We have problem of hard clinker used in cement grinding. This clinker is produced by using 100 per cent pet coke in firing. Although chemical composition of clinker is correct. It has 50 per cent C₃S, 5.5 per cent C₃A, & liquid approx 28.5 per cent & SO₃ in clinker 1.6 per cent. But minerology observed under microscopy reveals following: Mineralogical composition and Granulometry of - 6 mm clinker: Phases present Quantity (per cent) Granulometry (size in micron) Min. Max. Average required size Alite (C₃S) 46.5 8 82.69 42.14 20 Belite (C₂S) 34.5 3.5 93.00 38.26 15 Liquid phase (C₃A+C₄AF) 18.6 Porosity Low porous 22 120 65 (more data attached) Photomicrographs are given in attachment. Kindly suggest How to reduce Alite grain size & increase porousity of clinker. Our kiln is already running in full RPM. Is it possible to make softer clinker by changing chemical composition.

I have looked at the photomicrographs and read your analysis with interest. In order to properly answer your questions I would have to ask Dr Chromy to examine and analyse the mineralogy of the clinker. I'm afraid that Dr Chromy would charge for that and therefore Aditya Birla would have to pay. I will contact Mr Modi and Mr Agrawal to see whether they want me to refer this to Dr Chromy. One we have his analysis then we might be in a position to suggest the means to reduce the alite grain size and make softer clinker by adjusting the chemical composition.

What are the current international standards of MTBF for kilns and mills?

There is a difference between mean time between failures and mean time between stops. Best practice for kiln MTBF in the cement industry is in excess of 750 hours, while MTBS is somewhat shorter. The problem with MTBF is that it is easier to massage the data and cheat because some stops are planned and therefore do not count. In that situation it is easy to bring forward a planned stop when you have an unexpected unplanned stop.