Multicomponent Gas Diffusion in Nonuniform Tubes

作者：Veltzke Thomas^*; Kiewidt Lars; Thoeming Jorg

来源：AICHE Journal, 2015, 61(4): 1404-1412.

DOI：10.1002/aic.14711

• gas multicomponent diffusion
• experiments on conical tubes
• classical Maxwell-Stefan equations
• analytical transport model
• two-bulb diffusion experiment

In many technical processes gas, multicomponent diffusion takes place in confinements that are rarely uniform in direction of their long axis (e.g., catalysts pores). Here, we show that in conical tubes multicomponent diffusion is hindered. This effect increases with ratio of inlet to outlet cone radius K, indifferent of the orientation of the tube. Based on the Maxwell-Stefan equations, predictive analytical solution for ideal multicomponent diffusion in slightly tapered ducts is developed. In two-bulb diffusion experiments on a uniform tube, the results of Duncan and Toor (1962) were reproduced. Comparison of model and experiment shows that the solution presented here provides a reliable quantitative prediction of the temporal change of H-2, N-2, and CO2-concentration for both tube geometries, uniform and slightly conical. In the demonstrated case (Lambda = 3.16), mass diffusion is 68% delayed. Thus, for gaseous diffusion in "real," typically tapered pores the transport limitation is more serious than considered so far.

• 出版日期2015-4