Performance of the scaba 6SRGT agitator in mixing of simulated xanthan gum broths

Abstract

Power consumption under non-aerated and aerated conditions was measured in a 0.45 m diameter tank containing a range of xanthan gum solutions, using the Scaba 6SRGT impeller. Well-mixed caverns were measured in a transparent Carbopol solution. The data are compared with previous results obtained with a Rushton turbine in the range of Reynolds numbers, Re, between 1 and 2000. In each case, the non-aerated power numbers were similarly related to Re except that the Po values of the Scaba 6SRGT were 3 to 4 times smaller. Under aerated conditions, the aeration rate does not affect the power number, Po,, with the actual value falling as a result of increasing xanthan concentration. The Po,/Po vs Re curve passes through a minimum which is lower at higher xanthan concentrations. At the same Reynolds number, the decline in power consumption of the Scaba agitator due to aeration is 20 to 50% smaller than that observed with a Rushton turbine. Well-mixed cavern shapes and sizes are also very similar to those observed with Rushton turbines and can be predicted from equations available in literature. However, instabilities in torque could present a problem in broths containing xanthan in concentrations above 35 kg m-3. Nevertheless, the Scaba agitator offers an interesting retrofitting possibility for xanthan fermentation, which could lead to improved performance.

Measuring Mixing Time in the Agitation of Non‐Newtonian Fluids through Electrical Resistance Tomography

“…3 is similar to that reported by Galindo and Nienow [34] for the Scaba 6SRGT impeller. It can be seen that at Re < 10, the power number is proportional to Re -1 , which is in good agreement with that reported in the literature [34][35][36]. Therefore, we can say that P 0 Re is constant for the laminar flow.…”

Investigation of Mixing in Shear Thinning Fluids Using Computational Fluid Dynamics

“…This result is in good agreement with that reported by Galindo & Nienow (1993) Their CFD results were in good agreement with those reported by Galindo & Nienow (1992) for the axial-flow Lightnin A315 impeller.…”

Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

“…Xanthan gum is an extracellular polysaccharide produced by the fermentation of the bacteria, Xanthomonas campestris [29][30][31]. As a yield-stress fluid exhibiting pseudoplastic behavior, its rheology can be described by the Hershel-Bulkley rheological model [19,30]:…”

“…The values of these parameters utilized in this work, Tab. 1, are based on measurements conducted by Galindo and Nienow [29]. …”