Mathematical modeling and cascade design of hollow fiber membrane contactor for CO2 absorption by monoethanolamine

The absorption of CO2 from the gas mixture (CO2–CH4) by polyvinylidenefluoride (PVDF) hollow fiber membrane contactor using monoethanolamine (MEA) as the absorbent was performed. The mathematical model has been developed to predict the absorption performance. The model is validated with the experimental results for estimating the wetting ratio (x*) as the function of liquid velocity and MEA concentration. The suitable hollow fiber membrane module with effective fiber length of 50 cm is selected for the design of multistage membrane contactors. The absorption flux of multistage membrane contactor is simulated based on the value of x* obtained from the experiments. The three-stage cascade design is selected to compare the system performance with different gas and liquid flow patterns. The results of the simulation show that the individual gas flow (G-ID) gives higher performance compared to the gas flow in series (G-IS) for all operating conditions studied. The three different flow patterns of liquid including (i) liquid flow in series (L-IS), (ii) liquid flow in series with splitting (L-ISS) and (iii) liquid flow in series with recycle (L-ISR) are compared. At low MEA concentration (0.25 M), the L-ISR can improve the system performance at low liquid velocities, while L-ISS shows the highest performance at high liquid velocities. For the system with high MEA concentration (1.0 M), L-ISR can improve the performance at low to moderate liquid velocities, whereas L-ISS does not improve the system performance at any liquid velocity.

► Absorption of CO2 by MEA using membrane contactor was performed. ► Wetting ratio as function of MEA concentration and liquid velocity is presented. ► Multistage cascade design of membrane contactor is proposed. ► The performance for different gas and liquid flow patterns is compared. ► Multistage membrane contactor can improve performance and MEA is used effectively.