Fluidized bed combustion of wet brown coal

Abstract

Abstract The behaviour of very wet Victorian brown coal was examined in a bed of sand fluidized, at temperatures around 1000 K, with either air or nitrogen. Small batches of coal with a narrow particle size range were added to the 76 mm diameter bed and the times required for devolatilization and total combustion were recorded. Changes in particle water content, volatiles level and particle size distribution were also measured. All the particles tested, up to 8.4 mm in diameter, dried rapidly and remained substantially intact throughout carbonization and combustion. Devolatilization was complete after about 60 s but extensive freeboard combustion of volatiles was evident. The water content of the coal had very little influence on burnout time. Char combustion dominated the overall combustion process and took place under kinetic control with significant pore burning.