Chemical Engineering - Mechanical Operations - Discussion

A ball mill generally loses its grinding efficiency remarkably at fine grinding. This is because fine particles from ground materials agglomerate and adhere to the mill liners or grinding media as coating, reducing the impulsive force of the mill.

In addition, the agglomerated particles are mixed into the coarse powder in the separator and recirculated through the mill. A grinding aid prevents this agglomeration to improves the grinding efficiency.

The aid is generally added to the clinker at a fixed rate from 0.01% to 0.03% before entering to a finishing mill. As a result, the grinding improves by 4% to 6% per 0.01% addition of aid. The aid also improved the dispersibility and fluid ability of cement (powder) and weathering is delayed.