Enhanced Carbon Dioxide Separation by Amine-Promoted Potassium Carbonate Solution in a Hollow Fiber Membrane Contactor

Abstract

An aqueous solution of potassium carbonate is an appropriate absorbent for cost-effective separation of CO2 from flue gas. Amine-promoted potassium carbonate has the potential to take advantage of both absorbents. In this study, a mathematical model has been developed to simulate the absorption of CO2 into promoted potassium carbonate solutions in a hollow fiber membrane contactor, where monoethanolamine, diethanolamine, and methyldiethanolamine have been considered as promoters. A numerical scheme was applied to solve the simultaneous partial differential equations in the liquid, membrane, and gas phases, and the results were validated with available experimental data in the literature for all promoters. The effects of the promoter concentration, temperature, gas and liquid flow rates, flow directions, axial diffusion in the gas phase, and possible wetting of the membrane were investigated using the model. The promoted solution with monoethanolamine had much higher flux, about 4 times superior to non-promoted absorbent. Simulation results indicated that the promoted potassium carbonate is only effective in a specific range of operating conditions. The membrane wetting can reduce the flux impressively for all solutions; however, the flux was still much higher than non-promoted solution even at high wetting fractions.