Experimental and theoretical study on strengthening mechanism of coarse coal slime classification process with cone wall structure

Abstract The accurate classification of coarse coal slime is the premise of efficient separation. Deep Cone Hydraulic Classifier (DCHC) is a new classification equipment for coarse coal slime classification, the content of fine particles (-0.2 mm) in coarse coal slime can be effectively reduced through classification, so as to create suitable feeding granularity for teetered bed separator (TBS) sorting. The DCHC designed includes a column structure area, deep cone structure area, and flush water mode of “bottom water + central water”. Experiments on the impact parameters were carried out, the results showed that: the classification efficiency increased with the decrease of feed concentration and feeding speed, increased first and then decreased with the increase of flush water flow rate. When the feed concentration was 40%, feeding speed is 0.8 m/s and flush water flow rate was 4 m3/h, the classification efficiency reached 69.3%, the content of the −0.2 mm particles in the bottom flow products was only 1.9%. The classification mechanism showed that the column structure area realized fluidization of the flow field and the deep cone structure area supplied the movement trace for the particles. Particularly the −0.074 mm particles movement trace was clear along the cone wall and could be collected as an overflow. A part of the −0.125 mm particles could be collected as an overflow, whereas the remaining part returned to the bottom flow, and increased fine particles content. In addition, the +0.2 mm particles were mostly collected as a bottom flow, and the 0.2–0.3 mm particles content are obviously affected by operating parameters. The results not only provide a new idea for the development of new classification equipment, but also provide a pathway for the efficient classification of coarse coal slime.