Study on the use of an imidazolium-based acetate ionic liquid for CO2 capture from flue gas in absorber/stripper packed columns: Experimental and modeling

摘要

In the present work, 1-Ethyl-3-methylimidazolium acetate ([Emim][Ac]) ionic liquid (IL) has been considered for experimental and theoretical investigation of post-combustion carbon dioxide (CO2) capture from flue gas. The absorption and stripping of CO2 into [Emim][Ac] IL has been studied in a typical absorber/stripper system that randomly packed with Raschig ring at absorption pressures of 5-8 bar, absorption temperatures of 298.15-338.15 K and stripping conditions of 1.5 bar in temperature range 363.15-398.15 K. A mathematical model was developed for absorption and stripping processes based on mass transfer concepts and Peng-Robinson equation of state (PR EOS). The validity of the model was verified via comparison of the results achieved by the model with data taken from the experiments performed in this work and VLE data given in the literature. The impacts of parameters such as absorption/stripping pressure and temperature on the performance of CO2 capture, the sorbent flow rate and energy demand at selected operating conditions and specified CO2 capture rates were examined. The experimental tests showed that the recovered CO2 from the stripper column was pure. The results demonstrated that the energy requirement for the CO2 capture IL-based process is about 4890 kW or 2.75 GJ/t CO2. It was also found that the degradation rate of ion liquid is 3.78 wt.% of circulated IL. Using the enhancement factor obtained based on experimental results, the pseudo-first order reaction constant of the CO2+[Emim][Ac] IL system was estimated. By fitting the kinetics data into Arrhenius equation, the activation energy and frequency factor of the reaction rate constant were found to be 10.317 kJ/mol and 1545 s(-1), respectively.