Evaluation CSTR series reactions

A first-order liquid-phase reaction takes place in a baffled stirred vessel of 2 volume under conditions when the flow rate is constant at 605 dm min and the reaction rate coefficient is 2.723 min the conversion of species A is 98%. Verify that this performance lies between that expected from either a PFR or a CSTR. Tracer impulse response tests are conducted on the reactor and the data in Table 6 recorded. Fit the tanks-in-series model to this data by (A) matching the moments, and (B) evaluating N from the time at which the maximum tracer response is observed. Give conversion predictions from the tanks-in-series model in each case. 

Here we use a single parameter to account for the nonideality of our reactor. This parameter is most always evaluated by analyzing the RTD determined from a tracer test. Examples of one-parameter models for a nonideal CSTR include the reactor dead volume V, where no reaction takes place, or the fraction / of fluid bypassing the reactor, thereby exiting unreacted. Examples of one-parameter models for tubular reactors include the tanks-in-series model and the dispersion model. For the tanks-in-series model, the parameter is the number of tanks, n, and for the dispersion model, it is the dispersion coefficient D,. Knowing the parameter values, we then proceed to determine the conversion and/or effluent concentrations for the reactor. 

To illustrate the design/control trade-off more quantitatively, let us consider a simple chemical engineering system a series of continuous stirred-tank reactors (CSTRs) with jacket cooling. This type of reactor system is widely used in industry. The reactions and the reactors are quite simple, but they provide some important into evaluating the tradc-offs between steady-state design id eontroL In this section we consider the sin pfe po ibie reai ih reaction A... 

Aris et al. have primarily analyzed whether the steady-state multiplicity features in a CSTR arising from a cubic rate law also can arise for a series of successive bimolecular reactions [26]. Aris et al. have showed that the steady-state equations for a CSTR with bimolecular reactions scheme reduces to that with a cubic reaction scheme when two parameters e(=k,Cg/k j) and K(=kjC /k j) arising in system equations for the bimolecular reactions tend to zero. Aris et al. have shown that the general multiplicity feature of the CSTR for bimolecular reactions is similar to that of the molecular reactions only at smaller value of e and K. The behavior is considerably different at larger values of e and K. Chidambaram has evaluated the effect of these two parameters (e and K) on the periodic operation of an isothermal plug flow reactor [18]. 

The main purpose of understanding the fluid mixing pattern in a reaction vessel is to use this knowledge for evaluating the performance of the reactor in terms of the conversion achieved in the reactor. Assume that an irreversible reaction A B is carried out in a reaction vessel of volume V. Let be the volumetric fluid rate, C,io the feed concentration of A, (-r ) = RCa is the kinetic rate equation and C fthe effluent concentration of A. According to the tanks in series model, the reactor is represented by N equal volume ideal CSTRs connected in series (Figure 3.59). 

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