Overcoming ash deposition: A case study. Part 1: Measurements and modeling -- The research perspective
- Univ. of North Dakota, Grand Forks, ND (United States). Energy and Environmental Research Center
- Montana-Dakota Utilities Co., Beulah, ND (United States)
- Knife River Coal Mining Co., Bismarck, ND (United States)
Coyote Station of Montana Dakota Utilities was experiencing increasingly severe ash slagging and fouling in its 425-MW cyclone boiler while burning a Beulah lignite coal from three seams of the adjoining Knife River Coal Mining Company Beulah Mine. A dual approach of assessing coal quality and examining plant operating characteristics was implemented to formulate mine-planning, coal-blending, and boiler-operating strategies to mitigate the slagging and fouling. Advanced coal analyses were performed on core samples in advance of the active mining operation for the three mine seams. Concurrently, a boiler inspection protocol was implemented by the plant personnel to quantitatively track the progress of ash deposition. A field test at Coyote Station was conducted to obtain furnace gas temperatures, ash deposit samples, and crucial operating data. Other valuable information was obtained by correlation of day-to-day mining records with plant operating data over a several-month period. Initial examination of coal loadout records prior to fouling-related outages suggested possible mine areas with significant fouling potential. This was supported by PCQUEST fireside performance modeling and by equilibrium thermodynamic calculations of ash viscosity, with sodium calcium silicates and sulfates the main contributors to problematic deposition. Correlations of the PCQUEST slagging and fouling index values were developed for this specific coal and mine to provide indicators of coal quality based on standard American Society for Testing and Materials (ASTM) analysis parameters. This allowed data from a large number of previous core samples to be used to map coal fouling and slagging potential on a minewide basis. Two areas of high-fouling coal were discovered across the lateral extent of the mine. In the vertical section, the top coal seam revealed much lower fouling propensity than the lower two seams. The same correlations also permitted assessment of the fouling and slagging potential of the coal delivered to the plant on a daily basis. Significant influxes of coal with high fouling potential were found to correlate with quantified observed increases in degree of boiler fouling. A coal quality and blending program was developed to assess coal quality based on standard ASTM analysis parameters and to assist in determining optimum blending proportions for the accessible coal seams in Beulah Mine. An analogous version of the program was developed for Coyote Station to assess coal quality based on daily coal analyses. The utility and mine are currently using the coal program to mitigate ash deposition and save costs in power production.
- OSTI ID:
- 349096
- Report Number(s):
- CONF-980985-; ISBN 1-890977-15-2; TRN: IM9924%%96
- Resource Relation:
- Conference: 15. annual international Pittsburgh coal conference, Pittsburgh, PA (United States), 14-18 Sep 1998; Other Information: PBD: 1998; Related Information: Is Part Of Fifteenth annual international Pittsburgh coal conference: Proceedings; PB: [1500] p.
- Country of Publication:
- United States
- Language:
- English
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