ANS:A - Rittinger's law

The most accurate law for predicting the energy required for size reduction of coal to -200 mesh in a ball mill is Bond's law. Here's why:

1. Rittinger's Law:
   • States that the work required for size reduction is directly proportional to the increase in surface area.
   • It is more applicable to fine grinding where the surface area dominates the energy requirement.
2. Kick's Law:
   • States that the energy required for size reduction is proportional to the reduction ratio.
   • It is more applicable to coarse crushing or when the initial size of the particles is large.
3. Bond's Law:
   • States that the energy required for size reduction in a ball mill is proportional to the square root of the surface to volume ratio of the product and feed materials.
   • This law is specifically formulated for ball mills and takes into account both the feed size and the desired product size, making it suitable for predicting the energy requirements for coal grinding to a specific fineness such as -200 mesh.