1、BRITISH STANDARDBS EN ISO 6978-2:2005IncorporatingAmendment No. 1(to remember BS ISO6978-2:2003 as BS EN ISO 6978-2:2005)Natural gas Determination of mercuryPart 2: Sampling of mercury by amalgamation on gold/platinum alloyICS 75.060BS EN ISO6978-2:2005Amendment No. 1(to remember BS ISO6978-2:2003 a
2、s BS ENISO 6978-2:2005) and corrigenda December 2004 and April 2006BS EN ISO 6978-2:2005ISBN 978 0 580 96182 3Amendments/corrigenda issued since publicationAmd. No. Date Comments16345 July 2006 Renumbers BS ISO 6978-2:2003 as BS EN ISO 6978-2:200531 March 2017 Implementation of ISO Corrigendum Decem
3、ber 2004: Clause 4 corrected31 March 2017 Implementation of ISO Corrigendum April 2006: Clause 4 correctedThis British Standard was published under the authority of the Standards Policy and Strategy Committee on 17 December 2003 The British Standards Institution 2017. Published by BSI Standards Limi
4、ted 2017National forewordThis British Standard is the UK implementation of EN ISO 6978-2:2005. It is identical to ISO 6978-2:2003, incorporating corrigenda December 2004 and April 2006. Together with BS ISO 6978-1 and -3, it supersedes BS 7678:1993 which is withdrawn.The UK participation in its prep
5、aration was entrusted to Technical Committee PTI/15, Natural gas and gas analysis.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its c
6、orrect application.Compliance with a British Standard cannot confer immunity from legal obligations.EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 6978-2May 2005ICS 75.060English versionNatural gas - Determination of mercury - Part 2: Sampling ofmercury by amalgamation on gold/platinum alloy
7、(ISO 6978-2:2003)Gaz naturel - Dtermination de la teneur en mercure -Partie 2: Echantillonnage du mercure par amalgamation suralliage or/platine (ISO 6978-2:2003)Erdgas - Bestimmung von Quecksilber - Teil 2:Probenahme von Quecksilber durch Amalgamierung aneiner Gold/Platin-Legierung (ISO 6978-2:2003
8、)This European Standard was approved by CEN on 17 April 2005.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical refere
9、nces concerning such nationalstandards 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 translationunder the responsibility of a CEN member into i
10、ts own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxem
11、bourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2005 CEN All rights of exploi
12、tation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 6978-2:2005: EEN ISO 6978-2:2005 (E)Foreword The text of ISO 6978-2:2003 has been prepared by Technical Committee ISO/TC 193 “Naturalgas” of the International Organization for Standardization (ISO) and has
13、 been taken over asEN ISO 6978-2:2005 by CMC.This European Standard shall be given the status of a national standard, either by publication ofan identical text or by endorsement, at the latest byNovember 2005, and conflicting nationalstandards shall be withdrawn at the latest by November 2005. Accor
14、ding to the CEN/CENELEC Internal Regulations, the national standards organizations ofthe following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,Iceland, Ireland, Italy, Latvia, Lithuania
15、, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Endorsement noticeThe text of ISO 6978-2:2003 has been approved byCEN as EN ISO 6978-2:2005 without anymodifications. BS EN ISO 6978-2:2005EN ISO 6978-2:2005EN ISO 69782:200
16、5INTERNATIONALSTANDARDISO6978-2First edition 2003-10-15Natural gas Determination of mercury Part 2:Sampling of mercury by amalgamation ongold/platinum alloyGaz naturel D termination de la teneur en mercure Partie 2: chantillonnage du mercure par amalgamation sur alliage or/platineReference number IS
17、O 6978-2:2003(E)BS EN ISO 6978-2:2005EN ISO 6978-2:2005ivEN ISO 6978-2:2005BS EN ISO 6978-2:2005EN ISO 6978-2:2005vContents PageForewordviIntroduction v1Scope12Normative references .13Terms and definitions.14Principle.15Apparatus.26Reagents and materials87Preparation of sampling and analytical tubes
18、 .97.1 Filling97.2 Cleaning.97.3 Efficiency testing 98Sampling98.1 General.98.2 Conditions for representative sampling.108.3 Sampling procedure at atmospheric pressure (see Figure 1).108.4 Sampling procedure at high pressure (see Figure 4).118.5 Removal of condensate from discarded sampling tubes.12
19、9Mercury determination .129.1 Transfer of mercury to the analytical tube (double amalgamation) 129.2 Transfer of mercury to AAS or AFS instrument.139.3 Calibration139.4 Blank test.1310 Calculation.1311 Precision1612 Test report16Bibliography.17EN ISO 69782:2005BS EN ISO 6978-2:2005EN ISO 6978-2:2005
20、viForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member bodyinterested in a subject for which a
21、technical committee has beenestablished has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closelywith the International Electrotechnical Commission (IEC) on all matters
22、of electrotechnicalstandardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standardsadopted by the technical committees are circulated to
23、 the member bodies for voting. Publication as an International Standard requires approval byat least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for i
24、dentifying any or all such patent rights. ISO 6978-2 was prepared by Technical Committee ISO/TC193, Natural gas, Subcommittee SC 1, Analysis ofnatural gas.This first edition of ISO6978-2, together with ISO 6978-1, cancels and replaces ISO 6978:1992, which hasbeen technically revised. ISO 6978 consis
25、ts of the following parts, under the general title Natural gas Determination of mercury: Part 1: Sampling of mercury by chemisorption on iodine Part 2: Sampling of mercury by amalgamation on gold/platinum alloyEN ISO 6978-2:2005BS EN ISO 6978-2:2005EN ISO 6978-2:2005vIntroduction Natural gases may c
26、ontain considerable amounts ofmercury,which are generally present in the elementalform. Gases with high mercury content have to be purified to avoid the condensation of mercury during processing and transport as well as to be compliant with the demands of gas sales contracts. Low mercury concentrati
27、ons are specified when natural gas is to be liquefied. This is to avoid severe corrosion problems,for instance in aluminium heat exchangers of liquefaction plants. Since the presence of hydrocarbons, in particular aromatic hydrocarbons present in low concentrations inalmost everynatural gas, interfe
28、res in the determination of mercury byatomic absorption spectrometry (AAS)or atomic fluorescence spectrometry (AFS), mercury cannot be determined directlyin natural gas. Therefore, prior to the analytical determination, mercuryhas to be collected and separated from aromatic hydrocarbons. The purpose
29、 of the determination of the mercury content can be to monitor gas quality, to monitor the operation of gas treatment plants for mercury removal. Several methods for the collection or enrichment of mercury from natural gas have been developed. The collection of mercury from dry natural gas normallyp
30、oses no particular problem. However, care should be taken when sampling mercury from natural gases under nearly condensing conditions (see ISO 6570). The two parts of ISO6978 describe the principles of sampling and specify the general requirements formethods for sampling mercury and for determining
31、total mercury in pipeline quality natural gas. This part ofISO 6978 specifies a method of sampling mercury by amalgamation on gold/platinum alloy thread whereas Part 1 specifies a method of sampling mercury by chemisorption on iodine-impregnated silica gel. EN ISO 6978-2:2005BS EN ISO 6978-2:2005EN
32、ISO 6978-2:2005blankINTENRATIONAL TSANDADRIS-8796 O2:(3002E)1Natural gas Determination of mercury Part 2: Sampling of mercury by amalgamation on gold/platinum alloyWARNING The use of this part of ISO 6978 may involve hazardous materials, operations and equipment. This part of ISO 6978 does not purpo
33、rt to address all of the safety problems, associatedwith its use. It is the responsibility of the user of this part of ISO 6978 to establish appropriate safety and health practices and to determine the applicability or regulatory limitations prior to use. 1 Scope This part of ISO 6978 specifies a me
34、thod for the determination of total mercury content of pipeline quality natural gas using a sampling method by amalgamation on gold/platinum (Au/Pt) alloy thread. This method isapplicable to the sampling of raw natural gas when no condensation is present. At atmospheric pressure, thismethod is suita
35、ble for the determination of mercury content within the range of 0,01 g/m3to 100 g/m3innaturalgas samples. At higher pressures (up to 8 MPa), this sampling method is suitable for the determinationof mercury contents within the range of 0,001 g/m3to 1 g/m3. The collected mercuryis determined bymeasur
36、ing the absorbance or fluorescence of mercuryvapour at 253,7 nm. NOTE ISO6978-1 gives a sampling method suitable for the determination of mercury contents in natural gas bychemisorption on iodine-impregnated silica gel for the working range of 0,1 g/m3to 5 000 g/m3for sampling atpressures up to 40 M
37、Pa. 2 Normative referencesThe following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenceddocument (including anyamendments) applies. ISO 10715, Natural gas Sam
38、pling guidelinesISO 14532, Natural gas Vocabulary Guide to the expression of uncertainty in measurement (GUM), BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 14532 apply. 4 Principle Sampling is performed at a
39、 temperature at least 10C higher than the dewpoint of the gas sampled. The gasis passed through two quartz glass sampling tubes in series containing fine gold/platinum alloy thread. The mercury is collected on the gold/platinum alloy thread by amalgamation. Subsequently, each sampling tube isseparat
40、elyheated to 700 C to desorb the mercury from the amalgam. The released mercury is transferred byEN ISO 6978-2:2005BS EN ISO 6978-2:2005EN ISO 6978-2:20052a stream of air onto an analytical tube filled with gold/platinum alloy thread (double amalgamation). Thissecond quartz glass tube is then heated
41、 to 800 C and the mercury is transferred to an AAS or AFS formeasurement at 253,7 mm.This sampling method is suitable for the determination of mercury content in natural gas in the range of 0,01 g/m3to 100 g/m3for sampling at atmospheric pressure and 0,001 g/m3to 1 g/m3for sampling at high pressure.
42、 To avoid diffusion of mercury from the surface into the gold/platinum alloythread, which would reduce the recovery of mercuryunder the specified transfer conditions, it is necessary to determine theamount of collected mercury within one week after sampling. Other sorption materials such as gold-imp
43、regnated silica with a high specific surface may be used instead offine gold/platinum alloy thread, provided they show equivalent method performance in the natural gas matrix. Unless otherwise specified, gas volumes are expressed in cubic metres (m3) at 273,15 K and 1 013,25 hPa. NOTE The comparabil
44、ity of the two sampling techniques has been demonstrated by interlaboratory tests at two different concentration levels. 5 Apparatus The parameters influencing the measurement shall be traceable to national or International Standards. The uncertainty of the volume measurement (volume, temperature an
45、d pressure of the gas aswell as ambient airpressure) directly contributes to the uncertainty of the determined mercury content of the gas. Therefore suitable measuring equipment, calibrated against a commonly accepted reference, shall be used to minimize the uncertainty of the volumemeasurement to l
46、ess than 1 %.5.1 Sampling apparatus (see Figure 1). 5.1.1 Apparatus for sampling at atmospheric pressure, typically comprising the following: 5.1.1.1 Heated bypass valve.5.1.1.2 Heated flow control valve (needle type).5.1.1.3 Three-wayvalve, for the second bypass.5.1.1.4 Aluminium block, capable of
47、being heated to u100 C (see Figure2) and dividable into two halves with a central bore coated with a layer (about 2 mm) of silicon rubber for keeping the quartz glass sampling tubes filled with gold/platinum alloy thread (see Figure 3) during sampling at elevated temperature (if necessary) and equip
48、ped with a temperature gauge (not shown in Figure 1). 5.1.1.5 Flow meters (three): one for flowratesu 50 l/min; two for flowrates u 5 l/min. 5.1.1.6 Gas meter, suitable for measuring flowrates of u5 l/min, capable of allowing adjustment of thebypass flow and the volume measurement and equipped with
49、the following: a) pressure gauge;b) temperature gauge, formeasuring temperatures between 0 C to 40 C. 5.1.1.7 Barometer, required for measuring the ambient air pressure. EN ISO 6978-2:2005BS EN ISO 6978-2:2005EN ISO 6978-2:2005a stream of air onto an analytical tube filled with gold/platinum alloy thread (double amalgamation). This second quartz glass tube is then heated to 800 C and the mercury is transferred to an AAS or AFS for measurement at 253,7 nm.3Key1 pipeline 7 three-wayvalve 2 sampling valve 8 aluminium block
