ASTM_D_2597_-_10.pdf

Designation:D259710Standard Test Method forAnalysis of Demethanized Hydrocarbon Liquid MixturesContaining Nitrogen and Carbon Dioxide by GasChromatography1This standard is issued under the fixed designation D2597;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 analysis of demethanizedliquid hydrocarbon streams containing nitrogen/air and carbondioxide,and purity products,such as an ethane/propane mixthat fall within the compositional ranges listed in Table 1.Thistest method is limited to mixtures containing less than 5 mol%of heptanes and heavier fractions.1.2 The heptanes and heavier fractions,when present in thesample,are analyzed by either(1)reverse flow of carrier gasafter n-hexane and peak grouping or(2)precut column to eluteheptanes and heavier first as a single peak.For purity mixeswithout heptanes and heavier,no reverse of carrier flow isrequired.(CautionIn the case of samples with a relativelylarge C6+or C7+fraction and where precise results areimportant,it is desirable to determine the molecular weight(orother pertinent physical properties)of these fractions.Sincethis test method makes no provision for determining physicalproperties,the physical properties needed can be determinedby an extended analysis or agreed to by the contractingparties.)1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.NOTE1Annex A2 states values in manometric units,which are to beregarded as the standard in that section.Approximate SI units(fromconversion)are given in parentheses.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.For specific hazardstatements see Annex A3.2.Referenced Documents2.1 ASTM Standards:2D1265 Practice for Sampling Liquefied Petroleum(LP)Gases,Manual MethodD2163 Test Method for Determination of Hydrocarbons inLiquefied Petroleum(LP)Gases and Propane/PropeneMixtures by Gas ChromatographyD3700 Practice for Obtaining LPG Samples Using a Float-ing Piston CylinderD6299 Practice for Applying Statistical Quality Assuranceand Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD6849 Practice for Storage and Use of Liquefied PetroleumGases(LPG)in Sample Cylinders for LPG Test Methods2.2 GPA Standard:3GPA 2177 Analysis of Demethanized Hydrocarbon LiquidMixtures Containing Nitrogen and Carbon Dioxide byGas Chromatography3.Summary of Test Method3.1 Components to be determined in a demethanized hydro-carbon liquid mixture are physically separated by gas chroma-tography and compared with calibration data obtained underidentical operating conditions.Afixed volume of sample in theliquid phase is isolated in a suitable sample inlet system andentered onto the chromatographic column.3.1.1 Components nitrogen/air through n-hexane are indi-vidually separated with the carrier flow in the forward direc-tion.The numerous heavy end components are grouped into anirregularly shaped peak by reversing direction of carrier gasthrough the column by means of a switching valve immediatelyfollowing the elution of normal hexane.(See Fig.1.)Samplesthat contain no heptanesplus fraction are analyzed until thefinal component has eluted with no reverse of carrier flow.1This test method is under the jurisdiction of Committee D02 on PetroleumProducts and Lubricants and is the direct responsibility of Subcommittee D02.H0 onLiquefied Petroleum Gas.Current edition approved May 1,2010.Published July 2010.Originally approvedin 1967.Last previous edition approved in 2004 as D259794(2004).DOI:10.1520/D2597-10.2For 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 Gas Processors Association(GPA),6526 E.60th St.,Tulsa,OK74145,http:/gpaglobal.org/.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.1.2 An alternate procedure to the single column backflushmethod is the use of a precut column which is backflushed toobtain the heptanesplus as a single peak at the beginning ofthe chromatogram.NOTE2Two advantages of the alternate procedure are as follows:(1)better precision in measuring the C7+portion of the sample and(2)reduction in analysis time over the single column approach by approxi-mately 40%.3.2 The chromatogram is interpreted by comparing the areasof component peaks obtained from the sampl