Abstract: In a process for the carbothermal reduction of alumina, carbon and alumina are supplied to a molten reaction bed in a hearth in the floor of a reactor. The reaction bed is supplied with energy by contact with plasma or with plasma effluents. For this purpose the reaction bed itself may form the counter-electrode for a plasma gun orbiting about the vertical axis of the reactor or there may be an intermediate counter-electrode. In either case the hearth is preferably electroconductive to provide a current path from the material in the reaction bed. Some or all of the feed material entering the reaction bed may enter the upper end of the reactor and descend through the plasma. At least part of the carbon may be in the form of coarse lumps which are fed to the reactor via an entry duct in counter-current relation to evolved carbon monoxide which preheats and partially scrubs it.

Abstract: In a plasma reactor for reducing stable oxides, particularly alumina, oxide and carbon in particle form are allowed to descend through an upper plasma zone in which there is a precessive plasma column, into a lower collection zone, which has one or more gas outlets leading from a central region of its floor and a peripheral collection trough. The precessive plasma column imparts a rotational movement to descending particles so that solid or liquid droplets are separated from evolved carbon monoxide in the collection zone in the manner of a cyclone separator. High tension electrodes and/or liquid metal sprays may be provided to assist coalescence of fine droplets in the collection zone.