ASTM D7061-04
(Test Method)Standard Test Method for Measuring n-Heptane Induced Phase Separation of Asphaltene-Containing Heavy Fuel Oils as Separability Number by an Optical Scanning Device
Standard Test Method for Measuring <bdit>n</bdit>-Heptane Induced Phase Separation of Asphaltene-Containing Heavy Fuel Oils as Separability Number by an Optical Scanning Device
SCOPE
1.1 This test method covers the quantitative measurement, either in the laboratory or in the field, of how easily asphaltene-containing heavy fuel oils diluted in toluene phase separate upon addition of heptane. This is measured as a separability number (%) by the use of an optical scanning device.
1.2 The test method is limited to asphaltene-containing heavy fuel oils. ASTM specification fuels that generally fall within the scope of this test method are Specification D 396, Grade Nos. 4, 5, and 6, Specification D 975, Grade No. 4-D, and Specification D 2880, Grade Nos. 3-GT and 4-GT. Refinery fractions from which such blended fuels are made also fall within the scope of this test method.
1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.
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An American National Standard
Designation:D7061–04
Standard Test Method for
Measuring n-Heptane Induced Phase Separation of
Asphaltene-Containing Heavy Fuel Oils as Separability
Number by an Optical Scanning Device
This standard is issued under the fixed designation D 7061; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.1.1 Discussion—Asphaltenes are found largely in crude
oils and in heavy fuel oils containing residual fractions. They
1.1 This test method covers the quantitative measurement,
are insoluble in alkanes, such as n-heptane and cetane, but
eitherinthelaboratoryorinthefield,ofhoweasilyasphaltene-
soluble in aromatic solvents, such as benzene, toluene, and
containing heavy fuel oils diluted in toluene phase separate
1-methylnaphthalene.
upon addition of heptane. This is measured as a separability
3.1.2 compatibility, n—of crude oils or of heavy fuel oils,
number (%) by the use of an optical scanning device.
the ability of two or more crude oils or fuel oils to blend
1.2 The test method is limited to asphaltene-containing
together within certain concentration ranges without evidence
heavy fuel oils. ASTM specification fuels that generally fall
of separation, such as the formation of multiple phases.
within the scope of this test method are Specification D 396,
3.1.2.1 Discussion—Incompatible heavy fuel oils or crude
Grade Nos. 4, 5, and 6, Specification D 975, Grade No. 4-D,
oils, when mixed or blended, result in the flocculation or
and Specification D 2880, Grade Nos. 3-GT and 4-GT. Refin-
precipitation of asphaltenes. Some oils may be compatible
ery fractions from which such blended fuels are made also fall
within certain concentration ranges in specific mixtures, but
within the scope of this test method.
incompatible outside those ranges.
1.3 This standard does not purport to address all of the
3.1.3 flocculation, n—of asphaltenes from crude oils or
safety concerns, if any, associated with its use. It is the
heavy fuel oils, the aggregation of colloidally dispersed as-
responsibility of the user of this standard to establish appro-
phaltenes into visibly larger masses that may or may not settle.
priate safety and health practices and determine the applica-
3.1.4 peptization, n—of asphaltenes in crude oils or heavy
bility of regulatory limitations prior to use.
fuel oils, the dispersion of asphaltenes to produce a colloidal
2. Referenced Documents dispersion.
3.1.5 stability reserve, n—in petroleum technology, the
2.1 ASTM Standards:
property of an oil to maintain asphaltenes in a peptized state
D 396 Specification for Fuel Oils
and prevent flocculation of the asphaltenes.
D 975 Specification for Diesel Fuel Oils
3.1.5.1 Discussion—An oil with a low stability reserve is
D 2880 Specification for Gas Turbine Fuel Oils
likelytoundergoflocculationofasphalteneswhenstressed(for
D 4057 Practice for Manual Sampling of Petroleum and
example, extended heated storage) or blended with a range of
Petroleum Products
other oils.Two oils each with a high stability reserve are likely
D 4177 Practice for Automatic Sampling of Petroleum and
to maintain asphaltenes in a peptized state and not lead to
Petroleum Products
flocculation when blended together.
3. Terminology
3.1.6 transmittance, n—of light, the fraction of the incident
light of a given wavelength that is not reflected or absorbed,
3.1 Definitions:
but passes through a substance.
3.1.1 asphaltene, n—in petroleum technology, a molecule
3.2 Definitions of Terms Specific to This Standard:
of high molecular mass, high carbon/hydrogen ratio, and
3.2.1 separability number, n—in petroleum technology,a
containing heteroatoms.
number that estimates the stability reserve of an oil, as
described in this test method.
This test method is under the jurisdiction of ASTM Committee D02 on
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
4. Summary of Test Method
D02.14 on Stability and Cleanliness of Liquid Fuels.
Current edition approved June 1, 2004. Published July 2004. 4.1 Dilution of oil with toluene followed by addition of
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
heptane causes asphaltenes to flocculate, and the oil to phase
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
separate. The rate of the phase separation is determined by
Standards volume information, refer to the standard’s Document Summary page on
measuring the increase in transmittance in the sample from the
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D7061–04
bottom of a test tube to the top (or a portion thereof) over time.
The standard deviation of the average transmittance from a
number of scans gives a separability number (%).
4.2 The oil is first diluted with toluene in ratios that depend
on the oil type (Annex A1). Mix 2 mL of the oil/toluene
solution with 23 mL of heptane. Transfer 7 mL of the
oil/toluene/heptanemixtureintoaglassvialthatisinsertedinto
an optical scanning device.
4.3 The change in light transmittance through the glass vial
containing the oil/toluene/heptane mixture is recorded by
scanning the vial vertically with the optical scanning device.
One scan is run every 60 s for 15 min. An average of the
transmittance is calculated from 1125 readings at 0.04-mm
intervals along the glass vial, starting 10 mm above the bottom
of the vial and continuing up to 55 mm for each scan. The
separability number from 16 scans is calculated and reported.
5. Significance and Use
5.1 This procedure describes a rapid and sensitive method
for estimating the stability reserve of an oil. The stability
reserve is estimated in terms of a separability number, where a
FIG. 1 Schematic Representation of a Typical Measurement
low value of the separability number indicates that there is a
Using an Optical Scanning Device
stabilityreservewithintheoil.Whentheseparabilitynumberis
between 0 to 5, the oil can be considered to have a high
stability reserve and asphaltenes are not likely to flocculate. If
6.2 Optical Scanning Device—The apparatus consists of a
theseparability numberisbetween5to10,thestabilityreserve
reading head, composed of a pulsed infrared light source that
in the oil will be much lower. However, asphaltenes are, in this
uses a wavelength of 850 nm. A detector is situated opposite
case, not likely to flocculate as long as the oil is not exposed to
from the light source and reads the transmittance through the
anyworseconditions,suchasstoring,aging,andheating.Ifthe
glass vial containing the specimen. During a scan, the reading
separability number is above 10, the stability reserve of the oil
head moves up and down along the glass vial and scans the
is very low and asphaltenes will easily flocculate, or have
whole vial going up. The transmittance is automatically mea-
already started to flocculate.
sured every 0.04 mm. During one measurement, the time
5.2 This test method can be used by refiners and users of
interval between each scan shall be 60 s and 16 scans shall be
oils, for which this test method is applicable, to estimate the
run. The measuring principle is schematically shown in Fig. 1.
stability reserves of their oils. Hence, this test method can be
The measured transmittance along the glass vial is reported
used by refineries to control and optimize their refinery
every 0.04 mm and is automatically stored on the hard disk in
processes. Consumers of oils can use this test method to
the computer and can be further processed as described in
estimate the stability reserve of their oils before, during, and
Section 10.
after storage.
5.3 This test method is not intended for predicting whether
6.3 Cylindrical Clear Glass Vial with Screw Cap,15mL,16
oils are compatible before mixing, but can be used for
mmoutsidediameter,12mminnerdiameter,and140mmhigh,
determining the separability number of already blended oils.
shall be used as a sample container.
However, oils that show a low separability number are more
6.4 Pipette, Graduated or Automatic, 5 and 10 mL.
likely to be compatible with other oils than are oils with high
6.5 Graduated Cylinder,25mL.
separability numbers.
6.6 Clear Glass Bottle with Cap, 250 mL.
6. Apparatus
6.7 Clear Glass Bottle with Cap,50mL.
6.8 Magnetic Bar, TFE-fluorocarbon-coated.
6.1 PC-Based Computer, into which the software that
controls the apparat
...
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