Primary fragmentation of coal particles at high heating rate

The present work reports a study of primary fragmentation of coals under a wide range of temperatures, starting from those typical of fluidised bed combustion (800-900 degrees C) up to more severe temperatures typical of pulverised combustion (1400 degrees C). Fast heating conditions have been achieved in an inert atmosphere using an heated strip reactor with heating rate of 10(5)degrees C/min.

Attrition phenomena during combustion of solid fuels in fluidised beds has been the object of extensive research in the past (Beer 1987, Scala et al 2006, Dakic ct al 1986), It was demonstrated, in fact, that attrition influences the fuel particle size distribution and ultimately the overall carbon conversion efficiency. Attrition phenomena include primary fragmentation of fuel particles during devolatilization, char particles attrition by abrasion and secondary percolative fragmentation. Primary fragmentation is that occurring immediately after the injection of the solid particles in the bed and is caused by thermal stresses as well as by internal overpressures associated with volatiles release. It is likely that primary fragmentation plays an important role not only in fluidised beds, but also in other applications characterised by high temperature and high heating rates such as in Pulverized combustion, in coal-water combustion, in oxy-fuel combustion.