Power consumption and gas–liquid mass transfer in a hot-sparged three-phase stirred reactor

Abstract

The volumetric mass transfer coefficient (kLa) is one of the most important parameters for design and scale-up of gas–liquid–solid three-phase mechanically stirred tank reactors. In this work, the effects of agitation speed, superficial gas velocity, temperature, and volumetric solid concentration (CV) on the power consumption and kLa were discussed and quantitatively analyzed. In an air-water-glass beads system, the gassed power number (NPG) and kLa increase remarkably with the temperature. At ambient temperature, kLa decreases significantly with increasing CV with a power law exponent of 3.10, but this decreasing effect becomes weaker at higher temperatures. In this hot-sparged three-phase system, the addition of solids slows down the increasing tendency of NPG with the temperature, but enhances the increasing tendency of kLa. The increase in temperature weakens the decreasing effect of CV on kLa. Compared with the effect of temperature on NPG and kLa, the effect of CV is nearly negligible. As a practical guide to industrial applications, it is more effective to enhance the gas–liquid mass transfer by increasing the temperature or power consumption than by changing CV or increasing superficial gas velocity. The empirical correlations of power consumption and kLa obtained in this work can provide helpful guidance for the industrial design and operation of hot-sparged three-phase stirred tank reactors.