&EPA
United States
Environmental Protection
Agency .
Research antyDevelopment
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
EPA-600/S7-81-121 Sept 1981
Project Summary
Control of Hydrocarbon
Emissions from Gasoline
Loading by Refrigeration
Systems
W. Battye, P. Brown, D, Misenheimer, and F. Seufert
The capabilities of refrigeration
systems operated at three tempera-
tures to control volatile organic
compound (VOC) emissions from
truck loading at bulk gasoline terminals
were investigated in this study. Elec-
tricity requirements and relative costs
associated with systems operating at
each temperature were calculated.
Achievable VOC emission rates
were calculated for refrigeration sys-
tems cooling various gasoline/air
mixtures to temperatures of -62°C (-
80°F). -73°C |-100°F), and -84°C (-
120°F) by estimating vapor-liquid
equilibrium compositions for VOC/air
mixtures. Equilibrium compositions
were estimated using a computer
simulation program and the Soave-
Redlich-Kwong and Peng-Robinson
methods of predicting thermodynamic
properties of mixtures. Emission rates
were calculated for inlet streams
containing vapors from low- and high-
volatility gasolines, at concentrations
of 15, 30, and 50 percent by volume
(22.5, 45, and 75 percent measured
as propane). Predicted VOC emission
rates for systems cooling various inlet
streams to -62°C ranged from 48 to
59 mg VOC/I of gasoline loaded.
Predicted VOC emissions were 21 to
28 mg/l loaded for systems operating
at -73°C and 8.7 to 12 mg/l loaded
for systems operating at -84°C.
Compressor electrical requirements
and relative capital costs for systems
operating at the above temperatures
were estimated for model systems
using the results of the computer
simulation. Compressor electricity
requirements ranged from 0.11 to
0.45 Whr/l loaded depending upon
the inlet VOC concentration and the
outlet temperature. The electricity
requirement to cool vapors to -84°C
was estimated to be 54 to 77 percent
greater than the requirement to cool
vapors to -62°C, depending on the
organic content of the inlet stream.
The electricity requirement to cool
vapors to -73 °C is estimated to be 23
to 36 percent greater than to cool
vapors to -62°C. The capital cost to
build a system designed to cool vapors
to -84°C is estimated to be about 9
percent higher than the capital cost to
build a system designed to operate at
-73°C, which is estimated to be about
12 percent higher than the cost to
build a system designed to operate at
-62°C.
. This Project Summary was devel-
oped by EPA's Industrial Environmen-
tal Research Laboratory. Research
Triangle Park. NC, to announce key
findings of the research project that is
fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
The primary objective of this study
was to investigate the capabilities of
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refrigeration systems operated at
various temperatures to control volatile
organic compound emissionsfrom truck
loading at bulk gasoline terminals. A
secondary objective was to estimat&the
electricity requirements and the relative
capital costs of systems operated at
various temperatures.
Achievable emission rates for refrig-
eration systems were calculated by
estimating vapor-liquid equilibrium
compositions for hydrocarbon/air mix-
tures at three system operating tem-
peratures: -62°C, -73°C, and -84°C.
Equilibrium compositions were deter-
mined using a computer simulation
program and the Soave-Redlich-Kwong
and Peng-Robinson methods of pre-
dicting the thermodynamic properties of
mixtures and mixture components.
These methods were also used to
predict the amount of heat removal
required to cool hydrocarbon/air mix-
tures to the three system operating
temperatures. Model refrigeration
systems were designed based on the
predicted heat removal requirements.
Electricity requirements and relative
capital costs were estimated for the
model systems.
Volatile organic compounds (VOC) are
emitted from bulk gasoline terminals as
a result of the displacement of gasoline-
laden vapors from trucks during truck
loading. These emissions are generally
controlled by ducting the displaced
vapor—a mixture of air and hydro-
carbons—to a system which removes
the hydrocarbons. One of the techniques
which can be used to control these
emissions is refrigeration. In refrigera-
tion systems, the gasoline-laden air is
cooled to cryogenic temperatures in
order to condense the gasoline vapors.
Refrigeration systems currently in
use to control gasoline vapor emissions
operate at temperatures between -46°C
and -84°C. Emissionsfrom refrigeration
systems have been tested and range
from 30 to 130 mg/l of vapor entering
the refrigeration control system. Test
data are not available to accurately
determine the relationship between
emissions from refrigeration systems
and system operating temperature, or
other parameters.
In this study the emission reduction
capabilities and electricity requirements
of refrigeration systems used to control
VOC emissions from gasoline terminals
were determined as functions of the
refrigeration system operating temper-
ature and the concentration of hydro-
carbons entering the' refrigeration
system. In addition, relative capital
costs were estimated for refrigeration
systems designed to operate at different
temperatures.
Discussion and Procedure
Achievable VOC emission rates were
calculated for systems cooling various
gasoline vapor/air mixtures to temper-
atures of -62°C, -73°C, and -84°C. The
control systems studied would first cool
the mixtures to 4.4°C in a precooler in
order to remove most of the moisture
present. Vapors from the precooler
would then be cooled to -62°C, -73°C,
or -84°C in the main condenser.
Calculations of controlled emission
rates and electricity requirements were
performed for inlet streams containing
typical low- and high-volatility gasoline
vapors in concentrations of 15, 30, and
50 percent by volume.
The lowest achievable emission rate
for refrigeration to a given temperature
occurs when the vapor and liquid
streams leaving the main condenser are
at thermodynamic equilibrium. Thus,
thelowest achievable emission rate for
a given operating temperature can be
calculated by determining the equilibrium
composition of the vapor phase at that
temperature. Equilibrium compositions
were estimated using a computer simu-
lation program and the Soave-Redlich-
Kwong and Peng-Robinson methods of
predicting thermodynamic properties of
mixtures. Heat removal requirements to
cool gasoline-laden vapors to cryogenic
temperatures were also estimated
using these methods. The predicted
heat removal requirements were used
to design model refrigeration systems,
which are parametric descriptions of
refrigeration systems including equip-
ment sizes, and refrigerant and heat
flow rates. The model refrigeration
systems were used to estimate electricity
requirements to cool the inlet vapor
mixtures under study to cryogenic
temperatures. The costs of components
were estimated for the model systems
designed to treat mixtures containing
30 percent by volume hydrocarbons, in
order to estimate the relative capital
costs of systems designed to cool vapors
to various temperatures.
Results
Achievable emission rates were
calculated in terms of the mass of VOC
emissions per unit volume of vapor
entering the control system. Assuming
that the trucks being loaded and the
ducts carrying vapors from the trucks to
the control system are vapor-tight, the
volume of vapor entering the control
system is equal to the volume of
gasoline loaded. The calculated emis-
sion rates can be expressed in terms of
mg VOC/I gasoline loaded. Note that
VOCs are defined by EPA to include any
organic compound which participates in
atmospheric photochemical reactions.
With the exception of methane and
ethane, all hydrocarbons present in
gasoline vapors are considered VOCs.
Thus, VOC emission rates calculated in
this study are emission rates of non-
methane non-ethane hydrocarbons.
Figure 1 illustrates the dependence of
VOC emissions on condenser outlet
temperature for inlet air streams
containing low-volatility gasoline vapors
in concentrations of 15, 30, and 50
percent by volume. Figure 2 illustrates
the dependence of VOC emissions on
condenser outlet temperature for inlet
streams containing 15, 30 and 50
percent by volume high-volatility gas-
oline vapors. Low-volatility gasolines
are generally loaded in the summer, and
high-volatility gasojines are generally
loaded in the winter. Therefore, for inlet
streams containing low-volatility vapors,
emissions were calculated assuming an'
inlet temperature of 27°C; and for inlet
streams with high-volatility gasoline
vapors, emissions were calculated
assuming an inlet temperature of 4.4°C.
Predicted VOC emission rates for
systems cooling various inlet streams to
-62°C ranged from 48 to 59 mg VOC/I
of gasoline loaded, depending on the
percentage of hydrocarbons in the inlet
stream. Predicted VOC emissions were
21 to 28 mg/l loaded for systems
operating at -73°C and 8.7 to 12 mg/l
loaded for systems operating at -84°C.
As shown in Figures 1 and 2, the
logarithm of the VOC emission rate is
approximately proportional to the re-
ciprocal of the system operating terrf-
perature for a given set of inlet
conditions.
Predicted compressor electricity
requirements ranged from 0.11 to 0.45
Whr/l loaded depending on the inlet
VOC concentration and the outlet
temperature. The electricity required to
cool vapors to -84°C is estimated to be
54 to 77 percent greater than that
required to cool vapors to -62°C,
depending on the hydrocarbon content
of the inlet stream. The electricity
requirement to cool vapors to -73°C is
estimated to be 23 to 36 percent greater.
than that to cool vapors to -62°C. ThJI
capital cost to build a system designed
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70
-^ 60
"I
% 50
i 40
30
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W. Battye, P. Brown, D. Misenheimer, andF. Seufert are with GCA/Technology
Division. 500 Eastowne Drive, Chapel Hi/I, NC 27514.
Samuel L. Rakes is the EPA Project Officer fsee below).
The complete report, entitled "Control of Hydrocarbon Emissions from Gasoline
Loading by Refrigeration Systems," (Order No. PB 81-240 335; Cost: $8.OO,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
U S GOVERNMENT PRINTING OFFICE. 1981 — 757-012/7357
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
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