A separator consisting of two concentric right-vertical tubes, a conventional cyclone header at the top, and a froth pedestal at the bottom. The inner tube is a porous-wall tube. The slurry is fed tangentially through the cyclone header to develop a radial swirl flow. Air is sparged through the jacketed, inner porous tube wall and is sheared into small bubbles by the swirl flow. Hydrophobic coal particles in the slurry attach to the air bubbles and report as overflow product. The hydrophilic refuse particles remain wetted and report as underflow product.