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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.

Hot potassium carbonate solution is a promising absorbent for economical sequestration of CO 2 from flue gas. In the present study, a 2D mathematical model was developed to analyze the absorption of carbon dioxide from a gas mixture into an aqueous solution of potassium carbonate using a microporous hollow fiber membrane contactor operated under nonwetted or partially wetted conditions. The set of partial differential equations for the liquid, membrane and gas phases were solved by applying a numerical procedure, and the model results were validated with available experimental data in the literature. A parametric study was done using the validated model in order to achieve an optimized CO 2 capture. It was found that the rate of absorption increases significantly with increasing the liquid temperature, and there is an optimum carbonate concentration which gives maximum absorption flux at each solution temperature. A comparison between potassium carbonate and diethanolamine solutions was done under nonwetted and partially wetted conditions. The results revealed that potassium carbonate can give higher CO 2 recovery at optimum conditions. Considering the other advantages of K 2 CO 3 solution over alkanolamines such as lower cost and easier regeneration, it can be a suitable choice for CO 2 absorption by hollow fiber membrane contactors.

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