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Accueil du site > Publications > 2016 > Hydrodynamics and mass transfer in a tubular reactor containing foam packings for intensification of G-L-S catalytic reactions in co-current up-flow configuration

Hydrodynamics and mass transfer in a tubular reactor containing foam packings for intensification of G-L-S catalytic reactions in co-current up-flow configuration

19 avril 2016

Stainless steel open-cell solid foams of various linear pore densities (20, 40, 60 PPI) arewash-coated with a commercial catalyst and are evaluated as internals for G-L-S reactionsin co-current up-flow configuration. Hydrodynamics parameters such as liquid mean res-idence time, axial dispersion and pressure drop have been determined for an air/watersystem with superficial velocities between 0.8 mm/s and 25 mm/s for liquid and between100 and 900 mm/s for gas. A generic piston-dispersion model represents well the liquidhydrodynamics and is used to estimate axial Péclet number and mean residence time forthis phase. The Péclet number appears to increase with liquid velocity and foam linear poredensity (5 < Pe < 60 for 20 PPI, 10 < Pe < 140 for 40 PPI and 60 < Pe < 200 for 60 PPI). Determinedliquid holdups (0.4 < εL< 0.8) are always higher than those encountered in conventional up-flow fixed beds under comparable flow conditions. Liquid superficial velocity and foam linearpore density appear to be the most influent parameters while the gas superficial velocitypossesses a less pronounced impact. Pressure drop measurements may indicate the exist-ence of two different flow regimes (bubbly and pulsed regime) and globally the total pressuredrop remains low in the experimental domain tested with a maximum value of 0.2 bar/m,comparable to literature data. The overall external mass transfer efficiency was determinedthrough the gas/liquid/solid catalytic reaction of alpha-methylstyrene (AMS) hydrogenation andis compared to theoretical values obtained through correlations for conventional up-flowfixed beds. Very high mass transfer coefficients, in the range of 0.2–0.9 s−1were obtained atlow Re numbers, which is one order of magnitude higher than in up-flow fixed beds. A set ofcorrelations is derived for the calculation of the gas/liquid and liquid/solid contributionsto external mass transfer and allows explaining the unique bell-shaped Re dependencedisplayed by the overall mass transfer coefficient.

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