Combustion of coal—water slurries: Evolution of particle size distribution for coals of different rank

Abstract

The effect of coal rank on pulverized coal and coal—water slurry combustion was examined in a laboratory laminar flow reactor. Two coals were used: a low-rank lignite with high mineral matter content and a high-rank bituminous coal with low mineral matter content. The evolution of the particle size distribution of these two coals in both dry and slurry form during combustion was measured with an in situ optical particle counter. Samples were also collected after different combustion durations and were examined with a scanning electron microscope. The results indicate that the coal slurry atomization process affects the particle size distribution, but inherent coal properties associated with coal rank do not significantly affect the initial and early combustion behaviour of the pulverized coal or coal—water slurry. During char oxidation, the ash constituent of the coal dominates the small particle size distribution, while the behaviour of the large particle size distribution and agglomerates depends on the coal rank.