Overcoming Oxygen Transfer Limitations with the Aachen™ High Shear Reactor

Oxygen plays a critical role in gold cyanidation, directly influencing leaching kinetics and gold recovery. Conventional sparging often yields low volumetric mass transfer coefficients (kLa), limiting oxygen availability, particularly in ores containing oxygen consuming minerals. To address this, Aachen™ High Shear Reactors have been integrated into leaching circuits to enhance gas-liquid transfer through intensified turbulence and fine bubble dispersion. An empirical model was developed and validated to predict kLa in a leach tank equipped with an REA 030 Aachen™ reactor. Batch tests were conducted at a 2100 L scale using water and a 40% (m/m) silica flour slurry across three oxygen flow rates. Transient dissolved oxygen data were used to determine kLa, with performance benchmarked against ring and 0.5 μm frit spargers. The Aachen™ reactor achieved a maximum oxygen transfer efficiency of 91.7%, nearly double that of the frit sparger. A maximum standard oxygen transfer rate of 118 g/m³/h was obtained, with a saturation concentration of 38 mg/L at 20°C. The model showed strong predictive performance, with mean absolute percentage errors below 2% for both water and slurry systems. Continuous operation with silica slurry and sodium sulfite dosing confirmed the robustness of the approach under highly reactive conditions (~25 to 60 g/m³/h oxygen consumption load), with predicted apparent saturation concentrations agreeing with measured values within 1.86%. Under high oxygen demand, the Aachen™ reactor maintained dissolved oxygen concentrations above 20 mg/L at gas flow rates where conventional sparging systems became oxygen limited. The model enables reliable estimation of oxygen requirements and optimisation of delivery strategies, supporting improved oxygen utilisation and metallurgical performance.