In particle-size reduction, what is the general dominant mechanism in intermediate and fine grinders used in chemical and mineral processing (consider mills such as ball, hammer, and pin mills operating beyond coarse crushing)?

Introduction / Context:
Industrial comminution equipment for intermediate and fine grinding—such as ball mills, hammer mills, and pin mills—rely primarily on impact and attrition to reduce particle size. Recognizing the dominant mechanism guides equipment selection and operating parameter optimization.

Given Data / Assumptions:

• Equipment considered: common intermediate/fine grinders.
• Feed is already below coarse-crushing range.
• Objective is to identify the main breakage mode.

Concept / Approach:
In tumbling and impact mills, particles are broken when grinding media or hammers strike (impact) and when particles rub or slide against media/surfaces (attrition). Compression and cutting dominate in crushers and knife mills used for coarse reduction or fibrous materials, not for general fine grinding of minerals and chemicals.

Step-by-Step Solution:
List typical fine grinders and their actions.Identify impact from falls/strikes and attrition from inter-particle/media rubbing.Conclude the combined mechanism rules performance.

Verification / Alternative check:
Design texts describe selection charts linking fine product sizes with impact–attrition mills, confirming the mechanism pairing.

Why Other Options Are Wrong:
Cutting: suits fibrous materials.Compression/tearing: characteristic of crushers, not fine grinders.

Common Pitfalls:
Assuming one mechanism only; real mills combine actions, but impact + attrition dominate.

Final Answer:
Impact and attrition