Valves for copper concentrates production, smelting and electrolysis

Each ore deposit is unique in its concentration and mineral composition. Therefore, the most economical plant flowsheet varies from site to site. Even though the unit processes might be site-specific, the principle for the processing of sulfide ore remains the same.

Copper processing plants turn to flow control experts to isolate and control various process flows. In the upstream processing, valves regulate, for example, flotation and dewatering. In the downstream smelting and electrolysis processes, valves control, gas, air and electrolyte solution flows.

Valves for froth flotation

Valves commonly control the slurry feed and discharge, reagent addition and water flows in flotation equipment. Knife gate valves are used extensively in this application.

Another typical valve type is rubber-lined butterfly valve. Segment valves are an excellent solution for the reagent feed and control.

Valves for dewatering

As particles become finer, the resistance against removing water increases. Dewatering can no longer be achieved by gravitation, so pressure must be utilized.

A mechanical filter press is one option for the dewatering service. The machine contains several valves: Pinch valves are typically used in the slurry inlet feed, while the rest of the valves for water and air service often consist of butterfly valves.

Valves for the smelting process

The smelting process is a complex, multi-stage process involving high temperatures and molten liquids. Oxygen and air control are key to a reliable and efficient process.

For these operations, valve materials need to be carefully selected, and cleanliness is of paramount importance due to the inherent danger of oxygen reacting with any grease, oil, or combustible material left in a piping system.

The evaluation of valves for an oxygen application requires an understanding of metallurgy as well as valve geometries.

Valves for electrolysis

The electrolyte solution is piped to the tank. As pressures are typically rather low, butterfly valves are a good choice and provide the lowest total cost of ownership.

Refining copper starts with crushing and grinding; at some sites, this is followed by hydrocyclone separation. The slurry then moves to a flotation stage where reagents are added to the feed.

The reagents bind to the copper particles making them hydrophobic. As the air bubbles that are generated in the bottom of the tank rise to the surface, copper-bearing minerals attach to the rising bubbles. The copper-rich froth at the top the tank is then skimmed off and taken to a thickening stage, which is followed by dewatering. The resulting copper concentrate typically contains around 30% copper.

The copper concentrate is transported to a smelter where it is purified at high temperatures. Pyro processing begins with a smelting furnace where the concentrate is converted into molten liquid. The temperatures at this phase are as high as 1200 ᵒC (2300 ᵒF). The hot liquid is then poured into a slag-settling furnace. The output product, copper matte, contains some 60% copper.

The molten matte then moves to the next furnace, called a converter, where most of the remaining impurities are burned off. The converter produces an output, referred to as blister copper, now at 98% concentration. In the following anode smelter, the purity of the copper increases to 99%. In the final processing step, electrolysis, copper anode slabs are refined by applying electric current. The result is 99.99% pure copper.