Appling the computational fluid dynamics studies of the thermogravitational column for N2-CO2 and He-Ar gas mixtures separation

In the present work, three-Dimensional stationary numerical simulations were accomplished for a deeper understanding of the gas mixtures separation by the thermogravitational column. To address the optimum condition and examine the limitation of the process, the thermogravitational column behavior has been thoroughly analyzed. First, the simulation model was validated by the experimental results of Youssef et al. then the model was developed for the pilot column. The mixture of helium-argon was chosen as feed composition. It was concluded that the variation of the separation factor in relation to pressure for both columns was almost the same. The optimum condition verified as p = 0.2 atm , θ = 0.4 , m ° = 4 SCCM $p=0.2\text{atm},\theta =0.4,m{\degree}=4\,\text{SCCM}$ .

Modeling of Separation in a Binary Mixture with Negative Soret Effect in a Cylindrical Thermogravitational Column

A numerical simulation of convective instability of a binary fluid with negative Soret effect in a cylindrical thermogravitational column is performed. The general problem statement, including equations of motion and heat/mass transfer with boundary conditions, are written in cylindrical coordinates. This is implemented in order to take into account the impact of the column geometry on the separation process and stability of the convective flow. The calculations for two cylindrical columns are performed in Ansys Fluent 14.5. The used parameters and values of applied temperature differences between the walls correspond to the reported experimental data. The considered binary fluid is an ethanol–water mixture at a concentration ratio of 0.2204/0.7796. At such a composition the mixture exhibits a negative Soret effect (the lighter component, ethanol, is enriched in the cold region). The results of simulation show that the convective flow in the column with a smaller gap between the walls is unstable for all applied temperature differences, while it remains stable in the column with a larger gap.