We are facing serious problem of build-ups at stage four riser duct starting from kiln housing and at start of mix chamber it becomes to thick and remains thick through out the riser duct so that opening remains only 30-40 per cent. Some coating has also observed at cylindrical part of cyclone and at its roof, but coating at riser duct becomes very tough and hard and similar to sintered material. My first question: is there any special method to get rid off it during operation as normal pocking do not results any way. Is there any chemical treatment, operational technique or physical methods. Secondly, what could we do to prevent such things.

It is no surprise that you have problems. Your instrumentation and control technology is inadequate. I am surprised that you can operate a large modern kiln without coal flow metering equipment to the main burner. I think your problems are caused by an excess of sulphate over alkalis. This results in the very hard coating in the riser duct. The best solution is to increase the alkli content and pass the alkali sulphate out in the clinker. However, with your inadequate coal flow control there is likely to be reductive burning and then there will be a heavy sulphate cycle in the kiln. This is also likely to be contributing to your current problems. You could try installing acoustic cleaners to try to prevent the sulphate build-up in the riser. The high temperature excursions in the precalciner and stage four cyclone are caused by interruption in feed down the preheater tower caused by the build-up. Solve the build-up problem and you will solve the high temperature problem. For the oil compensation you need expert control, however it is doubtful if your general control can be the basis for expert control.

We have a 1000tpd FLS kiln with a five-stage preheater. We are having a lot of clinker dust formation which is causing great wear at the kiln hood. What would you recommend to get rid of the clinker dust.

It is difficult to diagnose the problem over the internet, however these problems are often caused by inefficient combustion of the fuel in the main burner, long flames and poor heat flux in the kiln. I suggest you increase the axial primary to the maximum and see if that helps.