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  • 1
    ISSN: 0006-3592
    Keywords: bioreactor ; tower loop bioreactor ; yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The local properties of the dispersed gas phase (gasholdup, bubble diamater, and bubble velocity) were measured and evaluated at different positions in the riser and downcomer of a pilot plant reactor and, for comparison, in a laboratory reactor. These were described in Parts I and II of this series of articles during yeast cultivation and with model media. In the riser of the pilot plant reactor, the local gas holdup and bubble velocities varied only slightly in axial direction. The gas holdup increased considerably, while the bubble velocity increased only slightly with aeration rate. The bubble size diminished with increasing distance from the aerator in the riser, since the primary bubble size was larger than the equilibrium bubble size. In the downcomer, the mean bubble size was smaller than in the riser. The mean bubble size varied only slightly, the bubble velocity was accelerated, and the gas holdup decreased from top to bottom in the downcomer. In pilot plant at constant aeration rate, the properties of the dispersed phase were nearly constant during the batch cultivation, i.e., they depended only slightly on the cell concentration. In the laboratory reactor, the mean bubble sizes were much larger than in the pilot plant reactor. In the laboratory reactor, the bubble velocities in the riser and downcomer increased, and the mean gas holdup and bubble diameter in the downcomer remained constant as the aeration rate was increased.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0006-3592
    Keywords: bioreactor ; tower loop bioreactor ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Investigations were carried out in a 9 m high, 4 m3 volume, pilot plant airlift tower loop bioreactor with a draft tube. The reactor was characterized by measuring residence time distributions of the gas phase using pseudostochastic tracer signals and a mass spectrometer and by evaluating the mixing in the liquid phase with single-pulse tracer inputs. The local gas holdup and the bubble size (piercing length) were measured with two-channel electrical conductivity probes. The mean residence times and the intensities of the axial mixing in the riser and downcomer and the circulation times of the phases as well as the fraction of the recirculated gas phase were evaluated. The gas holdup in the riser is nearly uniform along the reactor. In the downcomer, it diminishes from top to bottom. The liquid phase dispersion coefficients, DL, are smaller than those measured in the corresponding bubble columns. In the pilot plant with tap water the following relationship was found: DLr = cwSGn; with c = 203.4; n = 0.5;DLr(cm2 s-1;) and WSG(cm s-1) where DLr is the longitudinal dispersion coefficient in the riser and WSG is the superficial gas velocity. The gas phase dispersion coefficients in the riser of the pilot plant, DGr, are also enlarged with increasing superficial gas velocity, WSG, however, no simple relationship exists. Parameter DGr is the highest in the presence of antifoam agents, intermediate in tap water, and the smallest in ethanol solution.
    Additional Material: 24 Ill.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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