Treatment of matter in low temperature plasmas

Abstract

A plasma reactor, in which particulate matter is caused to interact with low temperature plasma (i.e. below 100,000 K) comprises spaced stationary electrode structures 2, 11 of which at least one is annular, between which an arc or arcs 7 is established by a power supply which may include a thyristor (SCR) 9. The arc is pulsated and caused to orbit or circulate round the or each annular electrode structure to form a conical plasma zone between the electrodes, while particulate solids are introduced through inlets 5 to enter the plasma zone and interact with the plasma therein. Extended dwell periods and highly effective interaction are brought about by circulation and pulsation of the arc and a high particle population density. The arc can be circulated at high speed by electrical means, for example by sequential energization of plasma torches 1 in an annular array or of the segments 8 of a segmental anode, or by electromagnetic circulation of the arc attachment round an annular cathode or round a segmental anode with the help of coils 10 fitted between the segments. Examples of reactions that can be efficiently conducted by this method include the reduction of metal ores, beneficiation of low grade chromite ores, recovery of energy values from low grade carbonaceous matter such as colliery wastes and the formation of pozzolanic material and cements from siliceous minerals.