Study of thermodiffusion of carbon dioxide in binary mixtures of n-butane & carbon dioxide and n-dodecane & carbon dioxide in porous media

Convection due to a thermodiffusion phenomenon has an important effect on component separation of hydrocarbon mixtures in a porous medium. A numerical study of carbon dioxide diffusion in porous medium is investigated in the presence of different fluid mixtures such as n-butane & carbon dioxide and n-dodecane & carbon dioxide single phase. In this paper, all physical properties with an exception of the mixture conductivity are assumed as varying with temperature and concentration. The fluid is maintained at a pressure of 150 bar and remains in the liquid state. Constant temperature gradients in horizontal and vertical directions are applied on the three-dimensional porous domain. Thermodiffusion coefficients applied in simulation were calculated by using Abbasi et al.’s [J. Non-Equilib. Thermodyn. 35 (2010) 1] thermodiffusion model. Results reveal that for a certain concentration of carbon dioxide, the thermodiffusion coefficient reaches a maximum leading to large separation. In the presence of the Soret effect, the vertical density distribution tends closer to the one without the Soret effect. With an increase in the permeability, the convection becomes dominant and contributes to a decrease in the vertical and horizontal component separation considerably.