How To Evaluate Grinding Mill Performance Using The Bond Work Index To Measure Grinding Efficiency

With the rapidly rising cost for electrical energy and the long range predictions for continued rising costs and even possible shortages, operation of rod, ball, autogenous and partial autogenous grinding circuits to efficiently utilize the power delivered to the mills will be demanded. This calls for a method that can be used to evaluate grinding circuit performance that is accurate, reliable and readily usable as an operating tool by supervisory, technical and operating personnel.

Neither the Rittinger and Kick theories of comminution, which precede the Bond theory by more than 50 years, had a mathematical means that could be used to predict and evaluate the performance of crushers and grinding mills used to comminute ores and rocks. This soverly limited the practical use of these two theories, which were contradictory to each ether and which have been superseded by the Bond Third Theory of Comminution.

In addition to the Third Theory of Comminution, better known as the Bond Theory, Fred Bond made three significant contributions so assist in the efforts to change the art of comminution into a science.

1. The Bond rod milling and ball milling closed circuit grindability test.
2. The Bond impact crushing test.
3. The Bond equation, the mathematical statement for applying the Bond Theory to comminution practice, which is as follows: (1)

Where W = Kw hrs per short ton

• W_i = Work Index
•  P = Product site in micrometers which 80% passes
•  F = Feed size in micrometers which 80% passes.

Power per metric tonne (1000 kilograms) can be obtained by multiplying W by 1.102.