On the base of optimal thermal condition of coal gangue de－watering defined in laboratory, a new technique of coal gangue de－watering by using kiln dust from by－pass system is proposed by the author． Through thermal calculation, the equipment, technical process flow and primary thermal parameters of by－pass system are presented here． Overall evaluation of this system is also made by the author．   

The granularity distribution of slag under ball grinding method in different specific surface area was examined by Laser granularity analyzing instrument． The results showed that the fine particles lead great increment and n value raised along with the increase of specific surface area． The investigation also indicated: The change of specific surface area of slag powder has little effect on water content of paste at standard consistency． In addition, the increase of specific surface area is benefit for improving the strength of slag cement, but no specific law can be followed on the effect of rheological property．

Sealing effect has great influence on the final product of vortex classifier. This paper made an analysis on the principle of mechanical sealing and traditional mode of sealing. The characteristics and shortage of such sealing are given by the author. Using the principle of dynamic blade wheel to improve sealing structure has gain good result in actual production.

The current status of automation technology in cement industry is analyzed. The fuzzy control technique, the DCS structure and its applied software development on rotary kiln temperature control are introduced here. The operation result shows that the system is stable and the control effect is satisfied with process requirement.