ASTM D 66-2003

StandardTestMethodfor

DeterminationoftheAcceleratedHydrogenSulfide

BreakthroughCapacityofGranularandPelletizedActivatedCarbon1ThisstandardisissuedunderthefixeddesignationD66;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(e)indicatesaneditorialchangesincethelastrevisionorreapproval.

1.Scope

1.1Thistestmethodisintendedtoevaluatetheperformanceofvirgin,newlyimpregnatedorin-service,granularorpellet-izedactivatedcarbonfortheremovalofhydrogensulfidefromanairstream,underthelaboratorytestconditionsdescribedherein.Ahumidifiedairstreamcontaining1%(byvolume)hydrogensulfideispassedthroughacarbonbeduntil50ppmbreakthroughofH2Sisobserved.TheH2Sadsorptioncapacityofthecarbonperunitvolumeat99.5%removalefficiency(gH2S/cm3carbon)isthencalculated.Thistestisnotnecessarilyapplicabletonon-carbonadsorptivematerials.

1.2Thisstandardaswrittenisapplicableonlytogranularandpelletizedactivatedcarbonswithmeanparticlediameters(MPD)lessthan2.5mm.Seeparagraph5.3ifactivatedcarbonswithlargerMPDsaretobetested.

1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.

2.ReferencedDocuments2.1ASTMStandards:2D2652DefinitionofTermsRelatingtoActivatedCarbonD2854DeterminationofApparentDensityofActivatedCarbon

D2867TestForMoistureinActivatedCarbonE300PracticeforSamplingIndustrialChemicals3.Terminology

3.1TermsrelatingtothisstandardaredefinedinD2652.

ThistestmethodisunderthejurisdictionofASTMCommitteeD28onActivatedCarbonandisthedirectresponsibilityofSubcommitteeD28.04onGasPhaseEvaluationTests.

CurrenteditionapprovedOct.1,2003.PublishedNovember2003.Originallyapprovedin2001.Lastpreviousversionapprovedin2001asD66–01.2ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.ForAnnualBookofASTMStandardsvolumeinformation,refertothestandard’sDocumentSummarypageontheASTMwebsite.

14.SummaryofTestMethod

4.1Breakthroughcapacityisdeterminedbypassingastreamofhumidifiedaircontaining1volume%hydrogensulfidethroughasampleofgranularorpelletizedactivatedcarbonofknownvolumeunderspecifiedconditionsuntiltheconcentrationofhydrogensulfideintheeffluentgasreaches50ppmv.

5.SignificanceandUse

5.1Thismethodcomparestheperformanceofgranularorpelletizedactivatedcarbonsusedinodorcontrolapplications,suchassewagetreatmentplants,pumpstations,etc.Themethoddeterminestherelativebreakthroughperformanceofactivatedcarbonforremovinghydrogensulfidefromahumidi-fiedgasstream.OtherorganiccontaminantspresentinfieldoperationsmayaffecttheH2Sbreakthroughcapacityofthecarbon;thesearenotaddressedbythistest.Thistestdoesnotsimulateactualconditionsencounteredinanodorcontrolapplication,andisthereforemeantonlytocomparethehydrogensulfidebreakthroughcapacitiesofdifferentcarbonsundertheconditionsofthelaboratorytest.

5.2Thistestdoesnotduplicateconditionsthatanadsorberwouldencounterinpracticalservice.Themasstransferzoneinthe23cmcolumnusedinthistestisproportionallymuchlargerthanthatinthetypicalbedusedinindustrialapplica-tions.ThisdifferencefavorsacarbonthatfunctionsmorerapidlyforremovalofH2Soveracarbonwithslowerkinetics.Also,the1%H2Schallengegasconcentrationusedhereengendersasignificanttemperatureriseinthecarbonbed.Thiseffectmayalsodifferentiatebetweencarbonsinawaythatisnotreflectedintheconditionsofpracticalservice.

5.3Thisstandardaswrittenisapplicableonlytogranularandpelletizedactivatedcarbonswithmeanparticlediameterslessthan2.5mm.Applicationofthisstandardtoactivatedcarbonswithmeanparticlediameters(MPD)greaterthan2.5mmwillrequirealargerdiameteradsorptioncolumn.TheratioofcolumninsidediametertoMPDshouldbegreaterthan10inordertoavoidwalleffects.Inthesecasesitissuggestedthatbedsuperficialvelocityandcontacttimebeheldinvariantattheconditionsspecifiedinthisstandard(4.77cm/secand4.8

Copyright©ASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959,UnitedStates.

1

sec).Althoughnotcoveredbythisstandard,dataobtainedfromthesetestsmaybereportedasinparagraph12alongwithadditionalinformationaboutcolumndiameter,volumeofcarbon,andvolumetricflowrateused.

5.4Forpelletizedcarbons,itisfeltthattheequivalentsphericaldiameterofthepelletisthemostsuitableparameterfordeterminingtheappropriateadsorptioncolumninsidediameter.Theequivalentsphericaldiameteriscalculatedaccordingtothefollowingequation.

D3XdXh

eqv5d12Xh(1)

where:

d=thediameter,and

h=thelengthofthepelletinmm.

Anaverageof50to100measurementsisrecommendedtodeterminetheaveragelengthofapellet.AnnexA3isatabletoguidetheuserinselectingbeddiameterandflowratesfromtypicalequivalentdiameters(orMPD)ofpelletizedcarbon.6.ApparatusandMaterials

6.1(561)%HydrogenSulfideinNitrogenMixture.Theconcentrationofhydrogensulfideinthegastestmixturemustbeknown.Itisrecommendedthatgascylindersspecificallymanufacturedforholdinghydrogensulfidegasbeused.Ana-lyzedandcertifiedhydrogensulfideinnitrogengasmixturescanbepurchasedfromspecialtygassuppliers.AnnexA1andAnnexA2presentmethodsthatmaybeusedtocheckthehydrogensulfideconcentrationofhydrogensulfide/nitrogengasmixtures.Itisrecommendedthatthehydrogensulfideconcentrationbecheckedifgascylindersarestoredformorethanthreemonths,particularlyafterbeingpartiallydepleted.Otherorganiccontaminantsthatmaybepresentinthehydro-gensulfidetankcanaffecttheadsorptioncapacityofthecarbonbeingtested.

6.2HydrogenSulfideDetector.Thehydrogensulfidedetec-torusedinthistestmustbedemonstratedtoreliablydetect50ppmhydrogensulfideinahumidifiedairstream.Inadditiontocertain“solidstate”detectors,electrochemicaltypehydrogensulfidesensors,e.g.,EcolyzerModel00orInterscanLD-17,havebeenevaluatedandfitthisrequirement.Othermeansofhydrogensulfidedetectionmaybeselected,aslongastheyarecarefullycalibratedandevaluatedforthisapplication.

6.3AdsorptionTube.TheadsorptiontubeisshowninFig.1.Adsorptiontubesarenotcommerciallyavailable;however,theycanbecustomfabricatedbyascientificglassblower.Theperforatedsupportshownisnecessarytosupportthecarbonbedandtoenhancediffusionofthegases.(AdjustdimensionsaccordinglyfromAnnexA3,specificallydiameter.)

6.4Flowmeter(0-500mL/minNitrogen;seeAnnexA3forGuidetoHigherFlowRangeforParticles>2.5mmMPD).Forhydrogensulfide/Nwettablepartsofthisflow2control,itisrecommendedthatthemeterbemadeofPTFEorothercorrosionresistantmaterial.Rotameterfloatsshouldbemadefromnon-metallicmaterialssuchasglassorsapphire.

6.5Flowmeter(0-2000mL/minAir;seeAnnexA3forGuidetoHigherFlowRangeforParticles>2.5mmMPD).

NOTE1—Massflowcontrollershavebeenfoundtobemorereliablethanflowmetersandarehighlyrecommendedduetotheirabilityto

FIG.1SchematicofAdsorptionTube

automaticallymaintainprecisegasflowrates.Rotametersaresatisfactoryforthismethod,butmayrequiremorefrequentattentioninmaintainingpropertestgasflowsforthedurationofthetest.

6.6TwoStageCylinderRegulator,SuitableforCorrosiveGasService,forHydrogenSulfideGasCylinder.

6.7AirLinePressureRegulator—LowPressure.Tomain-tainupto10psigpressureforupto2litersofair/minflowrate(seeAnnexA3forguidetoairflowfortubesusedforparticles>2.5mmMPD)

6.8TwoMeteringValves.SuitablevalvesaretheWhiteySS-21-RS4(H2S/N2)andB-21-RS4(air).Othersimilarvalvesmaybeused.Iftherotametersin6.4and6.5areequippedwiththeirownhighqualitymeteringvalves,thesevalvesarenotneeded.

6.9SourceofDry,Contaminant-FreeAirCapableofDeliv-eringupto2liters/minThroughtheTestSystem(higherflowforlargerparticles,>2.5mmMPD,seeTableA3.2.)

6.10GasBubbler.(AceGlasscat.#5516gaswashingbottleequippedwithgasdispersionfrittedtube,cat.#7202,porositycode“C”,orequivalenttothis.)Theglassbubblershouldbeimmersedinaconstanttemperaturebathregulatedat25°Ctoensurethegenerationofa80%RHairstreamforthefinalgas

D66–03

mixture(aftermixingwithdryH2S/N2).Theporousbubblershouldbeimmersedunderatleast3inchesofwatertoconsistentlysaturatetheairstreamwithwaterduringthecourseofthetest.(Alargergaswashingbottleshouldbeusediflargerparticlesthan2.5mm(EquivalentDiameter)andalargerbedareused.Increasesizeproportionatelywithairflow).

6.11HydrogenSulfideCalibrationGasMixture,20to50ppmv,innitrogen,tobeusedasaspanorcalibrationgasforthehydrogensulfidedetector.(Availablefromspecialtygassupplycompanies.)

6.12Timer.Acountuptimerthatcanbetrippedatthe50ppmvsetpointoftheH2Smonitorandiscapableofretainingthetrippedtime.

6.13VibratoryFeeder(seeAS2854).6.14PowderFunnel.

6.15TemperatureControlledWaterBathtomaintainthewaterbubblerat25°C62°C.

6.16OthermiscellaneoushardwareneededtosetuptheapparatusinFig.2.PolyethylenetubingissuitableforcarryingtheH2S/N2flow.Clampedballandsocketjointsareconvenientforquickconnectanddisconnectoftheabsorptioncolumnandcalibrationbubbler(seeAnnexA2)fromthesystem.7.SafetyPrecautions

7.1Severalpotentialhazardsareassociatedwithconductingthistestprocedure.Itisnotthepurposeofthisstandardtoaddressallpotentialhealthandsafetyhazardsencounteredwithitsuse.Theuserisresponsibleforestablishingappropri-atehealthandsafetypracticesbeforeuseofthistestprocedure.

DeterminetheapplicabilityofFederalandStateregulationsbeforeattemptingtousethisstandardtestmethod.

7.2Personnelconductingthehydrogensulfideadsorptioncapacityprocedureshouldbeawareofpotentialsafetyandhealthhazardsassociatedwiththechemicalsusedinthisprocedure.The“MaterialSafetyDataSheet”(MSDS)foreachreagentlistedinSection6shouldbereadandunderstood.SpecialprecautionstobetakenduringuseofeachreagentareincludedontheMSDS.FirstaidproceduresforcontactwithachemicalarealsolistedonitsMSDS.TheMSDSforeachreagentmaybeobtainedfromthemanufacturer.

7.3Safetyandhealthhazardinformationonreagentsusedinthisproceduremayalsobeobtainedfrom:

7.3.1Sax’sDangerousPropertiesofIndustrialMaterials/RichardJ.Lewis,Sr.,NewYork:J.Wiley,2000.

7.3.2NIOSH/OSHAPocketGuidetoChemicalHazards,1997,U.S.DepartmentofLabor,OccupationalSafetyandHealthAdministration,Washington,D.C.AvailablefromU.S.GovernmentPrintingOffice,Washington,D.C.orathttp://www.cdc.gov/niosh/npg/npg.html.

8.Sampling

8.1GuidanceinsamplinggranularactivatedcarbonisgiveninrecommendedPracticeE300.

9.Calibration

9.1Calibrationofflowmeters,massflowcontrollers,andhydrogensulfidedetectorsshallbeperformedbystandardlaboratorymethods.

NOTE2—Thetestapparatus(Fig.1)hasmeteringvalvesatthe

FIG.2SchematicofApparatusforDeterminationofH2SBreakthroughCapacity

3

rotameteroutlets.Thisisdonetominimizechangesingasflowratescausedbysmallbackpressurechangesduringthislongdurationtest.However,placementofmeteringvalvesinthispositioninvalidatestheatmosphericpressurecalibrationusuallysuppliedbytherotametermanu-facturer.TheapparatusinA2.4.2maybeusedtocalibratetherotameters.Duringthiscalibration,thegasdeliverypressuremustbethesameasthatusedduringtheactualtest.

9.2DeterminethepercentHthemethodsoutlinedinAnnex2SintheHA1orAnnex2S/nitrogentankusingA2iftheH2S/nitrogentankwasnotcertifiedbythemanufacturer.10.Procedure

10.1AssemblethetestapparatusasshownintheschematicdiagramofFig.2.

10.2AdjusttheH%H2S/N2andairflowratestogeneratea1.0one-inch2Sstreamatatotalflowrateof1450cm3/minatthediameteradsorptiontube(seeAnnexA3forhigherflowrateswithlargerthan2.5mm(EquivalentDiameter)particles).ThisadjustmentwilldependontheconcentrationofH2SintheHDetermine2S/N2gasmixture.

10.3theH2Sconcentrationoftheactualmixedtestgasusingmethod(s)asoutlinedinAnnexA1orAnnexA2ofthisprocedure.Thistestshouldberepeatedifanyadjust-mentismadeontheflowmeter(s).

10.4Obtainarepresentativesampleoftheas-receivedgranularorpelletizedactivatedcarbontobetested.A300cm3sampleissufficientforapparentdensity,moistureandreplicateperformancetesting.(Alargeramountshouldbeusediftheparticleslargerthan2.5mm(EquivalentDiameter)andalargerdiameterbedareused).

10.5ReducethesamplesizetoanaliquotfortestingusingtherifflingproceduredescribedinE300.

10.6DeterminetheapparentdensityofthesamplebyAS2854.

10.7Useanadsorptiontubewhosevolumehasbeencali-bratedtocontain116mL(seeAnnexA3forlargervolumes)whenfilledfromthetopofthecarbonsupporttoabeddepthofapproximately22.9.(Thecalibratedvolumeforanadsorp-tiontubecanbedeterminedbyusingagraduatedburettodeterminethevolumeofwaterrequiredtofilltheadsorptiontubefromthetopofthecarbonsupporttoapproximatelythe22.9cmmark.)

10.8Tareaclean,dryadsorptiontubetothenearest0.1g.Noteandrecord.

10.9Filltheadsorptiontubewith116mLofcarbon[beddepthofapproximately22.9cm]usingavibratoryfeeder.(TheapparatusdescribedinAS2854,“StandardTestMethodforApparentDensityofActivatedCarbon”,orequivalentissuitableforfillingtheadsorptiontube.)Thevibratoryfeederistobeadjustedsotheadsorptiontubeisfilledataratenotlessthan0.75orexceeding1.0mL/sec.(SeeAnnexA3forguidetolargervolumeiflargerthan2.5mm(EquivalentDiameter)particlesaretested.)

10.10Weighthefilledadsorptiontubetothenearest0.1gm.Noteandrecord.

10.11Carefullytransferthefilledadsorptiontubetothetestsystemandconnectittothetestapparatus.

NOTE3—Ifasampleofnon-impregnated,lowmoisture,virgincarbonisbeingevaluatedforadsorptioncapacity,itisadvisedthatitbe

conditionedforseveralhourswithonlyhumidifiedairpassingthroughittoequilibratethemoisturecontentofthecarbonwiththemoistureintheairstream.Themoisturecontentofthecarbonwillaffectthebreakthroughcapacity

StarttheH2S/airflowandsimultaneouslystartthetimer.10.12ContinuetheH2S/airflowuntilabreakthroughof50ppmvisindicated.RecordthetimeelapsedfromthestartofH2S/airflowto50ppmbreakthrough.

10.13Repeat10.2-10.12onreplicateportionsofthecarbonsample.Aminimumofonereplicateanalysesmustbeper-formed.

11.Calculation

11.1Calculatethehydrogensulfidebreakthroughcapacityofthetestsampleusingthefollowingequation:

gH2S

3SGAC

(2)

C100D3F3T3Scm5

1L1mole34.1gH2S

1000cm

3D3S22.4LD3SmoleDVwhere:

C=concentrationofhydrogensulfideinairstream,vol-ume%,

F=totalH2S/airflowrate,cm3/min(shouldbe1450

cm3/min)(AdjustfromAnnexA3ifnecessary),T=timeto50ppmvbreakthrough,minutes,and

V=actualvolumeofthecarbonbedintheabsorptiontube,

cm3(AdjustfromAnnexA3ifnecessary).

NOTE4—Forsimplicityandwithoutintroducingsignificanterrorintothecalculation,itcanbeassumedthegasstreamsareatstandardconditionsandcorrectionsforambienttemperatureorpressureareunnecessary.)

Thisequationsimplifiesto:

gH2S~1.5231025!3C3Fcm3GAC

53T

V(3)

TodeterminetheH2SbreakthroughcapacityingH2S/g

GAC,usethefollowingequation:

gH2SgH2S/cm3GAC

gGAC5apparentdensity~from10.6!(4)

11.2Thehydrogensulfidebreakthroughcapacityisdeter-minedforeachreplicateportionofthecarbonsample.TheaverageandsamplestandarddeviationforthehydrogensulfidebreakthroughcapacitiesisthencalculatedusingN-1weight-ing.Ifthestandarddeviationoftheanalysesislessthanorequalto10%oftheaveragehydrogensulfidebreakthroughcapacity,theaveragevalueandstandarddeviationarereportedasthehydrogensulfidebreakthroughcapacity.Ifnot,anadditionalreplicateportionmustbeanalyzeduntiltheabovecriteriaisobtained.

12.Report

12.1Reportthefollowing:12.1.1Sourceofthesample.

12.1.2Typeanddesignationofthesample.12.1.3Nameofcarbonsupplier.

12.1.4Suppliername,lotnumber,batchnumber.

12.1.5H2SbreakthroughcapacityinH2Sg/cm3ofGAC.13.PrecisionandBias

13.1Precision—Around-robintestofthisproposedmethodwasconductedin1995,withfivelaboratoriestestingfourdifferentsamplesofimpregnatedactivatedcarbonforH2Sremoval,eachsamplebeingtestedintriplicate.Thefollowingisasummaryoftheprecisionparametersoftheround-robin:

materialCDBA

average0.08470.11470.12070.1480

Sr0.006830.005160.012110.00966

SRr=2.83Sr3gH2S/cmGAC0.011830.019130.008750.014450.012110.033910.023190.02705

R=2.83SR0.03313

0.024510.033910.093

laboratoryresults.Theprecisionofinterlaboratoryreproduc-ibilityresultsisindicatedbyR=2.83SR,the95%confidencelimitofthetestmethod.Therepeatabilityofresultsbythismethodisindicatedbyr=2.83Sr,the95%confidencelimitofinterlaboratoryrepeatability.

13.2Bias—Withrespecttobiasofthemethod,thereseemstobeadeclineinrepeatabilityandreproducibilitywiththeincreaseofbreakthroughcapacity,asindicatedbythegeneralupwardtrendintheconfidencelimitswiththeincreaseinH2Scapacity.14.Keywords

14.1activatedcarbon;breakthroughcapacity;hydrogensulfide

Sristherepeatabilitystandarddeviationforinterlaboratoryresults,SRisthereproducibilitystandarddeviationforinter-

ANNEXES

(MandatoryInformation)

A1.ANALYSISANDCALIBRATIONOFH2STESTGASSTREAMWITHGASCHROMATOGRAPHY

A1.1Scope

A1.1.1Theexactconcentrationofthehydrogensulfidetestgasstreamneedstobeknown.Agaschromatographcanbeusedtoanalyzethegasstreamanddetermineitsconcentrationagainstanindependentlycertifiedcalibrationgas.ThismethodcanbeusedtodeterminetheH2Sgasconcentrationsinbothnitrogenandairmixtures.Thismethodisbelievedtobemorereliablethanwet-chemicalmethodsandcanindicatethepresenceofcontaminantgasesthatmaybepresentinsomegradesofhydrogensulfide.

A1.2SummaryofMethod

A1.2.1Asampleofthegastobeanalyzedistakenoveraperiodofseveralminutes,collectedinaone-timeuseTedlartbagorflow-throughgas-samplingbottle.Agas-tightsyringeisusedtowithdrawasampleofthegasandinjectitintoapreviouslycalibratedgaschromatograph.

A1.3Apparatus

A1.3.1Column:6ft34mm(ID)glasscolumn,Chromosil310(orsimilar)packing,openbore,oranycapillarycolumnsuitableforpermanentgasseparation.A1.3.2Conditions:Injector60°C.

Columnoven:42-46°C(optimizeforseparation).Detector:60°C(forFIDorFPD).

A1.3.3Detectortype:Flameionizationdetector,flamepho-tometricdetector,orHalldetectoroptimizedforsulfur(mostsensitive).

A1.3.4Gassamplingbag(s)orglasscollectingtube.A1.3.5Gastightsyringe.

A1.3.6Integratororcomputerizeddatacollectiontointe-gratepeakareasofsamplegases.

A1.4Procedure

A1.4.1TheGCcolumnisglass,packedwithChromosil310(Supelcoorsimilar),6ft.34mmID.Theflowrateissetat40mL/min,thecarriergashelium.Aflameionization(orflamephotometric)detectorshouldbeused.Thecolumntemperatureshouldbemaintainedat42-46°C,dependingontheefficiencyofseparationoftheairpeakfromthehydrogensulfidepeak.Injectoranddetectortemperatureshouldbemaintainedat60°C.TheconditionsdescribedareageneralguidetoGCoperationforthisanalysis;individualsystemoperationswillvary.

A1.4.2Thecalibrationgasortestgasmaybecollectedinseveralways.AdisposableTedlartgassamplebagmaybefilledwiththegasofinterest,oraglassgascollectingtubewithasamplingport(suchasAceGlass7395or7401-TB)maybeused.Theglassgassamplingtubeispreferredasitcanbepurgedofatmosphericgasesbyacontinuousflowofthetestgasstream.Thegasofinterest(testgasorcalibrationgas)shouldbewithdrawnbymeansofagastightsyringeandinjectedontothecolumn.Atypicalinjectionvolumeis2mLofgas.Theretentiontimeforhydrogensulfideistypically1.2to1.3minutesundertheseconditions.

A1.4.3Fivereplicateinjectionswitharelativestandarddeviationoflessthan2%intheaveragepeakareasarerequiredforthecalibrationgasstandardbeforedeterminingtheconcentrationofthehydrogensulfidetestgasusedinthisprocedure.

A1.4.4Atleasttworeplicateinjectionsofthetestgasshouldbemadetocalculatetheconcentrationofhydrogensulfideinthetestgas.

A2.DETERMINATIONOFTHECONCENTRATIONOFHYDROGENSULFIDEINMIXTURESWITHAIRORNITROGEN

A2.1Scope

A2.1.1Thismethodmaybeusedtodeterminetheconcen-trationofhydrogensulfideinmixtureswithairornitrogen.ItmaybeusedtoverifytheHobtained5%H2Sconcentrationofthecommer-ciallyconcentrationofthe1%2SinN2mixtureinpara6.1.TheH2Stestgasmixturewhichispassedthroughthecarboncolumnmayalsobeconfirmedusingthismethod(para10.3).

A2.2SummaryofMethod

A2.2.1AknownvolumeofamixtureofHhydroxidesolution.2SinairornitrogenispassedthroughasodiumTheH2Sisabsorbedwiththeformationofsulfide.Thesulfideisquantitativelyoxidizedtoelementalsulfurbyusinganexcessofanacidiciodinesolution.Theexcessiodineaddedisdeterminedbytitrationwithastandardsodiumthiosulfatesolutiontothestarchendpoint..ThisdeterminationoftheamountofiodinerequiredtooxidizethecapturedHanalyzed2SgasalongwiththevolumeoftheH2SgasmixtureallowstheconcentrationofH2Stobecalculated.

A2.3Reference:Bethge,P.O.,AnalyticaChimicaActa,9,1953,pg129.

A2.4Apparatus

A2.4.1Flowmeter(s)withregulatingvalve(s)ormassflowcontroller(s)capableofcontrollingH500mL/min2S/N2orHtoabout2S/airflowratesintherangefromabout1500mL/min.

A2.4.2Soapbubbleflowmeter(AceGlass7441-40orsimilar).

A2.4.3Pipets,TD,ASTMclassA,20mL,25mL,and50mL.

A2.4.4Buret,TD,ASTMclassA,50mL.

A2.4.5Bubblerwith1mmcapillaryorificetip(AceGlass7529-16orequivalent).

A2.4.6Iodineflaskwithstopper,(Kimble27200-125orsimilar).

A2.4.7Graduatedcylinder,TD,ASTMclassA,25mL.A2.4.8Volumetricflasks,TC,ASTMclassA,100mLand250mL.

A2.4.9Timerorstopwatch.

A2.4.10Magneticstirrerandstirbar.

A2.5Reagents

A2.5.1Sodiumhydroxidesolution,approximately0.5M,preparedbydissolvingabout5gofACSsodiumhydroxidepelletsinabout250mLdistilledwater.

A2.5.2Sulfuricacidsolution,approximately3M,preparedbyslowlyaddingwithswirling(Caution:Muchheatevolved.)about42mLofACSconcentratedsulfuricacid(95-98%)toabout100mLofdistilledwaterina250mLvolumetricflask.Allowtocool.Makeupwithwatertothemark.

A2.5.3Starchsolution,1%inwater(AldrichChemical31,955-4orequivalent)

A2.5.4Standardiodinesolution,0.5N[0.25M]Thismaybepreparedbypipetting50mLofstandard1.0Niodine(AldrichChemical31,900-7orequivalent)intoa100mLvolumetricflask,dilutingtothemarkwithdistilledwaterandinvertingflaskseveraltimestothoroughlymixthecontents.

A2.5.5Standardsodiumthiosulfatesolution,0.1N[0.1M](AldrichChemical31,954-6orequivalent)

A2.6Procedure

A2.6.1Recordtheambienttemperature(inK)andbaromet-ricpressure(inmmHg).

A2.6.2AssembletheapparatusasshowninFig.2.Removethegasinlettubefromthebubbleratthequickdisconnectandconnectittothesoapfilmflowmeter.

A2.6.3OpentheH2SinNabout10psi,andadjustthe2cylindervalve,setthepressuretoregulatingvalveormassflowcontrollertogiveabout500mL/minflowfora5%Hmixture(para6.1).Forthe1%challengetestmixtureofH2Sinair,positiontheflowmeterafteradditionoftheH2Smixturetotheairstreamandsettheflowto1450mL/min2S/N(para210.2).Recordtheflow.

A2.6.4Addabout50mLofthe0.5MNaOHsolutiontothebubbler.

A2.6.5Reconnectthequickdisconnecttothegasinlettubeofthebubbler.

A2.6.6Insertthegasinlettubeintothebubblerandsimul-taneouslystartthetimer.

A2.6.7BubblethegasmixturethroughtheNaOHsolutionforabout5minutesforthe5%mixtureandabout2.5minutesforthe1%mixture.Thistimemustbemeasuredaccurately.A2.6.8Attheendofthetimeperiod,disconnectthequickconnectandstopthetimersimultaneously.Recordthetime(inminutes).Discontinuetheflowofgasfromthecylinder.

A2.6.9Pipet25mL(forthe5%mixture)or10mL(forthe1%mixture)ofastandard0.5Niodinesolutionintoaniodineflaskcontainingamagneticstirbar.Addabout15mLof3Msulfuricacidandstoppertheflask.

NOTEA2.1—Theiodine/iodidestandardsolutionissusceptibletoairoxidationinthisstronglyacidicsolution.Soaddtheacidjustbeforethetitrationisperformed.

A2.6.10Transferthebubblercontentstotheiodineflaskcontainingtheacidifiediodinesolution.Dothisbypouringaliquotsfromthebubblerintotherimoftheiodineflaskandliftingthestoppersothatthebubblercontentsflowdownthesidesoftheflaskintotheiodinesolution.Thesolutionshouldbestirredatmoderatespeedduringthisprocedure.Washthelastcontentsofthebubblerintotheflaskwithdistilledwaterfromasqueezebottle.Sincethereisanexcessofiodineintheflask,thesolutionshouldbeamilkishbrowncoloratthispoint.A2.6.11Titrateimmediatelywith0.1Nsodiumthiosulfatesolution.Whenitlookslikemosttheexcessiodineisgone,addafewdropsofstarchindicatorandcontinuetitratinguntilthebluecolordisappears.Theendpointisextremelysharp.RecordthemLofthiosulfatesolutionused.

A2.7Calculation

FppmH2S5

(A2.1)

FG~mLI2solution3I2normality!–~mLthiosulfate3thiosulfatenormality!

3

23~flowrateinmL/min!3~timeinminutes!22.437603~TinK!~mLI2solution3I2normality!–~mLthiosulfate3thiosulfatenormality!3102

32733PinmmHg!~23~flowrateinmL/min!3~timeinminutes!IftheH2Sinairconcentrationisnotthedesired1%,adjusttheH2S/N222.437603~TinK!flowupordownwhilekeepingthetotalflowat1450mL/min.Repeatthe31062733~PinmmHg!determinationuntila1%H2Sconcentrationisattained.

%H2S~byvol!5(A2.2)

FGGFGA3.TABLES

TABLEA3.1PelletTable(alldimensionsinmm)

Diameter

(average)1111111.51.51.51.51.52222222.52.52.52.52.52.52.533333333444444444

Length(average)0.511.522.5311.522.5311.522.53411.522.533.541.522.533.544.5522.533.544.555.56

Deqv(mm)0.751.001.131.201.251.291.291.501.1.731.801.501.802.002.142.252.401.672.052.312.502.652.762.862.252.572.813.003.153.273.383.463.003.333.603.824.004.154.294.404.50

TABLEA3.2FlowRange

EquivalentSphericalDiameter,DeqvDeqv=33d3hd+23w

Upto2.5mmMeanParticleDiameter(or<2.5mmEquiv.

Sphericaldiameterpellet)Upto3.8mmMeanParticleDiameter(upto3.8mmEquiv.

Sphericaldiameterpellet)Upto5.1mmMeanParticleDiameter(upto5.1mmEquiv.

Sphericaldiameterpellet)Upto6.35mmMeanParticleDiameter

(upto6.35mmEquiv.Sphericaldiameterpellet)Upto7.7mmMeanParticleDiameter(upto7.7mmEquiv.

Sphericaldiameterpellet)

GasVolumeFlowRateAir

(cc/min)1150

FaceVelocity(constant)(cm/sec)4.78

RecommendedBedDiameter2.54cm(1inch)

BedDepth(constant)23cm(9inches)

H2S/N2(nominal5%)300

3.8cm(1.5inches)23cm(9inches)25806734.78

5.08cm(2inches)23cm(9inches)461012034.78

6.35cm(2.5inches)23cm(9inches)721118814.78

7.62cm(3inches)23cm(9inches)10,374270.78

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