Electrical selection theory

Theoretical basis of electrification Electrification is a physical beneficiation method that uses various minerals and materials to conduct electrical separation.

The content of electrification is very wide, including electrical selection, electrical grading, triboelectric charging sorting, dielectric sorting, high gradient electrification, and electric dust removal.

The electric selection is based on the electrical properties of various minerals. Under the action of the electric field, the electric power and mechanical force (referred to as centrifugal force, gravity, resistance, etc.) of the ore particles are different, and the generated trajectories are also different, so that they are separated. A method of mineral processing. The electric grading is different according to the particle size, density or shape of the material, and the trajectories generated in the high-voltage electric field are also different, so that the materials are divided into different granules or types to meet the needs of the next operation.

Frictional electrification uses two kinds of ore particles to contact, collide and rub each other, or to make friction with a material made of a certain material to produce a different size and opposite sign charge, and then into the high voltage electric field, due to the mine Different particle charging symbols produce distinct trajectories that separate the two minerals.

Dielectric sorting is carried out in a liquid medium or an air medium, usually in a liquid medium. Two kinds of ore particles or materials with different dielectric constants. In a non-uniform electric field, if the dielectric constant of a certain ore particle is greater than the dielectric constant of the liquid, the ore particle is attracted; otherwise, the dielectric constant is smaller than the liquid. Then they are excluded, so that they are separated.

High-gradient electrification is a new method developed on the basis of dielectric separation principle. It is mainly for the separation of fine-grain minerals. A dielectric (non-conductor) fiber or pellet is placed in the dielectric liquid. After being polarized by the electric field, the dielectric body generates a highly uneven electric field on the surface thereof, thereby increasing the force of the non-uniform electric field. When the dielectric constant of one of the ore particles is greater than the dielectric constant of the liquid, the particles are attracted to the electric field strength and the maximum gradient region, and vice versa, and then enter the low electric field region, and the movement trajectories of the two ore particles are also different. Can make it separate. High-gradient electrification, much like high-gradient strong magnetic separation, is placed in a sorting tank of fiber or ball media, similar to high-gradient magnetically selected steel wool or other media, and is also a capture medium.

At present, except for a few minerals directly using electro-selection, in most cases, electrification is mainly used for the selection of various minerals and products. Before electrification, most of them are coarsely selected by re-election or other beneficiation methods to obtain coarse concentrate, and then a single electrification or electrification is combined with magnetic separation to obtain the final concentrate. Some minerals are similar in magnetic properties, density and floatability. Reselection, magnetic separation and flotation are not possible or difficult to sort effectively, but they can be sorted by using their electrical properties. Except for dielectrophoresis and high-gradient electrification, which are carried out in dielectric liquids, the rest are dry-type operations, which are superior to water-deficient areas. For some materials that are only suitable for dry grading, electrical grading has significant advantages. Electrification does not pollute the surrounding environment, so it has been widely used in some developed countries in the world. The effective treatment particle size of electric electrification is usually 2 mm to 0.1 mm, but for the sheet or density materials such as mica , graphite , coal, etc., the maximum processing particle size can reach about 5 mm, while the wet high gradient electric separator The processing particle size can be reduced to the micron level. Some people in China have studied that even the general drum type electric separator can reduce the lower limit of particle size to 20 microns. In most cases, the electrification is carried out in a high-voltage electric field. Except for a few high-voltage AC power supplies, most of them use a high-voltage DC power supply to deliver negative electricity to the electrodes. In some cases, positive power is used.

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