A comparative experimental study on energy and exergy performance of cascade electrical-temperature vacuum swing adsorption (C-ETVSA) for carbon capture

Temperature vacuum swing adsorption is an effective technology for carbon capture to mitigate the carbon dioxide (CO₂) emission. Nevertheless, the adsorption capacity commonly presents downtrend along the bed at the end adsorption step and the supplied heat cannot be fully utilized for adsorbent regeneration. In this study, the cascade electrical-temperature heating (C-ETVSA) is proposed and further designed, using the electrothermal film (which is operated through the electrical-thermal conversion) to better match the non-uniform adsorption capacity distribution and simply realize the zoning-heating within the bed. The system energy, exergy performance is evaluated and compared with the constant electrical-temperature heating method (ETVSA) under the actual experiment. Based on the test results, the front half part adsorption bed temperature is 15.1 K higher than latter one in C-ETVSA but presents opposite trend in ETVSA, showing the cascade heating is better for matching the required heat energy distributed along the bed. Besides, the metal wall temperature is 3.0 K lower, demonstrating less heat is transferred to the metal wall in C-ETVSA. The 3.0 % higher purity is obtained due to more CO₂ is desorbed within the high adsorption capacity zone in C-ETVSA and specific heat consumption is reduced over 4.8 % at desorption temperature of 363 K and vacuum pressure of 10 kPa. Furthermore, the exergy efficiency is lifted from the range of 7.8–6.8 % to 8.4–7.2 %, proving superior overall energy and exergy performance of C-ETVSA. Results present the advantages of temperature vacuum swing adsorption using the cascade heating method and help promote the energy utilization for carbon capture.