Temperature Effects on Gas Dispersion and Solid Suspension in a Three-Phase Stirred Reactor

Temperature effects on gas dispersion and solid suspension have been investigated in a fully baffled, dished-base stirred tank of 0.48 m diameter holding 0.145 m3 of liquid stirred by a triple-impeller combination. The impeller combination consisted of a half-elliptical disk turbine below two up-pumping wide-blade hydrofoils (WHU). This configuration is efficient for both gas dispersion and solid suspension. Power consumption, gas holdup, and the critical off-bottom just-suspension agitation speed have been measured at solid concentrations up to 21 vol % at six different temperatures ranging from 24 to 95 °C in increments of about 14 °C. The results confirm significant effects of temperature on the hydrodynamic characteristics. The relative power demand increases somewhat at increased temperature, although this effect is less when more solids are present. Gas holdup decreases significantly at higher temperatures, again an effect that is reduced at higher solid concentrations. The critical impeller speed for off-bottom just suspension (N JSG) increases with increasing gas rates over the whole temperature range of this work, though the effect of the gas rate on N JSG is less at higher temperatures. The effects of the temperature on power consumption, gas holdup, and N JSG have been quantified in a series of correlations that are relevant for the design and operation of hot-sparged three-phase reactors.