Extracting values from mine dumps and tailings

Abstract

The mineral processing industry is the largest user of magnetic separation. This market is largely made up of low-gradient separators using iron circuits. The Superconducting High Gradient Magnetic Separators (SHGMS), originally developed at English China Clays, has resulted in approximately 30 large machines using liquid helium, with separation channels of 0.5–1 m diameter, distributed throughout the world. The recently developed so-called Dry Superconducting Magnetic Separators with two stage coolers used between 8 and 12 kW replace the liquid helium. These machines are lighter and much more mobile than the liquid helium machines and show promise for the upgrading of many low grade ores. There is a continual pressure in the mineral industry to cut costs or increase efficiency and this applies particularly to the metal industry. This pressure comes from at least two quarters and these are the discovery and use of replacement materials and the use of lower grade ores having lower concentrations of value and with a smaller liberation size. This paper considers a few examples of where superconducting separators can be used to concentrate low grade minerals from mine dumps which exist across the world. Often the gangue materials are coated with small quantities of magnetite which saturates at less than 2 T but with 6 T available from SHGMS, there is a large difference in magnetic moment between the gangue materials and the value to be concentrated. This paper discusses the concentration of uranium and gold from the leached residues from Witwatersrand, South Africa, dumps from other regions of South Africa for the concentration of platinum group metals, concentration of V, Pb and Zn from dumps of 8 million tonnes in Zambia. The recovery of titanium from mining dumps in China is also a real possibility as described below. The recovery of U and Au from Olympic Dam, Australia, the extraction of Au from slag at Zalau, Romania, the extraction of tungsten and tin from mining dumps in England are interesting possibilities. Mining dumps exist throughout the world and can be exploited whenever the economics are suitable.