Energy-efficiency analysis of industrial CO₂ removal system using nanoabsorbents

CO₂ physical absorption process is typically operated at a low temperature as low as −40 °C and high pressure. In this study, nanoabsorbents are applied to increase the operating temperature by improving the absorption performance. Herein, CO₂ absorption performance is analyzed in a column absorber based on the Eulerian-Eulerian and population balance models. The computational results are verified experimentally under the same conditions and flow regimes can be classified into two regions in terms of the Reynolds numbers of the CO₂ gas and absorbent. Dimensionless correlations are developed to predict the CO₂ mass transfer coefficient for each region, which can be scaled up for industrial applications of the nanoabsorbents. The input power of the CO₂ absorption system is calculated by considering each component. Finally, an operational map of the CO₂ absorption and regeneration system, including both CO₂ mass transfer coefficient and the input power, is presented. The operational map will be a guideline to optimize operating conditions. Specifically, when the CO₂ absorption/regeneration industrial system is optimally designed, energy consumption can be reduced by approximately 40.5% with the CO₂ mass transfer coefficient of 0.475 m/s. When SiO₂/MeOH nanoabsorbents are used as a working fluid of CO₂ absorption system, the operational energy can be additionally saved by 23.2%. In addition, CO₂ mass transfer coefficient can be improved by 11.9% using nanoabsorbents for same Reynolds number. It is expected that the energy consumption in the industrial MeOH-based CO₂ absorption system will be greatly reduced by using the nanoabsorbents and the present optimization methods.