Do you think that pre-dedusting in a raw mill circuit by means of cyclone with a separation efficiency of 91-93 will have negative influence on the raw mill bag filter or ESP in regard to the fact that after pre-dedusting only rather fine grain and rather low quantity of dust will enter the filter? Could it become difficult to clean the bags due to fine dust getting deeper into the pores of the filterbag and could the fine dust have negative influence on the ESP?

I cannot foresee that reduces the load of dust entering a filter will have any detrimental effect on its performance. Certainly no problem with an ESP. Your point regarding fine dust blinding the cloth of fabric filters may be valid, but I would be surprised.

What is the effect of cooler dust on flame?

Air-cooled blast furnace slag can be added to the inlet of the cement kiln. The effect of dust recirculating from the cooler in the secondary air is potentially disastrous. I have seen occasions where the dust keeps increasing until the kiln is full of dust and the firing has to stopped while the kiln is emptied of dust. The dust affects the combustion of the fuel in the flame and the problems tends to intensify in a vicious circle. Potential causes are poor combustion in the flame or elevated sulphate content in the clinker. (See the April 2003 issue of International Cement Review for an article about dust formation with pet coke firing in cement kilns).