ASTM_D_4891_-_13.pdf

Designation:D489113Standard Test Method forHeating Value of Gases in Natural Gas and Flare GasesRange by Stoichiometric Combustion1This standard is issued under the fixed designation D4891;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of the heatingvalue of natural gases and similar gaseous mixtures within therange of composition shown in Table 1,and Table 2 that coversflare components but is not intended to limit the components tobe measured in flare gases.1.2 This standard involves combustible gases.It is not thepurpose of this standard to address the safety concerns,if any,associated with their use.It is the responsibility of the user ofthis standard to establish appropriate safety and health prac-tices and determine the applicability of regulatory limitationsprior to use.2.Referenced Documents2.1 ASTM Standards:2D1826 Test Method for Calorific(Heating)Value of Gases inNatural Gas Range by Continuous Recording CalorimeterE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 EPA Standard:3EPA-600/2-85-106 Evaluation of the Efficiency of IndustrialFlares:Flare Head Design and Gas Composition3.Terminology3.1 All of the terms defined in Test Method D1826 areincluded by reference.3.2 Definitions of Terms Specific to This Standard:3.2.1 combustion ratio,nthe ratio of combustion air togaseous fuel.3.2.2 burned gas parameter,na property of the burned gasafter combustion which is a function of the combustion ratio.3.2.3 critical combustion ratio,n for a specific burned gasparameter,the combustion ratio at which a plot of burned gasparameter versus combustion ratio has either maximum valueor maximum slope.3.2.4 combustion air requirement index(CARI),nis theamount of air required for complete combustion of the gasbeing measured and can be used to index against othermeasured values such as the Wobbe Index or Heating Value.3.2.5 stoichiometric ratio,nthe combustion ratio when thequantity of combustion air is just sufficient to convert all of thecombustibles in the fuel to water and carbon dioxide.4.Summary of Test Method4.1 Air is mixed with the gaseous fuel to be tested.Themixture is burned and the air-fuel ratio is adjusted so thatessentially a stoichiometric proportion of air is present.Moreexactly,the adjustment is made so that the air-fuel ratio is in aconstant proportion to the stoichiometric ratio that is a relativemeasure of the heating value.To set this ratio,a characteristicproperty of the burned gas is measured,such as temperature oroxygen concentration.5.Significance and Use5.1 This test method provides an accurate and reliableprocedure to measure the total heating value of a fuel gas,ona continuous basis,which is used for regulatory compliance,custody transfer,and process control.5.2 Some instruments which conform to the requirementsset forth in this test method can have response times on theorder of 1 min or less and can be used for on-line measurementand control.5.3 The method is sensitive to the presence of oxygen andnonparaffin fuels.For components not listed and compositionranges that fall outside those in Table 1 and Table 2,modifi-cations in the method and changes to the calibration gas orgasses being used may be required to obtain correct results.6.Apparatus6.1 A suitable apparatus for carrying out the stoichiometriccombustion method will have at least the following four1This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.03 on Determination ofHeating Value and Relative Density of Gaseous Fuels.Current edition approved May 1,2013.Published May 2013.Originallyapproved in 1989.Last previous edition approved in 2001 as D489189(2001).DOI:10.1520/D4891-89R06.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3Available from United States Environmental Protection Agency(EPA),ArielRios Bldg.,1200 Pennsylvania Ave.,NW,Washington,DC 20004,http:/www.epa.gov.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 components:flow meter or regulator,or both;combustionchamber;burned gas sensor;and electronics.The requirementfor each of these components is discussed below.The detaileddesign of each of these components can vary.Three differentapparatus are shown in Fig.1,Fig.2 and Fig.3.In each figurethe equivalent of the four necessary components are enclosedin dashed lines.6.2 OverviewAir and fuel enter the apparatus and the flowof each is measured.Alternativ