Inter-particle fluid flow visualisation of larger packed beds pertaining to heap leaching using X-ray computed tomography imaging

Abstract

X-ray computed tomography (XCT) is a non-destructive 3-D imaging technique that permits visualisation of the internal structure within a sample, avoiding the stereological error found in conventional two-dimensional (2-D) image analysis. Its small-scale variant, in the present manuscript, referred to as X-ray micro-computed tomography (XMT) but more commonly referred to as µCT, has been widely studied for the characterisation of mineral particle beds, with a common focus in recent years being heap leaching applications. Several technical and computational factors have however limited the size of the configurations and samples studied with this methodology and thus CT flow path visualisation studies on packed beds larger than a few centimetres are uncommon in the literature. The methodology is also rarely used for fluid flow path identification, with other non-invasive alternatives being preferred. To remediate, the authors used a large medical XCT scanner to image a 266 * 200 * 100 mm3 rectangular bed configuration filled with non-porous 8 mm glass beads and porous 16–20 mm rock particles. The fluid flow was for its part imaged through the addition of Gastrografin®, a common medical contrast agent. Using Thermo Fisher Scientific's Avizo software, 3-D images of the beds, the liquid flows, as well as the pore networks were constructed and their parameters were computed. Validation experiments were also carried through ultraviolet (UV) fluorescence imaging using sodium fluorescein dye addition. By comparing the computed results of sphericity and equivalent diameter to the known values and the computed flow images to the UV fluorescence results, the authors conclude that their methodology is of adequate accuracy for further developments towards comprehensive analyses of unsaturated heap flow behaviour.