Stirred reactors, with pitched blade turbine

Double-impeller combinations Bouaifi et al. (2001) derived the following correlations for stirred gas-liquid reactors with various combinations of double impellers. The impellers used were the lightning axial flow impeller (A-310), the four 45° pitched blade turbine pumping down (PBTD) and the Rushton disk turbine (RDT). Furthermore, the tank was a dish-bottom cylindrical tank equipped with four baffles, while the gas was introduced by a ring sprager. The gas-flow rate ranged from 0.54 to 2.62 L/s, whereas the rotational speed was from 1.66 to 11.67 s. The gas holdup is... 

Pitch-blade turbine (paddle stirrer with pitched blades) and propeller stirrers provide high mixing with an axial flow pattern. Both of these stirrers are normally used for low-viscosity liquids and in vessels with baffles. They are well suited for providing liquid homogenization and suspension of solids in slurry reactors. The stirrers can also be used in viscous fluids and for vessels with H/dT > 1, which are generally encountered in fermentation processes. For these situations, axial flow is increased with the use of multistage stirrers with pitched stirring surfaces. 

A typical stirred-tank reactor is shown in Fig. 5.4-3. It is a cylindrical vessel with elliptical or torospherical bottom and cover. It is equipped with an axially mounted stirrer rotating with a speed from 25 rpm (large scale) to 2000 rpm (laboratory). Fig. 5.4-4 shows the stirrers that are mostly used in fine chemicals manufacture, viz. the marine propeller, turbine, flat- or pitched-blade agitator, and anchor. Agitators move the fluid into axial and radial direction. Marine propellers and pitched-blade stirrers predominantly impose axial motion. 

FIGURE 7A.3 Some commonly used impellers for two-/three-phase stirred reactors, (a) Standard six-blade Rushton turbine, (b) Six-blade 45° pitched turbine, (c) Lightnin A315 . (d) SC ABA 6SRGT. (Reproduced from Middleton 2000 with permission from Elsevier. 1992.)... 

Duty It is required to design a stirred reactor using microcarrier-supported animal cells. The working capacity of the reactor (volume of broth) is 20 m The dispersion height to diameter ratio = 1. Disengagement volume equivalent to 1/3 of the total volume is to be provided above the broth level. Therefore, total reactor volume is 30 m and vessel diameter is 3 m. Impeller to be used is six-blade upflow pitched turbine with DIT = CIT = 0.33. 

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