1156 posts
Re: Fuels
I agree with you that the high quartz content above three per cent over 45 micron is the root of the problem. The new burner and the improved coal dosing can only be advantages but they are unlikely to solve this problem of low reactivity of the kiln feed. There are many white cement factories that are operating with very high silica sand additions. These would be the best references. My suggestion of a remedy would be to introduce duplex grinding where the rejects from the raw mill classifer are separately ground and reintroduced to the raw mix. This is a radical solution and requires process modifications to introduce, however it will solve the problem.
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1156 posts
Fuels Question 14
We are analysing particle size distribution of raw meal, coal mill product and cement mill product through CELAS PSA having facility to determine 0.7 to 400 micron. Q1. What is the best particle distribution (on various micron sizes) of raw mill in terms of best mill performance, burnability and kiln performance and which plant in the world is producing? Q2. What is the best particle distribution(on various micron sizes) of coal mill in terms of best mill and kiln performance? Our coal ash is 28. Q3. What is the best particle distribution( on various micron sizes) of cement mill product to have optimum power consumption, best strength and good performance in concrete.
1156 posts
Re: Fuels
There is no straightforward answer to your questions. For raw mix the optimum particle size distribution depends on the mineral composition of your raw materials. If you have a high content of quartz then you must have a very tight fine particle size distribution with low content of oversize particles where the quartz will concentrate. On the other hand with a homogenous raw mix with no quartz it is not beneficial to have too small a particle size distribution as this will increase the dust losses from the top stage of the preheater. Similarly with coal there is no hard and fast rule. It is said that the 90 micron residue should not be more than 50 per cent of the volatile content of the coal. Increasing the fineness beyond that is counter-productive. For cement the optimum particle size distribution depends on the cement performance characteristics that your customers have come to expect. Ring formation is caused by the formation of liquids in the kiln at a particular position. These penetrate the refractory lining and cause a localised thickening of the coating. Fe2O3 can be a cause of these problems and I am not surprised that raising the alumina modulus has solved the problem. Many cement factories operate with higher alumina modulus than 1.7 and I would recommend keeping the kiln feed mix design with the higher alumina modulus. A snowman is the formation of a large build-up on the first grate of the cooler where the clinker falls from the kiln rather than a build-up in the kiln.
1156 posts
Fuels Question 15
We are manufacturing white cement. Previously we used oil fuel, now gradually we have switch over to petcoke and now a days we are using almost 85 per cent of petcoke and 15 per cent of LSHS oil as a fuel. After this we are facing a problem that clinker is not coming out in a nodular form and it is almost in dusty condition. Kindly suggest that what corrective or preventative measure should be taken for getting the clinker in the nodular form from the kiln.