Coal Middlings Recycling – A Route for Increasing the Yield of Sellable Concentrate

Because of the low quality, middlings from the coal preparation often remain unused and are stored on the industrial site or simply landfilled. The authors offer a possible solution to this problem; its main idea is to upgrade the flowsheet of the coal processing plant by recycling the by-product that will turn it into valuable concentrate. Such approach would increase the efficiency of processing, allow comprehensive utilization of mineral raw materials, reduce the loss of combustible matter from coal with rejects, and would result in higher revenue from the sales of high-quality coal concentrate. This article represents outcomes of the studies of coarse coal middlings as potential raw material for producing sellable concentrate. The middlings are obtained from a coal preparation plant located in Kuznetsk coal basin, Russia. Samples have been crushed down to a size of 13 mm, and then a float-sink analysis has been completed from which the liberation degree is calculated. Performance of gravity separation and flotation of slimes has been evaluated with a laboratory scale equipment. It is shown that middlings of the coking coal have high potential to yield a high-quality concentrate. Forecasted mass balance of the proposed flowsheet for the middlings reprocessing shows that 50 to 80% of total middlings production might be transformed into low-ash coal concentrate.