ISO/TR 29922:2017

TECHNICAL ISO/TR
REPORT 29922
First edition
2017-03
Natural gas — Supporting information
on the calculation of physical
properties according to ISO 6976
Gaz naturel — Informations supplémentaires pour le calcul des
propriétés physiques selon l’ISO 6976
Reference number
©
ISO 2017
© ISO 2017, Published in Switzerland
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Contents Page
Foreword .vi
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols, units and abbreviated terms . 1
4.1 Quantities . 1
4.2 Subscripts . 3
4.3 Superscripts . . 3
4.4 Abbreviated terms . 3
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 .15
7.4 Limitations of the modified IGT-32 method .17
7.5 Uncertainty in compression factor .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
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 Recalculation of Rossini values .46
11.1.4 Evaluation of selected data .48
11.1.5 Selected value and uncertainty .52
11.2 Derived calorific values .52
11.3 Comparisons between calorimetric methodologies .54
12 Calorific values on a mass basis .56
12.1 Calorific values on a mass basis for components of natural gas .56
12.2 Alternative (non-normative) method of calculation for mass-basis calorific values .57
13 Calorific values on a volume basis .
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