Effect of heat of adsorption on the adsorptive drying of solvents at equilibrium in a packed bed of zeolite

A packed bed of 3 Angstrom zeolite is used to dry ethanol solutions initially at 24 degrees C and containing up to 6.6 wt.% water. In view of the highly exothermic nature of the process, the progress of the thermal wave through the bed is followed and its effect on product dryness identified. The thermal wave is found to leave the bed around the time at which breakthrough of water begins to occur. For a given flow rate, the water concentration in the initial effluent and the peak temperature rise are found to be directly proportional to the water concentration in the feed. For a given feed concentration, both the initial effluent water concentration and the peak temperature rise can be reduced by decreasing the feed velocity. However, very low water concentrations should be achievable by removing the exotherm. In addition, equilibrium isotherms are reported for the adsorption of water on 3 Angstrom molecular sieve zeolite, and the individual isotherms conform closely to Langmuir and Freundlich models. (C) 1999 Published by Elsevier Science S.A. All rights reserved.