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Talking about the multi-level and second-level ball of the

Date:2019-06-04 13:21     writer:cement editor     Views:

 

  1. Basic requirements for a grading of abrasive bodies


  The material should be effectively crushed in a warehouse and meet the particle size requirements for the second warehouse grinding. When selecting the grading parameters of a warehouse, the following basic requirements must be considered comprehensively.

  1)There must be sufficient impact force, that is, the steel ball serving as the crushing medium has an impact energy exceeding the strength limit of the material.

  2) Enough number4 of impacts. When the load is constant, it is related to the size of the ball. Under the premise of ensuring enough impact force, it is an important means to improve the grinding efficiency by minimizing the diameter of the steel ball and increasing the number of steel balls to increase the impact on the material.

  3)Appropriate storage capacity. In order to ensure that the material can be fully pulverized, it is required that the material has a certain residence time in the warehouse, that is, material flow rate should be controlled to prevent the material flow rate from being too fast and the digging phenomenon occurs.

  2. Multi-level ball method


  The multi-stage ball method is a traditional ball-matching method, and usually 3 to 5 steel balls of different specifications are used. Its most prominent feature is based on the particle size of the material being ground. Mainly in the following aspects:

  1)The maximum ball diameter D is determined according to the maximum particle diameter of the material, and is generally calculated as D=28.

  2) The ratio of various steel balls generally follows the principle of “large in the middle and small in both ends”, which is like the particle size distribution characteristics of the materials.

  First, the process of the steel ball on the material is random and there is no selectivity. It is impossible for the steel ball to act on the material without the granularity corresponding to the magnitude of the impact force. A steel ball with a small energy will have insufficient impact when it encounters a hard-large particle material. For small particle materials, large steel balls will appear to be overcapacity. Since the energy cannot be reasonably distributed, it is difficult to achieve the original intention of multi-level ball.

  Secondly, during the grinding process, the particle size gradually decreases along the axial direction of the mill, while the steel balls are distributed in the axial direction of the mill but are disordered (except for the graded liner). Therefore, it is impossible to fully utilize the advantage of multi-stage ball adaptation to material changes in the mill.

  3. Second ball method


  In the secondary ball, the large ball acts as a crushing medium: The role of the ball is mainly the following:

  1) filling effect. Reduce the void ratio between the large balls and limit the materials flow rate.

  2) Energy transfer. The large ball passes energy through it to the material in the gap.

  3) Squeeze the material in the gap and place it in the active area of the large ball.

  The second ball is mainly considered by the following parameters:

  1) The diameter of the big ball. As with multi-stage ball, it depends on the particle size of the material being ground. The difference is that it is based on the representative particle size of the material. In practical applications, the secondary ball diameter in the multi-stage ball can be used as the standard.

  2) The ratio of two balls. In principle, it should be ensured that the incorporation of the pellet does not affect the filling rate of the large sphere. Generally, the small ball accounts for 3%-5% of the weight of the big ball. In practical applications, the lower limit should be taken first, and then the production should be supplemented according to the production situation.

  3) The diameter of the ball. It depends on the size of the gap between the large spheres, that is, the diameter of the large sphere. According to relevant information, the diameter of the ball should be 13% to 33% of the big ball.

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