Tank reactor , continuous

There is flow through the reactor and one aims to determine the total volume of the reactor in order to achieve a desired final conversion. Usually one knows the reaction intrinsic kinetics, but additional data such as feed flow and mean residence time are necessary. The residence time of the molecules is not uniform and there is dead volume with preferential paths. In this reactor, let us consider the steady state, disregarding the accumulation term. 

From general equation, we will consider the inlet and outlet flows, i.e., terms (1) and (2), but will disregard the accumulation term, thus Equation 14.13 becomes  

This equation applies for each component, reactant or product. Since, in most cases, the reactor is used for processing liquid phase reactions, one can consider the volume constant. Therefore, considering the conversion of A (limiting reactant)  

The signal of rate tr) is now positive, indicating the product formation rate, considering no initial flow of product (Fro = 0). The ratio between the reaction stoichiometric coefficients [aA + bB- rR) is given by (r/a). This equation is also valid for 

Therefore, to calculate the reactor volume, we have the following general equation  

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Achieving steady-state operation in a continuous tank reactor system can be difficult. Particle nucleation phenomena and the decrease in termination rate caused by high viscosity within the particles (gel effect) can contribute to significant reactor instabilities. Variation in the level of inhibitors in the feed streams can also cause reactor control problems. Conversion oscillations have been observed with many different monomers. These oscillations often result from a limit cycle behavior of the particle nucleation mechanism. Such oscillations are difficult to tolerate in commercial systems. They can cause uneven heat loads and significant transients in free emulsifier concentration thus potentially causing flocculation and the formation of wall polymer. This problem may be one of the most difficult to handle in the development of commercial continuous processes. 

Experiments were performed in an isothermal, well-mixed, continuous tank reactor. Uncoupled kinetic parameters were evaluated as follows from steady state observations. 

In this chapter the simulation examples are described. As seen from the Table of Contents, the examples are organised according to twelve application areas Batch Reactors, Continuous Tank Reactors, Tubular Reactors, Semi-Continuous Reactors, Mixing Models, Tank Flow Examples, Process Control, Mass Transfer Processes, Distillation Processes, Heat Transfer, and Dynamic Numerical Examples. There are aspects of some examples which relate them to more than one application area, which is usually apparent from the titles of the examples. Within each section, the examples are listed in order of their degree of difficulty. 

Figure 5.30. A continuous-tank reactor with nth-order reaction.

For a steady-state continuous tank reactor only the flow terms and the dissipation terms are important. Thus... 

Case B Cas-Liquid Mass Transfer to a Continuous Tank Reactor with Chemical Reaction... 

The example simulation THERMFF illustrates this method of using a dynamic process model to develop a feedforward control strategy. At the desired setpoint the process will be at steady-state. Therefore the steady-state form of the model is used to make the feedforward calculations. This example involves a continuous tank reactor with exothermic reaction and jacket cooling. It is assumed here that variations of inlet concentration and inlet temperature will disturb the reactor operation. As shown in the example description, the steady state material balance is used to calculate the required response of flowrate and the steady state energy balance is used to calculate the required variation in jacket temperature. This feedforward strategy results in perfect control of the simulated process, but limitations required on the jacket temperature lead to imperfections in the control. 

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