화학공학소재연구정보센터
Chemical Engineering Research & Design, Vol.151, 91-99, 2019
Equilibrium theory analysis of thermal regeneration of a humid adsorption column: Selection of optimal hot purge gas temperature
A Thermal Swing Adsorption (TSA) process has been widely commercialised for its application to air drying. In designing an air-drying TSA, zeolite 13X is chosen as a desiccant when required to produce a very low dew point dry air due to its highly nonlinear, favourable isotherm. It is essential to make use of an external hot purge gas in producing such an extremely low dew point dry air, as the column has to be regenerated thoroughly for the next adsorption step. In case of the externally heated TSA, usage of a hot purge gas gives rise to huge energy consumption. Also the cycle time has to be made as short as possible to enhance the bed productivity. To optimise this energy-intensive process, it is crucial to find an optimal hot purge gas temperature at which the column can be regenerated as quickly as possible with less energy consumed. In this study, Equilibrium Theory approach was taken to analyse the thermal regeneration breakthrough of a zeolite 13X column saturated with a water vapour in which the equilibrium isotherm is estimated by Toth or Aranovich-Donohue isotherms. As a result of Equilibrium Theory analysis, it was found that the trailing front of a thermal regeneration breakthrough would exhibit a transition of the shape from simple to shock wave with increasing purge gas temperature. The purge gas temperature has to be chosen so that after thermal regeneration the targeted water vapour concentration remaining in the column lies within the concentration range occupied by the shock wave. A useful correlation that relates the targeted dew point of the remaining water vapour with the purge gas temperature was proposed. The presence of the optimal hot purge gas temperature estimated by Equilibrium Theory was validated by both full numerical simulation and ideal work consumption. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.