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High interphase contact is essential to processes involving gas-liquid reactions, and can be accomplished using gas dispersion or gas induction. In gas dispersion, gas is sparged into the vessel below the impeller, and then dispersed throughout the liquid by agitation. Gas induction is an alternative approach, which uses a hollow impeller and shaft to draw gas into the liquid phase and distribute it throughout the vessel. The GS-4 impeller is a novel gas induction impeller that is unique due to its large openings in the impeller blades and generation of an axial flow pattern. This impeller is characterized based on the power number, pressure coefficient, and modeling of the induced gas flow rate. The power number at ungassed conditions is independent of impeller size and submergence, but is higher when up-pumping than down-pumping. This parameter decreases as gas is induced, and is modeled using the relative power number as a function of the relative speed. The pressure coefficient is examined using two approaches, one using speeds below the onset of induction and the other using the critical speed. Comparison of these methods shows that the pressure coefficient is more accurately determined independently of the minimum induction speed. This information is used to relate the available pressure difference to the gas flow rate. This relationship is affected by impeller diameter, with larger impellers inducing a higher flow rate than smaller impellers for a given pressure difference. The accuracy of this model is improved by assuming that the gas flow rate is also a function of the gas-liquid contact area within the impeller.
Kevin J Myers
Primary Advisor's Department
Stander Symposium poster
"Performance Characterization of the GS-4 Gas Induction Impeller" (2018). Stander Symposium Posters. 1221.