Experimental Study on the Selective Removal of SO₂ from a Ship Exhaust Gas Stream Using a Membrane Contactor

In this study, we investigated the selective SO₂ removal performance of three absorbents-distilled water (DW), aqueous NaOH, and Na₂SO₃ solutions-from a typical ship exhaust gas stream using a hollow-fiber membrane contactor. SEM and contact angle analyses were performed to apprehend the morphological and water interaction characteristics of the membrane. A SO₂/CO₂/N₂ gas mixture (1000 ppm of SO₂, 5.50 mol % CO₂, balance N₂) was used and the absorbents were thoroughly evaluated in terms of SO₂ gas removal efficiency over a range of operating parameters including absorbent flow rate, feed gas flow rate, absorbent concentration, and L/G ratio. The aq. NaOH absorbent had the best SO₂ removal efficiency among the three absorbents under all conditions, mainly due to high alkalinity. Notably, around 100% SO₂ removal efficiency can be achieved with the NaOH absorbent. The Na₂SO₃ solution closely followed the NaOH in SO₂ removal efficiency. DW was the worst performer under all conditions. This study confirms that the use of membrane contactor is advantageous over the conventional packed towers because the membrane contactors are compact, offer high contact area, and achieve higher removal efficiencies.