CFD simulation of CO2 removal from hydrogen rich stream in a microchannel

Abstract

The main object of this research is to perform computational fluid dynamics simulation of CO2 capturing from hydrogen-rich streams by aqueous DEA solution in a T-Junction microchannel contactor with 250 μm diameter and 5 mm length at dynamic conditions. To develop a comprehensive mathematical framework to simulate the flow hydrodynamics and mass transfer characteristics of system, the continuity and Navier-Stokes equations, two phase transport, and reaction rate model are coupled in COMSOL Multiphysics software. The developed model is solved and the effects of gas and liquid velocities as well as amine concentration on the CO2 absorption rate, hydrogen purification fraction, and flow hydrodynamic are investigated. The absorption process consists of CO2 diffusion from bubble bulk toward the bubble boundary, CO2 solubility in the liquid boundary, diffusion from the boundary into the liquid bulk, and reaction with the amine molecules. The results show that when the gas and liquid streams are mixed in the junction point to form a bubble, the gas cross-section area becomes narrow, and the fluid velocity increases due to the applied force on the bubble by the liquid layers. It appears that increasing the DEA concentration in the inlet from 5% to 20% increases hydrogen purification fraction from 42.3 to 66.4%, and up to 96.7% hydrogen purity is achieved by 20% aqueous solution of DEA.