September 26, 2019
Journal Article

Direct Effect of Solvent Viscosity on the Physical Mass Transfer for Wavy Film Flow in a Packed Column

Chao Wang
Zhijie Xu
Rajesh Singh
Jie Bao
ABSTRACT Post-combustion carbon capture via solvent absorption in a packed column can be a promising technology for mitigating greenhouse gas emissions. The mass transfer between gas and liquid solvent phases plays a critical role in determining the packing height of the packed column. Recent experiments [1] involving physical mass transfer for aqueous amine in a packed column have distinguished the direct and indirect impacts of viscosity (µ_L) on the mass transfer coefficient ?( k?_L). The direct impact of viscosity on the mass transfer coefficient has been found to be significantly higher for a packed column ?(k?_L~µ_L^(-0.38)) than a wetted wall column (WWC) ?(k?_L~µ_L^(-0.17)). To explain the deviation from the well-controlled uniform film flow in a WWC, we propose a mechanism involving the unavoidable wavy film flow and eddy-enhanced mass transfer in a packed column. A mathematical analysis based on fundamental flow and mass transfer equations is presented to quantify this deviation. The correlation for mass transfer coefficient derived from the mathematical analysis is found to match the corresponding one derived from the experiments for a packed column. Multiphase flow simulations using the Volume of Fluid method also are conducted to verify the direct impact of viscosity on the mass transfer coefficient for both uniform and wavy film flows. The mass transfer coefficient calculated from simulations shows steeper variation with viscosity for wavy film compared to the uniform film, further confirming our proposed theory. A similar relation ?(k?_L~µ^(-0.38)) for wavy film flow in a packed column is observed for aqueous solvent from both theory, experiment, and computer simulations.

Revised: September 26, 2019 | Published: September 18, 2019

Xu Z., R.K. Singh, J. Bao, and C. Wang. 2019. "Direct Effect of Solvent Viscosity on the Physical Mass Transfer for Wavy Film Flow in a Packed Column." Industrial and Engineering Chemistry Research 58, no. 37:17524-17539. PNNL-SA-139101. doi:10.1021/acs.iecr.9b01226