My only suggestion would be to adjust the kiln feed chemistry to achieve the same flux content as applied with the Indian coal. The other possibility is that the problem is caused by elevated sulphate in the clinker arising from the petroleum coke.

I would not use air or gas of any kind to agitate the coal in the fine coalbins. I suggest using acoustic cleaners and sounding these at regular intervals to prevent bridging in the bins.

I agree with you that the high quartz content above three per cent over 45 micron is the root of the problem. The new burner and the improved coal dosing can only be advantages but they are unlikely to solve this problem of low reactivity of the kiln feed. There are many white cement factories that are operating with very high silica sand additions. These would be the best references. My suggestion of a remedy would be to introduce duplex grinding where the rejects from the raw mill classifer are separately ground and reintroduced to the raw mix. This is a radical solution and requires process modifications to introduce, however it will solve the problem.

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.