Definition and theoretical basis

Definition: Use large and small steel balls with different diameters for grading.

Basis: The gaps between large balls are filled with small balls to increase the packing density of steel balls, which can improve the impact capacity and impact times, so that the material can be ground.

Function of large balls and small balls

Function of large balls: mainly impact and crush materials.

Function of small balls: fill the gaps between large balls, increase the packing density to control the material flow rate and increase the grinding capacity; play the role of energy transfer; squeeze the coarse particles in the gaps into the impact area of large balls.

Parameters to be determined

Diameter of large balls: depends on the specifications of the ball mill, the particle size and grindability of the materials entering the mill, generally based on the second-level ball diameter in the multi-level ball distribution.

Diameter of small balls: depends on the size of the gaps between large balls, usually 20%-30% of the diameter of large balls.

Ratio of large and small balls: The amount of small balls added does not affect the filling rate of large balls. Generally, small balls account for 3%-5% of the weight of large balls.

Advantages

Relieve contradictions: The impact force and impact times of the steel ball are determined by the diameter of the large ball, and the ability to control the material flow rate is mainly determined by the small ball, which alleviates the contradiction between the impact force, impact times and the ability to control the material flow rate.

Stable output: When the hardness and particle size of the material increase, compared with the multi-stage ball distribution, the two-stage ball distribution does not have a prominent contradiction between the impact force and the material flow rate control ability, and the output change is not obvious.

Improve the operation rate: It can reduce the number of warehouse clearances, generally do not stop the warehouse clearance, and improve the operation rate of the ball mill.

Two ball distribution methods are applicable to scenarios

Multi-stage ball distribution: It is suitable for materials with small particle size and good grindability. At this time, increasing the number of impacts is the main thing.

Two-stage ball distribution: It is suitable for materials with large particle size and high strength. It can better improve the impact force of the steel ball, the output is relatively stable, and it is not sensitive to material changes.