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Technology, Air Blowers

Low-Pressure Blowers and Mining: Froth Flotation and Tank Leaching

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In our last post on mining, we covered several applications that use low-pressure compressed air as a part of each process. In this post we will look at two applications – froth flotation and tank leaching. We will review each application, how compressed air is used in the processes, and what type of low-pressure compression equipment might be used.

What is froth flotation?

The first application covered in this post is froth flotation, which is the most widely used method for ore beneficiation. Ore beneficiation is a process in which valuable minerals are separated from worthless material, known as gangue, or other valuable minerals. This is a key process in the recovery of most of the world’s copper, lead, molybdenum, nickel, platinum group elements, silver and zinc, and in the treatment of certain gold and tin ores.

How does froth flotation work?

Froth flotation is a process for separating minerals from gangue by taking advantage of differences in their hydrophobicity (how much they are attracted to water) and is enhanced through the use of surfactants. Surfactants are chemicals that act as a wetting agent to attach to particles and increase their attractiveness to air bubbles. The first step in the flotation process involves crushing the ore. The powder is then mixed with water and chemicals, and the resulting pulp slurry is fed to a series of flotation cells.

Once in the flotation cell, physical separation of the desired particles will be completed based on the air bubbles ability to selectively adhere to specific mineral surfaces in the slurry. The particles attached to the air bubbles are carried to the surface and removed. Blowers provide the required air to create the small bubbles used in this process, generally at pressures less than 1 bar.

What types of low-pressure blowers are best for froth flotation?

In the past, multistage blowers have been traditionally used for this process, but low-pressure screw blowers such as Atlas Copco’s ZS line are becoming popular for this application. ZS screw blowers can operate at higher pressures than traditional multistage blowers, and as have the advantage of a wider turndown range. ZS screw blowers can be installed outdoors as well – even with integrated VFD and controls.

What is leaching, and how does it work?

Our next application is leaching through cyanidation, or the process of dissolving gold with a cyanide solution, which is the most common method used in the leaching of gold from ore material. Leaching is the process where a liquid substance extracts or dissolves minerals or other materials from a solid material. Tank leaching is carried out in multiple tanks installed in series where the gold ore is mixed with a cyanide solution, limestone and activated carbon and aerated with air bubbles.

Activated carbon is a very important component in the process of dissolved gold recovery because it adsorbs dissolved gold from gold leach pulp complex through its pores. Unfortunately, activated carbon is subject to fouling with inorganic and organic matter. Fouling means that material other than gold is absorbed onto the carbon, decreasing the efficiency to adsorb the valuable metal. It is therefore very important to supply high quality, oil-free air to the cyanidation tanks.

Which blowers are best for leaching?

Atlas Copco’s ZE and ZA line of low-pressure compressors provide oil free air to meet the demands of this application for pressures over 20 psi. The ZE/A line offers a heavy-duty air filter designed to provide contaminant-free air even in the harshest environment. Finally, Atlas Copco offers an industry leading 5-year warranty on the compression element to prove its unquestionable reliability.

Regardless of the application, Atlas Copco has low-pressure equipment that meets the demanding needs of the mining industry. Atlas Copco’s low-pressure machines are the most efficient and most reliable options for an industry that requires just that. With a complete line of blower equipment, we can help guide the correct blower selection for the application and offer the best solution based on the customer’s needs.

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