ASTM D7112-12(2017)
(Test Method)Standard Test Method for Determining Stability and Compatibility of Heavy Fuel Oils and Crude Oils by Heavy Fuel Oil Stability Analyzer (Optical Detection)
Standard Test Method for Determining Stability and Compatibility of Heavy Fuel Oils and Crude Oils by Heavy Fuel Oil Stability Analyzer (Optical Detection)
SIGNIFICANCE AND USE
5.1 Automatic determination of stability parameters using a light back-scattering technique improves accuracy and removes human errors. In manual testing, operators have to visually compare oil stains on pieces of filter paper to determine if asphaltenes have been precipitated.
5.2 Refinery thermal and hydrocracking processes can be run closer to their severity limits if stability parameters can be calculated more accurately. This gives increased yield and profitability.
5.3 Results from the test method could be used to set a standard specification for stability parameters for fuel oils.
5.4 The compatibility parameters of crude oils can be used in crude oil blending in refineries to determine, in advance, which crude oil blends will be compatible and thus can be used to minimize plugging problems, unit shut downs, and maintenance costs. Determination of crude oil compatibility parameters also enables refineries to select crude oil mixtures more economically.
5.5 This test method can measure stability and compatibility parameters, and determine stability reserve on different blends for particular applications to optimize the blending, storage, and use of heavy fuel oils
Note 1: Users of this test method would normally use stability and compatibility parameters to determine stability reserve of residual products, fuel blends and crude oils. However, the interpretation of stability, stability reserve and compatibility is heavily ‘use dependent,’ and is beyond the scope of this test method.
SCOPE
1.1 This test method covers an automated procedure involving titration and optical detection of precipitated asphaltenes for determining the stability and compatibility parameters of refinery residual streams, residual fuel oils, and crude oils. Stability in this context is the ability to maintain asphaltenes in a peptized or dissolved state and not undergo flocculation or precipitation. Similarly, compatibility relates to the property of mixing two or more oils without precipitation or flocculation of asphaltenes.
1.2 This test method is applicable to residual products from atmospheric and vacuum distillation, from thermal, catalytic, and hydrocracking processes, to products typical of Specifications D396, Grades No. 5L, 5H, and 6, and D2880, Grades No. 3-GT and 4-GT, and to crude oils, providing these products contain 0.05 mass % or greater concentration of asphaltenes.
1.3 This test method is not relevant to oils that contain less than 0.05 % asphaltenes, and would be pointless to apply to unstable oils that already contain flocculated asphaltenes.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: D7112 − 12 (Reapproved 2017)
Standard Test Method for
Determining Stability and Compatibility of Heavy Fuel Oils
and Crude Oils by Heavy Fuel Oil Stability Analyzer (Optical
Detection)
This standard is issued under the fixed designation D7112; 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 reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method covers an automated procedure involv- 2.1 ASTM Standards:
ing titration and optical detection of precipitated asphaltenes D396 Specification for Fuel Oils
for determining the stability and compatibility parameters of D2880 Specification for Gas Turbine Fuel Oils
refinery residual streams, residual fuel oils, and crude oils. D4057 Practice for Manual Sampling of Petroleum and
Stability in this context is the ability to maintain asphaltenes in Petroleum Products
a peptized or dissolved state and not undergo flocculation or D4175 Terminology Relating to Petroleum Products, Liquid
precipitation. Similarly, compatibility relates to the property of Fuels, and Lubricants
mixingtwoormoreoilswithoutprecipitationorflocculationof D4177 Practice for Automatic Sampling of Petroleum and
asphaltenes. Petroleum Products
D6299 Practice for Applying Statistical Quality Assurance
1.2 This test method is applicable to residual products from
and Control Charting Techniques to Evaluate Analytical
atmospheric and vacuum distillation, from thermal, catalytic,
Measurement System Performance
and hydrocracking processes, to products typical of Specifica-
D6560 Test Method for Determination ofAsphaltenes (Hep-
tions D396, Grades No. 5L, 5H, and 6, and D2880, Grades No.
tane Insolubles) in Crude Petroleum and Petroleum Prod-
3-GT and 4-GT, and to crude oils, providing these products
ucts
contain 0.05 mass % or greater concentration of asphaltenes.
1.3 This test method is not relevant to oils that contain less
3. Terminology
than 0.05 % asphaltenes, and would be pointless to apply to
3.1 Definitions:
unstable oils that already contain flocculated asphaltenes.
3.1.1 For definitions of some terms used in this test method,
1.4 The values stated in SI units are to be regarded as
such as crude oil, repeatability, reproducibility, and residual
standard. No other units of measurement are included in this
fuel oil, refer to Terminology D4175.
standard.
3.1.2 asphaltenes, n—(rarely used in the singular), in petro-
1.5 This standard does not purport to address all of the leum technology, represent an oil fraction that is soluble in a
safety concerns, if any, associated with its use. It is the specified aromatic solvent but separates upon addition of an
responsibility of the user of this standard to establish appro- excess of a specified paraffinic solvent.
3.1.2.1 Discussion—In this test method, the aromatic sol-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. vent is xylene and the paraffinic solvent is n-heptane.
1.6 This international standard was developed in accor-
3.1.3 compatibility, n—of crude oils and of heavy fuel oils,
dance with internationally recognized principles on standard-
the ability of two or more crude oils or fuel oils to be blended
ization established in the Decision on Principles for the
together within specified ratios without evidence of separation,
Development of International Standards, Guides and Recom-
such as flocculation or separation of asphaltenes.
mendations issued by the World Trade Organization Technical
3.1.4 flocculation, n—of asphaltenes in crude oils or heavy
Barriers to Trade (TBT) Committee.
fuel oils, the aggregation of colloidally dispersed asphaltenes
into larger, visible masses that may or may not settle.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.14 on on Stability, Cleanliness and Compatibility of Liquid
Fuels. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2017. Published November 2017. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 2005. Last previous edition approved in 2012 as D7112–12. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D7112-12R17. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7112 − 12 (2017)
3.1.5 stability reserve, n—of crude oils, heavy fuel oils, and 3.2.8 P-value, n—of refinery residual steams, residual fuel
residual streams containing asphaltenes, the property of an oil oils and crude oils, an indication of the stability or available
to maintain asphaltenes in a peptized (colloidally dispersed) solvency power of an oil with respect to precipitation of
state and prevent their flocculation when stored or when asphaltenes.
blended with other oils. 3.2.8.1 Discussion—Since the equation defining P-value is
P=(1+ X ),where X istheminimumvolumeofparaffinic
3.1.5.1 Discussion—An oil with a high stability reserve can
min min
solvent, n-heptane, (in mL) needed to be added to1gofoilto
be stored for a long period of time or blended with a range of
result in flocculation of asphaltenes, the smallest P-value is 1,
other oils without flocculation of asphaltenes.
which means the oil is unstable and can precipitate asphaltenes
3.2 Definitions of Terms Specific to This Standard:
without addition of any paraffinic solvent. A higher P-value
3.2.1 aromatic solvent equivalent (xylene equivalent), SE,
indicates that an oil is more stable with respect to flocculation
n—the lowest aromatic solvent (xylene) content, expressed as
of asphaltenes. P-value by this test method relates specifically
a volume %, in a mixture containing aromatic and paraffinic
toxyleneand n-heptaneasthearomaticandparaffinicsolvents,
solvents (xylene and n-heptane) which, when mixed with oil,
respectively.
will not result in flocculation of asphaltenes. See flocculation
3.2.9 P,n—the P-value of an asphaltene, which is the
a
ratio.
peptizability or ability of an asphaltene to remain colloidally
3.2.1.1 Discussion—SE is defined as FR multiplied by
5/1
dispersed.
100 %, as shown in Eq 2.
3.2.10 P,n—the P-value of an oil matrix. See oil matrix.
o
3.2.2 evaporation correction coeffıcient, n—the rate of
3.2.11 peptize, v—of an oil or cutter stock, to dissolve an
evaporation of aromatic solvent (xylene) from the sample cup,
asphaltene or to maintain an asphaltene in colloidal dispersion.
measured in grams per hour.
3.2.12 solubility blending number, S ,n—a crude oil
BN
3.2.3 flocculationratio(FR),n—thelowestaromaticsolvent
blending model parameter which can be used to determine if
(xylene) concentration, expressed as a proportion of xylene to
blends of oils are incompatible or compatible. See insolubility
xylene plus n-heptane which, when mixed with an oil, will not
number.
result in flocculation of asphaltenes. See 15.1, Eq 1.
3.2.12.1 Discussion—Solubility blending numbers for indi-
3.2.4 FR ,n—theflocculationratioatadilutionof5mLof vidual oils are determined and calculated from the density of
5/1
xylene and n-heptane solvent mixture to1gof oil.
the oil, aromatic solvent equivalent value, and volume of
paraffinic solvent that can be added to 5 mL of oil without
3.2.4.1 Discussion—The ratio 5 to 1 is used internally by a
asphaltene precipitation. The equations are given under Calcu-
number of oil companies involved with the stability and
lation of Results (see 15.2).
compatibility of heavy fuel oils and crude oils. This ratio is
chosen so that a P-value of six represents an FR of zero.
5/1 3.2.13 step size, n—the volume in mL of each portion of
n-heptane added to the stock solution in the course of the test
3.2.5 insolubility number, I ,n—a crude oil blending model
N
procedure.
parameter which can be used to determine if blends of oils are
compatible or incompatible. See solubility blending number. 3.2.14 stock solution, n—a solution of a sample dissolved in
a specific amount of xylene.
3.2.5.1 Discussion—Insolubility numbers for individual oils
are determined and calculated from the density of the oil,
3.3 Symbols:
aromatic solvent equivalent value and volume of paraffinic
FR = flocculation ratio
solvent (n-heptane) that can be added to 5 mL of oil without
FR = flocculation ratio at a dilution of 5 mL solution
5/1
asphaltene precipitation. The equations are given under Calcu-
(xylene plus n-heptane) to1gofoil
lation of Results (see 15.2).
FR = maximum flocculation ratio
max
I = insolubility number
3.2.6 maximumflocculationratio,FR ,n—ofasphaltenes N
max
P = the P-value of an oil
in residual fuel oils and crude oils, the minimum required
P = the P-value of an asphaltene
a
solvency power of a solvent mixture, expressed as a ratio by
P = the P-value or peptizing power of an oil matrix
volume of aromatic solvent (xylene) to aromatic solvent plus o
S = solubility blending number
BN
paraffinic solvent (n-heptane) to keep the asphaltenes in an oil
SE = xylene equivalent, volume %
colloidally dispersed.
X = n-heptane consumption of undiluted oil, in mL/g of
min
3.2.6.1 Discussion—FR is determined from a plot of
max
oil
flocculation ratios versus the oil concentration in solvent,
extrapolated to infinite dilution of the sample at the y-axis
4. Summary of Test Method
(where (1/X)=0.See Eq 3).
4.1 Stability and compatibility parameters are determined
3.2.7 oil matrix, n—that portion of a sample of heavy fuel
by titration and optical detection of precipitated asphaltenes.A
oil or crude oil that surrounds and colloidally disperses the
stock solution is prepared and three different mixtures of the
asphaltenes.
sample oil plus xylene are titrated with n-heptane to cause
3.2.7.1 Discussion—For purposes of this test method, an oil precipitation of asphaltenes. The titrated mixture is continu-
sample is considered to be composed of an oil matrix (some- ously circulated through an optical detector which detects
times called an oil medium) and asphaltenes. precipitatedasphaltenesbyback-scatteringofvisiblelight.The
D7112 − 12 (2017)
amounts of oil, xylene, and n-heptane are used to calculate 7.1.1.1 Sample Cup, light weight, inert cups designed to fit
stability parameters: solvent equivalent, P-value, and FR .If the sample carousel, with a smooth, flat bottom, volume
5/1
the density of a crude oil sample is known, then the compat- approximately 100 mL. Typically, aluminum cups have been
ibility parameters (S and I ) of the crude oil may also be used.
BN N
calculated. 7.1.1.2 Sample Carousel, typically a four-position sample
cup holder delivering the sample cups sequentially to the
measurement position.
5. Significance and Use
7.1.1.3 Mixer Lift System, vertically moving lift system,
5.1 Automatic determination of stability parameters using a
forming a seal with the sample cup in the measurement
light back-scattering technique improves accuracy and re-
position and incorporating a mechanical stirrer which starts to
moves human errors. In manual testing, operators have to
rotate when the seal is made. It also incorporates delivery lines
visually compare oil stains on pieces of filter paper to deter-
for n-heptane and xylene addition, the circulation line for
mine if asphaltenes have been precipitated.
passing the sample through the detector and the exhaust line,
5.2 Refinery thermal and hydrocracking processes can be
which empties the sample cup after analysis.
run closer to their severity limits if stability parameters can be
7.1.1.4 Aromatic Solvent Pump, accurate and adjustable
calculated more accurately. This gives increased yield and ceramic piston pump, capable of delivering xylene at a rate of
profitability.
0.01 mL⁄s to 0.5 mL/s.
7.1.1.5 Paraffınic Solvent Pump, accurate and adjustable
5.3 Results from the test method could be used to set a
ceramic piston pump, capable of delivering n-heptane at a rate
standard specification for stability parameters for fuel oils.
of 0.01 mL⁄s to 0.5 mL/s.
5.4 The compatibility parameters of crude oils can be used
7.1.1.6 Circulation Pump, accurate and adjustable ceramic
in crude oil blending in refineries to determine, in advance,
pistonpumpusedtocirculatethesampleundertestthroughthe
which crude oil blends will be compatible and thus can be used
detector system.
to minimize plugging problems, unit shut downs, and mainte-
7.1.1.7 Exhaust Pump, accurate and adjustable ceramic
nance costs. Determination of crude oil compatibility param-
piston pump used to empty the sample cup at the end of the
eters also enables refineries to select crude oil mixtures more
measurement.
economically.
7.1.1.8 Detector System, (see Fig. 3) optical detector
through which the sample solution is continuously circulated.
5.5 Thistestmethodcanmeasurestabilityandcompatibility
The detector is composed of a visible light source and a
parameters, and determine stability reserve on different blends
photodiode for recording the light reflecting from asphaltene
for particular applications to optimize the blending, storage,
particles in the test sample.
and use of heavy fuel oils
7.1.1.9 Hot Plate, a temperature controlled heating system
NOTE 1—Users of this test method would normally use stability and
maybelocatedbelowthesamplecups,whichwillwarmupthe
compatibility parameters to determine stability reserve of residual
sample so that the titration may be performed at an elevated
products, fuel blends and crude oils. However, the interpretation of
temperature. The temperature of the hot plate should be
stability,stabilityreserveandcompatibilityisheavily‘usedependent,’and
adjustable between 20 °C and 100 °C.
is beyond the scope of this test method.
7.1.2 Computer, controls the measurement and calibration
6. Interferences programs and is an interface between the operator and the
analyzer.
6.1 Free water present in the oil can cause difficulties with
7.1.3 PORLA Step Measurement Screen, computer display,
the optical detector and should be removed by centrifuging
allowing data about the sample and operator to be input as well
prior to testing.
as showing the results of each titration (see Fig. 4).
6.2 Solid particles, such as coke or wax particles, mud, 7.1.4 Parameter Screen, computer display, allows all of the
sand, or catalyst fines, in the oil will not affect the optical
measurement cycle parameters to be adjusted from the default
detector or interfere with the results. va
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7112 − 12 D7112 − 12 (Reapproved 2017)
Standard Test Method for
Determining Stability and Compatibility of Heavy Fuel Oils
and Crude Oils by Heavy Fuel Oil Stability Analyzer (Optical
Detection)
This standard is issued under the fixed designation D7112; 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 reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*Scope
1.1 This test method covers an automated procedure involving titration and optical detection of precipitated asphaltenes for
determining the stability and compatibility parameters of refinery residual streams, residual fuel oils, and crude oils. Stability in
this context is the ability to maintain asphaltenes in a peptized or dissolved state and not undergo flocculation or precipitation.
Similarly, compatibility relates to the property of mixing two or more oils without precipitation or flocculation of asphaltenes.
1.2 This test method is applicable to residual products from atmospheric and vacuum distillation, from thermal, catalytic, and
hydrocracking processes, to products typical of Specifications D396, Grades No. 5L, 5H, and 6, and D2880, Grades No. 3-GT and
4-GT, and to crude oils, providing these products contain 0.05 mass % or greater concentration of asphaltenes.
1.3 This test method is not relevant to oils that contain less than 0.05 % asphaltenes, and would be pointless to apply to unstable
oils that already contain flocculated asphaltenes.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D396 Specification for Fuel Oils
D2880 Specification for Gas Turbine Fuel Oils
D4057 Practice for Manual Sampling of Petroleum and Petroleum Products
D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants
D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products
D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measure-
ment System Performance
D6560 Test Method for Determination of Asphaltenes (Heptane Insolubles) in Crude Petroleum and Petroleum Products
3. Terminology
3.1 Definitions:
3.1.1 For definitions of some terms used in this test method, such as crude oil, repeatability, reproducibility, and residual fuel
oil, refer to Terminology D4175.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee
D02.14 on Stability and Cleanlinesson Stability, Cleanliness and Compatibility of Liquid Fuels.
Current edition approved Nov. 1, 2012Oct. 1, 2017. Published February 2013November 2017. Originally approved in 2005. Last previous edition approved in 20092012
as D7112–09.–12. DOI: 10.1520/D7112-12.10.1520/D7112-12R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7112 − 12 (2017)
3.1.2 asphaltenes, n—(rarely used in the singular), in petroleum technology, represent an oil fraction that is soluble in a specified
aromatic solvent but separates upon addition of an excess of a specified paraffinic solvent.
3.1.2.1 Discussion—
In this test method, the aromatic solvent is xylene and the paraffinic solvent is n-heptane.
3.1.3 compatibility, n—of crude oils and of heavy fuel oils, the ability of two or more crude oils or fuel oils to be blended
together within specified ratios without evidence of separation, such as flocculation or separation of asphaltenes.
3.1.4 flocculation, n—of asphaltenes in crude oils or heavy fuel oils, the aggregation of colloidally dispersed asphaltenes into
larger, visible masses that may or may not settle.
3.1.5 stability reserve, n—of crude oils, heavy fuel oils, and residual streams containing asphaltenes, the property of an oil to
maintain asphaltenes in a peptized (colloidally dispersed) state and prevent their flocculation when stored or when blended with
other oils.
3.1.5.1 Discussion—
An oil with a high stability reserve can be stored for a long period of time or blended with a range of other oils without flocculation
of asphaltenes.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 aromatic solvent equivalent (xylene equivalent), SE, n—the lowest aromatic solvent (xylene) content, expressed as a
volume %, in a mixture containing aromatic and paraffinic solvents (xylene and n-heptane) which, when mixed with oil, will not
result in flocculation of asphaltenes. See flocculation ratio.
3.2.1.1 Discussion—
SE is defined as FR multiplied by 100 %, as shown in Eq 2.
5/1
3.2.2 evaporation correction coeffıcient, n—the rate of evaporation of aromatic solvent (xylene) from the sample cup, measured
in grams per hour.
3.2.3 flocculation ratio (FR), n—the lowest aromatic solvent (xylene) concentration, expressed as a proportion of xylene to
xylene plus n-heptane which, when mixed with an oil, will not result in flocculation of asphaltenes. See 15.1, Eq 1.
3.2.4 FR , n—the flocculation ratio at a dilution of 5 mL of xylene and n-heptane solvent mixture to 1 g of oil.
5/1
3.2.4.1 Discussion—
The ratio 5 to 1 is used internally by a number of oil companies involved with the stability and compatibility of heavy fuel oils
and crude oils. This ratio is chosen so that a P-value of six represents an FR of zero.
5/1
3.2.5 insolubility number, I , n—a crude oil blending model parameter which can be used to determine if blends of oils are
N
compatible or incompatible. See solubility blending number.
3.2.5.1 Discussion—
Insolubility numbers for individual oils are determined and calculated from the density of the oil, aromatic solvent equivalent value
and volume of paraffinic solvent (n-heptane) that can be added to 5 mL of oil without asphaltene precipitation. The equations are
given under Calculation of Results (see 15.2).
3.2.6 maximum flocculation ratio, FR , n—of asphaltenes in residual fuel oils and crude oils, the minimum required solvency
max
power of a solvent mixture, expressed as a ratio by volume of aromatic solvent (xylene) to aromatic solvent plus paraffinic solvent
(n-heptane) to keep the asphaltenes in an oil colloidally dispersed.
3.2.6.1 Discussion—
FR is determined from a plot of flocculation ratios versus the oil concentration in solvent, extrapolated to infinite dilution of
max
the sample at the y-axis (where (1/X) = 0. See Eq 3).
3.2.7 oil matrix, n—that portion of a sample of heavy fuel oil or crude oil that surrounds and colloidally disperses the
asphaltenes.
D7112 − 12 (2017)
3.2.7.1 Discussion—
For purposes of this test method, an oil sample is considered to be composed of an oil matrix (sometimes called an oil medium)
and asphaltenes.
3.2.8 P-value, n—of refinery residual steams, residual fuel oils and crude oils, an indication of the stability or available solvency
power of an oil with respect to precipitation of asphaltenes.
3.2.8.1 Discussion—
Since the equation defining P-value is P = (1 + X ), where X is the minimum volume of paraffinic solvent, n-heptane, (in mL)
min min
needed to be added to 1 g of oil to result in flocculation of asphaltenes, the smallest P-value is 1, which means the oil is unstable
and can precipitate asphaltenes without addition of any paraffinic solvent. A higher P-value indicates that an oil is more stable with
respect to flocculation of asphaltenes. P-value by this test method relates specifically to xylene and n-heptane as the aromatic and
paraffinic solvents, respectively.
3.2.9 P , n—the P-value of an asphaltene, which is the peptizability or ability of an asphaltene to remain colloidally dispersed.
a
3.2.10 P , n—the P-value of an oil matrix. See oil matrix.
o
3.2.11 peptize, v—of an oil or cutter stock, to dissolve an asphaltene or to maintain an asphaltene in colloidal dispersion.
3.2.12 solubility blending number, S , n—a crude oil blending model parameter which can be used to determine if blends of
BN
oils are incompatible or compatible. See insolubility number.
3.2.12.1 Discussion—
Solubility blending numbers for individual oils are determined and calculated from the density of the oil, aromatic solvent
equivalent value, and volume of paraffinic solvent that can be added to 5 mL of oil without asphaltene precipitation. The equations
are given under Calculation of Results (see 15.2).
3.2.13 step size, n—the volume in mL of each portion of n-heptane added to the stock solution in the course of the test
procedure.
3.2.14 stock solution, n—a solution of a sample dissolved in a specific amount of xylene.
3.3 Symbols:
FR = flocculation ratio
FR = flocculation ratio
FR = flocculation ratio at a dilution of 5 mL solution (xylene plus n-heptane) to 1 g of oil
5/1
FR = maximum flocculation ratio
max
I = insolubility number
N
P = the P-value of an oil
P = the P-value of an asphaltene
a
P = the P-value or peptizing power of an oil matrix
o
S = solubility blending number
BN
SE = xylene equivalent, volume %
X = n-heptane consumption of undiluted oil, in mL/g of oil
min
FR = flocculation ratio at a dilution of 5 mL solution (xylene plus n-heptane) to 1 g of oil
5/1
FR = maximum flocculation ratio
max
I = insolubility number
N
P = the P-value of an oil
P = the P-value of an asphaltene
a
P = the P-value or peptizing power of an oil matrix
o
S = solubility blending number
BN
SE = xylene equivalent, volume %
X = n-heptane consumption of undiluted oil, in mL/g of oil
min
4. Summary of Test Method
4.1 Stability and compatibility parameters are determined by titration and optical detection of precipitated asphaltenes. A stock
solution is prepared and three different mixtures of the sample oil plus xylene are titrated with n-heptane to cause precipitation of
asphaltenes. The titrated mixture is continuously circulated through an optical detector which detects precipitated asphaltenes by
D7112 − 12 (2017)
back-scattering of visible light. The amounts of oil, xylene, and n-heptane are used to calculate stability parameters: solvent
equivalent, P-value, and FR . If the density of a crude oil sample is known, then the compatibility parameters (S and I ) of
5/1 BN N
the crude oil may also be calculated.
5. Significance and Use
5.1 Automatic determination of stability parameters using a light back-scattering technique improves accuracy and removes
human errors. In manual testing, operators have to visually compare oil stains on pieces of filter paper to determine if asphaltenes
have been precipitated.
5.2 Refinery thermal and hydrocracking processes can be run closer to their severity limits if stability parameters can be
calculated more accurately. This gives increased yield and profitability.
5.3 Results from the test method could be used to set a standard specification for stability parameters for fuel oils.
5.4 The compatibility parameters of crude oils can be used in crude oil blending in refineries to determine, in advance, which
crude oil blends will be compatible and thus can be used to minimize plugging problems, unit shut downs, and maintenance costs.
Determination of crude oil compatibility parameters also enables refineries to select crude oil mixtures more economically.
5.5 This test method can measure stability and compatibility parameters, and determine stability reserve on different blends for
particular applications to optimize the blending, storage, and use of heavy fuel oils
NOTE 1—Users of this test method would normally use stability and compatibility parameters to determine stability reserve of residual products, fuel
blends and crude oils. However, the interpretation of stability, stability reserve and compatibility is heavily ‘use dependent,’ and is beyond the scope of
this test method.
6. Interferences
6.1 Free water present in the oil can cause difficulties with the optical detector and should be removed by centrifuging prior to
testing.
6.2 Solid particles, such as coke or wax particles, mud, sand, or catalyst fines, in the oil will not affect the optical detector or
interfere with the results.
7. Apparatus
3,4
7.1 PORLA Heavy and Crude Oil Stability and Compatibility Analyzer —See Figs. 1 and 2.
7.1.1 A portion of the apparatus is shown diagrammatically in Fig. 2 and is comprised of the following parts:
7.1.1.1 Sample Cup, light weight, inert cups designed to fit the sample carousel, with a smooth, flat bottom, volume
approximately 100 mL. Typically, aluminum cups have been used.
7.1.1.2 Sample Carousel, typically a four-position sample cup holder delivering the sample cups sequentially to the
measurement position.
7.1.1.3 Mixer Lift System, vertically moving lift system, forming a seal with the sample cup in the measurement position and
incorporating a mechanical stirrer which starts to rotate when the seal is made. It also incorporates delivery lines for n-heptane and
xylene addition, the circulation line for passing the sample through the detector and the exhaust line, which empties the sample
cup after analysis.
7.1.1.4 Aromatic Solvent Pump, accurate and adjustable ceramic piston pump, capable of delivering xylene at a rate of
0.010.01 mL ⁄s to 0.5 mL/s.
7.1.1.5 Paraffınic Solvent Pump, accurate and adjustable ceramic piston pump, capable of delivering n-heptane at a r
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