1、BRITISH STANDARDBS EN ISO 6978-2:2005IncorporatingAmendment No. 1 (to remember BS ISO 6978-2:2003 as BS EN ISO 6978-2:2005)Natural gas Determination of mercury Part 2: Sampling of mercury by amalgamation on gold/platinum alloyThis European Standard EN ISO 6978-2:2005 has the status of a British Stan
2、dardICS 75.060BS EN ISO 6978-2:2005This British Standard was published under the authority of the Standards Policy andStrategy Committee on 17 December 2003 BSI 2006ISBN 0 580 43102 9National forewordThis British Standard is the official English language version of EN ISO 6978-2:2005. It is identica
3、l with ISO 6978-2:2003. Together withBS ISO 6978-1 and -3, it supersedes BS 7678:1993 which is withdrawn.The UK participation in its preparation was entrusted to Technical CommitteePTI/15, Natural gas and gas analysis, which has the responsibility to:A list of organizations represented on this commi
4、ttee can be obtained on request to its secretary.Cross-referencesThe British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled“International Standards Correspondence Index”, or by using the “Search”facility
5、of the BSI Electronic Catalogue or of British Standards Online.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunityfrom legal obligations. aid
6、enquirers to understand the text; present to the responsible international/European committee anyenquiries on the interpretation, or proposals for change, and keep theUK interests informed; monitor related international and European developments andpromulgate them in the UK.Summary of pagesThis docu
7、ment comprises a front cover, an inside front cover, EN ISO title page,the EN ISO foreword page, the ISO title page, pages iv to vi, a blank page,pages 1 to 17 and a back cover.The BSI copyright notice displayed in this document indicates when thedocument was last issued.Amendments issued since publ
8、icationAmd. No. Date Comments16345 July 2006 Renumbers BS ISO 6978-2:2003 as BS EN ISO 6978-2:2005EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 6978-2May 2005ICS 75.060English versionNatural gas - Determination of mercury - Part 2: Sampling ofmercury by amalgamation on gold/platinum alloy (I
9、SO 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)T
10、his 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 referenc
11、es 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 its
12、 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, Luxembo
13、urg, 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 exploita
14、tion 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 “Natural gas” of the International Organization for Standardization (ISO) and has
15、 been taken over as EN ISO 6978-2:2005 by CMC. 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 November 2005, and conflicting national standards shall be withdrawn at the latest by November 2005.
16、According to the CEN/CENELEC Internal Regulations, the national standards organizations of the 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, Li
17、thuania, 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 by CEN as EN ISO 6978-2:2005 without any modifications. EN ISO 69782:2005INTERNATIONALSTANDARDISO6978-
18、2First edition 2003-10-15Natural gas Determination of mercury Part 2:Sampling of mercury by amalgamation on gold/platinum alloyGaz naturel Dtermination de la teneur en mercure Partie 2: chantillonnage du mercure par amalgamation sur alliage or/platineReference number ISO 6978-2:2003(E)ivEN ISO 6978-
19、2:2005vContents PageForeword viIntroduction v1 Scope 12 Normative references . 13 Terms and definitions. 14 Principle . 15 Apparatus. 26 Reagents and materials 87 Preparation of sampling and analytical tubes .97.1 Filling 97.2 Cleaning . 97.3 Efficiency testing 98 Sampling 98.1 General. 98.2 Conditi
20、ons 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. 129 Mercury determination . 129.1 Transfer of mercury to the analytical tube (double
21、amalgamation) 129.2 Transfer of mercury to AAS or AFS instrument. 139.3 Calibration 139.4 Blank test . 1310 Calculation. 1311 Precision 1612 Test report 16Bibliography . 17EN ISO 69782:2005viForeword ISO (the International Organization for Standardization) is a worldwide federation of national stand
22、ards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International orga
23、nizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given
24、in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75
25、% 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 identifying any or all such patent rights. ISO 6978-2 was prepared by Technical Committee ISO/TC 193, Nat
26、ural gas, Subcommittee SC 1, Analysis of natural gas.This first edition of ISO 6978-2, together with ISO 6978-1, cancels and replaces ISO 6978:1992, which has been technically revised. ISO 6978 consists of the following parts, under the general title Natural gas Determination of mercury: Part 1: Sam
27、pling of mercury by chemisorption on iodine Part 2: Sampling of mercury by amalgamation on gold/platinum alloy EN ISO 6978-2:2005vIntroduction Natural gases may contain considerable amounts of mercury, which are generally present in the elemental form. Gases with high mercury content have to be puri
28、fied 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 concentrations are specified when natural gas is to be liquefied. This is to avoid severe corrosion problems, for instance in aluminium heat excha
29、ngers of liquefaction plants. Since the presence of hydrocarbons, in particular aromatic hydrocarbons present in low concentrations in almost every natural gas, interferes in the determination of mercury by atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS), mercury canno
30、t be determined directly in natural gas. Therefore, prior to the analytical determination, mercury has to be collected and separated from aromatic hydrocarbons. The purpose of the determination of the mercury content can be to monitor gas quality, to monitor the operation of gas treatment plants for
31、 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 normally poses no particular problem. However, care should be taken when sampling mercury from natural gases under nearly condensing cond
32、itions (see ISO 6570). The two parts of ISO 6978 describe the principles of sampling and specify the general requirements for methods for sampling mercury and for determining total mercury in pipeline quality natural gas. This part of ISO 6978 specifies a method of sampling mercury by amalgamation o
33、n gold/platinum alloy thread whereas Part 1 specifies a method of sampling mercury by chemisorption on iodine-impregnated silica gel. EN ISO 6978-2:2005blankINTENRATIONAL TSANDADR IS-8796 O2:(3002E)1Natural gas Determination of mercury Part 2: Sampling of mercury by amalgamation on gold/platinum all
34、oy WARNING The use of this part of ISO 6978 may involve hazardous materials, operations and equipment. This part of ISO 6978 does not purport to address all of the safety problems, associated with its use. It is the responsibility of the user of this part of ISO 6978 to establish appropriate safety
35、and health practices and to determine the applicability or regulatory limitations prior to use. 1 Scope This part of ISO 6978 specifies a method for the determination of total mercury content of pipeline quality natural gas using a sampling method by amalgamation on gold/platinum (Au/Pt) alloy threa
36、d. This method is applicable to the sampling of raw natural gas when no condensation is present. At atmospheric pressure, this method is suitable for the determination of mercury content within the range of 0,01 g/m3to 100 g/m3in natural gas samples. At higher pressures (up to 8 MPa), this sampling
37、method is suitable for the determination of mercury contents within the range of 0,001 g/m3to 1 g/m3. The collected mercury is determined by measuring the absorbance or fluorescence of mercury vapour at 253,7 nm. NOTE ISO 6978-1 gives a sampling method suitable for the determination of mercury conte
38、nts in natural gas by chemisorption on iodine-impregnated silica gel for the working range of 0,1 g/m3to 5 000 g/m3for sampling at pressures up to 40 MPa. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the
39、edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 10715, Natural gas Sampling guidelines ISO 14532, Natural gas Vocabulary Guide to the expression of uncertainty in measurement (GUM), BIPM, IEC, IFCC, ISO, IUPAC, IUPA
40、P, OIML 3 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 temperature at least 10 C higher than the dewpoint of the gas sampled. The gas is passed through two quartz glass sampling tubes in series con
41、taining fine gold/platinum alloy thread. The mercury is collected on the gold/platinum alloy thread by amalgamation. Subsequently, each sampling tube is separately heated to 700 C to desorb the mercury from the amalgam. The released mercury is transferred by EN ISO 6978-2:20052a stream of air onto a
42、n 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 mm. This sampling method is suitable for the determination of mercury content in natural gas
43、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. To avoid diffusion of mercury from the surface into the gold/platinum alloy thread, which would reduce the recovery of mercury under the specified transfer conditions, it is
44、 necessary to determine the amount of collected mercury within one week after sampling. Other sorption materials such as gold-impregnated silica with a high specific surface may be used instead of fine gold/platinum alloy thread, provided they show equivalent method performance in the natural gas ma
45、trix. Unless otherwise specified, gas volumes are expressed in cubic metres (m3) at 273,15 K and 1 013,25 hPa. NOTE The comparability of the two sampling techniques has been demonstrated by interlaboratory tests at two different concentration levels. 5 Apparatus The parameters influencing the measur
46、ement shall be traceable to national or International Standards. The uncertainty of the volume measurement (volume, temperature and pressure of the gas as well as ambient air pressure) directly contributes to the uncertainty of the determined mercury content of the gas. Therefore suitable measuring
47、equipment, calibrated against a commonly accepted reference, shall be used to minimize the uncertainty of the volume measurement to less 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 va
48、lve.5.1.1.2 Heated flow control valve (needle type). 5.1.1.3 Three-way valve, for the second bypass. 5.1.1.4 Aluminium block, capable of being heated to u 100 C (see Figure 2) and dividable into two halves with a central bore coated with a layer (about 2 mm) of silicon rubber for keeping the quartz
49、glass sampling tubes filled with gold/platinum alloy thread (see Figure 3) during sampling at elevated temperature (if necessary) and equipped with a temperature gauge (not shown in Figure 1). 5.1.1.5 Flow meters (three): one for flowrates u 50 l/min; two for flowrates u 5 l/min. 5.1.1.6 Gas meter, suitable for measuring flowrates of u 5 l/min, capable of allowing adjustment of the bypass flow and the volume measurement and equipped with the following: a) pressure gauge;b) temperature gauge, for measuring temperat
