Reactors pitched blade turbine

The polymerizations were conducted in a 20-liter stainless steel reactor with a pitched-blade turbine agitator and four side-wall baffles. The monomer was polymerized at the same temperature, initiator and monomer concentration in two different inert diluents. The data (Figure 6) illustrate the substantial lowering of the overall heat transfer coefficient for the system with the more highly swollen particles. 

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. 

Flow patterns in a mechanically agitated reactor with disk turbine, pitched-blade turbine, and propeller types of agitator are schematically illustrated by Joshi et al. (1982). The flow pattern in the presence of gas is described later in the section on slurry reactors. In each of these cases, the dimensionless velocity profile with respect to the impeller tip velocity has been found to be independent of the impeller speed and has shown slight dependence on the impeller diameter. 

Numerous types of stirrers are used in practice, and Fig. 3.2 shows the most commonly used ones. The stirrers for low-viscosity media are typically marine propeller and pitched-blade turbine stirrers, which cause axial fluid motion, and flat-blade turbines and impellers, which generate radial fluid motion. The former stirrers are suitable for uniformly suspending solids. The latter type are the preferred ones for carrying out exothermic reactions, like autooxidation reactions (see Section 8.3), where the heat generated dining the process has to be removed effectively through the reactor walls. 

Fig. 6.4. Reactor agitation using a pitched blade turbine. (Courtesy Autoclave Engineers.)...

FIGURE 9.4 Two alternatives to enhance reactor performance, (a) Four pitched blade turbine, (b) two pitched blade turbine with cage. 

FIGURE 9.5 Simulated flow field for two alternative reactor configurations (red high values blue low values legend not shown due to confidentiality constraints), (a) Four pitched blade turbine, (b) two pitched blade turbine with cage (left vector plots right contours of turbulent kinetic energy.)... 

The mixer as a solid liquid reactor is generally most elTicient, i.e. Rq/cj is a maximum) at the just fully suspended condition for all impellers and for any particular solid-liquid pair, constant. Thus the overall optimum is obtained when (eT)ts lowest and an impeller-tank configuration that is eflicient for suspension is also efficient for reaction. In many cases, this corresponds to a large low-speed hydrofoil impeller, or pitched blade turbines of D/T 0.4. In this respect, the recent development of cheap and reliable gearboxes capable of handling the larger torques that low speeds imply is noteworthy. ... 

Bujalski W, Nienow AW, Hnoxing L. (1990) The use of upward pumping 45° pitched blade turbine impellers in three phase reactor. Chem. Eng. Sci., 45 415-421. 

Two impellers are included in the reactor configuration shown in Figure 2. A three-bladed turbine with 45° pitch and blades 1/8 in X 5/8 in is mounted on the impeller shaft at the top of the reactor. A three-bladed propeller with 45° pitch is mounted at the bottom of the impeller shaft at approximately two-thirds of the reactor depth. 

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. 

Rewatkar, V.B., Deshpande, A.J., Pandit, A.B., and Joshi, J.B. (1993), Gas hold-np behavior of mechanically agitated gas-liquid reactors using pitched blade downflow turbines, Canadian Journal of Chemical Engineering, 71(2) 226-237. 

Pitched-blade disk turbine [27] Reactor diameter 0.33 0.53... 

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