Question

(b) Explain the operating principles of a jaw crusher and a gyratory crusher. Under what circumstances would you consider replacing the jaw crusher in your process flowsheet with a gyratory crusher?

Answer 1

Solution:

Operating principle of a jaw crusher

The working principle of jaw crushers is based on the reciprocating movement of the movable jaw that compresses and crushes the rock or ore between itself and the fixed jaw, as the material enters the zone between the jaws. The moving jaw moves back and forward against the fixed jaw, and material fed from the top of the machine is compressed between the two, breaking it into smaller pieces. As the moving jaw moves away from the fixed jaw, the crushed material is discharged from the crusher at the bottom, with the size of the ejected material determined by the gap between the jaws.

Operating principle of a Gyratory crusher

Gyratory crushers work on a similar principle to jaw crushers but have a circular gap. Rock is compressed between a static conical bowl and a concave mantle which oscillates about the central axis. The crushing action is caused by the closing of the gap between the mantle line (movable) mounted on the central vertical spindle and the concave liners (fixed) mounted on the main frame of the crusher. The gap is opened and closed by an eccentric on the bottom of the spindle that causes the central vertical spindle to gyrate. The vertical spindle is free to rotate around its own axis. The crusher illustrated is a short-shaft suspended spindle type, meaning that the main shaft is suspended at the top and that the eccentric is mounted above the gear. The short-shaft design has superseded the long-shaft design in which the eccentric is mounted below the gear.

Circumstances that should be consider by replacing the jaw crusher in your process flowsheet with a gyratory crusher are as follows,

1. Primary crushing in large-scale rock crushing applications up to 6000 t/h.

2. When continuous work and high productivity required.

3. Feeding size is more.

4. Need of crushed material in smaller size.

5. Less production fine particulates.