Capabilities and limitations of electrodynamic fragmentation for processing and separation of minerals

H. Bluhm

Forschungszentrum Karlsruhe

Institut für Hochleistungsimpuls- und Mikrowellentechnik

Karlsruhe, Germany

ABSTRACT

The physical basis of electric impulse fragmentation and its applications to the recycling of composite materials are described. The method is based on the initiation of a pulsed electric discharge inside a solid dielectric material. With pulse amplitudes of a few 100 kV material layers of a few cm can be punctured. Specific energy deposition of up to 100 J/cm at Gigawatt power levels leads to pressure built-up of up to 10¹⁰ Pa in the discharge channel. Pressure waves and radially propagating cracks are launched into the solid body, which can lead to the separation of inclusions from the matrix or to the detachment at material boundaries. To induce the discharge in the solid dielectric it must be immersed in a dielectric liquid with higher breakdown strength. Most applications use water, which has excellent breakdown strength at fast ramp rates and because of its high dielectric constant leads to field concentration in the solid dielectric. Electric impulse fragmentation is a clean physical method without any environmental burden. In the paper we consider applications in the field of mining. The main advantages are to separate components if their acoustic impedances or their dielectric constants or conductivities are sufficiently different. Thus it seems possible to maintain the initial size of the embedded inclusions. Finally the economy and the scaling of the technique to large material throughput will be discussed.