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

The combustion behaviour of blends of coals of different rank was studied 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 predictable from the reactivities of the individual coals. Characteristic temperatures were determined from the t.g.a. burning profiles. The temperature corresponding to the maximum reactivity and the burnout temperature of a coal did not change when it was blended with another coal. However, the initial temperature decreased linearly with an increase in the content of the more reactive coal in the blend. Combustion efficiencies in the drop-tube reactor were determined at 900-degrees-C and 25% air excess. Combustion efficiencies of the blends were linearly predictable from the combustion efficiencies of the individual coals in the blends. In summary, blending of high- and low-rank coals did not affect the combustion behaviour of the component coals in the t.g.a. or DTR.