Multizone reaction

Chapter 8 provides original results for optimal configurations of multizone reaction-diffusion reactors, and compares these with results for a cascade of reactors known from the literature. 

This distinction is historic but does not appear to be very usefiil. In fact, for kinetic studies, experience shows us that it is more appropriate to separate single zone reactions from multizone reactions. We will see that differences appear at this level. Thus, in our previous examples we will classify reaction [1.R1] in gas phase and the catalytic reaction in Figure 1.1a in the same category of single zone reactions while the reaction presented in Figure 1.1b will be a multizone reaction. In addition to this, it should be noted that the same chemical reaction might occur with a different number of zones depending on the conditions of the experiment. 

David, R., Muhr, H. and Villermaux, J., The Yield of a Consecutive-Competitive Reaction in a Double Jet Semi-Batch Reactor Comparison between Experiments and a Multizone Mixing Model, Chem. Eng. Sci. 1992, 47 (9-11), 2841-2846. 

Autoclave reactors differ from tubular reactors in two respects. Autoclave reactors have much smaller length-to-diameter ratios (2-4 for single-zone and up to 15-18 for multizone reactors) and operate at a much narrower reaction temperature range. 

The arenediazonium solution can also be manufactured in a continuous way either in two consecutive loop reactors76 or in a multizone reactor, run by the arylamine solution, and where a part of the nitrite solution is fed into the upstream portion of each reaction zone.77,78... 

If this trend is extrapolated to lower temperatures it is clear that at temperatures varying between -78 and -150°C for carbon—hydrogen bonds on various types of hydrocarbons, AF becomes zero and then endothermic. Under these conditions (AG < 0) the reaction with elemental fluorine will not and should not proceed at all Wfe have observed this in many cases experimentally. At temperatures as low as -150°C the reaction of fluorine with all studied organic compounds either does not occur or is extremely slow. We have occasionally reported reactions in the cryogenic reactor as low as -120°C. It should be explained that the — 120°C reported is the temperature of a single trap in a multizone reactor rather than that for the entire reactor. It is possible that fluorination occurs during the volatilization process at such low temperatures. 

Also, polymerization reactions are carried out in a variety of reactors including agitated batch reactors, continuous stirred tank reactors (CSTR), multizone autoclaves, loop reactors, tubular reactors, fluidized bed reactors, and a combination of these reactors. 

Schmidt, C.U., Mei, G., Meier, G., Bertolini, S., Busch, M., Wulkow, M., Schwibach, M., Prem, A., Batschkin,T. and Weickert, G. (2003) Training simulator for PP multizone circulating reactor process. Polymer Reaction Engineering V,... 

In spite of the success of CFD simulations for the multiphase turbulent fluid flow in stirred-tank bioreactors (see Section 3.4), their application to coupled material balance equations in case of more complicated reaction networks is still limited by the required computing power. Even in case of successful approaches for model reduction, the number of compounds necessary for reliable portrayal of cellular dynamics in response to spatial variation of extracellular compounds may be still too large. An interesting method to overcome these numerical difficulties is the general hybrid multizonal/CFD [27-36], which gave momentum to the application of CFD modeling for bioreactors. 

A recent development in this technology is the multizone circulating reactor (MZCR) developed by Basell ( Spherizone process), in which a given polymer particle flows back and forth between two reaction zones of a loop reactor, in each of which the conditions are different... 

Although heterogeneous reactions have the same basic equations as homogeneous reactions, they featnre very different properties - mainly related to their multizone nature - and lead to very different kinetic laws and mathematical formulations of speed. Moreover, two new processes are involved ... 

A second consequence of the multizone nature of heterogeneous reactions is that the elementary chemical steps will most often take place in 2D zones and will therefore be characterized by surface reactivities and surface space functions. 

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