In mining, hydrometallurgy is a technique extensively used within the field of extractive metallurgy. Its purpose is to obtain metals from their ores. According to Nick Dempers, Principal Process Engineer at SENET, the team focuses on the extraction of gold, copper, and cobalt, and to a lesser extent uranium, nickel, manganese, and zinc.

While these are the more common metals extracted, Jan Du Preez, General Manager: Process at SENET confirms that, globally, the periodic table is your playground – including rare and exotic metals like those in the platinum group and rare earth elements.

The Hydromet Process

 

The Hydromet process varies depending on the metal being extracted and the environmental factors around the extraction. However, Dempers offers the following simplified steps:

  1. Size reduction (comminution)
  2. Leach process to dissolve valuable metal
  3. Purification process to refine the solution
  4. Recovery
  5. Final product recovery

“Within these processes there are slight variations, particularly in the recovery phase,” adds Du Preez. “There are various processes that can be used for recovery, including solvent extraction or ion exchange and selective precipitation. In the final production the engineer could choose between precipitation, electrowinning, or crystallisation. These processes are the current general trend in hydromet.”

A Quartet of Considerations Driving Success in Hydrometallurgy

  1. Dempers and Du Preez agree that leaching is one of the most important considerations in hydromet. “If you can’t leach your metal, you can’t purify and recover it. The temperature, concentration of acid, and how long the leaching process takes must be carefully managed,” says Dempers.

  1. To ensure superior quality product, the separation process is crucial. “It is vital that the engineer understands which deleterious elements may be present and how they’ll respond during the separation process. This ensures that contaminants – which could be radioactive - are not extracted along with the metals, and clients receive a clean product,” advises Du Preez.

  1. The availability of utilities is a significant consideration, with many sites being remote and lacking access to a stable power grid or water. “In hydromet, many processes are energy intensive, and water is essential in the process. Access to these resources can make or break a project,” confirms Dempers.

  1. The last consideration in the quartet is ensuring you can produce the exact specifications and purities required. “Especially as SENET moves into the battery area, the specs are very tight and you have to be absolutely certain that you understand what’s required and have a very firm handle on how you are going to produce that product,” warns Du Preez.

Overcoming Challenges in the Process

Overcoming challenges is an integral part of the work done at SENET. Technical challenges are a daily factor, and one that the team has a good handle on. These include:

  • Energy challenges, which are overcome with alternative solutions. In SENET, the provision of energy is an integral part of the project design. It includes the use of heavy fuel oil generators, diesel generators, or solar power where it’s feasible.
  • In terms of water, process facilities are designed to reuse water as far as possible. Some plants are designed to use sea water, and water treatment plants are developed where required.
  • Environmental challenges are overcome with a constant focus on reducing environmental impact. Pollutants such as dust, liquid effluents, and gaseous effluents are carefully considered and diminished. The reduction of water egress from plants to tailings ensures better water balance.
  • For process efficacy, hypotheses are created and tested to determine whether the chemistry works and will produce the desired result. This involves expert knowledge and research and development (R&D). Here SENET relies on independent laboratories such as Mintek or CM Solutions to test the team’s process designs.
  • Process safety is integral, especially when working with reagents that vary from slightly caustic to highly toxic. With a strong dedication to safety, SENET conducts constant hazard studies, ensuring it meets safety standards and its people are working in a safe environment.

Innovation and Excellence in Hydromet

Dempers confirms that SENET strives for innovation and excellence in its hydromet processes.

“We rely on testing institutions, expert consultants, and equipment specialists to ensure we’re at the forefront of what’s happening in the industry. The SENET team is dedicated to designing plants that embrace value improvement practices, employing optimal solutions to increase return on investment for customers,” concludes Du Preez.

For more information from SENET’s hydromet experts, contact Jan Du Preez (j.dupreez@senet.co.za) or Nick Dempers (n.dempers@senet.co.za).

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