coal mill

coal mill

The medium-speed coal mill operates through a coal feeder that delivers coal into the mill's central chute. The coal falls onto rotating grinding bowls, where centrifugal force drives it toward the bowl's periphery. Three independently-loaded spring-loaded rollers are mounted at 120-degree intervals on the bowl's upper section, maintaining a controlled gap to prevent direct contact. These rollers apply grinding pressure via spring mechanisms, pulverizing coal as it passes through the bowl. The rotating grinding components then eject the pulverized coal into the air ring chamber, where hot air carries it to the upper coal separator. Coarse particles are separated and regrind, while the hot air simultaneously dries the coal. During this process, small fragments of rocks and metal debris from the raw coal are also ejected into the air ring chamber, eventually falling into a debris bin for periodic removal.

The HP coal mill consists of the following components:

1. The motor drives the gearbox, which is directly connected to the grinding bowl. The gearbox consists of planetary gears with an appropriate reduction ratio to achieve the required rotational speed of the grinding bowl. The following figure shows the KMP series gearbox:

2. The side body is equipped with a liner plate, which forms an air inlet around the grinding bowl and serves as a support for the separator body. The hot air used for drying and conveying coal powder is introduced through the air inlet and rises along the periphery of the grinding bowl.

3. The coal is ground into powder on the grinding bowl driven by the gearbox.

4. The impeller is installed on the outer circumference of the grinding bowl, which can make the hot air passing through the annular gap between the outer diameter of the grinding bowl and the separator body be evenly distributed, thus controlling the air-powder mixture in the grinding area of the coal mill.

5. Three separate spring-loaded or hydraulic-loaded grinding rollers are suspended inside the separator, positioned above the grinding bowl. When the raw coal fills the gap between the grinding rollers and the grinding bowl, the rollers can rotate freely.

6. The separator body, guide liner, separator top cover equipped with deflector device and inner cone, and the separator itself. These components contain pulverized coal and guide the air-pulverized mixture upward, where the deflector device separates coarser coal particles from the airflow, allowing them to fall back into the grinding bowl for further pulverization.

7. The Venturi and porous outlet devices distribute the coal powder and airflow into four uniform streams.