An Experimental Investigation into the Fragmentation of Coal Particles in a Fluidized-Bed Combustor

Abstract

The fragmentation of coal plays a significant role in combustion in fluidized-bed boilers because it accelerates combustion and influences the distribution of particle sizes in the bed. Fine char particles produced by comminution can be carried out and increase the heat loss due to incomplete carbon conversion. The thermal fragmentation depends on the initial structure of the coal and how this structure changes with an increase in temperature when the particle is dropped into the combustion chamber. Experinments with nine Polish coals were carried out to quantify the fragmentation of burning coal particles. A bench-scale bubbling fluidized bed combustor was used to determine the degree of fragmentation for spherical coal particles during devolatilization and combustion. The effects of bed temperature, particle size and coal properties on the extent of primary and secondary fragmentation have been determined. It has been found that the combination of low porosity and high volatile content is the main factor responsible for the observed extent of fragmentation.