Our ball mill is closed circuit. Its design capacity is 70tph, but we can run 85tph. However, we run it now 80tph, ie total feed is 80tph. We add limestone feed with clinker & gypsum. The limestone percantage is increasing & deceasing based on LOI. The Blaine is: 3300 to 34700 cm²/g Residue (return): 12-13 per cent SO3: 2.6-3.0. LOI: 0 to 2.5. When mill is in steady condition our seperator speed is 76 and sepex damper position within 59 to 61. But now my new terget is that Blaine is same i.e. within 3300 to 3400 cm²/g but residue to be within 8-9 per cent. Is it possible to control the blaine with respect to the requisite residue levels?

To control the residue separately to the Blaine you need to vary the recirculating load of the cement mill. To maintain the same Blaine and reduce the residue you will need to operate with a higher recirculating load.

What will be the effect of clinker on cement grinding which is produced from 100 per cent petcoke. The chemistry of clinker is as equivalent as when produced with other fuels. Also nodulisation of petcoke clinker is good. Kindly advice how to improve cement grinding performance with petcoke clinker.

It is not clear what problem you are suffering from. With petcoke clinker I expect there is a higher sulphate content in the clinker. Therefore you have to reduce the amount of gypsum addition and that will adversely affect the performance of the cement mill. I'm afrain there is no ready solution to that problem. The clinker might also be denser resulting in loss of milling efficiency. In that case addition of calcium fluoride to the kiln feed will probably help.