CSTR comparison with

Comparison of performance of a series of N equal-size CSTR reactors with a plug flow reactor for the first-order reaction... 

For a continuous-flow reactor, such as a CSTR, the energy balance is an enthalpy (H) balance, if we neglect any differences in kinetic and potential energy of the flowing stream, and any shaft work between inlet and outlet. However, in comparison with a BR, the balance must include the input and output of H by the flowing stream, in addition to any heat transfer to or from the control volume, and generation or loss of enthalpy by reaction within the control volume. Then the energy (enthalpy) equation in words is... 

The table shows final results for several values of Pe and also a comparison with CSTR at Pe = 0 and PFR at Pe - oo. 

The previous chapters have discussed the behaviour of non-linear chemical systems in the two most familiar experimental contexts the well-stirred closed vessel and the well-stirred continuous-flow reactor. Now we turn to a number of other situations. First we introduce the plug-flow reactor, which has strong analogies with the classic closed vessel and which will also lead on to our investigation of chemical wave propagation in chapter 11. Then we relax the stirring condition. This allows diffusive processes to become important and to interact with the chemistry. In this chapter, we examine one form of the reaction-diffusion cell, whose behaviour can be readily understood by comparison with the responses observed in the CSTR. 

Figure 3.35 Comparison of CSTR-stripper with 1-CSTR and 2-CSTR +20% feedrate disturbances.

Experimental. Figure 2 compares molecular weight data reported by Garden (J 0) for batch reactors and by Poehlein for CSTR reactors ( ), with the data obtained in this study for a tubular reactor. The solid lines are predicted by Garden s theory (10). The molecular weights obtained in this experimenTal study were predicted within a factor of 3 by Garden s theory. No direct comparison can be made with the data of other workers, yet this molecular weight data is consistent (at least within experimental error) with data obtained in other types of reactors. 

Petroleum refinery flowsketch, 26 PER (plug flow reactor), 55,558 comparison with CSTR, complex reactions, 569 volume ratio to CSTR, 571 Phase diagrams nitrotoluene isomers, 544 salt solutions, 526 use of example, 528 Phenol bv the chlorbenzene process, 34 Phosgene synthesis, 594 PhthMic anhydride synthesis, 593 PID (proportional-integral-derivative) controllers, 41, 42... 

Nitric acid removal from an aqueous stream was accomplished by continuously passing the fluid through a hollow fiber supported liquid membrane (SLM). The nitric acid was extracted through the membrane wall by coupled transport. The system was modeled as a series of (SLM)-continuous stirred tank reactor (CSTR) pairs. An approximate technique was used to predict the steady state nitric acid concentration in the system. The comparison with experimental data was very good. 

An approximate analytical solution has been developed to calculate the exit concentration from a continuously recirculating facilitated transport liquid membrane system. The system is modeled as a series of SLM-CSTR pairs. The solution allows for two-dimensional transport (axial convective and radial diffusive) and laminar flow. The solution allows one to estimate the effect of a change in system variables on the operating performance. Comparison with experimental data was very good. 

Figure 8.15 Comparison of performance of a series of N equal-sized CSTR reactors with a plug flow reactor for elementary second-order reactions 2A -> products and A -I- B -> products with C o == Bo negligible expansion (5 = 0). For the same processing rate of identical feed, the ordinate measures the volume...

When used in laboratory-scale operations CSTRs are frequently referred to as chemostats. Chemostats are often employed in scientific studies intended to elucidate the metabolic processes associated with particular microorganisms because they are better equipped to monitor transient situations involving a transition from one set of operating conditions to another, for example, when there is a shift in the composition of the stream being fed to a unit operating at steady state. By comparison with large-scale CSTBRs, small-scale chemostats are characterized by shorter response times and are more readily instrumented to facilitate acquisition of data that are useful in optimization of the performance of these reactors. 

Depending upon the particular polymer system, a CSTR or a series of CSTRs may offer several advantages over batch and tubular flow reactors both with respect to polymer production rate and polymer quality. With a perfectly mixed CSTR it is often possible to achieve a molecular weight distribution considerably narrower than can be obtained with a batch (or tubular) reactor with the same holdup time. This is true with any polymerization where molecular weights are controlled by termination. By running CSTRs in series or in parallel it is possible to produce tailor-made polymers with a broader MWD simply by operating each CSTR at a different temperature and/or with different residence times. Another feature of CSTRs is that the CCD can be very narrow in comparison with batch (or tubular) reactors, where the CCD is broadened due to the drift in monomer composition. 

Figure 3.22 Concentration profile in a cascade with five stages in comparison with a PFR and a single CSTR.

CPFR (cf. Fig. 3.10d) in comparison with a single CSTR (-) in four different cases ... 

When the behavior of the studied system departs from a first-order behavior, which is the case for numerous chemical reactions, more complex relations can be developed between the efficiency and the NOU, whose expressions will not be detailed here. In a plug-flow system, and also in a CSTR, a direct relation, either explicit or implicit, exists between the efficiency and the NOU. Figure 2.1 presents the evolution of the efficiency as a function of the NOU for reaction orders between —1 and 2. The shape of the curves clearly depends on the reaction order, therefore enabling identification of the system order by comparison with experimental data and estimation of the operation time. 

FIGURE 51.4 Time dependences of the logarithmic isotope fraction in the reaction product for different types of reaction mechanisms in a CSTR (B) and plug-flow reactor (C) in comparison with a differential reactor (A). 

This is a Hory distribution or most probable distribution and much broader (D>1) than the Poisson distribution (D=l) resulting from batch polymerization. The increase in molecular weight polydispersity is due to the fact that the chains are living, and so are directly impacted by the RTD. Recall that the polydispersity of the RTD for a CSTR is 2. For long residence time, approaches 1 and D becomes 2. Thus, the number chain length distribution (NCLD) takes on the breadth characteristics of the RTD, due to the living nature of the polymer chains. For comparison, one should recall that the lifetime of a free radical is 1-10 s. This is insignificant in comparison with the RTD and so that RTD has little to no effect on D in free radical polymerization. 

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