Could you please advise us with optimum length for preheater cyclones inner pipes for increasing cyclones separation efficiency and increasing decarbonation degree. Because we have kiln capacity 5000tpd, kiln length 100m, kiln diameter 5.0m, preheater two-string, four stage cyclones, calciner system and bypass system.

Varying the length of the dip tube in a preheater cyclone will have two effects: (i) the cyclone collection efficiency will be improved which is a good thing, however (ii) the pressure drop across the cyclone and the whole preheater will be increased. If your kiln runs with the induced draft fan close to maximum speed then the increased pressure drop will create a restriction on the process. Because of these conflicting effects it is not possible for me to tell you an "optimum" length for the dip tube in a cyclone. This depends on other factors in the process and the kiln, and also whether you want to push the kiln to the highest output possible.

I am working out the percentage by-pass required for a large precalciner-preheater kiln for the production of low alkali cement. As the presence of chloride in the raw meal is noted, the volatility of the K₂O and Na₂O is supposed to increase. Can you provide me some relationship between the increase in the volatility of the alkalis with the increase in Cl content.

There is no absolute relationship between chloride content and alkali volatility. This depends on the other anoins present and also the burning zone temperature in your kiln. However, it is possible to say that the presence of chloride will increase the volatility of alkalis.