PelletAshCompositionanditsPotentialEffectsonStoveandBoilerPerformanceandtheEnvironmentR.W.RiceUniversityofMaineIncreasingComplaintsaboutSinter,SlagandClinkersinBiomassBurner/boilerSystemsIncreasingconcernsaboutparticulateandcriteriagaspollutantsCombustionofWoodCloseupofCoalVolatilesandChar:WhereistheFuelValue?Coal WoodShouldavolatilestestberequiredaspartofthepelletfuelsstandards?Pollution,ParticulatesandAshfromBiomassBurningStoves,FurnacesandAppliancesGasParticlesCombustionAerosolsGassesfromcombustionincludingtarsFlyashFineashBottomAshPollution,AgglomerationandAshfromBiomassBurningIIFunctionof:•ChemicalCompositionoffuel•Temperature•Burnerdesigncharacteristics(airflow)•Moisturecontent•CombustionTime•Other...ParticulateSizesReleasedinCombustionSmallBurnerSystemsAdaptedfrom:http://www.dustconf.com/CLIENT/DUSTCONF/UPLOAD/S4/EHRLICH_.PDFStove burning: Mean Particulates PM10 PM2.5 PM1.0mg/cubic meter % % %Hardwood logs 83 98.6 93 81.9Softwood logs 82.5 99.2 97.6 94.1Pellets (clean) 21 99 95.3 92.9SlaggingPotentialofBottomAsh:BurnerCharacteristicsSource:Ohman etal,2004PureWoodForestResiduesBarkIfthewood/pellet/coaletc.wasbonedrywhenfired,wouldtherestillbeflyash?BottomAshTemperaturesTheagglomerationofashparticlesasaresultofincreasedtemperatureexposure.A– Ashsampleat525°C.B– Ashsampleat1025°C.Soot:BurnerDesignandCompositionThelignincontentofbiomasstendstoincreasetheamountofsoot.•Hardwoodlignincontent,onaverage:28%byweight•Softwoodlignincontent,onaverage:20%byweightCompositionoftheFuelandCombustionTheFormationofPollutantsfromBiomassandPelletFuelsCreosoteHEARTH.COMARTICLESTheDynamicsofPollutionfromwood,biomassandfuelpelletsFuelspeciescharacteristicsAirflowdynamicsofstoveorfurnaceProductsformedbyreactions:NO,NO2,N2O,HCl etcVapors(aerosols):potassium,sodium,etcsalts.(inorganic)Unburnedfuelduetopoormixingandairflowdynamics:smoke,PAH,CO,VOC’sAdaptedfromWilliams,etal,2012andBryers,1996ParticleSizeandPollution:MCandTemperatureTheComponentsofPureWoodAsh:EuropeantoEasternUS(Percentofash)Oxide European EasternUSAl2O3 6.76 3.63CaO 28.9 33.1Fe2O3 5.12 2.68K2O 13.2 16.34MgO 5.4 6.78MnO 2.77 2.34Na2O 1.42 2.05P2O5 2.64 3.52SO3 2.67 2.65SiO2 31.6 18.67WhereistheClandN?LevelsofClandNinBiofuelsObernberger etal2006Importance•CaandMgnormallyincreasethemeltingtemperatureofashes.•KandNadecreasethemeltingpointofashesleadingto“stickiness”•SiandCaformlargeportionsofbottomash/clinkersandflyashparticulatesSlagandClinkerFormationLargeparticlescontainingCa,Si,Mg,Mn,K,Al,VaporsAerosolsandfineparticulates,mostlyCaONa,K,S,Cl,SOx andSO2,CO,CO2heavymetalsKCl,K2SO4,NacompoundsMeltingandCondensation,“Stickiness”NucleationandCondensation,“Stickiness”Agglomeration/sinter/slagAgglomeration/sinterSOx andSO2,CO,CO2etcWhereisthePotassium?ComparisonofcompositionbeforeashingWerkelin etalFuel89(2010)481–493Species %WoodSpruce 0.0215Pine 0.0407Birch 0.0315Aspen 0.137BarkSpruce 0.203Pine 0.318Birch 0.171Aspen 0.473TwigsSpruce 0.356Pine 0.304Birch 0.302Aspen 0.587NeedlesSpruce 0.427Pine 0.47700.10.20.30.40.5Wood Bark Twigs Needles

Percent K in CategorySpruceOneSpecificCase:BottomandAgglomeratedAshElementPellet AshFly AshNormalized %Ca54% 31%K30% 53%Mg5% 3%Na0% 1%S2% 7%Si3% ----BottomAshDepletion:OxideLossesOnHeating0.0000.1000.2000.3000.4000.5000.600525°C 825°C 1025°C

Oxide/CaOMixedHardwoodPelletAshCAl2O3Fe2O3K2OMgOMnONa2OP2O5ZnOSO3SiO2BottomAshDepletion:OxideLossesOnHeating0.0000.1000.2000.3000.4000.5000.6000.7000.800525°C 825°C 1025°C

Oxide/CaOPineBottonAshCAl2O3CuOFe2O3K2OMgOMnONa2OP2O5ZnOSO3SiO2OxideLossesOnHeating0.0000.1000.2000.3000.4000.5000.6000.700525°C 825°C 1025°C

Oxide/CaOPineBottonAshCK2O0.0000.1000.2000.3000.4000.5000.600525°C 825°C 1025°C

Oxide/CaOMixedHardwoodPelletAshCK2OFlyAshComposition:AerosolAshFraction8.3μmAshFractionSource:Chenevert,1998ThankYou