The present invention is directed to a type of flotation machine that combines three separate operations in a single unit. The flotation machine is a hydraulic separator that is capable of reducing the pyrite and other mineral matter content of a coal. When the hydraulic separator is used with a flotation...http://www.google.com.au/patents/US5472094?utm_source=gb-gplus-sharePatent US5472094 - Flotation machine and process for removing impurities from coals
