We are facing problem of poor fluidity of cement while extracting cement from silo even with fresh cement stock. We are having only Ordinary Portland Cement grinding with no water cooling facility in mill. Cooling takes place only in O-sepa. Since the last two months we started water spray in mill inlet to control mill outlet product temperature of around 108 to 113 deg C. Product temp. entering to silo is around 85 deg C and at outlet 72 to 75 deg C. Humidity is around 40 to 60 per cent in air because of coastal area. Please highlight some of the possible causes for such phenomenon and also give the method normally applied to determine moisture content in cement. As additional information we are using mineral gypsum 5 to 5.5 per cent in the cement.

I suggest you should raise the mill outlet temperature setpoint of the PID loop controlling the water injection rate. This should allow more water to be driven off the gypsum in the cement mill. At the same time you shouod attempt to maximise the cooling in the O-Sepa.

During winter time we have a problem with keeping the temperature high enough in the mill while grinding a blended type of cement. This problem is caused by false air that enters the system. Now we want to determine the amount of false air that enters do you know a accurate way to measerure it? And do you have a solution to solve this problem?

The way to determine the amount of false air entering the mill would be to construct and masss and energy balance for the mill based on gas flow measurements around the circuit. The problem with low temperatures when grinding blended cements is a common one. The only solution is apply some heat energy either to preheat the mill ventilation air or pre-dry the components of the blended cement. Alternatively produce a different grade of blended cement during the winter with a lower proportion of supplementary cementitious material.