1、BRITISH STANDARD BS EN ISO 6326-3:1998 BS 3156-11.4.3: 1994 Incorporating Amendment No. 1 to BS 3156-11.4.3:1994 (renumbers the BS as BS EN ISO 6326-3: 1998) Natural gas Determination of sulfur compounds Part 3: Determination of hydrogen sulfide, mercaptan sulfur, and carbonyl sulfide sulfur by pote
2、ntiometry ICS 75.060BSENISO6326-3:1998 This British Standard, having been prepared under the directionof the Materials and Chemicals Sector Board (I/-), waspublished under the authorityof the Standards Boardand comes into effect on 15 December 1994 BSI 04-1999 The following BSI references relate to
3、the work on this standard: Committee reference PTI/15 Special announcement in BSI News, September 1994 ISBN 0 580 23614 5 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee PTI/15, Natural gas and gas analysis upon which the
4、 following bodies were represented: AEA Technology British Coal Corporation British Compressed Gases Association British Gas plc British Glass Manufacturers Confederation Chemical Industries Association Department of Trade and Industry (Gas and Oil Measurement Branch) Department of Trade and Industr
5、y (National Physical Laboratory) Institute of Petroleum Institution of Gas Engineers Sira Limited Society of Chemical Industry Society of Glass Technology Amendments issued since publication Amd. No. Date Comments 9993 June 1998 Indicated by a sideline in the marginBSENISO6326-3:1998 BSI 04-1999 i C
6、ontents Page Committees responsible Inside front cover National foreword ii Foreword 2 1 Scope 3 2 Normative references 3 3 Principle 3 4 Reagents and materials 3 5 Apparatus 3 6 Sampling 4 7 Procedure 4 8 Expression of results 5 9 Test report 6 Figure 1 Test apparatus 5 Figure 2 Example of a titrat
7、ion curve 6 Table 1 Precision data 7 List of references Inside back coverBSENISO6326-3:1998 ii BSI 04-1999 National foreword This British Standard has been prepared by Technical Committee PTI/15, and is the English language version of ENISO6326-3:1997 Natural gas Determination of sulfur compounds Pa
8、rt3: Determination of hydrogen sulfide,mercaptan sulfur and carbonyl sulfide sulfur by potentiometry, published by theEuropean Committee for Standardization (CEN). It is identical with ISO6326-3:1989, published by the International Organization for Standardization (ISO). ISO6326-3 was prepared by Te
9、chnical Committee158, Analysis of gases, in which the United Kingdom participated. BS EN ISO 6326-3 retains the secondary identifier BS3156-11.4.3, so that it remains cross-referenced within the BS3156 series of standards. Each Subsection of Section11.4 of BS3156 is identical with the corresponding
10、Part of ISO6326, and Section11.4 of BS3156 consists of the following Subsections: In the United Kingdom the preferred method is that given in Subsection11.4.4 of BS3156. The flame photometric detector is available from most manufacturers of chromatographs, both laboratory and process units, and is a
11、pplicable to any sulfur compound. By contrast, the electrochemical detector is available from a single supplier and is operated under completely different conditions in order to measure carbonyl sulfide, to those used for all other sulfur compounds. A British Standard does not purport to include all
12、 the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Subsection 11.4.1 Subsection 11.4.2 Subsection 11.4.3 (BS EN ISO 6326-3) Subsection 11.4.4
13、Subsection 11.4.5 (BS EN ISO 6326-5) Introduction Odoriferous sulfur compounds by gas chromatography using an electrochemical detector Hydrogen sulfide, mercaptan sulfur, and carbonyl sulfide sulfur by potentiometry Hydrogen sulfide, carbonyl sulfide and sulfur-containing odorants by gas chromatogra
14、phy using a flame photometric detector Lingener combustion method Cross-reference Publication referred to Corresponding British Standard ISO 1042:1983 BS 1792:1982 Specification for one-mark volumetric flasks Summary of pages This document comprises a front cover, an inside front cover, pagesi andii
15、, theEN title page, pages2 to8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM ENISO6326-3 De
16、cember1997 ICS75.060 Descriptors: Natural gas, gas analysis, determination of content, sulfur, potentiometric methods English version Natural gas Determination of sulfur compounds Part3: Determination of hydrogen sulfide, mercaptan sulfur and carbonyl sulfide sulfur by potentiometry (ISO 6326-3:1989
17、) Gaz naturel Dtermination des composs soufrs Partie 3: Dtermination du sulfure dhydrogne, des thiols et du sulfure de carbonyle par potentiomtrie (ISO 6326-3:1989) Erdgas Bestimmung von Schwefelverbindungen Teil3: Bestimmung von Schwefelwasserstoff, Mercaptanschwefel und Kohlenstoffoxidsulfidschwef
18、el durch Potentiometrie (ISO 6326-3:1989) This European Standard was approved by CEN on6November1997. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. U
19、p-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation un
20、der the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, CzechRepublic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Lux
21、embourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CEN European Committee for Standardization Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels 1997 CEN All rights of exploitation in any form and
22、 by any means reserved worldwide for CEN national Members Ref. No. EN ISO 6326-5:1997 EENISO6326-3:1997 BSI 04-1999 2 Foreword The text of the International Standard from Technical Committee ISO/TC193, Natural gas, of the International Organization for Standardization (ISO) has been taken over as a
23、European Standard by CEN/CS. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June1998, and conflicting national standards shall be withdrawn at the latest by June1998. According to CEN/CENELEC Int
24、ernal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, CzechRepublic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland
25、 and the United Kingdom.ISO6326-3:1989(E) BSI 04-1999 3 1 Scope This part of ISO 6326 specifies a potentiometric method for the determination of hydrogen sulfide, mercaptan sulfur, and carbonyl sulfide sulfur in natural gas in the concentration range equal to or above1mg/m 3 . The gas must be free o
26、f dust, mist, oxygen, hydrogen cyanide and carbon disulfide. The hydrogen sulfide/mercaptan sulfur ratio and also the mercaptan sulfur/hydrogen sulfide ratio should not exceed50 : 1. The method is not recommended for gases containing more than approximately1,5% (V/V) carbon dioxide. NOTEIn all parts
27、 of ISO6326,1m 3of gas is expressed at normal conditions (0C;101,325kPa). 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this part of ISO6326. At the time of publication, the editions indicated were valid. All standar
28、ds are subject to revision, and parties to agreements based on this part of ISO6326 are encouraged to investigate the possibility of applying the most recent editions of the standards listed below. Members of IEC and ISO maintain registers of currently valid International Standards. ISO 385-1:1984,
29、Laboratory glassware Burettes Part1: General requirements. ISO 648:1977, Laboratory glassware One-mark pipettes. ISO 1042:1983, Laboratory glassware One-mark volumetric flasks. 3 Principle Hydrogen sulfide and mercaptans are absorbed in a35% (m/m) aqueous potassium hydroxide solution and carbonyl su
30、lfide in a5% (m/m) ethanoholic monoethanolamine solution. The solutions are titrated potentiometrically using silver nitrate solutions with a silver/silver sulfide electrode system to indicate the end point. 4 Reagents and materials During the analysis, use only reagents of recognized analytical gra
31、de and only distilled water or water of equivalent purity. 4.1 Potassium hydroxide, solution. Dissolve 35 g of potassium hydroxide (KOH) in65g of water. NOTEIn order to prevent interference by heavy metal ions,0,5g of a mixture of polyaminoacetic acids is added for each50ml of absorption solution to
32、 inactivate the heavy metal ions. The mixture consists of equal parts of the pentasodium salt of diethylenetriamine pentaacetic acid (Na 5 DTPA); the trisodium salt of N-hydroxyethylenediamine triacetic acid (Na 3 HEDTA); the sodium salt of N,N-di(2-hydroxyethyl-glycin) (NaDHEG); the tetrasodium sal
33、t of ethylenediamine tetraacetic acid (Na 4 EDTA). 4.2 Monoethanolamine, solution. Dissolve 5 g of monoethanolamine (C 2 H 7 ON) in95g of ethanol. 4.3 Nitrogen, purity better than99,95%, oxygen-free, under pressure. 4.4 Silver nitrate, standard volumetric solution, c(AgNO 3 ) 0,01mol/l. For the prep
34、aration of the silver nitrate solution use boiled distilled water, cooled to20C while bubbling with nitrogen (4.3), to remove all traces of oxygen. Dissolve about1,7g of silver nitrate in200ml of water in the1000ml one-mark volumetric flask(5.6) and make up to the mark with water. Standardize the so
35、lution with hydrochloric acid c(HCl) = 0,01mol/l. 4.5 Ammonium hydroxide solution (A 20C =0,90g/ml). 4.6 Electrolyte solution. Mix 1000ml of methanol and25ml of ammonium hydroxide solution (4.5). 4.7 Cotton-wool, for the removal of dust. 5 Apparatus Ordinary laboratory apparatus and 5.1 Test apparat
36、us, (seeFigure 1), consisting of three washing bottles (high-speed absorbers of any suitable design), maximum pore diameter904m to1504m;1 washing bottle for the removal of dust, if required; gas meter, wet design, tolerance0,1litre, with thermometer and water manometer. The thermometer shall have a
37、measuring range of0C to at least30C. The scale intervals shall be not less than0,5C. The connections between the three washing bottles shall be glass to glass sealed by fluorelastomer tubing. NOTEFor low levels of sulfur compounds, butt connections and stop cocks with polytetrafluoroethylene plugs i
38、nstead of the screw clamps are recommended. 5.2 One-mark pipette, of capacity10ml, complying with ISO648. 5.3 Microburette, of capacity10ml, complying withISO385-1. 5.4 Beaker, of capacity300ml. 5.5 Measuring cylinder, of capacity50ml. 5.6 One-mark volumetric flask, of capacity1000ml, complying with
39、 ISO1042.ISO6326-3:1989(E) 4 BSI 04-1999 5.7 High-resistance voltmeter, range1000mV, accuracy better than 5mV. (An automatic titrimeter may be used, providing that it meets the above specification.) 5.8 Silver/silver sulfide measuring electrode NOTEIon-selective silver/silver sulfide crystal membran
40、e electrodes are commercially available and allow faster and more precise titration, especially at low sulfur concentrations. If such an electrode is not available, a conventional silver/silver sulfide electrode may be prepared according to the following procedure. Prepare a solution of sodium sulfi
41、de and sodium hydroxide by dissolving1,2g of sodium sulfide nonahydrate (Na 2 S,9H 2 O) and40g of sodium hydroxide in1litre of water. Clean the silver metal of the electrode with fine abrasive paper and immerse it in100ml of the sodium sulfide/sodium hydroxide solution, stir the solution and add10ml
42、 of the silver nitrate solution (4.4) over a period of10min to15min. Remove the electrode from the solution, wash it with water and wipe it lightly with a clean cloth. The coating should last for several weeks. Before use, soak the electrode for at least5min in100ml of the electrolytic solution (4.6
43、) to which0,5ml of silver nitrate solution(4.4) has been added. Store the electrode in this solution. 5.9 Silver/silver chloride reference electrode. 5.10 Electric stirrer. 6 Sampling On-line sampling is recommended. In the case where indirect sampling is indispensable, use sampling cylinders in acc
44、ordance with clause3 of ISO6326-1:1989. 7 Procedure 7.1 Preliminary operations Assemble the absorbers in series, as shown inFigure 1. Place 50ml of potassium hydroxide solution (4.1) in the washing bottle (E), and50ml of monoethanolamine solution (4.2) in each of the two washing bottles (F). In orde
45、r to remove the oxygen dissolved in the absorption solutions, purge the assembly with nitrogen (4.3) for a period of5min to10min, at a rate of1l/min to2l/min. Transfer the washing bottles, closed hermetically with screw-clamps (D), to the sampling point andassemble the testing apparatus as shown inF
46、igure 1. If required, connect an additional washing bottle filled with cotton-wool (4.7) between the sampling cock (B) and the T-piece (C) to intercept any solid particles. 7.2 Absorption (see Figure 1) Flush the sampling line and the T-piece (C) with gas. Open the screw-clamps (D) at the inlet and
47、outlet of the washing bottles (E and F) and record the initial reading of the gas meter (G). The gas is passed through the absorption solutions at a flow rate of120l/h 20l/h. Read the temperature and pressure of the gas and the atmospheric pressure during the absorption period. The amount of gas dep
48、ends on the content of sulfur compounds;100 litres to200litres are sufficient in most cases. Close the sampling valve (B) and read the amount ofgas passed through the solutions on the gas meter(G). By the free end of the T-piece, pass10litres of nitrogen (4.3) through the washing bottles to transfer
49、 the dissolved carbonyl sulfide from the potassium hydroxide into the monoethanolamine solution. Close the washing bottles (E and F) hermetically and titrate the solutions containing the absorbed sulfur compounds immediately. 7.3 Potentiometric titration 7.3.1 Determination of hydrogen sulfide and mercaptan sulfur Flush the300ml beaker (5.4) with nitrogen (4.3). Quantitatively transfer the contents of the washing bottle (E) into the beaker and dilute with approximately200ml boiled distilled water, cooled to20C. While bub
