The pulverizer shown in Fig:1 has grinding elements consisting of stationary rollers and a power-driven bowl in which pulverization takes place as the coal passes between the sides of the bowl and the rollers. A primary air fan draws a stream of heated air though the mill,carrying the fine particles of coal into a two-stage classifier located on the top of the pulverizer. The vanes of the classifier return the coarse particles of coal through the center cone to the bowl for further grinding, while the coal that has been pulverized to the desired fineness passes out of the mill, through the fan, and into the burner lines. The automatic control changes the supply of coal to the bowl of the mill by adiusting the feeder speed and the flow of primary air by regulating a damper in the line from the pulverizer to the fan. This arrangement of primary air fan has the advantage of having a cleaner facility because the mill is under suction rather than being pressurized, thereby eliminating coal leakage. However, the fan now must handle a coal-air mixture and, therefore, its design must incorporate additional preventivewear features to offset the erosion caused by the coal-air mixture.
Pulverized coal may be radily transported through a pipe by means of a high-velocity stream of air, but the coal will not be equally distributed through the cross section of the pipe. This causes difficulty when two burners are supplied from one pulverizer mill.the distributor (Fig.2) divides the cross section of the main pipe into several narrow strips. The mixture of pulverized coal and air that enters these strips is directed into the two burner pipes in order to obtain equal amounts of coal to the burners.
Bowl-type Pulverizer
留言列表
