ASTM D3230-2008 Standard Test Method for Salts in Crude Oil (Electrometric Method).pdf

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1、Designation: D 3230 08An American National StandardStandard Test Method forSalts in Crude Oil (Electrometric Method)1This standard is issued under the fixed designation D 3230; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye

2、ar 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This test method covers the de

3、termination of the ap-proximate chloride (salts) concentration in crude oil. The rangeof concentration covered is 0 to 500 mg/kg or 0 to 150 lb/1000bbl as chloride concentration/volume of crude oil.1.2 This test method measures conductivity in the crude oildue to the presence of common chlorides, su

4、ch as sodium,calcium, and magnesium. Other conductive materials may alsobe present in the crude oil.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3.1 Acceptable concentration units are g/m3or PTB (lb/1000 bbl).1.4 This s

5、tandard does not purport to address all of thesafety concerns, if any, 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. For specificwarning stat

6、ements, see 7.3, 7.4, and 7.11.2. Referenced Documents2.1 ASTM Standards:2D 381 Test Method for Gum Content in Fuels by JetEvaporationD 1193 Specification for Reagent WaterD 4928 Test Methods for Water in Crude Oils by Coulom-etric Karl Fischer TitrationD 5002 Test Method for Density and Relative De

7、nsity ofCrude Oils by Digital Density Analyzer3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 PTBlb/1000 bbl.3.1.2 salts in crude oilcommonly, chlorides of sodium,calcium, and magnesium dissolved in crude oil. Other inor-ganic chlorides may also be present.4. Summary of Test M

8、ethod4.1 This test method measures the conductivity of a solutionof crude oil in a mixed alcohol solvent when subjected to anelectrical stress. This test method measures conductivity due tothe presence of inorganic chlorides, and other conductivematerial, in the crude oil. A homogenized test specime

9、n isdissolved in a mixed alcohol solvent and placed in a test cellconsisting of a beaker and a set of electrodes. A voltage isimpressed on the electrodes, and the resulting current flow ismeasured. The chloride (salt) content is obtained by referenceto a calibration curve of current versus chloride

10、concentrationof known mixtures. Calibration curves are based on standardsprepared to approximate the type and concentration of chlo-rides in the crude oils being tested.5. Significance and Use5.1 This test method is used to determine the approximatechloride content of crude oils, a knowledge of whic

11、h isimportant in deciding whether or not the crude oil needsdesalting. The efficiency of the process desalter can also beevaluated.5.2 Excessive chloride left in the crude oil frequently resultsin higher corrosion rates in refining units and also hasdetrimental effects on catalysts used in these uni

12、ts.5.3 This test method provides a rapid and convenient meansof determining the approximate content of chlorides in crudeoil and is useful to crude oil processors.6. Apparatus6.1 The apparatus (see Annex A1) shall consist of a controlunit capable of producing and displaying several voltage levelsfor

13、 applying stress to a set of electrodes suspended in a testbeaker containing a test solution. The apparatus shall be1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.03 on Elemental Analysis.Curre

14、nt edition approved May 1, 2008. Published May 2008. Originallyapproved in 1973. Last previous edition approved in 2006 as D 323006.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume inform

15、ation, 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.capable of measuring and displaying the current

16、(mA) con-ducted through the test solution between the electrodes at eachvoltage level.NOTE 1Some apparatus are capable of measuring voltage and currentinternally and, after comparison to internal calibration curves, of display-ing the resultant concentration.6.2 Test BeakerSee Annex A1.6.3 Pipet, 10

17、 mL (total delivery)The type of pipet that isrinsed to ensure the entire volume of the material is containedin the intended volume.6.4 Cylinders, 100 mL, stoppered.6.5 Other volumetric and graduated pipets and volumetricflasks.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals sh

18、all beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of theAmericanChemical Society, where such specifications are available.3Other grades may be used, provided it is first ascertained thatthe reagent is of sufficiently high purity

19、to permit its usewithout lessening the accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type II in Specification D 1193.7.3 Mixed Alcohol SolventMix 63 volumes of 1-butanoland 37 volumes of absolute

20、 methyl alcohol (anhydrous). Toeach litre of this mixture, add 3 mL of water. (WarningFlammable. Liquid causes eye burns. Vapor harmful. May befatal or cause blindness if swallowed or inhaled.)NOTE 2The mixed alcohol solvent is suitable for use if its conduc-tivity is less than 0.25 mA at 125 V ac.

21、High conductivity can be due toexcess water in the solvent and can indicate that the methyl alcohol usedis not anhydrous.7.4 Hexanes, Reagent Grade,(WarningExtremely flam-mable, harmful if inhaled.)NOTE 3Hexanes solvent is sometimes referred to or sold by othernames, such as petroleum naphtha, petro

22、leum ether, ligroine, petroleumbenzin, and industrial naphtha. One should confirm that it meets therequirements of 7.4.7.5 Calcium Chloride (CaCl2) Solution (10 g/L)Transfer1.006 0.01 g of CaCl2, or the equivalent weight of a hydratedsalt, into a 100-mL volumetric flask and dissolve in 25 mL ofwater

23、. Dilute to the mark with mixed alcohol solvent.7.6 Magnesium Chloride (MgCl2) Solution (10 g/L)Transfer 1.00 6 0.01 g of MgCl2, or the equivalent weight ofa hydrated salt, into 100-mL volumetric flask and dissolve in25 mL of water. Dilute to the mark with mixed alcohol solvent.7.7 Sodium Chloride (

24、NaCl) Solution (10 g/L)Transfer1.00 6 0.01 g of NaCl into a 100-mL volumetric flask anddissolve in 25 mL of water. Dilute to the mark with mixedalcohol solvent.7.8 Oil, Refined NeutralAny refined chloride-free oil ofapproximately 20 mm2/sec (cSt) viscosity at 40C and free ofadditive.7.9 Salts, Mixed

25、 Solution (Concentrated Solution)Combine 10.0 mL of the CaCl2solution, 20.0 mL of the MgCl2solution, and 70.0 mL of the NaCl solution, and mix thor-oughly.NOTE 4The 10:20:70 proportions are representative of the chloridespresent in a number of common crude oils. When the relative proportionsof calci

26、um, magnesium, and sodium chlorides are known for a given crudeoil, such proportions should be used for most the accurate results.7.10 Salts, Mixed Solution (Dilute Solution)Transfer 10mL of the concentrated mixed chlorides solution into a1000-mL volumetric flask, and dilute to the mark with mixedal

27、cohol solvent.7.11 Xylene, reagent grade, minimum purity. (WarningFlammable. Vapor harmful.)8. Sampling8.1 Obtain a sample and test specimen in accordance withTest Methods D 4928. Ensure that the sample is completelyhomogenized with a suitable mixer. See Annex A1 of TestMethods D 4928 for suitable a

28、pparatus and proving.8.2 Samples of very viscous materials may be warmed untilthey are reasonably fluid before they are sampled; however, nosample shall be heated more than is necessary to lower theviscosity to a manageable level.8.3 Samples of crude oil contain water and sediment and areinhomogeneo

29、us by nature. The presence of water and sedimentwill influence the conductivity of the sample. The utmost careshall be taken in obtaining homogenized representativesamples.9. Preparation of Apparatus9.1 Support the apparatus on a level, steady surface, such asa table.9.2 Prepare the apparatus for op

30、eration in accordance withthe manufacturers instructions for calibrating, checking, andoperating the equipment. (WarningThe voltage applied tothe electrodes can be as great as 250 V ac, and hazardous.)9.3 Thoroughly clean and dry all parts of the test beaker, theelectrodes, and its accessories befor

31、e starting the test, beingsure to remove any solvent that had been used to clean theapparatus.10. Calibration10.1 The conductivity of solutions is affected by the tem-perature of the specimen when measurements are made. Thetemperature of the test specimen at the time of measurementshall be within 3C

32、 of the temperature at which the calibrationcurves were made.10.2 Establish a blank measurement by following the pro-cedure in 10.3 and 10.4, omitting the mixed salts solution.When the indicated electrode current is greater than 0.25 mAat3Reagent Chemicals, American Chemical Society Specifications,

33、AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc.

34、(USPC), Rockville,MD.D3230082125 V ac, water or another conductive impurity is present andits source must be found and eliminated before calibration canbe completed. Determine a blank measurement each time freshxylene or mixed solvent is used.10.3 Into a dry, 100-mL graduated, glass-stoppered mixing

35、cylinder, add 15 mL of xylene. From a pipet (total delivery),add 10 mL of neutral oil. Rinse the pipet with xylene until freeof oil. Make up to 50 mL with xylene. Stopper and shake thecylinder vigorously for approximately 60 s to effect solution.Add a quantity of dilute mixed salts solution, in acco

36、rdancewith Table 1, that is appropriate to the range of salt contents tobe measured. Dilute to 100 mL with mixed alcohol solvent.Again shake the cylinder vigorously for approximately 30 s toeffect solution, and allow the solution to stand approximately 5min. Pour the solution into a dry test beaker.

37、10.4 Immediately place the electrodes into the solution inthe beaker, making sure that the upper edge of the electrodeplates are below the surface of the solution. Adjust theindicated electrode voltage to a series of values, for example25, 50, 125, 200, and 250 V ac. At each voltage, note thecurrent

38、 reading and record the voltage displayed and thecurrent to the nearest 0.01 mA. Remove the electrodes from thesolution, rinse with xylene followed by naphtha, and allowthem to dry.NOTE 5With some apparatus, the detailed settings will not berequired since the electronics are built-in for auto-rangin

39、g. Determinationof the blank and the calibration standard responses are the same.10.5 Repeat the procedure in 10.3, using other volumes ofmixed salts solution (dilute solution) as needed to cover therange of chloride contents of interest.10.6 Subtract the value obtained for the blank measurementfrom

40、 the indicated current readings of each standard sample,and plot the chloride content (ordinate) against net current(mA) readings (abscissa) for each voltage on 3 by 3 cyclelog-log paper, or other suitable format.NOTE 6Some apparatus are capable of internally recording thecurrent readings, standard

41、concentration, and blank, and they provide anoutput in direct concentration units.NOTE 7The apparatus are calibrated against standard solutions ofneutral oil and mixed chloride solutions in xylene because of the extremedifficulties in keeping crude oil-brine mixtures homogeneous. The cali-bration ma

42、y be confirmed, if desired, by careful replicate analysis ofcrude-oil samples by exhaustive extraction of salts with hot water,followed by titration of the chlorides in the extract.NOTE 8In calibrating over a wide range of chloride concentrations, itmay be necessary to apply several voltages to obta

43、in current readingswithin the limit of the apparatus current level display (0 to 10 mA). Highervoltages are applied for low concentrations and lower voltages are appliedfor high concentrations.11. Procedure11.1 To a dry, 100-mL graduated, glass-stoppered cylinder,add 15 mL of xylene and pipet (total

44、 delivery) in 10 mL of thecrude oil sample. Rinse the pipet with xylene until free of oil.Make up to 50 mL with xylene. Stopper and shake the cylindervigorously for approximately 60 s. Dilute to 100 mL withmixed alcohol solvent, and again shake vigorously for approxi-mately 30 s. After allowing the

45、solution to stand for approxi-mately 5 min, pour it into the dry test beaker.11.2 Follow the procedure in 10.4 to obtain voltage andcurrent readings. Record the indicated electrode current to thenearest 0.01 mA and the nearest voltage.11.3 Remove the electrodes from the sample solution, andclean the

46、 apparatus.12. Calculation12.1 Subtract the value obtained for the blank measurementfrom the value obtained from the specimen measurement toobtain the net current reading. From the calibration graph, readthe indicated salt concentration corresponding to the netcurrent (mA) reading of the sample.12.2

47、 Calculate the concentration in mg/kg by using theappropriate equation given below:Salt, mg/kg 51000Xd(1)Salt, mg/kg 5 2853 Y/d (2)where:X = measured salt concentration in g/m3,Y = measured salt concentration in PTB, andd = specimen density at 15 C in kg/m3.NOTE 9The density of the specimen can be d

48、etermined by variousmethods, such as Test Method D 5002 or other density measurementmethods.13. Report13.1 Report the following information: The concentration inmg/kg as electrometric chloride in crude oil per Test MethodD 3230. Alternately, report the concentration directly in g/m3or lb/1000 bbl, i

49、f so required.NOTE 10For reporting purposes, the values stated in PTB are thepreferred units in the United States; in other countries, their common unitscan be used.14. Precision and Bias414.1 PrecisionThe precision of this test method as deter-mined by the statistical examination of the 1997 interlaboratorytest results is as follows:4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D02-1470.TABLE 1 Standard SamplesSalt, g/m3of Crude OilSalt, lb/1000 bblof Crude OilMixed Salts Solutio