Abstract
Experimental and theoretical studies have been conducted on the control of the particle size distribution and the crystallinity of the product powder in a closed-circuit pulverization system. The performances of a pulverizer and a classifier were modeled by the experimental data. By use of these performances, the particle size distribution of the product powder was simulated numerically by an iterative method. The change in the crystallinity of the product powder was also simulated, based on the two hypotheses. Namely, one is that the crystallinity of the product powder is determined by the pulverization times, another is that the crystallinity is determined by the particle size distribution.
The product powders, which have the same mass median diameter, have different crystallinity, when the closed-circuit pulverization system is operated with the different conditions. It is found that the product which has relatively low crystllinity can be obtained, when the rotational speed of pulverizer is high. This is why the pulverizer reduce the particle size with inhibiting the breakage of the crystal structure in the case of the lower rotational speed. Furthermore, in the closed-circuit pulverization system, it takes longer time to attain the steady state of the product properties, when the rotational speed of pulverizer is lower.
We can successfully simulate the change in the flow rate, particle size distribution of product powder with elapsed time. On the other hand, the change in the crystallinity of the product powder can be expressed by the simulation based on the latter assumption. But the crystallinity difference of the steady state can be simulated by not this simulation but the simulation based on the former assumption. Therefore, this fact suggests that the crystallinity of the product powder is determined by both the particle size distribution and the pulverization times.
