Power Requirement of Crushing System

In crushing , the useful or meaningful work is that expended to reduce the material to a given size. A number of theories have been expressed to define the relationship between work input and size reduction. Kick’s Law states that work done is proportional to the reduction in volume of particles, a theory which applies to the crushing of large particles. However , finer product sizes conform more closely to Rittinger ’s Theory which concludes that work required is proportional to the new surface area formed, and inversely proportional to the product diameter . In any case, reduction ratio is not the only factor in determining power requirements. Nearly all crushing projects differ from one another in one or more aspects, and no hard and fast rule can be applied with regard to power consumption. However through extensive experience in the field of mechanical reduction , some average values have been compiled regarding the power requirements of different types of crushers.

Typical Power Requirements

A primary single roll crusher reducing run of quarry medium hard limestone to a 165 mm product will require about 400 watts per ton per hour. When this type of crusher is used to crush medium hard bituminous coal to the same specifications only about 65 watts per ton per hour is needed. Even with the hardest minerals single rolls use about 750 watts per ton per hour of power. Impact crushers (used as primary crushers) require about 760 watts per ton per hour of the gross load to drive them. This only increases slightly if the rotor speed is very high. A jaw crusher needs approximately 250 watts per ton per hour for its maximum size reduction. If the ratio of feed to product size is reduced then this will decrease.