Theoretical reassessment of the first Stefan diffusion column experiment with a two-component liquid phase, consisting of a high-density volatile solvent and a low-density nonvolatile diluent

• Published in: Chemical engineering communications 2022-09, Vol.209 (9), p.1277-1292
• Main Author: Ramírez, Carlos A.
• Format: Article
• Language: English
• Subjects: Binary liquid mixture; Carbon tetrachloride; Chemical engineering; Data points; Density; Dibutyl phthalate; diffusive and convective mass transfer; Distillation; experimental binary gas and binary liquid diffusivities; Gaseous diffusion; high-density volatile solvent in a low-density nonvolatile diluent; Liquid phases; mass transfer resistances; Rare gases; stagnant species in a transport system; steady-state mass transfer at a liquid-gas interface; Stefan diffusion column operated isothermally at one atmosphere; Time dependence; transient mass transport modeling
• ISSN: 0098-6445; 1563-5201
• DOI: 10.1080/00986445.2022.2070484

The Stefan column was designed in the 19th century to allow the experimental estimation of binary gas diffusion coefficients starting with a pure volatile liquid A placed at the bottom overlaid with a stagnant/inert gas B. A sweeping B stream was provided at the top to remove the diffused gas A. In 1959, Richardson first studied a two-component liquid mixture in the Stefan column. One of his systems, a high-density volatile liquid A (carbon tetrachloride) dissolved in a low-density nonvolatile liquid O (dibutyl phthalate), is of interest to our ongoing research efforts. He collected interfacial descent-time data in his single isothermal Stefan column experiment, and analyzed them with a diffusion transport model, which contained unnecessary assumptions and simplifications, to obtain the binary liquid diffusivity of A in O, D AO . The present study removes the major restrictions of the previous model, reanalyzing the reported data with an improved numerical diffusion model that includes realistic features of the one-dimensional transport problem and statistical information on the estimated D AO . The average ± standard deviation of D AO were 8.82E-10 ± 1.85E-15 m 2 /s (12 data points), with an error of −13.3% relative to the Richardson value. The new model also provides detailed insight on the diffusive transport dynamics of liquid A by predicting interfacial descent rates, instantaneous concentration profiles in the liquid phase, and the time-dependent fraction of the mass of A lost from the original solution. The model is valuable to chemical engineering researchers studying diffusion-evaporation phenomena and multicomponent distillation processes.