p.1 

OAR Box 1870 

Prepped by Ollie Stewart 

Document Number: 

24) ll-A-27 

Docket Number: 

A-90-19 

Printed 11/28/2008 7:05:04 AM Sheet 24 of 67 
P.2 

a _ * • 

V>_:PA 

United States 

Environmental Protection 

Agency 

Air and Energy Engineering 

Research Laboratory 

Research Triangle Park, NC 27711 

Technology Transfer 

A-90-19 

ll-A-27 

Handbook 

Control Technologies for 

Hazardous Air Pollutants 
P.3 

I 

EPA/625/6-86/014 

September 1986 

Handbook 

Control Technologies for 

Hazardous Air Pollutants 

Air and Energy Engineering Research Laboratory 

Office of Research and Development 

U.S. Environmental Protection Agency 

Research Triangle Park, NC 27711 

Center for Environmental Research Information 

Office of Research and Development 

U.S. Environmental Protection Agency 

Cincinnati, OH 45268 
1 P.4 

Notice 

This document has been reviewed in accordance with the U.S Environmental Protection Aqency's peer and administrative review policies and approved for publication. Mention of trade names or commercial products does 

not constitute endorsement or recommendation for use. 
rx 

P.5 

Foreword 

Today's rapidly changing industrial technologies, products, and practices 

frequently carry with them an increasing generation of hazardous air pollutants (HAPs). When energy and material resources are extracted, processed, 

converted, and used, the consequent impacts on health and the environment 

require that efficient pollution control methods be used. 

The 1970 amendments to the Clean Air Act require the U.S. Environmental 

Protection Agency (EPA) to set National Ambient Air Quality Standards for 

criteria air pollutants found throughout the country. The Clean Air Act 

Amendments also require EPA to review and regulate hazardous air pollutants, defined as those air pollutants that can contribute to increased mortality or serious illness but which are not already regulated as criteria pollutants. 

Since the definition of a HAP is very broad and encompasses thousands of 

specific compounds, it is not practical to develop an all-inclusive list of HAP 

compounds and compound-specific control techniques. However, the number of generic air pollution control techniques available is small, and the 

factors affecting the cost and performance of these controls as applied to 

many noncriteria pollutants have been identified and discussed in the literature. 

The purpose of this handbook is to help EPA regional, State, and local air 

pollution control agency technical personnel select, evaluate, and cost air 

pollution control techniques for reducing or eliminating the emission of 

potentially hazardous air pollutants from industrial/commercial sources. The 

information provided by this document will be useful for reviewing permit 

applications or for informing interested parties of the type, basic design, and 

cost of available HAP control systems. 
P.6 

Acknowledgments 

This handbook has been adapted from a two-volume EPA report titled Evaluation of Control Technologies for Hazardous Air Pollutants. The report was 

written by Robert Y. Purcell, Pacific Environmental Services Inc., Durham, 

North Carolina, and Gunseli Sagun Shareef, Radian Corporation, Research 

Triangle Park, North Carolina. They were assisted by: Vishnu S. Katari, Karin 

C. C. Gschwandtner, Michael K. Sink, and Charlotte R. Clark of Pacific Environmental Services Inc.; and Andrew J. Miles, D. Blake Bath, and Glynda E. 

Wilkins of the Radian Corporation. Dr. Bruce A. Tichenor of EPA's Air and 

Energy Engineering Research Laboratory, Research Triangle Park, North 

Carolina, was the EPA project officer for the report. 

This handbook was adapted and produced by JACA Corporation, Fort Wash- [ 

ington, Pennsylvania. Norman Kulujian of EPA's Center for Environmental '. 

Research Information, Cincinnati, Ohio, was the EPA project officer for this 

publication. 

i 

If you wish to obtain the more detailed two volume report, is is available from | 

the National Technical Information Service (NTIS), 5285 Port Royal Road, j 

Springfield, Virginia 22161; (703) 487-4650. The order numbers are: j 

Volume I. Technical Report; PB 86-167 020; EPA/600/7-86/009a 

Volume II. Appendices; PB 86-1670038; EPA/600/7-86/009b 

k__ 
P.7 

for specific HAP's are available. Therefore, without 

actual source test data for a specific emission 

stream and control system, HAP removal efficiency 

is assumed to equal total volatile organic compound (VOC) removal efficiency. 

3.2.1.1 Thermal Incinerators 

Thermal incinerators are used to control a wide 

variety of continuous emission streams containing 

VOC's. Compared to the other techniques, thermal 

incineration is broadly applicable; that is, it is much 

less dependent on HAP characteristics and emission stream characteristics. Destruction efficiencies 

up to 99+ percent are achievable with thermal incineration. Although they accommodate minor 

fluctuations in flow, thermal incinerators are not 

well suited to streams with highly variable flow 

because the reduced residence time and poor mixing during increased flow conditions decrease the 

completeness of combustion. This causes the combustion chamber temperature to fall, thus decreasing the destruction efficiency. 

Thermal incineration is typically applied to emission streams that are dilute mixtures of VOC and 

air. In such cases, due to safety considerations, 

concentration of the VOC's is generally limited by 

insurance companies to 25 percent of the LEL (lower explosive limit) for the VOC in question (see 

Section 4.2.2 for more details). Thus, if the VOC 

concentration is high, dilution may be required. 

When emission streams treated by thermal incineration are dilute (i.e., low heat content), supplementary fuel is required to maintain the desired combustion temperatures. Supplementary fuel 

requirements may be reduced by recovering the 

energy contained in the hot flue gases from the 

incinerator. For emission streams with high heat 

contents (e.g., > 150 Btu/scf), the possibility of using the emission stream as fuel gas should be considered. 

Packaged single unit thermal incinerators are available in many sizes to control emission streams with 

flow rates from a few hundred up to about 100,000 

scfm. 

3.2.1.2 Catalytic Incinerators 

Catalytic incinerators are similar to thermal incinerators in design and operation except that the former employ a catalyst to enhance the reaction rate. 

Since the catalyst allows the reaction to take place 

at lower temperatures, significant fuel savings are 

possible with catalytic incineration. 

Catalytic incineration is not as broadly applied as 

thermal incineration since performance of catalytic 

incinerators is more sensitive to pollutant characteristics and process conditions than is thermal incinerator performance. Materials such as phosphorus, bismuth, lead, arsenic, antimony, mercury, 

iron oxide, tin, zinc, sulfur, and halogens in the 

emission stream can poison the catalyst and severely affect its performance. (Note: Some catalysts can handle emission streams containing halogenated compounds.) Liquid or solid particles that 

deposit on the catalyst and form a coating also 

reduce the catalyst's activity by preventing contact 

between the VOC's and the catalyst surface. Catalyst life is limited by thermal aging and by loss of 

active sites by erosion, attrition, and vaporization. 

With proper operating temperatures and adequate 

temperature control, these processes are normally 

slow, and satisfactory performance can be maintained for 3 to 5 years before replacement of the 

catalyst is necessary. 

Catalytic incineration is generally less expensive 

than thermal incineration in treating emission 

streams with low VOC concentrations. Emission 

streams with high VOC concentrations should not 

be treated by catalytic incineration without dilution 

since such streams may cause the catalyst bed to 

overheat and lose its activity. Also, fluctuations in 

the VOC content of the emission stream should be 

kept to a minimum to prevent damage to the catalyst. 

Destruction efficiencies of up to 95 percent of 

HAP's are generally achieved with catalytic incineration. Higher destruction efficiencies (99 percent) 

are also achievable, but require larger catalyst volumes and/or higher temperatures. 

Catalytic incinerators have been applied to continuous emission streams with flow rates up to about 

100,000 scfm. 

3.2.1.3 Flares 

Flares are commonly used for disposal of waste 

gases during process upsets (e.g., start-up, shutdown) and emergencies. They are basically safety 

devices that are also used to destroy waste emission streams. 

Flares can be used for controlling almost any VOC 

emission stream. They can be designed and operated to handle fluctuations in emission VOC content, inerts content, and flow rate. There are several 

different types of flares including steam-assisted, 

air-assisted, and pressure head flares. Steam-assisted flares are very common and typically employed in cases where large volumes of waste gases are released. Air-assisted flares are generally 

used for moderate relief gas flows. Pressure head 

flares are small; they are used in arrays of up to 100 

individual flares. Normally, only a few of the flares 

operate. The number of flares operating is increased as the gas flow increases. 

Flaring is generally considered a control option 

when the heating value of the emission stream 

25 
P.8 

' cannot be recovered because of uncertain or intermittent flow as in process upsets or emergencies. If 

the waste gas to be flared does not have sufficient 

heating value to sustain combustion, auxiliary fuel 

may be required. 

Based on studies conducted by EPA, 98 percent 

destruction efficiency can be achieved by steamassisted flares when controlling emission streams 

with heat contents greater than 300 Btu/scf. Depending on the type of flare configuration (e.g., 

elevated or ground flares), the capacity of flares to 

treat waste gases can vary—up to about 100,000 

lb/hr for ground flares and 2 million lb/hr or more 

for elevated flares. The capacity of an array of pressure head flares depends on the number of flares in 

the array. 

3.2.1. < 

Existing boilers or process heaters can be used to 

control emission streams containing organic compounds. These are currently used as control devices for emission streams from several industries 

(e.g., refinery operations, SOCMI reactor processes 

and distillation operations, etc.) 

Typically, emission streams are controlled in boilers or process heaters and used as supplemental 

fuel only if they have sufficient heating value 

(greater than about 150 Btu/scf). In some instances, 

emission streams with high heat content may be 

the main fuel to the process heater or boiler (e.g., 

process off-gas from ethylbenzene/styrene manufacturing). Note that emission streams with low 

heat content can also be burned in boilers or process heaters when the flow rate of the emission 

stream is small compared to the flow rate of the 

fuel/air mixture. 

When used as emission control devices, boilers or 

process heaters can provide destruction efficiencies of greater than 98 percent at small capital cost 

and little or no fuel cost. In addition, near complete 

recovery of the emission stream heat content is 

possible. 

There are some limitations in the application of 

boilers or process heaters as emission control devices. Since these combustion devices are essential 

to the operation of a plant, only those emission 

streams that will not reduce their performance or 

reliability can be controlled using these devices. 

Variations in emission stream flow rate and/or 

heating value could adversely affect the performance of a boiler or process heater. By lowering 

furnace temperatures, emission streams with large 

flow rates and low heating values can cause incomplete combustion and reduce heat output. The performance and reliability of the process heater or 

boiler may also be affected by the presence of corrosive compounds in the emission stream; such 

streams are usually not destroyed in these devices. 

26 

3.2.UJ Csirbotn _k9_ortb>®.s 

Carbon adsorption is commonly employed as a 

pollution control and/or a solvent recovery technique. It is applied to dilute mixtures of VOC and 

air. Removal efficiencies of 95 to 99 percent can be 

achieved using carbon adsorption. The maximum 

practical inlet concentration is usually about 10,000 

ppmv. The inlet concentrations are typically limited 

by the adsorption capacity of the carbon bed or 

safety problems posed by high bed temperatures 

produced by heat of adsorption and presence of 

flammable vapors. Outlet concentrations of 50 to 

100 ppmv can be routinely achieved with state-ofthe-art systems; concentrations as low as 10 to 20 

ppmv can be achieved with some compounds. In 

contrast to incineration methods whereby the 

VOC's are destroyed, carbon adsorption provides a 

favorable control alternative when the VOC's in the 

emission stream are valuable. 

High molecular-weight compounds that are characterized by low volatility are strongly adsorbed on 

carbon. The affinity of carbon for these compounds 

makes it difficult to remove them during regeneration of the carbon bed. Hence, carbon adsorption is 

not applied to such compounds (i.e., boiling point 

above 400°F; molecular weight greater than about 

130). Highly volatile materials (i.e., molecular 

weight less than about 45) do not adsorb readily on 

carbon; therefore, adsorption is not typically used 

for controlling emission streams containing such 

compounds. 

Carbon adsorption is relatively sensitive to emission stream conditions. The presence of liquid or 

solid particles, high boiling organics, or polymerizable substances may require pretreatment procedures such as filtration. Dehumidification is necessary if the emission stream has a high humidity 

(relative humidity > 50 percent) and cooling may 

be required if the emission stream temperature exceeds 120°-130°F. 

To prevent excessive bed temperatures resulting 

from the exothermic adsorption process and oxidation reactions in the bed, concentrations higher 

than 10,000 ppmv must frequently be reduced. This 

is usually done by condensation or dilution of the 

emission stream ahead of the adsorption step. Exothermic reactions may also occur if incompatible 

solvents are mixed in the bed, leading to polymerization. If flammable vapors are present, the VOC 

concentrations may be limited by insurance companies to less than 25 percent of the LEL. If proper 

controls and monitors are used, LEL levels up to 40 

to 50 percent may be allowed. 

Packaged carbon adsorption systems are available 

that can handle emission streams with flow rates 

from a few hundred to above 100,000 scfm. 

___Q___r____i _r_______r_si_n_____i 
P.9 

3.2.1.6 Absorbers (Scrubbers) 

Absorption is widely used as a raw material and/or 

a product recovery technique in separation and purification of gaseous streams containing high concentrations of VOC's. As an emission control technique, it is much more commonly employed for 

inorganic vapors (e.g., hydrogen sulfide, chlorides, 

etc.) than for organic vapors. Using absorption as 

the primary control technique for organic vapor 

HAP's is subject to several limitations and problems as discussed below. 

The suitability of absorption for controlling organic 

vapor emissions is determined by several factors; 

most of these factors will depend on the specific \ 

HAP in question. For example, the most important 

factor is the availability of a suitable solvent. The 

pollutant in question should be readily soluble in ' 

the solvent for effective absorption rates and the \ 

spent solvent should be easily regenerated or dis- < 

posed of in an environmentally acceptable manner. J 

Another factor that affects the suitability of absorption for organic vapor emissions control is the 

availability of vapor/liquid equilibrium data for the 

specific HAP/solvent system in question. Such data 

are necessary for design of absorber systems. For 

uncommon HAP's, these data are not readily available. 

Another consideration involved in the application 

of absorption as a control technique is disposal of 

the absorber effluent (i.e., used solvent). If the absorber effluent containing the organic compounds 

is discharged to the sewer, pond, etc., the air pollution problem is merely being transformed into a 

water pollution problem. Hence, this question 

should be addressed (e.g., are there chemical/physical/biological means for treating the specific effluent under consideration?). In solvent recovery, 

used organic solvents are typically stripped (reverse of absorption) and recycled to the absorber 

for economic reasons. However, in HAP control 

applications, stripping requirements will often be 

very expensive because the residual organic concentrations in the solvent must be extremely low 

for it to be suitable for reuse. Also, if the VOC's in 

the effluent from the absorber have appreciable 

vapor pressure (e.g., > 0.1 mm Hg), the possibility 

of VOC emissions to the atmosphere should be 

considered. 

In organic vapor HAP control applications, low outlet concentrations will typically be required. Trying 

to meet such requirements with absorption alone 

will lead to impractically tall absorption towers, 

long contact times, and high liquid-gas ratios that 

may not be cost effective. Therefore, absorbers will 

generally be effective when they are used in combination with other control devices such as incinerators. 

Removal efficiencies in excess of 99 percent can be 

achieved with absorption. 

3.2.1.7 Condensers 

Condensers are widely used as raw material and/or 

product recovery devices. They are frequently applied as preliminary air pollution control devices 

for removing VOC contaminants from emission 

streams prior to other control devices such as incinerators, adsorbers, or absorbers. 

Condensers are also used by themselves for controlling emission streams containing high VOC 

concentrations (usually > 5,000 ppmv). In these 

cases, removal efficiencies obtained by condensers 

range from 50 to 90 percent. The removal efficiency 

of a condenser is dependent on the emission 

stream characteristics including the nature of the 

HAP in question (vapor pressure-temperature relationship) and HAP concentration, and the type of 

coolant used. Note that a condenser cannot lower 

the inlet VOC concentration to levels below the 

saturation concentration (or vapor pressure) at the 

coolant temperature. When water, the most commonly used coolant, is employed, the saturation 

conditions represent high outlet concentrations. 

For example, condenser outlet VOC concentrations 

are often limited to above 10,000 to 20,000 ppmv 

due to the saturation conditions of most of the 

organic compounds at the temperature of the cooling water. Therefore, it is not possible for condensation with water as the coolant to achieve the low 

outlet concentrations that would be required in 

HAP control applications. 

Removal efficiencies above 90 percent can be 

achieved if lower temperatures than those possible 

with cooling water are employed. These low temperatures can be obtained with coolants such as 

chilled water, brine solutions, or chlorofluorocarbons. However, for extremely low outlet HAP concentrations, condensation will usually be economically infeasible. 

Depending on the type of condenser used, there 

may be potential problems associated with the disposal of the spent coolant. Therefore, using contact 

condensers that generate such effluents for controlling HAP emissions is not recommended. 

Flow rates up to about 2,000 scfm can be considered as representative of the typical range for condensers used as emission control devices. Condensers for emission streams with flow rates above 

2,000 scfm and containing high concentrations of 

noncondensibles will require prohibitively large 

heat transfer areas. 

27