1156 posts
Burning Question 65
We have a problem related with high sand usage to make the consistent raw material mix. Sand addition for silica correction is roughly five per cent into raw material results roughly three per cent quartz content in the raw meal over 45 micron residue. Consequently the overall effect is frequent free lime formation in the clinker due to high quartz content in the raw meal, negatively effecting quality and high heat consumption in burning. In order to tackle with the problem following activities are already done
1. The burner pipe is replaced by a new design burner pipe with high momentum to improve burning and have stronger flame.
2. New coal dosing system is installed to have stable and accurate kiln fuel feed. Also with this system, we started to grind petcoke and other types of coal separately to facilitate burning. However the problem still persists.
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1156 posts
Re: Burning
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.
1156 posts
Burning Question 66
Do you have an idea of each point decreased in the standard deviation of the kiln feed and how it affects to the specific heat consumption? (for example:40 kj/kg of clinker for every additional 0.1 by which the standard deviation is raised in the usual range).
1156 posts
Re: Burning
The effect of kiln feed standard deviation on unit energy consumption is complex and is likely to vary from kiln to kiln. For a precalciner kiln each one per cent increase in the standard deviation of the kiln feed lime saturation factor you might expect an increase in the energy consumption by 150 kJ/kg clinker. However, this relationship is unlikely to be linear and will vary around that figure from kiln to kiln.