Reactor systems cascade

In practice the sulphonation conditions required for FAMES are much more severe than for the other materials, with the result that FAMES poses the worst colour problems. Branched alkylbenzenes may require bleaching notably from long residence-time reactor systems (cascade of continuous stirred tank reactors). 

Crameri et al. (1997) have reported an asymmetric hydrogenation constituting an important step in the production of a new calcium antagonist, Mibefradil (POSICOR) (of Hoffmann-LaRoche). Pilot-scale synthesis of (S)-2-(4-flurophenyl)-3-methylbutanoic acid by the asymmetric hydrogenation of 2-(4-fluorophenyl)-3-methyl but-2-enoic acid with a [Ru (/ )-MeOBIPHEP)(OAc)2]-catalyst has been described. The hydrogenation was performed in a continuous mode in a cascade stirred-tank reactor system at a pressure of 270 bar. A large reduction in total reactor volume compared to the batch mode was realized. 

Cross-flow reactors are fed continuously with streams of components of the reaction mixture whereby some components are introduced at the inlet, while others are introduced at other locations. The reaction mixture flows out continuously from the end of the reaction zone. A cascade of CSTRs with additional feeds to individual reactors represents a cross-flow reactor system. Cross-flow reactors are also operated at steady-state conditions ... 

This section is concerned with batch, semi-batch, continuous stirred tanks and continuous stirred-tank-reactor cascades, as represented in Fig. 3.1 Tubular chemical reactor systems are discussed in Chapter 4. 

In continuous reactor systems, all reactants are continuously fed to the reactor, and the products are continuously withdrawn. Typical continuous reactors are stirred tanks (either single or in cascades) and plug flow tubes. Continuous reactors are characterized by stationary conditions in that both heat generation and composition profiles remain constant during operation (provided that operating conditions remain unchanged ). 

Cascade reactor systems, 20 170 Cascade refrigeration systems, 27 547-550 three-stage, 27 549-550 two-stage, 27 548... 

The system mostly applied in practice for supply of ozone is the bubble column and the stirred tank reactor. With these reactor systems it is always possible to set up the complete reactor modification as a plug flow reactor, a continuous flow single stirred tank reactor or a cascade of stirred tank reactors. 

Many commercial photochemical reactor systems make use of the batch recirculation mode for the treatment of highly contaminated wastewaters of limited volume. On the other hand, cascades of photoreactor modules (in serial or parallel mode) allow the gradual treatment of contaminated water streams with a very high photon flow Op in total. Hence, there exist powerful photochemical waste-... 

Sane of the results obtained experimentally are oatiared in table III with those predicted by the model. The agreeroent is excellent and, as e 5)ecbed, the amounts of dinitroanthraquinene formed in this reactor system are higher than in the plug flew reactor. Using this model we were able to shew that for this nitration a cascade of at least 20 stirred vessels are required in order to obtain the same product-mixture as with the ideal tubular reactor (fig. 2). 

We have simulated the complete (stirred tank and tube) reactor system combining our model for the cascade reactor, with only one stirred tank, with the model for the adiabatic ideal tubular reactor. An example of the excellent fit between simulated and eiq)eriinentally found resiUts is given in fig. 3. ... 

When a number of cells are connected in series as a cascade, reaction occurs stepwise in each of the reactors resulting in high overall conversion. Both CSTR and PER models can be analyzed as cascades. This reactor system is identical to that developed in Chapter 10 but with appropriate electrochemical parameters. Thus for a system of N CSTRs in a cascade, the design equation is... 

In plants of a capacity up to 150,000 tpa, the reactor system is arranged as a three-stage cascade. 

There are seven main sulphonation reactor systems used world-wide for SOs/air sulphonation for which there is proven practical and documented experience The Ballestra Sulphurex continuous stirred tank reactor (CSTR) cascade, the Ballestra Sulphurex F (a multitube falling-film reactor (MT-FFR)) the Chemithon falling-film reactor (FFR), the Chemithon Jet Impact Reactor, the MM falling-film reactor (FFR), the Mazzoni Sulpho film reactor (a multitube falling-film reactor) and the Japanese T-0 FFR reactor system. 

Back-mixing and short-circuiting of the liquid stream must inevitably occur to some extent in a cascade reactor system of the Ballestra type. Thus for a reactor train of 4 reactors where the mean residence time is 90 minutes, 15% of the material passes through in approx. 45 minutes, while 5% of the material has a residence time approaching 180 minutes. 

Troubleshooting a reactor system requires the student to become familiar with the typical operation of the unit. As equipment and instrumentation fails, the student sees the cascading effect a single problem can have on the unit. A single problem can create a series of other problems, so students must learn to identify the primary problem that started the system failure(s). 

Figure 11.11 Biotransformation of 4-cyanopyridine into isonicotinic acid by a nitrilase-amidase cascade in a single reactor and a two-reactor system [56].

One such approach is called cascade control, which is routinely used in most modern computer control systems. Consider a chemical reactor, where reac tor temperature is to be controlled by coolant flow to the jacket of the reac tor (Fig. 8-34). The reac tor temperature can be influenced by changes in disturbance variables such as feed rate or feed temperature a feedback controller could be employed to compensate for such disturbances by adjusting a valve on me coolant flow to the reac tor jacket. However, suppose an increase occurs in the... 

During the manufacturing process, if the grafting increases during early stages of the reaction, the phase volume will also increase, but the size of the particles will remain constant [146-148]. Furthermore, reactor choice plays a decisive role. If the continuous stirred tank reactor (CSTR) is used, little grafting takes place and the occlusion is poor and, consequently, the rubber efficiency is poor. However, in processes akin to the discontinuous system(e.g., tower/cascade reactors), the dispersed phase contains a large number of big inclusions. 

A modern sulfochlorination is run continuously (Fig. 7). To limit the formation of di- and polysulfochlorides (Fig. 8) up to eight reactors are connected in a cascade. For a 25% alkane conversion, a residence time of 4-5 h is necessary if the circulating and cooling systems are appropriately designed. Since a lower gas flow rate promotes the formation of di- and polysulfochlorides, it makes no sense to run a sulfochlorination plant much below name-plate capacity. 

An example of cascade control could be based on the simulation example DEACT and this is shown in Fig. 2.35. The problem involves a loop reactor with a deactivating catalyst, and a control strategy is needed to keep the product concentration Cp constant. This could be done by manipulating the feed rate into the system to control the product concentration at a desired level, Cjet- In this cascade control, the first controller establishes the setpoint for flow rate. The second controller uses a measurement of flow rate to establish the valve position. This control procedure would then counteract the influence of decreasing catalyst activity. 

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