Mechanism and Countermeasures for Voltage Increase of Transferred Arc Plasma after Feeding Burnable Waste

Abstract

Miscellaneous solid waste contains burnable and/or non-burnable materials besides metallic waste. When non-metallic waste is treated by transferred arc plasma, plasma stability may be decreased by the low electrical conductivity of the materials. This paper describes the result of an experiment in which rubber and wood chips as typical burnable wastes were fed into the crucible of an operating experimental plasma furnace. The average power of the plasma was 20 to 50kW, however it fluctuated at waste feeding. The base materials of the simulated waste were 10kg of steel and 3kg of fly-ash. Up to 8g of burnable waste was fed after the base materials had melted. The voltage of the arc plasma increased just after the feed, and the increase was almost proportional to the weight of the fed waste. The intrusion of thermally decomposed products of the waste into the plasma dominated the voltage increase. The voltage increase was investigated for several operating conditions of the furnace. The increase of air injection into the furnace and that of arc current controlled the voltage increase during feeding, but the increase of plasma working gas aggravated it.