Crusher classification: which of the following is considered a fine crusher in size-reduction practice?

Introduction / Context:
Crushers are categorized by the typical product size they deliver. Primary crushers (jaw, gyratory) produce coarse product, secondary/tertiary machines push toward finer sizes. Recognizing which equipment fits the “fine crusher” category is key for flowsheet design.

Given Data / Assumptions:

• “Fine” here refers to finer than primary reduction, often a few millimeters.
• Feed is pre-broken, moderately hard, and free-flowing.
• Options include jaw, gyratory, and toothed rolls.

Concept / Approach:
Jaw and gyratory crushers are primarily coarse breakers. Toothed roll crushers, particularly in tertiary service, can deliver relatively small product sizes by nipping and shearing, making them suitable as “fine crushers” compared with primary machines.

Step-by-Step Solution:
Identify typical duty of each machine: jaw/gyratory → primary; toothed rolls → finer service.Match “fine crusher” descriptor to the most appropriate option.Select toothed roll crusher.

Verification / Alternative check:
Vendor sizing charts show roll crushers producing smaller top sizes at controlled reduction ratios suited to fine crushing stages.

Why Other Options Are Wrong:
Blake/Dodge jaw: primary/secondary, coarse to intermediate product.Gyratory: primary to secondary, not a fine crusher.

Common Pitfalls:
Assuming “jaw variant” implies finer operation; geometry primarily suits coarse reduction.

Final Answer:
Toothed roll crusher