We have ESP at the kiln system. It is also used for raw mill system. System is sent ESP's feedback to kiln feeding silo. There are two homogeneous silos and two stockage silos. Material is sent from ESP to homogeneous silos. So, my question is that, I am thinking to feed the ESP's feedback directly to preheater system but this line will be entered to system after weighfeeder. We have got line to feed this material before weighfeeder but it causes to reduce of fresh feeding. In this way I want to increase clinker production with same feeding amount. What do you think?

Your idea is a very good one. There are plants that do exactly what you propose. This has the advantage that the chemistry of the kiln feed is more stable because it is not destabilised by slugs of ESP dust being added to the homogenisation silo when the raw mill is not running. I am not sure that you will get more output but the kiln operation and clinker quality should be more stable.

I have a question with regards to the sulphur cycle and a method that I adopt to mitigate the effects. Usually in the raw mix we usually run 0.07 per cent sulphur all of a sudden the value increases to 0.12 per cent and the operations are upset. What I have done is to add sodium carbonate in the kiln feed bin to force an increase in the alkali content in the internal cycle. I usually add approximately 100-150kg. What do you think about this? I have often read that sodium carbonate should not be added to the burning zone. I don't know why they say this. All that I think of is that the sodium reduces the viscosity of the liquid melt, making it more penetrating towards the brick!

I'm surprised that a rise from 0.07 to 0.12 per cent sulphur in the raw mix causes upset conditions. These are low values compared to many kilns whose companies add much more in the petroleum coke they use to fire their kilns. The sodium carbonate will dissociate in the kiln and the Na₂O will combine with the sulphur (as sodium sulphate) and pass out in the clinker. Your strategy is sound and based on known principles of the alkali cycle. There is no doubt that alkali penetration is one potential cause of refractory failure but at the levels you are using there should be no problem. There is wealth of material on the alkali cycle. The best reference I know is S.Sprung, "Technological problems in pyroprocessing cement clinker: cause & solution" published by Beton-Verlag.