Abstract: The device according to the invention for separating or classifying material to be fed into at least two different grain fractions comprises a screen device, which is formed by rotatable elements, particularly a roller table screen, wherein at least one finer grain fraction passes between the rotatable elements and means are provided for cooling the rotatable elements.

Abstract: The present invention pertains to the separation of mixtures of plastics, contaminated with, among other things, mineral heavy materials such as e.g. sand or metal refuse. Separation occurs according to density in a separating liquid in the centrifugal field of the rotating suspension. The present invention provides the connection of a hydrocyclone before a separating centrifuge. The mineral heavy materials are separated in advance in the hydrocyclone and the plastic mixture is further separated in the centrifuge. Wear on components of the separating centrifuge caused by these heavy materials can be avoided, and in some applications a second separating stage at a higher separation density can be eliminated.

Abstract: The invention consists of forming an aqueous slurry of water and particles of ore carrying both metals and/or minerals which are passed at relatively high speed along an electrically isolated path in contact with electrically insulating materials and in the presence of air. This generates a positive electrostatic charge in the water droplets and enclosed particles and a negative charge in the electrically insulating materials through which they are being driven. The water droplets and hence the particles become differentially charged so that when they pass over an oppositely charged negative field, they are driven into the lower oppositely charged field body by the strong force of electrical attraction and the relatively weaker force of gravity. Should the negative collector contain an amalgamating material such as mercury and the ore, as an example contain gold, electrons are exchanged providing instant amalgamation of the surface of the gold.