Abstract: A system for dry separation of powders into at least two fractions including a powder to be separated and a separator including a hollow body rotating about an axis and defining a cavity having a powder engaging surface, the surface of the cavity being a surface of revolution which rotates about the axis, an upper edge of the cavity having a greater diameter than a lower edge, a system controlling the rotation of the body, at least one feeder continuously feeding dry powder into a feeding zone adjacent to the cavity surface near the lower edge, the length of the feeding zone being at least an order of magnitude less than a circumference of the cavity surface of the lower edge, at least one discharge device continuously discharging the powder from the cavity surface, the at least one discharge device including a body arranged along substantially the entire length of the generatrix of the cavity surface and located immediately in front of the feeding zone aligned with the rotation of the cavity surface, a first

Abstract: A centrifugal separator for separating two components of a dry mixture has an annular surface inclined upwardly outwards and having a vertical axis of symmetry and a drive mechanism for rotating the surface around the vertical axis of symmetry. A centrally located feed mechanism feeds the mixture onto the surface. At least a first part of the surface is configured such that particles of one component are retained on the surface while particles of the other component progress upwards across the surface and over the upper edge. The separation process may be based on ridges or barriers which prevent upward movement of small particles, or on frictional differentials between types or shapes of particles. Multiple concentric surfaces may be used to separate mixtures in multiple components.