We are getting very high free lime in clinker. Some times it goes up to 5 per cent. Normally it remains 2 to 2.5 per cent. We are firing 100 per cent South African and Chinese origin coal. Our kiln feed analysis is 95 -96 per cent LSF, 2.35 Silica Modulus, and 1.85 - 1.900 Alumina modulus. In clinker we get 92 per cent, LSF, 2.10 SM and 2.1 AM. We are using Duoflex burner of FLS. What is your opinion about the causes of free lime.

There could be a number of causes of the high free CaO content of your clinker despite the fact that the lime saturation of the clinker is only 92 per cent. The fineness of the kiln feed is one factr and also the contents of MgO and K₂O. If you can tell me those I will be in a better position to diagnose the problem.