Heap Leach Characterization
HGI applies heap leach characterization technology to investigate preferential flow and channeling to optimize metal recovery in potential unleached areas in heap piles to increase inventory. Heap construction and structural non-uniformity is a main component to the movement of leachate and the recovery of metal. The movement of leachate is controlled by the permeability, which is influenced by dumping practices, geology, and ore pre-treatment. Low permeability zones, for example, may cause the leachate to bypass large portions of ore for more accessible regions by way of preferential flow. HGI has investigated preferential flow and channeling in heaps of low grade ore and concluded the phenomena may be attributed to a number of factors, including variance in the agglomeration schedule, compaction of fine-grained material near the surface, or from a wide grain size distribution, where the makeup of rock piles can be from the very finely textured silty material to large boulders.
Heap leach characterization technology is used to investigate preferential flow and channeling to optimize metal recovery.
The problem of preferential flow is the large amount of metal inventory that remains in unleached portions of the heap. The leachate will typically flow through those zones of highest permeability, and over a short period of time the high permeability zones are effectively leached. To gain insight in how fluid moves through heaps and possibly explain the reduced efficiency of metal capture over time, HGI has conducted many heap leach characterization and mapping investigations on copper, gold, and silver heaps. As an example, a mapping exercise was conducted at Newmont’s Gold Quarry mine to understand the distribution of wet and dry areas. Typically, wet areas will exhibit lower resistivity values, where as dry zones will show high resistivity.
HGI has conducted many heap characterization investigations on copper, gold, and silver heaps.
The top figure in the set of plots below shows a slice through the heap at about 50 ft below the pad surface. High and low resistivity features are comingled to show how moisture is distributed in the heap. Three-dimensional views are shown at the bottom to highlight the wettest and driest material. Logically, the driest material is at the surface where evaporation has removed much of the moisture during the summer acquisition.
HGI provides innovative solutions and top-quality results that push the scientific envelope. Our proven concepts have been published in many different forums including invited talks, conference proceedings, and peer-reviewed journals. We invite you to peruse the our most recent web site dedicated to all aspects of heap leach characterization and monitoring.