Controller for powdered coal mfg. plant - uses hot air to dry coal in ball mill, and for pneumatic conveying of powdered coal, under constant pressure

摘要

The plant includes a ball mill, which is fed with crude coal and hot air so the coal is both milled and dried. A stream of air then carries the powdered coal up a pipe to a separator which returns coarse powder to the mill. The fines are carried by the air to cyclone separators in order that the air is sepd. from the powdered coal. The air then flows through a return pipe towards the bottom end of pipe. The difference in pressure between the mill outlet and pipe is kept below a standard value; and the pressure in pipe is kept constant. The temp. in the mill is pref. kept at max. 80-85 deg.C. Numerous swivel shutters are pref. used for air pressure control. Powdered coal with a constant grain size and a constant residual moisture content, can be made at a constant rate of production. Coal leaving a magnetic separator is fed by a conveyer belt into bunker and then by a chain conveyor and inlet into a ball mill supplied with hot air by a generator. The air carries the dried and milled coal up pipe to a static separator, allowing the coarse coal to be recycled to inlet.