ISO/TR TECHNICAL REPORT 29922 First edition 2017-03 Natural gas Supporting information on the calculation of physical properties according to IS0 6976 Gaz naturel - Informations supplémentaires pour le calcul des propriétés physiques selon l'lSO 6976 Reference number ISO/TR 29922:2017(E) International Organization for Standardization @ IS0 2017 ee=ZHEJIANG INST OF STANDARDIZATION C1 5956617 mitted without license from IHS IS0/TR 29922:2017(E) COPYRIGHT PROTECTED DOCUMENT IS0 2017, Published in Switzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 . CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +4122 749 09 47 [email protected] www.iso.org Licensee-ZHEJIANG INST OF STANDARDIzRoISQ 7 - All rights reserved networking permited without license from IHS IS0/TR 29922:2017(E) Contents Page Foreword ..vi Introduction. ..vii 1 Scope. 2 Normative references 3 Terms and definitions 4 Symbols, units and abbreviated terms 4.1 Quantities. .1 4.2 Subscripts. .3 4.3 Superscripts. .3 4.4 Abbreviated terms 5 Enthalpy of combustion of the ideal gas and its variation with temperature ..4 5.1 Preamble.. .4 5.2 Standard enthalpy of combustion at 25 °C .4 5.3 Standard enthalpy of combustion at other temperatures. .5 5.4 Formulation of the ideal-gas enthalpy. ..6 5.5 Illustrative examples. ..7 5.6 Uncertainty in enthalpy of combustion. ..8 6 Non-ideality: Variation of real-gas enthalpy of combustion with pressure .9 6.1 Preamble.. .9 6.2 Formulation of the enthalpic correction. ..10 6.3 Estimation of the enthalpic correction. ..12 6.4 Conclusion... ..13 7 Non-ideality: Compression factor effect on volume-basis calorific values ..13 7.1 Compression factor. ..13 7.2 Virial equation of state. ..14 7.3 Estimation of mixture compression factor 7.4 Limitations of the modified IGT-32 method ..17 7.5 Uncertaintyincompressionfactor .18 8 Quantitation of volumetric non-ideality ..18 8.1 Second virial coefficients of pure components .18 8.1.1 Preliminary procedures. 18 8.1.2 Improved procedure.. .19 8.2 Summation factors of pure components. 21 8.2.1 Overview. 21 8.2.2 Major components of natural gas 21 8.2.3 Hydrogen and helium . 22 8.3 Compression factors of the permanent gases 23 8.4 Pure component uncertainties. 25 8.4.1 Uncertainty of second virial coefficients. 25 8.4.2 Truncation error 25 8.4.3 Linearization error. 27 8.4.4 Berlin versus Leiden. .28 8.4.5 Hydrogen and helium .29 8.4.6 Water. .30 8.4.7 Combination of uncertainties .31 8.5 Mixture uncertainty. 31 9 Miscellaneous data .31 9.1 Atomic weights of the elements .31 9.1.1 Atomic weights 2007 31 9.1.2 Atomic weights 2009 and 2011 .32 9.1.3 Discussion. 34 Intemainal oganzation @s1Sr217 - All rights reserved ii icensee=ZHEJIANG INST OF STANDARDIZATION C1 5956617 vided by IHS under license with ISt ed without license from IHS Not for Resale, 2017/5/11 02:06:25 IS0/TR29922:2017(E) 9.2 Composition and molecular weight of dry air .35 10 Effects of water vapour on calorific value .36 10.1 Preamble 36 10.2 Excluded volume effect. 37 10.3 Latent heat (enthalpic) effect. 38 10.4 Compression factor effect 39 10.5 Combination of effects. 39 10.6 Spectator water 40 10.7 Effect of humid air. 41 10.7.1 Preamble 41 10.7.2 Stoichiometric combustion with oxygen. 42 10.7.3 Combustion of dry gas with excess dry air 42 10.7.4 Combustion of wet gas with excess dry air. 43 10.7.5 Combustion of wet gas with excess humid air 43 11 Summary, discussion and selection of the calorific value of methane .45 11.1 Standard enthalpy of combustion 45 11.1.1 Background. 45 11.1.2 Selection of data. 45 11.1.3 Recalculatio