GCA-TR-75-32-GI1)
ASSESSMENT OF ACETYLENE
AS A POTENTIAL AIR POLLUTION PROBLEM
VOLUME I
FINAL REPORT
Contract No. 68-02-1337
Task Order No. 8
Prepared For
U.S. ENVIRONMENTAL PROTECTION AGENCY
Research Triangle Park
North Carolina 2771 1
January 1976
GCA TECHNOLOGY DIVISION
BEDFORD, MASSACHUSETTS 01730
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GCA-TR-75-32-0(1)
ASSESSMENT OF ACETYLENE
AS A POTENTIAL AIR POLLUTION PROBLEM
Volume I
by
Robert M. Patterson
Mark I. Bornstein
Eric Garshick
GCA CORPORATION
GCA/TECHNOLOGY DIVISION
Bedford, Massachusetts
January 1976
Contract No. 68-02-1337
Task Order No. 8
EPA Project Officer
Michael Jones
EPA Task Officer
Justice Manning
U.S. ENVIRONMENTAL PROTECTION AGENCY
Research Triangle Park
North Carolina 27711
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This report was furnished to the U.S. Environmental Protection Agency by the
GCA Corporation, GCA/Technology Division, Bedford, Massachusetts 01730, in
fulfillment of Contract No. 68-02-1337, Task Order No. 8. The opinions,
findings, and conclusions expressed are those of the authors and not neces-
sarily those of the U.S. Environmental Protection Agency or of the cooperating
agencies. Mention of company or product names is not to be considered as an
endorsement by the U.S. Environmental Protection Agency.
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ABSTRACT
This report is one of a series which assesses the potential air pollution
impacts of 14 industrial chemicals outside the work environment. Topics
covered in each assessment include physical and chemical properties,
health and welfare effects, ambient concentrations and measurement meth-
ods, emission sources, and emission controls. The chemicals investigated
in this report series are:
Volume I
Volume II
Volume III
Volume IV
Volume V
Volume VI
Volume VII
Volume VIII
Volume IX
Volume X
Volume XI
Volume XII
Volume XIII
Volume XIV
Acetylene
Methyl Alcohol
Ethylene Bichloride
Benzene
Acetone
Acrylonitrile
Cyclohexanone
Formaldehyde
Methyl Methacrylate
Ortho-Xylenc
Maleic Anhydride
Dimethyl Terephthalate
Adipic Acid
Phthalic Anhydride.
ill
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CONTENTS
Page
Abstract ill
List of Tables v
Sections
I Summary and Conclusions 1
II Air Pollution Assessment Report 2
Physical and Chemical Properties 2
Health and Welfare Effects 2
Ambient Concentrations and Measurements 6
Sources of Acetylene Emissions 9
Acetylene Emission Control Methods 11
III References 12
iv
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TABLES
No. Page
1 Significant Properties of Acetylene 3
2 Effect of Acetylene and Ethylene on Plants 5
.*•
3 Acetylene Consumption for End Products 10
4 Acetylene Producers 10
5 Estimated Installed and Operating Costs for an Absorber/
Scrubber System H
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SECTION I
SUMMARY AND CONCLUSIONS
Pure acetylene is relatively nontoxic to man. It acts as a simple as-
phyxiant and produces ill effects only by reducing available oxygen. A
concentration of 10 percent produces only slight intoxication, and there
is no evidence of adverse effects from chronic exposure. Some damage will
occur to sensitive plants at concentrations of the order of 100 ppm.
Acetylene does not appear to be a significant component of photochemical
smog.
Emissions of acetylene are estimated to have been 9 million pounds in 1974.
These occur only from manufacturing and end use. Acetylene production
and consumption have declined 47 percent since 1966 to a current pro-
duction of 617 million pounds per year. Although there are no specific
processes mentioned in the literature for the control of acetylene emis-
sions, absorber/scrubber systems are used in manufacturing operations for
product purification.
Simple diffusion model calculations place maximum expected 1-hour average
ambient concentrations at about 5.5 ppm, and at about 3 ppm for 24-hour
values near a plant boundary. Urban concentrations of about 80 ppb and
rural values of 1 ppb have been measured.
Based on the low toxicity and expected low ambient concentrations, it
appears that acetylene does not pose a health or environmental hazard as
an air pollutant. Phosphine, a poisonous gas, is often present as an
impurity with acetylene, but at such low concentrations (less than 0.06
percent of the mixture) that it generally poses no hazard.
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SECTION II
AIR POLLUTION ASSESSMENT REPORT
PHYSICAL AND CHEMICAL PROPERTIES
Pure acetylene is a colorless, odorless gas made up of two hydrogen and
two triple-bonded carbon atoms. Commercially it can be made by the hy-
drolysis of calcium carbide, by thermal cracking or partial combustion
of natural gas. The acetylene obtained from the calcium carbide pro-
cess, the most usual method of manufacture, has a garlic-like odor due
to contamination by phosphine, hydrogen sulfide, and ammonia produced
from calcium carbide impurities. The oxygen-acetylene torch is used for
welding and cutting of metal. The reactive triple bond makes acetylene
an ideal starting material for the synthesis of flexible vinyl plastics,
rigid plastics, paints, and chlorinated hydrocarbon solvents. Selected
physical and chemical properties are presented in Table 1.
HEALTH AND WELFARE EFFECTS
Effects on Kan
Acute Poisoning - Pure acetylene is relatively nontoxic. Only at high
concentrations does inhalation of the gas begin to affect man, as shown
below:
Concentration
100,000 ppm (10%)
200,000 ppm (20%)
300,000 ppm (30%)
350,000 ppm (35%)
Response
Slight intoxication
Marked intoxication
Incoordination
Unconsciousness in 5 minutes
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Table 1. SIGNIFICANT PROPERTIES OF ACETYLENE
Synonyms
Ethine, ethyne, narcylene
Chemical formula
Molecular weight
Boiling point (sublimes)
Melting point
Vapor density
Solubility
Explosive limits
Auto ignition temperature
Pure grade
Commercial grade
At 25°C and 760 mm
26.04
-83.6°C
-81.8°C
0.9073 (dry air = 1)
1.1 volumes of gas per volume of
water at 15.5°C
The gas is soluble in many organic
materials.
*
2.5% to 85% in air
2.8% to 93% in oxygen
Varies with impurities
644°C (100% gas)
300°C minimum for mixtures of 30-70%
in air. Concentrations other than these
require higher ignition temperatures.
3
1 ppra = 1.065 mg/m
1 mg/rt3 = 0.939 ppm
The gas acts as a simple asphyxiant, producing ill effects in man only
due to a diminished oxygen concentration in the ambient air. Recovery
is complete upon removal from the gas. There is no hazard from skin or
eye contact, and ingestion is impossible.
Illnesses attributed to acetylene exposure during welding have not
been substantiated due to the presence of other hazardous materials, such
as metal fumes. With a lower explosive limit of 2.5 percent in air, it
is clear that in the presence of a flame, an explosion would occur long
4 5
before the acetylene could have any effect on man. Two reported deaths '
attributable to acetylene generators were due to phosphine impurities in
one case, and a combination of phosphine and acetylene asphyxiation in
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the second case. In the second case, It was estimated that the operator
was exposed to 80 percent acetylene, resulting in unconsciousness and
as phyxia t ion.
Acetylene has been used as an anesthetic, and has been administered both
intravenously saturated in a saline solution, and inhaled under controlled
conditions at 25 percent concentration in air. In addition, it has been
inhaled at 25 percent concentration to measure pulmonary elimination rate
in patients with heart or lung disease as an indication of cardiac or
pulmonary output. Acetylene is soluble in live lung tissue with no ill
effects.
NIOSH has not established a recommended maximum workplace atmospheric
concentration value for acetylene. However, the atmospheric concentra-
tion should be maintained below 5000 ppm to reduce the hazard of an ex-
plosion, or maintained at a lower value depending on the presence of
impurities. In the United States raw materials are selected such that
carbide-produced acetylene will not contain more than 0.05 percent phos-
phine, with actual concentrations usually in the vicinity of 0.00025 per-
cent. Since the NIOSH recommended time weighted average value for exposure
o
to phosphine is 0.3 ppm, acetylene containing 0.05 percent phosphine could
have maximum ambient concentration of approximately 500 ppm acetylene.
Chronic Poisoning - There is no evidence that chronic exposure to acety-
lene at tolerable levels has any ill effects on man.
Effects on Animals - Acute and Chronic Poisoning
Animal exposure to acetylene has not been documented. However, as in
man, acetylene will act as an asphyxiant only at high concentrations,
depriving the animal of oxygen.
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Effects on yGg°tati<)n
Acetylene will produce abscission (separation of flowers, fruit, or
leaves), epinasty (curling of leaves), and inhibition of growth in sensi-
tive plants. Its toxicity to plants is related to that of ethylene which
9
is widely regarded as the hydrocarbon most toxic to vegetation. Ethylene
is a naturally produced plant hormone, active in the regulation of growth,
development, and related processes such as the ripening of fruit. Expo-
sure to higher than the biologically permitted level may result in growth
retardation, epinasty, or abscission and discoloration of plant parts.
Unsaturated hydrocarbons such as acetylene act'as ethylene analogues, but
must be present in much higher concentrations to produce the identical
toxic effects. Atmospheric gases are taken up by plants through their
leaves. Thus a primary result of acetylene and ethylene action is the
discoloration, abnormal growth, and/or death or plant leaves. No charac-
teristic markings are produced as is the case with sulfur dioxide, ozone,
photochemical smog, or fluorides.
Acetylene doses and plant response are presented in Table 2. The concen-
tration of ethylene needed to produce the same response is included as
reference.
Table 2. EFFECT OF ACETYLENE AND ETHYLENE ON PLANTS ' '
Plant
Red kidney bean
Tomato
Pea stem
Pea seedlings
Concentration, ppm
Acetylene
125
50
280
250
Ethylene
0.1
0.1
0.1
0.2
Duration
4 hours
2 days
Rate comparison
3 days
Response
Abscission
Epinasty
Growth inhibition
Decimation
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Abscission was determined after 4 hours, and refers to the half maximal
abscission produced compared to a control. A concentration of 10,000 ppm
produced the maximal abscission, 65 percent, after 4 hours. A study of the
kinetics of the growth inhibition of the pea stem revealed that 2,800 times
more acetylene was needed to produce the same rate of inhibition produced
by ethylene.
Other Effects
Effects on Materials - Acetylene will react with copper, silver, and mer-
cury to form spontaneously explosive heavy metal acetylides. Its reaction
with the halogens, especially chlorine and fluorine, is rapid and explosive.
Effects on Photochemical Smog - It has been well documented that reactions
taking place between hydrocarbons and nitrogen oxides in photochemical
smog produce ozone and perotyacyl nitrate (PAN), two chemical species in-
jurious to man, animals, plants, and various materials. Acetylene is not
photochemically reactive enough or present in sufficient concentrations
in the ambient air to contribute significantly to the atmospheric produc-
13 14
tion of ozone and FAN. '
AMBIENT CONCENTRATIONS AND MEASUREMENTS
Measurements of acetylene in air have.been made in Riverside, California,
with morning values of 78 ppb and afternoon values of 27 ppb reported.
In contrast, concentrations of about 1 ppb were measured in "pure moun-
tain air" near Riverside. Estimates of likely maximum concentrations
near a production facility are presented below.
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Ambient Concentration Estimates
The largest production facility for acetylene has a capacity of 180 mil-
lion pounds per year. Assuming a 1.5 percent loss, this converts to an
emission rate of:
(0.015 emission factor)(180 x 106 lb/yr)(453.6 g/lb)
3.1536 x 107 sec/yr
= 38.8 g/sec of acetylene.
Some assumptions must be made regarding the characteristics of this
acetylene release to the atmosphere.
In the first place, it is assumed that the concentrations of acetylene
are likely to be highest around production facilities. Secondly, the
acetylene emissions do not all come from one source within the plant,
but rather from the numerous points of leakage at the facility. Thus
the emissions can be characterized as coming from an area source which
will be taken to be 100 meters on a side. Finally, the emissions do not
occur at ground level, but at different heights, and an average emission
height of 10 meters is chosen as a characteristic value.
Ground level concentrations can then be estimated at locations downwind
of the facility. To do this a virtual point source of emissions is
assumed upwind of the facility at a distance where the initial horizontal
dispersion coefficient equals the length of a side of the area divided
by 4.3. In this case:
o = 100m/4.3 - 23.3m
yo
Assuming neutral stability conditions (Pasquill-Gifford Stability Class D)
with overcast skies and light winds, the upwind distance of the virtual
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point source is approximately 310 meters. With consideration of the
plant boundary, it is reasonable to assume that the nearest receptor
location is thus about 500 meters from the virtual point source. Finally,
taking 2 m/sec as an average wind speed, the ground level concentration may
be calculated from:
X =
U1TO 0
y
or
38.8
X
^18.:
(2)77(36) (18. 5)
= 8.01 x 10~3 g/m3
for a 10-minute average concentration. Over a period of an hour this
becomes :
8.01 x 10~3 g/m3 (0.72) = 5.77 x 10~3 g/m
or 5.5 ppm 1-hour average concentration at the plant boundary (190 a).
Over a 24-hour period, the average concentration might roughly be ex-
pected to be about 3 ppm.
Measurement Technology
Acetylene at ambient air concentrations may be determined by wet chemical
18
or gas chromatographic techniques. The former method will detect con-
centrations of between 10 ppb and 10 ppm, while the latter method will
detect concentrations as low as 0.01 ppm and can be modified to detect
acetylene concentrations to 0.1 ppb by volume.
8
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In the first technique, acetylene is collected by adsorption on silica gel
contained in a narrow glass tube cooled by dry ice. A pink to red color
is developed in the silica gel by addition of ammonlacal cupric chloride
and hydroxylamine hydrochloride. Concentrations of acetylene are deter-
mined by comparing the resulting color with colors of tubes containing
known concentrations. This method provides reliable results at low con-
centrations, but the need for handling dry ice in the field makes the
method somewhat cumbersome. Also, the method is not specific for acety-
lene but will determine any alkyne with the triple bond occurring at the
end of the chain.
The gas chromatographic method is simpler to perform. Either integrated
or grab samples may be collected for subsequent analysis in the lab. A
portion of the air sample is injected into a chromatograph column from
which it enters a flame ionization detector. The presence of acetylene
is determined by its characteristic retention time, and concentrations
are determined by comparing the peak height of the recorder response to
heights produced by known concentrations.
SOURCES OF ACETYLENE EMISSIONS
Acetylene Production and Consumption
The consumption of acetylene has steadily dropped, for the last 8 years,
i Q 20
from 1,161 million pounds in 1966 to 617 million pounds in 1974. *
Competition from other less expensive raw materials has caused the de-
crease in acetylene consumption. Little, if any, growth is predicted for
the future. Approximately 10 percent is used for welding, scarfing and
cutting operations and the remainder as a chemical intermediate. Table 3
presents estimated consumption of acetylene for various end products.
Presently five companies with seven locations are manufacturing acetylene
from other hydrocarbon sources (see Table 4). The number of locations
producing calcium carbide acetylene is estimated to exceed 100 sites.
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Table 3. ACETYLENE CONSUMPTION FOR END PRODUCTS
Vinyl chloride
Neoprene
Vinyl acetate
Acrylonitrile
Welding
Trichloroethylene
Acrylic acid and ester
Perchloroethylene
Other
Total
Million pounds/year
165
122
90
90
61
45
26
. 8
10
617
Table 4. ACETYLENE PRODUCERS3
Company
Dow
Monochem
Rohm and Haas
Tenneco
Union Carbide
Union Carbide
Union Carbide
Total
Location
Freeport, Texas
Geismas , La •
Deer Park, Texas
Houston, Texas
Seadrift, Texas
Taft, La.
Texas City, Texas
Capacity,
million pounds /year
15
180
35
100
20
12
25
387
July 1974. Not including producers using the carbide
process.
Acetylene Sources and Emissions
Very little data exist in the literature concerning acetylene emissions.
Based on other chemical processes, it is estimated that 1.5 percent of
10
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21
total production is lost, resulting in 9 million pounds of emissions.
Primary sources of acetylene emissions are acetylene production and end
product manufacturing. Acetylene is produced from natural gas or petro-
leum derivatives by partial oxidation or by electric arc processes, and
also by the reaction of calcium carbide with water. This last method
accounts for 38 percent of total production. The 61 million pounds
(10 percent) of acetylene used for welding and cutting is believed to
be produced solely by the calcium carbide method.
Since acetylene is an extremely flammable gas (explosive between con-
centrations of 2.5 percent and 85 percent), special precautions are taken
during its handling and distribution. It is stored in steel cylinders
at 250 psi pressure dissolved in acetone. Because there is no venting
of the storage tanks, emissions from storage and handling are negligible.
Production and end product manufacturing are believed to be the only
significant sources of acetylene emissions.
ACETYLENE EMISSION CONTROL METHODS
Presently there are no specific processes mentioned in the literature for
the control of acetylene emissions. Industry, however, does use absorber/
scrubber systems in manufacturing operations for product pruification.
In this process diacetylene and acetylene are separated by using dimethyl
formamide. Yields of acetylene ranging from 98.5 to 99.3 percent purity
22
are accomplished by this method. Estimated installed capital costs and
operating costs for a general absorber/scrubber system are presented in
23
Table 5.
Table 5. ESTIMATED INSTALLED AND OPERATING COSTS FOR
AN ABSORBER/SCRUBBER SYSTEM23
System capacity SCFM
Installed capital cost
Annual operating cost
§
$
1,000
10,900
5,900
4,000
24,800
12,100
8,000
37,400
19,500
20,000
65,500
40,200
11
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SECTION III
REFERENCES
1. Chemical Technology: An Encyclopedic Treatment. Volume IV.
Petroleum and Organic Chemicals. New York, Barnes and Noble Books,
1972. p. 155.
2. Gerarde, H. W. The Aliphatic (Open Chain, a Cyclic) Hydrocarbons.
In: Industrial Hygiene and Toxicology, Volume II, 2nd Ed., Patty, F. A.
(ed.). John Wiley & Sons, Inc., 1963. p. 833.
3. International Acetylene Association, Proceedings, 40th Convention,
Milwaukee, 1940. p. 140-49.
4. Jones, A. T. Fatal Gassing in an Acetylene Manufacturing Plant.
Arch Environ Health. 1:417-22, 1960.
5. American Industrial Hygiene Association: Hygienic Guide Series on
Acetylene. Amer Ind Hyg Assoc J. 28:191-194, 1967.
6. Colldahl, H. The Pulmonary Elimination Capacity of Acetylene,
Administered Intravenously in Saline Solution. Acta Med Scand.
169:27-42, 1961.
7. Jernerus, R., G.- Lundin, L.G.C.F. Pugh. Solubility of Acetylene in
Lung Tissue as an Error in Cardiac Output Determination With the
Acetylene Method. Acta Physiol Scand. 59:1-6, 1963.
8. The Toxic Substances List, 1974 Edition, HEW Publication No.
(NIOSH), 74:134.
9. Air Quality Criteria for Hydrocarbons. National Air Pollution Control
Administration, 1970, No. AP-64.
10. Abeles, F. B., H. E. Gahagan. Abscission: The Role of Ethylene,
Ethylene Analogues, Carbon Dioxide, and Oxygen. Plant Physiol.
43:1255-58, 1968.
11. Burg, S. P., E. A. Burg. Molecular Requirements for the Biological
Activity of Ethylene. Plant Physiol. 42:144-52, 1967.
12
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12. Clayton, G. G. and T. S. Platt. Evaluation of Ethylene as an Air
Pollutant Affecting Plant Life. Am Ind Hyg Assoc J. 28:151-160,
1967.
13. Altshuler, A. P. Reactivity of Organic Substances in Atmospheric
Photo-oxidation Reactions. Public Health Service Publication No.
999-AP-14, 1965.
14. Air Quality Criteria for Photochemical Oxidants. National Air
Pollution Control Administration. Publication No. AP-63, 1970.
15. Stephens, Edgar R. Hydrocarbons in Polluted Air. Summary Report.
Coordinating Research Council, Statewide Air Pollution Research
Center, California University. Riverside, California. NTIS Report
No. PB-230 993. June 1973.
16. Turner, D. Bruce. Workbook of Atmospheric Dispersion Estimates.
U.S. Environmental Protection Agency. Report No. AP-26. January
1973.
17. Ruch, Walter E. Quantitative Analysis of Gaseous Pollutants.
Ann Arbor, Michigan, Ann Arbor-Humphrey Science Publishers. 1970.
18. Methods of Air Sampling and Analysis. American Public Health
Association. Washington, D.C. 1972.
19. Chemical. Profile. Schnell Publishing Co. July 1974.
20. Hahn, A. The Petrochemical Industry. McGraw-Hill, 1970.
21. Survey Reports on Atmospheric Emissions From the Petrochemical
Industry, 1974. U.S. Environmental Protection Agency. Report No.
EPA-450/3-73-005.
22. Faith, W. L. Industrial Chemicals. New York, John Wiley & Sons,
1965.
23. Hydrocarbon Pollutant Systems Study, Volume I. MSA Research Corp.
October 1972.
13
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