1、BRITISH STANDARD BS EN ISO 6978-1:2005 Incorporating Amendment No. 1 to BS ISO 6978-1:2003 (renumbers BS ISO as BS EN ISO 6978-1:2005) Natural gas Determination of mercury Part 1: Sampling of mercury by chemisorption on iodine The European Standard EN ISO 6978-1:2005 has the status of a British Stan
2、dard ICS 75.060 BS EN ISO 6978-1:2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 17 December 2003 BSI 16 February 2006 ISBN 0 580 43103 7 National foreword This British Standard is the official English language version of EN ISO 6978-1:2
3、005. It is identical with ISO 6978-1:2003. Together with BS ISO 6978-2 and -3, it supersedes BS 7678:1993 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee PTI/15, Natural gas and gas analysis, which has the responsibility to: aid enquirers to understan
4、d the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this com
5、mittee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European 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
6、“Search” facility 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 immunity from leg
7、al obligations. Summary of pages This document comprises a front cover, an inside front cover, the EN ISO title page, the EN ISO foreword page, the ISO title page, pages ii to v, a blank page, pages 1 to 16, an inside back cover and a back cover. The BSI copyright notice displayed in this document i
8、ndicates when the document was last issued. Amendments issued since publication Amd. No. Date Comments 16103 January 2006 Renumbers BS ISO 6978-1:2003 as BS EN ISO 6978-1:2005EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 6978 1 May2005 ICS75.060 Englishversion Naturalgas Determinationofme
9、rcury Part1:Samplingofmercuryby chemisorptiononiodine(ISO69781:2003) Gaznaturel Dterminationdelateneurenmercure Partie1:Echantillonnagedemercureparchimisorptionsur iode(ISO69781:2003) Erdgas BestimmungvonQuecksilber Teil1: ProbenahmevonQuecksilberdurchChemisorptionanlod (ISO69781:2003) ThisEuropeanS
10、tandardwasapprovedbyCENon17April2005. CENmembersareboundtocomplywiththeCEN/CENELECInternalRegulationswhichstipulatetheconditionsforgivingthisEuropean Standardthestatusofanationalstandardwithoutanyalteration.Uptodatelistsandbibliographicalreferencesconcerningsuchnational standardsmaybeobtainedonappli
11、cationtotheCentralSecretariatortoanyCENmember. ThisEuropeanStandardexistsinthreeofficialversions(English,French,German).Aversioninanyotherlanguagemadebytranslation undertheresponsibilityofaCENmemberintoitsownlanguageandnotifiedtotheCentralSecretariathasthesamestatusastheofficial versions. CENmembers
12、arethenationalstandardsbodiesofAustria,Belgium,Cyprus,CzechRepublic,Denmark,Estonia,Finland,France, Germany,Greece,Hungary,Iceland,Ireland,Italy,Latvia,Lithuania,Luxembourg,Malta,Netherlands,Norway,Poland,Portugal,Slovakia, Slovenia,Spain,Sweden,SwitzerlandandUnitedKingdom. EUROPEAN COMMITTEE FOR ST
13、ANDARDIZATION COMITEUROPENDENORMALISATION EUROPISCHESKOMITEEFRNORMUNG ManagementCentre:ruedeStassart,36B1050Brussels 2005CEN Allrightsofexploitationinanyformandbyanymeansreserved worldwideforCENnationalMembers. Ref.No.ENISO69781:2005:E Foreword The text of ISO 6978-1:2003 has been prepared by Techni
14、cal Committee ISO/TC 193, Natural gas, of the International Organization for Standardization (ISO) and has been taken over as EN ISO 6978-1:2005 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 lates
15、t by November 2005, and conflicting national standards shall be withdrawn at the latest by November 2005. 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
16、Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Endorsement notice The text of ISO 6978-1:2003 has been appr
17、oved by CEN as EN ISO 6978-1:2005 without any modifications. EN ISO 6978-1:2005 Reference number ISO 6978-1:2003(E)Natural gas Determination of mercury Part 1: Sampling of mercury by chemisorption on iodine Gaz naturel Dtermination de la teneur en mercure Partie 1: chantillonnage de mercure par chim
18、isorption sur iode Referecne unbmer OSI 1-8796:002)E(3 OSI 3002INTERNATIONAL STANDARD ISO 6978-1 First edition 2003-10-15 imreteD sag larutaNntanoi of rucremy :1 traP ilpmaSem fo gnrucry by chemsiitprono i noidoen Gaz narute l retDmniitad noe la etruen en mercrue raPtie :1 cahitnllnnoega de remcrue
19、rap chimsiroptois nur oied EN ISO 6978-1:2005 ii iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Normative references . 1 3 Terms and definitions. 2 4 Principle . 2 5 Apparatus. 2 6 Reagents 9 7 Sampling 10 7.1 General . 10 7.2 Sampling procedure (see Figures 1 and 2) 11 7.3 Sample treatment
20、 12 8 Mercury determination . 13 8.1 Transfer of mercury to AAS or AFS instrument. 13 8.2 Calibration 13 8.3 Blank test . 13 9 Calculation . 14 10 Precision 15 10.1 General . 15 10.2 Repeatability and reproducibility 15 10.3 Uncertainty. 15 11 Test report 15 Bibliography . 16 EN ISO 6978-1:2005iv Fo
21、reword 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 body interested in a subject for which a tec
22、hnical committee has been established 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 closely with the International Electrotechnical Commission (IEC) on all matters o
23、f electrotechnical standardization. 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 Standards adopted by the technical committees are circulated
24、to the member bodies for voting. Publication as an International Standard requires approval by at 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 fo
25、r identifying any or all such patent rights. ISO 6978-1 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis of natural gas. This first edition of ISO 6978-1, together with ISO 6978-2, cancels and replaces ISO 6978:1992, which has been technically revised. ISO 697
26、8 consists 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 alloy EN ISO 6978-1:2005 vIntroduction Natural gases may contain considerable amounts o
27、f mercury, which are generally present in the elemental form. 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 concentrations are specified when nat
28、ural 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 in almost every natural gas, interferes in the determinatio
29、n of mercury by atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS), mercury cannot 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 determinati
30、on 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 normally poses no particular
31、 problem. However, care should be taken when sampling mercury from natural gases under nearly condensing conditions (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
32、 pipeline quality natural gas. This part of ISO 6978 specifies a method of sampling mercury by chemisorption on iodine-impregnated silica gel whereas Part 2 specifies a method of sampling mercury by amalgamation on gold/platinum alloy thread. EN ISO 6978-1:2005blank 1Natural gas Determination of mer
33、cury Part 1: Sampling of mercury by chemisorption on iodine 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
34、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 method for the determination of total mercury content in natural gas using a sampling method at pressures
35、 up to 40 MPa by chemisorption on iodine-impregnated silica gel. This sampling method is suitable for the determination of mercury contents within the range of 0,1 g/m 3to 5 000 g/m 3in natural gas. This method is applicable to sampled gas volumes containing less than 20 mg hydrogen sulfide (absolut
36、e content) and less than a total liquid hydrocarbon condensate of 10 g/m 3under the sampling conditions. The collected mercury is determined by measuring the absorbance or fluorescence of mercury vapour at 253,7 nm. NOTE ISO 6978-2 gives a sampling method suitable for the determination of mercury co
37、ntent of pipeline natural gas by amalgamation of mercury on gold/platinum alloy thread at atmospheric pressure for the range of mercury from 0,01 g/m 3to 100 g/m 3and for sampling at high pressure (up to 8 MPa) from 0,001 g/m 3to 1 g/m 3 . 2 Normative references The following referenced documents ar
38、e indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 6570, Natural gas Determination of potential hydrocarbon liquid content Gravimetri
39、c methods ISO 10715, Natural gas Sampling guidelines ISO 14111, Natural gas Guidelines to traceability in analysis ISO 14532, Natural gas Vocabulary Guide to the expression of uncertainty in measurement (GUM), BIPM, IEC, IFCC, ISO, IUPAC, IUPAP, OIML AISI Steel Code 1)1) Available from the American
40、Iron and Steel Institute, c/o James McCarl, 131 Huron Drive, Carnegie, PA 15106, USA. EN ISO 6978-1:2005 2 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 14532 apply. 4 Principle The gas is passed through a glass tube containing silica gel impregnat
41、ed with iodine. Mercury (Hg) present in the gas as elemental mercury or organic mercury compounds e.g. dimethyl mercury, Hg(CH 3 ) 2 , or diethyl mercury, Hg(C 2 H 5 ) 2 is chemisorbed: Hg + I 2 HgI 2 Hg(CH 3 ) 2+ 2 I 2 HgI 2+ 2 CH 3 I The mercury iodide (HgI 2 ) formed is then dissolved in an ammon
42、ium iodide/iodine solution (NH 4 I/I 2 ) in the laboratory. Hydrocarbon condensates are removed by vacuum stripping at this stage. Mercury, present in the form of a water-soluble complex, is determined by reducing aliquot portions of this solution with alkaline tin(II) solution to elemental mercury.
43、 The mercury is stripped from the solution by an inert gas and the mercury vapour is transferred to a cold vapour atomic absorption spectrometer (AAS) or atomic fluorescence spectrometer (AFS) for measurement at 253,7 nm. Calibration for the final mercury determination is performed in the same way u
44、sing an aqueous mercury standard solution which is matrix-matched to the sample. Unless otherwise specified, gas volumes are expressed in cubic metres (m 3 ) at 273,15 K and 1 013,25 hPa. 5 Apparatus The parameters influencing the measurement shall be traceable to national or International Standards
45、. 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 equipment, calibrated against a commonly accepted reference, sh
46、all be used to minimize the uncertainty of the volume measurement to less than 1 %. 5.1 Sampling apparatus see Figure 1 a) for sampling up to 10 MPa and Figure 1 b) for up to 40 MPa, comprising the following: 5.1.1 High-pressure sampling cell (see Figure 1 with details given in Figure 2), made of Ni
47、Mo16Cr15W (material no. 2.4819 in accordance with the Steel Code), which includes a temperature gauge and a pressure gauge and the following components. 5.1.1.1 Acid-washed glass wool. 5.1.1.2 Sampling tube (see Figure 1 with details given in Figure 3), made of borosilicate glass and fitted with a s
48、crew cap. Fit the sampling tube (Figure 3) first with a layer, 0,5 cm thick, of acid-washed glass wool (5.1.1.1) to retain the absorbent. Then fill the tube with 4,00 g of iodine-laden silica gel (6.2.3) to obtain a 5 cm absorption layer. Then add another layer, 0,5 cm thick, of glass wool (5.1.1.1) to retain the top of the absorbent layer. Close the tube with a screw cap. 5.1.2 Temperature gauges or thermometers (see Figure 1 with detail
