(137d) An Investigation of SO2 Interference on Separation Performance of Amine-Containing Facilitated Transport Membrane for CO2 Capture from Flue Gas

Post-combustion carbon capture is a key approach to control CO₂ emissions from power plants using fossil fuels. Treating real flue gas may be problematic as it contains not simply just CO₂ and N₂. The minor contaminants, such as SO₂ and O₂, may be the major factors that can limit the long-term stability of a membrane. The typical flue gas after flue gas desulfurization (FGD) treatment is at its discharge temperature of 57°C with 40 â?? 50 ppm SO₂. The SO₂ level can be further reduced to even 1 ppm by a caustic scrubber, i.e., 20 wt.% NaOH. With the presence of SO₂ in the feed gas, SO₂ could preferably react with amine carriers and hinder the permeation of CO₂ in amine-containing facilitated transport membranes. Possible amine degradation and competitive reactions raise the concerns on the membranes for use in real flue gas. Amine-containing facilitated transport membranes were tested at 102 and 57°C, respectively. SO₂ concentrations of 0.7 â?? 5 ppm were employed in our transport study. Unstable membrane performance was observed for the membrane tested at 102°C in the presence of SO₂. It was found that amines reacted with SO₂ to form bisulfite and sulfite products irreversibly at 102°C. On the contrary, the membrane showed a stable separation performance in the presence of 1 â?? 3 ppm SO₂ at57°C. Moreover, an O₂ concentration of 3% was also added in the feed gas to simulate the real flue gas conditions. The membrane also showed a stable separation performance upon exposure to 3 ppm SO₂ and 3% O₂ for > 100 hours. In addition, infrared spectra were collected with respect to time by using an in-situ FTIR, and the growth of sulfite characteristic peaks was identified. The spectra results were consistent with the observed membrane separation performance, which is an affirmation of the SO₂ interference of the amines in the membrane. The stable membrane performance at 57°C with SO₂ at ppm levels and O₂ at 3% indicates the applicability of the developed amine-containing membrane for use in CO₂ capture from flue gas.