Simple approach to estimation of the work index

Abstract

The work index of the mill feed of any mineral processing plant, determined according to the procedure prescribed by F. C. Bond in 1961, is still considered useful for estimation of the required size and power of a mill, especially in the preliminary phases of a feasibility study. The index, however, is no longer considered very important from economic or operational points of view. Moreover, scientific and technological advances in the design, operation and control of comminution circuits have rendered very precise determination of the work index unnecessary. It is, therefore, considered logical to develop a simple method of obtaining a fair estimate of the index that does not require special equipment and experimental procedures.

An approach is presented that is based on a statistical analysis of data accumulated over four decades of experimental determination of the work indices of a large number of ores, minerals and rocks. A simple model has been developed that correlates the work index of a material and the parameters of the Rosin-Rammler size distribution of an experimental feed passing 6 mesh (-3327 μm). All that is needed is to crush a sample of the mill feed to -3327 μm, determine the size-distribution parameters from sieve analysis with the aid of a computer and compute the work index from the correlation model.