Comminution of raw materials

The collision mechanics of impact and percussion comminution – Part 1 and Part 2

Impact crusher opened up at the Institute of Mineral Processing Machines after general overhaul and new paintwork

The impact crusher crushes the feed material according to the impact crushing principle

1 Closed system

2 Time sequence of the impact

3 Impact phases (elastic-plastic impact)

4 Forces during impact

5 Force development during impact

6 Types of collision

7 Velocity curves for different types of collision

8 Coefficient of collision c as a function of the velocity relations ∆w/∆v for different types of collision

9 Striking mechanism

10 Coefficient of collision c as a function of the particle-mass-specific loading energy E_spec (glass balls), data from [17], mean values

11 Coefficient of collision c as a function of the particle-mass-specific loading energy E_spec (quartz porphyry, Hartmannsdorf), data from [32], mean values

In numerous machines, the comminution of primary and secondary raw materials is based on the physical effect of collision. This effect is realized by means of the active principles of impact and percussion. These active principles effect four types of collision either between the raw material particles or with machine components: elastic-plastic, rebounding, penetrating and energy-releasing collisions.

Widening of the theory of restitution to the theory of collision enables its formulation in physical terms. For this purpose, the coefficient of restitution is extended and termed the coefficient of collision. The value range then extends from - 1 to ∞. Here the coefficient of collision from - 1 to 0 characterizes the penetrating collision, from 0 to 1 the elastic-plastic and rebounding collisions and from 1 to ∞ the energy-releasing collision. Comminution is effected in all collision types apart from in elastic-plastic collisions.

Part 1 of the technical contribution published in AT 10/2023, pp. 46-56.

Part 2 of the technical contribution published in AT 11/2023, pp. 42-51.

The collision mechanics of impact and percussion comminution – Part 1 and Part 2

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