Study of the Mineral Matter Distribution in Pulverized Fuel Coals with Respect to Slag Deposit Formation in Boiler Furnaces: Phase 1. Interim Report, April-June 1978

摘要

Four samples of H.V. bituminous (Upper Freeport, PA), bituminous(Ill. No. 6), sub-bituminous (School, WY) and lignite (Wilcox, TX) coals were subjected to quantitative emission spectrometric analysis. Two different techniques to analyze coal particles on polished sections using the SEM under computer control are in progress. The furnace characterization tests at 39.3kW (10 lbs/hr) at 10% fuel-rich, stoichiometric and 10% excess air conditions showed flat temperature profiles and peak wall temperatures ranging from 1220 exp 0 C to 1330 exp 0 C. The gas temperatures are about 180 exp 0 C higher than the wall temperatures in the maximum region of the lower portion of the furnace. Ash balance tests showed that the estimated percentage distribution of the ash and slag was approximately 16 to 27% collected at the furnace base, approx. 0.3 to 2.5% leaving as fly ash in the flue gas and approx. 73 to 82% as wall slag. The probe surface of a newly constructed water-cooled, slag deposition probe could be controlled with 5 to 15 exp 0 C in the temperature range of 200 to 600 exp 0 C, while in the furnace. The sticking behavior of ash pellets from four coals was tested on a mild steel substrate. The sticking temperatures ranged from 430 to 500 exp 0 C and adhesion strengths from 50 to 5000 g/cm exp 2 at 600 exp 0 C. Various tests using pellets made of a synthetic mixture of powdered mineral matter showed no effect of the particle size of the material making up the pellet and no effect of the height of fall of the drop to the substrate on adhesion force. It was observed, however, that a larger pellet give a lower sticking temperature and higher adhesion forces. (ERA citation 04:052498)