Temperature control in copper heap bioleaching

Heap leaching is being increasingly explored as a lower cost metallurgical technology to extract copper from sulfide ores of low grade and quality. Heap temperature is a critical factor in achieving economic copper extraction. The determination and control of heap temperature is challenging due to the intrinsic complexity of the intertwined fundamental processes occurring simultaneously inside a heap. In this study, we applied the HeapSim-2D model, calibrated using data provided by the Quebrada Blanca Mine, to study the response of heap temperature to variations of four key design parameters: raffinate flow rate, raffinate temperature, the extent of pyrite oxidation, and the application of a thermal cover. Note that the reported results have not been validated against experimental data and other possible rate-limiting factors are presently ignored. The modelling results showed that at a fixed raffinate temperature, the average heap temperature approached the raffinate temperature faster at a high flow rate than at a low flow rate. The heat generated by the oxidation of pyrite led to an increase in the heap temperature, but the magnitude of the increase was negligible at high raffinate flow rates, which would remove the generated heat via convection by the bulk movement of the leaching solution. The model predicted that the application of a thermal cover had a positive effect on maintaining the heap temperature, but the effect also depended on the raffinate flow rate. Understanding the effects of these design parameters on heap temperature is critical for achieving optimum copper extraction in heap leaching.