Summary

As a serious social problem, the regulation on the air pollution from fine particles of nitrogen oxides (NOx) exhausted from diesel engines has been tightened. DPF (Diesel Particle Filter) has been developed for the solution of this problem. DPF is constantly exposed to very high temperature of exhaust gas and should be regularly cleaned by heating up to 450°C. So material such like SiC, having very stable nature under high temperature are suited. DPF is made by press-formation SiC compound. Raw material of ceramics (matrics) consists of fine particles with precisely controlled particle size distribution. There are wet milling process and dry milling process in the industry. Hosokawa introduces a dryer for wet milled SiC and dry grinding system.

Among various characteristics, particle size distribution is the most important for SiC compound for filters. This SiC compound is sometimes fine-ground by the closed circuit grinding system with ball mill and air classifier. A classifier classifies ground particles by the ball mill, fines are removed from the circuit and coarse is returned to the mill for further grinding.