Dispersion efficiency of ejector-type gas distributors in different operating modes

The effect of ejector configuration on the energetic efficiencp of gas-liquid contacting and on the efficiency of gas-phase utilization was examined in the two alternative operating modes of ejector-distributor reactors, i.e. under conditions of free suction or forced gas supply to the ejector. Data for the free suction regime proved the independence of the gas phase utilization from the ejector configuration. The dependence of gas holdup (epsilon(G)) on the superficial gas velocity (u(0G)) was, within the whole range of our experimental conditions, well described by a single empirical equation, epsilon(G) = 2.8u(0G)(0.9). Good agreement of the experimental data with calculations based on the slip velocity concept confirmed the 'homogeneous' character of gas-liquid beds in the ejector distributor reactors. The energy effectiveness of bubble bed formation in the free suction regime varied with the ejector geometry. The optimal values of the mixing tube and diffuser length derived from our experimental data agreed well with those proposed previously by Henzler (1983). No significant differences were, however, observed between the energy effectiveness data for the two different ejector configurations, with and without the mixing tube, at constant values of the total ejector length. Experimental data obtained under conditions of the forced, gas supply clearly demonstrated a decrease of the ejector dispersion efficiency with increasing gas feed rate as well as significant non-uniformity of gas holdup distribution at high gas flow rates. A critical ratio of the gas and liquid flow rates was determined, representing the upper limit of the ejectors working region in the forced-gas-supply regime. (C) 1997 Elsevier Science Ltd.