Grinding mill separation
Jul 10, 2024
In actual production, materials cannot leave the mill freely from the discharge end. The discharge end of the mill has the function of inhibiting the discharge of large particles. Small particles can be discharged smoothly, while large particles remain in the mill and continue to be ground. This function is called outlet classification. This function of the mill itself will affect the time the material stays in the mill, and different discharge methods have different inhibitory effects. For the grid-type ball mill, the grid has a greater inhibitory effect on the discharge of large particles. Even if the grid opening is large, it will still prevent some large particles from being discharged. This effect also exists in the overflow ball mill, but it is smaller than that of the grid ball mill. In modeling, if this function is ignored, the large particle content of the model prediction value will be too large.
In order to reflect this function, four methods can be used to deal with it:
1. Introduce the classification effect in the mill model, and let the classified return sand return directly to the mill entrance;
2. Use different axial speeds for different particle sizes to represent the advancement of particles in the mill, which can be equivalent to returning the classified return sand to the entrance of each mixer;
3. Modify the expression of the comparative crushing rate. The idea of this method is that the suppression of large particles means that the average residence time of large particles is long. Therefore, if the residence time of large particles is the same as that of other particles, and the crushing rate of large particles is accelerated while the crushing rate of small particles is slowed down, the same effect as the long residence time of large particles will be achieved. This method has the same idea as the pseudo-time method;
4. Use a non-first-order crushing rate and the crushing rate increases with time, and make the crushing rate of large particles increase faster, while the crushing rate of small particles increases slower, so as to achieve the same effect as the long residence time of large particles.
