Intensification of TSA processes using a microwave-assisted regeneration step

The energy consumption in the temperature swing adsorption (TSA) process is essentially due to the heating of the purge gas used in the regeneration of the adsorbent bed. The use of microwave (MW) irradiation, replacing the traditional heating technique, can result in process acceleration and energy costs reduction: the electromagnetic energy is directly converted into thermal energy inside the adsorbent bed, all the resistances to the heat transfer are overcome, and the heat flow becomes the opposite of the conventional one. In this work, the innovative MW-assisted regeneration of zeolites bed is investigated. A dedicated laboratory plant was set up, and the optimal operating conditions were studied and determined. The results highlighted (i) the heating of the zeolites up to 300°C, (ii) an energy efficiency of 75 % (due to a more uniform heat transfer to the adsorbent) and (iii) the consecutive tests showed a perfect repeatability of the results in terms of CO2 adsorption and desorption, so evidencing that no modification occurred in zeolites after MW irradiation. In addition, both the adsorption and desorption steps were modelled through a simulation tool specifically realized in Air Liquide, and the results showed a good agreement between the predicted and experimental values.