Tenova Advanced Technologies (TAT) employs the Sensoil Vadose Zone Monitoring System (VMS) for heap leach applications.
The VMS technology enhances the monitoring of heap leach pads by providing on-line temperature, moisture, pressure measurement and continuous solution sampling.
The VMS technology was originally developed for monitoring solution conditions in the Vadose (unsaturated) Zone between the surface and the water table for farming applications, chemical spills, tank farms, surface containment monitoring and has now also been adapted for monitoring ore-heaps under leach.
The core of the VMS technology is a series of special probes with multiple discrete sensors and sampling devices encased in hard wearing flexible pipes which are distributed diagonally through the zone of interest. The monitoring units are composed of Flexible Time-Domain Reflectometry (FTDR) probes, which are designed to provide on-line measurements of water content, temperature and porous Vadose Zone Sampling Points (VSP). Solution samples collected continuously by the VSP in the subsurface are frequently analyzed in order to determine their chemical composition.
VMS System for Heap Leaching Applications
Heap leaching is a common extraction technique employed in the processing of metals such as gold, copper, silver and uranium. A typical heap leach operation involves ore excavation from open pit or underground mining, milling of the ore to a particular required size and then heaping the crushed ore on an impervious pad. The ore heap is subsequently leached with a solvent such as a diluted acid or a cyanide solution using an irrigation system such as sprinklers or drippers. Upon percolation of the leaching solvent through the heap, metal oxides dissolve from the crushed ore and drain to the bottom of the heap. As a result, this drained solution is now enriched (pregnant) with the desired metal and this is then processed to arrive at final product.
Real time monitoring of the heap’s hydraulic and chemical properties can therefore lead to significant savings in important and often scarce resources such as water (especially relevant in arid regions) and chemical inputs, as well as increasing overall mineral extraction efficiency.
More than 70 monitoring devices with a depth of more than 60 meters have been successfully implemented in various hydrological applications. The systems have been installed in Spain, USA, Israel, South Africa and Namibia.