EPA 909/9-81-004
ANALYSIS OF POTENTIAL METHODS
TO DETERMINE VOLATILITIES OF
HEAVY CRUDE OILS
DECEMBER 1981
FINAL REPORT
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U. S. ENVIRONMENTAL PROTECTION AGENCY
REGION IX
215 FREMONT STREET
SAN FRANCISCO, CALIFORNIA 94105
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EPA 909/9-81-004
December 1981
ANALYSIS OF POTENTIAL METHODS
TO DETERMINE VOLATILITIES
OF HEAVY CRUDE OILS
by:
Robert J. Bryan
ENGINEERING-SCIENCE
Contract No. 68-02-3509
Work Assignment No. 11
Project Officer:
Don Harvey
Prepared for:
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION IX
215 FREMONT STREET
SAN FRANCISCO, CALIFORNIA 94105
December 1981
ENGINEERING-SCIENCE
125 West Huntington Drive
Arcadia, California 91006
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DISCLAIMER
This report has been reviewed by the U.S. Environmental Protection
Agency, Region IX, and approved for publication. Approval does not
signify that the contents necessarily reflect the views and policies
of the U.S. Environmental Protection Agency, nor does mention of trade
names or commercial products constitute endorsement or recommendation
for use.
ii
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CONTENTS
Figures iv
Tables v
1. Introduction 1
2. Background 2
3. Approach 10
4. Discussion 11
Alternative Methods for Crude Oil Volatility
Cons idered 12
5. Conclusions and Recommendations 19
References 22
Non-Referenced Contacts 22
Appendices
A. Santa Barbara Modified RVF Approach A-l
B. California Air Resources Board Vapor Composition Method....B-l
C. Chevron Vapor Composition Method C-l
D. Evaporation Method D-l
E. Equipment Costs E-l
Report Documentation Page
iii
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FIGURES
Number Page
1 Extrapolation of RVP versus TVP nomograph from API 2518 5
r p "i
2 Hydrocarbon vapor concentration versus L14.7-P-I 0.68
for crude oil standing storage tanks 6
3 Emission concentration versus crude oil RVP, standing
storage tanks 7
4 Emission concentration versus crude oil TVP, standing
storage tanks 8
TABLES
Measures of Heavy Crude Oil Volatility Versus
Evaluation Criteria 18
iv
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SECTION 1
INTRODUCTION
This project, titled "Analysis of Potential Methods to Determine
the Volatilities of Heavy Crude Oils", was conducted under Contract No.
68-02-3509, Work Assignment No. 11.
The purpose of the project was to screen alternatives for measuring
the vapor pressure of heavy crude oils considering the cost of method
development, equipment, and laboratory costs for using the developed
method, repeatability, and the degree of conformity with API Nomograph
results. Four alternatives including (1) extrapolation of the API
nomograph, (2) measuring equilibrium vapor pressure, (3) using the Reid
Method with modifications, and (4) measuring weight loss with time were
to be initially considered. A method for measuring evaporation loss
similar to (4) above was also to be studied for use in calculating
evaporative emissions for open tanks and basins. Several other
approaches to determining heavy crude oil vapor pressure were added to
the list for preliminary evaluation.
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SECTION 2
BACKGROUND
Compliance with the Clean Air Act Amendments of 1977 require that
a number of states, including California, prepare and submit by July 1,
1982 a plan detailing the control measures which will be implemented to
achieve attainment of the NAAQS for ozone by 1987. All such plans will
depend heavily on comprehensive inventories of volatile organic compounds
(VOCs) as a basis for determining the level of control of such emissions
needed to attain compliance with the standard.
Compilation of an accurate VOC inventory will be necessary, but
especially difficult, for those counties in California in which a
substantial portion of such emissions emanates from crude oil production
and associated storage and transfer. Determination of emissions from
these sources requires the measurement of the volatility of the crude
oil at the source temperature. This measurement in turn is dependent
upon a knowledge of the "true vapor pressure" (TVP) of the crude oil.
Unfortunately, methods currently available for making such
measurements (principally the Reid Vapor Pressure [RVP] method) are
not satisfactory for measuring the TVP of crude oil because its normal
source temperature is usually too high and its RVP too low. Therefore,
estimates of emissions from sources associated with the production of
crude oil are of questionable accuracy. Further, it is not possible to
handle some high viscosity crudes at temperatures specified in the ASTM
Method for RVP.
Several examples are cited to illustrate the problems associated
with determining the vapor pressure of heavy crude oil or with use of
vapor pressures to predict hydrocarbon emission losses from storage and
trans fe r.
(1) In Kern County, California, an assumption is made for use in
preparing the 1982 SIP revisions that all crude oil has the
same vapor pressure as kerosene (reference personal communica-
tion between Larry Landis, Kern County APCD, and Stephanie
Fullmer, Engineering-Science, Inc., April 20, 1981) While
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this may be useful for preparing countywide emission inven-
tory estimates, the assumption is based upon a limited number
of vapor pressure-temperature plots. Further, there is a
weakness in comparing a narrow boiling range product such as
kerosene with unprocessed crude oils.
(2) The Second Edition of API Publication 2517, "Evaporation Loss
from External Floating-Roof Tanks"1), discusses the devel-
opment of a product factor for use in their standing storage
loss equation. The basis for this factor was data from
pilot tank tests conducted with an octane/propane mixture,
gasoline, and crude oil. It was found that after normalizing
for differences in true vapor pressure and vapor molecular
weight, crude oil losses were significantly lower than the
octane/propane losses under the same conditions of seal
configuration and wind speed. This was attributed to evapor-
ation at non-equilibrium conditions, caused by the slower
rate of migration of light ends from the bulk liquid to the
liquid surface in crude oil as compared to the octane/propane
mixture because the light ends migration rate is strongly
viscosity dependent.
The average of crude oil losses to octane/propane losses was
0.4, with a range of 0.3 to 0.6. Therefore, it is obvious
that factors other than the ability to obtain a reliable
vapor pressure method for heavy crude oil must be considered
in developing emission estimate procedures.
(3) Data on crude oil vapor pressures, hydrocarbon emissions during
marine loading of crude oils, and composition of emissions were
reported in a study conducted by Chevron Research Company
for the Western Oil and Gas Association.2) Vapor pressures
were calculated from liquid compositional data using various
vapor-equilibrium correlation procedures. In all cases
these vapor pressures were higher than those predicted by
the RVP-TVP correlation of API Bulletin 2514, "Hydrocarbon
Emissions from Marine Vessel Loading of Gasolines", 1976.
After recalculating on a methane and ethane free basis, the
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vapor pressures obtained from vapor-liquid equilibrium proce-
dures compared favorably with the API correlation of TVP
with RVP for the total (methane and heavier) crude oil.
This suggests that substantial amounts of light ends are
lost during the sampling and analysis of crude oil for vapor
pressure by the RVP method even when substantial care is taken.
Also, the RVP procedure tends to slightly de-emphasize the
influence of methane and ethane.
The emissions composition data obtained in the WOGA marine
loading of crude oil study are also of interest. On the
average, propane and heavier components comprised 95 weight
percent of the hydrocarbon emissions. On a volume basis,
the propane and components account for about 85 percent of
the emissions. Therefore, volumetric vapor concentrations
and thus vapor pressure can be significantly affected by
methane and ethane content of crude oil. It follows that
the value of vapor pressure as a predictor of emissions on a
mass basis can be impaired by unknown variability in light
ends because the mass concentration of hydrocarbon vapors
present over crude oil is much less affected by light ends
than is the volumetric concentration.
(4) Several studies in recent years have shown that hydrocarbon
vapor concentration is not well correlated with various
measures of crude oil vapor pressure. Engineering-Science
(ES), in a study for the Western Oil and Gas Association^,
prepared an extrapolated version of the API TVP-RVP nomograph
(Figure 1). This nomograph was used to determine TVP (accor-
ding to the API terminology). The RVPs, TVPs, and a function
of vapor pressure used in API Bulletin 2518 for prediction
of breathing losses in fixed-roof tanks were all plotted
versus measured hydrocarbon vapor concentrations. These
plots are reproduced in Figures 2, 3, and 4. It is interes-
ting to note while there is a good deal of scatter in all
the plots, the RVP shows the highest correlation coefficient
of the three parameters considered. It should be recognized,
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TRUE VAPOR PRESSURE IN POUNDS PER SQUARE INCH ABSOLUTE
|l I I I | I I I I |l|l|l|l| I |I | I | I | I | I |llll|llI I | I I I I Jill I| I I I I | I I I I I
REID VAPOR PRESSURE
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TEMPERATURE IN DEGREES FAHRENHEIT ~^
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B 4. Emission concentration versus crude oil TVP, standing storage tanks.
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however, that there are a number of factors other than vapor
pressure which influence vapor concentration in a tank head
space. These include approach to equilibrium, presence of
leaks, and immediate tank history as to product characteristics.
(5) A special problem exists with unstabilized crudes. Crude oil
from wells can be subjected to a number of treatments to
separate gas, water, and contaminants from the crude oil.
Operations are performed in oil/gas separators, heater
treaters, free water knockout tanks, and wash tanks to name
several of these process vessels. Some of these tanks may be
pressurized, others are at or close to atmosphere pressures.
In some situations the crude oil is hot enough for flashing
to occur. In oil field tank operations conducted prior to
custody transfer (the last transfer from the field to a means
of transportation), then, it is quite possible for the
concentration of light ends, and thus the vapor pressure, to
change quite rapidly along the processing steps, and even with
time in any given tank. This obviously complicates the
problem of collecting representative crude oil samples.
Further, when the crude oil is held at temperatures sig-
nificantly above ambient temperature and turn-over is rapid,
there exists a significant potential for temperature strati-
fication in the tank, thus raising a question as to what
temperature is to be selected for reporting true vapor pressure
or other measure of volatility.
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SECTION 3
APPROACH
This project was based upon'review of literature and direct contact
with knowledgeable persons in the field. No laboratory or field work
was conducted. The project was divided into two phases. Phase I
covered the screening of alternative methods for measuring the vola-
tilities of heavy crude oils other than the four approaches specified
in the Work Assignment. The principal alternatives reviewed during
Phase I were methods which had been the subject of a staff study by
the California Air Resources Board. Verbal suggestions were obtained
from several petroleum industry sources which generally addressed the
need for some technique to account for the influence of methane and
ethane when measuring vapor pressure of crude oils. A report was
submitted on the Phase I effort. Following submission of this report,
a specific written procedure was submitted by Chevron Research Company
for the determination of vapor composition and vapor pressure of heavy
crude oils. This method was also considered.
The methods selected for further study were evaluated using the
following criteria:
0 Cost of method development
0 Equipment and laboratory costs for using the developed method;
0 Repeatability of the method
0 Possible sources of error
0 Degree of expected conformity with API Nomograph results
Problems with use as a predictive parameter for hydrocarbon
emissions
0 Problems of field and laboratory use
As a result of this analysis, the methods were rated as candidates
for further developmental work.
10
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SECTION 4
DISCUSSION
This project is concerned with potential methods of determining
the volatilities of heavy crude oils. Volatility is a term relating to
the potential of a substance to evaporate. Vapor pressure is probably
the most common measure of volatility but measures of evaporation such
as distillation have also been used. Vapor pressure, for our purposes,
is defined as a measure of the force that tends to volatilize any
volatile liquid. This force is conventionally measured as pressure
under specified conditions. The term "true vapor pressure" has a
special meaning in multi-component mixtures because composition of the
mixture will be changed as vaporization occurs and vapor pressure will
be lowered concurrently. Thus, true vapor pressure of mixtures must
be measured without vaporization taking place. This is difficult to
carry out experimentally with a high degree of accuracy. True vapor
pressure is also termed as the "bubble point" pressure.
Because of the experimental difficulties in directly determining
true vapor pressures, the Reid Vapor Pressure (RVP) is most often used
to express the vapor pressure of petroleum mixtures. The RVP is the
absolute pressure in pounds per square inch determined at 100°F and
V/L = 4 (ratio of vapor volume to liquid volume, as defined in ASTM
Designation : D323-72) by using the apparatus and procedures as stan-
dardized under the auspices of the American Society for Testing Materials.
Thus, the RVP represents the vapor pressure of a sample which has had
its composition changed during the vaporization required to saturate
the vapor space of the measuring apparatus.
Correlations have been developed relating true vapor pressure to
Reid vapor pressure. These are prepared in the form of nomographs
included in a number of American Petroleum Institute (API) publica-
tions. ' For gasoline and finished petroleum products, the alignment
charts include RVP, temperature, the slope of the ASTM distillation
curve at the 10 percent point, and the "true vapor pressure". For
crude oil, however, there is no provision for consideration of the
11
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distillation curve slope. This alignment chart is limited to crude
oils with RVPs above 2 psi and storage temperatures below 140°F.
There is still another problem having to do with the use of ASTM Method
D323-72 for RVP with some crude oils. This is the requirement that
the sample container and its contents be cooled to 32 to 40°F before
the container is opened and the contents transferred to the liquid
chamber of the RVP bomb (a term for the apparatus). Some crude oils
cannot be poured at these temperatures. The alternative methods for
crude oil volatility considered in this project take into account one
or more of the problems discussed previously. They include modifying
the TVP-RVP nomograph to take into account distillation slope or gravity,
methods of minimizing transfer loss, extending the applicable temperature
and vapor pressure range, and determining the methane and ethane influence
on vapor pressure.
Alternative Methods for Crude Oil Volatility Considered
Each of the alternative approaches considered as a measure of
heavy crude oil volatility is discussed below. Some of the approaches
are in the form of fairly detailed methods and some are conceptual
only. Those in the former category are attached in the appendix to
this report. Following the narrative discussion of the methods, a
matrix chart rating the methods against certain evaluation criteria is
given.
1. Extrapolation or Modification of the API Nomograph
This approach would require the acquisition of more data on
true vapor pressures versus Reid vapor pressures covering a
variety of crude oils. Possibly the minimum RVP could be
lowered and the temperature limit raised. This would extend
the range of applicability but would not solve sampling, crude
oil transfer, and light ends problems. It is possible that
sufficient data could be obtained that ASTM distillation curve
slope or API gravity could be included to refine the TVP-RVP
nomograph. The Chairperson of the API Committee on Evaporation
Loss, Karen Hanzevack of Exxon Research, stated (personal
12
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communication with Robert Bryan of Engineering-Science, Inc.,
July 17, 1981) that the Committee is not satisfied with the
existing crude oil nomograph and is collecting existing data
on a wider range of crude oils. The intent would be to add a
grid of lines for crudes of different API gravities as a
substitute for the single correlation line in the current
chart. The Chairperson further gave the opinion that no
measure of volatility better than the RVP method has yet been
developed. She believes field work is necessary to confirm
the value of any revised procedure for vapor pressure deter-
mination.
The WOGA sponsored marine crude oil loading study also com-
ments on this matter. Their report^) states that an alignment
grid which includes both temperatures and slope of the ASTM
distillation curve or API gravity would improve the present
API nomograph for obtaining TVP from RVP.
The method development and equipment costs would be relatively
low using this approach if existing data were to be used to
construct a new TVP-RVP nomograph for heavy crude oil as the
actual test procedures would not be changed. The limitations
on sampling and handling heavy crude oils would remain.
Direct Measurement of True Vapor Pressure
Essentially no support was found for pursuing this approach.
The method requires use of an air-free sample and a V/L ratio
approaching zero. There is no standardized method for the
measurement of true vapor pressure. On a theoretical basis,
the method is very sensitive to methane and other light ends
content of the stock being measured. Thus the sampling
procedure would be even more critical than with the RVP method.
Methods development cost would be rather high. Equipment
costs may not be too high as no compositional data are speci-
fically required. Laboratory costs may be high depending
upon the care needed to obtain accurate and repeatable results.
13
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3. Modified RVP Method (Santa Barbara Approach)
This method involves collecting the crude oil sample directly
in the liquid container portion of the vapor pressure apparatus
thus eliminating the transfer of sample after collection. It
is run at stock storage temperature. This eliminates the
problem implicit in ASTM D323-72 requiring cooling of sample
to 32-40°F before transferring it from the sample container to
the test apparatus liquid chamber. Thus, samples which cannot
be poured at 32 to 40°F still can be run using the modified
procedure. The complete procedure as supplied by the Santa
Barbara County Air Pollution Control District is given in
Appendix A of this report.
The modified RVP procedure has several advantages and dis-
advantages. Already mentioned is elimination of the sample
transfer problem. However, this also eliminates the oppor-
tunity for partial air saturation of the sample. Therefore,
the developmental work should include parallel determinations
by the standard RVP procedure where possible to determine the
influence of this change. In general, a lesser degree of
sample air saturation would tend to lower the vapor pressure
measured as some of the air in the air chamber would dissolve
in the sample during conduct of the test.
Perhaps a more serious problem with this method is that related
to air saturation of the sample. In the Reid method, there is
provision for partial air saturation by means of shaking the
sample container after cooling to 32 to 40°F. The sample
container has an air space so the shaking action results in
the partial saturation. In the Santa Barbara modification,
the sample is collected in the analysis container and there is
no means for conducting the air saturation step. Thus, upon
connecting the air chamber to the sample container and heating
to the analysis temperature, there is some possibility that
additional air will be dissolved depending upon the degree of
saturation of air in the crude oil at time of sample collection.
14
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The error will be in a negative direction, but is not determinate.
The modified method is designed to conduct the vapor pressure
measurement at stock storage temperature. This eliminates the
need for a correlation nomograph. On the other hand, individual
determinations would be necessary for each temperature of
interest.
Because the test proposed uses the same V/L ratio as the
standard RVP method, the influence of light ends should not
change greatly.
Fairly extensive field testing of this method would be required
in the developmental stage. Equipment and laboratory costs
should not differ greatly from the standard RVP method.
4. Vapor Composition Method
The general principal of this approach involves analysis of
the headspace vapor in equilibrium with a liquid crude oil
sample. The vapor pressure is assumed to be a product of the
mol fraction of hydrocarbon vapor in the headspace times
the absolute pressure. The method eliminates interference from
water vapor and dissolved air. It does assume that an accurate
measurement of the hydrocarbon present in the vapor space can
be made, however. Normally this would be done by an appropriate
gas chromatographic method.
Two methods involving this approach have been reviewed. One,
from the California Air Resources Board, involves collection
of a sample in a 300 cc cylinder, which prior to the vapor
analysis step, is connected to a 30 cc evacuated chamber. The
two are connected, creating a vapor space. After the connected
vessels are held for 30 minutes at the analysis temperature,
the vapor space is opened to atmosphere long enough for the
vapor space pressure to rise to one atmosphere. Aliquot
samples of the vapor-air mixture are thus withdrawn and
analyzed by gas chromatograph. As can be seen, the
15
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determination is made at a V/L ratio or 1/11 (30/330). A
preliminary draft of this method is given in Appendix B.
A second vapor composition method was submitted by Chevron
Research Company. In this method a sample is collected by the
water displacement method. Prior to sample collection the
sample container is filled with water on the clean side of a
flexible impervious membrane. The membrane is free to move so
as to allow the entire volume of a rigid container to be
filled. The sample is collected from a sampling tap on the
sampling side of the container by displacing an exact volume
of water into another container. This latter container is
removed and the remaining water drains from the clean side of
the membrane. At the same time the sample side of the container
is pressurized with nitrogen. The container is then allowed
to come to equilibrium at the desired analysis temperature.
Aliquot vapor-N2 samples are then withdrawn for gas chromatograph
analysis similar to the GARB approach. The method as submitted
suggests a V/L ratio of 4/1. This mthod is included as Appendix
C to this report.
Both of the vapor composition methods can provide results on a
methane or methane + ethane-free basis; thus reducing the
variable influence of non-reactive hydrocarbons on the vapor
pressure. Both specific methods require a reliable gas
chromatographie analysis step. The Chevron method, as submitted,
is restricted to tap or line sampling.
The vapor composition methods would require rather extensive
field and laboratory testing and would increase the cost of
analysis because of the gas chromatograph step. Not all
control agencies have access to such equipment in-house.
5. Evaporation Method
This method involves determination of the loss of mass over
time of a sample held at a specified temperature. While it is
16
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one approach at obtaining a direct measure of evaporation loss
instead of one which uses a measure of the potential to
evaporate (such as vapor pressure), substantial questions on
design of the test conditions would have to be answered.
These include method of achieving test temperature — oven or
bath, rate of air or nitrogen sweep across the liquid surface,
surface to volume ratio of the evaporation container, length
of test, and quantity of stock to be used in the test. Finally,
some new criterion would have to be developed as to whether
the stock tested would have to be stored in a controlled tank.
The method might be more applicable to open storage or waste
ponds than it would be to tanked storage. This method is
described more fully in Appendix D. This method would require
extensive developmental work, but would be low in equipment
and laboratory costs.
The various measures of heavy crude oil volatility are sum-
marized in Table 1 against the evaluation criteria specified
for use in this study.
17
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TABLE 1. MEASURES OF HEAVY CRUDE OIL VOLATILITY VERSUS EVALUATION CRITERIA
Evaluation Criteria
Methods
Coat of
Method
Development
Equipment
and Lab
Costs
Repeatability
Conformity to
Sources of Error API Nomograph
oo
Extrapolate API
Nomograph
Gather additional
data which in
part should be
available.
No new c os t s.
Equilibrium (True)
Vapor Pressure
Method
Modified RVP
Vapor Composition
Method
Evaporation
Method
Extensive field
testing.
Extensive field
testing.
Extensive lab and
field testing.
Extensive lab and
field testing.
Also need to cor-
relate with loss
tests.
Unknown to fair.
Takes into account
gravity.
Modest.
Modest.
Fairly high -
need G.C.
Poor
Fair to good,
Possibly good.
Modest if lab
has balance and
oven.
Poor
Sampling - Loss of
GI and G£ in
various amounts.
Needs to be run
correctly re-
garding H20 and
barometric
pressure.
Extremely sensi-
tive to Ci and C2
loss.
No opportunity for
air saturation.
Accuracy of C.C.
analysis possible
problem. Elimin-
ates water and
diss. air problem.
Conditions have to
be carefully con-
trolled. How to
relate to losses.
Could be good de-
pending on
sampling and
can par ability of
new curve data.
Not good. GI and
C2 effect.
Should measure
all GI and C-±
to gut good
correlation.
Probably not
good because of
unknown influ-
ence of GI and
in API method.
Unknown to poor
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SECTION 5
CONCLUSIONS AND RECOMMENDATIONS
The results of our analysis of methods potentially useful for
measuring the volatilities of heavy crude oil were reviewed to deter-
mine whether any single candidate method clearly outranked the others
according to the rating criteria. This appeared to us not to be the
case. We did eliminate two methods from further consideration. These
were (1) the Equilibrium (True) Vapor Pressure Method, and (2) the
Evaporation Method. The former was eliminated because of the per-
ceived experimental difficulties, the extreme sensitivity to methane
and ethane content, and the lack of any information suggesting that
any of the problems with use of the current RVP method would be elimin-
ated. The evaporation approach was eliminated because of the significant
departure from current measures of volatility, particularly as related
to predictive loss equations for tank storage of petroleum. The method
does appear to be useful for sumps, pits and open oil tanks.
Further review of the analysis results suggested that several rather
specific objectives should be achieved by any new method. These include:
(1) It should permit sampling and testing of higher viscosity
crude oils.
(2) It should permit determination of a volatility parameter for
storage temperature above 140°F and RVPs (as currently
measured) below 2 psi.
(3) It should reduce substantially the variable influence of
methane and ethane present in the crude oil.
(4) It should be rugged enough to be conducive to good repeatability.
(5) The equipment and laboratory costs should permit reasonably
widespread use.
Our recommendations were also influenced by the information that
the American Petroleum Institute Committee on Evaporation Loss in the
19
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process of collecting currently available data relating RVP to TVP
measurements. This could result in the publication of a revised RVP
versus TVP nomograph utilizing a broader data base and which includes
an alignment grid for crude oils of different API gravities. The
current nomograph has a single correlation line representing all crude
oils instead of a grid. Therefore, we do not recommend at this time
any supplemental work to extrapolate the current API nomograph.
The two remaining methods in consideration are the Santa Barbara
modification of the RVP method and the vapor composition method. While
the modified RVP method does address the sampling and transfer problems
with the current RVP method, it does not solve the problem caused by
light ends and possibly exacerbates the air saturation effect. Therefore,
we recommend selection of the vapor composition method as a subject for
a methods development and evaluation program. Where restrictions on
ASTM D323-72 for determination of RVP permit, intercomparisons between
vapor composition results and RVP should be included in the research
program.
We suggest that the following parameters be considered in any
experimental design developed for a reasearch program:
0 Crude type - covering a range of API gravities, viscosities,
light ends content
0 Sampling procedure - dip, water displacement, with and without
transfer from sample container to analysis container
0 Vapor to liquid ratio
0 Temperature of analysis
0 Specific analytical procedure - standard RVP, vapor composi-
tion, etc.
0 Number of replicates
Because the light ends content of some crudes can change quite
rapidly after withdrawal from a well in a production field, it will be
20
-------
important to consider exact location of sample withdrawal. It may be
desirable to carry out analyses of liquid composition in at least a
portion of the crude samples.
We have prepared a preliminary estimate of the level of effort to
conduct the research and development effort suggested. Our estimate is
based upon examination of ten crude oil types, two methods of analysis,
three V/L ratios, two temperatures, and three replications. This
results in about 450 samples. For this program we estimate an overall
technical effort in the range of 2,000 to 3,000 hours. Other direct
charges would include equipment, travel, per diem, expendable supplies,
computer costs, communication, and reproduction.
A preliminary cost estimate has also been made for equipment needed
by users to conduct both the standard RVP method and the vapor composition
method. This estimate is given in Appendix E.
For sumps, ponds, and open tanks, we suggest further development of
the procedure described in Appendix D.
21
-------
REFERENCES
1. "Evaporation Loss from External Floating-Roof Tanks," API Publication
2517, Second Edition, February 1980, American Petroleum Institute,
Washington, D.C.
2. "Hydrocarbon Emissions During Maring Loading of Crude Oils," Chevron
Research Corporation for Western Oil and Gas Association, August 1977.
3. "Hydrocarbon Emissions from Fixed-Roof Petroleum Tanks," for Western
Oil and Gas Association by Engineering-Science, Inc., July 1977.
4. "Evaporation Loss in the Petroleum Industry - Causes and Control,"
API Publication No. 2513, reaffirmed 1973, American Petroleum
Institute, Washington, D.C.
NON-REFERENCED CONTACTS
1. Richard Burr, U.S. Environmental Protection Agency, OAQPS, RTP,
NC.
2. Harry Metzger, California Air Resources Board, Sacramento, CA.
3. Abe Moore, South Coast Air Quality Management District, El Monte,
CA.
4. T. H. Gouw, Chevron Research Co., Richmond, CA.
5. Sam Fett, Union Oil Research Co., Brea, CA.
6. John English, Santa Barbara County Air Pollution Control District,
Santa Barbara, CA.
7. Robert A. Farnham, Chevron Research Co., Richmond, CA.
22
-------
APPENDIX A
SANTA BARBARA MODIFIED RVP APPROACH
-------
SANTA BARBARA VAPOR PRESSURE FOR CRUDE OILS
SCOPE
This method is designed to determine a vapor pressure of crude oils
at the temperature at which they are being stored.
EQUIPMENT
Equipment and apparatus are those used in the Reid Method (ASTM D323)
with the modification shown in Figure 1.
PROCEDURE
Sampling:
1. Evacuate a clean, dry liquid chamber by suitable means to
1 mm Hg or less absolute and close the valves.
2. Submerge the evacuated liquid chamber 31 to 5' below the
surface of the crude oil in the storage tank and open the
top valve to allow the crude to enter and fill the chamber.
Reclose the chamber while submerged and remove from the tank.
Clean the crude from the outside of the liquid chamber.
3. Place the sealed liquid chamber in an ice water bath or
crushed ice to transport it to wherever the test is to be
conducted.
4. Determine the temperature of the crude in the storage tank.
MEASUREMENT OF THE VAPOR PRESSURE
1. Prepare the air chamber as outlined in the modified ASTM
procedure Section 6.3 attached. The test is run at the
nearest 5°F above the temperature of the tank sampled.
A-l
-------
- 2 -
2. Quickly assemble the liquid and air chambers and return to
the bath at the test temperature. Do not open the inter-
connecting valve until the sample is at the test temperature
(about 20 minutes). Agitate the sample as described in the
ASTM procedure, following that procedure from Section 7.4
to completion. Record the gauge reading as the vapor
pressure and indicate the temperature at which the measure-
ment was made.
A-2
-------
Figure 1
A-3
-------
Designation: 0 323 - 72
American National Standard 211 44-1973
Approved Jung 4 1973
By American National Standards Institute
Standard Method of Test for
VAPOR PRESSURE OF PETROLEUM
PRODUCTS (REID METHOD)1
This Standard is issued under the fixed designation D 323. the number immediately following the designation indicates the
year of original adoption or. in the case of revision, the year of last revision A number in parentheses indicates the year of
last rcapproval
1. Scope
is method covers the determination
of tnTSpksolutc vapor pressure (Note I) of vol-
atile CTOBL oil and volatile nonviscous petro-
leum prtmcts, except liquefied petroleum
gases (Note1
NOTE 1—BcSbf the external atmospheric pres-
sure is counter«fi\by the atmospheric pressure
initially present tnwkair chamber, the "Reid va-
por pressure" is arrBaWute pressure at 100 F in
pounds per square in&pRie "Reid Vapor Pres-
sure" differs from the tnwapor pressure of the
sample due to some small *KBRle vaporization and
the presence of water vapor aSEw m the confined
space.
NOTE 2—For determination oTtjai^vapor pres-
sure of liquefied petroleum gases rBSj^fc should
be made to Method D 1267.
NOTE 3—The values stated in
umis are to be regarded as the standard.
^Applicable Documents
ISTM Standards-
D 2?5fampling Petroleum and Petroleum
Produ
D 1267 TesT^^yapor Pressure of Lique-
fied PetroleurH^&£.) Gases (LP Gas
Method)1
E I Specification for A
3. Summary of Method
J. 1 The gasoline chamber of the vapor pres-
tus is filled with the chilled sample
andl&ficctcd to the air chamber at 100 F or
other leTHhuture. The apparatus is immersed
in a constan^jkjpperature bath <100 ± 02 F)
and is shakenpl&dically until equilibrium is
reached. The "rrBimmeter reading" corre-
sponding to the prnsQt read on the gage
attached to the apparanJBhaiitably corrected
(Table 1) if the air cbambejBks initially at a
temperature other than I00"|ni$ the Reid
vapor pressure.
3.2 This method provides Tor 'What air
saturation of products with Reid vap
sure below 26 Ib (Sections I to 9. and
saturation for products above 26 Ib
and 17) and for narrower
i for the measure-
ment of the vap"o?$S^jSiSfc4y^lJon Baso~
lines (Sections 16 and 17)
4. Apparatus
^fcjGie construction of the required appa-
rat^SEafasbed in the Appendix. For sam-
ples havin'Pttfcpfcatressures below 26 Ib. use
the gasoline cnnlkCjwUn one opening
(AI.I.2) and for iiii|ili lj^jiii|gryaBpr pres-
sures above 26 Ib, use the gaffS8jggȣfacr
with two openings (Al.1.3). ^"w
S. Handling of Samples
The general provisions in 5.2 and 5.6
IPJwAwilj to all samples for vapor pressure
den erfiifcat ions, except as specifically ex-
fe samples having vapor pressures
above 26^thL
-------
D323
1 \quid
.quid
i< test
'i erature
is opened
$omple Transfer— The, Reid vapor
ion shall be the first test
run on*e. In the instances of transfer
of liquids mS^fteer sample containers or of
withdrawal oTfsrates for other tests, the
transfer connectionol^^J shall be used.
5.6 Care of Sample&&ti$K shall be put
in a cool place as soon as pfc&J&kafter they
have been obtained and held TntSSuuil the
test has been completed. Sa
containers shall not be considered for
shall be discarded and new samples obtain
6. Preparation for Test
'> Saturation of Sample in Sample
the sample at a temperature
of 32 too^take the container from the
water coohng^ab|Unseal it, and examine it
for its liquid comci^%hicri shall be between
70 and 80 percent oftnQUiainer capacity.
After the correct liquid
sured. reseal the container,
1v and rgturn il_lA-thc-
6.2 Preparation of
Completelv immerse the
been as-
Chamber—
cham-
beranTtne sample transfer connection in the
water cooling bath for a sufficient time to al-
low the chamber and connection to reach the
bath temperature (32 to 40 F).
6.3 Preparation of Air Chamber 0HHE
^ggfff)—After purging and rinsing the air
chamber and pressure gage in accordance
with 7.5, connect the gage to the air chamber.
Immerse the air chamber to at least 1 in.
above its top in the water bath maintained
^jfgfaf, for not less than 10 nun just be-
fore coupling u to the gasoline chamber. Do
not remove the air chamber from the bath
until the gasoline chamber has been filled
with sample as described in 7.1
Preparation of Air Chamber (Ambient
Procedure)—*.* an alternative
to fetet the air chamber to ambient or
other -tempSraihfewhich may-be-determined
with an accuraBjj^^jjeasr I "Pin the-follow- •-
ing manner Afteroi^M^and.Tinsunnheair.
chamber and pressure*l9^in accordance
with 7.1, conned the gageTSiralur chamber.
Insert ihc-thcunometcr Jnto/
supporting it by means of a looselylwfcL(nol
airtight) stopper in the opening orNw air
Camber Adjust the position of the thermom-
>t u is aligned as closely as possible
with HfSfexis of the air chamber, and with the
ihermomefeVbulb located in the air chamber,
about 9 in. frxWthc opening. Leave the ther-
mometer in posntai until the temperature
reading has remamecratasiani within I F for
a period of 5 mm or more^sjbcfore coupling
the air chamber to the gasoTrH^jchambcr. At
this time, record the thermomeieTO^gjling as
the "initial air temperature "
7. Procedure
Sample Transfer—With everything in
redWiess. .remove the chilled sample con-
laineraom the bath, uncap it, and insert the
chilled nvsfer connection and air tube (see
Fig. 1). Qwcly empty the chilled gasoline
chamber and^hue it over the sample delivery
tube of the tran»LConnection. Invert the en-
tire system rapidly^kJhat the gasoline cham-
ber is finally in an upBohi position with the
delivery tube extending t&rithin '/« in. of the
bottom of the gasoline charrnr. Fill the gaso-
line chamber to ovcrflowine.^hhtlv tap the
gasoline chamber against the woq^.bcnch to
ensure that the sample is free of
If any sample is displaced, refill the
to overflowing.
7.2 Assembly of Apparatus—Without de-
lay, and as quickly asDOssible^ttachjJjeju^
chamber to the •••CUecharnDerNoi more
than 20 s shall be consumed in completing the
assembly of the apparatus after .filling the
gasoline chamber, using the following se-
quence of operations.
~"~ " line
_ remove the air cham-
ber from the I^^P water bath (6.3).
7.2.3 Connect the air chamber to the <
chamber.
7J Introduction of Apparatus into Bath—
is
[us. Immerse the assem-
bled apparatus in the bath, maintained at _
4BBH, in an inclined position so that the
connection of the«nMint and air chambers is
liquid
liquid
the test
temperature
liquid
199
A-5
-------
with a'sultable solvent and dry
with air and heat as may be required,
Care should be taken to be sure that
the Bourdon tube of the pressure
gauge is thoroughly clean and dry.
liquid
below the water level and may be observed
closely for leaks. If no leaks are observed.
immerse the apparatus to at least I in. above
the top of the air chamber Observe the appa-
ratus for leaks throughout the test. When at
any lime a leak is detected, discard the test
NOTE 4—Liquid leaks are more difficult to delect
than vapor leaks, and because the much-used cou-
pling device is normally in the liquid section or the
apparatus, give it particular attention
7.4 Measurement of Vapor . Pressure—
After the assembled vapor pressure apparatus
has been immersed in the bath for 5 mm, tap
the pressure gage lightly, and observe the
reading. Withdraw the apparatus from the
bath, invert it, shake it vigorously, and re-
place it in the bath in the shortest possible
time to avoid cooling the apparatus. At inter-
vals of not less than 2 mm, repeat this agita-
tion and gage observation ar least five times.
until the last two consecutive gage readings
are constant, to ensure equilibrium. These
operations normally require 20 to 30 mm.
Read the final gage pressure to the nearest
0.05 Ib for gages with intermediate gradua-
tions of 0.1 psi and to the nearest 0.1 Ib for
gages with graduations of 0.2 to 0.5 psi, and
record this value as the "uncorreeled vapor
pressure" of the sample under test. Immedi-
ately remove the pressure gage and check its
reading against that of the manometer, re-
cording the value found as the Reid vapor
pressure (under the procedure of 6.3). or as
the "manometer reading" to be used in the
calculations of Section 9 (under the procedure
of 6.4)
_ 7.5 Preoaranon of Apparatus for Next
fesi—Disconnect the air chamber^
chamber, and pressure
in the Bourdon lube by repeated
eaTthrusts. This may be accomplished
in Ilirnowing manner: hold the gage be-
tween thlaklms of the hands with the right
hand on uWtface side and the threaded
connection of^e gage forward. Extend the
arms forward annupward at an angle of 45
deg with the coupnaLpf the gage-pomting in
the same direction. ^WP the arms downward
through an arc of aboOW35 deg so that the
centrifugal force aids grav^kjn removing the
trapped liquid. Repeat this^fctration three
times to expel all liquid. Purgc"^uressure
gage by directing a small jet of air^W* its
tease of crude oil. the Bourdon
.with a volatile solvent after
D323
don tube for at least 5 mm Thorough!)
\thc air chamber of residual sample b\
Jhe air chamber with warm water
I F) and allowing it lo drain (Noie 6)
kis purging at least Five times After
lhorouu\ removing the previous sample
from Um^tasolinc chamber, immerse the
chamber iw\ice bath for the next lest
NOTE 5—IB
lube musl be
each test
NOTE 6—If the"'tegl&Jyof the air chamber is
done in a bath, be sureTJfey8>CsmaII and unnonce-
able films of floating sampreitj^Bj^HUvthe bottom
and top openings of the chanfrWJSs^ped as thex
pass through ihe'surface of water
8. Precautions
8.1 Gross errors can be obtained in vapor
pressure measurements if the prescribed pro-
cedure is not followed carefully. The following
list emphasizes the importance of strict ad-
herence to the precautions given in the proce-
dure:
8.1.1 Cheeking the Pressure Cage—Check
all gages against a manometer after each test
in order to ensure higher precision of results
(7.4). Read all gages while ihe gage is in a
vertical position
Air Saturation of Sample—Open and
container once after the con-
id a temperature of 32 to 40
F. ShaHK^kkCpntamer vigorously to ensure
equilibnunlH&ibSample with the air in the
container I ^—_._
8.1.3 Checking JorTeaks—Check all appa-
ratus before and during each lest for liquid
and vapor leaks (A 1.1.6 and Note 4).
Sampling—Because initial sampling
handling of samples will greatly affect
s. employ the utmost precaution
and Bgg^pst meticulous care to avoid losses
througnBraknoration and slight changes in
compositraUnuons 5 and 7.1). In no case
shall any parr^HMkRe'd apparatus itself be
used as the samtS|Mp^iner previous to ac-
1 conducting the
urging the
purge fn^gessure gage, the gasoline cham-
ber, and the'fifebarnber to be sure that they
are free of residuaT^fcBle.frhis is most con-
veniently done at the enW^^BiauaiiS test.)
(See 7.5).
8.1.6 Coupling the Apparatus—Carefully
200
A-6
-------
liquid
with
observe the requirements of 7.2
8.1.7 Shaking the Apparatus—Shake the
apparatus "vigorously" as directed in 7 4 in
order to ensure equilibrium
8.1.8 Temperature Control— Carefully con-
trol the temperature at the time of air satura-
tion and the temperature of the 100 F bath
(Appendix, A1.3 and A1.4, respectively). Be
certain that the temperature of the air in the
airj:hambcr at the time of coupling with the
Re chamber (7.2) has remained constant
within I F for a period of 5 mm or more.
Jculation
ange in Pressure of Water Vapor
and ^ISfiJ the ambient temperature proce-
dure deflipjL in 6.4. calculate the "Reid
vapor presrlHsSjfthe sample under lest by
applying to inwjgfefjioineier reading" the
correction given irSfegjhJfor the change in
pressure of the wateSj^gjg^and air in the
chamber on healing frn mfffJi^mSTttitJ t tem-
perature" to 100 F.
9.2 Recording KesuJts-
^•^B^M^MBftBfP*). record the result
observed in 7.4 as the "•• vapor pressure"
in poundsBE reference to temperaiurefl|
from the application of the
vapor pres-
MODIFICATIONS FOR PRODUCTS HAVING
REID VAPOR PRESSURES
ABOVE 26 LB
10. General
With products having vapor pressures
ovelH6 Ib (Note 7), the procedure described
in Sea»ns 5 to 8 is hazardous and inaccurate.
Conseqowty, the following sections define
changes m^taparalus and procedure for the
determinationl^vapor pressures above 26 Ib.
Except as -speci^^ly stated, all the require-
ments of Sections T^g 9 and Section 17 shall
apply.
NOTE 7—When the questi^Lariscs. the air satu-
ration method shall be used ur^knnine whether or
not a product-has a vapor nressurtiVbove 26 Ib.
II. Appmratus
_ 11.1 Bomb, as described in the
D323
the gasoline chamber with two openings
pressure Cage Calibration—A dead-
(AI.7) may be used in place of
the merctft&Qanometer (A 1.6) for checking
gage readmgs^^e 26 Ib. In 7.4p -8.1.1. and
9.1. and Table Iw^jcihc words "manom-
eter" and "manomelerS^duig" appear, in-
clude as an alternate "dcad-wSSfehl tester" and
"calibrated gage reading,"
12. Handling of Samples
nSl^^j^j.4. and 5.5 shall not apply.
the sample contarn^^^p^iwhich the vapor
pressure sample is takensWa^^^be less than
1 pt liquid capacity. ^^^^^fea^.
13. Preparation for Test
&3-I 6.] and 6.2 shall not apply.
IB.2 Any safe method of displacement of
thonest sample from the sample container
thaCwsures filling the gasoline chamber with
a'chflBd, unweathered sample may be em-
ployed:@jhe following 13.3 to 13.5, together
with SecrokU, describe displacement by self-
induced preotte.
13.3 Maiivfflb the sample container at a
temperature suffiunlly high to maintain su-
peratmospheric pMBure but not substantially
over 100 F. ^1^
13.4 Completely ^nrnerse the gasoline
chamber, with both vamtopen. in the water
cooling bath for a sufficiCTklength of time to
allow it to reach the bath Iguxraturc (32 to
40 F). ^».
I3.S Connect a suitable Jcc^jJcd coil to
the outlet valve of the sample conuj^v.
NOTE 8—A suitable ice-cooled coil c^ae pre-
pared by immersing a spiral of approxiinaifi^^& ft
of Vj-in. copper tubing in a bucket of ice waicr^^
. Procedure
7.1 and 7.2 shall not apply.
^Connect the '/«-in. valve of the chilled
gasolTwfchambcr to the ice-cooled coil. With
the >/i3^h^aTve~ of "the gasoline chamber
closed, oplwhe outlet valve of the sample
container ana*^^V«-in. valve of the gasoline
chamber. Open ofc^asoli ne chamber Vi-in.
valve slightly-and-alWfcAe gasoline -chamber-
to fill slowly. Allow the^Mole to overflow
until the overflow volume is^B^n] or more.
Control this operation so that no^Bicjable
201
A-7
-------
D323
CO
po
Who1
rupt
the .
must
and the
p in pressure occurs at the gasoline cham-
'/4-in. valve. In the order named, close the
line chamber V2-m. and '/«-m. valves: and
close all other valves in the sample sys-
Disconnect the gasoline chamber and the
coil. (Caution: Safe means for dis-
hquid and vapor escaping during this
Deration must be provided. To avoid
because of the liquid-full condition of
chamber, the gasoline chamber
,uickly attached to the air chamber
. valve opened.)
14.3 1
chamber li
oline cham
s shall be
bly of the a
chamber, usi
erations: (I)
or remove tl
bath, (2) con
line chamber, an
bcr Vj-in. valve.
14.4 If a dead-
of the mercury m
calibration factor
established for the
the "uncorrecled va
corrected vapor
found as the "calibrat!
used in the calculation
ble 1 in place of the "m
^d iatcly attach the gasoline
ie air chamber and open the gas-
'/j-in. valve. Not more than 25
med in completing the asscm-
ratus after filling the gasoline
he following sequence of op-
the initial air temperature
r chamber from the water
e air chamber to the gaso-
) open the gasoline cham-
:ht tester is used instead
meter (11.2). apply the
unds per square inch
issure gage at or near
pressure" to the "un-
recording the value
gage reading" to be
if Section 9 and Ta-
mcter reading."
15. Precautions
IS.I The precaution 8. HI
MODIFICATIONS FOR A VIA:
OF ABOUT 7 LB
hall not apply.
f GASOLINE
KESSURE
16. General
16.1 The following paragra&s define
changes in apparatus and proccdiAfor the
determination of the vapor pressuremf avia-
tion gasoline. Except as specificallv^ktated
herein, all the requirements set forth
tions 1 to 9 and 17 shall apply.
16.1.1 Ratio of Air and Gasoline ChaZ
hers — The ratio of the volume of the air cham-
to the volume of the gasoline chamber
ill be between the limits of 3 95 and 4.05
A I in the Appendix)
LI .2 Water Cooling Bath— The water
jg bath shall be held at a temperature of
F (See A 1. 3)
Checking the Pressure Cage — The
be checked at 7 Ib against a mer-
mn before each vapor pressure mcas-
to ensure that it conforms to the re-
s of Section A 1. 2. This preliminary
I be made in addition to the final
nson specified in 7.4
Chamber Temperature — The
6.3 shall be followed: the provi-
sions of 6.4Hhall not apply
all
The
iwmg criteria should be used
acceptability of results (95
bitity—Duplicate results by
should be considered sus-
oy more than the following
gaso-
Re pea lability
(Same Operator
and Apparatus)
0 I
0.2
17. Preci
17.1
for judging
percent confide'
17.1:1 Repe,
the same opera
peel if they diffi
amounts:
Range
0 to S Ib
5 to 16 Ib (except aviat
line)
16 to 26 Ib
Above 26 Ib
Aviation gasoline (approxn
7lb)
17.1.2 Reproducibili
muted by each of two
considered suspect if they
the following amounts:
telv
0 3
04
0 I
The results sub-
ratones should be
by more than
er
Range
0 to 5 Ih
5 to 16 Ih (excepi aviation gaso-
line)
16 to 26 Ib
. Above 26 Jb
Aviation gasoline (approximate)}
7 Ib)
Reproducibility
(Different Oper-
ator and
Appjratus)
0 35
0 .1
202
A-8
-------
D 323
TABLE 1 Corrections to be Subtracted from
"Minometer Readings" for Calculating Reid Vapor
Pressure
Barometric Pressure,'
Initial Air
Temperature,"
degF
32
40
50
60
70
80
90
100
110
760
2.90
2.60
2.20
1.80
1.40
0.95
0.50
0.00
-0.55
700
2.70
2.45
2.10
1.70
1.30
0.90
0.50
0.00
-0.55
'mm Hg
600
2.45
2.20
1.90
1.55
1.20
0.85
0.45
0.00
-0.50
* I-or other temperatures and pressures, the correc-
tions may be calculated by means of the following
equation:
Correction -
\(F - P,)(i - I00)/460 + /) -.(/•,«, - />,)
where:
/ - air chamber temperature at beginning of
lest, deg F.
P " barometric pressure, psi, at time of lest (if a
barometer is not available, the normal baro-
metric pressure may be used),
P, - vapor pressure of water, psia, at / deg F, and
Pirn - vapor pressure of water, psia, at 100 F - 0.95.
Calculated corrections arc to be rounded off to the
nearest 0.05 psi.
Example—The pressure gage gives an "uncorrected
vapor pressure" reading of 11.6 psi. When the gage
is compared to a mercury column, a "manometer
reading" of 11.5 psi is obtained. For an "initial air
temperature" of 80 F and atmospheric pressure of
700 mm Hg, the correction shown in Table I is 0.90
psi. Because the "initial air temperature" is below
100 F, this correction of 0.90 psi is subtracted from
the "manometer reading" of 11.5 psi giving, a "Reid
vapor pressure" of 10.60 psi.
Chilled Gosolmt Chambtr
(d)
fcsrtion of System for
Sample Transfer
(b)
Sealing Closure
OrpHcri ly Samplt PtocedOwl
r Cofwcnon
to)
Sample Container
Pnor to Transfer
of Sample transfer Connection Dekvtry Tubi
FIG. I SinpiifM Sketekcs OwtiMof MetlM4 of Trusfenug Sup
from Opcs-Typc CMUUCTI (V. bk - 6.25 ••).
203
A-9
-------
D323
APPENDIX
Al. APPARATUS FOR REID VAPOR PRESSURE TEST
iquid.
liquid.
iquid
liquid -
iqriri.
A 1.1 Reid Vapor Pressure Bomb, consisting of
two chambers—an air chamber (upper section) and
a gasoline chamber (lower section)—shall conform
to the following requirements
NOTE Al: Caution—To maintain the correct vol-
ume ratio between the air chamber and the gasoline
chamber, the units shall not be interchanged wifA-
out recalibrating to ascertain thai the volume ratio
is wiiftin satisfactory limns
A 1.1.1 Air Chamber—The upper section or air
chamber, as shown in Fie. Al. shall be a cylindrical
vessel 2 ± '/§ in. in diameter and 10 ± '/• in. in
length, inside dimensions, with (he inner surfaces of
the ends slightly sloped to provide complete drain-
age from either end when held in a vertical position
On one end of the air chamber, a suitable gage cou-
pling with an internal diameter not less than V,. in.
shall be provided to receive the '/.-in. gage connec-
tion. In the other end of the air chamber an opening
approximately '/, in. in diameter shall be provided
for coupling with the gasoline chamber. Care shall
be taken that the connections lo the end openings
do not prevent the chamber from draining com-
pletely.
Al.1.2 Gasoline Chamber (One-Optning)—Tt\t
lower section or gasoline chamber, as shown in Fig.
Al. shall be a cylindrical vessel of the same inside
diameter as the air chamber and of such volume
that the ratio of the volume of the an chamber to
the volume of the gasoline chamber shall be be-
tween the limits of 3.8 and 4.2 (see Now A2). In
one end of the gasoline chamber an opening approx-
imately V, in. in diameter shall be provided for
coupling with the air chamber. The inner surface
of the end containing the coupling member shall
be sloped to provide complete drainage when in-
verted. The other end of (he gasoline chamber
shall be completely closed.
Non A2—The ratio for units to be used foi
aviation gasoline testing shall be between 3.95 to
4.0S. .
A LI.3 G*tmtme Chamber (Two-Opening}— For
^Smpiin^fSm closed vessels, the lower section or
gasoline chamber, as shown in Fig. Al shall be es-
—...IK. .u- .—uj^jhejjjKm chamber de-
except tbaiT '/.-in. valve shall be
mAf-ih^^Mfcv chamber
TH
TrT
MdaVr-in. straigm-ihrough. full-opening valve
shall be introduced in the coupling between the
chambers. The volume of the_HOTMK chamber,
T by the valves.
mliiuiuu limy uit uiuuij
shall fulfill the volume ratio requirements as set
forth in Al.1.2.
meats as set lortb in Al.1.2.
NOTE A3—In determining capacities for the two- .
chamber (Fig. AI), the capacity of
^ __ jnber shall be considered as that
below me Vr-m. valve closure. The volume above
the '/.-in. valve closure including the portion of the
204
coupling permanently attached to the gasoline
chamber shall be considered as a part of the air
chamber capacity
A1 1.4 Method of Coupling Air and'*
Chambers—My method of coupling the air and
chambers mav h^ nv^ >lrovif1rH thfll
-
TnToTTWiraDTrcoupling be on the
no giwvfle is losi during the coupling operation.
that no compression effect is caused by (lie an of
coupling, and thai the assembly is free from leaks
under the conditions of the tests. To avoid displace-
ment of •••*«: during assembly
thatthe male fiuT
ng tlTeassernolyoaTuTTSoTeTcrewcoupiing. a vent
hole may be used to ensure atmospheric pressure in
the air chamber at the instant of sealing
Al.1.5 Volumetric Capacity of Air and <
Chambers — In order to ascertain if the volume ratio
of the chambers is between the specified limits of
3.8 to 4.2 (see Note A2). measure a quantity of wa-
ter greater than will be needed to fill the
and air chambers. The
completely filled with
between the original volume and the remaining vol-
ume IS the volume of the aaaahae chamber Then
after connecting the
air chamber shall be filleono tne seat of the gage
connection with more of the measured water, and
the difference in volumes shall be the volume of the
air chamber
A 1.1.6 Checking for Freedom from Leaks—Be-
fore placing new apparatus in service and as often
as necessary thereafter, the assembled vapor pres-
sure apparatus shall be checked for freedom from
leaks by filling with air to 100-psi gage pressure and
completely immersing in a water bath. Only appa-
ratus which stands this test without leaking shall be
used.
A1.2 Pressure Cage—The pressure gage shall be
a Bourdon-type spring gage of test gage quality 4 Vi
to S'/i in in diameter provided with a nominal 'If
in. male thread connection with a passageway not
less than s/« in. in diameter from the Bourdon lube
to the atmosphere. The range and graduations of
the pressure gage used shall be governed by the
Cage to be Used
Reid Vapor
Pressure.Ib
4 and under
3to 12
10 to 26
10 to 36
30 to JJ
30 and higher
Scale
Range.
psi
Oto 3
Oto 13
0(o 30
Olo45
Oto 60
0 to 100
Maximum
I
3
5
5
10
10
ations.
psi
O.I
O.I
0.2
0.2
0.25
0.5
liquid
liquid
liquid
liquid
liquid
liquid
liquid
liquid
liquid
A-10
-------
D323
.iquid
vapor pressure of the sample being tested, as fol-
lows:
Only accurate gages shall be continued in use.
When the gage reading differs from the manometer
(or dead-weight tester when testing gages above 26
Ib) reading by more than I percent of the scale
range of the gage, the gage shall be considered inac-
curate. For example, the calibration correction shall
not be greater than 0.15 psi for a 0 to 15-psi gage or
0.3 psi for a 0 to 30-psi gage.
NOTE A4—Gages 3'/» in. in diameter mav be
used in the 0 to 5 Ib range.3
A 1.3 Water Cooling Bath—A. water cooling bath
shall be provided of such dimensions that the sam-
ole comameii_and MWffiie chambers may be com-
plcieiy immersed. Means for maintaining the bath
at a temperature of 32 to 40 F shall be provided.
NOTE AS—Solid carbon dioxide shall not be used
to cool samples in storage or in the preparation of
the air saturation step. Carbon dioxide is apprecia-
bly soluble in gasoline, and its use has been lounrl to
be the cause of erroneous vapor pressure data.
A 1.4 Water Baih—Jhe water bath shall be of
such dimensions that the vapor pressure apparatus
may be immersed to at least 1 in. above the top of
the air chamber. Means for maintaining the bath at
a constant temperature of 100 ± 0.2 F shall be
provided. In order to check this temperature, the
bath thermometer shall be immersed to the 98 F
mark throughout the vapor pressure determination.
A 1.5 Thermometers:
A 1.5.1 For 100 F Air Chamber Procedure— An
ASTM Reid Vapor Pressure Thermometer No. 18F
having a range from 94 to 108 F and conforming to
the requirements in Specification E 1.
A 1.5.2 For Water Bath— Use the ASTM Ther-
mometer I8F described in Al.5.1.
Al.5.3 For Air Chamber— When the ambient
temperature procedure is employed, a thermometer
conforming to the following requirements shall be
used: Length, approximately 12 in.; range, —40 or
-30 F to +120 or +130 F; graduated in 1 F divi-
sions; total irnmcrsion. scale error not greater than
1 F.
A 1. 6 Mercury Manometer — A mercury mano-
meter. having a range suitable for checking the
pressure gage employed shall be used. The ma-
nometer scale may be graduated in steps of 1 mm.
0.1 in., or 0.1 psi.
A 1.7 Dead-Weight Tester— A dead-weight tester
may be used in place of the mercury manometer
(AI.6) for checking gage readings above 26 Ib.
' Suitable gapes are available from the Fisher Scientific
Co. (Special Order), Pittsburgh. Pa. and U. S. Gauge Co.
(Catalog No. 510SP). Sellersville. Pa.
Coupling
1/2 O.Q
liquid
Coiptng.l/ZLO.
Air Chombar
M»<«; Al Dl
FIG. Al V
Goiellnt Chombtr
(O«t Opining)
By publication of tUs standard no position it taken with respect to the validity of any patent rights in connection thert-
MiA. and ine American Society for Testing and Materials does not undertake to insure anyone utilizing tni standard
against liability for infringement of any Letters-Patent nor assume any suck liability.
205
A-ll
-------
APPENDIX B
CALIFORNIA AIR RESOURCES BOARD
VAPOR COMPOSITION METHOD
-------
Determination of Crude Oil Vapor Pressure
by Gas Chromatographic Vapor Analysis
(Draft Proposed Method)
SCOPE
This method is proposed to determine the approximate true vapor pressure
(bubble point pressure), exclusive of the partial pressure of methane,
for any crude oil at temperatures high enough for the oil to flow.
The practicality and validity of the method for crude oil will be
demonstrated in the laboratory. If subsequent testing of the method
with other liquids is successful, the method's scope may be expanded.
The method will be applicable only if the total vapor pressure, including
.methane, is less than 14.7 psia.
SUMMARY OF METHOD
Oil will be collected, by methods described elsewhere, in a 300 cc cylinder
equipped with leak-tight valves at both ends and a rubber septum at one
end. The entire volume of the cylinder will be full. The sample will
be kept on ice pending analysis.
Jn the laboratory, an empty chamber of exactly 30 cc volume will be attached
to the lower sample cylinder valve and evacuated. The cylinder valve will
then be opened, creating a vapor space in the sample cylinder. The
assembly, with the 30 cc chamber at the bottom, will be placed in a
temperature bath until it has reached the desired analysis temperature
throughout. Aliquots of equilibrium vapors will then be withdrawn through
the septum at the upper cylinder valve with a syringe which is at the
test" temperature. The aliquots will be analyzed by gas chromatography
B-l
-------
-2-
for the mass concentrations of hydrocarbons of each carbon number.
The total non-methane vapor pressure will be calculated according to the
perfect gas relationship from the sum of each mass concentration
divided by the appropriate molecular weight.
EQUIPMENT
1. 300 cc stainless steel sampling cylinder equipped with vacuum-tight
valves at each end and with a rubber sampling septum. See Figure 1.
The total volume between the two valve closures shall be between
295 and 305 cc.
Z. ' Vacuum chamber with two openings, one fitted with a vacuum tight valve,
the other with a connector compatible with the lower sample cylinder
.valve. The volume of the chamber between the valve closure and the opening
of the connector (points 1 and 2 in Figure 1) shall be 30.0 cc.
3. Vacuum pump capable of achieving 1.0 mm Hg.
4. Temperature bath capable of maintaining within 0.3°F of the desired
temperature.
5. Gas chcomatograph meeting the following specifications: - (to be
reconmended by AIHL).
6. (Chromatographic column to be recommended by AIHL).
7. Syringe for chromatograph sample injection.
SAMPLING PROCEDURE
Samples will be collected in a 300 cc sample cylinder according to methods
approved by the Air Resources Board. (A draft method is enclosed.) The
sample cylinder will be completely full. The sample will be kept in ice
until the headspace analysis is performed.
B-2
-------
-3-
LABORATORY PROCEDURE
A. Gas Chromatograph Preparation (to be recommended by AIHL).
B. Sample Preparation
1. Clean the outlet of valve B (Figure 1).
2. Attach the 30.0 cc vacuum chamber to valve B and evacuate it to
1.0 mm Hg or less. Close valve D and verify that the chamber is
vacuum-tight.
3. Close valve C, disconnect it from the vacuum line and place a rubber
stopper over the valve outlet to prevent any leak through
the valve.
4. Open valve B and immerse the entire assembly, with the 30 cc
chamber down, in the temperature bath. Also immerse the syringe,
enclosed to prevent contact with the Bath fluid. Agitate the
cylinder at five minute intervals.
5. After 30 minutes, open slightly valve A to allow the total pressure
to rise to one atmosphere. Close the valve.
6. Insert the sample syringe, with the plunger slightly out, through
the septum and depress the plunger completely (to eject any oil
which enters the syringe needle during insertion).
7. Withdraw the desired aliquot volume and inject the aliquot into the
Chromatograph. Steps 6 and 7 should be done quickly to prevent
cooling of the aliquot.
8. At ten minute intervals, withdraw and inject two additional aliquots
per steps 5-7.
B-3
-------
-4-
CALCULATIONS
1. Determine the total mass in the aliquot of each group of compounds
with the same carbon number.
2. Calculate the total vapor pressure in the aliquot as:
p s RT VMi
Where:
R s gas constant
•
V = aliquot volume
T = test temperature
ft. - mass of compounds with carbon number i; all measurable hydrocarbons
•except methane
- molecular weight of carbon number i compounds
P&csr./r^jm,,.:-,
rf iJI'VV .:,:- '. :::•: ' ' -^ ! '' ' '• "."
1 7 . f -•,-,..-!.•;•••'
< -.. .- '' • • -•"-.:.-•, ''4
' " ' • ~L'," • .'-, v .':'' .,'•;') J .
• - --. *;u. ';-,tj :..•;. :-; .
*
B-4
-------
I
01
cc
>le
Cylinder
Chamber
I
I
2
4^>
-------
APPENDIX C
CHEVRON VAPOR COMPOSITION METHOD
-------
Chevron
Chevron Research Company
Ifc^^^ A Standard Oil Company of California Subsidiary
*^^P 576 Standard Avenue, Richmond, California
Mail Address PO Box 1627, Richmond, CA 94802
A. L. Grossberg . , Q loo,
V,ce-PreS,den, JulV 9, 1981
Mr. Robert J. Bryan
Supervising Engineer
Engineering Science
125 West Kuntington Drive
P.O. Box 358
Arcadia, California 91006
Dear Mr. Bryan:
Recently, Mr. R. A. Farnham of my staff contacted you in
response to your request to WOGA for industry assistance with
your EPA contract involving vapor pressures of heavy crudes.
At that time, he mentioned he had conceived a method which he
believed to be superior to other methods under considera-
tion. We are enclosing a report outlining the details of that
method.
We recommend that the method outlined in the report should
receive your careful consideration for further development.
Although the method has not been tested in the laboratory, it
has the potential of solving the difficult sampling and sample
transfer problems associated with other methods listed in your
letter to WOGA. The method also has other advantages:
1. It provides useful information on vapor composition for
calculating total hydrocarbon and reactive hydrocarbon
emissions.
2. The results are obtained at the temperature of interest.
If you have any questions regarding the above, please contact
Mr. R. A. Parnham at (415) 237-4411, Ext. 4882.
Sincerely yours,
Encl. - Report, "Apparatus and Method
for Determining Vapor
Composition and Vapor Presssure
of Heavy Stocks at 4:1 Ratio
of V/L," above date
cc: Mr. R. N. Harrison
C-l
-------
CHEVRON RESEARCH COMPANY
RICHMOND, CALIFORNIA
APPARATUS AND METHOD FOR JULY 9, 1981
DETERMINING VAPOR COMPOSITION
AND VAPOH PRESSURE OP HEAVY STOCKS
AT 4:1 RATIO OF V/L
Author - R. A. Farnham
Sampling and analyzing heavy stocks for vapor pressure Is difficult
and in many cases impossible when using the Reid Vapor Pressure
Test. The apparatus and method proposed herein resolves the problems
associated with the above. Also, the results of the proposed method
provide additional data which are directly applicable to emission
calculations which pose the most frequent need for testing of heavy
stocks.
The method using the apparatus described is not affected by the pres-
ence of water or dissolved air in the sample. The apparatus and
method can be easily modified to give results at different ratios of
V/L. The method involves use of the equipment shown on Attachment I.
Preparation for Sampling
Vessel A is first assembled as shown. Valve 2 is closed; the rest are
open. The vessel is inverted so Valve 3 is uppermost. Water or other
suitable liquid is introduced through Valve 4 until liquid overflows
from Valve 3» All valves are then closed, and the vessel is ready for
sample introduction.
Sampling
Vessel B (which is empty) is attached to Vessel A by screwing the
close Nipple 5 into Valve 3- Valve 1 is then connected to the vessel
to be sampled and then opened. Vessel B should be positioned so that
it is vertical and Valve 6 is uppermost. Valve 6 should be opened and
the air vented slowly until liquid appears in the gauge glass.
Valve 6 should then be closed quickly. Then close Valve 1 and discon-
nect from source. Close Valve 3 and remove Vessel B.
Analysis
In the laboratory connect a 10-psig pressure gauge to Valve 2 and a
nitrogen source regulated to 5 psig to Valve 1. Open Valve 3 and
slowly pressurize with N2 to 3 psig. Close Valves 3 and 1. Immerse
Vessel A into a water or an oil bath at desired temperature. If after
equilibrium is reached the pressure gauge reads less than 5 psig,
Encl. - Attachment I (RE 8163W
c-2
-------
-2-
pressurize slowly with nitrogen to 5 psig. After equilibrium is
peached, remove nitrogen source and withdrawn vapor sample from
Valve 1 for injection to chromatograph. Read pressure gauge and tem-
perature of bath.
Calculation and Reporting Results
Prom chromatograph analysis calculate the following:
1. Average Molecular Weight of Hydrocarbon (HC) in Vapor, Lb/Lb Mole,
. [A]
2. Molecular Fraction of HC in Vapor, [B]
3. Weight Fraction Reactive HC of Total HC in Vapor, [C]
Using above data and pressure gauge reading, the vapor pressure of the
hydrocarbon at 4:1 V/L and bath temperature can be calculated.
VP)T = [B] x [Gauge Reading + Barometric Pressure]
Calculation of Emissions Using Results
Emissions can be calculated from a source at bath temperature and
containing stock below its bubble point if the SCFH of vapor emitted
from the source and the fractional approach to equilibrium [F] are
known.
Total HC Emissions, Lb/Hr = [A] VP)T x SCFH x rpi
Barometric Pressure 379
Reactive HC Emissions, Lb/Hr = [C] x Total HC Emissions
Special Cases
If the stock to be sampled is at high temperature, a mineral oil can
be used in place of water. If cooling of the sample during sampling
is a problem or if very precise V/L is required, mineral oil can be
used and the apparatus containing oil can be heated to bath tempera-
ture (source temperature) before sampling. If heating is required,
Valve 3 should be uppermost and partially open during heating .
: cd
C-3
-------
ATTACHMENT I
APPARATUS FOR DETERMINING VAPOR COMPOSITION AND
VAPOR PRESSURE FOR HEAVY STOCKS AT
4:1 RATIO OF V/L
For Pressure Gauge
Identical
Vessels
Thermal
Relief
Valve
Sample Inlet and Vapor Withdrawal
Capped or Plugged
Flexible Neoprene or
Equivalent "Sack"
Screw Fit
'Bolted Threaded Flanges
•Total Volumn = A
(of Combined Vessels)
A*l Liter
Inert Liquid Fill
JInert Liquid Fill Vent
[inert Liquid Withdrawal
"T\ Close Couple
7 Nipple
Vessel B
Volumn = 1/5 Volumn A
C-4
/. &.. Cs&r7T,r~
EVRO* RESEARCH COMPANY
PROCESS ENGINEERING DEPARTMENT
ENOR. RES. AND DEV. DIVISION
D7V O
. DIP o i
-------
APPENDIX D
EVAPORATION METHOD
-------
Characterization of Crude Oil
Procedure for Gravimetric Method
The weights of several petri dishes with lids were measured and
recorded. In order to preserve a homogeneous sample, the crude was
vigorously shaken before pouring to an approximate depth of 1/8" in three
petri dishes. The dishes and lids containing the sample were again
weighed and placed in a laboratory oven at 100°F. The oven was main-
tained at 100°F throughout the test. A small Thomas pump purged the
oven (approx. val. 66 liters) at the rate of 2 liters/min. This small
flowrate did not disturb the evaporation while keepingthe percent of
hydrocarbons at an insignificant value in the oven vapor space. The
samples were removed from the oven and weighed at 1/2 hr. intervals
at the start of the test. After approximately 2-1/2 hrs., the weight loss
rate dropped to a value that allowed 1 hr. weighing intervals to be sufficient.
The test was conducted for approximately seven hours. Upon completion
of the test, weight loss and percent weight loss were calculated and
plotted versus time.
D-l
-------
COMPARISON OF
GRAVIMETRIC METHOD AND REID METHOD
SAMPLE SOURCE
CONOCO #66
EDGINGTON REFINERY #2
CONOCO #35
STD CARPINTERIA OFFSHORE
UNION SHIPPING TANK
GETTY OIL LOYD LEASE
ARCO RRU #6
PERCENT WEIGHT Loss
AT 100° F
AFTER 1 HR
98,9
98,3
96,4
89,4
88,1
85,3
81.7
AFTER 2 HR
97,7
96,9
93,2
86,5
85,6
81,6
77,9
AFTER 6 HR
94,4
94,4
87,1
82,7
82.2
77.4
73.0
REID VAPOR PRESSURE
AT 100° F
PER UNION OIL
0,4
0,4
0,6
4,0
2,9
5,2
3.8
-------
100.00
35.00
90.00
HT.
Knot
.MB-
o
U)
7S.BH
#
#
#
#
#
I EDEINETQN REFINERY 12
• 5TRNDRRO CflRPENTCRIR 'OFFSHORE*
« GETTY OIL 'LLOYD LER5E'
#
# #
eg
•
a-
ui
GO
TIME CHRJ
-------
HT.
0
I
7J.I
•
i CONOCO tEE
• OKOCOI3S
* UNION 5HIPPINE TBNK
X RRCO RRUIE
E9
ea
as
g
••
s
IM
g
in
S
X
ca
IA
S
•
10
g g
i^ m
TIKE: (HRJ
-------
APPENDIX E
EQUIPMENT COSTS
-------
APPENDIX E
EQUIPMENT COSTS
Costs are estimated for specialized and laboratory equipment to
conduct the standard Reid Vapor Pressure (RVP) test and the vapor
composition test. In the case of the RVP test, a container is required
for each sample collected at the same time. The RVP "bomb" apparatus
is used only during the analysis, but several bombs may be needed to
avoid delay in analysis caused by the need for cleaning the apparatus.
Sample containers used for the vapor composition method are considerably
more expensive than those used for RVP testing but are close in cost to
the RVP bombs. Unit cost estimates are given in all cases.
Only significant items of equipment are included in our estimate.
No attempt was made to estimate the number of sample containers or RVP
bombs needed. Costs are summarized in the attached table.
E-l
-------
SUMMARY OF EQUIPMENT COSTS
Cost Item
Reid
Vapor Pressure
Vapor
Composition
Laboratory Equipment
(1) Bath, Constant Temperature
(Thelco 261)
(2) RVP Bomb per ASTM D323-72
(VWR 51864-029)
(3) Pressure Gage
0-5 psi +0.1 psi
per ASTM D323-72
(VWR 51869-022)
(4) Gas Chromatograph,
single column, FID,
with linear temperature
program (Varian 1440)
(5) Gas Chromatograph Data
System (Varian CDS-III and
chart recorder)
(6) Flow meter, valves, flow
controller, filters,
regulators for gas chromato-
graph
Field Equipment
(1) Cooling Bath per ASTM D270-
2546
(2) Sample Containers, RVP
samples
(3) Sample containers, Chevron
vapor composition procedure
$545.00
345.00 ea.
156.95 ea.
S5030.00
4845.00
930.00
200.00 ea.
50.00 ea.
600.00 ea.
E-2
-------
50272-101
REPORT DOCUMENTATION
PAGE
1. REPORT NO.
EPA 909/9-81-004
4. Title and Subtitle
Analysis of Potential Methods to Determine the
Volatilities of Heavy Crude Oils
7. Author(s)
Robert J. Bryan
9. Performing Organization Name and Address
Engineering-Science, Inc.
125 West Huntington Drive
Arcadia, CA 91006
12. Sponsoring Organization Name and Address
U.S. Environmental Protection Agency, Region IX
215 Fremont Street
San Francisco, CA 94105
3. Recipient's Accession No
5. Report Date
December 1981
8. Performing Organization Rept. No
9211.00
10. Proiect/Task/Work Unit No.
W. A. 11
11. Contract(C) or Grant(G) No
(a 68-02-3509
(G)
13. Type or Report & Period Covered
Final Report
14.
IS. Supplementary Notes
16. Abstract (Limit- 200 >ords)
This report covers the investigation of possible alternative
methods to measure the volatility of heavy crude oil. The work was
restricted to a literature search and inquiries made to Informed govern-
ment and industry groups. The current method for determining vapor
pressure at storage temperature for crude oil and refined petroleum
products involves determination of Reid Vapor Pressure and use of a
correlation nomograph. The technique is not applicable to some heavy
crudes. Also, there can be an undue influence from methane and ethane.
Alternative methods investigated include developing data to extend
the temperature and vapor pressure range of the correlation nomograph,
modifying the Reid Vapor Pressure Method, use of a vapor composition
approach, and determining evaporation losses under controlled conditions.
Sampling and analytical problems were evaluated for the alternatives.
A recommendation was made to conduct further studies on the vapor
composition method.
17. Document Analysis a Descriptors
Crude oil, vapor pressure, Reid Vapor Pressure, volatility, evaporation loss.
b. Identifiers/Open-Ended Terms
c. COSATI Field/Group
8. Availability Statement
19. Security Class (This Report)
Unclassified
20. Security Class (This Page)
Unclassified
21. No of Pages
22. Price
(S«eANSI-Z39.18)
See Instructions on Reverse
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-35)
Department of Commerce
-------
|