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 Salt Lake City, Utah November 7-12, 2010

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

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.

Coal Analysis (on an as-received basis) Coal Chemistry Coal Analysis (on an as-received basis) Sample LOD Ash C H N S O (diff) Volatile Matter Fixed Carbon HHV BTU/lb % PRB 23.69 4.94 53.72 6.22 0.78 0.23 34.11 33.36 38.01 9078 Illinois 9.65 7.99 64.67 5.59 1.12 3.98 16.65 36.78 45.58 11598 Ash Analysis Al as Al2O3 Ca as CaO Fe as Fe2O3 Mg as MgO Mn as MnO P as P2O5 K as K2O Si as SiO2 Na as Na2O as SO3 Ti As TiO2 14.78 22.19 5.2 5.17 0.01 1.07 0.35 30.46 1.94 8.83 1.3 17.66 1.87 14.57 0.98 0.02 0.11 2.26 49.28 1.51 2.22 0.85

Coal Firing Rates and Combustion Conditions Coal feed rate (kg/h) Coal firing rate (kW) 36.64 PRB 6.26 Illinois Bituminous 4.89

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

Laboratory Combustor Sampling port Maximum capacity: 100 kW Primary Coal feeder 3.8 m Secondary 1.2 m Heat exchanger #1 - 8 Flue gas 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

Particle Size Distribution

Particle Size Distribution

Black Carbon (Soot) Emission by Photoacoustic Analysis

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.

Illinois Ash Composition by ICP-MS

PRB Ash Composition by ICP-MS

Comparison of Iron Emissions

Comparison of Calcium Emissions

Comparison of Sodium Emissions

Comparison of Arsenic Emissions

Ignition Loss

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.

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.

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.

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