1. 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

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 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

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

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

7. 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

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-NT
David Wagner, Ryan Okerlund, Brian Nelson, Rafael Erickson, and Colby Ashcroft Institute for Clean and Secure Energy, University of Utah