"Attrition" is not normally a problem.  You are heating carbon at 700deg in an inert (steam) atmosphere, and any variance in temperature or air entrainment will cause the carbon to burn.

Carbon "loss" depends on the unit you use, grams/ton of solution, g/t ore, g/t slurry g/oz gold.  Based on a study by David Seymour (1991) "Carbon consumption in precious metal recovery" a rule of thumb is 10-80g/ton ore.  But staff generally work to getting this as low as oissible

Thanks Peter for the reply. 

My thinking is that feeding of carbon in rotary kiln using screw conveyor and the tumbling action of hot carbon in the rotary kiln leads to attrition of carbon that results in generation of carbon fines.

Hi Adityakale - you are correct in that a rotary kiln with a screw feed conveyor is not the best for minimising carbon fines generation. however, if you have one installed there's not much you can do except make sure that the steam injection is working. If you are designing a new plant, have a look at a vertical kiln. It does not tumble the carbon and therefore should create less fines. Of course, there are many other areas where carbon fines generation occurs. Cheers