Hollow blade impeller

Marti NOV M., Vlaev S.D., Comparison of mixing power characteristicsfor curved blade / NS-60 flat-blade amd hollow-blade impellers, Hungar.). Ind. Chem. (Veszprem) 27 (1999), p. 179-181... 

Flower [25], Panda et al. [26], Doran [27]. and Payne et al. [28]. Several kinds of bioreactors, such as the stirred tank bioreactor with hollow paddle and flat blade impellers, the bubble column, the airlift bioreactor with internal and external loops, the rotating drum bioreactor, the stirred-tank with a draft tube, and the mist bioreactor have been attempted for plant cell, tissue and organ cultures (Fig. 1). 

Fig. 3 Various impellers (A) Rushton disk turbine, (B) hollow-blade turbine, (C) pitched-blade turbine, (D) narrow-blade hydrofoil (Lightnin A310), and (E) wide-blade hydrofoil (Lightnin A315). (From Ref. l)...

Agitator Type 54rin. three-blade impeller, glass-covered, hollow shaft for thermometer R.p.m. 90... 

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... 

Radial flow Flat-blade impeller, disk turbine (Rushton), hollow-blade turbine (Smith)... 

A hollow shaft/impeller system uses the acceleration of the liquid over the blades to reduce the pressure locally at an orifice and induce the gas flow through... 

Cronin et al. (1994) showed by a decolorization technique Ihe staged mixing associated with radial flow Rushton turbines, and Otomo et al. (1993) showed similar results with radial flow hollow-blade turbines. The latter also used conductivity probes and found mixing times about twice as long as with a single impeller, with values close to the predictions of the equation of Cooke et al. (1988). 

The constant A, which is often about unity, depends on the impeller type, (see Table 11-7). Impellers with a high gas-handling capacity, such as hollow-blade disk designs, have the highest values. As will also be seen in Table 11-7, the exponent B varies considerably with impeller type but is about 0.4 for Rushton and pitched blade turbines. Figure 11-16 reproduces some results for a six-blade Rushton turbine working at various submergences and boil-up rates. In this case the constant A in eq. (11-12) is 0.74. 

Figures 11-17 and 11-18 show data from Smith et al. (2001a) relating to various hollow-blade and hydrofoil impellers from which the values in Table 11-7 have been derived. Modem hydrofoil impellers, which are designed to have good gas-handling characteristics, almost maintain their cold ungassed power levels when up-pumping. In this respect they behave almost as if cavitation does not occur. This will be a very desirable feature of these impellers when used in evaporative crystallizers. Later work (Smith and Tarry, 1994) confirmed that the...

A basic stirred tank design is shown in Fig. 23-30. Height to diameter ratio is H/D = 2 to 3. Heat transfer may be provided through a jacket or internal coils. Baffles prevent movement of the mass as a whole. A draft tube enhances vertical circulation. The vapor space is about 20 percent of the total volume. A hollow shaft and impeller increase gas circulation (as in Fig. 23-31). A splasher can be attached to the shaft at the hquid surface to improve entrainment of gas. A variety of impellers is in use. The pitched propeller moves the liquid axially, the flat blade moves it radially, and inclined blades move it both axially and radially. The anchor and some other designs are suited to viscous hquids. 

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-... 

Self inducing agitators have been on the market for many years These communicate the low pressure region behind the blades with the head space Figure 15.4a) or a gas supply source via a hollow shaft and therefore use some of the input shaft energy to draw in the gas. Often they have multiple blades, sometimes curved like a centrifugal pump impeller,... 

Multi-impeller system hollow half-elliptical blade dispersing turbine below two up-pumping wide blade hydrofoils, identified as HEDT -r 2WHU. Air-hot water (temperature 355°K), polypropylene particles... 

In sewage treatment plant processes as well as in chemical and mining processes, gas is sparged in the hquid. The impeller of the mixer is then used to provide dispersion of the gas and circulation of the tank contents. For radial machines, a small radial impeller is installed at the bottom to mix the gas. In the case of hydrofoils, different approaches are used. If the shaft and blades are hollow, gas may be pumped through the shaft and blades. In other apphcations, the impeller is contained within a cylinder that is within the tank. This prevents flooding the impeller with gas. 

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