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2010 AIChE Annual Meeting Salt Lake City, Utah November 7-12, 2010

A Comparison of Particle Size Distribution, Composition, and Combustion Efficiency as a Function of Coal Composition. William J. Morris Dunxi Yu Jost O. L. Wendt Department of Chemical Engineering University of Utah, Salt Lake City, UT 84112. 2010 AIChE Annual Meeting

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2010 AIChE Annual Meeting Salt Lake City, Utah November 7-12, 2010

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  1. A Comparison of Particle Size Distribution, Composition, and Combustion Efficiency as a Function of Coal Composition William J.Morris Dunxi Yu Jost O. L. Wendt Department of Chemical Engineering University of Utah, Salt Lake City, UT 84112 2010 AIChE Annual Meeting Salt Lake City, Utah November 7-12, 2010

  2. Outline • Objectives • Coals examined • Furnace, sampling, and analysis • Particle Size Distribution • Soot Emissions • Chemical Composition • Loss on Ignition • Discussion • Conclusions

  3. Objectives • Provide a comparison of two different coal aerosols for use in deciding whether fuel switching is the best alternative for meeting EPA’s interstate sulfur emissions targets. • Examine aerosol emissions. • Use aerosol chemistry to provide information for those who wish to make predictions of fouling/slagging within the furnace. • Examine coal burnout performance when switching coals in a given furnace.

  4. Coal Chemistry

  5. Coal Firing Rates and Combustion Conditions

  6. Sampling Systems Bulk Ash Sampling (LOI) Black Carbon and PSD sampling

  7. Coal feeder Primary Flue gas Secondary 1.2 m 3.8 m Heat exchanger #1 - 8 Laboratory Combustor • Maximum capacity: 100 kW • Representative of full scale units: • Self sustaining combustion • Similar residence times and temperatures • Similar particle and flue gas species concentrations • Allows systematic variation of operational parameters Sampling port

  8. Particle Size Distribution

  9. Particle Size Distribution

  10. Black Carbon (Soot) Emission by Photoacoustic Analysis

  11. Ultrafine and BC Comparison Note that the ultrafine concentration and black carbon concentration of both coals show correlating trends. For the PRB coal, the ultrafine tracks the black carbon, while the Illinois black carbon mirrors the ultrafine concentrations. Here ultrafines are defined as particles with an aerodynamic diameter of ~15-650nm.

  12. Illinois Ash Composition by ICP-MS

  13. PRB Ash Composition by ICP-MS

  14. Comparison of Iron Emissions

  15. Comparison of Calcium Emissions

  16. Comparison of Sodium Emissions

  17. Comparison of Arsenic Emissions

  18. Ignition Loss

  19. Ignition Loss The PRB ignition loss begins to rise again at higher S.R. The Illinois coal ignition loss is reduced as S.R. increases.

  20. Discussion • Sulfur emissions are obviously reduced when switching from Illinois to PRB coal due to coal chemistry. • Black Carbon, or soot emissions are reduced using the higher rank Illinois coal, which is an important consideration due to black carbon aerosol’s effects on climate change as well as having significant health effects. • Residence time is important in ignition loss effects, and is likely responsible for the increased LOI at high S.R. for the PRB coal. Since more mass of PRB coal has to be fired to generate the same heat value, residence time in the furnace is decreased. • Iron emissions are very similar between the two coals. However, the PRB coal produces much more Na and Ca emissions which provide a sticky surface for Fe particles to attach to on boiler tubes thus affecting slagging and deposition within the furnace. • Arsenic emissions are much higher for the Illinois coal than the PRB coal, indicating there may be some health effects benefits from blending or switching to PRB coals.

  21. Conclusions • The high sulfur Illinois coal reduced black carbon emissions. • The PRB coal, known for high burnout, may not achieve optimum combustion completion in a furnace designed for Illinois coal due to the increased mass feed rate. • Ultrafine particle concentration is heavily dependent upon soot, and is also influenced by sulfates and mineral matter. • Future regulation of soot and black carbon aerosols may present conflicting solutions for current scheduled SO2 emission regulations.

  22. Acknowledgements • Financial support from the Department of Energy under Awards DE-FC26-06NT42808 and DE-FC08-NT0005015 • David Wagner, Ryan Okerlund, Brian Nelson, Rafael Erickson, and Colby Ashcroft Institute for Clean and Secure Energy, University of Utah

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