Mechanisms of ash liberation from included mineral matter during pulverised coal combustion

The float fraction (specific gravity of 2.0) of +63-90 μm bituminous coal sample was combusted in air in a drop tube furnace (DTF) at a gas temperature of 1300 degreesC. The data demonstrated that the char structure determines the ash formation at various burnoff levels. Char fragmentation was shown to be the determinative mechanism for fine ash formed at the early and middle combustion stages of char while coalescence of included mineral matter determines the formation of coarse ash in the later combustion stages. This study confirms that the char structure plays a key role in determining the ash liberation during pulverised coal combustion.