Why the Difference Method (Method25A) Should Not be Used for VOCAnalysis on CH4Rich EngineEmissionsWhy the Difference Method (Method25A) Should Not be Used for VOCAnalysis on CH4Rich EngineEmissionsPresented by Barbara Marshik, PhDMKS Instruments, Inc.Barbara_Marshik@mksinst.com40th Stationary Source Samplingand Analysis for Air PollutantsJW Marriott Tucson Starr Pass, Tucson, ArizonaMarch 20-25, 2016US Mobile Sources EngineCategoriesLight Duty: Model YR 2010–Passenger cars and trucks–Regulated by §86–Tested using §1065 and §1066Heavy Duty On-Road–Regulated by §86, subpart A and parts of subpart N–Tested using §10651EPA Non-Road EngineCertification2GeneralComplianceProcedures§1068Test Procedures§1065Non-roadDiesel§1039MarineDiesel§1042MarineSparkignition§1045Large nonroad Sparkignition§1048Locomotive§1033Small sparkignition§1054RecreationalVehicles§1051Non-roadDiesel§89MarineDiesel§94MarineSparkignition§91Large nonroadSparkignition§60 JJJJLocomotive§92Smallsparkignition§60 JJJRecreational Vehicles§1051Older Organization Newer OrganizationDifference Method Version 13Mobile SourceStationary SourceDifference MethodMethod 25A, Dual FID with NMCEPA Recommends Part 1065.365(d)RFCH4[THC-FID]~1.05 to 1.10Span FID to CH4 thru NMCRF*PFCH4[NMC-FID] = 1RF*PFC2H6[NMC-FID]~0.01 to 0.154NMHC Calculation according to§1065.365(d)Equation 1065.660-2ܺேெு஼ൌ்ܺு஼்ு஼ିிூ஽ ௖௢௥ି்ܺு஼ேெ஼ିிூ஽ ௖௢௥∗ ܴܨ஼ுସ்ு஼ିிூ஽1 െ ܴܨܲܨ஼ଶு଺ேெ஼ିிூ஽∗ ܴܨ஼ுସ்ு஼ିிூ஽χNMHCNMHC concentrationχTHC[THC-FID]corSample THC corrected to dry on THC-FIDRFPFCH4[NMC-FID]NMC C2H6 penetration fractionχTHC[NMC-FID]corSample THC corrected to dry on THC-FIDthrough NMCRFCH4[NMC-FID]NMC Methane response factor5Difference Method Version 26Stationary SourceMethod 25ATHC AnalysisExtracted Gas sample–Source through heated sample line, glass fiber filterthen sent to a flame ionization analyzer (FIA)–Sampling components shall be heated≥110°C–FIA shall be heated≥120°CCaution–Heavy HCs must be heated to 190oC to notcondense–If you are not running at 191oC5oC you are NOTcompliant if you are using NMC7NMHC Difference MethodVersion 1 (ppmC1)8Engine2 CH4/THC THC-FIDCH4NMC-FIDNMHCAnalyticalPropagationErrorFuel 1 0.93 9517 8865 -58260Fuel 2 0.94 4421 4158 -71121Fuel 3 0.94 3297 3103 -5491Fuel 4 0.93 6909 6440 -47189Fuel 5 0.56 956 539 37822Fuel 6 0.62 649 400 21915NMHC Difference MethodVersion 2 (ppmC1)9Engine2 CH4/THC THC-FIDCH4FTIRNMHCAnalyticalPropagationErrorFuel 1 0.96 9517 9152 365264Fuel 2 0.98 4421 4338 83124Fuel 3 0.96 3297 3180 11792Fuel 4 0.97 6909 6725 184193Fuel 5 0.58 956 552 40422Fuel 6 0.63 649 410 23915NMHC %Relative Differencebetween Version 1 and Version 210Engine 2Version 1FID (THC),NMC (CH4)Version 2FID (THC),FTIR (CH4)% RelativeDifference|E1-E2|/(|E1+E2|*0.5)*100CH4/THCFuel 1-58 365 68.90.96Fuel 2-71 83 607.60.98Fuel 3-55 117 137.70.96Fuel 4-47 184 84.40.97Fuel 5378 404 1.60.58Fuel 6219 239 2.10.6311CNGDieselAnalyzerTargetError 5%Random Error Growthusing the Difference MethodCriticalPointSpeciated MethodNMHC or VOC12Others?Proposed Speciated Gas Listfor CNG-based Emissions13SpeciatedFTIRComponentCommentRFEPAPart1065.8452RFSAE3FID‐equivalentRFforFTIRMethane Neededasinterferentforanalysis1.05‐1.15EthaneNeededasinterferentforanalysisforVOCStandardNMHCComponent1 1Ethylene StandardVOCComponent0.950.95Acetylene StandardVOCComponent1.21.2Propane StandardVOCComponent11Propylene StandardVOCComponent0.950.95Butane StandardVOCComponent1OxygenatedHCFormaldehyde StandardVOCComponent0 0Acetaldehyde StandardVOCComponent0.5 0.5FormicAcid StandardVOCComponentNA 0Methanol StandardVOCComponent0.63 0.63AddedifNeededDuringQA/QC1,3‐ButadieneNotStandardVOC1Benzene NotStandardVOC0.90.9Octane SurrogateforheavyHCsifpresent1Toluene SurrogateforAromaticHCsifpresent0.90.9Difference FID Method for NMHCError Estimate14TypicalConc5% Overall Error(C1)THC1575 ppm C1 78.9 ppm C1CH41500 ppm C1 75.0 ppm C1NMHC75 ppm C1(78.92+752)± 108.9 ppm(C1)Rel Error = 145%FTIR Speciated Method for NMHCError EstimateTypicalConc5% ErrorInstrumentErrorEthane30.0 ppm C1 1.5 ppm C1 1 ppm C1Ethylene10.0 ppm C1 0.5 ppm C1 1 ppm C1Acetylene1.0 ppm C1 0.05 ppm C1 1 ppm C1Propylene1.5 ppm C1 0.08 ppm C1 3 ppm C1Propane3.0 ppm C1 0.15 ppm C1 3 ppm C1Butane(C4+ Surrogate)2.5 ppm C1 0.13 ppm C1 4 ppm C1NMHC48 ppm C1(1.52+0.52+0.052+0.082+0.152+0.132)± 1.59 ppm (C1)(12+12+12+32+32+42)± 5.9 ppm (C1)Rel Error = 12%15‐300‐200‐1000100200300400500

NMHC (ppmv C1)EngineTestNumberTHC‐CH4(FID/NMC)Speciated(FTIR)Difference Method 1 (NMC) vsSpeciated FTIR Method16CH4/THC ~50%CH4/THC >85%Difference Method Version 317EPA Alternate GC-Backflush vsSpeciated Method 320 FTIR18LargeStationaryEngineNMHC (C3)NMHC - FIDMethod 25A withGC back flushNMHC(C3)FTIR SpeciatedFID-correctedMethod 320VOC(C3)NMHC - FIDFTIR EthaneFID-correctedVOC(C3)FTIR SpeciatedFID-corrected#136.3 38.9 2.55.1#243.2 39.2 9.15.1#336.1 38.0 3.45.4#434.2 38.7 0.95.4#535.1 38.53.5 6.9Average37.0 38.7 3.9 5.6StDev3.20.42.70.7LATE BREAKING NEWSEPA Mobile Source Group§1065–Found this argument to bepersuasiveNew section added§1065.266–FTIR Speciation for CNG andLPG emissions–Dual Fuel blends using CNGor LPG can use FTIR inDifference Method–Added NMNEHC forcompliance19SpeciatedFTIRComponentCommentEthane StandardNMHCComponentonlyEthylene StandardVOCComponentAcetylene StandardVOCComponentPropane StandardVOCComponentPropylene StandardVOCComponentButane StandardVOCComponentOxygenatedHCFormaldehyde StandardVOCComponentAcetaldehyde StandardVOCComponentFormicAcid StandardVOCComponentMethanol StandardVOCComponentFTIR SPECIATIONCOMPARISON TOSTANDARD EMISSIONSBENCH ANALYZERS20Speciation of HydrocarbonsGenerally need Surrogate for higher HC species–Speciate up to C3 plus Butane, Octane for C5+Comparing FTIR to FID Analyzer–Need to convert number using FID correction–Excellent match with Natural Gas≤5%–Very good match with Diesel (5-10%)–Gasoline and Ethanol Blends – issues withunconverted oxygenated THC in FIDNMOG (non-methane organic gases)–FTIR provides accurate values for non-methaneorganic gases which FID can not analyze.21Diesel Emissions ComparingCH4-FID to CH4-FTIR01020304050160 180 200 220 240 260Time (s)

CH 4 (ppm)MKS MG2030MKS MG2030 HSHoriba 7000 (1 Hz)22Comparison of Time-ResolvedCH4 DataFTIR = 1.083*RM + 0.0022R2= 0.99640.00.20.40.60.80.0 0.2 0.4 0.6 0.8Regulation Method (g/mi)

FTIR Method (g/mi)23Comparison of Time-ResolvedCH4 Data – Fuel Type0.000.010.020.030.040.050.06 T 1 - E 1 0 T 2 - E 1 0 T 4 - E 1 0 T 5 - E 1 0

T 10 - E 10 T 1 4 - E 15 T 15 - E 15 T 17 - E 15 T 18 - E 15 T 19 - E 15 T 20 - E 15 T 6 - E 5 0 T 7 - E 5 0 T 11- E 5 0 T 12 - E 50 T 13 - E 50 T 21 - E 85 T 2 2 - E 85 T 23 - E 85 T 24 - E 85Test No. / Fuel Type

CH 4 (g/mi)BAG FIDFTIR24Diesel Emissions ComparingTHC-FID to THC-FTIR25050010001500200025003000350040000 100 200 300 400 500Time (s)

THC (ppmC)FTIR THCFTIR FID Equivalent THCFID THCFTIR Corrected versus FID -DieselComparison FTIR / FID0250500750100012501500175020000 250 500 750 1000 1250 1500 1750 2000THC FID (ppm)

THC FTIR (ppm)Diesel Set #1Diesel Set #2Diesel Set #3Parity26SummaryWhat is the Problem?–It is not with FID Analyzers–It is not with the FTIR – values are 10%or better compared to FID THC, CH4–The problem is the Difference MethodDifference Method–Method error increases as the CH4and C2H6content rises–Can get negative concentrations!–Using different versions of the Methodgive very different answers – cherrypicking results–For Quad J and Quad Z emissions CH4/THC is >50% - method does not workSpeciated Methods–Provides lowest uncertainty when CH4/THC is >50% in emissions–Accepted method for Engineand Vehicle certificationMKS Offers Free Training on FTIR to Regulators–April 2016 ASTM D6348 Hands On Method Training at MKS Office in Austin,TXWebinar broadcast at the same time–2015 presented two webinars on how to validate the MKS FTIR data in thefield and a review of FTIR in general. Presentations available upon request.–Willing to host more hands on training and webinars – just say the word.27