GB244575A - Improvements relating to the pulverising and drying of materials - Google Patents

Abstract

244,575. Imray, O. Y., (International Combustion Engineering Corporation). Nov. 28, 1924. Gaseous currents, materials carried by.-A pulverizer mill having a reservoir in which the material is in agitation is used as a drier by operating the mill on the "in-circuit" system and either continuously or periodically withdrawing a portion of the air or gases in circulation, or periodically withdrawing the whole of such air or gases, fresh air or gases being admitted to take the place of that withdrawn. The air or gases are introduced into the system at a point close to that at which the air or gases are withdrawn. If an impact mill is used, it is provided with a chamber containing an agitator placed in the path of the air or gases where these enter the mill. The invention is particularly applicable to pulverizing fuel in that system of firing in which the powdered fuel is conveyed in suspension in air or gases directly from the collecting hopper of the mill to the furnace. The coal is fed to the mill a from a bin b, and a fan c withdraws air from the mill and delivers it to a cyclone separator d, the separated coal dust falling into a bin e and the air returning by a pipe f to the mill. The fan g which usually takes in air and delivers it charged with dust supplied by a rotary feeder h from the bin e to a furnace through a pipe i has its intake connected by a pipe k with the return air pipe f, which is connected by a pipe l with the source of hot combustion air supplied to the furnace so that a portion of the return air is continuously withdrawn from the system while a corresponding quantity of hot air is drawn into the system. Air-admission valves m, n are provided in the pipes k, l, and a control valve o in the pipe l.