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1、BRITISH STANDARD BS EN ISO 6976:2005 Natural gas Calculation of calorific values, density, relative density and Wobbe index from composition The European Standard EN ISO 6976:2005 has the status of a British Standard ICS 75.060 ? Licensed Copy: London South Bank University, London South Bank Univers
2、ity, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy, (c) BSI BS EN ISO 6976:2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2007 BSI 2007 ISBN 978 0 580 50066 4 National foreword This British Standard was published by B
3、SI. It is the UK implementation of EN ISO 6976:2005. It supersedes BS 7859:1996 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee PTI/15, Natural gas and gas analysis. A list of organizations represented on PTI/15 can be obtained on request to its secre
4、tary. 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 cannot confer immunity from legal obligations. Amendments issued since publication Amd. No. DateComments Licensed Copy:
5、 London South Bank University, London South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 6976 May 2005 ICS 75.060 English version Natural gas - Calculation of calorific values, density, relative density and W
6、obbe index from composition (ISO 6976:1995 including Corrigendum 1:1997, Corrigendum 2:1997 and Corrigendum 3:1999) Gaz naturel - Calcul du pouvoir calorifique, de la masse volumique, de la densit relative et de lindice de Wobbe partir de la composition (ISO 6976:1995, Corrigendum 1:1997, Corrigendu
7、m 2:1997 et Corrigendum 3:1999 inclus) Erdgas - Berechnung von Brenn- und Heizwert, Dichte, relativer Dichte und Wobbeindex aus der Zusammensetzung (ISO 6976:1995 + Corigendum 1:1997 + Corigendum 2:1997 + Corigendum 3:1999) This European Standard was approved by CEN on 17 April 2005. CEN members are
8、 bound to comply with the CEN/CENELEC Internal 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 t
9、he 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 translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same sta
10、tus as the official versions. 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, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Sloven
11、ia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels 2005 CENAll rights of exploitation in any form and by any means reserved worldwide for CEN na
12、tional Members. Ref. No. EN ISO 6976:2005: E Licensed Copy: London South Bank University, London South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy, (c) BSI Foreword The text of ISO 6976:1995 has been prepared by Technical Committee ISO/TC 193 “Natural gas” of the Internati
13、onal Organization for Standardization (ISO) and has been taken over as EN ISO 6976:2005 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 sh
14、all 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 Republic, Denmark, Estonia, Finland, France, Germany, Gre
15、ece, 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 6976:1995 has been approved by CEN as EN ISO 6976:2005 without any modifications.
16、EN ISO 6976:2005 Licensed Copy: London South Bank University, London South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy, (c) BSI INTERNATIONAL STANDARD IS0 6976 Second edition 1995-l Z-01 Corrected and reprinted 1996-02-01 Natural gas - Calculation of calorific values, dens
17、ity, relative density and Wobbe index from composition Gaz na turel - Calcul du pouvoir calorifique, de la masse volumique, de la densit relative et de I indice de Wobbe P partir de la composition Reference number IS0 6976:1995(E) EN ISO 6976:2005 Licensed Copy: London South Bank University, London
18、South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy, (c) BSI EN ISO 6976:2005 Licensed Copy: London South Bank University, London South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy, (c) BSI 0 IS0 IS0 6976: Annexes A Symbols and units . . . . . *. .
19、. . . . . . . . . . . . . 15 B Values of auxiliary constants, etc. . 17 B.l Molar gas constant 17 B.2 Critical constants and acentric factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 B.3 Properties of dry air . 17 B.4 Enthalpy of vaporization of water . . . . . . . . . .
20、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 C Conversion of volume fractions to mole fractions . . . . . . . . . . . . . . . . 20 D Examples of calculations . 21 D.l Calorific value on a molar basis (clause 5) . . . . . . . . . . . . . . . . . . . . . . . . . . 21 D.2 Calorific va
21、lue on a mass basis (clause 6) . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 D.3 Calorific value on a volumetric basis (clause 7) . . . . . . . . . . . . . . . . . . 21 D.4 Relative density, density and Wobbe index (clause 8) . 22 D.5 Precision (clause 9) 23 E Behaviour of ideal and real
22、gases . . 25 E.l Variation of ideal-gas enthalpy of combustion with temperature 25 E.2 Corrections for non-ideality: volumetric effects . 26 E.3 Corrections for non-ideality: enthalpic effects . 28 F Effects of water vapour on calorific value . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23、 30 F.l General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 F.2 Excluded volume effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
24、. . . . . . . . . 30 F.3 Latent heat (enthalpic) effect . 31 F.4 Compression factor effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 G Summary, discussion and selection of the calorific value of methane . . . . . . . . . . . . . . . . .
25、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 H Derivation of equations relating to precision . 36 H.l Methane by difference 36 H.2 Methane by analysis 36 J Approximate conversion factors between reference states .
26、. 38 K Computer implementation of recommended methods . . . . . . . . . 40 L Calorific values on a molar basis for 60 “F reference temperature . . 43 iii EN ISO 6976:2005 Licensed Copy: London South Bank University, London South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy,
27、 (c) BSI IS0 0 IS0 IV! Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . * 45 iv EN ISO 6976:2005 Licensed Copy: London South Bank University, London South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontro
28、lled Copy, (c) BSI 0 IS0 IS0 6976:1995(E) Foreword IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member
29、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 work. IS0 collaborates closely with the International Electr
30、otechnical Commission (IEC) on all matters of electrotechnical standardization. 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
31、 vote. International Standard IS0 6976 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC I, Analysis of natural gas. This second edition cancels and replaces the first edition (IS0 6976:1983), of which it constitutes a technical revision. Annexes A and B form an integral p
32、art of this International Standard. An- nexes C, D, E, F, G, H, J, K, L and M are for information only. EN ISO 6976:2005 Licensed Copy: London South Bank University, London South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy, (c) BSI blank Licensed Copy: London South Bank Un
33、iversity, London South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy, (c) BSI Natural gas - Calculation of calorific values, density, relative density and Wobbe index from composition 1 Scope This International Standard specifies methods for the calculation of the superior c
34、alorific value, inferior calorific value, density, relative density and Wobbe index of dry natural gases, natural gas substitutes and other combustible gaseous fuels, when the compo- sition of the gas by mole fraction is known. The methods provide a means of calculating the proper- ties of the gas m
35、ixture at commonly used metric ref- erence conditions. The methods of calculation require values for various physical properties of the pure components; these values are provided in tables and their sources are identified. Methods are given for estimating the precision of calculated properties. The
36、methods of calculation of the values of properties on either a molar or mass basis are applicable to any dry natural gas, natural gas substitute or other combustible fuel which is normally gaseous. For the calculation of the values of properties on a volumetric basis, the methods are restricted to g
37、ases consisting preponderantly of methane (not less than 0,5 mole fraction). Examples of calculations are given in annex D for the recommended methods of calculation. NOTES 1 The symbols used in this International Standard, to- gether with their meanings, are given in annex A. 2 The qualifiers “high
38、er”, “upper”, “total” and “gross” are, for the purposes of this International Standard, syn- onymous with “superior”; likewise, “lower” and “net” are synonymous with “inferior”. The term “heating value” is synonymous with “calorific value”; “specific gravity” is synonymous with “relative density”; “
39、Wobbe number” is synonymous with “Wobbe index”; “compressibility factor” is synonymous with “compression factor”. 3 If the composition of the gas is known by volume frac- tions these must be converted to mole fractions (see annex C). Note, however, that the derived mole fractions will have uncertain
40、ties greater than those of the original volume fractions. 4 For the purposes of this International Standard, the sum of the mole fractions used must be unity to the nearest 0,000 I, and all components with mole fractions greater than 0,000 05 must be accounted for. 5 For the calorific value calculat
41、ed on a volumetric basis, there are limitations on the amounts of components other than methane which may be present. It is impossible to be definitive on this matter, but the following guidelines may be useful: N, should not be present in amounts exceeding 0,3 mole fraction; CO, and C,H, should eac
42、h not exceed 0,15 mole frac- tion; no other component should exceed 0,05 mole fraction. Given these limits, the expected trueness of the calculation is within 0,l %. 6 The effects of water vapour on the calorific value, either directly measured or calculated, are discussed in annex F. 7 For the meth
43、ods of calculation described to be valid, the gas must be above its hydrocarbon dew-point at the pre- scribed reference conditions. 8 The values of basic physical property data are subject to revision as more accurate values become available from authoritative sources. EN ISO 6976:2005 Licensed Copy
44、: London South Bank University, London South Bank University, Tue Jan 23 07:47:54 GMT+00:00 2007, Uncontrolled Copy, (c) BSI IS0 6976:1995(E) 0 IS0 2 Definitions For the purposes of this International Standard, the following definitions apply. 2.1 superior calorific value: The amount of heat which w
45、ould be released by the complete combustion in air of a specified quantity of gas, in such a way that the pressure p1 at which the reaction takes place re- mains constant, and all the products of combustion are returned to the same specified temperature t, as that of the reactants, all of these prod
46、ucts being in the gaseous state except for water formed by com- bustion, which is condensed to the liquid state at t,. Where the quantity of gas is specified on a molar ba- sis, the calorific value is designated as on a mass basis the calorific value is designated as Hs (4 IPI - Where the quantity o
47、f gas is specified on a volumetric basis, the calorific value is designated as is t,p, V(t2,p2), where t2 and p2 are the gas volume (metering) reference conditions (see figure 1). 2.2 inferior calorific value: The amount of heat which would be released by the complete combustion in air of a specifie
48、d quantity of gas, in such a way that the pressure p1 at which the reaction takes place re- mains constant, and all the products of combustion are returned to the same specified temperature t, as that of the reactants, all of these products being in the gaseous state. Air z1 Metering /-p-t- i Gas at
49、 tz, P2 On molar, mass and volumetric bases, the inferior calorific value is designated respectively as q (tl ,I+), W,Pl) and 4Kb P1w(*P2)1 2.3 density: The mass of a gas sample divided by its volume at specified conditions of pressure and temperature. 2.4 relative density: The density of a gas divided by the density of dry air of standard composition (see annex B) at the same specified conditions of pressure and temperature. The term ideal relative density ap- plies when both gas and air a
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