour.
3. Burnt or empyreumatic.
4. Caprylic, goaty, or oenanthic.
b. Intensity
Intensity is described by some numerical or verbal indication of
the strength of an odor. Various intensity scales have been
devised. The average observer or complainant can be expected to
distinguish three levels of intensity, characterized as weak,
medium and strong. A useful rating system especially adapted for
field work is as follows:
Description
No detectable odor.
1 Odor barely detectable.
2 Odor distinct and definite, any unpleasant
characteristics recognizable.
3 Odor strong enough to cause attempts at
avoidance.
4 Odor overpowering, intolerable for any
appreciable time.
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6.5.10
This system depends on observation or reporting of behavior more
than on subjective impressions of the complainant. The fact that
a person desperately attempts to avoid a strong and unpleasant
odor is clear and verifiable indication of its intensity. Reports
of odor intensities of 2 or higher on this scale may be particularly
relevant in establishing the existence of a legal nuisance.
For scientific purposes, on the other hand, an odor rating which
does not depend so heavily on the objectionable character of an
odor is usually preferable. Such a system, long used by expert
evaluators, is the following:
Intensity Expert Description
0 No odor
1 Very faint
2 Faint
3 Easily noticeable
4 Strong
5 Very strong
This system has the advantage of distinguishing the intensity
parameter from the acceptability parameter in a more definite
Acceptability
An odor may be either acceptable or unacceptable depending on its
intensity and quality. Thus odors normally considered as pleasant,
such as flower fragrances and perfumes, may become unacceptable
only at very high concentrations (i.e., at very high intensities
on the scientific scale) whereas obnoxious odors may be unacceptable
at much lower concentrations, where they are not clearly recognizable,
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6.5.11
d. Pervasiveness
The parameter of pervasiveness refers to the tendency of an odor
to resist being dissipated by dilution of the air in which it
occurs. Pervasiveness in this sense is related to the nature of
odorant and is not readily determined except by experiment.
Nevertheless, a highly pervasive odor is one which, in the field,
will tend to be detectable in sheltered areas over a longer
period of time, and will therefore in some incidents be easier to
track than a less pervasive one.
C. DETERMINANTS OF ODOR PERCEPTION
Odor is a property of an odorant, but the report of a perceived odor is
mediated by the nervous system and the brain of an observer. Therefore
differences in reports of odor perceptions may be due partly to differences
in the physical conditions of exposure, and partly to differences in the
physiological and psychological status of the observer. In view of these
considerations, the main parameters determining an odor report may be
listed as
• Identity of odorant (or odorants)
• Concentration(s) of odorant(s).
• Ambient conditions.
• Status of observer.
The relevance of these parameters to problems of odor evaluation is
discussed in the following subsections.
1. Identity of Odorant
The chemical identity of the substance responsible for an odor is
usually the main determinant of the quality of the odor, as discussed
above. Thus, in principle, it should be possible to infer
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6.5.12
the identity of the odorant from the perception of odor quality.
To a certain extent this is feasible and is done. An expert
observer, trained to recognize the odors of various odorants at
various intensities, is an invaluable asset in odor evaluation
techniques.
The field enforcement officer should be trained to identify the
odorants most often responsible for complaints within his area.
So trained, he can often identify the cause of an odor problem by
his own investigation in the field, even when the complainants
are uncertain as to the nature or origin of the odor.
One difficulty that arises in the endeavor to associate particular
odorants with their odors is that the chemical identities of odorous
industrial air contaminants are not always known. Further, in some
cases the odors are caused by mixtures of odorants which may vary in
their proportions under different conditions of production; these
variations can lead to changes in perceived odor quality, but usually
within some limited range which does not prevent recognition by
a trained observer.
Another complication in the recognition problem arises from the fact
that odor quality may change with dilution. In mixtures of odorants
this may be due to a difference in pervasiveness of the individual
compounds; however, single odorants sometimes behave similarly.
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6.5.13
Even when the chemical identity of the odorant or odorants is not
known, it is often possible to attribute the problem to a particular
source on the basis of recognition of an odor quality which is
characteristic of that source. For example, Kraft pulp mill odors
are commonly characterized as similar to rotten cabbage. It is known
that such emissions contain several odorant compounds having
recognizably different odor quality and pervasiveness; yet, practically
anyone in a pulp mill community will identify the source from the
"rotten cabbage" description.
Concentration of Odorant
The concentration of the odorant in the ambient air is the main
parameter determining the intensity of the perceived odor, although
ambient conditions and observer status may cause appreciable variations
in perceived intensity. Other parameters being constant, the
relation of odor intensity to odorant concentration is given by the
Weber-Fechner law, which asserts that the intensity is proportional
to the logarithm of the concentration. Pervasiveness is inversely
related to the constant of proportionality (k) in the Weber-Fechner
equation,
I = k log(C/Ct)
(The larger: k^ is, the more rapidly the intensity decreases as the
concentration is reduced, and therefore the less pervasive the odor is.)
The Weber-Fechner law applies only for individual odorants, and
only in the concentration range equal to or greater than the threshold
concentration (C 2: C ). For consistency with the Weber-Fechner
equation, the threshold concentration should be defined as the
maximum concentration of odorant which fails to yield a detectable odor.
However, in practice it is usually defined as the minimum concentration
(detection threshold) that produces a detectable odor, as this quantity
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6.5.14
is easier to determine and can differ from the other only slightly.
Threshold concentrations of a given odorant as determined for
different individuals show large variations corresponding to
differences in individual sensitivities; therefore tabulations usually
show values determined on a statistical basis, such as the average
for several members of a panel.
In the case of perceived odors caused by mixed odorants, such as those
from pulp mills, there are no generally accepted rules which can be
used to relate odor intensity to the concentrations of the individual
odorants. Studies have shown that perceived odor intensities due
to mixed odorants are often not those which would result from simple
addition of the effects of the separated odorants. With some pairs
the intensities are approximately additive, but in others they may be
classified as
• Counteractive, in which the observed intensity is less than
expected for one of the odorants alone;
• Suppressive, in which the observed intensity is less than
expected for an additive effect, but greater than for a
counteractive effect;
• Synergistic, in which the observed intensity is greater than that
expected for an additive effect.
The determination of which of these categories applies to a given
pair of odorants can only be made by experiment. Few such
experiments have been carried out; therefore, it is not generally
possible to predict the intensity relations of mixtures from a
knowledge of the properties of the individual odorants.
-------
6.5.15
3. Ambient Conditions
It is recognized that the evaluation of quality and intensity of an
odor may be affected by the temperature and humidity of the air
presented for evaluation. Unfortunately, there has been no study of
the importance of these factors, and there is no known way of
accounting for any such effects. In evaluations under laboratory
conditions it is desirable to maintain such conditions reasonably
constant, and at levels near average ambient air levels, during any
series of tests designed to yield comparable results.
4. Status of Observer
The principal parameters of observer status which are
relevant to odor evaluation may be listed as sensitivity, expertise,
and physiological and psychological conditioning.
a. Sensitivity
The sensitivity of observers for any given odor varies widely,
and the relative sensitivities of two observers vary inconsistently
for different odors. Furthermore, independent observers often
disagree substantially regarding odor quality, particularly when
evaluating odors of mixed odorants. For these reasons statistical
evaluations using panels of observers are more likely to provide
reliable results than evaluations by individual observers.
b. Expertise and Training
As discussed above, expertise can be developed to a considerable ex-
(7 8}
tent by study and training, ' although it is necessarily limited
by the physiological sensitivity of the would-be expert. With
respect to quality, expertise consists in the ability to
recognize and discriminate between a number of odorants, either
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6.5.16
singly or in mixtures. Relative to intensity, expertise
permits reliable discrimination between a large number of
graded levels of intensity. Thus, a trained person can detect a
smaller percentage difference in concentration levels of a given
odorant than an untrained individual.( A recent study led to
the estimate that, at least for some odorants, there appear to
be 25 or 30 just-noticeable-differences over the range of
perceptible intensities (from threshold to the maximum
distinguishable), and that each j.n.d. corresponds to about a
60 percent increase in odorant concentration.
c. Physiological and Psychological Condition
A problem of physiological origin, in the evaluation or tracking
of odors, is fatigue of the olfactory nerves, which tends to
diminish the sensitivity of the evaluator. The effect is
especially noticeable after prolonged exposure to a rather high
intensity of odor, and may seriously complicate the conduct and
interpretation of odorant threshold determinations in the
laboratory.
Colds and other infections of the nasopharyngal tract can cause
serious, if temporary, interference with the sense of smell and
result in loss of sensitivity to many odorants. For observers in
an odor panel, a preparation of a standard odor can be useful in
checking on these variations in sensitivity from day to day; at
least when the condition is not too obvious to need confirmation.
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6.5.17
D. MEASUREMENT OF ODOR INTENSITY OR ODORANT CONCENTRATION
In odor incident investigations, it is desirable wherever possible to
establish some quantitative estimate of the degree of odor involved, and
of the relation between concentrations of odorant in the field and
quantities emitted at the source. In cases where a single odorant with
known characteristics is involved, this may sometimes be done by chemical
or physical methods of analysis, with comparisons based on weight of
odorant in various samples. However, for the rather more common case
where the identity of the odorant is not established, or where mixed
odorants are involved, the odor potential may be determined in terms
of "odor units."
An odor unit is defined as the quantity of any odorant (or mixture of
odorants) which, when dispersed in unit volume of odor-free air, produces
a threshold intensity response. If a sample of a gaseous emission contains
(say) 10 odor units per cubic foot, it can be inferred that when the
sample is diluted with nine parts of odor-free air, the resultant
mixture will have a barely detectable odor. Thus the "odor concentration"
in odor units per cubic foot also describes the dilution factor required
to reduce the odor to a just perceptible level. Although not directly
expressible in terms of contaminant weight per unit volume, the odor
concentration is analogous to other emission concentrations, for
engineering purposes.
Odors both in ambient air and in odorous effluent streams should be
evaluated by the inspector to confirm a pattern indicated by complaints.
A quantitative basis may be established by the use of a portable dilution
device, or samples of the air may be collected for later evaluation in
the laboratory to confirm the inspector's sensory evaluation. Appropriate
methods and devices for these purposes are discussed below.
-------
6.5.18
1. Sampling for Later Evaluation
To confirm field estimates of odor intensity, or to determine odor
removal efficiency of control equipment, the investigator may collect
samples of odorous gases of low moisture content by means of a glass
probe connected by a ball and socket joint with clamp to a gas
collection tube (e.g., a 250 ml. MSA sample tube) as shown in
Figure 6.5.2. The odorous gas is drawn into the tube by a rubber
squeeze bulb evacuator. (Rubber or plastic tubing or other absorptive
or heat sensitive materials on the probe side of the sample tube
should not be used.)
For gases with high moisture content, such as may be found in steam
plumes, precautions are required to prevent condensation of water vapor
and possible absorption of odorants in the liquid. This can be
achieved by using a syringe and hypodermic needle to aspirate a
smaller sample into the sample tube, previously filled with odor-free
air. A system of this sort is also illustrated in Figure 6.5.2. (A
capillary probe may be used, to minimize error due to dead space in
the probe.)
Sampling problems that must be dealt with include: (1) if sample is
warm, condensation and cooling may result in the selective removal
of odorants from the vapor phase; (2) odorous material may be sorbed
on the walls of containers and on particulates in sample; (3) chemical
changes after sampling may alter the odorant, etc.
A test kit convenient for field use consists of six 250 ml. sample
tubes, a hand aspirator, and several probes of glass tubing with ball
joints for attachment to the sample tubes. A special capillary probe
and syringe with hypodermic needle, for sampling gases of high
moisture content, may also be included.
-------
6.5.19
Ball and socket Joint (with clamp)
Capillary glass lube (2 mm. O.D.)
Hypodermic needle (18 gauge)
Cork stopper Ball joint
Figure 6.5.2. SCHEMATIC DIAGRAMS OF ODOR SAMPLING
APPARATUS. Method "A" is used to
collect samples low in moisture
content; Method "B," samples high in
moisture content. The latter method
permits primary dilution of odor
sample in the field, and minimizes
condensation of vapors on the inner
surface of the sample tube.
(SOURCE: Weisburd, Reference 14.)
-------
6.5.20
2. Dilution Techniques
Dilution techniques are applicable both to the inspector in his field
observations and to the laboratory investigating team in providing for
evaluation by odor panels.
For field use, either in odor patrol or in investigation of an odor
incident, ambient air may be tested with the aid of a portable
dilution device such as the "scentometer"^11' (Figure 6.5.3). This
device is actuated by inhalation by the operator, thus dispensing
with pumps and electrical power sources; holes which can be opened or
closed by the fingers permit precalibrated dilutions of the ambient
air stream with air which is simultaneously deodorized by an activated
charcoal filter. A useful feature is that the observer can combat
the effects of olfactory fatigue by breathing only deodorized air for
a period prior to an actual test.
Various devices, mainly constructed on similar principles, have been
used for dilution of odorants for laboratory evaluation. However,
the method of choice both for simplicity and accuracy appears to be
the syringe technique. The odorous gas is displaced from the
sample tube (for example, by mercury displacement) into a large
graduated syringe, in which it is diluted by addition of odor-free
air. Further dilutions are easily managed by the use of additional
syringes, as illustrated in Figure 6.5.4. The last dilution, usually
10 to 1, is performed by the panelist, who is furnished with 10 ml.
of sample injected into his 100 ml. syringe; he dilutes the sample
to 100 ml. with ambient air before sniffing it, and records a
positive or negative result as to detection of the odor.
For confirming the identity of suspected odorants, or for quantitative
determination of concentrations of identified odorants, gas chromatography
can be performed, using samples no larger than those necessary for the
organoleptic evaluation of odor.
-------
6.5.21
NOSEPIECES
, CHARCOAL
BED
ODOROUS AIR
Figure 6.5.3. SCHEMATIC OF SCENTOMETER. Odorous
air passes through graduated orifices
and is mixed with air from the same
source, which is purified by passing
through charcoal beds. Dilution rates
are fixed by the orifice selection.
(SOURCE: Gruber, Reference 11.)
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6.5.22
STEP 1
STEP 2
STEP 3
Figure 6.5.4. EQUIPMENT USED FOR TRANSFERRING AND DILUTING ODOR
SAMPLES (SOURCE: Air Pollution Engineering Manual,
Reference 15.)
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6.5.23
E. DETERMINING SOURCES RESPONSIBLE FOR ODORS
1. Odor Patrol
The possibilities of instituting quick, effective action to control
odors when complaints arise depend, to a large extent, on the field
officer's intimate knowledge of the odor potentials of the various
industrial and other sources within the community. It is therefore
necessary for him to become familiar with likely source
activities.
A simple odor patrol is probably the best indicator of existing or
potential nuisance from odorous discharges. This consists of a
regular periodic patrol around selected plants or in selected areas,
documented by notes as to observed odors, with time, location, and
wind direction. Special patrols for complex industries such as
refineries and chemical plants may be assigned to personnel specially
trained for them, and cognizant of the particular activities which
entail an odor potential. A record of such odor patrols is also
useful in indicating where odor control efforts are most required.
Fortunately, there is a substantial background of odor control
experience to indicate what types of activities are likely causes of
obnoxious odors. Where particular processes have not been subject
to odor control, odor problems are likely to arise from the
following industries or industrial activities:
a. Petroleum Industry
b. Petrochemical Plant Complexes
c. Chemical Industries
d. Pulp and Paper Mills
e. Coke Ovens and Coal Processing
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6.5.24
f. Metallurgical Industries and Foundries
g. Coffee Roasting and Other Food Processing Industries
h. Meat Processing and Animal Industries, including
(1) Feedlots
(2) Livestock Slaughtering
(3) Inedible Rendering
(4) Fish Canning and Processing
(5) Meat Packing
(6) Poultry Ranches and Processing
(7) Tanneries
i. Paint and Varnish Manufacture and Coating
j. Sewage Treatment Plants
k. Tar Coating Operations
1. Combustion Processes, including
(1) Gasoline and Diesel Engine Exhaust
(2) Maladjusted Heating Systems
(3) Incinerators
Further details regarding these industrial processes and their potential
for generating odors are presented in this and other chapters of tnis
manual. (See, in particular, Table 5.1 Chapter 5, Chapter 7: Kraft
Pulp Mills, Rendering Plants, Petroleum Industry, Aluminum Reduction
Plants, Fertilizer Plants and Roofing Plants.) Field officers should
become familiar with the details of all such operations in the area.
Of course, similar activities under nonindustrial auspices may also
cause odor problems. Not uncommon are odorous emissions from
domestic and municipal incinerators, burning dumps, trash fires,
agricultural burning, sewage plants, and diesel engine emissions.
-------
6.5.25
Field Investigations of Odor Incidents
In a routine inspection of an industrial plant, the normal air
pollution configuration is tracked from cause to effect—from the
feed input of equipment to the effects of the contaminant generated
from the equipment on receptors and the environment (see Chapter 4,
Section II). The tracing of an odor problem reported as a public
nuisance is just the reverse of this procedure. The investigation
begins with the complainant and his environment and works back to the
equipment responsible in the following steps:
• Interview of complainants to obtain as much factual information
as to the intensity, evidence and source of the contaminant.
• Identification of the contaminant causing the nuisance.
• Tracking the contaminant to its source or sources.
• Inspection of the equipment at the source to determine plant's
capacity to emit the contaminant.
• Collecting signed district attorney affidavits or other official
forms from complainants who desire to testify in court.
• Serving notices of violation to the source or motivating plant
management to remedy the situation.
-------
6.5.26
Most of these techniques are described in Chapters 2 and 4 of this
manual. This chapter is primarily concerned with the problem of
tracking and identifying sources of odors, assuming that the source
is not immediately determined.
In an odor nuisance, the field officer must establish the existence
of two areas: the effect area, that is, the area over which the
nuisance effect exists; and the source area—that area which can
be assumed by logical tracking techniques to contain the specific
source or sources of the nuisance contaminant. The determination
of a source area is often a first step in isolating the exact source
and cause of the nuisance, especially in those cases where the
specific source is difficult to establish initially.
a. Determining Air Flow from Source
The basic problem in an odor nuisance is to establish the flow
of air masses from a source of air pollution to establish
responsibility, or to determine relative contributions to the
problem from two or more sources. This procedure is otherwise
known as source tracking, and is especially applied when the
source of the nuisance is originally unknown. This basically
involves determination of wind direction and velocity for the
purpose of triangulating the source.
-------
6.5.27
In source triangulation, only two vectors are required, i.e., wind
directions taken on separate occasions and locations at times of
nuisance occurrence. Wind direction is always ascertained from
the direction in which it is blowing. (A south wind blows from
the south.) Wind direction can be determined from flags, steam
or smoke plumes, finger-wetting, or other indicators.
The interview with the complainant should also attempt to
establish the wind direction at the time of contamination. The
investigator should instruct complainants and/or observers in
recurring problems to maintain a record of time, intensity and wind
direction. If this is not possible, the investigator should attempt
to estimate the time the contamination is likely to occur, so that
he can logically schedule reinspections.
In complex cases involving heavily industrialized communities with
many possible sources, or where contamination or nuisance does not
appear to be localized according to wind direction, the inspector
may plot a wind rose, based on local meteorological data. A
check with the enforcement agency may disclose prevailing wind
patterns and other pertinent micrometeorological data for the
area in question.
A conclusive determination of air flow movement may be made by
tracer studies utilizing tracer materials and aerosol filter
sampling devices. Tracer material may consist of fluorescent
dusts, spores, lycopodium powder, radio-active materials, neutron
activation powders, zinc cadmium sulfide or zinc silicate, or
other material which can be recognized and counted under a
microscope and which range in size from 1.5 to 2 microns in
diameter. Tracer materials can be either introduced into a
-------
6.5.28
system at the source of air pollution or blown by portable
blower equipment into the atmosphere near the suspected source.
Enforcement officers may be deployed according to wind flow
for sampling in or near the receptor and suspected source areas.
The greater the distance to the suspected source area, the
greater the number of detection stations required. The sampling
is also performed either under atmospheric conditions which occur
during the nuisance or during periods of atmospheric stability.
In complex cases, the following tracking results are recorded on
a map as shown in Figure 6.5.5:
• Location of complainants and distances from possible sources
• Plant source layout showing principal types of equipment which
may be involved.
• The number of complaints, and frequency of complaints as well
as the time of day.
• Observations by inspectors at various points to fill in any
gaps in data.
• The tracked contaminant routes and vectors of triangulation.
• Wind roses or other indications of wind direction.
b. Tracking Odors
During the inventory inspection conducted at all of the industrial
plants, investigators attempt to initiate correction on all odor
potential processes in order to prevent nuisances. It should be
kept in mind, however, that if a plant is otherwise in compliance,
but produces odors, no nuisance is involved if no one is affected.
Nevertheless, in such cases, the investigator describes the odor
-------
LEGEND
Direction from which wind is blowing;
Complainant's Report
O Inspector's Report
R Rendering Odor
I Light
M Moderate
H Heavy
S Hoise Stable Odors
A Aluminum Dross Odors
5M.P.H.
e6:00 P.M.
Ul
NO
CITY OF ONYX
Figure 6.5.5. ODOR SURVEY. Although possibly malodorous industries are centered
between Onyx St. and End Road and along the Onyx Basin River, reports
and observations indicate that the Blameless Rendering Company is
the primary source of the odors. This finding is verified by the
fact that complaints are reported in two time periods—from 11:00 A.M.
to 5:00 P.M., from residents north of Arrow Highway and west of Onyx
Street, when the wind was from the southeast, and from 5:00 to 7:00 P.M.,
from residents in the area around Oakwood Street, south of Arrow Highway,
when the wind was from the west. Inspection reports, operating data
and point observations verify the existence of a public nuisance at
the Blameless Rendering Company. (SOURCE: Weisburd, Reference 14.)
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6.5.30
potential on his reports in the event that complaints are received
regarding that type of odor.
In most odor problems tracking is unnecessary. An experienced
investigator is often able to identify the source of an odor by its
quality and intensity and may be able to relate the odor to a
specific activity. Since enforcement officers are familiar with the
industrial establishments in their inspection sectors, they are
often able to connect the odor with a specific piece of equipment.
The enforcement officer verifies his findings by following an
odor route in order that he may prove that the odor emanates from
a specific piece of equipment. In such tracking situations it is
not necessary to rate odors numerically, but to describe the odors
as they are perceived. In these cases the inspector either
follows the odor from the suspected source as it moves downwind to
effect areas, or he proceeds from an effect area (i.e., from the
complainants themselves) upwind to the source. The first method
is for verification, the second for tracking an unknown source.
(1) Point Observations
The purpose of tracking odors or making odor surveys is
(1) to locate an unidentified source of an odor, and (2) to
prove to the satisfaction of the courts that a given odor
results from a contaminant emanating from a specific source
or sources. The proof can only be made by an expert witness,
the investigator, familiar with odors and the equipment and
operations located in a suspected area.
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6.5.31
In some cases, a recognized odor may be attributed
to a single source, if there is known to be
only one activity in the established source area capable of
emitting the odor. If the circumstances are less auspicious,
the recent operating experience of several suspect sources
may require investigation. Inventory and permit records at the
enforcement agency may be consulted to locate all potentially
suspect equipment in the source area.
The consensus of odor quality in the complaint area must be
identical to the odor quality emanating from the source. That
is, with the exception of "intensity" all significant point
observations should agree. The "intensity'1 should vary in a
geographical pattern. A point observation here is a
stationary location at which an evaluation was made of the
following:
• Odor quality and intensity.
• Wind direction and strength at time of odor.
• Duration of odor.
• Time of day and date.
Each nuisance complaint represents a point of observation.
Either the investigator verifies the complainant's information,
or if there are so many complainants that he cannot do so,
he requests the complainant to keep a record of this
information. The pattern of complaints may thus, in itself,
delineate a vector which will point upwind to the source.
Especially is this true when complainant locations form a
circle or a crescent on a map, when odors are reported under
relatively stable weather conditions. The projected center of
any circular locus of point observations can be assumed to be
the source area.
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6.5.32
Where an insufficient number of point observations are
disclosed, scheduled point observations may be conducted
to triangulate the source. At such point observations, the
investigator may, when odors are detected, make use of the
scentometer described previously or take several samples of
the air with evacuated flasks. One flask can be used for
comparison purposes in an odor-free room at the enforcement
agency and another for lab analysis of the odorants. For
even more effective analysis, odorants can be sampled from
the atmosphere at point observations by activated carbon
sorption or by freeze-out trapping; analysis can then be
made by infrared or mass spectrometry.
(2) Micrometeorological Problems
Several complications with respect to odors due to the
micrometeorology of given areas may arise. The
distances and elevations at which odor travels may be very
considerable. Sour gas odors from oil fields have traveled
as much as 100 miles from a source, though this instance
is rare. Where meteorological conditions are favorable
to odor dissemination, the radius will not generally exceed
5 to 10 miles. Most odors seem to be confined in an area
1/2 to 2 miles in radius during stagnant air conditions.
Odor dissipation may depend on temperature, humidity, wind
velocity and steadiness of prevailing wind.
Some estimate of wind velocity may be useful in determining
relative distances at which a source might be located from
the complaint area. A weak breeze, for example, suggests that
a source may be nearby, since a slow moving odor stream may
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6.5.33
dissipate by diffusion before it is carried very far. If
the breeze is strong, on the other hand, and no suspected
sources are nearby, the odor may have traveled a long
distance, especially if it is a particularly pervasive odor.
The tracking of an odor from a complaint area to a source is
a matter of following an increasing intensity of a given
quality of odor. This can be accomplished by making
representative point observations along the odor route. To
avoid odor fatigue, field officers may travel with their vehicle
windows closed to maintain as relatively odor-free vehicle
as possible, then open them upon arrival at a new point
(12)
observation for purpose of comparison.
Actual "skips'1 in the odor route may be observed due to
local turbulence, eddies, etc. Odorants may also travel in
air streams at varying elevations above the ground, then
strike a neighborhood or community situated on a rise of land.
To positively establish an "odor route," Gruber suggests
the use of balloons to plot low-level wind directions along
the path of the wind itself. He suggests partially inflating
such balloons with helium gas so that they will rise slowly
and indicate a low-level wind direction which can be plotted
with a compass and recorded on a map.
(3) Approaching the Plant
The investigator in tracking problems travels towards the plant
on its downwind side and notes the intensity of the odor.
In more complicated cases, several radio-equipped cars are
deployed to transmit intensities which are then recorded and
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6.5.34
interpreted at the communication center. Several cars may
be necessary when the odor fluctuates, the wind direction
changes, or a complex of possible sources in an area makes
positive identification of a source difficult.
If the odor is traced to an industrial community and to a
group of industrial plants all performing similar industrial
operations, it will be necessary to determine whether all of
the plants, a few, or just one plant is responsible. Because
the responsibility must be clearly determined, a studied
surveillance of the inside and outside of each suspected
plant may be required. Action can be taken against multiple
sources, as well as single sources, as long as the odor
concentration arising from each, and together, can account
for the intensities noted.
If the odor is not chronic, and was reported for the first time,
it may be due to deviation in operational practice, to a
breakdown of equipment or to the introduction of a new process.
Because of these probabilities, a one-time odor is likely to
originate from one industrial source. An inspection of the
plant may disclose the specific operation which has caused the
nuisance. When the odor has been traced to the equipment,
the conditions under which the malodorous contaminants were
emitted must be fully documented.
Although the odors which are detected in the field arise from
the diffusion of gases and vapors, the source of the odors
may be in solid or liquid form. Samples of petroleum
products, chemical fluxes, solvents, decomposed organic
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6.5.35
matter, materials from open dumps, etc., can be taken as
evidence, or the material can be photographed. The fact that
substances may have vapor pressures sufficient to yield an
odor or have low odor thresholds can be substantiated by
expert testimony, as long as other operational and
conditioning factors which caused the odor are reported.
F. INVESTIGATION OF ODOR POTENTIALS OF SOURCES
During the inventory inspection at industrial plants, field officers normally
attempt to initiate corrective steps on processes entailing potential odor
problems, in order to prevent nuisances.
1. Plant Inspection and Source Testing^
On suspicion of odor nuisance emissions, plant inspection may be
undertaken, supplemented by source testing for evaluation of the
odor potential. As soon as practical after identifying the
suspected source of odor emissions, the field officer should proceed
to gain entry into the plant for the purpose of: (1) gathering the
evidence needed to prove that the violation has occurred, namely that:
a person discharged into the atmosphere, from a single source, a
contaminant in greater amount or quality than allowed
for more than the specified time; (2) determining the cause; and
(3) ascertaining the necessary corrective measures.
In some of the larger control agencies the inspection is carried out
by two levels of staff. Item (1), above, is the responsibility of the
field patrol; while items (2) and (3) are assigned to engineering
inspectors. In the smaller agencies, one man must carry out all
three investigations.
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6.5.36
After gaining entry, the investigator should seek the highest
ranking person he can reach who will have intimate knowledge of the
plant operations and who has authority to speak for the company
management.
a. Interrogation
By proper interrogation, the field officer should establish the
circumstances leading to the emission violation. He .should be
alert for observations he can make to verify the truthfulness and
accuracy of the statements made to him. For example, a common
cause of dense smoke emission is rodding a stoker-fired boiler.
If this has occurred and the inspection immediately follows the
observation, the firing bar will be warm. A simple check is to
feel the firing bar.
b. Equipment Data
Next, the equipment data is obtained unless it is, to the
inspector's knowledge, already a part of the plant record. This
should include the make, type, size, and capacity of all
equipment or processes involved. Note should also be made of
general conditions which have a bearing on the air pollution potential
of the equipment. Observations should be made of gages and monitoring
instruments, particularly temperature charts on odor incinerators,
load charts on boiler instrument panels, photoelectric opacity
recorders, etc. Information on operating failures which lead to
excessive emissions are being published in the technical
literature. Much benefit can be gained from process studies which
point out operating conditions which cause high pollution discharge.
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6.5.37
2. Evaluating Odor Concentrations
Where the odor being investigated has been identified as caused by
a known odorant it should be measured by chemical or physical
means in the laboratory. This is especially true when the
known odorant also has toxic or irritant potential, as
in the case of hydrogen sulfide, sulfur dioxide, ammonia, chlorine,
various aldehydes and some other organic and inorganic compounds. In
many such cases, the criteria for acceptable concentrations in
ambient air are already established in terms of mass concentrations
which are lower than odor thresholds, so that evaluation in terms
of odor units is superfluous.
However, when the odor nuisance is the only suspected effect, or
whenever the identity of the odorant is in doubt, or more specific
methods of measurement are unavailable, the samples collected at the
source should be evaluated by an odor panel using dilution techniques,
as described previously.
G. RELATING SOURCE STRENGTH TO CONTROL REQUIREMENTS
In correcting an odor problem, the contaminants responsible for an odor
should be controlled so that threshold levels are never reached in the
outdoor atmosphere of the community. Some industries incorrectly assume
that they will have no odor problems, because they consider their own
discharges to be unobjectionable or even pleasant. However, the presence
of any odor which persists and is not normally associated with the daily
routine of living will be a source of annoyance to the neighborhood.
Complaint records show that this applies to such comparatively acceptable
odors as those of baking bread and roasting coffee; therefore, it is wise
to consider any odor as potentially objectionable.
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6.5.38
The odor evaluations of source samples provide estimates of
odor concentrations in terms of odor units per unit volume,
which can serve as guidelines in the development of control methods.
Thus, if a stack effluent is normally diluted by a factor of 1,000 before
it arrives at a breathing level in the surrounding neighborhood, an odor
concentration of 1,000 odor units per standard cubic foot could be
considered to be on the verge of acceptability, while an odor
concentration of 10,000 would require at least 90% control.
This sort of guideline can be refined by calculating an odor emission
rate in odor units per minute. This is equal to the product of the odor
concentration by the volume rate of the stack exhaust, in standard cubic
feet per minute (scfm). Table 6.5.1 illustrates some examples of typical
results using this approach (as reported by Benforado, et al. ).
Dilution factors required for positive control can be estimated either
by surveying ambient air in the vicinity to determine the maximum odor
concentrations observable, or by standard engineering design procedures
based on plume dilution equations or community experience. It should,
of course, be remembered that dilution of odorous gas to the median
odor threshold level can be expected to render it undetectable by only about
half of the people in the community; therefore the use of an additional safety
factor in design for positive control is ordinarily advisable. Also, dilution
factors work better near the source and tend to break down with distance.
An application of odor measurement in improving neighborhood odors would
be to survey all the operations in a plant and determine the odor emission
rate from each. Listing such emissions together with estimates of costs
for control can help management pick out the largest odor sources (rather
than the largest stacks or largest volume discharges) and concentrate
effort initially on those which are likely to provide the greatest
improvement per dollar of expenditure.
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6.5.39
Table 6.5.1. MISCELLANEOUS TESTS: RENDERING PLANT;
COFFEE ROASTER; RUBBER PROCESSING PLANT
Application
Rubber processing
Coffee roaster
Rendering plant
Average
Exhaust Average Emission" Rate
Flow Odor Strength (odor units/
(scfm) (odor units/scf) mm) Remarks
6900 50 350.000 Acceptable— controlled
by direct-flame fume
incinerator
3600 2000 7,200,000 Not acceptable—
uncontrolled ef-
fluent from roasters
29,000 1500 - 25.000 55,000,000 Not acceptable—
730,000,000 uncontrolled ef-
fluent from dryer
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6.5.40
H. ODOR CONTROL
The elimination of odors is the most important part of any odor problem.
Air contaminants responsible for an odor should be controlled so that
threshold concentrations are never reached in the outdoor atmosphere.
This is accomplished by adopting any one or a combination of control
devices or techniques such as waste gas incinerators, catalytic
oxidation, and adsorption in activated carbon. Such common-sense con-
trol methods as general sanitation, refrigeration of animal tissue,
improved maintenance and operational techniques should also be applied
where odors arise from plant housekeeping.
The abatement of odors is accomplished either by complete destruction of
odorants and prevention of odorant emissions, or neutralizing the
malodorous effects of contaminants. Odor prevention or odor destruction
is generally preferable since air pollution control in critical pollution
areas seeks control of contaminants, not the effects of contaminants.
For this reason, the ideal odor control method is perfect combustion.
This is accomplished by an afterburner or waste gas incinerator. To be
effective, such devices must maintain complete combustion at proper
temperatures and exposure times, reducing all contaminants to odorless
water and carbon dioxide. Partial or incomplete combustion may result
in a series of reactive secondary products which may not only be
malodorous, but eye-irritating and corrosive as well.
Other methods of preventing the escape of odors to the atmosphere include
chemical scrubbing and charcoal filtering described in other Sections
of this Manual.
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6.5.41
REFERENCES
1. Moncrieff, R. W. The Chemical Senses. John Wiley & Sons, Inc.
1944. pp. 166-235.
2. Nader, J. S. Current Techniques of Odor Measurement. Chemical-
Toxicological Conference. A.M.A. Archives of Industrial Health.
Vol. 17, No. 5, May 1958.
3. Crocker, E. C., and C. F. Henderson. Analysis and Classification of
Odors. American Perfumer and Essential Oil Review. 22:325, 1927.
4. McCord, C. P., and W. N. Witherridge. Odors, Physiology and Control.
McGraw-Hill Book Co., Inc., 1949.
5. Rosen, A. A., J. B. Peter, and F. M. Middleton. Odor Thresholds of
Mixed Organic Chemicals. J. Water Pollution Control Federation.
34 (1):7, 1962.
6. Byrd, J. F., and A. H. Phelps, Jr. Odor and Its Measurement.
In: Air Pollution, Vol. II. A. C. Stern (ed.). New York City,
Academic Press, 1968.
7. Turk, A. Selection and Training of Judges for Sensory Evaluation of
the Intensity and Character of Diesel Exhaust Odors. DHEW, PHS,
Pub. No. 999-AP-32. 1967. 45 pp.
8. Prince, R. G. H., and J. H. Ince. J. Appl. Chem. 8, 314-321, 1958.
9. Leonards, G., D. Kendall, and N. Barnard. Odor Threshold Determinations
of 53 Odorant Chemicals. J. Air Pollution Control Association. Vol. 19,
No. 2, February 1969.
10. Benforado, D. M., W. J. Rotella, and D. L. Horton. Development of an
Odor Control Equipment. J. Air Pollution Control Association. Vol. 19,
No. 2, February 1969.
11. Gruber, C. W., G. A. Jutze, and N. A. Huey. J. Air Pollution Control
Association. 10, 1960. 327-330.
12. Gruber, C. W. Odor Potential from the Official's Viewpoint. Chicago Fifty-
Seventh Annual Meeting, American Society for Testing Materials, June 15,
1954. p. 16, pp. 56-88.
13. Gruber, C. W. Source Inspection, Registration and Approval. In: Air
Pollution, Vol. II. A. C. Stern (ed.). New York City, Academic Press,
1968.
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6.5.42
14. Weisburd, M. I. Air Pollution Control Field Operations Manual. DREW, PHS,
DAP. Washington 25, D.C. (PHS #937).
15. Danielson, J. A. (ed.). Air Pollution Engineering Manual. Cincinnati,
DHEW, PHS, National Center for Air Pollution Control and the Los Angeles
County Air Pollution Control District. PHS No. 999-AP-40. 1967
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6.6.1
VI. MOTOR VEHICLE VISIBLE EMISSIONS
A. INTRODUCTION
Motor vehicles make up by far the largest source of transportation emissions
and in some urban areas are the predominant contributor to total air
pollution. Collectively, motor vehicles emit large quantities of particulates,
carbon monoxide, hydrocarbons and oxides of nitrogen (see Section II,
Chapter 1).
The control of motor vehicle emissions ultimately depends on technological
solutions leading to the mass production of low-emission vehicles. Current
approaches include:
(1) Engine exhaust control systems such as blow-by gas recycle,
catalytic converter and exhaust gas recirculation systems.
(2) Engine modifications including manifold air injection and adjust-
ment of ignition timing and air-fuel mixture.
(3) Evaporative controls for fuel systems.
(4) Alternative propulsion systems such as electric battery, gas
turbines and rotary engines.
(5) Alternative fueling systems including liquified natural gas (LNG)
or liquified petroleum gas (LPG).
Beginning with the 1968 model year, all new passenger vehicles, both foreign
and domestic, had factory installed exhaust control and closed crankcase
control systems in compliance with Federal law.
Enforcement of regulatory standards affecting motor vehicles can be
accomplished in three distinct ways: (1) systematic inspection and testing
of motor vehicles initially at assembly plants and periodically at official
inspection stations to ensure that vehicles are maintained within acceptable
ranges of air pollution control system effectiveness; (2) spot-checking of
vehicles for defects or disconnected control systems usually performed by
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6.6.2
state highway patrols or police agencies as part of an overall vehicle
safety check; (3) surveillance of moving behicles for violations involving
excessive emissions conducted by law enforcement officers or air pollution
control field enforcement officers. Field enforcement includes inspection
of vehicle control systems to see that they are installed, connected and in
operation.
Field enforcement officers in air pollution control agencies perform
functions related primarily to (3) above. Enforcement practices among
agencies may vary from no activity in this area to an organized vehicle
surveillance and enforcement program conducted by a special vehicle patrol
unit operating within the enforcement branch of the agency. Two types of
motor vehicles are basically involved: the gasoline powered and diesel-
powered vehicles.
B. GASOLINE-POWERED VEHICLES
In addition to their contribution to background pollution, gasoline-powered
vehicles are important because they are dispersed with the general popula-
tion, and pedestrians and drivers are directly exposed to both visible and
nonvisible emissions.
Motor vehicles that are maintained in good condition and are normally
operated should not emit visible emissions. Visible emissions may result
from:
(1) Poor engine condition, engine not tuned properly, worn plugs,
valves and rings and faulty choke mechanism, timing and
carburetor settings.
(2) Abnormal driving practices including operation of the vehicle
in a manner that results in rapid acceleration or deceleration
under load and speed shifting.
(3) Unorthodox fuels or use of engine and fuel additives to "clean-
out" the engine.
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6.6.3
(4) Unorthodox engine modifications.
(5) Disconnection or corruption of vehicle pollution control systems.
(6) Deterioration of control systems on aged or poorly maintained
vehicles.
(7) Various combinations of the above.
1. Vehicle Emission Control Systems
Typical vehicle emission control systems that may be checked by field
enforcement officers include the following:
a. Crankcase Control Devices
(1) Type 1; Open system; valve controlled by intake manifold
vacuum; approved when factory installed on 1961 through some
early 1964 models. This type of system is shown in
Figure 6.6.1.
(2) Type 2: Valve controlled by crankcase vacuum; approved for
both factory and station installation (Figure 6.6.2).
(3) Type 3; Tube-to-air cleaner; no devices approved for station
installation (Figure 6.6.3).
(4) Type 4: Combination system; approved for both factory and
station installation (Figure 6.6.4).
b. Exhaust Control Systems
These are intended to control emissions from the engine exhaust
either by promoting combustion at the engine exhaust ports or
manifold or in the exhaust system, or by modifying engine operation
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6.6.4
COMBINATION OIL FILLER CAP
AND VENTILATION AIR INLET
FRESH AIR IN
INTAKE
MANIFOLD
EXHAUST
PIPE
ROAD DRAFT
TUBE PLUGGED
VARIABLE (OR FIXED)
ORIFICE CONTROL
VALVE, WITH VENT
TUBE TO INTAKE
MANIFOLD
Figure 6.6.1. CRANKCASE VENTILATION SYSTEM USING VARIABLE
ORIFICE CONTROL VALVE (TYPE 1) (SOURCE:
CALIFORNIA HIGHWAY PATROL, Reference 1)
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IDLE
GROOVE
MODULATOR ON SEAT
BLOWBY GASES TO
INTAKE MANIFOLD
MODULATOR
SPRING
DIAPHRAGM
Engine at idle
Valve closed, modulator on seat. Blowby
gases and ventilating air tlow through idle
groove at about 3 cfm.
BLOWBY GASES FROM CRANKCASE
MODULATOR OFF SEAT
IDLE
GROOVE
BLOWBY GASES TO
INTAKE MANIFOLD
MODULATOR
SPRING
DIAPHRAGM
Engine at cruise
Valve open, modulator oft seat. Larger volume
of blowby gases and ventilating air now flow
through valve. Flow rate ot valve dependent
on amount of blowby generated by the engine.
BLOWBY GASES FROM CRANKCASE
Figure 6.6.2.
VALVE CONTROLLED BY CRANKCASE VACUUM (TYPE 2)
(SOURCE: CALIFORNIA HIGHWAY PATROL, Reference 1)
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6.6.6
COMBINATION OIL FILLER CAP AND
VENTILATION AIR INLET
INTAKE MANIFOLD
Figure 6.6.3.
CRANKCASE VENTILATION SYSTEM USING A VENT
TUBE TO THE AIR CLEANER (TYPE 3) (SOURCE:
CALIFORNIA HIGHWAY PATROL, Reference 1)
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6.6.7
OIL FILLER
CAP SEALED
VENT TUBE FROM VALVE ROCKER
ARM COVER TO AIR CLEANER
ROAD DRAFT
TUBE REMOVED.
EXHAUST
PIPE
VARIABLE (OR FIXED) ORIFICE
CONTROL VALVE, WITH VENT
TUBE TO INTAKE MANIFOLD
Figure 6.6.4.
SCHEMATIC VIEW OF COMPLETELY CLOSED TYPE
CRANKCASE VENTILATING SYSTEM (TYPE 4)
(SOURCE: CALIFORNIA HIGHWAY PATROL, Reference 1)
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6.6.8
so that air and fuel supplied results in combustion with reduced
hydrocarbon and carbon monoxide emissions. Vehicle control system
types include air injection, ignition induction, and various
variations of these including the Engine-Mod System (American
Motors), Improved Combustion Control (IMCO) on certain Ford Motor
Company models and the CCS or Controlled Combustion System on
several General Motors cars.
(1) Air Injection Systems
These typically consist of: air pump, air injection into
each exhaust port, and carburetor and distributor modifica-
tions. Typical systems for 6 and 8 cylinder engines are shown
in Figures 6.6.5 and 6.6.6.
(2) Engine Modification Exhaust Emission Control Systems
Examples of modified engine components include combustion
chambers altered in shape to decrease quench area, an intake
manifold redesigned to achieve complete vaporization of the
fuel, and a fuel injection system which replaces the
carburetor and allows leaner running.
Engine-modification type exhaust control systems usually
include minor charges such as a deceleration control device,
leaner carburetion, retarded spark at idle, and may include a
thermostatic valve for spark advance and an anti-dieseling
solenoid (see Figures 6.6.7 and 6.6.8).
c. Fuel-Evaporative Control Systems
All 1970 and later model gasoline-powered passenger and light duty
commercial vehicles first sold and registered in California and
having an engine displacement of 50 cubic inches or greater must
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6.6.9
AIR SUPPLY PUMP
VACUUM SENSING LINE _ Lt~"^LCHECK VALVE
.= -—•— TO AIR CLEANER
AIR FILTER
BACKFIRE-SUPPRESSOR VALVE
Figure 6.6.5. 6-CYLINDER ENGINE AIR INJECTION SYSTEM
(SOURCE: CALIFORNIA HIGHWAY PATROL, Reference 1)
-------
6.6.10
AIR FILTER
AIR NOZZLE
AIR SUPPLY PUMP
Figure 6.6.6. V-8 ENGINE AIR INJECTION SYSTEM (SOURCE:
CALIFORNIA HIGHWAY PATROL, Reference 1)
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6.6.11
VACUUM ADVANCE CONTROL VALVE
Figure 6.6.7. VACUUM ADVANCE CONTROL VALVE (SOURCE:
CALIFORNIA HIGHWAY PATROL, Reference 1)
-------
6.6.12
VACUUM ADVANCE
CONTROL VALVE
INTAKE
MANIFOLD
TDC
DISTRIBUTOR
VACUUM
CHAMBER
DISTRIBUTOR
CARBURETOR/CONTROL
VALVE/DISTRIBUTOR RELATIONSHIP
Figure 6.6.8. CARBURETOR/CONTROL VALVE/DISTRIBUTOR RELATIONSHIP
(SOURCE: CALIFORNIA HIGHWAY PATROL, Reference 1)
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6.6.13
be equipped with a fuel evaporative loss control device or systems.
These systems are intended to prevent evaporative losses from the
entire fuel system including the gas tank, the fuel filter valve,
breathing vents and carburetor. A typical system is shown in
Figure 6.6.9.
2. Types of Visible Vehicle Emission Violations
a. Nuisance Type Violation
The principal criterion in halting and citing gasoline-powered
vehicles is primarily one of nuisance. This may be taken to mean
the emission of any quantity of smoke which is outstanding in
terms of volume, color, and duration as to draw attention to the
offending vehicle. In traffic conditions such smoke is likely to
result in fumigating other vehicles on the roadway and to offending
drivers and pedestrians who are not in a position to avoid the
emissions or to register a formal complaint.
Some enforcement agencies have power to cite excessive emissions
under a general nuisance law or a specific nuisance type regulation
directed at this type of source. For example, the Motor Vehicle
Code of the State of California states that "no motor vehicle shall
be operated in a manner resulting in the escape of excessive smoke,
flame, gss, oil, or fuel residue." The enforcement officer must
precisely describe the character of the "excessive" emission in
each situation, e.g., volume of smoke emitted, opacity, effect of
emissions on other vehicles, and likely cause of the emissions. If
the smoke plume obscures the traffic area, is continuous through
more than one gear, is outstanding, or is a nuisance, action can
be taken under this criterion. This approach is generally suitable
for privately owned passenger vehicles. Examples of a citation
form is illustrated in Chapter 2.
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Fuel Vapor
Storage Case
Vacuum Switching Valve
Thermal
Expansion Tank
Sealed Cap
Figure 6.6.9.
EVAPORATIVE LOSS CONTROL SYSTEM—VAPOR
STORAGE CASE USED BY TOYOTA
(SOURCE: CALIFORNIA HIGHWAY PATROL, Reference 1)
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6.6.15
b. Opacity-Type Violation
Another form of vehicle violation is based on the principles of
reading emissions from stationary sources, e.g., application of
Ringelmann, opacity and time criteria (see Chapter 4, Section III).
The enforcement officer uses the accumulative stop watch method
by totaling the periods of time in which Ringelmann densities
exceed the prescribed standard (see Chapter 2). The observer
following a vehicle must avoid reading directly into the plume,
if possible. The line of observation should intersect the smoke
train at as wide an angle as possible. Error of reading smoke
in this fashion should be compensated for and smoke should be read
at its point of maximum density.
Recommended rules for gasoline-powered motor vehicles limit visible
(2)
air contaminants to five seconds.
The opacity-type violation is suitable for commercial vehicles and
is handled in a manner similar to stationary sources (see Chapter 2),
The commercial operator tends to own more than one vehicle, and to
have the resources to institute a preventive maintenance program
for all of his vehicles. For this reason, the violation notice
route provides the options to either prosecute the case in court
and/or to provide opportunity (through the administrative conference
process) for the owner to correct his problem with the specific
vehicle, or to institute a maintenance program for all vehicles, and
to train individual operators. These procedures may also provide
for increasing penalties for repeated violations either of the same
vehicle or other vehicles. It is sometimes desirable to include
an additional inspection report where the enforcement officer has
determined the causes of the violation from remarks made by the
operator or from inspection of the equipment.
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6.6.16
3. Following and Halting of Vehicles
In some control jurisdictions enforcement officers may not be authorized
to stop vehicles. License numbers are taken, and the owners and/or
operators are sent warning letters, or are requested to attend an office
hearing. In some regions private and commercial vehicles are halted
and detained on the road. In the latter case, special conditions and
rules of the road apply.
In performing vehicle patrol it is desirable to conduct systematic
patrols of expressways, freeways, major arteries, secondary and
residential streets. It is undesirable to patrol congested areas
where it is impractical to halt vehicles, or where the halting of such
vehicles presents hazards to the driver, to others and to the enforce-
ment officer. It is sometimes desirable to identify certain road
segments that can be observed which allow comparison of emissions of
vehicles operating under the same road conditions, and where shoulders
or other safe places to pull cars off the road are known to be present.
Such roadways may include signals or stop signs, long sections of
smooth traffic flow and inclines or hills which permit observation of
vehicles operating under load. Two officers should ride in each patrol
care. One procedure includes the following:
a. Go to area as directed.
b. Avoid road hazards, police radar sites, etc., or other impediments
which may interfere with the observation and pursuit of vehicles.
c. Select an observation point in a level area with wide shoulders.
d. Clock off a distance of at least 90 yards between two known points
(e.g., overpasses).
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6.6.17
e. Observe for violators. Pull out and follow only if it is safe to
do so.
f. Follow over the clocked course, observing the smoke constantly.
g. At a safe place overtake and flash red light; the second officer
holds out badge.
h. Use police procedures in approaching the other vehicle.
i. The enforcement officer takes the registration and completes the
notice or report. The other compares the registration number with
the license plate of the vehicle.
j . One of the enforcement officers takes the driver's license and
fills out the notice, summons, or citation. They then trade
license and registration and terminate the apprehension. The
license is generally not returned until the citation has been
written. The driver should be detained as little as possible.
The enforcement officer should listen more than talk, particularly
for any admission from the driver.
Certain types of vehicles may be exempt from being detained, particu-
larly vehicles which are impractical to halt or which may involve
legal difficulties such as the halting of passenger-carrying buses.
The license number and bus owner (when painted on the side of the
vehicle) can be taken, however, for handling of the violation by mail.
Every effort should be made to halt motor vehicles with complete regard
to the rules of the road as defined in the state vehicle code or else-
where, and to the safety and protection of other motorists using the
highway. In all cases the halting of a motor vehicle should be
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6.6.18
accomplished by at least two enforcement officers riding in an emergency
type vehicle, appropriately marked and equipped with red lights and siren,
If the vehicle which the officer is observing refuses to stop, the
officer writes down the vehicle license number, cab number or other
identification of the vehicle and observes the driver for the purpose
of later identification in court, if necessary. A full written report
of the occurrence is then made by the officer to his supervisor. This
information may be sufficient to warrant the issuance of a complaint.
C. EMISSIONS FROM DIESEL-POWERED VEHICLES
1. Cause of Diesel Emissions
Emissions from diesel-powered vehicles presents certain problems
which differ from gasoline-powered vehicles, namely: (1) diesel-
powered vehicles tend to produce both smoke and odors due
to the nature of the diesel fuel; (2) although diesel engines can be
operated in a smokeless condition, they have a greater tendency to
smoke during full throttle acceleration, under load, or from "lugdown"'
from maximum governed speed, at full throttle; (3) the color of the
emissions may be white, blue, or black, with black more commonly
observed; (4) the plume may be continuous and long and the volume of
smoke and particulates emitted fairly large; (5) odors associated
with unburned and partially burned organic material contained in the
smoke, together with the smoke, tend to cause frequent complaints;
(6) the engine design parameters contributing to the smoke emissions
differ from gasoline-powered vehicles; (7) diesel engines may
require a greater degree of maintenance from the standpoint of extent
of use, emission reductions, and should be more carefully operated
particularly when such vehicles pass through metropolitan areas. The
smoke emissions appear to be related to engine power requirements.
New smoke standards require that new engines be adjusted by the engine
manufacturer to a conservative fuel rate and power output.
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6.6.19
Like gasoline-powered vehicles, diesel-powered vehicles should not be
cited where emissions occur from engines which have been reasonably
operated and maintained, i.e., where emissions are due to the inherent
design of the diesel engine. This is an R&D problem affecting control
of all diesel-powered vehicles. Tractors climbing steep inclines
under heavy loads may tend to smoke excessively even with careful
operation. The enforcement officer must be trained to recognize
vehicles which for any given type of road and traffic condition and
engine selection is smoking excessively due to negligent operation
and maintenance of the vehicle. This training is possible only with
C4 51
experience in the field. The following inspection points ' may
be noted:
(1) Overfueling an engine causes an unbalanced air-fuel ratio.
Each engine or model of engine is designed to burn a given amount
of fuel per hour for its rated horsepower. Any amount above
will increase the exhaust smoke.
(2) Intake air system - The intake air system determines whether the
engine is getting sufficient air to maintain proper air-fuel
ratio. Dirty air cleaners restrict air flow, rubber hose
connections that have collapsed, restricts the air flow. Too
high an oil level in the air cleaner restricts air flow. Air
cleaners mounted under hoods or in places where the air tempera-
ture is much higher than ambient, also restricts the quality of
air needed.
(3) Low compression has a leading role in creating excessive smoke.
The chief causes of low compression come from rings not seating
or worn rings and liners and poor seating of valves. Either, or
both of these, cause low compression which in turn causes poor
combustion and smoke.
(4) Faulty fuel systems, poor or improper metering of fuel, faulty
spray nozzles and use of poor grades of fuel that do not meet
engine manufacturers specifications, contribute to smoke
formation.
(5) Faulty exhaust systems, either by incorrect piping or by
defective muffler can and does add to back pressure within the
system and increases smoke density.
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6.6.20
(6) Black smoke may result from unnecessary rapid acceleration,
unnecessary stop-and-go, and speed shifting—all associated with
negligent operation. Blue smoke generally results from excessive
lubricating oil consumption. This may be expensive to the opera-
tor. White smoke occurs only during start-up from cold starts,
and is due to unburned fuel.
(7) Diesel engines emit odors which can usually result in complaints
from motorists and pedestrians. The specific odorants have not
been positively identified, but these appear to fall into the
broad category of oxygenates. The two-cycle air-scavenged engine
presents the most serious problem. Acceleration following idle
and the high torque/mid speed range modes tend to produce the
most malodorous emissions. Combustion quenching, poor air
utilization and partial oxidation of unburned fuel also contribute
to odors.
The control of diesel emissions like the automobile continues to be
a matter of research and development, and many unknowns in the
relationship between engine design, engine fueling, fuels and emissions
must be resolved. Metal additives, particularly barium-based materials
have been used with some degree of success as smoke suppressant
additives (SSA). These appear to act catalytically by reducing the
ignition temperature and hence formation of soot particles. The
metal additive is discharged as barium sulfate and in this form has
very low toxicity; other barium compounds that may be emitted may
possess higher toxicity. The problem of odors is still little under-
stood—catalytic odor control systems employing oxidation catalysts,
and odor masking agents have been employed, but with uncertain effective-
ness at the present time. Exhaust gas dilution techniques have also
(4)
been applied, but with questionable effect.
2. Reading Visible Emissions, Halting and Inspection of Vehicles
The principles of reading visible emissions from diesel-powered
vehicles are generally similar to those applied to gasoline-powered
vehicles, described previously. The vertical stack and the black
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6.6.21
emissions of diesel exhaust tend to behave more like a stationary
source, and Ringelmann, rather than opacity is usually applied. Recom-
mended regulations limit smoke shades or densities equal to or greater
than No. 1 Ringelmann or 20 percent opacity for periods not exceeding
(2)
5 consecutive seconds. The vehicle patrol officer should in all
cases avoid reading into the horizontal plume, and must obtain a clear
view of the vertical cross-section of the plume. This will frequently
necessitate avoiding reading the plume while driving in the same lane
as the vehicle.
Special care must be taken in halting diesel-powered vehicles. Proce-
dures for halting will be dictated by the vehicle code that applies in
any given air quality control region. Ideally, enforcement officers
should have police powers and should be authorized to use lights and
sirens (if they are provided with emergency vehicles). The use of red
lights and sirens, however, where authorized should be used sparingly.
Flashing of emergency lights is generally sufficient to halt diesel-
powered vehicles. The rig should be allowed to find a safe place to
pull completely clear of the highway as shown in Figure 6.6.10. Because
of the height of the cab it may also be necessary for the driver to step
outside in order for the field enforcement officer to interview him
properly. The operator's license should be checked as described pre-
viously and the cause of the emissions should be determined. In many
cases, the driver is familiar with the condition of his vehicle.
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K>
to
Figure 6.6.10.
HALTING OF DIESEL CAB AND TKAILER ON THE HIGHWAY. THE
PATROL VEHICLE PULLS BEHIND THE TRUCK, CLEAR OF THE HIGHWAY.
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6.6.23
REFERENCES
1. California Highway Patrol. Handbook for Installation and Inspection
Stations, HPH 82.1. April, 1971.
2. Requirements for Preparation, Adoption, and Submittal of Implementation
Plans. Federal Register, Vol. 30, No. 158, Part II. Washington, D.C.
3. Job and Task Analysis Worksheets, Training Study, Vol. II. David Sage, Inc.
Prepared for the New York City Department of Air Resources. July 1969.
4. Hum, R. W. Mobile Combustion Sources. In: Air Pollution, Vol. Ill,
A. C. Stern (ed.). New York City, Academic Press, 1968.
5. Shaw, W. D. Diesel Engine Smoke. Associated General Contractors of
America. Communication to L.A. CO. APCD, 11-6-57.
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G.I
GLOSSARY
ABSORBER: A device utilized to extract selectively one or more elements of a
gas stream from others by absorption in a liquid medium. Usually the
process is performed in cylindrical towers packed with an inert material
thus providing a large surface area for intimate contact between the rising
gas and the falling liquid. (The process may also be carried out in a
tower containing perforated trays in which the rising gas bubbles through
the layer of liquid on the trays . )
ABSORPTION: A process in which one or more constituents are removed from a
gas stream by dissolving them in a selective liquid solvent. This may
or may not involve a chemical change.
ACCUMULATOR: A vessel for the temporary storage of a gas or liquid; usually
used for collecting sufficient material for a continuous charge to a
refining process.
ACID SLUDGE: The residue left after treating petroleum oil with sulfuric acid
for the removal of impurities. It is a black, viscous substance contain-
ing the spent acid and impurities which have been separated from the oil.
ACID TREATMENT: An oil-refining process in which unfinished petroleum pro-
ducts, such as gasoline, kerosene, diesel fuel, and lubricating stocks,
are contacted with sulfuric acid to improve color, odor, and other
properties.
ACIDULATE: To make acid, especially slightly acid; to treat with acid.
ADDITION REACTION: Direct chemical combination of two or more substances to
form a single product , such as the union of ethylene and chlorine to form
ethylene dichloride :
ADIABATIC LAPSE RATE: The rate at which a given mass of air lifted adiabatical-
ly (without loss or gain of heat) cools due to the decrease of pressure
with increasing height, 5.4°F/1000 ft (9.7°C/km).
ADIABATIC PROCESS: A thermodynamic change of state of a system in which there
is no transfer of heat or mass across the boundaries of the system.
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G.2
ADIABATIC TEMPERATURE: (Combustion) The theoretical temperature that would
be attained by products of combustion provided the entire chemical energy
of the fuel, the sensible heat content of the fuel, and combustion air
above the ambient temperature were transferred to the products of combus-
tion. This assumes (1) that combustion is complete, (2) that there is no
heat loss, (3) that there is no dissociation of the gaseous compounds
formed, and (A) that inert gases play no part in the reaction.
ADSORPTION: A reaction in which one or more constituents (adsorbates) are re-
moved from a gas stream by contacting and adhering to the surface of a
solid (adsorbent). Periodically the adsorbent must be regenerated to re-
move the adsorbate.
AEROSOL: A colloidal system in which particles of solid or liquid are sus-
pended in a gas. There is no clear-cut upper limit to the particle size
of the dispersed phase in an aerosol, but as in all other collodial sys-
tems, it is commonly set at 1 micro-meter. Haze, most smoke, and some fogs
and clouds may be regarded as aerosols.
AFTERBURNER: A burner located so that combustion gases are made to pass through
its flame in order to remove smoke and odors.
AGGLOMERATION: Groups of fine particles clinging together to form a larger
particle.
AIR ATOMIZING OIL BURNER: A burner in which oil is atomized by compressed air
which is forced into and through one or more streams of oil thus breaking
it into a fine spray.
AIR CURTAIN DESTRUCTOR: A device employing an air blower with pit incinerator.
Excess oxygen and turbulence result in apparent complete combustion, leaving
no residue unburned carbon (smoke) nor odorous hydrocarbons. The device
has been satisfactorily demonstrated for disposal of low-ash, high-Btu
waste, such as trees, tree trunks, brush (but not leaves), and wooden
crating material. Excessive pollution results when materials such, as
automobile tires, cushions, and other non-wood wastes are burned.
AIR HEATER OR AIR PREHEATER: Heat transfer apparatus through which combustion
air is heated by a medium of higher temperature, such as the products of
combustion or steam.
ALKYLATION: In petroleum refining, usually the union of an olefin (_ethylene
through pentene) with isobutane to yield high-octane, branched-chain paraf-
finic hydrocarbons. Alkylation may be accomplished by thermal and catalytic
reactions. Alkylation of benzene and other aromatics with olefins yields
alkyl aromatics.
ALUMINA: Aluminum oxide (Al 0 ) , an intermediate product of the production of
aluminum. This oxide also occurs widely in nature as corundum.
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AMBIENT AIR: That portion of the atmosphere, external to buildings, to which
the general public has access.
ANODE: In aluminum production, the positively charged carbon terminal in the
reduction cell or pot. Oxygen is attracted to the anode where it combines
with carbon plus any impurities, such as sulfur, which may be present. The
anode is consumed by this process and must be replaced periodically.
ANTHRACITE COAL: A hard, black, lustrous coal containing a high percentage of
fixed carbon and a low percentage of volatile matter. Commonly referred
to as "hard coal," it is mined in the United States, mainly in eastern
Pennsylvania, as well as in small quantities in other states.
AREA SOURCE: Any small residential, governmental, institutional, commercial,
or industrial fuel combustion operations, as well as on-site waste disposal
and transportation sources (see point source).
ASH: The noncombustible solid matter in fuel.
ASH-FREE BASIS: The method of reporting fuel analysis whereby ash is deducted
and other constituents are recalculated to total 100 percent.
ASME: The American Society of Mechanical Engineers.
ASPIRATING BURNER: A burner in which the fuel in a gaseous or finely divided
form is burned in suspension. The air of combustion is supplied by drawing
it through one or more openings by the lower static pressure created by
the velocity of the fuel stream.
ASTM: The American Society for Testing and Materials.
ATOMIZER: A device by means of which a liquid is reduced to a very fine spray.
ATMOSPERIC PRESSURE: The pressure due to the weight of the atmosphere. Normal
atmospheric pressure at sea level is approximately 14.7 p.s.i. or 29.92
inches of mercury.
AVAILABLE HEAT: The quantity of useful heat per unit of fuel available from
complete combustion after deducting dry flue gas and water vapor losses.
B
BAGASSE: Sugar cane from which the juice has been essentially extracted.
BAG FILTER: A device containing one or more cloth bags for recovering particles
from the dust-laden gas which is blown through it.
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G.4
BAGHOUSE: Structures containing several bag filters (see bag filters).
BAG-TYPE COLLECTOR: A filter wherein the cloth filtering medium is made in the
form of cylindrical bags.
BANKING: Burning solid fuels on a grate at rates sufficient to maintain igni-
tion only.
BARK BOILER: A combustion unit designed to burn mainly bark and wood residues,
used to produce steam for process or electrical energy.
BAROMETRIC CONDENSER: An inexpensive direct contact condenser used when con-
densate recovery is not a factor. In this type of condenser, steam rises
into a rain of cooling water, and both condensed steam and water flow out
of the bottom of the condenser, maintaining a partial vacuum in the con-
denser .
BASE STOCK: A sheet, usually produced from unbleached kraft pulp, formed into
linerboard on a fourdrinier machine.
BATCH FED INCINERATOR: An incinerator that is charged with refuse periodically,
the charge being allowed to burn down or burn out before another charge is
added.
BINDER: See core binder.
BITUMINOUS COAL: Soft coal, dark brown to black in color, having a relatively
high proportion of gaseous constituents and usually burning with a smoky
luminous flame.
BLACK LIQUOR: Spent chemical solution which is formed during the cooking of
wood pulp in the digester. The black liquor is burned as a fuel in the
recovery furnace.
BLAST FURNACE: A shaft furnace in which solid fuel is burned with an air blast
to smelt ore.
BLEEDER: A bypass or relief valve used to relieve excess pressure.
BLISTER COPPER: An impure intermediate product in the refining of copper, pro-
duced by blowing copper bearing material in a converter; the name is
derived from the large blisters on the cast surface that result from the
liberation of SO and other gases.
BLOWBACK: The difference between the pressure at which, a safety valve opens
and at which it closes, usually about three percent of the pressure at
which the valve opens.
SLOWDOWN: Hydrocarbons purged during refinery shutdowns and startups which, are
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G.5
manifolded for recovery, safe venting, or flaring.
BOILER: A closed pressure vessel In which the liquid, usually water, is vapor-
ized by the application of heat.
BOILER HORSEPOWER: A unit of rate of water evaporation. One boiler horsepower
equals the evaporation of 34.5 Ib. of water per hour from a temperature of
212°F into dry saturated steam at the same temperature (equivalent to
33,472 Btu per hour),
BRASSESS: Copper-based alloy of 60-65% copper. Alloying material is usually
zinc.
BREAKER: In anthracite mining, the structure in which the coal is broken, sized,
and cleaned for market. Also known as a coal breaker. A machine used for
the primary reduction of coal, ore, or rock.
BREECHING: A sheet-iron or sheet-metal casing at the end of boilers for
conveying the smoke from the flues to the smokestack.
BRIGHTENING: The process of producing bright stock Csee bright stock).
BRIGHT STOCK: Refined high viscosity lubricating oils usually made from resi-
dual stocks by suitable treatment, such as a combination of acid treatment
or solvent extraction with dewaxing or clay finishing.
BRITISH THERMAL UNIT (Btu): The mean British thermal unit is 1/180 of the heat
required to raise the temperature of one pound of water from 32°F to 212°F
at a constant atmospheric pressure. It is about equal to the quantity of
heat required to raise one pound of water 1°F. A Btu is essentially 252
calories.
BRONZES: Copper based alloy of 85-90% copper. Alloying material is usually tin.
BUNKER C OIL: Residual fuel oil of high viscosity commonly used in marine and
stationary power plants (No. 6 fuel oil).
BURNER: A device for the introduction of fuel and air into a furnace at the
desired velocities, turbulence, and concentration to establish and main-
tain proper ignition and combustion of the fuel.
BUSS (BUSBAR): A heavy metal conductor, usually copper, for high amperage
electricity.
BUSTLE PIPE: In steel making, a metal tube of large diameter which surrounds
a blast furnace at a level a little above the tuyeres; it is lined with
refractory material and distributes the hot air from the blast stoves to
the pipes (goosenecks) which carry the air to the tuyeres.
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G.6
CALCINE: Ore or concentrate which has been treated by calcination or roasting
and which is ready for smelting.
CALCINING: Roasting of ore in an oxidizing atmosphere usually to expel sulfur
or carbon dioxide. If sulfur removal is carried to practical completion,
the operation is termed "sweet roasting"; if all C02 is removed, the opera-
tion is termed "dead roasting."
CALORIE: The mean calorie is 1/1000 of the heat required to raise the tempera-
ture of one gram of water from 0°C to 100°C at a constant atmospheric
pressure. It is about equal to the quantity of heat required to raise one
gram of water 1°C.
CARBONIZATION: The process of converting coal to carbon in the absence of air
by using intense heat to remove volative ingredients.
CARBON LOSS: The loss representing the unliberated thermal energy caused by
failure to oxidize some of the carbon in the fuel.
CARCINOGENIC: Producing or tending to produce cancer.
CARRYOVER: The chemical solids and liquid entrained in the steam from a boiler
or effluent from a fractionating column, absorber, or reaction vessel.
CATALYST: A substance capable of changing the rate of a reaction without itself
undergoing any net change.
CATALYTIC CRACKING: The conversion of high boiling hydrocarbons into lower
boiling substances by means of a catalyst which may be used in a fixed
bed, moving bed, or fluid bed. Natural or synthetic catalysts are employed
in bead, pellet, or powder form. Feedstocks may range from naphtha cuts
to reduced crude oils.
CATHODE: In aluminum production, the negatively charged terminal of the reduc-
tion cell to which the aluminum migrates. The terminal consists of the
carbon lining that makes up the bottom of the cell.
CAVING: In metal mining, caving implies the dropping of the over-burden as
part of the system of mining.
CHARGING: Feeding raw material into an apparatus, for example, into a furnace,
for treatment or conversion.
CHLOROSIS: A diseased condition in green plants marked by yellowing or blanch-
ing of the leaves.
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G.7
CINDERS: Particles not ordinarily considered as fly ash or dust because of
their greater size; these particles consist essentially of fused ash and/
or unburned matter.
CLEANING FIRES: The act of removing ashes from the fuel bed or furnace.
CLINKERS, CEMENT: The glassy, stony, lump-like product of fusing together clay
and limestone as the first stage in the manufacture of portland cement.
COAL DESULFURIZATION: See desulfurization.
COAL GAS: Gas formed by the destructive distillation of coal.
COAL TAR: A black viscous liquid formed as a by-product from the distillation
of coal.
COKE: Bituminous coal from which the volatile constituents have been driven
off by heat so that the fixed carbon and the ash are fused together.
COKE BREEZE: Fine coke particles leaving the coke quencher with the quenched
coke by conveyor. The particles are very fine and may be blown away.
COKE, PETROLEUM: The solid carbonaceous residue remaining as the final product
of the condensation processes in cracking. It consists of highly poly-
cyclic aromatic hydrocarbons very poor in hydrogen. It is used extensive-
ly in metallurgical processes. Calcination of petroleum coke can yield
almost pure carbon or artificial graphite suitable for production of
electrodes, motor brushes, dry cells, etc.
COKING: 1. Carbonization of coal by destructive distillation. 2. In petro-
leum refining: any cracking process in which the time of cracking is so
long that coke is produced as the bottom product; thermal cracking for
conversion of heavy, low-grade oils into lighter products and a residue
of coke; or the undesirable building up of coke or carbon deposits on
refinery equipment.
COLLECTION EFFICIENCY: The ratio of the weight of pollutant collected to the
total weight of pollutant entering the collector.
COLLOID: 1. A substance composed of extremely small particles, ranging from
0.005 micro—meters to 0.2 micro-meters, which when mixed with a liquid
will not settle, but will remain suspended. The colloidal suspension thus
formed has properties that are quite different from the simple solution of
the two substances. 2. In fuel burning, a finely divided organic sub-
stance which tends to inhibit the formation of dense scale and results in
the deposition of sludge, or causes it to remain in suspension, so that it
may be blown from the boiler.
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G.8
COLLOIDAL FUEL: Mixture of fuel oil and powdered solid fuel.
COMBINATION BOILER: A combustion unit used to produce steam for process or
electrical energy which is designed to burn bark and at least one other
fuel.
COMBUSTION CONTAMINANTS: Particulate matter discharged into the atmosphere from
the burning of any kind of material containing carbon.
COMBUSTION TOWER: Refractory graphite-lined or water-jacketed stainless steel
tower in which phosphorus is burned to phosphorus pentoxide.
CONDENSED FUMES: Minute solid particles generated by the condensation of vapors
from solid matter after volatilization from the molten state, or generated
by sublimation, distillation, calcination, or chemical reaction when these
processes create airborne particles.
CONDENSER BOILER: A boiler in which steam is generated by the condensation of
a vapor.
CONTACT CONDENSER: A condenser in which coolant, vapors, and condensate are
mixed.
CONTINUOUS-FEED INCINERATOR: An incinerator into which refuse is charged in a
nearly continuous manner in order to maintain a steady rate of burning.
CONTROL STRATEGY: A combination of measures designed to achieve the aggregate
reduction of emissions necessary for attainment and maintenance of a
national ambient air quality standard.
CONVECTION: The transmission of heat by circulation of a liquid or a gas. Con-
vection may be natural or forced.
CONVERTER: 1. A furnace in which air is blown through, a bath of molten metal
or matte, oxidizing the Impurities and maintaining the temperature through
the heat produced by the oxidation reaction. 2. In nitric acid produc-
tion, the chamber In which ammonia is converted to nitric oxide and water
by reacting it with air over a platinum-rhodium catalyst.
CONVERTING: The process of removing impurities from molten metal or metallic
compounds by blowing air through the liquid. The impurities are changed
either to gaseous compounds, which are removed by volatilization, or to
liquids or solids which are removed as slags.
CORE: The central part of a sand mold as used in foundries. The device placed
in a mold to make a cavity in a casting.
CORE BINDER: Organic material added to foundry sand to aid in formation of a
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G.9
strong core for casting. Flour, linseed oil, starch, and resins are among
materials used.
CRACKING: Chemical reaction by which large oil molecules are decomposed into
smaller, lower-boiling molecules. At the same time, certain of these
molecules, which are reactive, combine with one another to give even larger
molecules than those in the original stock. The more stable molecules
leave the system as cracked gasoline, but the reactive ones polymerize,
forming tar and even coke. Cracking may be in either the liquid or vapor
phase. When a catalyst is used to bring about the desired chemical reac-
tion, this is called "catalytic cracking1'; otherwise, it is assumed to be
"thermal cracking" (see catalytic cracking).
CRACKLINGS: The crisp residue left after the fat has been separated from the
fibrous tissue in rendering lard or frying or roasting the skin of pork,
turkey, duck, or goose.
CRUSHER: A machine for crushing rock or other materials. Among the various
types of crushers are the ball mill, gyratory crusher, Hadsel mill, ham-
mer mill, jaw crusher, red mill, rolls, and stamp mill.
CRYOLITE: Sodium aluminum fluoride (Na A1F ) used as an electrolyte in smelting
of alumina to provide aluminum. 3 6
CULM: The fine refuse from anthracite coal production.
CUPOLA: A vertical shaft furnace used for melting metals, especially grey
iron, by having the charge come in contact with the hot fuel, usually
metallurgical coke. Metal, coke, and flux are charged from the top of the
furnace onto a bed of hot coke through which air is blown.
CURTAIN WALL: A partition wall between chambers in an incinerator under which
combustion gases pass.
CYCLONE: A structure without moving parts in which the velocity of an inlet
gas stream is transformed into a confined vortex from which centrifugal
forces tend to drive the suspended particles to the wall of the cyclone
body. The particles then slide down the cyclone wall and are collected
at the bottom.
CYCLONE SCRUBBERS: Devices ranging from simple dry cyclones with spray nozzles
to multistage devices. All feature a tangential inlet to a cylindrical
body.
CYCLONIC SPRAY TOWER: Liquid scrubbing apparatus where sprays are introduced
countercurrent to gases for removal of contaminants.
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G.10
D
DEHYDROGENATION: The removal of hydrogen from a chemical compound; for example,
the removal of two hydrogen atoms from butane to make butylene, and the
further removal of hydrogen to make butadiene.
DEMISTER (COLLECTOR): 1. A mechanical device used to eliminate finely divided
liquid particles from process streams By impaction and agglomeration.
2. Apparatus made of wire mesh or glass fiber and -used to eliminate acid
mist as in the manufacture of sulfuric acid.
DESTRUCTIVE DISTILLATION: 1. A process of distillation in which an organic
compound or mixture is heated to a temperature high, enough, to cause de-
composition. 2. 'The heating of organic matter when air is not present,
resulting in the evolution of volatile matter and leaving char consisting
of fixed carbon and ash.
DESULFURIZATION: 1. In coal processing, the removal of sulfur from the coal,
often by mechanical cleaning processes. 2. In petroleum refining, remov-
ing sulfur or sulfur compounds from a charge stock Coil that is to be
treated in a particular unit).
DIFFUSION: The spreading or scattering of a gaseous or liquid material.
1. Eddy diffusion: diffusion caused by turbulent activity in a fluid
system. 2. Molecular diffusion: a process of spontaneous intermixing
of different substances, attributed to molecular motion and tending to
produce uniformity of concentration.
DIRECT-FIRED BOILER: Commonly used to denote a boiler and furnace fired by
pulverized coal.
DISPERSION: The dilution of a pollutant by diffusion, or turbulent action, etc.
Technically, a two-phase system of two substances, one of which (the dis-
persed phase) is uniformly distributed in a finely divided state through
the second substance (the dispersion medium). Either phase may be a gas,
liquid, or solid.
DISTILLATE: The product of distillation obtained by condensing the vapors from
a still.
DISTILLATE FUELS: Liquid fuels distilled usually from crude petroleum, except
residuals such as No. 5 and No. 6 fuel oil.
DISTILLATE OILS: The lighter oils produced by distilling crude oil.
DISTILLATION: The process of heating a substance to the temperature at which
it is converted to a vapor, then cooling the vapor, and thus restoring it
to the liquid state.
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G.ll
DOCTOR TREATMENT: Treatment of gasoline with sodium-plumbite solution and sul-
fur to improve its odor.
DOPES FOR GASOLINES: Materials added in small amounts to gasoline to increase
the octane number and thus help to prevent knocking.
DOUBLE DECOMPOSITION: A chemical reaction between two compounds in which part
of the first compound becomes united with the remainder of the second, as:
AB + CD = AD + BC.
DRAFT: A gas flow resulting from the pressure difference between the incinera-
tor, or any component part, and the atmoshpere, which moves the products
of combustion from the incinerator to the atmosphere. 1. Natural draft:
the negative pressure created by the difference in density between the hot
flue gases and the atmosphere. 2. Induced draft: the negative pressure
created by the vacuum action of a fan or blower located between the in-
cinerator and the stack. 3. Forced draft: the positive pressure created
by the action of a fan or blower, which supplies the primary or secondary
air.
DROP ARCH: A refractory construction or baffle which serves to deflect gases
in a downward direction.
DROSS: 1. Impurity formed in melted metal. A zinc-and-iron alloy forming in
a bath of molten zinc, in galvanizing iron. 2. The scum that forms on
the surface of molten metals usually due to oxidation, but occasionally
due to the rising of impurities to the surface.
DRUM, FLASH (OR FLASH TOWER): A drum or tower into which the heated outlet
products of a preheater or exchanger system are conducted, often with some
release in pressure. The purpose of the drum is to allow vaporization and
separation of the volatile portions for fractionation elsewhere.
DRY BOTTOM FURNACE: A furnace designed to burn pulverized coal at temperatures
low enough to prevent the ash from fusing or slagging.
DUST: Generally particles from 1 to 100 micro-meters in size that become air-
borne by natural or mechanical means. These particles do not diffuse but
will settle under the influence of gravity Csee also particle).
DUST COLLECTING FAN: A centrifugal fan which concentrates dust and skims it
into a cyclone or hopper.
DUSTLESS LOADING: The amount of dust in a gas, usually expressed in grains per
cubic foot or in pounds per thousand pounds of gas Csee also grain load-
ing).
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G.12
ECONOMIZER: A heat recovery device designed to transfer heat from the products
of combustion to a fluid, usually feedwater for a steam boiler. The water
flows through a bank of tubes placed across the flue gases and is heated by
these gases prior to entering the boiler.
EFFICIENCY: The ratio of output to input. The efficiency of a steam generating
unit is the ratio of the heat absorbed by the water or steam to the heat in
the fuel fired, expressed in percent.
EFFLUENT: Any waste material Csolid, liquid, gas) emitted by a process.
EFFLUENT WATER SEPARATOR: A container designed to separate volatile organic
compounds from waste water prior to discharge or reuse.
ELECTROLYSIS: 1. Chemical change resulting from the passage of an electric
current through an electrolyte. 2. Transfer or transport of -matter
through a medium by means of conducting ions Cpositively or negatively
charged particles). The medium may consist of fused salts or conducting
solutions which permit free movement of ions toward the countercharged
electrodes immersed in the system.
ELECTROSTATIC PRECIPITATOR: Devices that separate particles from a gas stream
by passing the carrier gas between two electrodes across which a unidirec-
tional, high—voltage electrical charge is placed. The particles pass
through this field, become charged and -migrate to the oppositely charged
electrode. Single-stage precipitators are those in which gas ionization
and particulate collection are combined into a single step. In the two-
stage unit, ionization is achieved by one element of the unit and the col-
lection by the other. Electrostatic precipitators are highly efficient
collectors for minute particles.
ELUTRIATOR: A vertical tube through which a gas or fluid passes upward at a
specific velocity while a solid mixture whose separation is desired is fed
into the top of the column. The large particles which settle at a veloci-
ty higher than that of the rising fluid are collected at the bottom of the
column, and the smaller particles are carried out of the top of the column
with the fluid.
EMISSION: The total amount of a solid, liquid, or gaseous pollutant emitted
into the atmosphere from a given source in a given time, and indicated in
grams per cubic meter of gas, pounds per hour, or other quantitative
measurement.
ENDOTHERMIC REACTION: A reaction which requires the addition of heat for its
continuation.
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G.13
ENTRAINMENT: The process of particulates or other materials being carried
along by a gas stream.
EVAPORATOR: Usually a vessel which, receives the hot discharge from a heating
coil and, by a reduction in pressure, flashes off overhead the light pro-
ducts and allows the heavy residue to collect in the bottom (see flash
tower).
EXCESS AIR: Air supplied for combustion in excess of that theoretically re-
quired for complete combustion, usually expressed as a percentage of
theoretical air, such as "130 percent excess air."
EXOTHERMIC REACTION: A reaction which produces heat.
FABRIC FILTER: See bag filter.
FIXED CARBON: That part of the carbon which remains when coal is heated in a
closed vessel until the volatile matter is driven off. IX is the nonvola-
tile matter minus the ash.
FEEDSTOCK: Starting material used in a process. This may be raw material or
an intermediate product that will undergo additional processing.
FLOATING ROOF: A special tank roof which floats upon the oil in a storage tank.
FLUE: Any duct, passage, or conduit through which the products of combustion
are carried to a stack or chimney (see also breeching).
FLUE GAS: The gaseous products of combustion passing from the furnace into the
stack.
FLUIDIZED ROASTING: Oxidation of finely ground pyritic minerals by means of
upward currents of air, blown through a reaction vessel (fluid bed roaster)
with sufficient force to cause the bed of material to expand (toil). Re-
action between mineral and air is maintained at a desired exothermic level
by control of oxygen entry, by admission of cooling water, or by addition
of fuel.
FLUOROSIS: A chronic poisoning resulting from the presence of 0.9 milligrams
or more per liter of fluorine in drinking water. Teeth became brittle and
opaque white with a mottled enamel.
FLUOROSPAR: A natural calcium fluoride CCaF.) used as a flux in open hearth steel
furnaces and in gold, silver, copper, and lead smelting.
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G.14
FLUX: 1. In chemistry and metallurgy, a substance that promotes the fusing
of minerals or metals or prevents the formation of oxides. 2. A substance
added to a solid to increase its fusibility. 3. A substance to reduce
melting temperature. 4. Any chemical or rock added to an ore to assist
in its reduction by heat, such as limestone with iron ore in a blast fur-
nace.
FLY ASH: In incineration, suspended incombustible particles, charred paper,
dust, soot, or other partially Incinerated matter, carried in the gaseous
products of combustion.
FOOD-GRADE ACID: Phosphoric acid that has been treated for removal of heavy
metals and is suitable for use in food products.
FORCED DRAFT: See draft.
FRACTIONAL DISTILLATION: The separation of the components of a liquid mixture
by vaporizing and collecting the fractions which condense in different
temperature ranges.
FUEL: Any form of combustible matter—solid, liquid, vapor, or gas, excluding
combustible refuse.
FUEL-BURNING EQUIPMENT: Any furnace, boiler, apparatus, stack, and all appur-
tenances thereto, used in the process of burning fuel for the primary pur-
pose of producing heat or power by indirect heat transfer.
FUGITIVE DUST: Solid airborne particulate matter emitted from any source other
than a flue or stack.
FUME: Fine solid particles predominately less than 1 micro-meter in diameter
suspended in a gas. Usually formed from high-temperature volatilization
of metals, or by chemical reaction.
FUMIGATION: Fumigation is an atmospheric phenomenon in which pollution, which
has been retained by an inversion layer near its level of emission, is
brought rapidly to ground level when the inversion breaks up. High con-
centrations of pollutant can thus be produced at ground level.
FUMING NITRIC ACID: A mixture of 98 percent nitric acid and an equilibrium
mixture of nitrogen tetroxide (NO ) and nitrogen dioxide (NO ).
24 "2
FURNACE OIL: A distillate fuel primarily intended for domestic heating use.
No. 1 commercial standard grade is intended for "vaporizing" burners re-
quiring a volatile fuel, whereas No. 2 and No. 3 commercial standard
grades are less volatile, and are thus usable in the "atomizing" type of
burners.
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G.15
GAGE PRESSURE: The pressure above atmospheric pressure, expressed as pounds
per square Inch, gage (psig).
GOB PILES: Large piles of low-combustible refuse from coal mine preparation
plants. Fires may develop in these waste material piles by liberation of
heat through slow oxidation, until ignition temperature is reached Csee
also culm).
GRAIN LOADING: Concentration of particulates in exhaust gas, expressed as
grains per standard cubic foot (7000 grains = 1 pound) (see also dust
loading).
GRAVITATIONAL SETTLING: Removal of material from the atmosphere due to the ac-
tion of gravity.
GREEN COKE: Coke that has not been fully cooked. Green coke produces exces-
sive emissions when pushed from a coke oven.
GREEN FEED (CALCINED FEED): Not fully processed or treated feed.
GROUT (GROUTING): A pumpable slurry of portland cement or a mixture of port-
land cement and fine sand commonly forced into a borehole to seal crevices
in a rock to prevent ground water from seeping or flowing into an excava-
tion or for extinguishing underground fires.
HEAT ISLAND EFFECTS: Meteorological characteristics of an urban area or large
industrial complex which differentiates it from its surroundings. Gener-
ally, the urban area has (1) higher temperatures, (?) a less stable noc-
tournal lapse rate immediately above the surface, C.3) lower relative
humidities, (4) greater cloudiness, (5) more frequent fogs, (6) less in-
coming radiation, (7) lower wind speeds, and (8) greater precipitation.
HEAT RELEASE RATE: The amount of heat liberated during the process of combus-
tion and expressed in Btu per hour per cubic foot of internal furnace vol-
ume in which the combustion takes place.
HOG FUEL BOILER: See bark boiler.
HOT BLAST MAIN: A duct lined with refractory material, through which hot air
passes from a hot blast stove to the bustle pipe of a blast furnace.
HOT WELL: A reservoir for receiving warm condensed steam drawn from a con-
denser.
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G.16
HYDRATOR-ABSORBER: A single or double tower in which phosphorus pentoxide is
hydrated to phosphoric acid and the resulting acid mist is absorbed.
HYDRAULIC FLY ASH. HANDLING: A system using water-filled pipes or troughs in
which fly ash is conveyed By .means of gravity, water jets, or centrifugal
pumps.
HYDROCARBONS: Organic compounds which consist solely of carbon and hydrogen
and occur in petroleum, natural gas and coal.
HYDROCRACKING: A low-temperature catalytic method of converting crude oil,
residual oil, petroleum tar, and asphalt to high-octane gasoline, jet fuel,
and/or high-grade fuel oil. The process combines cracking, hydrogenation,
and isomerization.
HYDRODESULFURIZATION: A desulfurization process in which the oil is heated
with hydrogen.
HYDROGENATION: The chemical addition of hydrogen to a material at high pres-
sure in the presence of a catalyst.
HYDROMETALLURGY: The treatment of ores, concentrates, and other metal-bearing
materials by wet processes, usually involving the solution of some compo-
nent, and its subsequent recovery from the solution.
HYDROTREATING: A treating process using hydrogen for the desulfurization of
cracked distillates.
IMPINGEMENT: In air sampling, impingement refers to a process for the collec-
tion of particulate matter in which the gas being sampled is directed
forcibly against a surface. 1. Dry impingement: the process of impinge-
ment in the gas stream where particulate matter is retained upon the sur-
face against which the stream is directed. The collecting surface may
be treated with a film of adhesive. 2. Wet impingement: the process of
impingement in a liquid which retains the particulate matter.
IMPINGEMENT SEPARATORS: Devices using the principle that when a gas stream
carrying particulate matter impinges on a body, the gas is deflected
around the body, while the particles, because of their greater inertia,
tend to strike the body and be collected on its surface. The bodies may
be in the form of plates, cylinders, ribbons, or spheres.
INCINERATION: The process of burning solid, semi-solid, or gaseous combustible
waste.
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G.17
INCINERATOR: An apparatus designed to burn solid, semi-solid, or gaseous waste
leaving little or no combustible material Csee tmultlple chamber incinera-
tor) .
INERTIAL SEPARATOR: The most widely used device for collecting medium and
coarse sized particles. Inertlal separators operate By the principle of
imparting centrifugal force to the particle to Be removed from the car-
rier gas stream.
INTERRUPTIBLE GAS: Gas sold whereBy the seller may curtail or stop delivery,
generally at his option. The gas customer under these conditions is ex-
pected to have standby equipment capable of taking over 100% of his needs
by an alternate fuel.
INVERSION: A stratum in the atmosphere through which the temperature increases
with height. The layer is thermally stable and vertical -motion within the
layer is suppressed.
INVERSION BASE: The lowest height in the atmosphere at which the temperature
ceases to decrease with height.
ISOMERIZATION: A reaction which alters the fundamental arrangement of the
atoms in a molecule without adding or removing anything from the original
material. In the petroleum industry, straight-chain hydrocarbons are con-
verted catalytically to branched-chain hydrocarbons of substantially high-
er octane number by isomerization.
JIG: A device which separates coal from foreign matter by means of their dif-
ference in specific gravity in a water medium. The water pulsates up and
down causing the heavy material to work to the bottom.
K
KETTLE: 1. An open-top vessel used in carrying out metallurgical operations
on low-melting-point metals; for example, in dressing and desilverizing
lead. 2. An open or (usually) closed vessel for preparing paints, var-
nishes, and resins.
KILN: A furnace in which the heating operations do not Involve fusion. Kilns
are most frequently used for calcining, and free access of air is permit-
ted. The raw rmaterials may be heated By the combustion of solid fuel with
which they are mixed, but more usually they are heated by gas or the waste
heat from other furnaces.
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G.18
KILN GAS: Hot effluent gases from a kiln. Unless controlled, these gases can
be the largest source of partlculates in a plant.
KNOCKOUT DRUM: A drum or vessel constructed with baffles through which a mix-
ture of gas and liquid is passed to disengage one from the other. As the
mixture comes in contact with the baffles, the Impact frees the gases and
allows them to pass overhead; the heavier substance falls to the bottom of
the drum.
LAPSE RATE: The decrease of temperature with altitude.
LAUNDER: A trough, channel, or gutter usually of wood, by which water is con-
veyed. Specifically, in mining, a chute or trough for conveying powered
ore, or for carrying water to or from the crushing apparatus.
LEACHING: Extracting a soluble metallic compound from an ore by selectively
dissolving it in a suitable solvent, such as water, sulfuric acid, hydro-
chloric acid, etc.
LIGNITE COAL (BROWN COAL): A brownish-black variety of coal, usually high in
moisture and low in Btu's. Lignite is one of the earlier stages in the
formation of bituminous coal.
M
MANIFOLD: A pipe or header for collecting a fluid or gas from, or distributing
a fluid or gas to, a number of pipes or tubes.
MANUFACTURED GAS: Fuel gas manufactured from coal, oil, etc., as differenti-
ated from natural gas.
MATERIAL BALANCE: An accounting of the weights of material entering and leav-
ing a process.
MATTE: A metallic sulfide mixture formed in smelting sulfide ores of copper,
lead, and nickel.
MECHANICAL, CENTRIFUGAL SEPARATORS: A device for separating particulates. A
rotating fan blade exerts a large centrifugal force on the particulates,
ejecting them from the tips of the blades to a skimmer bypass leading into
a dust hopper.
MECHANICAL SCRUBBER: A scrubber in which the water spray is generated by a ro-
tating element or disk (see also scrubber).
MECHANICAL TURBULENCE: In meteorology, the induced eddy structure of the at-
mosphere due to the roughness of the surface over which the air is passing.
The height and spacing of the elements causing the roughness will affect
the turbulence.
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G.19
MERCAPTANS: Organic compounds having the general formula R-SH. (where R repre-
sents any hydrocarbon radical) which are analogous to the alcohols and
phenols but which contain sulfur in place of oxygen. The simpler mercap-
tans have strong, repulsive odors.
MESH: The number of holes per linear unit in a sieve or gauze, or the space
between the wires of the sieve expressed in inches or millimeters.
METRIC TON: 2204.6 pounds or 1000 kilograms.
MIST: A suspension of any finely divided liquid in a gas.
MODIFIED COAL: Coal of a stoker size containing a controlled percentage of
fines.
MULTICYCLONE (ALSO MULTIPLE CYCLONE OR MULTICLONE): A dust collector consisting
of a number of cyclones, operating in parallel, through which the volume
and velocity of gas can be regulated by means of dampers to maintain dust-
collector efficiency over the load range.
MULTIPLE-CHAMBER INCINERATOR: Any incinerator consisting of a primary combus-
tion chamber, mixing chamber, and secondary combustion chamber in series.
The chambers are separated by refractory walls, and interconnected by gas
passage ports.
MULTIPLE-HEARTH TYPE ROASTER: See roasting furnace.
MUNICIPAL INCINERATOR: An incinerator owned or operated by government or by a
person who provides incinerator service to government or others; a device
designed for and used to burn waste materials of any and all types.
N
NATURAL GAS: Gaseous forms of petroleum occurring in nature and used directly
as a fuel. Natural gas consists of mixtures of hydrocarbon gases and va-
pors, the more important of which are methane, ethane, propane, and butane.
NET TON: 2000 pounds (sometimes known as a "short ton").
NITROGEN OXIDES: A general term pertaining to a mixture of nitric oxide (NO)
and nitrogen dioxide (NO ).
0
ODORANT: A gaseous nuisance that is offensive or objectionable to the smell.
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G.20
ODOR INTENSITY: The numerical or verbal indication of the strength of an odor.
ODOR PERVASIVENESS: The ability of an odor to diffuse into a large volume of
air and still continue to possess a detectable intensity. A pervasive odor
is one whose odor intensity changes very little on dilution.
ODOR QUALITY: A verbal description of an odor. The quality may be described
in terms of such familiar odorants as coffee, onions, lemons, or by asso-
ciating an unfamiliar odor with a familiar odor.
ODOR THRESHOLD: The lowest concentration of an odor in air that can be detected
by a human.
ODOR UNITS: That quantity of odor necessary to contaminate one cubic foot of
air to threshold or barely perceptible level. The number of odor units
is equal to the volumes Cscf) of air necessary to dilute the concentration
of odorant in one volume (scf) of air to the threshold concentration.
OIL BURNER: Any device for the introduction of vaporized or atomized fuel oil
into a furnace.
OIL-EFFLUENT WATER SEPARATOR: Any tank, box, sump, or other container in which
any petroleum product entrained in water is physically separated and re-
moved prior to out-fall, drainage, or recovery of the water.
OITICICA (OIL): A drying oil obtained from the kernels of the fruit of the
oiticica tree that is similar to tung oil in many properties and is used
chiefly in varnishes, paints, and printing inks.
OLEORESIN: A varnish or paint vehicle, made of plant oils and resins, usually
cooked.
OLEUM (FUMING SULFURIC ACID): A heavy, oily, strongly corrosive liquid that
consists of a solution of sulfur trioxide in anhydrous sulfuric acid. It
fumes in moist air and reacts violently with water.
ONSTREAM TIME: The length of time a unit is in actual production.
OPACITY: The degree to which emissions reduce the transmission of light and
obscure the view of a distant object.
OPEN BURNING: The burning of any matter in such a manner that the products of
combustion are emitted directly into the ambient air without passing
through a stack, duct, or chimney.
OPEN HEARTH. FURNACE: Reverberatory furnace, containing a basin-shaped hearth,
for melting and refining suitable types of pig iron, iron ore, and scrap
for steel production.
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G.21
ORE AND LIME BOIL: Reactions which occur in an open hearth furnace when carbon
monoxide is produced by the oxidation of carbon. Ore boil is a violent
agitation of the metal as it escapes during this process; lime boil occurs
when the limestone decomposes and the carbon dioxide gas escapes. The
second reaction begins before the first is completed.
ORGANIC SULFUR: The difference between the total sulfur in coal and the sum of
the pyritic sulfur and sulfate sulfur.
ORGANOLEPTIC: Affecting or making an impression upon one or more of the sense
organs.
ORIFICE SCRUBBERS: Devices for the removal of particulates from gas streams in
which the flow of air through a restricted passage partially filled with
water causes the dispersion of the water and consequent wetting and col-
lection of the particulates.
ORSAT: An apparatus used for analyzing flue gases volumetrically.
OVERBURDEN: Material of any nature, consolidated or unconsolidated, that over-
lies a deposit of useful material, ores, or coal, especially those deposits
that are mined from the surface by open cuts.
OVERFIRE: Air for combustion admitted into the furnace at a point above the
fuel bed.
OXIDATION: The act or process of combining oxygen with a substance, with or
without the production of a flame.
OXYGEN LANCING: In steel making, a procedure in which oxygen is injected into
the bath of molten metal through a water cooled lance. The oxygen oxidizes
carbon, silicon, manganese, and some iron in exothermic reactions. The
procedure materially shortens the time needed to tap the furnace.
PACKED COLUMN (PACKED SCRUBBER OR PACKED TOWER): A vertical column used for
distillation, absorption, and extraction, containing packing; e.g., Raschig
rings, Berl saddles, or crushed rock, which provide a large contacting
surface area between phases. Normally, gas flow is countercurrent to
liquid flow.
PAN: Peroxyacyl nitrates. Secondary pollutants formed in photochemical oxida-
tion and major eye irritants of photochemical smog.
PARTICLE CONCENTRATION: Concentration expressed in terms of number of particles
per unit volume of air or other gas.
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G.22
PARTICULATE MATTER: Any dispersed matter, solid or liquid, in which the indi-
vidual aggregates are larger than single small molecules CO-0002 micro-
meters) but smaller than 500 micro-meters.
PERCOLATOR: A device used in rendering plants for the separation of dry pro-
teinaceous crackling from the clear moisture-free tallow. They are gener-
ally perforated pans which allow the tallow to drain away from the crack-
lings.
PERFORMANCE TEST: Measurements of emissions used for the purpose of determin-
ing compliance with a standard of performance.
PETROCHEMICAL INDUSTRY: A branch of the petroleum industry in which refined
crude oil is manufactured into various chemicals.
PETROLEUM COKE: See coke, petroleum.
PHOTOCHEMICAL REACTION: A chemical reaction which involves either the absorp-
tion or emission of radiation in the form of light energy.
PLUME: The path taken by the continuous discharges of products from a chimney
or stack. The shape of the path and the concentration distribution of
gas plumes is dependent on turbulence of the atmosphere.
POINT SOURCE: Any stationary emitting point or plant/facility whose summation
of emitting points totals 100 tons (or some other fixed amount) per year
of any pollutant in a given region.
POLYCYCLIC MOLECULE: A molecule containing two or more fused rings (as in
anthracine).
POLYMERIZATION: 1. A reaction combining two or more molecules to form a
single molecule having the same elements in the same proportions as in the
original molecules. 2. The union of light olefins to form hydrocarbons
of higher molecular weight. The process may be thermal or catalytic.
POLYNUCLEAR AROMATIC HYDROCARBONS: Compounds consisting of two or more aro-
matic rings which share a pair of carbon atoms. The simplest and most
important is naphthalene CC H; also polycyclic).
10 o
PRECLEANERS: Collectors of limited efficiency used ahead of the final cleaner.
If the gas contains an appreciable amount of hard, coarse particles, a
precleaner can materially reduce erosive wear of the more efficient final
collector.
PRECURSORS: Gaseous air pollutants which react with other substances in the
atmosphere to produce different pollutants; e.g., photochemical reactions
of NO and N02 with the oxygen of the air which produce ozone.
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G.23
PRILLING: A combination spray drying and crystallization technique used in the
production of ammonium nitrate. A hot ammonium nitrate solution is sprayed
in the top of a tower, and air is. blown in at the bottom. The liquid is
converted into spherical pellets.
PRIMARY AIR: In incineration, air which, is introduced with, the refuse into
the primary chamber.
PRIMARY EMISSION: Pollutants emitted directly into the air from identifiable
sources.
PRIMARY STANDARD: The national primary ambient air quality standard which de-
fines levels of air quality which are necessary to protect public health.
PROCESS WEIGHT: The total weight of all materials introduced into a source
operation, including solid fuels, but excluding liquids and gases used
solely as fuels, and excluding air introduced for purposes of combustion.
PUG MILL: A machine for mixing water and clay which consists of a long hori-
zontal barrel within which is a long longitudinal shaft fitted with knives
which slice through the clay, mixing it with water which is added by
sprayers from the top. The knives are canted to give some screw action,
forcing the clay along the barrel and out one end.
PUMP, RECIPROCATING: A positive-displacement type of pump consisting of a
plunger or a piston moving back and forth within a cylinder. With each
stroke of the plunger or piston, a definite volume of liquid is pushed
out through the discharge valves.
PYRITIC SULFUR: Sulfur combined with iron, found in coal.
PYROLYSIS: Chemical change brought about by the action of heat upon a sub-
stance.
PYROMETER: An instrument for measuring temperatures beyond the range of thermo-
meters.
R
RECOVERY BOILER: In wood pulping, a combustion unit designed to recover the
spent chemicals from the cooking liquor and to produce steam for pulping
and recovery operations.
REDUCTION: 1. The addition of hydrogen or the abstraction of oxygen from a
substance. 2. The extraction of any metal from its ore.
REFINERY GAS: Any form or mixture of still gas gathered in a refinery from the
various stills.
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G.24
REFINING: In metallurgy, the removal of impurities necessary to produce an
ingot or alloy of desired specification. In petroleum, the process of
separating, combining, or rearranging petroleum oil constituents to pro-
duce salable products.
REFORMING: The thermal or catalytic conversion of naphtha into more volatile
products of higher octane number. It represents the total effect of nu-
merous reactions, such as cracking, polymerization, dehydrogenation, and
isomerization, taking place simultaneously.
REFRACTORY: A ceramic material of a very high, melting point with properties
that make it suitable for such uses as furnace and kiln linings.
RERUN OIL: Oil which has been redistilled.
RESIDUAL: Heavy oil left in the still after gasoline and other distillates
have been distilled off, or residue from the crude oil after distilling
off all but the heaviest components.
RESISTIVITY: The property of a body whereby it opposes and limits the passage
of electricity through it. Resistivity of dust is an important factor in
the performance of electrostatic precipitators. Tf the resistivity of the
collected dust is higher than about 2 x 10^ ohm-cm, excessive arcing or
reverse corona can occur, thereby limiting precipitator performance.
REVERBERATORY FURNACE: A furnace with a shallow hearth; having a roof that de-
flects the flame and radiates heat toward the surface of the charge. Fir-
ing may be with coal, pulverized coal, oil, or gas.
RINGELMANN CHART: A standardized chart giving shades of gray by which the
densities of columns of smoke rising from stacks may be compared.
ROAST: To heat to a point somewhat short of fusing, with access to air, so as
to expel volatile matter or effect oxidation. In copper metallurgy, ap-
plied specifically to the final heating which causes self-reduction to oc-
cur by the reaction between the sulfide and the oxide.
ROASTER: 1. A contrivance for roasting, or a furnace for drying salt cake.
2. A reverberatory furnace or a muffle used in roasting ore.
ROASTING: 1. Heating an ore to effect some chemical change that will facili-
tate smelting. 2. The heating of solids, frequently to promote a reac-
tion with a gaseous constituent in the furnace atmosphere.
ROASTING FURNACE: A furnace in which finely ground ores and concentrates are
roasted to eliminate sulfur; heat is provided by the burning sulfur.
RUN OF MINE COAL: Unscreened bituminous coal as it comes from the mine.
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G.25
SALAMANDER: A small portable Incinerator, or a small portable heater burning
coke or oil.
SCRUBBER: A device used to remove entrained liquids and solids from a gas
stream by passing the gas through, wetted "packing" or spray (see absorber).
SECONDARY ATR: Air Introduced into a combustion chamber beyond the point of
fuel and primary air introduction for the purpose of achieving -more com-
plete oxidation.
SECONDARY STANDARD: The national secondary ambient air quality which, defines
levels of air quality judged necessary to protect the public welfare from
any known or anticipated adverse effects of a pollutant.
SINTERING: A heat treatment that causes adjacent particles of material to
cohere or agglomerate at a temperature below that of complete melting.
SKIMMING PLANT: An oil refinery designed to remove and finish only the lighter
constituents from the crude oil, such, as gasoline and kerosene. In such a
plant the portion of the crude remaining after the above products are re-
moved is usually sold as fuel oil.
SKIP HOIST, INCLINED: A bucket or can operating up and down, receiving, ele-
vating, and discharging bulk materials.
SLAG: The non-metallic top layer which, separates from the metallic products in
smelting of ores.
SLOP OR SLOP OIL: A term rather loosely used to denote odds and ends of oil
produced at various places in a plant, which must be rerun or further pro-
cessed in order to get in suitable condition for use. When good for noth-
ing else, such oil usually goes into pressure-still charging stock, or to
coke stills.
SMELT: In wood pulping, the molten chemicals from the kraft recovery furnace
consisting mostly of sodium sulfide and sodium carbonate.
SMELTING: Any metallurgical operation in which metal is separated by fusion
from impurities with which, it may be chemically combined or physically
mixed, such as in ores.
SMOKE: Small gas-borne particles resulting from incomplete combustion, con-
sisting predominantly but not exclusively of carbon, ash., and other com-
bustible material, and present in sufficient quantity to be observable.
SMOKE CANDLE(S): Apparatus used in collecting acid mists. Tubes or candles
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G.26
made from glass or plastic fibers are pressed into pads with, thicknesses
up to 2 inches and mounted in banks. Efficiency is much, increased when
the glass is treated with silicone oil to repel water, or when normally
water-repellent plastic is used.
SMOKE UNIT: The number of "smoke units" is obtained by multiplying the smoke
density in Ringelmann numbers by the time of occurrence in minutes. For
the purpose of this calculation, a Ringelmann density reading is made at
least once per minute during the period of observation. The sum of the
Ringelmann density readings (made once per minute) during the period of
observations would equal the number of smoke units.
SOILING: Visible damage to materials by deposition of air pollutants.
SOOT: Agglomerated particles consisting onainly of carbonaceous material.
SOUR: Gasolines, naphthas, and refined oils are said to be "sour" if they show
a positive "doctor test"; i.e., if they contain hydrogen sulflde and/or
mercaptans. Sourness Is directly connected with, odor, while a "sweet"
gasoline has a good odor.
SOURCE: Any property, real or personal, or person contributing to air pollution.
SOURCE SAMPLE: A sample of the emission from an air contamination source, col-
lected for analysis from within a stack.
SPARK ARRESTOR: A screenlike device to prevent sparks, embers, and other ig-
nited materials larger than a given size from being expelled to the atmos-
phere.
SPEISS: Metallic arsenides and antimonides smelted from cobalt and lead ores.
SPRAY CHAMBER: The simplest type of scrubber consisting of a chamber in which
spray nozzles are placed. They are used extensively as gas coolers be-
cause they have a low collection efficiency for anything but coarse particles.
STABILITY (STATIC STABILITY) : The state of the atmosphere when it Is stable
relative to vertical displacements.
STACK OR CHIMNEY: Any flue, conduit, or duct arranged to conduct an effluent
to the open air.
STACK SPRAY: A nozzle or series of nozzles Installed in a stack above the
breeching, used to inject wetting agents at high pressure to suppress the
discharge of particulate matter from the stack.
STANDARD CONDITIONS: For source testing, 70°F (21.1°C) and 29.92" Hg (760mm
Eg); for air quality measurements, 77°F (25°C) and 29.92" Hg (76"0mm Hg) ;
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G.27
for chemistry, 273. 1°K CO°C) and one atmosphere Q6Qnm Hg] ; for petroleum
refining, 60°F (15.55°C) and 14.7 psi (76Qram Hg) .
STATIONARY SOURCE: Any non-mobile building, structure, facility, or installa-
tion which emits or may emit any air pollutant.
STEAM DISTILLATION: Introduction of "open" steam into the liquid during dis-
tillation to assist In vaporizing the volatlles at a lower temperature.
STILL: A closed chamber, usually cylindrical, in which heat is applied to a
substance to change it into vapor, with or without chemical decomposition.
The substance, in its vapor form, is conducted to some cooling apparatus
where it is condensed, liquefied, and collected In another part of the unit.
STOCK: In general, any oil which is to receive further treatment before going
into finished products.
STOKER: A machine for feeding coal into a furnace, and supporting it there
during the period of combustion. It may also perform other functions,
such as supply air, control combustion, or distill volatile matter. Modern
stokers may be classified as overfeed, underfeed, and conveyor. Any mech-
anical device that feeds fuel uniformly onto a grate or hearth within a
furnace may be termed a "stoker."
STOPING: In mining, any process of excavating ore which has been made acces-
sible by shafts and drifts.
STRAIGHT -RUN DISTILLATION: Continuous distillation which separates the products
of petroleum in the order of their boiling points without cracking.
STRIPPER: Equipment in which the lightest fractions are removed from a mixture.
In a natural-gasoline plant, gasoline fractions are stripped from rich oil.
In the distillation of crude petroleum, light fractions are stripped from
the various products.
SUBSTITUTION: A chemical reaction In which one or more atoms or groups of a
molecule are replaced by equivalent atoms or groups to form at least two
products, especially the replacement of hydrogen in an organic compound by
another element or group.
SULFIDITY: An expression of the percentage makeup of chemical kraft cooking
liquor obtained by the formula
X100
Na2S + NaOtL
where the sodium compounds are expressed as Na20.
SUPERPHOSPHATE: Products obtained by mixing phosphate rock with either sul-
fur ic or phosphoric acid, or both-
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SURFACE CONDENSERS: A condenser in which, the coolant does not contact the
vapors or condensate. Most are of the tube and shell type. Water flows
inside the tubes and vapors condense on the shell side.
SURGE TANK: A storage reservoir at the downstream end of a feeder pipe to ab-
sorb sudden rises of pressure and to furnlsfi. liquid quickly during a drop
in pressure.
SWEETENING: The process by which, petroleum products are Improved In odor and
color by oxidizing or removing the sulfur-containing and unsaturated com-
pounds .
SYNERGISM: Cooperative action of discrete agents such, that the total effect is
greater than the sum of the two effects taken Independently.
SYNTHETIC CRUDE: The total liquid, multi-component mixture resulting from a
process involving molecular rearrangement of charge stock. Term commonly
applied to the product from cracking, reforming, visbreaking, etc.
TAIL OIL: That portion of an oil which vaporizes near the end of the distil-
lation; the heavy end.
TAIL GAS: The exhaust or waste gas from a process.
TALLOW: The rendered fat of animals that is white and almost tasteless when
pure, composed of glycerides of fatty acids containing a large proportion
of palmitic acid and stearic acid, and that is used chiefly in making
soap, glycerol, margarine, candles, and lubricants.
TAPPING: Removing molten metal from a furnace.
TEMPERATURE INVERSION: An atmospheric layer in which, temperature increases
with altitude. The principal characteristic of a temperature Inversion is
its marked static stability, so that very little turbulent exchange can
occur within it (see also inversion].
THEORETICAL AIR: The exact amount of air (stolchiometric airj required to sup-
ply the ccxygen necessary for the complete combustion of a given quantity
of a specific fuel or refuse.
THERMAL TURBULENCE: Air movement and mixing caused by temperature differences.
TOPPED CRUDE PETROLEUM: A residual product remaining after the removal, by
distillation, of an appreciable quantity of the more volatile components
of crude petroleum.
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G.29
TOPPING: The distillation of crude oil to remove light fractions only.
TOTAL REDUCED SULFUR COMPOUNDS (TRS): Malodorous gases produced in the wood
pulping industry exclusive of sulfur oxides. TRET usually includes hydro-
gen sulf ide OL^S] , methyl mercaptan (CH-jSHl) , dimethyl sulf ide CCHL,SCH.) ,
and dimethyl disulfide (CH^SSCILJ . The concentration of TRS is usually
expressed as H^S regardless of the constituent compounds.
TURBULENCE: Atmospheric motions which produce a thorough horizontal and verti-
cal mixing of the air.
TURNAROUND: The time between shutting down and starting up of process equip-
ment for repair or maintenance.
TUYERES: Openings or nozzles in a metallurgical furnace through which air is
blown as part of the extraction or refining process.
TWADDELL DEGREES C°TW): A measure of acid density and strength:
°TW = sp. gr. (60°/60°F)
0.005
Each twaddell degree corresponds to a specific gravity interval of 0.005.
ULTIMATE ANALYSIS (OF COAL): Contains the following, expressed in percent by
weight:
Carbon
Hydrogen
Sulfur
Oxygen
Nitrogen
Moisture
Ash
(C) %
(H2) %
(SJ %
(o2) %
(N2) %
(H20) %
(H00) %
UNDERFEED STOKER: A stoker consisting of a trough or pot-shaped report into
which coal is forced by an endless screw or ram. Coal is fed to the fire
zone by being pushed up from underneath.
UNIT OPERATION: 1. Methods by which raw materials may be altered into states,
such as vapor, liquid, or solid without being changed into new substances
with different properties and composition. 2. Recognition, study, appli-
cation and control of the principles and factors utilized in a distinct
and self-contained process (for example, filtration). This avoids the
duplication of effort which attends the study of similar processes as
though each process involved a unique set of principles.
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G.30
UNIT PROCESS: 1. Reactions where raw materials undergo chemical change. 2.
See unit operation C2)•
UREA FORMS: A urea-formaldehyde reaction product that contains more than one
molecule of urea per molecule of formaldehyde.
7
VACUUM JET CSTEAM JET EJECTOR): A fluid nozzle that discharges a high velocity
jet stream across a section chamber that is connected to the equipment to
be evacuated. The gas in the chamber is entrained by the jet stream.
VAPOR: The gaseous phase of a substance that generally exists as a liquid or
solid at room temperature.
VAPOR PLUME: The stack effluent consisting of flue gas made visible by con-
densed water droplets or mist.
VAPOR RECOVERY SYSTEM: System used in petroleum refining for separating a
mixed charge of miscellaneous gases and gasolines into desired intermedi-
ates for further processing.
VENTURI SCRUBBER: A type of high energy scrubber in which the waste gases pass
through a tapered restriction (venturi) and impact with low-pressure water.
Gas velocities at the restriction are from 15,000 to 20,000 fpm and pres-
sure drops from 10 to 70 inches water gage.
VISBREAKING: Viscosity breaking; lowering or "breaking" the viscosity of resi-
dual oil by cracking at relatively low temperatures.
VISIBILITY: In United States weather observing practice, the greatest distance
in a given direction at which it is just possible to see and identify with
the unaided eye (a) in the daytime, a prominent dark object against the
sky at the horizon, and (b) at night, a known, preferably unfocused,
moderately intense light source. After visibilities have been determined
around the entire horizon circle, they are resolved into a single value
of prevailing visibility for reporting purpose.
VISIBLE EMISSION: An emission of air pollutants greater than 5 percent opacity
or 1/4 Ringelmann.
VOLATILE OR VOLATILE MATTER: 1. The gasoline constituents that can be driven
off liquids and solids by the application of heat. 2. Specifically for
coal, that portion which, is driven off in gas or vapor form when coal is
subjected to a standardized temperature test.
VOLATILE ORGANIC COMPOUNDS: Any compound containing carbon and hydrogen or
containing carbon and hydrogen in combination with any other element which
has a vapor pressure of 1.5 pounds per square inch absolute or greater
under actual storage conditions.
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G.31
W-X-Y-Z
WASTE HEAT BOILERS: Boilers which utilize the heat of exhaust gas or process
gas to generate steam or to heat water.
WEAK WASH: In wood pulping, a liquid stream in the kraft process which results
from washing of the lime mud.
WET COLLECTORS: Devices which use a variety of methods to wet the contaminant
particles in order to remove them from the gas stream Csee scrubbers).
WET FILTERS: A spray chamber with filter pads composed of glass fibers, knit-
ted wire mesh, or other fibrous materials. The dust Is collected on the
filter pads.
WHITE LIQUOR: Cooking liquid used in the wood pulping industry. Kraft process:
consists of approximately 1/3 sodium sulflde (Na S) and 2/3 sodium hydroxide
(NaOH). Sulfite process: consists of sulfurous acid plus one of the fol-
lowing: calcium bisulfite, sodium bisulfite, magnesium bisulfite, or
ammonium bisulfite.
U. S. GOVERNMENT PRINTING OFFICE: 1972-—746763/4IJ3
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