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 CO 2 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 ( K G a v ). An enhancement factor ( E ), defined as the ratio of K G a v with and without nanoparticles, was further introduced to evaluate the enhancement effect of the addition of nanoparticles. The effects of TiO 2 nanoparticle concentration, MDEA concentration, liquid flow rate, liquid temperature, inert gas flow rate, and CO 2 loading on K G a v 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 0.09 wt %, the liquid flow rate is 21.22 m 3 /m 2 ·h, the liquid temperature is 27°C, the MDEA concentration is 30%, the gas flow rate is 7.58 kmol/m 2 ·h and the CO 2 loading is 0.2 mol CO 2 /mol MDEA. Usually, the K G a v 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 CO 2 loading of absorption exceeds 50%, E becomes less than 1.0, which means that high CO 2 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. L ̂ $\hat{L}$ , T ̂ $\hat{T}$ , C ̂ nf ${\hat{C}}_{{\rm{nf}}}$ and C ̂ MDEA ${\hat{C}}_{{\rm{MDEA}}}$ ) is proposed and fitted with an average absolute deviation of 14%. © 2022 Society of Chemical Industry and John Wiley & Sons, Ltd.