Abstract: Brittle material (1) is ground batchwise as a bed of particles by compression between non-yielding hard surfaces at a pressure of at least 50 MPa. In order to reduce the energy requirement and machine expenditure needed for fine, superfine and microfine comminution, the bed of particles is subjected to repeated stressing by pistons (4) in different directions and at least in part successively. The stressing preferably is accomplished by groups of two opposed pistons (4), which are offset at an angle with respect to each other and which are rendered active one after the other. The stressing is repeated in another plane of the grinding chamber. Wet grinding is carried out in a closed grinding chamber from which the liquid expelled from the voids between the particles being ground can drain through at least one aperture of narrow cross section.

Abstract: An apparatus and a method of effecting the separation of paramagnetic particles from non-paramagnetic particles in the fine and finest particle size ranges of approximately below 1 mm suspended in a fluid medium by the passage of the fluid medium through an apparatus having a separation channel suitable for containing a flow of the fluid medium flowing therethrough and which includes at least two exits suitable for separating the paramagnetic particle enriched fluid medium from the paramagnetic particles depleted fluid medium into two product streams, the separation channel defining the direction of the fluid medium flow being at least partially paralleledly oriented with respect to a magnetic induction member such that the magnetic flux exerted upon the paramagnetic particles within the fluid medium flow are repulsed from the induction member and entrained within the fluid medium to countereffect the effect of inertial forces or gravitational forces on the fluid flow, and separated from the non-paramagnetic

Abstract: In jigging for purposes of gravity separation of material to be concentrated the material is sorted into a heavy fraction which is withdrawn through a screen (2) and a light fraction withdrawn above the screen (2), by periodically passing flows from the bottom to the top through the feed material. If the material is predominantly of finer character, there will be a ragging (3) on the screen (2) composed of particles which are larger and usually also specifically heavier than those of the feed material. In this manner, however, the separation of feed material will be unsatisfactory in the fine particle size range having upper particle size limits between 300 .mu.m and 1 mm, particularly so if the particle size ratio of the material is rather broad.