Loop type circulation reactors

A schematic of the propeller loop reactor is shown in Fig. 37. In this case, the circulation flow of the fluid phases is created by a hydromechanical propeller flow drive. The use of a draft tube often improves the mass and heat transfer efficiency in these reactors (Blenke, 1967). This type of reactor involves complicated construction and leads to operating problems related to the sealing of the shaft. It is not suitable for biosystems due to possible damage to sensitive organisms in the high shear fields at the propeller. However, it is especially suitable for highly viscous polymeric fluids and for medium-size units. 

In bubble columns, agitation of the liquid phase, and hence suspension of the catalyst is effected by the gas flow. The gas is often recycled to cause more turbulence and thus better mixing. Circulation of the liquid is often required to obtain a more uniform suspension. This can either be induced by the gas flow (airlift loop reactor) or by use of an external pump. In the latter instance it is possible to return the slurry to the reactor at a high flow rate through an ejector (Venturi tube). The local under-pressure causes the gas to be drawn into the passing stream, thus affording very efficient mixing. This type of reactor is called a Jet-loop or Venturi reactor. 

The ejector-based reactor can be constructed in various configurations. Firstly, the jet can be either upflow or downflow, hi this book, only the downflow type is considered. In this type, the venturi loop reactor can be with or without a draft mbe. In case there is a draft tube, there is an additional internal circulation loop within the reactor. An outer circulation loop already exists because the hquid + catalyst slurry is continuously recycled by the external pump through the heat exchanger and the primary nozzle. 

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

Bioreactors. Bioreactors that utilize hving cells are typically called fermenters. There are several different types of bioreactors mechanically stirred or agitated tanks bubble columns (cylindrical tanks that are not stirred but through which gas is bubbled) loop reactors, which have forced circulation packed-bed reactors membrane reactors microreactors and a variety of different types of reactors that are not easily classified (such as gas-Uquid reactors and rotating-disk reactors). Biochemical engineers must choose the best bioreactor type for the desired purpose and outfit it with the right instrumentation and other features. 

Various loop-type reactors, consisting of a circulation pump, homogeniser (where the acid is introduced in Ae circulating alkaline paste) and heat exchanger, are used for the complex neutralisation step. 

The loop circulating reactor outlined above expresses in chemical engineering terms, the characteristics of a perfect mixer. This type of reactor presents the following characteristics required for the neutralisation step ... 

Natural circulation DHR experiments u g the eiq)erimental fast reactor Joyo [5.42], The tests are intended to demonstrate the natural convection DHR capability of Joyo and serve as a basis for the confirmation of similar but larger loop-type reactors. 

Sasaki, K., et al.. Study on Decay Heat Removal Characteristics by Natural Circulation for Top Entry Loop-Type FBR, Proc. of the Intemat. Conference on Fast Reactors and Related Fuel Cycles, Kyoto, Japan, 1991. 

Koga, T., et al.. Natural Circulation Water Tests for Top Entry Loop-Type LMFBR, Proc. of the Sixth Intemat. Topical Meeting on Nuclear Reactor Thermal Hydraulics, Grenoble, France, 1993. 

Thermal hytt-aulics. Three kinds of thermal hydraulic tests were conducted to confirm the technical feaability of the top entry loop type reactor a natural circulation flow test, a multiple-surface sloshing test and a gas entrainment test. These tests were conducted with the cooperation of CRDEPI, PNC and various universities. 

Fixed-bed and fluidized-bed bioreactors consist of macroporous carriers on which the cells are immobilized. In the case of fixed-bed bioreactors, these carriers are packed in a column, and In the case of fluidized-bed bioreactors they float in a column. The column is permanently perfused with a conditioned medium from a reservoir in a circulation loop. These types of reactors enable long-term perfusion culture of mammalian cells. They have been successfully applied for the long-term production of biopharmaceuticals such as monoclonal antibodies [37, 122]. 

The design concept of JSFR, Japan s Generation IV reactor, was reviewed. It is a loop type and is characterized, in terms of safety, by a self-actuated (passive) RSS, a re-criticality free core design, and a natural-circulation DHRS. It is also characterized, from the viewpoint of economy, as a two-loop heat transport system, integrated IHX/ pump component, and others. 

Table I provides an overview of general reactor designs used with PS and HIPS processes on the basis of reactor function. The polymer concentrations characterizing the mass polymerizations are approximate there could be some overlapping of agitator types with solids level beyond that shown in the tcd>le. Polymer concentration limits on HIPS will be lower because of increased viscosity. There are also additional applications. Tubular reactors, for example, in effect, often exist as the transfer lines between reactors and in external circulating loops associated with continuous reactors.

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