1156 posts
Quality control Question 41
I wrote you before. Thanks for response. Our problem is high free lime. Here I am giving you the complete analysis of clinker and kiln feed: (data enclosed). We are using South African and Indonesian coal. What may be the cause of high free lime. Other than that kiln feed and clinker analysis, I want to tell you that we have two kilns and free lime increased on both kilns at the same time.
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1156 posts
Re: Quality control
I presume the analysis should read K2O and Na2O in the clinker? If so we can discount the K2O content as the reason for the high free CaO. The K2O will preferentially combine with the SO3 in clinker and therefore there will be little surplus to combine in the clinker minerals and inhibit the formation of C3S. The 90 micron residue of the kiln feed is also low at 12% per cent. However the critical factor is the mineral composition of this residue. If there is a high quartz content in these coarse particles that might be the cause of the problems. If not then it is some factor we haven't identified yet. Possibly the kiln operation or the combustion.The fact that the free CaO has risen simultaneously on both kilns suggests that this is a material or chemistry related problem rather than a process equipment problem. What has changed before the rise in free CaO? Raw material sources? A new level in the quarry? Introduction of a new fuel? You should also check the calibration of the equipment (XRF?) used in the quality control of the kiln feed.
1156 posts
Quality control Question 42
We operate one open circuit two chambers ball mill of size 4m dia X 13.5m long for Cement grinding. Capacity:100tpd drive motor: 2x1500 kW (twin drive) Power drawn: 2500 kW (more data on grinding media). >We are maintaining a blaines of 2700 to 2800. The cement is coarser having a residue of 10 per cent over 90 micron sieve and 30 per cent over 45 micron sieve. Increasing the blaines reduces output and increases the power consumption. How to achieve lesser residue keeping the same blaines.
1156 posts
Re: Quality control
There is no easy way to adjust the particle size distribution of an open circuit mill while maintaining the same Blaine. To do that you need a separator in closed circuit with the mill to send the oversize material for regrinding. You may have some success with grinding aids. Alternatively you could try for a more coarse media grading in the second chamber. However the results of doing that cannot be precisely predicted.