Effects of the heating source on the regeneration performance of different adsorbents under post-combustion carbon capture cyclic operations. A comparative analysis

This work presents a comparative study of microwave and conventional (conductive) heating for adsorbent regeneration. A binary gas mixture representative of pre-dried flue gas from coal-fired power plants (15% v/v CO2 in N2) was passed through a rotatory fixed-bed adsorption column filled with a zeolite molecular sieve (13X) and an activated carbon (Norit R2030CO2). The impact of the two regeneration methods on both the textural properties and the carbon capture performance (CO2 uptake capacity, regeneration efficiency, and rate of regeneration) were assessed and compared after consecutive adsorption/desorption cycles. Overall, Norit R2030CO2 maintained stable adsorption capacity and regeneration efficiency with both conventional and microwave heating but slightly better with the latter. Additionally, power consumption per adsorbent unit mass and per adsorbate removed were reduced with microwave regeneration by 18.69 and 17.76% respectively compared to conventional regeneration. In the case of 13X, adsorption capacity and regeneration efficiency were found to be relatively stable after a drop in the first cycle in both heating modes, whereas power requirement was found higher in microwave regeneration than in conventional regeneration. NoritR2030CO2 showed a slightly higher maximum desorption rate when regenerated with microwave heating compared to conductive heating. Contrarily, the maximum desorption rate for the molecular sieve is higher with conductive heating as opposed to microwave heating. However, the data indicated a bigger desorption rate with the microwave regeneration in both adsorbents in later stages of the heating process (i.e. from min 16th for NoritR2030CO2 and from min 18th for 13X until process completion). The breakthrough time (tb) of Norit R2030CO2 was unaffected by cyclic operation or the heating methods, whereas in 13X this value varied over the cycles. The latter observation indicates that 13X requires either longer times or higher temperatures to achieve full regeneration compared to Norit R2030CO2. It can be concluded that microwave-assisted regeneration presented slight advantages over regeneration with conductive heating in delivering more steady capture capacity and regeneration efficiency for Norit R2030CO2 under the test conditions employed here whereas 13X exhibited indifference.