Gas-phase influence on the mixing in a fluidized bed bio-reactor |
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Authors: | P. J. F. Gommers L. P. Christoffels J. G. Kuenen K. Ch. A. M. Luyben |
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Affiliation: | (1) Department of Microbiology and Enzymology, Delft University of Technology, Julianalaan 67a, 2628 BC Delft, The Netherlands;(2) Department of Biochemical Engineering, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands |
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Abstract: | Summary The liquid and solids mixing in fluidized bed bio-reactors containing particles with a density only slightly higher than water (1100 kg/m3) is generally consistent with the results found in previous studies for reactors with particles of higher density. The liquid mixing can be described by an axial dispersion model for a large variety of conditions while the solids follow the streamlines of the liquid. In the presence of a gas phase the degree of mixing of both the liquid and the solid phase increased. This effect became larger with increasing reactor diameter. In the extrapolation of laboratory data of three phase fluidized bed bio-reactors to pilot plant systems this effect should be taken into account. The liquid and solids mixing may have a substantial effect on overall conversion rates and on possible microbial stratification in the reactor.Nomenclature Bo Bodenstein number v L/D (-) - Dr diameter of the fluidized bed reactor (m) - D1 Dispersion coefficient of the liquid phase (m2/s) - Dg dispersion coefficient of the solid phase (m2/s) - E(in) normalized dye concentration function entering the ideally mixed tank reactor (-) - E(t) normalized dye concentration function as measured (-) - L length of the axial dispersed reactor (m) - t time after dye injection (s) - tm time constant for microbial selection (s) - ts solid mixing time constant (s) - t time interval in which a particle migrates within the bed (s) - vt superficial gas velocity (m/s) - vg superficial liquid velocity (m/s) - z migration distance of a particle in the bed (m) - 1 in situ growth rate of a dominant organism (s-1) - 2 in situ growth rate of a recessive organism (s-1) - average residence time in the axial dispersed reactor (s) - t average residence time in the ideally mixed tank reactor (s) |
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