1、Designation: D7112 12Standard 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 (Hep-tane Insolubles) in Crude Petroleum and Petroleum Prod-ucts3. Terminology3.1 Definitions:3.1.1 For definitions of some terms used in this test method,such as crude
10、oil, repeatability, reproducibility, and residualfuel oil, refer to Terminology D4175.3.1.2 asphaltenes, n(rarely used in the singular), in petro-leum technology, represent an oil fraction that is soluble in aspecified aromatic solvent but separates upon addition of anexcess of a specified paraffini
11、c solvent.3.1.2.1 DiscussionIn this test method, the aromatic sol-vent is xylene and the paraffinic solvent is n-heptane.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 specified ratios without evidence of sep
12、aration,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 oils, heavy fuel oils, andresid
13、ual 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 for a long period of time or blen
14、ded 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.Current edition approved Nov. 1,
15、 2012. Published February 2013. Originallyapproved in 2005. Last previous edition approved in 2009 as D711209. DOI:10.1520/D7112-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume inform
16、ation, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2 Definitions of Terms Specific to This Standard
17、: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 flocculation of asphaltenes. See flocculation
18、ratio.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 lowest aromatic solvent(xylene) concentr
19、ation, expressed as a proportion of xylene toxylene plus n-heptane which, when mixed with an oil, will notresult in flocculation of asphaltenes. See 15.1, Eq 1.3.2.4 FR5/1,nthe flocculation ratio at a dilution of 5 mL ofxylene and n-heptane solvent mixture to1gofoil.3.2.4.1 DiscussionThe ratio 5 to
20、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 modelparameter which can be used to determine i
21、f 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-heptane) that can be added to 5 mL o
22、f 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 as a ratio byvolume of aromatic sol
23、vent (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 dilution of the sample at the y-axis(whe
24、re (1/X)=0.SeeEq 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 (some-times called an oil medium) and a
25、sphaltenes.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 =(1+Xmin), where Xminis the minimum volu
26、me 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-valueindicates that an oil is more stable w
27、ith 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 asphaltene to remain colloidallydispersed.3.2.10
28、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 be used to determine ifblends of oils are i
29、ncompatible 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 added to 5 mL of oil withoutasphaltene precip
30、itation. 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 ina specific amount of xylene.3.3 Symbols:
31、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 power of an oil matrixSBN= solubility blending
32、 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 solution is prepared and three different mixtures
33、 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. Theamounts of oil, xylene, and n-heptane are used to
34、 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 stability parameters using alight back-scat
35、tering technique improves accuracy and re-moves human errors. In manual testing, operators have toD7112 122visually compare oil stains on pieces of filter paper to deter-mine if asphaltenes have been precipitated.5.2 Refinery thermal and hydrocracking processes can berun closer to their severity lim
36、its 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 of crude oils can be usedin crude oil blendi
37、ng 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 select crude oil mixtures moreeconomically.5
38、.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 use stability andcompatibility parameters t
39、o determine stability reserve of residualproducts, fuel blends and crude oils. However, the interpretation ofstability, stability reserve and compatibility is heavily use dependent,andis beyond the scope of this test method.6. Interferences6.1 Free water present in the oil can cause difficulties wit
40、hthe 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 PORLA Heavy and Crude Oil Stability and Compatibil
41、-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, volumeapproximately 100 mL. Typically, aluminum c
42、ups 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 measurementposition and incorporating a mechanic
43、al 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.7.1.1.4 Aromatic Solvent Pump, accurate and a
44、djustableceramic 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, accurate and adjustable ceramicpiston pump used t
45、o 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 the sample solution is continuously circulated.T
46、he 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 warm up thesample so that the titration may be p
47、erformed 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 Measurement Screen, computer display,allowing data a
48、bout 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 calibration procedure to berun (see Fig. 5).8.
49、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 a mixtureof ortho, meta, and para isomers and
