Batch reactors worked example problems

Suppose the reactor in Example 14.8 remains in batch mode after the fast-fill-and-hold startup. Will the temperature control system still work A preliminary answer based on the approximate kinetics of Example 14.7 is sufficient, but see the next problem. 

If the rate equation is to be employed in its integrated form, the problem of determining kinetic constants from experimental data from batch or tubular reactors is in many ways equivalent to taking the design equations and working backwards. Thus, for a batch reactor with constant volume of reaction mixture at constant temperature, the equations listed in Table 1.1 apply. For example, if a reaction is suspected of being second order overall, the experimental results are plotted in the form ... 

This temperature dependency is exploited in optimal control problems of batch reactor where optimal temperature profile is obtained by either maximizing conversion, yield, profit, or minimizing batch time for the reaction. One of the earliest works on optimal control of batch reactor was presented by Denbigh[25] where he maximized the yield. The review paper by Srinivasan et al.[26] describes various optimization and optimal control problems in batch processing and provides examples of semi-batch and fed-batch reactor optimal control. 

This latter interpretation would mean that with the approach depicted in Fig. 10, the catalyst itself could be monitored. The authors reported that the silica-supported Nafion could not be observed in the beginning of their experiments and appeared in the spectra only after the catalyst interacted with octanol. This observation may indicate that the octyl groups promote the sticking of the catalyst particles onto the ATR probe, within the evanescent field. However, the example also shows that this approach may not be without problems, because it depends on the adsorption of the particles from the slurry reactor onto the ATR element. This process is accompanied by the adsorption of molecules on the catalyst surface and complicates the analysis. More important, as also indicated by the work of Mul et al. (74). this adsorption depends on the surface properties of the catalyst particles and the ATR element. These properties are prone to change as a function of conversion in a batch process and are therefore hardly predictable. 

A few experiments have been carried out in the laboratory scale with a one litre hydrolysis vessel, connected to a small impeller pump and a Sartorius laboratory module fitted with DDS GR6-P membranes (0.2 m ). However, the flow resistance in this module was too large, and it was soon concluded that a resonably constant flux was unattainable. Despite these difficulties, the qualitative behaviour of the reactor variables could be predicted from the model and verified experimentally. For example, with decreasing flux DH increased, but the rate of the base consumption decreased, while the protein concentration in the permeate remained quite stable as predicted. The hydrolysate was evaluated and found comparable in quality to ISSPH produced in the batch process. These results have encouraged us to continue the work in pilot plant with the DDS-35 module, where we can expect considerably more favourable flow conditions. The first experiments carried out so far indicate that a reasonable flux in the order of 50 1/m /h (approx. 1 1/m /min.) can be attained but that foaming problems necessitate the construction of pressurized air free reactor. Future studies will therefore be needed to produce a complete experimental verification of the derived model. 

---