THE EVOLUTION OF MINERAL PARTICLE-SIZE DISTRIBUTIONS DURING EARLY STAGES OF COAL COMBUSTION

Data are presented which illustrate the evolution of the particle size distribution (psd) of included mineral grains in coal particles during coal particle heatup and the early stages of combustion. The data indicate that pyrite fragments during its thermal decomposition to form pyrrhotite and oxides of iron. Two to three fragments are formed per original pyrite particle. The mineral psd for silica also significantly changes in the early residence time. The data indicate the production of many small particles, with diameters approximately 4-5 times smaller than the original particles. These results indicate that the original mineral grain size distribution in the coal is not a reliable indicator of the grain size distributions in the resultant char. © 1990.