1、PD CEN ISO/TR24094:2007ICS 75.060NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWPUBLISHED DOCUMENTAnalysis of natural gas Validation methodsfor gaseous referencematerials (ISO/TR24094:2006)This Published Documentwas published under theauthority of the StandardsPolicy and Strat
2、egyCommittee on 31 December2008 BSI 2008ISBN 978 0 580 59401 4Amendments/corrigenda issued since publicationDate CommentsPD CEN ISO/TR 24094:2007National forewordThis Published Document is the UK implementation of CEN ISO/TR24094:2007. It is identical to ISO/TR 24094:2006.The UK participation in its
3、 preparation was entrusted to TechnicalCommittee PTI/15, Natural gas and gas analysis.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its
4、 correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.TECHNICAL REPORTRAPPORT TECHNIQUETECHNISCHER BERICHTCEN ISO/TR 24094November 2007ICS 75.060English VersionAnalysis of natural gas - Validation methods for gaseousreference materials (ISO/TR 24094:200
5、6)Analyse du gaz naturel - Mthodes de validation pourmatriaux de rfrence gazeux (ISO/TR 24094:2006)Erdgasanalyse - Validierungsverfahren fr gasfrmigeReferenzmaterialien (ISO/TR 24094:2006)This Technical Report was approved by CEN on 2 November 2007. It has been drawn up by the Technical Committee CE
6、N/SS N21.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia,
7、Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2007 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national M
8、embers.Ref. No. CEN ISO/TR 24094:2007: EPD CEN ISO/TR 24094:2007ISO/TR 24094:2006(E) ISO 2006 All rights reserved iiiContents Page Foreword iv 1 Scope . 1 2 Normative references . 1 3 Development of the validation methods. 2 4 Results of the VAMGAS project 5 Annex A (informative) Report on the valid
9、ation methods for gaseous reference materials 6 Bibliography . 47 PD CEN ISO/TR 24094:2007ISO/TR 24094:2006(E) iv ISO 2006 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of prep
10、aring 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 organizations, governmental and non-governmental, in
11、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 in the ISO/IEC Directives, Part 2. The main task
12、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 % of the member bodies casting a vote. In excepti
13、onal circumstances, when a technical committee has collected data of a different kind from that which is normally published as an International Standard (“state of the art”, for example), it may decide by a simple majority vote of its participating members to publish a Technical Report. A Technical
14、Report is entirely informative in nature and does not have to be reviewed until the data it provides are considered to be no longer valid or useful. 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
15、 for identifying any or all such patent rights. ISO/TR 24094 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis of natural gas. PD CEN ISO/TR 24094:2007TECHNICAL REPORT ISO/TR 24094:2006(E) ISO 2006 All rights reserved 1Analysis of natural gas Validation methods
16、 for gaseous reference materials 1 Scope This Technical Report describes the validation of the calorific value and density calculated from current practice natural gas analysis by statistical comparison with values obtained by measurement using a reference calorimeter and a density balance. 2 Normat
17、ive references The following referenced documents are 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 6142, Gas analysis Preparation
18、 of calibration gas mixtures Gravimetric method ISO 6974-1, Natural gas Determination of composition with defined uncertainty by gas chromatography Part 1: Guidelines for tailored analysis ISO 6974-2, Natural gas Determination of composition with defined uncertainty by gas chromatography Part 2: Mea
19、suring-system characteristics and statistics for processing of data ISO 6974-3, Natural gas Determination of composition with defined uncertainty by gas chromatography Part 3: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and hydrocarbons up to C8 using two packed columns ISO 6
20、974-4, Natural gas Determination of composition with defined uncertainty by gas chromatography Part 4: Determination of nitrogen, carbon dioxide and C1 to C5 and C6+ hydrocarbons for a laboratory and on-line measuring system using two columns ISO 6974-5, Natural gas Determination of composition with
21、 defined uncertainty by gas chromatography Part 5: Determination of nitrogen, carbon dioxide and C1 to C5 and C6+ hydrocarbons for a laboratory and on-line process application using three columns ISO 6974-6, Natural gas Determination of composition with defined uncertainty by gas chromatography Part
22、 6: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and C1 to C8 hydrocarbons using three capillary columns ISO 6976, Natural gas Calculation of calorific values, density, relative density and Wobbe index from composition Guide to the expression of uncertainty in measurement (GUM
23、), BIPM/IEC/IFCC/ISO/IUPAC/IUPAP/OIML, 1995 PD CEN ISO/TR 24094:2007ISO/TR 24094:2006(E) 2 ISO 2006 All rights reserved3 Development of the validation methods The validation methods for gaseous reference materials (VAMGAS) project was established by a group of European gas companies as an approach t
24、o confirming the practices used in natural gas analysis and physical property calculations. The VAMGAS project proposed comparing the calorific value and density calculated from the current practices for natural gas analyses with values obtained by measurement using a reference calorimeter (located
25、at the Ofgas, UK laboratory) and density balance (located at the Ruhrgas, Germany laboratory). Robust statistical comparisons allowed an assessment of the validity of the practices. The natural gas analysis practice covered by the VAMGAS project can be divided into the following steps: The gravimetr
26、ic preparation of gas mixtures used as calibrants in the analysis of natural gas in accordance with ISO 6142. At the highest level, these mixtures are categorized as primary reference gas mixtures (PRMs) and are available from national institutes such as Bundesanstalt fur Materialforschung und -prfu
27、ng (BAM) of Germany and Nederlands Meetinstituut (NMi) of the Netherlands. The analysis of natural gas by gas chromatographic methods, such as those given is ISO 6974 (all parts). This is a multiple part International Standard that provides a number of different approaches to the gas chromatographic
28、 analysis of natural gas. ISO 6974-2 describes the processing of calibration and analytical data to determine the uncertainties on sample component concentrations that are required for the calculation of uncertainties on calculated physical property values of the sample gas. The calculation of the v
29、alues of physical properties from the results of the gas chromatographic analyses as described in ISO 6976. The VAMGAS project was divided in two parts: a) Part 1: comparison of the calorific values and densities of two PRMs calculated from the gravimetric preparation data against the values obtaine
30、d from the reference calorimeter and density balance (see Figure 1); b) Part 2: gas chromatography intercomparison exercise, in which calorific values and densities calculated from the analyses of two natural gases (with bracketing calibration using PRMs) were compared to the values obtained from th
31、e reference calorimeter and density balance (see Figure 2). The two separate exercises would enable problems arising from either the gravimetric preparation or the gas chromatographic analyses to be identified. The participants in the VAMGAS project were Ruhrgas AG (Germany and project co-ordinator)
32、, Gasunie (the Netherlands), Gaz de France (France), BAM (Germany), NMi (the Netherlands) and Ofgem (previously Ofgas, the UK). In addition, a total of 18 laboratories participated in the gas chromatography intercomparison. The technical report from the VAMGAS is given in Annex A. PD CEN ISO/TR 2409
33、4:2007ISO/TR 24094:2006(E) ISO 2006 All rights reserved 3Figure 1 Schematic concept of part 1 of the VAMGAS project PD CEN ISO/TR 24094:2007ISO/TR 24094:2006(E) 4 ISO 2006 All rights reservedFigure 2 Schematic concept of part 2 of the VAMGAS project PD CEN ISO/TR 24094:2007ISO/TR 24094:2006(E) ISO 2
34、006 All rights reserved 54 Results of the VAMGAS project The project report provides results on two sets of comparisons. a) The results of the exercise using the PRMs showed statistical agreement between the calorific values and densities calculated from the gravimetric preparation data and the valu
35、es of these physical properties obtained from direct measurement using reference instruments. b) The results of the gas chromatographic intercomparison showed statistical agreement between the calorific values and densities calculated from gas chromatographic analyses, carried out using PRMs as cali
36、brants, and the values of these physical properties obtained from direct measurements using reference instruments. It can be concluded that the VAMGAS project has validated the current systems of natural gas analyses and calculation of physical property data involving the previously mentioned ISO In
37、ternational Standards. As a result, all parties in the supply and use of natural gas, whether supplier or consumer, can have confidence in these. The current ISO International Standards for calibration gas preparation and natural gas analysis, if carefully applied, give values of calorific value and
38、 density that are in agreement with values that were independently determined by reference measurements. This also includes the tabulated values in ISO 6976, which are used in calculations of thermal energy for billing/fiscal transfer purposes. The VAMGAS project was carried out as an integrated pro
39、ject to study the complete system of natural gas analysis involving the gravimetric preparation of calibration gas mixtures, the gas chromatographic analysis and calculation of physical properties. Reference measurements of the physical properties were applied during the VAMGAS project as a means of
40、 assessing the system. It is stressed that readers take account of the whole project; and it is totally wrong to take isolated parts and results of the project and use these for other purposes in the belief that the project results justify such an approach. For example, in the first part of the proj
41、ect comparison was made between the physical property values calculated from the gravimetric preparation data of the PRMs and the values obtained from the reference measurements. It is important not to use the results from this part of the project to justify using reference measurements of a physica
42、l property to validate the composition of a prepared natural gas mixture. There are three reasons. The VAMGAS project was not designed to investigate the applicability, or otherwise, of such a procedure. The VAMGAS project was designed to investigate whether or not a cylinder of gas designated as a
43、PRM can provide gas of the composition given on the certificate attached to that cylinder. In the preparation of the PRMs, the national institutes have rigorous procedures including a system of validating the mixture composition by gas chromatographic analysis to give confidence in the composition o
44、f the gas mixture. Whereas it is true that a gas mixture of known composition has an unique calorific value or density, the same is not true of the reverse relationship: a specific calorific value or density does not have a corresponding unique gas composition; in fact a calorific value or density c
45、an result from an almost infinite number of different gas compositions. Hence, it is not technically feasible to validate gas mixture compositions using measurements of a physical property. As a simple illustration, consider the manufacture of a multi-component mixture containing both isomers of but
46、ane. If, by mistake, the same isomer was added twice then the resulting mixture would have the same calorific value and density as the required mixture but the composition would be incorrect. Measurements of the calorific value or density would appear to validate the mixture composition when it was,
47、 in fact, in error. PD CEN ISO/TR 24094:2007ISO/TR 24094:2006(E) 6 ISO 2006 All rights reservedAnnex A (informative) Report on the validation methods for gaseous reference materials A.1 General A.1.1 Summary In the first part of the project, 12 primary reference gas mixtures were produced by BAM and
48、 NMi. As regards composition, the gas mixtures produced were similar to type L Groningen gas and type H North Sea gas. The superior calorific value, Hs, molar mass, M, and density at normal conditions of the mixtures were calculated from the component concentrations specified by the producers. The c
49、alculated data were then compared with the results of direct measurements of physical properties. The methods used for direct measurement of physical properties were reference calorimetry1and precision densitometry2. Statistically significant agreement was found between the calculated data and the measurements. Table A.1 Comparison of experimental (Mexp) and calculated (Mcalc) values of the molar mass for different PRMs aGas mixture Type of gas Mexpg/mol Mcalcg/mol Relative difference % BAM 9605
