1、BS EN ISO 6976:2016Natural gas Calculationof calorific values, density,r e l a t i v e d e n s i t y a n d W o b b eindices from composition(ISO 6976:2016)BSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS EN ISO 6976:2016 BRITISH STANDARDNational forewordThis Britis
2、h Standard is the UK implementation of EN ISO 6976:2016.It supersedes BS EN ISO 6976:2005 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PTI/15, Natural Gas and Gas Analysis.A list of organizations represented on this committee can beobtained on reques
3、t to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016.Published by BSI Standards Limited 2016ISBN 978 0 580 84128 6ICS 75.060Compliance with a British Standar
4、d cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 30 September 2016.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO
5、 6976 August 2016 ICS 75.060 Supersedes EN ISO 6976:2005English Version Natural gas - Calculation of calorific values, density, relative density and Wobbe indices from composition (ISO 6976:2016) Gaz naturel - Calcul des pouvoirs calorifiques, de la masse volumique, de la densit relative et des indi
6、ces de Wobbe partir de la composition (ISO 6976:2016)Erdgas - Berechnung von Brenn- und Heizwert, Dichte, relativer Dichte und Wobbeindex aus der Zusammensetzung (ISO 6976:2016) This European Standard was approved by CEN on 24 August 2016. CEN members are bound to comply with the CEN/CENELEC Interna
7、l Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CE
8、N member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versi
9、ons. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, P
10、oland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey andUnited Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2016 CEN All rights of exploitatio
11、n in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN ISO 6976:2016 EBS EN ISO 6976:2016EN ISO 6976:2016 (E) 3 European foreword This document (EN ISO 6976:2016) has been prepared by Technical Committee ISO/TC 193 “Natural gas” in collaboration with Technical Commit
12、tee CEN/TC 278 “Test gases, test pressures, appliance categories and gas appliance types” the secretariat of which is held by AFNOR. 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 February 2017,
13、and conflicting national standards shall be withdrawn at the latest by February 2017. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights.
14、This document supersedes EN ISO 6976:2005. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former
15、Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endorsement notice The text of ISO 6976:2016
16、 has been approved by CEN as EN ISO 6976:2016 without any modification. BS EN ISO 6976:2016ISO 6976:2016(E)Foreword vIntroduction vi1 Scope . 12 Normative references 23 Terms and definitions . 24 Symbols and units . 54.1 Quantities 54.2 Subscripts 64.3 Superscript . 65 Principles . 66 Behaviour of i
17、deal and real gases . 76.1 Enthalpy of combustion 76.2 Calculation of compression factor 87 Calculation of calorific value on a molar basis 87.1 Gross calorific value 87.2 Net calorific value . 98 Calculation of calorific value on a mass basis 98.1 Gross calorific value 98.2 Net calorific value 109
18、Calculation of calorific value on a volume basis .109.1 Ideal-gas gross calorific value . 109.2 Ideal-gas net calorific value 109.3 Real-gas gross calorific value . 119.4 Real-gas net calorific value 1110 Calculation of associated properties 1110.1 Ideal-gas relative density 1110.2 Ideal-gas density
19、 . 1210.3 Ideal-gas gross Wobbe index . 1210.4 Ideal-gas net Wobbe index . 1210.5 Real-gas relative density 1310.6 Real-gas density 1310.7 Real-gas gross Wobbe index . 1310.8 Real-gas net Wobbe index 1411 Uncertainty of calculation .1411.1 Principles 1411.2 Formulae for the analytical method 1511.3
20、Inputs for the analytical method 1511.3.1 Composition and compositional uncertainties .1511.3.2 Non-compositional inputs 1611.4 Expanded uncertainty . 1711.5 Expression of results . 1711.5.1 General. 1711.5.2 Analytical method 1711.5.3 Generic method 1711.5.4 Contingency method 1711.6 Application of
21、 uncertainty . 1812 Tables of data 19Annex A (normative) Values of auxiliary constants .25 ISO 2016 All rights reserved iiiContents PageBS EN ISO 6976:2016ISO 6976:2016(E)Annex B (normative) Formulae for uncertainty calculations 27Annex C (informative) Conversion factors .32Annex D (informative) Exa
22、mple calculations .34Bibliography .57iv ISO 2016 All rights reservedBS EN ISO 6976:2016ISO 6976:2016(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normall
23、y 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 liaison with ISO, also take part in the
24、work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the di
25、fferent approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).Attention is drawn to the possibility that some of the elements of this document
26、may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/pat
27、ents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the World Trade
28、 Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: www.iso.org/iso/foreword.html.The committee responsible for this document is ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis of natural gas.This third edition cancels and replaces the second edition (
29、ISO 6976:1995), which has been technically revised. ISO 2016 All rights reserved vBS EN ISO 6976:2016ISO 6976:2016(E)IntroductionBoth international and intra-national custody transfer of natural gas usually require precise determination of both the quantity and the quality of the gas to be traded. T
30、his document specifies methods for the calculation of key properties that describe gas quality, namely gross and net calorific value, density, relative density, and gross and net Wobbe index. The methods provide the means of calculating these properties and their uncertainties for any natural gas, n
31、atural gas substitute or similar combustible gaseous fuel of known composition at commonly used reference conditions.Values of the various properties calculated in accordance with this document will, in general, differ only by very small amounts from those calculated using the second (1995) edition
32、of this document. In this context, it is recognized that:a) adoption of the revisions detailed in this document will not be without cost, since instrumentalsoftware will need updating;b) recorded energy content and hence billed energy will, in consequence of these revisions, change bysmall amounts;c
33、) unintended impacts could occur if the revisions are implemented uncritically; for instance, if therevisions are implemented at input points to a pipeline system but not at exit points, then a costlyaccountancy imbalance may result;d) commercial, contractual, regulatory and legislative obligations
34、will need to be taken into account.For these reasons, and depending upon the users application, it may be appropriate to undertake an impact assessment in order to determine an agreed timing and procedure for implementation of the provisions of this document.vi ISO 2016 All rights reservedBS EN ISO
35、6976:2016Natural gas Calculation of calorific values, density, relative density and Wobbe indices from composition1 ScopeThis document specifies methods for the calculation of gross calorific value, net calorific value, density, relative density, gross Wobbe index and net Wobbe index of natural gase
36、s, natural gas substitutes and other combustible gaseous fuels, when the composition of the gas by mole fraction is known. The methods specified provide the means of calculating the properties of the gas mixture at commonly used reference conditions.Mole fractions by definition sum to unity. Guidanc
37、e on the achievement of this requirement by chromatographic analysis is available in ISO 6974-1 and ISO 6974-2.The methods of calculation require values for various physical properties of the pure components; these values, together with associated uncertainties, are provided in tables and their sour
38、ces are identified.Methods are given for estimating the standard uncertainties of calculated properties.The methods of calculation of the values of properties on either a molar, mass or volume basis are applicable to any natural gas, natural gas substitute or other combustible fuel that is normally
39、gaseous, except that for properties on the volume basis the method is restricted to mixtures for which the compression factor at reference conditions is greater than 0,9.Example calculations are given in Annex D for the recommended methods of calculation.NOTE 1 The qualifiers “superior”, “higher”, “
40、upper” and “total” are, for the purposes of this document, synonymous with “gross”; likewise, “inferior” and “lower” are synonymous with “net”. The term “heating value” is synonymous with “calorific value”; “mass density” and “specific density” are synonymous with “density”; “specific gravity” is sy
41、nonymous with “relative density”; “Wobbe number” is synonymous with “Wobbe index”; “compressibility factor” is synonymous with “compression factor”. The dimensionless quantity molecular weight is numerically equal to the molar mass in kgkmol1.NOTE 2 There are no explicit limits of composition to whi
42、ch the methods described in this document are applicable. However, the restriction of volume-basis calculations to mixtures with a compression factor greater than 0,9 at reference conditions sets implicit limits on composition.NOTE 3 Because the mole fraction of any water present is not normally ava
43、ilable from chromatographic analysis, it is common practice to calculate the physical properties on a dry gas basis and to allow for the effects of water vapour in a separate procedure. However, if the mole fraction of water vapour is known then the property calculations can be carried out completel
44、y in accordance with the procedures described herein. The effects of water vapour on calorific value, whether the latter is directly measured or calculated, are discussed in ISO/TR 29922.NOTE 4 For aliphatic hydrocarbons of carbon number 7 or above, any isomer present is included with the normal iso
45、mer of the same carbon number.NOTE 5 If the users requirement includes the replacement of, for example, a C6+ or C7+ grouping of analytically unresolved components by a single pseudo-component, then it is the users own task to set the mole fraction composition, and hence properties, of this pseudo-c
46、omponent so as to be fit for purpose in the particular application. Any so-called “spectator water” and “non-combustible hydrogen sulfide” are treated as pseudo-components by setting the appropriate enthalpy of combustion values to zero.INTERNATIONAL STANDARD ISO 6976:2016(E) ISO 2016 All rights res
47、erved 1BS EN ISO 6976:2016ISO 6976:2016(E)2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edit
48、ion of the referenced document (including any amendments) applies.ISO 6974-1, Natural gas Determination of composition and associated uncertainty by gas chromatography Part 1: General guidelines and calculation of compositionISO 6974-2, Natural gas Determination of composition and associated uncerta
49、inty by gas chromatography Part 2: Uncertainty calculationsISO 14912:2003, Gas analysis Conversion of gas mixture composition data3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.ISO and IEC maintain terminological databases for use in standardization at the following addresses: IEC Electropedia: available at http:/www.electropedia.org/ ISO Online browsing platform: available at http:/www.iso.org/obp3.1gross calorific valueamount of heat that would be released by the complete combustion
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