Abstract
Heap leaching is a hydrometallurgical processing technique where the effective mass transfer between the multiple phases dictates the process efficiency. It is employed to process low grade mineral deposits, which cannot be treated economically by conventional mineral processing techniques, such as flotation followed by smelting. While the noteworthy merits of heap leaching are low capital and operational costs, a significant shortcoming is the low recovery efficiencies. Heap hydrodynamics is a vital contributor to the overall recovery as it facilitates the transport of both the chemical reagents and the dissolved metal species. Although a uniform liquid distribution is a requisite for an improved metal recovery, often an anomalous liquid distribution (liquid channelling) is observed in industrial heaps. This study explores the effect of the heap packing structure on heap hydrodynamics by introducing non-ore particles as a packed bed modification strategy, which is analogous to novel heap construction methods. It was studied by introducing planar printed circuit board (PCB) pieces (25*25 mm2 and 50*50 mm2) and those were used to form the layered and mixed packed beds. Out-flow liquid distribution, ultraviolet (UV) fluorescence based flow paths visualisation, liquid holdup measurements, and liquid mal-distribution factors were determined and the results were compared again with the same given by the two control packed beds, namely, the ore bed and the PCB bed. The out-flow liquid distributions and liquid holdup profiles were combined to asses heap hydrodynamics and mass transport mechanisms. The layered beds and the mixed bed with larger PCB pieces contributed to a widely distributed out-flow profile by creating more liquid flow paths and thus the channelling effect was alleviated. The result of this work could be used to develop novel heap construction techniques with further studies on introducing non-ore particles into ore systems.
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