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Frequency response methods to model the rinsing behavior of spent heaps Illerbrun, Dwayne G.

Abstract

The frequency response method has been applied to determine the pore structure within columns of run-of-heap ore for the purpose of validating an existing heap rinsing model. In the heap leaching of gold ores, a dilute cyanide solution is applied to ore stacked on an impermeable pad. As the solution trickles through the heap, precious metals are complexed and dissolved. The solution is collected and the precious metals recovered. The barren solution is then recycled to the top of the heap. When it is no longer profitable to recover metal values, the heap is allowed to drain and the heap is decommissioned. However, some of the leachate will remain trapped within the heap. Due to the toxic nature of cyanide, the heap is a liability to the company until the cyanide is removed to regulatory limits. The main method for removal of cyanide from spent heaps is water rinsing. The water rinsing process is poorly understood, with most cases in the literature being site specific. The one systematic approach to modeling the rinsing behavior of spent heaps assumed an isochoric pore structure. However, upon scale-up the method met with only limited success. The reason proposed for the inability to scale the model was an inadequate understanding of the pore structure. The main objective of this work was to determine the pore structure within a column of ore using the frequency response method. Results from the frequency response trials were used to assign parameters to the rinsing model. The rinsing model was then used to predict rinsing profiles obtained from the ore columns. The predictions obtained from the rinsing model were inadequate to predict the time necessary for rinsing to regulatory limits.

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