Parameters in wet grinding : the influence of process variables on autogenous and conventional grinding

Sammanfattning: The effects of autogenous and conventional grinding on the liberation of particles have been studied on the laboratory, pilot and industrial scales. It appears that autogenous grinding, down to flotation fineness, results in a higher degree of liberation and smoother particle surface for flotation, than is obtained with conventional grinding. An energy-liberation model is derived which provides a rapid analysis technique for determination of the optimum net energy consumption. It reveals the importance of ore characteristics in liberation. The relative importance of the effects of charge volume, feed rate, feed size or classification efficiency, mill speed and pulp density on fineness, net energy consumption and mean residence time have been studied using a multiple parameter approach. Computer-based response surfaces delineate all aspects of the comprehensive effects of the process variables on conventional grinding. The work described here also includes a study of the transport behaviour of particles flowing through conventional mills. A new RTD-model is established and confirmed under practical conditions. The implication of the mean residence time in net energy consumption and grinding fineness is investigated. On the other hand, the relations between fineness and net energy consumption are also modelled. Here, the importance of classi fication on efficiency in continuous grinding is demonstrated.