1、ICS 75.080Prfung von Minerall-Kohlenwasserstoffen Bestimmung des SalzgehaltesIn keeping with current practice in standards published by the International Organization for Standardization(ISO), a comma has been used throughout as the decimal marker.Ref. No. DIN 51576 : 2003-01English price group 08 S
2、ales No. 010805.04DEUTSCHE NORM January 2003 No part of this translation may be reproduced without the prior permission ofDIN Deutsches Institut fr Normung e.V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).Translation by DIN-Spra
3、chendienst.In case of doubt, the German-language original should be consulted as the authoritative text.Determining the salt content of petroleumproductsContinued on pages 2 to 6.SupersedesApril 1983 edition.51576ForewordThis standard has been prepared by Technical Committee Prfung von flssigen Kraf
4、tstoffen und Heizlenof the Fachausschuss Minerall- und Brennstoffnormung of the Normenausschuss Materialprfung (Mate-rials Testing Standards Committee).This standard is based on IP 77/72(96), from which it differs in the following respects:a) the number of digits to be reported in the result has bee
5、n made compatible with the repeatability limit;b) there are no data on precision in terms of mass per volume since the density of the samples examinedmay vary considerably;c) the water is to be added dropwise within thirty minutes;d) potentiometric titration has been included.In addition to the meth
6、od specified in this standard, for in-house analyses, the salt content of crude oils canbe determined rapidly and with a minimum of equipment by measuring the conductivity. A standard methodof this type that is suitable for routine analyses is described in ASTM D 3230-99.AmendmentsThis standard diff
7、ers from the April 1983 edition in that the procedure to be followed depends on watercontent and that it has been editorially revised.Previous editionsDIN 51576: 1959-09, 1965-07, 1968-02, 1975-03, 1983-04.1 ScopeThe method specified in this standard serves to determine the salt content of petroleum
8、 products since suchcontamination may cause corrosion and equipment breakdowns. It is applicable to crude oil, crackingresidues, fuel oil and related products, and also to used turbine oils, marine diesel fuel and marine fuel oilcontaminated with seawater.The method is not restricted in terms of wat
9、er content, but the sodium chloride content is to be more than10 mg/kg. For petroleum products with a water content of more than 2% (m/m), however, particular atten-tion is to be paid to the specifications given in subclause 11.1.3.Page 2DIN 51576 : 2003-01CAUTION. Users of this standard should be f
10、amiliar with standard laboratory practice. It is not claimedthat all the safety problems associated with the use of the method have been dealt with exhaustivelyhere. It is therefore the responsibility of the user to take appropriate safety precautions and to ensurethat these comply with national reg
11、ulations.2 Normative referencesThis standard incorporates, by dated or undated reference, provisions from other publications. These norma-tive references are cited at the appropriate places in the text, and the titles of the publications are listed below.For dated references, subsequent amendments t
12、o or revisions of any of these publications apply to thisstandard only when incorporated in it by amendment or revision. For undated references, the latest edition ofthe publication referred to applies.DIN 51750-1 Sampling of petroleum products GeneralDIN 51750-2 Sampling of liquid petroleum product
13、sDIN 51769-5 Determination of total lead content of petrol Complexometric methodDIN EN ISO 4259 Petroleum products Determination and application of precision data in relation to meth-ods of test (ISO 4259 : 1992 + Corr 1 : 1993)ISO 385-1 : 1984 Laboratory glassware Burettes General requirementsISO 3
14、696 : 1987 Water for analytical laboratory use Specification and test methodsISO 3819 : 1985 Laboratory glassware BeakersIP 77/72 : 1996 Determination of salt content Extraction and volumetric titration methodASTM D 3230-99 Standard test method for salts in crude oil (electrometric method)3 ConceptS
15、altWater-soluble halide, expressed as a content by mass of sodium chloride.4 Unitsmg/kg and % are used in this standard to express the sodium chloride content.5 PrincipleThe water-soluble halides in an extract obtained using water and a demulsifier from a sample diluted withsolvents are determined a
16、nalytically by precipitation titration or potentiometric titration (with any sulfides in theextract removed prior to titration).6 DesignationDesignation of the method of determining the salt content by precipitation titration (A) in accordance with thisstandard:Method DIN 51576-ADesignation of the m
17、ethod of determining the salt content by potentiometric titration (B) in accordance with thisstandard:Method DIN 51576-B7 Reagents7.1 GeneralOnly reagents of known analytical purity shall be used.The following reagents shall be used.7.2 Toluene, C7H8.7.3 Acetone, CH3COCH3.7.4 Ethanol, C2H5OH, pure,
18、or denatured by adding not more than 5% (V/V) methanol, CH3OH.7.5 Lead(II) acetate paper, Pb(CH3COO)2, for detecting sulfide.Page 3DIN 51576 : 2003-017.6 Nitrobenzene, C6H5NO2.7.7 Isoamyl alcohol, (CH3)2CHCH2CH2OH (as an alternative to nitrobenzene).7.8 0,05 mol/l or 0,01 mol/l silver nitrate soluti
19、on, AgNO3.7.9 Distilled or demineralized water, grade 3, as in ISO 3696.7.10 30% (m/m) nitric acid, HNO3, prepared by diluting one part by volume of concentrated nitric acid (ofdensity 1,42 g/ml at 20 C) with two parts by volume of distilled or demineralized water and boiling until thesolution is co
20、lourless, cooling, and passing air through the solution to remove nitrogen oxides, which mayinterfere with the titration.7.11 Iron alum indicator, prepared by dissolving 350 g of ammonium iron(III) sulfate dodecahydrate,(NH4)Fe(SO4)212 H2O, in 1l of distilled or demineralized water and adding 200 ml
21、 of 30% (m/m) nitric acid,HNO3.7.12 0,05 mol/l potassium thiocyanate solution, KSCN.8 Apparatus8.1 In addition to standard laboratory equipment and glassware, the following shall be used.8.2 Titration equipment8.2.1 pH meter, potentiometer or automatic titrator (analog or digital), for measuring the
22、 electrode poten-tiometric signals. The apparatus and electrodes shall be protected against strong electrostatic fields by suitablescreening.NOTE: Protection is satisfactory if the electrodes, the cable connections and the potentiometer itself areearthed and no permanent deflections occur.8.2.2 Pote
23、ntiometer, having a maximum error of t 1 mV, enabling voltages to be read over a range of at least50 mV to +200 mV.8.2.3 Silver combination electrode or combined silver/calomel electrode.8.3 Graduated cylinder, of capacity 100 ml, capable of being read to t 0,5 ml at 20 C.8.4 Burette, manual or auto
24、matic, complying with the requirements of ISO 385-1 and having a capacity of5ml, 10 ml, 20 ml or 25 ml, with scale intervals of 0,05 ml and a maximum error of 0,03 ml.8.5 Wide mouth conical flask.8.6 Filter paper, chloride-free.8.7 High-power stirrer, operating at a minimum speed of 10 000 min1, for
25、 homogenizing the sample.8.8 Extraction apparatus, as in DIN 51769-5, having a capacity of 500 ml and a double surface refluxcondenser.8.9 Stirrer, mechanical, electrical or magnetic, having continuous control and fitted with a propeller, a paddleor stirring arm, made of a chemically resistant mater
26、ial. If an electrical stirrer is used, it shall be earthed (see notein subclause 8.2.1).8.10 Titration beaker, made of borosilicate glass or a chemically resistant plastic, meeting the generalrequirements of ISO 3819, or a titration beaker suitable for a titration stand.NOTE: It is preferable to use
27、 a tall beaker having a capacity that ensures that the specified amount of titrationsolution covers the electrodes.8.11 Titration stand, suitable for accommodating a beaker, electrodes, stirrer and burette.9 SamplingWhen sampling in accordance with DIN 51750-1 and DIN 51750-2, make sure that the sam
28、ple taken does notcontain any salty water that may have settled in the tank or tank wagon. Particular care shall be exercised duringcollection in view of the considerable difficulty encountered in obtaining a representative sample for the analysis.Page 4DIN 51576 : 2003-0110 Sample preparationEnsure
29、 that the sample material is as homogeneous as possible by homogenizing each sample for ten minutesusing a high-power stirrer at a speed of at least 10 000 min1prior to every analysis. Immediately after homog-enization, weigh 80 g of sample material into a beaker and add 40 ml of toluene while stirr
30、ing.Transfer the contents of the beaker quantitatively to an extraction apparatus and add the washings obtained byrinsing twice with 15 ml of toluene. Then add 25 ml of ethanol and 15 ml of acetone immediately as demulsifiers.11 Procedure11.1 Extraction and settling11.1.1 GeneralBring the mixture pr
31、epared as described in clause 10 to the boil with the power fully on, and then adjust theheating until the mixture is boiling and circulating throughout to ensure good homogenization. After boiling itfor five minutes, extract the mixture with 125 ml of doubly distilled or demineralized water added u
32、sing adropping funnel with the dropping rate adjusted so that the addition takes at least 30 minutes.NOTE: Ensure that the cooling is efficient since otherwise solvent or components of the sample may evaporate,thereby adversely affecting demulsifiability and settling, with the result that the salt c
33、ontents found wouldbe too high.After 60 minutes, switch off the heating and cool the mixture to ambient temperature. After a further 30 minutes,drain the aqueous phase completely into the graduated cylinder and determine the total quantity settled (in ml).11.1.2 Water content not exceeding 2% (m/m)S
34、ince some acetone remains in the oil phase, the total volume of the aqueous phase is taken as 160 ml if thesample does not contain more than 2% (m/m) of emulsified water. If the quantity settled is less than(155 t 10) ml, this is indicative of inadequate cooling with associated evaporation losses, a
35、nd the extract is tobe discarded.11.1.3 Water content of more than 2% (m/m)If the sample contains more than 2% (m/m) of water, the total volume of aqueous phase will be greater than160 ml and the total quantity settled will be not less than (155 + water content of the sample, as a percentage)t 10) m
36、l. In carrying out the analyses as in subclauses 11.3 and 11.4, factor a shall take account of the watercontent in the evaluation as in clause 12.11.2 Filtration and testing for sulfidesIf necessary, filter the aqueous phase through filter paper and, in order not to lose any salt, wash the filter pa
37、perout once with a known quantity of water. Take account of this quantity when determining factor a. Check theaqueous phase with lead(II) acetate paper for sulfide. If the paper remains colourless, titrate the extract as insubclause 11.4, but if it is coloured, remove the sulfides as specified in su
38、bclause 11.3 prior to titration.11.3 Removal of sulfidesPour 100 ml of extract, if necessary after filtering, into a beaker and add 5 ml of nitric acid. Cover the beakerwith a watch glass and boil its contents until all the hydrogen sulfide is removed (do not evaporate down by morethan 50% of volume
39、).NOTE: It is advisable always to perform this treatment in the case of endpoint titrations or precipitationtitrations. The occurrence of two potential jumps during the titration is indicative of an incomplete removalof hydrogen sulfide or mercaptan.11.4 Determination of halide ions11.4.1 Precipitat
40、ion titrationNOTE: Adding nitrobenzene or 3-methyl-1-butanol (isoamyl alcohol) will facilitate the precipitation titrationdescribed below since they rapidly coagulate the precipitate.Transfer 100 ml of extract (filtered if necessary) or the remaining contents of the beaker (as in subclause 11.3)quan
41、titatively to a conical flask, then add 3 ml of iron alum indicator, 10 ml of nitrobenzene (or 3-methyl-1-butanol), 5 ml of nitric acid if the treatment described in subclause 11.3 has not been carried out, and 0,4 mlto 0,6 ml of potassium thiocyanate solution from a burette. The potassium thiocyana
42、te solution added is to betaken into account in the subsequent calculation.Titrate this mixture while shaking continuously with 0,05 mol/l silver nitrate until it is colourless and add a further5ml of 0,05 mol/l silver nitrate in excess. Now close the flask with a stopper and shake it vigorously for
43、15 seconds to coagulate the precipitate.CAUTION. Take care when opening the flask since pressure may develop during shaking and the solu-tion, which contains nitric acid, may spurt out when the stopper is removed.Page 5DIN 51576 : 2003-01Finally, back-titrate the excess silver nitrate with potassium
44、 thiocyanate solution until the endpoint is ap-proached, as indicated by slower fading of the red colour. Towards the end, continue titration dropwise untilthe red colour persists even after shaking vigorously.11.4.2 Potentiometric titrationRinse the silver electrode or combined electrodes with doub
45、ly distilled or demineralized water and wipe theelectrode or electrodes with a soft cloth prior to every titration.Transfer 100 ml of extract (filtered if necessary) or the remaining contents of the beaker (as in subclause 11.3)quantitatively to a titration vessel and acidify with a few drops of nit
46、ric acid (if the treatment in subclause 11.3has not been carried out). Immerse the electrodes and then titrate with 0,01 mol/l silver nitrate solution in smallportions of between 0,1 ml and 0,5 ml, depending on the change in potential, which should not exceed 6 mVfor each portion added. Record the p
47、otential as a function of the quantity of silver nitrate solution added eitherby reading it off from the pH meter or by recording the titration curve by means of a potentiograph. Continuethe titration beyond the equivalence point, which may determined by calculation or graphically.NOTE: The equivale
48、nce point is indicated by the point of inflection in the steepest part of the recorded titrationcurve. Modern digital titrators are adjusted so that they also record any second jump in potential (see notein subclause 11.3). If there is only a small jump in potential, it can be increased considerably
49、 by taking only25 ml of extract and making it up to 100 ml with acetone. Take account of this change in the evaluation.11.5 Blank testTo eliminate errors due to any halide content in the reagents and solvents used, perform a blank test with thesame reagents using the same quantities and replacing the sample with 95 ml of toluene.12 Evaluationa) Precipitation titrationCalculate the salt content, w(NaCl), as sodium chloride, in mg/kg, using equation (1), or as a percentage bymass using equation (2):(V1 V0)C1(R1 R0)C3w(NaCl)=ab1 (1)mE(V1 V0)C1(R1 R0)C
