Material separation by dielectrophoresis

A method of separating a mixture of polarizable and non-polarizable electrically neutral solid coarse particles comprising

• (a) introducing the mixture of particles onto the inlet end of a substantially horizontal surface;
• (b) conveying the mixture of particles along a longitudinal path on the surface while subjecting the particles to a nonuniform electric field in air, the field being strong enough to cause polarizable particles to move transversely across the path while being conveyed longitudinally;
• (c) recovering from the edge of the electric field where the field intensity is at a maximum the polarizable particles;
• and
• (d) recovering from the outlet end of the horizontal surface the non-polarizable particles that moved substantially longitudinally and completely along the path.

A method of separating a mixture of low and high dielectric contants, electrically neutral, solid, coarse particles comprising

• (a) introducing the mixture of particles onto the inlet end of a substantially horizontal surface;
• (b) conveying the mixture of particles along a longitudinal path on the surface while subjecting the particles to a nonuniform electric field in air, the field being sufficiently strong to cause high dielectric constant particles to move transversely across the path while being conveyed longitudinally;
• (c) recovering from the edge of the electric field where the field intensity is at a maximum the high dielectric constant particles;
• and
• (d) recovering from the outlet end of the horizontal surface the low dielectric constant particles that moved substantially longitudinally and completely along the path.

Apparatus for separating electrically neutral solid particles of different dielectric dipole moment, shape and/or density properties from a mixture thereof comprising

• an electrically conductive grounded substantially horizontal surface having a receiving end, a discharge end, and two lateral edges;
• an electrically charged electrode having an arcuate surface spaced above said horizontal surface and extending substantially over the entire length of said horizontal surface from said receiving end to said discharge end, the perpendicular distance from one lateral edge of said horizontal surface to said arcuate surface being less than that measured at any location away from said lateral edge, and the perpendicular distance between said horizontal surface and said arcuate surface along said lateral edge being substantially constant over the entire length of said arcuate surface;
• means for introducing a mixture of electrically neutral solid particles of different dielectric properties onto said horizontal surface;
• means for charging said electrode;
• means for moving said particles at a steady rate across said horizontal surface from said receiving end to said discharge end;
• means for recovering particles from said discharge end of said horizontal surface;
• and
• means for recovering particles from said lateral edge of said horizontal surface.

Apparatus for separating electrically neutral solid particles of different dielectric dipole moment, shape and/or density properties from a mixture thereof comprising

• two spaced surfaces in substantially the same horizontal plane, each having a receiving end, a discharge end, an inner lateral edge and an outer lateral edge, said surfaces being electrically conductive and being grounded, and the space between said inner lateral edges being electrically nonconductive and extending substantially entirely from said receiving ends to said discharge ends;
• an electrically charged electrode having a smooth surface having the shape of one generated by rotating about an axis a substantially straight line lying in the same plane as the axis, said electrode being positioned with its axis vertically above the longitudinal centerline of said space between inner lateral edges and positioned such that said substantially straight line is substantially parallel to and closely adjacent to said centerline in said horizontal plane;
• means for electrically charging said electrode;
• means for introducing a mixture of electrically neutral solid particles of different dielectric properties onto said two spaced surfaces at said receiving ends;
• means for moving said particles across said spaced surfaces to said discharge ends;
• and
• means for recovering particles in said space between said inner lateral edges and for recovering particles from said discharge ends.