New Model for Turbulent Mass Transfer and Its Application to the Simulations of a Pilot-Scale Randomly Packed Column for CO2-NaOH Chemical Absorption

A complex model for simulating the mass transfer process in gas-liquid system is introduced by combining the computational fluid dynamics (CFD) model, the turbulent mass transfer model with the C^2-(epsilon)c equations for its closure, and the heat balance equation. By the proposed complex model, the axial and radial concentration distributions along the packed column can be obtained without assuming the "turbulent Schmidt number" or experimentally measuring the turbulent mass transfer diffusivity. The validation of the proposed model is tested by its application to a pilot-scale randomly packed 7 m high chemical absorption column with a 0.1 m internal diameter packed with 1/2 in. ceramic Berl saddles for CO2 removal by NaOH aqueous solutions. The simulated results are compared with the experimental data by Tontiwachwuthikul et al. (Chem. Eng. Sci. 1992, 47 (2), 381-390). Satisfactory agreement between the simulation and experiment in terms of the temperature and concentration distributions along the column height is found. Furthermore, the present model is able to predict the axial and radial turbulent mass transfer diffusivities, which are found to vary with the height of the packed column.