EFFECT OF PROCESS PARAMETERS ON THE GRINDABILITY AND BOND INDEX OF BAUXITES AND ALUMINA-BEARING ORES

A specially designed laboratory model of a universal Hardgrove mill was used to study the grindability and Bond-work index of a wide range of bauxites and other alumina-bearing ores. The method of investigation that was used conforms to the standards ASTM D409, ISO 5074 1980, and BS: 1016 Part 20 1980. The resulting values make it possible to rank bauxites based on their grindability. An attempt was made to correlate this characteristic with the mineralogical composition and textural-structural features of bauxite. A single method was used to obtain reference values of the Bond-work index of bauxites from most of the mines in the world. Temperature, grinding conditions, and other factors have a significant effect on the grinding of bauxites. The method developed in this study makes it possible to select operating regimes with allowance for the mechano-chemical reactions that take place. The method can also be used to speed up the grinding operation. The completed study showed that the accessibility of the measurements and the use of a lightweight sample in the method employed to simulate the industrial grinding of bauxites are two features that can be put to good use in the design of new, more powerful grinding equipment and the optimization of existing units. This will yield significant savings in terms of both capital investment and operating costs, i.e., a decrease in the amount of energy needed for grinding. Studies made of the grindability of Guinea bauxites (from the ore regions of Kindiya, Friya, and Dian-Dian) under different conditions (dry grinding, wet grinding in water and a commercial alkali-aluminate solution within a broad range of temperatures) have made it possible to more reliably select grinding equipment in the modernization and design of wet-grinding sections as part of projects that are currently under way.