77-9.4
THE CONTROL OF HYDROCARBON EMISSIONS FROM
GASOLINE MARKETING OPERATIONS
VINCENT J. PITRUZZELLO
U.S. ENVIRONMENTAL PROTECTION AGENCY
NEW YORK, NEW YORK
For Presentation at the 70th Annual Meeting of the
Air Pollution Control Association
Toronto, Ontario, Canada June 20-June 24,1977
Printed in U.S.A.
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NOTE TO EDITORS
Publication rights to this paper are
reserved for the Journal of the Air
Pollution Control Association. Any
use by other journals is limited to
twenty per cent of text and figures.
a.
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The purpose of this report is to review methods currently available for
controlling hydrocarbon emissions generated during gasoline marketing
operations. For this purpose, gasoline will be defined as a petroleum
distillate with a Reid Vapor Pressure of 4 pounds or greaterJ The need
for controlling this source of emissions was initiated by Federal regula-
tions promulgated in November of 1973. It was mandated that oxidant con-
centrations, in specific areas of the country, be reduced. This was to be
achieved by limiting the amounts of oxidant-forming hydrocarbons from both
stationary and mobile sources. The gasoline marketing network accounts for
approximately 28% of total hydrocarbons being emitted from the petroleum
industry and as such was a prime target for control. Hydrocarbon emissions
from gasoline marketing result in about 1.4 million tons per year.2 This
paper discusses the methods of control which have been instituted within
recent years for meeting the requirements of the regulations.
NETWORK OPERATION
The gasoline marketing industry contributes hydrocarbon compounds to the
atmosphere through the mechanism of evaporation during the many handling
processes involved in transferring gasoline from the terminal to the vehicle.
If left uncontrolled, the industry would become a greater relative contributor
to hydrocarbon emissions because other emission sources are being brought into
control, because gasoline sales are increasing and because of increased reacti-
vity of non-leaded gasoline vapors.
Terminal operations are the central point of the gasoline marketing network.
Here the product is received by rail, truck, barge and pipeline and transported
to the service station by tank trucks. Emissions are generated during the bulk
terminal loading operation, during delivery to the service station and during
vehicular refueling operations. Regulations have been promulgated for controlling
emissions from the terminal and service station sources; regulations have been
proposed for the vehicular refueling operation.
During the year 1973 106.5 billion gallons of gasoline were consumed in the United
States.An average annual increase in consumption of about 5% is expected for
the foreseeable future. The distribution was made through more than 25,000
bulk stations and terminals to over a quarter million service stations. Vir-
tually, all gasoline product was transported by tank truck to the retail outlet.
Because of the nature of this operation, the gasoline product can be subject to
two or three transfers before being consumed. This factor makes the control of
this source category increasingly important.
In most terminal operations, tank trucks ranging in size from 500 to 8500 gallons
are loaded by a variety of techniques. The method used for loading has the
greatest influence on the amount of emissions generated at the loading rack.
Product can be transferred by splash loading techniques, where the stock is dis-
charged into the upper part of the truck compartment through a short spout which
never dips below the surface. The fall increases evaporation and can result in
the loss of liquid droplets and subsequent entrainment of vapors. Subsurface or
submerged loading operations result in rapid evaporation loss until the end of
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77-9.4
the loading spout is covered to give a calm surface. Most loading of
this type requires that, ideally, the spout be within a few inches of
the bottom of the compartment. However, because of the size and shapes
of the various transport trucks, this ideal situation can be realized in
only a certain percentage of the delivery vessels. Loading losses can
be kept to a minimum by the use of bottom loading techniques where the
transfer piping is connected directly to the tank bottom.*
To insure the maximum degree of control, regulations required that all
displaced vapors and air be vented to a vapor collection or disposal system.
This is accomplished by connecting a vapor recovery arm to the delivery vessel
during loading. The vapor arm is a permanent fixture at the rack and allows
the vapor to be directed to the control unit for processing. Recently, there
have been many advances in the technology of controlling emissions at the ter-
minal. To date, there are seven different types of systems available for this
purpose. Vapor recovery or disposal units are connected to the loading rack
and process gasoline vapors into liquid product, combust the vapors, or use
the vapors as a source of fuel gas.
TERMINAL CONTROL SYSTEMS
Each type of system will be briefly described below:
(a) The operation of the cotnpression-refriqeration-absorption system
is based on absorbing vapors with cool gasoline. The vapors are first satu-
rated to insure that they are above the upper explosive limit (UEL), com-
pressed and then cooled before introduction into the absorber. Here, the
vapors are bubbled through cold gasoline (at -10°F) and absorbed. Air is
vented at the top of the absorber and gasoline product,drawn from the bottom
of the absorber,is returned to storage. As in most recovery systems, the
efficiency of the unit is dependent on the inlet hydrocarbon concentration.
If necessary, booster compressors can be installed to increase recovery effi-
ciency.
(b) Compress ion-refrigeration-condensation units recover vapor by first
saturating the vapors above the UEL and then by compressing the vapors in a
two cycle compressor equipped with an inter-cooler. Condensate is drawn from
the inter-cooler prior to the second stage compressor. Compressed vapors are
sent to a condenser where they are cooled and condensed. The vapors are then
returned along with the condensate, from the inter-cooler, to storage.
(c) Lean-oil-absorption units operate by allowing the gasoline vapor to
flow into a packed absorption column. The packing is continuously wetted by a
stream of lean oil, which is gasoline stripped of its light ends. The clean
air is usually passed through a demister to remove any entrained absorbent and
the enriched gasoline is returned to storage. Lean or "sponge oil" absorbent
is produced by heating gasoline from storage. All light ends from this heating
are condensed and returned to storage. The quantity of lean oil is variable
and is a direct function of the quantity of vapor flow to the absorber, the
vapor temperature and the degree of vapor saturation.5
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77-9.4
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(d) Another method used for recovering gasoline vapor is the
refrigeration system, based on condensing vapor at atmospheric pressure.
This system employs a typical cascade refrigeration operation which pro-
duces temperatures in the evaporator-interchanger in the order of -100°F.
A brine coolant is circulated through the finned tube sections of the vapor
condenser and the gasoline vapor is passed over the sections of the con-
denser. Entrained moisture in the entering vapor condenses and collects
as frost on the cold plate fins. Liquid hydrocarbon is collected at the
bottom of the condenser. At periodic intervals, defrosting of the finned
surfaces is accomplished by circulating warm brine from a separate storage
reservoir. A two-stage refrigeration unit is used to cool the stored brine
to about -120°F. Vapor holders are not required, since the unit operates on
demand.6
(e) A recent development in reducing emissions of gasoline vapor has
been the adsorption-absorption system. This process operates by adsorbing
gasoline vapors on activated charcoal to near the saturation point of the
charcoal and follows this with absorption of the recovered vapors with liquid
gasoline. The design includes a duel charcoal bed system which allows one
bed to operate while the other is being regenerated. Upon completion of re-
generation, the bed operation is switched. Vapor holder tanks are not required
since the vapor flow is directed straight to the charcoal bed.''
(f) One of the most direct vapor control systems is the flame oxidation
method. Vapor emissions are controlled by combusting the vapor rather than
recovering it. Gasoline vapor, displaced from the loading operation, is sent
to a holder tank, which is used to reduce surging to the system and allow for
an even air flow. Vapor is then drawn from the tank by a blower, compressed
and fed to the oxidizer. A propane pilot light is used for oxidizer ignition
and thus, a source of propane must be made available. The oxidizer operation
is controlled by the gas volume in the vapor holder tank and starts at about
30% capacity and shuts down at about 10%capacity. Because of the nature of the
operation, no recovered product tanks or lines are necessary. Capital and
operating costs for these units are usually lower than that required for recovery
units, but this can be offset by the economic loss of combusting the vapor rather
than recovering it.5,8
(g) Another method of vapor disposal, by combustion, uses the heat genera-
ted by the operation as a source of space or process heat. Gasoline vapors are
conducted to a saturator to obtain concentrations above the UEL. The enriched
vapor is then sent to a vapor-holder tank, which is fitted with an internal
diaphragm. When a preset level is approached, a negative pressure pump is acti-
vated and the vapors are sent to a standard burner. If the burner is oil-fired,
a dual-burner system is needed to allow for proper combustion of the vapor feed.
The capital expenditure necessary for this system includes ductwork, the vapor-
holder tank and burner adjustment. However, this can be offset by savings in
fuel oil consumption. High levels of burner efficiency must be maintained for
compliance with Federal, State, or local regulations.
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77-9.4
COST DATA
Table I depicts actual installed costs for a variety of systems presently
in operation in New Jersey. Column I represents the cost of the unit and
Column II shows an installed cost which includes all associated terminal
work such as loading rack retrofit piping, electrical work, etc. Column
III gives gasoline throughput at the rack to describe the units' work load.
This data has been presented to illustrate the range of costs that may be
encountered when installing a vapor recovery unit. Expenditures for each
type of unit will fluctuate with the work load but not necessarily in arith-
metic proportion. Most terminal units have been oversized to compensate for
expected growth in gasoline consumption. Where cost data were available for
more than one installation of a particular type unit, a range of costs and
throughputs are supplied. It is difficult to generalize and use these
figures for cost estimation at other terminals since different parameters
will be encountered at each facility. For example, it may be desirable to
retrofit an existing rack instead of demolishing it and rebuilding a new one.
Piping costs will be dependent on diameter and lengths of pipe required.
Labor costs will differ with geographical areas. The desired quality of
the completed terminal will affect overall costs; resurfacing costs and
quality of equipment must also be considered.
Table II presents an analysis of the actual associated costs for retrofitting
a two-rack top loading operation to bottom loading. When considering annual-
ized cost for the various types of units, utility and maintenance costs must
be included in the estimates. Depending on the type and size of the unit, these
costs can range from 2-5% of capital cost. Annualized costs for oxidation
systems are dependent on the pilot light propane requirements.
Operating costs can be offset by the recovery of saleable product. For example,
a 500,000 gallon/day terminal can recover about 600 gallons of gasoline product
per day if all the displaced vapor is sent to the recovery unit and if the unit
is operating at 90% efficiency. This also assumes bottom or submerged loading
into trucks used exclusively for gasoline delivery to service stations equipped
with vapor recovery. The recovered product consists of light ends, and is mixed
in storage, usually with regular grades of gasoline. Thus, this product can be
worth several hundred dollars per day, based on current resale value of gasoline.
A typical calculation is shown in Figure I.
The reliability of vapor recovery systems must also be considered. For example,
in New Jersey there are 26 terminals equipped with vapor recovery systems. As
of March, 1977 there have been 257 total operating months, with a reported down-
time of 10 months or 4%. Thus, reliability of operation is 96%. Most units are
automated and require very little maintenance except for daily checks on operating
parameters which are usually displayed on a control board for easy access. In
the event of a system or component failure, the manufacturer will supply the re-
quired technical assistance. Units are commercially available for terminals
with daily throughputs as low as 70,000 gallons and as high as one million gallons
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SERVICE STATION CONTROLS
Recovery of vapor generated during bulk delivery at the service station
can be accomplished by a closed loop balance system which simply returns
the displaced vapors to the delivery vessel. The liquid gasoline acts
as a driving force sending the vapors back to the tank truck. Some im-
portant factors in designing an efficient balance system are the type of
loading technique, vapor and liquid line fitting, vent pipe restrictions
and vapor-tight delivery vessels. Design criteria calls for loading to
be done with the use of a submerged fill pipe to keep splash effects at
a minimum. Systems will also include dry-break or cam-lock fittings on
the product and vapor return lines, to insure a tight fit and eliminate
leaks. A restriction on the underground tank "breathing" vent line is
necessary to establish a path of least resistance thus assuring a high
percentage return to the tank truck.
Also, the tightness of the delivery vessel is extremely important. The
trucks should be kept vapor-tight so that a maximum amount of recycled
vapor can be returned to the terminal for processing through the recovery
or disposal unit. Systems currently available on the market, include a
two-point system (separate vapor and product line) and one-point or co-
axial system where the liquid line is surrounded by an outer annular space
for vapor return to the truck.
Recovery of vapors from vehicle refueling operations has generated much
disagreement among the participating interests. It is uncertain whether
balance-type systems can meet the requirements of the various codes. Effi-
cient gasoline dispensing nozzle designs have been questionable. Vacuum-
assisted systems, which create a negative pressure at the pump to capture
the expelled vapors, are not desireable to the industry because of the high
capital cost and questionable dependability. The vacuum-assist systems must
be equipped with a secondary recovery or disposal unit to control the excess
emissions generated by the evaporation of additional hydrocarbons in the
additional ingested air. The main processing systems used in conjunction
with vacuum assist are refrigeration, absorption, compression and oxidation.
Some recent technology has sought to combine balance and vacuum-assist systems
into a "hybrid" system which uses gasoline circulated through the dispensing
nozzle as a source of vacuum. Hopefully, technology will soon be developed
to satisfy both industrial and regulatory interests. Some typical cost data
for retrofitting a service station for compliance with the bulk delivery and
vehicular refueling regulations are given in Table III.9>10
SECONDARY BENEFITS
There are some ancillary benefits to be derived from controlling vapors generated
during gasoline marketing operations. These will be considered below:
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77-9.4
(1) Bottom loading techniques reduce the amount of vapor generated since
there is less splashing of product. This is a direct saving of a valuable
fuel. Tight fitting systems decrease the occurrence of spillage and thus,
make the terminal area a safer place to work. Since bottom loading does
not require the driver to load from the top of the truck, the incidence of
falls will be eliminated. Bottom loading allows the operator to fill several
compartments simultaneously and reduces overall fill time. The loading racks
are equipped with automatic sensors to terminate loading and prevent compart-
ment overfill.
(2) The gasoline fraction that is recycled results in a direct conservation
of a valuable resource. It has been estimated that about 9 million gallons
per year of gasoline fractions can be recycled in N.J., based on 1973 con-
sumption. Resale of the recovered fraction will assist in recouping capital
and operating expenses.
(3) By returning service station losses to the delivery trucks, a level
above the UEL is constantly maintained in tight trucks, thus, eliminating
any explosion hazard. Vapor concentration in retrofitted trucks is about
15-20? and does not approach the UEL of 7.6%. Criteria require that delivery
vessels are to be inspected at least semi-annually by leak testing procedures
to insure vapor tightness.
(4) Systems that use the captured vapor as a source of fuel result in a
saving of valuable fuel oil and utilize an energy source that would have
been wasted.
(5) The use of vapor recovery and disposal systems can reduce the emissions
os suspected carcinogenic compounds of gasoline. Benzene and associated
aromatic components constitute the largest percentage of suspected carcino-
genic agents in the stock. The liquid phase content of benzene can range
from 0.5% to 2.0% by liquid volume percent for regular and premium grades.
For purposes of maintaining octane ratings, unleaded gasolines contain a
higher benzene content, usually about 2.5% liquid volume percentage. With
the increased use of unleaded fuels, (projected as a 10% increase per year)
this problem will grow. More data must be compiled to adequately determine
the magnitude of the problem.
(6) It is also possible that lead particles may be transported and emitted
in the vapor phase. However, due to the lack of available data, this state-
ment cannot be made with a high level of confidence. Further studies into
this area are necessary.
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CONCLUSIONS
Systems are currently available for meeting requirements of regulations
controlling vapor emissions generated during the gasoline marketing opera-
tion. Technology has been developed to recover or dispose of 90% of vapors
displaced during truck loading operations at the bulk terminal. Service
station control systems can also effectively recover 90% of normal vapor
loss during delivery operations. A cost-effective technology for vehicular
refueling control is still in the development stage. The available control
systems have been found to be reliable and will aid in the achievement and
maintenance of the national ambient air quality standard for oxidants by
reducing the emissions of precursor hydrocarbons.
Secondary benefits will also be realized by the implementation of these
controls. Gasoline product will be recovered and recycled, the terminal
and service station environment will be a safer and more pleasant area to
work. Valuable fuel will be conserved and emissions of suspected carcino-
genic agents will be reduced.
FUTURE CONSIDERATIONS
It is not yet known to what geographical extent these regulations will be
applied. Presently, there are portions of seven states and Washington, D.C.
where gasoline marketing controls have been required. Since technology is
proven and available, this source of emissions can readily be controlled.
Vapor balance systems can be used at bulk loading stations which are secondary
distribution facilities that receive gasoline from larger terminals by tank
truck. Recovery and disposal systems can be sized for controlling emissions
generated during marine loading operations. Losses from this source can be
significant because of the large volumes handled. Marine controls should be
considered for transporting the new sources.of oil from the Alaska North Slope
to the West Coast and for similar oil discoveries off the East Coast. Marine
controls are being contemplated for the Houston-Galveston Area. In some cases,
product is stored in underground tanks in waterfront terminal operations.
Breathing and working losses, from these tanks, can also be controlled in
conjunction with barge loading.
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Table I
Type Unit
Compression-Refrigeration
Absorption (range)
Compression-Refrigeration
Condensation
Lean-Oi1-Absorpti on
Refrigeration (range)
Adsorption-Absorption
Flame Oxidation
Fuel Disposal System
ire Vapor
Column
Unit Cost
60-80
250
140
50-155
80
90
—
A
Recovery at the Terminal
I Column II
Associated [
($103) Installed Cost ($10J)
70-90
125
Not Available (N.A.)
N.A. 500
50
300
350D
Column III
j Product
Throughput
80,000-
325,000 gal /day
385,000 gal/day
500,000 gal /day
70,000-
1 ,000,000 gal/day
70,000 gal/day
200,000 gal/day
820,000 gal/day
A
Data supplied is in 1974-76 dollars.
D
Assume, two gasoline loading racks with a total of 12 loading arms.
It is believed that this type of system has been removed from the market.
Cost is $100,000 for saturator and vapor holder; $100,000 for piping
(1300 ft.) and $150,000 for rack retrofit.
D
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Table II
Associated Capital Expenditures
Item
A
Rack Conversion^
Combined Piping
Labor .
MetersL _
Land Improvement
Truck Retrofit (Bottom Load)
80,000 (2 racks, 4 positions)
125,000
42,000
25,000
33,000
1500-2500 per compartment
Includes reworking of rack from top splash to bottom load.
(Cost of a top submerged arm $3500; cost of bottom load
arm = $1100)
D
Dependent on distance from loading rack to vapor recovery unit.
P
Includes electrical meters and pre-set shut off switches.
Includes unit foundation, area resurfacing, drainage system.
Dependent on desired quality of completed retrofit terminal.
Note: The above represents actual on-site costs incurred by terminal
operators throughputting 500,000 gallons/day.
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77-9.4
Table III
Costs Service Station
A. Delivery Controls Only
Two-Point System $3100
Co-Axial System $2000
Component Estimates Excavation 42%
Labor 32%
Piping 20%
Valve Fittings 6%
Assume balance system for a station equipped with four underground
tanks.
B. Delivery and Vehicular Refueling Controls
Drybreak fittings $ 320
Excavation $ 600
Vapor pipes from dispenser $1350 (assume 450 ft. total)
Installation of pipes $1300
Nozzles and hoses $ 870
Installation of nozzles $ 240
Trucks, compressor and
misc. piping - $ 300
TOTAL - $4,980
Vacuum assist unit $3000- $5800
Total cost $8000 $10,800 (approximate)
Costs include total service station retrofit for a station with a
throughput of 30,000 gal. per month using six nozzles.
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Example Calculation
Assume gasoline product throughput of 500,000 gallon/day with an
RVP=10. Product temperature is 60°F and is loaded into trucks
returning from service stations equipped for vapor recovery.
Uncontrolled Emission Factor for Gasoline 8 lb/1000 gallons
transferred
500'00° ^T X fool gallons ^ 90% control 3600 lo/day
Liquid density 6.2 Ib/gaTlon
Thus,
3600 Ib ;6.21b 581 „
day gallon 3
Net price; ex-tax of gasoline (1/76) - 35.2£/gallon
Dollar value of recovered product is:
$204.51/day
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77-9.4
References
1. Environmental Protection Agency "New Jersey Transportation Control
Plans: Approval and Promulgation of Implementation Plans."
Federal Register 38 (218), 31399, November 13, 1973
2. Environmental Protection Agency Office of Air Quality Planning and
Standards Revision of Evaporative Hydrocarbon Emission Factors
EPA-450/3-76-039 August, 1976
3. National Petroleum News Mid-May Factbook 1974
4. American Petroleum Institute, Evaporation Loss Committee, Evaporation
Loss From Tank Cars, Tank Trucks, and Marine Vessels.
Bulletin 2514 N.Y. 1959
5. Environmental Protection Agency Office of Air Quality Planning and
Standards A Study of Vapor Control Methods for Gasoline Marketing
Operations: Volume I - Industry Survey and Control Techniques
EPA-450/3-75-046-a, Research Triangle Park, N.C. April 1975
6. Edwards Engineering Corporation Hydrocarbon Vapor Recovery Unit
May 1976
7. Hydrotech Engineering Incorporated Vacuum Stripping, Water
Deaerating, Odor Control, B.O.D. Reduction, Hydrocarbon Removal
1976
8. Environmental Protection Agency Office of Research and Development
Demonstration of Reduced Hydrocarbon Emissions From Gasoline Loading
Terminals EPA-650/2-75-042, Washington, D.C. June 1975
9. Environmental Protection Agency "Stage II Gasoline Vapor Recovery:
Proposed Decisions, Amendments,: Test Procedures," Federal Register
40 (197) 47670 October 9, 1975
10. Cost Data Vapor Recovery Systems at Service Stations Pacific
Environmental Services Incorporated, September 1975 (Prepared
under Environmental Protection Agency contract #68-02-1405)
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