1、BRITISH STANDARDBS EN ISO 18453:2005Natural gas Correlation between water content and water dew pointThe European Standard EN ISO 18453:2005 has the status of a British StandardICS 75.060g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g
2、55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN ISO 18453:2005This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29 December 2006 BSI 2006ISBN 0 580 49782 8National forewordThis British Standard was p
3、ublished by BSI. It is the UK implementation of EN ISO 18453:2005. It is identical with ISO 18453:2004.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 sec
4、retary.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 publicationAmd. No. Date CommentsEUROPEAN STANDAR
5、DNORME EUROPENNEEUROPISCHE NORMEN ISO 18453November 2005ICS 75.060English VersionNatural gas - Correlation between water content and water dewpoint (ISO 18453:2004)Gaz naturel - Corrlation entre la teneur en eau et le pointde rose eau (ISO 18453:2004)Erdgas - Beziehung zwischen Wassergehalt und Taup
6、unkt(ISO 18453:2004)This European Standard was approved by CEN on 7 October 2005.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bi
7、bliographical references concerning such nationalstandards may be obtained on application to the 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 translationunder the responsibility of
8、 a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latv
9、ia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2005 CEN
10、All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 18453:2005: EForeword The text of ISO 18453:2004 has been prepared by Technical Committee ISO/TC 193 “Natural gas” of the International Organization for Standardization (ISO) and has be
11、en taken over as EN ISO 18453:2005 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 May 2006, and conflicting national standards shall be withdrawn at the latest by May 2006. According to t
12、he 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, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxem
13、bourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. Endorsement notice The text of ISO 18453:2004 has been approved by CEN as EN ISO 18453:2005 without any modifications. EN 18453:2005Reference numberISO 18453:2004(E)INTERNATIONAL S
14、TANDARD ISO18453First edition2004-07-01Natural gas Correlation between water content and water dew point Gaz naturel Corrlation entre la teneur en eau et le point de rose de leau EN ISO 18453:2005ii iiiContents Page Foreword iv Introduction v 1 Scope 1 2 Terms and definitions. 1 3 Development of the
15、 correlation . 2 4 Range of application and uncertainty of the correlation 3 5 Correlation . 4 Annex A (normative) Thermodynamic principles . 8 Annex B (informative) Traceability . 15 Annex C (informative) Examples of calculations 17 Annex D (informative) Subscripts, symbols, units, conversion facto
16、rs and abbreviations . 19 Bibliography . 21 EN ISO 18453:2005iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical co
17、mmittees. 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 work. ISO collaborates closely with th
18、e International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft Internati
19、onal 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 vote. Attention is drawn to the possibility that some of the elements of this document may be
20、the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 18453 was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis of natural gas. EN ISO 18453:2005vIntroduction ISO/TC 193, Natural gas, was established in
21、 May 1989, with the task of creating new standards, and updating existing standards relevant to natural gas. This includes gas analysis, direct measurement of properties, quality designation and traceability. This document provides a reliable mathematical relationship between water content and water
22、 dew point in natural gas. The calculation method was developed by GERG; it is applicable in both ways, i.e. either to calculate the water content or to calculate the water dew point. Information relating to the thermodynamic principles is given in Annex A; information relating to the traceability,
23、applications and uncertainties associated with this work is given in Annex B. Some of the operational problems in the natural gas industry can be traced back to water content in natural gases. Even with low water vapour content in the gas, changing operating pressure and temperature conditions can c
24、ause water to condense and thus lead to corrosion problems, hydrates or ice formation. To avoid these problems, expensive dehydration units have been installed by natural gas companies. The design and cost of these installations depend on the exact knowledge of the water content at the dew point and
25、 the (contractually) required water content. The instruments resulting from the improvements of moisture measurement equipment during the last decades focus on the determination of water content rather than on water dew point. Therefore, if the water content is measured, a correlation is needed for
26、the expression of water dew point. The GERG1)Group identified a need to build a comprehensive and accurate database of measured water content and corresponding water dew point values for a number of representative natural gases in the range of interest before validating the existing correlations bet
27、ween water content and water dew point. It was subsequently shown that the uncertainty range of the existing correlations could be improved. Therefore, as a result, a more accurate, composition-dependent correlation was successfully developed on the basis of the new database. The aim of this Interna
28、tional Standard is to standardize the calculation procedure developed by GERG concerning the relationship between water content and water dew point (and vice versa) in the field of natural gas typically for custody transfer. 1) GERG is an abbreviation of Groupe Europen de Recherche Gazire. EN ISO 18
29、453:2005blank1Natural gas Correlation between water content and water dew point 1 Scope This International Standard specifies a method to provide users with a reliable mathematical relationship between water content and water dew point in natural gas when one of the two is known. The calculation met
30、hod, developed by GERG; is applicable to both the calculation of the water content and the water dew point. This International Standard gives the uncertainty for the correlation but makes no attempt to quantify the measurement uncertainties. 2 Terms and definitions For the purposes of this document,
31、 the following terms and definitions apply. 2.1 correlation relationship between two or several random variables within a distribution of two or more random variables ISO 3534-1 NOTE The indication of the range of temperature, pressure and composition for which the correlation was validated is given
32、 in Clause 3. 2.2 working range range of parameters for which the correlation has been validated 2.3 extended working range range of parameters for which the correlation has been developed, but outside the range for which the correlation has been validated 2.4 uncertainty of the correlation absolute
33、 deviation of calculated value from the experimental database NOTE This does not include any measurement uncertainty in the field. 2.5 acentric factor parameter to characterize the acentricity or non-sphericity of a molecule NOTE This definition was taken from reference 1 in the Bibliography. EN ISO
34、 18453:20052 2.6 normal reference conditions reference conditions of pressure, temperature and humidity (state of saturation) equal to 101,325 kPa and 273,15 K for the real, dry gas ISO 14532:2001 2.6 traceability property of the result of a measurement or the value of a standard whereby it can be r
35、elated to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties ISO 14532:2001 3 Development of the correlation In the past, GERG has identified the necessity for an accurate conversion between the water content and t
36、he water dew point for natural gases with sales gas characteristics. To achieve this goal, the GERG defined a research program. In the first phase of the project, reliable data on water content together with data on water dew point were collected for several natural gases for the dew-point temperatu
37、re range of interest: 15 C to +5 C and for the (absolute) pressure range of interest: 0,5 MPa to 10 MPa. In addition to the measurements on the seven representative natural gases, measurements were also carried out on the key binary system methane/water. The procedure used for gathering the measured
38、 data was the saturation method. Taking the determined values for the repeatability and reproducibility of the Karl Fischer instrument as consistency criteria for all measured water contents, only a few inconsistent values were detected, which were mainly situated in the range of low water content (
39、high pressure, low temperature range). Values which failed the consistency check were either rejected or, in a few cases, weighted much lower in the data pool. In most cases, these values were replaced by repeated measurements carried out at the same pressure and temperature conditions. Detailed inf
40、ormation on the experimental procedure and the composition of the natural gases used during the experiments can be found in the GERG Monograph2. The developed relationship is validated for dew-point temperatures ranging from 15 C to +5 C and (absolute) pressures ranging from 0,5 MPa to 10 MPa. The r
41、epresentative natural gases used for validating the correlation were sampled technically free of glycol, methanol, liquid hydrocarbon and with a maximum content of H2S of 5 mg/m3(in normal conditions). No attempt was made to investigate the impact of the uncertainties resulting from the inclusion of
42、 such contaminants. The thermodynamic background of the developed relationship makes it possible to extend the range of applicability outside the working range to temperatures of 50 C to +40 C and (absolute) pressures from 0,1 MPa to 30 MPa with unknown uncertainties. It is intended that the correla
43、tion be interpreted as reciprocal between the water content and the water dew point. Note that this relationship was derived under laboratory conditions using several compositions of natural gas sampled in the field. Under practical field operational conditions, significant additional uncertainties
44、are generated. Besides the uncertainty in the conversion of the measurement itself, the uncertainties of the measured values should also be considered. Unless explicitly otherwise stated, the volume is stated under normal reference conditions (2.6). EN ISO 18453:200534 Range of application and uncer
45、tainty of the correlation 4.1 Working range The working range is within the ranges defined above, and the associated uncertainties are as follows. a) Range of pressure: 0,5 MPa u p u 10 MPa b) Range of dew-point temperature: 15 C u t u +5 C c) Range of composition: the correlation accepts water and
46、the components given in Table 1 as input parameters. The calculation method is applicable to natural gases that meet the limitations listed in Table 1. Examples of the influence of composition are given in Annex C. Table 1 Range of composition for percentage molar composition Compound Percentage mol
47、ar composition Methane (CH4) W 40,0 % Nitrogen (N2) u 55,0 % Carbon dioxide (CO2) u 30,0 % Ethane (C2H6) u 20,0 % Propane (C3H8) u 4,5 % 2-Methyl propane (C4H10) u 1,5 % n-Butane (C4H10) u 1,5 % 2,2-Dimethyl propane (C5H12) u 1,5 % 2-Methyl butane (C5H12) u 1,5 % n-Pentane (C5H12) u 1,5 % C6+(sum of
48、 hexane + higher hydrocarbons) (C6H14) u 1,5 % NOTE C6+is treated as n-hexane. Within the range above the uncertainty are the following: for the water dew point calculated from the water content: 2 C for the water content calculated from the water dew point: 1) w(A.4) the equilibrium is said to be u
49、nstable. When some of the higher order terms are positive: 2340 and 0 but 0 0SSSS= (A.5) the equilibrium is said to be metastable. The limit of metastability is defined by the following: 20S = (A.6) EN ISO 18453:20059The study of the thermodynamic state of equilibrium of a system is conducted on the basis of thermodynamic potentials; in terms of Gibbs free energy, G, at fixed T and p, the state of equilibrium is defined by a minimum: 2d 0 and d 0GG= (A.7) In the same way, at fixed T and V the state of equilibrium will be defined by
