How can we reduce the clinker size -5mm >35 per cent (existing),we want to reduce to under 20 per cent. Our plant is a 1Mta capacity unit. Fuel is pet coke 70 per cent balance Indian coal.

The only way to change the clinker size will be to change the kiln feed chemistry or the operation of the kiln. To have less fines in the clinker you should try to increase the flux content by reducing the silica modulus. Alternatively, adjust the rotational speed of the kiln by slowing slightly to increase the residence time.

I am working in a grinding unit having a vertical roller mill for slag grinding (UBE VRM). Initially this mill is for only slag grinding but we are also able grind clinker. We are getting clinker from various sources. Because of this we are getting different output & power consumption. I want to ask you is this normal to get different output & power consumption? How much influence does the wear rate of table & rollers have on output & power consumption. Also I want to know what are ways to increase the output of the vertical roller mill.

It is normal to get different outputs from the mill with materials from different sources. This will depend on the hardness of individual materials. There are ways to increase the output from a vertical mill. These involved justments to the separator and the airflow through the mill. A number of case studies have been reported by Siam Cement where major increases in output were achieved by these means.