Microwave enhanced regeneration of CO2 adsorbents: Mechanistic study and theoretical modeling via fluorescence thermometry

Hot spots (δT = 13–40 °C) on adsorbents during MW heating were quantified. • Localized hot spots accelerated the desorption rate by 18%. • Influences of microwave power and N 2 rates on desorption efficiency were studied. • Cyclic regeneration efficiency was improved by 49% using microwave technology. Temperature swing adsorption (TSA) for CO 2 capture generally suffers from slow thermal response and high energy demand during adsorbent regeneration. Microwave swing adsorption (MSA) has emerged as a promising alternative to enable fast regeneration of CO 2 adsorbents. However, the mechanism of microwave-enhanced desorption remains unclear due to the difficulty in determining the actual surface temperature of adsorbents under microwave irradiation. This challenge is overcome in this study by coating a temperature-sensitive fluorescence thermometer onto the adsorbent particles, confirming the existence of a temperature difference (δT) between the adsorbent surface and the bulk bed measured by a fiber-optic sensor. Subsequently, a convective heat transfer model coupled with an electromagnetic heating equation was established to quantitatively predict the influence of purge flow rate and microwave power on δT. The model predictions agree well with the results of systematic experiments with an error < 20%, revealing that MSA can achieve a desorption efficiency at a bulk temperature of 88 °C comparable to that of conventional TSA at 100 °C, therefore reducing the specific regeneration energy consumption by 55% (to 1.91 MJ/kg CO 2 ) and nearly doubling the cyclic processing efficiency. The quantification of hotspot effect drives rational regulation of microwave enhanced CO 2 desorption, thereby advancing the development of energy-efficient carbon capture technologies.