On the separation of multicomponent mixtures in a cylindrical thermogravitational column

Тип публикации: статья из журнала

Год издания: 2016

Идентификатор DOI: 10.1063/1.4966640

Ключевые слова: Cylinders (shapes), Diffusion, Equations of motion, Mixtures, Thermal diffusion, Concentration gradients, Cylindrical coordinates, Multi-component systems, Multicomponent mixture, Separation process, Ternary hydrocarbon mixtures, Vertical diffusion, Vertical separation, Separation

Аннотация: This work studies the stationary separation of a multicomponent mixture in a thermogravitational column (TGC). The existing theory for a flat-plate column is extended to the case of a cylindrical column. The equations of motion and heat/mass transfer are written in cylindrical coordinates to take into account the impact of the cylinders curvature and the ratio of their radii on the separation process. To characterize the impact of each component on convective motion induced by thermal diffusion, the dimensionless separation ratios are used. A multicomponent system as a whole is described by the net separation ratio. The approximation neglecting vertical diffusion in the column is employed and conditions for its validity are analyzed. The profiles of velocity, temperature, composition, and density in the column with a multicomponent mixture are found and their dependence on the separation ratios and the ratio of cylinders radii is analyzed. The vertical separation is described by the solutal Rayleigh numbers, which are proportional to the vertical concentration gradients. It is shown that the key relation of TGC theory, which relates the net solutal Rayleigh number to the net separation ratio, essentially depends on the ratio of cylinders radii. The working formulas for the thermal diffusion coefficients are derived and the importance of forgotten effect is discussed. It is found that the vertical separation in the column increases with decreasing the ratio of inner and outer cylinders radii. A detailed comparison of results with the case of a flat-plate column is performed. Example of a ternary hydrocarbon mixture is analyzed on the basis of obtained solution and numerical simulation. Published by AIP Publishing.

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Издание

Журнал: PHYSICS OF FLUIDS

Выпуск журнала: Vol. 28, Is. 11

ISSN журнала: 10706631

Место издания: MELVILLE

Издатель: AMER INST PHYSICS

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