What is Heap Leaching or Leach Pads?
PPM Global has been involved with a vast number of heap leach projects around the globe.
A Leach Pad is defined as a continuously lined area which may contain one or more ‘heaps’.
Leach Heaps (Cells) are stacked on prepared pads to a height from 4m to 8m. The nominal heap height is 6m. The heaps are approximately 50-60m wide. Heaps may contain between 50,000t and 250,000t of ore each. Heap leach solution is irrigated over the ore and percolates by gravity through the ore. It’s collected at the base of the pad in a collection drainage system. As the solution (eg acid) passes through the ore, various metals including copper (Cu), for the purpose of writing this piece based on copper bearing deposit, are dissolved from the ore into the passing leach solution (Leachate). The primary chemical in the leach solution is sulphuric acid (H2SO4). The copper (Cu) is solubilised (dissolved into solution) according to the following simplified reaction: