Abstract: Spent activated-carbon is fluidized and directly heated at a temperature of 100.degree. to 700.degree. C in the first zone with an off gas from the second zone to remove volatiles from the spent carbon. The carbon so treated is then indirectly heated in the second zone at a temperature of 500.degree. to 1000.degree. C in the substantial absence of oxygen with a combustion gas while being fluidized with steam or a steam-containing inert gas to activate the carbon. The process ensures effective utilization of heat energy and substantially reduces the loss of carbon.

Abstract: A device for detecting short-circuit between electrodes in electrolytic cells constituting an electrolytic plant in which a plurality of switch elements turned on and off under control of an external magnetic field are disposed to be vertically movable toward and away from the current collecting end portions of the individual anodes or cathodes in the electrolytic cells. These switch elements are moved downward to detect occurrence of short-circuit between the electrodes in one of the electrolytic cells, and when no short-circuit is detected in this electrolytic cells, the switch elements are automatically conveyed to the detecting position on the next electrolytic cell.