(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 57Â°C with 40 â?? 50 ppm SO2.Â 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 57Â°C, respectively.Â SO2 concentrations of 0.7 â?? 5 ppm were employed in our transport study. Unstable membrane performance was observed for the membrane tested at 102Â°C in the presence of SO2.Â It was found that amines reacted with SO2 to form bisulfite and sulfite products irreversibly at 102Â°C. On the contrary, the membrane showed a stable separation performance in the presence of 1 â?? 3 ppm SO2 at57Â°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.