Unsteady-State Operation of Stirred Reactors

Use of Membrane Reactors to Enhance Selectivity. In addition to species leaving through the sides of the membrane reactor, species can also be fed to the reactor through the side.s of the membrane. For example, for the reaction 

As we will see in Chapter 8, this arrangement is often used to improve selectivity when multiple reactions take place. Here. B is usually fed uniformly through the membrane along the length of the reactor. The balance on B is 

Isothermal Reactor Design Molar Flow Rates Chapter 6 

There are two basic types of semibatch operations. In one type, one of the reactants in the reaction 

1 iSurc 4-14 Semibatch reactors, (a) Reactor startup, (h) semihatch with cooling, and tc) reactive distillation. [Excerpted by. special permission from Chum. Eng.. di(IO) 211 (Oct. 1956). Copyright 1956 by McGraw-Hill. Inc.. New York, NY 10020.) 

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Section 6.5 Unsteady State Operation of Stirred Reactors... 

Batch-stirred tank reactor (BSTR) In this type of reactor, the reactants are fed into the container, they are well mixed by means of mechanical agitation, and left to react for a certain period of time. This is an unsteady-state operation, where composition changes with time. However, the composition at any instant is uniform throughout the reactor. 

Fig. 1.9. Continuous stirred-tank reactor showing steady state operation (a) and two modes of unsteady state operation (b) and (c)...

Poehlein [81] identified major problems encountered with the development of continuous emulsion polymerization processes. It was shown that the development of commercial continuous emulsion polymerization processes involves the consideration of many factors associated with process design and product quality. These factors include the effects of inhibitor, polymerization rate, particle size distribution, copolymer composition, addition strategy of feed streams, unsteady-state operation, and reactor design on continuous emulsion polymerization processes. The author then used a two-continuous stirred tank reactor series to elucidate key continuous emulsion polymerization mechanisms and generate the knowledge necessary for the development of commercial continuous processes. 

The general characteristics of a batch reactor (BR) are introduced in Chapter 2, in connection with its use in measuring rate of reaction. The essential picture (Figure 2.1) in a BR is that of a well-stirred, closed system that may undergo heat transfer, and be of constant or variable density. The operation is inherently unsteady-state, but at any given instant, the system is uniform in all its properties. 

After specifying the energy form, the catalyst and the phases in contact, the next task is to decide whether to conduct the reaction in a batch or continuous mode. In the batch mode, the reactants are charged to a stirred-tank reactor (STR) and allowed to react for a specified time. After completing the reaction, the reactor is emptied to obtain the products. This operating mode is unsteady state. Other unsteady-state reactors are (1) continuous addition of one or more of the reactants with no product withdrawal, and (2) all the reactants added at the beginning with continuous withdrawal of product. At steady-state, reactants flow into and products flow out continuously without a change in concentration and temperature in the reactor. 

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