I work at a plant 4500tpd, based on FLS design, with a five-stage preheater and precalciner, Our problem is repeated blockage in cyclone stage five (some four times at period of five months). We calculated the sulphate/alkali ratio before each blockage, we found it between 1.45 to 1.7. As we know the normal value should be less than 1.2. The LSF between 92 and 105, also the analysis result of a sample from the blockage material are: SiO₂=19.5, Al₂O₃ =4.76, Fe₂O₃ =3.63, CaO=62.1, SO₃=2.31, K₂O=1.37, Na₂O=0.93. Can you advise if the values of SO₃/AlK ratio to cause the blockage in Cyclone 5 or is it another reason?

From the information you have sent there seem to be two problems, (i) the SO₃/Alkali ratio between 1.45 and 1.7 is very high and would be expected to cause very hard dense coatings, (ii) the variability of the LSF from 92 to 105 is much too high and would be expected to cause major process and quality variability. However. the samples from the blockage do not show very high SO levels and have an SO₃/alkali ratio of 0.87 which should not cause any problems. The other cause could be premature calcination in the cyclone 5 due to variable LSF. This would happen with the change to low LSF, easy burning material.

I am working on a project for my university studying the different technologies used in the cement production process from different companies, and I would like to know if any corporation has already constructed its process with a fluidised bed cement kiln for commercial operation and could reach acceptable efficiency. Also, I am researching for the system with most number of steps at the preheater, and the performance of the process compared to other ones.

I am not aware of any commercial operations using fluidised bed for industrial cement clinker production. There are pilot and research installations but not of commercial capacity. There are number of kilns with six-stage preheaters. This brings the exhaust gas temperature down to less than 300 degrees Celcius. However, the most economic number of preheater stages is usually five as increased capital costs for six stages cannot be recovered by the energy savings. A company might choose a six-stage preheater if there is a shortage of water for exhaust gas cooling and conditioning. Therefore most of the existing six-stage preheater kilns are in desert environments.