We are a cement plant, operating with 100 per cent petroleum coke with 6 per cent sulphur. If the amount of SO₂ in the waste gas is less than 100mg/m³,and no ring problem in the kiln what is in your opinion the disadvantage of using this product in the environment.

I see no environmental or pollution related disadvantages in using petroleum coke to fire your kilns.

We are having a 1.5Mt six-stage Precalciner kiln operating with South African coal having a VM of 28 per cent. Now we thinking to switch over to Indonesian coal with high VM content (up to 42 per cent) and Chinese coal (VM up to 32 per cent). The coal mill is a VRM having hot gases from cooler. Up to what maximum VM we can go without having explosion problems. With high VM coal what are the other changes to be carried out to regarding coal residue so that we do not get problems in the flame shape.

There are well established guidelines for the safety operation of coal grinding equipment. These fall into two broad categories:
(i) explosion prevention, and
(ii) explosion protection.
For prevention the best solution is to ensure that there is less than 12 per cent oxygen in the atmosphere. You cannot do that when cooler exhaust air is used for coal drying. As a general guideline drying with cooler exhaust air is suitable with direct firing systems. Other prevention measures are to ensure there are no fine coal dust accumulations in the system and no possible sources of ignition. These are determined by the design of the coal milling and storage system.