1. The granularity of the feeding material
The energy availability factor of the dry-process grinding by ball mill was only 2%-3%. After years’ scientific research and production practice, the foreign engineers and technicians come up with the precomminution technology of “more crush, less grinding, crush instead of grinding”, which substantially and perfectly increase the ball mill output, and lower the grinding current drain.
2. The moisture of the feeding material
The moisture of the material affects the accuracy of the ingredient and the ball mill output and current drain directly. The reasons are: first, the high moisture affects the uniformity of feeding material and prolongs the feeding time; second, the overfed wet material may lead to ball paste inside the mill and lining plate paste, even the full grinding and a forced stop of the ball mill. Generally speaking, 1% increases on the overall moisture of the feeding material will lead to 8%-10% decrease of the ball mill output. The dry-process ball mill can’t work any more when the moisture is more than 5%.
3. The feature of the feeding material
The variety and match of the feeding material affect the ball mill output, quality and per unit yield current drain. Research shows that any mixture will decrease the strength of the cement, and the difference lies in the degree which varies by the liveness of mixture. Among the common mixture, the liveness of the slag is the best. But when the specific surface area of slag is below 300m/kg, its influence to the cement strength doesn’t reflect its advantage.
4. The grinding technological process
Apart from the precomminution before grinding, the grinding technological process can be divided into open circuit process and closed circuit process (open process and closed process for short). The output of the latter is about 20%-30% higher than the former. The new standard’s requirement to the screen residue of the out-mill cement decreases greatly, and the closed process grinding cement needs a higher specific surface area. So the initial strength advantage of the open process grinding cement is no longer obvious. The suggestions are made to the cement plant that to adopt the closed process grinding technology which can avoid the excessive grinding of the open process grinding as well as ensure the energy conservation and high yield of ball mill.