Hydrodynamics and mass transfer performance of a microreactor for enhanced gas separation processes

Abstract

Chemical absorption processes for gas separation applications can be substantially enhanced using microreactors that utilize micro-structured surfaces/channels and fluid feed systems. The present paper focuses on the absorption of CO2 using aqueous diethanolamine solvent in microreactors having hydraulic diameters ranging from 254 to 762μm. The performance of the reactor was studied with respect to the absorption efficiency, pressure drop, mass transfer coefficient, interfacial area, enhancement factor, and Sherwood number. Parametric studies were conducted varying the channel hydraulic diameter, liquid solvent concentration, and CO2 concentration in the gas phase. The two-phase pressure drop was compared against an available empirical model and a reasonably good agreement was obtained for the present range of channel diameters. An empirical model for the Sherwood number was developed and compared against experimental data. Absorption efficiencies close to 100% were observed under certain operating conditions. Liquid-side volumetric mass transfer coefficients close to 400s−1 were achieved, which is between 2 and 4 orders of magnitude higher than those reported for most conventional gas–liquid absorption systems. Such high levels of process intensification were attributed to the increased area per unit volume offered by microchannels, thus increased gas–liquid specific interfacial area at reduced channel diameters. Interfacial areas close to 15,000m2/m3 were achieved which is between 1 and 2 orders of magnitude higher than those of conventional absorption systems.