Screening and classification

The processing of minerals almost invariably involves the reduction in size of the minerals contained in an ore to effect liberation of disseminated values or, in other instances, to effect increased surface area. Separation of solids according to size usually is undertaken to promote maximum production from crushing and grinding equipment. Screens are generally used for making this size separation when coarse material is involved, whereas classifiers and cyclones usually are employed when fine particulate material is being processed. However, special screening devices may be used for separations as fine as 325 mesh. The term "mesh" refers to the number of openings per linear inch on a screen. Mesh number vs. size of screen opening is listed in Table 27-12.