At present, there are many processes and methods of the domestic cement production. Depending on the different options of the grinding equipment it can be divided into open circuit grinding, circle circuit grinding and pre-grinding.
1. Open stream grinding process
The open circuit grinding process uses the tube mill, making the different hardness and different sizes of grinding mixture sent in the grinding mill. The particle size ratio of this process is better than that of circuit grinding process, meanwhile the strength is higher. However due to the over grinding of mixture, such kind of grinding process will produce a high false specific surface area, at the same time the over grinding will spend a lot of energy and time and increase the exercise in futility.
2. Pre-grinding process
At present, China's new dry process cement production line commonly uses the pre-grinding system which is composed by roller press machine and ball mill. The power-saving level of the system changes according to the size of the power consumption, its saving effect is remarkable. However, due to the level of China's industry lags behind, so the roller press of the roll press machine can only be maintained at about 80Mpa, the power consumption of the entire system is greater than that of foreign countries. Therefore, the energy saving space of grinding process in China is still increasing.
3. Circle circuit grinding process
Circuit grinding process is to make the powder through the mill grinding deliver to the classifier for sorting, The fine powder reaches the fineness degree is called cement finished products, and then coarse powder is sent to the head for secondary grinding. Circuit grinding is conducive to the regulation and control of product fineness and temperature, its grinding efficiency is about 10-20% higher than that of the open circuit grinding process, the finer of the finished product fineness, the more obvious of the advantages. However, the grinding process has a drawback, that is, the 10-40um average particle diameter of the obtained cement products obviously increased, 5-20um or less the average particle size significantly decreased, this method leads to unreasonable particle size distribution of the cement, and does not maximize the strength of the clinker.
