FLOW REGIMES, GAS HOLD-UP AND AXIAL GAS MIXING IN THE GAS-LIQUID MULTISTAGE AGITATED CONTACTOR

BB BREMAN, AACM BEENACKERS, MJ BOUMA

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    Abstract

    Experimental data are reported on Row regimes, gas hold-up and axial gas mixing of a gas-liquid Multi-stage Agitated Contactor (MAC), consisting of nine compartments [height, H, over diameter, D = 1; D = 0.09 m) separated by horizontal baffles with an opening of 0.04 m and with one centrally positioned impeller per compartment (12-bladed turbine disk; impeller diameter. d(1) = 0.03 m). For air-water and the liquid in batch, a homogeneous gas-liquid dispersion is realized with a stirring speed, N, above 15 s(-1) and a superficial gas velocity, u(G), below 0.12 ms(-1). These boundaries are affected unfavourably by either a cocurrent or a countercurrent liquid Row. For nine combinations of three gases (air, helium and dichloro-difluoro methane) and three liquids (water, n-octane and monoethylene glycol) the gas holds-up, epsilon(G), and the axial gas mixing were determined with the liquid in batch. Experimental conditions were varied as follows: u(G), 0.01-0.09 ms(-1); N, 10-36.7 s(-1); liquid viscosity, eta L, 0.00041-0.021 Pa s; surface tension, sigma, 0.02-0.073 Nm(-1); liquid density, rho(L), 684-1113 kgm(-3) and gas density, rho(G), 0.16-5.16 kgm(-3) For all experiments, the residence time distribution of the gas phase could be described excellently with a Cascade of ideally mixed Tanks in series with Alternating Backflow model (CTAB model). All 85 data epsilon(G) could be correlated with an average relative deviation of 11.0% by an extension of Van Dierendoncks' empirical gas hold-up relation. The relative gas backflow (ratio between gas backflow and net gas Row) data could be correlated by a novel relation with average relative deviations of 14.5, 17.7 and 19.5% For air-water(18 data points), helium-n-octane (19 data points) and air-monoethylene glycol (12 data points) systems, respectively.

    Original languageEnglish
    Pages (from-to)2963-2982
    Number of pages20
    JournalChemical Engineering Science
    Volume50
    Issue number18
    Publication statusPublished - Sep-1995

    Keywords

    • MODEL

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