6-flat blade disc turbine-type impeller

The impellers used in this study are shown in Figure 1. They are both of the radially discharging type which is characterized by a strong radial jet of fluid that moves out to the vessel walls while entraining fluid from above and below. Near the wall it splits into two circulation zones. The flat blade turbine (FBT) is commonly used in industry and consists of a disc with several paddles fixed normal to the disc which serve to generate the radial flow. The novel impeller design... 

Three types of impellers are commonly used in the low viscosity region, propellers, Fig. 1 turbines. Fig. 2 and axial flow turbines. Fig. 3. Impellers used on small portable mixers shown in Fig. 4, are oflen inclined at an angle as well as being off-center to give a good top-to-bottom flow pattern in the system. Fig. 5. Large top-entering drives usually use either the axial flow turbine or the radial flow flat blade turbine. For aerobic fermentation, the radial flow disc turbine is most common and is illustrated in Fig. 6. 

Figure 4.1. Stirred vessels with baffles, and common impeller types flat disc turbine, propeller, and pitched blade impeller.

In those gas/liquid processes where the gas flow is not sufficient for obtaining an effective contact between the phases, a stirrer can be used for disperging the gas. This applies particularly to small and medium sized reactors. A turbine impeller combined wiA baffles is quite effective (see figure 4.1). The gas can best be introduced via a perforated ring that is placed underneath the impeller. Another well known impeller type has a hollow shaft and hollow blades, through which the gas is sucked from the gas space and introduced into the liquid at the blade tips. When a common flat disc turbine is used, the gas phase is dispersed into small bubbles that circulate with the liquid in upward and downward directions (compare section 4.2.1). Particularly in the zones with lower flow rates, the bubbles will coalesce at a certain rate. A fraction of the larger bubbles will return with the circulating liquid flow to the impeller zone, where they are redispersed, but the... 

Rushton turbine A type of impeller used for gas dispersion such as in biochemical reactors and consists of a flat disc with six vertical flat blades mounted on the circumference (see Fig. 54). It therefore provides radial-flow mixing. It is named after American chemical engineer John Hetuy Rushton (1905-85), who was noted for his work on mixing. There have been many subsequent modiflcations and improvements to the basic design. 

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