1、BSI Standards PublicationBS EN ISO 6974-5:2014Natural gas Determinationof composition andassociated uncertainty by gaschromatographyPart 5: Isothermal method for nitrogen,carbon dioxide, C1 to C5 hydrocarbons andC6+ hydrocarbonsBS EN ISO 6974-5:2014 BRITISH STANDARDNational forewordThis British Stan
2、dard is the UK implementation of EN ISO6974-5:2014. It supersedes BS EN ISO 6974-5:2001 which iswithdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee PTI/15, Natural Gas and Gas Analysis.A list of organizations represented on this committee can beobtained on request t
3、o its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution 2014. Published by BSI StandardsLimited 2014ISBN 978 0 580 79166 6ICS 75.060Compliance with a British Standard c
4、annot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 July 2014.Amendments issued since publicationDate Text affectedEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN ISO 6974-5 July 2014 ICS 75.060
5、Supersedes EN ISO 6974-5:2001English Version Natural gas - Determination of composition and associated uncertainty by gas chromatography - Part 5: Isothermal method for nitrogen, carbon dioxide, C1 to C5 hydrocarbons and C6+ hydrocarbons (ISO 6974-5:2014) Gaz naturel - Dtermination de la composition
6、 et de lincertitude associe par chromatographie en phase gazeuse - Partie 5: Mthode isotherme pour lazote, le dioxyde de carbone, les hydrocarbures C1 C5 et C6+ (ISO 6974-5:2014) Erdgas - Bestimmung der Zusammensetzung und der zugehrigen Unsicherheit durch Gaschromatographie - Teil 5: Isothermes Ver
7、fahren fr Stickstoff, Kohlenstoffdioxid, C1- bis C5-Kohlenwasserstoffe und C6+-Kohlenwasserstoffe (ISO 6974-5:2014) This European Standard was approved by CEN on 28 June 2014. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this Eur
8、opean 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 versio
9、ns (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, B
10、elgium, 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, Swi
11、tzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels 2014 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN natio
12、nal Members. Ref. No. EN ISO 6974-5:2014 EBS EN ISO 6974-5:2014EN ISO 6974-5:2014 (E) 3 Foreword This document (EN ISO 6974-5:2014) has been prepared by Technical Committee ISO/TC 193 “Natural gas“. This European Standard shall be given the status of a national standard, either by publication of an
13、identical text or by endorsement, at the latest by January 2015, and conflicting national standards shall be withdrawn at the latest by January 2015. 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
14、held responsible for identifying any or all such patent rights. This document supersedes EN ISO 6974-5:2001. 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, C
15、roatia, 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 an
16、d the United Kingdom. Endorsement notice The text of ISO 6974-5:2014 has been approved by CEN as EN ISO 6974-5:2014 without any modification. BS EN ISO 6974-5:2014ISO 6974-5:2014(E) ISO 2014 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Normative references 23 Principle 2
17、4 Materials . 45 Apparatus . 46 Scheme of the configuration . 67 Procedure. 77.1 Control of the apparatus . 77.2 Operation of the apparatus 88 Expression of results .118.1 Uncertainty 118.2 Test report 11Annex A (informative) Example of application .12Annex B (informative) Procedure for Setting Valv
18、e timings and Restrictor Setting 22Bibliography .24BS EN ISO 6974-5:2014ISO 6974-5:2014(E)ForewordISO (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
19、 through ISO technical committees. 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 col
20、laborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different appro
21、val criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 www.iso.org/directives.Attention is drawn to the possibility that some of the elements of this document may be the subject
22、of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received www.iso.org/patents.Any trade name used
23、 in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barr
24、iers to Trade (TBT), see the following URL: Foreword - Supplementary informationThe committee responsible for this document is ISO/TC 193, Natural Gas, Subcommittee SC 1, Analysis of Natural Gas.This second edition cancels and replaces the first edition (ISO 6974-5:2000).ISO 6974 consists of the fol
25、lowing parts, under the general title Natural gas Determination of composition and associated uncertainty by gas chromatography: Part 1: General guidelines and calculation of composition Part 2: Uncertainty calculations Part 3: Determination of hydrogen, helium, oxygen, nitrogen, carbon dioxide and
26、hydrocarbons up to C8 using two capillary columns and one packed column Part 4: Determination of nitrogen, carbon dioxide and C1to C5and C6+ hydrocarbons for a laboratory and on-line measuring system using two columns Part 5: Isothermal method for nitrogen, carbon dioxide, C1to C5hydrocarbons and C6
27、+ hydrocarbons Part 6: Determination of helium, oxygen, nitrogen, carbon dioxide and C1to C8hydrocarbons using three capillary columnsiv ISO 2014 All rights reservedBS EN ISO 6974-5:2014ISO 6974-5:2014(E)IntroductionThis part of ISO 6974 describes a method for the analysis of natural gas that is com
28、monly used for online process applications, but can be applied to laboratory instruments. The compositional data obtained are used for the calculation of calorific value, density and Wobbe index.It is assumed that the natural gas does not contain any oxygen at source and that any oxygen which may be
29、 present is due to contamination during sampling.The primary use of this chromatographic method is the calculation of calorific value (CV) according to ISO 6976. It is based on a column switching technique in which multiple columns, chosen for their separating ability for particular groups of compon
30、ents, are switched under automatic control.Only one injection is necessary and the first phase of the method involves accelerated backflush of C6+ (which is measured as a recombined “pseudo component” rather than by the summation of individual component measurements). Lighter components (nitrogen, m
31、ethane, carbon dioxide and ethane) are stored on the appropriate separating column while the heavier, C3to C5hydrocarbons are eluted. The lighter components are then separated by redirecting carrier gas on to the appropriate column.A Thermal Conductivity Detector (TCD) is used for measurement of the
32、 above components.When the method is first set up, the repeatability of measurement is established by repetitive analysis of a cylinder of test gas, commonly a typical natural gas. For each component, a control chart showing the mean value, and the bounds representing 2 and 3 standard deviations, is
33、 drawn up. Subsequently, this test gas is analysed after each calibration of the analyser, and the results are compared with the data in the control charts. The performance of the analyser is assessed by this procedure.Any change in the method setup can give rise to differences in component response
34、s and hence (where applied) to calculated uncertainties. In these circumstances fitting data to an existing control chart is not a suitable procedure, and the operations that were undertaken when the method was first set up shall be repeated.This part of ISO 6974 provides one of the methods that may
35、 be used for determining the compositions of natural gas in accordance with ISO 6974-1 and ISO 6974-2. ISO 2014 All rights reserved vBS EN ISO 6974-5:2014BS EN ISO 6974-5:2014Natural gas Determination of composition and associated uncertainty by gas chromatography Part 5: Isothermal method for nitro
36、gen, carbon dioxide, C1to C5hydrocarbons and C6+hydrocarbons1 ScopeThis part of this International Standard describes a gas chromatographic method for the quantitative determination of the content of nitrogen, carbon dioxide and C1to C5hydrocarbons individually and a composite C6+ measurement, which
37、 represents all hydrocarbons of carbon number 6 and above in natural gas samples. It is applicable to the analysis of gases containing constituents within the working ranges given in Table 1.Table 1 Component working rangesComponentMole fraction%Min. Max.Nitrogen N20,1 22Carbon dioxide CO20,05 15Met
38、hane CH434 100Ethane C2H60,1 23Propane C3H80,05 10iso-Butane i-C4H100,01 2,0n-Butane n-C4H100,01 2,0neo-Pentane neo-C5H120,005 0,35iso-Pentane i-C5H120,005 0,35n-Pentane n-C5H120,005 0,35Hexanes + C6+ 0,005 0,35NOTE 1 The working ranges in Table 1 are those for which the method has been shown to be
39、satisfactory, and are offered for guidance. However, there is no reason why wider ranges should not be used, provided that the successful measurement of such wider ranges has been demonstrated.NOTE 2 Hydrocarbons above n-pentane are expressed as the “pseudo-component” C6+ which is measured as one co
40、mposite peak and calibrated as such. The properties of C6+ are calculated from an extended analysis of the individual C6and higher hydrocarbons.NOTE 3 Oxygen is not a normal constituent of natural gas and would not be expected to be present in gas sampled to an online instrument. If any oxygen is pr
41、esent as a result of air contamination, it will be measured with the nitrogen. The resulting measured (nitrogen + oxygen) value will be in error to a small extent because of the slight difference between the detector responses of oxygen and nitrogen.NOTE 4 The helium and argon contents are assumed t
42、o be sufficiently small and unvarying that they need not be analysed for.NOTE 5 The gas sample shall not contain any hydrocarbon condensate and/or water.INTERNATIONAL STANDARD ISO 6974-5:2014(E) ISO 2014 All rights reserved 1BS EN ISO 6974-5:2014ISO 6974-5:2014(E)2 Normative referencesThe following
43、documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 6974-1, Natural ga
44、s Determination of composition and associated uncertainty by gas chromatography Part 1: General guidelines and calculation of compositionISO 6974-2, Natural gas Determination of composition and associated uncertainty by gas chromatography Part 2: Uncertainty calculations3 PrincipleFigure 1 is a flow
45、chart showing the steps involved in the analytical process. It is based on more detailed flowcharts in ISO 6974-1 and ISO 6974-2, simplified to represent the procedure described in this part. References are given at each step to the relevant clause in this part and, where appropriate, to the relevan
46、t clauses in ISO 6974-1 and ISO 6974-2.2 ISO 2014 All rights reservedBS EN ISO 6974-5:2014ISO 6974-5:2014(E)Figure 1 Operational flowchartNOTE The steps referred to in Figure 1 are identical to the steps in flowcharts A and B in ISO 6974-1 Step 5 refers to the use of relative response factors for in
47、directly measured components. Indirect components are not used in this part of ISO 6974, so step 5 is not used.The chromatographic method uses a column switching/backflush arrangement, configured as shown in Figure 2. The sample is injected onto a boiling-point column which is divided into short and
48、 long sections (columns 1 and 2). The long section (column 2) provides separation of C3to C5hydrocarbons, while C6and heavier hydrocarbons are retained on the short section (column 1), from which they are ISO 2014 All rights reserved 3BS EN ISO 6974-5:2014ISO 6974-5:2014(E)backflushed and measured b
49、y the detector as a single peak. Two six-port valves can handle the sample injection and backflushing operations, or they may be dealt with together by a single 10-port valve.Nitrogen, carbon dioxide, methane and ethane pass rapidly and unresolved through the boiling-point column onto a porous polymer bead column (column 3), suitable for their separation. A six-port valve either connects this column or by-passes it during measurement of C3to C5components.The separations that occur in the columns are as follows:Column 1 Retains
