Application of seawater to enhance SO2 removal from simulated flue gas through hollow fiber membrane contactor

In this paper, seawater was applied as absorbent for the removal of sulfur dioxide (SO2) from flue gas in a hollow fiber membrane contactor. In order to verify the application feasibility of seawater on SO2 removal, tap water, aqueous NaOH solution with a pH value of 8.35 and seawater were used as absorbents, respectively. The impacts of various factors such as three different absorbents, pressure gradient between gas and liquid, flow rate of absorbents, flow rate and concentration of feed gas on the overall mass transfer coefficient were investigated. The experimental results indicated that owing to the existence of complex CO2–H2O–HCO3−–CO32− equilibrium system, the mass transfer coefficient of seawater was about twice as large as that of aqueous NaOH solution with pH value of 8.35. In addition, seawater could withstand the sudden increase of SO2 loading rate. When the pressure gradient between gas and liquid kept under the penetration pressure, the membrane contactor could obtain high overall mass transfer coefficient, especially when seawater was used as absorbent. The height of transfer unit (HTU) of the membrane contactor was relatively small, and HTU increased hardly with increasing flow rate of flue gas when seawater was used as absorbent. Membrane contactor coupled with seawater absorption is a prospective technology for sulfur dioxide (SO2) removal in coastal area.