Continuously Operated Isothermal Ideal Tank Reactor

2 Continuously Operated Isothermal Ideal Tank Reactor 

The ideally stirred tank reactor is perfectly uniform with regard to concentration and temperature, and both parameters are identical to the values at the exit of the reactor. 

For isothermal operation (for non-isothermal operation see Section 4.10.3.2) and a constant volume first-order reaction with respect to reactant A with va = - 1, Eq. (4.10.16) leads to  

Using the (mean) hydrodynamic residence time r, defined as r = Vr/V, we 

Note that the volumetric rate V and thus the residence time t are related to the reaction conditions, that is, to the reaction temperature and reaction pressure. 

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Continuously Operated Non-isothermal Ideal Tank Reactor (CSTR)... 

In an ideal continuous stirred tank reactor, composition and temperature are uniform throughout just as in the ideal batch reactor. But this reactor also has a continuous feed of reactants and a continuous withdrawal of products and unconverted reactants, and the effluent composition and temperature are the same as those in the tank (Fig. 7-fb). A CSTR can be operated under transient conditions (due to variation in feed composition, temperature, cooling rate, etc., with time), or it can be operated under steady-state conditions. In this section we limit the discussion to isothermal conditions. This eliminates the need to consider energy balance equations, and due to the uniform composition the component material balances are simple ordinary differential equations with time as the independent variable ... 

The ideal reactor for the direct measurement of reaction rates is a flow, isothermal, constant-pressure reactor operating at the stationary state with such thorough mixing that the composition is the same everywhere in the reactor. Because of its shape the reactor is frequently called a stirred-tank reactor. If it operates at the stationary state it is sometimes called a continuous flow stirred-tank reactor (CFSTR) or more simply a stirred-flow reactor. In such a system, the composition in the reactor is ideally identical to that of the effluent stream and all the reaction therefore takes place at this constant composition of the effluent stream (Fig. 1.6.1). 

In order to deduce fundamental information on intrinsic catalyst performance it is important to reduce the influence of the chosen reactor set-up on catalyst performance to a minimum. The first reactor requirement is ideal isothermal operation conditions. The second requirement is continuously operated ideal plug flow without axial hackmixing, this being identical to a series of infinitesimally small, continuously stirred tank reactors each fulfilling the stationary concentration requirement The realization of such an optimum reactor concept is not trivial, and in 1969 Temkin and Kul kova developed a concept in which actual-size catalyst bodies could be tested under ideal conditions. Catalyst spheres and inert cylinders are alternately placed in a tube with a diameter slightly bigger than the catalyst spheres. Inert cylinders and catalyst spheres are fixed by three wires. Excellent heat transport... 

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