In CSTR

Styrene—maleic anhydride (SMA) copolymers are used where improved resistance to heat is required. Processes similar to those used for SAN copolymers are used. Because of the tendency of maleic anhydride to form alternating copolymers with styrene, composition drift is extremely severe unless the polymerization is carried out in CSTR reactors having high degrees of back-mixing. 

Selectivity A significant respect in which CSTRs may differ from batch (or PFR) reaclors is in the product distribution of complex reactions. However, each particular set of reactions must be treated individually to find the superiority. For the consecutive reactions A B C, Fig. 7-5b shows that a higher peak value of B is reached in batch reactors than in CSTRs as the number of stages increases the batch performance is approached. 

For the consecutive reactions A B C, a higher yield of intermediate B is obtained in batch reac tors or PFRs than in CSTRs. 

Multiple Phases Reaclions between gas/liquid, liquid/liquid, and fluid/solid phases are often tested in CSTRs. Other laboratoiy types are suggested by the commercial units depicted in appropriate sketches in Sec. 23. Liquids can be reacted with gases of low solubili-... 

Exploration for an acceptable or optimum design of a new reaction process may need to consider reactor types, several catalysts, specifications of feed and product, operating conditions, and economic evaluations. Modifications to an existing process hkewise may need to consider many cases. These efforts can oe eased by commercial kinetics services. A typical one can handle up to 20 reactions in CSTRs or... 

Instances of multiplicities in CSTR batteries and in PFRs also can be developed. 

A factor in addition to the RTD and temperature distribution that affects the molecular weight distribution (MWD) is the nature of the chemical reaciion. If the period during which the molecule is growing is short compared with the residence time in the reactor, the MWD in a batch reactor is broader than in a CSTR. This situation holds for many free radical and ionic polymerization processes where the reaction intermediates are very short hved. In cases where the growth period is the same as the residence time in the reactor, the MWD is narrower in batch than in CSTR. Polymerizations that have no termination step—for instance, polycondensations—are of this type. This topic is treated by Denbigh (J. Applied Chem., 1, 227 [1951]). 

As can be seen for infinite recycle ratio where C = Cl, all reactions will occur at a constant C. The resulting expression is simply the basic material balance statement for a CSTR, divided here by the catalyst quantity of W. On the other side, for no recycle at all, the integrated expression reverts to the usual and well known expression of tubular reactors. The two small graphs at the bottom show that the results should be illustrated for the CSTR case differently than for tubular reactor results. In CSTRs, rates are measured directly and this must be plotted against the driving force of... 

This result was very conservative, i.e., too restrictive for production units much higher temperature differences were observed in the industry (Nelson 1974). The better results measured in CSTRs were still about two thirds of... 

Hamielec and coworkers (, 42, 43) have conducted extensive experimental and theoretical studies with styrene polymerization in CSTR s. Theirs represent probably the first published work in this area at commercially interesting temperatures and conversions relating theory to experiment, and determining the effects of reactor configuration and conditions on conversion, molecular weight and MWD. 

Summary of Catalyst Composition and Reaction Conditions Selected for Comparing Fischer-Tropsch Synthesis Activity in CSTR... 

Figure 14.6 Illustration of range of feed temperatures (T 0 to T ) for multiple stationary-states in CSTR for adiabatic operation (autothermal behavior occurs for T0 > T )...

Reactions between phases — gas-liquid, liquid-liquid or fluid-solid — is carried out in CSTR-like devices. With granular solids such as catalysts or immobilized enzymes, the preferred laboratory equipment nowadays is a rotating basket or fixed basket through which the fluid is recirculated continuously, with net input and output to the chamber. 

Compare conversions in CSTRs and in segregated flow with Erlang or Gaussian RTDs, for second order reactions. 

In CSTR, with n this large, the behavior, will be essentially plug flow, with C/C0 = 0.20 (b2)... 

Testing of catalyst poisoning is best done in CSTRs since then all of the catalyst is exposed to the same concentration of impurity and the temperature is uniform. 

The centralized control can be approached using different techniques pole-placement, optimal control and loop decoupling. When the whole state is not accessible, a motivation to introduce a state observer is discussed. A detailed example when all state variables are accessible, i.e. when the state observer it is not necessary, has been explained. It is important to remark that the previously cited techniques are not widely used in CSTR control. This is due to the fact that these procedures require non-intuitive matrix tuning and computations, which are not familiar in the process industry. Nevertheless, for complex processes, these procedures can be the only solution to the control problem, when a limited set of sensors are available. 

It is well known that self-oscillation theory concerns the branching of periodic solutions of a system of differential equations at an equilibrium point. From Poincare, Andronov [4] up to the classical paper by Hopf [12], [18], non-linear oscillators have been considered in many contexts. An example of the classical electrical non-oscillator of van der Pol can be found in the paper of Cartwright [7]. Poore and later Uppal [32] were the first researchers who applied the theory of nonlinear oscillators to an irreversible exothermic reaction A B in a CSTR. Afterwards, several examples of self-oscillation (Andronov-PoincarA Hopf bifurcation) have been studied in CSTR and tubular reactors. Another... 

J.B. Planeaux and K.F. Jensen. Bifurcation phenomena in CSTR dynamics A system with extraneous thermal capacitance. Chem. Eng. Sci., 41 (6) 1497-1523, 1986. 

Example 3-1 The reaction A B, r = kCA occurs in CSTR with 90% conversion. If... 

Ratio of Residence Times and Reactor Volumes in CSTR and PFTR versus Conversion for a First-Order Irreversible Reaction... 

Figure 3-5 Residence times in CSTR (shaded rectangle) and PFTR (area under curve) from the 1/r plot.

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