Naoya Kotake

Experimental study on the grinding rate constant of solid materials in a ball mill

Abstract The grinding rate constant, in the widely accepted first-order expression of grinding rate, is one of the important factors required to evaluate a grinding process particularly for its initial grinding stage of various mill types. In this study, we conducted grinding tests on silica glass, limestone and gypsum using a laboratory ball mill, and measured the grinding rate constant of the feed size reduction. We investigated the effects of feed size and ball diameter on the grinding rate constant of the materials used when the mass of balls, mass of feed, and the mills rotational speed were constant. The results indicate that the variation of the grinding rate constant with feed size of the materials can be expressed by revising the equation proposed by Snow. For the grinding rate constant of each material, empirical equations were developed to express it as a function of feed size and ball diameter.

Chapter 12 Comminution Energy and Evaluation in Fine Grinding

Publisher Summary This chapter highlights comminution energy and evaluation in fine grinding. The purposes for comminution are to liberate minerals for concentration processes, to reduce the size, to increase the surface area, and to free the useful materials from their matrices. Comminution is an old mechanical unit operation for size reduction of solid materials and an important operation in the field of mineral processing, the ceramic industry, the electronics industry and so on. The energy efficiency of comminution is very low and the energy required for comminution increases with a decrease in feed or produced particle size. Research and development to find energy saving and the energy required in comminution processes have been performed. In design, operation and control of comminution processes, it is necessary to evaluate the comminution energy of solid materials. In general, the comminution energy (i.e., the size reduction energy) is expressed as a function of the particle size of feed and product. In addition, the chapter also presented various Laws of comminution energy including Rittingers law Kicks law Bonds law, and Holmess law.

Production of fine Sr-ferrite particles by ball mill grinding in various grinding conditions

The processes for obtaining fine Sr-ferrite particles have direct efects upon the crystallite size and distribution of sintered Sr-ferrite specimens. The influence of grinding conditions on the production of fine Sr-ferrite particles during ball mill grinding was investigated. The grinding experiments were carried out under dry and wet conditions, and dry condition with methanol as a grinding aid. Particle size distributions of the ground products were measured by the microscopic method, and could be expressed accurately as described by a modified Gaudin-Schuhmann equation. The fine grindability of Sr-ferrite particles was evaluated by the median particle size in undersize distribution, and the ratio of 10% and 90% cumulative weight passing sizes that showed the broadness of the size distribution. Sr-ferrite particles with a median particle size of 0.8-1.0μm were produced. The broadness of the size distribution increased with decreasing median particle size of the ground products. The broadness of the size distribution by wet grinding and dry grinding with a grinding aid was lowered using larger grinding media.