Function of a ball mill:\nIn comminution, a ball mill is primarily used for which mode of size reduction?

Introduction / Context:
Different mills operate effectively over different size ranges. Recognising that ball mills are designed to reduce mill feed to fine powders using a combination of impact and attrition is fundamental when selecting equipment for a grinding circuit or interpreting plant data sheets and P&IDs.

Given Data / Assumptions:

• Ball mill equipped with steel balls as grinding media.
• Operated below critical speed to promote cascading/cataracting.

Concept / Approach:
Ball mills handle feed sizes typically below 25 mm and deliver product fine enough for downstream classification or finish requirements (e.g., cement, mineral liberation). The mechanism involves both impact (media dropping) and attrition (sliding), producing fine grinding. Crushing is achieved by jaw, gyratory, and cone crushers at larger sizes; coarse grinding may be handled by rod mills or SAG mills depending on circuit design.

Step-by-Step Solution:

Verification / Alternative check:
Comminution flow sheets routinely list ball mills in the fine grinding stage following primary/secondary crushing and sometimes rod milling or SAG milling.

Why Other Options Are Wrong:

• Crushing: upstream, not a ball mill function.
• Coarse grinding only: ball mills excel at finer reductions.
• Pure attrition: impact is also significant.
• Cutting: unrelated to tumbling mills.

Common Pitfalls:
Overlapping rod and ball mill roles; rod mills better suit coarser, more uniform product with fewer fines.

Final Answer:
Fine grinding