Atmospheric Emissions from
Petroleum Refineries
U. S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE
Public Health Service
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Atmospheric Emissions from
Petroleum Refineries
A Guide for Measurement and Control
U.S. DEPARTMENT OF
HEALTH, EDUCATION, AND WELFARE
Public Health Service • Division of Air Pollution
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Public Health Service Publication No. 763
1960
UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON : 1980
For sale by the Superintendent of Document*. U.S. Government Printing Office
Washington 25, D.C. - Price 30 cents
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Contents
Page
Foreword vii
Acknowledgments ix
Introduction 1
Petroleum refining 2
Crude oil distillation 5
Conversion 7
Cracking 7
Catalytic reforming 10
Polymerization, alkylation, isomerization 12
Treating 12
Hydrogen treating 13
Chemical treating 13
Treatment by physical means 14
Blending 14
Atmospheric emissions from oil refineries. 15
Sources of emissions from oil refineries in the Los Angeles
area 18
Storage tanks . 18
Catalyst regeneration units 19
Pipeline valves and flanges 20
Pressure relief valves 21
Pumps and compressors 22
Compressor engines 22
Cooling towers 23
Loading facilities 23
Waste water separators and process drains 24
Slowdown systems 24
Pipeline blind changing 25
Boilers and process heaters 26
Vacuum jets ( 27
Sampling 28
Air blowing 29
Acid treating 30
Control of emissions from oil refineries 30
Process changes 31
Control equipment 31
Improved housekeeping 31
Economics of control 31
• ••
111
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iv Atmospheric Emissions from Petroleum. Refineries
Page
Estimation of atmospheric emissions from oil refineries 32
First estimate of gross hydrocarbon emissions 33
Detailed survey of atmospheric emissions 34
Emissions of sulfur oxides 35
Miscellaneous combustion emissions 35
Hydrocarbon emissions 36
References 39
Appendix I—Method for calculating hydrocarbon vapor losses
from storage tanks 41
Appendix II—Control methods 45
Appendix III—Glossary of terms used in petroleum refining .. 47
List of Tables
Tabk
1. Survey of refineries in United States 3
?. Potential sources of specific emissions from oil refineries. _ 15
3. Average hydrocarbon emission factors for refinery storage
tanks in the Los Angeles area 19
4. Emissions from catalytic cracking unit regenerator stacks—
Los Angeles area refineries 20
5. Turnaround frequencies 25
6. Emissions from boilers and process heaters in Los Angeles
County refineries 28
7. Hydrocarbon emission values—Los Angi les survey 34
8. Sample calculation of hydrocarbon emission—first estimate. 34
9. Factors for particulate emissions 35
10. Factors for emissions of nitrogen oxides, carbon monoxide,
aldehydes, and ammonia 36
11. Factors for hydrocarbon emissions from combustion
sources 37
12. Factors for hydrocarbon emissions from equipment leakage. 37
13. Factors for hydrocarbon emissions from miscellaneous
process equipment 38
List of Illustrations
Figure
1. Processing plan for minimum refinery 5
2. Processing plan for intermediate refinery 5
3. Processing plan for complete modern refinery 6
4. Typical crude unit 8
5. Typical moving-bed catalytic cracking unit (T.C.C.) 10
6. Fluidized bed catalytic cracking unit (F.C.C.) 11
7. Typical pressure relief installation showing three single-
type relief valves 21
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Contents v
Figure Page
8. Cooling tower 23
9. Elevated flare showing effect of steam injection 26
10. Main oil transfer area showing Hamer blinds 27
11. Box-type heater 28
12. Vertical cylindrical heater 29
13. Two-stage, steam ejection vacuum jet 30
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Foreword
In September 1955 a study, known as the "Joint Project," was
started to determine the quantity and nature of emissions from oil
refineries located in Los Angeles County. At that time there were
18 refineries in Los Angeles County with a combined capacity of over
700,000 barrels of crude oil per day. These refineries are located in
or near the city of Los Angeles, often adjacent to commercial or
residential areas.
The following agencies participated in the Joint Project: Los
Angeles County Air Pollution Control District; U.S. Department of
Health, Education, and Welfare, Public Health Service, Air Pol-
lution Engineering Research; State of California, Department of
Public Health, Bureau of Air Sanitation; and representing the oil
industry, the Western Oil and Gas Association, Air Pollution Con-
trol Committee. Formally titled the "Joint District, Federal and
State Project for the Evaluation of Refinery Emissions," the Joint
Project took about 3 years to complete and was designed to be the
first comprehensive field study of atmospheric emissions from oil
refineries. The program to obtain this objective included:
1. A study of all refinery operations with respect to equipment,
products, operating conditions, and points of possible
emissions to the atmosphere.
2. Development or adaptation of sampling and analytical
methods.
3. Field testing.
4. Evaluation, classification, and extrapolation of test results to
the total petroleum refining industry in Los Angeles County.
The work of the Joint Project has been presented in nine reports
published by the Los Angeles County Air Pollution Control District
in behalf of the collaborating agencies. These reports are collectively
titled: Joint District, Federal and State Project for the Evaluation of
Refinery Emissions. (Los Angeles County Air Pollution Control
District, 434 South San Pedro Street, Los Angeles 13, Calif.) The
individual titles are:
a. Kanter, C. V., et al., "Interim Progress Report" (July 1956).
b. Palmer, R. K., "Hydrocarbon Losses from Valves and Flanges,"
Report No. 2 (March 1957).
vii
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viii Atmospheric Emissions from Petroleum Refineries
c. Steigerwald, B. J., "Hydrocarbon Leakage from Pressure Be-
lief Valves," Report No. 3 (May 1957).
d. Sussman, V. H., "Atmospheric Emissions from Catalytic
Cracking Unit Regenerator Stacks," Report No. 4 (June
1957).
e. Bonamassa, F., "Emissions of Hydrocarbons to the Atmos-
phere from Cooling Towers," Report No. 5 (August 1957).
f. Steigerwald, B. J., "Emissions of Hydrocarbons from Seals on
Pumps and Compressors," Report No. 6 (December 1957).
g. DeVorkin, H., Steigerwald, B. J., "Emissions to the Atmos-
phere from Boilers and Process Heaters," Report No. 7 (May
1958).
h. Kanter, C. V., et al., "Emissions to the Atmosphere from Eight
Miscellaneous Sources in Oil Refineries," Report No. 8
(June 1958).
i. Kanter, C. V., et al., "Emissions of Air Contaminants from Oil
Refineries," Final Report (June 1958).
For each source studied these reports detail sampling and analytical
techniques, results of field testing programs, data evaluation tech-
niques, and total emissions from the refineries in Los Angeles County.
This manual supplements the Joint Project reports and stresses the
use which can be made of the methodology and results of the Joint
Project in estimating emissions from refineries. It also includes a
discussion of equipment and processes, and details on the sources, mag-
nitude of emissions, and methods of control in effect in Los Angeles
County refineries.
It is designed to be of use to three groups of people:
(1) Persons not technically trained in either air pollution control
or petroleum refining technology who need some understanding of
refinery emissions to the atmosphere and their control;
(2) Persons trained in air pollution control who need a better un-
derstanding of petroleum refining technology;
(3) Persons trained in petroleum refining technology who need a
better understanding of air pollution control.
ARTHUR C. STERN, Chief
Air Pollution Engineering Research
Robert A. Taft Sanitary Engineering Center,
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Acknowledgments
The reports cited in the bibliography list the names of the many
people who provided the test methods and data without which this
manual could not have been prepared. The manual was principally
prepared by Bernard J. Steigerwald (while he was with the Public
Health Service prior to joining the faculty of Case Institute of Tech-
nology, Cleveland, Ohio) and Andrew H. Rose, Jr., Chief, Engineer-
ing Research & Development Unit, Air Pollution Engineering Re-
search, Robert A. Taft Sanitary Engineering Center. The assistance
of the American Petroleum Institute and the air pollution control
agencies of Los Angeles County and the Bay Area, California, and of
Philadelphia, Pa., in critically reviewing the several drafts of this
manuscript is gratefully acknowledged.
IX
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Introduction
The Engineers Joint Council has defined air pollution as "the pres-
ence in the outdoor atmosphere of one or more contaminants, such as
dust, fumes, gas mist, odor, smoke or vapors in quantities, of charac-
teristics, and of duration, such as to be injurious to human, plant, or
animal life or to property, or which unreasonably interfere with the
comfortable enjoyment of life or property."
The assessment of potential sources of contaminants from a modern
oil refinery which may contribute to air pollution is a difficult job
because of the complexity of the refining process, the unique nature of
any one refinery, the large number and wide distribution of possible
sources, the variety of emissions, the inaccessibility of some sources,
and difficulties in the identification of some emissions. The processes
and equipment in a refinery depend on the age of the refinery, the types
of the crude oil used, and the products manufactured. Nearly all
refineries have many possible emission sources, ranging from stacks
on combustion units to pipeline flanges. Some of these emissions will
not be visible; many will be odorless.
With the general acceptance of the theory that certain hydrocarbons,
innocuous in themselves, can react photochemically in the atmosphere
to produce characteristic smog or air pollution manifestations (1),
there has been special interest in those activities and operations which
emit hydrocarbons. Because of the nature of the processes involved
and the type of materials handled, the refining of petroleum may be
an important source of hydrocarbon emission.
The evaluation of these hydrocarbon emissions presents a particu-
larly difficult problem. Due to the chemical characteristics of hydro-
carbons, the usual equipment and techniques used for air analyses are
not effective for sampling and determining hydrocarbon emissions.
Petroleum hydrocarbons vary from light, highly volatile materials
to heavy, nonvolatile residues. Only a few of these hydrocarbons par-
ticipate to any great extent in the chemical reactions leading to air
pollution manifestations. In this manual no attempt has been made
to differentiate between hydrocarbons which are known to be active
in smog formation and those which are nonreactive. Hydrocarbon
emissions cited herein are based on total hydrocarbons without respect
to type. Unsaturated hydrocarbons are presently believed to be the
ones most active in smog formation. Unsaturated hydrocarbons con-
stitute only a fraction of the total hydrocarbon emissions from petro-
leum refining.
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Petroleum Refining
The petroleum industry can logically be divided into three major
divisions: production, refining, and marketing. Production includes
the operations involved in locating and drilling oil fields, removing
oil from the ground, pretreatment at the well site, and transporting
the crude to the refinery. The extent of pretreatment depends on the
type of crude oil, and usually includes removal of gas and brine. Re-
fining is limited to the operations necessary to convert the crude into
salable products. Marketing involves the distribution and sale of
the finished petroleum products. All of these activities may be sources
of emissions to the air. Emissions from the marketing of petroleum
products will generally be limited to hydrocarbons which escape dur-
ing filling operations and product storage, while production and
refining may be the sources of many types of emissions from the com-
plex equipment and operations involved. This manual is limited to
the discussion of atmospheric emissions from petroleum refining.
Some knowledge and understanding of the equipment and processes
of petroleum refining are necessary to make a reliable survey of emis-
sions to the atmosphere from petroleum refineries. Detailed informa-
tion concerning capacities, type of equipment, and control measures is
necessary and usually can be obtained through conferences with re-
finery personnel, inspection of plant flowsheets, and trips through the
refinery. Detailed descriptions and flowsheets for all commercial proc-
esses, and information on the capacities of the various processes for
each refinery in the country are also available from the literature
(3) (4).
Oil refining began about 100 years ago with the separation of kero-
sine from crude oil' in simple batch stills. Demand for gasoline, fuel
oils, lubricating oils, solvents, asphalt, petrochemicals, and other
petroleum products soon developed. To supply these needs, plants
were built to separate more effectively the crude oil, crack or split
heavy hydrocarbon molecules, polymerize or join light gaseous hydro-
carbons, rearrange the internal structure of hydrocarbon molecules,
and effectively remove impurities. The modern oil refinery is a com-
plex array of equipment and processes, and mirrors present demands
for a wide variety of high quality products.
Future changes in refinery technology will occur to meet develop-
ing needs. A few of the factors which might influence future changes
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M».»linJ
Location and Capacities as of January /, 7960
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4 Atmospheric Emissions from Petroleum Refineries
include rapid growth in the use of petrochemicals, a shift in emphasis
from the fuel requirements of internal combustion engines to those of
jet aircraft and possibly automobile turbine engines, the development
of power from nuclear and solar sources, and the use of coal, oil shale,
and less desirable crudes as refinery raw material.
At the present time there are over 300 refineries distributed through-
out the United States with a combined crude oil capacity of about
10 million barrels per day (table 1). Predictions indicate a continued
rapid growth pattern, with a domestic demand for petroleum products
in 1965 of almost 13 million barrels per day. It is anticipated that
refinery expansion costing $11.4 billion will be necessary to meet this
demand (5).
Although a modern refinery is a complex integration of many
processes and appears to be a maze of pipelines, valves, pumps,
towers, and vessels, the entire operation can be conveniently discussed
in terms of four major steps—separation, conversion, treating, and
blending. The crude oil is first separated into selected fractions;
the relative volume of each fraction (e.g., gasoline, kerosine, fuel
oil, etc.) is determined by the type of crude oil used. Since the rela-
tive volumes of each fraction produced by merely separating the
crude may not conform to the relative demand for each fraction,
some of the less valuable separation products are converted to prod-
ucts with a greater sale value (e.g., heavy naphtha to gasoline) by
splitting, uniting, or rearranging the original molecules. The prod-
ucts from both the separation and conversion steps are treated, usually
by the removal or inhibition of gum-forming materials. As a final
step, the refined base stocks are usually blended with each other and
various additives to meet product specifications and to arrive at the
most valuable and salable combination of products.
Although petroleum refining may be discussed generally in terms
of the unit processes of separation, conversion, treating, and blending,
each refinery is unique in design and no two will have exactly the
same processing scheme. Some refineries employ minimum process-
ing, limited to crude topping or skimming and simple treating (fig.
1); other intermediate refineries practice crude skimming, limited
cracking, treating, and some manufacture of heavy products such as
lube oil, grease, and coke (fig. 2); many large refineries practice
complete refining, including crude topping, catalytic cracking, light.
hydrocarbon processing such as polymerization or alkylation, manu-
facture of lube oils, greases, asphalts, and waxes, and usually catalytic
reforming or isomerization to improve gasoline quality (fig. 3).
The following sections include general information on the proc-
esses and equipment used in oil refineries to manufacture petroleum
products.
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Petroleum Refining
Gas
-^-Refinery Fuel Gas
Crude Oil-
Gasoline Blending
Stock
»-Keroslne
>J_!ght Fuel Oil
Reduced Crude Oil
->-Heavy Fuel Oil
Crude 011-
FIQUBB 1. Processing plan for minimum refinery
Cos . —^.Refinery Fuel Gos
Gasoline Blending
Stock
^Domestic Healing Oils
and Diesel Fuels
.^Industrial Fuel Oil!
>4_ube Oils
>-Woxes
^Asphalt
Bottoms
FIOUBE 2. Processing plan for intermediate refinery
Crude Oil Distillation
Crude oil is a mixture of many different hydrocarbons, some of
them combined with small amounts of impurities. Crudes vary in
appearance from dense black semisolids resembling tar to light, almost
colorless fluids. Crudes vary considerably in composition and physi-
cal properties, and usually consist of three families of hydrocarbons:
paraffins—saturated hydrocarbons having the empirical formula
CnH2n+2; naphthenes—ring-structure saturated hydrocarbons having
the empirical formula CnH2n; and aromatics-rcharacterized by hav-.
ing a benzene ring, C6H6, in the molecular structure. Significant
elements other than carbon and hydrogen in the crude petroleum
include sulfur, oxygen, and nitrogen.
Since crude oil is composed of hydrocarbons of different physical
properties, it can be separated by physical means into its various
constituents. In practice, primary separation is usually accomplished
by distillation, with collected fractions consisting of hydrocarbons
of specified boiling ranges. The fractions usually include refinery
gas, gasoline, kerosine, light fuel oil, diesel oils, gas oil, lube distillate,
and heavy bottoms, the amount of each being determined by the type
and composition of the crude oil. These are called straight run prod-
-------
Crude Oil.
— >
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Crud
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Raw Gasoline
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51
»-Lube Stocks S
^-Greases *
^-Waxes J5)
^ ir
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fc.Coke
FIOUBE 3. Processing plan for complete modern refinery
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Petroleum Refining 7
ucts. Some are treated to remove impurities and used as base stocks
or sold as finished products; the remainder are used as feedstock for
other refinery units.
Primary separation is accomplished by simple distillation in crude
topping or skimming units. Crude is heated in pipe stills and passed
to fractionating towers or columns for vaporization and separation.
Heavy fractions of the crude which do not vaporize in the topping
operation are separated by steam or vacuum distillation. These
processes accomplish vaporization of the high-boiling fractions at
relatively low temperatures by maintaining a vacuum above the hot
oil in the tower or by introducing into the tower an inert gas, usually
steam or recycled vapor, to lower the partial pressure in the vapor.
Destructive distillation and coking are severe forms of reduction
employed to convert heavy residuum to coke and more valuable volatile
products.
Combinations of all of these methods and occasionally solvent ex-
traction and adsorption techniques are used to separate crude oil in
most refineries, the combination being determined by the boiling range
of the stock, the stability of the stock with respect to heat, and product
specifications. Figure 4 shows a typical crude oil distillation unit.
Conversion
The relative amounts of various products obtained by a simple sepa-
ration of crude oil usually do not conform to the existing demand for
these products. For example, the yield of gasoline from the separa-
tion of most crude oils is about 25 percent of the volume of crude
processed. However, the crude must be made to yield almost 50 per-
cent gasoline to supply the demand for gasoline without producing
excess quantities of other crude oil constituents such as kerosine, fuel
oil, and heavy residuum. Also, much of the gasoline must be of better
quality than occurs naturally in the crude oil.
To obtain a more desirable product distribution and quality, heavy
hydrocarbon molecules are cracked or split to form low-boiling hydro-
carbons in the gasoline range, and light gaseous hydrocarbons are
united in polymerization or alkylation units to form gasoline blending
stock. The processes of reforming and isomerization rearrange the
molecular structure of gasoline to produce a higher octane fuel with
better performance characteristics.
Cracking
In the cracking operation, large molecules are decomposed by heat
and pressure (sometimes using catalysts) into smaller, lower-boiling
molecules. At the same time, some of the molecules combine (poly-
merize) to form larger molecules. The products of cracking are
gaseous hydrocarbons, gasoline, gas oil, fuel oil, and coke.
-------
00
Side Strippers
Topping
Heat
Exchanger
Exhaust Steam and
condensed Hydrocar-
bons to Atmosphere or Fireba
Vacuum «
Distillation
Tower
*—*-Odor
Condenser
Sump
Jo Separator
>-Gos to Refinery Fuel
Gas System or Gas
Treating Units
>-Gasoline
>-Kerosine
Light Fuel Oil
->-Gos Oil to Catalytic
Cracking Unit
*-Lube Stock
-^-Residuum to Coker,
Asphalt Plant
s-
r
t
sr
FIGURE 4. Typical crude unit employing topping and vacuum distillation
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Petroleum Refining 9
Thermal Cracking
Thermal cracking is giving way to catalytic cracking. However,
thermal cracking still constitutes about one-third of the total cracking
capacity in the United States, equivalent to about 20 percent of total
refinery crude capacity.
In thermal cracking units, the charge stock, usually a topped crude
or other heavy residual product, is heated to about 1,000° F. at high
pressures to produce gaseous hydrocarbons, gasoline, gas oil, and
residual fuel oil. A small amount of coke is deposited in the coils
of the heater and reactor, and the units must be shut down periodically
for cleaning.
Other forms of thermal cracking may include coking, a severe crack-
ing operation; visbreaking, a mild cracking to reduce the viscosity of
the feedstock, usually fuel oil; and combination units which combine
crude oil distillation and some form of cracking.
Catalytic Cracking
Catalytic cracking is the backbone of the modern refinery. The
capacity of these units amounts to about 4 million barrels per day,
equivalent to about 40 percent of total refinery crude capacity. Crack-
ing over a catalyst, usually an alumina-silicate, is accomplished at
slightly greater than atmospheric pressures and about 900° F. It
gives a higher gasoline yield and better quality gasoline than thermal
cracking. The charge stock is usually gas oil, a distillate inter-
mediate between kerosine and fuel oil. Catalytic cracking yields a
"synthetic crude" which is separated into gaseous hydrocarbons, gaso-
line, gas oil, and fuel oil.
During the cracking process, which is usually continuous, coke
deposits on the catalyst and is burned off in separate regenerating
vessels.
Catalytic cracking units may be classified according to the method
used for catalyst transfer. There are four main methods: (1) fixed-
bed, utilizing a number of reaction-regeneration chambers in a batch-
type operation, (2) moving-bed, (3) fluidized bed, and (4) a once-
through catalyst system which does not attempt catalyst regeneration.
Fixed-bed and once-through systems are no longer used to any great
extent. The moving-bed system, typified by the Thermofor Catalytic
Cracking Units (T.C.C.), and the Houdriflow Units, and the fluidized
bed or Fluid Catalytic Cracking Units (F.C.C.) are now almost uni-
versally used in refinery operations.
A typical moving-bed "cat" cracker is shown in figure 5. The
catalyst, in the form of beads or pellets, passes through the reactor,
then through a regeneration zone where coke deposited on the catalyst
is burned off in a continuous process. The regenerated catalyst is
lifted by air, or in the older units by bucket elevators, to catalyst
storage bins atop the reactor vessel.
-------
10 Atmospheric Emissions from Petroleum Refineries
In fluidized systems, figure 6, finely powdered catalyst is lifted
into the reactor by the incoming oil charge, which vaporizes upon
contact with the hot catalyst. The catalyst which does not settle out
in the reactor is removed from the cracked product stream by a system
of cyclonic separators located in the reactor vessel. Catalyst is drawn
off at a controlled rate, purged with steam, and lifted into the regen-
erator by a stream of air where the coke is removed by burning. The
regenerator flue gases containing entrained catalyst pass through a
series of cyclonic separators in the regeneration vessel, often followed
by an electrostatic precipitator, before discharge to the atmosphere.
Catalytic Reforming
In the past 7 years there has been a tenfold increase in the use of
catalytic reforming by oil refineries, and the present capacity is nearly
2 million barrels per day. Unlike catalytic cracking, catalytic reform-
ing does not increase the gasoline yield from a ban el of crude oil;
it uses gasoline as a feedstock and by molecular rearrangement, usually
including hydrogen removal, produces a gasoline of higher quality
and octane number, along with large quantities of hydrogen.
Some fixed-bed installations have facilities for the regeneration of
the catalyst in place with the resulting discharge of combustion prod-
ucts. Since coke deposition is not severe in reforming operations.
catalyst regeneration in place is not always used. In this case, the
Surge
Separator
Products
Regenerated
Catalyst
Airlift or
Elevator
.^Wet Gat to Poly, or
"^"Alkylation Units
—^•Crocked Gasoline
Fuel Oil
Oil Recycle
Fuel Oil
Fractionating
Tower
FIGURE 5.
Typical moving-lied catalytic cracking unit, similar to Thermofor
Catalytic Cracking (T.C.C.) and Houdry processes
-------
Regenerator
Vir ^
Regeneratedxv \^
Catalyst >i^=^
Wet Gas to Poly.
or Alkylation Units
„ ^ |_j£ up) oil
Fuel Oil
O
I
t
Gas Oil Charge
Fluidized T>e& catalytic cracking unit. (F.C.C.)
-------
12 Atmospheric Emissions from Petroleum Refineries
catalyst is physically removed and replaced periodically. The follow-
ing lists include most commercial fixed-bed catalytic reforming
processes (3).
Fixed-bed processes which require regeneration of catalyst in place:
Cycle version Sinclair—Baker Kellogg
Fixed-Bed Hydrof orrning Powerf orming
Ultraforming
Fixed-bed processes in which the catalyst is infrequently
regenerated:
Platforming Catforming
Rexforming Houdriforming
Iso-Plus Sovaforming
Also commercially available are two fluidized processes, Fluid Hy-
drof orming and Orthoforming, and one moving-bed type, Thermofor
Catalytic. These three types use continuous catalyst regeneration
similar to cracking units.
Polymerization, Alkylation, Isomerization
Polymerization and alkylation are processes used to produce gaso-
line from the gaseous hydrocarbons formed during cracking opera-
tions. Polymerization joins two or more olefins (noncyclic unsatu-
rated hydrocarbons with C=C double bonds), and alkylation unites an
olefin and an iso-paraffin (noncyclic branched-chain hydrocarbon sat-
urated with hydrogen). Isomerization is the process for altering the
arrangement of atoms in a molecule without adding or removing
anything from the original material, usually used in the oil industry
to form branched-chain hydrocarbons. A number of catalysts such
as phosphoric acid, sulfuric acid, platinum, aluminum chloride, and
hydrofluoric acid are used to promote the combination or rearrange-
ment of these light hydrocarbons.
These three processes, including regeneration of any necessary
catalysts, form essentially closed systems and they have no unique,
major source of atmospheric emissions.
Treating
As noted earlier, crude oils may contain small amounts of many im-
purities. Sulfur is a major undesirable constituent in petroleum from
a refining standpoint; also, some attention is being given to nitrogen
which may adversely affect the catalysts used in some processes.
Sulfur in crude oil is usually found in combination with hydrogen
or hydrocarbons as hydrogen sulfide (H2S), mercaptans (R-SH),
sulfides (R-S-R), polysulfides (R-SX-R) and thiophenes, ring com-
pounds with sulfur as a member of the ring structure. During the
refining process, part of the original sulfur compounds is often con-
verted to H2S and to lower molecular weight mercaptans.
-------
Petroleum Refining 13
Sulfur removal from both product and intermediate feedstocks is
becoming more universal in oil refineries for a number of reasons,
including improved product quality, sensitivity of certain catalysts to
sulfur poisoning, and the use of crude oils relatively high in sulfur
content due to the depletion of low sulfur crudes. At the present
time about 40 percent of the crude oil produced in the United States
contains over 0.5 percent sulfur, and about 10 percent of the crude
contains over 2 percent sulfur. The cost of removing this sulfur
may amount to 10 to 15 percent of total refinery operating expenses (6).
Although treatment varies widely, some degree of removal is neces-
sary because of the effect sulfur has on refinery processes and product
quality. Sulfur compounds are frequently odorous and may cause
corrosion, reduce octane number and lead susceptibility, decrease yields
from cracking operations, poison certain catalysts, and adversely af-
fect product qualities such as stability and burning characteristics.
Petroleum products and feedstocks are treated by many methods,
utilizing both physical separations and chemical reactions.
Hydrogen Treating
Catalytic hydrogen treating is relatively new, but it is becoming a
widely used method of removing impurities from petroleum products.
It involves a mild selective hydrogenation which converts organic
compounds of sulfur, nitrogen, and oxygen into hydrocarbons and
removable hydrogen sulfide, ammonia, and water. In addition the
process converts diolefins, gum-forming hydrocarbons, into stable
compounds, while minimizing saturation of desirable aromatics.
Hydrogen treating requires large quantities of relatively pure hydro-
gen, most economically supplied by catalytic reforming units, and
the two processes—catalytic reforming and hydrogen treating—are
often found together. Some new installations combine hydrogen
treating and catalytic reforming into a two-stage integrated unit.
Nearly all hydrogenation units are the fixed-bed type. Catalyst re-
placement or regeneration cycles vary from a few days to greater
than a year, depending on operating conditions and the product being
treated; high temperatures and heavy feedstocks accelerate coke dep-
osition on the catalyst and force frequent regeneration. The catalyst
is regenerated in the usual manner by controlled combustion of the
deposited coke. Hydrogen sulfide is removed from the hydrogen
stream in an extraction system and converted to elemental sulfur or
sulfuric acid; or when the quantity is too small to justify recovery, is
burned to SO2 in a flare or boiler firebox.
Chemical Treating
A number of chemical methods are used throughout the refinery
to treat hydrocarbon streams. Equipment used for most chemical
treating units includes a mixing chamber, a separation vessel, a water
-------
14 Atmospheric Emissions from Petroleum Refineries
wash system, and, in some processes, a regeneration unit to reactivate
or recover spent chemicals. Chemical treatments can conveniently be
classified into four groups: (1) acid treatment, (2) sweetening,
(3) solvent extraction, and (4) additives.
Acid treatment involves contacting the hydrocarbons with con-
centrated sulfuric acid which partially removes sulfur and nitrogen
compounds, precipitates asphaltic or gum-like materials, and im-
proves color and odor. Where this type of process is still used, spent
acid sludges are usually converted to ammonium sulfate or sulfuric
acid.
Sweetening processes oxidize mercaptans to disulfides, without
actual removal of sulfur. The most common sweetening processes
are the doctor (sodium plumbite), lead sulfide, hypochlorite, and
copper chloride processes. In some sweetening processes, air and
steam are used for agitation in mixing tanks and also to reactivate
chemical solutions.
Treatment by solvent extraction involves the use of a solvent with
an affinity for the undesirable compounds, and which can be sepa-
rated easily from the product stream. Sulfur compounds, particu-
larly mercaptans, are extracted using a strong caustic, sometimes
fortified with solubility promoters such as alcohol, organic acids, or
alkyl phenols. Commercial processes of this type include the Tannin-
Solutizer, Mercapsol, Unisol, and Dualayer processes. The solvents
are usually regenerated by heat, steam stripping, or air blowing.
Hydrogen sulfide is removed from both gaseous and liquid hydro-
carbon streams by solvent extraction in a number of commercial
processes including the Girbotol, Phenolate, Alkazid, Ferrox, Phos-
phate, and Glycol-Amine processes.
Additives or inhibitors are primarily materials added in small
amounts to oxidize mercaptans to disulfides and retard gum
formation.
Treatment by Physical Means
Physical methods, including electrical coalescence, filtration, ab-
sorption, and air blowing, are often used in refineries to treat hydro-
carbon streams or remove undesirable components as intermediate
steps in the processing scheme. Applications include desalting crude
oil, wax removal, decolorizing lube oils, and brightening diesel oil
(removal of turbidity due to moisture).
Blending
The oil industry produces almost 2,500 finished petroleum prod-
ucts. These include over 10 types of liquefied gases, about 40 dif-
ferent gasolines, nearly 300 types of greases, and over 1,000 different
lubricating oils. These products each conform to separate specifica-
tions, often including standards for vapor pressure, specific gravity,
-------
Atmospheric Emissions from Oil Refineries 15
sulfur content, viscosity, octane number, initial boiling point, pour
point, etc. The many products are made, or fabricated, by blending
relatively few refinery base stocks in varying proportions until the
desired products are obtained.
Atmospheric Emissions From Oil Refineries
Refineries vary greatly in both the quantity and type of emissions.
The most important factors affecting refinery emissions are crude oil
capacity, air pollution control measures in effect, general level of main-
tenance and good housekeeping in the refinery, and the processing
scheme employed. The emissions which may contribute to air pollu-
tion are sulfur oxides, nitrogen oxides, hydrocarbons, carbon monox-
ide, and malodorous materials. Other emissions of lesser importance
include particulates, aldehydes, ammonia, and organic acids. Table
2 indicates potential sources of the various contaminants from re-
fineries and emphasizes the variety of equipment and operations
which must be considered in a complete survey of refinery emissions.
An attempt to categorize these potential sources into the four major
refinery operations of separation, conversion, treating, and blending
developed in the preceding section on refinery technology is difficult
because many of the potential sources such as pipeline valves are found
throughout the refinery, while others such as waste gas flares cannot
be assigned to any one refinery operation. Rather, for an air pollu-
tion survey an oil refinery should be considered an integrated system
of pumps, valves, cooling towers, process heaters, and other equipment
and operations listed in table 2. These are the primary sources of
possible emissions, and an estimate of emissions is best accomplished
by summing the contribution of each of these potential sources.
TABLE 2. Potential sources of specific emissions from oil refineries
Emission
Potential sources
Oxides of sulfur.
Hydrocarbons.
Oxides of nitrogen..
Particulate matter.
Aldehydes
Ammonia.—-
Odors
Carbon monoxide.
Boilers, process heaters, catalytic cracking unit regenerators, treating units,
HjS flares, dccoking operations.
Loading facilities, turnarounds, sampling, storage tanks, waste water separators,
blow-down systems, catalyst regenerators, pumps, valves, blind changing,
cooling towers, vacuum jets, barometric condensers, air-blowing, high pressure
equipment handling volatile hydrocarbons, process heaters, boilers, compres-
sor engines.
Process heaters, boilers, compressor engines, catalyst regenerators, flares.
Catalyst regenerators, boilers, process heaters, decoking operations, incinerators.
Catalyst regenerators.
Catalyst regenerators.
Treating units (air-blowing, steam-blowing), drains, tank vents, barometric
condenser sumps, waste water separators.
Catalyst regeneration, decoking, compressor engines, incinerators.
-------
16 Atmospheric Emission* from Petroleum Refineries
While it is not practicable to make a survey of refinery emissions
based on the refinery divisions of separation, conversion, treating, and
blending, it is helpful to consider in a general way the major or unique
sources for each of these major operations, and to indicate the possible
emissions in a qualitative manner.
Of special interest in the separation of crude oil into petroleum
products is the barometric condenser sometimes used to maintain a
vacuum on the vacuum distillation tower. Noncondensables, includ-
ing light hydrocarbons, pass through the condenser and may be
discharged to the atmosphere. This can be a major source of hydro-
carbon emissions, depending on the size of the unit, the type of
feedstock, and the temperature of the cooling water. In addition,
the condenser sump may be a source of odor emissions.
Cracking operations may be a significant source of atmospheric
emissions because of the necessity for removing the coke which forms
during cracking operations. The coke deposits on the catalyst itself
or in the reactor tubes during thermal cracking operations and may
include sulfur and other impurities present in the feedstock. It is
usually removed by a controlled combustion process with resulting
discharge of the combustion gases including catalyst fines, unburned
hydrocarbons, sulfur oxides, carbon monoxide, ammonia, and nitrogen
oxides. A persistent plume will often accompany the discharge from
catalytic cracking unit regenerators. In addition to combustion gases,
catalyst fines may be discharged by vents on the catalyst handling
systems on both T.C.C. and F.C.C. units.
The conversion processes of alkylation, polymerization, and isomeri-
zation, although having no unique source of potential emissions, de-
serve special mention. The highly volatile nature of the hydrocarbons
handled and the high process pressures required make valve stems and
pump shafts difficult to seal, and a greater emission rate from these
two sources can generally be expected in these process areas than is
normal throughout the refinery. It is generally true that processes or
refineries handling L.P.G., gasoline, or other highly volatile products
will have a higher hydrocarbon emission rate than similar processes
or refineries limited to production of lubricants, asphalts, fuel oils,
or other materials with low vapor pressures.
Emissions from treating operations may vary widely and depend
particularly on the methods used for handling spent acid and acid
sludges, and on the method employed for recovery or disposal of the
hydrogen sulfide. These operations are potential sources of sulfur
oxides, hydrocarbons, and visible plumes. Other potential sources of
SO2, hydrocarbons, and particulate matter in the treating area include
catalyst regeneration, air agitation in mixing tanks, and other air
blowing operations. Trace quantities of malodorous substances such
as H2S and mercaptans may escape from numerous sources through-
-------
Atmospheric Emissions from Oil Refineries 17
out the treating area including settling tank vents, surge tanks, water
treatment units, waste water drains, valves, and pump seals.
Pipeline blind changing is a potential source of hydrocarbon emis-
sion generally found concentrated in the refinery product blending
area. Blinds are circular metal plates inserted into the pipeline at
flanged connections to insure product separation and minimize, the
possibility of accidental product mixing. During blind changing
operations some hydrocarbons probably escape.
The Joint Project (2) evaluated emissions from petroleum refineries
in Los Angeles County by an extensive study of most of the primary
sources of emissions listed in table 2, usually with a field testing
program.
A knowledge of these potential sources, their distribution in the
refinery, the mode of escape, and the type and magnitude of emissions
for refineries in Los Angeles County can aid in making air pollution
surveys in other areas. However, care must be taken in the use of
Joint Project loss data for estimating losses from other refineries.
Processing schemes may not be the same and may influence the type
and amount of emissions. The following list summarizes the process
capacities for refineries in Los Angeles County during the Joint
Project investigations:
Distillation units—685,000 barrels charged per calendar day.
Vacuum distillation—310,000 barrels charged per calendar day.
Thermal operations—280,000 barrels charged per calendar day.
Catalytic cracking, total feed—290,000 barrels charged per
calendar day.
Percent recycle—25 percent.
Catalytic reforming—58,000 barrels charged per calendar day.
Hydrogen treating—41,000 barrels charged per calendar day.
Alkylation—33,000 barrels produced per calendar day.
Polymerization—4,000 barrels produced per calendar day.
Lube—230 barrels produced per calendar day.
Asphalt—25,000 barrels produced per calendar day.
Coke—1,000 tons produced per calendar day.
It should be borne in mind that, due to the unique topographical
and climatic conditions in the area, emissions from refineries in Los
Angeles County are controlled to a high degree. The Los Angeles
County Air Pollution Control District enforces a number of rules and
regulations, some of which apply specifically to the oil industry in that
area. These rules specify types of storage tanks which may be used,
require controls on waste water separators and gasoline loading
operations, and limit the emission of dusts, smoke, and SO2.
In complying with these regulations and inaugurating voluntary
control and employee educational programs, oil refineries in Los
-------
18 Atmospheric Emissions from Petroleum Refineries
Angeles County in the past 10 years have reduced sulfur emissions
by 600 tons daily and controlled several hundred tons of hydrocarbons
per day, at a cost of about $33 million. Because of the emphasis placed
on air pollution control in Los Angeles, the Joint Project (2) emission
figures approach the lowest values currently obtainable.
Sources of Emissions From Oil Refineries in the Los Angeles Area
This section of the manual enumerates sources of emissions from oil
refineries in the Los Angeles area, summarizes the results of the Joint
Project studies, gives average data on emissions, and describes control
measures applied by these refineries.
Storage Tanks
Storage tanks are an important source of hydrocarbon emissions
in petroleum refineries. Hydrocarbon vapors may be released through
a number of mechanisms, including tank breathing caused by tem-
perature changes, displacement during filling operations, and a small
amount of direct evaporation from tanks equipped with floating roofs.
The Joint Project canvassed all refineries in Los Angeles concern-
ing hydrocarbon storage. The information requested for each tank
included capacity, dimensions, type of roof, controls, construction and
maintenance, product stored, vapor pressure of product, average
throughput, and other data in sufficient detail to allow calculation of
vapor losses. Losses were calculated using equations and nomographs
presented at the 32d Annual Meeting of the American Petroleum
Institute (7). This method of calculation, along with a calculation
sheet, is shown in appendix I. This method of calculation is now in
process of modification. Reference should be made to API Bulletins
2512, 2513, and others planned on this subject for up-to-date informa-
tion on the magnitude, causes, and control of evaporation losses.
In 1956, refineries in Los Angeles County had 135 crude oil storage
tanks and 704 tanks for distillate products, with capacities of 7.4 and
20.8 million barrels respectively. The calculated emissions from crude
oil storage tanks amounted to 15 tons per day and from distillate
tanks were 27 tons per day. It was assumed that no emissions oc-
curred from pressure storage of liquefied petroleum gases (L.P.G.).
These emissions are not typical for an area processing 700,000 barrels
of crude daily.
All refineries have some facilities to reduce hydrocarbon emissions
to the economic level. For the reasons previously mentioned, how-
ever, refineries in the Los Angeles area are required to exercise an
even greater degree of control than has been found necessary in other
areas. For example, a control rule (rule 56) has been established
which applies to all tanks of greater than 40,000-gallon capacity
which store petroleum distillate products having vapor pressures
greater than 1.5 p.s.i.a. under actual storage conditions. Under this
-------
Atmospheric Emissions from Oil Refineries
19
rule floating roof tanks are permissible for materials with vapor
pressures not exceeding 11 p.s.i.a. at storage temperature, and vapor
recovery systems are required for storage tanks handling more volatile
materials. Although crude oil storage is not covered by rule 56, over
two-thirds of crude storage capacity in Los Angeles is in tanks with
some form of vapor control.
Table 3 presents average loss figures for storage in fixed roof and
floating roof tanks in the Los Angeles area. These averages are not a
direct measure of the relative effectiveness of various types of tanks.
(Refer to the publications of the API Evaporation Loss Committee,
Bulletins 2512, 2513.) Tanks connected to vapor recovery systems
were assumed to have no loss.
TABLE 3. Average hydrocarbon emission factors for refinery storage tanks in
the Los Angeles area
Material stored
Crude oil:
Vapor pressure >1.5
p.s.i.a
Vapor pressure <1.5
p.s.i.a _
Emission factor
(pounds of hydro-
carbon per day
per 1,000 barrel
storage capacity)
Fixed
roof
9.1
4.5
Floating
roof
4.8
1.8
Material stored
Petroleum distillate:
Vapor pressure >1.5
p.s.i.a .
Vapor pressure <1.5
p.s.i.a .
Emission factor
(pounds of hydro-
carbon per day
per 1,000 barrel
storage capacity)
Fixed
roof
*47
1.6
Floating
roof
4.8
1.7
•All tanks in this group were of less than 1,000 barrels capacity. Larger tanks would have somewhat
lower emission factors.
Catalyst Regeneration Units
During catalytic cracking, reforming, and hydrogenation, coke
formed on the surface of the catalyst is burned off in regenerating ves-
sels by controlled combustion. The flue gases from the catalyst re-
generator may contain fine catalyst dust, and the products of combus-
tion of the coke may include some of the impurities contained in the
charging stock. Cracking unit regenerators are usually large and op-
erate continuously and are potential sources of'dust, carbon monoxide,
hydrocarbon (nearly all methane), and sulfur oxide emissions. Ke-
forming and hydrogen treating units usually regenerate catalysts in-
termittently and are a less important source of emissions.
Table 4 summarizes the results of the Joint Project data on emis-
sions from catalytic cracking unit regenerators. It should be noted
that because of higher catalyst circulation rates, Fluid Units (F.C.C.)
have significantly higher average emission rates than Thermofor
(T.C.C.) Units, based on unit capacity. Also, the values for all
emissions vary greatly, even between the same types of units. There-
fore, the use of average values may introduce large inaccuracies.
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20 Atmospheric Emissions from Petroleum Refineries
One Thermofor Catalytic Reformer Unit (T.C.R.) was tested and had
emissions similar to the T.C.C. units, except for sulfur emissions,
which were very low.
Dust emissions in Los Angeles County are limited to 40 pounds per
hour from any one unit, processing in excess of 60,000 pounds per hour.
To meet this regulation, all T.C.C. units in refineries in Los Angeles
County are equipped with high-efficiency cyclonic separators; F.C.C.
units are controlled by more elaborate dust removal equipment, in-
cluding cyclones and electrostatic precipitators.
Pipeline Valves and Flanges
Under the influence of heat, pressure, vibration, friction, and cor-
rosion, valves and flanged connections may develop leaks. These leaks
may be liquid, vapor, or both, depending on the product carried and
on temperature.
Tests made on almost 10,000 valves indicated a total emission from
all valves of 10 tons per day. Average emissions were 0.5 pound of
hydrocarbons per day from valves handling light materials (vapor
pressure greater than 15 p.s.i.a. at 60° F.), and average vapor emissions
of 0.05 pound per day from valves handling heavier, liquid products.
Emissions from this source averaged 28 pounds per day per 1,000
barrels of crude throughput.
TABLE 4. Emissions from catalytic oraokinff unit regenerator stacks,
Los Angeles area refineries
Number of nnfts
Fresh feed rat*, barrels per day . . .- n-™.. . ...
Catalyst circulation rate, tons per hour -
Stack discharge rate, SCFM, 60° F. and 1 atm. (dry basis)....
Emissions:
Tons per day
Tons per day .
Sulfur trioxide, tons per day
Ainnionia as NHt, p p.m. range ^ *..
Tons per day
Aldehydes, as HCHO, p. p.m. range
Tons per day - - - - -
Tons per day . - - ,
Tons per day r - - - - f -
Total particnlate matter, tons per day ^ -
Tons per day -
Typo of catalytic cracking
unit
Fluid
6
156,000
35,000
14,000
484,000
98-1213
17
308-2190
41
2.3
67-675
4.2
3-130
1.5
8-394
4.9
0.19-0.94
0.01
4.8
0-7.8
1,070
Thennofor
9
69,000
38,000
1,400
134,000
87-1655
3
65-141
2
0.4
29-103
0.2
9-177
0.4
7-62
0.3
0.07-0.7
0.002
0.6
0-4.1
130
Total all units
15
225,000
73,000
15,400
618,000
87-1655
20
65-2190
43
2.7
29-675
4.4
3-177
1.9
7-394
5.2
0.07-0.94
0.012
«.•!
Oi-7.3
1,200
-------
Atmospheric Emissions from Oil Refineries
21
Tests made on pipeline flanges indicated negligible emissions from
this source.
Pressure Relief Valves
The pressure relief valves commonly used by oil refineries are spring
loaded and fitted with a discharge pipe called a "horn" (fig. 7).
Horns are often manifolded to a common header or a blowdown sys-
tem; occasionally they are fitted with steam purge lines for fire control
or to aid the dispersion of gases.
Corrosion may cause pressure relief valves to reseat improperly
after blowoff. Since routine maintenance and observation are some-
times difficult because of inaccessibility, relief valve installations can
leak substantially before repair. The Joint Project study considered
only valve leakage; emissions due to pressure relief valve blowoffs
were not considered.
FIGURE 7. Typical pressure relief installation showing three tingle-type relief
valves
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22 Atmospheric Emissions from Petroleum Refineries
Over 400 pressure relief valves were tested. These had average
emissions of 2.9 pounds per day for valves on operational vessels, and
0.6 pound per day for valves on pressure storage tanks. The total
emission was 3,500 pounds per day from almost 1,500 valves. An addi-
tional 1,800 relief valves were manifolded to vapor recovery or blow-
down systems and had no emission to the atmosphere. The leakage
from valves on liquid lines was negligible.
Pumps and Compressors
Pumps and compressors can leak product at the contact between
the moving shaft and stationary casing. Packing and mechanical
seals are almost universally used in oil refineries to retard leakage
through this junction. Packing or packed seals retard leakage by forc-
ing asbestos or other fibers around the shaft, and can be used to seal
both rotary and reciprocating shaft motions. Mechanical seals have
two plates set perpendicular to the shaft, one stationary and connected
to the pump casing, and a second connected to the shaft and rotating
with it. These plates, or rings, are forced together and effect the
closure. In normal service both packed and mechanical seals can leak
product when shafts become scarred or move eccentrically, or when
the packing or seal faces become defective.
Emissions from pump seals in the Los Angeles area refineries totaled
about 6 tons of hydrocarbons per day, with average hydrocarbon losses
for various types of seals and pumps as follows:
Centrifugal pumps—packed seals—4.8 pounds per day per seal
Centrifugal pumps—mechanical seals—3.2 pounds per day per
seal
Reciprocating pumps—packed seals—5.4 pounds per day per seal
All pump seals—4.2 pounds per day per seal
Tests on over 300 compressor seals indicated a total loss from this
source of 1.5 tons per day, and an average daily hydrocarbon emission
of 8.5 pounds per compressor seal.
Compressor Engines
Gas compressors are often driven by internal combustion engines,
usually fueled by natural or refinery gas. Although these engines are
normally operated at steady load conditions and have good efficiency,
as in all engines of this type, some of the fuel passes through the
engine and out the exhaust unburned. In addition, as a result of
nitrogen fixation in the combustion cylinder, oxides of nitrogen are
found in the exhaust gases. Other emissions such as aldehydes may
also be present.
Refineries in Los Angeles County use 130 internal combustion com-
pressor engines which burn daily 10,500,000 c.f. of fuel gas. These
have a total daily exhaust rate of 165,000 cubic feet per minute (60° F.
and 1 atmosphere pressure), including 6.5 tons of hydrocarbons
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Atmospheric Emissions from Oil Refineries
23
(mostly methane) and 4.f> tons of nitrogen oxides. Average emissions
per 1,000 cubic feet of fuel gas were 1.2 pounds of hydrocarbons and
0.8 pound of nitrogen oxides. Some minor emissions of ammonia
and aldehydes were reported, hut the data were inconclusive.
Cooling Towers
Petroleum refineries use large quantities of water for cooling.
Before, the water ran l>e reused, the heat absorbed in passing through
process heat exchangers mnst be removed. This cooling is usually
accomplished by allowing the water to cascade, through a series of
decks and slat-type grids in a cooling tower (fig. 8). Evaporation
occurs in passing through the tower, removing sensible heat from the
water.
FIGURE 8. Cooling tower
Water which enters the tower may contain hydrocarbons from
leaking heat exchangers, either dissolved or as discrete entrained
globules. These hydrocarbons may escape to the atmosphere as the
water passes through the cooling tower.
Oil refineries in Los Angeles County reported a total of 93 cooling
towers having a combined capacity of 700,000 gallons of water per
minute. The circulation rates of individual towers varied from 200
to 40,000 gallons per minute. Seventeen towers were emitting hydro-
carbons totaling 3 tons per day. Individual towers emitted from 3
to 1,500 pounds per day. Emissions averaged about 9 pounds per
day per 1,000 gallons per minute of water circulated.
Loading Facilities
When vessels used for the transfer of petroleum products are filled,
a volume of gas is displaced equal to the volume of liquid loaded.
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24 Atmospheric Emissions from Petroleum Refineries
The displaced gas contains hydrocarbon vapors remaining from the
previous filling or generated by the evaporation of the product as it
is being loaded into the container.
In Los Angeles County about 90 percent of refinery output leaves
the refineries through pipelines with no emission to the atmosphere.
The remaining 10 percent is loaded at the refineries into tank trucks,
tank cars, and containers, such as drums or barrels. Vapor recovery
systems are required in Los Angeles County when loading volatile
petroleum products (Reid vapor pressure greater than 4 p.s.i.a.).
About 95 percent of the gasoline loaded is handled by these systems
with essentially no emission to the atmosphere.
Daily emissions were calculated as 0.9 ton of hydrocarbons under
the present system of controls.
Waste Water Separators and Process Drains
Some equipment and a number of operations in oil refineries may
allow hydrocarbons to reach the drains and eventually the waste water
separators. These include blind changing, sampling, turnarounds,
leaks in process equipment, and spills. In addition, much of the
water reaching the drains has been used for processing, cooling pump
seals, or flushing purposes, and may already be contaminated. As the
hydrocarbon-water mixture flows through the drainage system and
waste water treatment plant, hydrocarbons evaporate from the sur-
face and may escape to the atmosphere.
All major or primary oil-water separator boxes in refineries in Los
Angeles County are covered or under vapor recovery. These units,
28 in number, process about 760,000 barrels of waste water daily, and
recover about 3,300 barrels of slop oil a day. In addition to these
main separators, final oil removal is accomplished in 68 uncovered
ponds and secondary separators.
Present emissions from process drains and waste water separators
were estimated at 3 tons of hydrocarbons per day.
Slowdown Systems, Including Turnarounds, Equipment Main-
tenance, and Flares
One of the essentials of refinery operation is the periodic mainte-
nance and repair of equipment. This includes shutting down and
starting up process units, usually called turnarounds, and the inspec-
tion, maintenance, and repair of storage tanks. Table 5 taken from
Nelson (8) shows some average shutdown times for various process
units.
Hydrocarbons purged during shutdowns and startups are often
manifolded to blowdown systems for recovery, flaring, or, at minimum,
safe venting to the atmosphere. Refineries in Los Angeles County
reported a total of 382 process shutdowns in one year; 169 of these
were accomplished with essentially no emission of hydrocarbon to the
-------
Atmospheric Emissions from Oil Refineries
TABLE 5. Turnaround -frequencies
25
Units
Crude and vacuum. .
Thermal cracking
Catalytic polymerization and reforming
Catalytic crocking .
Alkylation
Solvent extraction
Months of operation
Average
9.7
4.3
9.4
11.6
13.3
12.9
Range
8. 2-13. 8
3.3- 5.3
7. 8-14. 0
9. 4-13. 6
9. 3-16. 3
10. 3-15. 6
Average
stream
time
efficiency,
percent
96
92
95
94
95
94
atmosphere. The others, venting to the atmosphere or to less efficient
blowdown systems, emitted varying amounts totaling about 250 tons
per year, a daily average of 0.7 ton.
Storage tanks must be drained periodically for inspection and main-
tenance. After draining, the tanks contain hydrocarbon vapors which
must be purged before workmen can enter. Emissions from this
source were calculated and totaled 500 tons per year, a daily average
of 1.3 tons of hydrocarbons.
All flares in refineries in Los Angeles County are the smokeless type,
utilizing either steam injection or air injection (fig. 9). Sufficient
information was available to determine that essentially complete
combustion occurs in flares of this type, and emissions of hydrocarbon
and smoke are negligible. No estimate was made of emissions of
sulfur oxides, nitrogen oxides, and other possible combustion effluents.
Present emissions of hydrocarbons from blowdown systems are very
minor in refineries in Los Angeles County.
Pipeline Blind Changing
In ordinary refinery operations a single pipeline connected through
a manifold to a number of feeder lines may be used to carry several
different products. To avoid the possibility of contaminating one
product with another, it is customary to "blind off" the unused feeder
lines. This is usually accomplished by loosening a flanged pipe
connection, inserting a flat plate between the flanges and retightening
the connection. This operation spills some of the product in the
pipeline, and depending on product volatility, temperature, drainage
and flushing facilities, evaporation occurs. Several devices have been
developed to reduce spillage, including Hamer and Greenwood blinds
(fig. 10). With highly volatile products, water or air is often forced
into the pipeline to displace the product, precluding any product
spillage during the change.
A 2-month record was kept of blind changing activities in re-
fineries in Los Angeles County, including information on product
volatility, amount spilled, existing drainage and flushing facilities.
-------
26 Atmospheric Emissions from Petroleum Refineries
FIGURE 9. Elevated flare showing tlir effect of steam injection
Top. burning with steam injection
Bottom, the same installation without steam injection
During the fil-dav period, over 'J.500 blinds were changed, about one-
half with no spillage. The other one-half spilled about 11,000 pal-
Ions of product: an estimated 2,000 gallons of this evaporated for
an average daily emission of 0.1 ton of hydrocarbons.
Although never a major source of air pollution, emissions from
blind changing activities have been reduced considerably in refineries
in Los Angeles County by redesign of pipeline manifold systems, use
of quick-change blinds, and stressing the need for immediately flush-
ing the spilled product with water.
Boilers and Process Heaters
Many processes and operations in oil refineries necessitate the use
of high pressure steam, or require feedstock at an elevated tempera-
ture. A wide variety of boilers and process heaters are used to fill
-------
Atmospheric Emission* from Oil Refineries
27
Kioi'RE 10. Main oil tranxfer area nhou'iny manifold* <-i/uipi>rd irith llamrr
blinds in the foreground
these needs. Heaters may he of unique design, although most units
are the. box-type shown in figure 11. or the cylindrical, vertical-type
illustrated in figure 1± Boilers are generally of conventional design.
The fuel may he refinery gas, natural gas, heavy fuel oil, coke, or
combinations depending on economics and operating conditions.
In the Joint Project study, sulfur emissions were calculated from
the sulfur content of the fuels burned. Average emissions of the
other combustion products, as well as the SO3/SO2 ratio were de-
termined by field tests on 14 heaters and 10 boilers. These results
are shown in table 6.
Vacuum Jets
Most refineries operate some process equipment at less than atmos-
pheric pressure. A steam-driven vacuum jet or ejector (fig. 13),
sometimes coupled with a barometric condenser, frequently is used to
produce and maintain a vacuum in refinery process equipment. Light
hydrocarbons which do not condense in the barometric condenser are
discharged with the exhaust steam.
Discharges from vacuum jets in refineries in Los Angeles ( ounty
have been completely controlled by venting exhaust lines to a fume
burner or to fireboxes on boilers and heaters.
-------
28
Atmospheric Emissions from Petroleum Refineries
FIGURE 11. A conventional box-type heater
TABLE 6. Emissions from boilers and process heaters in Los Angeles County
refineries
Emission
Aldrhydes as HCHO
Organic acids, as acetic acid
Particular matter
Sulfur dioxide
Sulfur trioxide --..
Average emissions
Fuel pis,
pounds per
1,000 cu. ft.
0 23
0.0031
0.026
0.014
0.021
Fuel oil.
pounds per
gallon
0.068
0.0006
0.0034
0.011
0.020
Total emis-
sions from
refineries in
Los Angeles
County, tons
per day
46
0.5
5
3.5
5
•72
"2
•Calculated from sulfur content of fuel.
•• Ratio of SOi to total S as SOi averaged 0.03.
Sampling
The operation of process units is constantly checked throughout the
refinery by routine analyses of feedstocks and products. To obtain
representative samples for these analyses, sampling lines must be
purged, resulting in possible hydrocarbon vapor emissions. Emis-
sions from this source have been reduced in refineries in Los Angeles
County by installation of drains and water flushing facilities at sam-
pling points, and by employee educational programs. This source
-------
Atmospheric Emissions from Oil Refineries
29
FIGURE 12. A vertical, cylindrical heater
was not studied by the Joint Project; however, an estimation of emis-
sions from refineries in Los Angeles County is available and indi-
cates an emission of 0.8 ton of hydrocarbon daily from sampling
operations (9).
Air Blowing
In some refineries air is blown through petroleum products for
brightening (removal of turbidity due to moisture), for agitation
during treating operations, and during asphalt processing. The
effluent air may contain hydrocarbon vapors and mists, and malodorous
compounds. Also, air or steam blowing is used to oxidize or strip
spent chemicals or catalysts in various treating operations, with pos-
sible emissions of sulfur oxides, hydrocarbons, odors, and other
materials.
Air blowing is a minor operation used intermittently at three re-
fineries in Los Angeles County.
-------
30 Atmospheric Emissions from Petroleum Refineries
^— STEAM INLET
STEAM INLET
SUCTION
WATER
INLET _
\
DISCHARGE TO
HEATER FIREBOX
-WATER OUTLET
FIGURE 13. Schematic drawing of a two-stage, steam ejection, vacuum jet
Acid Treating
The operation of acid treating units, including acid concentrators
and the disposal of acid sludge, may include sources of sulfur oxide
emissions as well as of small amounts of hydrocarbons. The amount
of sulfur oxides released will vary widely depending on the amount
of acid used, products treated, and methods of acid concentration and
acid sludge disposal. Emissions from these sources have been essen-
tially eliminated in refineries in Los Angeles County, and were not
studied by the Joint Project.
Control of Emissions From Oil Refineries
Although this manual is a survey manual and not primarily directed
toward the problem of control, a general discussion of this aspect of
refinery emissions is desirable. Control can be accomplished by three
methods: process changes, installation of control equipment, and im-
proved housekeeping, usually involving employee education and bet-
ter maintenance. Combinations of these methods often prove the
most practical solution to an air pollution problem. A list of possible
-------
Atmospheric Emissions from Oil Refineries 31
control techniques for most sources in oil refineries is presented in
appendix II.
Process Changes
Some sources of atmospheric emissions can best be controlled by
changing refining methods or altering the operation of the refining
equipment. Typical examples of process changes which eliminate or
reduce emissions include improved procedure for equipment shut-
downs and startups, piping changes to eliminate blinds, substitution
of catalytic hydrogen treating for chemical treating, use of harder
catalysts to reduce attrition losses, and product shipping by pipeline
rather than by tank truck or tank car. Some of these process changes
are an integral part of normal refinery modernization and improve-
ment ; others may become economically feasible when compared with
the cost of installing air pollution control equipment.
Control Equipment
Common methods of reducing air pollution include installation of
equipment to remove contaminants from emissions and facilities to
decrease the volume of emissions. Control equipment in refineries
may include floating roofs for storage tanks, covers for waste water
separators, high-efficiency dust removal equipment on catalytic crack-
ing units, waste heat boilers on catalyst regenerators, smokeless flares,
vapor recovery systems, and sulfur recovery plants.
Improved Housekeeping
Improved housekeeping, including maintenance and employee edu-
cation, is often a very practical method for alleviating odor problems
and reducing hydrocarbon emissions. It is often the only practical
control method for some sources, such as pipeline valves, pump seals,
and sampling operations. For nearly all sources, especially process
drains, waste water separators, treating units, blind changing, and
loading operations, employee awareness of the air pollution problem
will reduce emissions.
Economics of Control
The economics of air pollution control can be determined only for
individual refineries and for specific sources within the refinery.
The cost of control is a function of the accumulated capital investment
for equipment, amortization time, and interest rates. It is also a
function of maintenance and other operating expenses. However,
the amount of money spent is a very poor measure of accomplishment
in air pollution control. Frequently, oil refineries have been required
to spend large sums to meet arbitrary limits in regulations which are
not based on sound technical data giving reasonable assurance of
benefits commensurate with costs. In some cases, control equipment
has a "payout," but in more cases, especially control of odor and par-
-------
32 Atmospheric Emissions from Petroleum Refineries
ticulate emissions, the dollars spent are never fully returned (10). Air
pollution control activities may improve plant safety, employee morale,
and community relations.
A plant which was well designed when built may not require addi-
tional capital expenditures for emission control for many years. On
the other hand, in a less carefully built plant or in one where new
processes have been added, it may be necessary to spend large sums
to achieve comparable control.
Estimation of Atmospheric Emissions
From Oil Refineries
Many factors must be considered before an attempt is made to
apply the results of the Los Angeles refinery studies to other refineries.
The types of crude run and the processes used must be considered.
The status of control efforts in the refinery in question must be ap-
praised. Comparisons of emissions from one refinery with emissions
from another on the basis of refining capacity or fuel consumption
can be grossly misleading. When an estimate of emissions is required,
judgment must be used in evaluating the foregoing factors.
The most reliable estimate of emissions from oil refineries should
be based on on-site test results, particularly for sources with highly
variable emission rates such as evaporation from tankage, catalytic
cracking regenerators, air blowing, blowdown systems, and vacuum
jets. However, for many sources, field testing programs are compli-
cated, time-consuming, and expensive, and may not be practical for
estimation of gross emissions. In such cases, average on-site test data
obtained from other refinery studies may be used to prepare a rough
estimate of emissions. The estimates so obtained may have large
inherent errors, and should not be used as the sole basis for conclusions
or recommendations relating to regulations. Nor should the estimates
be used as a basis for requiring installation of control facilities.
Emission factors calculated from the Los Angeles survey are re-
ported herein. Where a range of values is presented, the low value
represents a figure derived from recent surveys of Los Angeles plants.
The high values are rough estimates of the emissions in the Los Angeles
area before the extensive control programs were inaugurated. It
should be recognized that in most instances these high values are only
educated guesses with limited measurements to substantiate the
figures.
The data from the Los Angeles survey were used to calculate two
factors for some sources of emissions: one based on the easily obtained
refinery capacity data, and a second based on the number of units
such as valves or pump seals in the refinery.
-------
Estimation of Atmospheric Emissions 33
Refinery air pollution surveys may be necessary for a number of
purposes, and the survey method should be consistent with the in-
tended use of the estimated figures. It would be wasteful to make
extensive calculations and perhaps run field tests when only a rough
estimate of emissions is required, and rash to expect an accurate, reli-
able result from a few simple calculations based on refinery capacity.
This section presents two methods for approximating emissions from
oil refineries: a very rough estimate of gross hydrocarbon emissions
based essentially on refinery capacity, and an approximation involving
calculations based on detailed refinery information and the Los An-
geles refinery experience for specific emission sources. These are two
examples of possible uses of Joint Project data. The best type of
refinery survey must be determined for each case, depending on the
time and refinery information available, and the expected use of the
survey.
First Estimate of Gross Hydrocarbon Emissions
A very rough estimate of total hydrocarbon emissions may be made
using information concerning refinery capacity, including vacuum
distillation and catalytic cracking capacities, and some knowledge of
the status of the control program in effect. Table 1 gives refinery
capacities and the capacities of various processes summarized by
States. Similar information for every refinery in the United States
and Canada is available in the literature (4). The status of emission
control must be evaluated individually for each refinery or area being
surveyed. Generally, initial control efforts are directed against SO2,
smoke, dust, and other more noticeable forms of air pollution. The
magnitude of programs to control emissions is usually dictated by
refinery location, proximity of urban areas, and geographical and
meteorological conditions.
Hydrocarbon emissions from petroleum refineries may range from
0.1 to 0.6 percent by weight of the crude throughput. The lower value
is applicable to refineries practicing extensive hydrocarbon control
activities, and may seldom be found outside Los Angeles County. The
higher value may be found at refineries where stringent control of
hydrocarbon emissions is not practiced. Both values refer to refineries
with nearly complete processing schemes. Smaller refineries practic-
ing only crude topping, treating, and blending will tend toward the
lower values.
Table 7 shows factors proposed for making a gross estimate of
hydrocarbon emissions. Ranges of values have been given for those
sources from which emissions may vary greatly. The values and
ranges shown are based on the best data available from refineries
in Los Angeles County before inauguration of hydrocarbon control
programs and after application of these programs. The preceding
-------
34 Atmospheric Emissions from Petroleum Refineries
section of this manual details the control measures used by the Los
Angeles refineries to achieve these lower values.
The following example illustrates the use of table 7 for estimating
gross hydrocarbon emissions. Assume a 20,000 barrel per day re-
finery, with vacuum distillation and catalytic cracking units of 6,000
barrels per day capacity each. Further assume that control efforts
have been directed toward storage and blowdown systems, and assign
midrange factors to these sources. The higher factors should probably
be used for separators and vacuum jets since controls on the sources
may not have been applied. Table 8 illustrates the calculation of
hydrocarbon emissions for this hypothetical case.
TABLE 7. Hydrocarbon emission values, Los Angeles survey
Source
Storage tanks - -
Blowdown systems
Waste water separators
Leakage (valves, pumps, etc.)
Others Goading, cooling towers,
boilers, blind changing, etc.)
Catalytic cracking unit regenerators
Vacuum jets
Emission factors
Units
Pounds per 1 ,000 barrels refinery capacity
Pounds per 1 ,000 barrels refinery capacity
Pounds per 1,000 barrels refinery capacity
Pounds per 1,000 barrels fresh feed rate
Value
60
160
170
Possible
ranee of
values*
100-1,000
5- 350
10- 200
0-130
•Range indicates average emissions for refineries in Los Angeles County before inauguration of special
air pollution control programs, and at present, with extensive controls.
TABIE 8. Sample calculation of hydrocarbon emissions—first estimate
Source
Storage.. . -
Blowdown system
Waste water separator
Leakage .. .
Other
Catalytic cracker
Vflomim distillation , - -
Total loss
Refinery or
process
capacity,
1,000 barrels/
day
20
20
20
20
20
8
6
Emission
factor,
pounds
per 1,000
barrel
capacity
500
200
260
60
160
170
130
Emissions
pounds/day
10,000
4,000
5,000
1,200
3,000
1,000
800
25,000
This is about 12 tons daily, amounting to
12X2,000
20,000X300
X100=0.4
percent of crude throughput.
Detailed Survey of Atmospheric Emissions From Oil Refineries
The procedure outlined below makes full use of average emission
data, and will allow an estimate of emissions from nearly every signifi-
-------
Estimation of Atmospheric Emissions
35
cant source in oil refineries. This method requires the cooperation
of the refinery or refineries being surveyed. Detailed information
must be obtained on process capacities, fuel requirements, production
figures, and result of sulfur analyses.
The indicated emission factors for various sources should not be
considered absolute values, but, where possible, should be used in
conjunction with refinery inspections and available refinery emission
data. This manual includes much information on the control measures
and refinery process schemes incorporated into the emission factors.
This information should be compared with the refinery being sur-
veyed for a realistic interpretation of the emission factors presented
here.
Emissions of Sulfur Oxides
Emissions of sulfur oxides are a function of the sulfur content of
the crude oil being processed, and do not lend themselves to estimates
based on average values for other refineries. However, a knowledge
of the distribution of sulfur throughout the plant is important to
the refiner to attain maximum process efficiency and product quality,
and, if available, these data can be used to make a gross sulfur balance
for the refinery.
Sulfur enters the refinery in the crude oil, in purchased fuel oil or
gas, and as sulfuric acid used in various processes. Most of this sulfur
routinely leaves the refinery in the various products, as spent sulfuric
acid shipped out for regeneration, as sulfides or sulfates in the liquid
wastes, or is recovered in sulfur recovery plants. The difference will
be emitted to the atmosphere mainly as sulfur dioxide, although some
SO3 and H2S may be released.
Miscellaneous Combustion Emissions
Along with the SO2 and hydrocarbons, oil refineries emit carbon
monoxide, nitrogen oxides, aldehydes, organic acids, ammonia, and
particulate matter. These are discharged from combustion sources,
including catalyst regeneration units, boilers and process heaters, and
compressor internal combustion engines. Tables 9 and 10 give factors
for combustion emissions, excepting sulfur oxides and hydrocarbons,
based primarily upon the Los Angeles refinery studies.
TABLE 9. Factors for particulate emissions
Source
Units of factor
Value
Boilers and process heaters.
Fluid catalytic units:
With electric precipitation
Without electric precipitation
Moving-bed catalyst units, high efficiency cen-
trifugal separators.
Pounds per 1,000 cu. ft. of fuel gas burned.
Pounds per barrel of fuel oil burned
Percent of catalyst circulated..
Percent of catalyst circulated..
Percent of catalyst circulated..
0.02
.8
.0009
.005
.002
-------
36 Atmospheric Emissions from Petroleum Refineries
Hydrocarbon Emissions
Calculated Emissions From Storage Tanks and Loading Operations
Hydrocarbon emissions from storage tanks and product loading
operations can be calculated directly. These emissions accounted for
about one-half the total hydrocarbon emissions from the Los Angeles
refineries during the survey.
TABLE 10. Factors for emissions of nitrogen oarides, carbon monoxides, aldehydes,
and ammonia from oil refineries
Source
Boilers and process heaters
Compressor internal combus-
tion engines.
Fluid-bed catalytic cracking
units.
Moving-bed catalytic cracking
units.
Units of factor
[Founds per 1,000 cu. ft. of fuel
1 gas burned.
1 Pounds per barrel of fuel oil
1 burned.
Pounds per 1,000 cu. ft. of fuel
gas burned.
Pounds per 1.000 barrels of
fresh feed.
Pounds per 1,000 barrels of
fresh feed.
Value of factor for various emissions
NO, as
NOj
0.23
2.9
.86
63
5.0
CO
Neg.
Neg.
Neg.
13,700
3,800
Aldehydes
asHCHO
0.0031
.025
.11
19
12
Ammonia
asNH,
Nee.
Neg.
0.2
54
5.0
A method of calculating emissions from fixed roof and floating roof
storage tanks is presented in appendix I, along with a typical calcula-
tion sheet. This method is presented in greater detail, including
nomographs to simplify calculations, in publications of the American
Petroleum Institute (7), and the Los Angeles County Air Pollution
Control District (11). This method of calculation is now in process
of modification. Reference should be made to API Bulletins 2512,
2513, and others planned for future release. Pressure storage tanks
and storage tanks connected to vapor recovery systems, if operated
correctly, will have negligible losses.
Losses from product loading into tank cars and tank trucks can be
calculated using the following formula:
F=0.063 PV
where
F=weight of hydrocarbon vapors vented, pounds.
P=partial pressure at 60° F. of the hydrocarbon vapors in the air-
vapor mixture (usually .considered to be the true vapor pres-
sure of the liquid remaining in the vessel before filling),
pounds per square inch absolute.
V=volume of product loaded, barrels.
The derivation of this formula is based on the following assumptions:
1. The hydrocarbon vapors vented occupy 6 cubic feet per pound.
-------
Estimation of Atmospheric Emissions
37
2. The volume of gases vented is equal to the volume of liquid
loaded.
3. The displaced gases are saturated with hydrocarbon vapors.
4. The hydrocarbon vapor-air mixture conforms to Dalton's law
of partial pressures.
Hydrocarbon Emissions From Combustion Sources
In most refineries combustion operations are not a major source of
hydrocarbon emissions. Table 11 presents average factors for com-
bustion sources.
TABLE 11. Factors for hydrocarbon emissions from combustion sources
Source
Units of factor
Value
Boilers and process beaters.
Fluid catalytic cracking units.
Moving-bed catalytic cracking units
Compressor internal combustion engines.
[Pounds per 1,000 cubic feet of fuel gas
{ burned.
[Pounds per barrel of fuel oil burned
Pounds per 1,000 barrels fresh feed
Pounds per 1,000 barrels fresh feed
Pounds per 1,000 cubic feet of fuel gas
burned.
0.026
.14
220
87
1.2
Hydrocarbon Emissions From Equipment Leaks
Four types of equipment—pumps, compressors, pipeline valves, and
pressure relief valves—may leak hydrocarbons to the atmosphere.
Factors for these sources should be given as the average for a particular
type of equipment in a specific service, such as mechanical pump seals
handling L.P.G., or pressure relief valves on storage tanks. However,
detailed information on the number and distribution of this equip-
ment is seldom available, so two factors for each source are presented
in table 12. One is based on the number of units, and a second factor
is based on the easily obtained refinery capacity. While both factors
are subject to error, the second factor is less reliable.
Emissions from these leak sources are strongly affected by the degree
of maintenance in the refinery. The factors presented for average
TABLE 12. Factors for hydrocarbon emissions from equipment leakage
Source
Pipeline valves
Vessel relief valves
Pipeline relief valves
Compressor seals
Pipeline valves -
Vessel relief valves
Pump seals
Compressor seals . . -
Units of factor.
Pounds per day per valve
Pounds per day per valve
Pounds per day per seal ..
Pounds per day per seal
Pounds per 1,00ft barrels refinery capacity.
Pounds per 1,000 barrels refinery capacity-
Pounds per 1,000 barrels refinery capacity.
Pounds per 1,000 barrels refinery capacity.
Value
0.15
2.4
Neg.
4.2
8.6
28
11
17
5
-------
38 Atmospheric Emissions from Petroleum Refineries
unit emissions reflect the high degree of maintenance demanded of
refineries in Los Angeles County. The factors based on refinery
capacity are for complete refineries with extensive processing equip-
ment. It has been assumed that maintenance is the only control
activity used on these leak sources. In practice, some refineries may
vent some of their pressure relief valves and compressor seals to
blowdown systems, and the factors based on refinery capacity should
be reduced in these cases.
Hydrocarbon Emissions From Other Process Equipment
Emissions from many sources in oil refineries are strongly affected
by existing control programs, and make the use of average data from
Los Angeles County refineries precarious. A few of these may be
major sources of hydrocarbon emissions, and an estimate of the effec-
tiveness of existing control measures is necessary before an average
factor can be selected. The range of factors for these sources is
derived from the survey of emissions from refineries in Los Angeles
County. The lowest values assume the use of the control techniques
described in previous sections, whereas the higher value is based
on rough estimates of the emissions that may have occurred from the
same refineries before the extensive control programs were initiated.
Factors for emissions from process equipment are shown in table
13. The "other" source includes air blowing, blind changing, and
sampling.
TABIJE 13. Factors for hydrocarbon emissions from miscellaneous process
equipment
Source
Blowdown systems
Process drains and waste water
separators.
Vacuum jets
Cooling towers
Other
Units of factor
Pounds per 1 000 barrels refining capacity
Pounds per 1,000 barrels waste water processed
capacity.
toted.
Value
6
10
Range of
values
5-300
8-210
0-130
In concluding it should be emphasized that the methods for esti-
mating emissions presented in this manual are not a substitute for
actual testing work. Because of differing maintenance, process meth-
ods, crude sources, control measures, and other factors, the use of
average data can give only a very rough indication of the magnitude
of emissions. When a reliable estimate is needed, survey work must
be carried out. The procedures suggested in this manual will be
of greatest value when used in conjunction with available refinery
test data and actual surveys on the most significant sources of
emissions.
-------
References
1. A Symposium, "Chemistry of Pollutants in the Atmosphere," In-
dustrial and Engineering Chemistry, vol. 48, pp. 1484-1527 (Sep-
tember 1956).
2. Joint District, Federal and State Project for the Evaluation of
Eefinery Emissions, Los Angeles County Air Pollution Control
District, 434 South San Pedro Street, Los Angeles 13, Calif. Nine
reports (see Foreword, p. vii, for titles).
3. Process Handbook—1958, Petroleum Refiner, vol. 37, No. 9, pp.
209-315 (September 1958).
4. Anon., "Journal Survey of Refineries in United States," Oil and
Gas Journal, vol. 56, No. 12 (March 24,1958).
5. Anon., "Refining Forecasts," Petroleum Refiner, vol. 35, No. 2,
page 152 (February 1956).
6. Kay, Herbert, "What Hydrogen Treating Can Do," Petroleum
Refiner, vol. 35, No. 9, pp. 306-318 (September 1956).
7. "Evaporation Loss of Petroleum From Storage Tanks," 32d An-
nual Meeting, American Petroleum Institute (November 1952).
8. Nelson, W. L., Petroleum Refinery Engineering,, McGraw-Hill
Book Co., New York, N. Y. (1958).
9. Gofer, R. C., "Emission of Hydrocarbons from Refineries and
Petroleum Distribution Facilities in Los Angeles County," Los
Angeles County Air Pollution Control District, Los Angeles,
Calif. (May 1958).
10. Stormont, D., "Air Pollution Control," Oil and Gas Journal, vol.
56, No. 7 (February 17,1958).
11. Lunche, R. G., and Deckert, I. S., "Hydrocarbon Losses from
Petroleum Storage Tanks," Air Pollution Engineering Report,
Los Angeles County Air Pollution Control District, Los Angeles,
Calif. (December 1956).
39
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Appendices
I—Method for Calculating Hydrocarbon Vapor Losses From Stor-
age Tanks.
II—Control Methods.
Ill—Glossary of Terms Used in Petroleum Refining.
Appendix I
Method for Calculating Hydrocarbon Vapor Losses From
Storage Tanks
Many methods for calculating hydrocarbon losses from storage
tanks have been developed by various groups from experimental
studies. The method described below was used by the Joint Project
and is presented in greater detail in the literature (7) (11), including
nomographs to simplify calculations.
The equations used for making the calculations are as follows:
1. Breathing Losses From Fixed Roof Tanks
PD1-8
B= ^g-FoFp
2. Filling Losses From Fixed Roof Tanks
™ 3PV „
3. Evaporation Losses From Floating Roof Tanks
E=CPD
4. Filling Losses From Floating Roof Tanks
F_ V
" 10,000
Where:
B=breathing loss from a fixed roof tank, in barrels per year.
F=filling loss from a fixed roof tank, in barrels per year.
E=evaporation loss from a floating roof tank, in barrels per year.
Fe=filling loss from a floating roof tank, in barrels per year.
P =true vapor pressure at the average liquid body temperature,
in pounds per square inch absolute.
41
-------
42 Atmospheric Emissions from Petroleum Refineries
D =tank diameter, in feet.
V = volume of liquid product added to the tank, in barrels per
year (in the case where product is being withdrawn simul-
taneously with product addition, V is the excess of addition
over withdrawal).
F0=outage factor for fixed roof tanks.
Fp=paint factor for fixed roof tanks.
Kf=throughput factor.
C = floating roof factor for type of shell construction, seal, and
roof.
Values to be used for the outage, paint, throughput, and floating
roof factors are:
1. Outage Factor, F0
Where H=outage, or height between top angle of the tank and
the liquid surface, in feet.
A table of outages versus outage factors prepared from the equation
is as follows:
H F0
1 0.39
5 0.55
10 0.72
15 0.87
20 1.00
25 1.12
30 1.23
35 1.33
40 1.43
45 1.53
50 1.62
Some adjustments may have to be made to the outage value used if
the volume under the tank roof is much different from the volume
under a conical roof with a pitch of % inch per foot. A larger volume
will call for a higher outage, and a lower volume a lower outage.
2. Paint Factor, FP
Paint Fp
Chalking white 0. 75
Aluminum 1. 00
Light gray — - 1. 10
Black, no paint, or needs repainting 1. 25
-------
Appendix I
3. Throughput Factor, Kf
43
Tank turnovers
per year
0-10
12
15
20
25
30
40
40-60
60-100
Kifor
general
refinery
service
1 00
91
75
59
50
.47
44
Kifor
marketing
plants ana
terminals
1 00
1 00
1 00
1.00
1 00
1.00
1 00
.80
.50
4. Floating Roof Factor, C
Shell construction
Welded
Riveted
Riveted
Seal
Single or double
Double
Single
C
n
-------
44 Atmospheric Emissions from Petroleum Refineries
Calculation Sheet—Emissions From Fixed Roof and Floating
Roof Tanks*
Table of data and assumptions
1. Product 9. Throughput, (V) bbls/yr.
2. Reid Vap. Press Ibs. 10. Turnovers per year
3. Avg. Stge. Temp °F 11. Throughput Factor,
4. True Vap. Press., (Kf)
(P) p.s.i.a. 12. Type F.R. Seal
5. Tank Diam., (D) ft. 13. Shell Construction
6. Avg. Outage ft. 14. F.R. Evap. Factor,
7. Outage Factor, (C)
(F0) 15. Density of Con-
8. Paint Factor, (Fp) densed Vapors
(W)-_- Ibs/bbl.
I. LOSSES FROM FIXED ROOF TANKS
1. BREATHING LOSS: B
or from Nomograph: B= --
yr
W
2. FILLING LOSS: F- X, X-
or from Nomograph: F= -- Xo^c=
yr oOo
3. TOTAL FIXED ROOF LOSSES= BREATHING
LOSS + FILLING LOSS = _ Ibs/day
II. LOSSES FROM FLOATING ROOF TANKS
W
1. EVAPORATION LOSS: E=C,P,D,X^-.=
ooo
V W
2. FILLING LOSS: F- X -
3. TOTAL FLOATING ROOF LOSSES= EVAPORA-
TION LOSS+ FILLING LOSS = _ Ibs/day
•Taken from Lunche and Deckert, "Hydrocarbon Losses from Petroleum Storage Tanks," Los Angeles
County Air Pollution Control District (December 1956).
-------
Appendix II
Control Methods
1. Storage—
A. Connect to vapor recovery systems.
B. Floating roofs.
C. Pressure tanks.
D. Connect to gas holder (vapor balance).
2. Catalyst regenerators—
A. High-efficiency separators on flue gas stack.
B. Maintain slight vacuum on catalyst elevators and vent
exhaust to separators.
C. Vent exhaust from airlift catalyst systems to separators.
D. Waste heat boiler to burn CO and hydrocarbons.
3. Pipeline valves—
A. Inspection and maintenance.
4. Pressure relief valves—
A. Manifold to vapor recovery system or flares.
B. Rupture discs in addition to relief valves.
C. Dual valves with shut-offs.
D. Inspection and maintenance.
5. Pump and compressor seals—
A. Mechanical seals on pumps in difficult service.
B. Sealing glands with oil under pressure.
C. Venting glands to vapor recovery system.
D. Inspection and maintenance.
6. Loading facilities—
A. Vapor collection equipment.
B. Careful operation to decrease spillage.
C. Subsurface loading arms.
7. Drains and waste water separators—
A. Enclosing initial separator boxes.
B. Cover sewer junction boxes.
C. Good housekeeping to reduce spillage to sewer.
D. Liquid seals in drains.
8. Slowdown systems—
A. Smokeless flares.
B. Vapor recovery systems, usually a gas holder, gas com-
pressor, and discharge to refinery fuel gas system or ab-
sorber unit.
45
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46 Atmospheric Emissions from Petroleum Refineries
9. Turnarounds—
A. Depressurizing and purging to vapor recovery prior to
opening vessels.
B. Depressurizing and water displacement to vapor recovery
prior to" opening vessels.
10. Boilers and process heaters—
A. Electronic smoke indicators.
B. Maintain proper operating conditions.
C. Use of gaseous fuel where possible in place of fuel oil.
D. Removal of hydrogen sulfide and mercaptans from fuel
gas.
11. Vacuum jets—
A. Venting to a boiler or heater firebox.
12. Acid treating—
A. Convert batch-type agitators, which use air blowing, to
continuous treating with mechanical mixing.
B. Replace hydrolysis-concentration method of acid recovery
with acid regeneration technique.
C. Replace acid sludge combustion with methods involving
dumping or chemical destruction.
D. Vent gases generated by acid sludge storage and shipping
to caustic scrubber to remove SO2 and malodors, and to
firebox to burn hydrocarbons and malodors.
E. Replace acid treating units with catalytic hydrogenation
units.
13. Doctor treating—
A. Steam stripping of spent doctor solution to remove and
recover hydrocarbons prior to air blowing for regeneration.
B. Burning effluent from air blowing.
14. Noxious gases from sour water strippers—
A. Recovery of H2S and ammonia by conversion to salable
products.
B. Oxidize by converting sulfides to thiosulfates.
15. Spent caustic disposal—
A. Venting stripping effluent gases through furnace fireboxes.
16. Mercaptan disposal—
A. Convert to disulfides.
B. Use of mercaptans in organic synthesis.
C. Combustion in furnace fireboxes.
17. Recovery of H2S from sour gases—
A. Collection by liquid absorption, and conversion to sulfur
or sulfuric acid by refinery or others.
18. Fume disposal from air blowing operations—
A. Incineration.
B. Scrubbing.
-------
Appendix III
Glossary of Terms Used in Petroleum Refining1
absorption oil — An oil of high affinity for the light hydrocarbons, but
containing few or none of the light compounds composing gasoline
and natural gas.
absorption plant — A plant for recovering the condensable portion of
natural or plant gas, by absorbing these heavier hydrocarbons in an
absorption oil (often under pressure), followed by separation and
f ractionation of the absorbed material.
accumulator — A vessel for the temporary storage of a gas or liquid ;
usually used for collecting sufficient material for a continuous charge
to some refining process.
acid sludge — The residue left after treating petroleum oil with sul-
furic acid for the removal of impurities. It is a black, viscous
substance containing the spent acid and the impurities which the
acid has separated from the oil.
acid treatment — An oil-refining process in which unfinished petroleum
products, such as gasoline, kerosine, diesel fuel, and lubricating
stocks, are contacted with sulfuric acid to improve color, odor, and
other properties.
alicyclic hydrocarbons — Hydrocarbons which contain a ring of carbon
atoms but do not belong to the aromatic series.
aliphatic hydrocarbons — Hydrocarbons of open-chain structure such
as ethane, butane, octane, butene, acetylene.
alkylation — Formation of complex saturated molecules by direct union
of a saturated and an unsaturated molecule.
API — American Petroleum Institute.
API gravity — An arbitrary scale expressing the gravity or density of
liquid petroleum products. The measuring scale is calibrated in
terms of "API" degrees. It may be calculated in terms of the fol-
lowing formula :
degAPI= - nvT*- 131.5
6 sp gr 60/60 F
aromatic compounds — Those derived from benzene with one or more
benzene rings of carbon atoms as distinct from those of aliphatic or
alicyclic character.
i Taken from API Manual "Glossary of Terms Used In Petroleum Refining," 1953.
47
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48 Atmospheric Emissions from Petroleum Refineries
aspirator—An apparatus which serves to create a partial vacuum
through pumping a jet of water, steam, or some other fluid or gas
past an orifice opening out of the chamber in which the vacuum is
to be produced.
B
barometric condenser—A device which, by condensing steam, produces
a partial vacuum in a piece of refinery equipment, such as a vacuum
pipe still.
barrel—As the standard unit of measurement of liquids in the pe-
troleum industry, it contains 42 U.S. standard gallons.
base stocks2—Any oil fraction which has been refined for use as a
component in a finished product.
batch still—A petroleum still in which the distillation is carried out
in "batches," the entire still charge being introduced before the fires
are lighted, and the distillation being completed without the intro-
duction of an additional charge.
benzene—This is an old term for light petroleum distillates covering
the gasoline and naphtha range.
blended fuel—Fuel oil which is a mixture of two or more types (re-
sidual, distillate, or cracked fuel).
blowdown stack—A stack &et upon a small tank into which the con-
tents of a unit are emptied when an emergency arises. Connections
are usually made so that steam can be injected into the tank to pre-
vent ignition of the material therein. Also water quench is fre-
quently provided to reduce the amount of oil vapors issuing from
the stack.
blowing—Agitating a liquid by the introduction of compressed air
near the bottom of the tank or container. In "blowing bright," the
air assists in carrying off moisture, whereas, in acid treating, the
air is used only for agitation.
bottoms—The liquid which collects in the bottom of a vessel, either
during a fractionating process or while in storage (tower bottoms,
tank bottoms).
breathing—The movement of gas (oil vapors or air) in and out of the
vent lines of storage tanks due to alternate heating and cooling.
bright—The term applied generally to lubricating oils, meaning clear
or free from moisture.
bubble tower or column—A fractionating tower so constructed that the
vapors rising pass up through layers of condensate on a series of
plates.
bulk plant—A bulk plant is a distributing unit for petroleum products
usually having car-load unloading facilities for light oils on rail-
road sidings. It has aboveground storage for one or more car loads
* Not taken from API Manual "Glossary of Terms Used in Petroleum Refining."
-------
Appendix III 49
of light oils and a warehouse with storage for petroleum products
sold in barrels or packages.
bunker "C" fuel oil—A heavy residual fuel oil used by ships, industry,
and for large-scale heating installations.
C
casinghead gasoline—The liquid hydrocarbon product extracted from
natural gas.
charge—A quantity of feed stock for a refinery processing unit.
coke drum—A vessel in which coke is formed and which can be cut
off from the process for cleaning.
coking—The process of distilling a petroleum product to dryness.
The undesirable building up of coke or carbon deposits on refinery
equipment.
combination cracking—A process involving crude distillation, viscosity
breaking, naphtha reforming, and gas-oil cracking, and one which
in the extreme might also involve gas recovery and even coking.
cooker—A lead-lined vat or tank in which acid sludge resulting from
chemical treatment of lubricating oils is subjected to agitation for
recovery of acid. These vats are used also for mixing the acid
sludge from light distillates with water.
cooling tower—A unit or structure, usually built of wood, for the
purpose of cooling water by evaporation.
cracked fuels—Fuels consisting predominantly of cracked residuum
which may or may not be blended with cracked distillate.
cracked gases—The gases resulting from the breaking down or crack-
ing of petroleum oils.
cracking—Cracking is a phenomenon by which large oil molecules are
decomposed into smaller lower-boiling molecules; at the same time
certain of these molecules, which are reactive, combine with one
another to give even larger molecules than those in the original
stock. The more stable molecules leave the system as cracked gaso-
line, but the reactive ones polymerize, forming tar and even coke.
crude still—A piece of refinery equipment designed to permit physical
separation of crude oil by the application of heat.
cuts—Petroleum fractions obtained in the distillation of oil.
cycle stock—Product taken from some later stage of a process and re-
charged to the process at some earlier stage.
cylinder stock—The residuum remaining in a still after the lighter
parts of a crude have been vaporized.
D
dehydrogenation—The removal of hydrogen from a chemical com-
pound.
-------
50 Atmospheric Emissions from Petroleum Refineries
destructive distillation—A process of distillation in which an organic
compound or mixture is heated to a temperature high enough to
cause decomposition.
diolefins—Open-chain hydrocarbons having two double bonds per
molecule. The empirical formula is CnH2n-2. They have been
shown to be particularly conducive to oxidation, gum formation,
and loss of octane rating on storage. They are readily removed
from cracked naphthas by clay or acid treating.
distillate—The product of distillation obtained by condensing the
vapors from a still.
doctor test—A qualitative method of detecting undesirable sulfur
compounds in petroleum distillates, i.e., of determining whether an
oil is "sour" or "sweet."
doctor treatment—Treatment of gasoline with sodium-plumbite solu-
tion and sulfur to improve its odor.
dopes for gasolines—Materials added in small amounts to gasoline to
increase the octane number and thus help to prevent knocking.
Tetraethyllead is the most common dope used.
drum, flash—A drum or tower into which the heated outlet products
of a preheater or exchanger system are conducted, often with some
release in pressure. The purpose of the drum is to allow vaporiza-
tion and separation of the volatile portions for fractionation else-
where.
dry gas—A gas which does not contain the heavier fractions which
may easily condense under normal atmospheric conditions. In the
hydrocarbon series, methane and ethane, for example, are dry gases.
E
engine distillate—Refined or unrefined petroleum distillate similar to
naphtha but often of higher distillation range.
evaporator—Usually a vessel which receives the hot discharge from
a heating coil and, by a reduction in pressure, flashes off overhead
the light products and allows the heavy residue to collect in the
bottom.
F
fixed gas—Gas which will not condense under pressure and tempera-
ture conditions available in the process under consideration.
flashing—Effecting a separation of products by releasing the pressure
on a hot oil as it enters a vessel; the lighter fractions vaporize or
"flash" off and heavy oil drops to the bottom.
floating roof—A special tank roof which floats upon the oil.
fractional distillation—The separation of the components of a liquid
mixture by vaporizing and collecting the fractions which condense
in different temperature ranges.
-------
Appendix III 51
furnace oil—A distillate fuel primarily intended for domestic heating
use. No. 1 commercial standard grade is intended for "vaporiz-
ing" burners requiring a volatile fuel, whereas Nos. 2 and 3 com-
mercial standard grades are less volatile, are usable in the ''atomiz-
ing" type of burners and, also, generally are cheaper.
G
gas oil—A liquid petroleum distillate with a viscosity and boiling
range between kerosine and lubricating oil.
gum—In the petroleum industry, the term is descriptive of rosin-like
insoluble deposits formed during the deterioration of petroleum
and its products, particularly gasoline.
H
heart-cut—A narrow-range "cut" usually taken near the middle por-
tion of the stock being distilled or treated.
heavy ends—The highest-boiling portion present.
hydrocarbon—A compound containing only hydrogen and carbon.
The simplest hydrocarbons are gases at ordinary temperatures, but
with increasing molecular weight they change to the liquid form
and finally to the solid state. They form the principal constituents
of petroleum.
hydrogenation—The chemical addition of hydrogen to a material.
I
ibp—Initial boiling point.
innage—Converse of outage; refers either to the volume of liquid
or the measured height of liquid in a tank or container, as meas-
ured from the bottom of the tank.
isomate—Product obtained as a result of isomerizing a straight-run
low-boiling naphtha.
isomerization—Process for altering the fundamental arrangement of
the atoms in the molecule without adding or removing anything
from the original material.
K
knockout drum—A drum or vessel constructed with baffles through
which a mixture of gas and liquid is passed to disengage one from
the other. As the mixture comes-in contact with the baffles, the
impact frees the gases and allows them to pass overhead; the
heavier substance falls to the bottom of the drum.
lead susceptibility—Ability of gasoline to respond to the addition
of tetraethyllead as reflected in the increase in anti-knock quality
per increment of lead added.
-------
52 Atmospheric Emissions from Petroleum Refineries
lean oil—Absorption oil from which natural-gasoline fractions have
been removed. Oil leaving the stripper in a natural-gasoline plant.
light ends—The lower-boiling components of a mixture of hydro-
carbons.
LPG—Industry initials for certain liquefied petroleum gases. These
are hydrocarbon fractions lighter than gasoline, such as butane,
propane, etc., which are kept under pressure in a liquid state and
marketed for various industrial and domestic gas uses.
M
manifold—A piping arrangement which allows one stream of liquid
or gas to be divided into two or more streams, as the manifold of
an automobile engine.
M c.f.—The abbreviation for "thousands of cubic feet."
mercaptans—Organic compounds having the general formula B—
SH, meaning that the thiol group, —SH, is attached to a radical
such as CH3 or C2H5, etc. The simpler mercaptans have strong,
repulsive, garlic-like odors which become less pronounced with in-
creasing molecular weight and higher boiling points.
N
natural gas—Gaseous forms of petroleum, commonly called "natural
gas," consist of mixtures of hydrocarbon gases and vapors, the more
important of which are methane, ethane, propane, butane, pentane,
and hexane, all of .the paraffin series (CnH2n+2).
O
olefins—Open-chain hydrocarbons having one or more double bonds
per molecule; -specifically, hydrocarbons belonging to the mono-
olefin or ethylene series (CnHzn) having one double bond per mole-
cule (as compared with diolefin, triolefin, etc.).
oleum spirits—A petroleum cut, boiling between 300° and 400° F.,
meeting certain other specifications.
onstream time—The length of time a unit is in actual production.
operating efficiency—The percentage of the time during which a unit
is performing its function; e.g., if a unit runs 800 hours (onstream
time), takes 100 hours for reconditioning and inspection, and 100
hours for starting up and shutting down, the operating efficiency
would be 80 percent.
outage—The difference between the full or the rated capacity and
the actual contents of a barrel, tank, or tank car. The vertical
distance between the surface of the liquid in a barrel, tank, or tank
car, and the top of the container.
overhead—In a distilling operation, that portion of the charge which
is vaporized.
-------
Appendix 111 53
P
pipe still—Still in which heat is applied to the oil while being
pumped through a coil or pipe arranged in a suitable firebox. After
leaving the heating zone, the pipe runs to a fractionator where a
portion of oil is taken off overhead as vapor, and the liquid portion
removed continuously.
polymerization—The process of combining two or more molecules to
form a single molecule having the same elements in the same propor-
tions as in the original molecules. Specifically, in the petroleum
industry, the union of light olefins to form hydrocarbons of higher
molecular weight.
pressure distillate—The light, gasoline-bearing distillate product from
the pressure stills which has been produced by cracking, as con-
trasted with virgin or straight-run stock.
pump, reciprocating—A positive-displacement type of pump con-
sisting of a plunger or a piston moving back and forth within a
cylinder. With each stroke of the plunger or piston, a definite
volume of liquid is pushed out through the discharge valves.
R
reboiler—An auxiliary of a fractionating tower designed to supply
additional heat to the lower portion. Liquid is usually withdrawn
(or pumped) from the side or bottom of the tower; is reheated by
means of heat exchange; and the vapors and residual liquid,
separately or together, are re-introduced to the tower.
reducing—In petroleum refining, the removal of light hydrocarbons
by distillation.
refinery gas—Any form or mixture of still gas gathered in a refinery
from the various stills.
reflux—In fractional distillation, part of the distillate may be re-
turned to the fractionating column to assist in making a more
complete separation into the desired fractions. The material
returned is the reflux; the process is refluxing.
regeneration—In a catalytic process, the burning of the catalyst
deposit with an oxygen-containing gas.
Reid vapor pressure—One of the important specifications for gaso-
lines. It is a measure of the vapor pressure of a sample at 100° F.,
and the test is commonly made in a bomb. The results are reported
in pounds per square inch.
rerun oil—Oil which has been redistilled.
residual—Heavy oil or residuum left in the still after gasoline and
other distillates have been distilled off, or residue from crude oil
after distilling off all but the heaviest components.
-------
54 Atmospheric Emissions from Petroleum Refineries
rich oil—Absorption oil containing dissolved natural-gasoline frac-
tions.
run—The amount of stock processed by a particular unit in a given
time. It is often used colloquially in relation to the type of stock
being processed.
Evp—Reid vapor pressure.
S
saturated hydrocarbons—Hydrocarbons of such molecular structure
that all adjacent carbon atoms are connected by not more than one
valence or bond, or graphically, as follows: C—C. Each valence
not taken up by adjacent carbon atoms connects with, or is satis-
fied by, a hydrogen atom. These compounds cannot take on other
products or the atoms of other elements without giving up an
equivalent amount of hydrogen.
scrubber—Equipment used for the removal of entrained liquids and
solids from gas, usually installed upstream from gas compressors.
skimming plant—An oil refinery designed to remove and finish only
the lighter constituents from the crude oil, such as gasoline and
kerosine. In such a plant the portion of the crude remaining after
the above products are removed is usually sold as fuel oil.
slop or slop oil—A term rather loosely used to denote odds and ends
of oil produced at various places in the plant, which must be rerun
or further processed in order to get in suitable condition for use.
When good for nothing else, such oil usually goes into pressure-still
charging stock, or to coke stills.
sour—Gasolines, naphthas, and refined oils are said to be "sour" if they
show a positive "doctor test," i.e., contain hydrogen sulfide and/or
mercaptans. Sourness is directly connected with odor, while a
"sweet" gasoline has a good odor.
stabilizer—A distilling plant in which "wild" or low-boiling hydro-
carbons (which have high vapor pressure) are removed from
pressure distillate or gasoline.
steam distillation—Introduction of "open" steam into the liquid
during distillation to assist in removing the vapors from the still.
still—A closed chamber, usually cylindrical, in which heat is applied
to a substance to change it into vapor, with or without chemical
decomposition. The substance, in its vapor form, is conducted to
some cooling apparatus where it is condensed, liquefied, and collected
in another part of the unit to which the still belongs.
stock—In general, any oil which is to receive further treatment before
going into finished products.
straight-run distillation—Continuous distillation which separates the
products of petroleum in the order of their boiling points without
cracking.
-------
Appendix III 55
straight-run products—Products produced by straight-run distillation.
stripper—Equipment in which the lightest fractions are removed from
a mixture. In a natural-gasoline plant, gasoline fractions are
stripped from rich oil. In the distillation of crude petroleum, light
fractions are stripped from the various products.
sweet—Having a good odor; pleasant to the sense of smell; negative
to the "doctor test."
sweetening—The process by which petroleum products are improved
in odor and color by oxidizing the sulfur products and unsaturated
compounds.
synthetic crude—The total, liquid, multi-component mixture resulting
from a process involving molecular rearrangement of charge stock.
Commonly applied to such product from cracking, reforming, vis-
breaking, etc.
T
tail—That portion of an oil which vaporizes near the end of the dis-
tillation; the heavy end.
tank farm—Land on which a number of storage tanks are located.
topped crude petroleum—A residual product remaining after the re-
moval, by distillation or other artificial means, of an appreciable
quantity of the more volatile components of crude petroleum.
topping—The distillation of crude oil to remove light fractions only.
turnaround—Time necessary to clean and make minor repairs on
refinery equipment after a normal run. It is the elapsed time be-
tween drawing the fires (shutting the unit down) and putting the
unit onstream again.
U
unsaturated hydrocarbons—Hydrocarbons of such molecular struc-
ture that at least two adjacent carbon atoms are connected by
two or three valences or bonds, or graphically, as follows: C=C
or C=C. Each valence not taken up by an adjacent carbon atom
is satisfied by a hydrogen atom.
vacuum distillation—Distillation under reduced pressure. The boil-
ing temperature is thereby reduced sufficiently to prevent decom-
position or cracking of the material being distilled.
vacuum jets—Steam ejectors for removing air and non-condensable
gases from barometric condensers on distillation equipment.
virgin stock—Oil derived directly from crude oil which contains no
cracked material. Also called "straight-run" stock.
viscosity breaking—Lowering or "breaking" the viscosity of residuum
by cracking at relatively low temperatures.
-------
56 Atmospheric Emissions from Petroleum Refineries
w
weathered crude—The product resulting from crude petroleum
through loss, due to natural causes during storage and handling,
of an appreciable quantity of the more volatile components.
wet gas—A gas containing a relatively high proportion of hydrocar-
bons recoverable as liquids.
Y
yield—The percentage of specification material obtained in distilling,
extracting, etc.
* U.S. GOVERNMENT PRINTING OFFICE : 1966 O—210-755
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