13

The most efficient technique for controlling organic emissions is
to design equipment that completely consumes the materials being processing.
Improved operating and maintenance procedures can sometimes substantially
reduce or eliminate organic emissions. New process technologies can reduce
organic emissions by avoiding inefficient or poorly controlled operations.

Secondary environmental impacts of stationary source controls are
generally insignificant if properly designed and operated, however,. control
systems employing internal combustion engines to drive compressors may
create NO, problems that are not justified. Such cases should be carefully

evaluated to establish the net environmental benefit.

Environmental Impacts of Mobile Source Controls

Section 202 of the Clean Air Act, as amended, required substantial
reduction of certain specified emission products from automobiles. The
automotive industry, to achieve these reductions, chose the oxidation
catalytic convertor as the primary method of emission control.

In 1974 EPA established the Catalyst Research Program to determine
what, if any, new pollutants might be emitted into the atmosphere as a
result of the application of this technology.* The effects of fuel
composition and fuel additives on these emissions were also studied.
Results from the EPA research program indicated that although emissions of
hydrocarbons, carbon monoxide, and certain organics would be dramatically
lowered, sulfuric acid aerosol emissions would increase and slight emissions
of platinum, palladium, and aluminum might also be expected. EPA sub-
sequently initiated a broad research study to examine the public health

impact of catalyst-emitted sulfates, platinum, and palladium.


known to experience respiratory distress at (.25 ppm) and healthy adults
experience significant adverse changes in lung function at concentra-

tions of 725 ug/m (0.37 ppm). New studies have demonstrated lung function
decrements in human subjects at ozone concentrations as low as 0.15 ppm

and some animal studies indicate adverse effects at 0.08 ppm ozone.?

Ozone in low concentrations are significant non-human health effects such

as accelerated aging of rubber, paint, and dye, and damage to vegetation.

Environmental Impacts of Stationary Source Controls.

Strategies for control of ambient ozone are directed toward emissions
of volatile organic compounds. These compounds are emitted by a variety
of stationary sources and by gasoline and diesel powered vehicles. The
following summary of current ‘control technology and practice is based
upon and extracted from the report "Control Techniques for Voltatile
Organic Emissions from Stationary Sources"? which was prepared for EPA
by Radian Corporation under contract No. 68-02-2608.

There are three basic methods used to control emissions of hydro-
carbons and other organics from stationary sources. They are:

1. the installation of control equipment to recover or destroy

the organic vapors,

2. the substitution of less photochemically reactive materials

in the process, and
3. the incorporation of process and material changes that reduce

or eliminate vapor emissions.


The liquid effluent from an absorber can frequently be used else-
where in the process. When this is not possible, the non-regenerated
absorbent effluent should be treated to provide good water quality. Such
treatment may include a physical separation process (decanting or
distilling) or a chemical or biological treating operation.

Regeneration consists of heating the liquid effluent stream to
reduce the solubility of the absorbed organics and separate them from the
absorbent. These concentrated organics can then be oxidized in an after-
burner. Emissions of SO, NO, and other incomplete oxidation products
may be a result, depending on the nature of the regenerated gas stream.

The control of one type of volatile organic emission can result in
the emission of another at an even greater rate when liquid absorption is
employed. For example, vapors of trichloroethylene can be substantially
reduced in an air stream by absorption in a lean mineral oi1; however,
at ambient temperature the air stream leaving the absorber might
contain 120 ppm mineral oil.

Use of water absorption increases plant water requirements.

However, an add-on water scrubbing system will usually mean only a minimal
increase in the throughput to the existing water treatment facilities in

a plant.

Condensation

Condensers operate by preassurizing or lowering the temperature
of an exhaust vapor thereby condensing out the organic contaminants.
Condensation is usually applied in combination with other air pollution
control systems. Condensers located upstream of afterburners, carbon

beds, or absorbers can reduce the total load entering the more expensive


atmosphere. For an afterburner combusting a 15% LEL gas stream containing
no appreciable sulfur compounds with No. 2 fuel oi], SQ) emissions are
approximately 50 ppm.

In addition, nitrogen-containing compounds may be oxidized to NO, .
increasing pollution emissions. Due to thermal fixation of air, no nitrogen
compounds need be found in the fuel or waste gas to produce NO, emissions.
NO, emissions result from all combustion processes. The estimated No,
concentration for effluent from natural gas-fired, noncatalytic after-
burners is 40 to 50 ppm.

Incineration of any halogen-containing compound causes acid
formation, which is undesirable.

If a distillate fuel oi] is used to fire an incinerator, particulate
emissions may become an air pollution concern. An afterburner designed
for the disposal of volatile organic emissions usually does not have
sufficient residence time to combust organic particulates efficiently.

In catalytic incineration, the regeneration or replacement of the
catalyst can present a secondary pollution problem. When the catalyst
needs to be completely replaced, the used catalyst is treated as solid
waste, and an acceptable means for disposal must be found. If the
catalyst can be reused, the suggested cleaning or reactivation process,
usually supplied by the manufacturer, requires provisions for proper

disposal of any waste material.


The five major technologies for the recovery or destruction of organics
are: incineration, adsorption, absorption, condensation, and flaring.
Each technology and the associated enviornmental impacts are summarized

on the following pages.

Incineration

The control of organic emissions by combustion, is the control
technology most universally applied by industry. Because of its need for
supplemental fuel, incineration is most useful when the heat developed
during combustion is recovered and used to meet other plant energy needs.

Afterburners, also called vapor incinerators, are devices in which
dilute concentrations of organic vapors are burned with additional fuel.
Afterburners oxidize organic emissions either by direct flame
(thermal) incineration or by catalytic oxidation. Under the proper
conditions, the firebox of a process heater or boiler may also be used
as an afterburner.

Possible adverse environmental effects must be considered in choosing
thermal or catalytic incineration as a means of controlling volatile organic
vapor emissions. The benefits from incineration must be weighed against
the adverse effects of implementing this control method.

The process stream, fuel gas, or fuel oi? to be combusted in an
incinerator may contain sulfur compounds. Oxidation of these compounds

produces varying amounts of sulfur oxides which are then released to the


Some process streams contain particulates which plug the void spaces
in the adsorbent bed and render it ineffective much sooner than normal. This
problem is solved by precleaning the gas feed stream. However, an
effective means for disposing of the particulates must then be found. The
disposal of spent adsorbent is also an environmental concern, but this may

be necessary only once in: three to five years.

Absorption

Absorption is the process in which certain constituents of a gas
stream are selectively transferred to a liquid solvent. Absorption may be
purely physical, in which the solute simply dissolves in the absorbent
or with reagents dissolved in the absorbent.

The generally low concentrations of exhaused organics require long
contact times and large quantities of absorbent for adequate emissions
control. Absorption is, therefore, less desirable than adsorption or
incineration, unless the absorbent is easily regenerated or the solution
can be used as a process makeup stream. Absorption may be best suited for
use in conjunction with other control methods such as incineration or
adsorption to achieve the prescribed degree of emissions removal.

Adverse environmental effects resulting from the operation of an
absorber include improper disposal of the organic-laden liquid effluent,
undesired emissions from the incineration of the regenerated waste gas,

loss of absorbent to the atmosphere, and increased water usage.


ENVIRONMENTAL IMPACT ASSESSMENT OF CONTROL MEASURES
REQUIRED FOR ATTAINMENT OF THE
NATIONAL AMBIENT AIR QUALITY STANDARD FOR OZONE

June 1978

Strategies and Air Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711


i

Flares

Flares are most commonly used to incinerate waste gases from
petroleum refining and petrochemical manufacturing operations. Flares are
preferred when treating gas streams with sufficient heat value to attain
the combustion temperature without the use of supplemental fuel. Flares
are also preferred when treating gases with little recovery value, or for
gases containing contaminants that make recovery unprofitable.

The operation of a flare affects the environment in the following
areas: chemical and oxidation emissions, particulate emissions, thermal
and visible radiation, and noise. Elevated flares are primarily intended
for plant emergencies and are inherently not as efficient in the above areas
as new, enclosed, ground-level flares.

Chemical emissions are the direct result in incomplete combustion
of the volatile organics contained in the waste gas stream. Carbon
monoxide and partially oxidized hydrocarbons such as aldehydes are known
to be products of elevated flares. Because of lower design velocities,
emission of unburned hydrocarbons is much lower in an enclosed, ground-
level flare.

Sulfur compounds, nitrogen compounds, and other undesirable chemicals
are also completely oxidized and emitted to the atmosphere. In particular,
hydrogen sulfide streams are often routed to flares and burned. SO,
emissions from refinery flares average 27 1b/10° bb1 refinery feed.

NO, emissions from flares are also common due to direct contact

of nitrogen with oxygen at the flame temperature. But NO, emissions from


10

control equipment. Unless concentrated vapors are to be removed,
condensation is rarely the sole means of controlling organic emission.
When used alone, condensation often requires costly refrigeration to
achieve the low temperatures needed for adequate control.

A condenser will create few secondary environmental problems when
the condensation process is considered by itself. Problems that do arise
include disposal of non-condensibles in surface condensers and refrigera-
tion systems, and the need for proper treatment of the liquid effluent in
contact condenser systems. Condensation is rarely used alone as a control
method; therefore, it is imperative that all associated equipment produce
effluent streams of sound environmental quality.

The non-condens ible gas effluent from surface condensers is either
vented to the atmosphere or further processed (e.g., via incineration),
depending on the effluent composition. The coolant never contacts the
vapors or condensate in the surface condenser; therefore, the recovered
organic compounds are usually reusable. The condensate might not be saved
if more than one compound is condensed and separation is costly. Proper
treatment of the condensate is then imperative before final disposal.
This also applies for the recovery of volatile organic emissions by
refrigeration.

In contact condensation, the condensate is contaminated with the
coolant liquid. The usual procedure is treatment of the waste stream
and disposal. The amount of organic material entrained in the existing

wastewater depends upon the extent of treatment.


Adsorption

Adsorption is the process by which components of a gas are retained
on the surface of granular solids. The solid adsorbent particles are
highly porous and have a very large surface-to-volume ratio. Gas
molecules penetrate pores of the material and contact the large surface area
available for adsorption. Organic vapors retained on the adsorbent are
subsequently desorbed, usually with steam. Both the vapors and the
adsorbent are recovered and may be reused.

Complete package adsorption systems are available from a number of
manufacturers. The economic feasibility of organic vapor emission
control by adsorption depends on the value of solvent recovered from the
adsorbent and the cost of removing adsorbed organics from the adsorbent
bed.

There are some potential environmental impacts caused by adsorption
systems, including both air and water pollution. Loss of organic sol-
vent with wastewater, oxidation product emissions with incineration, and
solid waste disposal are possible results depending upon the type of
adsorption system utilized.

If a steam desorption cycle is used and the recoverable organic
solvents are soluble in water, then some form of water treatment or
separation process is required to minimize the organic concentration in
the wastewater.

Incineration can be used to control emissions from the adsorber
during steam or hot air desorption. The type and amount of emission are

very dependent on the nature of the exit stream.


the ozone concentration to increase. ! )

The photochemical oxidants that combine to form smog, include N02,
03, and smaller concentrations of peroxyacetyl nitrates and other
peroxy compounds. Efforts toward regulation of photochemical oxidants
have previously attempted to deal with that entire class of pollutants.
However, measurement of total oxidants is imprecise and the health and
welfare effects of most of many non ozone photochemical oxidants are not
known. Ozone is the most abundant member of the photochemical oxidant
family occurring in the atmonphere. Ambient levels of ozone can be
measured very acurately (Appendix D, 40 CFR, Part 50 for the measurement
of Photochemical Oxidants) and many of the health and welfare effects of ozone
are well understood. Thus, an ambient air quality standard for ozone
would be more precise and meaningful than the present standard for
total photochemical oxidant.

Ozone. is an extremely irritating gas and cannot be tolerated by
some subjects at concentrations in the range of 1960-7850 ua/m a-
4ppm) for more than a few minutes. Minor throat irritation and chest
congestion are caused by exposure to concentrations of approximately 590
ug/m3 (0.3ppm) and progressively more severe respiratory effects have

been measured with higher exposure concentrations. Asthmatics have been


14

EPA and other researchers have continued these investigations and
have included work on other emissions including manganese, ruthenium,
hydrogen cyanide, ammonia, and polynuclear aromatic compounds .> While
much of this work is still on going, results have indicated that the
magnitude of these secondary impacts is not of major concern.© Results
of studies of the emissions of various metals are nearing completion.
Emissions of HCN were found to be at acceptable levels under worst-case
conditions. The investigation of possible adverse health effects of
ammonia emissions is now in progress. Emissions of HpS04 have been found
to vary widely depending upon engine and convertor mileage, engine
design, mode of driving, etc. Although recent tests of California
equipped autos have shown HyS04 emissions as high as 136 mg/mi, recent
tésting of non-air-injection equipped vehicles indicates emissions of
less than 10 mg/mi and air-injection equipped vehicles emit 20 mg/mi or
more.° This recent testing also indicates that as HC and CO emissions
increase with age and mileage of the equipment, H,S0q, emissions decline.°

This research together with research on human health effects of HSO4

is continuing and major reports of findings are expected to be avail-

able during the coming year. The ruthenium testing is precipated by the
possibility that auto manufacturers are considering its use in NO,

reduction catalysts, and the fact that ruthenium oxides may be highly
toxic.® EPA is not currently in a position to quantify what, if any,

levels of ruthenium emissions would be considered significant.° Polynuclear

aromatic compounds are primarily a concern with respect to diesel engine


7

List of References

"Control Techniques for Volatile ORganic Emissions From Stationary
Sources”, Radian Corporation, Austin, Texas, 1977, pp. 4-7 (EPA
Contract No. 68-02-2608).

"Air Quality Criteria for Ozone and Other Photochemical Oxidants",
Volume II, U.S. Environmental Protection Agjency, Washington, D.C.,
p. 9-22, 1978.

Control Techniques for Volatile Organic Emissions From Stationary
Sources" op cit. pp. 24-106.

Lee, R., and F. Duffield, "EPA's Catalyst Research Program: Environmental
Impact of Sulfuric Acid Emissions: Jour. Air Pollution Control Ass'n.,
Vol. 27, No. 7, July, 1977.

"Third Annual Catalyst Research Program Report" Health Effects Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle Park,
N.C., January, 1978, (EPA-600/3-78-012).

Duffield, F., personal communication, March 20, 1978.
"National Ambient Air Quality Standard for Lead - Draft Environmental

Impact Statement", U.S. Environmental Protection Agency, Research
Triangle Park, N.C. December, 1977, p. 2-53.


Although the natural contribution is the greater of the two, sources
resultant of man's activities, in combination with favorable meteoro-
logical conditions, produce locally excessive concentrations of oxidants.
A very simplified description of the atmospheric photochemistry is given

by the following equations:

Sunlight
NO2 > NO+ 0 (1)
M
0 + O + 03 + M (2)
03 + NO > NOp + 09 (3)
RO, + NO + NOp + — ROy (4)

where M is a third body (usually No, 02, or H20) stabilizing the molecule;

- 1
R is an organic or inorganic radical; x = 1,2, or 3; and y= x - 1.
Reactions 7 through 3 are very rapid and their rates are nearly equal.

At steady state conditions, ozone and NO are formed and destroyed in equal

quantities. The equilibrium equation is:

(0a) = « {gg (5)

Thus the concentration of ozone in the polluted atmosphere is controlled
by the intensity of sunlight and the ratio of NO. to NO. Hydrocarbons and
other pollutants - such as aldehydes, ketones, chlorinated hydrocarbons
and carbon monoxide - react to form peroxy radicals. These, in turn,

react with nitric oxide, causing the ratio (NO2) : (NO) to increase, and


Environmental Impact Assessment of Control Measures
Required for Attainment of the
National Ambient Air Quality Standard for Ozone

Introduction

The Clean Air Act, as amended, requires that the Administrator of
the U. S. Environmental Protection Agency periodically review the basis
for the ambient air quality standards. A review of the National Ambient
Air Quality Standard (NAAQS) for photochemical oxidants has recently

been concluded and the Air Quality Criteria for Ozone and other Photo-

chemicals Oxidants and Control Techniques for Hydrocarbons and Volatile

Organic Compounds have been reissued. The criteria document has been
revised to incorporate new information about the health and welfare
effects of oxidants. The control techniques documents presents availa-
ble control technology based on experience and new developments since
the previous publications.

The purpose of this assessment is to review the information presen-
ted in the control techniques document and to present an analysis of the
environmental impact of control measures required for attainment of the

air quality standard for ozone.

Background

Photochemical oxidants occur as a result of a complex series of
chemical reactions in the atmosphere. Precursors of the oxidants are

emitted to the atmosphere from both natural and man-made sources.


12

elevated flares using steam to inject air are lower than for gas-fired
burners due to the lower flame temperature. A typical emission rate for a
flare system in a petroleum refinery is 19 1b No,/10" bb1 refinery feed.

Air must be well mixed with the gas at the point of combustion in
a flare or soot will escape from the flare. A smokeless flame is attained
when an adequate amount of air is kept well mixed at the point of combustion.
This is usually accomplished by injecting steam to provide the needed
turbulance.

Other emissions include thermal and visible radiation.

Steam injection can reduce thermal radiation by lowering the flame temperature.
Luminosity cannot be completely reduced, but enclosing a ground level flare
is desirable, especially in populated areas.

Low frequency combustion noise and high frequency jet noise in
flares is an environmental problem for elevated flares in populated areas.
The jet noise is not a problem with ground level flares, and the combustion
noise is reduced significantly.

Other control methods in many instances may completely avoid the
emission of chemically reactive organic vapors. Compounds of Tow
photochemical reactivity can sometimes be substituted for highly-reactive
compounds currently in use. The resultant total organic emissions do not
necessarily decrease and may increase, but the substitution of non-reactive
or less reactive organic compounds can reduce urban photochemical oxidant
formation. Few volatile organic compounds are of such low photochemical

reactivity that they can be ignored in oxidant control programs.


15

emissions. However, they are also emitted by gasoline power engines.
Emissions from catalyst equipped engine are substantially less than are
those from noncatalyst equipped engines, thus environmental impact is
favorable.° In summary, much research and investigative work remains to
be completed prior to a clean bill of health regarding secondary impacts
of oxidation catalyst; however, earlier concerns of excessive secondary
impact have been lessened as the research proceeds.

A favorable secondary impact accrues from the increasing use of
non-leaded gasoline in catalyst equipped automobiles. Some recently
reported declines in airborne lead concentrations are probably being

attributed to the increasing use of non-leaded gasoline.”