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.

We are 3100tpd cement plant situated in the Arabian Gulf. We have four cement silos 10,000 tons each at our plant, we are facing the problem of lump formation in silos, which is causing cement extraction delays and is also effecting our market reputation as well. Our cement mill is 136tph rated capacity (OPC) closed circuit with water spray system (made in-house). The humidity reaches 80 to 90 per cent in summers, as it is a coastal area. Till now we have not come to any conclusion about the cause of lump formation in our plant. Can you please suggest us if grinding aid may help in solving the above said problem, how technically, and of course to what extent.

Given your location and the humidity you suffer in the summer, the question you must answer is whether the lump formation is caused by the ambient humidity in the air in the free space in the silo or continued dehydration of gypsum in the silo. I suspect the problem will be continued dehydration of gypsum in the silo. To solve this you must carefully control the temperature of the cement entering the silo. The installation of a cement cooler may be necessary in your climate to bring the cement temperature below 80 degrees centigrade.