Mass Transfer Enhancement by Solution Pulsing in Laboratory Scale In-Situ Recovery

Low-permeability deposits currently yield insufficient metal recovery using in-situ recovery (ISR) due to the weak interaction between lixiviant solution and the ore body as a result of low fluid flow and mineral/lixiviant contact. To improve the lixiviant/ore interaction, the use of a solution pulsing method (intermittent rather than continuous pumping) to improve the mass transfer of ions and fluid flow in such deposits could be an option. Solution pulsing alters the solution flow and mass transfer at the microscale between low- and high-permeability regions and can result in a higher overall mass transfer. This paper reports on research in which laboratory-scale solution pulsing-ISR experiments were undertaken to assess the effects of various parameters on lixiviant movement through ideal synthetic core samples. The concentration of lixiviant solution was tracked. The findings revealed that when the pump resting period was too long, the pulsed pumping was inefficient. A short pumping on-and-off time (30 min) was found to be more efficient. The results also confirmed that an increase in the hydrostatic pressure that drives the pumping increased the migration of ions. For the most effective pumping parameters, the effect of synthetic core sample permeability was also measured to confirm that a lower permeability results in a lower ion movement, as is expected from continuous pumping experiments.