Electrical behaviour of activated carbon cloth heated by the joule effect:desorption application

Activated carbon cloth in a recent form of porous material that reveals ver y interesting properties for the treatment of air loaded with volatile orga nic compounds. Adsorption-desorption processes using this material may be p roposed as an effluent concentration unit. In situ regeneration using Joule effect heating is very promising. Because of the diversity of the physical properties of the fabrics due to the manufacturing processes, it is essent ial for the design of a treatment unit and the choice of relevant activated carbon cloth to understand and assess the electrical behaviour of these ma terials. Moreover, the great majority of the studies found in the literatur e concern the electrical properties of carbon fibers and not the carbon clo th media, and yet the knowledge of the macroscopic properties are required for industrial implementation. This paper presents the measurements of elec trical resistance according to the intrinsic characteristics of various fab rics and to the temperature reached at the surface of the material. Measure ments show that the electrical resistance of activated carbon cloth could b e determined from the geometrical size of the piece and the electrical resi stivity of the fabric, which is a relevant parameter to characterize these materials. The influence of certain intrinsic characteristics of the cloths , such as the specific surface, the activation process, or the carbonizatio n temperature is presented. A transport mechanism of the current into the a ctivated carbon cloths is proposed. Finally on pilot unit, desorption steps are performed using Joule effect in the case of ethanol vapors treatment. (C) 2001 Elsevier Science Ltd. All rights reserved.