Grinding in a ball mill: which combined statements about wet vs. dry grinding, capacity vs. fineness, and power/cost vs. fineness are correct?

Introduction / Context:
Ball mill performance depends on mill charge, speed, classification, and whether the circuit is wet or dry. Fineness targets directly affect throughput and energy consumption.

Concept / Approach:
Wet grinding suppresses dust, improves classification, and reduces coating on media and liners, typically achieving finer sizes than dry grinding. As fineness increases (smaller P80), specific energy per tonne rises; at fixed power, throughput decreases. Consequently, operating cost and power per tonne also increase with tighter grinds.

Step-by-Step Solution:
Evaluate (a): Wet circuits commonly reach finer sizes due to better transport and classification.Evaluate (b): Higher fineness requires more energy/tonne → lower t/h at fixed power.Evaluate (c): More energy and media wear mean higher cost → true.Therefore, (d) all three are correct.

Final Answer:
All of the above (a), (b) and (c).