1、Designation: D7157 12 (Reapproved 2018)D7157 18Standard Test Method forDetermination of Intrinsic Stability of Asphaltene-ContainingResidues, Heavy Fuel Oils, and Crude Oils (n-HeptanePhase Separation; Optical Detection)1This standard is issued under the fixed designation D7157; the number immediate
2、ly following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 Th
3、is test method covers a procedure for quantifying the intrinsic stability of the asphaltenes in an oil by an automaticinstrument using an optical device.1.2 This test method is applicable to residual products from thermal and hydrocracking processes, to products typical ofSpecifications D396 Grades
4、No. 5L, 5H, and 6, and D2880 Grades No. 3-GT and 4-GT, and to crude oils, providing these productscontain 0.5 % by mass or greater concentration of asphaltenes (see Test Method D6560).1.3 This test method quantifies asphaltene stability in terms of state of peptization of the asphaltenes (S-value),
5、intrinsic stabilityof the oily medium (So) and the solvency requirements of the peptized asphaltenes (Sa).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 conc
6、erns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1.6 This international standard was developed in accordance with inte
7、rnationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D396 S
8、pecification for Fuel OilsD2880 Specification for Gas Turbine Fuel OilsD4057 Practice for Manual Sampling of Petroleum and Petroleum ProductsD4175 Terminology Relating to Petroleum Products, Liquid Fuels, and LubricantsD4177 Practice for Automatic Sampling of Petroleum and Petroleum ProductsD4870 Te
9、st Method for Determination of Total Sediment in Residual FuelsD6560 Test Method for Determination of Asphaltenes (Heptane Insolubles) in Crude Petroleum and Petroleum ProductsD6792 Practice for Quality Management Systems in Petroleum Products, Liquid Fuels, and Lubricants Testing Laboratories3. Ter
10、minology3.1 Definitions:3.1.1 For definitions of some terms used in this test method, refer to Terminology D4175.3.1.2 asphaltenes, n(rarely used in the singular), in petroleum technology, represent an oil fraction that is soluble in a specifiedaromatic solvent but separates upon addition of an exce
11、ss of a specified paraffinic solvent.3.1.2.1 Discussion1 This test method is under the jurisdiction of Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of Subcommittee D02.14on Stability, Cleanliness and Compatibility of Liquid Fuels.Current edition
12、approved June 1, 2018Dec. 1, 2018. Published June 2018February 2019. Originally approved in 2005. Last previous edition approved in 20122018 asD7157 12.D7157 12 (2018). DOI: 10.1520/D7157-12R18.10.1520/D7157-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Custo
13、mer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.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
14、 previous version. Becauseit 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 versionof the standard as published by ASTM is to be considered the official document.*A Summary o
15、f Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1In this test method, the aromatic solvent is toluene and the paraffinic solvent is n-heptane.3.1.3 compatibility, nof crude oils or o
16、f heavy fuel oils, the ability of two or more crude oils or fuel oils to blend togetherwithin certain concentration ranges without evidence of separation, such as the formation of multiple phases.3.1.3.1 DiscussionIncompatible heavy fuel oils or crude oils, when mixed or blended, result in the flocc
17、ulation or precipitation of asphaltenes. Someoils may be compatible within certain concentration ranges in specific mixtures, but incompatible outside those ranges.3.1.4 flocculation, nof asphaltenes from crude oils or heavy fuel oils, the aggregation of colloidally dispersed asphaltenes intovisible
18、 larger masses which may or may not settle.3.1.5 peptization, nof asphaltenes in crude oils or heavy oils, the dispersion of asphaltenes to produce a colloidal dispersion.3.1.6 stability reserve, nin petroleum technology, the property of an oil to maintain asphaltenes in a peptized state and prevent
19、flocculation of asphaltenes.3.1.6.1 DiscussionAn oil with a low stability reserve is likely to undergo flocculation of asphaltenes when stressed (for example, extended heatedstorage) or blended with a range of other oils. Two oils each with a high stability reserve are likely to maintain asphaltenes
20、 in apeptized state and not lead to flocculation when blended together.3.2 Definitions of Terms Specific to This Standard:3.2.1 intrinsic stability (S-value), n of refinery residual streams, residual fuel oils and crude oils, an indication of the stabilityor available solvency power of an oil with r
21、espect to precipitation of asphaltenes.3.2.1.1 DiscussionSince the equation defining S-value is S = (1 + Xmin), where Xmin is the minimum volume (in mL) of paraffinic solvent, n-heptane,to be added to 1 g of oil to result in flocculation of asphaltenes, the smallest S-value is 1, which means the oil
22、 is unstable and canprecipitate asphaltenes without addition of any paraffinic solvent.Ahigher S-value indicates that an oil is more stable with respectto flocculation of asphaltenes. S-value by this test method relates specifically to toluene and n-heptane as the aromatic andparaffinic solvents, re
23、spectively.3.2.2 inversion point, npoint in the n-heptane titration curve, where the onset of asphaltene flocculation leads to inversion ofthe light intensity.3.2.2.1 DiscussionAt the first stage of the addition of n-heptane to a dilution of specimen and toluene, light intensity increases through di
24、lution. Whenasphaltenes start to flocculate, there will be a point where the increase in light intensity through dilution matches the light intensitydecrease (inversion) as a result of coagulated asphaltenes obstructing the light beam.3.2.3 Sa, nthe S-value of an asphaltene, which is the peptizabili
25、ty or ability of an asphaltene to remain in a colloidaldispersion.3.2.3.1 DiscussionSa can also be described as one minus the ratio of So to S.Sa is linked to the length and number of aromatic chains within theasphaltenes.3.2.4 So, nthe S-value of an oil.3.2.4.1 DiscussionSo can also be described as
26、 the aromatic equivalent of the oil expressed as the ratio of the aromatic solvent to the aromatic plusparaffinic solvent mixture having the same peptizing power as the oil.3.2.5 solvent aromaticity, nof a binary mixture of a paraffnic and an aromatic solvent, the solvency power of the binarymixture
27、.D7157 1823.2.5.1 DiscussionFor the purpose of this test method, solvent aromaticity is defined as a ratio by volume of the aromatic solvent (toluene) to theparaffinic solvent (n-heptane).3.3 Symbols:3.3.1 FRflocculation ratioFR = flocculation ratioFRmax = maximum flocculation ratioS = the intrinsic
28、 stability of an oilSa = the peptizability of an asphalteneSo = the peptizing power of an oilXmin = paraffinic solvent consumption of undiluted oil, in mL/g of oil3.3.2 FRmaxmaximum flocculation ratio3.3.3 Sthe intrinsic stability of an oil3.3.4 Sathe peptizability of an asphaltene3.3.5 Sothe peptiz
29、ing power of an oil3.3.6 Xminparaffinic solvent consumption of undiluted oil, in mL/g of oil4. Summary of Test Method4.1 This test method uses an integrated automated analytical measurement system with an optical probe for the detection ofasphaltene precipitation from a toluene solution of the sampl
30、e.4.2 Three test specimens are dissolved in three different quantities of toluene. The three specimen/toluene solutions areautomatically and simultaneously titrated with n-heptane to cause precipitation of the asphaltenes. The optical probe monitors theformation of flocculated asphaltenes during the
31、 titration. Flocculated asphaltenes will alter the detected light intensity. Start offlocculation is interpreted when the optical probe detects a significant and sustained decrease in rate-of-change of the light intensity.4.3 A computer routine calculates stability parameters and subsequently the in
32、trinsic stability of the oil from the addedn-heptane at the inversion point, the mass of specimen, and the volume of toluene, for the three specimen/toluene solutions.5. Significance and Use5.1 This test method describes a sensitive method for estimating the intrinsic stability of an oil. The intrin
33、sic stability isexpressed as S-value. An oil with a low S-value is likely to undergo flocculation of asphaltenes when stressed (for example,extended heated storage) or blended with a range of other oils. Two oils each with a high S-value are likely to maintain asphaltenesin a peptized state and not
34、lead to asphaltene flocculation when blended together.5.2 This test method can be used by petroleum refiners to control and optimize the refinery processes and by blenders andmarketers to assess the intrinsic stability of blended asphaltene-containing heavy fuel oils.6. Interferences6.1 High content
35、 of insoluble inorganic matter (sediment) has some interference in this test method. In this case, the insolublematter shall be removed by filtration according to Test Method D4870.6.2 Free water present in the oil can cause difficulties with the optical detector and should be removed by any suitabl
36、e means(for example, centrifugation) prior to testing.7. Apparatus7.1 General(See Fig. 1) This test method uses an integrated automated analytical measurement system3,4 comprised of aPC-based computer and three titration stations.7.1.1 Computer, PC-based computer with associated software, capable of
37、 controlling up to three independent titration stations,controlling test sequencing, and acquisition of optical probe signal data. The associated software also provides for processingcalculations and automatically produces a report of important test parameters.3 The sole source of supply of the appa
38、ratus (Automated Stability Analyser)Analyzer) known to the committee at this time is Rofa France, 6 Rue Raymond Poincare,F-25300, LesAllies, France. If you are aware of alternative suppliers, please provide this information toASTM International Headquarters.Your comments will receive carefulconsider
39、ation at a meeting of the responsible technical committee,1 which you may attend.4 The Rofa stability analyzer is covered by a patent; patent owned by Total Raffinage France; INPI, date 18/05/04, registration number 04.05406; Rofa France, 6TotalRaffinage France has granted to Rofa France (6 Rue Raym
40、ond Poincare, F-25300, Les Allies, France.France) a non-exclusive license to manufacture and sell such stabilityanalyzer.D7157 1837.1.2 Titration Stations:7.1.2.1 Titration Unit, automatic computer controlled, adjustable motor-driven ceramic piston pump, capable of deliveringsolvent at a rate of 0.0
41、1 mLs to 0.5 mLs, with a volume dispensing accuracy of 60.01 mL.7.1.2.2 Magnetic Stirrer, adjustable from 200 rmin to 400 rmin.7.1.2.3 Optical Probe, consisting of a system of three areas of light emitters (880 nm) and three areas of light receivers. Theanalytical measurement system will automatical
42、ly select the optimum area, based on the level of translucency of the sample.7.1.2.4 Titration Cell, of borosilicate glass, flat bottom, outside diameter 30 mm 6 2 mm, volume 95 mL 6 15 mL, fitted witha tapered ground glass joint (female).7.2 Balance, capable of reading to 0.1 mg or better.7.3 Dispe
43、nser, capable of delivering up to 10 mL of toluene with an accuracy of 60.1 mL.7.4 Condenser, double surface with a tapered ground-glass joint (male) at the bottom to fit the top of the titration cell.7.5 Magnetic Stirrer/Hotplate, stirrer speed adjustable from 100 rmin to 1000 rmin.7.6 Stirring Bar
44、, magnetic, PFTE-coated, 20 mm in length.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Socie
45、ty where suchspecifications are available.5 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purityto permit its use without lessening the accuracy of the determination.8.1.1 Toluene. (WarningFlammable. Health hazard. Vapor may cause flash fire.) (S
46、ee Annex A1.)8.1.2 n-Heptane. (WarningFlammable. Vapor harmful. Vapor may cause flash fire.) (See Annex A1.)8.2 Quality Control SampleA stable and homogeneous residual fuel oil having physical and chemical properties similar tothose of typical sample fuels routinely tested.9. Sampling and Test Speci
47、mens9.1 Sampling:9.1.1 Obtain representative samples in accordance with recognized sampling procedures such as Practices D4057 or D4177.9.1.2 Samples of very viscous materials may be warmed until they are reasonably fluid before they are sampled.9.1.3 Store samples prior to taking test specimens at
48、ambient temperatures.5 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed bythe American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the
49、United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.FIG. 1 Schematic Drawing of the Integrated Automated Stability AnalyserAnalyzer SystemD7157 1849.2 Test Specimen Preparation:9.2.1 Sample TemperatureIf necessary, warm viscous samples until they can be mixed readily before opening the storagecontainer. For fuels with a high wax content (high pour point) the temperature must be at least 15 C above the pour point.9.2.2 Manually shake the sample thoroughly. If the sample contains high
