Dry concentration by electrostatic separation
In the early 1900s, electrostatic separation became popular in mineral processing, until the advent of froth flotation. Since then, mineral processing has moved towards eco-sustainable processing techniques (ie, reducing the use of chemicals) and more recently, without the use of water. The
electrostatic separation of minerals highlights the significance of a dry state. Electrostatic separation is a process that uses electrostatic charges to separate crushed particles of material. These methods separate valuable minerals from gangues using differences in their electrical properties. Particles of different electrical charges or polarities are separated in an electric field because they follow different motion trajectories. This way, valuable material is separated
from ore or slag. In general, electrostatic separators are classified as electrodynamic (high
tension) rollers and electrostatic plate separators. The chemical composition of the particle surface affects electron affinity, resulting in significant differential charging of materials in a mixture of discrete particles of diverse composition. The electrostatic plate separators work by passing a stream of particles past a charged anode. In high tension rollers, a corona discharge charges the particles that subsequently travel on a drum. The conducting particles lose their electrons to the drum and are then repelled from the drum; the drum attracts non-conducting particles. These separators have a low load capacity (less than a hundred kilograms per hour). These are useful for particles between 75 and 250 microns, which does not aid the separation of minerals due to the size of the ore particles. For example, the Quadrant Roller Electrical Sorter is a significant piece
of equipment in electrical mineral separation. The disadvantage of the roller type is a limitation for separating small particles. However, in 1989, Massachusetts Institute of Technology (MIT) developed a belt-type separator that works with triboelectricity (charge separation by friction). This separator works for micron-sized particles and has a large separation capacity of 5 tons per hour, but the unit cost is several million USD. For this reason, Avimetal has developed low-cost electrostatic separators. The advantages of this system compared to our competitors
are compact size, low sales price, the ability to separate micron-sized particles, large production capacity and low power usage. They also have several advantages over other mineral processing techniques due to their high efficiency, low capital and operating costs, no addition of chemicals and consequently, being environmentally friendly. Avimetal is a technology leader providing dry concentration, milling and non-cyanide leaching systems without wastewater generation.
Avimetal’s dry concentration technology was first successfully commercialized in Quilabamba, Peru,
by Picchu Rio Gold Inc. The company’s mining permit had been suspended since 2012 as a result of
mercury and cyanide poisoning of water downstream of the Amazon River. Picchu Rio Gold was granted a processing permit in 2018 after the Peruvian government approved an EPA (Environmental Protection Agency) rule permitting the use of Avimetal’s technology.