Analysis of the operating mechanism of a Knelson concentrator

Abstract

In this study, the operating mechanism of a Knelson concentrator (KC) is analyzed by considering the concentration mechanisms of dense minerals obtained based on the feed properties, operating parameters, and design parameters of the KC bowl. The efficiency of the KC is affected by all the studied factors, i.e., the structural parameters of the ring, water flow rate, rotating speed, and gangue size distribution, which further restrict each other and act together. A concentration criterion (Xi), which is the ratio of the settling velocity to the fluidized water flow velocity, is defined to obtain the correlation between these four key factors. Based on the mechanistic linkage provided by the aforementioned criterion, these factors affect the KC performance because they influence the concentration mechanism. This determination was obtained as follows: as the magnitude of Xi increased, the concentration mechanism of the dense mineral transformed from surface plating to substitution and then to elutriation, followed by overload. In case of surface plating, the size distribution of the dense mineral in each ring was similar to that of the feed, and recovery increased gradually from ring R1 to ring R5. In case of substitution, the coarse and dense particles replaced the light particles and formed a thick concentrate layer, with high concentrate grade and tungsten recovery. In case of elutriation, the tungsten particles completely replaced the quartz particles and preferential enrichment could be observed at the bottom of the ring; in this case, the concentrate grade and recovery were the highest and the tungsten particle size was the coarsest. Further, some fine and dense particles were carried into the tailings because of the large water flow velocity.