Enhancement of mass transfer performance by nanoparticles during the CO2 absorption with MDEA solution in a randomly packed tower

In this study, the mass transfer enhancement by nanoparticles during CO2 absorption process with MDEA solution in a randomly packed tower was investigated. The mass transfer performance of MDEA solution with and without nanoparticles were quantified and analyzed in terms of the volumetric overall mass transfer coefficient (KGav). An enhancement factor (E), defined as the ratio of KGav with and without nanoparticles, was further introduced to evaluate the enhancement effect of the addition of nanoparticles. The effects of TiO2 nanoparticle concentration, MDEA concentration, liquid flow rate, liquid temperature, inert gas flow rate, and CO2 loading on KGav and E were systematically studied in the packed tower. It is found that the maximum value of E can reach 1.37, when the nanoparticle concentration is 0.09wt%, the liquid flow rate is 21.22 m3/m2·h, the liquid temperature is 27°C, the MDEA concentration is 30%, the gas flow rate is 7.58 kmol/m2·h and the CO2 loading is 0.2 mol CO2/mol MDEA. Usually, the KGav of the MDEA nanofluids can be increased by 10–37% in a randomly packed tower compared to that of the MDEA solution, which is consistent with the results from the bubbling reactors. However, when the CO2 loading of absorption exceeds 50%, E becomes less than 1.0, which means that high CO2 loading inhibits the enhancement effect of nanoparticles. In order to predict the mass transfer performance of MDEA nanofluid, a formula correlating E and various dimensionless operating parameters (i.e. L̂$\hat{L}$, T̂$\hat{T}$, Ĉnf${\hat{C}}_{{\rm{nf}}}$ and ĈMDEA${\hat{C}}_{{\rm{MDEA}}}$) is proposed and fitted with an average absolute deviation of 14%. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.