Basic knowledge of ball loading in ball millDate: 2019-07-09 Views:
The main function of steel ball in ball mill is to impact and break the material, and also play a certain grinding role.Therefore, the purpose of steel ball gradation is to meet the requirements of these two aspects.The crushing effect directly affects the grinding efficiency and ultimately affects the output of the ball mill. Whether the crushing requirements can be met depends on whether the gradation of steel balls is reasonable, which mainly includes the size of steel balls, the diameter of balls and the proportion of balls of various specifications.To determine these parameters, in addition to the size of the ball mill, the internal structure of the ball mill, product fineness requirements and other factors, but also to consider the characteristics of grinding materials (grinding, particle size, etc.).
To effectively crush materials, the following principles must be followed in determining gradation:
First of all, the steel ball should have enough impact force to make the ball of the ball mill have enough energy to smash the granular material, which is directly related to the maximum ball diameter of the steel ball.
Secondly, steel balls should have enough impact times on materials, which is related to the filling rate of steel balls and the average ball diameter.When the loading quantity is fixed, on the premise of ensuring sufficient impact force, try to reduce the diameter of grinding body and increase the number of steel balls to improve the impact times on the material, so as to improve the crushing efficiency.
Finally, the material in the mill has enough time to ensure that the material is fully crushed, which requires the steel ball to have a certain ability to control the flow rate of the material.
The so-called two-gradation ball method is to use two different sizes of steel balls with a large difference in diameter to grade.The theory is that the space between the big balls is filled by small balls to increase the density of steel balls.In this way, on the one hand, the impact capacity and impact times of the mill can be improved, in line with the functional characteristics of the abrasive body; on the other hand, a higher accumulation density can enable the material to get a certain grinding effect.In the two-stage distribution ball, the function of the big ball is mainly to impact and break the material. The function of the small ball is to fill the gap between the big balls and improve the accumulation density of the abrasive body, so as to control the flow rate of the material and increase the grinding capacity.Second, it plays the role of energy transfer, transferring the impact energy of the big ball to the material;The third is to squeeze out the coarse particles in the gap and put them in the impact zone of the big ball.
The following parameters need to be determined for the two-stage spherical method:
(1) determination of the diameter of the big ball.
Depends on the size of the ball mill, grinding material size and easy to wear.Generally, the diameter of the second stage of the multi-stage distribution ball shall prevail.If the maximum ball diameter of a ball mill is 100mm in multi-stage ball distribution, steel balls with a diameter of 90mm should be selected for two-stage ball distribution.
(2) determination of ball diameter.
It depends on the size of the space between the big balls, which depends on the diameter of the big balls.In general, 20%-30% of the diameter of the small ball is appropriate.
(3) ratio of large and small balls.
In principle, the incorporation of small balls should not affect the filling rate of large balls.The average small ball accounts for 3-5% of the weight of a large ball.
When the particle size of the material is small and easy to wear, it is advisable to use multistage ball distribution, because it is important to improve the impact times of the steel ball.On the contrary, when the particle size of the material is large and the strength is high, improving the impact force of the steel ball is the key, so using two-stage ball can reflect obvious advantages.
The effects of two kinds of ball distribution are greatly different from each other, the multi-stage ball distribution is sensitive to the change of material, and the output of ball mill fluctuates greatly.The two-stage ball is less sensitive to the change of material and the yield is relatively stable.That is to say, the higher the grinding property of the material is, the higher the increase rate of the output of the multistage ball matching is than that of the two-stage ball matching.On the contrary, the production of multi - level distribution ball decreased more than two - level distribution ball.Therefore, multistage ball distribution is suitable for materials with small particle size and good abrasion ability, while two-stage ball distribution is suitable for materials with large particle size and poor abrasion ability.