In this study, an amine absorption column in a petrochemical plant was investigated. The column consists of two sections with different diameters: The column’s upper section features a smaller diameter, while the lower section is broader. The column receives lean amine at its uppermost section, with semi-lean amine being fed where the diameter changes. Nanofluid solutions containing Al₂O₃, SiO₂, and TiO₂ nanoparticles were utilized. The flow rates of both amine streams were kept constant, while the inlet gas flow rates were set at 215, 161, and 140 tons per hour. Nanofluids with weight concentrations of 0.03, 0.05, and 0.1 wt% and particle sizes of 20, 50, and 80 nanometers were considered. The study focused on analyzing CO2 concentration profiles along the column, mass transfer coefficient, absorption efficiency and pressure drop in the presence of amine and nanofluid solutions. Results show elevated gas velocities correlate with diminished CO2 removal performance in all cases. Also, the numerical simulation results indicate that increasing wt% leads to higher CO2 absorption efficiency and mass transfer coefficient. Al2O3 exhibited the best performance for CO2 removal efficiency. For Al2O3 nanoparticle at 140 ton/hr gas flow rate and 0.1 wt% concentration and 20 nm size, the absorption efficiency increased to 99.95%, and the CO2 outlet concentration decreased to 0.877 mol%. Furthermore, comparison between nanoparticles of different sizes shows that smaller particles exhibit better performance. An index was defined as the ratio of absorption efficiency to pressure drop, where a higher index value indicates more favorable operating performance. According to the simulation outcomes, the highest index values 0.97, 0.96 and 0.95 were obtained for TiO2 nanofluid (0.03 wt%, 80 nm), SiO2 nanofluid (0.03 wt%, 80 nm), and TiO2 nanofluid (0.05 wt%, 80 nm), respectively, suggesting that the column achieves its optimum absorption performance under these specific conditions.