The design of a full-scale industrial mineral leaching process

The movement of water through the ground is of great industrial importance, and has applications in mining. This paper uses a mathematical model for ground-water flow to present a new design methodology for in situ leaching of minerals. This is a process in which a lixiviant (a solution capable of dissolving the mineral of interest) is pumped into a mineral-bearing rock in order to dissolve the mineral at its own location within the rock itself. The fluid is then pumped to the surface and the mineral is recovered chemically. A major problem with this technology comes from the need to predict accurately where the leaching fluid will go within the ore. Of particular concern is the need to recover as much of the fluid as possible at an appropriate later time. This paper proposes a design strategy that enables the complete recovery of all the mineral leaching fluid, in a full-scale three-dimensional operation. It relies on a spatially periodic arrangement of injection and recovery wells, with a type of secondary recovery process using injected water. The mathematical problem for homogeneous rock is posed, and an extremely accurate asymptotic solution is given. This is sufficient for experimental design purposes. In addition, the full problem is solved numerically using a boundary-in- tegral approach, to investigate limiting cases. © 2001 Elsevier Science Inc. All rights reserved.