Dispersion and Holdup in Multiphase Packed Bed Microreactors

• Published in: Chemical engineering & technology Vol. 31; no. 8; pp. 1130 - 1139
• Main Authors: Márquez, N., Castaño, P., Makkee, M., Moulijn, J. A., Kreutzer, M. T.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01-08-2008; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Applied sciences; Chemical engineering; Dispersions; Exact sciences and technology; Holdup; Hydrodynamics of contact apparatus; Microreactors; Multiphase flows; Reactors; Peclet number; Packed bed; Multiphase flow; Vapor pressure; Gas flow; Liquid holdup; Hydrodynamics; Microreactor; Spherical particle; Diffusion coefficient; Dispersion; Tracers
• ISSN: 0930-7516; 1521-4125
• DOI: 10.1002/ceat.200800198

Liquid holdup and dispersion are reported for a column of 2 mm internal diameter, filled with 0.1 mm spherical particles, for multiphase flows with hydrocarbon liquid flow rates of 10–100 μL/min and nitrogen gas flow rates of 50–1000 μL/min using different tracers with varying diffusion coefficients and vapor pressures. It was found that the liquid holdup (liquid volume/external void volume) was between 0.65 and 0.85, with variations between different experiments and limited impact of flow rate on the holdup. The dispersion characteristics were very similar to single‐phase dispersion. The particle Peclet number for dispersion was close to 0.2. This value was of the same order of magnitude – just a factor of two to three lower – as the value that was obtained without gas flow. Tracer volatility did cause the tracer to elude earlier, but did not cause significant additional dispersion. The results suggest that the fluid mechanical interaction between the gas and the liquid was very limited.
Dispersion and hold‐up are reported for a multiphase flow in a packed bed microreactor using a variety of tracers. The particle Placet number was of the same order of magnitude as the equivalent liquid‐only flow. The results indicate that the hydrodynamic interaction between the phases was very limited.