TGA AND DROP-TUBE REACTOR STUDIES OF THE COMBUSTION OF COAL BLENDS

The combustion behaviour of blends of coals of different rank was stud ied with a thermogravimetric analyser (t.g.a.) and a drop-tube reactor (DTR). T.g.a. reactivities at constant temperature were determined in air at 1 atm and 450-degrees-C. The reactivities of the blends were p redictable from the reactivities of the individual coals. Characterist ic temperatures were determined from the t.g.a. burning profiles. The temperature corresponding to the maximum reactivity and the burnout te mperature of a coal did not change when it was blended with another co al. However, the initial temperature decreased linearly with an increa se in the content of the more reactive coal in the blend. Combustion e fficiencies in the drop-tube reactor were determined at 900-degrees-C and 25% air excess. Combustion efficiencies of the blends were linearl y predictable from the combustion efficiencies of the individual coals in the blends. In summary, blending of high- and low-rank coals did n ot affect the combustion behaviour of the component coals in the t.g.a . or DTR.