Turbine impellers power input, dispersers

POWER INPUT TO TURBINE DISPERSERS. The power consumed by a turbine impeller dispersing a gas is less than that indicated by Fig. 9.12 for agitating just liquids. The ratio of the power when gas is present to that for the liquid alone... 

Figure 8.22 Typical relationship between hold-up and power input when dispersing gas in a high viscosity, shear-thinning fluid (a) A single disc turbine (b) A combination of 45° downward pumping impeller and disc turbine...

Concave blade disc turbines are of interest in gas-liquid dispersion because they are able to handle more gas than Rushton-type turbines before flooding (Smith et al., 1977 Vasconcelos et al., 2000). The mass transfer capacity for the concave blade disc turbine is very similar to the Rushton-type turbine, but Chen and Chen (1999) found that the blade curvature could be optimized for a certain power input to produce higher gas-liquid mass transfer coefficients. Unlike the Rushton-type turbine, the concave blade disc turbine requires the cup orientation to be in the direction of impeller rotation (Tatterson, 1994). 

When the polymer does not agglomerate, the essential technical requirements of a reactor are obtaining a good liquid in liquid dispersion, and a sufficient heat transfer at the wall. Since limited quantities of surfactant are used (for economic reasons), a good agitation is essential. A turbine (in a baffled reactor) is generally the most suitable impeller for liquid dispersions. Again, the specific power input is the essential characteristic for scale-up (see section 4.6A2). 

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