Ideal Continuously Operated Stirred Tank Reactor CSTR

Ideal Continuously Operated Stirred Tank Reactor (CSTR) 

If the amount Wg of a tracer is added in the form of a pulse to an ideally mixed stirred tank, the maximum concentration is established instantaneously 

The concentration time course can then be predicted from the mass balance by integration 

From this it follows by integration for the cumulative RTD (curve E t))-. 

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In Figures 3.4 and 3.5, the RTDs of ideal reactors are presented together with the RTD of a real reactor. The ideal, continuously operated stirred tank reactor (CSTR) has the broadest RTD between all reactor types. The most probable residence time for an entering volume element is t = 0. After a mean residence time t = t), 37% of the tracer injected at time t = 0 is still present in the reactor. After five mean residence times, a residue of about 1% still remains in the reactor. This means that at least five mean residence times must pass after a change in the inlet conditions before the CSTR effectively reaches its new stationary state. 

The cascade consists of a series of ideal continuously operated stirred tank reactors, CSTR, connected one after the other. The outlet function of one CSTR is... 

A continuous stirred-tank reactor (CSTR) is an ideal reactor which is based on the assumption that the reactor contents are well mixed. Therefore, the concentrations of the various components of the outlet stream are assumed to be the same as the concentrations of these components in the reactor. Continuous operation of the enzyme reactor can increase the productivity of the reactor significantly by eliminating the downtime. It is also easy to automate in order to reduce labor costs. 

The continuous-stirred tank reactor (CSTR) has continuous input and output of material. The CSTR is well mixed with no dead zones or bypasses in ideal operation. It may or may not include baffling. The assumptions made for the ideal CSTR are (1) composition and temperature are uniform everywhere in the tank, (2) the effluent composition is the same as that in the tank, and (3) the tank operates at steady state. 

Reactors are conveniently considered in three idealized categories batch, tubular, and continuous stirred tank reactors (CSTR). The operations of real reactors may be modeled on the basis of one of these types or combination thereof. 

There are two common types of continuous reactors continuous stirred tank reactors (CSTRs) (53), and plug flow reactors (PFRs). CSTRs are simply large tanks that are ideally well-mixed (such that the emulsion composition is uniform throughout the entire reactor volume) in which the polymerisation takes place. CSTRs are operated at a constant overall conversion. CSTRs are often used in series or trains to build up conversion incrementally. Styrene-butadiene rubber has been produced in this manner. Not all latex particles spend the same amount of time polymerising in a CSTR. Some particles exit sooner than others, producing a distribution of particle residence times, diameters and compositions. 

Thus, for Michaelis-Menten kinetics, a PFR type reactor, predominantly a packed-bed reactor (PBR, Figure 9.1b) is preferred to the continuous stirred-tank reactor (CSTR, Figure 9.1a), since it requires less biocatalyst to reach the same level of conversion. In this case, ideal reactors are those with high space time/yield to increase the efficiency of the transformation. PBRs with immobilized catalyst have a clear advantage in that voidage is low 34% compared to over 80-90% for CSTR [35]. However, if pH control is required, the use of a PFR is not advised. In case of substrate inhibition, a CSTR (Figure 9.1a) operated at high conversion is to be preferred. On the other hand, when product inhibition is pronounced, a... 

For a continuously operated ideally stirred tank reactor (CSTR, Figure 4.10.15), the accumulation term dc/dt in the general mass balance of a stirred tank reactor [Eq. (4.10.1)] vanishes ... 

Figure 12.4 Relative concentrations ofthe ideal PFTR and continuous stirred tank reactor (CSTR) in comparison with the microreactor for different operating conditions, that is, different Pe numbers (0.01

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 ... 

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