Pyrolysis Behavior of Large Coal Particles in a Lab-Scale Bubbling Fluidized Bed

Abstract

The results of pyrolysis of coal particles with size ranging from 2 to 14 mm in a bubbling fluidized bed are presented in this paper. The investigation is focused on the effect of the coal particle size and pyrolysis temperature on the product distribution and devolatilization time. Fragmentation of coal particles was observed during pyrolysis. It is found that the extent of fragmentation is more serious for larger coal particles at high temperatures. This leads to a quite different variation trend of the yields of pyrolysis products with temperature between the small and large particles examined in this work. No significant effect of the particle size was noticed at low temperatures because the secondary reaction is not active. The devolatilization times of the coal particles tested in this work can be described with the classic particle size power law relation: t = Ad(p)(n). However, the value for the exponent n is much smaller than those obtained by previous researchers, which could be attributed to the fragmentation of coal particles and relative low fluidization velocity employed in this work.