Reactive transport numerical modeling of CO<sub>2</sub>+O<sub>2</sub> <italic>in-situ</italic> leaching in sandstone-type uranium ore

Abstract

The CO2+O2 in situ leaching (ISL) technique represents the third generation of in situ uranium leach mining in China. The key point of CO2+O2 ISL is the interaction between the complex hydrodynamic behavior and geochemical reactions. To deal with hydrodynamic evolution, leaching solutions-rock interaction, and reactive kinetics of uranium minerals during ISL uranium mining, a CO2+O2 ISL reactive transport numerical simulation implemented in TOUGHREACT is proposed herein in Qianjiadian uranium deposit. In this study, we developed a chemical thermodynamic database suitable for sandstone-hosted uranium deposits and a method for modeling the kinetic uranium dissolution under the control of oxygen (O2(aq)) and bicarbonate (HCO3–). We conduct a sensitivity analysis to assess the effect of the uncertainties associated with the modeling parameters on the simulation results. The reactive transport simulation successfully reproduced the behavior of dynamic uranium recovery. The sensitivity analysis showed that the initial volume of uranium (uranium grade) and injecting oxygen concentration were very sensitive to changes in the leaching concentration of uranium. This study provides technical support for accurate simulation and dynamic regulation of the CO2+O2 leaching process at a large mining area.