Surface flow of hydrocarbons, such as ethylene, propylene and isobutane, through activated alumina at 10°C and 30°C is measured over a mean pressure level range of a few kPa to about 100 kPa using a permeation apparatus. The surface flow coefficient is also determined as a function of amount adsorbed and temperature. The dependence of the surface flow coefficient on the above quantities can be well correlated using the random hopping model previously proposed by the authors. In addition, data from the literature for three other systems are correlated by this model. Intr oductionIt is of considerable interest from the viewpoint of fundamental research or practical applications such as adsorption, catalytic reaction, gaseous separation and drying to evaluate the mass transfer rate through adsorptive porous materials. Whenadsorbable gases flow or diffuse through porous media, the flux is increased appreciably in the presence of the adsorbed phase. This additional flow, that is, the surface flow, is important in order to estimate the mass transfer rate.

A method was developed for calculating the distributions of weight loss and temperature of spent activated carbon in a moving-bed regenerator in which the solid flow was regarded as being plug flow. A kinetic model developed earlier, which was based on regeneration consisting of many first-order reactions each with different frequency factors and different activation energies, was successfully applied to a design method for the regenerator. The flow pattern of the solid particles and heat transfer characteristics in a small moving bed were clarified experimentally, and the information obtained was used to calculate the distributions of weight loss of the spent carbon and temperature in the moving-bed regenerator by means of the design method. The calculated results were in fairly good agreement with the experimental data obtained in a small moving-bed regenerator. The adsorption capacity of the regenerated carbon was comparable to or greater than that of the virgin carbon. Activated carbon has been used in many adsorption processes for removal of toxic substances, recovery of valuable substances, separation of mixtures, and so on. Recently, the use of activated carbon in advanced waste-water treatment has attracted attention. For this treatment to be economical, the spent activated carbon must be repeatedly regenerated and reused. KENJI HASHIMOTOThe granular activated carbon used in waste-water treatment can be regenerated thermally in a steam atmosphere. The regenerator used is usually a moving-bed reactor, which provides uniform regeneration and minimizes the loss due to abrasion. The spent carbon fed into the regenerator is heated from room temperature to almost l,OOO°C. During the heating process the spent carbon i s regenerated through such reactions as thermal desorption and pyrolysis of the adsorbates, and gasification of the carbonized adsorbates and the activated carbon itself. To design such a moving-bed regenerator, the kinetics of the thermal regeneration reactions and the heat transfer characteristics and flow pattern of the solid particles in the regenerator must be investigated. This paper aims to present a rational design method for a moving-bed regenerator in which solid particles descend in a plug flow, and to examine whether thermal regeneration in the moving bed effectively restores the adsorption capacity of the activated carbon. CONCLUSIONS AND SIGNIFICANCEA method was developed for calculating the distributions of temperature and weight loss of spent carbon in a moving-bed regenerator where the solid flow was assumed to be plug flow. The kinetics of thermal regeneration was represented by a distribution curve of the activation energy for pyrolysis and the rate constant for gasification obtained by measurement of thermogravimetric curves. The effective thermal conductivity and the wall heat transfer coefficient were measured for the same moving bed. The distributions of temperature and weight loss in the moving-bed regenerator were calculated by applying the method developed to the data obta...