An electrical impedance sensing system for monitoring hydraulic flow transport in heap leach test columns

The rapid adaptation and maturation of heap leaching is primarily due to its low capital investment and production costs which make the processing of low grade ores profitable when conventional methods prove too expensive. Heap leaching has other advantages as well, such as a comparatively shorter start up time and the ability to economically mine deposits too small or too low grade for conventional processing methods. This paper will endeavour to demonstrate application of electrical resistance tomography (ERT) methods to monitor the passage of fluids through structured rock heaps and columns. ERT is being applied to exploit the principle that different materials have different electrical properties. ERT imaging takes advantage of these properties to produce a cross sectional image in a non-invasive manner. Modelling of heaps and columns has been developed extensively over the last thirty years, but to date there has been no satisfactory physical measurement of flow through heaps, and the behaviour of solution within a heap is still largely unknown. It is shown that ERT has been successfully coupled to a test heap leach column in order to be able to monitor in real time the flow of leachate through a column, as well as being able to map the nature of the hydraulic flow, and also showing the use of cross correlation to extract velocity and volumetric flow rate data.