1、Designation: D7112 09Standard Test Method forDetermining Stability and Compatibility of Heavy Fuel Oilsand Crude Oils by Heavy Fuel Oil Stability Analyzer (OpticalDetection)1This standard is issued under the fixed designation D7112; the number immediately following the designation indicates the year
2、 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*1.1 This test method covers an automated procedure involv-i
3、ng titration and optical detection of precipitated asphaltenesfor determining the stability and compatibility parameters ofrefinery residual streams, residual fuel oils, and crude oils.Stability in this context is the ability to maintain asphaltenes ina peptized or dissolved state and not undergo fl
4、occulation orprecipitation. Similarly, compatibility relates to the property ofmixing two or more oils without precipitation or flocculation ofasphaltenes.1.2 This test method is applicable to residual products fromatmospheric and vacuum distillation, from thermal, catalytic,and hydrocracking proces
5、ses, to products typical of Specifica-tions D396, Grades No. 5L, 5H, and 6, and D2880, Grades No.3-GT and 4-GT, and to crude oils, providing these productscontain 0.05 mass % or greater concentration of asphaltenes.1.3 This test method is not relevant to oils that contain lessthan 0.05 % asphaltenes
6、, and would be pointless to apply tounstable oils that already contain flocculated asphaltenes.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any,
7、associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D396 Specification for Fuel OilsD2880 Specification f
8、or Gas Turbine Fuel OilsD4057 Practice for Manual Sampling of Petroleum andPetroleum ProductsD4175 Terminology Relating to Petroleum, PetroleumProducts, and LubricantsD4177 Practice for Automatic Sampling of Petroleum andPetroleum ProductsD6299 Practice for Applying Statistical Quality Assuranceand
9、Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6560 Test Method for Determination of Asphaltenes(Heptane Insolubles) in Crude Petroleum and PetroleumProducts3. Terminology3.1 Definitions:3.1.1 For definitions of some terms used in this test method,such as crude oil,
10、 repeatability, reproducibility, and residualfuel oil, refer to Terminology D4175.3.1.2 asphaltenes, nin petroleum technology, moleculesof high molecular mass, high carbon/hydrogen ratio, andcontaining hetero-atoms.3.1.2.1 DiscussionAsphaltenes are generally found incrude oils and in heavy fuel oils
11、 containing residual fractions.Their presence is determined by their insolubility in alkanessuch as n-heptane and solubility in aromatics such as xylene.3.1.3 compatibility, nof crude oils and of heavy fuel oils,the ability of two or more crude oils or fuel oils to be blendedtogether within specifie
12、d ratios without evidence of separation,such as flocculation or separation of asphaltenes.3.1.4 flocculation, nof asphaltenes in crude oils or heavyfuel oils, the aggregation of colloidally dispersed asphaltenesinto larger, visible masses that may or may not settle.3.1.5 stability reserve, nof crude
13、 oils, heavy fuel oils, andresidual streams containing asphaltenes, the property of an oilto maintain asphaltenes in a peptized (colloidally dispersed)state and prevent their flocculation when stored or whenblended with other oils.3.1.5.1 DiscussionAn oil with a high stability reserve canbe stored f
14、or a long period of time or blended with a range ofother oils without flocculation of asphaltenes.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.14 on Stability and Cleanliness of Liquid Fuels.
15、Current edition approved Dec. 1, 2009. Published February 2010. Originallyapproved in 2005. Last previous edition approved in 2005 as D711205a. DOI:10.1520/D7112-09.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Bo
16、ok of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*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.3.2 Definitions
17、 of Terms Specific to This Standard:3.2.1 aromatic solvent equivalent (xylene equivalent), SE,nthe lowest aromatic solvent (xylene) content, expressed asa volume %, in a mixture containing aromatic and paraffinicsolvents (xylene and n-heptane) which, when mixed with oil,will not result in flocculati
18、on of asphaltenes. See flocculationratio.3.2.1.1 DiscussionSE is defined as FR5/1multiplied by100 %, as shown in Eq 2.3.2.2 evaporation correction coeffcient, nthe rate ofevaporation of aromatic solvent (xylene) from the sample cup,measured in grams per hour.3.2.3 flocculation ratio (FR), nthe lowes
19、t aromatic sol-vent (xylene) concentration, expressed as a proportion ofxylene to xylene plus n-heptane which, when mixed with anoil, will not result in flocculation of asphaltenes. See 15.1,Eq1.3.2.4 FR5/1, nthe flocculation ratio at a dilution of 5 mLofxylene and n-heptane solvent mixture to1gofoi
20、l.3.2.4.1 DiscussionThe ratio 5 to 1 is used internally by anumber of oil companies involved with the stability andcompatibility of heavy fuel oils and crude oils. This ratio ischosen so that a P-value of six represents an FR5/1of zero.3.2.5 insolubility number, IN, na crude oil blending modelparame
21、ter which can be used to determine if blends of oils arecompatible or incompatible. See solubility blending number.3.2.5.1 DiscussionInsolubility numbers for individual oilsare determined and calculated from the density of the oil,aromatic solvent equivalent value and volume of paraffinicsolvent (n-
22、heptane) that can be added to 5 mL of oil withoutasphaltene precipitation. The equations are given under Calcu-lation of Results (see 15.2).3.2.6 maximum flocculation ratio, FRmax, nof asphaltenesin residual fuel oils and crude oils, the minimum requiredsolvency power of a solvent mixture, expressed
23、 as a ratio byvolume of aromatic solvent (xylene) to aromatic solvent plusparaffinic solvent (n-heptane) to keep the asphaltenes in an oilcolloidally dispersed.3.2.6.1 DiscussionFRmaxis determined from a plot offlocculation ratios versus the oil concentration in solvent,extrapolated to infinite dilu
24、tion of the sample at the y-axis(where (1/X) = 0. See Eq 3).3.2.7 oil matrix, nthat portion of a sample of heavy fueloil or crude oil that surrounds and colloidally disperses theasphaltenes.3.2.7.1 DiscussionFor purposes of this test method, an oilsample is considered to be composed of an oil matrix
25、 (some-times called an oil medium) and asphaltenes.3.2.8 P-value, nof refinery residual steams, residual fueloils and crude oils, an indication of the stability or availablesolvency power of an oil with respect to precipitation ofasphaltenes.3.2.8.1 DiscussionSince the equation defining P-value isP
26、=(1+Xmin), where Xminis the minimum volume of paraffinicsolvent, n-heptane, (in mL) needed to be added to1gofoiltoresult in flocculation of asphaltenes, the smallest P-value is 1,which means the oil is unstable and can precipitate asphalteneswithout addition of any paraffinic solvent. A higher P-val
27、ueindicates that an oil is more stable with respect to flocculationof asphaltenes. P-value by this test method relates specificallyto xylene and n-heptane as the aromatic and paraffinic solvents,respectively.3.2.9 Pa, nthe P-value of an asphaltene, which is thepeptizability or ability of an asphalte
28、ne to remain colloidallydispersed.3.2.10 Po, nthe P-value of an oil matrix. See oil matrix.3.2.11 peptize, vof an oil or cutter stock, to dissolve anasphaltene or to maintain an asphaltene in colloidal dispersion.3.2.12 solubility blending number, SBN, na crude oilblending model parameter which can
29、be used to determine ifblends of oils are incompatible or compatible. See insolubilitynumber.3.2.12.1 DiscussionSolubility blending numbers for indi-vidual oils are determined and calculated from the density ofthe oil, aromatic solvent equivalent value, and volume ofparaffinic solvent that can be ad
30、ded to 5 mL of oil withoutasphaltene precipitation. The equations are given under Calcu-lation of Results (see 15.2).3.2.13 step size, nthe volume in mL of each portion ofn-heptane added to the stock solution in the course of the testprocedure.3.2.14 stock solution, na solution of a sample dissolved
31、 ina specific amount of xylene.3.3 Symbols:FR = flocculation ratioFR5/1= flocculation ratio at a dilution of 5 mL solution(xylene plus n-heptane) to1gofoilFRmax= maximum flocculation ratioIN= insolubility numberP = the P-value of an oilPa= the P-value of an asphaltenePo= the P-value or peptizing pow
32、er of an oil matrixSBN= solubility blending numberSE = xylene equivalent, volume %Xmin= n-heptane consumption of undiluted oil, in mL/g ofoil4. Summary of Test Method4.1 Stability and compatibility parameters are determinedby titration and optical detection of precipitated asphaltenes. Astock soluti
33、on is prepared and three different mixtures of thesample oil plus xylene are titrated with n-heptane to causeprecipitation of asphaltenes. The titrated mixture is continu-ously circulated through an optical detector which detectsprecipitated asphaltenes by back-scattering of visible light. Theamount
34、s of oil, xylene, and n-heptane are used to calculatestability parameters: solvent equivalent, P-value, and FR5/1.Ifthe density of a crude oil sample is known, then the compat-ibility parameters (SBNand IN) of the crude oil may also becalculated.5. Significance and Use5.1 Automatic determination of
35、stability parameters using alight back-scattering technique improves accuracy and re-moves human errors. In manual testing, operators have tovisually compare oil stains on pieces of filter paper to deter-mine if asphaltenes have been precipitated.D7112 0925.2 Refinery thermal and hydrocracking proce
36、sses can berun closer to their severity limits if stability parameters can becalculated more accurately. This gives increased yield andprofitability.5.3 Results from the test method could be used to set astandard specification for stability parameters for fuel oils.5.4 The compatibility parameters o
37、f crude oils can be usedin crude oil blending in refineries to determine, in advance,which crude oil blends will be compatible and thus can be usedto minimize plugging problems, unit shut downs, and mainte-nance costs. Determination of crude oil compatibility param-eters also enables refineries to s
38、elect crude oil mixtures moreeconomically.5.5 This test method can measure stability and compatibilityparameters, and determine stability reserve on different blendsfor particular applications to optimize the blending, storage,and use of heavy fuel oilsNOTE 1Users of this test method would normally
39、use stability andcompatibility parameters to determine stability reserve of residual prod-ucts, fuel blends and crude oils. However, the interpretation of stability,stability reserve and compatibility is heavily use dependent, and isbeyond the scope of this test method.6. Interferences6.1 Free water
40、 present in the oil can cause difficulties withthe optical detector and should be removed by centrifugingprior to testing.6.2 Solid particles, such as coke or wax particles, mud,sand, or catalyst fines, in the oil will not affect the opticaldetector or interfere with the results.7. Apparatus7.1 PORL
41、A Heavy and Crude Oil Stability and Compatibil-ity Analyzer3,4See Figs. 1 and 2.7.1.1 A portion of the apparatus is shown diagrammaticallyin Fig. 2 and is comprised of the following parts:7.1.1.1 Sample Cup, light weight, inert cups designed to fitthe sample carousel, with a smooth, flat bottom, vol
42、umeapproximately 100 mL. Typically, aluminum cups have beenused.7.1.1.2 Sample Carousel, typically a four-position samplecup holder delivering the sample cups sequentially to themeasurement position.7.1.1.3 Mixer Lift System, vertically moving lift system,forming a seal with the sample cup in the me
43、asurementposition and incorporating a mechanical stirrer which starts torotate when the seal is made. It also incorporates delivery linesfor n-heptane and xylene addition, the circulation line forpassing the sample through the detector and the exhaust line,which empties the sample cup after analysis
44、.7.1.1.4 Aromatic Solvent Pump, accurate and adjustableceramic piston pump, capable of delivering xylene at a rate of0.01 to 0.5 mL/s.7.1.1.5 Paraffnic Solvent Pump, accurate and adjustableceramic piston pump, capable of delivering n-heptane at a rateof 0.01 to 0.5 mL/s.7.1.1.6 Circulation Pump, acc
45、urate and adjustable ceramicpiston pump used to circulate the sample under test through thedetector system.7.1.1.7 Exhaust Pump, accurate and adjustable ceramicpiston pump used to empty the sample cup at the end of themeasurement.7.1.1.8 Detector System, (see Fig. 3) optical detectorthrough which th
46、e sample solution is continuously circulated.The detector is composed of a visible light source and aphotodiode for recording the light reflecting from asphalteneparticles in the test sample.7.1.1.9 Hot Plate, a temperature controlled heating systemmay be located below the sample cups, which will wa
47、rm up thesample so that the titration may be performed at an elevatedtemperature. The temperature of the hot plate should beadjustable between 20 and 100C.7.1.2 Computer, controls the measurement and calibrationprograms and is an interface between the operator and theanalyzer.7.1.3 PORLA Step Measur
48、ement Screen, computer display,allowing data about the sample and operator to be input as wellas showing the results of each titration (see Fig. 4).7.1.4 Parameter Screen, computer display, allows all of themeasurement cycle parameters to be adjusted from the defaultvalues and also allows the pump c
49、alibration procedure to berun (see Fig. 5).8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society where suchspecifications are available.5Other grades may be used, pro-vided it is first determined that the reagents are of sufficientlyhigh purity to permit their use without lessening the accuracyof the determination.8.2 Xylene (C8H10)The xylene used is generally
