Valves for copper leaching, solvent extraction and electrowinning
Optimally selected valves simplify copper leaching, solvent extraction and electrowinning process control
The leaching, solvent extraction and electrowinning (LX-SX-EW) process is a widely used method in the production of copper from low-grade oxidized ore. Copper is the most common metal to be processed by LX-SX-EW, but the process can also be used to extract, purify and concentrate other metals, such as nickel, cobalt and zinc.
Valves play an important role in the LX-SX-EW process by ensuring that various liquid flows are kept within the optimum range. Because of the demanding requirements for some of the valve installations and the constant acidity, selecting the optimal valves can have a positive impact on the plant’s overall profitability.
Valves for the pregnant leach solution
The pregnant leach solution is the output product of leaching. It forms as sulfuric acid percolates through the ore pile while the copper content of the ore is introduced in the aqueous solution. At some sites, drainage systems move the solution to the next processing stage using gravity; other sites use pumps.
Butterfly and ball valves are good choices for PLS flow control. Chloride sometimes poses a challenge in PLS feed, in which case the valve material selection is an important factor to be considered. For instance, hastelloy steel is a typical choice, as it exhibits a very high resistance against corrosion.
Valves for the raffinate feed
Raffinate is a mild solution of sulfuric acid with a pH typically between 1.2-2.0. When choosing a valve, many of the choices are typically straightforward in terms of size and pressure class, but there are also factors that may need a proper evaluation to ensure the best possible outcome. In addition to material selection, the right body and seat designs ensure that the valves perform at their peak.
Valves for the rich electrolyte solution
In the stripping stage of the process, the copper in the organic solution transfers to an aqueous solution, resulting in a rich electrolyte solution. This solution is piped to the electrowinning stage. Pipe sizes vary from site to site and can be DN1000 or even bigger. As pressures are typically in the lower range, butterfly valves are a good choice and provide the lowest total cost of ownership.