Magnetic resonance imaging characterisation of the influence of flowrate on liquid distribution in drip irrigated heap leaching

• Effects of lixiviant irrigation rate changes in ore beds quantified using MRI.
• Increase in the number of liquid rivulets observed with increases in flowrate.
• More rivulets cause an increase in the liquid–solid contacting area.
• Rivulets established at higher flowrates were thicker.
• Liquid distribution changes were limited to macro-pore flow below the drip emitter.

Liquid irrigation is one of the key process control parameters following the construction of an ore leaching heap. This study uses 3D magnetic resonance imaging (MRI) to examine non-invasively the effect of liquid flowrate changes on heap hydrology when drip irrigation is used. Experimental results from a vertical column show that the increase in flowrate causes an increase in the number of rivulets in the ore bed. The new rivulets were found to be thicker, and their development caused an increase in liquid–solid contacting area which is considered advantageous for metal ion recovery. Experiments performed on larger samples showed that the effects of flowrate changes were limited to the region directly below the drip emitter because the increase in flowrate caused an increase in macro-pore flow and not capillary retention of liquid. Therefore the increase in flowrate was not found to perturb liquid distribution patterns in a way that would be substantially advantageous to heap leaching recoveries.