Abstract
Liberation is very important for recycling. This paper describes a new separation process using a high voltage discharge impulse. High frequency heating and microwave heating were also shown to be of potential use in processing of the minerals granodiorite and taconite. A concrete disk sample was prepared using 6 mm and 10 mm diameter borosilicate glass beads as aggregate. The sample was placed between the ground electrode and a rod like electrode in water, to which a high voltage impulse was applied. The high voltage discharge impulse liberated the glass beads from the concrete. A needle like electrode was more effective for fragmentation of concrete. The concrete was mainly broken by exceeding its tensile strength due to thermal expansion of the heated portion from a large current flow of plasma. The energy consumption was greatly reduced compared to a conventional compression test. The liberation of iron bars from concrete and metal from ceramics were also possible by using this process. High-frequency heating was applied to wet granodiorite. The tensile strength was reduced and the boundaries of mineral grains were observed on the breakage surface. Microwave heating was applied to a taconite sample in Minnesota. As with high-frequency heating, the tensile strength was reduced and the boundaries of magnetite grains were observed on the surface. These two methods may be useful for mineral liberation in combination with general crushing methods.
