Ar torch plasma characteristics and its application to waste treatment

The effect of the axial gas flow-rate on the characteristics of torch plasma, which is a DC are plasma produced by a transferred type torch, has been investigated. The voltage gradient is approximately 2-4 V/cm. It increases with the axial gas flow-rate and decreases with the current. However, it becomes constant near a current of 200 A and an axial gas flow-rate of 4 Nl/min. The axial temperature is not affected by the axial gas flow-rate and increases with the current. The radial temperature distribution becomes flatter when the current increases and the axial gas flow-rate decreases. An application of the torch plasma was carried out to melt fly ash into a glassified slag with a hardness of 6 Mohs. The leakage tests of the solution in pH 6 or 8 were examined. (C) 1998 Elsevier Science S.A.