Sulfuric acid injection in copper heap leaching

Copper mining from oxide ores demand sulfuric acid that percolates the heap leaching pill. From there acid is debilitated while copper goes to the electro winning process.

LEWA process pumps are used to reinject sulfuric acid at 98% into the main pipelines that go to the heap leach sprinklers, recovering the concentration with safety, efficiency and long lifecycle, while reducing chemicals’ consumption.

Solutions

Safety, efficiency and economy to harsh applications

The following advantages are offered by the LEWA process pumps for the injection of sulfuric acid in tanks and pipelines:

  • Hermetically tight: reduced risks of accidents and waste of chemicals due to leakage
  • High efficiency: energy in mines is a limited resource. The LEWA process pumps have a higher efficiency than centrifugal ones, demanding less power to run and smaller motors, cables and panels 
  • Low maintenance: pumped fluid does not have contact with rotating parts, while all movable parts operate in protective, lubricating hydraulic fluid 
  • Easy control: pumped volume is known and proportional to motor speed, making it easy to control the concentration of the solution 
  • Lowest downtime: often more than 10,000 hours of continuous operation 
  • Flexibility: landscape of mine sites changes all time, so does the pump installation. Our pumps keep the desired flow rate regardless the new counterpressure of the installation
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Background

Copper oxide heap leaching 

Copper oxide ores are processed using aqueous solutions to extract and purify copper in three steps:

Heap leaching is the use of percolating chemical solutions to leach out metals. Following mining, transporting and crushing to a consistent gravel-size, the ore is piled into a heap on top of an impenetrable layer on a slight slope. The leaching reagent (dilute sulfuric acid) is sprayed through sprinklers on top of the heap pile and allowed to trickle down through the heap, where it dissolves the copper from the ore. The resulting solution of sulfuric acid and copper sulfate is collected in a small pool. Copper concentration is around 65%.

Next step is solvent extraction. The leach solution is mixed vigorously with a solvent. The copper migrates from the leach solution into the solvent. The two liquids are then allowed to separate based on solubility, with copper remaining in solution in the solvent, and impurities remaining in the leach solution. 

The leftover leach solution is then recycled by adding additional acid – the LEWA pump application – and sent back to the sprinklers in the heap leaching process.

The last step is electro winning. An electrical current passes through an inert anode (positive electrode) and through the copper solution from the previous step, which acts as an electrolyte. Positively-charged copper ions (called cations) come out of solution and are plated onto a cathode (negative electrode) as 99.99% pure copper.

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© 2020 LEWA GmbH