A model for heap bioleaching of chalcocite with heat balance: Mesophiles and moderate thermophiles

The interaction of mesophiles and moderate thermophiles (MT) in a 3-phase computational fluid dynamics model for heap bioleaching of chalcocite is investigated. The model assumes that both bacterial types undergo the same death, attachment and detachment processes, with different growth rate temperature dependency. The model allows an investigation of how the bacterial types vary in space and time as the conditions (such as the temperature) in the heap change. The model results are compared to the case with a single bacterial type (mesophiles) from previous work, showing that the bottom-up and top-down leaching fronts which develop in that case are also present here. The bottom-up leaching front is found to move faster than in the case with only mesophiles, and the leaching front from the top-down is slower here. Both these effects are due to the high temperature gradient in the heap (due to MT), and higher associated evaporation and condensation (and associated release or consumption of latent heat) across the respective leaching fronts. The addition of MT allows a longer period before overheating occurs, so that there is more leaching in the initial stage. The ambient temperature and inoculation method were varied to show the impact on leaching.