Fragmentation and swelling of various coals during devolatilization in a fluidized bed

The combustion rate of large coal particles in a fluidized bed is to a large extent controlled by the external diffusion. This rate will depend on the particle diameter. There are several processes that affect this diameter: the combustion process itself; attrition; fragmentation; and swelling. The last two processes can cause large diameter changes in a relatively short period, mainly during devolatilization. The experiments reported in this paper are aimed at finding a simple relationship between some properties of the parent coal particles, and the fragmentation and swelling during devolatilization.