OVERVIEW

From the standpoint of chemical processing, size reduction of solids is most often performed to make them more reactive chemically or to permit recovery of valuable constituents. Common examples of comminution are of ores for separation of valuable minerals from gangue, of limestone and shale for the manufacture of cement, of coal for combustion and hydrogenation to liquid fuels, of cane and beets for recovery of sugar, of grains for recovery of oils and flour, of wood for the manufacture of paper, of some flora for recovery of natural drugs, and so on.

Since the process of disintegration ordinarily is not highly selective with respect to size, the product usually requires separation into size ranges that are most suitable to their subsequent processing. Very small sizes are necessary for some applications, but in other cases intermediate sizes are preferred. By-product fines are frequently briquetted with a binder for ease of handling. Agglomeration in general is practiced when larger sizes are required for ease of handling, or to reduce dust nuisances, or to densify the product for convenient storage or shipping, or to prepare products in final form as tablets, granules, or prills.

Comminution and size separation are characterized by the variety of equipment devised for them. Examples of the main types are described in this chapter with a few case studies. For equipment, it is essential to consult manufacturers' catalogs for details of construction, sizes, capacities, space, and power requirements. Textbooks give general information for these operations but there...