Power Consumption for non-Aerated Na–CMC Solutions in Multiple Bioreactors Agitated
Advancing the chemical engineering fundamentals
Multifase Flows (T2-5P)
Keywords: multiple agitator vessel, power consumption, non-Newtonian fluid
Mechanically agitated vessels are generally used in many industries, i.e. chemical, biochemical, environmental remediation, etc. In biochemical processes, vessels with multiple impellers are used, because of the advantages of the longer residence time, lower decrease of heat exchange area in scale-up treatment, the smaller occupying area per unit volume, lower power consumption per impeller compared with single-impeller systems. The power characteristic of impellers is important for mixing performance and has influence on the agitation process cost.
The experiments presented were carried out in a flat-bottomed cylindrical vessel with internal diameter T = 0.19 m and liquid level of HL = 2.3•T equipped with various turbine impeller of the diameter of D = 0.065 m combinations. Experiments were carried out with various Na-CMC aqueous solutions (shear thinning fluid) in transitional flow regime (Rem (100,10000)). In the study three types of impellers were used: Rushton turbine, six pitched blade turbine and six flat blade turbine. The various impeller hangings were used: for the tank equipped with two impellers the turbine hangings as follows: h1 = D and h2 = 0,15D, h2 = D, h2 = 2D, h2 = 3D; for 3 impellers on the common shaft: h1 = D, h2 = 3D and h3 = 5D, for 4 impellers system: h1 = 0.85D, h2 = 2.54D, h3 = 4.23D, h4 = 5.92D as well as for the 5 impellers on the common shaft: h1 = 0.68D, h2 = 2.03D, h3 = 3.38D, h4 = 4.74D and h5 = 6.1D. The power drawn was measured with strain gauges technique. The effect of the distance between impellers on power consumption for double impeller systems as well as the influence of impellers number on mixing power for vessel equipped with three, four and five impellers, have been observed. The experimental data obtained showed that in double impeller systems the power consumption very strongly depends on the distance between impellers. The optimal distance between impellers with the smallest power consumption has been proposed. For three and more impellers it has been shown that mixing power depends on number of impellers.
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Presented Tuesday 18, 13:30 to 15:00, in session Multifase Flows (T2-5P).
