United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/3-91-007
December 1990
Air
* EPA Alternative Control
Technology Document -
Organic Waste
Process Vents
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EPA-450/3-91-007
Alternative Control
Technology Document
Organic Waste
Process Vents
Emission Standards Division
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
December 1990
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DISCLAIMER
This report has been reviewed by the Emission Standards Division
of the Office of Air Quality Planning and Standards, EPA, and
approved for publication. Mention of trade names or commercial
products is not intended to constitute endorsement or
recommendation for use. Copies of this report are available
through the Library Services Office (MD-35), U.S. Environmental
Protection Agency, Research Triangle Park NC 27711, or from
National Technical Information Services, 5285 Port Royal Road,
Springfield VA 22161.
11
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CONTENTS
Chapter
List of Figures
List of Tables
1.0 Introduction
Page
2.0 Industry Description, Processes, and Emissions .......... 2-1
2.1 Industry Description ............................... 2-1
2.1.1 The Waste Management Industry ............... 2-1
2.1.2 Current Regulations Applicable to Waste
Management Unit Process Vents ............... 2-7
2.2 Process Descriptions ............................. " 2-16
2.2.1 Distillation ....................... ......... 2-19
2.2.2 Solvent Extraction ....................... ' . . 2-29
2.2.3 Air Stripping ............................. ]. 2-30
2.3 Air Emission Sources ....................... ........ 2-34
2.3.1 Process Vent Emissions from Distillation/
Steam Stripping Units ....................... 2-34
2.3.2 Process Vent Emissions from Air Stripper
Units ....................................... 2-43
2.4 Emission Estimates ......................... ........ 2-47
2.4.1 Air Emissions from Distillation and
Steam Stripping Units ....................... 2-47
2.4.2 Air Emissions from Air Strippers ............ 2-48
2.5 References .................................... .'.'.'.'.' 2-51
3.0 Emission Control Techniques ............................. 3_1
3.1 Vapor Recovery Control Devices ................ '...'.'. 3-1
3.1.1 Adsorption .......................... '.'.'.'.'.'.'.'. 3-2
3.1.2 Absorption ........................ ."..'.'.".'.'.'.'.' 3.9
3.1.3 Condensation ........................... '.'.'.'.'. 3-13
3.2 Combustion Control Devices .................... ..... 3-18
3.2.1 Flares ................................. '.'.'.'.', 3-19
3.2.2 Thermal Incineration ................. '.'.'.'.'.'.'. 3-26
3.2.3 Boiler and Process Heater Combustion
Control Devices ............................ 3_32
3.2.4 Catalytic Oxidation .............. .'.'.'.'.'.'.'.'.'.'.' 3-36
3.3 Summary of Data on Control Devices Applied ..........
to Process Vents ................................... 3_3g
3 . 4 References ............................... ....... 3.44
4.0 Environmental and Cost Impacts ......................... 4_1
4.1 Control Technology Analysis Methodology—Model' ......
Units .............................................. 4-1
4.1.1 Emission Rates .............................. [ 4,4
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CONTENTS (continued)
Chapter
Page
4.1.2 Flow Rates 4-4
4.1.3 Temperatures 4-5
4.1.4 Waste Constituents 4-5
4.1.5 Operating Hours 4-9
4.2 Emission Reductions Using Alternative Control
Technologies 4-9
4.3 Control Costs 4-13
4.3.1 Condensation 4-14
4.3.2 Carbon Adsorption 4-18
4.3.3 Thermal Incineration 4-23
4.3.4 Vent to Existing Control Device 4-35
4.4 Cost Effectiveness of Control Alternatives 4-39
4.4.1 Condensers 4-43
4.4.2 Carbon Adsorbers 4-43
4.4.3 Thermal Incineration 4-46
4.5 Cross-Media and Secondary Air Pollution and
Energy Impacts 4-46
4.5.1 Condenser Environmental Impacts 4-48
4.5.2 Carbon Adsorption Environmental Impacts 4-49
4.5.3 Thermal Incineration Environmental Impacts .. 4-55
4.6 References 4-59
Appendixes
A-l Summary of Site-Specific Process and Emission
Test Data from Distillation/Steam Stripping
Units at TSDF A-l
B-l Summary of Available Data on Air Stripper
Loadings and Performance B-l
C-l Estimates of Uncontrolled Emissions from
AirStrippers C-l
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LIST OF FIGURES
Number
2-1 Simplified waste management system from generation
to disposal 2-2
2-2 Schematic diagram of batch distillation with
fractionating column 2-21
2-3 Schematic diagram of a thin-film evaporator system 2-25
2-4 Schematic diagram of a steam stripping system 2-27
2-5 Schematic diagram of solvent extraction system 2-31
2-6 Schematic diagram of an air stripping system 2-33
2-7 Potential emission points for a nonvacuum
distillation column 2-36
2-8 Potential emission points for a vacuum
distillation column using steam jet ejectors
with barometric condenser 2-37
2-9 Potential emission points for a vacuum
distillation column using a steam jet ejector
and surface condensers 2-38
2-10 Potential emission points for a vacuum
distillation column using a vacuum pump 2-39
3-1 Two-stage regenerative adsorption system
process flow diagram 3-3
3-2 Packed tower for gas absorption 3-11
3-3 Schematic diagram of a shell-and-tube surface
condenser 3-15
3-4 Schematic diagram of a contact condenser 3-15
3-5 Condensation system 3-16
3-6 Steam-assisted elevated flare system 3-20
3-7A Flare tip 3-21
3-7B Ground flare 3-21
3-8 Discrete burner, thermal oxidizer 3-28
3-9 Distributed burner, thermal oxidizer 3-28
3-10 Catalytic incinerator ,. 3-37
4-1 Condenser efficiency for distillation-type process
vents as a function of organic concentration 4-17
4-2 Cost effectiveness for condensers 4-44
4-3 Cost effectiveness for carbon adsorbers 4-45
4-4 Cost effectiveness for thermal incinerators 4-47
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Number
LIST OF TABLES
Page
2-1 Resource Conservation and Recovery Act (RCRA)
Hazardous Waste Management Definitions
2-2 Quantities of Waste Managed in, and RCRA Permit
Status of, Selected Treatment Units in 1986... *->•'
2-3 Overview of Distillation Units in the Chemical ^
Manufacturing Industry ~.?
? 4 Overview of Distillation Unit Operations
2-5 Distillation, Separation, and Stripping Units ^ ^^
2-6 Summary'of'caicuiated'Loadings for Air Strippers 2-46
2-7 Summary of Estimated Air Emissions from Air Strippers.... 2-50
3-1 Overview of Distillation Units in Chemical ^_^
Manufacturing Industry • •••••••:;••'I';;;;^"49
3-2 Distillation, Separation, and Stripping Units at TSDF ... J ^
4-1 Process Vent Model Unit Parameters 4"
4-2 Properties of Chemical Constituents Used in Process ^
Vent Impacts Analyses '."-"r"!
4-3 Condenser Operating Conditions Used in Lost
Analysis and Condenser Control Efficiencies
Predicted for Model Unit Cases ••
4-4 Summary Control Costs for Condenser Control ^g
Alternative • ;:
4-5 Summary Control Costs for Carbon Adsorption ^^
Control Alternative : ;:
4-6 Summary Control Costs for Thermal Incineration ^g
Control Alternative : . -,,
4-7 incinerator General Design Specifications
4-8 Summary Control Costs for Venting to an Existing ^^
Control Device • 'y,"l'
4-9 Summary Control Costs for Most Cost-Effective ^Q
Control Device •••• /, rn
4-10 Model Unit Cross-Media Impacts for Condensers * ™
4-11 Model Unit Cross-Media and Energy Impacts for ^^
Carbon Adsorbers ;•: • •: . r7
4-12 Effect of Modifications in Operation on Emissions <*-a/
4-13 Model Unit Secondary Air Pollution, Cross-Media,
and Energy Impacts for Thermal Incinerators t'30
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1.0 INTRODUCTION
The Clean Air Act (CAA) Amendments of 1990 established new
requirements for State implementation plans (SIP) for many areas that have
not attained thp national ambient air quality standards (NAAQS) for ozone.
These requirements include an expansion of the applicability of reasonably
available control technology (RACT) to smaller sources of volatile organic
compounds (VOC) than had previously been required by the U.S. Environmental
Protection Agency (EPA). They also include a requirement that certain
nonattainment areas reduce VOC emissions beyond the existing RACT
requirements so that continual progress is made toward attainment of the
ozone NAAQS. In addition, certain areas require a demonstration through
atmospheric dispersion modeling that VOC emission reductions will produce
ozone concentrations consistent with the ozone NAAQS. To help the States
identify the kinds of VOC control needed to meet these and other
requirements, the 1990 Amendments also required EPA to publish Alternative
Control Technology (ACT) documents for VOC sources. This document was
produced in response to that requirement.
The EPA has determined that organic emissions from process vents on
management units treating hazardous and nonhazardous wastes may contribute
to the formation of atmospheric ozone and may pose a risk to human health
and the environment. Organic emissions from waste management unit process
vents include photochemically reactive and nonphotochemically reactive
organics, some of which are toxic or carcinogenic.
On June 21, 1990, EPA promulgated standards (55 FR 25454) that limit
organic air emissions from process vents at new and existing hazardous
waste treatment, storage, and disposal facilities (TSDF) permitted under
Subtitle C of the Resource Conservation and Recovery Act (RCRA). However,
RCRA-permitted TSDF are only a subset of the waste management universe with
process vents. These standards regulated organic emissions from process
vents associated with distillation, fractionation, thin-film evaporation,
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solvent extraction, and air or steam stripping operations that manage
hazardous wastes with 10 parts per million by weight (ppmw) or greater
total organics concentration. Owners or operators subject to the standards
are required either (1) to reduce total organic emissions from all affected
vents at the facility to below 1.4 kg/h (3 Ib/h) and 2.8 Mg/yr (3.1
ton/yr), or (2) to install and operate a control device(s) that reduces
total organic emissions from all affected vents at the facility by 95
weight percent.
The purpose of this ACT document is to provide information to address
VOC emissions from process vents on waste management units treating
organic-containing wastes that are exempted from the RCRA process vent
standards (40 CFR Part 264 and 265, Subpart AA). It is important to note
that the treatment technologies are the same; i.e., the technologies
regulated by the RCRA process vent standards are also the most common ones
with process vents that are exempt from the RCRA process vent standards.
The information developed to support the RCRA process vent standards is
also applicable to similar sources that are not subject to the RCRA air
rules. The nonregulated units are a significant contributor to total air
emissions from waste management unit process vents. For example, in 1986,
steam stripping units that were exempt from RCRA permit requirements (and
therefore exempt from the RCRA process vent standards in most cases)
treated more than 30 times as much hazardous waste as did steam strippers
that were regulated units under RCRA. The process vents addressed in this
ACT include those on waste management units (i.e., distillation and
stripping operations) at TSDF treating wastes with total organics
concentration of less than 10 ppmw and those on treatment units that are
part of a waste management system exempt from RCRA permitting, e.g., a
nonhazardous waste treatment system or wastewater treatment system.
This ACT document presents technical information that State and local
agencies can use to develop strategies for reducing VOC emissions from
process vents on waste management units not regulated by the RCRA process
vent rules. The information in this document will allow planners to
identify process vent emission sources, identify available control alterna-
tives, and evaluate the VOC reduction and cost of implementing controls.
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Chapter 2.0 describes the waste industry, the operations commonly
associated with process vents, and typical process vent emission sources
and rates. Chapter 3.0 describes alternative control techniques for the
reduction of VOC emissions from waste management unit process vents.
Chapter 4.0 presents air, cross-media, and capital and annual cost analyses
of the alternative control techniques.
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2.0 INDUSTRY DESCRIPTION, PROCESSES, AND EMISSIONS
This chapter presents an overview of waste generation, the waste
treatment processes and technologies with associated process vents, the
sources and quantities of organic air pollutants emitted from these process
vents, and current State and Federal regulations that are applicable to
waste management unit process vents.
2.1 INDUSTRY DESCRIPTION
2.1.1 The Waste Management Industry
The waste management industry in the United States is diverse and
complex, covering a broad spectrum of industry types and sizes. Wastes,
both hazardous and nonhazardous, vary considerably in both composition and
form, and the waste management processes and practices used in treating,
storing, and disposing of these wastes also vary widely. Figure 2-1
presents a simplified waste system flowchart for the waste management
industry indicating key elements of the industry. These major elements--
generation, transportation, storage, treatment, and disposal-are discussed
in the following sections.
2-1.1.1 General Waste Description. Title 40 of the Code of Federal
Re3u]at1ons (CFR)- Part 261.2 (40 CFR 261.2), defines a solid waste as any
discarded material (e.g., garbage, refuse, sludge, or other waste material)
that is not excluded by definition. Part 261.3 divides hazardous waste
into four categories:
Characteristic wastes-wastes that exhibit any hazardous
characteristic identified in 40 CFR Part 261, Subpart C
including ignitability, corrosivity, reactivity or
extraction procedure (EP) toxicity
Listed waste-wastes listed in 40 CFR Part 261, Subpart D
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Generation
Transportation
Storage
Treatment
RCRA Wastes
Large & Small
Quantities
Disposal
rv>
i
ro
Drum, Tank
impound- ^
ment Storage
^
f^.
^
Commercial
Incinerators*
Onsite
Incinerators*
Solvent &
Other
Recovery
Operations
Other
Treatment
Operations^
Industrial
Furnaces
or Boilers*
^
••^
Commercial
Land
Disposal
Onsite
Land
Disposal
Deep Well
Injection
Figure 2-1. Simplified waste management system from generation to disposal.
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Mixture rule wastes—wastes that are (1) a mixture of solid
waste and a characteristic waste unless the mixture no
longer exhibits any hazardous characteristic, or (2) a mix-
ture of a solid waste and one or more listed hazardous
wastes
• Derived from rule wastes—any solid waste generated from the
treatment, storage, or disposal of a hazardous waste,
including any sludge, spill residue, ash, emission control
dust, or leachate (but not including precipitation runoff).
Hazardous wastes are designated by Resource Conservation and Recovery
Act (RCRA) alphanumeric codes. Codes D001 through D017 are referred to as
"characteristic wastes." D001 represents wastes that are ignitable in
character; D002, those that are corrosive; and D003, those that are reac-
tive. Extracts of wastes that contain toxic concentrations of specific
metals, pesticides, or herbicides are assigned one of the codes D004
through D017.
"Listed wastes" encompass four groups of alphanumeric codes published
in 40 CFR Part 261, Subpart D. Hazardous wastes generated from nonspecific
industry sources such as degreasing operations and electroplating are
listed as codes beginning with the letter "F" (e.g., F001). Hazardous
wastes from specific generating sources such as petroleum refining are
assigned codes beginning with the letter "K" (e.g., K048). Waste codes
beginning with "P" or "U" represent waste commercial chemical products and
manufacturing chemical intermediates (whether usable or off-specification).
40 CFR Part 261, "Identification and Listing of Hazardous Wastes," not
only lists hazardous wastes but also identifies specific wastes that are
excluded from regulation as hazardous. These excluded wastes can be
stored, treated, or disposed of without a RCRA permit.
General waste descriptions include hazardous wastes in the following
forms: contaminated wastewaters, spent solvent residuals, still bottoms,
spent catalysts, electroplating wastes, metal-contaminated sludges,
degreasing solvents, leaded tank bottoms, American Petroleum Institute
(API) separator sludges, off-specification chemicals, and a variety of
other waste types. In reviewing waste data, more than 4,000 chemical
constituents have been identified as components of the various waste types
examined.1
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2.1.1.2 Generators. The overwhelming majority of hazardous wastes
are produced by large-quantity generators, those firms that generate more
than 1,000 kg of hazardous waste per month.2-3 Hazardous waste generators
are most prevalent in the manufacturing industries (standard industrial
classification [SIC] codes 20-39). Manufacturing as a whole accounts for
more than 90 percent of the total quantity of hazardous waste generated.
Two industry groups that stand out as generators are the chemical and
petroleum industries (SIC 28 and 29); these industries alone account for
more than 70 percent of total waste generation. The chemical industry (SIC
28), with only 17 percent of the generators, generated 68 percent of all
the hazardous wastes produced in 1981.4
The 1981 National Survey of Hazardous Waste Generators and Treatment,
Storage, and Disposal Facilities (Westat Survey)^ provides estimates of the
number of generators producing specific types of hazardous wastes. Just
over half the generators indicated that they generate spent solvents, both
halogenated and nonhalogenated (RCRA waste codes F001-F005). Only 10 per-
cent of the generators generated listed hazardous wastes from specific
industrial sources (e.g., slop oil emulsion solids from the petroleum
refining industry--K049). Forty-three percent of generators produce ignit-
able wastes (RCRA waste code 0001), a third generated corrosive wastes
(D002), and more than a quarter generated wastes that failed EPA's test for
toxicity (D004-D017). Just under 30 percent of the generators reported
hazardous wastes that were spilled, discarded, or off-specification commer-
cial chemical products or manufacturing chemical intermediates ("P" and "U"
prefix waste codes).
Once a RCRA hazardous waste is generated, it must be managed (i.e.,
stored, treated, or disposed of) in accordance with legal requirements.
Although nearly all hazardous waste is managed to some degree at the site
where it is generated, the Westat Survey has shown that only about one in
six generators manages hazardous waste exclusively onsite.6 Of those
generators that ship hazardous wastes to offsite management facilities for
treatment, storage, and disposal, roughly a quarter still manage part of
their hazardous wastes onsite. Although the survey estimated that 84
percent of the generators ship some or all of their hazardous wastes
offsite, the vast majority of the quantities of hazardous waste are
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nonetheless managed onsite. About 96 percent of all generated hazardous
wastes are managed onsite, with only 4 percent being shipped offsite for
treatment, storage, or disposal.
Preliminary results of the National Survey of Hazardous Waste Treat-
ment, Storage, Disposal, and Recycling Facilities (TSDR Survey) indicate
that the total volume of hazardous waste managed in units onsite during
1986, regardless of the permit status of the units, was about 500 million
Mg.7 The physical characteristics of the 500 million Mg of RCRA hazardous
waste managed in 1986 vary from dilute wastewater to metal-bearing sludges
to soils contaminated with polychlorinated biphenyl (PCB). Over 90 percent
(by weight) of RCRA hazardous waste is in the form of dilute aqueous waste
(i.e., hazardous wastewater). The remaining wastes are organic and inor-
ganic sludges and organic and inorganic solids.
2.1.1.3 Treatment, Storage, and Disposal Facilities. A significant
segment of the hazardous waste industry is involved in hazardous waste
management (i.e., treatment, storage, and disposal activities). Table 2-1
provides the RCRA definition of treatment, storage, and disposal.8 Treat-
ment, storage, and disposal facilities (TSDF) must apply for and receive a
permit to operate under RCRA Subtitle C regulations. The RCRA Subtitle C
permit program regulates 13 categories of waste management processes.
There are four process categories each within storage and treatment
practices and five categories within disposal practices.
The industry is complex and not easily characterized. The hazardous
waste industry is also dynamic; that is, in response to changing demands
and regulations, the facilities change the ways wastes are treated, stored,
and disposed of. Of the treatment processes, tank treatment is most widely
practiced, but no single treatment process is used in a majority of facil-
ities. 9
Evaluation of the various treatment technologies associated with TSDF
has shown that waste management unit process vents are a significant source
of organic air emissions, particularly process vents associated with
distillation and other separation operations. Air emissions associated
with process vents from distillation and stripping (air and steam)
technologies used to treat hazardous waste, especially spent solvents
(e.g., hazardous waste numbered F001-F005), are major contributors to the
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TABLE 2-1. RESOURCE CONSERVATION AND RECOVERY ACT (RCRA)
HAZARDOUS WASTE MANAGEMENT DEFINITIONS3
Term
Definition
Storage
Treatment
Disposal facility
"Storage" means the holding of hazardous
waste for a temporary period, at the end of
which the hazardous waste is treated, dis-
posed of, or stored elsewhere.
"Treatment" means any method, technique, or
process, including neutralization, designed
to change the physical, chemical, or biologi-
cal character or composition of any hazardous
waste so as to neutralize such waste, or so
as to recover energy or material resources
from the waste, or so as to render such waste
non-hazardous, or less hazardous; safer to
transport, store, or dispose of; or amenable
for recovery, amenable for storage, or
reduced in volume.
"Disposal facility" means a facility or part
of a facility at which hazardous waste is
intentionally placed into or on any land or
water, and at which waste will remain after
closure.
^Definitions are presented as stated in RCRA regulations (40 CFR 260.10)
as of July 1, 1988.
Source:
U.S. Environmental Protection Agency. Code of Federal Regulations
Title 40, Part 260.10. Washington, DC. Office of the Federal
Register. July 1, 1988.
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process vent emissions total. Organic emissions are discharged from proc-
ess vents on distillation and separation units such as air strippers, steam
strippers, thin-film evaporators, fractionation columns, batch distillation
units, pot stills, and condensers and distillate receiving tanks that vent
emissions from these units. Distillation and separation processes that
treat wastes may be found in solvent reclamation operations, wastewater
treatment systems, and in other waste pretreatment processes.
2.1.2 Current Regulations Applicable to Waste Management
Unit Process Vents
2.1.2.1 State Regulations. The EPA examined State regulations, as
well as existing Federal standards (including those under development), to
determine the applicability of existing regulations to the control of waste
management unit process vents.10 The EPA found (as of 1987) that 6 States
had established air toxics programs, 21 States had established generic
standards for volatile organic compounds (VOC) independent of Federal
regulations, and several States had extended control techniques guidelines
(CTG) for VOC to TSDF. However, the standards vary widely in scope and
application and, in many cases, controls have not been required when
emissions are below 40 ton/yr, even in the 37 States with ozone nonattain-
ment areas. Although a few States have controls in place, it appears that
there were no general control requirements for TSDF process vents. More-
over, because TSDF with solvent recycling, one of the most typical waste
management unit operations with associated process vents, generally are
small operations, any new waste management units with process vents would
likely have potential VOC emissions of less than 40 ton/yr; thus, preven-
tion of significant deterioration (PSD) permit requirements may not apply.
Existing Clean Air Act (CAA) standards that apply to the Synthetic Organic
Chemical Manufacturing Industry (SOCMI) and petroleum refineries typically
control emissions from production processes and generally do not apply to
waste management sources/ In addition, EPA sent information requests to
several large and small TSDF as part of the survey of existing regulations;
2n rrnmner °L19?3' EPA ProPosed New Source Performance Standards (NSPS)
(40 CFR Part 60, Subpart NNN) to control emissions from SOCMI distil la-
tion operations. The recommended standards would require VOC emissions
from new, modified, and reconstructed distillation operations to be
reduced by 98 percent.
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respondents to the EPA questionnaires did not indicate control requirements
for process vents. Several of the facilities that were asked to provide
information reported requirements for obtaining air contaminant source
operating permits, but they reported no specific permit requirements for
controlling process vent emissions.
2.1.2.2 RCRA Air Regulations. The process vent standards in 40 CFR
Part 264 and 265, Subpart AA (promulgated 55FR 25454, June 21, 1990), limit
emissions of organics from certain waste management unit process vents at
new and existing hazardous waste TSDF requiring a RCRA permit (i.e., TSDF
that need authorization to operate under RCRA Section 3005). The standards
are applicable to all hazardous waste management units that are subject to
the permitting requirements of Part 270 and hazardous waste recycling units
that are located on hazardous waste management facilities otherwise subject
to the permitting requirements of Part 270. Process vent air emissions
from facilities or units that manage solid wastes not regulated as
hazardous wastes pursuant to 40 CFR Part 261 and air emissions from
hazardous waste from units or facilities exempt from the permitting
provisions of 40 CFR 270.1(c)(2) are not regulated by the process vent
standards in 40 CFR Part 264 and 265, Subpart AA (i.e., exempt units, other
than recycling units, are not subject to the RCRA process vent standards
even when they are part of a permitted facility).
The standards are applicable to process vents on affected hazardous
waste management units that manage hazardous waste with an annual average
total organics concentration of 10 parts per million by weight (ppmw) or
greater and specifically include: (1) process vents on distillation,
fractionation, thin-film evaporation, solvent extraction, and air or steam
stripping operations and vents on condensers serving these operations; and
(2) process vents on tanks (e.g., distillate receivers, bottoms receivers,
surge control tanks, separator tanks, and hot wells) associated with
distillation, fractionation, thin-fi1m evaporation, solvent extraction, and
air or steam stripping processes if emissions from these process operations
are vented through the tanks.
2.1.2.3 RCRA Exemptions. In the RCRA regulations that define both a
solid waste and a hazardous waste (i.e., 40 CFR 261.4), there are a number
of general exclusions identifying materials that are not solid wastes and
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solid wastes that are not hazardous wastes. Because these excluded
materials cannot be considered either a "solid waste" or "hazardous waste,"
as the case may be, these wastes (RCRA exempt wastes) are not subject to
hazardous waste regulations under RCRA Subtitle C.* In addition, the RCRA
regulations that codify the hazardous waste permit program (i.e., 40 CFR
270.1) identify specific facilities and/or units that are not required to
obtain a RCRA permit (RCRA-exempt units). Because of these general RCRA
exemptions, the following types of facilities or units are exempt from the
RCRA process vent air emission standards in Subpart AA of 40 CFR Part 264
and 265 (it is the control of organic air emissions from these exempt waste
management units that is the subject of this document):
Generators that accumulate hazardous waste in tanks and
containers for 90 days or less. (Note; The EPA intends to
modify this exemption at a later date.)
Units such as product (not hazardous waste) distillation
columns generating organic hazardous waste still bottoms.
• Totally enclosed treatment facilities.
• Closed-loop recycling (reclamation) units.
Elementary neutralization and wastewater treatment tanks.
Units covered under the domestic sewage exclusion (i.e.
publicly owned treatment works [POTW] receiving hazardous
wastes).
• Units managing Subtitle D wastes.
These units are discussed in the following sections. Explanations are
provided on why these units are not regulated by the RCRA air emission
standards in 40 CFR Part 264 and 265, Subpart AA.
Generators' 90-Day Accumulation Tanks and Containers. In 40 CFR Part
270, hazardous waste generators who accumulate waste onsite in containers
or tanks for less than the time periods provided in Section 262.34 are
Subtitle C-Hazardous Waste Management-of the RCRA statute as amended by
Hazardous and Solid Waste Amendments (HSWA) establishes the program to
regulate hazardous wastes from generation through proper disposal or
destruction. Subtitle C contains the bulk of the requirements for RCRA
permitting, closure, and post-closure, including criteria for identifying
2-9
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specifically excluded from RCRA permitting requirements (i.e., a generator
may accumulate hazardous waste onsite for 90 days or less without a RCRA
permit or without having interim status (40 CFR 264.34)). To qualify for
the exclusions in Section 262.34, generators who accumulate hazardous waste
onsite for up to 90 days must comply with the substantive requirements for
RCRA tanks and containers. Small-quantity generators (i.e., generators who
generate more than 100 kg [222.2 Ib] but fewer than 1,000 kg [2,222.2 Ib]
per calendar month) are allowed to accumulate waste onsite for up to 180
days or, if they must ship waste offsite for a distance of 320 km (200
miles) or more and if they meet certain other requirements set out in
Section 262.34, for up to 270 days.
The promulgated regulation for process vents does not create a new
exemption for 90-day accumulation, nor does it modify the existing
regulation. However, because analysis indicates that 90-day tanks and
containers have significant organic air emissions, EPA plans to propose (in
1990) a modification of the exemption to require that 90-day tanks meet the
control requirements of the TSDF air standards that include the RCRA
process vent standards. Until a final decision is made on regulating the
emissions from these units, 90-day tanks that involve distillation/separa-
tion operations are not subject to additional controls under the process
vents rules (Subpart AA). Therefore, generators of hazardous wastes (e.g.,
spent solvents identified as F001-F005 wastes) with onsite "90-day" tanks
may have process vents associated with these nonpermitted units that are
not controlled for organic air emissions. This document provides guidance
on control technologies for these units until the proposed regulation is
promulgated. [Note: Generators of hazardous wastes who ship these wastes
offsite are required to designate, on the manifest, one facility that is
authorized to handle the waste described on the manifest (40 CFR
262.20(b)). Hence, TSDF such as solvent recyclers that receive hazardous
waste (e.g., spent solvents) should be RCRA-permitted facilities and thus
potentially subject to the process vent rules.]
Process/Production Equipment. Under 40 CFR 261.4(c), hazardous wastes
that are generated in process-related equipment such as product or raw
material storage tanks or pipelines are exempt from RCRA regulation. This
2-10
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exemption applies until the waste is physically removed from the unit in
which it was generated, unless the unit is a surface impoundment or unless
the hazardous waste remains in the unit more than 90 days after the unit
ceases to be operated for manufacturing, storage, or transportation of
product or raw materials. Therefore, units such as product (not hazardous
waste) distillation columns generating organic hazardous waste still
bottoms are not subject to the RCRA process vent standards while the wastes
are in the product distillation column unit. These product distillation
columns may be subject to standards developed under the CAA, such as the
proposed standards of performance for new stationary source VOC emissions
from the SOCMI distillation unit operations (48 FR 57538, December 30,
1983) or similar standards proposed for the polymers and resins industry
(52 FR 36678, September 30, 1987). However, distillation columns that
manage such hazardous wastes (i.e., hazardous waste management units) are
subject to the RCRA process vent standards (Subpart AA) if they are located
at a RCRA-permitted facility.
Totally Enclosed Treatment Facilities. A "totally enclosed treatment
facility" is a hazardous waste treatment facility that is "directly
connected to an industrial production process and which is constructed and
operated in a manner that prevents the release of any hazardous waste or
any constituent thereof into the environment during treatment" (40 CFR
260.10). Totally enclosed treatment facilities are exempt from RCRA
Subtitle C permit requirements under 40 CFR 264.1(g)(5), 40 CFR
265.1(c)(9), and 270.1(c)(2).
Two important characteristics define a totally enclosed treatment
facility. The key characteristic of a totally enclosed treatment facility
is that it does not release any hazardous waste or constituent of hazardous
waste into the environment during treatment. Thus, if a facility leaks,
spills, or discharges waste or waste constituents, or emits waste or waste
constituents into the air during treatment, it is not a totally enclosed
treatment facility within the meaning of these regulations. The second
important characteristic is that it must be directly connected to an
industrial production process. Treatment facilities located off the site
of generation (e.g., commercial TSDF) are not directly connected to an
industrial process and therefore are not exempt. In addition, storage and
2-11
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disposal units and ancillary equipment not used to treat hazardous wastes
fall outside the definition of a totally enclosed treatment facility.
The EPA believes that most onsite treatment facilities are not totally
enclosed. Distillation columns and other treatment technologies generally
are designed to release emissions into the air. Therefore, by definition,
these onsite technologies are generally not totally enclosed. (See 45 FR
33218, May 19, 1980 [no constituents released to air during treatment].)
As a result of this definition, there should be no process vent emissions
from units that are exempted as "totally enclosed treatment units."
Closed-loop Recycling Units. The RCRA process vent rules regulated
the activity of reclamation at RCRA facilities for the first time. The EPA
has amended 40 CFR 261.6, under its RCRA authority over reclamation, so
that reclamation of hazardous wastes in waste management units of the type
affected by the process vent rules (e.g., distillation columns or thin-film
evaporators) is covered by the process vent rules. It should be recog-
nized, however, that the rules apply only at facilities otherwise needing a
RCRA permit. In addition, the closed-loop reclamation exemption in Part
261.4(a)(8) is not changed by these rules. Therefore, not all reclamation
units will necessarily be affected by the process vent and equipment leak
rules. "Closed-loop reclamation units" are exempt. As a result, process
vents on distillation/separation operations exempted from the Subpart AA
process vent rules as part of a closed-loop reclamation system may have
significant uncontrolled organic air emissions.
Elementary Neutralization and Wastewater Treatment Tanks. The RCRA
regulations also exclude elementary neutralization and wastewater treatment
units as defined by 40 CFR 260.10 from obtaining a permit. The EPA amended
these definitions (see 53 FR 34080, September 2, 1988) to clarify that the
scope of the exemptions applies to the tank systems, not just the tank.
For example, if a wastewater treatment or elementary neutralization unit is
not subject to RCRA Subtitle C hazardous waste management standards,
neither is ancillary equipment connected to the exempted unit. The amend-
ments also clarify that a wastewater treatment tank must be part of an
onsite wastewater treatment facility in order to be exempt. Thus, emis-
sions from process vents on distillation, fractionation, thin-film evapora-
tion, solvent extraction, or air or steam stripping operations that are
2-12
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considered a tank regulated under Section 402 or 307(b) of the Clean Water
Act (CWA) are not subject to the RCRA process vent standards.
Domestic Sewage Units. Under the "domestic sewage exclusion" (DSE)
[specified in Section 1004(27) of RCRA and codified in 40 CFR 261. 4(a) (1)] ,
solid or dissolved material in domestic sewage is not, by definition, a
"solid waste" and, as a corollary, cannot be considered a "hazardous
waste." Thus, the DSE covers:
"Untreated sanitary wastes that pass through a sewer system"
• "Any mixture of domestic sewage and other wastes that passes
through a sewer system to a POTW for treatment" [40 CFR
The exclusion allows industries connected by pipeline to POTW to
discharge hazardous wastes to sewers containing domestic sewage without
having to comply with certain RCRA generator requirements such as manifest-
ing and reporting requirements. Moreover, POTW receiving excluded wastes
are not deemed to have received hazardous wastes and, therefore, are not
subject to RCRA requirements for TSDF. [Note: The premise of the
exclusion is that it is unnecessary to subject hazardous wastes mixed with
domestic sewage to RCRA management requirements because these DSE wastes
receive the benefit of treatment offered by POTW and are already regulated
under CWA programs such as the National Pretreatment Program.]
Subtitle D Waste Management Units. RCRA Subtitle D wastes are all
solid wastes regulated under RCRA not subject to hazardous waste regula-
tions under Subtitle C. These wastes are defined in 40 CFR Part 257. In
accordance with the above-mentioned definitions and exclusions, several
categories of Subtitle D wastes have been identified. At least two of
these categories include wastes with significant amounts of organics that
could eventually be managed in units having associated process vents.11
These two categories, industrial nonhazardous waste and smal 1 -quantity
generator waste, are discussed briefly.
The principal source of data on industrial Subtitle D wastes is
Summary of Data on Industrial Nonhazardous Waste Disposal Practices. 12
This report includes a review of compiled available data on industrial
nonhazardous wastes characteristics and generation rates from 22 major
2-13
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manufacturing industries and indicates that the characteristics of
industrial nonhazardous wastes vary from industry to industry and within
each industry. Twelve of the twenty-two industries studied are expected to
generate nonhazardous wastes that contain relatively high levels of organic
constituents (and heavy metals). The information available on management
practices of industrial nonhazardous wastes did not address waste treatment
processes of the type that have associated process vents.
Hazardous wastes generated by conditionally exempt smal1-quantity
generators are solid wastes that are exempt, under 40 CFR 261.5, from
Subtitle C regulations and thus are Subtitle D wastes. Conditionally
exempt wastes are defined as those wastes that meet the definition of a
hazardous waste under 40 CFR Part 261 and that are generated at a rate of
less than 100 kg/month. The National Small Quantity Hazardous Haste
Generator Survey13 indicates that about 18 percent of conditionally exempt
wastes are spent solvents. The report also states that most small-quantity
generator (SQG) (i.e., <1,000 kg/month) waste is managed offsite (85 per-
cent), with about 65 percent being recycled offsite. Also, according to
the survey, SQG wastes are managed onsite by: recycling (65 percent),
discharge to public sewers (8 percent), solid waste facilities (5 percent),
and Subtitle C facilities (4 percent).
Detailed data on the types of facilities and process units that manage
Subtitle D wastes are not available (with the exception of data on surface
impoundments, landfills, land application units, and wastepiles); there-
fore, no characterization can be made regarding the type of process vents
and their operating parameters for those waste treatment units managing
Subtitle D wastes (such as industrial nonhazardous waste and conditionally
exempt hazardous wastes).
2.1.2.4 Exemptions to the Process Vent Standards. As promulgated,
the RCRA process vent standards control organic emissions as a class from
affected process vents at hazardous waste TSDF that are subject to
permitting requirements under RCRA Section 3005. In addition, the rules
are applicable only to specific types of waste management units that manage
wastes classified as hazardous and that contain organics above a specific
concentration.
2-14
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Specified Waste Management Units. The RCRA standards for process
vents apply only to those waste management units that are known to have
associated process vents. These include (1) process vents on distillation,
fractionation, thin-film evaporation, solvent extraction, and air or steam
stripping operations and vents on control devices (e.g., condensers)
serving these operations, and (2) process vents on tanks or vessels (e.g.,
distillate receivers, bottoms receivers, surge control tanks, separator
tanks, and hot wells associated with distillation, fractionation, thin-film
evaporation, solvent extraction, and air or steam stripping processes) if
emissions from these operations are vented through the tank. The RCRA
process vent standards exclude air emissions from vents on other closed
(covered) and vented tanks not associated with the specified distillation/
separation processes. For example, uncondensed overhead emitted from a
distillate receiver (i.e., a tank) serving a hazardous waste distillation
process unit is subject to the RCRA process vent regulations. On the other
hand, if emissions from the distillation unit or a condenser serving the
unit are not vented through the tank (i.e., they are vented directly to the
atmosphere or through a vacuum pump), then vents that may be present on the
tank are not subject to the RCRA standard for process vents. Unenclosed or
uncovered processes, storage tanks, treatment tanks, and transfer facil-
ities are not covered by the process vent rules, but EPA plans to regulate
these sources with additional RCRA TSDF air standards for tanks and con-
tainers; proposal is planned for 1990.
Units Managing Waste with Less than 10 ppmw Total Qrqanics Content.
A hazardous waste management unit is not subject to the RCRA process vent
rules if it treats wastes with less than a 10-ppmw total organics content
on an annual average basis. Of the distillation/separation operations used
to manage wastes, air stripping is the treatment device most commonly used
with low organic concentration streams. Distillation-type operations would
not likely be used to treat wastes with organic concentrations of less than
10 ppmw. Examples of facilities managing low-concentration wastes are
sites where ground water (or wastewater) is undergoing remedial action
under the Comprehensive Environmental Response, Compensation, and Liability
Act (CERCLA) or corrective action persuant to RCRA.
2-15
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It should also be noted that, with the annual average applicability
criterion, a waste management unit would not be subject to the RCRA process
vent standards if it occasionally treats hazardous wastes that exceed
10 ppmw and if at other times the organic contents of the wastes being
treated in the unit are such that the weighted annual average total organic
concentration of all wastes treated is less than 10 ppmw.
2.1.2.5 Haste Treated in RCRA-Exempt Units. As noted above, the RCRA
process vent standards do not apply to all distillation, fractionation,
thin-film evaporation, solvent extraction, and air and steam stripping
operations managing hazardous waste even when they are part of a permitted
facility. RCRA-exempt units, other than some recycling units, are not
subject to the process vent rules. Neither are units of the type specified
in the rule that do not meet all the applicability criteria contained in
the rules; i.e., wastes may not be hazardous under RCRA or may not contain
an organic concentration that triggers regulation.
Preliminary results of the National Survey of Hazardous Waste Treat-
ment, Storage, Disposal, and Recycling Facilities (TSDR Survey) indicate
about 3.6 million tons of hazardous waste were managed in units of the type
specified in the RCRA process vent rules that required a RCRA permit during
1986.14 About 10.6 million tons of hazardous waste were managed in units
of the type specified in the process vent rules that were exempt from RCRA
permitting requirements that same year. Table 2-2 summarizes the data on
quantities of wastes managed in, and the RCRA permit status of, these
selected treatment units. As these data indicate, there are a number of
distillation/stripping units at TSDF exempt from the RCRA permit require-
ments that nonetheless treat both hazardous and nonhazardous wastes. These
units may not be subject to the RCRA process vent rules in 40 CFR Part 264
and 265, Subpart AA, even though these nonregulated units have process
vents that potentially emit organics to the atmosphere in quantities
similar to process vents on units regulated under the RCRA process vent
rules. These unregulated units are the focus of this ACT document.
2.2 PROCESS DESCRIPTIONS
The processes discussed in this section are those waste management
operations that are used to treat, store, or dispose of organic-containing
wastes and are known to have associated process vents. Distillation/
2-16
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TABLE 2-2. QUANTITIES OF WASTE MANAGED IN, AND RCRA PERMIT STATUS OF, SELECTED TREATMENT UNITS IN 1986
Type of unit
Air strippers
Steam strippers
Fractional distillation
Batch distiI I at ion
Solvent extraction
Thin-film evaporation
•Regulated units include units with a RCRA final permit and those operating under RCRA interim status.
bExempt units include wastewater treatment/elementary neutralization units, recycling units, 90-day
accumulation tanks, and other exempt units. Some recycling units would be regulated under the RCRA process
vent rules.
cWaste quantity values are not additive horizontally because some wastes are managed in both units requiring
a RCRA permit and those exempt from RCRA permitting requirements. However, a waste treated in one of the
specified units is not likely to be treated in any other of the specified units.
Source: 1987 National Survey of Hazardous Waste Treatment, Storage, Disposal, and Recycling Facilities (TSDR
Survey). Alpha Database. July 1989.
RCRA permit
(number of
Regulated3
10
17
53
185
32
52
status
un i ts)
Exemptb
42
23
72
185
10
25
Quantity of hazardous
waste managed (tons)0
Regulated units Exempt units
3,077,000
96,000
90,400
150,000
61,300
136,000
6,877,000
3,251,000
187,000
178,000
4,000
85,000
Quantity of nonhazardous
w^ste managed . (tons)^
Regulated units Exempt units
0
0
112,200
3,500
101,500
1,000
89,700
0
79,000
800
100
100
-------
stripping operations of the type described below are used to reprocess,
reduce total volume, or treat organics in the waste before the waste is
properly disposed of. These distillation/stripping process units may or
may not be controlled by the RCRA process vent standards described in
Section 2.1.
For the purpose of this document, a process vent is defined as any
open-ended pipe or stack that is vented to the atmosphere either directly,
through a vacuum-producing system, or through an associated tank (e.g.,
distillate receiver, condenser, bottoms receiver, surge control tank,
separator tank, or hot well). Vented means discharged through an opening,
typically an open-ended pipe or stack, allowing the passage of a stream of
liquids, gases, or fumes into the atmosphere. Under the process vent
definition, the passage of liquids, gases, or fumes is caused by mechanical
means such as compressors or vacuum-producing systems or by process-related
means such as evaporation produced by heating and is not caused by tank
loading or unloading or by natural means such as diurnal temperature
changes.
The above vent description is the same as the definition used in the
RCRA process vent standards discussed previously. Under this definition,
the scope of this process vent control technology document is limited and
does not include nonprocess-related vents such as those on storage tanks.
This definition excludes tank working (loading and unloading) losses and
tank breathing losses; tank working and breathing losses are not considered
process vent emissions. Information on the control of sources with
nonprocess-related vents is presented in other EPA documents. For example,
the Hazardous Waste TSDF--Backqround Information for Proposed RCRA Air
Emission Standards (February 1990, draft document) provides technical
support for the upcoming RCRA air rules: Subpart CC--Air Emission
Standards for Tanks, Surface Impoundments, and Containers of 40 CFR Parts
264 and 265, which is planned for proposal in 1990; and the VOC Emissions
from Volatile Organic Liquid Storage Tanks—Background Information for
Proposed Standards (EPA-450/3-81-003a), which provides technical support
for the CAA rules: Standards of Performance for Volatile Organic Liquid
Storage Vessels in 40 CFR Part 60, Subpart Kb.
2-18
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Review of the various waste treatment technologies used at TSDF
indicates that distillation and stripping operations (i.e., separation
processes) are the waste management units most typically having associated
process vents.15 The following sections provide brief process descriptions
and typical process vent configurations for the most common distillation
and stripping operations.
2.2.1 Distillation
Distillation is the most commonly used separation and purification
procedure in refineries, solvent recovery systems, large organic chemical
manufacturing plants, and TSDF. The fundamental operating principles for a
distillation column are the same regardless of the application. This
section briefly discusses some of the principles involved in the various
types of distillation operations to provide a better understanding of the
operating characteristics of distillation units.
Distillation is an operation separating one or more feed stream(s)
into two or more product streams, each product stream having component
concentrations different from those in the feed stream(s). The separation
is achieved by the redistribution of the components between the liquid and
vapor phase as they approach equilibrium within the distillation unit. The
more volatile component(s) concentrate in the vapor phase; the less vola-
tile components(s) concentrate in the liquid phase. Both the vapor and
liquid phases originate predominantly by vaporization and condensation of
the feed stream.
Distillation systems can be divided into subcategories according to
the operating mode, the method of applying heat to volatilize components,
the operating pressure, the number of distillation stages, the introduction
of inert gases, and the use of additional compounds to aid separation. A
distillation unit may operate in a continuous or a batch mode. The
operating pressures can be below atmospheric (vacuum), atmospheric, or
above atmospheric (pressure). Distillation can be a single-stage or a
multistage process. Inert gas, especially steam, is often introduced to
vaporize the volatile constituent or to improve separation. In some cases,
compounds are introduced to aid in distilling hard-to-separate mixture
constituents (azeotropic and extractive distillation). Those types of
2-19
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distillation operations commonly used to manage wastes containing organic
constituents are discussed below.
2.2.1.1 Batch Distillation. Batch distillation is commonly used to
recover organics from hazardous wastes. Its principal use is for recovery
of valuable organic chemicals (e.g., spent solvents) for recycling or reuse
and the re-refining of waste oil. It also can be applied to reduce the
organic air emission potential of hazardous and nonhazardous wastes by
separating the volatile compounds from the wastes. Although it has been
applied to aqueous wastes, its predominant application has been to organic
wastes (i.e., wastes with high organic concentrations).
The simplest form of distillation is a batch operation that consists
of a heated vessel (called the pot), a condenser, and one or more distil-
late receiving tanks. The waste material is charged to the pot and heated
to boiling; vapors enriched in organics are then removed, condensed, and
collected in receiving tanks. The distillation is continued to a cutoff
point determined by the concentration of organics in the condensate or the
concentration of organics remaining in the batch. A common modification is
to add a rectifying column and some means of returning a portion of the
distillate as reflux (see Figure 2-2). Rectification, or fractionation, is
a multistage distillation operation that enables the operator to obtain
products from the condensate that have a narrow composition range. Frac-
tionating distillation is accomplished by using trays, packing, or other
internals in a vertical column. The light end vapors evolving from the
column are condensed and collected in a distillate receiver tank. Part of
the distillate is returned to the top of the column so it can fall counter-
current to the rising vapors. Different distillate cuts are made by
switching to alternate receivers, at which time the operating conditions
may be changed. If the distillate is collected as one product, the
distillation is stopped when the combined distillate reaches the desired
average composition. Several references'"^ are available that discuss
batch distillation design and operation at a temperature determined by the
boiling point of the waste, which may increase with the time of operation.
The distillation can be carried out under pressure or under vacuum. The
use of a vacuum reduces the operating temperature and may improve product
2-20
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ro
i
ro
Wastes
In
Storage
Tank Pump
Feed
S Heat — >
Column
J_
Reflux
Batch Still >• jj
(d
Condenser
1
Overhead
ottoms Product
roduct
isposal, recycle, fuel)
r
— Distil
Rece
| ,
1 ^
late
ver
Storage
Tank
— **Re
Recycle, Fuel
Figure 2-2. Schematic diagram of batch distillation with fractionating column.
-------
recovery, especially when decomposition or chemical reaction occurs at
higher temperatures.
Batch distillation provides a means for removing organics from a waste
matrix and recovering the organics by condensation for recycle, sale as
product, or for fuel. The products and residues include the condensate
that is enriched in organics and recovered, noncondensibles that escape
through the condenser vent, and the waste residue that remains in the pot.
The noncondensibles are composed of gases dissolved in the waste and very
volatile organic compounds with relatively low-vapor-phase concentrations.
The waste material after distillation may have been concentrated with high-
boiling-point organics or solids that are not removed with the overhead
vapors. These still bottoms may be a free-flowing liquid, a viscous
slurry, or an organic material that may solidify upon cooling. If the
waste material contains water, a separate aqueous phase may be generated
with the condensate. This phase may be returned to the batch or processed
with additional treatment to remove organics or other contaminants.
Batch distillation is typically used for wastes that have a signifi-
cant vapor-phase concentration of organics at the distillation temperature.
If the waste can be pumped and charged to the still pot and the residue can
be removed from the pot, then the waste is likely to be treatable for
organic removal by this process. Such waste forms include dilute aqueous
wastes (the operation would be similar to batch steam stripping, which is
discussed later in this chapter), aqueous or organic sludges, or wastes
with volatiles in a high-boiling-point organic solvent or oil. The batch
distillation of sludges has not been demonstrated and evaluated in full-
scale units; consequently, the processing of sludges in a batch distilla-
tion unit is subject to the same limitations described later for the batch
steam stripping of sludges. Batch distillation has been used to remove
organics from plating wastes and phenol from aqueous wastes, to recover and
separate solvents, and to re-refine waste oils.20,21 jne applicability of
batch distillation for a specific waste type can be evaluated by a simple
laboratory distillation to assess potential organic recovery. As with
other organic removal techniques, the process may require optimization in a
pilot-scale or full-scale system for different types of wastes to determine
operating conditions that provide the desired distillate composition or
percent removal from the waste.
2-22
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Batch stills usually are operated as a single equilibrium stage (i.e.,
with no reflux); consequently, the organic removal efficiency is primarily
a function of the vapor/liquid equilibrium coefficient of the organics at
distillation temperature and the fraction of the waste boiled over as
distillate. The use of a rectifying section yields an overhead product
with a composition that can be controlled by the operator. The removal
efficiency for various waste types can be highly variable because of the
dependence on both the properties of the waste (e.g., organic equilibrium)
and the operating conditions that are used.
2.2.1.2 Continuous Distillation. Continuous distillation is used
routinely in the chemical manufacturing industry. In a continuous distil-
lation unit, one or more feed streams are separated into two or more
product streams on a continuous, steady-state basis. Continuous fraction-
ating distillation is the most commonly used type of distillation unit
operation in large organic chemical plants. The efficiency of a continuous
system at removing organics from a feed or waste stream is related to the
equilibrium coefficient and the number of trays or height of packing. In
principle, the removal efficiency in a multistage system can be designed to
achieve almost any level. In practice, removal efficiencies are determined
by practical limits in column design (such as maximum column height or
pressure drop) and cost.
Continuous distillation operations require a feed stream that is a
free-flowing liquid with a negligible solids content. Solids, including
tars and resins, tend to foul the column trays or packing and heat
exchangers. Consequently, wastes containing solids may require removal of
the solids prior to processing through a continuous distillation unit.
Unlike the batch operation, a continuous distillation unit requires a
relatively consistent feed composition to maintain a consistent removal
efficiency from the waste material. A continuous distillation unit may
offer cost advantages over a batch operation for applications in which
there is little variation in the type of feed and for relatively high
volumes of waste materials.
2.2.1.3 Thin-Film Evaporation. Thin-film evaporators (TFE) are
designed to promote heat transfer by spreading a thin layer of liquid on
2-23
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one side of a metallic surface while supplying heat to the other side.22
The unique feature of this equipment is the mechanical agitator device,
which permits the processing of high-viscosity liquids and liquids with
suspended solids. However, if solid particles are large, a coarse filtra-
tion operation may be required to pretreat the waste stream going to the
TFE. The mechanical agitator promotes the transfer of heat to the material
by exposing a large surface area for the evaporation of volatile compounds
and agitates the film to maintain the solids in suspension without fouling
the heat transfer area. Heat can be supplied by either steam or hot oil;
hot oils are used to heat the material to temperatures higher than can be
achieved with saturated steam. TFE can be operated at atmospheric pressure
or under vacuum as needed depending on the characteristics of the material
treated. A TFE distillation operation is illustrated in Figure 2-3.
The two types of mechanically agitated TFE are horizontal and verti-
cal. A typical unit consists of a motor-driven rotor with longitudinal
blades that rotate concentrically within a heated cylinder. The rotating
blade has a typical tip speed of 9 to 12 m/s (30 to 39 ft/s) and a clear-
ance of 0.8 to 2.5 mm (0.032 to 0.098 in.) to the outer shell. In a
vertical design, feed material enters the feed nozzle above the heated zone
and is transported mechanically by the rotor and grating down a helical
path on the inner heat transfer surface while the volatile compounds are
volatilized and leave the evaporator on the top. The vapor-phase products
from TFE are condensed in a condenser, and the bottom residues are
collected for disposal.
TFE have been used widely for many years in a number of applications
such as processing of chemicals, Pharmaceuticals, plastics, and foods.23
Because of their unique features, their use in chemical and waste material
processing has expanded rapidly. The flexibility in operating temperature
and pressure add potential to TFE for recovering low-boiling-point organics
from a complex waste matrix.
Waste forms suitable for TFE treatment include organic liquids,
organic sludge/slurry, two-phase aqueous/organic liquids, and aqueous
sludges. TFE would not be an economical means of treating dilute aqueous
waste because of the high water content in the waste.
2-24
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Vent
Vent
ro
en
Storage
and
Feed Tank
Pump
Condenser
Thin-Film
Evaporator
Decanted
Water
Vent
J
Recovered
Organics
Storage
Tank
'Recycle
Bottom Stream
Figure 2-3. Schematic diagram of a thin-film evaporator system.
-------
2.2.1.4 Steam Stripping. Steam stripping involves the fractional
distillation of volatile constituents from a less volatile waste matrix.
Both batch and continuous steam stripping are commercially proven processes
and have been commonly used to remove organics from aqueous streams such as
process wastewater. Several references discuss steam stripping in detail,
including a steam-stripping manual published by EPA,24 descriptions of the
theory and design procedures,25-28 ancj descriptions of applicability to
hazardous wastes.29-32 The basic operating principle of steam stripping is
the direct contact of steam with the waste, which results in the transfer
of heat to the waste and the vaporization of the more volatile constitu-
ents. The vapor is condensed and separated (usually decanted) from the
condensed water vapor. A simplified diagram of a steam stripping operation
is shown in Figure 2-4.
The batch steam stripping process is identical in principle to batch
distillation except that the waste charge is heated by direct steam injec-
tion instead of being heated indirectly. Batch steam stripping may offer
advantages at waste facilities because the unit can be operated in a manner
most suitable for the particular batch of waste to be stripped. For
example, the same unit may be used to remove volatiles from a batch of
wastewater, from a waste containing solids, or from a high-boiling-point
organic matrix. Batch stills may also be used if the material to be
separated contains solids, tars, or resins that may foul or plug a contin-
uous unit.
The heat input rate and fraction boiled over can be varied for each
waste composition to obtain the recovery or removal desired for the
specific batch of waste. If the system is cleaned between batches, an
aqueous waste stream may be generated from the rinse water. This rinse
water may be added to a similar batch to be stripped, accumulated in a
separate batch for treatment, or sent to a wastewater treatment (WWT) unit.
However, wastewater may be generated from cleaning any organic removal or
treatment system and would not be unique to batch operations.
Continuous steam stripping requires a feed stream that is a free-
fTowing liquid with a negligible solids content. Solids, including tars
and resins, tend tq foul the column trays or packing and heat exchangers.
Consequently, wastes containing solids may require removal of the solids
2-26
-------
ro
Condenser
Waste
In
Storage
and
Feed Tank
Feed
Pump
Trays
or
Packing
Effluent ^ I
(wastewater treatment)
Steam
Stripper
Steam
Condensed
Liquids
Decanter
Decanted Water
to Feed Tank
Recovered Organics
Storage
Tank
'Recycle, Fuel
Figure 2-4. Schematic diagram of a steam stripping system.
-------
prior to processing through a continuous steam stripper. Unlike the batch
operation, a continuous steam stripper requires a relatively consistent
feed composition to maintain a consistent removal efficiency from the waste
material.33 A continuous steam stripper may offer cost advantages over a
batch operation for applications in which there is little variation in the
type of feed and for relatively high volumes of waste materials.
The products and residues from steam stripping include the condensed
vapors (condensate), noncondensible gases, and the treated waste or efflu-
ent. The condensate usually is decanted to remove any separate organic
layer from the aqueous layer. The aqueous condensate is then recycled to
the feed stream. The separate organic layer may be recovered and reused as
product or fuel. If the condensate is a single phase of water containing
dissolved organics, then additional treatment of the condensate may be
necessary for ultimate control of organics. Most commercial processes rely
on the formation of a separate organic phase and decanting for economical
removal and recovery of organics. Noncondensibles in the overhead stream
include gases dissolved in the waste material and very volatile compounds
in low concentrations that are not condensed in the overhead system. The
effluent from the steam stripper should be essentially free of the most
volatile compounds; however, semivolatiles and compounds that are rela-
tively nonvolatile may still be present in the stripper bottoms or
effluent.
Preliminary treatment such as solids removal or pH adjustment is often
used before wastewater is stripped in a continuous unit. Steam stripping
of wastewaters that contain significant quantities of dissolved solids,
emulsified oil, and suspended solids may in some cases foul the stripper
and make it unusable. Therefore, removal of any separate oil or solid
phase in the wastewater prior to stripping will improve performance and
minimize maintenance problems. Continuous steam stripping has been used
routinely in the chemical industry to recover organics for recycle and to
pretreat wastewater for organic removal prior to the conventional WWT
process. Some common applications include recovery of ethylene dichloride,
ammonia, sulfur, or phenol for recycle and removal of phenol, mercaptans,
vinyl chloride, and other chlorinated compounds from wastewater.34 Batch
2-28
-------
steam stripping appears to be more common at hazardous waste facilities
because it is adaptable to different types of wastes that may be received
in batches.35 For any given waste type, pilot-scale evaluations or trials
in the full-scale process may be required to optimize the operating
conditions for maximum removal at the lowest cost.
Removal efficiencies on the order of 95 to 100 percent are 'achievable
for volatile compounds such as benzene, toluene, and one- or two-carbon
chlorinated compounds.36,37 Batch operations usually provide a single
equilibrium stage of separation, and the removal efficiency is determined
essentially by the equilibrium coefficient and the fraction of the waste
distilled. The efficiency of a continuous system is related to the
equilibrium coefficient and the number of equilibrium stages, which is
determined primarily by the number of trays or height of packing. The
organic removal efficiency also is affected by the steam input rate, column
temperatures, and, in some cases, the pH. Temperature affects the solubil-
ity and partition coefficient of the volatile compound. The liquid pH also
may affect the solubility and treatability of specific compounds, such as
phenol. In principle, the removal efficiency in a multistage system can be
designed to achieve almost any level. In practice, removal efficiencies
are determined by practical limits in the column design (such as maximum
column height or pressure drop) and cost. Consequently, steam stripping is
difficult to characterize in terms of maximum achievable performance with
respect to organic concentration in the treated waste.
2.2.2 Solvent Extraction38,39
Solvent extraction (in terms of waste treatment) is a process whereby
a substance dissolved in or adsorbed by a waste is transferred from the
waste to a solvent that preferentially dissolves that substance. When the
waste to be treated is a liquid, the process may be called liquid-liquid
extraction. The substance transferred is the solute; the treated effluent
is referred to as the raffinate; and the solute-rich solvent phase is
called the extract. For the process to be effective, the extracting
solvent must be immiscible in the liquid and differ in density so that
gravity separation is possible and there is minimal contamination of the
raffinate with solvent. Solvents typically used include benzene, toluene,
chloroform, methylene chloride, isopropyl ether, and butylacetate.
2-29
-------
Solvent extraction can be performed as a batch process or by the
contact of the solvent with the feed in staged or continuous contact equip-
ment. There are two main classes of solvent extraction equipment—tanks in
which mechanical agitation is provided for mixing of the two phases and
tanks in which the mixing is done by the flow of the fluids themselves
(e.g., a spray tower, packed tower, or sieve plate tower). Liquid-liquid
extraction results in two streams, the raffinate and the extract, which
usually require further treatment. If aqueous, the raffinate may be
contaminated with small quantities of both the solute and the solvent.
These may have to be removed by carbon adsorption. Solvent is typically
recovered from the extract by use of one of the distillation processes
described in this chapter, leaving a concentrated solute-solvent waste
stream for recycle, reuse, incineration, or disposal. Distillation proc-
esses have potential organic emissions from condenser vents, accumulator
tank vents, and storage tank vents. A schematic diagram of a solvent
extraction system is illustrated in Figure 2-5.
The solvent extraction process is most suitable for the pretreatment
of aqueous waste streams with high levels of organic constituents. It is a
proven method for removing phenol, acetic acid, salicylic (and other
hydroxy aromatic) acids, and petroleum oils from aqueous solutions.
Solvent extraction is used to remove organic contaminants from aqueous
wastes in several industries including petroleum refining, organic chemi-
cals manufacturing, pulp and paper, and iron and steel. Solvent extraction
is a limited technology in that it is almost always necessary to further
treat the raffinate and/or the extract. Other limitations include the
difficulty in finding a suitable solvent low in cost, high in extraction
efficiency, and easily separable from the extracted substance. Though not
as popular as distillation or stripping due to its higher cost, solvent
extraction is widely used to recover valuable solvents. Typical removal
efficiencies of solvent extraction range from 80 percent to close to 100
percent.
2.2.3 Air Stripping
Air stripping is a process that uses forced air to remove volatile
compounds from a less volatile liquid. The contact between air and liquid
2-30
-------
Solvent
Storage
Tank
Waate Out
-ft
Solvent Feed
IX)
I
GO
Solvent
Exkactor
(Ralflnale)
Vapors
Column
Feed
Condenser
n
Distillate
Receiver
Overhead \
product
Separation
Device
Heat-
Watte In
Impure
Extract
Pump
Bottom* Product
(return to solvent
•torago tank)
Storage
K
Tank
"Recycle, fuel
Figure 2-5. Schematic diagram of solvent extraction system.
-------
can be accomplished in spray towers, mechanical or diffused-air aeration
systems, multiple tray columns, and packed towers.40,41 -fne focus of this
section is on packed tower air strippers because packed tower aeration is
the most common air stripper design (the other systems are not as effi-
cient) and with this design the vapor-laden air can be sent to a control
device for ultimate control of organic air emissions. In packed towers,
the liquid to be treated is sprayed into the top of a packed column and
flows down the column by gravity. Air is injected at the bottom of the
column and rises countercurrent to the liquid flow. The air becomes
progressively richer in organics as it rises through the column and can be
sent to a control device to remove or destroy organics in the airstream.
See Figure 2-6 for a schematic of a typical air stripping system with gas-
phase organic emission control.
The principle of operation is the equilibrium differential between the
concentration of the organics in the waste and the air with which it is in
contact. Consequently, compounds that are very volatile are the most
easily stripped. The packing in the column promotes contact between the
air and liquid and enhances the mass transfer of organics to the air. The
residues from air stripping include the organic-laden air and the water
effluent from the air stripper. This effluent will contain very low levels
of the most volatile organic compounds; however, semivolatile compounds
that are not easily air-stripped may still be present. The process does
not offer a significant potential for recovery and reuse of organics.
Condensers generally are not used to recover the stripped organics because
of the large energy requirements to cool the large quantity of noncondens-
ibles (primarily air) and to condense the relatively low vapor-phase
quantities of organic compounds.
Air stripping has been used primarily on dilute aqueous waste streams
with organic concentrations that range from a few parts per billion to
hundreds of parts per million. The feed stream should be relatively free
of solids to avoid fouling in the column; consequently, some form of solids
removal may be required for certain aqueous hazardous wastes. In addition,
dissolved metals that may be oxidized to an insoluble form should be
removed. Equipment may be designed and operated to air-strip organics from
2-32
-------
ro
i
CO
CO
Waste
In
Overhead Vapors
Feed
Storage
and
Feed Tank
Pump
Effluent
Air
Stripper
Air
Control Device
T
Vented Air
Control Device Residue
(e.g., spent carbon)
Figure 2-6. Schematic diagram of an air stripping system.
-------
sludges and solids in a batch operation; however, this application has not
been demonstrated extensively and is not a common practice. The major
industrial application of air stripping has been in the removal of ammonia
from wastewater.4? jn recent years, the use of air strippers has become a
widely used technology in the removal of volatile compounds from contami-
nated ground water.43,44
Packed towers can achieve up to 99.9 percent removal of volatiles from
water.45 The major factors affecting removal efficiency include the
equilibrium between the organics and the vapor phase (usually measured by
Henry's law constant for dilute aqueous wastes) and the system's design,
which determines mass transfer rates. Removal efficiency increases as the
equilibrium coefficient increases; consequently, the extent of removal is
strongly affected by the type of waste and the volatility of the individual
organic constituents. Mass transfer rates (and removal efficiency) are
also a function of the air-to-water ratio, height of packing, and type of
packing.46 The operating temperature is also an important variable that
affects efficiency because of its direct effect on the vapor/liquid
equilibrium. Higher temperatures result in higher vapor-phase concentra-
tions of organic and higher removal rates. Air strippers have operational
difficulties in freezing weather that may require heating the input waste
stream, heating and insulating the column, or housing the operation inside
an enclosure. Air strippers are typically designed to remove key or major
constituents. Compounds more volatile than the design constituent are
removed at or above the design efficiency, and less volatile compounds are
removed at a lower efficiency.
2.3 AIR EMISSION SOURCES
2.3.1 Process Vent Emissions from Distillation/Steam Stripping Units
The discussions on distillation column and steam stripping operating
theory and design show the basic factors of column operation. Vapors
separated from the liquid phase in a column (by direct application of heat
[i.e., steam stripping] or by indirect heating [e.g., batch distillation or
thin-film evaporation]) rise out of the column to a condenser. The gases
and vapors entering the condenser can contain organics, water vapor, and
2-34
-------
noncondensibles such as oxygen (02), nitrogen (1^2), and carbon dioxide
(C02). The vapors and gases originate from vaporization of liquid feeds,
dissolved gases in liquid feeds, inert carrier gases added to assist in
distillation (only for inert carrier distillation), and air leaking into
the column, especially in vacuum distillation. Most of the gases and
vapors entering the condenser are cooled enough to be collected as a liquid
phase. The noncondensibles (02, N2, C02, and other organics with low
boiling points), if present, are not usually cooled to the condensation
temperature and are present as a gas stream at.the end of the condenser.
Portions of this gas stream are often recovered in devices such as
scrubbers, adsorbers, and secondary condensers. Vacuum-generating devices
(pumps and ejectors), when used, might also affect the amount of noncon-
densibles. Some organics can be absorbed by condensed steam in condensers
located after vacuum jets. In the case of oil-sealed vacuum pumps, the oil
losses increase the organic content of the noncondensibles exiting the
vacuum pump. The noncondensibles from the last process equipment (condens-
ers, pumps, ejectors, scrubbers, adsorbers, etc.) constitute the emissions
from the distillation unit unless they are controlled by combustion devices
such as incinerators, flares, and boilers.
The most frequently encountered emission points from distillation and
steam stripping operations are condensers, accumulators, hot wells, steam
jet ejectors, vacuum pumps, and pressure relief valves. These emission
points are illustrated for several types of units in Figures 2-7 through
2-10. Emissions of organics are created by the venting of noncondensible
gases that concurrently carry out some hydrocarbons.
The total volume of gases emitted from a distillation or steam
stripping operation varies from unit to unit and depends upon air leaks
into the vacuum column (reduced pressure increases leaks and increased size
increases leaks), the volume of inert carrier gas used, gases dissolved in
the feed, efficiency and operating conditions of the condenser and other
process recovery equipment, and physical properties of the organic constit-
uents. Knowledge of the quantity of dissolved gases in the column in
conjunction with information on organic vapor physical properties and
condenser operating parameters allows estimation of the organic emissions
that may result from a given distillation unit operation.
2-35
-------
Vapor phase
Process
vent*
Cooling
water
Primary
condenser
Liquid reflux
Distillation
column
Accumulator
Pressure relief
valve*
Overhead product
'Potential emission point
Figure 2-7. Potential emission points for a nonvacuum
distillation column.
2-36
-------
Steam
Vapor Phase
Cooling
Water
Primary
Condenser
Ejector
Process
Vent or
Pressure
Relief
alve*
Accumulator
Liquid Reflux
Overhead Product
Cooling
Water
Barometric^
Condenser
Distillation
Column
Steam
1
tricj I
'T
Ejector
Process
Vent*
Hotwell
'Potential emission point
Figure 2-8. Potential emission points for a vacuum distillation column using steam jet
ejectors with barometric condenser.
-------
Steam
CO
00
I
s^
Vapor Phase
i
>
^\
(
Distillation
Column
,
!
_J
\ t Ejector
Cooling 1
^^s Water
^\ Cooling
^J Primary JLx" Water
Condenser /^ Secondary
\^^J Condenser
Process
r Vent*
) Accumulator ' T
f
(
j Accumulator
Overhead Product ... . _
Waste Stream
\ i
'Potential emission point
Figure 2-9. Potential emission points for a vacuum distillation column
using a steam jet ejector and surface condensers.
-------
Vapor Phase
Cooling
Water
Primary
Condenser
d_D
Accumulator
Process
Vent*
Vacuum Pump
Liquid Reflux
Overhead Product
Distillation
Column
"Potential emission point
Figure 2-10. Potential emission points for a vacuum distillation column
using a vacuum pump.
2-39
-------
The operating parameters for distillation-type units tend to be unit-
specific and vary to such a great extent from unit to unit that it is
difficult to develop precise emission factors for distillation and steam
stripping operations that can be applied industry-wide. However, extensive
data bases have been gathered for both the organic chemical industry
distillation units and the hazardous waste treatment, storage, disposal,
and recycling industry management units, which includes distillation and
stripping units. The chemical manufacturing industry data base4? contains
information on operating characteristics, emission controls, process vent
flows, and emission characteristics. The data base was developed from
extensive data for organic chemical plants available from surveys performed
for EPA.48.49 This data base provides some insight into the types of
distillation operations in use in the organic chemical manufacturing
industry. Table 2-3 gives the total number and types of distillation units
in the survey.
The data base contains information on the type of distillation
involved, the product recovery and emission control equipment, the vent
stream characteristics, and the other distillation units in the plant. The
vent stream characteristics listed for each column in the data base (deter-
mined downstream of product recovery devices, but upstream of combustion
devices) include:
• Volumetric flow rate
• Heat content
• VOC emission rate
• VOC concentration.
Complete information on vent stream characteristics was not available
for some of the reported distillation units. Also, there were units with
zero flow rate (because no noncondensible gases were vented to the
atmosphere) and units for which offgases were recycled to the manufacturing
process. However, only those distillation columns for which complete vent
stream characterization was available for all columns in a plant were
retained in the screened data base. Table 2-4 gives an overview of the
screened data base.
2-40
-------
TABLE 2-3. OVERVIEW OF DISTILLATION UNITS IN THE CHEMICAL
MANUFACTURING INDUSTRY
Number of units Percentage of total
1. Operating pressure
a. Vacuum
b. Nonvacuum
c. Information not available3
318
582
137
1,037
«* *
31
56
13
100
2. Mode of operation
a. Batch 4 <1
b. Continuous 1,033 >99
i f \J*J / AV/W
3. Type of unit
a. Flash 37 3
b. Fractionating 1,000 _iZ
1,037 100
4. Units with no flow rate from the 231 22
process vent
5. Units with process vent emissions 219 21
recycled
aFor 13 percent of the 1,037 total units, operating pressure information is
not given because it is claimed to be confidential.
Source: U.S. Environmental Protection Agency. Distillation Operations in
Synthetic Organic Chemical Manufacturing—Background Information
for Proposed Standards. Appendix C. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. Publication No. EPA-450/3-83-005a.
December 1983.
2-41
-------
TABLE 2-4. OVERVIEW OF DISTILLATION UNIT OPERATIONS
Screened Units
Total number of units in survey
Units at plants with incomplete data available
Units with recycled emissions, or zero flow rate
Number of units in the screened
data base
1,037
392
450
195
2. Operating Characteristics of Units in the Screened Data Base
Offgas flow rate,
VOC emission rate
kg/h (Ib/h)
VOC emission rate
kg/h (Ib/h)
m^/min (scfm)
precontrolled,3
control led,b
Average
1.0 (36)
36 (78)
5.9 (13)
Range
0.001-18
(0.005-637)
0-1670
(0-3668)
VOC = Volatile organic compounds.
Calculated downstream of product recovery devices (i.e., adsorbers,
absorbers, and condensers), but upstream of combustion devices.
bControlled VOC emission rates were estimated using a 98-percent destruc-
tion efficiency for flares, boilers, and incinerators (where it was
indicated that control devices were being used).
Source: U.S. Environmental Protection Agency. Distillation Operations in
Synthetic Organic Chemical Manufacturing—Background Information
for Proposed Standards. Appendix C. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. Publication No. EPA-450/3-83-005a.
December 1983.
2-42
-------
With regard to distillation and stripping units processing wastes,
limited information is available on process vent operating characteristics.
However, EPA is completing a multiyear project to collect information on
the Nation's generation of hazardous wastes and the capacity available to
treat, store, dispose, and recycle (TSDR) that waste (i.e., the 1987
National TSDR Survey). The TSDR data base50 contains up-to-date nationwide
information on the hazardous waste management technologies each facility
has onsite, including the number of hazardous waste management units by
process type (e.g., number of batch distillation, fractionation, thin-film
evaporation, steam stripping, and air stripping units), annual waste
throughput by process units, and type of air pollution control device
serving the unit. The TSDR data base does not contain information on the
process vent stream characteristics such as volumetric flow, temperature,
and organic concentration. Because of the lack of adequate process vent
stream data, estimation of organic air emissions by process unit type,
e.g., fractionation as opposed to thin-film evaporation, is not possible.
The preliminary results of the TSDR Survey data base have been
screened to identify the number of waste management units at TSDF that are
likely to have associated process vents. Table 2-5 presents these prelimi-
nary results.
2.3.2 Process Vent Emissions from Air Stripper Units
As previously discussed in Section 2.2, air stripping is a technology
that transfers organic contaminants from water (i.e., wastewater or, in
some cases, ground water) to air. Unless the contaminated airstream is
routed to an air emissions control device, the organic compounds volatil-
ized from the water become air emissions. There are four major factors
that affect air emissions from air strippers: (1) the pollutant loading to
the air stripper, (2) the removal efficiency obtained by the air stripper,
(3) the changes in the pollutant loading with time, and (4) the annual
period of operation. Each of these factors is discussed below.
The single most important factor affecting organic emissions from an
air stripper is the pollutant loading. Air strippers generally achieve
high removal efficiencies, e.g., greater than 90 percent. Therefore, the
majority of pollutant quantities contained in the influent water to the air
stripper are transferred to the air. The pollutant loading is a function
2-43
-------
TABLE 2-5. DISTILLATION, SEPARATION, AND STRIPPING UNITS AT TSDF
Type of unit
Fraction at ion
Batch distillation
Solvent extraction
Thin-film evaporation
Air stripping
Steam stripping
Total
Number of units
125
370
42
77
52
40
706
Percentage of total
18
52
6
11
7
6
100
Note: The total number of units shown includes both RCRA-regulated units
and RCRA-exempt units operating in 1986.
Source: 1987 National Survey of Hazardous Waste Treatment, Storage,
Disposal, and Recycling Facilities (TSDR Survey). Alpha
Database. July 1989.
2-44
-------
of two parameters, the pollutant concentration in the water and the flow
rate (of water) to the air stripper. The pollutants present and the load-
ings vary widely at actual air stripper locations. Pollutant loadings for
more than 50 air strippers were calculated from data collected on influent
water flow rates and pollutant concentrations for these strippers.51 These
calculated loadings are summarized in Table 2-6. As shown in this table,
total organic loadings for air strippers range from 1.7 kg/yr to 29.3
Mg/yr.
The air stripper removal efficiency can also affect air emissions.
The greater the removal efficiency, the higher the organic emissions.
However, the removal efficiencies reported for operating air strippers are
almost all above 90 percent; and over 50 percent of the reported effi-
ciencies are greater than 99 percent.52 This makes the effect of removal
efficiency on air emissions less significant. The removal efficiency can
be enhanced by increasing the air-to-water ratio or increasing the packing
height. Both of these parameters can be adjusted to achieve greater
removal efficiencies. Compounds removed at less than 90 percent efficiency
were observed to have higher water solubility and less volatility than the
compounds removed at greater than 90 percent. The compounds observed
having lower removal efficiency have lower Henry's law constants. The
Henry's law constant is the constant of proportionality for equilibrium
between low concentrations of a compound in water and air. As the Henry's
law constant increases, the ease of removal increases.
As discussed above, the major factor affecting emissions from air
strippers is the organic loading in the contaminated water being treated.
For wastewaters, both the organic loading and the flow rate would typically
remain fairly constant, especially for wastewater generated as part of a
continuous industrial process. However, organic loading does not usually
remain constant for ground water. The water flow rates to air strippers
generally remain constant, but ground water pollutant concentration typi-
cally varies with time. Variance in influent concentration at fairly con-
stant flow rate results in pollutant loading changes. Historical influent
pollutant concentrations for air strippers treating ground water show that
air emission rates generally decrease as a function of time. Generally,
the initial air emission rate decreases rapidly and then levels off for a
2-45
-------
TABLE 2-6. SUMMARY OF CALCULATED LOADINGS FOR AIR STRIPPERS
Influent
concentration,
Calculated loading,
Pollutant
Aniline
Benzene
Bromoform
Chloroform
CHBr2Cl
CHBrCl2
Chlorobenzene
Dichloroethylene
Diisopropylether
Ethyl benzene
Ethylene dichloride
Methylene chloride
Methyl ethyl ketone
2-Methylphenol
Methyl tertiary butyl ether
Perchloroethylene
Phenol
1,1,2, 2-Tetrachl oroethane
Trichloroethane
Trichloroethylene
1,2,3-Trichloropropane
Toluene
Xylene
Other volatile organic
compounds
No. of
occurences
1
3
1
3
1
1
1
7
2
3
8
2
1
1
2
19
1
1
9
35
1
4
5
3
/
Average
226
3,730
8
530
34
36
95
409
35
6,370
173
15
100
160
90
355
198
300
81
7,660
29,000
6,710
14,823
44,000
*g/L
Range
NA
200-10,000
NA
1,500
NA
NA
NA
2,3,000
20-50
100-1,400
5-1,000
9-20
NA
NA
50-130
3-4,700
NA
NA
5-300
1-200,000
NA
30-23,000
17-53,000
57-130,000
Average
15.1
4,200
137
590
584
618
6.3
365
71
2,350
360
2.8
190
11
93
370
74
2,000
225
2,360
1,940
719
2,450
838
kq/yr
Range
NA
382-11,400
NA
2.1-1,320
NA
NA
NA
0.6-1,720
8-134
7-5,720
1.3-1,600
2.6-2.9
NA
NA
53-134
4.1-1,710
NA
NA
1.7-800
2-28,600
NA
114-2,190
65-5,720
109-1,740
Total volatile organics
51
11,120 12-205,000 2,740
1.7-29,300
NA = Not applicable. Data available for only one stripper.
Source: U.S. Environmental Protection Agency. Air Stripping of Contaminated
Water Sources—Air Emissions and Controls. U.S. Environmental
Protection Agency. Research Triangle Park, NC. Publication No.
EPA-450/3-87-017. August 1987.
2-46
-------
period of time. After this period of leveling off, the ground-water
pollutant concentrations and resulting emissions are expected to drop
gradually.
The period of annual operation can affect the annual emissions from
air stripping. Cold temperatures in some parts of the Nation can cause
freezing problems that prevent year-round operation. However, this
situation is uncommon. Most of the operating strippers are operated year-
round, 24 hours per day, and incur very few operational problems. Gener-
ally, only normal preventive maintenance is required with special attention
given to bacterial buildup on the packing.
2.4 EMISSION ESTIMATES
2.4.1 Air Emissions from Distillation and Steam Stripping Units
As noted above, a condenser system is typically used to recover the
organic (and water) vapors present in the overheads stream from distillation
units (e.g., pot stills, fractionation units, thin-film evaporators, and
batch distillation units) and steam stripping units. The condensed over-
heads stream is fed to a decanter where the organic and water phases are
usually gravity-separated. Any noncondensible gases (e.g., highly volatile
organic compounds) not recovered by the condenser system make up the process
vent emissions from distillation and steam stripping units.
Review of recent emission test data gathered by EPA provided a number
of organic emission rates for condenser (process) vent emissions at waste
solvent treatment facilities (WSTF, a subset of TSDF).53 These process vent
emission rates are based on site-specific data for TSDF/WSTF utilizing some
form of distillation technology; operations tested included batch
distillation, steam stripping, and thin-film evaporation units. The vent
data consist of results of emission tests of vents on primary or secondary
condensers, condensers vented to distillate receiving tanks (i.e., accumu-
lator tanks or overheads receivers), or vacuum distillation vents; results
of the tests are presented in Appendix A.
Emission tests conducted by EPA show waste management unit process vent
flow rates ranging from 0.0014 to 3.1 L/s (0.003 to 6.6 cfm) and mass
organic emission rates ranging from 0.0015 to 34.8 Mg/yr (0.0017 to 38.4
2-47
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ton/yr) at hazardous waste management units involving distillation/separa-
tion operations. (See Appendix A.) The organic emission rates for primary
condensers, expressed in pounds/hour, varied from a few hundredths of a
pound to nearly 10 Ib/h; secondary condensers had emission rates of between
2 and 5 Ib/h. Because process vent emissions vary to such a great extent
from unit to unit, accurate emission factors for distillation and steam
stripping operations that can be applied to specific units in the waste
management industry are not presented. Emissions estimates for individual
units must be made on a case-by-case basis.
In addition, insufficient data and information were available to allow
characterization of other process vents such as those on accumulator tanks,
separator tanks, surge control tanks, or hot wells in service at TSDF/WSTF
process units. Emissions from these points in the process are not consid-
ered significant, unless the uncondensed overhead from the distillation
operation is vented at this point in the process. For example, the primary
condenser may be vented through an accumulator tank or a separator tank. A
bottoms receiver should contain the waste only after the more volatile
constituents have been removed; therefore, emissions from vents on these
tanks should be low relative to the process vents on the unit.
Table 2-4 presents the organic emission rates for process vents on
distillation operations at organic chemical manufacturing plants. These
distillation units are production related and tend to be much larger than
units treating wastes only. As a result, process vent flow rates and
emissions from production units are generally higher than those from waste
treatment units.
2.4.2 Air Emissions from Air Strippers
To characterize emissions from air strippers, data on pollutant
loadings, design, operation, and performance were collected from operating
air strippers nationwide.54 Although the completeness of data available for
individual air strippers varied, the data collected were sufficient to
characterize air pollutant loadings. The data collected on organic pollut-
ant loadings, design, operation, and performance for the air strippers are
presented in Appendix B.
The quality of the data collected varied widely. Concentration data
were from weekly or monthly inlet water sampling, pilot studies, and
2-48
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estimates used for design of the air strippers. A single concentration was
usually obtained for a contaminant although the inlet concentration
typically may vary with time. The water flow rates were either design
capacities or actual measured rates. The removal efficiency data were from
actual influent and effluent monitoring data in some cases and from esti-
mated design efficiency in others.
The water treated by air stripping contains various pollutants. By
far, the majority of sites reported being contaminated with chlorinated
ethanes or ethylenes. Of the sites for which loadings were presented, 34
were contaminated with trichloroethylene, 17 with perchloroethylene, 9 with
1,1,1-trichloroethane, 7 with dichloroethylene, and 8 with dichloroethane
contamination. The remaining sites were contaminated by toluene, xylenes,
benzene, and several chlorinated methanes, ethers, and aromatics.
The data collected from the facilities were used to estimate and
characterize uncontrolled organic air emissions from each air stripper.
Because contaminants are simply transferred from the influent water to air,
the air emissions were estimated by multiplying the influent loading by the
reported removal efficiency. Assuming 8,400 h/yr of air stripper operation,
annual emissions were calculated for each stripper by pollutant. The total
organic emissions were also calculated for each air stripper as the sum of
the individual pollutants.
The estimates of uncontrolled air emissions are summarized in Table
2-7. The averages and ranges of estimated annual emissions and concentra-
tions are presented by pollutant. As shown in Table 2-7, the average total
volatile org'anic emissions from air strippers is 2.0 Mg/yr. The range of
estimated total volatile organic emissions is 1.6 kg/yr to 24 Mg/yr. The
average concentration of total volatile organics in the effluent air is 7.8
parts per million by volume (ppmv). Effluent air concentrations of total
volatile organics range from 0.03 ppmv to 110 ppmv. Air flow rates from the
air strippers surveyed varied from a low of 170 cfm to a high of about
145,000 cfm; the average volumetric flow rate for these air strippers was
about 17,000 cfm. The estimated air emissions are also presented in
Appendix C together with the air flow rates and calculated pollutant
concentrations. The emission estimates presented in Appendix C do not
2-49
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TABLE 2-7. SUMMARY OF ESTIMATED AIR EMISSIONS FROM AIR STRIPPERS55
Pollutant
No. of
data
points Average
Concentration,
ppmv
Range Average
Annual emissions,
kg/yr
Range
Aniline
Benzene
Bromoform
Chloroform
CHBr2Cl
CHBrd2
Chlorobenzene
Dichloroethylene
Diisopropylether
Ethyl benzene
Ethylene dichloride
Methyl ene chloride
Methyl ethyl ketone
2-Methyl phenol
Methyl tertiary butyl ether
Perchloroethylene
Phenol
1 , 1 ,2,2-Tetrachloroethane
Trichloroethane
Trichloroethylene
1,2,3-Trichloropropane
Toluene
Xylene
Other volatile organic
compounds
1
3
1
2
1
1
0
7
2
1
73
1
1
1
2
15*>
1
1
8C
34d
1
2
4«
3*
ND
22
0.01
2.4
0.05
0.09
ND
2.3
0.04
22
1.8
0.01
ND
ND
0.11
0.49
ND
0.13
0.41
4.7
NA
1.3
8.2
0.2
ND
1-66
NA
0.16-4.7
NA
NA
ND
X). 01-15
0.02-0.06
NA
9.02-5.5
NA
ND
ND
0.06-0.16
X). 01-2.1
ND
NA
0.01-2.03
0.01-55.7
ND
0.12-2.6
0.06-22
NA
5.0
4,190
60
540
350
500
NO
400
66
5,710
410
2.6
190
2.1
90
360
9.8
1,900
250
1,440
1,920
250
1,790
820
NA
380-11,400
NA
440-635
NA
NA
ND
0.6-1,660
7.8-130
NA
6.1-1,590
NA
ND
NA
53-130
4.0-1,660
ND
NA
2.3-800
1.6-10,600
NA
110-380
62-5,710
110-1,700
Total volatile organics9
46n
7.8 0.03-110 2,020
1.6-24,000
ND = No data. Insufficient data available.
NA = Not applicable. Data available for only one stripper.
Sufficient data were available to calculate concentration for only 6 of the
7 data points.
^Sufficient data were available to calculate concentration for only 15 of
the 17 data points.
Sufficient data were available to calculate concentration for only 6 of the
8 data points.
Sufficient data were available to calculate concentration for only 29 of
the 34 data points.
Sufficient data were available to calculate concentration for only 3 of the
4 data points.
'Sufficient data were available to calculate concentration for only 2 of the
3 data points.
9Values presented for total volatile organics represent the averages and
ranges of values presented in Appendix B.
"Sufficient data were available to calculate concentration for only 37 of
the 46 data points.
Source: U.S. Environmental Protection Agency, Air Stripping of Contaminated
Water Sources—Air Emissions and Controls. Control Technology Center.
Research Triangle Park, NC. Publication No. EPA-450/3-87-017. August
1987. 125 p.
2-50
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account for air emission controls in place at some facilities. As is the
case for distillation and steam stripping operations, emission factors are
not presented for air strippers because of the variability in emissions
from unit to unit. Emission estimates for individual units should be made
on a case-by-case basis.
2.5 REFERENCES
1. Memorandum from Coy, David, RTI, to Docket. December 9, 1987.
Hazardous waste treatment, storage, and disposal facility (TSDF)
universe of waste constituents.
2. U.S. Environmental Protection Agency. Summary Report on RCRA Activi-
ties for May 1986. Office of Solid Waste. Washington, DC. June 16,
1986. p. 4.
3. U.S. Environmental Protection Agency. The Hazardous Waste System.
Office of Solid Waste and Emergency Response. Washington, DC. June
1987. p. 1-4.
4. Westat, Inc. National Survey of Hazardous Waste Generators and Treat-
ment, Storage and Disposal Facilities Regulated Under RCRA in 1981.
Prepared for the U.S. Environmental Protection Agency, Office of Solid
Waste. April 1984. p. 141.
5. Reference 4, p. 65.
6. Reference 4, p. 69.
7. 1987 National Survey of Hazardous Waste Treatment, Storage, Disposal,
and Recycling Facilities (TSDR Survey). Alpha Database. July 1989.
8. U.S. Environmental Protection Agency. Code of Federal Regulations.
Title 40, Part 260.10. Washington, DC. Office of the Federal
Register. July 1, 1988.
9. Memorandum from Maclntyre, Lisa, RTI, to Docket. November 4, 1987.
Data from the 1986 National Screening Survey of the Hazardous Waste
Treatment, Storage, Disposal and Recycling Facilities used to develop
the Industry Profile.
10. Memorandum from York, S., and Branscome, M., RTI, to Colyer, R.,
EPA:SDB, and Lucas, B., EPA:CPB. August 21, 1987. Review of State
regulations affecting process vents and equipment leaks at hazardous
waste treatment, storage, and disposal facilities (TSDF).
11. U.S. Environmental Protection Agency. Subtitle D Study Phase I
Report. Office of Solid Waste and Emergency Response. Washington,
DC. Publication No. EPA 530-SW-86-054. October 1986.
2-51
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12. Science Applications International Corporation. Summary of Data on
Industrial Nonhazardous Waste Disposal Practices. Prepared for U.S.
Environmental Protection Agency. Washington, DC. Contract No.
68-01-7050. 1985.
13. Abt Associates, Inc. National Small Quantity Hazardous Waste
Generator Survey. Prepared for U.S. Environmental Protection Agency,
Office of Solid Waste and Emergency Response. Washington, DC.
Contract No. 68-01-6892. 1985.
14. Reference 7.
15. U.S. EPA, Office of Air Quality Planning and Standards. Hazardous
Waste Treatment, Storage, and Disposal Facilities—Background
Information for Promulgated Organic Emission Standards for Process
Vents and Equipment Leaks. Research Triangle Park, NC. Publication
No. EPA-450/3-89-009. June 1990.
16. Van Winkle, M. Distillation. New York, McGraw-Hill. 1967.
17. King, C. J. Separation Processes. New York, McGraw-Hill. 1971.
18. Foust, A. S., et al. Principles of Unit Operations. New York, John
Wiley & Sons. 1960.
19. Treybal, R. E. Mass Transfer Operations, 2nd edition. New York,
McGraw-Hill. 1968.
20. Exner, J. H. Detoxification of Hazardous Waste. Ann Arbor, MI, Ann
Arbor Science. 1980. p. 3-25.
21. Metcalf and Eddy, Inc. Briefing: Technologies Applicable to
Hazardous Waste. Prepared for U.S. Environmental Protection Agency.
Cincinnati, OH. May 1985. Section 2.9.
22. Allen, C. C., et al. (Research Triangle Institute). Field Evaluations
of Hazardous Waste Pretreatment as an Air Pollution Control Technique.
Prepared for U.S. EPA/ORD/HWERL. Cincinnati, OH. Contract No. 68-03-
3253. March 31, 1987. p. 23.
23. Luwa Corporation. Product Literature—Luwa Thin-Film Evaporation
Technology. P.O. Box 16348, Charlotte, NC 28216.
24. U.S. EPA/ORD/IERL. Process Design Manual for Stripping of Organics.
Cincinnati, OH. Publication No. EPA-600/2-84-139. August 1984.
25. Schweitzer, P. A. Handbook of Separation Techniques for Chemical
Engineers. New York, McGraw-Hill Book Co. 1979. p. 1-147 through
1-178.
26. Perry, R. H. (ed.). Chemical Engineer's Handbook. 5th Ed. New York,
McGraw-Hill Book Co. 1973. p. 13-1 through 13-60.
2-52
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27. King, C. J. Separation Processes. New York, McGraw-Hill Book Co.
1971. 809 p.
28. Treybal, R. E. Mass-Transfer Operations. New York, McGraw-Hill Book
Co. 1968. p. 220-406.
29. Berkowitz, J. B., et al. Unit Operations for Treatment of Hazardous
Industrial Wastes. Noyes Data Corporation, Park Ridge, NJ. 1978.
p. 369-405, 849-896.
30. U.S. EPA/ORD/HWERL. Preliminary Assessment of Hazardous Waste
Pretreatment as an Air Pollution Control Technique. Publication No.
EPA-600/2-86-028, NTIS PB46-17209/A6. March 1986.
31. Reference 20, p. 1-39.
32. Reference 21, Sections 2.9, 2.15, 2.16.
33. Reference 30, p. 45.
34. Reference 30, p. 43.
35. Reference 22, p. 63.
36. Reference 24.
37. Hwang, S. T., and P. Fahrenthold. Treatability of Organic Priority
Pollutants by Steam Stripping. AIChE Symposium Series 197, Volume 76.
1980. p. 37 through 60.
38. ICF Consulting Associates, Incorporated. Guide to Solvent Waste
Reduction Alternatives. 707 Wilshire Blvd., Los Angeles, CA 90017.
October 10, 1986. p. 5-27, 5-28.
39. Reference 21, Section 2.17.
40. Reference 32, Section 2.16.
41. Hazardous Waste Engineering Research Laboratory, Office of Research
and Development. Air Strippers and Their Emissions Control at
Superfund Sites. U.S. Environmental Protection Agency. Cincinnati,
OH. Publication No. EPA-600/D-88-153. August 1988.
42. Reference 29, Section 2.16.
43. Reference 32, p. 869.
44. U.S. Environmental Protection Agency. Air Stripping of Contaminated
Water Sources—Air Emissions and Controls. Control Technology Center.
Research Triangle Park, NC. Publication No. EPA-450/3-87-017. August
1987. 125 p.
45. Reference 29, Section 2.16.
2-53
-------
46. Reference 29, p. 869-880.
47. U.S. Environmental Protection Agency. Distillation Operations in
Synthetic Organic Chemical Manufacturing—Background Information for
Proposed Standards. Appendix C. U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards. Research
Triangle Park, NC. EPA Publication No. EPA-450/3-83-005a. December
1983.
48. Houdry Division, Air Products and Chemicals, Inc. Survey Reports on
Atmospheric Emissions from the Petrochemical Industry. Prepared for
U.S. Environmental Protection Agency. Research Triangle Park, NC.
Data on file in Docket No. A-80-25. 1972.
49. Trip Reports. Hydroscience, Inc. EPA Contract No. 68-02-2577.
Docket No. A-80-25, Subcategory II-B. 1977-1980.
50. Reference 7.
51. Reference 38, p. 3-19.
52. Reference 44, p. 3-20.
53. Memorandum, Zerbonia, R., RTI, to Colyer, R., EPA/SDB, and Lucas, R.,
EPA/CPB. October 19, 1987. Evaluation and development of emission
factors for (TSDF process) vents. (RCRA Docket Item: F-90-AESF-
S0021.)
54. Reference 44, p. 3-17.
55. Reference 54.
2-54
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3.0 EMISSION CONTROL TECHNIQUES
This chapter discusses organic emission control techniques applicable
to waste management unit process vent streams. These control techniques
are grouped into two broad categories: vapor recovery (noncombustion)
control devices and vapor combustion control devices.
Design and operating efficiencies of this emission control equipment
are also discussed in this chapter. Basic design considerations for
condensers, absorbers, adsorbers, flares, industrial boilers, process
heaters, thermal oxidizers, and catalytic oxidizers are explained briefly.
The conditions affecting the organic removal efficiency of each type of
device are examined, and its applicability to process vents is evaluated.
Performance monitoring practices for these control devices are also
addressed.
3.1 VAPOR RECOVERY CONTROL DEVICES
This section describes three noncombustion control processes that
involve recovery of the captured organics—adsorption, absorption, and
condensation. The organic removal efficiency and applicability of each
device to process vent streams is also discussed.
Vapor recovery control devices are generally applied to recover
organics from a vent stream for use as a product or to recycle a compound
to the feed stream. The chemical structure of the organic removed is
usually unaltered. Although vapor recovery control devices are widely
applied in industry, they are not universally applicable to all process
vent streams. The conditions under which these systems are and are not
applicable are identified in the following sections.
3-1
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3.1.1 Adsorption
3.1.1.1 Control Description. Adsorption is a mass transfer operation
involving interaction between gaseous and solid-phase components. The gas-
phase (adsorbate) surface is captured on the solid-phase (adsorbent)
surface by physical or chemical adsorption mechanisms. The most commonly
encountered industrial adsorption systems use activated carbon as the
adsorbent. Activated carbon is effective in capturing certain organic
vapors by the physical adsorption mechanism. However, activated carbon has
a finite adsorption capacity. When the carbon becomes saturated (i.e., all
of the carbon surface is covered with organic material), there is no
further organic removal; all vapors pass through the carbon bed. At this
point (referred to as "breakthrough"), the organic compounds must be
removed from the carbon before adsorption can resume. This process is
called desorption or regeneration.
The two basic configurations for carbon adsorption systems are regen-
erative and nonregenerative systems. Regenerative systems can be
categorized as fixed, moving, or fluidized. The most common adsorption
system for controlling air pollutants is the fixed carbon bed. Fixed-bed
carbon adsorbers are used for controlling continuous, organic gas streams
with flow rates ranging from 30 to 3,000 m3/min (1,000 to over 100,000
ft^/min). The organic concentration can be as low as several parts per
billion by volume (ppbv) or as high as 25 percent of the lower explosive
limit of the vapor stream constituents. Fixed-bed carbon adsorbers may be
operated in either intermittent or continuous modes. For intermittent
operation, the adsorber removes organics only during a specific time
period. Intermittent mode of operation allows a single carbon bed to be
used because it can be regenerated during the off-line periods. For
continuous operation, the unit is equipped with two or more carbon beds so
that at least one bed is always available for adsorption while other beds
are being regenerated. A schematic diagram of a typical fixed-bed,
regenerative carbon adsorption system is given in Figure 3-1.1 yne process
vent gases are filtered and cooled before entering the carbon bed. The
inlet gases to an adsorption unit are filtered to prevent bed contamina-
tion. The gases are cooled to maintain the bed at optimum operating
3-2
-------
CO
CO
Flllar Blow*
Haal Exchangar
(optional)
f
Amblant
Air Inlaka
lor Cooling/Drying
OH
Flllar Blower
Slaam.
Exhaust
Venl
Carbon
Abaorbar
Carbon
Abaorbar
Aquaoua Phaaa to
DUposal or
Traatmant
Oacantar
Condanaar
Organic Phaaa to Hacowary
Figure 3.1. Two-stage regenerative adsorption system process flow diagram.
-------
temperature and to prevent fires or polymerization of the hydrocarbons.
Vapors entering the adsorber stage of the system are passed through the
porous activated carbon bed.
Adsorption of inlet vapors occurs in the bed until the activated
carbon is saturated with organics. The dynamics of the process may be
illustrated by viewing the carbon bed as a series of three layers or mass
transfer zones (MTZ). Gases entering the bed are highly adsorbed first in
the upper zone. Because most of the organic is adsorbed in the upper zone,
very little adsorption takes place in the middle and lower zones.
Adsorption in the middle zone increases as the upper zone becomes saturated
with organics and proceeds through the lower zone. When the bed is
completely saturated (breakthrough), the incoming organic-laden vent gases
are routed to an alternate bed while the saturated carbon bed is
regenerated. Typically, the duration of the adsorption cycle varies
considerably depending on the solvent being reclaimed and its regeneration
characteristics.
Regeneration of the carbon bed is accomplished by heating the bed or
applying vacuum to draw off the adsorbed gases. Low-pressure steam is
frequently used as a heat source to strip the adsorbent of organic vapor.
The steam-laden vapors from regeneration are then sent to a condenser, and
the condensate typically is sent on to some type of solvent recovery
system. The regenerated bed is put back into active service while the
saturated bed is purged of organics. (Note; Organic emissions resulting
from regeneration should also be controlled and accounted for in the
efficiency determination of the overall system.) The regeneration process
may be repeated many times, but eventually the carbon must be replaced.
The life span of activated carbon depends on the nature of the
pollutants being controlled. For clean organics, a carbon life of 10 to 20
years can be expected; for a stream containing trace amounts of high-
boiling-point materials, 5 to 10 years is reasonable; but the presence of
polymerized organics may require carbon reactivation every 1 to 3 years.2
Nonregenerative systems (e.g., carbon canisters) are applicable for
controlling organic emissions that are expected to vary in types of
organics and concentrations and to occur at relatively low total mass
rates. Nonregenerated systems are carbon canisters typically consisting of
3-4
-------
a 0.21-m3 (55-gal) drum with inlet and outlet pipe fittings. Use of carbon
canisters is limited to controlling low-volume gas streams with flow rates
less than 3 m3/min (100 ft3/min). Carbon cannot be regenerated directly in
the canister. Once the activated carbon in the canister becomes saturated
by the organic vapors, the carbon canister must be removed and replaced
with a fresh carbon canister. The spent carbon canister is then recycled
or discarded depending on site-specific factors.
The design of a carbon adsorption system depends on the chemical
characteristics of the organic compound being recovered (the adsorbate),
the physical properties of the vent gas stream (temperature, pressure,
humidity, and volumetric flow rate), and the physical properties of the
adsorbent. The adsorbent concentration and type are key factors in the
design of a carbon adsorption system. The adsorption characteristics of
each compound are assessed based on their physical properties data, for
example, polarity, refractive index, boiling point, molecular weight, and
solubility in water. Nonpolar compounds and compounds with high refractive
indices tend to be adsorbed more readily3 than polar compounds such as
water. High vapor pressure/low boiling point adsorbates and low molecular
weight compounds adsorb less readily.4 Compounds with molecular weights
greater than 142 adsorb readily but are difficult to desorb.5
If the adsorbate is water-soluble, water left as condensate in the bed
after steaming and cooling can contain adsorbate.6 When the adsorber is
brought on-line, the water and adsorbate will evaporate from the bed during
the first part of the adsorption cycle, slightly increasing the initial
outlet concentration for a brief time.
The temperature of the vent gas also influences the design of a carbon
adsorption system. The capacity of an adsorbent decreases as system
temperature increases. Carbon bed operating temperature can also affect
carbon adsorber performance. Excessive bed temperatures can result from
the release of heat from exothermic chemical reactions that may occur in
the carbon bed. Typical heat generation is 465 to 700 kilojoules (kJ) per
kg (200 to 300 British thermal units [Btu] per Ib) of organic adsorbed.
Ketones and aldehydes are especially reactive compounds that exothermically
polymerize in the carbon bed. If temperatures rise too high, spontaneous
3-5
-------
combustion will result in carbon bed fires. To avoid this problem, carbon
adsorbers applied to gas streams containing these types of compounds must
be carefully designed and operated to allow sufficient airflow through the
bed to remove excess heat.
High humidity will decrease capacity. Above an organic concentration
of 1,000 ppm, high moisture does not significantly affect performance.
Thus, obtaining good adsorber performance for gas streams with a high
relative humidity (i.e., >50 percent) and low organic concentration (i.e.,
<1,000 ppm) requires preconditioning the gas stream upstream of the carbon
bed. In addition to humidity, contaminants such as particulate, entrained
liquid droplets, and organic compounds with high boiling points can also
reduce adsorber efficiency.
Adsorption capacity increases with an increase in the partial pressure
of the vapor, which is proportional to the total pressure of the system.
Residence time in the bed is a function of gas velocity. Capture effi-
ciency, the percentage of organics removed from the inlet gas stream by the
adsorbent, is directly related to residence time. Gas velocity can be
determined for a given volume of contaminant gas as a function of the
diameter of the adsorber.
The physical properties of the adsorbent affect the adsorption
capacity, rate, and pressure drop across the adsorber bed. The more
important physical properties of the adsorbent that promote effective
adsorption include a large surface-to-volume area and a preferential
attraction for the compound being adsorbed.
Providing a sufficient bed depth is very important in achieving effi-
cient organic removal. If the adsorber bed depth is shorter than the
required MTZ, breakthrough will occur immediately, thus rendering the
system ineffective. Actual bed depths are usually many times the MTZ to
allow for adequate cycle times.
3.1.1.2 Performance Monitoring. The purpose of performance monitor-
ing is to ensure that the carbon adsorption system is being operated
properly and maintained within design specifications. To ensure that the
carbon adsorption system is operated within design specifications, the
owner or operator should:
3-6
-------
1. Install a flow indicator that provides a record of vent stream
flow to the control device. The flow indicator sensor should be
installed in the vent stream as near as possible to the control
device inlet but before being combined with other vent streams.
2. For carbon adsorption systems, such as fixed-bed carbon adsorb-
ers, that regenerate the carbon bed directly in the control
device, install a monitoring device to measure the concentration
level of the organic compounds in the exhaust vent stream from
the carbon bed or install a monitoring device to measure a
parameter that demonstrates the carbon bed is regenerated at a
predetermined time cycle.
3. For a carbon adsorption system, such as a fixed-bed carbon
adsorber, that regenerates the carbon bed directly onsite in the
control device, replace the existing carbon in the control device
with fresh carbon at a regular, predetermined time interval that
is no longer than the carbon service life.
4. For a carbon adsorption system, such as a carbon canister, that
does not regenerate the carbon bed directly onsite in the control
device, replace the existing carbon in the control device with
fresh carbon regularly by using one of the following procedures:
• Monitor the concentration level of the organic compounds in
the exhaust vent stream from the carbon adsorption system on
a regular schedule and replace the existing carbon with
fresh carbon immediately when carbon breakthrough is
indicated. The monitoring frequency should be at an
interval no greater than 10 percent of the time required to
consume the total carbon working capacity.
• Replace the existing carbon with fresh carbon at a regular,
predetermined time interval that is less than the design
service life of the carbon.
The amount of organic recovered from the regenerated bed as a function of
cycle time provides a secondary indicator of system efficiency and can be
monitored.
Also, the carbon bed temperature (after regeneration and completion of
any cooling cycles) and the amount of steam used to regenerate the bed have
been identified as indicators of product recovery efficiency for regenera-
tive systems. Temperature monitors and steam flowmeters, which indicate
the quantity of steam used over a period of time, are available.'
3.1.1.3 Control Effectiveness. The organic removal efficiency of an
adsorption unit depends upon the physical properties of the compounds
present in the offgas, the gas stream characteristics, and the physical
properties of the adsorbent.8
3-7
-------
Gas temperature, pressure, and velocity are important in determining
adsorption unit efficiency. The adsorption rate in the bed decreases
sharply when gas temperatures are above 38 °C (100 °F).9,10 High tempera-
ture increases the kinetic energy of the gas molecules, preventing the
organics from being retained on the surface of the carbon. Increasing
stream pressure generally will improve organic capture efficiency; however,
care must be taken to prevent solvent condensation and possible fire. The
gas velocity entering the carbon bed must be quite low to allow time for
adsorption to take place. The required depth of the bed for a given
compound is directly proportional to the carbon granule size and porosity
and to the gas stream velocity (bed depth must increase as the gas velocity
increases for a given carbon type).
Emission source test data for full-sized, fixed-bed carbon adsorbers
operating in industrial applications have been compiled by EPA for a study
of carbon adsorber performance. The analysis of these data supports the
conclusion that for well-designed and -operated carbon adsorbers, continu-
ous organic removal efficiencies of at least 95 percent are achievable over
long periods. Several units have been shown to achieve organic removal
efficiencies of 97 to 99 percent continuously.H An equivalent level of
performance is indicated by results of emission source tests conducted on
carbon canisters.
3.1.1.4 Applicability of Adsorption to Vent Streams. Although carbon
adsorption is an excellent method for recovering some valuable process
chemicals, it cannot be used as a universal control method for process
vents. The conditions under which carbon adsorption is not recommended may
exist in some process vents. These include streams with very high or low
molecular weight compounds, and mixtures of high- and low-boiling-point
organic compounds. The range of organic concentration to which carbon
adsorption can be applied is from only a few parts per million to concen-
trations of several percent.12 Adsorbing process vent streams with high
organic concentration may result in excessive temperature rise in the
carbon bed due to the accumulated heat of adsorption of the organic
loading. However, high organic concentrations can be diluted to make a
workable adsorption system. The molecular weight of the compounds to be
3-8
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adsorbed should be in the range of 45 to 130 g/g-mol for effective
adsorption. Carbon adsorption may not be the most effective emission
control technique for compounds with low molecular weights (below 45
g/g-mol) owing to their smaller attractive forces or for high molecular
weight components (>130 g/g-mol) that attach so strongly to the carbon bed
that they are not easily removed.13 properly operated adsorption systems
can be very effective for homogeneous offgas streams but can have problems
with a multicomponent system containing a mixture of light and heavy
hydrocarbons.14 The process vent gas streams addressed in this document
are likely to be a mixture of organics, with one or two major constituents
and one or more minor constituents. Two or more organics in the vent gas
streams, as a general rule, will have the following effects:
• The adsorption of organic compounds having higher molecular
weights will tend to displace those having lower molecular
weights. Lighter compounds will tend to be separated or
partitioned from the heavier compounds and will pass through the
bed at a faster rate. This will increase the MTZ and may require
additional carbon bed depth or shorter operating cycles.
• Carbon retentivity may be reduced.
• Efficiencies of any given system will tend to be lower on a
multiple organic application.
The lower explosive limit (LEL) of the mixture will vary directly
with the LEL of the individual components. Safety considerations
may dictate more or less dilution air to reduce flammability
potential.li3 J
3.1.2 Absorption
3-l-2-l Control Description. Absorption is the selective transfer of
one or more components of a gas mixture into a solvent liquid. The
transfer consists of solute diffusion and dissolution into a solvent. For
any given solvent, solute, and set of operating conditions, there exists an
equilibrium ratio of solute concentration in the gas mixture to solute
concentration in the solvent. The driving force for mass transfer at a
given point in an operating absorption tower is related to the difference
between the actual concentration ratio and the equilibrium ratio.16
Absorption may entail only the dissolution of the gas component into the
3-9
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solvent or may also involve chemical reaction of the solute with constit-
uents of the solution.!'7 The absorbing liquids (solvents) used are chosen
for high solute (organic) solubility and include liquids such as water,
mineral oils, nonvolatile hydrocarbon oils, and aqueous solutions of
oxidizing agents like sodium carbonate and sodium hydroxide.^
Devices based on absorption principles include spray towers, venturi
scrubbers, packed columns, and plate columns. Spray towers require high
atomization pressure to obtain droplets ranging in size from 500 to
1,000 urn to present a sufficiently large surface contact area.19 Although
they can remove particulate matter effectively, spray towers have the least
effective mass transfer capability and, thus, are restricted to particulate
removal and control of high-solubility gases such as sulfur dioxide and
ammonia.20 Venturi scrubbers have a high degree of gas-liquid mixing and
high particulate removal efficiency but also require high pressure and have
relatively short contact times. Therefore, their use is also restricted to
high-solubility gases.21 As a result, organic control by gas absorption is
generally accomplished in packed or plate columns. Packed columns are used
primarily for handling corrosive materials and liquids with foaming or
plugging tendencies or where excessive pressure drops would result from use
of plate columns. They are less expensive than plate columns for small-
scale or pilot plant operations where the column diameter is less than .
0.6 m (2 ft). Plate columns are preferred for large-scale operations,
where internal cooling is desired or where low liquid flow rates would
inadequately wet the packing.22
A schematic of a packed tower is shown in Figure 3-2. The gas to be
absorbed is introduced at the bottom of the tower and allowed to rise
through the packing material. Solvent flows from the top of the column,
countercurrent to the vapors, absorbing the solute from the gas phase and
carrying the dissolved solute out of the tower. Cleaned gas exits at the
top for release to the atmosphere or for further treatment as necessary.
The saturated liquid is directed to a regeneration unit. Here, the
absorbent is treated in such a way that the absorbent may be recycled and
the pollutant disposed of appropriately. Regeneration may be achieved by
various processes such as vaporization, rectification, steam stripping,
desorption, or extraction.
3-10
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ABSORBING
LIQUID IN
CLEANED GAS OUT
TO FINAL CONTROL DEVICE
ABSORBING LIQUID
WITH ORGANICS OUT
To Disposal or Organic Solvent Recovery
Figure 3-2. Packed tower for gas absorption.
ORGANIC LADEN
GAS IN
3-11
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The major tower design parameters to be determined for absorbing any
substance are column diameter and height, system pressure drop, and liquid
flow rate required. These parameters are derived from considering the
total surface area provided by the tower packing material, the solubility
and concentrations of the components, and the quantity of gases to be
treated.
3.1.2.2 Performance Monitoring. The purpose of performance
monitoring is to ensure that the absorption system is being operated
properly and maintained within design specifications. A viable monitoring
program is mandatory in "tracking" the performance of the air pollution
control equipment. To ensure that the absorber is operated within design
specifications, the owner or operator should:
1. Install a flow indicator that provides a record of vent stream
flow to the control device. The flow indicator sensor should be
installed in the vent stream as near as possible to the control
device inlet but before being combined with other vent streams.
2. Install a monitoring device to measure the concentration level of
the organic compounds in the exhaust vent stream from the
absorber.
A secondary parameter that can be monitored to give an indication of the
operating or removal efficiency is the quantity of organic removed over
time.
3.1.2.3 Control Effectiveness. The organic removal efficiency of an
absorption device depends on the solvent selected and on proper design and
operation. For a given solvent and solute, an increase in absorber size or
a decrease in the operating temperature can affect the organic removal
efficiency of the system. It may be possible in some cases to increase
organic removal efficiency by a change in the absorbent. Typical gas
absorption efficiencies range from 60 to 96 percent.23 in an EPA survey of
methylene chloride emission sources, two process vent gas absorbers were
controlled by wastewater scrubbers at an estimated 87-percent methylene
chloride control efficiency.24
Systems that use organic liquids as solvents usually include the
stripping and recycling of the solvent to the absorber. In this case, the
organic removal efficiency of the absorber depends on the solvent stripping
efficiency.
3-12
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3-1.2.4 Applicability of Absorption to Vent Streams. Gas absorption
as an emission control method is currently most widely used for the removal
of water-soluble inorganic contaminants (e.g., sulfur dioxide, hydrogen
sulfide, hydrogen chloride, and ammonia) from airstreams, with water being
the most common solvent or scrubbing fluid used. Water may also be used
for the absorption of organic compounds that have relatively high water
solubilities (e.g., most alcohols, organic acids, aldehydes, ketones,
amines, and glycols). For organic compounds that have low water solubil-
ities, other solvents (usually organic liquids with low vapor pressures)
are used. Although absorption will be attractive for some process vents,
it cannot be used to control all process vents. Because its use depends on
the economics of recovery, absorption can be better classified as a product
recovery device rather than an organic control device. Absorption is
attractive if a suitable solvent is available, a significant amount of
organics can be recovered, and the recovered organics can be reused. It is
usually not considered when the organic concentration is below 200 to 300
ppmv.25 Generally, vent gas streams will consist of low-concentration
organics. The control of low-concentration organics by absorption,
however, usually requires long contact times and large quantities of
absorbent for adequate emissions control. Adsorption may be best suited
for use in conjunction with other control methods such as incineration or
adsorption to achieve a desired degree of emissions control.
3.1.3 Condensation
3-1.3.1 Control Description. Condensation is a process of converting
all or part of the condensible components of a vapor phase into a liquid
phase. This is achieved by the transfer of heat from the vapor phase to a
cooling medium. If only a part of the vapor phase is condensed, the newly
formed liquid phase and the remaining vapor phase will be in equilibrium.
In this case, equilibrium relationships at the operating temperatures must
be considered. The heat removed from the vapor phase should be sufficient
to lower the vapor-phase temperature to (or below) its dewpoint temperature
(temperature at which first drop of liquid is formed).
Condensation devices are of two types: surface condensers and contact
condensers.26 Surface condensers generally are shell-and-tube types of
heat exchangers. The coolant and the vapor phases are separated by the
3-13
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tube wall, and they never come in direct contact with each other (see
Figure 3-3). Vapors are cooled in contact condensers by spraying a
relatively cold liquid directly into the gas stream. The coolant is often
water, although in some situations another coolant may be used. Most
contact condensers are simple spray chambers, like the one pictured in
Figure 3-4.
Contact condensers are, in general, less expensive, more flexible, and
more efficient in removing organic vapors than surface condensers. On the
other hand, surface condensers may recover marketable condensate and mini-
mize waste disposal problems. Often, condensate from contact condensers
cannot be reused and may require significant wastewater treatment prior to
disposal. Surface condensers must be equipped with more auxiliary equip-
ment and have greater maintenance requirements. Surface condensers are
considered in the discussion of control efficiency and applicability
because they are used more frequently in the hazardous waste management
industry.
The major equipment components used in a typical surface condenser
system for organic removal are shown in Figure 3-5. This system includes
shell-and-tube dehumidification equipment, shell-and-tube heat exchanger,
refrigeration unit, and recovered organic storage tanks and operating
pumps. Most surface condensers use a shell-and-tube type of heat exchanger
to remove heat from the vapor.27 As the coolant passes through the tubes,
the organic vapors condense outside the tubes and are recovered. The
coolant used depends on the saturation temperature of the organic vapor
stream. Chilled water can be used down to 7 °C (45 °F), brines to -34 °C
(-30 °F), and chlorofluorocarbons below -34 °C (-30 °F).28 Temperatures as
low as -62 °C (-80 °F) may be necessary to condense some organic vapors.29
Designing surface condensers involves calculating the rate of heat
transfer through the wall of the exchanger per unit time, its "duty," or
calculating the heat-transfer area. If the heat-transfer area, the overall
heat-transfer coefficient, and the mean temperature difference are known,
the condenser duty can easily be calculated. Calculation of heat-transfer
coefficients, a tedious step in definitive design, is avoided in predesign
evaluations where approximate values are adequate. An extensive tabulation
3-14
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COOIAHT INUt
VAfOd OUTlIT
VAPOR INLET
COOLANT OUTLET
CONOtNUO VOC
Figure 3-3. Schematic diagram of a shell-and-tube surface condenser.
VAPORIMLET-
VAPOR ounn
WATER IMLH
• OSTRItUTlON
TRAY
LIOUIO LEVEL
LIQUID OUTLET
Figure 3-4. Schematic diagram of a contact condenser.
3-15
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Cleaned Gas Out
to Primary Control
Rare, Afterburner, etc.
Organic-Laden
Gas
Oehumldlflcatlon
Unit
To remove water
and prevent
freezing in
main condenser
Coolant
Return
Main Condenser
J
Coolant
Refrigeration
Plant
Condensed
Organic
Storage
To Process
or Disposal
Figure 3-5. Condensation system.
3-16
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of typical overall coefficients, based on industrial practice, is found in
Reference 30 (pp. 10-39 to 10-42) along with the information needed to
determine the appropriate mean temperature difference, Tm. In practice,
the vapor stream will contain multicomponents, air, and at least one other
gas, thus complicating the design procedures.31
3.1.3.2 Performance Monitoring. To ensure that the condenser is
operated within design specifications, the owner or operator should:
1. Install a flow indicator that provides a record of vent stream
flow to the control device. The flow indicator sensor should be
installed in the vent stream as near as possible to the control
device inlet but before being combined with other vent streams.
2. Install a monitoring device to measure the concentration level of
the organic compounds in the exhaust vent stream from the
condenser.
3. Install a temperature monitoring device. The device should be
capable of monitoring temperature at two locations and have an
accuracy of ±1 percent of the temperature being monitored in
degrees Celsius or ±0.5 °C, whichever is greater. One tempera-
ture sensor should be installed at a location in the exhaust vent
stream from the condenser, and a second temperature sensor should
be installed at a location in the coolant fluid exiting the
condenser.
A secondary parameter that can be monitored to give an indication of the
operating or removal efficiency is the quantity of organic removed over
time.
3.1.3.3 Control Effectiveness. The organic removal efficiency for a
condenser depends upon the gas stream organic composition and concentra-
tions as well as the condenser operating temperature. Condensation can be
an effective control technique for gas streams having high concentrations
of organic compounds with high boiling points. However, condensation is
not effective for gas streams containing low organic concentrations or
composed primarily of organics with low boiling points. At these condi-
tions, organics cannot readily be condensed at normal condenser operating
temperatures. This point is demonstrated in the results of an EPA field
evaluation of a condenser used to recover organics from a steam stripping
process treating wastewater at a plant manufacturing ethylene dichloride
and vinyl chloride monomer. Condenser removal efficiencies for specific
3-17
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organic constituents in the controlled vent stream ranged from a high value
of 99.5 percent for 1,2-dichloroethane to a low value of 6 percent for
vinyl chloride. Efficiencies of condensers usually vary from 50 to 95
percent.32
3.1.3.4 Applicability of Condensers to Vent Streams. A primary
condenser system is usually an integral part of distillation operations.
These condensers are needed to provide reflux in fractionating columns and
to recover distilled products. At times, additional (secondary) condensers
are used to recover more organics from the vent stream exiting the primary
condenser. Condensers are sometimes present as accessories to vacuum-
generating devices (e.g., barometric condensers).
The use of a condenser to control organic emissions may not be
applicable to some process vent streams. Secondary condensers used as
supplemental product recovery devices are not well suited for vent streams
containing organics with low boiling points or for vent streams containing
large quantities of inerts such as carbon dioxide, air, and nitrogen. Low
boilers and inerts cannot be condensed at normal operating temperatures,
and they usually carry over some organics. For example, condensation is
not generally considered effective for process vents on air stripping units
and other streams that contain less than 10,000 ppm organics.33
3.2 COMBUSTION CONTROL DEVICES
Combustion control devices, unlike vapor recovery control devices,
alter the chemical structure of the organic compounds. Combustion is
complete if all organics are converted to carbon dioxide and water.
Incomplete combustion results in some of the organic compounds being
totally unaltered or being converted to other organic compounds such as
aldehydes or acids.
The combustion control devices discussed in the following sections are
flares, thermal incinerators, catalytic incinerators, and boilers and
process heaters. Each device is discussed separately with respect to its
operation, destruction efficiency, and applicability to process vent
streams. Many combustion devices are widely applied where organic control
of process vent streams is mandated by current regulations.
3-18
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3.2.1 Flares
3-2-1-1 Control Description. Flaring is an open combustion process
in which the oxygen required for combustion is provided by the ambient air
around the flame. Good combustion in a flare is governed by flame tempera-
ture, residence time of components in the combustion zone, turbulent mixing
of the components to complete the oxidation reaction, and oxygen for free
radical formation.
There are two types of flares: ground-level flares and elevated
flares. Reference 34 presents a detailed discussion of different types of
flares, flare design and operating considerations, and a method for
estimating capital and operating costs for flares. The basic elements of
an elevated flare system are shown in Figure 3-6. Process offgases are
sent to the flare through the collection h.eader. The offgases entering the
header can vary widely in volumetric flow rate, moisture content, organic
concentration, and heat value. The knock-out drum removes water or
hydrocarbon droplets that could create problems in the flare combustion
zone. Offgases are usually passed through a water seal before going to the
flare. This prevents possible flame flashbacks, caused when the offgas
flow to the flare is too low and the flame front pulls down into the stack.
Purge gas (nitrogen, carbon dioxide, or natural gas) also helps to
prevent flashback in the flare stack caused by low offgas flow. The total
volumetric flow to the flame must be controlled carefully to prevent low-
flow flashback problems and to avoid a detached flame (a space between the
stack and flame with incomplete combustion) caused by an excessively high
flow rate. A gas barrier or a stack seal is sometimes used just below the
flare head to impede the flow of air into the flare gas network.
The organic vapor stream enters at the base of the flame where it is
heated by already burning fuel and pilot burners at the flare tip (see
Figure 3-7A). Fuel flows into the combustion zone where the exterior of
the microscopic gas pockets is oxidized. The rate of reaction is limited
by the mixing of the fuel and oxygen from the air. If the gas pocket has
sufficient oxygen and residence time in the flame zone, it can be burned
completely. A diffusion flame receives its combustion oxygen by diffusion
of air into the flame from the surrounding atmosphere. The high volume of
fuel flow in a flare requires more combustion air at a faster rate than
3-19
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Slum
Howies
Helps prevent flash back
fla«
Slid
GU Collcclioa Headet
and Transfer Liac
Knock-o
Orua
Steam
Line
Ignition
Device
Air Line
Gas Line
Drain
Figure 3-6. Steam-assisted elevated flare system.
3-20
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Warn fw Stnm mjccooo
burner x point
Figure 3-7A. Flare tip.
&uroen
Liquid wane
injcctori
@L.:--. •.--.:
" S • •-*>'-S-:-•
Ldfty.
Figure 3-7B. Ground flare.
3-21
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simple gas diffusion can supply, so flare designers add steam injection
nozzles to increase gas turbulence in the flame boundary zones, thus
drawing in more combustion air and improving combustion efficiency. This
steam injection promotes smokeless flare operation by minimizing the
cracking reactions that form carbon. Significant disadvantages of steam
usage are the increased noise and cost. The steam requirement depends on
the composition of the gas flared, the steam velocity from the injection
nozzle, and the tip diameter. Although some gases can be flared smoke-
lessly without any steam, typically 0.15 to 0.5 kg of steam per kilogram of
flare gas is required.
Steam injection is usually controlled manually with the operator
observing the flare (either directly or on a television monitor) and adding
steam as required to maintain smokeless operation. Several flare manufac-
turers offer devices that sense a flare's flame characteristics and adjust
the steam flow rate automatically to maintain smokeless operation.
Some elevated flares use forced air instead of steam to provide the
combustion air and the mixing required for smokeless operation. These
flares consist of two coaxial flow channels. The combustible gases flow in
the center channel, and the combustion air (provided by a fan in the bottom
of the flare stack) flows in the annulus. The principal advantage of air-
assisted flares is that expensive steam is not required. Air assistance is
rarely used on large flares because airflow is difficult to control when
the gas flow is intermittent. About 597 W (0.8 hp) of blower capacity is
required for each 45 kg/h (100 Ib/h) of gas flared.35
Ground flares are usually enclosed and have multiple burner heads that
are staged to operate based on the quantity of gas released to the flare
(see Figure 3-7B). The energy of the gas itself (because of the high
nozzle pressure drop) is usually adequate to provide the mixing necessary
for smokeless operation, and air or steam assist is not required. A fence
or other enclosure reduces noise and light from the flare and provides some
wind protection.
Ground flares are less numerous and have less capacity than elevated
flares. Typically, they are used to burn gas "continuously," while steam-
assisted elevated flares are used to dispose of large amounts of gas
released in emergencies.
3-22
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3.2.1.2 Performance Monitoring. To ensure that flares meet a reason-
able emission control efficiency, EPA prescribed design and operating
guidelines in 40 CFR 60.18 and 40 CFR 264.1033 that should be followed.
They are:
1. Install a flow indicator that provides a record of vent
stream flow to the control device. The flow indicator sensor
should be installed in the vent stream as near as possible to
the control device inlet but before being combined with other
vent streams.
2. Design a flare to operate with no visible emissions.
3. Use EPA Reference Method 22 in 40 CFR Part 60 to determine if
a flare is being operated with no visible emissions. The
observation period is 2 hours and can be used according to
Method 22.
4. Operate a flare with a flame present at all times.
5. Calculate the net heating value of the gas being combusted in
a flare using the following equation:
HT = K
n
I
li=l
..
(3-1)
where
Hj = Net,heating value of the sample, MJ/scm; where
the net enthalpy per mole of offgas is based on
combustion at 25 °C and 760 mm Hg, but the
standard temperature for determining the volume
corresponding to 1 mol is 20 °C
K = Constant, 1.74 x 10'7 (1/ppm) (g-mol/scm)
(MJ/kcal) where standard temperature for
(g-mol/scm) is 20 °C
Ci = Concentration of sample component i in ppm on a
wet basis, as measured for organics by Reference
Method 18 in 40 CFR Part 60 and measured for
hydrogen and carbon monoxide by ASTM D1946-82
Hi = Net heat of combustion of sample component 1,
kcal/g-mol at 25 °C and 760 mm Hg. The heats of
combustion may be determined using ASTM D 2382-83
if published values are not available or cannot
be calculated.
3-23
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6. Use a flare only if the net heating value of the gas being
combusted is 11.2 MJ/scm (300 Btu/scf) or greater, if the
flare is steam-assisted or air-assisted, or if the net
heating value of the gas being combusted is 7.45 MJ/scm (200
Btu/scf) or greater if the flare is nonassisted.
7. Operate steam-assisted and nonassisted flares with an exit
velocity less than 18.3 m/s (60 ft/s).
8. Operate a steam-assisted or nonassisted flare with an exit
velocity equal to or greater than 18.3 m/s (60 ft/s) but less
than 122 m/s (400 ft/s) if the net heating value of the gas
being combusted is greater than 37.3 MJ/scm (1,000 Btu/scf).
9. Operate a steam-assisted or nonassisted flare with an exit
velocity less than the velocity, Vmax, and less than 122 m/s
(400 ft/s). For a steam-assisted or nonassisted flare, Vmax
is determined using the following equation:
Log10 (Vmax) = (HT + 28.8)731.7 , (3-2)
where
Vmax = Maximum allowed velocity, m/s
Hj = Net heating value
28.8 = Constant
31.7 = Constant.
10. Operate an air-assisted flare with an exit velocity less than
the velocity, Vmax, which is determined using the following
equation:
Vmav = 8.706 + 0.7084 (H,) , (3-3)
rndx i
where
Vmax = Maximum allowed velocity, m/s
8.706 - Constant
0.7084 = Constant
Hj = Net heating value.
11. Determine the actual exit velocity of a flare by dividing the
volumetric flow rate (in units of standard temperature and
pressure), as determined by Reference Methods 2, 2A, 2C, or
2D in 40 CFR Part 60 as appropriate, by the unobstructed
(free) cross-sectional area of the flare tip.
12. Use a steam-assisted, air-assisted, or nonassisted flare.
3-24
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3.2.1.3 Control Effectiveness. The flammability limits of the gases
flared influence ignition stability and flame extinction (gases must be
within their flammability limits to burn). When flammabi1ity limits are
narrow, the interior of the flame may have insufficient air for the mixture
to burn. Outside the flame, so much air may be induced that the flame is
extinguished. Fuels with wide limits of flammability are therefore usually
easier to burn (e.g., hydrogen and acetylene). However, despite wide
flammability limits, some chemicals such as carbon monoxide are difficult
to burn because of low heating value and slow combustion kinetics.
The autoignition temperature of a fuel affects combustion because gas
mixtures must be at high enough temperature and at the proper mixture
strength to burn. A gas with low autoignition temperature will ignite and
burn more easily than a gas with a high autoignition temperature. Hydrogen
and acetylene have low autoignition temperatures and carbon monoxide has a
high one.
The heating value of the fuel also affects the flame stability,
emissions, and flame structure. A lower heating value fuel produces a
cooler flame that does not favor combustion kinetics and is more easily
extinguished. The lower flame temperature will also reduce buoyant forces,
which reduces mixing (especially for large flares on the verge of smoking).
For these reasons, organic emissions from flares burning gases with low-Btu
content may be higher than those from flares burning high-Btu gases.
The density of the gas flared also affects the structure and stability
of the flame through the effect on buoyancy and mixing. The velocity in
many flares is very low; therefore, most of the flame structure is
developed through buoyant forces as a result of the burning gas. Lighter
gases therefore tend to burn better. The density of the fuel also affects
the minimum purge gas required to prevent flashback and the design of the
burner tip.
Poor mixing at the flare tip or poor flare maintenance can cause
smoking (particulate). Fuels with high carbon-to-hydrogen ratios (greater
than 0.35) have a greater tendency to smoke and require better mixing if
they are to be burned smokelessly.
3-25
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A series of flare destruction efficiency studies has been performed by
EPA. Based on the results of these studies, EPA concluded that 98-percent
combustion efficiency can be achieved by steam-assisted and air-assisted
flares burning gases with heat contents greater than 11 MJ/m3 (300
Btu/ft3).36 To achieve this efficiency level, EPA developed the set of
flare design guidelines presented in Section 3.2.1.1 of this chapter.
3.2.1.4 Applicability of Flares to Vent Streams. The flare is a
useful emission control device and can be used for most nonhalogenated
organic streams. It can handle fluctuations in organic concentration, flow
rate, and inerts content very easily. However, the low volumetric flows
typically associated with waste distillation-unit process vents and the low
organic concentrations in process vent streams from air strippers are
conditions that do not favor the use of flares. Flares are best suited and
generally designed to control normal operating vents or emergency upsets
that release large volumes of gases; and, in the case of dilute gas
streams, supplemental fuel costs can eliminate flares as a viable control
alternative. On the other hand, it is possible (as is done in refineries)
to combine a number of process vents in a common gas line, which can be
sent to a flare.
3.2.2 Thermal Incineration
3.2.2.1 Control Process Description. Any organic chemical heated to
a high enough temperature in the presence of enough oxygen will be oxidized
to carbon dioxide and water. This is the basic principle of operation of a
thermal incinerator. The theoretical temperature required for thermal
oxidation to occur depends on the structure of the chemical involved. Some
chemicals are oxidized at temperatures much lower than others. The organic
destruction efficiency of a thermal oxidizer can be affected by variations
in chamber temperature, residence time, inlet organic concentration,
compound type, and flow regime (mixing). An efficient thermal incinerator
system must provide:
• A chamber temperature high enough to enable the oxidation
reaction to proceed rapidly to completion
• Enough turbulence to obtain good mixing between the hot combus-
tion products from the burner, combustion air, and organics
3-26
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• Sufficient residence time at the chosen temperature for the
oxidation reaction to reach completion.
A thermal incinerator is usually a refractory-lined chamber (fire-box)
containing a burner at one end. As shown in Figure 3-8, discrete dual fuel
burners and inlets for the vent gas and combustion air are arranged in a
premixing chamber to mix the hot products from the burners thoroughly with
the vent gas airstreams. The mixture of hot reacting gases then passes
into the main combustion chamber. This section is sized to allow the
mixture enough time at the elevated temperature for the oxidation reaction
to reach completion (residence times of 0.3 to 1 s are common). Energy can
then be recovered from the hot flue gases in a heat recovery section.
Preheating of combustion air or vent gas is a common mode of energy recov-
ery; however, it is sometimes more economical to generate steam. Insurance
regulations require that if the waste stream is preheated, the organic
concentration must be maintained below 25 percent of the LEL to prevent
explosion hazards.
Thermal incinerators designed specifically for organic incineration
with natural gas as the auxiliary fuel may also use a grid-type (distrib-
uted) gas burner as shown in Figure 3-9.37 The tiny gas flame jets on the
grid surface ignite the vapors as they pass through the grid. The grid
acts as a baffle for mixing the gases entering the chamber. This arrange-
ment ensures burning of all vapors at lower chamber temperature and uses
less fuel. This system makes possible a shorter reaction chamber yet
maintains high efficiency.
Other parameters affecting incinerator performance (i.e., organic
vapor destruction efficiency) are the vent gas organic vapor composition,
concentration, and heating value; the water content in the stream; the
amount of excess combustion air (the amount of air above the stoichiometric
air needed for reaction); the combustion zone temperature; the period of
time the organics remain in the combustion zone (i.e., residence time); and
the degree of turbulent mixing in the combustion zone.
The vent gas heating value is a measure of the heat available from the
combustion of the organic in the vent gas. Combustion of vent gas with a
heating value less than 1.86 MJ/Nm^ (50 Btu/scf) usually requires burning
auxiliary fuel to maintain the desired combustion temperature. Auxiliary
3-27
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Vent Gas
Auxiliary Fuel
Burner ••••
(discrete)
Air
SUc*
Mixing
Seciion
Comowtion
Section
Optional
Heat
Recovery
Figure 3-8. Discrete burner, thermal oxidizer.
Burner Plate-> Plane Jets-
Auxiliary fuel
(natural gas)
Figure 3-9. Distributed burner, thermal oxidizer.
Slack
Optional
Heat
Recovery
3-28
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fuel requirements can be lessened or eliminated by the use of recuperative
heat exchangers to preheat combustion air. Vent gas with a heating value
above 1.86 MJ/Nm3 (50 Btu/scf) may support combustion but may need
auxiliary fuel for flame stability.
A thermal incinerator handling vent gas streams with varying heating
values and moisture content requires careful adjustment to maintain the
proper chamber temperatures and operating efficiency. Water requires a
great deal of heat to vaporize, so entrained water droplets in a vent gas
stream can substantially increase auxiliary fuel requirements because of
the additional energy needed to vaporize the water and raise it to the
combustion chamber temperature. Combustion devices are always operated
with some quantity of excess air to ensure a sufficient supply of oxygen.
The amount of excess air used varies with the fuel and burner type, but it
should be kept as low as possible. Using too much excess air wastes fuel
because the additional air must be heated to the combustion chamber tem-
perature. A large amount of excess air also increases flue gas volume and
may increase the size and cost of the system. Packaged, single-unit
thermal incinerators can be built to control streams with flow rates in the
range of 0.1 Nm3/s (200 scfm) to about 24 Nm3/s (50,000 scfm).
3.2.2.2 Performance Monitoring. To ensure that the thermal incin-
erator is operated within design specifications, EPA recommends the follow-
ing procedures (48 FR 57538, December 30, 1983):
1. Install a flow indicator that provides a record of vent stream
flow to the control device. The flow indicator sensor should be
installed in the vent stream as near as possible to the control
device inlet but before being combined with other vent streams.
2. Install a temperature monitoring device. The device should have
an accuracy of ±1 percent of the temperature being monitored in
degrees Celsius or ±0.5 °C, whichever is greater. The temperature
sensor should be installed at a location in the combustion chamber
downstream of the combustion zone.
Also, visible emissions from an incinerator indicate incomplete combustion,
that is, inefficient operation.
3.2.2.3 Control Effectiveness. The organic destruction efficiency of
a thermal oxidizer can be affected by variations in chamber temperature,
residence time, inlet organic concentration, compound type, and flow regime
3-29
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(mixing). Test results show that thermal oxidizers can achieve 98-percent
destruction efficiency for most organic compounds at combustion chamber
temperatures ranging from 700 to 1,300 °C (1,300 to 2,370 8F) and residence
times of 0.5 to 1.5 s.38 This information, used in conjunction with
kinetics calculations, indicates that the combustion chamber parameters for
at least a 98-percent organic destruction efficiency are a combustion
temperature of 870 °C (1,600 °F) and a residence time of 0.75 s (based upon
residence in the chamber volume at combustion temperature). A thermal
oxidizer designed to produce these conditions in the combustion chamber
should be capable of high destruction efficiency for almost any organic
even at low inlet concentrations.
At temperatures over 760 °C (1,400 °F), the oxidation reaction rates
are much faster than the rate of gas diffusion mixing. The destruction
efficiency of the organic then becomes dependent upon the fluid mechanics
within the oxidation chamber. The flow regime must ensure rapid, thorough
mixing of the organic stream, combustion air, and hot combustion products
from the burner. This enables the organic to attain the combustion
temperature in the presence of enough oxygen for a sufficient time for the
oxidation reaction to reach completion.
Previous EPA studies (48 FR 57538, Dec. 30, 1983; 48 FR 48932,
Oct. 21, 1983) that considered thermal oxidizer efficiency, auxiliary fuel
use, and costs concluded that 98-percent organic destruction or a 20-ppmv
compound exit concentration (whichever is less stringent) is the highest
reasonable control level achievable by all new incinerators in operations
such as distillation processes, considering current technology.39 Because
of much slower combustion reaction rates at lower inlet organic concentra-
tions, maximum achievable organic destruction efficiency decreases as inlet
concentration decreases. For vent streams with organic concentrations
above approximately 2,000 ppmv (corresponding to 1,000 ppm organics in the
incinerator inlet stream because air dilution is typically 1:1), a 98-
percent (by weight) organic destruction is achievable. For vent streams
with organic concentrations below approximately 2,000 ppmv, it has been
determined that an incinerator outlet concentration of 20 ppm (volume, by
compound) is the lowest achievable by all new thermal oxidizers.40 As a
result, combustion of inlet streams below approximately 2,000 ppmv may not
achieve the 98-percent-by-weight destruction efficiency.
3-30
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The 98-percent efficiency estimate is predicated upon thermal
incinerators operated at 870 °C (1,600 °F) with a 0.75-s residence time for
nonhalogenated organic compounds. If the vapor stream contains halogenated
compounds, a temperature of 1,100 °C (2,000 °F) and a residence time of 1 s
is needed to achieve a 98-percent destruction efficiency.
3.2.2.4 Applicability of Thermal Incinerators to Vent Streams. In
terms of technical feasibility, thermal incinerators are applicable as a
control device for many process vents. They can be used for organic
streams with any concentration and with any type of organic compounds.
They can be designed to handle minor fluctuations in flows. However,
excessive fluctuations in flow (upsets) might not allow the use of
incinerators and would require the use of a flare. The presence of
compounds such as halogens or sulfur might require some additional
equipment such as acid-gas scrubbers.
The practical application of thermal incinerators for control of
organic emissions from process vents is limited by the inlet (vent) stream
flow conditions. Both the vent stream volumetric flow rate and the vent
stream organic concentration limit applicability to some extent. Because a
combustion chamber volume of 1.01 n)3 (35.7 ft3) is the smallest size
commercially available, the use of thermal incinerators for low-flow
process vents (e.g., <10 scfm) may not be appropriate. At a residence time
of 1 s, a 1.01-m3 combustion chamber can accommodate a total volumetric
flow (i.e., a flue gas flow rate) of about 2,000 scfm. For a vent stream
requiring a combustion chamber volume smaller than 1 m3, natural gas and
air can be added to maintain the desired (or design) temperature and
residence time to compensate for the application of an oversized incin-
erator combustion chamber. However, dilution of the vent stream can lead
to reduced destruction efficiencies (<98 percent) if the organic concentra-
tion following dilution falls below 2,000 ppmv. The limit to which an
oversized thermal incinerator can be used for a low-flow rate vent stream
and the limit to which a vent stream with a flow rate within design
specifications (i.e., >500 scfm) but with a low organic concentration
(i.e., <2,000 ppmv) can be effectively controlled using thermal incinera-
tion is an engineering judgment based on the desired control device
efficiency and the limit on acceptable cost-effectiveness values (the cost
per unit of emission reduction).
3-31
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3.2.3 Boiler and Process Heater Combustion Control Devices
3.2.3.1 Control Description. Fired-process equipment or furnaces
include boilers, heaters, and incinerators. Such equipment is employed in
most chemical plants to provide heat conveniently, efficiently, and at the
temperature level required. Indirect-fired furnaces (boilers and process
heaters) are those in which heating media are separated from process
streams.
Industrial boilers are of two types: fire-tube and water-tube. Fire-
tube units are similar to shell-and-tube heat exchangers with combustion
gases flowing through the tubes. The center tube of the bundle, much
larger than the rest, constitutes the combustion chamber. Flow reverses at
the end of the bundle and passes back through numerous smaller outer tubes.
Efficient and compact, fire-tube boilers are always shop-fabricated. Steam
pressures are limited by the strength of the large cylindrical shell and
are, of course, less than could be contained in smaller tubes. Thus, fire-
tube furnaces are employed primarily for generating modest amounts of low-
pressure saturated steam. Because of geometry, the combustion chamber and
flue gas tubes are not compatible with continuous cleaning. This, in
addition to a limited combustion residence time, restricts fire-tube
boilers to fuels no dirtier or less convenient than residual oil.
Water-tube boilers contain steam within the tubes while combustion
occurs in a boxlike open chamber. In large boilers, hundreds to thousands
of tubes, usually 7 to 12 cm (2.7 to 4.7 in.) in diameter, are installed
side by side, forming the walls of the combustion chamber and of baffles
that control flow of, and remove heat from, combustion gases. In the
combustion area, known as the radiant section, gas temperatures drop from
about 1,930 °C (3,506 °F) to 1,030 °C (1,886 °F). After combustion
products have been thus cooled by radiation to wall tubes, they pass at
high velocity through slots between more tubes suspended as large banks in
the gas stream. This is known as the convection section. In the radiant
section, such direct exposure to higher-temperature gases would damage the
tube metal. Gas entering the convection section at about 1,030 °C
(1,886 °F) leaves near 330 °C (626 °F). Tubes in the radiant section are
normally filled with circulating, boiling liquid to avoid hot spots. Any
superheating desired occurs in the hot end of the convection system.
3-32
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Because of the large, open combustion chambers, coal and wood fueling
are common in water-tube furnaces. Flyash and soot are cleaned from
convection tubes by automatic "soot blowers" that direct high-velocity
steam or air jets against outer surfaces of tubes while the boiler is
operating. Water-tube boilers can be shop-fabricated with heating duties
up to 100,000 kJ/s (94,860 Btu/s). Modern units burning coal and wood or
residual oil are fitted with dust collectors for flyash removal.
Frequently, the need arises for process heat at temperatures above
those available from the systems already described. In these situations
and even where an intermediate medium can be used, the process fluid itself
is passed through tube coils in a fired furnace. The process system may be
reactive, as with pyrolysis furnaces, which have been used extensively to
thermally crack hydrocarbons for ethylene and propylene manufacture. The
process stream may be nonreactive as well. Such is the case when a fired
furnace is used as a reboiler in the distillation of heavy petroleum
1iquids.
Boilers and process heaters can be designed as control devices to
limit organic emissions by incorporating the vent stream (e.g., the
uncondensed overhead from distillation) with the inlet fuel, or by feeding
the stream into the boiler or process heater through a separate burner.
These devices are most applicable where high vent stream heat recovery
potential exists.
The parameters that affect the efficiency of a thermal incinerator
(e.g., boilers and process heaters) are the same parameters that affect the
efficiency of these devices when they function as air pollution control
devices. These parameters are temperature, residence time, inlet organic
concentration, compound type, and flow regime (mixing).
3.2.3.2 Performance Monitoring. To ensure that the boilers or proc-
ess heaters are operated within design specifications, the owner or
operator should:
1. Install a flow indicator that provides a record of vent stream
flow to the control device. The flow indicator sensor should be
installed in the vent stream as near as possible to the control
device inlet but before being combined with other vent streams.
3-33
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2. For boilers or process heaters having a design heat input capac-
ity less than 44 MW, install a temperature monitoring device
equipped with a continuous recorder. The device should have an
accuracy of ±1 percent of the temperature being monitored in
degrees Celsius or ±0.5 °C, whichever is greater. The tempera-
ture sensor should be installed at a location in the furnace
downstream' of the combustion zone.
3. For boilers or process heaters having a design heat input
capacity greater than or equal to 44 MW, install a monitoring
device to measure a parameter that demonstrates that good
combustion operating practices are being used (e.g., concen-
tration of CO, 02, hydrocarbons).
3.2.3.3 Control Effectiveness. A boiler or process heater furnace
can be compared to an incinerator where the average furnace temperature and
residence time determine the combustion efficiency. However, when a vent
gas is injected as a fuel into the flame zone of a boiler or process
heater, the required residence time is reduced due to the relatively high
flame zone temperature. The following test data, which document the
destruction efficiencies for industrial boilers and process heaters, are
based on injecting the wastes identified into the flame zone of each
combustion control device.
A series of EPA-sponsored studies of organic vapor destruction effi-
ciencies for industrial boilers and process heaters have been conducted.
One study investigated the destruction efficiency of five process heaters
firing a benzene vapor and natural gas mixture. The results of these tests
showed 98 to 99 percent overall destruction efficiencies for C\ to CQ
hydrocarbons.41
3.2.3.4 Applicability of Industrial Boilers and Process Heaters as
Control Devices for Process Vent Streams. Industrial boilers and process
heaters are currently used by industry to combust offgases from refinery
operations. These devices are most applicable where high vent stream heat
recovery potential exists.
The primary purpose of a boiler is to generate steam. Process heaters
are applied within a plant for a variety of reasons including natural gas
reforming, thermal cracking, process feedstock preheating, and reboiling
3-34
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for some distillation operations. Both devices are essential to the opera-
tion of a plant and, as a result, only streams guaranteed not to reduce the
device's performance or reliability warrant use of a boiler or process
heater as a combustion control device. Variations in vent stream flow rate
and/or heating value could affect the heat output or flame stability of a
boiler or process heater and should be considered when using these combus-
tion devices. Performance or reliability may be affected by the presence
of corrosive products in the vent stream. Because these compounds could
corrode boiler or process heater materials, vent streams with a relatively
high concentration of halogenated or sulfur-containing compounds are
usually not combusted in boilers or process heaters. When corrosive
organic compounds are combusted, the flue gas temperature must be
maintained above the acid dewpoint to prevent acid deposition and
subsequent corrosion from occurring.
The introduction of some process vent streams into the furnace of a
boiler or heater could alter the heat transfer characteristics of the
furnace. Heat transfer characteristics depend on the flow rate, heating
value, and elemental composition of the process vent stream and the size
and type of heat-generating unit being used. Often, there is no signifi-
cant alteration of the heat transfer, and the organic content of the
process stream can, in some cases, lead to a reduction in the amount of
fuel required to achieve the desired heat production. In other cases, the
change in heat transfer characteristics after introduction of the process
stream may adversely affect the performance of the heat-generating unit and
increase fuel requirements. If, for a given process vent stream, increased
fuel is required to achieve design heat production to the degree that
equipment damage (e.g., tube failure due to local hot spots) might result,
then a heat-generating unit would not be applicable as an organic control
device for that vent stream. In addition to these reliability problems,
there also are potential safety problems associated with ducting process
vents to a boiler or process heater. Variation in the flow rate and
organic content of the vent stream could, in some cases, lead to explosive
mixtures that could cause extensive damage. Another related problem is
flame fluttering, which could result from these variations.
3-35
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When a boiler or process heater is applicable and available, it is an
excellent control device because it can provide at least 98-percent
destruction of organics. In addition, near-complete recovery of the vent
stream heat content is possible. However, both devices must operate
continuously and concurrently with the pollution source unless an alternate
control strategy is available in the event the heat-generating capacity of
either unit is not required.
3.2.4 Catalytic Oxidation
3.2.4.1 Control Description. A catalyst is a substance that changes
the rate of a chemical reaction without being permanently altered.
Catalysts in catalytic incinerators cause the oxidizing reaction to occur
at a lower temperature than is required for thermal oxidation. Catalyst
materials include platinum, platinum alloys, copper oxide, chromium, and
cobalt. These materials are plated in thin layers on inert substrates
designed to provide maximum surface area between the catalyst and the
organic vapor stream.
Figure 3-10 presents a catalytic incinerator. The vent gas is intro-
duced into a mixing chamber where it is heated to approximately 320 °C
(~600 °F) by the hot combustion products of the auxiliary burners. The
heated mixture then passes through the catalyst bed. Oxygen and organics
diffuse onto the catalyst surface and are adsorbed in the pores of the
catalyst. The oxidation reaction takes place at these active sites.
Reaction products are desorbed from the active sites and diffuse back into
the gas. The combusted gas can then be routed through a waste heat
recovery device before exhausting into the atmosphere.
Combustion catalysts usually operate over a temperature range of 320
to 650 °C (600 to 1,200 °F). Lower temperatures can slow down or stop the
oxidation reaction. Higher temperatures can shorten the life of the cata-
lyst or evaporate the catalyst from the inert substrate. Vent gas streams
with high organic concentrations can result in temperatures high enough to
cause catalyst failure. In such cases, dilution air may be required.
Accumulations of particulate matter, condensed organics, or polymerized
hydrocarbons on the catalyst can block the active sites and reduce effi-
ciency. Catalysts can also be deactivated by compounds containing sulfur,
3-36
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Auxiliary Fuel
Burners
CO
i
CO
Vent gas
Optional
Heat Recovery
Mixing Chamber
Figure 3-10. Catalytic incinerator.
-------
bismuth, phosphorus, arsenic, antimony, mercury, lead, zinc, tin, or
halogens. If these compounds deactivate the catalytic unit, organics will
pass through unreacted or be partially oxidized to form compounds (alde-
hydes, ketones, and organic acids) that are highly reactive atmospheric
pollutants that can corrode plant equipment. As a result, gases containing
compounds with chlorine, sulfur, and other atoms that may deactivate the
supported noble metal catalysts often used for VOC control were not suit-
ably controlled by catalytic oxidation systems. Therefore, the use of
catalytic oxidation for control of gaseous pollutants has generally been
restricted to organic compounds containing only carbon, hydrogen, and
oxygen.
Catalysts now exist, however, that are tolerant of some deactivating
compounds. Most of the development of poison-tolerant catalysts has
focused on the oxidation of chlorine-containing organics. These organic
compounds are widely used as solvents and degreasers and are often the
subject of concern in VOC control. Catalysts such as chromia/alumina,
cobalt oxide, and copper oxide/manganese oxide have been used for oxidation
of gases containing chlorinated compounds in limited applications.
Platinum-based catalysts are active for oxidation of sulfur-containing
VOCs, although they are rapidly deactivated by the presence of chlorine.
Compounds containing atoms such as lead, arsenic, and phosphorous should,
in general, be considered poisons for most oxidation catalysts.
3.2.4.2 Performance Monitoring. To ensure that the catalytic incin-
erator is operated within design specifications, the owner or operator
should:
1. Install a flow indicator that provides a record of vent stream
flow to the control device. The flow indicator sensor should be
installed in the vent stream as near as possible to the control
device inlet but before being combined with other vent streams.
2. Install a temperature-monitoring device. The device should be
capable of monitoring temperature at two locations and have an
accuracy of ±1 percent of the temperature being monitored in
degrees Celsius or ±0.5 °C, whichever is greater. One tempera-
ture sensor should be installed in the vent stream as near as
possible to the catalyst bed inlet, and a second temperature
sensor should be installed in the vent stream as near as possible
to the catalyst bed outlet.
3-38
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Also, as with thermal incineration, visible emissions from a catalytic
incinerator indicate incomplete combustion, that is, inefficient operation.
3-2.4.3 Control Effectiveness. Catalytic incineration destruction
efficiency depends on organic composition and concentration, operating
temperature, oxygen concentration, catalyst characteristics, and space
velocity. Space velocity is commonly defined as the volumetric flow of gas
entering the catalyst bed chamber divided by the volume of the catalyst
bed. The relationship between space velocity and organic destruction
efficiency is strongly influenced by catalyst operating temperature. As
space velocity increases, organic destruction efficiency decreases, and as
temperature increases, organic destruction efficiency increases. A
catalytic unit operating at about 450 °C (840 °F) with a catalyst bed
volume of 0.014 to 0.057 m3 (0.5 to 2 ft3) per 0.47 scm/s (1,000 scfm) of
vent gas passing through the device can achieve 95-percent organic destruc-
tion efficiency.42,43 Destruction efficiencies of 98 percent or greater
can be obtained on some streams by using the appropriate catalyst bed
volume to vent gas flow rate. Some catalytic units have been reported to
achieve 97.9- to 98.5-percent destruction efficiencies.44 These higher
efficiencies are usually obtained by increasing the catalyst bed volume to
offgas flow ratio. The cost of this increased catalyst bed can be
prohibitive.
3.2.4.4 Applicability of Catalytic Qxidizers to Vent Streams. The
sensitivity of catalytic oxidizers to organic inlet stream flow conditions,
their inability to handle high organic concentration offgas streams, the
sensitivity of the catalyst to deactivating compounds, and their higher
cost for destruction efficiencies comparable to thermal oxidizers may limit
the application of catalytic units for control of organics from process
vent streams.
3.3 SUMMARY OF DATA ON CONTROL DEVICES APPLIED TO PROCESS VENTS
The chemical manufacturing industry data base (discussed in Section
2.3) contains information on the types of control devices used to control
process vent stream emissions from distillation units used in the chemical
manufacturing industry. These data provide some indication of the types of
distillation operations in use in organic chemical manufacturing and the
3-39
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control systems currently being used for control of process vent emissions.
The total number and types of distillation units in the survey as well as a
summary of the types of combustion control devices and product recovery
devices used are presented in Table 3-1.
With regard to distillation and stripping units that process only
wastes, the TSDR data base (discussed in Section 2.3) contains up-to-date
information on the types of air pollution control devices serving waste
management units at TSDF. The preliminary results of the TSDR Survey were
used to identify units of the type that are likely to have associated
process vents (e.g., thin-film evaporators [TFE], batch stills, and steam
strippers) and the types of air pollution control devices serving these
units. Those preliminary results are presented in Table 3-2.
As shown in Table 3-2, vapor recovery devices (i.e., condensers,
adsorbers, and absorbers) are the technology of choice to control distilla-
tion and stripping units at TSDF; more than 80 percent of the reported
control devices utilize a form of vapor recovery. In general, these
devices are most attractive for the control of process vents on waste
management units in cases where a significant quantity of usable organics
can be recovered. Condensers are by far the most commonly reported tech-
nology used. However, the survey did not distinguish between condensers
primarily used for product recovery and those used to reduce air pollutant
emissions. As a result, the application of condensers may appear somewhat
skewed because unit operations of this type (i.e., distillation operations)
are expected to utilize primary condensers for recovery of usable organics
as a part of the process. Vapor recovery as a control device (i.e.,
adsorbers, absorbers, and condensers) may not be applicable to some process
vent streams. For example, adsorbers may not always be applicable to vent
streams containing very low molecular weight compounds. Absorbers are
generally not applied to streams with organic concentrations below 200 to
300 ppmv. Condensers are not well suited for application to vent streams
containing low-boiling-point organics or to vent streams with large inert
concentrations. Even though these restrictions exist, condensers and
adsorbers are the primary technology applied to process vent streams in the
Synthetic Organic Chemical Manufacturing Industry (SOCMI) and at TSDF and
3-40
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TABLE 3-1. OVERVIEW OF DISTILLATION UNITS IN CHEMICAL
MANUFACTURING INDUSTRY
11- Operating pressure
*. Vacuum
b. Nonvacuum
c. Information not available3
2. Mode of operation
a. Batch
fr. Continuous
3>. Type of unit
a. Flash
b. Fractionating
4L Installed product recovery
devices^
a. Scrubbers
b. Absorbers
c. Carbon adsorption
5. Installed combustion controls
a. Flares
b. Incinerators
c. Boilers
§- Units with no flow rate
T, Units with emissions recycled
Q?Cs\\tft 1 O n A »....._ -L- __f il * A M « . _
Number of units
318
582
137
1,037
4
1,033
1,037
37
1,000
1,037
79
12
5
96
78
/ \J
72
• (~
9
159
231
219
— 1^:
Percentage of total
31
13
100
.
>99
100
•5
j
97
100
1
i
10
1
16
22
21
rust given or is report^ as confidential.
Sou-rce: U.S. Environmental Protection Agency. Disti 1 lation Operations in
for Prnnn,oHr9S7CHCh71Ca ^^acturing-Background Information
for Proposed Standards. Appendix C. Office of Air Qua! ity
n^5^^ Jlian9le Park' NC" Publication
December 1983.
3-41
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TABLE 3-2. DISTILLATION, SEPARATION, AND STRIPPING UNITS AT TSDF
Type of unit Number of units Percentage of total
1. Type of unit
a. Fractionation 125 18
b. Batch distillation 370 52
c. Solvent extraction 42 6
d. Thin-film evaporation 77 11
e. Air stripping 52 7
f. Steam stripping 40 6
2. Units with air pollution controls
a. Fractionation 104 22
b. Batch distillation 255 53
c. Solvent extraction 8 2
d. Thin-film evaporation 69 14
e. Air stripping 15 3
f. Steam stripping . 27 6
3. Units reporting no air
pollution controls
a. Fractionation 8 4
b. Batch distillation 143 75
c. Solvent extraction 5 3
d. Thin-film evaporation 15 8
e. Air stripping 17 9
f. Steam stripping 3 2
4. Type of air pollution controls
installed
a. Condenser 339 69
b. Wet ionizing scrubber 5 1
c. Packed bed scrubber 14 3
d. Carbon adsorption device 39 8
e. Vapor/fume incinerator 24 5
f. Flare 9 2
g. Boiler 9 2
h. Other 50 10
Note: The total number of units shown includes both RCRA-regulated units
and RCRA-exempt units operating in 1986. Totals are not shown
because some units were reported to have more than one control
device (e.g., a condenser followed by a vapor incinerator) and
some facilities did not complete the section on control devices.
Source: 1987 National Survey of Hazardous Waste Treatment, Storage,
Disposal, and Recycling Facilities (TSDR Survey). Alpha
Database. July 1989.
3-42
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these technologies are expected to remain the technology of choice to
control process vent organic emissions from waste management units.
The combustion control devices typically used are incinerators,
flares, and industrial boilers. However, these technologies account for
less than 10 percent of the reported control devices in use at TSDF. In
general, these devices are applicable to a wide variety of vent stream
characteristics and can achieve at least 98-percent destruction effi-
ciency. 45 combustion devices are capable of adapting to moderate changes
in effluent flow rate and concentration while control efficiency is not
affected by the type of organic present. This is generally not the case
with noncombustion (vapor recovery) control devices. In general, combus-
tion control devices are both capital- and energy-intensive except where
boilers or process heaters are applied and the energy content of the vent
stream is recovered. However, because boilers or process heaters are
essential to the operation of a plant, only streams that are certain not to
reduce performance and reliability warrant use of these systems for air
pollution control. Application of a scrubber prior to atmospheric dis-
charge may be required when vent streams containing high concentrations of
halogenated or sulfonated compounds are combusted in an enclosed combustion
device. The TSDR data base did not indicate if the scrubbers, which
constituted 4 percent of the air pollution controls installed at TSDF, were
operated in association with combustion devices. In addition, vent streams
with high concentrations of corrosive halogenated or sulfonated compounds
may preclude the use of flares because of possible flare tip corrosion and
may preclude the use of boilers and process heaters because of potential
internal (boiler) corrosion.
There are some disadvantages associated with organic control by
combustion: (1) high capital and operating costs result from thermal
oxidation techniques, which could require a plot of land as large as 90 m
by 90 n. (300 ft by 300 ft) for installation; (2) because offgas must be
collected and ducted to the combustion device, long duct runs may lead to
condensation of combustibles and possibly to duct fires; and (3) because
thermal oxidizers use combustion with a flame for achieving organic
destruction, the unit must be located at a safe distance from process
equipment in which flammable chemicals are used. However, it is likely
3-43
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that high operating cost is the principal reason vapor/fume incinerators
are used in 'only 5 percent of the reported cases.
3.4 REFERENCES
1. Barnett, K. W., P. A. May, and J. A. Elliott (Radian). Carbon
Adsorption for Control of VOC Emissions: Theory and Full Scale System
Performance. Prepared for U.S. Environmental Protection Agency.
Research Triangle Park, NC. EPA Contract No. 68-02-4378. June 6,
1988. p. 3-14.
2. Tomany, James P. Air Pollution: The Emissions, the Regulations, and
the Controls. American Elsevier Environmental Science Series.
American Elsevier Publishing Co., Inc. 1975. p. 284.
3. Memorandum from Barnett, K. W., Radian Corporation, to Carbon
Adsorber/Condensation Project File. February 29, 1988. Meeting
Minutes EPA/Calgon Carbon Corporation, p. 4.
4. Reference 3, p. 4.
5. Reference 3, p. 8.
6. Reference 3, p. 10.
7. U.S. Environmental Protection Agency. Polymeric Coating of Supporting
Substrates—Background Information for Proposed Standards. Research
Triangle Park, NC. Publication No. EPA-450/3-85-022a. April 1987.
p. D-20.
8. Stern, A. C. Air Pollution, Volume IV, 3rd Edition. New York,
Academic Press. 1977. p. 355.
9. Reference 8, p. 356.
10. Basdekis, H. S. (Hydroscience.) Emissions Control Options for the
Synthetic Organic Chemical Industry. Control Device Evaluation:
Carbon Adsorption. Prepared for U.S. Environmental Protection Agency.
Research Triangle Park, North Carolina. EPA Contract No. 68-02-2577.
February 1980. p. 11-15.
11. See Reference 1, p. 3-46 through 3-67.
12. Reference 10, p. 11-15.
13. Reference 10, p. 1-4.
14. Staff of Research and Education Association. Modern Pollution Control
Technology. Volume I. New York, Research and Education Association,
1978. pp. 22-23.
3-44
-------
15. Theodore, Louis, and Anthon J. Buom'core. Air Pollution Control
Equipment Selection, Design, Operation, and Maintenance. Englewood
Cliff, NJ, Prentice-Hall Inc. 1982. pp. 113-115.
16. Standifer, R. L. (Hydroscience). Emissions Control Options for the
Synthetic Organic Chemical Industry. Control Device Evaluation- Gas
Absorption. Prepared for U.S. Environmental Protection Agency
Research Triangle Park, North Carolina. EPA Contract No. 68-02-2577
May 1980. p. III-5.
1?* ??!7£l.R: H" and C' H' Chl'lton (eds.). Chemical Engineers' Handbook
5th Edition. New York, McGraw-Hill. 1973. p. 14-2.
18. U.S. Environmental Protection Agency. Control Techniques for Volatile
Organic Emissions from Stationary Sources. Office of Air and Waste
Management. Research Triangle Park, NC. Publication No. EPA-450/2-
78-022. May 1978. p. 76.
19. Reference 8, p. 24.
20. Reference 18, p. 72.
21. Reference 16, p. II-l.
22. Reference 17, p. 14-1.
23. Hesketh, Howard E. Understanding and Controlling Air Pollution Ann
Arbor, Michigan, Ann Arbor Science Publishers, Inc. 1974. n 327
through 331. '
24. U.S. Environmental Protection Agency. Survey of Methylene Chloride
Emission Sources. Research Triangle Park, NC. Publication No
EPA-450/3-85-015. June 1985. p. 3-5 through 3_17DnCatl0n No'
25. Reference 16, p. III-5.
26. Erikson, D. G. (Hydroscience). Emission Control Options for the
Synthetic Organic Chemical Industry; Control Device Evaluation-
CondensatTon. Prepared for U.S. Environmental Protection Agency
Research Triangle Park, NC. EPA Contract No. 68-02-2577. July 1980.
27. Reference 18, p. 83.
28. Reference 26, p. IV-1.
29. Reference 26, p. II-3, III-3.
30. Reference 17, p. 10-39 through 10-42.
3-45
-------
31. Reference 17, p. 10-13 through 10-25.
32. Reference 26, p. III-5.
33. U.S. Environmental Protection Agency. Organic Chemical Manufacturing.
Volume 5: Adsorption, Condensation, and Absorption Devices. Research
Triangle Park, NC. Publication No. EPA-450/3-80-027. December 1980.
34. Kalcevic, V. (IT Enviroscience). Control Device Evaluation—Flares
and the Use of Emissions as Fuels. In: Organic Chemical Manufac-
turing. Volume 4: Combustion Control Device. U.S. Environmental
Protection Agency. Publication No. EPA-450/3-80-026. December 1980.
Report 4.
35. Klett, M. G., and J. B. Galeski (Lockheed Missiles and Space Co.,
Inc.). Flare System Study. Prepared for U.S. Environmental
Protection Agency. Huntsville, AL. Publication No. EPA-600/2-76-079.
36. U.S. Environmental Protection Agency. Distillation Operations in
Synthetic Organic Chemical Manufacturing - Background Information for
Proposed Standards. Research Triangle Park, NC. Publication No. EPA-
450/3-83-005a. December 1983.
37. Reference 2, p. 269.
38. Memo and attachments from Farmer, J. R., EPA, to Distribution.
August 22, 1980. 29 pp. Thermal incinerator performance for NSPS.
39. U.S. Environmental Protection Agency. APTI Course 415 Control of
Gaseous Emissions Student Manual. Research Triangle Park, NC.
Publication No. EPA-450/2-81-005. December 1981.
40. Reference 36.
41. U.S. Environmental Protection Agency. Emission Test Report. El Paso
Products Company. Odessa, Texas. Research Triangle Park, NC. EMB
Report No. 79-OCM-15. April 1981.
42. McDaniel et al. (Engineering-Science). A Report on a Flare Efficiency
Study (Draft). Prepared for U.S. Environmental Protection Agency.
Research Triangle Park, NC. September 1982.
43. Key, J. A. (Hydroscience). Emissions Control Options for the
Synthetic Organic Chemicals Manufacturing Industry. Control Device
Evaluation: Catalytic Oxidation. Prepared for U.S. Environmental
Protection Agency. Research Triangle Park, NC. EPA Contract No. 68-
02-2577. March 1980. p. 1-1.
44. Reference 43.
3-46
-------
45.
Blackburn, J. w. (Hydroscience). Emissions Control Options for the
Synthetic Organic Chemicals Manufacturing Industry; Control Device
Evaluation: Thermal Oxidation. Prepared for U.S. Environmental
Protection Agency. Research Triangle Park, NC. EPA Contract No. 68-
02-2577. July 1980. p. IV-1, V-l.
3-47
-------
4.0 ENVIRONMENTAL AND COST IMPACTS
This chapter presents the emission reductions, costs, and cost-
effectiveness values of various options for control of organic emissions
from waste management unit process vents. Waste management unit process
vents encompass a wide range of equipment types, sizes, and operating tech-
niques. Therefore, a wide range of vent stream parameters were used to
characterize waste management unit process vents industry-wide in order to
evaluate the potential impacts of controlling organic emissions from these
sources.
The individual technologies for controlling organic emissions from
waste management unit process vents are discussed in Chapter 3.0. Due to
the wide variation in process vent operating parameters (i.e., flow rates
and organic concentrations), the most effective control technology for a
given type of waste management unit process vent stream will vary. In this
chapter, example options for controlling process vents are presented with
cost analyses for each control option.
4.1 CONTROL TECHNOLOGY ANALYSIS METHODOLOGY--MODEL UNITS
Because of the large variation in waste management unit process vent
stream characteristics, a model unit approach was used to characterize this
source on an industry-wide basis. A range of model unit cases was devel-
oped to represent typical process vent streams associated with currently
operating waste management units. Table 4-1 presents the model unit
parameters for each process vent case used in the analysis. The process
vent stream model unit parameters selected for analysis in this document
include those used in the development of Resource Conservation and Recovery
Act (RCRA) air emission standards to characterize waste management unit
process vents at treatment, storage, and disposal facilities (TSDF).1 Also
4-1
-------
TABLE 4-1. PROCESS VENT MODEL UNIT PARAMETERS
i
ro
Case
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
Vent
c lass
D
D
D
D
D
D
D
D
D
D
D
0
0
D
D
D
D
D
D
D
D
D
D
D
0
0
D
D
D
D
D
0
0
D
D
0
D
0
D
D
Total
flow,
scfm
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
Organic
emission
rate, Ib/h
0.40
0.40
0.40
0.40
4.20
4.20
4.20
4.20
10.60
10.60
10.60
10.60
0.17
0.17
0.17
0.17
0.42
0.42
0.42
0.42
1.20
1.20
1.20
1.20
5.00
5.00
5.00
5.00
0.08
0.08
0.08
0.08
0.24
0.24
0.24
0.24
1.00
1.00
1.00
1.00
Operating
hours ,
h/yr»
4,160
4,160
4,160
4,160
4,160
4,160
4,160
4,160
4,160
4,160
4,160
4,160
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
2,080
Const! tuent
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
Resulting organic
concentration,
volume %
0.3174
0.2933
0 . 2022
0.3742
3.3328
3.0792
2.1236
3.9291
8.4114
7.7714
5.3562
9.9163
0.9331
0.8621
0.5945
1 . 1000
2.3052
2.1298
1.4688
2.7176
6.5863
6.0851
4 . 1967
7.7647
27.4428
25.3548
17.4860
32.3528
0.8782
0.8114
0.5596
1.0339
2.6345
2.4341
1.6787
3.1059
10.9771
10.1419
6.9944
12.9411
Uncontro 1 led
organic emissions,
Mg/yr
0.76
0.76
0.76
0.76
7.94
7.94
7.94
7.94
20.04
20.04
20.04
20.04
0.16
0.16
0.16
0.16
0.40
0.40
0.40
0.40
1.13
1.13
1.13
1.13
4.73
4.73
4.73
4.73
0.08
0.08
0.08
0.08
0.23
0.23
0.23
0.23
0.95
0.95
0.95
0.95
(continued)
-------
TABLE 4-1 (continued)
CO
Case
No.
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
ME
1,1,1
Vent
c \ass
D
D
D
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A =
D =
DCE =
EDC =
CHI =
MEK =
TOL =
-TCE =
TCE =
Total Organic
flow, emission
scfm rate, Ib/h
26 7.00
26 7.00
26 7.00
2,100 0.10
2,100 0.50
2,100 1.50
2,100 5.00
2,100 0.10
2,100 0.50
2,100 1.50
2,100 5.00
2,100 0.10
2,100 0.50
2,100 1.50
2,100 6.00
6,200 0.10
6,200 10.00
6 , 200 0 . 10
6,200 10.00
6,200 0.10
6 , 200 1 . 50
6,200 10.00
14,500 0.50
14,500 5.00
14,500 10.00
14,500 0.50
14,500 5.00
14,500 10.00
14,500 0.50
14,500 5.00
14,500 10.00
Air-stripper-type vents
Distillation-type vents
D i ch 1 oroethy 1 ene .
1, 2-Dich loroethane.
Methyl ene chloride.
Methyl ethyl ketone.
To 1 uene .
1 , 1 , 1-Tr i ch 1 oroethane.
Tr i ch 1 oroethy 1 ene .
Operating
hours,
h/yr*
4,160
4,160
4,160
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
8,760
(i.e., high
(i.e, low f
3
Const! tuent
TOL
MEK
1,1,1-TCE
TCE
TCE
TCE
TCE
DCE
DCE
DCE
DCE
EDC
EDC
EDC
EDC
TCE
TCE
DCE
DCE
EDC
EDC
EDC
TCE
TCE
TCE
DCE
DCE
DCE
EDC
EDC
EDC
f low rates) .
low rates) .
Resulting organic
concentration,
volume 55
1.6383
2.0905
1.1299
0.0002
0.0009
0.0027
0.0091
0.0002
0.0012
0.0037
0.0123
0.0002
0.0012
0.0036
0.0121
0.0001
0.0061
0.0001
0 . 0082
0.0001
0.0012
0.0081
0.0001
0.0013
0.0026
0.0002
0.0018
0.0035
0.0002
0.0017
0.0034
^
Uncontro 1 led
organic emissions,
Mg/yr
13.24
13.24
13.24
0.40
1.99
5.97
19.91
0.40
1.99
6.97
19.91
0.40
1.99
5.97
19.91
0.40
39.82
0.40
39.82
0.40
6.97
39.82
1.99
19.91
39.82
1.99
19.91
39.82
1.99
19.91
39.82
aDistiI I ation-type units are assumed to operate one or two 8-h shifts per day and air-stripper-
type units 24 h/day.
-------
included in the model units examined in this document are a selection of
process vent stream parameters previously established by EPA to evaluate
the cost of controlling air emissions from air strippers used in ground-
water remediation.2 Selection of the process vent stream parameters is
discussed below.
4.1.1 Emission Rates
Review of data on actual emission rates from waste management unit
process vents (see Section 2.4) indicates that a model unit organic
emission rate range of 0.1 to 10 Ib/h is appropriate. Process vent organic
emissions were found generally to fall into this range regardless of the
type of distillation or stripping process involved.3 Emissions data from
batch distillation operations, steam strippers, thin-film evaporators, and
air strippers were examined, and emission rates were found to be in this
general range on a mass per unit time basis (e.g., pound/hour). The large
range in process vent organic emissions reported in test data for TSDF is
due to the variation in primary condenser collection (or recovery)
efficiencies from unit to unit. The data also include test results from
units using secondary condensers on primary condenser vents. Efficiencies
for the secondary condensers tested were, in some cases, quite low, and
emissions from these units also varied over the range reported above.
4.1.2 Flow Rates
Because of physical differences in the unit operations themselves, air
stripping operations inherently have a much higher process vent volumetric
flow rate than the distillation-type operations (i.e., batch stills, thin-
film evaporators, and steam strippers). In addition, a primary condenser
system is usually an integral part of most distillation operations.
Condensers are needed to provide reflux in fractionating columns and to
ultimately recover distilled products. With primary (or product recovery)
condensers typically applied to distillation-type operations, process vent
flow rates are even further reduced. Therefore, in Table 4-1, each process
vent model unit is assigned a vent class that indicates that the vent is
either representative of a distillation-type operation assumed to be
equipped with a primary condenser as part of the process (i.e., the stream
has a low total volumetric flow) or representative of an air stripping
4.4
-------
operation (i.e., the stream has a high exhaust flow rate). With higher
flow rates, the organic concentrations associated with air strippers are
considerably lower than the organic concentrations in distillation unit
process vent streams.
To account for the contrast or bracketing of process vent flow rates
at the two extremes (i.e., very high flows of over 2,000 scfm and very low
flows of less than 10 scfm), the process vent model unit cases include
analyses of both high and low flow rate units. It should be noted that
emission levels for the model units cover the same basic range of about 0.1
to 10 Ib/h of organics, regardless of vent flow rates. As can be seen by
examining Table 4-1, seven flow rates were selected, based on site-specific
data, to characterize process vents on waste management units. Four flow
rates are used to represent distillation units with low overhead gas flows
(e.g., exhaust gases from a primary condenser). Three flow rates are used
to represent air stripper exhaust vents. For each of the flow rates,
several organic emission rates were selected based on source test data from
tests conducted for EPA. From the flow rate and emission rate data, the
stream's organic concentration can be determined for each constituent.
4.1.3 Temperatures
Vent stream exhaust gas temperatures were also found to be in the same
general range for both distillation-type process vents and air stripping
process vents (i.e., 10 to 27 °C [50 to 80 °F]).4 A model unit vent stream
temperature of 16 °C (60 °F) was used in the analysis for air stripper
vents (i.e., average ambient air temperature) and 24 °C (75 °F) for
distillation-type vents (i.e., uncondensed overheads exhaust temperature).
4.1.4 Haste Constituents
The waste constituents selected for use in the analysis of waste
management unit process vent emission controls are toluene, methyl ethyl
ketone, 1,1,1-trichloroethane, methylene chloride, trichloroethylene,
1,1-dichloroethylene, and 1,2-dichloroethane. Of these, 1,1,1-
trichloroethane and methylene chloride have been identified as nonreactive
organic chemicals, i.e., non-VOC (45 FR 48941, July 22, 1980); however, all
of the waste constituents are toxic chemicals. The constituents were
selected for use in the analyses because the constituent properties are
4-5
-------
considered to span the range of values exhibited by organic constituents
typically found in waste streams managed in distillation/stripping units.
The chemical and physical properties relevant to the analyses are presented
in Table 4-2.
The model unit constituents are grouped according to vent type or
classification. The constituents that most typically occur in vents
associated with distillation-type operations differ from those most
frequently associated with air stripper process vents. Four chemicals are
used in the distillation-type process vent analysis; these are toluene,
methyl ethyl ketone, methylene chloride, and 1,1,1-trichloroethane. Three
chemical constituents, trichloroethylene, 1,1-dichloroethylene, and
1,2-dichloroethane, were used in the air stripper process vent analysis.
The EPA conducted a review of the available information regarding
waste stream organic constituents and concentrations as part of efforts to
develop the RCRA TSDF air emission standards. The EPA TSDF Waste
Characterization Data Base (WCDB),5 information from numerous plant trip
reports, and data from a limited number of emission test reports were used
to characterize waste streams managed at TSDF and Comprehensive Environ-
mental Response, Compensation, and Liability Act (CERCLA) sites in terms of
constituents and concentrations of components. Plant trip reports and
emission test reports from site visits, conducted in connection with the
evaluation of organic removal through treatment processes involving distil-
lation (i.e., waste management units that have associated process vents),
provided organic composition and concentration data for 22 waste stream
cases at TSDF. In general, the waste streams were comprised of one or two
major constituents with two or more minor constituents. The constituent
that showed up most frequently in the site-specific data was toluene, which
was reported as being present in about 55 percent of the streams examined.
Other major constituents and their percent occurrence included methyl ethyl
ketone (36 percent), acetone (32 percent), xylene (27 percent), ethyl
benzene (36 percent), isopropyl alcohol (36 percent), methylene chloride
(32 percent), 1,1,1-trichloroethane (45 percent), trichloroethylene
(36 percent), chloroform (18 percent), tetrachloroethylene (18 percent),
and carbon tetrachloride (23 percent).
4-6
-------
TABLE 4-2. PROPERTIES OF CHEMICAL CONSTITUENTS USED IN PROCESS VENT IMPACTS ANALYSES
Const! tuent*
Methyl ene chloride
To 1 uene
1,1, 1-Tr i ch 1 oroethane
Methyl ethyl ketone
Tr i ch 1 oroethy 1 ene
1 , 1-Dich 1 oroethy lene
1 , 2-D i ch 1 oroethane
Mo 1 ecu lar
we i gh tb
85.00
92.00
133.40
72.12
131.39
97.00
98.76
Vapor pressure,
26 °C, mm Hg»
438
30
123
100
75
630.1
82
Henry's law
Boiling point, constant,
"cb atm-m3/mo|l>
39.8
110.6
81.0
79.6
87.0
-99.8
83.5
3.19 x
6.68 x
3.00 x
4.35 x
9.10 x
1.50 x
1.20 x
10-3
10-3
10-2
10-5
10-3
10-2
10-3
Heat of
combustion,
Btu/lbc
2,260
18,280
2,760
14,580
3,260
5,030
4,740
aMethylene chloride, toluene, 1,1,1-trichIoroethane, and methyl ethyl ketone were used in the
analyses of the efficiency and cost effectiveness of controlling distillation-type process vents.
Trichloroethylene, 1,1-dichloroethylene, and 1,2-dichIoroethane were used in the analyses of the
efficiency and cost effectiveness of controlling air stripping process vents.
^Source: U.S. EPA. Hazardous Waste Treatment, Storage, and Disposal Facilities (TSDF)—Air Emission
Models. Appendix D. U.S. Environmental Protection Agency, Office of Air Quality Planning
and Standards. Research Triangle Park, NC. Publication No. EPA-450/3-87-026. December
1987.
cSource: Weast, R. C. (ed.). CRC Handbook of Chemistry and Physics. 56th edition. CRC Press.
Cleveland, OH. 1975-1976. p. D-274 through D-279.
-------
The most comprehensive source of waste information currently available
is the TSDF WCDB. This data base, used to support the development of com-
prehensive air emission regulations for hazardous waste TSDF, was developed
by merging five existing data bases:
• National Survey of Hazardous Haste Generators and Treatment,
Storage, and Disposal Facilities (Hestat Data Base)
• Industrial Studies Data Base (ISDB)
• Listing documentation of 40 CFR 261.32 hazardous wastes from
specific sources (K waste codes)
• WET Model Hazardous Waste Data Base
• A data base created by the Illinois EPA.
An examination of information in the WCDB for D001 wastes and spent
solvent wastes (i.e., wastes that are typically treated in distillation-
type units) indicates the same general trend as the plant-specific data.
The waste streams were composed of one or two major constituents with one
or more minor constituents present in low concentrations. The major con-
stituents identified included those found in the plant-specific data. This
review led to the selection of the four constituents that were used in the
analysis of distillation-type process vents.
The three chemical constituents used in the analysis of air stripper
process vents were chosen as follows because they represent the range of
volatilities of chemicals commonly air stripped. Trichloroethylene was
selected because it was a volatile organic compound (VOC) commonly found in
contaminated ground water at Superfund sites, air stripping is commonly
used to remove it from contaminated water, and it has a midrange Henry's
law constant.* Selection of the other two constituents was made after
consulting the chemical data table in the Superfund Public Health
Evaluation Manual (SPHEM) and reviewing the Superfund Records of Decision
System (RODS) data base.6 The constituent 1,1-dichloroethylene was
eThe Henry's law constant is a measure of the diffusion of organics into
air relative to diffusion through liquids and is used in predicting
emissions for aqueous systems. A high range Henry's law constant indi-
cates that rapid volatilization will generally occur.
4-8
-------
selected from the chemicals commonly air stripped as the VOC with a higher-
range Henry's law constant, and 1,2-dichloroethane was selected as the VOC
with a low-range Henry's law constant.
4.1.5 Operating Hours
The annual operating hours assigned to the process vent model units
were based on results of EPA information requests, under RCRA 3007
authority, regarding actual waste stream distillation, steam stripping, and
air stripping operations. Hours of operation for large distillation and
steam stripping units treating waste streams were found to be best
characterized as intermittent operation at two 8-h shifts per day, 5 days
per week, and 52 weeks per year (i.e., 4,160 h/yr). Small- and medium-
sized distillation and steam stripping units, those handling less than
100,000 gal of waste per year, were found typically to operate only one
shift per day, 5 days per week, and 52 weeks per year (i.e., 2,080 h/yr).7
On the other hand, most air strippers usually are operated 24 h/day, 365
day/yr (i.e., 8,760 h/yr).8
4.2 EMISSION REDUCTIONS USING ALTERNATIVE CONTROL TECHNOLOGIES
Emission control technologies applicable to waste management unit
process vent organic emissions include condensers, carbon adsorbers,
flares, incinerators, and scrubbers. Although the emission reduction
potentially achievable by each control technology depends on the physical
parameters associated with the process vent stream and the design and
operation of the control device, the control technology options that are
feasible for application to waste management unit process vents generally
represent two levels of control: 95 percent control and 98 percent con-
trol.
Review of available information on the operations of TSDF indicates
that condensers, carbon adsorbers, and incinerators are the most widely
used air pollution control technologies and will be the technologies of
choice to reduce process vent organic emissions (see Table 3-2). Properly
designed and operated, each of these control technologies can achieve at
least a 95-percent emission reduction for most situations. However, there
are situations where a particular technology may not be applicable as a
4-9
-------
control method for a particular waste management unit process vent stream.
For example, the efficiency of a condenser depends on the physical prop-
erties of the organics being condensed, the organic concentration in the
vent stream, and the operating temperature of the condenser. As a result,
condensers are not well suited for vent streams containing organics with
low boiling points, high moisture content, large quantities of inerts
(e.g., C02 or N2), or low concentrations of organics (i.e., too low
thermodynamically to support a liquid phase). Flares are not widely used
to control waste management unit process vent emissions in part because
these streams typically contain halogenated organics. Flares are not
recommended for halogenated streams because of the corrosion caused by the
products of combustion.
The 95-percent control efficiency alternative for waste management
unit process vents is analyzed on the basis of applying a (secondary)
condenser to the vent stream as the initial choice of control technology.
This is because, in cases where condensation is feasible, condensers
provide the most cost-effective means to control organic emissions from
process vents. Condenser and other control technology cost effectiveness
is discussed in more detail later in this chapter. Because the organic
concentrations associated with air stripper process vent streams are
typically quite low (i.e., less than 100 ppm), control devices involving
condensation are not applicable to these streams. Condensers are generally
not effective for gas streams containing less than 10,000 ppmv organics.9
Because of the low organic concentration, condensation is not considered
applicable for the model units used to characterize air stripping process
vents (Model Unit Case Nos. 44 through 71).
Carbon adsorption was examined as an alternative control technology in
the emission reduction and cost analyses. A well-designed, operated, and
maintained adsorption system can achieve a 95-percent (by weight) control
efficiency for all organics under a wide variety of stream conditions over
both short-term and long-term averaging periods. The major factors affect-
ing performance of an adsorption unit are temperature, humidity, organic
concentration, volumetric flow rate, "channelling" (nonuniform flow through
the carbon bed), regeneration practices, and changes in the relative
4-10
-------
concentrations of the organics admitted to the adsorption system. A review
of plant data indicates that waste management unit process vent stream
characteristics are typically within design limits for carbon adsorbers in
terms of parameters such as gas temperatures, pressures, and velocities.
The EPA does not support assigning a higher control efficiency (i.e., 98
percent as opposed to 95 percent) to carbon adsorption units applied to
waste management unit process vents, particularly in light of the design
considerations related to controlling multicomponent vent streams when the
organic constituent mix is subject to frequent change.
Incineration also was examined as a control alternative in the
emission reduction and cost analyses. However, as noted in Section
3.2.2.3, both the vent stream volumetric flow rate and the vent stream
organic concentration can potentially limit the applicability of thermal
incinerators as process vent control devices. Because several of the
process vent model unit cases examined in this document (see Table 4-1)
have a low volumetric flow rate (i.e., <10 scfm) and/or a low organic
concentration, use of thermal incineration is not appropriate for all of
the model units. In evaluating the applicability of thermal incinerators
to the model unit cases, the desired control device efficiency was used as
the decision criterion. Maximum achievable organic destruction efficiency
decreases as inlet concentration decreases below 2,000 ppmv. Therefore,
model unit cases with process vent stream organic concentrations that
result in estimated control device efficiencies of less than 95 percent
were judged inappropriate for application of thermal incinerators (as
dedicated units) for the cost analysis. With an incinerator outlet
concentration of 20 ppmv as the lowest achievable by all new thermal
oxidizers, the 95-percent control efficiency corresponds to a minimum vent
stream concentration of about 400 ppmv. This concentration limit was
therefore used to evaluate the appropriateness of applying a thermal
incinerator to each vent stream case.
The model unit volumetric flow rates (see Section 4.1) fall into two
groups or vent classes. The high flow rates (Model Unit Case Nos. 44
through 71) are within typical thermal incinerator design specifications
(i.e., >500 scfm) for minimal flow. However, because organic
4-11
-------
concentrations for these streams are below 400 ppmv, thermal incineration
is not considered appropriate for these cases. For analysis of the low-
flow model units (Model Unit Case Nos. 1 through 43), natural gas and air
can be added to the stream to maintain the desired minimum temperature and
residence time to compensate for application of an oversized incineration
chamber. However, dilution of these vent streams to 500 scfm results in
many of the process vent model unit cases having organic concentrations of
less than 400 ppmv, the limit for acceptable control device efficiency.
Therefore, thermal incineration is not considered applicable in many of
these cases.
In general, a tradeoff exists between the higher capital costs of
catalytic incinerators and the higher operating costs of thermal
incinerators. Thermal units typically require more auxiliary fuel than
catalytic units and operate at temperatures that are roughly 538 °C
(1,000 °F) higher. This results in a disparity in operating costs that in
some cases is enough to offset the higher capital costs of the catalytic
incinerator. Other factors also should be considered when evaluating the
applicability of thermal and catalytic incinerators for control of process
vents. For example, the 98-percent level of destruction attained by
thermal incineration may be difficult to reach by the catalytic system.
The potential for fouling of the catalyst in a catalytic system could
increase the operating expense of the unit because of the replacement cost
of the catalyst. In addition, the fluid-bed catalytic incinerator capacity
range has a higher minimum flow rate and lower maximum flow rate than the
thermal (recuperative) incinerators (i.e., 2,000 vs. 500 scfm and 25,000
vs. 50,000 scfm, respectively) for commercially available packaged units.
The limited availability of small packaged catalytic units limits their
appropriateness for low flow-rate streams such as those model unit streams
characterizing distillation process vent streams. Because of this and the
potential for catalyst fouling by chlorine and other compounds in the waste
stream, catalytic incineration was not included as a control device in this
environmental and cost impacts analysis. However, catalytic incineration
may be applicable for control of some waste management unit process vent
streams, and this alternative can be examined on a case-by-case basis.
4-12
-------
The emission reduction and cost analyses also include the option of
venting the waste management unit process vent to an existing, in-use
control device at the facility. Because the flow rates associated with the
distillation-type process vents are low (e.g., <10 scfm) , control devices
such as fixed-bed carbon adsorption units, condensers, and incinerators
would require only marginal excess capacity to accommodate introduction of
the process vent stream. For the high flow-rate process vent streams
(i.e., >2,000 scfm), the use of an existing, in-use control device such as
a condenser or carbon adsorber is less likely. However, these streams are
low organic concentration and consist principally of air; as a result, they
can be used to substitute for auxiliary air in existing incinerators,
boilers, or process heaters.
4.3 CONTROL COSTS
The capital and operating costs presented below include basic
installed equipment costs and minimum expected operation and maintenance
costs, which include operating labor requirements. Other direct or
indirect costs associated with control of organic emissions from waste
management unit process vent streams may be applicable depending on site-
specific conditions. The following general assumptions were made in
determining control costs:
All costs are presented in second-quarter 1989 dollars.
Electricity, gas, and water are readily available.
The site is readily accessible by road or railway.
No civil engineering work is required.
Closed-vent system (i.e., piping and ductwork) and control
devices are dedicated units (i.e., each device serves a
single process vent stream and is not used to control other
air pollution sources).
A net salvage value determined by the heating value for the
recovered organics is credited in computing the condenser
and regenerable carbon adsorption system control costs.
serv7ceSlif Salvage Va1ue for the used ecluipment at end of
4-13
-------
Except where noted, the following items were not included in the cost
estimates:
• Design, engineering, and contingencies
• Treatability studies or pilot-scale testing
• Site work
• Installation of utility lines
• Storage tanks, auxiliary equipment, and supplies
• Heating of vent stream
• Ambient air monitoring.
4.3.1 Condensation
The control costs for the 95-percent level of control for the model
unit cases that involve the use of condensers for organic emission control
were estimated using a chemical engineering process simulator known as
ASPEN (Advanced System for Process Engineering).10 The chemical constit-
uents and operating conditions that were used in the ASPEN runs are
provided in Table 4-3 together with the condenser efficiencies that were
calculated. The ASPEN condenser configuration consisted of (1) a floating-
head, one-pass, shel1-and-tube heat exchanger; (2) a refrigeration unit
capable of producing chilled brine at a temperature of -29 °C (-20 °F); and
(3) an optional primary water-cooled heat exchanger. The design of an
optimum condenser system for a given emission control application requires
the selection of a combination of equipment and operating conditions that
will satisfy emission control requirements at minimum total annual cost. A
change that reduces the cost of one element (e.g., condenser size) must
often be balanced against the effect it has on other costs (e.g.,
refrigeration requirements). In this design effort, the cooling
temperature of -29 °C (-20 °F) was set in ASPEN, and the heat exchanger
size was allowed to vary. Lower coolant temperatures were not examined;
chilled brine can be used down to -34 °C (-30 °F), and direct-expansion
coolants such as chlorofluorocarbons can be used at temperatures below
-34 °C (-30 °F). The final item, the water-cooled heat exchanger, is
4-14
-------
TABLE 4-3. CONDENSER OPERATING CONDITIONS USED IN COST ANALYSIS AND
CONDENSER CONTROL EFFICIENCIES PREDICTED FOR MODEL UNIT CASES
-£»
I
Case
No.
1
2
3
4
5
6
7
9
10
11
12
13
14
16
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
ME
Total flow,
scfm
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
8.3
1.2
1.2
1.2
1.2
1.2
1.2
1.2
.2
.2
.2
.2
.2
1.2
1.2
1.2
1.2
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.9
26,0
26.0
26.0
Inlet organic flow rate.
Mg/yr (Ib/h)
0.76
0.76
0.76
0.76
7.94
7.94
7.94
7.94
20.04
20.04
20.04
20.04
0.16
0.16
0.16
0.16
0.40
0.40
0.40
0.40
1.13
1.13
1.13
1.13
4.73
4.73
4.73
4.73
0.08
0.08
0.08
0.08
0.23
0.23
0.23
0.23
0.95
0.95
0.96
0.96
13.24
13,24
13.24
CHL = Methyl ene chloride.
MEK = Methyl ethyl ketone.
NC = Neglible condensation
(0.40)
(0.40)
(0.40)
(0.40)
(4.20)
(4.20)
(4 . 20)
(4.20)
(10.60)
(10.60)
(10.60)
(10.60)
(0.17)
(0-17)
(0.17)
(0.17)
(0-42)
(0.42)
(0-42)
(0.42)
(1.20)
(1-20)
(1.20)
(1.20)
(5.00)
(5.00)
(5.00)
(5.00)
(0.08)
(0.08)
(0.08)
(0.08)
(0.24)
(0.24)
(0.24)
(0.24)
(1.00)
(1.00)
(1.00)
(1.00)
(7.00)
(7.00)
(7.00)
1,1,1-TCE
TOL
ach ieved .
Constituent
ME CHL
TOL
1,1,1-TCE
MEK
ME CHL
TOL
1,1,1-TCE
MEK
ME CHL
TOL
1,1,1-TCE
MEK
ME CHL
TOL
1,1,1-TCE
MEK
ME CHL
TOL
1,1,1-TCE
MEK
ME CHL
TOL
1,1,1-TCE
MEK
ME CHL
TOL
1,1,1-TCE
MEK
ME CHL
TOL
1,1,1-TCE
MEK
ME CHL
TOL
1,1,1-TCE
MEK
ME CHL
TOL
1,1,1-TCE
MEK
TOL
MEK
1,1,1-TCE
Condenser8
efficiency, %
NC
45
16
NC
NC
96
95
87
44
98
97
96
NC
82
72
50
NC
82
89
80
26
97
96
95
87
98
98
98
NC
80
70
47
NC
95
90
83
58
98
98
96
95
95
95
Emission reduction,
Mg/yr
0.0
0.34
0.12
0 0
0 0
7 E4
7 54
6Q1
8.82
19.63
19.44
19.04
00.
0.13
0.12
0.08
0a
0.33
0.36
0.32
0.29
1.10
1.08
1.07
4.12
4.64
4.64
4.64
0.0
0.06
0.06
0.04
0.0
0.23
0.22
0.19
0.65
0.93
0.93
0.92
12.58
12.58
12.68
= 1,1,1-Tr ichloroethane.
— Toluene
at a temperature of -29 °C (-20
-------
necessary in some instances of volatile organic condensation to reduce the
size of the refrigeration unit or to remove water vapor and avoid freezing
problems. In this design effort, removal of water vapor prior to organics
condensation is included to prevent ice buildup on heat transfer surfaces.
The ASPEN's cost correlation for heat exchangers, developed originally
for plant-scale processes, does not extend to the low flows examined for
distillation-type waste management unit process vents. Therefore, vendor
quotes for condenser costs were added to the ASPEN to allow cost scaling by
condenser area for the low-flow cases (i.e., the distillation-type vents,
Model Unit Case Nos. 1 through 43). Model Unit Case Nos. 44 through 71
were not examined because of the low organic concentrations in the vent
streams.
As shown in Table 4-3, in only 18 of the 43 model unit cases examined
was a removal efficiency of 95 percent achievable at the condenser
conditions examined (i.e., a coolant temperature of -29 °C [-20 °F]).
Figure 4-1 presents a graphic comparison of achievable condenser
efficiencies versus vent gas concentration for the four chemical
constituents analyzed at the selected condenser operating conditions.
This illustrates the point, made previously in the Chapter 3.0 discussion
on condensers, that condensation is not universally applicable to all waste
management unit process vents. Again, this is because the efficiency of
vent condensers depends on the physical properties of the organics being
condensed, the organic concentration in the vent stream, and the operating
temperature of the condenser. It should also be pointed out that other
condenser designs may achieve different efficiencies than those reported in
this analysis. For example, if a coolant temperature of -34 °C (-30 °F) or
less had been used instead of -29 °C [-20 °F], slightly higher efficiencies
might have been attained for some of the model unit cases, but capital and
operating costs would have increased significantly.
4.3.1.1 Condenser Capital Costs.11 The design condenser area, as
calculated by ASPEN, is used in estimating capital costs. A 25-percent
overdesign factor was added to the calculated (theoretical) condenser area
to determine the base equipment cost. Instrumentation costs were estimated
at 10 percent of the base equipment cost. Sales tax and freight were
4-16
-------
0>
o
I
I
o
o
0%
0.0%
4.0%
8.0%
12.0% 16.0% 20.0% 24.0% 28.0% 32.0%
Organic concentration in vent stream (VOL %)
Figure 4-1. Condenser efficiency for distillation-type process vents as a function of organic concentration
(Note: Condenser operating at a coolant temperature of -20°F.)
-------
estimated at 8 percent of base equipment cost plus instrumentation costs.
The purchased equipment cost was determined as the sum of the base equip-
ment cost, instrumentation costs, sales tax, and freight. Total installa-
tion costs were estimated at 67 percent of the purchased equipment cost:
Total capital investment for the condensers was calculated as purchase cost
plus installation cost. The total capital investment, total annualized
cost, and cost effectiveness (i.e., $/Mg of organic controlled) for this
control technology alternative are presented in Table 4-4.
4.3.1.2 Condenser Annualized Costs.12'13 The total annualized costs
are the sum of the annual operating costs and the capital recovery costs.
Annual operating costs consist of costs for electricity, labor, supervisory
labor, labor overhead, taxes, insurance, administration, and maintenance
parts. Capital recovery costs are calculated by multiplying total capital
costs by the capital recovery factor of 0.16275 (10-percent capital
recovery for a 10-year service life).
The procedures and assumptions used by the ASPEN condenser design and
costing algorithm in calculating the annual operating costs are described
below. Electricity costs are calculated by multiplying the estimated
electricity use by the price of electricity. Annual labor costs are
calculated by multiplying the number of labor hours required by the labor
wage rate. Supervisory (and administrative) labor is estimated at 15
percent of operating (or direct) labor costs. Total annual maintenance
costs, including maintenance materials and maintenance labor, are estimated
at 3 percent of total capital investment. Labor overhead equals 60 percent
of the total of operating, supervisory, and maintenance labor. Finally,
total annual labor costs equal the sum of operating (direct) labor,
supervisory/administrative labor, maintenance labor, and labor overhead.
The annual cost of taxes, insurance, and administration equals 4 percent of
total capital investment. In addition, recovery credits are provided for
the value of recovered organics captured by condensation using the net
salvage value (i.e., heating value) of the recovered organics.
4.3.2 Carbon Adsorption
Carbon adsorption was also examined as the control technology for the
emission reduction and cost analysis for the 95-percent organic reduction
4-18
-------
TABLE 4-4. SUMMARY CONTROL COSTS FOR CONDENSER CONTROL ALTERNATIVE
-fs.
I
Case
No.
1
2
3
4
5
6
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Vent
class
D
0
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
0
0
D
D
D
D
D
D
Emission
rate,
Ib/h
0.40
0.40
0.40
0.40
4.20
4.20
4.20
4.20
10.60
10.60
10.60
10.60
0.17
0.17
0.17
0.17
0.42
0.42
0.42
0.42
1.20
1.20
1.20
1.20
5.00
5.00
5.00
5.00
0.08
Const! tuent
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
Control device
efficiency, X
NC
45
16
NC
NC
95
95
87
44
98
97
95
NC
82
72
50
NC
82
89
80
26
97
96
95
87
98
98
98
NC
Emission
reduction,
Mg/yr
0.0
0.34
0.12
0.0
0.0
7.54
7.54
6.91
8.82
19.63
19.44
19.04
0.0
0.13
0.12
0.08
0.0
0.33
0.36
0.32
0.29
1.10
1.08
1.07
4.12
4.64
4.64
4.64
0.0
TCI,
1989 t
5,670
5,550
8,480
7,510
8,800
8,340
12,090
10,240
13,180
2,040
1,940
1,990
2,040
2,220
2,480
2,250
3,460
2,960
3,690
5,690
5,840
4,900
7,040
TAC, S/yr
3,070
3,150
450
240
810
(150)
(4,190)
(4,520)
(3,700)
2,380
2,360
2,390
2,290
2,310
2,390
2,350
2,250
2,150
2,320
1,380
1,180
960
1,440
Cost
effectiveness,8
S/Mg
"
9,030
26 , 250
60
30
120
(20)
(210)
(230)
(190)
18,310
19,670
29,880
6,940
6,420
7,470
8,100
2,050
1,990
2,170
330
250
210
310
...
(continued)
-------
TABLE 4-4 (continued)
I
ix>
o
Case
No.
30
31
32
33
34
35
36
37
36
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
Vent
class
D
D
D
0
0
D
D
D
D
D
D
D
D
D
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Emission
rate,
Ib/h
0.08
0.08
0.08
0.24
0.24
0.24
0.24
1.00
1.00
1.00
1.00
7.00
7.00
7.00
0.10
0.50
1.50
5.00
0.10
0.60
1.50
5.00
0.10
0.50
1.50
5.00
0.10
10.00
0.10
10.00
i
Constituent
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
TOL
MEK
1,1,1-TCE
TCE
TCE
TCE
TCE
DCE
DCE
DCE
DCE
EDC
EDC
EDC
EDC
TCE
TCE
DCE
DCE
Control device
efficiency, %
80
70
47
NC
95
90
83
68
98
98
96
95
96
95
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
Emission
reduction,
Mg/yr
0.06
0.06
0.04
0.0
0.23
0.22
0.19
0.55
0.93
0.93
0.92
12.58
12.58
12.58
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
TCI,
1989 S TAC, S/yr
1,370 2,250
1,300 2,240
1,340 2,260
—
1,710 2,260
1,540 2,220
1,740 2,280
2,130 2,200
2,710 2,150
2,410 2,100
3,140 2,260
4,320 (3,640)
3,750 (3,770)
2,950 (4,050)
Cost
effectiveness,8
S/Mg
37,500
37,330
56 , 500
— —
9,830
10,090
12,000
4,000
2,310
2,260
2,460
(280)
(300)
(320)
(continued)
-------
Case
No.
60
61
62
63
64
65
66
67
68
69
70
71
-P»
ro
i— >
ME
Emiss ion
Vent rate,
class Ib/h Constituent
.. . .
A
D
CHI
OCE
tuc
MbK
IUL
A
A
A
A
A
A
A
A
A
A
A
A
=
=
=
=
=
1,1,1-TCE =
ICE
111
TAC
NC
NA
=
=
=
0.10 EDC
1 . 50 EDC
10.00 EDC
0.50 TCE
5.00 TCE
10.00 TCE
0.50 DCE
6.00 DCE
10.00 DCE
0 . 50 EDC
6.00 EDC
10.00 EDC
Air-stripper-type vents (i .
Distillation-type vents (i.
Methyl ene chloride.
0 i chl oroethy 1 ene.
1, 2-0 ichl oroethane.
Methyl ethyl ketone.
To luene.
1,1, 1-Tr i ch 1 oroethane .
Tr i ch 1 oroethy 1 ene .
Total capital investment in
organ ics.
Negligible condensation.
Emission Cost
Control device reduction TCT ** ^.
aff;_- „_„ ~ a i '*••*•• effectiveness,8
efficiency, K Mg/yr 1989 3 TAC, S/yr $/Ma
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
e., high flow rates).
e. , low flow rates) .
second-quarter 1989 dol
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
lars.
Bcond-quarter 1989 dollars per year; includes a credit for recovered
= Not appropriate; condensation was not considered an
the model unit vent stream.
appropriate or feasible control technology for
aCost effectiveness = TAC/emission reduction
Manual. Vo,ume2. OOE/MC/16481-1202.
-------
or control efficiency. Carbon adsorption costs were estimated using EPA's
OAQPS Control Cost Manual (OCCM) (EPA 450/3-90-006, January 1990)14
together with vendor price quotations. Carbon adsorption system costs were
obtained from two leading manufacturers for both regenerative and
nonregenerative carbon systems based on the model unit parameters such as
volumetric flow rate and organic emission rate. These vendor costs were
used for comparison with the costs estimated using the cost manual as a
test for reasonableness.
When treating low organic concentration process vent streams with
carbon adsorption technology, consideration must be given to the type of
system required. Carbon adsorbers that make one-time use of the carbon
(i.e., nonregenerative systems) or carbon adsorbers that regenerate the
carbon onsite for reuse can have cost and/or technical advantages depending
on the vent stream conditions. The organic concentration and flow rate
where nonregenerative carbon use becomes preferable to a regenerative
system on technical and economic grounds is very situation-specific. The
information presented in this document is therefore a generalization, and
specific comparisons are good only for the stated conditions.
The regenerative unit is fully automated and generally has low
operating costs (mostly utilities); however, regenerative systems have a
much higher initial capital cost and therefore incur large fixed costs due
to capital recovery, maintenance, taxes, and insurance. On the other hand,
the nonregenerative unit has a low initial capital cost, but high operating
costs for carbon replacement or offsite carbon regeneration. In each case,
the total annualized costs for each type of system (regenerative or
nonregenerative) were compared to determine whether a regenerative or
nonregenerative system should be used in the analysis. The system with the
lowest total annualized cost is presented in the analysis results.
4.3.2.1 Carbon Adsorption Capital Costs.15,16 The capital cost for a
carbon adsorber is a function of the volumetric flow rate, the type and
mass emission rate of the pollutant, the length of the adsorption and
regeneration cycles, and the adsorption capacity of the carbon at operating
conditions. Capital costs for the regenerative carbon system include the
carbon tanks (two or three depending on stream conditions), carbon, fans,
4-22
-------
ductwork, organic vapor monitor, steam boiler, and air compressor. Capital
costs for nonregenerative systems include ductwork, fans, organic vapor
monitor, and carbon exchange setup charges (i.e., replacement contract
charges). Equipment installation is also included as a percentage (i.e.,
67 percent) of the purchased equipment costs. The total capital
investment, total annualized cost, and cost effectiveness (i.e., $/Mg of
organic controlled) for this control technology alternative are presented
in Table 4-5.
4.3.2.2 Carbon Adsorption Annualized Costs.17.18 The annual
operating costs for carbon adsorbers were estimated as follows. Utility
costs were estimated using the equations in the OCCM. Maintenance labor
was estimated at 0.5 h per shift at a cost of $13.20/h, and maintenance
materials were estimated at 100 percent of maintenance labor. Taxes and
insurance and administration were each estimated at 2 percent of total
capital cost (a total of 4 percent). Operating labor was estimated at
1 h/d at $20/h (including labor overhead charges). Steam costs are
calculated at 0.5 Ib of steam required to strip 1.0 Ib of carbon at a cost
of $6/1,000 Ib of steam. Capital recovery costs are calculated by
multiplying total capital costs by the capital recovery factor of 0.16275
(10 percent for 10 years). Carbon costs for nonregenerative systems are
calculated using the working capacity of carbon for each constituent, the
organic flow rate, and an average carbon cost of about $2/lb (exchange
cost).
4.3.3 Thermal Incineration
The cost analysis for the 98-percent level of control is based on the
use of thermal incineration as the control technology for each waste
management process vent model unit case. Catalytic incinerators and flares
can also achieve 98-percent control but are not recommended for halogenated
streams because such streams may cause corrosion, fouling, or scaling
problems, significantly shortening the life of the control device or
greatly increasing operating costs. Five of the seven constituents
specified for the model unit cases are halogenated; therefore, thermal
incinerators rather than catalytic incinerators are costed for the model
4-23
-------
TABLE 4-5. SUMMARY CONTROL COSTS FOR CARBON ADSORPTION CONTROL ALTERNATIVE
-P*
I
ro
Case
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Vent
c lass
D
D
D
D
D
D
0
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
0
D
Emission
rate,
Ib/h
0.40
0.40
0.40
0.40
4.20
4.20
4.20
4.20
10.60
10.60
10.60
10.60
0.17
0.17
0.17
0.17
0.42
0.42
0.42
0.42
1.20
1.20
1.20
1.20
5.00
5.00
5.00
5.00
0.08
Const! tuent
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
Carbon system
N
N
N
N
R
R
R
R
R
R
R
R
N
N
N
N
N
N
N
N
R
R
R
R
R
R
R
R
N
Emi ssion
reduction,
Mg/yr
0.72
0.72
0.72
0.72
7.54
7.54
7.64
7.64
19.04
19.04
19.04
19.04
0.15
0.15
0.15
0.15
0.38
0.38
0.38
0.38
1.08
1.08
1.08
1.08
4.49
4.49
4.49
4.49
0.07
TCI,
1989 S
1,180
1,180
1,180
1,180
227,000
227,000
227,000
227,000
217,000
217,000
217,000
217,000
1,180
1,180
1,180
1,180
1,180
1,180
1,180
1,180
218,000
218,000
218,000
218,000
226,000
226,000
226,000
226,000
1,180
TAC, S/yr
19,870
26,730
14,290
24,410
69,810
69,810
69,810
69,810
62,430
62,430
62,430
62,430
8,440
11,360
6,070
10,370
20,770
28,070
14,180
26,260
66,910
66,910
66,910
66,910
67,380
67,380
67,380
67,380
3,970
Cost
effect i veness , *
S/Mg
27,650
37,200
19,890
33,970
9,260
9,260
9,260
9,260
3,280
3,280
3,280
3,280
55,280
74 , 400
39,760
67,910
55,060
74,410
37 , 590
69,590
61,950
61,950
61,950
61,950
16,010
15,010
15,010
15,010
55,250
(continued)
-------
TABLE 4-5 (continued)
I
ro
LTl
Case
No.
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
Vent
c lass
D
D
0
D
D
D
D
D
D
D
D
D
D
D
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Emi ssion
rate,
Ib/h
0.08
0.08
0.08
0.24
0.24
0.24
0.24
, 1.00
1.00
1.00
1.00
7.00
7.00
7.00
0.10
0.50
1.50
5.00
0.10
0.50
1.50
5.00
0.10
0.50
1.50
5.00
0.10
10.00
0.10
10.00
Constituent
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
TOL
MEK
1,1,1-TCE
TCE
TCE
TCE
TCE
DCE
DCE
DCE
DCE
EDC
EDC
EDC
EDC
TCE
TCE
DCE
DCE
Carbon system
N
N
N
N
N
N
N
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
Emission
reduction,
Mg/yr
0.07
0.07
0.07
0.22
0.22
0.22
0.22
0.90
0.90
0.90
0.90
12.57
12.57
12.57
0.38
1.89
5.67
18.91
0.38
1.89
5.67
18.91
0.38
1.89
5.67
18.91
0.38
37.83
0.38
37.83
TCI,
1989 9
1,180
1,180
1,180
1,180
1,180
1,180
1,180
219,000
219,000
219,000
219,000
216,000
216,000
216,000
216,000
216,000
216,000
214,000
216,000
216,000
216,000
214,000
216,000
216,000
216,000
214,000
292,200
289,000
292 , 200
289,000
TAC, S/yr
5,340
2,860
4,880
1 1 , 990
16,040
9,050
14,930
65,200
65 , 200
65,200
65,200
65,040
65,040
65,040
85,730
85,050
83,450
77,400
85,730
85,050
83,450
77,400
85,730
85,050
83,450
77,400
101,830
85,980
101,830
85 , 980
Cost
effect! veness,8
*/Mg
74,320
39,800
67,910
55,620
72,900
41,980
69,260
72,440
72,440
72,440
72,440
6,170
5,170
5,170
225,600
45,000
14,700
4,100
225,600
45,000
14,700
4,100
225,600
45,000
14,700
4,100
268,000
2,300
268,000
2,300
(continued)
-------
TABLE 4-5 (continued)
ro
CTl
Case Vent
No. class
60
61
62
63
64
65
66
67
68
69
70
71
1,1
A
A
A
A
A
A
A
A
A
A
A
A
A =
D =
ME CHI =
DCE =
EDC =
N =
MEK =
R =
TOL =
,1-TCE =
TCE =
TCI =
TAC =
Emission
rate, reduction,
Ib/h Constituent Carbon system Mg/yr
0.10 EDC
1 . 50 EDC
10.00 EDC
0.50 TCE
6 . 00 TCE
10.00 TCE
0.50 DCE
5.00 DCE
10.00 DCE
0 . 50 EDC
5.00 EDC
10.00 EDC
Air-stripper-type vents
Distillation-type vents
Methyl ene chloride.
Dich loroethy lene.
1 , 2-D i ch 1 oroethane .
R
R
R
R
R
R
R
R
R
R
R
R
(i.e., high f 1 ow
(i.e., 1 ow f 1 ow
Nonregenerable carbon absorption system
Methyl ethyl ketone.
Regenerable, fixed-bed
Toluene.
1,1, 1-Tr i ch 1 oroethane .
Tr ich loroethy lene.
carbon adsorption
0.38
6.67
37.83
1.89
18.91
37.83
1.89
18.91
37.83
1.89
18.91
37.83
rates) .
rates) .
TCI,
1989 S
292 , 200
291,000
289,000
445,000
460,000
460,000
445,000
460,000
460,000
445,000
460,000
460,000
TAC, l/yr
101,830
99,450
85,980
141,150
137,500
128,980
141,150
137,500
128,980
141,150
137,500
128,980
Cost
effect i veness , a
S/Mg
268,000
17,500
2,300
74 , 700
7,300
3,400
74 , 700
7,300
3,400
74 , 700
7,300
3,400
(e.g., carbon canisters).
system.
Total capital investment in second-quarter 1989 dollars.
Total annualized costs
in second-quarter
1989 dol lars per
year.
•Cost effectiveness = TAC/emission reduction.
Note: The technical feasibility of using regenerable carbon adsorption systems for control of very low
concentration streams is uncertain; the concentration at which regenerative systems are not considered to
be technically feasible (i.e., capable of achieving the desired control efficiency) depends on the
hydrocarbon being adsorbed and the flow rate, temperature, and relative humidity of the stream fed to the
adsorber.
Source: U.S. Environmental Protection Agency, QAQPS Control Cost__Manya I . Fourth Ed. Office of Air Quality
Planning and Standards. Research Triangle Park, NC. Publication No. EPA-450/3-90-006. January 1990.
-------
unit cases to put the costs on a common basis. The total capital invest-
ment, total annualized cost, and cost effectiveness for those model unit
cases for which a 95-percent or greater destruction efficiency is 'estimated
to be achievable are presented in Table 4-6.
The background information document (BID) for the proposed standards
for distillation operations in the Synthetic Organic Chemical Manufacturing
Industry (SOCMI)19 presents a series of capital cost equations that include
purchase costs and installation costs for thermal incinerators,
recuperative heat exchangers, ductwork, fans, and stacks and support
structures for the ductwork. Equations are available for two incineration
temperatures, 870 °C (1,600 °F) and 1,100 °C (2,000 °F), for application to
either halogenated or nonhalogenated streams. For halogenated streams, the
purchase and installation costs of waste heat boilers and flue gas
scrubbers are also included. The equations use capital cost data obtained
from vendor quotations. Heat and material balance also are analyzed to
estimate annualized costs for incinerators and incinerator/scrubber
systems. A FORTRAN computer program (the SOCMI incinerator/flare costing
algorithm), which incorporates the incinerator cost equations, was used to
generate both capital and annualized cost estimates for the model unit vent
streams. The general design specifications that serve as the basis for the
cost estimates are presented in Table 4-7.
The main data input file to the SOCMI incinerator/flare costing
algorithm that was used to estimate thermal incineration costs included
information on each process vent model unit case. The required information
included vent stream flow rate (scfm), vent stream heating value (Btu/scf),
organic flow rate (Ib/h), halogenation status (halogenated or nonhalogen-
ated), and stream molecular weight (Ib/lb-mol). Table 4-1 lists vent
stream flow rate, organic flow rate, and constituent for each model unit
case examined in the analysis. The heat of combustion of each constituent
also was needed to calculate vent stream heating value. Table 4-2 presents
the heat of combustion for each of the seven constituents used in the model
unit cases. In calculating each stream molecular weight, it was assumed
that the nonorganic portion of each stream was air.
4-27
-------
TABLE 4-6. SUMMARY CONTROL COSTS FOR THERMAL INCINERATION CONTROL ALTERNATIVE"
i
ro
oo
Case
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
16
16
17
18
19
20
21
22
23
24
25
26
27
28
29
Vent
c lass
D
D
D
0
D
D
D
D
D
0
D
D
D
D
D
0
0
0
D
D
D
D
D
D
0
D
D
D
D
Emission
rate,
Ib/h
0.40
0.40
0.40
0.40
4.20
4.20
4.20
4.20
10.60
10.60
10.60
10.60
0.17
0.17
0.17
0.17
0.42
0.42
0.42
0.42
1.20
1.20
1.20
1.20
5.00
5.00
5.00
5.00
0.08
Emission reduction
Constituent Mg/yr
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
NA
NA
NA
NA
7.65
7.63
7.78
7.70
19.64
19.64
19.59
19.64
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
4.59
4.57
4.50
4.61
NA
TCI, 1989 3
—
—
1,319,530
464,850
1,319,530
464,850
1,319,530
464,850
1,319,530
464,850
—
—
—
—
—
—
—
—
—
—
—
—
1,319,530
464 , 850
1,319,530
464,850
«
Cost
effect i veness , "
TAC, S/yr $/Mg
—
—
600,060
205 , 280
600,030
205,570
599,860
203,070
599,780
203,810
—
—
—
—
—
—
—
—
—
—
—
—
525,460
201,750
525,440
201,930
"
—
—
78,440
26,900
77,100
26 , 700
30,540
10,340
30,620
10,380
— —
__
~~
"~~
~~"
— —
- —
— —
— ~
— —
114,480
44,150
116,760
43,860
(continued)
-------
TABLE 4-6 (continued)
i
ro
10
- - -
Case
No.
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
___ _.
Vent
class
D
D
0
D
D
D
D
0
0
0
D
D
D
D
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Emission
rate,
Ib/h
0.08
0.08
0.08
0.24
0.24
0.24
0.24
1.00
1.00
1.00
1.00
7.00
7.00
7.00
0.10
0.50
1.50
5.00
0.10
0.50
1.50
5.00
0.10
0.50
1.50
5.00
0.10
10.00
0.10
10.00
^ ....
Const! tuent
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
TOL
MEK
1,1,1-TCE
TCE
TCE
TCE
TCE
OCE
DCE
DCE
OCE
EDC
EDC
EDC
EDC
TCE
TCE
OCE
DCE
Emission reductior
Mg/yr
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
12.93
12.97
12.79
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
>i
TCI, 1989 S TAC, S/yr
--
~" ~~
464,850 204,310
464 , 860 204 , 800
1,319,530 599,920
— — ....
~~ ——
~~ — —
~"~ — —
~~ ——
~°~ ~~
"~~ ——
~"~ ~ —
--
Cost
effectiveness,^
S/Mg
—
—
15,800
16,790
46,900
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
(continued)
-------
TABLE 4-6 (continued)
i
Co
O
Case
No.
60
61
62
63
64
65
66
67
68
69
70
71
ME
Vent
class
A
A
A
A
A
A
A
A
A
A
A
A
A =
D =
DCE =
EDC =
CHI =
MEK =
NA =
TAC =
1,1,1-TCE =
TCE =
TCI =
TOL =
. . Cost
rate!" Emission reduction, effectiveness^
Ib/h Constituent Mg/yr TCI, 1989 $ TAC, S/yr S/Mg
0.10 EDC
1 . 50 EDC
10.00 EDC
0.50 TCE
5.00 TCE
10.00 TCE
0 . 50 DCE
5.00 DCE
10.00 DCE
0 . 50 EDC
5 . 00 EDC
10.00 EDC
Air-stripper-type vents (i
Distillation-type vents (i
D i ch 1 oroethy 1 ene .
1 , 2-D i ch 1 oroethane .
Methyl ene chloride.
Methyl ethyl ketone.
Not appropriate because of
Total annual) zed costs in
1 , 1 , 1-Tr i ch 1 oroethane .
Tr i ch 1 oroethy 1 ene .
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
NA
.e. , high f low rates) .
.e., low flow rates).
low vent stream volumetric flow rate or low vent stream organic content
second-quarter 1989 dollars per year.
Total capital investment in second-quarter 1989 dollars.
Toluene.
ain all cases, the control device analyzed is a thermal incinerator, estimated to attain at least a 95-percent
destruction efficiency.
bCost effectiveness = TAC/emission reduction.
Source- U S. Environmental Protection Agency. The SOCMI Incinerator/Flare Costing Algorithm. Distillation
Operations in Synthetic Organic Chemical Manufacturing—Background Information for Proposed Standards.
Office of Air Quality Planning and Standards. Research Triangle Park, NC. Publication No. EPA-450/3-
83-005a. December 1983.
-------
TABLE 4-7. INCINERATOR GENERAL DESIGN SPECIFICATIONS
I
CO
Item
Emission control efficiency
Minimum incinerator volume'
Incineration temperature
• Low-temperature incineration
• High-temperature incineration"
Furnace residence times
• Low-temperature incineration
* High-temperature incineration
Primary fuel requirement
Supplemental fuel requirement (h = vent
stream heating value in MJ/Nm3 (Btu/scf)
• 0 < h < 1.9 (0 < h < 50)
• 1.9 3.7 (h > 100)
Recuperative heat exchanger
• Overall heat transfer coefficient
Scrubber system
• Type
* Packing height
• Liquid/gas ratio
• Gas velocity
* Scrubber gas temperature
Specif icat ion
98-percent destruction
1.01 m3 (36.7 ft3)
870 °C (1,600 °F)
1,100 °C (2,000 °F)
0.75 s
1.00 s
Fuel required to maintain incinerator temperature
with 18 percent excess air
Required for flame stability
Add 0.38 MJ/Nm3 (10 Btu/scf)
Add 10 percent of stream heating value
No supplemental fuel required
Not applicable when vent stream heating value is sufficient to
maintain design incinerator temperature
23 W/m2«K (4.0 Btu/h»ft2*°F)
Used when corrosive VOC is present
Packed tower
11.0 m (36.0 ft)
1,337 L/m3 (10 gal/scf)
0.9 m/s (3.0 ft/s)
100 °C (212 °F)
alf calculated incinerator combustion chamber volume is less than 1.0 m3 (35.7 ft3), natural gas and air are
added to maintain the design temperature and residence time for a 1.01-m3 (35.7-ft3) incinerator volume.
when corrosive volatile organic compounds (VOC) are present due to the difficulty of achieving complete
combustion of corrosive VOC at lower temperatures.
Source: U.S. Environmental Protection Agency. Distillation Operations in Synthetic Organic Chemical
Manufacturing—Background Information for Proposed Standards. Office of Air Quality Planning and
Standards. Research Triangle Park, NC . Publication No. EPA-450/3-83-005a . December 1983. p. 8-4.
-------
4.3.3.1 Thermal Incineration Capital Costs. The design process vent
flow rate is used in estimating capital costs. Packaged, single-unit
thermal incinerators typically can be built to control streams with flow
rates up to about 24 Mm3 (50,000 scfm). Therefore, the number of incinera-
tors required to destroy the vent gas organics is calculated by dividing
the design flow rate by the maximum size incinerator flow rate. In the
SOCMI incinerator/flare costing algorithm, the maximum incinerator flow
rate for all halogenated streams equals 50,000 cfm. The maximum
incinerator flow rate for nonhalogenated streams with heating values less
than or equal to 52,000 Btu/ft3 is 44,000 cfm. All nonhalogenated streams
with heating values greater than 52,000 Btu/ft3 have a corresponding
maximum incinerator flow rate of 50,000 cfm. The greatest model unit flow
rate is 16,400 cfm; therefore, none of the process vent model units would
require more than one incinerator.
Total capital costs for the incinerators and supporting equipment
consist of the sum
-------
of 1.4521. duct capital costs by a factor of 1.8188, and pipe rack capital
costs by a factor of 1.2213.
Use of the SOCMI algorithm required that costs be scaled over a
relatively long time, which has the potential for increasing the
uncertainty of the derived values. More recent cost estimating protocols,
such as the OCCM, are available for thermal incinerators but do not include
the cost of flue gas scrubbers, which, because of the high percentage of
chlorinated wastes in the model units, are a necessary part of the
incineration system. The requirement for acid-gas scrubbers led to the use
of the SOCMI procedure as the vehicle for estimating thermal incineration
costs.
A simple test of the SOCMI algorithm as a means of estimating current
incineration costs was conducted by using the OCCM to estimate the cost of
an incinerator for one of the waste management process vent model units.
The costs derived with the OCCM procedure were compared with the
incinerator costs, exclusive of scrubber costs, derived with the SOCMI
algorithm. The agreement between the two costs was reasonable, which would
imply that the SOCMI algorithm generated representative and reasonable
costs even though the costs were scaled over a relatively long time.
Although the cost comparison is not rigorous and cannot be construed as a
verification of the SOCMI algorithm, the good agreement between the two
results provides a small measure of increased confidence in the validity of
the incineration cost estimates derived from the SOCMI algorithm.
4'3-3'2 Thermal Incineration Annualized Costs. The total annualized
costs are the sum of the direct operating and maintenance costs and the
annualized capital costs. Direct operating and maintenance costs consist
of utilities, labor, supervisory labor, labor overhead, taxes, insurance
and administration, and maintenance parts. Utility requirements include
electricity (for fans and pumps) and natural gas to supplement the heating
value of many vent streams and to maintain the pilot flame. Annualized
capital costs are calculated by multiplying total capital costs by the
capital recovery factor of 0.16275 (i.e., 10 percent for 10 years).
The procedures and assumptions used in the SOCMI incinerator/flare
costing algorithm to calculate the annual operating costs are described as
4-33
-------
follows. Natural gas costs are determined by multiplying the natural gas
price by the amount of natural gas consumed. Similarly, electricity costs
are calculated by multiplying electricity use by the price of electricity.
Annual labor costs are calculated by multiplying the number of labor hours
required per incinerator by the labor wage rate and by the number of incin-
erators required per vent stream. Supervisory labor is 15 percent of
operating labor costs. Maintenance labor is equal to 3 percent of total
capital costs. Labor overhead equals 80 percent of the total of operating,
supervisory, and maintenance labor. Finally, total annual labor costs
equal the sum of operating labor, supervisory labor, maintenance labor, and
labor overhead. The annual cost of taxes, insurance, and administration
equals 4 percent of total capital costs, and total annual maintenance costs
equal 3 percent of total capital costs. The following table presents the
cost factors used in calculating the annual operating costs.
Cost component
Natural gas
Electricity
Operating labor
Water
Caustic soda
Cost factor, $
3.34/109 joules
0.0472/kWh
14.60/h
1.00/103 gal
0.28/lb
Reference
24
25
26
27
28
In addition to the costs described above, the annual operating costs
for incinerators for halogenated vent streams include a heat recovery
credit, quench water, scrub water, and neutralization. The heat recovery
credit is only applicable for streams with flows exceeding 700 scfm. When
the vent stream flow rate exceeds 700 scfm, the heat recovery credit is a
function of the operating flow rate and the price of natural gas. The
annual costs of both quench and scrub water are a function of the price of
water and the operating flow rate. Finally, neutralization costs are a
function of the price of caustic and the operating flow rate.
4-34
-------
4-3.4 Vent to Existing Control Device
In addition to analyzing the emission reduction and cost impacts based
on the purchase and installation of new, dedicated add-on control devices
for process vents, the costs for venting the process stream to an existing
in-use control device were also estimated. Existing control devices
capable of handling waste management process vent emissions include
existing condensers, carbon adsorption units, and thermal or catalytic
incinerators that have sufficient excess capacity to handle introduction of
the vent stream. High flow-rate process vent streams can be substituted
for auxiliary air in combustion devices such as incinerators, boilers, and
process heaters. Table 4-8 presents the total capital investment, total
annualized cost, and cost effectiveness (i.e., $/Mg of organic controlled)
for venting to an existing control device.
4-3-4'1 Capital Cost to Vent to Existing Control Device. The capital
cost for venting an existing process vent to an existing in-use control
device includes the purchase costs and installation costs for vent piping
and a flame arrestor. For each process vent model unit, 200 ft of vent
piping and one flame arrestor were included; instrumentation costs were not
included. The base equipment purchase costs are in second-quarter 1989
dollars. The total capital investment includes sales tax and freight,
direct installation costs, and indirect installation costs.
Direct installation costs include foundation and supports, piping,
electrical, handling and erection, painting, insulation, and site
preparation and buildings. Indirect installation costs include
engineering, construction and field expenses, contractor fees, startup and
testing, and contingencies.
4'3'4-2 Annualized Cost to Vent to Existing Control Device. The
total annualized costs to vent to an existing in-use control device consist
of direct operating and maintenance costs and the annualized capital costs
It was assumed that the process vents were going into a negative static
pressure header system to the existing control device; therefore, no flow-
inducing device (e.g., fan) is necessary. A requirement of 1 h/yr of
maintenance labor was estimated at a rate of $13.20/h and the cost of
maintenance materials was calculated as 100 percent of the cost of
4-35
-------
TABLE 4-8. SUMMARY CONTROL COSTS FOR VENTING TO AN EXISTING CONTROL DEVICE*
I
OJ
cn
Case Vent
No. class
1
2
3
4
5
g
7
8
g
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
0
D
D
D
D
D
0
D
D
D
D
D
D
D
D
D
D
D
D
D
0
o
D
D
D
D
D
0
D
Emi ssion
rate,
Ib/h
0.40
0.40
0.40
0.40
4.20
4.20
4.20
4.20
10.60
10.60
10.60
10.60
0.17
0.17
0.17
0.17
0.42
0.42
0.42
0.42
1.20
1.20
1.20
1.20
5.00
5.00
5.00
5.00
0.08
Constituent
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
Emission reduction,
Mg/yr
0.74
0.74
0.74
0.74
7.78
7.78
7.78
7.78
19.64
19.64
19.64
19.64
0.16
0.16
0.16
0.16
0.39
0.39
0.39
0.39
1.11
1.11
1.11
1.11
4.63
4.63
4.63
4.63
0.07
TCI, 1989 $ TAC, $/yrb
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
effect! veness,b
S/Mg
530
530
530
530
50
50
50
50
20
20
20
20
2,440
2,440
2,440
2,440
1,000
1,000
1,000
1,000
350
350
350
350
85
85
85
85
5,570
(continued)
-------
TABLE 4-8 (continued)
-- -" - — __ - - - — — — ___ — .
Case
No.
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
Vent
c lass
0
D
0
D
0
D
D
D
D
D
D
0
0
D
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Emission
rate,
Ib/h
0.08
0.08
0.08
0.24
0.24
0.24
0.24
1.00
1.00
1.00
1.00
7.00
7.00
7.00
0.10
0.50
1.50
5.00
0.10
0.50
1.50
5.00
0.10
0.50
1.50
5.00
0.10
10.00
0.10
10.00
Constituent
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
TOL
MEK
1,1,1-TCE
TCE
TCE
TCE
TCE
DCE
DCE
DCE
DCE
EDC
EDC
EDC
EDC
TCE
TCE
DCE
DCE
Emission reduction,
Mg/yr
0.07
0.07
0.07
0.22
0.22
0.22
0.22
0.93
.93
0.93
0.93
12.97
12.97
12.97
0.39
.95
.Ob
19.61
0. 39
1.95
5.85
19.51
0.39
.95
5.85
19.51
0.39
39.02
0.39
39.02
TCI, 1989 $
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
TAC, $/yr»>
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
390
Cost
effectiveness,^
S/Mg
6,570
6,570
5,570
1,770
1,770
1,770
1,770
420
420
420
420
30
30
30
1,000
200
70
20
1,000
200
70
20
1,000
200
70
20
1,000
10
1,000
10
(continued)
-------
TABLE 4-8 (continued)
i
U>
CD
Case Vent
No. class
Kft
61
6?
6^
64
fit;
66
67
fifl
69
70
71
1,1
A
A
A
A
A
A
A
A
A
A
A
A
A =
D =
DCE =
EDC =
ME CHI =
MEK =
TAC =
,1-TCE =
TCE =
TCI =
TOL =
— _
rate, Emission reduction,
Ib/h Constituent Mg/yr TCI, 1989 S
0 . 10 EDC
1 . 50 EDC
10.00 EDC
0.50 TCE
5.00 TCE
10.00 TCE
0.50 DCE
5.00 DCE
10.00 DCE
0 . 50 EDC
5.00 EDC
10.00 EDC
Air-stripper-type vents (i
Distillation-type vents (i
Dichl oroethy lene.
1 , 2-D i ch 1 oroethane .
Methyl ene chloride.
Methyl ethyl ketone.
Total annua 1 i zed costs in
1, 1, 1-Tr ichl oroethane.
Tr i ch 1 oroethy 1 ene .
0.39
5.85
39.02
1.95
19.51
39.02
1.95
19.51
39.02
1.95
19.51
39.02
.«., high flow rates).
. e., low flow rates).
second-quarter 1989 dollars per
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
1,780
year.
TAC, $/yrt>
390
390
390
390
390
390
390
390
390
390
390
390
Cost
effectiveness,^
$/M9
1,000
70
10
200
20
10
200
20
10
200
20
10
Total capital investment in second-quarter 1989 dollars.
Toluene.
«The existing control device could be a thermal or catalytic incinerator, carbon adsorber, boiler, process heater,
condenser, or other device that can effectively accommodate addition of the process vent stream.
^No heat recovery or organic recovery credit is included.
-------
maintenance labor. Overhead was estimated as 60 percent of the sum of
maintenance labor and maintenance materials, and taxes, insurance, and
administration costs were estimated as 4 percent of total capital invest-
ment. A capital recovery factor of 0.16275 (10 percent for 10 years) was
used to calculate annualized capital costs.
4.4 COST EFFECTIVENESS OF CONTROL ALTERNATIVES
The three types of add-on control technologies examined in this
chapter provide similar control levels (i.e., 95-percent versus 98-percent
control). Therefore, for those facilities that are not covered by or are
exempt from State and Federal requirements for control of waste management
unit process vent emissions, the choice of a control technology is expected
to be made on the basis of costs and cost effectiveness (i.e., the cost per
ton of organic emission reduction). To obtain cost-effectiveness values,
the total annualized cost of the control device is divided by the tons of
organics removed per year. Tables 4-4, 4-5, and 4-6 present estimates of
cost effectiveness for the various model unit cases for the three control
technologies analyzed.
Table 4-9 presents a summary of the most cost-effective dedicated
control device of the three analyzed for each model unit case capable of
achieving at least a 95-percent emission reduction. As can be seen in the
table, in all cases, either a condenser or carbon adsorber is more cost
effective than a thermal incinerator.
In general, for those model unit process vent streams with emission
rates of less than 1 lb/h, cost-effectiveness estimates for condensers
(achieving a 95-percent emission reduction) are roughly half those for
carbon adsorbers. Cost-effectiveness values for carbon adsorption and
condensation decrease sharply as the emission rate increases from less than
1 lb/h to about 2 lb/h. From about 2 lb/h to about 10 lb/h, the cost-
effectiveness values decrease gradually; at emission rate values greater
than 10 lb/h, the cost-effectiveness values of these control technologies
converge. At emission rates greater than 10 lb/h, cost-effectiveness
values decrease only slightly as the emission rate increases.
4-39
-------
TABLE 4-9. SUMMARY CONTROL COSTS FOR MOST COST-EFFECTIVE CONTROL DEVICE"
-p»
o
Case
No.
I
2
3
4
5
6
7
8
9
\0
11
12
13
14
IS
16
n
16
19
20
21
22
23
24
25
26
27
28
29
Vent
c lass
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
D
0
D
0
D
0
D
D
Emission
rate,
Ib/h
0.40
0.40
0.40
0.40
4.20
4.20
4.20
4.20
10.60
10.60
10.60
10.60
0.17
0.17
0.17
0.17
0.42
0.42
0.42
0.42
1.20
1.20
1.20
1.20
6.00
6.00
6.00
6.00
0.08
Emission reduction,
Constituent Mg/yr
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
0.74
0.74
0.74
0.74
7.78
7.78
7.78
7.78
19.64
19.64
19.64
19.64
0.16
0.16
0.16
0.16
0.39
0.39
0.39
0.39
1.11
1.11
1.11
1.11
4.63
4.63
4.63
4.63
0.07
Cost
Type of effectiveness,
control device TAC, S/yr S/Mg
NC
NC
NC
NC
RC
C
C
RC
C
C
C
C
NC
NC
NC
NC
NC
NC
NC
NC
RC
C
C
C
RC
C
C
C
NC
19,870
26 , 730
14,290
24,410
69,810
460
240
69,810
(160)
(4,190)
(4,520)
(3,700)
8,440
11,360
6,070
10,370
20,770
28,070
14,180
26,260
66,910
2,250
2,160
2,320
67,380
1,180
960
1,440
3,970
27,650
37 , 200
19,890
33,970
9,260
60
30
9,260
(20)
(210)
(230)
(190)
55,280
74,400
39,750
67,910
55,060
74,410
37,590
69,590
61,590
2,050
1,990
2,170
16,010
250
210
310
55,250
(continued)
-------
Case
No.
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
67
58
59
Vent
c lass
D
D
0
D
D
D
D
D
D
D
D
D
D
D
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
TABLE 4-9 (continued)
Emission
rate,
Ib/h
0.08
0.08
0.08
0.24
0.24
0.24
0.24
1.00
1.00
1.00
1.00
7.00
7.00
7.00
0.10
0.60
1.50
5.00
0.10
0.50
1.50
5.00
0.10
0.50
1.50
5.00
0.10
10.00
0.10
10.00
Const! tuent
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
ME CHI
TOL
1,1,1-TCE
MEK
TOL
MEK
1,1,1-TCE
TCE
TCE
TCE
TCE
DCE
DCE
DCE
DCE
EDC
EDC
EDC
EDC
TCE
TCE
DCE
DCE
Emission reduction,
0.07
0.07
0.07
0.22
0.22
0.22
0.22
0.93
0.93
0.93
0.93
12.97
12.97
12.97
0.39
1.95
5.85
19.61
0.39
1.96
6.85
19.51
0.39
1.96
5.86
19.51
0.39
39.02
0.39
39.02
Type of
control device
NC
NC
NC
NC
NC
NC
NC
RC
C
C
C
C
C
C
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
TAC, S/yr
5,340
2,860
4,880
11,990
16,040
9,050
14,930
65 , 200
2,150
2,100
2,260
(3,540)
(3,770)
(4,050)
85,730
85,050
83,460
77,400
86,730
85,050
83,460
77,400
85,730
85,050
83,450
77,400
101,830
86 , 980
101,830
86,980
Cost
effectiveness,
*/Mg
74,320
39,800
67,910
55,620
72,900
41,980
69,260
72,440
2,310
2,260
2,460
(280)
(300)
(320)
225,600
45,000
14,700
4,100
225,600
46,000
14,700
4,100
226,600
45,000
14,700
4,100
268,000
2,300
268,000
2,300
(continued)
-------
TABLE 4-9 (continued)
-p»
ro
Case
No.
60
61
62
63
64
65
66
67
68
69
70
71
ME
1,1,1
Vent
c lass
A
A
A
A
A
A
A
A
A
A
A
A
A =
C =
D =
DCE =
EDC =
CHI =
MEK =
NC =
RC =
TAC =
-TCE =
TCE =
TOL =
Emi ssion
rate,
Ib/h
0.10
1.50
10.00
0.50
5.00
10.00
0.50
5.00
10.00
0.50
5.00
10.00
Constituent
HOC
EDC
EDC
TCE
TCE
TCE
DCE
DCE
DCE
EDC
EDC
EDC
Emission reduction,
Mg/yr
0.39
5.86
39.02
1.95
19.51
39.02
1.95
19.51
39.02
1.95
19.51
39.02
Type of
control device
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
RC
TAC, S/yr
101,830
99,450
85,980
141,150
137,500
128,980
141,150
137,500
128,980
141,150
137,500
128,980
Cost
effect! veness,
S/Mg
268,000
17,500
2,300
74 , 700
7,300
3,400
74,700
7,300
3,400
74,700
7,300
3,400
high flow rates).
low flow rates).
Air-stripper-type vents (i.
Condenser.
Distillation-type vents (i.
D i chIoroethyIene.
1,2-D i chloroethane.
Methylene chloride.
Methyl ethyl ketone.
Nonregenerable carbon adsorption system.
Regenerable fixed-bed carbon adsorption system.
Total annual)zed costs in second-quarter 1989 dollars per year.
1,1,1-Trichloroethane.
Tr ichIoroethyIene.
Toluene.
aMost cost-effective dedicated control device (condenser, carbon adsorber, or thermal incinerator) capable of
achieving at least a 95-percent emission reduction.
-------
4.4.1 Condensers
From a cost-effectiveness perspective, condensation should be the
preferred control technology for application to waste management unit
process vents regardless of emission rate. However, at emission rates of
about 1 Ib/h and less (a range where condensation clearly has significant
cost-effectiveness advantages), condensation becomes less technically
feasible of achieving the desired control efficiency of 95 percent. This
is because condenser efficiency depends on, among other things, the organic
concentration of the vent stream. At low emission rates, the concentration
of organics can become too low thermodynamically to achieve a high control
level. See Table 4-3 for condenser efficiencies.
Figure 4-2 shows the cost effectiveness of condensers as a function of
the uncontrolled organic emission rate. For condensers achieving the
95-percent control level, the cost-effectiveness values did not seem to
vary significantly by chemical species; i.e., for a particular constituent,
if 95-percent condensation is technologically feasible, then the costs per'
ton of organics controlled are about the same regardless of the con-
stituent.
4.4.2 Carbon Adsorbers
Carbon adsorption is generally more economical than thermal incin-
eration for the control of organics in low concentrations. Thermal
incineration with primary heat recovery is more economical than carbon
adsorption at high organics concentrations unless the recovered organic is
valuable and can be credited at market value. For both high and low
volumetric flow rates, the cost effectiveness of nonregenerable carbon
adsorption systems was determined to be more favorable than that for
regenerable systems at mass emission rates of less than 1 Ib/h. This is
shown in Figure 4-3. As the organic emission rate increases from zero to
1 Ib/h, the cost effectiveness increases for nonregenerable systems. The
total annual cost for operation of a nonregenerable carbon adsorption
system is directly proportional to the amount of organic captured (i.e.,
the organic emission rate). At an emission rate of about 1 Ib/h, the cost-
effectiveness values decrease as emission rate increases. The values of
cost effectiveness for regenerable carbon adsorption systems show economies
4-43
-------
60
JO -
40 -
-p.
-p.
cn
(A
tn
£ 8
1 §
Ib
to
o
O
20
10 -
-Q-
-Q-
T T
T 1 T
T
10
12
~T
14
16
Uncontrolled organic emissions (Mg/yr)
20
Figure 4-2. Cost effectiveness for condensers.
-------
100
I
-£»
(Jl
o>
OT ^
V> tfi
0> TJ
C C
£ S
s i
n
o
O
O Nonregenerative system
Regenerative (fixed-bed) system
10
Uncontrolled organic emissions (Mg/yr)
Figure 4-3. Cost effectiveness for carbon adsorbers.
-------
of scale (i.e., the unit costs of operating the system decrease as the
system size increases); therefore, the cost per ton of organic controlled
decreases as the emission rate increases. For the model unit cases,
differences in cost effectiveness for the various stream concentrations
become almost insignificant at mass emission rates of about 5 Ib/h.
4.4.3 Thermal Incineration
Cost-effectiveness estimates for thermal incineration of process vent
streams show considerable variability in relation to emission rate. Figure
4-4 presents incineration cost-effectiveness estimates as a function of
mass emission rate. For the process vent model unit cases examined,
incineration was the least cost-effective control alternative. The
difference in cost-effectiveness values for incineration and the other
control technologies (at the same emission rate) decreases as the emission
rate increases. Another factor that influences cost-effectiveness values
of incinerators is the organic constituent; the presence of halogenated
compounds requires special incinerator design considerations. Such
compounds require higher combustion temperatures to achieve high
destruction efficiencies. Also, because hydrogen chloride is a principal
combustion product for such compounds, acid gas scrubbers are required. A
comparison of the cost effectiveness of incineration of halogenated versus
nonhalogenated compounds for the low flow-rate model units is also
presented in Figure 4-4. As the figure indicates, the cost differential is
less significant as the emission rate increases.
4.5 CROSS-MEDIA AND SECONDARY AIR POLLUTION AND ENERGY IMPACTS
The previously described control devices (i.e., condensers, carbon
adsorbers, and thermal incinerators) all serve to reduce organic air
emissions from TSDF process vents. However, these same control devices may
as a result of operation generate other environmental pollutants. These
new pollutants can be gaseous, solid, or liquid. Impacts resulting from
emission of organic and nonorganic air pollutants are called "secondary air
impacts." Impacts resulting from the creation of new liquid or solid waste
are called "cross-media impacts."
4-46
-------
120
i
-p.
O)
CO ^
CO (0
CD TJ
C C
-------
The determination of the environmental impacts for the various control
technologies applicable to waste management unit emission sources should be
made on a case-by-case basis. In some instances (e.g., waste solvent dis-
tillation), the by-products can be recycled, used for resale, or burned for
fuel. In this case, no disposal problem or secondary environmental impacts
would exist. However, some applications afford no other alternative but to
dispose of the waste either by land disposal or wastewater treatment,
thereby imposing a cross-media impact.
Se9ondary air impacts are characteristic of combustion control devices
because nonorganic air pollutants are commonly formed during operation of
the control device. In addition, air emissions, wastewater discharges, and
solid waste from non-TSDF sources (e.g., industrial boilers and utility
power plants) may also be created because these facilities provide the
electricity and process steam needed to operate the air pollution control
devices applied to the waste management unit process vents.
The human health and environmental benefits gained from the organic
emission reduction achievable by applying a particular control technology
to a process vent emission source can and should be evaluated relative to
the secondary air and cross-media impacts the control technology creates as
a result of operation. Therefore, it is necessary that secondary air and
cross-media impacts be estimated and evaluated to the extent possible.
This section identifies the types of environmental impacts associated with
the control technologies previously discussed in Chapter 3.0 and provides
rough estimates of both secondary pollutants and cross-media impacts for
each of the process vent model unit cases examined.
4.5.1 Condenser Environmental Impacts
It is unlikely that the use of surface condensers for waste management
unit process vent organic air emission control will produce significant
cross-media impacts or secondary emissions with the exception of any
impacts produced by utilization of electricity (e.g., power needed to run
the refrigeration unit or to pump the coolant and condensate). The coolant
does not contact the condensate and can therefore be recycled or reused.
If the condensate contains a water fraction, then this contaminated water
will require treatment of some type. Whether the noncondensibles exiting
4-48
-------
the condenser will be vented to the atmosphere or further processed is for
the most part contingent upon the organic concentration of the noncon-
densibles exiting the condenser. If the condensed organics cannot be
recycled or reused, they must be stored, treated, and disposed of as a
solid (or hazardous) waste. Cross-media impacts resulting from the use of
condensation as a control technology for the model unit process vent
streams were estimated for each process vent model unit stream and are
presented in Table 4-10. These estimates assume that all condensed
organics will require solid waste disposal and that water from the
condensate will go to wastewater treatment. Energy consumption associated
with condensation (e.g., power required to operate the refrigeration unit,
pump) will depend on the design and operation of the condenser. These
utility requirements were estimated using a chemical engineering process
simulator known as ASPEN (see Section 4.3.1). Of the estimates made, the
worst case found the energy consumed to be on the order of 4,000 kWh/yr.
In most cases, energy requirements were found to be small and are
considered negligible.
4-5.2 Carbon Adsorption Environmental Impacts
Removal of organic compounds from process vent gases using carbon
adsorption systems can produce cross-media impacts. Specific cross-media
impacts include the disposal of both the organic/steam mixture from
desorption of the saturated carbon when regenerated and the solid waste
generated from the replacement of spent carbon. The extent of these
impacts, for the most part, will be determined by the type of adsorption
system used (e.g., fixed-bed carbon adsorption versus carbon canisters),
the method of adsorbent (i.e., carbon) regeneration utilized (e.g., thermal
swing-steam stripping versus pressure swing-vacuum desorption), and whether
the spent carbon canister is recycled or discarded (landfilled).
Low-pressure steam is a common regenerating gas for adsorption systems
and is expected to be utilized with most fixed-bed carbon adsorbers used
for organic air emission control of process vents. This provides a hot,
low concentration gas. Both of these factors enhance desorption.
4-49
-------
TABLE 4-10. MODEL UNIT CROSS-MEDIA IMPACTS FOR CONDENSERS
Case No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
Cross-media
Wastewater,3
gal/yr
332
332
332
331
320
321
325
318
300
303
312
294
24
24
24
24
18
18
18
18
22
22
23
22
16
17
19
15
12
12
12
12
10
10
10
10
10
11
11
10
1,240
1,240
1,240
impacts
Solid waste, b
Mg/yr
0.0
0.34
0.12
0.0
0.0
7.54
7.54
6.91
8.82
19.63
19.44
19.44
0.0
0.13
0.12
0.08
0.0
0.33
0.36
0.32
0.29
1.10
1.08
1.07
4.12
4.64
4.64
4.64
0.0
0.06
0.06
0.04
0.0
0.23
0.22
0.19
0.55
0.93
0.93
0.92
12.58
12.58
12.58
aCondensed water vapor.
^Condensed organics.
4-50
-------
During regeneration, the gas stream leaving the top of the adsorber
will contain desorbed organics. If the organic is not soluble in water, a
condenser-decanter can be used. The recovered organic material and
expended steam condensate are normally the only liquids discharged from
adsorption systems. The water obtained may be either discarded or reused
for steam. In either case, it would require treatment prior to disposal or
reuse. In some cases, recovered organics can be utilized (e.g., recycled
to the original process or used for resale), and no disposal problem per se
would exist. If the organic is not of a usable quality, it could be burned
as a fuel to produce heat plus steam for regeneration, or it could be
further enriched by chemical processing (distillation, etc.). Combustion
of the organic as a fuel may provide a lower monetary return than reuse as
a chemical in the process. When combustion is used, a check should be made
to be certain no excessive amounts of hazardous substances (e.g., secondary
air emissions) would be generated and released as a result of noncombust-
ibles, incomplete combustion, and/or combustion products.
Products removed from the adsorber cannot be separated from the steam
regeneration fluid by decantation if they are soluble in water. In these
instances, a more complex recovery procedure is needed. This could be a
distillation process if system cost and product values are favorable.
An onsite boiler is expected to supply the required steam for most
fixed-bed carbon adsorber regeneration. The production of the steam needed
for this regeneration creates secondary air emission impacts due to the
boiler air emissions. It is anticipated that these impacts will primarily
be an increase in nitrogen oxides (NOX) and carbon monoxide (CO) emissions
because natural gas or distillate fuel oil fuel is typically used in indus-
trial boilers.
Spent adsorbent from nonregenerable systems must be disposed of upon
removal, and regenerable system adsorbent does deteriorate and requires
replacement periodically. These materials must be handled and disposed of
in a safe and environmentally acceptable manner. To some extent, adsorbed
gas molecules will be present on all spent adsorbents and must be consid-
ered for flammability and toxicity. Often, spent organic adsorbents can be
disposed of safely and conveniently in a controlled combustion facility.
4-51
-------
If spent carbon from an air pollution control application is determined to
be a hazardous waste, it can be disposed of in a hazardous waste landfill.
If it is determined to be nonhazardous, it may be possible to dispose of
the spent carbon in a municipal solid waste landfill, depending on the
policies of that particular landfill site. More often, however, it will be
returned to the manufacturer for regeneration and then recycled back to an
adsorber for reuse. Recycling spent carbon in this manner reduces the
amount of solid waste generated by the control technology and submitted to
a solid waste disposal site or a combustion facility.
Because the disposal of spent adsorbent is an environmental concern,
estimates of the environmental impacts resulting from the disposal of spent
carbon were developed for the model units based on a worst-case scenario.
This worst-case assumption includes the following conditions: (1) for
regenerative systems, the carbon life is 2 years; (2) for nonregenerative
systems, the carbon life is equivalent to the time required for
breakthrough.
The quantity of solid waste produced using carbon adsorption on the
model unit process vent streams was estimated using a working capacity of
0.07 Ib of organic per pound of carbon. Furthermore, the system for regen-
erative carbon adsorption was assumed to consist of two units operating in
parallel, each having an adsorption cycle length of 8 h. Significant
quantities of solid waste were calculated for both the regenerative and
nonregenerative systems and are shown in Table 4-11. (Note: The solid
waste impact estimates include both the spent sorbent and the organics
adsorbed in the case of nonregenerative systems. Solid waste impact
estimates for regenerative systems include the spent sorbent and the
organic recovered from the regeneration process.)
The use of regenerative carbon adsorption systems also impacts water
quality. Steam is used in the regeneration of activated carbon at the
site. The resulting mixture of steam and organics, depending on the solu-
bility of the organic in water, generally will be separated from the waste-
water either by use of a condenser-decanter or some other more complex re-
covery procedure. In some cases, the separated organic may be reused
(e.g., recycled, resold), and the water reused for stean; no environmental
4-52
-------
TABLE 4-11.
MODEL UNIT CROSS-MEDIA AND ENERGY IMPACTS
FOR CARBON ADSORBERS
Case No.
1
2
3
4
5
8
9
13
14
15
16
17
18
19
20
21
25
29
30
31
32
33
35
36
37
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Control
device
CA-N
CA-N
CA-N
CA-N
CA
CA
CA
CA-N
CA-N
CA-N
CA-N
CA-N
CA-N
CA-N
CA-N
CA
CA
CA-N
CA-N
CA-N
CA-N
CA-N
CA-N
CA-N
CA
CA-N
CA
CA
CA
CA-N
CA
CA
CA
CA-N
CA
CA
CA
CA-N
CA
CA-N
CA
CA-N
Energy impacts
Steam generation,3
1,000 Btu/yr
NA
NA
NA
NA
99,677
99,677
251,567
NA
NA
NA
NA
NA
NA
NA
NA
14,239
59,332
NA
NA
NA
NA
NA
NA
NA
11,866
NA
24,987
74,963
249,879
NA
24,987
74,963
249,879
NA
24,987
74,963
249,879
NA
499,758
NA
499,758
NA
Cross-media impacts
Wastewater,
gal/yr
NA
NA
NA
NA
8,373
8,373
21,133
NA
NA
NA
NA
NA
NA
NA
NA
1,196
4,984
NA
NA
NA
NA
NA
NA
NA
996
NA
2,099
6,297
20,991
NA
2,099
6,297
20,991
NA
2,099
6,297
20,991
NA
41,982
NA
41,982
NA
Solid waste,
Mg/yr
13.33
13.33
13.33
13.33
0.26
0.26
0.65
2.83
2.83
2.83
2.83
7.00
7.00
7.00
7.00
0.07
0.30
1.33
1.33
1.33
1.33
4.00
4.00
4.00
0.06
7.02
0.03
0.09
0.30
7.02
0.03
0.09
0.30
7.02
0.03
0.09
0.30
7.02
0.61
7.02
0.60
7.02
(continued)
4-53
-------
TABLE 4-11 (continued)
Case No.
61
62
63
64
65
66
67
68
69
70
71
Control
device
CA
CA
CA-N
CA
CA
CA-N
CA
CA
CA-N
CA
CA
Energy impacts
Steam generation,3
1,000 Btu/yr
74,963
499,758
NA
249,879
499,758
NA
249,879
499,758
NA
249,879
499,758
Cross-media impacts
Wastewater.b
gal/yr
6,297
41,982
NA
20,991
41,982
NA
2,099
41,982
NA
20,991
41,982
Solid waste,0
Mg/yr
0.09
0.61
35.10
0.30
0.61
35.10
0.30
0.61
35.10
0.30
0.61
CA = Carbon adsorber.
CA-N = Nonregenerable carbon adsorber.
NA = Not applicable.
aSteam required for regeneration of the fixed-bed carbon adsorption units,
^Expended steam condensate resulting from regeneration of the fixed-bed
carbon adsorption unit.
cSpent adsorbent plus desorbed organics.
4-54
-------
impact would result. A worst-case assumption (i.e., the desorbed organics
are neither reusable nor resaleable and must be disposed of as solid waste
and the water [condensed steam] must be sent to a wastewater treatment
unit) is made in the estimation of the solid waste and wastewater impacts
shown in Table 4-11. A steam usage value of 4 Ib of steam per pound of
solvent desorbed was used to estimate the quantity of wastewater gener-
ated.29 Table 4_n presents the wastewater impacts estimated for the model
units under the conditions noted above. The use of nonregenerative systems
(assuming the life of the canister is equal to its breakthrough time) does
not result in any wastewater impacts.
The energy impacts resulting from the use of carbon adsorption to
control emissions are the energy required for steam for regeneration of the
carbon and electricity to power pumps, fans, and instrumentation. Energy
impacts are dependent on control device operating conditions such as elec-
tricity source, fuel type, and spent carbon practices. The energy needed
to produce the steam for regeneration represents the majority of the total
energy required for an adsorption system. Therefore, energy impact esti-
mates for carbon adsorbers using the model units only consider the energy
required to produce the steam for regeneration. The energy impacts from
electricity required to power pumps, fans, and instrumentation are
considered negligible. In addition, the following operating conditions are
assumed: steam is supplied at a pressure of 65 psia and is generated by a
boiler fueled by oil operating at approximately 80 percent overall
efficiency.30 Table 4-11 presents the energy impacts estimated for the
model unit process vent streams.
4-5-3 Thermal Incineration Environmental Impacts
While thermal incinerators are used to prevent air pollution, thermal
incinerators themselves exhibit an air pollution potential and can produce
cross-media impacts and secondary emissions depending on how they are
operated. It is possible to create a major pollution problem when burning
any waste gas if the waste gas is not burned with sufficient air for
combustion. Improper operating conditions can result in CO generation. If
proper combustion conditions are observed (i.e., correct air-to-fuel ratio;
sufficient mixing, adequate residence time, and peak flame temperature; and
4-55
-------
proper cooling rate of combustion products), essentially all the carbon
present in the waste gas should end up as carbon dioxide (C02)• All the
hydrogen should result in water as a product of combustion, and unburned
hydrocarbons should be minimal if not zero.
NOX emissions from thermal incinerators are another secondary
pollutant impact produced by thermal incinerators. Nitrogen oxides have
two sources: nitrogen in the fuel and the reaction between atmospheric
nitrogen and oxygen at high temperatures. One problem encountered in
reducing emissions from combustion sources is the fact that modifications
that reduce carbon monoxide and hydrocarbon emissions generally increase
NOX emissions and vice versa (see Table 4-12).
As noted above, some adverse effects on air quality can be associated
with the use of combustion devices to control organic emissions from waste
management unit process vents. Pollutants generated by the combustion
process (i.e., S02, CO, and particularly NOX) may have an unfavorable
impact on ambient air quality. Secondary air pollutant emissions resulting
from the incineration of the model unit process vent streams were estimated
for each vent stream case. Using the AP-42 emission factors for natural
gas combustion, the quantities of S02 and CO generated were found to be
relatively insignificant. The NOX emissions were estimated using an
emission factor developed from thermal oxidizer test data gathered at
incinerators controlling process vent organic emissions.31 These estimates
are presented in Table 4-13.
There is increasing concern about hydrogen chloride (HC1) emissions
from incinerators, owing to the growing amount of halogenated polymers
(e.g., polyvinyl chloride [PVC]) and halogenated solvent (e.g., methylene
chloride) used in chemical processes and therefore potentially present in
waste streams. In addition, hydrogen fluoride (HF) emissions arise from
the combustion of fluorinated hydrocarbons. Water scrubbing appears to be
an effective means of controlling these acid gases (HC1, HF). An increase
in wastewater, however, will result from the wet scrubbing of these gases.
The scrubber wastewater may require neutralization (addition of a caustic)
before being released into the wastewater treatment and disposal system.
The salts produced from the neutralization, though small, must be disposed
4-56
-------
TABLE 4-12. EFFECT OF MODIFICATIONS IN OPERATION ON EMISSIONS
Effect on
CO and HC Effect on
Change in operation emissions NOX emissions
Increase excess air Decrease Increase, then gradually
decrease
Increase flame temperature Decrease Rapid increase
Increase residence time at Decrease Small increase
high temperature
CO = Carbon monoxide.
HC = Hydrocarbons.
NOX = Nitrogen oxides.
Source: Engdahl, R. B., and R. E. Barrett. Fuels and Their Utilization.
In: Engineering Control of Air Pollution. Volume IV of
Environmental Sciences: An Interdisciplinary Monograph Series on
Air Pollution, Stern, A. C. (ed.). New York, Academic Press.
1977. p. 379-419.
4-57
-------
TABLE 4-13. MODEL UNIT SECONDARY AIR POLLUTION, CROSS-MEDIA,
AND ENERGY IMPACTS FOR THERMAL INCINERATORS
Case
No.
5
6
7
8
9
10
11
12
25
26
27
28
41
42
43
Energy
Gas use,
100 J/yr
16.0
6.1
16.0
2.2-
15.9
1.5
16.0
1.7
8.0
1.1
8.0
1.2
1.9
2.0
15.9
impacts
Electric use,
1,000 kWh/yr
26
8
26
8
26
8
26
8
13
4
13
4
8
8
26
Secondary
emissions
NOX,
kg/yr
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
0.2
0.2
0.2
0.2
10.3
10.3
10.3
Cross-media
impacts
Wastewater,
1E+6 gal/yr
20.7
0.0
20.7
0.0
20.7
0.0
20.7
0.0
1.5
0.0
1.5
0.0
0.0
0.0
64.9
4-58
-------
of as hazardous waste. Therefore, thermal incineration does produce a
solid waste impact.
The amount of wastewater (used to remove the acid gas contained in the
thermal incinerator outlet stream) was estimated for each model unit case
analyzed and is shown in Table 4-13. The quantities generated are, in most
cases, relatively small and for most plants would not affect waste treat-
ment or sewer capacity. However, the water used as a scrubbing agent will
need to be neutralized, prior to discharge or reuse, by adding caustic
(NaOH). The salt formed in the neutralization step must be purged from the
system and properly eliminated (e.g., direct wastewater discharge or salt
recovery). There are no other significant solid wastes generated as a
result of control waste management unit process vents by thermal
incineration.
The use of an incinerator to control organic emissions from waste
'management unit process vents results in a net energy usage for the model
vent cases because supplemental fuel is needed to support combustion and
promote flame stability. The determination of fuel use for select model
unit cases was made as a part of the SOCMI Incinerator/Flare Costing
Algorithm. These supplemental fuel requirements (in the form of natural
gas) are also presented in Table 4-13. Electrical energy is required to
operate the pumps, fans, blowers, and instrumentation that may be necessary
to control organics using an incinerator. Electrical energy requirements
as estimated by the costing model are presented in Table 4-13 as well.
4.6 REFERENCES
l' ^o;J;rirCTnnta1 Protection A9ency. Hazardous Waste Treatment
Storage, and Disposal Facilities-Background Information for Promul-
Le ks ^;JrpEin;S5-0nnSt?-dard? f°r Pr°CeSS Vents and Equipment
Leaks Office of Air Quality Planning and Standards. Research
n ' Pub1icati™ No. EPA-450/3-89-009. Section 5.2.
2. PEI Associates, Inc. Estimated Costs of Controlling Air Strippers
with Vapor-Phase Carbon Adsorption. Prepared for U S. Env roSal
Protection Agency Office of Air Qual ity Planning and Standard
Research Triangle Park, NC. EPA Contract No. 68-02-4394. July 1989.
3. Reference 1.
4-59
-------
5. Reference 1, Appendix D.
6. Reference 2.
7. Reference 1.
"
1987.
"
Publication No. EPA-450/3-80-027. December 1980. p. 2-i .
May 1982.
11. Reference 1, Appendix C.
12. Reference 1, Appendix C.
»• sME4^r-TDMrr^r ^.rriSr^MJ1 for
Company. 1980. p. 167.
15. Reference 1, Appendix C.
16. Reference 2.
17. Reference 1, Appendix C.
18. Reference 2
Research Triangle Park, NC. Publication No. EPA-450/3-83-005a.
December 1983.
4-60
-------
20. Chemical Engineering. 85(7):7. March 1978.
21. Chemical Engineering. 87(7):7. April 1980.
22. Chemical Engineering. 90(7) :7. April 1983.
23. Chemical Engineering. 97(12):224. June 1989.
24. Bureau of Census. United States Department of Commerce. 1989 Statis-
tical Abstract of the United States. 109th Edition. Table 964.
1989.
25. Reference 24, Table 951.
26. U.S. Environmental Protection Agency. Alternative Control Technology
Document—Halogenated Solvent Cleaners. Office of Air Quality
Planning and Standards. Research Triangle Park, NC. Publication No.
EPA-450/3-89-030. August 1989. p. 5-11.
27. Reference 26.
28. Chemical Marketing Reporter. Schnell Publishing Company, Inc.
October 23, 1989. p. 41.
29. Gard, Inc. Capital and Operating Cost of Selected Air Pollution
Control Systems. Prepared for U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards. Research Triangle Park,
NC. Publication No. EPA-450/5-80-002. December 1978. p. 5-47.
30. Ulrich, G. D. A Guide to Chemical Engineering Process Design and
Economics. New York, John Wiley and Sons. 1984. p. 44.
31. Reference 19, p. 7-6.
4-61
-------
APPENDIX A
SUMM?SL°^SITE-SPECIFIC PROCESS AND MISSION TEST DATA
FROM DISTILLATION/STEAM STRIPPING UNITS AT TSDF
A-l
-------
TABLE A-l^SUMMARY OF sm-SPECIFIC PROCESS AND EMISSION TEST DATA FROM DISTILLATION/STEAM
STRIPPING UNITS AT TSOF
Feed
F -i-t Material rate
__* Process processed (X Organic*) (L/min)
Plant A TFE Mixed chlor. 86 23
xy lenes
Plant Bl BD Aqu. MEK 6 3/
(30,000 L)
Plarit B2 BD Aqu. ac.ton. 23 24
(11,000 L)
Plant C TpE Acetone >83 27
w/xy lene
Plant Dl BSS Aqu. xylen. MEK 26 8
3... (1,260 L)
^PlantD2 BSS 1,1.1-Trichlo. 74 «
MEK (897 L)
P'ant E SS Aqu. nitro- Low 498
benzene
Plant F SS Aqu. method Low 19
ch loride
SS Aqu. eth. 0.6 816
dich loride
P!ant H SS Chlorinated 0.6 40
solvents (41.6)
-— .
See notes at end of table
Gas flow
Vent rate
location (L/s)
Condenser (P) 0.0014
Condenser (P) 0.64
PA tank 0.4
Condenser (P) <1.3
Rec . tank <0.8
Condenser (P) NA
Condenser (P) 0.11
Condenser (P) 0.063
Miscible solvent NA
tank
Condensate tankc 0.16
Gravity separatorc 1.0
Secondary 3.1
condenser
Primary condenser NA
Primary condenser 0.95
Secondary 0.20
condenser^
Solids decanter 0.70
Organic
cone.
(ppmv)
9,900
68,000
2,100
<630
750
20
(0.06 mg/L)
6,800
10,600
6,100
2,000
21,000
65,800
NA
394,000
437,000
394,000
Organic emissions*
(8/«) (Mg/yr)b (Ib/h)
0.00001 0.0016 0.0008
8-186 2.8 1.47
0.005 0.076 0.04
NA <0.04 NA
0.002 0.03 0.016
Negligible
0.0029 0.043 0.02
0.0035 0.052 0.03
0.0004 0.005 0.003
0.0026 0.03 0.02
0-13 2.0 1.06
0-63 9.4 5.0
NA NA NA
1-2 18 9.6
0-26 3.8 2.0
2-3 34.8 18.4
Emission
^factor
organic
feed)
2.5
6.0
0.18
NA
0.02
0.08
0.06
0.006
NA
NA
7.7
NA
NA
NA
NA
(continued)
-------
TAbUt A-l vcontinuwuj —
— —
Material
Facility Process processed (
Plant I TFE *••*• solvents"
2 units
Plant J BD Aqu. organic
so 1 vents
(26,400 L)
Plant K TFE A""Dt"yUne
2 units k IP A
Plant L SS(B) Organ, solv. I
waste fuels
(600 gal)
(1,892 L)
plant M COE 1 No process data,
(E) BD )
Pilot-scale test TFE Refinery sludge
I
*" . N TFEa p»int thinnersfl
Pl'nt B (batch)
Plant N BD Chlorinated
solvents
(3,785 L)
p,,nt o TFE t BD Waste solvents
I BD Waste sol .
non-ch 1 .
(10,000 gal)
p, fc p 2 BD Chloro. solv.
-_— - _ -. - - r.
Feed
rate
Organic*) (L/min)
High 20
(300 gal/h)
3-10 6
20 NA
NA 12.6
(260 gal/h)
6
only cost, has "backup"
1.6
78 14.3
High 6
-_ . .. -- -
n ti nr/i»ni<- Oraanic emissions*
w__f rate cone. « ...
/ % fa/s) (Ma/yr) Clo/")
location (L/s) (PPmvJ
M. NA 0.01 0-4 0-lf
3rd condenser NA "«
.,i UA K1A NA
Condenser (P) NA NA NA NA
Distill, recvr. (Vented to incinerator)
Condenser NA 36 mg/L NA NA NA
i,. NA NA
Condenser (P) NA NA NA
through disti 1 1 .
*
condenser (2nd condenser)
Primary condenser 1) ..£ >;..«. g«) |jj j* JJ
Condenser (P) NA NA NA NA NA
Condenser (P) NA NA NA NA NA
KIA NA NA NA
Emission
factor
(a/kg
organic
feed)
0.04
NA
NA
NA
NA
NA
NA
NA
NA
188,000 gal/wk treated "A
High 32
High 6.3
-
Condenser (P) NA NA NA NA NA
Condenser (P) NA NA NA NA NA
NA
NA
(continued)
See notes at end of table.
-------
TABLE A-l (continued)
Fac i 1 i ty
Plant Q
Plant q
Plant R
Plant S
Plant T
Plant U
Plant V
Process
TFE
BD
TFE(B)
SS
TFE
BD1
BD2
SS
TFE
Material
processed
Chloro. solv.
(1,700 L)
Waste sol .
Tol, MEK,
(15,000 L)
Ni trobenzene
Ni trotoluene
Halogenated
waste solvents
(4,000-6,000
gal /batch)
Chlorinated
degreasing
wastes
Ch lorinated
organ ics (2%)
Feed
rate
(X Organ ics) (L/min)
High 6.3-7.5
(100 gal/h)
65-100 5-15
High NA
H i gh NA
250 gal/h at 3-4
25 gal/h
250 gal/h
450 gal/h
Emission
factor
Gas flow Organic Organic emissions* (g/kg
Vent rate cone. organic
location (L/s) (ppmv) (g/s) (Mg/yr)b (Ib/h) feed)
Condenser (P) NA 0.06 mg/L NA NA NA NA
Condenser (P) NA NA NA NA NA NAh
Condenser vent 0.16 7.0 mg/L 0.001 0.02 0.01 NA
tank
Secondary NA NA NA NA NA NA
condenser
h NA NA NA NA NA NA
Demister A NA NA NA NA NA NA
condenser
98* waste solvent
(nonch lore)
(3,000 ga 1/6-7
h)
BD = Batch distillation.
BSS = Batch steam stripping.
CO = Continuous distillation.
NA = Not avai(able.
SS = Steam stripping.
TFE = Thin-film evaporator.
"Organic emissions are the sum of the individual constituent emissions for the detectable compounds.
"Based on 4,160 hours operation per year.
cCondenser vented through tank.
"Secondary condenser efficiency was negligible.
•Acetone, toluene, xylene, methylene chloride, et al. at 3.4 x 106 gal/yr.
fEstimated only.
SAcetone, toluene, MEK, xylene, isopropanol, et al.
"Some ambient air data available.
Source: Memorandum from Zerbonia, R., RTI, to Colyer, R., EPA/SDB, and Lucas, R., EPA/CPB. October 19, 1987. Evaluation and development of emission
factors for (TSDF process) vents. RCRA Docket Item: F-89-AESF-S0021.
-------
APPENDIX B
SUMMARY OF AVAILABLE DATA ON AIR STRIPPER
LOADINGS AND PERFORMANCE
B-l
-------
TABLE 8-1. SUMMARY OF AVAILABLE DATA ON AIR STRIPPER LOADINGS AND PERFORMANCE
._Air StrJPpaLdesjjin §nd operation
Fac i 1 i ty/ 1 ocat ion Water*
flow
Nsm* C'ty State (gal/min)
Confidential - Stover (1) 200'
Confidential - Stover (2) 600'
Unidentified Scottsdale AZ 3,700
Unidentified City of Scottsdale AZ 7
ro Hughes Aircraft Tucson AZ 4,200'
CO
AMD, Inc. Sunnyvale CA 176n
Baldwin Park Valley County CA 970
Unidentified South Chesire CT 1,700
CT American Water Co. CT 300
Private Industry CT 200
Unidentified Ft. Pierce FL 360h
Pol lutantb
BZ
TOL
XYL
VO
BZ
XYL
EBZ
EDC
VO
TCE
VOC
TCE
TCA
EDC
VO
VOC
TCE
PCE
VO
TCE
TCA
TCE
TCE
PCE
VO
Cone .
(ug/L)
1,000'
1,000'
1,000'
3,000
10,000'
5,000'
6,000'
1,000'
21,000
200h
130,000
800'
100'
200'
1,100
2,000h
710h
330
1,040
100h
75
20,000h
11. 3h
76h
87.3
Pol lutant
1 oad ingc
(kg/yr)
381.6
381.6
381.6
1,144.7
11,446.8
6,723.4
6,723.4
1,144.7
24,038.4
1,411.8
1,736.1
6,410.2
801.3
1,602.6
8,814.1
667.7
1,313.9
610.7
1,924. 6
324.3
42.9
7,631.2
7.6
60.7
68.3
Column Packing Air Air-to- Reported
diam. ht. No. of flow** water removal
(ft) (ft) cols. (ft3/min) ratiod eff. (*)'
4 20 1 2,700' 100 I00f
100f
100'
100
« 26 2 4,000f 60 99.9'
99 8'
99. &f
99f
99.8
10 14 1 26,000 60 99h
98
9/9 6/26 3/3 4,800' 30' 99. 4 '
99.6'
999
99.3
99. 6h
8 18 1 4,000 30 99h
99
99
9x8 26 1 8,000 36 99h
<-6 70
4 99.9
* 18 1 2,000 60' 99h
ggh
99
Unidentified Port Malabar FL 1,000' VOC 67»> 108.7 9«9 12 1 9,000* 70 99h
(conti nued)
-------
TABLE B-l (continu.d)
Air stripper design and operation
CO
Faci 1 ity/location
Name C i ty
Sydney Mine Hillaborough County
Boeing Wichita
Acton Water District Acton
Site A
Site B
Verona Well Field Battle Creek
Electronic Ind. New Hope
Water*
flow
State (gal/min)
FL 160f
KS 66"
MA 417"
MI l,400h
MI 166"
MI 1 , 900"
MN 75
Pol lutantb
EDC
MCL
TCA
OCE
VO
TCE
TCA
DCE
TCE
VO
TCE
TCA
VO
CF
MCL
EDC
EDC
TCA
DCE
TCE
PCE
VO
TCE
MCL
PCE
TCA
EDC
CF
VO
Cone .
("9 A)
24"
9"
8"
2"
43
6,000"
26"
26"
10"
60
4,000"
300"
4,360
1,600'
NO
NO
6"
12h
10"
1"
10"
38
200,000
20
4,700
160
8.9
16
204,893
Pol lutant
loadi ngc
6.9
2.6
2.3
0.6
12.3
641.0
19.9
19.9
8.0
47.7
10,683.7
801.3
11,646.2
440.0
18.1
43.6
36.2
3.6
36.2
137.7
28,617.1
2.9
672.6
21.6
1.3
2.1
29,317.3
Column Packing Air Air-to- Reported
diam. ht,. No. of flowd water removal
(ft) (ft) cola. (fts/min) ratiod eff. (X)
4 1 4,700' 220f 100h
100h
100h
100"
100
1 98'
6.6 20 1 3,000 60 99
99
99
99
8,000" 40 99.8"
100"
99
3 46 1 l,300h 60 99.9"
10 40 1 6,600' 20 100"
100h
100"
100"
100n
100
1 10,000 1,000 NO
NO
NO
NO
NO
NO
NO
(continued)
-------
TABLE 8-1 (continued)
f ....... Alr s^r''PP»r d«sian §nd oper.tipn
r.ci i ity/loc.tipn u,.. >
*'r. Air-to- Reported
\w- • / i • *, i i uv.nt" IUQ/L1 fkn/wrl /*t\ a.* ' i I ow w.ter remov. I
Whiter Sit. Minn..poli. w ,„ T (9/y) •
O0 Till o•a *XAA « « ^, —
' 270 40 NO
NO
NO
NO
W«ter»
a.l/min) Polluting
60 TOL
Efl/.
XYL
VO
1,918 TCE
1,400 TCE
MTBE
DIPE
VO
36 TCE
626 TCE
PCE
VO
3,600f PCE
500 TCA
PCE
VO
760 TCE
1,100 TCE
PCE
OCE
VO
30 TCE
i , 000 PCE
TCE
VO
, 200 PCE
Cone .
23,000
14,000
63,000
90,000
600'
50"
60"
350
80"
1,000"
100"
1 , 100"
200 f
6"
7"
12
50"
76"
3"
40"
118
30
300"
100"
400
90"
Pollut.nt Column
1 o.d i ngc d i .m.
(l<9/yr) (ft)
2,194.0
1,335.5
6,056.7
8,686.1
2,220.7 5
667.7 9
133.6
133.5
934.8
6.3 6
1.192.4 5 « 4
119.2
1,311.6
1,373.6 12 x 10
4.8 9
6.7
11.4
71.6 7 « 13.8
167.4 7
6.3
83.9
247.6
1.7 1.5
1,717.0 12 , 7
672.3
2,289.4
206 . 0 7.5
P.cki
ht.
(ft)
26
10
26
24
26
4.6
10
16
16
NE
Unidentified Rock.*., „, " """ <•"*>•' 6 1 10,000 40f 9a
Hock.w.y NJ , 400 TCE ^^^ ^^ __
1 37,600 200 ]00h
95 h
99"
99.1
Unidentified Rocky Hm
Unidentified Mount.insid. - • '~ °° *' * 6 " 2 2'6M 80t> »*
^ "~ """" ••""•'l S " ' "' » 3,300 40 99"
_ 90h
D.nvi I I. W.t.r O.pt. O.nvi.l. NJ '„„ E "" l/373'6 """ " * 19'2«"» <°f 99.6^
"J w00 TCA ch ^ rt
4,000 60f 100"
86"
E. H.nov.r W.t.r O.pt. E.stH.nov.r NJ ?B0 TC£ ^ "" 91-8
South Brunswick TWP Brunswick M . " "'6 ' * "^ ^'5 l 8l000 6"f 76"
NJ 1,100 TCP Teh .r, .
1 13,000 90 f 99h
99"
99"
H's- W.rren County ••• "
Unidentified qu..n, ^ ,_ _ ' ' 96
16,008 40 9/h
UnidMtifi-d G.rd.n City Park NY 1?BB «E ««,. 2,28;:; ^90"
5,600 35 94h
(continued)
-------
TABLE 8-1 (continued)
A]r stripper design §nd _og*ratjon
Fac i 1 i t.y/ locat i on
Name City State
Unidentified Brewster NY
Unidentified New Hyde Park NY
Unidentified Floral Park NY
Unidentified Northport NY
C3 Citizens Water Supply Great Neck, Long Island NY
CTi
EPA Region II Hicksville NY
Unidentified Zanesville OH
Unidentified Hatboro (fl) PA
Water*
flo.
(gal/min)
600
2,400
3,000
1,300
2,000
100
300
215
Pol lutantb
PCE
EDC
TCE
VO
TCE
PCE
VO
TCE
TCA
VO
PCE
BZ
PCE
TCE
VO
MEK
TCE
DCE
VO
TCE
MTBE
DIPE
EDC
PCE
VO
Cone .
(ugA)
49"
17"
176
300"
100"
400
300"
60"
360
460"
200"
66"
40"
296
1,000
16,000
3,000
18,000
300"
130"
20"
16"
10"
476
Pollutant Column
loadingc diam.
(kg/yr) (ft)
126.9 4.8
66.1
19.6
201.6
1,373.6 12 « 7
467.9
1,831.6
1,717.0 12 « 7
286.2
2,003.2
1,116.1 6
763.1 10
209.9
162.6
1,126.6
190.8 3.6
8,686.1 4
1,717.0
10,302.2
123.1 6.6
63.3
8.2
6.2
4.1
194.8
Pack ing
ht. No. of
(ft) cols.
17.8 1
21 1
18 1
16 1
24 1
20 1
26 1
Air
f lowd
(ft3/min)
3,000
12,800
16,000
6,200
21,400
1,860
6,300
Air-to-
water
ratio"*
38'
40
40
30
80'
46
220
Reported
remova 1
eff. (X)'
99"
99"
99"
99
97"
90"
96.3
97"
9Sh
96.7
99"
99"
99"
99"
99
99
97
97
97
99"
99"
96"
99"
98"
98.8
Unidentified Upper Merlon (#3) PA 690 TCE 15h 19.7 4.6 10 1 1,400 IS 95h
(continued)
-------
TABLE B-l (continued)
Facility/location Water*
N"m° Cit" State (gal/min) Pollutant^
Unidentified Warrington BA , ,,,
** r* 1 Mo TCE
Unidentif.ed Hatboro (»2) PA 278 TCE
EDC
PCE
VO
L.coming Ck. Well Field Wi 1 1 i am.port PA <.,«,„ TCE
PCE
OCE
VO
Superior Tube Co. Norristo.n PA 8S ,rc.
' n OD 1 L£
Tysons Dump Upper Mer ion PA 6h 1>2>3.TCP
XYL
TO TOL
1 ANILINE
\| PHENOL
2-MPH
EBZ .
VO
Upper Merlon Re. (»l) Upp.r Merion p/k l3/90a TCE
Unidentified rh. ..„-._[,
Lheaapeake VA 9,000 CF
CHBrC12
CHBr2C 1
CHBr3
Uni first „. . vo
VT 24" PCE
Cone .
(ug/L)
130"
300"
80"
10"
390
360"
10
10
370
9,000
30,000"
17,000"
210"
102"
109"
63*>
40"
47,614
20
77"
36"
34"
8"
156"
126"
Pol lutant
loadingC
("•9/y)
29.8
169.1
42.4
5.3
206.8
2,783.1
79.6
79.6
2,942.1
1,118.1
298.4
169.1
2.1
1 .0
1 .1
0.6
0.4
472.6
630.4
1,322.1
618.1
683.8
137.4
2,661 .4
6.7
A i r ,tr i eB.r de, i n\nd o .7.^
Column Packing Air Air-to- Reported
^J"1' J»- N°- °f '|o«<* water removal
27 18 1 Cdua k
* * D00 30 S7
99"
99"
95"
98.9
18/10 23/23 2/2 66,000 100 99h
NO
NO
NO
1'S - 3 3 300 30 98
1 170" 99h
98"
NO
68"
74"
70"
NO
NO
12 l4 2 27,900 16 90
13 7 30 2 64,100 46 48*
81"
80"
44"
68.1
98.6"
(continued)
-------
TABLE B-l (continued)
Air stripper de.ignind
CO
I
oo
Name
City of Tacoma
Unidentified
Unidentified
FaciIity/location
City
Tacoma
Wausau (*1)
Hart I and
State
WA
WI
Water*
flow
(gal/min) Pollutant6
3. 608 1,1,2,2-TCA
TCE
DCE
VO
2,000 TCE
DCE
PCE
TOL
XXL
VO
Cone.
(ug/L)
130"
I00h
630
72"
82"
SB*
30"
17"
261
Pol lutant
loading0
2,003.2
868.1
687.7
3,639.0
274.7
312.9
228.9
114.6
64.9
996.9
Co 1 umn
diam.
(ft)
12
9.3
Packing
ht. No. of
(ft) col..
23 6
24.6 1
Air Air-to- Reported
flo*d water removal
(ft3/min) ratio0 eff. (*)'
96h
99"
99h
96.7
146, 000
300
WI
1,000
TCE
240"
467.9
26.8
18,000
6,700
60
96"
98h
96"
96h
97.0
99"
ND = No data.
•This is the total flow to all air .tripper, at the site.
bpollutant abbreviations used are:
BZ = Benzene
CHL82 = Chlorobenzene
CF = Chloroform
DCE = Oichloroethylene
DIPE = Oiisopropylether
CO*- — I.VMJ «•*»"»•-••— .11 tt. «.
EDC = Ethylen. d, chloride or d.ch.oroeth.n.
MCL = Methylene chloride
MEK = Methyl ethyl ketone
MTBE = Methyl-tertiary-butyl-ether
2-MPH = 2-MethyI phenol
PCE = Perch Ioroethylene or tetrachloroethane
TOL • Toluene
TCA = Trichloroethane
„„
TCE = Trichloroethylene
1 2 3-TCP = 1 2,3-Trichloropropane
VO = Total volatile organic, (calculated
aa the .urn of pollutant, reported)
VOC = Volatile organic compound, (prov.ded
by facility rather th«n calculated)
XYL = Xylene
r.,ul t .„
Sourc*
.
- -
-------
APPENDIX C
ESTIMATES OF UNCONTROLLED EMISSIONS
FROM AIR STRIPPERS
C-l
-------
o
I
ro
-------
TABLE C-l. ESTIMATES OF UNCONTROLLED EMISSIONS FROM AIR STRIPPERS
Faci 1 ity/ location
Name C i ty
Confidential - Stover (1)
Confidential - Stover (2)
Unidentified Scottsdale
Unidentified City of Scottsdale
i Hughes Aircraft Tucson
OJ
AMD, Inc. Sunnyvale
Baldwin Park Valley Country
Unidentified South Chesire
CT American Water Co.
Private Industry
Unidentified Ft. Pierce
Unidentified Port Malabar
Air
flow
State (ft3/min) Pollutant8
2,700 BZ
TOL
XYL
VO
4,000 BZ
XYL
EBZ
EDC
VO
AZ 25,000 TCE
AZ VOC
AZ 4 , 800 TCE
TCA
EDC
VO
CA VOC
CA 4,000 TCE
PCE
VO
CT 8,000 TCE
CT TCA
CT TCE
FL 2,000 TCE
PCE
VO
FL 9,000 VOC
Pol lutant
cone, in
(ppmv)
3.00
2.55
2.21
7.76
60.77
22.34
22.34
4.75
110.19
0.69
ND
16.43
2.03
5.54
23.99
ND
4.02
1.51
5.53
0.50
ND
ND
0.05
0.25
0.30
0.20
Air
emissions6
0
-------
TABLE C-l (continued)
o
i
Faci 1 ity /location
Name C i ty
Sydney Mine Hillsborough County
Boeing Wichita
Acton Water District Acton
Site A
Site B
Verona Well Field Battle Creek
Monroe Auto Cozad
Unidentified Rockaway
Unidentified Rocky Hill
Air
flow
State (ft3/min) Pollutant*
FL 4 , 700 EDC
MCL
TCA
OCE
VO
KS TCE
MA 3,000 TCA
DCE
TCE
VO
MI TCE
TCA
VO
MI 1 , 300 CF
MCL
EDC
MI 6,600 EDC
TCA
DCE
TCE
PCE
VO
NE 10,000 TCE
NJ 37 , 600 TCE
MTBE
DIPE
VO
NJ 2,600 TCE
Pol lutant
cone, in
airb
(ppmv)
0.02
0.01
0.01
0.00
0.04
NO
0.08
0.11
0.03
0.22
NO
NO
NO
4.7
NO
NO
0.06
0.10
0.11
0.01
0.07
0.34
2.47
0.22
0.06
0.06
0.34
0.03
Air
emissions0
(kfl/yr)
6.9
2.6
2.3
0.6
12.3
628.2
19.7
19.7
7.9
47.3
10,662.3
801.3
11,628.8
439.6
NO
ND
18.1
43.6
36.2
3.6
36.2
137.7
1,998.6
667.7
126.9
132.2
926.8
6.3
(continued)
-------
TABLE C-l (continued)
o
i
Faci
Name
Unidentified
Un i dent i fed
Deny i lie Water Dept.
E. Hanover Water Dept.
South Brunswick TWP
VO-Tech H.S.
Unidentified
Unidentified
Unidentified
Un i dent i f i ed
Unidentified
1 ity/ location
City
Mountainside
Plainfield
Deny i 1 1 e
East Hanover
Brunswick
Warren County
Queens
Garden City Park
Brewster
New Hyde Park
Lake Success
State
NJ
NJ
NJ
NJ
NJ
NJ
NY
NY
NY
NY
NY
Air
flow
(ft3/min)
3,300
19,200
4,000
6,000
13,000
16,000
6,600
3,000
12,800
14,000
Pol lutant"
TCE
PCE
VO
PCE
TCA
PCE
VO
TCE
TCE
PCE
DCE
VO
TCE
PCE
TCE
VO
PCE
PCE
EDC
TCE
VO
TCE
PCE
VO
TCE
Pol lutant
cone, in
(ppmv)
4.43
0.32
4.76
0.71
0.01
0.01
0.03
0.11
0.16
0.00
0.11
0.26
ND
1.04
0.40
1.44
0.36
0.42
0.31
0.08
0.80
1.29
0.32
1.61
0.12
Air
emissions0
(kg/yr)
1,180.6
107.3
1,287.8
1,368.1
4.8
6.7
10.6
64.4
166.8
6.2
83.1
246.2
1.6
1,666.6
616.1
2,180.6
193.7
124.7
66.6
19.3
199.4
1,332.4
412.1
1,744.5
133.2
(continued)
-------
TABLE C-l (continued)
o
i
cr.
Name
Unidentified
Un i dent i f i ed
Citizens Water
EPA Region II
Un identified
Unidentified
Unidentified
Unidentified
Unidentified
Faci 1 ity/location
City State
Floral Park NY
Northport NY
Supply Great Neck, Long Island NY
Hicksville NY
Zanesville OH
Hatboro (#1) PA
Upper Morion (#3) PA
Warrington PA
Hatboro (#2) PA
Air
flow
(ft3 /mi n) Po 1 1 utant"
16,000 TCE
TCA
VO
6,200 „ PCE
21,400 BZ
PCE
TCE
VO
MEK
1,860 TCE
DCE
VO
6,300 TCE
MTBE
DIPE
EDC
PCE
VO
1,400 TCE
600 TCE
TCE
EDC
PCE
VO
Pol lutant
cone, in
air°
(ppmv)
1.29
0.21
1.60
2.12
0.76
0.10
0.09
0.93
NO
66.70
16.39
71.09
0.24
0.16
0.02
0.02
0.01
0.44
0.17
0.71
NO
NO
NO
NO
Air
emissions'*
(kg/yr)
1,666.6
271.9
1,937.4
1,104.9
766.6
207.8
161.1
1,114.3
188.9
8,327.6
1,666.6
9,993.1
121.8
62.8
7.8
6.1
4.0
192.6
18.8
28.9
167.6
42.0
6.0
204.6
(continued)
-------
o
I
— _ — : ••-
Facility^location
Name City
Lycoming Ck . Well Field Williamsport
Superior Tube Co. Norristown
Tysons Dump Upper Merion
Upper Merion Res. (#1) Upper Morion
Unidentified Chesapeake
Un i f i rst
City of Tacoma Tacoma
A J -.
flow
State (ftVmin) Pollutant"
PA 58,000 TCE
PCE
DCE
VO
PA 300 TCE
PA 1,2,3-TCP
XYL
TOL
ANILINE
PHENOL
2-MPH
EB2
VO
PA 27,900 TCE
VA 54 , 100 CF
CHBrC12
CHBr2CI
CHBr3
VO
VT PCE
WA 146,000 1,1,2,2-TCA
TCE
DCE
VO
Pol lutant
cone . i n
(ppmv)
0.61
NO
NO
NO
45.11
NO
NO
NO
NO
NO
NO
NO
NO
0.21
0.16
0.09
0.05
0.01
0.32
NO
0.13
0.07
0.08
0.28
Air
emissions0
2,765.3
NO
NO
ND
1,093.7
295.4
165.7
NO
0.6
0.8
0.4
NO
ND
477.3
634.6
600.7
360.3
60.4
1,546.0
6.6
1,903.0
869.4
661.1
3,423.5
(continued)
-------
TABLE C-l (continued)
Name
Unidentif ied
FaciIity/location
City
Wausau (#1)
State
Air
flow
(ft3/min)
WI
16,000
Unidentif ied
Hartland
WI
6,700
Pollutant8
TCE
DCE
PCE
TOL
XYL
VO
TCE
Pollutant
cone, in
airb
(ppmv)
0.21
0.32
0.14
0.12
0.06
0.85
0.84
Air
em!ssionsc
269.2
300.4
224.4
109.9
62.3
966.1
453.3
ND = No data. Insufficient data available to calculate this value.
o
i
00
aPoIlutant abbreviations used are:
BZ = Benzene
CHLBZ = Chlorobenzene
CF = Chloroform
DCE = Dichloroethylene
DIPE = DiisopropyIether
EBZ = Ethyl benzene
EDC = Ethylene dichloride
or dichIoroethane
MCL = Methylene chloride
MEK = Methyl ethyl ketone
MTBE = MethyI-tertiary-butyl-ether
2-MPH = 2-MethyI phenol
PCE = Perch Ioroethylene or
tetrachIoroethane
TOL = Toluene
TCA = TrichIoroethane
TCE = TrichIoroethylene
1,2,3-TCP = 1,2,3-Trichloropropane
VO = Total volatile organics
(calculated as the sum of
pollutants reported)
VOC = Volatile organic compounds
(provided by facility
rather than calculated)
XYL = Xylene
^Pollutants concentration in air calculated from air flow rate and estimated emission rate based on ideal
gas law. Molecular weight assumed to be 100 g/mol for VOC. Air temperature assumed to be 60 °F.
cAir emissions calculated from pollutant loading and reported removal efficiency based on 8,400 h/yr
operation.
Source: U.S. Environmental Protection Agency. Air Stripping of Contaminated Water Sources—Air
Emissions and Controls. Control Technology Center. Research Triangle Park, NC. Publication
No. EPA-450/3-87-017. August 1987.
-------
1. REPORT NO.
EPA 450/3-91-007
TECHNICAL REPORT DATA
ff lease read Instructions on the reverse before completing/
2.
». TITLE AND SUBTITLE
Alternative Control Technology Documertt--
Organic Waste Process Vents
7. AUTHOR(S)
9. PERFORMING ORGANIZATION. NAME AND ADDRESS
Emission Standards Division
Office of Air Quality Planning and Standards
Environmental Protection Agency
Research Triangle Park, North Carolina 27711
12. SPONSORING AGENCY NAME AND ADDRESS "
DAA for Air Quality Planning and Standards
Office of Air, Noise, and Radiation
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
15. SUPPLEMENTARY NOTES
3. RECIPIENT'S ACCESSION NO.
5. REPORT DATE
December 1990
6. PERFORMING_ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
68-02-4326
13. TYPE OF REPORT AND PERIOD COVERED
Final 1990
4. SPONSORING AGENCY CODE
EPA/200/04
16. ABSTRACT
The purpose of this Alternative Control Technology (ACT) document is to
c'omonunH6?5Sr?ai 1nformation to addre« ai> ^missions of volatile oraanic
compounds (VOC) from organic process vents on waste management units treatina
organic-containing wastes that are exempted from the RCRA process venfair
r'nn^r l*™**rds (40 CFR Parts 264 & 265, Subpart AA). This document
contains technical information on air emission rates, control technologies
and environmental and cost impacts of alternative control technologies
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Gr
Air pollution
Treatment, storage, and disposal
facilities
Hazardous waste
Process vents
Volatile organics
Wa«;to *v-Qafmont -Fari lj ties
Air pollution control
13 B
Unlimited
19. SECURITY CLASS (Tins Report)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page/
Unclassified
189
22. PRICE
EPA Form 2220-1 (R«v. 4-77) PREVIOUS EDITION is OBSOLETE
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