Separation Development Studies on the Beneficiation of Fine Lignite Coal Tailings by the Knelson Concentrator

While disposing of fine coal without use was cheaper and more permissible previously, recovering some of the fine coal changes the mass balance of wastes and makes co-disposal or integrated dumps possible. The present study aims to investigate the processing of fine lignite coal tailings with 59.08% ash content from Soma tailings ponds in Turkey using a Knelson concentrator and to identify in both numerical and experimental methods the fundamentals of the reason why the Knelson concentrator must be operated in hindered settling conditions for high efficiency separation of high ash-bearing fine lignite coal tailings. The lignite coal tailings were treated by a two-stage concentration scheme for the recovery of fine clean coal. Pre-enrichment experiment parameters were determined by the Taguchi experimental design method, and the results were interpreted by the SPSS 17.0 program to evaluate the optimum parameter values. After the pre-enrichment process, a coal concentrate (42.60% ash, 0.71% total sulfur, and 3350 kcal/kg calorific value) was obtained with a 37.67% yield of coal using a 44 mm hydrocyclone. Under optimum conditions, an underflow product of hydrocyclone was reprocessed in the Knelson concentrator to reduce the coal ash content. The process yielded a coal product containing 30.51% ash and 4259 kcal/kg base calorific value with a separation efficiency of 19.50% using the Knelson concentrator. Without coal tailings being classified in hydrocyclone, better separation efficiency was achieved under the hindered settling conditions when direct feeding was made to the Knelson concentration at solids concentrations as high as 40%.