Emissions Characterization of Three High Efficiency Wood Boilers James Laing, Sriraam Ramanathan Chandrasekaran, Suresh Raja, Thomas Holsen, Philip K. Hopke Center for Air Resources Engineering and Science, Clarkson University, Potsdam, NY 13699 Woody Biomass Energy Research Symposium University of Vermont, Burlington, VT, April 2830, 2011
Outline Study Objectives Boiler Description Sampling system Demonstrate near complete combustion Effect of Fuel Quality on Emissions PM chemical characterization Conclusions
Objectives of this study Demonstrate high efficiency, low emission European biomass combustion technology in the US Determine emissions dependence on fuel quality and fuel load Chemically characterize fine particulate matter (PM2.5)
Boilers Studied Advanced Climate Technologies, LLC, Schenectady, NY Two 150kW (514,000 Btu/hr) Output Boilers (Clarkson University, ACT facilities) 500kw (1.7 MM Btu/hr) Output (Wild Center, Tupper Lake)
Boiler Technology Air staging technology for near-complete combustion tertiary zone λ > 1 secondary zone λ > 1 primary zone λ < 1 fuel augur ash removal augurs
Sampling System Dilution Chamber Hot Box Sampling Ports Lipsky & Robinson (2006) HEPA filtered dilution air Heated Probe
Complete Combustion? Complete Combustion of Hydrocarbons CH 4 + 2O 2 CO 2 + 2H 2 O CO concentrations variable for Wild Center boiler because it was not running at steady state Concnetration [mg/mj] 2000 1500 1000 500 0 Wood Pellets Wood Chips Wild Center
Complete Combustion? Low CO concentrations when running at steady-state Low OC fraction of PM 2.5 Most of the carbon in the fuel fully oxidized to CO 2 OC EC Na + K + Ca + Mg + SO 4 2- Cl - NO 3- Zn Unresolved
Fuel composition Fuel composition can lead to higher emissions of criteria pollutants NO x, SO 2, PM 2.5 Fuel Property Wood Pellets (Walker) 150 kw Wood Chips (ACT Bioenergy) Curran Pellets (Wild Center) 500 kw 150 kw Heat Content (MJ/lbs) 8047 6369 8060 Moisture (%) 4.8 27 5.1 Ash (d.w. %) 0.6 1.79 0.6 Carbon (d.w. %) 51.5 45 48.74 Nitrogen (d.w. %) 0.13 0.37 0.15 Sulfur (d.w. ppm) 70.1 175 67.1
Wild Center Wood Chips Wood Pellets 160 140 120 100 80 60 40 20 0 NO x Concnetration [mg/mj]
Wild Center Wood Chips Wood Pellets 2.0 1.5 1.0 0.5 0.0 SO 2 Concnetration [mg/mj]
Wild Center Wood Chips Wood Pellets 60 50 40 30 20 10 0 PM 2.5 Concnetration [mg/mj]
Fine Particle Formation Organic Particles Condensation and/or nucleation of organic vapors Dependent on fuel quality Inorganic Particles Condensation of alkali chlorides Fine Particles (soot, alkali salts, organic matter) Dependent on Combustion Soot Oxidation and burn out Agglomeration Coagulation and condensation Surface growth and coagulation Formation of core particles Formation of primary soot particles Nucleation and condensation of alkali sulfates and Zinc Formation of Soot nuclei Oxidation and sulfation Vaporization (K, Na, S, Cl, Zn) PAH formation and polymerization Lightly et al. 2000, Tissari et al. 2008
Complete/Incomplete combustion Incomplete mostly Organic Carbon Complete mostly inorganic salts Toxicity depends on combustion conditions* Certain organic compounds (such as PAHs) are carcinogens or mutagens *Bölling 2009; Klippel & Nussbaumer 2007
Fine PM Chemical Composition from Wood Pellets 100 80 Unresolved Cl - (0.44%) w t.% of PM 2.5 60 40 SO 4 - NO 3 - (0.49%) 20 0 K + OC Na + (0.18%) Zn (0.15%)
Ultrafine Particle Number Size Distribution 2e+81.4e+8 3e+9 Start-up & Steady-state dn/dlogdp [#/cm 3 ] dn/dlogdp [#/cm 3 ] 1.2e+8 2e+8 1.0e+8 1e+8 8.0e+7 6.0e+7 4.0e+7 5e+7 2.0e+7 Start-up Steady State Shutdown Wood Chips Wood Pellets A Wild Center 3e+9 2e+9 2e+9 1e+9 5e+8 Shut-down dn/dlogdp [#/cm 3 ] 0 0.0 0 1 1 10 10 100 100 1000 1000 Electrical Electrical Mobility Mobility Diameter Diameter [nm] [nm]
Trace Metals Trace metals - 0.32 wt.% PM 2.5 Particle surface enriched with trace elements* Health implications due to higher bioavailability Cd, Pb, Tl, and Zn were enriched in fine PM (recoveries >30%) Element Al Ba Cd Co Cr Cu Li Mg Recovery in PM 2.5 (wt. %) <0.99 0.23 136 <13.2 2.73 15.4 9.61 0.04 Element Mn Ni Pb Rb Tl V Zn Recovery in PM 2.5 (wt. %) 0.46 <23.7 66.8 28.0 167 2.96 36.3 *Lightly 2000
Conclusions Advanced Climate Technologies Boilers demonstrated emission factors equivalent to the leading biomass combustion technology in Europe Emissions dependent on fuel High N in fuel higher NO x emissions High S in fuel higher SO 2 emissions More inorganic material in fuel (ash) higher PM2.5 emissions During near-complete combustion particulate matter mostly inorganic salts
Summary Advanced combustion technology can reduce CO and organic particle matter emissions Technology alone can t reduce emissions High quality fuel is necessary to further reduce SO 2, NO x, and inorganic PM emissions
Acknowledgments This study was funded by the New York State Energy Research and Development Authority (NYSERDA) under contract 10672 We want to thank David Dungate of ACT Bioenergy for his assistance in these studies 20
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