1156 posts
Precalciners Question 1
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?
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1156 posts
Re: Precalciners
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.
1156 posts
Precalciners Question 2
We wish to know about oxygen enrichment in the cement kilns/precalciners. Please brief us about the expected merits and demerits. Are there any cement plants using this technique? If yes, then why is it not used commercially on regular basis in most of the cement plants.
1156 posts
Re: Precalciners
This is a big question! The merit is that the output of the kiln can be boosted by up to 15 per cent, the demerit is that the oxygen is expensive and therefore the costs of producing the additional clinker are higher. If market demand exists with good prices for cement then oxygen enrichment can be a good option. There are a number of kilns in the USA using oxygen enrichment of either the main burner or the precalciner. It is worth noting that CEMEX USA consider oxygen enrichment of precalciner firing to be their technology for which they have lodged a patent. You can find papers on oxygen enrichment in the proceedings of the IEEE conference in Vancouver 2001.