Computational Fluid Dynamics Analysis of Gas Absorption Process in a Randomly Packed Column for Toluene Absorption from Air

Abstract

Packed towers are used extensively in the chemical industries for mass transfer operations such as gas absorption, desorption, extraction and distillation. In gas absorption process a soluble component is absorbed by contact with a liquid phase in which the component is soluble. This system is used for scrubbing gas streams of toxic components such as sulphur dioxide and carbon dioxide or volatile organic compounds such as toluene. This research studies the toluene absorption with a viscous absorbent, di(2-ethylhexyl)adipate. Hydrodynamics and mass transfer parameters of a packed column such as pressure drop and mass transfer coefficients have been investigated using computational fluid dynamics analysis. The computational fluid dynamics predictions are compared to the experimental data reported by Heymes et al. For validation of the computational fluid dynamics predictions, some theoretical models such as Billet model have also been used. The experimental results showed that the liquid phase mass transfer coefficients of the system depend on the gas and liquid phase velocities. This behaivour has also been observed in the computational fluid dynamics analysis. It is clear that the influence of viscosity on the phenomena is considerable, e.g., under the same conditions the pressure drop of air/water system is about 30 % lower than toluene/di(2-ethylhexyl)adipate system. Comparison between the computational fluid dynamics results, experimental data and theoretical models showed a good agreement and confirms the ability of the computational fluid dynamics for design and optimization of the absorber packed columns.