Comparison of experimental methods for determining coal particle devolatilization times under fluidized bed combustor conditions

Abstract

Numerous studies have measured the devolatilization times of coal particles ‘under fluidized bed conditions’, either in a hot fluidized bed or by holding the particle(s) stationary in a hot reactor. Here, two fluidized bed methods and one stationary particle method were compared, using the same three coal samples. Devolatilization times and fragmentation were studied. A new devolatilization endpoint definition from CO 2 evolution profiles gave good agreement with flame extinction time measurements, so either of these methods may be used in fluidized bed experiments to measure devolatilization time. The different environment around the coal particle in thermogravimetric experiments gave substantially longer devolatilization times, so the results from stationary particle experiments are not relevant to fluidized bed combustion. Coal particle fragmentation behaviour differed for the three coals studied, but no effect of coal properties on the devolatilization time in fluidized beds was observed, and an earlier correlation fitted these results well.