ASTM D7827-12

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Designation: D7827 − 12
Standard Test Method for
Measuring n-Heptane Induced Phase Separation of
Asphaltene from Heavy Fuel Oils as Separability Number by
an Optical Device
This standard is issued under the fixed designation D7827; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D7061TestMethodforMeasuringn-HeptaneInducedPhase
Separation of Asphaltene-Containing Heavy Fuel Oils as
1.1 This test method covers the quantitative measurement,
Separability Number by an Optical Scanning Device
eitherinthelaboratoryorinthefield,ofhoweasilyasphaltene-
containing heavy fuel oils diluted in toluene phase separate
3. Terminology
upon addition of heptane. The result is a separability number
3.1 Definitions:
(%). See also Test Method D7061.
3.1.1 asphaltenes (rarely used in the singular), n—in petro-
1.2 The test method is limited to asphaltene-containing
leum technology, represent an oil fraction that is soluble in a
heavy fuel oils. ASTM specification fuels that generally fall
specified aromatic solvent but separates upon addition of an
within the scope of this test method are Specification D396,
excess of a specified paraffinic solvent.
Grade Nos. 4, 5, and 6, Specification D975, Grade No. 4-D,
3.1.1.1 Discussion—In this test method, the aromatic sol-
andSpecificationD2880,GradeNos.3-GTand4-GT.Refinery
vent is toluene and the paraffinic solvent is heptane.
fractions from which such blended fuels are made also fall
3.1.2 compatibility, n—of crude oils or of heavy fuel oils,
within the scope of this test method.
the ability of two or more crude oils or fuel oils to blend
1.3 The values stated in SI units are to be regarded as
together within certain concentration ranges without evidence
standard. No other units of measurement are included in this
of separation, such as the formation of multiple phases.
standard.
3.1.2.1 Discussion—Incompatible heavy fuel oils or crude
oils, when mixed or blended, result in the flocculation or
1.4 This standard does not purport to address all of the
precipitation of asphaltenes. Some oils may be compatible
safety concerns, if any, associated with its use. It is the
within certain concentration ranges in specific mixtures, but
responsibility of the user of this standard to establish appro-
incompatible outside those ranges.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
3.1.3 flocculation, n—of asphaltenes from crude oils or
heavy fuel oils, the aggregation of colloidally dispersed as-
2. Referenced Documents
phaltenes into visibly larger masses that may or may not settle.
2.1 ASTM Standards:
3.1.4 peptization, n—of asphaltenes in crude oils or heavy
D396Specification for Fuel Oils
fuel oils, the dispersion of asphaltenes to produce a colloidal
D975Specification for Diesel Fuel Oils
dispersion.
D2880Specification for Gas Turbine Fuel Oils
3.1.5 stability reserve, n—in petroleum technology, the
D4057Practice for Manual Sampling of Petroleum and
property of an oil to maintain asphaltenes in a peptized state
Petroleum Products
and prevent flocculation of the asphaltenes.
D4177Practice for Automatic Sampling of Petroleum and
3.1.5.1 Discussion—An oil with a low stability reserve is
Petroleum Products
likelytoundergoflocculationofasphalteneswhenstressed(for
example, extended heated storage) or blended with a range of
otheroils.Twooilseachwithahighstabilityreservearelikely
This test method is under the jurisdiction of ASTM Committee D02 on
to maintain asphaltenes in a peptized state and not lead to
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.14 on Stability and Cleanliness of Liquid Fuels.
flocculation when blended together.
Current edition approved Nov. 1, 2012. Published March 2013. DOI: 10.1520/
3.1.6 transmittance, n—of light, the fraction of the incident
D7827-12.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or light of a given wavelength that is not reflected or absorbed,
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
but passes through a substance.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. 3.2 Definitions of Terms Specific to This Standard:
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7827 − 12
3.2.1 SEPView 6.1, n—the name of a proprietary computer is very low and asphaltenes will easily flocculate, or have
program designed to allow automatic control of test and already started to flocculate.
calculations of the results in Test Method D7827.
5.2 This test method can be used by refiners and users of
3.2.2 separability number, n—in petroleum technology, the heavyoils,forwhichthistestmethodisapplicable,toestimate
standard deviation of the average transmittance, determined in the stability reserves of their oils. Hence, this test method can
this test method, expressed as a percentage figure.
be used by refineries to control and optimize their refinery
processes. Consumers of oils can use this test method to
3.2.2.1 Discussion—The separability number estimates the
stability reserve of the oil, where a high separability number estimate the stability reserve of their oils before, during, and
after storage.
indicates that the oil has a low stability reserve and a low
separability number that the oil has a high stability reserve.
5.3 This test method is not intended for predicting whether
3.2.3 SEPCalc, n—the name of a proprietary computer oils are compatible before mixing, but can be used for
program modul of SEPView, designed to allow automatic determining the separability number of already blended oils.
calculation of the results in Test Method D7827. However, experience shows that oils exhibiting a low separa-
bility number are more likely to be compatible with other oils
3.2.4 STEP-Technology, n—parallellight(I )illuminatesthe
than are oils with high separability numbers.
entire sample cell and the transmitted light I is detected by
multiple sensors with a µm-scale resolution arranged linearly
6. Apparatus
from top to bottom. Transmission is recorded time- and
space-resolvedandmaybeconvertedintoextinctionbylgI/I . 6.1 Computer executing software SEPView ,fromaportable
storagemediaordirectlyfromthecomputer.SEPViewcontrols
4. Summary of Test Method the apparatus, acquires the data and accumulates it in a
database on the portable storage media, the hard disk in the
4.1 Dilution of oil with toluene followed by addition of
computer or at a server.
heptane causes asphaltenes to flocculate, and the oil to phase
6.2 Optical Device—The apparatus consists of an illumi-
separate. The rate of the phase separation is determined by
nation system, composed of a pulsed infrared light source that
measuring the increase in transmittance in the sample from the
uses a wavelength of 870 nm (6 10 nm) and means to
bottomofatesttubetothetop(oraportionthereof)overtime.
parallelize and expand the light to illuminate the entire
The standard deviation of the average transmittance from a
specimen height. A high-resolution line detector is situated
number of consecutive automatic measurements gives a sepa-
opposite from the light source and reads the transmittance
rability number (%).
through the vertical midline of the optical cell (6.3) containing
4.2 The oil is diluted with toluene in ratios that depend on
the specimen. The transmittance is automatically and instanta-
the oil type. Mix 2 mL of the oil/toluene solution with 23 mL
neously recorded at every pixel with a position resolution of
of heptane. Transfer 3.5 mLof the oil/toluene/heptane mixture
0.007 mm (STEP-Technology (trademarked) ). Time interval
into a disposable optical cell that is inserted into an optical
between each recording shall be 10 s. Total measurement time
scanning device.
shall be 15 min. The measuring principle is schematically
4.3 The change in light transmittance through the cell is
showninFig.1.Eachmeasuredtransmittanceprofilealongthe
recorded by proprietary STEP-Technology instantaneously optical cell is automatically stored on the hard disk in the
over the entire sample height without scanning. Measurements
computer or at a server and can be further processed as
are taken periodically every 10 s for 15 min.An average of the described in Section 10 and Annex A2.
transmittance is calculated from each reading of each of the 91
6.3 Rectangular Transparent Disposable Optical Polyamid
transmission profiles at each 0.007 mm distance along the
cells (PA-cells) with PP-stopper,5mLcapacity,cross-section8
opticalcell,startingfromthebottomofthecellandcontinuing
mm × 10 mm (optical path), wall thickness 1 mm and 80 mm
up to 44 mm.The separability number from multiple measure-
high, shall be used as a sample container.
ments is calculated and reported.
6.4 Pipette, Graduated or Automatic, 5 and 10 mL.
5. Significance and Use 6.5 Graduated Cylinder, 25 mL.
6.6 Clear Glass Bottle with Cap, 250 mL.
5.1 This procedure describes a rapid and sensitive method
for estimating the stability reserve of an oil. The stability
6.7 Clear Glass Bottle with Cap, 50 mL.
reserve is estimated in terms of a separability number, where a
6.8 Magnetic Bar, PTFE-coated.
low value of the separability number indicates that there is a
stabilityreservewithintheoil.Whentheseparabilitynumberis 6.9 Magnetic Stirrer.
between 0 to 5, the oil can be considered to have a high
6.10 Balance, precision 60.01 g.
stability reserve and asphaltenes are not likely to flocculate. If
theseparabilitynumberisbetween5to10,thestabilityreserve
intheoilwillbemuch
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