Segregation batch reactor

Segregated flow Occurs when all molecules that enter together also leave together. A state of aggregation is associated with every RTD. Each aggregate of molecules reacts independently of every other aggregate thus, as an individual batch reactor. 

Wang, Y.-D. and Mann, R., 1992. Partial segregation in stirred batch reactors effect of scale-up on the yield of a pair of competing reactions. Transactions of the Institution of Chemical Engineers, 70, 282-290. 

The concept of a well-stirred segregated reactor which also has an exponential residence time distribution function was introduced by Dankwerts (16, 17) and was elaborated upon by Zweitering (18). In a totally segregated, stirred tank reactor, the feed stream is envisioned to enter the reactor in the form of macro-molecular capsules which do not exchange their contents with other capsules in the feed stream or in the reactor volume. The capsules act as batch reactors with reaction times equal to their residence time in the reactor. The reactor product is thus found by calculating the weighted sum of a series of batch reactor products with reaction times from zero to infinity. The weighting factor is determined by the residence time distribution function of the constant flow stirred tank reactor. 

This equation predicts the intensity of segregation to decay with time in the batch reactor. It is also applicable to a steady-state plug flow system, where t is the residence time. 

Simple Reaction with Segregation in Batch Reactor... 

The basic premise of the segregated flow model is that the various fluid elements move through the reactor at different speeds without mixing with one another. Consequently, each little fluid element will behave as if it were a batch reactor operating at constant pressure. The conversions attained within the various fluid elements will be equal to those in batch reactors with holding times equal to the residence times of the different fluid elements. The average conversion level in the effluent is then given by... 

Dynamics of an Equalisation Basin 560 Dimensionless Kinetics in a Batch Reactor 235 Batch Reactor with Complex Reaction Sequence 240 Single Solute Batch Extraction 442 Mixing and Segregation 394... 

Batch Reactor. Let the batch reactor be filled with a macrofluid containing reactant A. Since each aggregate or packet of macrofluid acts as its own little batch reactor, conversion is the same in all aggregates and is in fact identical to what would be obtained with a microfluid. Thus for batch operations the degree of segregation does not affect conversion or product distribution. 

Though partial segregation requires an increase in reactor size, this is not the only consequence. For example, when reactants are viscous fluids, their mixing in a stirred tank or batch reactor often places layers or streaks of one fluid next to the other. As a result reaction occurs at different rates from point to... 

However, the solution for the CSTR obtained by the RTD equation is correct only for first-order kinetics. For other rate expressions the conversion predicted by the RTD is incorrect for a mixed reactor because molecules do not simply react for time t, after which they leave the reactor. Rather, the fluid is continuously mixed so that the history of the fluid is not describable in these terms. This expression for conversion in the CSTR is applicable for segregated flow, in which drops of fluid enter the reactor, swirl in the reactor, and exit after time t because then each drop behaves as a batch reactor with the RTD describing the probability distribution of the drops in the CSTR. 

This type of segregation, which may be considered as a microscale segregation, appears to be a state which in itself does not say anything about the concentration in the dispersed particles nor about their age. In a batch reactor, for instance, in which all the dispersed particles have the same size, there may be complete segregation (no interaction) and still all the particles will always have the same concentration. 

Fig. 7.2 Tank batch reactor with a segregated zone (a) modeled as two ideal suitably connected CSTRs (b)...

Since the fluid flows in clumps and is completely segregated by age (i.e., each clump behaves like a batch reactor), it is possible to determine the reactant concentration in every clump for a constant density fluid as ... 

The IAD I(a,t) in a chemical reactor is specially interesting and it does not seem that sufficient attention has been paid to the possibilities offered by this function. For instance, let us consider a semi-batch reactor, and let Q(t) be the feed flowrate of an incompressible fluid. The instantaneous fluid volume is V = /q Q(tf)dtf, from which the IAD is written I(a,t) = Q(t-a)/V. I(a,t) can be used to calculate the chemical conversion in different segregation states. Consider a species of concentration C produced with the rate t. If the mixture is assumed to be well mixed at the molecular scale, one obtains the familiar mass balance equation... 

Now consider a maximum segregation reactor (Danckwerts, 1958 Zwietering, 1959). Let C = pit) be the overall concentration in a batch reactor at time t. (This can be calculated for linear and for cooperative uniform kinetics.) Then the product overall concentration in a maximum segregation reactor is easily calculated as... 

In the segregation model globules behave as batch reactors operated for different times... 

Conversion if fluid is completely segregated. Tlhe batch reactor equation for a second-order reaction of this type is... 

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