A crushing duty with feed size 10–50 mm and product size 2–10 mm corresponds to which stage of comminution?

Introduction / Context:
Comminution stages are broadly classified by size ranges: primary (very coarse), secondary (intermediate), and fine crushing (small, near mill feed).

Given Data / Assumptions:

• Feed: 10–50 mm.
• Product: 2–10 mm.

Concept / Approach:
Primary crushing usually reduces run-of-mine sizes (0.5–1.5 m) to 50–150 mm. Secondary reduces roughly 50–150 mm to 10–20 mm. Fine crushing drives down to a few millimetres. The stated duty neatly fits the secondary regime.

Step-by-Step Solution:
Compare feed/product to typical stage ranges.10–50 mm → 2–10 mm aligns with secondary.

Verification / Alternative check:
Common secondary machines include cone crushers and roll crushers handling this band.

Why Other Options Are Wrong:
Primary: much coarser discharge.Fine/Ultrafine: target sizes smaller than stated.

Common Pitfalls:
Confusing fine crushing with grinding; grinding is a different unit operation.

Final Answer:
Secondary crushing