The influence of sparger design and location on gas dispersion in stirred vessels

A well designed agitated gas dispersion system should generate a large interfacial area between the gas and the liquid phases, exhibit minimal influence of gassing on the power draw, and not be prone to flooding. These characteristics are shown to be strongly affected by the location of the sparger. Significant performance improvements, in terms of improved power draw and delayed onset of flooding on aeration, are achieved through the use of 'larger than impeller' ring spargers, positioned within the discharge stream from the impeller. There is little or no penalty in terms of the gas holdup generated. Results for the Rushton and upward and downward pumping pitched blade impellers are reported. The observed behaviour may be explained in terms of the loading regime of the impeller and the cavity forms observed behind the blades, which is governed by the interaction between the sparger (gas discharge) position and the flow patterns generated by each impeller.