Greenhouse gas emission has been one of the most important concerns in the last three decades for humanity; and unfortunately, it continues to increase. Although several attempts have been made to reduce carbon emissions; it still requires significant efforts to minimize it. In the last couple of years, a novel method, Direct Air Capture (DAC), has received high attention to reduce carbon dioxide from air. However, DAC technology is still not mature yet; and requires a significant amount of thermal energy for the regeneration process.

While there are several methods to capture CO₂ from the flue gases, one of the most common methods, temperature swing adsorption process (TVSA), has been selected for the proposed study since it does not only require low temperature compared to the other methods but also has the advantage of having simple and less components. In the TVSA method, both adsorption and desorption processes occur in a single unit. In the conventional DAC units with TVSA method, steam is being used as a thermal energy source for the regeneration process. Due to thermal losses and long-time process heating of conventional conductive heating, the cost of desorption in the DAC system is considerably high mainly due to the desorption of CO₂.

Microwave Swing Desorption (MSD) could be an alternative way to provide thermal energy for CO₂ desorption process [1-4] compared to conventional heating process. Microwave irradiation has the advantages of volumetric heating, selective material heating, non-contact heating as well as fast heating and cooling.

In this work, experiments are performed to investigate the desorption of CO₂ under microwave conditions. Two different solid sorbents, Zeolite 13X and polyethyleneimine (PEI) impregnated monolith, have been used to compare adsorption and desorption rates. Several parameters, regeneration temperature ranging from 80 °C to 120 °C, microwave power from 168 W to 504 W, gas flow rate from 80 ml/min to 100 ml/min, have been varied to investigate not only adsorption and desorption rates but also energy requirements for the regeneration process. The results proved that the microwave assisted swing desorption process not only accelerated the CO₂ release but also reduced the energy consumption.

Acknowledgment

The funding from Alabama Transportation Institute (ATI) is acknowledged to carry out this work.

References

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