New process development and process evaluation for capturing CO2 in flue gas from power plants using ionic liquid [emim][Tf2N]

Using the ionic liquid [emim][Tf2N] as a physical solvent, it was found by Aspen Plus simulation that it was possible to attempt to capture CO2 from the flue gas discharged from the coal-fired unit of the power plant. Using the combination of model calculation and experimental determination, the density, isostatic heat capacity, viscosity, vapor pressure, thermal conductivity, surface tension and solubility of [emim][Tf2N] were obtained. Based on the NRTL model, the Henry coefficient and NRTL binary interaction parameters of CO2 dissolved in [emim][Tf2N] were obtained by correlating [emim][Tf2N] with the gas-liquid equilibrium data of CO2. Firstly, the calculated relevant data is imported into Aspen Plus, and the whole process model of the ionic liquid absorption process is established. Then the absorption process is optimized according to the temperature distribution in the absorption tower to obtain a new absorption process. Finally, the density, constant pressure heat capacity, surface tension, thermal conductivity, and viscosity of [emim][Tf2N] were changed to investigate the effect of ionic liquid properties on process energy consumption, solvent circulation and heat exchanger design. The results showed that based on the composition of the inlet gas stream to the absorbers, CO2 with a capture rate of 90% and a mass purity higher than 99.5% was captured. These results indicate that the [emim][Tf2N] could be used as a physical solvent for CO2 capture from coal-fired units. In addition, the results will provide a theoretical basis for the design of new ionic liquids for CO2 capture. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.