ASTM_D_4084_-_07_2012.pdf

Designation:D408407(Reapproved 2012)Standard Test Method forAnalysis of Hydrogen Sulfide in Gaseous Fuels(LeadAcetate Reaction Rate Method)1This standard is issued under the fixed designation D4084;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 hydrogensulfide(H2S)in gaseous fuels.It is applicable to the measure-ment of H2S in natural gas,liquefied petroleum gas(LPG),substitute natural gas,landfill gas,sewage treatment off gasses,recycle gas,flare gasses,and mixtures of fuel gases.Thismethod can also be used to measure the hydrogen sulfideconcentration in carbon dioxide.Air does not interfere.Theapplicable range is 0.1 to 16 parts per million by volume(ppm/v)(approximately 0.1 to 22 mg/m3)and may be extendedto 100%H2S by manual or automatic volumetric dilution.1.2 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.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1914 Practice for Conversion Units and Factors Relating toSampling and Analysis of AtmospheresD2420 Test Method for Hydrogen Sulfide in LiquefiedPetroleum(LP)Gases(Lead Acetate Method)D3609 Practice for Calibration Techniques Using Perme-ation TubesD7166 Practice for Total Sulfur Analyzer Based On-line/At-line for Sulfur Content of Gaseous FuelsE2165 Practice for Establishing an Uncertainty Budget forthe Chemical Analysis of Metals,Ores,and RelatedMaterials(Withdrawn 2007)33.Summary of Test Method3.1 Measurement of H2S is accomplished by ratiometricallycomparing a reading of an unknown sample with that of aknown standard using a differential colorimetric detection.Pure H2S is used as a primary standard and mixed volumetri-cally with a sulfur free matrix gas that is ideally similar incomposition to the sample gas.A gaseous sample at constantflow is humidified and passed over lead-acetate-impregnatedpaper.H2S reacts with lead acetate to form a brown stain on thepaper.The rate of reaction and resulting rate of color change isproportional to the concentration of H2S in the sample.Theanalyzer is comprised of an optical system,a photon detectionsystem,a signal differentiation system of first order,and asignal output system.When there is no change in the color ofthe tape,and no resulting change in photodetector output,E,the first derivative,dE/dt,is zero.This results in an analyzerthat automatically zeroes when there is no H2S.4.Significance and Use4.1 This test method is useful in determining the concentra-tion of hydrogen sulfide in gaseous samples and in verifyingcompliance with operational needs and/or environmental limi-tations for H2S content.The automated performance operationof this method allows unattended measurement of H2S con-centration.The user is referred to Practice D7166 for unat-tended on-line use of instrumentation based upon the leadacetate reaction rate method.5.Apparatus5.1 Volumetric Measuring DevicesA graduated 10-L cyl-inder(see Fig.1)having a movable piston for volumetricallymeasuring test gas.Gastight syringes of 0.1 and 0.5-mLvolume for volumetrically measuring 100%H2S.Gas tightsyringes of other volumes can be used.These graduateddevices are not needed when the permeation tube method ofdynamic mixing is used to prepare the reference sample sincethis method will generate a reference mixture.5.2 Sample PumpA pump capable of providing more than8 mL/s(approximately 1 ft3/h)or less than 1 mL/s at 70 kPa(approximately 10.15 psig).Gas-wetted parts are ideally con-structed from either aluminum or polytetrafluorethylene1This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.05 on Determination ofSpecial Constituents of Gaseous Fuels.Current edition approved Nov.1,2012.Published December 2012.Originallyapproved in 1981.Last previous edition approved in 2007 as D4084 07.DOI:10.1520/D4084-07R12.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1(PTFE).Stainless steel may be used when higher safety thanafforded by aluminum or PTFE is required.5.3 Colorimetric Rate of Reaction SensorSelect a deviceof sufficient sensitivity to measure a minimum rate