Abstract: Reducing apparatus includes a bottom rotor rotatable at a relatively high speed to provide relatively high centrifugal and G forces for reducing material disposed on the rotor. An upper conical element is disposed above the rotor and is free-wheeling relative to the bottom rotor, and thus rotates in response to rotation of the bottom rotor. Material to be reduced moves downwardly onto the bottom rotor through the conical element. High centrifugal and G forces resulting from the high rotational speed of the bottom rotor move the material outwardly to impinge upon the conical element for reduction. Vertical spacing between the two rotating members may be adjusted for varying the degree or extent of the reduction. The axes of rotation of the two members may be offset to provide additional G forces and a scrubbing action.

Abstract: The invention relates to a method of ore beneficiation.The process comprises:(1) grinding the ore to produce a first product comprising ground ore and ground gangue,(2) separating the first product into a fraction having particles of a selected size range and a remainder,(3) separating at least a part of the remainder into a ground ore fraction and a ground gangue fraction,(4) combining the particles of selected size range from step (2) with the ground ore fraction of step (3), and(5) autogenously and/or semi-autogenously grinding the combination of step (4).The process is particularly suitable for lead and/or zinc sulphide ores.In step (5) at least 80% of the resulting ore can be ground to a particle size of less than 6 microns.