-------
2.2.2.1 Sta^e I Control Technology (Cont.)
tanks which cannot be converted to submerged fill, e.g., tanks
with offset fill lines or poor accessibility.
(2) Gauge Well
If a gauge well separate from the fill tube is
used, it must be provided with a drop tube which extends to
within 6 inches of the tank bottom. This will prevent vapor
emissions in case the gauge well cap is not replaced during a
drop.
(3) Vapor Hose Return
Existing data indicate that a 3-inch ID hose is
needed to transfer vapors from the storage tank to the truck.
Smaller diameter hoses may be satisfactory where fill rates are
appreciably less than 400 gallons per minute. If a hose smaller
than 3 inches is to be used, the owner/operator is required to
show that the hose will achieve the required vapor recovery.
(4) Size of Vapor Line Connections
Where separate vapor lines are used with 4-inch
product tubes, nominal 3-inch or larger connections should be
utilized at the storage tank and truck-trailer. When smaller
product tubes are used, a smaller vapor line connection may be
used, provided the ratio of the cross-sectional area of the con-
nection to the cross-sectional area of the product tube is 1:2
or greater. If the ratio is smaller, test data must be provided
to show the required recovery efficiency will be met.
For concentric or other tube-in-tube fittings, operating
characteristics are unique to the particular design. To date,
adequate test data have been supplied for 4-inch and 6-inch
tube-in-tube adapters.
-124-
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2.2.2.1 Stage I Control Technology (cent.)
(5) Type of Liquid Fill Connection
Vapor tight caps are required for the liquid fill
connection for ail systems. A positive closure utilizing a
gasket or other similar sealing surface is necessary to prevent
vapors from being emitted at ground level. Cam-lock closures
meet this requirement. Dry-break closures also are acceptable,
but are not required.
(6) Tank Truck Inspection
Vapor tight tank trucks are specifically required
by TCP regulations. This is interpreted to mean that the truck
compartments won't vent gases or draw in air unless the settings
of the pressure-vacuum relief valves are exceeded. An inspection
procedure should be submitted to include frequent visual in-
spection and leak testing at least twice per year. Leak testing
should demonstrate that the tank truck when pressurized to 5
inches W.C. will not leak to a pressure of 2 inches W.C. in
less than 3 minutes. ~ {uent visual inspection is necessary
to insure proper operatic of manifolding and relief valves.
(7) Closures or Interlocks on Underground Tank Vapor
Riser
Closures or interlocks are required to assure
transfer of displaced vapors to the truck and to prevent ground
level gasoline vapor emissions due to failure to connect the
vapor return line to the underground tanks. These devices must
be designed:
-125-
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2.2.2.1 Stage I Control Technology (Cont.)
(a) to keep the storage tank sealed unless
the vapor hose is connected to it; or
(b) to prevent delivery of fuel until the
vapor hose is connected, i.e., an inter-
lock.
Concentric couplers are required to have acceptable closures on
the vapor line connection in the coupler itself rather than on
the riser pipe from the storage tank.
(8) Vapor Hose Connection to the Tank Truck
A means must be provided to assure that the vapor
hose is connected to the truck before fuel is delivered. Accept-
able, means of providing this assurance include:
(a) permanent connection of the vapor hose
to the truck;
(b) an interlock which prevents fuel delivery
unless the vapor hose is connected, such
as a bracket to which the product and vapor
hose are permanently attached so that
neither hose can be connected separately;
and
(c) a closure in the vapor hose which remains
closed unless the hose is attached to
the vapor fitting on the truck.
-126-
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2.2.2.1 Stage I Control Technology (Cont.)
(9) Vent Line Restrictions
Vent line restrictions improve recovery efficiency
and provide assurance that the vapor return line will be con-
nected during transfer. If the liquid fill line were attached
to the underground tank and the vapor return line disconnected,
closures would seal the vapor return path to the truck forcing
all vapors out the vent line. Restriction of the vent line
through the use of an orifice or pressure-relief valve greatly
reduces fill rate in such instances warning the operator that
the vapor line is not connected.
Where concentric or tube-in-tube connections are
utilized, a restriction should be installed in the underground
tank vent pipe. These connectors provide considerably less
cross-section area in the vapor return passage than do 3-inch
connectors. Hence, a restriction in the vent pipe is required
to insure that the required emission limit will always be met.
If systems utilizing tube-in-tube connections are to be installed
without vent pipe restrictions, testing data will be required
to show that the emission limit is being met.
Suitable restrictive orifices or pressure-relief
valves arr required whenever the systems would otherwise be in-
capable of achieving 90% control or would otherwise not assure
that the vapor return line is connected. For available hardware
this means that these restrictive devices are necessary for all
except systems with interlock connections at both the truck and
storage tank.
Either of the following restrictive devices are accept-
able :
(a) Orifice of 1/2 to 3/4 inch ID.
-127-
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(b) Pressure-vacuum relief valve set to open
at 8 oz per square inch or greater pressure
and 4 oz per square inch or greater vacuum.
The vacuum relief feature of a P-V valve is
not required for Stage I recovery purposes
but may be required by safety authorities.
Figure 2.2-21 shows a schematic sketch of a well-
designed vapor displacement system for recovery of underground
storage tank vapors. The system depicted employs a concentric
or coaxial vapor-liquid connector.
2.2.2.2 Stage II Control Technology
t
Stage II controls refer to control during vehicle
refueling. It is in this area where much disagreement remains
on the effectiveness of different means of emission control.
Most of the controversy centers on the relative advantages/
disadvantages of two basic types of emission control systems:
vapor displacement and vacuum assist.
The vapor displacement, or vapor balance system oper-
ates by simply transferring vapors to the underground tank where
they are stored until final transfer to a tank truck. Pressure
created in the vehicle tank and vacuum created in the underground
tank are the principal agents of vapor transfer. The main
pieces of equipment associated with a vapor balance system are
a specially designed nozzle which is designed to form a vapor
tight seal at the fill neck interface, a flexible hose, and an
underground piping system to transport the vapors to the under-
ground storage tank. The underground storage tank vent line
can either be open to the atmosphere or equipped with a P-V
valve to aid in retaining a vacuum in the underground tank.
-128-
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-129-
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2.2.2.2 Stage II Control Technology (Cont.)
Retaining a slight vacuum (2-4" H^0) in the underground
aids the operation of a displacement system in two manners.
First of all, it reduces the pressure drop through the vapor
piping system which aids the flow of vapors to the underground
tank and it also eliminates outbreathing.
Designs of commercially available vacuum assist systems
vary widely. All do, however, employ a blower or vacuum pump
and a secondary recovery device. The vacuum pump creates a
negative pressure in the vehicle fill neck which "pulls" hydro-
carbon vapors either directly to the secondary unit or to the
underground tank with the excess vapors going to a secondary
unit. The amount of vapor collected by this type system is
greater than the amount that would be displaced by the balance
system filling operations. The additional air ingested causes
the evaporation of additional hydrocarbons.
The main processing operations employed by secondary
control devices are compression, refrigeration, absorption,
and oxidation. One secondary control device may use one or
several of these operations to achieve the necessary control.
The equipment associated with these type systems is generally
complex, expensive, and subject to mechanical failure. Equip-
ment associated with a balance system on the other hand is simple,
less expensive, contains no moving parts (except for the nozzle)
arid is thus not subject to operational downtimes„
This section of the document will provide technical
assessments of each type vapor recovery system.
-130-
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2.2.2.2 Stage II Control Technology (Cont.)
(1) Vapor Balance or Displacement
Description of System
The major components of a vapor balance system
are a vapor recovery nozzle, a flexible hose, and underground
piping. The function of the vapor recovery nozzle is to effect
a leak-free seal at the fill pipe interface. When the seal is
made, vapors displaced from the vehicle tank will flow through
a vapor passage in the nozzle, but may also escape collection
through vents or leaks in the vehicle tank.
The function of the flexible hose is to provide a
means of transferring the displaced vapors from the nozzle to
the underground pipe. The hose is connected to the outlet of
the nozzle vapor passage and to the inlet of the underground
pipe which provides a path of vapor flow to the underground
tank. Experience with these systems has indicated that a flexible
hose size of at least 3/4" and an underground pipe size of at
least 2" are necessary to prevent excessive system pressure
drops. Furthermore, exp^ ience has shown that a slope of 1/8
to 1/4 " per foot will provide a sufficient gradient for any
condensed vapors to flow to the underground tank. Figure 2.2-22
shows a f3 .agram of a vapor balance system with manifolded vent
lines.
The major differences in vapor balance systems are
found in designs of nozzle, piping configurations, and under-
ground tank vent line controls. Some systems return the dis-
placed vapors to individual tanks while others manifold them
together. Pressure-vacuum valves can be used to control breath-
ing of the underground tank. In addition, they have the capa-
bility of taking advantage of the vacuum developed in the
underground tank upon vehicle refueling.
-131-
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2.2.2.2 Stage II Control Technology (Cont.)
Vapor Growth in Balance Systems
The operation of the displacement system includes
the phenomena of vapor growth or vapor shrinkage. Vapor growth
refers to a situation in which the volume of vapors displaced
from a vehicle tank is greater than the volume of dispensed
gasoline. When the volume displaced is less than the volume
dispensed, it is called vapor shrinkage. Vapor growth results
in outbreathing of hydrocarbon vapors from the underground tank
vent line while vapor shrinkage produces inbreathing followed
by partial saturation, expansion, and possible outbreathing.
In each case it is assumed that there are no leaks at the nozzle-
fill neck interface.
The degree of vapor growth is determined in part by
the relative temperatures and volatilities (RVP's) of the dis-
pensed fuel and residual fuel in the vehicle tank. Dispensing
cool gasoline into a warm tank or dispensing low RVP fuel into
a tank containing higher RVP fuel causes vapor shrinkage while
the reverse conditionr ^use growth.
Of these two effects, the temperature gradient appears
to have the greatest impact on vapor growth. EPA source testing
has indi dted that there is little difference in the RVP's of
dispei jed gasoline and gasoline in the vehicle tank. Tempera-
ture differences (vehicle tank temperature minus dispensed fuel
temperature), however, may vary from a &T of -25 to +25.
Figure 2.2-23, which is based on measured values, shows the effect
of RVP on hydrocarbon losses. Figure 2.2-24, which is based on
calculated values, assuming equilibrium between the displaced
vapor and dispensed fuel, illustrates how the temperature
gradient affects the amount of hydrocarbon emissions.
-133-
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FIGURE 2.2-23. SENSITIVITY OF
DISPLACED LOSS TO TEMPERATURE AT
VARIOUS VALUES OF RVP (SC-167)
10-
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RV
RV
= 13 PSI
A
11 PSI
- 9 PSI
= 7 PSI
30
'10 50 60 70 80
DISPENSED FUEL TEMPERATURE °F
^TDisp. Fuel = TRet. Vapor^
90
-134-
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: FIGURE 2.2-24
EFFECT^OF T$MP-ERATURE
pN EMISSION RATES, RVP
;AT=TT - T7
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iwhere: ;
:t-i =; vehicle -t-ank
= dispensed :fuel
DIFFERENTIAL
temp
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Dispensed Fuel Temp, F
-135-
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2.2.2.2 Stage II Control Technology (Cont.)
Other factors which may influence vapor growth are the
solubility of oxygen in dispensed gasoline, the fullness of the
vehicle tank upon refueling, the amount of fuel dispensed, the
rate of fuel dispensing the back pressure caused by the vapor
recovery system, and leakage around the fillneck-nozzle inter-
face. Only limited work has been completed at this time in
attempts to quantify these effects, although further work is
planned.
Source testing performed by EPA on vapor balance
systems has confirmed the phenomenon of vapor shrinkage during
warm weather. It has been reported but not confirmed that large
vapor growths occur during winter conditions (FU-035) resulting
mainly from dispensing relatively warm fuel (at say 60°F) to
cold vehicle fuel tanks (at say 30°F). It is also possible that
vehicle fuel tanks may become heated by the exhaust: system
during winter driving in which case vapor shrinkage could occur.
Further testing is planned to study this effect during cold
weather.
EPA - Source Tests
The following paragraphs contain discussions of
test results performed with the objective of demonstrating re-
covery efficiencies of balance systems under a variety of con-
ditions .
Balance System Efficiencies
Source testing performed by EPA in San Diego,
June 1974, showed daily percent recovery averages ranging from
62% to 8870 at two different balance systems. The only apparent
difference in the two systems was in piping which was somewhat
-136-
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2.2.2.2 Stage II Control Technology (Cont.)
more tortuous at the station with the lower overall average ef-
ficiency for the test period (72% versus 82%) (EN-182). Pre-
liminary analysis of source testing data which was also taken
by EPA in Hayward and Davis, California, August 1974, showed
daily percent recovery averages ranging from 58 to 86 at two
different stations. Reasons for the difference in overall
average efficiencies (7070 versus 84%) have not been fully ex-
plained .
The efficiencies reported refer to the difference
between actual emissions and baseline emissions. Data from
both sets of EPA tests indicate that the baseline emissions
average about four grams/gallon. Baseline emissions were deter-
mined from those vehicles which had no leaks at the nozzle-fill
neck interface and whose tank indicated no leak when submitted
to a leak check after the fill. Applying the recovery efficiencies
to the baseline emissions results in average hydrocarbon losses for
the vapor balance systems of 1.12 gm/gal and 0.72 gm/gal for the
two San Diego Systems and 1.2 gm/gal and 0.64 gm/gal for the Bay
Area systems.
Test report? t esented by several oil companies have
shown recovery efficiencies greater than 85%. The higher recov-
ery efficiencies obtained appear to result from greater dilligence
by the oper tor in effecting a seal at the nozzle fill neck inter-
face .
Scott Laboratories - API Tests
Testing performed by Scott Laboratories for the
APT (SC-186) indicated that recovery efficiencies of 9670 (ap-
jroximately 0.16 gm/gallon loss) were achievable with the balance
system when the following criteria are met:
A leak-free seal is made at the
fill neck interface.
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2.2.2.2 Stage II Control Technology (Cont.)
Vehicles being refueled have emission
control devices (carbon canisters).
These criteria were met during the study by testing
only post-1970 vehicles and by forcing seals at the nozzle-fill
neck interface. These tests illustrate the effectiveness of
the balance system under good conditions and thus represent
actual data on the maximum expected efficiencies.
SHED Tests
Field test data indicate that baseline hydro-
carbon emissions from vehicle refueling are 4 gm/gallon. SHED
test data (SC-167) indicate that normal uncontrolled hydro-
carbon emissions from vehicle refueling operations is 5 gm/
gallon. Possible reasons for the 1 gin/gallon difference in the
two values may be attributed to the use of vapor recovery
nozzles which may restrict hydrocarbon emissions from the fill
neck over completely uncontrolled systems and possible leaks
through carbon canisters or the vehicle tanks. Further study
is required in this area to investigate the difference in emis-
sion values.
Likely Emission Sources
Vapors lost from a balance system are currently
being lost from either the fill-neck interface or out a vehicle
gasoline tank external vent. EPA testing during warm weather
has shown zero outbreathing from the underground tank.
External vents are found on two-thirds of pre-1970
vehicles. The other one-third of pre-1970 vehicles vent through
the fill neck where capture is possible. The magnitude of the
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2.2.2.2 Stage II Control Technology (Cont.)
vent loss has been reported to be only six percent of the total
vapors displaced from each vehicle (ST-187, PO-100). By 1977,
at the current rate of phasing out, there should not be more
than 20 percent of pre-1970 vehicles on the road (EN-182) at
which time this source of vapor loss will become small.
The majority of reported hydrocarbon losses, therefore,
result from a poor seal at the nozzle-fill neck interface. If
the problem of leakage around this interface can be solved,
the displacement system will then become an efficient and re-
liable method of recovering vehicle refueling vapors.
There are a multitude of vehicle fill neck configura-
tions and sizes found in vehicles on the road today. It is
highly unlikely, therefore, that a single nozzle will be de-
veloped to provide leak-free seals on all vehicles. One means
of ensuring a tight seal could, however, be through development
of fill neck adapters which have been standardized for fill
necks on all vehicles. Agreement of automobile manufacturers
to supply standardized fill necks with all cars would, of
course, greatly simplify implementation of this plan.
Balance System Costs
Service station modification costs, including
both equipment and labor have been reported to vary from a low
of $5,000 to a high of $8,000 (RE-107, SC-186, EN-184). The low
values are based on bid prices and actual installed costs while
the high values were based on mid-1974 dollars allowing for
recent material escalation. Installation costs for a new service
station will be from $2,000 to $3,000 (RE-107, SC-186). Main-
tenance cost for the displacement system, which mainly involves
repairs to the nozzles and hoses has been estimated to be from
a low of $30/year (RE-107) to a high of $620/year (SC-186).
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2.2.2.2 Stage II Control Technology (Cont.)
Balance System Reliability
Once a vapor balance system is installed and
fully leak-tested, simple routine maintenance on the vapor re-
covery nozzles and hoses should ensure successful operations.
The system contains few moving parts and is not dependent on
the performance of electrical switch gear. Inefficient opera-
tions can be caused, however, by the deterioration of the rub-
ber boots on the nozzles, poor seals at the fill neck interface,
and liquid blockage of the vapor return line.
Deterioration of the rubber boot on one of the nozzles
used for source testing by EPA during the Bay Area tests was
observed after less than one week's operation. Replacement of
the boot was a very simple operation taking less than 15 minutes.
Frequent replacement of the nozzle boots may be anticipated.
Poor seals at the fill neck interface are to be ex-
pected on some cars. Standardized fill necks appear to be one
solution, although diligence of the operator in positioning the
nozzle on the fill neck is important. Certainly, leaks may occur
at any interface if the nozzle is not positioned properly.
It is possible that condensed vapors can collect in
the vapor return lines and impede the flow of displaced vapors.
Liquid blockage can result in overpressuring of a vehicle fuel
tank which may result in gasoline being sprayed from the tank
when the nozzle is removed. Liquid blockage of the vapor return
line is a potential problem of importance, but one that can be
controlled by designing the system to eliminate any pockets in
the vapor return hose in which condensed vapors can collect.
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2.2.2.2 Stage II Control Technology (Cont.)
Safety Considerations
Implementation of vapor balance systems will
result in a decrease of safety hazards over present refueling
operations as vehicle refueling vapor emissions will no longer
be present around the pumping islands. There is, however, a
possibility of overpressuring a vehicle fuel tank during re-
fueling which could ultimately result in the rupture of a
vehicle fuel tank. This possibility is, however, remote. A
safety relief system in the nozzle would be desirable.
Hydrocarbon leaks may occur in balance systems from
unused nozzles with faulty seals, from vapor return connections,
from external vents on vehicles, and from poor seals at the
nozzle-fill neck interface. Of these leaks only the vapor
return connections present a greater hazard than those found
with current refueling operations as explosive hydrocarbon
mixtures could be released at ground level. Periodic maintenance
inspection of the connections, however, should allow for suitable
control of these leaks.
(2) Compression-Refrigeration Condensation-
Description of System
The major pieces of equipment associated with a
compression-refrigeration-condensation (CRC) vapor recovery
system are:
vapor recovery nozzle,
flexible hose,
vacuum pumps,
underground piping system,
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2.2.2.2 Stage II Control Technology (Cont.)
vapor holder,
two stage compressor, and
refrigeration heat exchanger.
One commercially available system operates by pumping
the collected vapors through a bed of liquid contained within
a surge tank where the vapors become saturated. The purpose of
the surge tank is to ensure that the vapors are saturated be-
fore they are compressed and to even out large volume surges
which may occur during bulk drops. The saturated vapors from
the vapor holder, or surge tank, are compressed and cooled in
a two-stage high pressure refrigeration unit. The condensed
gasoline is returned to the underground storage tank and the
hydrocarbon-free vapors are vented. Figure 2.2-25 presents a
diagram of a compression-refrigeration-condensation vapor re-
covery system.
A carbon canister can be used in this system in place
of the vapor holder and saturator. When the canister is used,
all excess vapors pass through it and the hydrocarbons are
adsorbed while essentially hydrocarbon-free air exits. The
carbon is regnerated by heat assisted vacuum stripping and the
recovered vapors are condensed in the CRC unit.
System Efficiency
A system manufacturer claims the recovery ef-
ficiency across its process unit to be 9470 to 99% with most
units averaging 97% recovery. EPA testing of a CRC vapor re-
covery unit indicated that a processing efficiency of 96% was
achievable if there were no leaks in the storage bladder and if
all equipment was properly operating. The total system efficiency
-142-
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2.2.2.2 Stage II Control Technology (Cont.)
could not be determined, however, due to leaks in the system.
Hydrocarbon emissions were measured at 9.89 gm/gal compared to
mass emissions of about 4 gm/gal normally encountered in balance
systems. The vacuum measured at the nozzle during the EPA test
ranged from 10 to 15 inches of water. This high vacuum coupled
with a relatively good nozzle fit was responsible for the large
amounts of vapor pulled out.
Energy consumption values have been reported as 0.25
and 0.37 kwh/day per 1,000 gallons dispensed per month (EN-184).
Using the larger value (0.37) still results in a positive energy
balance; i.e., the energy recovered (as gasoline) is greater
than the energy consumed. Using these values results in an
equivalent value of hydrocarbon consumption of 1.12 gal/day
and a hydrocarbon recovery of 2.32 gal/day per 1,000 gal per
month dispensed. Net equivalent energy recovery is 1.1 gal/day
per 1,000 gallons per month (AT-047).
System Costs
The capital cost for a CRC processing unit as
reported by a unit manufacturer is $6,000. This price includes
only the vapor holder, vacuum blower, and processing unit.
Costs of the underground piping system, nozzles and fittings,
must be added, which is about $8,000 for retrofitting an existing
station and $4,000 for a new station (VI-023). The yearly main-
tenance and operating costs are reported by a system manufacturer
to be approximately 3% of the capital cost.
System Reliability
The manufacturer reports a 0.98 on-stream factor
for this system. This means one week per year downtime for
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2.2.2.2 Stage II Control Technology (Cont.)
preventative maintenance and repairs. Actual CRC operating
experience, however, has indicated a much lower on-stream factor
During an EPA test of this system an exhaust valve
froze up causing raw liquid to be discharged from the exhaust
vent. It was also determined that the expandable vapor holder
bladder was torn, allowing vapors to leak to the atmosphere.
Improvements are still being made on these systems.
While reliability is low today, it can be expected to improve
with experience and further advances in system design.
Safety Considerations
CRC processing units present several potential
safety hazards.
Explosive conditions in the underground
piping caused by introduction of air at
the nozzle-fill neck interface.
Explosive conditions in the vehicle tank
caused by pulling in air through an ex-
»
ternal vent when no liquid is dispensing.
Leakage of hydrocarbon vapors under high
pressure.
Hazards created by using non-explosion
proof electrical system components.
These safety hazards can be eliminated. UL or Factory
Mutual certification of packaged systems would certainly elimi-
nate many of them. Presumably explosion proof components will
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2.2.2.2 Stage II Control Technology (Cont.)
be required for certification. Nozzle modifications to elimi-
nate the accumulation of excess air in the vehicle tanks and
at the nozzle-fill neck interface can also be anticipated.
Approval of this type system by a certifying laboratory will
not only decrease the safety hazards, but will also increase
the performance reliability.
(3) Carbon Adsorption
Description of System
Hydrocarbon vapors emitted from vehicle refueling
are collected by a vacuum blower and returned via a vapor mani-
fold to the underground tank dispensing the fuel. Excess
vapors are displaced through the vapor manifold to carbon
canisters. These canisters employ activated carbon to adsorb
and store the hydrocarbon vapors.
The canisters would be regenerated offsite (air or
vacuum stripping) at a central location where the vapors would
be processed. The regeneration cycle time of each canister
will depend on many factors, such as gallons throughput, fuel
volatility, and canister size. Figure 2.2-26 is a diagram of
a carbon storage vapor recovery system.
System Efficiency
The adsorption efficiency of a well maintained
carbon adsorption system has been measured as high as 99.7%
(LE-132). Assuming a nozzle collection efficiency of 98%
(VO-032) and regeneration efficiencies of 90%, 95%, and 98%
results in the predicted potential system efficiencies tabu-
lated in Table 2.2-8.
-146-
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-147-
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TABLE 2.2-8
PREDICTED POTENTIAL EFFICIENCY OF A CARBON STORAGE SYSTEM
Assumed
Regeneration Total System Efficiency*
Efficiency Summer Winter
98 96.5 95.7
95 94.8 92.8
90 91.8 88.0
* Efficiencies for systems not returning a volume of vapors
equal to dispensed liquid volume to underground tank would
be lower. A vacuum regulating valve would be necessary to
maintain the low V/L ratios assumed and to prevent "pullout,
(V/L = 1.6 in the summer, 2.0 in the winter). Saturation
of excess air due to liquid vaporization in the under-
ground tank was assumed.
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2.2.2.2 Stage II Control Technology (Cont.)
System Costs
Installation costs for this system will approach
those of a displacement system. Extra costs are for the vacuum
blower, carbon canisters, and associated pipe and fittings.
Installation costs, including labor, are estimated to be $4,400
for a new station, and $6,900 for a retrofit (RE-107).
System Reliability
Due to its simplicity, the reliability of this
system should be relatively high if the system is properly
maintained. Potential problems exist, however. For example,
a carbon canister may become saturated with hydrocarbon vapors,
in which case all collected hydrocarbons will be emitted to the
atmosphere. Saturation of the canisters can be avoided by
regeneration at the proper time.
Safety Considerations
Explosive mixtures in the vapor recovery piping
and vehicle tank are possible hazards with this system. A
properly designed nozzle should, however, greatly reduce the
probability of these hazards occurring.
(4) Oxidation
Description of System(s)
There are two types of oxidation systems used to
eliminate hydrocarbon emissions. They are defined as catalytic
oxidation and thermal oxidation processes. Both employ the same
basic equipment: vapor recovery nozzles, vacuum blowers, piping
-149-
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2.2.2.2 Stage II Control Technology (Cont.)
systems, excess vapor holders, and an oxidation unit. Both
expandable bladder tanks and carbon canisters have been used for
vapor holders.
For regeneration of carbon bed vapor holders, a
vacuum blower pulls air through the canister in a reverse
direction, purging the adsorbed hydrocarbons. The regeneration
gases are then passed to the oxidation units. Both the catalytic
and thermal units add air to the hydrocarbon stream in a con-
trolled amount to support combustion. After adsorbed hydro-
carbons have been removed, the fuel/air mix passing to the
oxidation units becomes leaner. The catalytic unit automatically
shuts off when the temperature drops below a certain level (say
1100°F) and the thermal oxidation unit is automatically shut off,
when combustion is no longer supported. Figures 2.2-27 and
2.2-28 provide diagrams of catalytic and thermal oxidation vapor
recovery units.
System Efficiency
A catalytic oxidation unit was tested as part of
the EPA source testing program conducted in San Diego. The ef-
ficiency across the processing unit itself was measured to be
93.3. The overall processing efficiency, however, was calculated
to be 89.4. The low recovery in this case was due to the intro-
duction of a large amount of excess air into the system while
operating the nozzle-fill neck interface at a very high vacuum
(about 20 inches of water). In addition, relatively poor nozzle
fits which were attributed to a rather bulky modification of the
regular dispensing nozzle precluded obtaining tight seals on
many vehicles. Assuming a nozzle collection efficiency of 98%
for the vehicle emissions, an overall system efficiency of 88.1%
was achieved.
-150-
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-151-
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FIGURE 2.2-28.
SCHEMATIC DIAGRAM OF A
THERMAL OXIDATION UNIT
-152-
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2.2.2.2 Stage II Control Technology (Cont.)
Tests on a thermal oxidation unit have been reported
by the Bay Area APCD (LE-132). The efficiency across the process-
ing portion of that unit was 99%. Assuming a vapor liquid re-
turn ratio (V/L) of 1.6 for summer operations and 2.0 for winter
operations plus a nozzle collection efficiency of 98%, estimated
potential efficiencies for this system were 97.17, for summer
conditions and 96.570 for winter conditions.
It must be noted that these systems recover none of
the vapors adsorbed on the carbon; all collected hydrocarbon
are oxidized to C02 and H20.
Calculations performed by using energy consumption
data from an oxidation unit which adsorbed and combusted all
collected vapors indicated energy consumption for this system to
be 3.83 gal/day per 1,000 gallons per month dispensed (AT-047).
Calculations performed by EPA indicated that there would be a net
production of energy of 1.06 gal/day per 1,000 gallons per month
dispensed if the vapors were returned to the underground tank
and only the excess vap were burned. In this case, 2070
excess vapors were assumed. Another calculation was performed
assuming 407o excess vapors which resulted in a net expected pro-
duction of energy of 0.16 gal/day per 1,000 gallons dispensed
per month Greater than 407o excess vapors will result in a net
consumption of energy.
System Costs
Capital costs reported by a vendor of adsorption-
catalytic oxidation unit are shown below.
-153-
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2.2.2.2 Stage II Control Technology (Cont.)
Station Size Maximum Drop
gal/mo Gallons Cost ($)
12,000 5,000 3,100
12,000 8,400 3,600
70,000 8,400 4,295
100,000 8,400 5,395
These costs included only the processing equipment.
Labor and capital costs of installing the vapor return piping
plus the costs of vapor return nozzles and other fittings must
be added. These costs range from $5,000 to $8,000 for a retro-
fit and $3,000 to $5,000 for a new station (VI-023).
Costs were not available for the thermal oxidation
system.
System Reliability
The major problem experienced in catalytic oxida-
tion units has been catalyst overheating. When this occurs, the
catalyst is usually destroyed. The danger of explosion or fire
is also created by this unstable period. Improved fuel-air
ratio controllers appear to have greatly minimized this problem,
however. During EPA source testing of a catalytic oxidation
unit no major operational problems were experienced.
Safety Considerations
The creation of explosive mixtures in the vehicle
tank and in the underground piping system is a potential safety
hazard with this system. A properly designed vacuum limiting
device should, however, greatly reduce the probability of these
hazards occurring.
-154-
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2.2.2.2 Stage II Control Technology (Cont.)
An additional potential hazard in these systems is
fire in the combustion section of the units. Flame arresters
should require equipment on these units.
(5) Refrigeration-Adsorption
Description of^ System
Commercially available refrigeration vapor recovery
systems are designed to process the excess vapors from the
underground tank. When the system pressure reaches a designated
level (say 3" H20) the refrigeration unit is activated and
vapors are passed across the low temperature cooling coils. This
causes some of the excess vapors to be condensed, reducing the
volume of uncondensed vapors. Condensed product and contracted
vapors are returned to the underground tank.
Under extreme conditions, when large quantities of
excess air are suddenly introduced into the system, the system
pressure may rise above ^ 0" H20 operating level. When the
pressure reaches a maximum of seven inches of water excess vapors
vented through a carbon canister which may be regenerated off-
line after the system pressure -is lowered to its normal operating
level. F'gure 2.2-29 is the schematic diagram of a refrigera-
tion vppor recovery system.
System Efficiency
Evaluation of the vapor recovery efficiency of a
refrigeration system was planned as part of the EPA testing con-
ducted in San Diego. An overall system efficiency could not be
determined because of leaks in the underground piping.
-155-
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-156-
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2.2.2.2 Stage II Control Technology (Cont.)
System Costs
Capital costs of a refrigeration unit provided by
a manufacturer are listed below.
Service Station Capital
Capacity Cost
gal/mo $
10,000 2,500
100,000 3,000
200,000 3,500-3,900
These costs include only the processing unit. Costs of piping
including labor must be added to obtain a total system cost.
Total system costs have been estimated at $12,677 for
a retrofit and $10,177 for a new station. Yearly operating
costs have been estimated at $730 (RE-107).
System Reliability
Refrigeration technology is well established and
has been demonstrated to be reliable. The application of this
technology to service station vapor recovery should present little
or no problems assuming the refrigeration units are given proper
maintenance. One manufacturer reports only three days downtime
on a unit operating for 1% years.
Safety Considerations
The creation of explosive mixtures in the vehicle
tank, in the underground piping system and at electrical connec-
tions are potential safety hazards in this unit. Properly
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2.2.2.2 Stage II Control Technology (Cont.)
designed nozzles and the use of explosion proof equipment should
greatly reduce the magnitude of these hazards.
(6) Gasoline Engine
Description of System
Hydrocarbon vapors are collected from the dispens-
ing nozzle by a vacuum blower and discharged into a vapor mani-
fold. The major portion of the collected vapors are returned to
the underground tank dispensing the gasoline. Excess vapors are
conveyed either to an activated carbon bed or to the carburetor
of a one cylinder, four-cycle engine. The engine and blower are
automatically started when the gasoline dispenser is activated.
Excess vapors generated at rates greater than the engine can
consume bypass the engine and are stored on the carbon bed. The
engine is connected to a load blower which simply serves as a
sink for energy output.
When the nozzle and blower are cut off the engine con-
tinues to operate on hydrocarbons purged from the carbon bed by
reversed air flow. When the carbon bed is fully regenerated
the engine cuts off from lack of fuel. A special carburetor
maintains the fuel air ratio constant. The engine is equipped
with a catalytic muffler to oxidize any trace quantities of hydro-
carbons or carbon monoxide in the exhaust. Figure 2.2-30 is a
schematic of the gasoline vapor recovery system (CL-048).
System Efficiency
Efficiency tests on this system were performed by
San Diego APCD test engineers. Their analysis indicated the ef-
ficiency of the processing unit to be 95% (CL-048). This high
-158-
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efficiency is attributed to the complete oxidation in the engine
and catalytic muffler. Variations in hydrocarbon concentration
entering the recovery system do not affect the system efficiency
since the carburetor maintains a constant fuel-air ratio to the
engine.
Under present operations (utilization of a load blower)
no useful work is performed by Che gasoline engine. The load
blower serves only to circulate air and to keep a load on the
engine. This blower can, of course, be replaced by a generator
or compressor which will recover energy produced by the engine.
System Costs
The following costs have been reported by the
system manufacturer.
Station Size Maximum Drop Capital Cost
Gallons/Day Gallons $
500 4,500 2,600
1,000 9,000 3,000
2,500 9,000 3,560
5,000 9,000 4,550
7,500 9,000 5,000
10,000 9,000
12,000 9,000 7,500
These system costs include a vacuum blower, carbon bed, engine,
full instrumentation and a load blower. Costs of underground
piping and vapor recovery nozzles (5,000 to $8,000 for retrofit
and $3,000 to $5,000 for new stations) must be added to obtain
the total system costs (VI-023).
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2.2.2.2 Stage II Control Technology (Cont.)
System Reliability
As of September, 1974 only four of these systems
have been delivered, thus little information on reliability is
available.
Safety Considerations
Explosive hydrocarbon air mixtures in the vehicle
tank and in the vapor recovery piping is a potential hazard with
this system. Proper nozzle design should greatly reduce the
probability of these hazards occurring.
Vapor ignition from both electrical components and
the engine are further potential hazards. Flame arresters and
explosion proof components should be employed to control this
problem.
(7) Systems Under Development
Several au^ tional recovery units for use in vacuum
assist systems are under development. Prototypes of these
systems are being tested and commercial units are likely to be in
production by 1976. In this section, each of these basic types
of systems will be described.
Compression-Absorption-Adsorption
This system operates by compressing hydrocarbon
vapors to 22.5 psia and passing them through an absorption
column where they are contacted with 0°F gasoline. Air and un-
absorbed hydrocarbons are subsequently vented through a carbon
bed cooled by heat exchange with cold gasoline. The carbon bed
-161-
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2.2.2.2 Stage II Control Technology (Cont.)
is vacuum regenerated, with recycling of the desorbed hydrocarbons
through the absorption unit. Figure 2.2-31 is a schematic of
this type vapor recovery system (EV-013).
The capital cost for this processing unit is projected
to be $5,000 for the largest service stations. Installation
costs must be added to obtain a total system cost.
Compression-Refrigeration-Condensation
A CRC system under development offers a new re-
covery technique. It separates and bottles collected propane
and butane products. The collected hydrocarbon vapors are first
cooled to 60 F in an exchanger where pentanes and heavier fractions
are condensed and returned to the underground product storage
tanks. Uncondensed vapors are next compressed to 125 psig and
again cooled to 60°F where propanes and butanes are condensed
and bottled for sale. The small quantities of methane and
ethanes remaining in the vapor stream are adsorbed in a carbon
bed and air and unabsorbed hydrocarbons are vented from the bed.
For service stations pumping 35,000 to 90,000 gallons
per month, the complete system cost, including nozzles and
piping, is estimated to be $8,000.
Open Refrigeration
This system is in design stage only. Hydrocarbon
vapors generated during refueling are vacuum collected and re-
turned to the underground product storage tank through a common
vapor manifold. Excess vapors are displaced through a refrigera-
tion-condenser unit and cooled to -85°F. The hydrocarbon com-
ponents of the vapor are condensed out and returned to product
storage.
-162-
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This system also utilizes on-site regeneration with
a carbon adsorption system. Vacuum assist is used to return the
collected hydrocarbon vapors to the underground storage tank.
Excess vapors are vented through a carbon canister where the
hydrocarbon vapors are adsorbed. Regeneration is accomplished
by vacuum stripping the off-service carbon canister. The re-
covered hydrocarbons are returned to the underground storage tank
(premium grade) and absorbed into the liquid fuel.
A prototype system has been field tested which demon-
strated an overall efficiency of 98.2% including losses from
vacuum regeneration. Figure 2.2-32 is a schematic of this proto-
type system (WA-147).
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(8) Summary of Systems
Table 2.2-9 is a summary of efficiency ai>. cost
data for each of the vapor recovery systems discussed in this
section.
2.2.2.3 Nozzle Design-Effects on Vapor Recovery
Three design parameters appear dominant in the suc-
cessful operation of a vapor recovery nozzle; the fill neck seal,
the pressures created in both the vehicle tank and the vapor
recovery system, and the nozzle durability and reliability.
E<^ch of these parameters will be discussed individually.
(1) Fill Neck Seal
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neck locations, and the cosmetic treatments of vehicle areas
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-166-
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2.2.2.3 Nozzle Design-Effects on Vapor Recovery (Cont.)
surrounding the fill necks it is unlikely that a single nozzle
will be developed that will insure a tight seal on all vehicles
on the road today. A leaking seal at the fill neck will generally
produce the following effects:
(a) A displacement system will lose hydrocarbon
vapors out the leak. The hydrocarbons col-
lected will be less than those displaced and
the efficiency will be lower.
(b) A vacuum assist system will pull in excess
air through the leak. The volume of air-
hydrocarbon mixture to be processed by the
secondary control device will range from 20
to 100 percent or more of the volume of
liquid dispensed. System efficiencies, if
effected, will be lowered.
The effect of a leak at the nozzle-fill neck inter-
face is significantly greater for a displacement system than a
vacuum assist system. li. vapors lost in a displacement system
are unrecoverable; while the excess air introduced into a vacuum
assist unit will not significantly affect the operation of many
secondarv recovery facilities.
To aid in producing a tight interface seal, nozzle
manufacturers have incorporated the following concepts: ex-
pandable bellows, magnetic disc with flexible boot, hemispherical
nosepiece, conical concentric tube, expanded annulus, bell-
shaped housing, and ball joint flanges (OL-022). One manufacturer
has used modifications to the vehicle fill neck to achieve tight
seals on a fleet of test cars. It is conceivable that even
further nozzle modifications may be utilized in attempting to
obtain a tight seal at the fill-neck interface.
-167-
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2.2.2.3 Nozzle Design-Effects on Vapor Recovery (Cont.)
The issue of nozzle design is definitely unresolved.
Considerations should be given to requiring standardization of
fill necks by the vehicle manufacturers. This could be accom-
plished with vehicles on the road toady by the use of fill neck
adapters.
(2) Reliability
The factors to be considered in assessing the
reliability of vapor recovery nozzles are its durability,
simplicity, ability to prohibit vapor leaks, and dependability.
Simplicity is an important feature for nozzles to be used in
self-service operations. The mechanism affecting the seal at
the fill neck should be easy to activate and should be ef-
fective when hand held.
Nozzle durability is an important function of collec-
tion efficiency. As the vapor recovery components (expandable
bellows, flexible boots, etc.) start to wear out, significant
amounts of vapors may be lost to the atmosphere.
Vapor leaks from unused nozzles are a potential source
of hydrocarbon emissions, especially during an underground tank
drop. Check valves needed to be designed to prohibit these
leaks. Nozzles can also leak in air when not in use. The excess
air inbreathed through a nozzle will lower the vapor collection
efficiency of a system. Designs should eliminate this source of
leaks.
Nozzle dependability refers, in this case, to its
automatic shutoff controls. Vapor recovery nozzles, due to
their extra components, do not generally extend as far into the
fill neck as do conventional nozzles. Consequently, more
-168-
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2.2.2.3 Nozzle Design-Effects on Vapor Recovery (Cont.)
sensitive automatic shutoff mechanisms may need to be designed
to prevent overfills.
(3) Pressure
Vapor recovery nozzles may produce a pressure
effect both in the vehicle tank and in the vapor recovery system
itself. The driving agent for vapor recovery in a displacement
system is a slight negative pressure in the underground piping
system coupled with a positive pressure in the vehicle tank.
The tank pressure "pushes" the vapors into the underground
piping. They are "pulled" into the underground storage tank.
Excess pressure can be built up in the vehicle tank
which normally results in gasoline "spitback." Excess pressure
in a tank can also interfere with the automatic shutoff mechanism
on a nozzle. In an extreme situation, pressures could arise
that would rupture a vehicle tank. Vehicle tank pressure build
up normally results from blockage of the vapor return line.
An apparently sinple and effective means of prohibiting
pressure build up is to eliminate traps in the vapor return line
where condensed liquid can collect and stop the flow of vapors.
Another r thod is to install a pressure relief system in the
nozzle
Maintenance of low resistance in the vapor return line
is advantageous to the recovery efficiency. Check valves which
are necessary to prevent nozzle leaks can increase the resistance
to flow towards the underground storage tank. Care must be taken
in their design to prevent excess pressures from occurring. The
vapor return line through the nozzle should be an effective 3/4"
diameter to help eliminate flow resistance.
-169-
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U.L. approval of vapor recovery nozzles will probably
result in performance specifications for vapor recovery nozzles.
Adherence to performance criteria will eventually result in the
same type of reliability experienced by non-vapor recovery
nozzles.
2.2.3 Bulk Stations
Very few studies have been conducted on bulk station
emission controls, however, research on service station and
terminal control techniques is largely applicable to bulk stations
The two primary emission sources at bulk stations are transfer
operations and tankage. Emissions from transfer operations are
attributed to vapors displaced during the filling of bulk station
storage tanks and the filling of delivery trucks. Tankage emis-
sions are attributed to diurnal breathing losses. The two basic
approaches to controlling these emission sources is straight
vapor balance and vapor balance in conjunction with vapor re-
covery systems.
T.2.3.1 Vapor Balance
The control of transfer losses from bulk stations
centers mainly around vapor balance and bottom loading. Con-
verting to bottom loading and reducing transfer rates will tend
to reduce the generation of gasoline vapors. In Section 2.2.2.1
(Stage I Controls) it is reported that vapor balance systems at
service stations fuel drops achieve an average emission reduc-
tion efficiency of 95% to 96%, with very few efficiencies falling
below 907o. The same efficiency should be possible when applying
that system to bulk station transfer losses.
Bulk station storage tanks are usually truck portable
horizontal or vertical tanks. It is uneconomical to install
-170-
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variable volume vapor storage or floating covers on these tanks
to control breathing losses. One economical solution to breath-
ing losses is the installation of pressure-vacuum vents on the
tanks. Figure 2.2-33 (NI-027) indicates that tankage breathing
losses can be virtually eliminated by using a P-V vent with a
40 oz/in2 (2.5 psig) pressure setting and a reduction of 707o
can be achieved by using a P-V vent with a 16 oz/in2 (1 psig)
pressure setting. Since API tankage is already stressed for
higher working pressures than these, additional tankage costs
would not be incurred.
As pointed out in Section 3.9, air is soluble in gaso-
line. The gasoline delivered to bulk stations should be sub-
saturated with respect to air. Because of this it is expected
that some vapor shrinkage will occur within the tankage as air
is absorbed from the vapor space. This shrinkage further en-
hances the efficiency of the balance system.
2.2.3.2 Vapor Recovery Systems
If the ef f icj-etvy of the balance system proves in-
sufficient, bulk stations can be equipped with vapor recovery
systems. The vapor recovery systems would be installed in con-
junction ,'ith balance systems piping to process only the excess
vapors which the balance system fails to control. Large bulk
stations would employ one of the terminal size vapor recovery
systems outlined in Section 2.2.1, for terminals, and a small
bulk station would employ one of the service station size 'vapor
secondary recovery systems outlined in Section 2.2.2.
2.2.3.3. Cost
No data is available on the cost of installing a
balance system in a new bulk station or on the cost of retrofitting
-171-
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OPERATING PRESSURE RANGE
-172-
-------
existing bulk stations with the balance system. Costs for
terminal vapor recovery systems and for service station vapor
recovery systems are presented in Sections 2.2.1 and 2.2.2,
respectively.
2.2.3.4 Operating Reliability
The operating reliability of the balance system is very
high. It is simple with very few parts to fail. Vapor recovery
systems on the other hand are constructed of complex equipment
and are therefore more subject to failures. Considering the
sophistication of vapor recovery equipment, the lack of motiva-
tion at bulk stations to maintain non-profitable equipment, and
the fact that bulk stations are often situated in areas remote
to repair services, the vapor balance portion is significantly
more reliable than the secondary recovery portion of the systems
described above.
-173-
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2.3 Other Environmental Effects
2.3.1 Impact on Water Pollution
The control of air pollution from gasoline marketing
facilities need not adversely affect water pollution problems
at all. Liquid hydrocarbons removed in terminal secondary
recovery units can be recycled directly to fuel storage. In-
cidence of spillage and runoff to water collection systems is
likely to be lowered in recovery units than in primary gasoline
handling and storage areas.
2.3.2 Impact on Solid Wastes
In all cases, gasoline handling involves liquid and,
to a lesser degree, vapor phases. There are no naturally
occurring solids, nor are there chemical reactions that will
tend to form and precipitate solids. While gasoline liquid
discharged to the sewer can have solvent action on many solids
and liquids, this does not in itself promise to have an impact
on solid wastes.
2.3.3 Energy Considerations
There are two aspects of energy usage .in vapor
recovery units. One is net conservation because of recovered
liquid fuel. The other is energy (primarily electrical)
consumed in operation of secondary recovery units.
-174-
-------
Table 2.3-1 contains a summary of relative energy
conserved or spent at marketing locations for various typical
vapor recoveries. Overall, the energy value of fuel recovered
far outweighs energy consumed in recovery. For a typical ser-
vice station handling 25,000 gallons per month gasoline recover-
ies in the order of 700 gallons per year from the tank trucks
and terminal and 300 to 400 gallons per year refueling can be
realized at the anticipated control levels.
2.4 Advantages/Disadvantages of Various Regulation
Criteria
There are three regulation types which may be imple-
mented for hydrocarbon vapor emission controls. They are:
(1) a percent reduction regulation,
(2) a mass emission regulation, and
(3) an equip^^nt standard regulation.
The relative advantages/disadvantages of each regulation type
will be discussed in this section.
2.4.1 Regulations Based on Percent Reduction
Regulations based on a percent reduction criteria will
require rigorous monitoring procedures to evaluate compliance.
Monitoring procedures must be designed to determine the amount
of vapors emitted to the atmosphere under both controlled and
non-controlled conditions so that a percent reduction can be
calculated.
-175-
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-176-
-------
2.4.1 Regulations Based on Percent Reduction (cont.)
Regulations based on this criteria will require a
vapor recovery system which will produce less emissions during
the winter season than the summer season for a given percentage
recovery. This is because the non-controlled emissions tend to
be greater during the hotter months.
The percent reduction regulation has one advantage.
Monitoring procedures can provide data to support detailed ma-
terial balance calculations. The results of these calculations
can aid in detecting leaks in the vapor recovery system. A
regulation of this type would be applicable to all systems in
the gasoline marketing network.
The major problem in evaluating the percent reduc-
tion of hydrocarbon emissions from a bulk terminal is involved
in measurement of the vapors displaced from the truck as it is
filled. If three products are loaded simultaneously, the
vapor displacement rate can approach 270 CFM. Instruments cap-
able of measuring such a high of a flow rate are not readily
available. They are al^o quite expensive.
The percentage reduction of hydrocarbon vapors result-
ing from \\iderground tank filling operations could require that
all vapors being emitted from the underground tank to both the
truck and the underground tank vent line be monitored. For re-
cent test procedures, it has been assumed that the vapor to
liquid ratio is 1:1 and only the excess vapors emitted from
the underground tank vent have been measured. This is because
monitoring vapors returned to the truck is a difficult measure-
ment.
-177-
-------
2.4.1 Regulations Based on Percent Reduction (cont.)
Service station vehicle refueling operations present
the largest monitoring problem. For both vapor balance systems
and vacuum assist systems no monitoring procedure has yet been
agreed upon. In order to determine the percent reduction of
emissions, uncontrolled emissions must first be defined and
methods for doing this have not been developed.
Questions arise as to the type of test procedure to
be used in evaluating uncontrolled emissions, and whether or
not the uncontrolled emissions will be evaluated on an average
or a car-to-car basis. These questions must be resolved before
this type of regulation can be enforced.
2.4.2 Regulations Based on Mass Emissions
Regulations based on a mass emission criteria will
require a less complicated monitoring procedure than a regula-
tion based on percent reduction. This is because only the
vapors emitted to the atmosphere need be monitored to evaluate
compliance. This assumes, of course, that the system being
monitored has no leaks and that all vapors being emitted to
the atmosphere are being emitted at the location of the monitor-
ing equipment.
Seasonal operations will not affect a regulation based
on a mass emission. This is an advantage in that lower emission
levels will not be required during the winter months when oxidant
levels are low. Regulations based on this criteria would be
applicable to all systems in the gasoline marketing network.
Monitoring bulk terminals for mass emissions can be
relatively simple if it is assumed all displaced vapors are
captured and that the system is leak-free. The off-gas from
the secondary recovery unit would simply be monitored for quantity
and hydrocarbon concentration.
-178-
-------
2.4.2 Regulations Based on Mass Emissions (cont.)
An examination of test data taken at various bulk termi-
nals has indicated, however, that leaks in the transport trucks
may be a significant source of hydrocarbon emissions. Because
of this, complete material balance data may be necessary to eval-
uate compliance with mass emission regulations for bulk terminals,
Service station underground tank filling operations
would be evaluated by monitoring only the excess hydrocarbon
vapors emitted from the tank vent during filling operations.
Again, an assumption of leak-free transfer operations must be
made. All vapor connections can be checked with an explosimeter,
however, to verify the system is leak-free.
Mass emissions from vehicle refueling operations may
be easily determined for a vacuum assist recovery system by
measuring the hydrocarbon emissions from the exhaust line of the
secondary recovery unit. This assumes there is no leakage from
the nozzle-fill neck interface, an assumption that can be chal-
lenged. There is currently no common method of determining the
quantity of emissions from the nozzle-fill neck interface for
vacuum assist systems.
The major source of hydrocarbon emissions from a vapor
balance sv jem is through leakage at the nozzle-fill neck inter-
face. Monitoring methods to determine the quantity of these
leaks are currently being evaluated. If and when a "tight seal"
nozzle is developed, mass emissions may be determined by simply
sonitoring the underground tank vent vapors.
1.4.3 Regulations Based on Equipment Standards
The main advantage to a regulation based on equipment
standards is the virtual elimination of compliance monitoring.
Compliance could be achieved through only periodic inspections of
-179-
-------
2.4.3 Regulations Based on Equipment Standards (cont.)
vapor recovery facilities to check equipment for proper operation.
Detailed designs of each system would, however, probably need
to be approved by regulatory personnel.
Equipment specifications for secondary recovery systems
would not be practical due to the variety of processing opera-
tions which may be employed in the recovery of hydrocarbon vapors.
A regulation of this type would, therefore, not be practical as
a method of controlling emissions from bulk terminals and service
stations employing vacuum assist recovery systems.
Regulations'based on equipment specifications can, how-
ever, be an effective method of controlling hydrocarbon emissions
from vehicle refueling operations when a vapor balance recovery
system is employed and from underground tank filling operations.
In both cases, vapor recovery operations consist primarily of
containing the displaced vapors. Neither operation employs pro-
cessing equipment to recover vapors on-site; only vapor connec-
tors and transfer piping are used in the recovery operations.
Equipment specifications for these connectors and piping is
feasible as a method of insuring that a system will be capable of
collecting the vapors in a proper manner.
Leak tests should be performed on these systems. Once
a system is leak-free, periodic inspections of the equipment
should be satisfactory for assuring its proper operation.
-180-
-------
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NA-171 National Petroleum News, Fact Book, Mid - May 1973, N.Y.,
McGraw-Hill, 1973.
NE-069 Nelson, A.H., "Industry Experience Shows Internal Floating Covers
Score High", Oil Gas J. 13 Sept 1973.
NE-070 "New Effective Low-Cost Seal", OU Gas. J^_ .18. Oc_t. 1965, 97.
-192-
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NI-026 Nichols, Richard A. , Comparison of API and Exxon Fue 1 Model,
Contract No. 68-02-1311, Irvine, Ca., Parker-Hannifin, 1973.
NI-027 Nichols, Richard A., Control of Evaporation Losses in Gasoline
Marketing Operations, Irvin, Ca., Parker - Hannifin.
NI-028 Nichols, Richard A., Hydrocarbon Emission Sources at Service Sta-
tions, EPA 68-02-1311, Irvine, Ca., Parker - Hannifin, 1973.
NI-029 Nichols, Richard A., "Hydrocarbon—Vapor Recovery", Chem. En%.
80(6), 85 (1973).
NI-030 Nichols, R.A. and Lanson Le, Vapor Transfer Considerations Dur-
ing Fuel Drops at Service Stations, Contract No. 68-02-1311,
Irvine, Ca., Parker - Hannifin, 1973.
NI-033 Nichols, Richard A., Unit Recovery Relative Efficiency, Irvin,
Ca., Parker - Hannifin.
NI-034 Nichols, Richard A., Private Communication, Parker - Hannifin,
27 Sept. 1974.
OL-017 Olson Laboratories, Research Proposal Brief. Vehicle Refueling
Emiss"1' ons - Survey of Available Equipment, Anaheim, Ca. , 1974.
OL-018 Olson Labs., Inc., Control of Refueling Emissions with an Acti-
vated Carbon Canister on the Vehicle - Performance and Cost
Effectiveness Analyses, Project EF-14, Int. Rept, Anaheim, Ca.,
1973.
OL-022 Olson Laboratories, Inc., A Survey of Service Station Vapor Control
Systems and Equipment, Interim Report, Preliminary Draft, API
Project EF-14, Anaheim, Ca., 1974.
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PA-138 Parker - Hannifin, Systems Div., Proposal for Vehicle Refuel-
ing Emissions - Survey of Available Equipment, Irvine,Ca., 1974.
PE-090 Percy, Allan W., Report to the Marketins Facilities Subcommittee
of Operations and Engineering Committee, Div. of Marketing,
API, Subject: EF-14, Los Angeles, Ca., Union Oil, 1973.
PE-101 Perardi, T.E., Results of Source Test No. 74158; Gasoline
Vapor Control System, Shell Service Station, Concord, California,
San Francisco, Ca., Bay Area APCD Source Test Section, 1974.
PI-040 Pitts, James N., Jr., "Environmental Appraisal: Oxidants, Hydro-
carbons, and Oxides of Nitrogen", J_. APCA 19(5) , 658 (1969).
PO-100 Potter, G.C. and W.E. McDonald, Hydrocarbon Emission Control at
Service Stations, Houston, Tx., Exxon Co., U.S.A., 1974.
RE-067 "Restriction of Emission. Mineral-Oil Refineries", Translated
from German by Israel Program for Scientific Translations, Verein
Deutscher Ingenieure VDI 2440, 1-9 (1967).
RE-107 Refinery Management Services Co., Cost Effectiveness of Methods
to Control Vehicle Refueling Emissions, API Project EF-14, Phase
1 Interim Report, Pasadena, Ca., 1973.
RO-102 Ross, R.D., Air Pollution and Industry. Van Nostrand Reinhold
Environmental Engineering Series, N.Y., Van Nostrand Reinhold,
1972.
SA-121 Saenz, Oscar, Jr., et al., Measurement of Non-Methane Hydrocar-
bons. APTD-0905, PB 205-893, Houston, Tx., Southwest Research
Inst., 1971.
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SA-128 Saltzman, Bernard E., Wm. R. Burg, and Gopalakrishnan Ramaswamy,
"Performance of Permeation Tubes as Standard Gas Sources", Env.
Sci. Tech. 5_(11), 1121 (1971).
SA-129 San Diego Co. APCD, Analysis of_ the Displacement System,
San Diego, Ca., 1974.
SA-130 San Diego County, APCD,"Presentation of Air Pollution Control Rules
and Vapor Recovery Systems", El Cortez Hotel, San Diego, Ca.,
7 Feb. 1974, San Diego Country APCD Index of Information,
Vol. 1.
SC-167 Scott Research Labs., Investigation of Passenger Car Refueling
Losses, Contract No. CPA 22-69-68, San Bernadino, Ca., Sept.
1972.
SC-184 Schwartz, F.G., Storage Stability of Gasoline. Development
of a_ Stability Prediction Method and Studies of Gasoline Compo-
sition and Component Reactivity, Bull 660, Washington, D.C., 1972.
SC-186 Scott Research Labs., °erformance of Service Station Vapor
Control Concepts, API Project EF-14, Phase 2, Interim Report
CEA-8, San Bernadino, Ca., 1974.
SH-121 Shell Oil, The National Energy Outlook, Houston, Texas, 1973.
SH-137 Shelton, Ella Mae, Motor Gasolines, Winter 1971-72, Petroleum
Products Survey No. 75, Washington, D.C., Bureau of Mines.
SH-138 Shelton, Ella Mae, Motor Gasolines, Summer 1973, Petroleum Pro"
ducts Survey No. 83> Washington, D.C., Bureau of Mines.
SH-139 "Shape of Tank Can Affect Amount of Heat Absorbed from the Sun",
Oil Gas j;. 18_ Dec. 1967, 101.
-195-
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SO-063 Society of Automotive Engineers, Inc., Preprint, "SAE Recommended
Practice-SAE J 285: Gasoline Dispenser Nozzle Spouts", N.Y.,
1973.
ST-185 "State Projections of Income, Employment, and Population to
1990", Survey of Current Business 54(4), 19 (L974).
ST-187 Standard Oil Co. of California, The 'Displacement' System: An
Effective Method of Controlling Hydrocarbon Losses at Service
Stations, Revised, San Francisco, Ca., 1973.
SU-049 Survey of Energy Consumption Projections, 92nd Congress, 2nd
Session, Serial No. 92-19, Washington, GPO, 1972.
TA-057 "Tank-Emission Limits Set by EPA", NPN Oc_t. 1973, 84.
TR-037 TRW, Inc., Transportation Control Strategy Development for the
Greater Houston Area, EPA Contract No. 68-02-0048, Redondo Beach,
Ca., 1972.
TR-042 TRW, Inc., Transportation and Environmental Operations, Photo-
chemical Oxidant Control Strategy Development for Critical Texas
Air Quality Control Regions, Contract No. 68-02-0048, Redondo
Beach, Ca., 1973.
TR-043 TRW, Inc., Transportation and Environmental Operations, A Trans-
portation Control Strategy for the Phoenix - Tucson Air Quality
Area, EPA 68-02-0048, APTD 1369, Redondo Beach, Ca., 1973.
TR-044 TRW, Inc., Transportation and Environmental Operations, Prediction
of the Effects of Transportation Controls on Air Quality in
Major Metropolitan Areas, EPA 68-02-0048, APTD-1363, Mclean, Va. ,
1972.
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US-031 U.S. Dept. of Commerce, Bureau of the Census, 1967 Census of
Business, Vol. Ill, Wholesale Trade Subject Reports, Washington,
GPO, 1971.
VA-084 "Vapor-Recovery Equipment: What's Required hy States", Reprint,
National Petroleum News 1973.
VE-032 Vehicle Refueling Emissions Seminar, Proceedings, Anaheim, Ca.,
D_ec. 1973, Washington, B.C., API, 1974.
VI-019 Vincent, Edwin J., Private Communication, EPA, 1974.
VI-020 Vincent, Edwin, J., Private Communication, EPA, 1974.
VT-023 Vincent, Edwin, J., Private Communication, EPA, 1975.
VO-031 Vong, Richard J., Private Communication, EPA, 1974.
VO-032 Vong, Richard J., Private Communication, EPA, 30 Oct. 1974.
WA-086 Walters, R.M., "How < Urban Refinery Meets Air Pollution Require-
ments", CEP 68.(11), 85 (1972).
WA-123 Walker, B.C., Demonstration of Reduced Hydrocarbon Emissions
from ' isoline Loading Terminals, Contract No. 68-02-1314, Whiting,
Intl. , 1973.
WA-124 Walsh, Robert T., Private Communication, EPA, 29 April 1974.
WA-142 Walsh, Robert T. and Richard Kozlowski, Private Communication, EPA,
1974.
WA-143 Walsh, Robert T., Private Communication, EPA, 9 Sept. 1974.
WA-144 Walsh, Robert T., Private Communication, EPA, June 1974.
-197-
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WA-147 Walsh, Robert T., Private Communication, EPA, 23 Oct. 1974.
WE-111 West Coast Technical Service, Inc., Report of Lab Analyses
of Vapors from Gasoline Marketing Operations, San Gabriel, Ca.,
1973.
WI-100 Williams, F.A., et al., Technical Review and Evaluation of
Vapor Control Systems, La Jolla, Ca., Univ. Calif, at San
Diego, Dept. Applied Mechanics and Engineering Sciences, March
1974.
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Equipment Manufacturers' Brochures and Specifications
Chicago Bridge and Iron Co., Oak Brook, Illinois
Hortondome roof, vaporsphere, and vapor tank.
Edwards Engineering Co., Pompton Plains, N.J.
Hydrocarbon vapor recovery unit.
Emco-Wheaton, Inc., Conneaut, Ohio
Loading arm assemblies.
Niagara B 4000 Marine loading arms.
Transfer p_f gasoline vapors in petroleum marketing
operations. Revised. Catalog EF 10/72. (1973)
Vapor recovery with bottom loading.
Environics, Inc., Huntington Beach, California
Vapox vapor disposal units. (1973)
EVC Corporation, Rolling Hills Estate, California
Summary of performance evaluation, EVC vapor recovery
system.
Gasoline vapor recovery systems; design and development
Gulf Environmental Systems Co., San Diego, California
CRC vapor recovery systems.
CRC vapor recovery systems: terms of sale and
specifications.
GESCO systems.
Hydrotech Engineering, Inc., Tulsa, Oklahoma
Vapor recovery systems.
-199-
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Ingersoll-Rand, Southwest Industries Division
Gasoline vapor recovery systems.
Proposal for a southwest industries gasoline vapor
recovery system, unit ~1_.
Intermark Industries, Inc., Anaheim, California
Narrative description of the Intermark vapor recovery
system - models Mark I, Mark II, and Mark III.
Narrative description of_ the Intermark vapor recovery
nozzle adapter.
Fuel economy of vapor recovery.
OPW Division, Dover Corp., Cincinnati, Ohio
Bottom loading and tank equipment. Catalog TTE (1971).
V-63-F and V-63-FT vapor recovery loaders. H-5970-PA (1972)
V-63-FS vapor recovery loader. H-7838-PA (1971).
Service station vapor recovery system. Catalog SVR (1972).
Parker-Hannifin, Fueling Division, Irvine, California
Now...provides for vapor collection, tight fill and
top loading.
Parker vapor recovery system maintenance record.
Compressor safety.
Petroleum handling systems and components.
Water problems in vapor recovery systems.
Saturator-compressor-vapor holder safety.
Process Products, Inc., Gardena, California
Vapor-savor gasoline station vapor recovery system.
Vapor-savor installation instructions.
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Rheem Superior, Houston, Texas
Special operating data proposed to comply with the 90%
recovery required by Philadelphia under all conditions
Vaporex, Anaheim, California
Introduction to the Vaporex system.
Total on-line vapor recovery systems.
Vaportrol vapor recovery system.
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TECHNICAL REPORT I. \T
' read Instri.ctums on the reverst .'n 'ore
^ tint. >
1 -iLPORT NO.
EPA-450/3-75-046-3
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
A Study of Vapor Control Methods for Gasoline
Marketing Operations
Volume I - Industry Survey and Control Techniques
5. REPORT DATE
April 1975
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
C. E. Burklin, E. C. Cavanaugh,
J. C. Dickerman, and S. R. Fernandes
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Radian Corporation
8500 Shoal Creek Boulevard
P. 0. Box 9948
Austin, Texas 78766
10. PROGRAM ELEMENT NO,
11. CONTRACT/GRANT NO.
No. 68-02-1319
12 SPONSORING AGENCY NAME AND ADDRESS
U. S. Environmental Protection Agency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final Report
14. SPONSORING AGENCY CODE
It SUPPLEMENTARY NOTES
16. ABSTRACT
Background information is given on the size and extent of the gasoline
marketing industry and the magnitude of hydrocarbon vapor emissions. The
principal sources of emissions, tank truck filling at bulk terminals, service
station storage tank filling and vehicle refueling are characterized. Vapor
control techniques for bulk terminals are described: compression, refrigeration,
absorption, adsorption, incineration, and combinations of these techniques.
The two types of control systems for service stations are evaluated, vapor
balance systems and vacuum assist/secondary processing systems. Test data are
given.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Gasoline Service Stations
Gasoline Bulk Terminals
Vapor Processing
Vapor Balancing
Vapor Recovery
Air Pollution Control
Stationary Sources/
Mobile Sources
Organic Vapors
IS. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
211
20. SECURITY CLASS (This page)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
202
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