CO2 gas absorption by CH3OH based nanofluids in an annular contactor at low rotational speeds

In this work, carbon dioxide (CO2) absorption experiments are performed in a custom designed vertical annular contactor (AC) at low rotational speeds. Methanol is used as solvent and Al2O3, SiO2 and TiO2 nanoparticles are combined with the methanol to produce nanofluids. The AC performance is compared to that of a modified version in which trays are added to enhance the CO2 absorption rate (T-AC). Experiments in co-current and counter-current flows are carried out. In addition, two-phase flow patterns in the AC and in the modified version are analyzed by using a high speed visualization system. The results show no effect on the absorption rate for pure methanol at Reω < 17,000. In the counter-current flow, however, nanofluids show a better performance in the AC with maximum enhancements of 4.6% for TiO2, 1.2% for Al2O3 and 1.1% for SiO2 compared to pure methanol. The addition of trays enhances the CO2 absorption rate up to 9%, 10%, 6% and 5% for pure methanol, Al2O3, SiO2, and TiO2, respectively for the counter-current flow. Likewise, the highest rotation effectiveness is found in the T-AC for Al2O3 and TiO2 with 24.2% and 14.4%, respectively.