Liquid membranes for flue gas desulfurization

A number of aqueous liquid membranes were tested to study their efficacy in flue gas desulfurization. A simulated flue gas containing SO₂, CO₂, O₂, N₂ and moisture was used as the feed gas. The candidate membrane liquids were immobilized in microporous polypropylene Celgard® 2400 films. Permeabilities of the above species through the liquid membranes and the selectivities were determined using a sweep gas technique at 25°C. The feed and sweep gases were kept at essentially atmospheric pressure. The liquids tested as membranes included water, and aqueous solutions of NaHSO₃, Na₂SO₃, sulfolane, sulfolene, Fe²⁺ EDTA, and Fe³⁺ EDTA. Very favorable SO₂ permeabilities, and SO₂/CO₂ and SO₂/N₂ selectivities were obtained using some of these immobilized liquid membranes. Experimental permeabilities of SO₂ have been compared with predictions from equilibrium approximation as well as from non-equilibrium boundary layer approximation.