Multiple mixer

Fig. 15. Mechanically agitated columns (a) Scheibel column (b) rotating-disk contactor (RDC) (c) asymmetric rotating-disk (ARD) contactor (d) Oldshue-Rushton multiple-mixer column (e) Kuhni column and (f) reciprocating-plate column.

When using the clustered layout of multiple mixers, a mixer spacing of 22.5° is commonly used. It is important to position the clustered mixers opposite the cmde oudet in order to benefit from Hquid velocities during pump out. 

The reactions of an unstable intermediate can be studied by the use of multiple mixers. The transient is generated in one mixer and then mixed with a reagent in a second mixer. Monitoring after the second mixer is usually by spectra. The protonated superoxotitanium(IV) species TiO(H02) is formed by mixing a Ce(IV) solution with one containing HjOj and TiO (which gives Ti(02) ). 

Simplicity, mixing time can be controlled (with special mixers), possibility to incorporate multiple mixers... 

Some processes use a fine dusting agent to control agglomeration. This is used mostly in processes where there are multiple mixers. 

The purpose of mixing thoroughly is to achieve a homogeneous distribution of the various components in the final product. The machines most often used for this task are the mixing chamber and the multiple mixer. With the mixing chamber principle a very large volume (for example, 230 m ) is filled in horizontal layers and subsequently reduced vertically from one side. This may be done continuously... 

A multiple mixer (Figure 3.5) is composed of multiple chambers lined up behind each other. There are two working principles either flocks that had been fed at the same time are processed at different times, or flocks fed at different times are processed at the same time. 

Wetox uses a single-reactor vessel that is baffled to simulate multiple stages. The design allows for higher destmction efficiency at lower power input and reduced temperature. Its commercial use has been limited to one faciHty in Canada for treatment of a complex industrial waste stream. Kenox Corp. (North York, Ontario, Canada) has developed a wet oxidation reactor design (28). The system operates at 4.1—4.7 MPa (600 to 680 psi) with air, using a static mixer to achieve good dispersion of Hquid and air bubbles. 

Stationaiy. shell or trough. There are a number of different types of mixers in which the container is stationary and material displacement is accomplished by single or multiple rotating inner mixing devices. 

Mixers for gas-liquid contacting are often equipped with multiple impellers on a single shaft with the gas injected below the lowest impeller. Large commercial systems may use relatively deep cylindrical vessels. The usual ratio of liquid-depth to vessel-diameter lies between 1 and 3 (R3), and the maximum recommended is 4 (P3). In such deep systems, the question arises as to whether the use of multiple impellers would provide more effective contact than a single impeller. It must be kept in mind that if the impellers are spaced too widely the result may be ineffective agitation between the fields of action of the impellers. On the other hand, if they are too close, interference may occur between the flow streams from the adjacent impellers. 

From there, the reaction flow either leaves the total system to be quenched or, more commonly, enters the next plate which contains a delay loop, a spiral channel [56]. Leaving that plate, the streams flow to the last structured plate containing a bifurcation-mini mixer unit. The streams are distributed in multiple streams and contacted with a likewise split water stream. This leads to fast dilution, e.g., of a concentrated sulfuric acid stream, and rapidly cools the reaction stream. The reaction is quenched more or less initially. The final plate is unstructured and acts as a cover plate with holes for liquid withdrawal (Figure 4.28). 

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