Fixed bed adsorption for the removal of carbon dioxide from nitrogen: Breakthrough behaviour and modelling for heat and mass transfer

Concentration and temperature profiles for CO2 adsorption from a CO2-N-2 gas mixture (10% CO2 by vol in N-2) have been studied in a dynamic adsorption pilot plant unit to better understand the breakthrough behaviour. The scope of the present work is to study the adsorption characteristics and heat effects of this CO2-N-2 gas mixture and to develop a simple model for the dynamic simulation of non-isothermal adsorption in a fixed bed. Results indicated that adsorption heat effects were significant for this mixture while the breakthrough time obtained with Ceca 13X adsorbent was independent of the initial bed temperature. The cooling step that follows the thermal regeneration of the adsorption bed could be omitted entirely without affecting the adsorption performance. An earlier breakthrough time was observed for a higher feed flow rate of 6.6 SL/min compared to 4 SL/min. Cooling during the adsorption cycle decreased the width of the mass transfer zone and led to a longer breakthrough time. The study also indicated that online measurements of temperature at different locations along the column bed could be used to predict the concentration breakthrough for this CO2-N-2 gas mixture. The novel two-population model used in this study provided an adequate representation of the temperature and concentration breakthrough profiles within the adsorption column. (C) 2011 Elsevier B.V. All rights reserved.