EN ISO 6976:2016
(Main)Natural gas - Calculation of calorific values, density, relative density and Wobbe indices from composition (ISO 6976:2016)
Natural gas - Calculation of calorific values, density, relative density and Wobbe indices from composition (ISO 6976:2016)
ISO 6976:2016 specifies methods for the calculation of gross calorific value, net calorific value, density, relative density, gross Wobbe index and net Wobbe index of natural gases, 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. Guidance 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 sources 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 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", "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 synonymous 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 kg·kmol−1.
NOTE 2 There are no explicit limits of composition to which 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 available 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 completely 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 isomer of the same carbon number.
NOTE 5 If the user's 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 user's own task to set the mole fraction composition, and hence properties, of this pseudo-component 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.
Erdgas - Berechnung von Brenn- und Heizwert, Dichte, relativer Dichte und Wobbeindex aus der Zusammensetzung (ISO 6976:2016)
Gaz naturel - Calcul des pouvoirs calorifiques, de la masse volumique, de la densité relative et des indices de Wobbe à partir de la composition (ISO 6976:2016)
L'ISO 6976:2016 décrit des méthodes pour le calcul des pouvoirs calorifiques supérieur et inférieur, de la masse volumique, de la densité relative, des indices de Wobbe supérieur et inférieur de gaz naturels, de substituts du gaz naturel et d'autres combustibles gazeux, lorsque la composition du gaz par fraction molaire est connue. Les méthodes spécifiées permettent de calculer les propriétés du mélange de gaz dans des conditions de référence généralement utilisées.
Pour les besoins de ce document, la somme des fractions molaires données doit correspondre à l'unité exacte. L'ISO 6974‑1 et l'ISO 6974‑2 donnent des préconisations pour satisfaire à cette exigence. Tous les constituants dont la fraction molaire est supérieure à 0,00005 doivent être comptabilisés.
Les méthodes de calcul exigent des valeurs pour différentes propriétés physiques des constituants purs; ces valeurs ainsi que les incertitudes associées sont consignées dans des tableaux et leurs sources sont identifiées.
Des méthodes sont données pour estimer les incertitudes des propriétés calculées.
Les méthodes de calcul des valeurs des propriétés, qu'elles reposent sur une base molaire, massique ou volumétrique, sont applicables à tout gaz naturel, substitut de gaz naturel ou à tout autre combustible habituellement gazeux, à l'exception que dans le cas des propriétés calculées sur une base volumétrique la méthode se limite aux mélanges dont le facteur de compression est supérieur à 0,9 dans les conditions de référence.
L'Annexe D donne des exemples de calcul pour les méthodes de calcul recommandées.
NOTE 1 Pour les besoins de la présente Norme internationale, les qualificatifs «supérieur», «élevé», «plus haut» et «total» sont synonymes de «brut»; de la même façon, «inférieur» et «bas» sont synonymes de «net». Les termes «masse volumique» et «masse spécifique» sont synonymes; le terme «poids spécifique» est synonyme de «densité relative»; le terme «nombre de Wobbe» est synonyme d'«indice de Wobbe»; le terme «facteur de compressibilité» est synonyme de «facteur de compression». Le poids moléculaire d'une grandeur sans dimension est numériquement équivalent à la masse molaire en kg·kmol−1.
NOTE 2 Pour les hydrocarbures aliphatiques dont le nombre d'atomes de carbone est supérieur ou égal à 7, il convient d'inclure à l'isomère linéaire comportant le même nombre d'atomes de carbone tout isomère présent à une fraction molaire supérieure à 0,000 05.
NOTE 3 Si l'utilisateur a pour exigence de remplacer, par exemple, un groupement C6+ ou C7+ de constituants non résolus de manière analytique par un pseudo-constituant unique, alors il doit se charger de définir lui-même la composition de la fraction molaire et, par conséquent, les propriétés de ce pseudo-constituant, afin d'en garantir l'adéquation avec l'application concernée. L'«eau inerte» et le «sulfure d'hydrogène non combustible» ainsi nommés peuvent également être traités en tant que pseudo-constituants, en attribuant une valeur nulle aux valeurs d'enthalpie de combustion appropriées.
NOTE 4 Il n'existe pas de limites de composition explicites auxquelles les méthodes décrites dans la présente Norme internationale sont applicables. Toutefois, des limites de composition sont implicitement établies par la limitation des calculs sur une base volumétrique aux mélanges dont le facteur de compression est supérieur à 0,9 dans les conditions de référence.
NOTE 5 Étant donné que la fraction molaire de toute forme d'eau présen
Zemeljski plin - Izračun kalorične vrednosti, gostote, relativne gostote in Wobbejevega indeksa iz sestave (ISO 6976:2016)
General Information
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Standards Content (Sample)
SLOVENSKI STANDARD
01-marec-2017
1DGRPHãþD
SIST EN ISO 6976:2005
=HPHOMVNLSOLQ,]UDþXQNDORULþQHYUHGQRVWLJRVWRWHUHODWLYQHJRVWRWHLQ
:REEHMHYHJDLQGHNVDL]VHVWDYH ,62
Natural gas - Calculation of calorific values, density, relative density and Wobbe indices
from composition (ISO 6976:2016)
Erdgas - Berechnung von Brenn- und Heizwert, Dichte, relativer Dichte und Wobbeindex
aus der Zusammensetzung (ISO 6976:2016)
Gaz naturel - Calcul des pouvoirs calorifiques, de la masse volumique, de la densité
relative et des indices de Wobbe à partir de la composition (ISO 6976:2016)
Ta slovenski standard je istoveten z: EN ISO 6976:2016
ICS:
75.060 Zemeljski plin Natural gas
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN ISO 6976
EUROPEAN STANDARD
NORME EUROPÉENNE
August 2016
EUROPÄISCHE NORM
ICS 75.060 Supersedes EN ISO 6976:2005
English 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 Erdgas - Berechnung von Brenn- und Heizwert, Dichte,
masse volumique, de la densité relative et des indices relativer Dichte und Wobbeindex aus der
de Wobbe à partir de la composition (ISO 6976:2016) 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 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 the CEN-CENELEC Management Centre 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 CEN-CENELEC Management
Centre has the same status as the official versions.
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, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 6976:2016 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
European foreword
This document (EN ISO 6976:2016) has been prepared by Technical Committee ISO/TC 193 “Natural
gas” in collaboration with Technical Committee 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, 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.
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 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 has been approved by CEN as EN ISO 6976:2016 without any modification.
INTERNATIONAL ISO
STANDARD 6976
Third edition
2016-08-15
Natural gas — Calculation of calorific
values, density, relative density and
Wobbe indices from composition
Gaz naturel — Calcul des pouvoirs calorifiques, de la masse
volumique, de la densité relative et des indices de Wobbe à partir de la
composition
Reference number
ISO 6976:2016(E)
©
ISO 2016
ISO 6976:2016(E)
© ISO 2016, Published in Switzerland
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ii © ISO 2016 – All rights reserved
ISO 6976:2016(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 2
4 Symbols and units . 5
4.1 Quantities . 5
4.2 Subscripts . 6
4.3 Superscript . 6
5 Principles . 6
6 Behaviour of ideal and real gases . 7
6.1 Enthalpy of combustion . 7
6.2 Calculation of compression factor . 8
7 Calculation of calorific value on a molar basis . 8
7.1 Gross calorific value . 8
7.2 Net calorific value . 9
8 Calculation of calorific value on a mass basis . 9
8.1 Gross calorific value . 9
8.2 Net calorific value .10
9 Calculation of calorific value on a volume basis .10
9.1 Ideal-gas gross calorific value .10
9.2 Ideal-gas net calorific value .10
9.3 Real-gas gross calorific value .11
9.4 Real-gas net calorific value .11
10 Calculation of associated properties .11
10.1 Ideal-gas relative density .11
10.2 Ideal-gas density .12
10.3 Ideal-gas gross Wobbe index .12
10.4 Ideal-gas net Wobbe index .12
10.5 Real-gas relative density .13
10.6 Real-gas density .13
10.7 Real-gas gross Wobbe index .13
10.8 Real-gas net Wobbe index .14
11 Uncertainty of calculation .14
11.1 Principles .14
11.2 Formulae for the analytical method .15
11.3 Inputs for the analytical method .15
11.3.1 Composition and compositional uncertainties .15
11.3.2 Non-compositional inputs .16
11.4 Expanded uncertainty .17
11.5 Expression of results .17
11.5.1 General.17
11.5.2 Analytical method .17
11.5.3 Generic method .17
11.5.4 Contingency method .
...
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