Hydrodynamics and gas-liquid mass transfer of CO2 absorption into [NH2e-mim][BF4]-MEA mixture in a monolith channel

Abstract

This is the first work to investigate the hydrodynamics and gas-liquid mass transfer of carbon dioxide (CO2) absorbed into the amino-functionalized ionic liquid (IL) [NH2e-mim][BF4] and monoethanol-amine (MEA) mixture through a vertical circular monolith channel by means of computational fluid dynamics (CFD). It is shown that there are five flow patterns (i.e., bubbly flow, Taylor flow, slug-bubbly flow, slug-annular flow, and annular flow), and Taylor flow is the main flow pattern. The intrinsic kinetics of CO2 absorbed into the [NH2e-mim][BF4]-MEA mixture was obtained, the reaction orders relative to CO2, [NH2e-mim][BF4], and MEA being 1, and the activation energy Ea (19,313 and 28,991 J•mol−1) and pre-exponential factor k0 (3.34×105 and 7.04×106 mol-1•L•min−1) for CO2 absorbed in [NH2e-mim][BF4] and MEA were derived. After the kinetic parameters were imported into the mass transfer model, it was found that the liquid phase volumetric mass transfer coefficient (kLa) in the presence of a chemical reaction can be improved by three to eight times, indicating that mass transfer can be enhanced remarkably by chemical reaction. Moreover, a correlation formula is developed to predict kLa, which agrees well with the simulation results. This work provides a new way to capture CO2 with the combination of IL and MEA in a monolith reactor.