Improvements in or relating to the upgrading and dewatering of coal

In a process for upgrading small coal, a thick slurry of the coal is prepared and is mixed with a mixture of paraffinic and tar oils to form an oily pulp which is aerated in a flotation cell so that the clean coal is floated up as oiled flocs, the latter being then removed from the cell and dewatered in a centrifuge. Crushed coal or natural small coal is wet screened at 1.0 or 0.5mm. The undersized slurry is thickened to 35 to 40% solid content in a rake thickener, settling cone or hydrocyclone. The thickened slurry is treated with 1-5% by weight of a mixture of diesel and tar oils. The clean coal-flocs formed are floated by aeration in a flotation cell. The flocs are then partially dewatered on a curved static wedge-wire screen and delivered to a pug mill or screw mixer for blending back with the oversized fraction originating from the wet screening step. With slurry containing undersize in the range of - 1mm. or coarser, the blending back step may be eliminated. The blended product or the partially dewatered slurry (-1mm.), as the case may be, is then finally dewatered in a continuously operated basket centrifuge.