Graphite flotation, gravity separation and electrostatic separation purification

Graphite is an important carbonaceous non-metallic mineral. Its beneficiation methods mainly include flotation, gravity separation and electrostatic separation. Among them, flotation has become the most commonly used beneficiation method due to its wide applicability and excellent natural floatability of graphite. By adding suitable collectors, the grade of graphite concentrate can be effectively improved, although the grade obtained by traditional beneficiation methods can usually only reach 97% at most. In order to obtain higher purity graphite, purification technologies such as high-temperature alkali fusion acid leaching, acid leaching and chlorination roasting are also required.

1) Flotation

Flake graphite is usually separated by flotation due to its good natural hydrophobicity. Commonly used flotation collectors include non-polar hydrocarbon oils such as kerosene, diesel and heavy oil, while frothers are commonly used No. 2 oil or No. 4 oil. Internationally, new collectors such as phenols, sulfonates, sulfates or carboxylates are also used, or these agents are mixed for use.

In contrast, cryptocrystalline graphite has poor selectivity and flotation is difficult to significantly improve its grade. However, due to the high fixed carbon content of its raw ore, the concentrate and tailings obtained by flotation can be sold as products of different grades. When the content of silicate minerals in graphite ore is high, depressants such as water glass, starch and cellulose can be used for flotation. If the content of pyrite in the ore is high, the pH value can be adjusted by adding quicklime to inhibit its flotation.

2) Electrostatic separation

Graphite has better electrical conductivity than most gangue minerals, such as quartz, mica, feldspar and pyrite, which makes it possible to separate graphite from other minerals by electrostatic separation. However, due to the limited production capacity and low efficiency of electrostatic separation, its application is not as widespread as flotation.

3) Gravity separation

Gravity separation is based on the density difference between graphite and gangue minerals, and is separated by physical methods. Minerals in graphite ore can be divided into heavy minerals (specific gravity>3.32), medium-gravity minerals (specific gravity between 2.9 and 3.32) and light minerals (specific gravity<2.9) according to their specific gravity.

The specific gravity of graphite is 2.2~2.3, and the rough concentrate of graphite can be obtained by gravity separation. The gravity separation of graphite is usually carried out using a wet shaking table. Although gravity separation is rarely used alone, the combined process of gravity separation and flotation is more common, that is, the rough concentrate is first obtained by gravity separation, and then further purified by flotation.