EPA-450/4-84-007/
September 1986
Locating And Estimating Air Emissions
From Sources Of Ethylene Oxide
U.S. ENVIRONMENTAL PROTECTION AGENCY
• Office Of Air And Radiation
Office Of Air Quality Planning And Standards
Research Triangle Park, North Carolina 27711
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This report has been reviewed by the Office Of Air Quality Planning And Standards, U.S. Environmental
Protection Agency, and has been approved for publication as received from the contractor. Approval does
not signify that the contents necessarily reflect the views and policies of the Agency, neither does mention
of trade names or commercial products constitute endorsement or recommendation for use.
EPA-450/4-84-007
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TABLE OF CONTENTS
Section . . Page
1 Purpose of Document i
2 Overview of Document Contents 3
3 Background . 5
Nature of Pollutant ... , 5
Overview of Production and Use 7
References for Section 3 14
4 Emissions from Ethylene Oxide Production 16
Ethylene Oxide Production 16
References for Section 4 33
5 Emissions from Industries Which Use Ethylene Oxide 35
Ethylene-Glycol and Its Homologs 35
Glycol Ethers 41
Ethanolamines 45
Ethoxylation . . 43
Fumigation/Sterilization 49
References for Section 5 59
6 Source Test Procedures 61
Sampling and Analysis 61
Direct Instrumentation Methods :....... 64
References for Section 6 ............................. 66
APPENDICES
A Derivation of Emission Estimates for Fugitive Equipment
Leaks Based on EPA Emission Factors A-l
iii
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LIST OF TABLES
Table
1 Physical and Chemical Properties of Ethylene Oxide 6
2 Producers of Ethylene Oxide in the United States
in 1986 8
'3 Major Users of Ethylene Oxide as a Chemical Feedstock
in 1986 12
4 Descriptions of Streams and Vents Illustrated in Figure 3
for the Air Oxidation of Ethylene to Ethylene Oxide 20.
5 Descriptions of Streams and Vents Illustrated in Figure 4
for the Oxygen Oxidation of Ethylene to Ethylene Oxide .... 23
6 Emission Factors for the Release of Ethylene Oxide from
an Air-Oxidation Ethylene Oxide Production Plant 31
7 Emission Factors for the Release of Ethylene Oxide from
an Oxygen-Oxidation Ethylene Oxide Production Plant 32
8 Types of Ethylene Oxide Sterilization/Fumigation
Equipment Used at Different Sites 50
9 Miscellaneous Uses and Use Rates of Ethylene Oxide as a
Fumigant and Sterilant 54
10 Selected Procedures for Ethylene Oxide Monitoring 62
11 Selected Ethylene Oxide Direct Monitoring Methods 65
A-l Fugitive Equipment Leak Parameters - Air Oxidation Model
Ethylene Oxide Production Plant A-2
A-2 Fugitive Equipment Leak Parameters - Oxygen Oxidation
Model Ethylene Oxide Production Plant A-3
A-3 Fugitive Equipment Leaks Control Techniques A-4
iv
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LIST OF FIGURES
?age
1 Locations of Plants Which Manufacture Ethylene Oxide ...... 9
2 End Use Distribution of Ethylene Oxide ..... ........... .... 11
3 Basic Operations that may be Used in the Production of
Ethylene Oxide by Air Oxidation ....... .................... 19
4 Basic Operations that may be Used in the Production of
Ethylene Oxide by Oxygen Oxidation ........................ 22
5 Basic Operations that may be Used in the Production of
Ethylene Glycol, Diethylene Glycol, and T.riethylene
Glycol by Conventional Noncatalyzed Hydration of
Ethylene Oxide ....................................... ..... 38
6 Process Operations for Transfer of Ethylene Oxide to the
Ethylene Glycol Plant ..................................... 39
7 Basic Operations that may be Used in the Production of
Glycol Ethers from Ethylene Oxide ......................... 43
8 Production of Ethanolamines by the Ethylene Oxide -Ammonia
Process ...... ....... ........... ................. .......... 47
v
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SECTION 1
PURPOSE OF DOCUMENT
EPA, States and local air pollution control agencies are becoming
increasingly aware of the presence of substances in the ambient air that may
be toxic at certain concentrations. This awareness, in turn, has led to
attempts to identify source/receptor relationships for these substances and
to develop control programs to regulate emissions. Unfortunately, limited
information is available on the ambient air concentrations of these
substances or on the sources that may be discharging them to the atmosphere.
To assist groups interested in inventorying air emissions of various
potentially toxic substances, EPA is preparing a series of documents such as
•this that compiles available information on sources and emissions of these
substances. This document specifically deals with ethylene oxide. Its
intended audience includes Federal, State, and local air pollution personnel
and others who are interested in locating potential emitters of ethylene
oxide and making preliminary estimates of the potential for air emissions
therefrom.
Because of the limited amounts of data available on ethylene oxide
emissions, and since the configuration of many sources will not be the same
as those described herein, this document is best used as a primer to inform
air pollution personnel about 1) the type of sources that may emit ethylene
oxide, 2) process variations and release points that may be expected within
these sources, and 3) available emissions information indicating the
potential for ethylene oxide to be released into the air from each
operation.
The reader is strongly cautioned against using the emissions
information contained in this document to try to develop an exact assessment
of emissions from any particular facility. Since insufficient data are
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available to develop statistical estimates of the accuracy of these emission
factors, no estimate can be made of the error that could result when these
factors are used to calculate emissions for any given facility. It is
possible, in some extreme cases, that orders-of-magnitude differences could
result between actual and calculated emissions, depending on differences in
source configurations, control equipment and operating practices. Thus, in
situations where an accurate assessment of ethylene oxide emissions is
necessary, source-specific information should be obtained to confirm the
existence of particular emitting operations, the types and effectiveness of
control measures, and the impact of operating practices. A source test
and/or material balance should be considered a;s the best means to determine
air emissions directly from an operation.
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SECTION 2
OVERVIEW OF DOCUMENT CONTENTS
As noted in Section 1, the purpose of this document is to assist .
Federal, State and local air pollution agencies.and others who are
interested in locating potential air emitters of ethylene oxide and making
gross estimates of air emissions therefrom. Because of the limited
background data available, the information summarized in this document does
not and should not be assumed to represent the source configuration or
emissions associated with any particular facility.
This section provides an overview of the contents of this document. It
briefly outlines the nature, extent and format of the material presented in
the remaining sections of this report.
Section 3 of this document provides a brief summary of the physical and
chemical characteristics of ethylene oxide, its commonly occurring forms and
an overview of its production and uses. A chemical use tree is shown along
with a table summarizing the quantities of ethylene oxide consumed in
various end uses. This background section provides a general perspective on
the nature of the substance and where it is manufactured and consumed.
The fourth and fifth sections of this document focus on major
industrial sources of ethylene oxide air emissions. Section.4 discusses the
production of ethylene oxide and Section 5 discusses the use of ethylene
oxide as an industrial feedstock in the production of ethylene glycols,
glycol ethers, ethoxylates, and ethanolamines. For each major industrial
source category described in Sections 4 and 5, example process descriptions
and flow diagrams are given, potential emission points are identified, and
available emission factor information is summarized. The emission factors
show the potential for ethylene oxide emissions for uncontrolled operations
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as well as operations using controls typically employed in industry. Also
presented are names and locations of all major facilities reported to be
producing ethylene oxide or using it as a feedstock in other production
processes. ;
Also in Section 5 is a description of the use of ethylene oxide as a
r
fumigant and sterilant. Much of the ethylene oxide used for this purpose is
released directly to the atmosphere. Various equipment and procedures for
this use of ethylene oxide- are described. Use rates are given for the
various industries which use ethylene oxide for' this purpose.
The final section of this document summarizes available procedures for
source sampling and analysis of ethylene oxide.! Details are not prescribed
nor is any EPA endorsement given or implied to any of these sampling and
analysis procedures. At this time, EPA has generally not evaluated these
methods. Consequently, this document merely provides an overview of
applicable source sampling procedures, citing references for those
interested in conducting source tests.
i
This document does not contain any discussion of health or other
environmental effects of ethylene oxide, nor does it include any discussion
of ambient air levels or ambient air monitoring techniques.
Comments on the contents or usefulness of this document are welcomed,
as is any information on process descriptions, operating practices, control
measures and emissions information that would enable EPA to improve its
contents. All comments should be sent to:
Chief, Noncriteria Emissions Section
MD-14
Air Management Technology Branch
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
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SECTION 3
BACKGROUND
NATURE OF POLLUTANT
Ethylene oxide (EO) is one of the epoxide family of chemicals. In
addition to its International Union of Pure and Applied Chemistry (IUPAC)
name, oxirane, it is also called dihydrooxirene; dimethylene oxide;
1,2-epoxyethane; oxacyclopropane; oxane; oxidoethane; and a,p-oxidoethane.
The Chemical Abstracts Service (CAS) registry number for ethylene oxide is
75-21-8.
Ethylene oxide is normally handled under pressure as a liquid, but at
ambient conditions it is a gas with a pungent-, irritating, ether-like odor.
It condenses to a colorless liquid at 10°C (50°F). It is completely
miscible with water and with organic solvents. Ethylene oxide possesses
reactive and volatile properties which make it a highly flammable and
potentially explosive chemical. It has a flash point of <-18°C (0.4°F) and
is flammable in air at concentrations ranging from 3 to 100 volume percent.
Having no upper explosive limit, special safety precautions must be taken
when handling and storing EO. Additional physical and chemical properties
of EO are summarized in Table 1.
Ethylene oxide is reactive in the environment. Its atmospheric
residence time, the estimated time in days required for a given quantity to
f\
be reduced to 1/e (37 percent) of its original amount, is 5.8 days. In
water, EO reacts with anions such as chloride and carbonate; it has a fresh
Pi
1
water (pH 7, 25°C) half-life'of 2 weeks and a salt water half-life of
4 days.
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TABLE 1. PHYSICAL AND CHEMICAL PROPERTIES OF ETHYLENE OXIDE
1,3,4,5
Property
Coefficient of cubical expansion,
per °C at 20°C
Critical pressure, MPa
Critical temperature, C
Dielectric constant at C
Dipole moment, C-m
Heat of fusion, kJ/mol
Refractive index, nD at 4 C
Heat of solution, kJ/mol in pure
water at 25 C and constant pressure
lonization potential, J
experimental
calculated
Value
Molecular weight
Physical state, room temperature
Melting point, C
Boiling point, C
Density o
Vapor pressure, torr at 25 C
Viscosity, centipoises at 4 C
Specific heat, cal/°C-g at 20°C
Heat of vaporization, cal/g at 1 atm
Flash point, tag open cup, C
Autoignition temperature, C in air
at 1 atm
Flammability limits , vol percent
Heat of combustion, kJ/mol at 25 C
Partition coefficient, log P
44.053
gas
-112.44
10.5
0.8711
1305
0.31 ;
0.44
136.1
<-18
429 :
3-100
1306.04
-0.3
0.00161
7.19
195.8
13.71
6.34 x 10
5.17
1.3614
-30
6.3
1.73 - 1.80 x 10
1.65 x 10'18
-18
Solubility
Reactivity
Completely soluble in water,
acetone, benzene,,carbon
tetrachloride, ether, methanol
Potentially explosive when
heated or when in the presence
of alkali metal hydroxides and
highly active catalytic .
surfaces
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OVERVIEW OF PRODUCTION AND USE
Ethylene oxide (EO) is produced by direct oxidation of ethylene over a
silver catalyst. The.oxygen source can be either air or oxygen. Though
neither option has. been proven to be more economical than the other, there
appears to be a trend toward the use of oxygen in newer facilities. Both
options are discussed in this document. An alternative EO production
process, with a chlorohydrin intermediate, is no longer used in this
country.
About 60 to 77 percent of the ethylene consumed by the oxidation
reaction is converted to ethylene oxide. A side reaction produces Cc
dioxide, water, and small amounts of acetaldehyde and formaldehyde.
Twelve companies at 13 locations, most in the Gulf Coast area, produce
EO in the United States. Total 1986 capacity is estimated to be 2944 Gg
6 8
(6490 x 10 Ibs). Table 2 lists these producers, their locations, and
their method of oxidation. Figure 1 illustrates the geographical locations
of these facilities. In 1983, U.S. production constituted about 40 percent
9
of global EO production.
In the 1970's, the EO industry was operating at more than 80 percent of
its production capacity, peaking in 1979 at 2570 Gg (5665 x 106 Ibs).10
Production in 1983 was about 2271 Gg (5003 x 106 Ib), which is up slightly
from the 2212 Gg (4873 x 106 Ib) recorded for 1982.10'11'12 Average annual
growth for the industry in the past few years has been about 4 percent.
Ethylene oxide can form in the photochemical smog cycle by reaction of
ethylene with an organic peroxide by the following mechanism:
0
CH - CH + ROOH --> CH- CH + ROH
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TABLE 2. PRODUCERS OF ETHYLENE OXIDE IN THE UNITED STATES IN 1986
Producer
BASF Wyandotte
Celanese
Dow Chemical
Texas Eastman
ICI Americas
HNG/InterNorth, Inc.
Olin
PD Glycol
Shell
SunOlin
Texaco
Union Carbide
Location
Geismar , LA
Clear Lake!, TX
Plaquemine ', LA
Longview, TX
Bayport, TX
Morris, IL
Bradenburg, KY
Beaumont , TX
Geismar, LA
Claymont , DE
|
Port Neches , TX
Seadrift, TX
Taft, LA '
Process
Oxidant
oxygen '
oxygen
air
oxygen
oxygen
oxygen j
oxygen
oxygen
oxygen
oxygen
air
air
air
NOTE: This listing is subject to change as market conditions change,
facility ownership changes, plants are closed down, etc. The reader
should verify the existence of particular facilities by consulting
current listings and/or the plants themselves. The level of ethylene,
oxide emissions from any given facility is a function of variables
such as capacity, throughput, and control measures. It should be
determined through direct contacts with plant personnel.
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1. BASF Wyandotte Corp., Geismar, LA -8.
2. Celanese Chemical Co., Clear Lake City, TX 9.
3. Dow Chemical Co., Plaquemine, LA - 10.
4. Eastman Kodak Co., Longview, TX 11.
5. ICI Americas, Bayport, TX 12.
6. HNG/InterNorth, Inc., Morris, IL 13.
7. Olin Corp., Brandenburg, KY
PD Glycol, Beaumont, TX
Shell Chemical Co., Geismar, LA
SunOlin Chemical Co., Claymont, DE
Texaco, Port Neches, TX
Union Carbide Corp., Seadrift, TX
Union Carbide Corp., Taft, LA
Figure 1. Locations of plants which manufacture ethylene oxide.
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It can also form photochemically from the decomposition of alkyl peroxides:'
\
'0-0
V
'0-0
A
A
-I- CH30
HO
One reference suggests that EO may be present in automobile and
stationary source combustion exhaust. Howeveip, no direct measurements of
such emissions have been found to corroborate this claim.
More than 99 percent of all EO made is subsequently used as a chemical
intermediate in the production of mono-, di-, and triethylene glycols,
mono-, di-, and triethylene glycol ethers, ethanolamines, surface active
agents, and other chemicals. A large portion (about 80 to 90 percent) is
13
used captively by its producers to produce these derivatives. One reason^
for immediate captive use is because EO has definite limitations as a ;
transportable commodity due to safety considerations. ;
Figure 2 illustrates the end distribution of the EO produced in the
13 14
United States. ' Major chemical users of EO and EO products are liste
in Table 3. Users which are also producers are identified in the table.
Ethylene glycol (EG) is the predominant derivative of EO. Consumption
of EO has, in the past, largely depended on the EG market. A major use of
ethylene glycol is as automotive antifreeze. It is also used in the
manufacture of polyethylene terephthalate (PET) resin plastic film and
bottles and in the manufacture of polyester fibers. PET bottles are used in
the soft drink industry and have been approved for use by the liquor bottle
industry. '•
10
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-------
Ethylene oxide is also used as a fumigant, sterilant, and insecticide.
It is particularly useful for sterilizing items which would be damaged by
heat. For example, EO is use,d a fumigant/sterilant in the health products
and medical fields; in libraries, museums, research laboratories; during
beekeeping, dairy packaging, and cosmetics manufacturing; and fo'r animal and
plant quarantine at ports-of-entry. It is also used to fumigate spices and
seasonings, nut meats, tobacco, transportation vehicles, clothing, furs and
furniture.
Some potential exists for volatile substances, including EO, to be
emitted from waste treatment, storage, and handling facilities.
Reference 15 provides general theoretical models for estimating volatile
substance emissions from a number of generic kinds of waste handling
operations, including surface impoundments, landfills, landfarming (land
treatment) operations, wastewater treatment systems, and drum
storage/handling processes. If such a facility is known to handle EO, the
potential for some air emissions should be considered.
The Occupational Safety and Health Administration (OSHA) has enacted a
1 ppm, 8 hour time-weighted average occupational exposure standard that may
result in some control of EO emissions. OSHA states that the EO producers
and ethoxylator industry sectors could use rupture disks for minimizing
low-level leakage from pressure relief devices; closed sampling devices at
process sampling locations, and vapor-tight unloading connections, magnetic
level gauges, and nitrogen purge systems on tank car loading facilities.
For operators of large industrial sterilizers, engineering and work practices
include changer evacuation systems, liquid/gas separation units to prevent
excessive EO emissions during chamber evacuation, local exhaust hoods
installed over the sterilizer door, local ventilation of aeration chambers,
and allowing the sterilizer contents to aerate for a short period of time
after opening the sterilizer door. Hospital sterilizers are smaller than
sterilizers used by medical product manufacturers, but the control of EO
involves the same principles and types of control equipment and methodology
used for industrial sterilizers.
Emission controls are discussed further in Sections 4 and 5 of this
report.
13
-------
REFERENCES FOR SECTION 3
1. Bogyo, D.A. , et al. Investigation of Selected Potential Environmental^
Contaminants: Epoxides. Syracuse Research Corporation, Syracuse, New;
York. Prepared for the U.S. Environmental Protection Agency,
Washington, D.C. March 1980. NTIS Publication No. PB80-183197.
I
2. Cupitt, L.T. Fate of Toxic and Hazardous Materials in the Air
Environment. EPA-600/3-80-084. Environmental Sciences Research
Laboratory, U.S. Environmental Protection Agency, Research Triangle
Park, North Carolina. August 1980.
'
3. Assessments of Human Exposures to Atmospheric Concentrations of
Selected Chemicals. SAI, Inc. Prepared for the Office of Air Quality,
Planning and Standards, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina. Prepared under EPA Contract
No. 68-02-3066. 1981.
I
4. National Institute for Occupational Safety and Health. Current
Intelligence Bulletin 35, 22 May 1981: Ethylene Oxide. DHHS
Publication No. NIOSH81-130. Cincinnati, Ohio. 1981.
5. Kirk-Othmer Encyclopedia of Chemical Technology. Third Edition.
Volume 9, Ethylene Oxide. John Wiley and Sons. New York, New York.
1980. pp. 432-471.
j
6. Kuhn, W. What's Ahead for Propylene and Ethylene Oxide. Chemical
Engineering Progress. January 1980. pp. 53-56. ;
7. Kalcevic, V. and J.F. Lawson. Ethylene Oxide. In: Organic Chemical
Manufacturing, Volume 9. EPA-450/3-80-028d. U.S. Environmental
Protection Agency, Research Triangle Park> North Carolina.
December 1980.
8. SRI International. 1986 Directory of Chemical Producers, United States
of America. Menlo Park, California. 1986.
9. Ozero, B.J. and J.V. Procelli. Can Development Keep Ethylene Oxide !
Viable? Hydrocarbon. Processing. March 1984. pp. 55-61.
10. Chemical Products Synopsis. Mansville Chemical Products. Cortland,
New York. December 1982.
11. Telecon. Smith, C., Radian Corporation with Strasser, J., Chemical
Marketing Reporter. May 1983. Ethylene oxide production.
14
-------
12. Chemical Marketing Reporter. 223(13). 28 March 1983.
13. Markwordt, D.W. Sources of Ethylene Oxide Emissions.
EPA-450/3-85-014. Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North
Carolina. April 1985.
14. SRI International. Chemical Economics Handbook. Stanford Research
Institute, Menlo Park, California. 1980.
15. Farino, W. et al. Evaluation and Selection of Models for Estimating
Air Emissions from Hazardous Waste Treatment, Storage, and Disposal
Facilities. EPA-450/3-84-020. U.S. Environmental Protection Agency,
Research Triangle Park, North Carolina. December 1984.
16. Federal Register. Volume 50, Number 1. January 2, 1985. pp. 64-77.
U.S. Government Printing Office, Washington, D.C.
15
-------
-------
SECTION 4
EMISSIONS FROM ETHYLENE OXIDE PRODUCTION
Ethylene oxide can be released to the atmosphere during its production,
during its consumption as a raw material in other manufacturing processes,
and during its use as a fumigant/sterilant. This section details the
production of EO and the emission factors associated with that production.
Manufacturing processes which use EO as a feedstock are also described in
Section 3, as is the use of EO as a fumigant/sterilant.
ETHYLENE OXIDE PRODUCTION
1-3
Process Description
Ethylene oxide is produced by continuous direct oxidation of ethylene
over a silver catalyst. Either air or pure oxygen can be used as the
oxidant for the process. Before 1957, ethylene oxide was produced from
ethylene with an ethylene chlorohydrin intermediate. This chlorohydrin
process for EO production was phased out in the U.S. because it could no
longer compete economically with the direct oxidation process. Of the
total amount of EO produced in the United States in 1983, 60 percent was
produced at six locations by air oxidation of ethylene; the other 40 percent
was produced at nine locations by oxygen oxidation. Neither process is
clearly considered economically superior to the other at this time.
However, there appears to be a trend toward the use of oxygen in newer
facilities. Plant capacities in the U.S. range from about 50 to 600 Gg/yr
of EO production.
In the direct ethylene oxidation process, reactions take place in the
vapor phase. The two main reactions are:
16
-------
Ag20
H2C - CH2 + 1/2 02 --->
(1)
2C0
2H20
(2)
The loss of 25 to 30 percent of the ethylene to carbon dioxide and water by
I
Reaction 2 is a major drawback of the oxidation process. Reaction 2 also
releases 13 times as much heat energy as does Reaction 1. Reaction 2 can be
suppressed by replacing the catalyst regularly and by carefully controlling
the temperature on the surface of the catalyst, thereby limiting the
conversion of ethylene to CCL and H20 on each catalyst pass to less than
30 percent. These reactions also produce small amounts of acetaldehyde
(less than 1 percent of the EO product) and trace amounts of formaldehyde.
For certain uses, EO is now produced with an aldehyde content of less than
10 ppm.
In both the air and oxygen oxidation processes, the ethylene feed must
be >98 mole percent pure. Air feed in the air oxidation process must be
purified to minimize the presence of contaminants which may deactivate the
catalyst or react to form unwanted by-products. Most EO plants include an
associated glycol plant which is able to procesis aqueous and organic bleeds
from the EO plant and recover the EO contents as glycol. By integrating the
two plants, it is not always necessary to dry a.nd purify the EO needed for :
fiber grade glycol production, yielding substantial capital cost and
utilities savings.
Specific characteristics of the air and oxygen oxidation processes for !
EO production are discussed below.
17
-------
Air Oxidation--
Figure 3 illustrates the basic operations that may be found in the
continuous air oxidation process. The process streams and vents shown in
Figure 3 are described in Table 4. Ethylene and compressed air (Streams 1
and 2) combine with a recycle ethylene stream (Stream 3), then enter one of
several primary reactors operated in parallel. The air-to-ethylene feed
ratio is usually about 10:1 by weight. The reaction takes place over a
silver catalyst packed in tubes; the heat from the reaction is dissipated by
a jacket of heat transfer fluid. Reaction temperature and pressure are
maintained at 220° to 280°C and 1 to 3 MPa (427° to 536°F; 10-20 atm). The
activity of the catalyst can be enhanced by the addition of promoters such
as alkali metals or alkali earth metals. Catalyst inhibitors such as
halides may be added to suppress conversion of ethylene to carbon dioxide
while not interfering with the primary reaction. In addition to the main
by-product, carbon dioxide, small amounts of formaldehyde and acetaldehyde
are also formed.
The effluent from the reactor (Stream 4) contains 1 to 2 mole percent
ethylene oxide, 2 to 3 mole percent ethylene and about 7 mole percent carbon
dioxide. It is cooled, compressed, and passed through the primary absorber.
As it passes up the packed column absorber countercurrent to cold water, the
ethylene oxide and some of the carbon dioxide, hydrocarbons, and aldehydes
dissolve in the water.
Most of the unabsorbed gas that exits the top of the absorber is cooled
and becomes the recycle ethylene stream (Stream 3). A smaller portion of
the unabsorbed gas stream (Stream 5) is purged to prevent the accumulation
of inert gases such as nitrogen and carbon dioxide in the system. To
recover its ethylene content, the purged stream enters a secondary purge
reactor. The effluent from the secondary purge reactor (Stream 6) enters a
purge absorber which operates on the same principle as the primary absorber.
The overhead gas from the purge absorber is recycled to the purge reactor
(Stream 8) or, in larger plants, sent to yet another purge reactor and
18
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TABLE 4. DESCRIPTIONS OF STREAMS AND VENTS ILLUSTRATED IN FIGURE 3
FOR THE AIR OXIDATION OF ETHYLENE TO ETHYLENE OXIDE
2,3
Code Number
Description
Stream
1
2
3
4
5
6
7
8
9
10
11
Vent
A
B
C
D
E
Ethylene feed, >98 mole percent
Purified process air
Recycle to primary reactor
Primary reactor product gas, 1 to 2 percent EO
Purge reactor feed
Purge reactor effluent, 2 percent EO
Process air
Recycle from purge absorber
Absorber bottoms, minor EO levels
Recycle water to absorbers
Ethylene oxide product, 99.5 percent EO
Main process vent (CO nitrogen purge)
Stripper vent (light gas purge)
Fugitive losses (pumps, valves, compressors, etc.)
Storage and loading losses
Waste ponds
20
-------
absorber (not shown) to achieve an overall ethylene conversion well in
excess of 95 percent of the total feed. A portion of the stream from the
last absorber is vented (Vent A). The number of purge stages depends on the
value of ethylene recovered versus the cost of additional purge stages.
I
i
The dilute- aqueous solutions of EO, CO^, and other volatile organic
compounds (VOC) from the absorbers are combined (Stream 9) and fed to the
desorber where the EO and dissolved inerts are distilled under reduced
pressure. The desorber water, virtually, free of EO, is recirculated to the
absorbers (Stream 10). The crude EO from the desorber is then sent to a
stripper for removal of CO- and inert gases and then sent to a final [
refining column. (Note that in some plants the EO from the absorbers
[Stream 9 in Figure 3] may go first into a stripper and then into a light
ends refractory column. The nomenclature is different but the basic
operations are the same.) Light gases separated in the stripper are vented,
overhead (Vent B). The final product (Stream 11), 99.5 mole percent EO, is!
stored under a nitrogen atmosphere in pressurised tanks. In some plants,
crude EO is sent directly to a glycol plant rather than undergoing complete
refining.
Oxygen Oxidation--
Virtually all of the differences between the air oxidation and oxygen
oxidation processes result from the difference in oxygen content of the
oxidants (^20 mole percent,versus 98 mole percent). Figure 4 illustrates a
continuous oxygen oxidation process. The streams and vents shown in
Figure 4 are described in Table 5.
In the oxygen oxidation process, ethylene and oxygen (Streams 1 and 2)
enter.the reactor, which is operated under conditions similar to that in the
air oxidation process. The effluent from the ireactor (Stream 4) passes
through the absorber, in which the EO product and some of the carbon •
dioxide, hydrocarbons, and aldehydes dissolve in the water. Most of the
unabsorbed gas that leaves the top of the absorber is cooled and becomes the
recycle ethylene stream (Stream 3) .
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22
-------
TABLE 5. DESCRIPTIONS OF STREAMS AND VENTS ILLUSTRATED IN FIGURE 4
FOR THE OXYGEN OXIDATION OF ETHYLENE TO ETHYLENE OXIDE2'3
Code Number
Description
Stream
1
2
3
4
5
6
7
8
9
10
11
Vent
A
B
C
D
E
F
Ethylene feed, >98 mole percent
Oxygen feed, >97-99 mole percent
Recycle to primary reactor, 0.006 percent EO
Primary reactor product gas, 2 percent EO
C09 purge stream
C0_-free recycle to primary reactor
C02-rich CO absorbent (KHCO_)
Reactivated CO 'absorbent (KHCO.) i
i
Absorber bottoms, minor EO levels
Recycle water to absorbers '•
Ethylene oxide product, 99.5 percent EO
-
:
Main process vent (argon purge)
C09 desorber vent (COI?, nitrogen purge) :
Stripper vent (light gas purge)
Fugitive losses (pumps, valves, compressors, etc.)
Storage and loading losses
Waste ponds
23
-------
Gaseous impurities from the oxygen feed, such as argon, are purged from
the recycle gas stream through the main process vent (Vent A). Because
there are fewer impurities in the oxygen feed than in air feed, the purge
stream can be much smaller and there is no need for a purge reactor system.
There can be almost total recycling of unreacted ethylene.
There is still, however, a buildup of by-product CO,, which could reduce
catalytic selectivity to EO at high levels if not removed from the system.
A portion of the overhead gas from the absorber (Stream 5) passes through a
COg absorber which uses potassium carbonate as an absorbent, then (as
Stream 6) joins the recycle to the reactor. The spent CO absorbent
(Stream 7) is reactivated in the CO- desorber, then recycled to the CO
absorber (Stream 8). The CO is vented from the CO desorber (Vent B).
The desorption, stripping, and refining steps are basically the same as
those in the air oxidation process. The stripper vent labeled Vent B in the
air oxidation process corresponds to Vent C in the oxygen oxidation process.
An alternative to stripping inerts from the EO stream is to vent these gases
from the reabsorber tower? where EO is reabsorbed in water. Inert gases can
also be purged from the EO purification tower.
Process Emissions from Vents--
1,2
Air Oxidation--The main process vent (Vent A) is the larger of the two
sources of EO process emissions in the air oxidation plant. The vented
gases contain nitrogen and unreacted oxygen from the air feed, ethane and
unreacted ethylene from the ethylene feed, product EO and by-product CO
The exact composition of the vent stream depends on the reactor conditions,
absorber conditions, purity of the ethylene feed, and number of purge
stages.
The air feed rate is kept consistent with the ethylene feed rate during
start-up; therefore, the emission rate from the main process vent during
start-up is about the same as that for normal operation. Process upsets,
24
-------
however, can cause a sharp increase in emissions. When an upset occurs, the
ethylene feed rate is re'duced to lessen the amount of VOC in the vent |
stream. j ;
:
Because EO is completely soluble in water, the purge absorber shown in
2
Figure 3 can be 99.9+ percent effective for its removal. The EO content of
the main process vent stream (Vent A) is therefore quite low. The ethane :
and ethylene contents, however, are sufficient for combustion. This stream
o
is now normally burned in a thermal or catalytic oxidizer, but in the
2
past, was commonly vented to the air. During upsets, the main process vent
stream can be directed to an emergency flare.
j
The stripper vent (Vent B) of the air oxidation process releases the
inert gases and ethylene which were absorbed into the main and purge
absorber waters. The composition of the stream depends on the solubilities
of the gases in the circulating water. The amount of emissions is affected.
by the water use rate, but not be process start-ups or shutdowns. Ethylene
oxide is normally scrubbed from the stripper vent stream with water and
returned to the process. The resulting vent stream is normally combusted in
8
a boiler, effecting virtually 100 percent EO emissions control. :
Some plants route both vent streams (Vents A and B) to an absorber for
recovery of EO, then to a boiler or flare.
j [
Oxygen Oxidation--The volume of the main process vent (Vent A) of the
oxygen oxidation process is much less than tha/t of the corresponding vent in
the air oxidation process, but it contains about the same mole percent EO, ,
ranging from about 0.005 to 0.01 percent. This vent stream also contains
argon and nitrogen from the oxygen feed and the ethane from the ethylene
feed. The composition and quantity of the stream depend directly on the
purity of the feed materials and are not affected by process upsets or
start-ups if the composition of the oxygen feed is established before
start-up.
25
-------
The ethylene content of the main process vent stream (Vent A) is
sufficient to support combustion and is routinely vented to a boiler or
Q
incinerator. In some plants, methane is added to facilitate a higher safe
oxygen concentration. The methane, inert in the oxidation reaction, also
allows more flexibility in the feed rates to the reactor by narrowing the
flammability limits of the incoming gas.
The CO- desorber vent (Vent B) is more than 99.7 percent CO- and water.
No information is available on the EO content. The vent stream is sometimes
processed or sold to recover C0«. If the stream is sold, there is
intermittent discharge during start-up, malfunction, and maintenance,
9
estimated by one producer as 6 percent of the time. The stream can also.be
vented to the atmosphere; in this case, a carbonate flasher and vent
Q
condenser reduce emissions. One producer uses the stream in another
process (not specified in reference). In this case, the VOC content is
ultimately thermally oxidized or fed to an incinerator.
The stripper vent stream (Vent C) has sufficient ethylene content to
support combustion in a boiler or flare. If methane is added to the reactor
stream some will also be vented in this stream. In newer installations, the
vent stream is compressed and recycled to the CO- absorber feed. No EO
content is reported for this stream.
• When inerts are purged from a reabsorption tower, the vent stream from
the reabsorber can be incinerated. When inerts are also purged from the EO
purification tower, this stream can be scrubbed, vented to an absorber, and
recycled to a reabsorber.
Most modern EO producers employ closed cooling cycles to cool the
oxygen oxidation process' recirculated effluent from the EO stripper column;
however, cooling towers are sometimes used. With cooling towers, the
cooling process is achieved by evaporation when the process cooling water
and air are contacted. The emission rate is inversely proportional to the
efficiency of the stripper column in EO removal.
26
-------
Fugitive Emissions-- ' .
Fugitive EO emissions in either the air or oxygen oxidation process
emanate from pump seals, compressors, valves, flanges, pressure relief
devices and sample connections. Fugitive emisision estimates can be made by
applying emission factors to the number of pumps seals, valves, flanges,
etc., in a typical EO production facility, and by adjusting these totals to,
reflect the EO content in each stream. An example of this type of analysis
is shown in Reference 8, excerpts of which are included in Appendix A of
this report. For a hypothetical model plant, this analysis yields fugitive
EO emission estimates ranging from 148 to 188 kg/day in oxygen and air >
oxidation facilities, respectively. These estimates are for relatively
uncontrolled facilities employing no measures for leak detection and repair •
and maintenance. These fugitive emission levels will be reduced
considerably by inspection and maintenance (I/M) programs in which equipment
is routinely monitored and leaks corrected. Depending on the stringency of
the I/M measures, varying levels of control are possible, ranging from
38 percent reduction for the measures in EPA1s Control Techniques Guideline
mt
12
(CTG) to 65-78 percent if the I/M measures reflect EPA's New Source
Performance Standards.
I
Several EO producers indicate that because of process safety ;
I
considerations, EO handling units have always been designed, built and ;
maintained to tight standards because of flammability, explosion and health
hazards inherent in the chemical. Measures taken for safety reasons also
1'J
reduce EO emissions. These measures include:
Installation of EO and flammable gas detectors in strategic plant
locations, with sample analyses performed regularly (e.g., every
20 minutes)
Equipping EO pumps with double mechanical seals having liquid ;
buffer zones and alarms or automatic pump shutoffs in case of seal
failure
Routine gasket replacement during planned maintenance turnarounds
Using pressurized nitrogen in labyrinth shaft seals of centrifugal
EO compressors
27
-------
Use of all welded construction, where possible, to minimize the
number of flange joints
Using leak detectors for critical flanges in EO piping
Use of closed loop sample systems
Providing extra maintenance for EO piping
Preventing relief .valve leaks by use of upstream rupture disks
Analyses of rotating equipment for vibration characteristics to
anticipate pending problems
Collecting, absorbing in water and discharging to sewer any EO
leakage or drainage from sampling operations and pump vents
Daily inspection for leaks by plant personnel
Immediate leak repair
Note that not all of these measures are applied at any one plant.
Sources desiring not to use the fugitive emission factor development
approach outlined in Appendix A for assessing EO fugitive emissions may
instead use EPA's Reference Method 21 and the procedures specified in
15 16
Reference 14. ' Method 21, "Determination of Volatile Organic Compound
Leaks," is intended to be used as- a screening tool for detecting, locating,
and classifying leaks. It is not designed to be a direct measure of mass
emissions from individual sources. Method 21 is used to produce a
statistical leak/no leak frequency. Reference 14 describes the approach of
how the leak/no leak frequency (or screening distribution), produced by
Method 21 for a particular piece of equipment, can be statistically
correlated with empirical data on chemical industry fugitive VOC emissions
and extensive statistical analyses of leakers and non-leakers (for that
equipment) to generate average fugitive VOC (or compound specific) emission
factors for pumps, valves, flanges, compressors, and pressure relief
devices.
Waste Ponds--
Emergency holding ponds may also be sources of EO emissions. One
source uses a pond for emergency twentyfold dilution of EO to reduce the
possibility of explosions, during shutdowns. As much as 5,000 to
28
-------
10,000 pounds of EO may have to be dumped at once. The company assumes'that
the EO converts to ethylene glycol, but is considering the addition of
catalysts to speed this conversion. It is riot known how much EO is lost
to the atmosphere from such ponds, or how common this practice is in the
industry. '.
Other Secondary Emissions--
',
Wastewater streams from various processes; may contain some, albeit !
generally low levels of EO. These streams are commonly treated by
bio-oxidation. Most producers report negligible or no EO emissions from
13
this source. One producer reports one EO unit wastewater stream having an
EO content of 280 ppm, of which 75 percent, or about 92 kg/day, is estimated
18
to be stripped into the atmosphere. \
Storage and Loading Losses-- ;
Because product EO is a gas at ambient temperatures, it is generally
stored under nitrogen at approximately 10-C (!»0 F) . Some plants may store
EO at ambient temperatures and elevated pressxtres. Losses from storage :
tanks are assumed to occur only because of displacement during filling
19
operations. If not used captively, EO is normally shipped in 38,000 and
76,000 liter (10,000 and 20,000 gallon) railroad tank cars, which are '.
normally loaded directly from plant storage tanks. The transfer generally;
20
occurs at about 50 psi nitrogen pressure. At most facilities, displaced
vapors from the filling of tank cars and storage tanks are either recycled
Q
to the process or scrubbed prior to incineration or flaring. When the
vapors are scrubbed, the liquid effluent from the scrubber is routed to the
desorber for EO recovery. Emissions of EO from storage and loading are
assumed to be nearly zero if either control approach is used. However, one
producer reports 39 Mg/yr (86 x 10 Ib/yr) of EO emissions from storage and
loading. No explanation was given for this emission rate; the producer uses
Q
a caustic scrubber for control of emissions. '
29
-------
Emission Factors--
Tables 6 and 7 give EO emission factors for air and oxygen oxidation
plants, respectively. Because the production of EO and the production of EO
derivatives are often closely related, the factors in Tables 6 and 7 do not
necessarily represent the isolated production of EO. For example, 'the
fugitive emission source counts used for the calculation of fugitive
emissions include components used in derivative production as well as EO
production (albeit many fewer components in EO service will be present in
derivative production processes). Similarly, the process vent emissions may
reflect the recycle of certain vents in derivative plants back to the EO
plant. The contribution to total EO emissions from vents, fugitive
components, and storage in derivative production is not believed to be
significant compared to overall emissions from EO production operations.
30
-------
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REFERENCES FOR SECTION 4 j
1. Kalcevic, V. and J.F. Lawson. Ethylene Oxide. In: Organic Chemical
Manufacturing, Volume 9: Selected Processes. EPA-450/3-80-028d.
Prepared for the U.S. Environmental Protection Agency, Research .
Triangle Park, North Carolina. December 1980.
2. Field, D.D., et al. Engineering and Cost Study of Air Pollution :
Control for the Petrochemical Industry, Volume 6: Ethylene Oxide
Manufacture by Direct Oxidation of Ethylene. Prepared for the U.S.
Environmental Protection Agency, Research Triangle Park, North
Carolina. Prepared under EPA Contract No. 68-02-0255. June 1975.
3. Kirk-Othmer Encyclopedia of Chemical Technology. Third Edition,
Volume 9. Ethylene Oxide. John Wiley and Sons. New York, New York. '
1980. pp. 432-471.
4. Telecon. Smith, C., Radian Corporation with Arnold, S., Dow Chemical.
May 1983. Ethylene oxide production processes. '
5. Kuhn, W. What's Ahead for Propylene and Ethylene Oxide. Chemical
Engineering Progress. January 1980. pp. 53-56.
6. Ozero, B.J. and J.V. Procelli. Can Development Keep Ethylene Oxide
Viable? Hydrocarbon Processing. March 1984. pp. 55-61.
7. DeMaglie, B. Oxygen Best for EO. Hydrocarbon Processing. March 1976.
pp. 78-80. i
8. Markwordt, D.W. Sources of Ethylene Oxide Emissions. ;
EPA-450/3-85-014. Office of Air Quality Planning and Standards, U.S. ;
Environmental Protection Agency, Research Triangle Park, North
Carolina. April 1985.
9. Nonconfidential portions of a letter from R.K. Bernard, Northern
Petrochemical Company to J.R. Farmer, U.S. Environmental Protection
Agency. 4 January 1984. Ethylene oxide production information.
10. Letter from Macauley, D.C., Union Carbide: to Lahre, T., U.S. •'
Environmental Protection Agency. 10 April 1986. Comments on draft
ethylene oxide emission factor document.
11. Control of Volatile Organic Compound Leaks from Synthetic Organic
Chemical and Polymer Manufacturing Equipment. EPA-450/3-83-006.
Office of Air Quality Planning and Standa.rds, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina. March 1984.
33
-------
12. VOC Fugitive Emissions in Synthetic Organic Chemicals Manufacturing
Industry - Background Information for Proposed Standards.
EPA-450/3-80-033a. Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North
Carolina. November 1980.
13. Nonconfidential portions of letters submitted to J. Farmer or
D. Markwordt, Emission Standards and Engineering Division, Office of
Air Quality Planning and Standards, U.S. Environmental Protection
Agency, Research Triangle Park, North Carolina, by industrial producers
and users of ethylene oxide. October 1983 to January 1984.
14. Stelling, J.H. Emission Factors for Equipment Leaks of VOC and HAP.
EPA-450/3-86-002. Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency. January 1986.
15. Federal Register. Volume 48, 18 August 1983. p. 37600. U.S.
Government Printing Office, Washington, B.C.
16. Federal Register. Volume 48, 22 December 1983. p. 56581. U.S.
Government Printing Office, Washington, D.C.
17. Telecon. Smith, G., Radian Corporation with Dorgant, G., Celanese
Chemical Corporation. 9 September 1983. Emissions from ethylene oxide
production.
18. Letter from Macauley, D.C., Union Carbide to Markwordt, D.W. , U.S.
Environmental Protection Agency. 23 April 1984. Emissions from
ethylene oxide production.
19. Compilation of Air Pollutant Emission Factors, Third Edition. AP-42.
U.S. Environmental Protection Agency, Research Triangle Park, North
Carolina. August 1977, with supplemental updates.
20. Bogyo, D.A., et ai. Investigation of Selected Potential Environmental
Contaminants: Epoxides. Prepared for the U.S. Environmental
Protection Agency, Washington, D.C. March 1980. NTIS Publication
No. PB80-183197.
21. Memo from Mascone, D.C., U.S. Environmental Protection Agency to
Farmer, J.R., U.S. Environmental Protection Agency. 11 June 1980.
Thermal Incinerator Performance for NSPS.
22. Memo from Mascone, D.C., U.S. Environmental Protection Agency to
Farmer, J.R., U.S. Environmental Protection Agency. 22 July 1980.
Thermal Incinerator Performance for NSPS, Addendum'.
34
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SECTION 5 -
EMISSIONS FROM INDUSTRIES WHICH USE ETHYLENE OXIDE
This section describes several production processes which use EO as a
feedstock. The processes included are for the production of ethylene
glycol, di-, tri- and polyethylene glycols, glycol ethers, ethoxylates, and
ethanolamines„ No specific information is available on the use of EO in the
production of surface active agents or other miscellaneous chemicals.
Therefore, these production processes are not included in this section.
The use of EO as a fumigant, sterilant, and insecticide is included
because, although only a small percentage of the total EO produced is used
for these purposes, a large percentage of that used is released directly to
the atmosphere.
Specific estimates of EO emissions are not available for processes
using EO as a feedstock. Hence, the following discussions mainly describe
the basic operations found in each process and identify the potential
emitting points therein. Control devices, operating practices, etc., are
also discussed that are known to reduce emissions.
In most cases, as shown in Table 3 in Section 3, EO derivatives are
manufactured at the same plants' that produce EO. This practice is
especially common in glycol production since it is advantageous to integrate
the oxide unit with the glycol unit to optimize energy utilization.
ETHYLENE GLYCOL AND ITS HOMOLOGS1
About 60 percent of the EO produced in the United States is used
directly in the production of ethylene glycol (EG). Another 15 percent is
reacted with the glycol produced to form the homologs diethylene glycol
35
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(DEC), triethylene glycol (TEG), and higher polyethylene glycols. Some
producers market all homologs higher than ethylene glycol as unspecified
polyethylene glycol. - | .
•
Most ethylene glycol (and its homologs) is produced commercially by !
noncatalyzed hydration of ethylene oxide. This is the only process
discussed in detail in this section. Ethylene,glycol and its homologs can
also be produced from EO by contact with a 0.5 to 1.0 percent sulfuric acid
catalyst solution maintained at 50 to 70°C (122 to 158°F). A major drawback
to this method is an acid contaminant left in the product. No estimate is
available of the amount of EG produced by this method. Other methods for
the production of EG, some of which do not use EO as a feedstock, have been'
used in the past or are in various stages of development. One process ;'
nearing commercialization involves the synthesis of ethylene carbonate, from
CO
and EO, which is then hydrolized to glycol.'
Process Description
In most cases, ethylene glycol and its homologs are produced by
noncatalyzed hydration of ethylene oxide at a temperature of 200 C (392 F]
and pressure of 1380 kPa (200 psia) according to the following equations:
CH,.
CH
(ethylene oxide)
CH-OH
CH2OH
(1)
(water) (ethylene glycol)
r*u r*u
Uti2UH
(ethylene
glycol)
(ethylene
oxide)
:H2-o-CH2CH
(diethylene
glycol)
36
(2)
.OH
-------
CH. OH CEn CH« - 0 - CH,, CH« OH
2
CH2-0-CH2CH2OH
0 >
f\ V >^**rt >-'**rt >
(3)
(diethylene glycol) .(ethylene oxide) (triethylene glycol)
Theoretically, yields of EG from Reaction 1 are 87 to 88.5 weight
percent, while yields of DEC from Reaction 2 are 9.3 to 10.5 weight percent,
and yields of TEG from Reaction 3 are 2.2 to 2.5 weight percent of the total
product. However, because there is more demand for TEG, conversion of DEG
to TEG (Reaction 3) is promoted by varying the feed ratio and/or other
process variables.
Figure 5 shows a simplified process flow diagram for the production of
EG and its homologs by the conventional noncatalyzed ethylene oxide
hydration process. In some plants, refined liquid EO (Stream 1) and water
(Stream 2) are fed to the hydrolyzer. In other plants, however, crude EO
vapor from the EO desorber or stripper/light ends column (see Figures 3 and
4) is fed directly to the EG plant. These two options are illustrated in
Figure 6. In either case, the product stream (Stream 3) from the hydrolyzer
is passed through a. multiple -effect evaporation system for removal of water.
The concentrated glycol solution (Stream 4) is further dried in a water
removal column, then the individual glycols are distilled in vacuum
distillation columns. Bottoms from the last distillation column (Stream 5)
are disposed of or sold as by-products .
Emissions
Uncontrolled emissions from the hypothetical plant illustrated in
Figure 5 originate from the evaporator calandria vents (Vent A) , the water
removal column steam- jet ejector (Vent B) , the distillation column ejectors
(Vent C) , and the evaporator first-effect purge stream (Vent D) . The plant
shown in Figure 5 uses barometric condensers to condense and absorb the
vapor from the evaporator purge and the steam- jet ejectors. The emissions
37
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CO rH
U1
CU
00
•H
38
-------
VENT
COMPRESSOR
n
VENT
•**
L
DESORBER REFINING
COLUMN(S)
(LIQUID) HYDROLYZER
EVAPORATOR
GLYCOL
CONVENTIONAL PROCESS: REFINED ETHYLENE OXIDE FED TO GLYCOL UNIT
OXIDE UNIT *4-
GLYCOL UNIT
VENT
CRUDE EO
(VAPOR)
DESORBER
OR
STRIPPER/LIGHT
ENDS COLUMN
EVAPORATOR
HYDROLYZER
STRIPPER
PROCESS VARIATION: CRUDE ETHYLENE OXIDE FED TO GLYCOL UNIT
Figure 6. Process operations for transfer of ethylene oxide
to the ethylene glycol plant,1
39
-------
from these sources then circulate with the cooling water. Partial
desorption occurs as the cooling water passes through the cooling water
circuit and the cooling tower. The remainder of the contaminants end up in
the cooling tower blowdown stream. The evaporator calandria emissions for
the uncontrolled plant are vented directly to the atmosphere. One source
reports that the EO content of the evaporator overheads and the water !
3
removal column overheads should be minimal.
To prevent contamination of the cooling water, controlled plants ;
commonly use surface condensers instead of barometric condensers. The
condensate from the surface condensers is discharged to wastewater i
treatment. Uncondensed gases are vented to the atmosphere. A surface
condenser may also be used to control emissions from the evaporator
calandria vents in the controlled plant.
.
The installation of surface condensers to isolate the condensate from
',
the cooling water eliminates fugitive emissions from the cooling tower, but
increases emissions from wastewater treatment.! Also, the uncondensed gases:
vented from the surface condensers contain some VOC. However, there is a i
net reduction in overall plant emissions when surface condensers are used
because the emissions from condensers and wastewater treatment are small in
comparison to those from cooling tower blowdowm when barometric condensers ;
are used.
The hypothetical plant in Figure 5 is estimated to have 7 pumps,
38 process valves, and 3 relief valves handling light organics in the feed
i
and water removal sections. Only a small portion of the emissions from ;
these sources can be assumed to be EO. The typical level of fugitive •
emission control is not known.
~
! i
Emissions from storage and handling of EO depend on whether or not it
is piped directly to the glycol production process. Presently, all EG is
produced at sites where EO is also produced. Because the EO can be piped !
directly to the EG process, emissions of EO from storage and handling are '<
40
-------
negligible. Several companies do, however, produce other glycols at
locations where EO is not produced on-site (see Table 3). At these sites
emissions do occur from storage and handling of EO.
Waste liquid streams (particularly cooling tower blowdown) may be
treated by a primary clarifier followed by activated sludge treatment. No
control system has been identified for" the control of the secondary
emissions from wastewater treatment.
Source Locations
Table 3 lists the names and locations of companies which in 1986
produced EG, DEC, TEG, and polyethylene glycols from EO. Total production '
capacities for 1986 are 2629 Gg (5795 x 106 Ib) for EG, 276 Gg (609 x
10 Ib) for DEC, and 68 Gg (149 x 106 Ib) for TEG.4 Production rates for
plants manufacturing glycols, especially DEG and TEG, fluctuate greatly with
markets for the products. Diethylene glycol production capacity is
sometimes reported simply as 10 percent of EG capacity.
GLYCOL ETHERS5
About 5 percent of the EO produced is used as a feedstock in the
production of mono-, di-, tri-, and polyethylene glycol ethers. As in the
production of glycols, additional EO reacts with the product glycol ether to
simultaneously 'form higher glycol ethers.
Process Description
Ethylene oxide is reacted with anhydrous alcohols such as methyl,
ethyl, or n-butyl alcohol to form the corresponding glycol ethers. Ethylene
glycol monomethyl ether and its homologs are produced according to the
following equations :
CH2OH
(ethylene glycol
(methanol) (ethylene oxide) monomethyl ether)
41
-------
2 -CH,
(ethylene glycol (ethylene oxide)
monomethyl ether)
(diethylene glycol
monomethyl ether)
CH,OCH0CH0OCH0CH_OH
J / / / /
(diethylene glycol
monomethyl ether)
(ethylene oxide)
CH,OCH_CH0OCH0CH0OCH0CH0OH
J / Z Z Z / /
(triethylene glycol
monoethyl ether)
Figure 7 is a simplified process flow diagram for the production of ;
glycol ethers from EO. An anhydrous primary alcohol and a sodium hydroxide
or acid catalyst are blended in a mix tank, combined with EO and recycled
alcohol, and sent to the glycol ether reactor. A mixture of mono-, di-, and
I ,
triethylene glycol ethers is formed in the reactor. A high alcohol-to-EO
ratio inhibits the formation of di- and triethylene glycol ethers.
Unreacted alcohol is separated from the product stream in a
distillation column and recycled to the reactor. The distillation column is
normally operated at atmospheric pressure, but is sometimes operated under a
slight vacuum to accommodate the higher vapor pressures of ethyl or n-butyl
alcohol. The product stream then passes through consecutive vacuum
distillation columns where the various glycol ethers are separated. The
vacuum system consists of a four stage steam-jet series with surface
intercondensers. The bottoms from the last column are disposed of, probably
by incineration or landfill.
42
-------
O
a
00
C
O
•H
4-1
a
T3
o
S-l
a.
T3
OJ
CO
S
cu •
.a cu
-a
>. -H
cS >«
cu
3
•H
43
-------
Emissions
•
Emission factors for EO (as opposed to other VOC) are not available
because the percentages of EO in the emission streams are not known. The
vent from the vacuum system is the only process emission source for which
there are VOC emissions, some portion of which could be EO. Volatile
organic compound emissions from this vent are reported as 0.013 g per kg of;
product. No emission control devices are used by the industry for this
vent. A vent from the alcohol distillation column releases alcohol and '.
inert gases. Other process vents are in the alcohol section which contains
no EO.
'
Emissions of EO from storage and handling1 depend on whether or not EO /
is piped directly to the process. It is normal practice to pipe EO directly
from the EO production facility to the glycol ether production facility. In
this case, emissions of EO from storage and handling are negligible. One
I
company, however, produces glycol ethers at a location where EO is not
produced on-site. At this site, emissions do bccur from storage and
handling of EO.
The hypothetical glycol ether production process in Figure 7 has
approximately 34 pumps, 300 process valves, and 30 pressure relief valves !
handling VOC. The emission factor for fugitive VOC emissions from glycol
ether production is reported as 0.28 g VOC per kg product. Only a small
part of these emissions can be assumed to be EO. The level of fugitive '.
emission control is not known.
I
Source Locations
Table 3 lists the names and locations of companies which produce glycol
ethers. Production rates for glycol ethers fluctuate according to the
market for the products. Total 1986 capacity for the production of glycol
ethers is 483 Gg (1065 x 106 lb).4 '
propylene oxide-based glycol ethers.
ethers is 483 Gg (1065 x 10 lb). This production total may include some
44
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ETHANOLAMINES
About 5 percent of the total EO produced in the United States is, used
as feedstock in the production of monoethanolamine (MEA), diethanolamine
(DEA), and triethanolamine (TEA). As in the production of glycols,
additional EO reacts with the product ethanolamine to simultaneously form
higher ethanolamine homologs.
Process Description
Ethylene oxide is reacted with aqueous ammonia in the liquid phase to
form the ethanolamines. Monoethanolamine and its homologs are produced
according to the following equations:
NIL
CH,
(ammonia)
(ethylene oxide)
[monoethanolamine (MEA)]
(MEA)
V
(ethylene oxide)
[diethanolamine (DEA)]
NH(CH2CH2OH)2
(DEA)
CH
2
V
(ethylene oxide)
[triethanolamine (TEA)]
No catalysts are used in any of the above reactions. The product
distribution depends on the ammonia-to-EO ratio. Excess ammonia favors a
larger proportion of MEA in the product blend.
45
-------
The continuous manufacture of ethanolamiiies is shown schematically in
Figure 8. Ethylene oxide (Stream 1) and aqueous ammonia (Stream 2) are fed
to a reactor. The reaction conditions usually are a temperature range of 50
to 100°C (122°-212°F), a pressure of 1 to 2 MPa (10-15 atm), and an excess
of 28 to 50 percent aqueous ammonia. The reactor effluent (Stream 3) is
stripped of unreacted ammonia and some water (Stream 4) in an ammonia
stripper operated under pressure. This ammonia, together with fresh feed
(Stream 5), is absorbed in recycled water in the ammonia absorber and fed
back to the reactor (Stream 2). The nonconderisable overhead gas (Stream 6)
from the ammonia stripper is scrubbed of ammonia in an ammonia scrubber with
recycle water (Stream 7) and is vented (Vent A). Inert gases enter the
system with the ethylene oxide feed, which is stored under a nitrogen
pressure pad.
The ammonia stripper bottoms (Stream 9) a.re vacuum distilled in a
series of distillation columns to sequentially remove overhead water
(Stream 7), which is recycled, and MEA, DEA, a.nd TEA (Streams 10, 11, 12),
which are products. Noncondensables from the vacuum distillation columns
are vented (Vent B) from the vacuum-jet discharges, and the vacuum-jet
wastewaters are discarded to waste treatment. The bottoms residue I
(Stream 13) from the triethanolamine column is sent to waste treatment or is
sold. The product storage tanks are ordinarily equipped with steam-heating
coils to keep the products liquid and are padded with a dry inert gas, such
as nitrogen, to prevent product discoloration.
Emissions
Total VOC emissions from the production of ethanolamines are at most
only a trace, therefore no emission controls are used for process sources.
No sources of EO emissions from the process have been identified.
The potential for EO emissions from feed storage and handling during
ethanolamine production is negligible if the EO is produced at the same
facility and piped directly to the ethanolamine process. In 1983, all
domestic producers of ethanolamine had captive! EO production.
46
-------
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en
01
u
o
•H
O
cd
I
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X
o
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CO
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c
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4-1
o
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oo
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M
oo
•H
47
-------
No information is available on fugitive emissions from valves and
pumps.
Source Locations
The names and locations' of companies which produce ethanolamines are
given in Table 3. Total 1986 capacity is 327 Gg (722 x 106 lb)/yr,4 !
ETHOXYLATION
I [
Detergent alcohol ethoxylates are produced by reacting detergent linear
alcohols with ethylene oxide in the presence of a base catalyst such as
potassium hydroxide. The general reaction may be represented as follows:
KOH
n CH
CH
..... > RO(CH0CH_0) H
l L n
(ethylene oxide) :
The molar ratio of ethylene oxide to alcohol in the final product may vary
from 2 to 40. Ethoxylates produced for subsequent conversion to alcohol
ether sulfates usually contain 3 moles of ethylene oxide per mole of
alcohol. Products made for direct use as nonionic surfactants usually
contain 6 to 12 moles of ethylene oxide per mole of alcohol.7
The primary source of EO emissions is assumed to be fugitive leaks from
equipment components, although minimal data have been collected. As a rough
estimate, the number of components handling EO at ethoxylation facilities is
approximately 10 percent of those at EO production facilities. Other
emission sources at these facilities are assumed to be negligible.7
48
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FUMIGATION/STERILIZATION
The use of ethylene oxide as a fumigant and sterilant is a potentially
large source of atmospheric EO-emissions. Although a very small amount of
all EO produced is used as fumigants or sterilants, a large portion of the
EO used for this purpose eventually reaches the atmosphere.
o
Types of Equipment
The type of equipment used for EO fumigation/sterilization varies with
the application as shown in Table 8. Each type of equipment is discussed in
the following sections.
Vacuum Chambers - -
Vacuum chambers are pressure vessels with a vacuum pump to remove air
from the chamber before sterilization begins and to remove some of the
EO/air mixture after sterilization. Though the units vary widely in size
and design features, the operating procedure is essentially as follows:
1. Contaminated material is loaded into the chamber.
2. The chamber door is closed and hermetically sealed.
3. Air is vacuumed from the chamber.
4. The sterilant (100 percent EO, 12 percent EO/88 percent Freon, or
10 percent EO/90 percent carbon dioxide) is introduced into the
chamber to a set pressure or concentration and for a specified
time period. 100 percent EO is used with negative pressure; EO
mixtures are used with positive pressure. Pressure, concentration
of sterilant, and time period are adjusted for the individual
situation.
5. An exhaust vacuum removes the EO or EO/gas mixture from the
chamber. The EO or EO/gas mixture is vented through a vent line
to the atmosphere or to a sewer drain.
49
-------
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CO
W
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!_ J
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fa
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O
5
a
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EH
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fa
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0
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W
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^^
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EC
EH
Ed
fa
O
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w
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5- *r4
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X X
X
X
X X
CO
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6. Fresh air is drawn into the chamber until 'atmospheric pressure is
reached.
7. The door is opened and the treated material removed.
8. The treated material may be transferred to an aeration cabinet
which circulates heated air.around the material until residual EO
has escaped. (Aeration cabinets are used almost exclusively in
hospitals.)
Small countertop models with capacities less than 0.1 m (<4 ft3) are
most commonly used in health care and health diagnosis facilities. In
hospitals they are used in areas such as operating rooms. One industrial
use is in the manufacture of contact lenses. Ethylene oxide is supplied .
either in single-dose cartridges of 100 percent EO or in pressurized
cylinders of 12 percent EO/88 percent Freon. Small chambers generally vent
directly into the atmosphere through a length of tubing. Some models vent
into a sponge kept damp in a bucket of water.
Intermediate-sized chambers of from 0.1 to 2.8 m3 (4-100 ft3) are used
primarily in hospital central supply facilities. They are also used in
research and industrial facilities, libraries, museums, and beehive
fumigation facilities. An EO mixture is supplied in pressurized cylinders.
Intermediate-sized chambers of this type may vent emissions to the
atmosphere or the emissions may be mixed with water, then routed to a sewer
drain.
Large chambers with capacities greater than 2.8 m3 (100 ft3) are used
primarily for industrial sterilization of medical products, spices, and
other products. They may be as large as 85 m3 (3000 ft3) in capacity and
are custom-made. In such large capacity custom chambers, an EO mixture or
100 percent EO is fed from pressurized cylinders or from large tanks.
Emissions from large chambers of this type are generally mixed with water,
then routed to a sewer drain.
51
-------
Atmospheric Chambers--
Atmospheric chambers are primarily used in health care and health
diagnosis centers, in museums, and in the beekeeping industry. They do not
evacuate air before treatment, therefore a longer exposure time is usually
necessary. Some units introduce EO into the chamber under pressure, then
after treatment, flush out the EO with pressurized air. Ethylene oxide is :
supplied as a gas mixture in cartridges. Some; units have no venting
mechanism and release all of the EO used directly into the workplace. Other
units vent emissions by manual pumping through a charcoal adsorbent on the
top of the unit.
Ampule/Liner Bag I
With this method, the article to be sterilized and a broken ampule of
100 percent EO are put into a plastic liner bag. The bag is closed with a
twist-tie, put into a non-gasketed metal container and left undisturbed for
12 hours. The EO is intended to escape slowly into the atmosphere. The
purpose of the metal container is to prevent inadvertent ignition of the
EO/air mixture in the bag.
Sterijet System--
The Sterijet system is marketed to hospitals and the medical products
industry. It is similar to the ampule/liner bag in that the EO used is
intended to escape slowly from a confining enclosure. After the article to
be sterilized is placed in a pouch, the pouch is attached to a gas delivery
machine which closes the bag around a protruding nozzle, draws a slight
vacuum on the pouch, injects a premeasured amount of EO mixture and
heat-seals the pouch. The pouch is then placed in an aeration cabinet at !
50°C (122°F) for 12 hours as most of the EO leaks out. After 12 hours, the
package has a vacuum-tight appearance which remains until the -package is '
opened either intentionally for use of the contents or accidentally.
Because the' vacuum-tight appearance is lost if the package is accidentally <
punctured, the appearance serves as a visible indicator of sterility. Some
EO remains in the pouch for as long as 36 hours after sterilization.
52
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Tent Fumigation--
Tent fumigation is used only at ports of entry to fumigate cargo
infested with snails or certain plant disease organisms. Procedures are
specified by the U.S. Department of Agriculture (USDA) and treatment is
supervised by USDA inspectors.
The cargo to be fumigated is placed on a concrete or other impervious
surface and is covered with a vinyl, rubber-coated nylon, or polyethylene
tarpaulin which is sealed around the edges. A wooden frame built over the
cargo supports the tarpaulin. A 10 percent EO/90 percent carbon dioxide
mixture is used for fumigation. Air in the enclosure is circulated by fans.
After the fumigation period is over, the EO is dispersed from the enclosure
either by the circulation fans or by large exhaust fans.
No Containment--
In some instances, the article to be fumigated serves as the container
for the EO fumigant. This method is used primarily for the fumigation of
railroad cars, but may also be used for rooms or entire buildings. In the
case of a railroad car, the car is isolated, all openings but one are
sealed, and warning signs are posted. An operator places a cylinder of EO
in the car, opens the valve, exits the car and seals the opening. After
about 6 hours, the seals are removed and the car is aired out.
Emissions
An estimate of the amounts of EO used per year for various
fumigation/sterilization purposes is given in Table 9. This estimate was
prepared by EPA1s Office of Pesticide Programs. It shows that a total of
2600 to 3900 Mg (5.7 to 8.6 x 106 lb)/yr of EO is estimated to be used for
these purposes. This amount is 0.1 to 0.17 percent of the total predicted
g
1983 EO production. About 0.024 percent of the total EO production
(0.5 Gg, 1.1 x 10 Ib) is used for sterilization/fumigation in medical
facilities.10
53
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TABLE 9. MISCELLANEOUS USES AND USE RATES OF ETHYLENE OXIDE
AS A FUMIGANT AND STERILANT9!'&
Site
Ethylene Oxide Used, Mg/yr
b
Manufacturing Facilities
(production of sterile medical
disposables)
Medical Facilities
Hospitals
Medical clinics
Dental clinics
Doctors (private)
Dentists (private)
TOTAL
Veterinarians (private and clinics)
Museums
Libraries/archives
Research Laboratories
Annual breeding
Drug/medical devices
Microbiological/cancer
TOTAL
Railroad Cars
Beehives (State, USDA)
USDA High Containment Research Labs
USDA APHIS Quarantine Port of Entry
Spices
Black Walnuts
Cosmetics
Dairy Packaging
TOTAL
400 to 450
50
29.7
16.8
3.3
22.7
250 to 410
2.3 to 11.4
1,500 to 2,600
500 to 550
0.045
0.3
0.86
275 to 444
1.0
0.68 to 0|.9
2.0 :
0.3
340
1.5
11 ;
14.5 \
2,600 to 3,900
Estimates prepared by Benefits and Use Division, Office of Pesticide
Programs, U.S. Environmental Protection Agency, 1983.
Multiply by 2,200 to convert to millions of pounds.
21976 value.
54
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Much of the EO used for sterilization/fumigation is released, either
immediately or gradually, to the environment. In most sterilization
facilities, EO emissions are released directly to the atmosphere. Some
industrial sterilization facilities do, however, control EO emissions with
add-on equipment such as incinerators, scrubbers, and chemical conversion
vessels. Emissions from some vacuum sterilizers are vented to a sewer or to
a damp sponge. In some installations, EO emissions are passed through an
evacuation pump where process water strips out EO and the EO-containing
wastewater is discharged to a municipal sewer or recycled.11'12 No estimate
is available for the amount of EO emissions released to a sewer versus the
amount released directly to the atmosphere. Although EO is completely
soluble in water, it has been shown to revolatilize into air due to its •
having a vapor pressure greater than that of water.13 Estimates of the
amount of dissolved EO that will volatilize into air from drainage water
range from 60 to 95 percent; however, definitive data documenting the amount
of EO volatilized are not available.
Some portion of the EO charged to sterilizers has also been shown to be
retained in the treated materials and the containers used to hold the
treated materials. ' In a test at a spice sterilizing operation,
immediately after sterilization the spice materials were found to contain
23 percent of -the total amount of EO originally used for sterilization.
After 24 hours, the treated spices contained about 9 percent of the original
EO charge and after 1 week, the retained amount was about 3 percent.14
Atmospheric EO emissions from sterilizers can be controlled by either
chemical conversion, wet scrubbing, incineration, or reclamation. A
description of each of these methods is given below.15
• Chemical conversion - In chemical conversion processes, a weak
acid solution is used to convert EO gaseous emissions to ethylene
glycol liquid. The ethylene glycol can be sold to reprocessors or
disposed of. This method of EO emissions control is greater than
99 percent effective.
55
-------
One prominent chemical conversion system for controlling
R :
sterilizer EO emissions is the DEOXX, system designed by Chemrox,
Inc. In an application at a spice sterilizing operation, the •
R
DEOXX system achieved an average EO emissions reduction of
14 R :
greater than 99.98 percent. DEOXX, EO emission control systems
have been or are scheduled to be installed in New York, Maryland,
Michigan, Utah, Hawaii, California, Florida, Connecticut, Texas, ,
Rhode Island, Illinois, Pennsylvania:, South Carolina, and ;
Minnesota. Chemrox, Inc. has estimated that by the end of 1986,
35 to 40 percent of medical supply manufacturing sterilization
R
facilities will have installed or committed to install DEOXX
systems. !
Wet Scrubbing - In scrubbing devices, gaseous EO emissions are
passed through water or a weak acid solution which absorbs EO and
produces limited conversions of EO to ethylene glycol. Some
sources have judged scrubbing to be minimally effective; '
however, one test of an industrial sterilizer controlled by
scrubbing produced an EO reduction efficiency of 99.3 percent.
The scrubber used at the sterilizer operation was a bubble plate
with a 3 inch demister. The scrubbing medium was a weak sulfuric
acid solution with a water to 'sulfuric acid ratio of 10:1.
Incineration - In this process, gaseous EO emissions are converted
to constituent elements and compounds, such as carbon, hydrogen,
oxygen, water, and carbon dioxide, by combusting the stream using
common fuels like propane. Incineration processes are greater
than 99 percent effective at reducing EO emissions. :
Reclamation - In this process, refrigeration is used to condense '
gaseous EO emissions to a liquid for recycle and reuse.
Reclamation systems are specially designed for use in EO :
sterilization operations with a gas mixture of 12 percent EO and ;
R
88 percent Freon . These systems are greater than 99 percent
effective at collecting reusable EO. It has been reported that ;
only one sterilization operation in the United States is using
18
this reclamation procedure.
56
-------
The decision on which EO emissions control method is most appropriate for a
particular sterilization operation is dependent on the size of the
sterilizer units, the type of sterilization gas mixture used, frequency of
use of the sterilizer, and the number of sterilization units that can be
ducted to a single control system.
It has been reported that one facility in the United States ducts
potential atmospheric emissions from EO sterilization chambers to storage
18
vessels for recycle and reuse. Because some air will be introduced into
the EO/Freon sterilization mixture during sterilization, the EO
concentration will be lower than at the start of the sterilization cycle.
To compensate for the EO dilution effect, higher pressures are used on each
additional sterilization pass. As the EO concentration systematically
decreases, higher and higher pressures are required for the sterilization.
At some point, the required pressures are too high for safe sterilization.
When the EO concentration drops below some minimum level, it is discharged
12 18 '
and the cycle starts over. '
Source Locations
• In 1976 there were less than 50 very large [>28.3 m3 (1000 ft3)]
industrial sterilizers and about the same number of smaller industrial
units. These were primarily in facilities which manufacture sterile
disposable medical supplies such as syringes, needles and microbiological
laboratory supplies. Life-support items such as pacemakers, blood
oxygenators and dialyzers are also sterilized with EO. These facilities are
in SIC Group Number 384. The trade association, Health Industry
Manufacturers Association (HIMA), in Washington, D.C. would be a good source
of information on the number and distribution of medical supplies
sterilizers.
Most hospitals have at least one and perhaps more EO sterilizers.
These units are also used in smaller medical, dental and veterinary clinics.
In 1977 there were an estimated 1,000 to 2,000 intermediate to large
57
-------
sterilizers used in hospitals and more than 10,000 units in all used in
hospitals and other medical facilities.
!
No detailed survey is available of the locations of these sterilizers,
or of other fumigating equipment which uses EO.
58
-------
REFERENCES FOR SECTION 5
1. Lovell, Ralph. Ethylene Glycol. In: Organic Chemical Manufacturing,
Volume 9: Selected Processes. EPA-450/3-80-028d. U.S. Environmental
Protection .Agency, Research Triangle Park, North Carolina.
December 1980.
2. Ozero, B.J. and J.V. Procelli. Can Development Keep Ethylene Oxide
Viable? Hydrocarbon Processing. March 1984. pp. 55-61.
3. Letter from Macauley, D.C., Union Carbide to Lahre, T., U.S.
Environmental Protection Agency. 10 April 1986. Comments on draft
ethylene oxide report.
4. SRI International. 1986 Directory of Chemical Producers, United States
of America. Menlo Park, California. 1986.
5. Schomer, T.L. Glycol Ethers: In: Organic Chemical Manufacturing,
Volume 9: Selected Processes. EPA-450/3-80-028d. U.S. Environmental
Protection Agency, Research Triangle-Park, North Carolina.
December 1980.
6. Schomer, T.L. Ethanolamines. In: Organic Chemical Manufacturing,
Volume 9: Selected Processes. EPA-450/3-80-028d. U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina.
December 1980.
7. Markwordt, D.W. Sources of Ethylene Oxide Emissions.
EPA-450/3-85-014. U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina. April 1985.
8. Goldgraben, R., et al. Mitigation of Worker Exposure to Ethylene
Oxide. Mitre Corporation. McLean, Virginia. March 1981.
9. Memo from Reinhart, J., U.S. Environmental Protection Agency to
Smith, C., Radian Corporation. 26 May 1983. Ethylene oxide used in
fumigation.
10. Glaser, Zorach. Special Occupational Hazard Review with Control
Recommendations for the Use of Ethylene Oxide as a Sterilant in Medical
Facilities. National Institute for Occupational Safety and Health
(NIOSH). Rockville, Maryland. August 1977.
11. California Air Resources Board. Performance Evaluation Test Report -
Supplement to Number C-83-049. Ethylene Oxide Emissions from a
Sterilization Chamber at McCormick and Company, Inc. (Schilling),
Salinas, California. December 1983.
59
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12. Desai, P.R. and A.J. Buonicore. Toxic Air Pollutant Emission
Measurement Techniques for Non-Steady-State Processes: A Case Study |
with Ethylene Oxide Sterilizers. Paper presented at the 1986 EPA/APCA
Symposium on the Measurement of Toxic Air Pollutants,
April 27-30, 1986, Raleigh, North Carolina.
13. Letter from Macauley, D.C., Union Carbide to Lahre, T., U.S.
Environmental Protection Agency. 10 April 1986. Comments on draft •
ethylene oxide emission factor document. ;
14. Letter and attachments from Thoits, F., Monterey Bay Unified Air
Pollution Control District to Honrath, R., Radian Corporation.
4 April 1986. Test report on the DEOXX ethylene oxide detoxification
system. . !
•
15. Letter from Jorkasky, J.F., Health Industry Manufacturers Association
to Lahre, T.F., U.S. Environmental Protection Agency. 30 January 1986.
Comments on draft ethylene oxide emission factor report.
16. Letter from Myers, R., New Jersey Department of Environmental
Protection to Lahre, T.F., U.S. Environmental Protection Agency.
3 March 1986. Comments on draft ethylene oxide emission factor report.
17. Telecon. Brooks, G.W. , Radian Corporation with Myers, R., New Jersey.
Department of Environmental Protection. 17 April 1986. Description of
the scrubbing system used to control ethylene oxide emissions.
18. Telecon. Brooks, G.W., Radian Corporation with Desai, P.R., Chemrox,:
Inc. 14 July 1986. Description of ethylene oxide reclamation and
recycle/reuse systems. :
60
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SECTION 6
SOURCE TEST PROCEDURES
The U.S. EPA Office of Research and Development (ORD) is currently
investigating viable source sampling and analytical procedures for EO air
emissions, but has not yet published or recommended any particular method.
The sampling and analysis methods presented in this chapter represent a
collection of EO emission detection and quantification techniques that have
been published in the literature as viable methods. These methods are
adaptable both for grab sampling with subsequent laboratory analysis of the
sample and for continuous monitoring with direct readout of the EO
concentration. The presentation of these published methods in this report
does not constitute endorsement or recommendation, nor does it signify that
the contents necessarily reflect the views and policies of the U.S. EPA.
SAMPLING AND ANALYSIS
The various sampling and analysis methods found in the literature are
listed in Table 10 along with a brief description of the advantages and
disadvantages of each. Sampling and analysis techniques are discussed in
general terms below.
Sampling Methods
Most sampling methods for EO are oriented to personnel monitoring or,
more generally, to ambient air monitoring. The most widely reported of
these employ solid adsorbent tubes of charcoal or Tenax-GC. The EO is
desorbed from the -tube either with carbon disulfide or by thermal
desorption. The breakthrough volumes of both charcoal and Tenax-GC are
adversely affected by high humidity. Since EO control processes use water
absorption, it might be expected that these sampling procedures would not
perform well in source sampling. The National Institute for Occupational
61
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Safety and Health (NIOSH) sampling tube assembly consists of two separate
large tubes, the first containing 400 mg and the second (a backup)
containing 200 mg of activated coconut charcoal.
Impingers, when used, are filled with a dilute sulfuric acid solution
which converts the captured EO to ethyl glycol. Before analysis, the
solution is neutralized with 50 percent potassium hydroxide;2'3
For stack gases, particularly those from incineration, a known volume
of gas is collected in an evacuated 2-liter gas bulb. The bulb should be
coupled directly to a separate sampling line from the stack and not coupled
.with any other sampling train.
Tedlar bags, though bulky, may be used to capture a known volume of
ambient air. This sampling procedure should also be adaptable to source
sampling.
When attempting to establish a material balance for EO charged to and
released from sterilizer facilities, all possible paths for EO releases need
to be assessed. In addition to atmospheric discharges, some EO may also be
absorbed in evacuation pump water, retained in the treated product, and bled
off and recycled for reuse. Desai and Buonicore have recently presented
procedures for use in testing EO sterilizers that assess all these pathways
for EO emissions.
Analytical Methods
Gas chromatography (GC) coupled with flame ionization detection (FID)1
is currently the method of choice for EO analysis and is the basis for the
NIOSH method for determination of EO. For the NIOSH method, the column is
filled with Porapak QS. The NIOSH method is considered specific for EO as
long as there is no other compound present with the same retention time. A
change in the separation conditions, such as column packing or temperature,
will usually circumvent interference problems. The method is accurate over
63
-------
a wide concentration range. It was validated at EO concentrations of 41 to
•3 3
176 mg/m . At the OSHA standard of 90 mg/m (50 ppm), the total sampling
3
and analytical method has a standard deviation of 9.3 mg per cubic meter.
Other available analytical methods include: 1) hydration to EG (in an
impinger), oxidation to formaldehyde, then colorimetric determination of the
formaldehyde by its reaction with sodium chromotropate; 2) spectrophotometry;
3) volumetric methods; and 4) conversion to ethylene chlorohydrin, then :
analysis of the chlorohydrin by mass spectrometry or gas chromatography.
DIRECT INSTRUMENTATION METHODS \
|
A variety of direct-reading instruments are available for determination
of EO concentrations in air. These instruments, which may be portable or
fixed continuous monitors, are primarily intended for area monitoring
situations. Available instruments for direct monitoring of EO
concentrations are described in Table 11. ;
I
j
The most commonly used instrument for direct reading of EO
concentrations is the infrared gas analyzer. It may be a portable unit or
part of a fixed, multi-point continuous monitoring system. Two wavelengths
are used for EO monitoring--11.8 urn and 3.3 um. Freon, a common
nonflammable carrier in EO/gas mixtures, interferes at the 11.8 um
wavelength. Alcohols interfere at 3.3 um.
j i
GC-FID, the most commonly used method for grab sample analysis, is also
used in portable instruments. One such unit features a selective absorbent
filter in the input line to the FID to eliminate interference from Freon.
64
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REFERENCES FOR SECTION 6
1. Goldgraben, R., et al. Mitigation of Worker Exposure to Ethylene
Oxide. Mitre Corporation. McLean, Virginia. March 1981.
2. Bogyo, D.A., et al. Investigation of Selected Potential Environmental
Contaminants: Epoxides. Prepared for the U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina. March 1980.
NTIS Publication No. PB80-183197.
3. National Institute for Occupational Safety and Health (NIOSH). NIOSH
Manual of Analytical Methods, Second Edition. Part II: Standards :
Completion Program Validated Methods, Volume 3. U.S. Department of
Health, Education, and Welfare. Cincinnati, Ohio. April 1977.
4. Harris, Judith C. Sampling and Analysis Methods for Hazardous Waste
Incineration, First Edition. Arthur D. Little, Cambridge,
Massachusetts. February 1982.
•
5. Desai, P.R. and A.J. Buonicore. Toxic Air Pollutant Emission :
Measurement Techniques for Non-Steady-State Processes: A Case Study •
with Ethylene Oxide Sterilizers. Paper presented at the 1986 EPA/APCA
Symposium on the Measurement of Toxic Air Pollutants, ;
April 27-30, 1986, Raleigh, North Carolina.
66
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APPENDIX A .
DERIVATION OF EMISSION ESTIMATES FOR FUGITIVE
EQUIPMENT LEAKS BASED ON EPA EMISSION FACTORS
The material in this appendix supports the emission estimates for
fugitive equipment leaks presented in Tables 6 and 7 of the main text.
These derivations assume "model" air oxidation and oxygen oxidation plants,
having a specified number of valves, pump seals, compressors, etc. As such,
the estimates will not necessarily apply to a particular facility.
Incorporated in these estimates are EPA's emission factors for fugitive
leaks and EPA's estimates of control efficiencies that would result from
application-of Reasonably Available Control Technology (RACT), as defined in
the Control Techniques Guideline (CTG), and the New Source Performance
Standards (NSPS).
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A-3
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TABLE A-3. FUGITIVE EQUIPMENT LEAKS CONTROL TECHNIQUES1
Control Technique
Emission Source CTG NSP.S
Pump seals (light liquid) LDAR ' LDAR 't
(quarterly monitoring) (monthly monitoring)
Valves (gas or LDAR LDAR
light liquid) (quarterly monitoring) (monthly monitoring)
Safety/relief valves LDAR Performance
£
(gas) (quarterly monitoring) standards+
Open-ended lines Caps Caps
Compressors LDAR Seal system
(quarterly monitoring)
Sampling connections None i Closed purge system
References 2 and 3, respectively, discuss control measures that constitute
those corresponding to the CTG (Control Techniques Guideline) and NSPS
(New Source Performance Standard).
LDAR - Leak Detection and Repair. !
c
Except during pressure releases, relief valves must be operated with no
detectable emissions as indicated by an instrument reading of less than
500 ppm above background. After a pressure release episode, a relief i
valve must be returned to a condition of no detectable emissions as
indicated by an instrument reading of less than 500 ppm above background, ,
as soon as practicable, but no later than five calendar days after the
release. See 40 CFR, Subpart W, 60.482-4 for more information on relief;
valve requirements.
A-4
-------
REFERENCES FOR APPENDIX A
1. Markwordt, D.W. Sources of Ethylene Oxide Emissions.
EPA-450/3-85-014. Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North
Carolina. April 1985.
2. Control of Volatile Organic Compound Leaks from Synthetic Organic
Chemical and Polymer Manufacturing Equipment. EPA-450/3-83-006.
Office of Air Quality Planning and Standards, U.S. Environmental
Protection Agency, Research Triangle Park, North Carolina. March 1984,
3. VOC Fugitive Emissions in Synthetic Organic Chemicals Manufacturing
Industry - Background Information for Proposed Standards.
EPA-450/3-80-033a. Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, Research Triangle Park, North '
Carolina. November 1980.
A-5
-------
INSTRUCTIONS
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EPA Form 2220-1 (Rev. 4-77) (Reverse)
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/4r-84-007l
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
LOCATING AND ESTIMATING AIR EMISSIONS FROM SOURCES
OF ETHYLENE OXIDE
5. REPORT DATE
September 1986
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO
Radian Corporation
3024 Pickett Road. Durham. NC 27705
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Management Technology Branch (MD-14)
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
EPA Project Officer: Thomas F. Lahre
16. ABSTI
VCT
To assist groups interested in inventorying air emissions of various potentially
toxic substances, EPA is preparing a series of documents such as this to compile
available information on sources and emissions of these substances. This document
deals specifically with Ethylene Oxide. Its intended audience includes Federal,
State and local air pollution personnel and others interested in locating potential
emitters of Ethylene Oxide and in making gross estimates of air emissions therefrom.
This document presents information on 1) the types of sources that may emit
Ethylene Oxide, 2) process variations and release points that may be expected
within these sources, and 3) available emissions information indicating the
potential for Ethylene Oxide release into the air from each operation.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Ethylene Oxide
Sources
Locating Emissions Sources
Toxic Substances
19. SECURITY CLASS (ThisReport}
21. NO. OF PAGES
79
2O. SECURITY CLASS (This page)
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
-------
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-45074-84-0071
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
LOCATING AND ESTIMATING AIR EMISSIONS FROM SOURCES
OF ETHYLENE OXIDE
5. REPORT DATE
September 1986
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Radian Corporation
3024 P'ickett Road, Durham, NC 27705
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Air Management Technology Branch (MD-14)
Research Triangle Park, NC 27711
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
EPA Project Officer: Thomas F. Lahre
16. ABSTRACT • ————— . _ . _ _
To assist groups interested in inventorying air emissions of various potentially
toxic substances, EPA is preparing a series of documents such as this to compile
available information on sources and emissions of these substances. This document
deals specifically with Ethylene Oxide. Its intended audience includes Federal,
State and local air pollution personnel and others interested in locating potential
emitters of Ethylene Oxide and in making gross estimates of air emissions therefrom.
This document presents information on 1) the types of sources that may emit
Ethylene Oxide, 2) process variations and release points that may be expected
within these sources, and 3) available emissions information indicating the
potential for Ethylene Oxide release into the air from each operation.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Ethylene Oxide
Sources
Locating Emissions Sources
Toxic Substances
^IBUTION STATEMENT
19. SECURITY CLASS {This Report)
21. NO. OF PAGES
79
20. SECURITY CLASS (This page)
22. PRICE
EPA Form 2220-1 (Rev. 4—77) PREVIOUS EDITION is OBSOLETE
-------
INSTRUCTIONS
1. REPORT NUMBER . . I
Insert the EPA report number as it appears on the cover of the publication. ,
2. LEAVE BLANK
3. RECIPIENTS ACCESSION NUMBER
Reserved for use by each report recipient.
Title should indicate clearly and briefly the subject coverage of the report, arid be displayed prominently. Set subtitle, if used, in smaller
• pe or otherwise subordinate it to main title. When a report is prepared in more than one volume, repeat the primary title, add volume
.•mber and include subtitle for the specific title.
Each report shall carry a date indicating at least month and year. Indicate the basis on which it was selected (e.g., date of issue, date of
apt-foval, date of preparation, etc.).
6. PERFORMING ORGANIZATION CODE :
Leave blank. , :
Give name(s) in conventional order (John R. Doe, J. Robert Doe, etc.). List author's affiliation if it differs from the performing organi
zation.
8. PERFORMING ORGANIZATION REPORT NUMBER
Insert if performing organization wishes to assign this number.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Give name, street, city, state, and ZIP code. List no more than two levels of an organizational hirearchy.
10. PROGRAM ELEMENT NUMBER :
Use the program element number under which the report was prepared. Subordinate numbers may be included in parentheses.
11. CONTRACT/GRANT NUMBER
Insert contract or grant number under which report was prepared.
12. SPONSORING AGENCY NAME AND ADDRESS
Include ZIP code.
13. TYPE OF REPORT AND PERIOD COVERED
Indicate interim final, etc., and if applicable, dates covered.
14. SPONSORING AGENCY CODE
Insert appropriate code.
15. SUPPLEMENTARY NOTES
Enter information not included elsewhere but useful, such as: Prepared in cooperation with, Translation of, Presented'at conference of,
To be published in, Supersedes, Supplements, etc.
16. ABSTRACT ' .
Include a brief (200 words or less) factual summary of the most significant information contained in the report. If the report Contains a
significant bibliography or literature survey, mention it here.
17. KEY WORDS AND DOCUMENT ANALYSIS
(a) DESCRIPTORS - Select from the Thesaurus of Engineering and Scientific Terms the proper authorized terms that identify the major
concept of the research and are sufficiently specific and precise to be used as, index entries for cataloging.
(b) IDENTIFIERS AND OPEN-ENDED TERMS - Use identifiers for project names, code names, equipment designators, etc. Use open-
ended terms written in descriptor form for those subjects for which no descriptor exists.
(c) COSATI FIELD GROUP - Field and group assignments are to be taken from the 1965 COSATI Subject Category List. Since the ma-
jority of documents are multidisciplinary in nature, the Primary Field/Group assignment(s) will be specific discipline, area of human
endeavor, or type of physical object. The application(s) will be cross-referenced with secondary Field/Group assignments that will follow
the primary posting(s).
18. DISTRIBUTION STATEMENT
Denote reusability to the public or limitation for reasons other than security for example "Release Unlimited. Cite any availability to
the public, with address and price.
19. & 20. SECURITY CLASSIFICATION
DO NOT submit classified reports to the National Technical Information service.
21. NUMBER OF PAGES
Insert the total number of pages, including this one and unnumbered pages, but exclude distribution list, if any.
22. PRICE
Insert the price set by the National Technical Information Service or the Government Printing Office, if known. i
EPA Form 2220-1 (Rev. 4-77) (Reverse)
------- |