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 very interesting properties for the treatment of air loaded with volatile organic compounds. Adsorption-desorption processes using this material may be proposed 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 essential for the design of a treatment unit and the choice of relevant activated carbon cloth to understand and assess the electrical behaviour of these materials. Moreover, the great majority of the studies found in the literature concern the electrical properties of carbon fibers and not the carbon cloth media, and yet the knowledge of the macroscopic properties are required for industrial implementation. This paper presents the measurements of electrical resistance according to the intrinsic characteristics of various fabrics and to the temperature reached at the surface of the material. Measurements show that the electrical resistance of activated carbon cloth could be determined from the geometrical size of the piece and the electrical resistivity 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 carbonization temperature is presented. A transport mechanism of the current into the activated 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.