Combustion Reactivity of Smoky River Coal Mine By-Products

H. R. Milner Generating Station of Alberta Power Limited (145-MW capacity, down-shut firing mechanism of Combustion Engineering Ltd.) utilizes the by-products of the Smoky River coal (low-volatile bituminous) mine. These by-products are composed of run-of-mine, tailings, and rejects. High-ash, low-volatile matter content and low char combustion reactivity cause low carbon burnout and low flame stability, and high auxiliary fuel consumption. To improve combustion efficiency of the generating station, combustion reactivity tests were conducted using a thermo-gravimetric analyzer and a laminar drop tube reactor. In addition, the microscopic characteristics of the coal, bottom ash, and fly ash were also studied. Some of the chars formed from vitrinite, causing low combustion reactivity. Particle size, gas temperature, and oxygen partial pressure have an effect on the apparent rate of coal combustion. Char combustion rate is controlled by oxygen diffusion. Combustion efficiency could be improved by increasing turbulence intensity in the furnace, by blending the coal with a more reactive fuel, or by reducing the ash content of the coal.