Investigation of mass transfer characteristics under turbulent condition in adsorption separation process for CO2 capture

Turbulence caused by high superficial gas velocity has significant impact on the CO2 capture process by adsorption. However, the poor consideration of turbulent diffusion in existing methods limits the further analysis of mass and heat transfer in CO2 adsorber. In this study, a novel computational fluid dynamics (CFD) model was introduced for CO2 capture with fixed bed, which is based on the methodology of computational mass transfer (CMT)[1]. Compared with traditional CFD models, it rigorously considers turbulent diffusion and can more accurately predict the mass and heat transfer behavior of CO2 capture processes at high gas superficial velocity while reducing computer resources. Through the comparison of simulation with breakthrough experiment, the feasibility of proposed approach was verified. In addition, the simulated results indicated that the turbulent mass diffusion causes a more uniform distribution of CO2 in the radial direction of adsorption bed. As Reynolds number decreases, turbulent mass diffusivity gradually weakens, and it could be neglected when the Reynolds number is below 10. Besides, adsorbent size and adsorber size was found to have significant influences on turbulent mass diffusion. They affect turbulent diffusion by changing the condition of fluid flow, then having influences on the mass transfer characteristics in CO2 capture process. Our results can provide a valuable guide for the structural design and optimization of industrial CO2 adsorber.