Nanofluid and nanoemulsion absorbents for the enhancement of CO2 absorption performance

Abstract

Research on CO 2 capture using nanofluids and nanoemulsions has been actively conducted in recent decades, and numerous studies have achieved improvements in the CO 2 absorption performance of nanofluids and nanoemulsions. In this study, to analyze the enhancement of CO 2 absorption performance achieved by nanofluids and nanoemulsions, experiments are conducted for visualizing the diffusion of CO 2 inside absorbents using the shadowgraph method. The nanofluid absorbents are prepared using SiO 2 solid particles, and the nanoemulsion absorbents are prepared using dodecane as the dispersed phase. The effects of concentration are analyzed through the absorption experiments performed for each concentration. The diffusion coefficient is calculated experimentally and theoretically based on the results of the visualization tests. The absorption of CO 2 begins at the absorbent’s upper interface when the CO 2 gas is stationary or moving. The highest absorption is observed at 0.05 vol% of nanoparticles. The absorption performances of the nanofluid and nanoemulsion absorbents are improved by 23.05% and 26.80%, respectively. As CO 2 is absorbed, the absorbent density changes and the Rayleigh convection becomes prominent, resulting in a plume-like flow. The plume formation and growth stages are subdivided into four stages, and both absorbents are compared. The visualization test results indicate that the hydrodynamic effect is a dominant factor in improving nanofluids’ mass transfer and nanoemulsions. Hydrodynamic effect model. • Enhancement mechanism of CO 2 absorption performance by nanoabsorbents is firstly clarified. • As CO 2 absorption starts, the Rayleigh convection becomes prominent, resulting in a plume-like flow. • The absorption performances of the nanofluid and nanoemulsion absorbents are improved by 23.05% and 26.80%, respectively. • Hydrodynamic-effect model plays an important role in improving the absorption performance.