| Gas-liquid-solid stirred reactors are widely used in petrochemical, biochemical, pharmaceutical processes, water treatment etc. Though most of multi-phase stirred reactors are operated at the elevated temperature, little attention has been paid to those systems. Experimental study were carried out in the paper on the hydrodynamics of the three phase stirred reactor at different temperatures.Power consumption, gas holdup and critical impeller speed for just complete off-bottom solid suspension have been measured in a triple-impeller stirred tank of0.476m diameter with dished base under six different temperatures from24℃to95℃. The impeller combination consisted of a half elliptical disk turbine (HEDT) as the bottom and two up-pumping wide-blade hydrofoils (WHU) above HEDT. The results show that the temperature has a great effect on the hydrodynamic characteristics. Relative power demand (RPD, the ratio of gassed power to ungassed power) increases for the higher temperature, but the effect of temperature on RPD becomes weaker when more solids added in the system. At a given temperature, the presence of solid leads to the decrease of gas holdup, but the effect of solid concentration on gas holdup becomes weaker when temperature is elevated, and when temperature approaches to boiling point, solid concentrations nearly have no effect on gas holdup. Gas holdup decreases apparently with the increasing of temperature, which becomes less at higher solid concentration. Critical impeller speed for just complete off-bottom (NJSG) increases with the increasing of gas rates. However, the effect of gas rates on NJSG decreases for the higher temperature.The influence of impeller blade length and impeller diameter on critical impeller speed for gas dispersion, power consumption and gas holdup have been studied in stirred tank agitated by single HEDT.The results and the correlations are of particular relevance to the design and operation of hot sparged three-phase reactors. |
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