Recent Advancements on Hydrodynamics and Mass Transfer Characteristics for CO₂Absorption in Microreactors

Process intensification for CO₂absorption using microreactors has received growing interest from both academia and industry because of their great ability to overcome the mass transfer resistance across the phases boundaries, giving rise to significant improvement in process efficiency. Mass transfer is strongly linked with two-phase flow patterns of CO₂-absorbent in microreactors and, subsequently, overall volumetric mass transfer coefficient (ka) intensification relies on hydrodynamics, microreactor structures and applied absorbents. Reviewed literature on this subject indicated that the Taylor flow pattern, spiral and meandering microreactor structures, and primary and secondary amines absorbents were preferred to use for the CO₂absorption in microreactors. Moreover, ka models developed through offline and online characterizations were presented to analyze the contribution of liquid film and bubble caps in mass transfer. Economic analysis was executed to assess the operating feasibility of microreactors at industrial scale throughputs of feed gas and absorbent. The results indicated that the capital expenses of microreactors were significantly higher than those of conventional absorbers because of their extensive number of units and complex design of flow distribution network requirements with high throughputs. However, microreactors exhibited lower operating expenditures than conventional absorbers because of their excellent transport characteristics. Finally, the persisting challenges and remarking conclusions are presented relating to the implementation of microreactors for CO₂absorption.