What should be the standard sieve sizes for limestone feeding to Vertical roller mill. We were earlier using Limestone having bond index of 8-9kWh/short tonne. Now we are having limestone with bond index 11-14kWh/ short tonne. Wether any reduction in mill feed size will improve the output of the rawmill. How to calculate finess modulus of crushed limestone and what is the optimum value for VRM.

Yes, reducing the size of the feed to the raw mill should result in an increase in output. Bond's equations use the size grading where 80 per cent of the feed is passing to characterise the size of the feed to the mill. The optimum size of mill feed is related to the nip angle between the rollers and table. 60mm is quoted as the maximum size.

We have a plant of short kiln with two stations 52m length and 4.8m dia since some months we are facing problem of red glow under tyre 2 which is in burning zone the temperature increased more than 500C and also in this location contineous sliding of material is available.can u give us any solution to get rid of sliding and also make some coating in that place. The temperature sometimes reaches to 570 degrees C

These temperatures are serious and will damage the kiln. You need to change the kiln chemistry to adjust the flux content in the burning zone. You can also try increasing the rotational speed of the kiln to try to eliminate the sliding of the charge at this point.