Continuous Flow Solar Desorption of CO2 from Aqueous Amines

Recovery of captured carbon dioxide (CO2) is considered the most energy-intensive stage of postcombustion CO2 capture strategies by aqueous amines. In response, an optically transparent flow reactor with continuous in operando CO2 collection using light-absorbing, graphite-titania composite microparticles is developed for the energy-efficient solar desorption of CO2 from saturated aqueous amine absorbents. The synthesized graphite-titania composite microparticles are demonstrated to be a more effective packing material for continuous CO2 solar desorption in the packed-bed flow reactor compared to other candidates, including titania and carbon black. The effect of continuous and discrete parameters, including irradiance, residence time, amine concentration, and amine chemical structure on the efficiency of solar-enabled CO2 desorption using the developed continuous flow strategy with the graphite-titania composite microparticle packing is studied in detail. Furthermore, the potential for the implementation of a control strategy by adjusting the aqueous amine stream flow rate to achieve constant CO2 desorption efficiency with dynamic solar irradiance is discussed. Finally, the continuous CO2 desorption stability over an extended period of time (12 h) is examined with an average single-pass efficiency of 64%.