Characterization and numerical simulation on preparation of super-low ash clean coal by two-stage cyclones

Abstract

ABSTRACT This study used two-stage cyclones combined with a full cylinder and a short cone cyclone to recover super-low ash clean coal from the coal slime to solve problems of coal slime such as large production, difficult recovery, and low value-added used. After two-stage cyclones separation and screening, super-low ash clean coal with an ash content of 2.74% was obtained, and the mass yield was 10.56% via a simple and easy method that realized high value-added utilization of coal slime. The separation test indicated that the grading effect caused the first-stage cylinder to remove a large amount of high-ash fine mud in the coal slime and water, decreased the complexity of the particle size, and provided favorable conditions for the density separation of the second-stage cyclone. Through density separation effect in the second-stage cyclone, the recovery of −1.3 g/cm3 density grade in Cyc.O/F is 84.15%, which led to effective coal recovery. Additionally, its cutting density exceeds 2 g/cm3. Computational fluid dynamic simulations indicate that the high turbulence zone corresponds to the main gradation and separation action area and the high turbulence due to the existence of circulating flow, due to its circulating flow, particle separation and grading is obtained.