Application of Hydrodynamics Using CFD in Evaluating Efficacy of External Loop Air-lift Reactor Biochemical Leaching of Sea Nodules

Abstract

Biochemical leaching of sea nodules using Bacillus circulans was carried in an external circulation-loop airlift bioreactor. In contrast to the slightly high recovery (92% Cu, 73% Ni, 72% Co, 38% Mn, and 17% Fe) with fine particles (<75 μm) on shake flasks in 25d, the leaching of metals using coarser lumps (1190– 250 μm size fraction) were found to be 76% Cu, 69% Ni, 65% Co, 29% Mn and 12% Fe in the same duration in an air-lift reactor with airflow of 500L min−1. The use of air flow assisted in retaining good metal recoveries with reduced grinding costs in the air lift reactor. Computational Fluid Dynamics (CFD) with a multiphase mixture model was used to describe the mass transfer and hydrodynamics vis-à-vis its role in improved leaching efficacy. The leach liquor was treated to eliminate iron, followed by selective extraction of copper by 10% Acorga M5640. The remaining leach liquor with Mn, Co and Ni were separated as respective salts by sulfide/carbonate precipitation.