Liquid-impelled loop reactor

Figure 2.5 Possible technological solutions to bioprocess problems a) Fed-batch culture b) Continuous product removal (eg dialysis, vacuum fermentation, solvent extraction, ion exchange etc) c) Two-phase system combined with extractive fermentation (liquid-impelled loop reactor) d) Continuous culture, internal multi-stage reactor e) Continuous culture, dual-stream multi-stage reactor f) Continuous culture with biomass feedback (cell recycling). (See text for further details).

Liquid-impelled loop reactor Production of anthraquinones Plant cell culture 124... 

In the literature many examples of more or less exotic bioreactors can be found. Few actually are applied, outside the laboratory. Here two novel designs, the membrane and the liquid-impelled loop reactor, are discussed briefly. These two reactors are simple to use and, to a certain extent, liable to scale-up and both integrate the actual biocatalysis with part of the down-stream processing. 

A novel bioreactor, especially designed to work with two liquid phases, is the liquid-impelled loop reactor (Figme 11.10), in which the advantages of air lifts and... 

Figure 11.10 Schematic representation of a liquid-impelled loop reactor.

Fig. 7.5. The liquid-impelled loop reactor organic solvent less dense (left) and denser (right) than...

An example of integration of part of the downstream processing in the actual bioreactor is two-liquid-phase biocatalysis (see above), in which the organic-solvent phase is used as extractant for the product. The liquid-impelled loop reactor (Fig. 7.3) is specifically designed for this purpose. It is based on the well-known air-lift principle, but instead of air, a water-immiscible, heavier or lighter organic solvent is injected. 

Liquid-impelled loop reactors In this type of reactor, liquid is forced to circulate through the action of jets or pumps. 

A gas-inducing agitator system is an alternative to a multistirrer system. It contains a hollow shaft with orifices above the liquid level and a hollow impeller. A typical hollow impeller consists of a tube that is, at the centre, connected to the hollow shaft. Both ends of the impeller are cut at 45 so that, at rotation, the open portions of the tube are at the near side of the stirrer. There are several modifications of this design. Obviously, there is a minimum impeller speed at which the onset of gas induction occurs. Loop reactors are also successfully used. 

FIGURE 7A.8 Hydrodynamic regimes in two-phase (gas-liquid) stirred tank reactor. 1, flooding of the impeller 2, gas dispersion above the impeller 3, gas circulation above the impeller with marginal dispersion helow the impeller 4, gas circulation both above and below the impeller 5, recirculation of the gas resulting in the formation of secondary loops besides main discharge streams from the impeller. (Reproduced from Middleton 2000 with permission from Elsevier. 1997, Elsevier.)... 

Kinetics can be screened in a screw impeller-stirred reactor (SISR) [7] (Figure 9.8). The reactor system comprises a screw impeller that pumps the liquid upwards, and the high exit velocity of the liquid results in an effective foam formation in the top section of the reactor. A slug flow (Chapter 6) is thus established in the monolith channels. Consequently, the liquid and gas are pumped from the lower section to the upper section of the reactor, over and over again. In fact, the concept resembles that of a loop reactor. Cylindrical monoliths are placed in the stator of an SISR (Figure 9.8), and a foam of gas and liquid is forced through the monolith channels by a screw. 

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