Primary size reduction of hard rock: which equipment is typically selected for the preliminary breaking (coarse crushing) stage before secondary reduction?

Introduction / Context:
Primary crushing handles run-of-mine hard rock, reducing it to manageable sizes for subsequent secondary/tertiary crushers or grinding mills. The machine must accept large lumps, deliver high throughput, and provide a controlled top size.

Given Data / Assumptions:

• Very hard, abrasive rock in large lump sizes.
• Objective: coarse crushing to a product suitable for conveyors and secondary crushers.
• Continuous, high-capacity duty.

Concept / Approach:
Gyratory crushers provide continuous crushing action with high capacity and can accept very large feed sizes due to their open intake and robust design. They are the standard choice for primary crushing of hard rock in large mines and quarries, delivering a relatively uniform product for downstream processing.

Step-by-Step Solution:
Identify primary duty requirements: large feed, high throughput.Match equipment features: gyratory offers continuous compression and large gape.Select gyratory crusher over mills and specialized disintegrators intended for finer or softer materials.

Verification / Alternative check:
Flowsheets in hard-rock mining typically list “ROM → gyratory → conveyors → secondary cone/crusher,” confirming standard practice.

Why Other Options Are Wrong:
Ball/tube mills: grinding equipment for much finer sizes, not for ROM lumps.Squirrel-cage disintegrators: used for soft/brittle materials, not massive hard rock.

Common Pitfalls:
Attempting to feed very large boulders into jaw-only small primaries; gyratories are preferred for the largest capacities and feeds.

Final Answer:
Gyratory crusher