Continuous flow stirred tank reactors CFSTR

A continuous flow stirred tank reactor (CFSTR) differs from the batch reactor in that the feed mixture continuously enters and the outlet mixture is continuously withdrawn. There is intense mixing in the reactor to destroy any concentration and temperature differences. Heat transfer must be extremely efficient to keep the temperature of the reaction mixture equal to the temperature of the heat transfer medium. The CFSTR can either be used alone or as part of a series of battery CFSTRs as shown in Figure 4-5. If several vessels are used in series, the net effect is partial backmixing. 

CONTINUOUS FLOW STIRRED TANK REACTOR (CFSTR) ... 

We first consider the continuous flow stirred tank reactor (CFSTR). A schematic presentation of the continuous flow stirred tank reactor is given in Figure 1. It is assumed that no mass transfer limitations exist regarding the supply of ozone. The accuracy of this assumption depends on the way ozone is supplied to the system and the reaction rate constants of the components involved. 

With these parameters we can set-up a mass balance on the system, which is the basis for evaluating the experimental results. The mass balance for the absorption (of any gas, e. g. ozone) in a continuous-flow stirred tank reactor (CFSTR) under the assumption that the gas and liquid phases are ideally mixed (cL = cLe, cG = cGe), are as follows ... 

In the previous sections, the use of surfactants to increase the rate of desorption of hydrophobic organic contaminants was discussed. For the current study, several different surfactants were tested to determine whether the rate of TCE desorption from a peat soil could be increased. The effects of the surfactants on the rate of TCE desorption was tested using a continuous-flow stirred-tank reactor (CFSTR) methodology. The observed data were simulated using a distributed-rate kinetic desorption model. The parameters determined from the model simulation were then use to discern the effects of the surfactants on the rate of TCE desorption from the peat soil. The experimental methodology and the modeling procedure are now described in detail. 

The type of optimum reactor that will process 200 m3/hr is a continuous flow stirred tank reactor (CFSTR). This configuration operates at the maximum reaction rate. The volume VR of the reactor can be determined from the design equation ... 

Figure 5-21. The continuous flow stirred tank reactor (CFSTR).

In many cases, the heat flow (Q) to the reactor is given in terms of the overall heat transfer coefficient U, the heat exchange area A, and the difference between the ambient temperature, Ta, and the reaction temperature, T. For a continuous flow stirred tank reactor (CFSTR) in which both fluid temperatures (i.e., inside and outside the exchanger) are constant (e.g., condensing steam), Q is expressed as... 

An endothermic reaction A — R is performed in three-stage, continuous flow stirred tank reactors (CFSTRs). An overall conversion of 95% of A is required, and the desired production rate is 0.95 x 10 3 kmol/sec of R. All three reactors, which must be of equal volume, are operated at 50°C. The reaction is first order, and the value of the rate constant at 50°C is 4 x 10-3 sec-1. The concentration of A in the feed is 1 kmol/m3 and the feed is available at 75°C. The contents of all three reactors are heated by steam condensing at 100°C inside the coils. The overall heat transfer coefficient for the heat-exchange system is 1,500 J/m2 sec °C, and the heat of reaction is +1.5 x 108 J/kmol of A reacted. 

Battery of continuous flow stirred tank reactors (CFSTRs)... 

The various types of reactors employed in the processing of fluids in the chemical process industries (CPI) were reviewed in Chapter 4. Design equations were also derived (Chapters 5 and 6) for ideal reactors, namely the continuous flow stirred tank reactor (CFSTR), batch, and plug flow under isothermal and non-isothermal conditions, which established equilibrium conversions for reversible reactions and optimum temperature progressions of industrial reactions. 

An example of a system which most nearly meets these requirements is a quartz continuous-flow stirred-tank reactor (CFSTR) (99-101,140,1%, 197) with catalyst configurations in which all surface metal atoms are on the exterior surface of the support. It satisfies the relevant requirements listed above and allows investigation over a broad range of both product and reactant concentrations. Furthermore, true poisoning rates can be measured directly, without requiring assumption of a model for the poisoning. The amount of sulfur adsorbed can be directly determined as a function of time and gas-phase H2S concentration, and the catalytic activity of the metal can be measured as a function of sulfur on the surface. 

The continuous-flow stirred-tank reactor (CFSTR) of 50 ml capacity was constructed of stainless steel and was jacketed for temperature control. The reactor was 5.08 cm high and had 3.8 cm inside diameter. Four equally spaced 0.32 cm baffles were welded to the bottom of the reactor. The agitator was a 2.5 cm diameter standard four-blade turbine impeller operated at 3000 rpm. 

Table 1 draws up a list of the main products formed during the oxidation of the two reference molecules n-heptane and iso-octane, for experiments carried out in a continuous flow stirred tank reactor (CFSTR) at 1 MPa between 500 and 1200 K. The... 

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). 

Fundamental work on the kinetics of hydrocarbon cracking is fully justified by strong industrial interest (1 to 5), Up to now kinetic studies of complex radical reactions in the gaseous phase have been conducted mainly in batch reactors. Nevertheless, the use of a continuous flow stirred tank reactor (CFSTR) seems very promising because it gives a direct measurement of reaction rates (6) and also it is well adapted to the study of fast reactions. 

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