Our plant has four cement mills (closed circuit with first generation seprator) - we use about 20 per cent slag , the output is 100tph ,the dimension of every mill is 15.5 x 4.4, the liners in the first chamber are lifting and in second chamber classifier. Are there any ways to increase mill production? How about for a raw mill?

There are numerous ways to increase the production from your cement mills. In the short term use of grinding aids combined with optimisation of the ball charge and drafting would be the best method. Longer term (and at greater cost) you could upgrade the separators to third generation or install a roll press to pre-crush the clinker ahead of the mills. With regard to raw mills you can again use grinding aids or install pre-grinding equipment.

I would like to know the influence of iron ore addition in raw mix ie in burnability, specific heat consumption, etc.

The iron oxide additions in your raw mix increase the melt content at the clinkering temperature in the kiln. The iron oxide forms the mineral C₄AF which is a liquid in the burning zone. This fluxes the combination into the clinker minerals increasing the burnability and reducing the fuel consumption.