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.

We carryout refractory work with screw jacks, maximum 10m lining at a time (ie 5m maximum simultaneously at two different locations in same kiln). As ours is a small plant of 1000tpd, with single kiln of 64m length, deploying brick lining machine and dismantling machines are not viable in terms of cost for us. What therefore is the maximum length of refractory work can be done at a time, in how many parts, simultaneously, from the various aspects such as safety, life of refractory etc.

I would recommend using the glueing method rather than screw jacks and then you can replace as long a section as you like without the concern of installing and removing the jacks. My understanding is that the glueing method will have no problems with a kiln of 3.95m diameter. However, you would be better to check this with suppliers of the refractory glue when placing your order.