Abrasion is another important principle in lignite grinding.

Abrasion is another important principle in lignite grinding. Machines like ball mills and certain types of grinding wheels rely on abrasive materials to wear away the surface of the lignite. In a ball mill, grinding media such as steel balls or ceramic balls are placed inside a rotating cylindrical shell along with the lignite. As the shell rotates, the balls are lifted and then cascade down, striking the lignite.

The continuous impact and rolling action of the balls against the lignite surface cause abrasion. The rough surfaces of the balls scrape and chip away at the lignite, gradually reducing its particle size. The size and hardness of the grinding media, along with the rotational speed of the mill, influence the rate of abrasion and the final fineness of the ground lignite. In grinding wheels, the abrasive particles are bonded together in a matrix. When the wheel rotates, these particles scrape against the lignite, removing material and achieving the grinding effect.

 

Some lignite grinding machines, such as roller mills, use the shearing principle. In a roller mill, two or more rollers rotate in opposite directions. The lignite is fed between these rollers, and as they rotate, a shearing force is applied to the lignite. This shearing force causes the lignite to be split and crushed. The gap between the rollers can be adjusted to control the particle size of the ground lignite.

A smaller gap results in a more intense shearing action, producing finer - sized particles, while a larger gap yields coarser particles. The shearing principle is effective for lignite as it can break the coal along its internal planes of weakness, facilitating efficient grinding.