Electrostatic separation method and apparatus

Claim 2

A process for sorting mixed particles comprising the steps of releasing the mixed particles to fall freely in a substantially laminar stream; charging the mixed particles electrically through a corona discharge within the path of the freely falling mixed particles; discharging said particles after charging as a function of their surface conductivities through contact with ground potential into differently discharged particles; and separating said differently discharged particles through an electrostatic field within the path of the freely falling particles into groups of sorted particles.

Claim 3

The process for sorting mixed particles as defined in claim 1 wherein said mixed particles are electrically charged to their maximum possible value.

Claim 4

The process for sorting mixed particles as defined in claim 1 including the step of applying mechanical vibrations to said mixed particles for controlling the rate of flow of said particles in said laminar stream.

Claim 5

The process for sorting mixed particles as defined in claim 1 wherein said mixed particles are charged through an ionic current of negative polarity of said corona discharge.

Claim 6

The process for sorting mixed particles as defined in claim 4 including the step of varying the ionic current for varying rates of flow of said freely falling particles by varying the applied voltage associated with said corona discharge.

Claim 7

The process for sorting mixed particles as defined in claim 1 including the step of applying mechanical vibrations of varying intensity to said particles during the contact thereof with said ground potential for inducing free flow of said particles.

Claim 8

An arrangement for sorting mixed particles comprising, in combination, feed hopper meaNs; perforated plate means on said feed hopper means for adjusting the rate of flow of said particles from said feed hopper means, said plate means including a perforated movable plate overlapping a perforated fixed plate; corona discharge electrode means beneath said plate means and said feed hopper means and having openings for passing said freely falling particles; a source of high voltage for applying high voltage to said corona discharge electrode means for charging said freely falling particles; baffle means below said corona discharge electrode means in the path of said freely falling particles whereby said particles strike said baffle means and thereupon fall through spaces between individual baffles in said baffle means, said baffle means being connected to ground potential; plate capacitor means beneath said baffle means and having one fixed capacitor plate and one capacitor plate adjustable in a direction toward and away from said fixed capacitor plate, said freely falling particles passing through the space between said capacitor plates, one plate being connected to ground potential and the other plate of said capacitor means being connected to said source of high voltage; and V-shaped grounded guide means beneath said capacitor plate means for collecting said freely falling particles into groups of sorted particles.

Claim 9

An arrangement for sorting mixed particles comprising, in combination, feed hopper meaNs; perforated plate means on said feed hopper means for adjusting the rate of flow of said particles from said feed hopper means, said plate means including a perforated movable plate overlapping a perforated fixed plate; corona discharge electrode means beneath said plate means and said feed hopper means and having openings for passing said freely falling particles; a source of high voltage for applying high voltage to said corona discharge electrode means for charging said freely falling particles; baffle means below said corona discharge electrode means in the path of said freely falling particles whereby said particles strike said baffle means and thereupon fall through spaces between individual baffles in said baffle means, said baffle means being connected to ground potential; plate capacitor means beneath said baffle means and having one fixed capacitor plate and one capacitor plate adjustable in a direction toward and away from said fixed capacitor plate, said freely falling particles passing through the space between said capacitor plates, one plate being connected to ground potential and the other plate of said capacitor means being connected to said source of high voltage; and V-shaped grounded guide means beneath said capacitor plate means for collecting said freely falling particles into groups of sorted particles.

Claim 10

The arrangement as defined in claim 7 including vibrating means mounted on said feed hopper means.

Claim 11

The arrangement as defined in claim 7 wherein said plates include perforated holes with diameter substantially larger than the largest expected diameter of said particles.

Claim 12

The arrangement as defined in claim 9, and including means connected to said movable plate for changing the position thereof relative to said fixed plate to thereby change the overlap of the perforations provided in said plates.

Claim 13

The arrangement as defined in claim 7 including vibrating means for applying vibrations to said baffle means.

Claim 14

The arrangement as defined in claim 7, wherein said corona discharge electrode means comprise a pair of high-voltage electrodes arranged in a vertical plane one above the other and a pair of ground electrodes respectively located to opposite sides and spaced from said plane and wherein each of said perforated plates comprises a narrow strip free of perforations located above said pair of high-voltage electrodes.

Claim 15

An arrangement for sorting mixed particles comprising, in combination, feed hopper means for storing and releasing said mixed particles to fall freely along a predetermined path of free fall; perforated plate means on said hopper for controlling the rate of flow of particles from said hopper; particle-charging means within the path of said freely falling particles for electrically charging said mixed particles through a corona discharge; particle-discharging means for discharging said particles and located beneath said particle-charging means, said discharging means discharging said particles as a function of their surface conductivities through contact with ground potential and thereby passing differently discharged particles from said discharge means; and separating means for separating said differently discharged particles through an electrostatic field within the path of said freely falling particles, said separating means separating said particles into groups of sorted particles.

Claim 16

An arrangement for sorting mixed particles comprising, in combination, feed hopper means for storing and releasing said mixed particles to fall freely along a predetermined path of free fall; perforated plate means on said hopper for controlling the rate of flow of particles from said hopper; particle-charging means within the path of said freely falling particles for electrically charging said mixed particles through a corona discharge; particle-discharging means for discharging said particles and located beneath said particle-charging means, said discharging means discharging said particles as a function of their surface conductivities through contact with ground potential and thereby passing differently discharged particles from said discharge means; and separating means for separating said differently discharged particles through an electrostatic field within the path of said freely falling particles, said separating means separating said particles into groups of sorted particles.