Impeller flat blade turbine type

Mechanically agitated reactors have been used for cultivation of plant cells (Kato et al., 1972 Tanaka, 1981). Ajar fermenter with a six fiat-blade turbine and a modified paddle has been used by Tanaka (1981) and a similar jar fermenter with two disk turbine impellers has been used by Kato et al. (1972) at about 50 rpm with no significant shear damage to plant cells. Paddle-type impellers were found to be more appropriate (less shear damage) than flat-blade turbine type impellers (Kato et al., 1972). The only production-scale reactor used for shikonin production in Japan is also an agitated vessel. 

Calculate mass transfer coefficient in a 60 m3 fermenter with a gas and liquid interfacial area of a = 0.3 m2-m 3, given pbroth = 1200kg m-3. The small reactor has working volume of 0.18m3, 1 vvm aeration rate. Oxygen transfer rate (OTR) is 0.25kmol in 3 h 3. There are two sets of impellers, and flat-blade turbine types of impeller were used, HL= 1.2/),. Find the exact specifications of a large fermenter. 

Stirred vessel Figure 2.5(a) (Cylindrical flat bottom vessel, four baffles). Impeller six-flat blade turbine type. 

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. 

Impellers are usually of the flat-blade turbine type, Fig. 6.36 and c, either centrally located in the vessel or nearer the bottom entry of the liquids. The impeller-tank-diameter ratio d /T is ordinarily in the range 0.25 to 0.33. 

Figures 5-3 and 5-5 illustrate a few of the types of impellers used for mixing. They may be basically classified as axial, radial and mixed. In general the most generally applicable are the. 3-bladed propeller, the flat-blade turbine, the curved blade turbine, and the paddle. The many other designs are either modifications of these or specially designed for a very special purpose with respect to a fluid system and/or its performance.

Furthermore, the flat-bladed turbine impeller would seem more suitable for agitation under such conditions than the marine-type impeller. 

Figure 7.7 shows three commonly used types of impellers or stirrers. The six-flat blade turbine, often called the Rushton turbine (Figure 7.7a), is widely used. The standard dimensions of this type of stirrer relative to the tank size are as follows ... 

Figure 7.7 Typical impeller types (a) a six-flat blade turbine (b) a two-flat blade paddle and (c) a three-blade marine propeller. See the text for details of the abbreviations. 

In Figure 7.8, the curves a, b, and c correlate data for three types of impellers, namely, the six-flat blade turbine, two-flat blade paddle, and three-blade marine propeller, respectively. It should be noted that, for the range of (Re) >10, Afp is independent of (Re). For this turbulent regime it is clear from Equation 7.30 that... 

Until now, bioreactors of various types have been developed. These include loop-fluidized bed [14], spin filter, continuously stirred turbine, hollow fiber, stirred tank, airlift, rotating drum, and photo bioreactors [1]. Bioreactor modifications include the substitution of a marine impeller in place of a flat-bladed turbine, and the use of a single, large, flat paddle or blade, and a newly designed membrane stirrer for bubble-free aeration [13, 15-18]. Kim et al. [19] developed a hybrid reactor with a cell-lift impeller and a sintered stainless steel sparger for Thalictrum rugosum cell cultures, and cell densities of up to 31 g L1 were obtained by perfusion without any problems with mixing or loss of cell viability the specific berberine productivity was comparable to that in shake flasks. Su and Humphrey [20] conducted a perfusion cultivation in a stirred tank bio-... 

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. 

Equations (9.6) to (9.8) imply that Nq is constant for each type of impeller. For a standard flat-blade turbine, in a baffled vessel, Nq may be taken as 1.3. This gives the discharge flow from the tips of the impeller and not the total flow produced. The high-velocity stream of liquid leaving the tip of the impeller entrains some of the slowly moving bulk liquid, which slows down the jet but increases the total flow rate. For flat-blade turbines, the total flow, estimated from the average circulation time for particles or dissolved tracers, was shown to be... 

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