kiln RPM increasing

Kiln rpm,kiln slope,kiln diameter and clinker production rate data are needed to calculate % volumetric filling in any kiln.Could you please tell me what is your objective to increase kiln rpm?

Gear box ratio is required and the other parmeters like Volumetric load,power max.capacity.And also if you change the Gear box ratio corresponding changes from the electrical engineering also should be studied from them.If the ultimate aim is to increase in production ,you have to check the other process fans capacities and PH ducts handling capacities of high draughts also to be considered.

You may not need to change the gearbox ratio, it may be possible to just increase the motor speed with your frequency inverter on the motor (assuming you have this type of variable speed).  The gearbox, girthgear and pinion arrangement would need to be checked to ensure it can still operate safely (Service Factor) within the new parameters?

 It is all down to "Torque" and as we know, torque reduces with speed increase, it would very much depend on the amount of extra power you may require and of course, whether your kiln CSA can take any further increase in load?