Abstract: The specification describes particle-charging, specie-separating and concentration-enhancing methods and apparatus which operate on a substantially continual basis. The particles of each specie in a mixture are charged by surface contact, separated in an electric field according to their respective polarities by motion in the direction of the field, and the particles of like net polarities are transported in substantially continuous streams, each of opposite net polarity, running near each other, in a direction or directions transverse to the electric field, the streams being in communication parallel to the electric field, so as to transfer particles of at least one of the species to the other of the respective streams by virtue of continued particle contact and field separation of charged particles as the respective streams progress transversely to the electric field. The two streams can run in the same direction (co-current) or in respectively opposite directions (counter-current).

Abstract: A mixture of particles of different materials is further comminuted by rubbing contact while moving at high relative velocity along a surface of a solid body to a substantially smaller size range during which the particles of different materials acquire a very high differential charge, and while bearing such high differential charge the particles of different material are entered into an electric field for efficient separation of particles of one material from particles of another material.

Abstract: After pulverizing feed coal to a range of particle sizes from 1 to 250 microns, the particles are divided at approximately a micron level in the range from 37 to 74 microns into a coarse fraction and a fine fraction. The inorganic material is separated from the organic material, at least in the coarse fraction, and the particles of inorganic material are excluded from the coal that is fed to the boiler.

Abstract: A rotor-type electrostatic separator is described with means to remove a boundary layer of entrained air from the rotating collector surface prior to depositing on the surface a particulate feed for particle separation. Following the feed hopper a new boundary layer of air with particles in it is entrained on the rotating collector surface. Means are also provided to shield from the action of corona wind the region immediately following the feed hopper where the particles enter the newly-forming boundary layer.

Abstract: After pulverizing to minus 200 mesh, a mixture of coal and pyrite particles is passed through an A.C. silent corona discharge in the presence of a reactant gas. Simultaneously, the particles are de-agglomerated and an electrical or magnetic difference between them is enhanced. Thereafter, the pyrite is separated from the coal. The effectiveness of the pulverizing step in separating pyrite particles from the coal matrix, especially small-size particles approximately 50 micrometers and less, is enhanced by pretreating the coal with a chemical comminutant. One example is a solution of ammonia, used to presoak the coal for a short time, at, for example, atmospheric pressure and ambient temperature.