The Continuous-Stirred-Tank Reactor CSTR

During the manufacturing process, if the grafting increases during early stages of the reaction, the phase volume will also increase, but the size of the particles will remain constant [146-148]. Furthermore, reactor choice plays a decisive role. If the continuous stirred tank reactor (CSTR) is used, little grafting takes place and the occlusion is poor and, consequently, the rubber efficiency is poor. However, in processes akin to the discontinuous system(e.g., tower/cascade reactors), the dispersed phase contains a large number of big inclusions. 

Based on the kinetic mechanism and using the parameter values, one can analyze the continuous stirred tank reactor (CSTR) as well as the dispersed plug flow reactor (PFR) in which the reaction between ethylene and cyclopentadiene takes place. The steady state mass balance equations maybe expressed by using the usual notation as follows ... 

One of the simplest models for convective mass transfer is the stirred tank model, also called the continuously stirred tank reactor (CSTR) or the mixing tank. The model is shown schematically in Figure 2. As shown in the figure, a fluid stream enters a filled vessel that is stirred with an impeller, then exits the vessel through an outlet port. The stirred tank represents an idealization of mixing behavior in convective systems, in which incoming fluid streams are instantly and completely mixed with the system contents. To illustrate this, consider the case in which the inlet stream contains a water-miscible blue dye and the tank is initially filled with pure water. At time zero, the inlet valve is opened, allowing the dye to enter the... 

The classical CRE model for a perfectly macromixed reactor is the continuous stirred tank reactor (CSTR). Thus, to fix our ideas, let us consider a stirred tank with two inlet streams and one outlet stream. The CFD model for this system would compute the flow field inside of the stirred tank given the inlet flow velocities and concentrations, the geometry of the reactor (including baffles and impellers), and the angular velocity of the stirrer. For liquid-phase flow with uniform density, the CFD model for the flow field can be developed independently from the mixing model. For simplicity, we will consider this case. Nevertheless, the SGS models are easily extendable to flows with variable density. 

In the continuous stirred tank reactor (CSTR) instant mixing to achieve a homogeneous reaction mixture is assumed so that the composition throughout the reactor is uniform. During the reaction, monomer is fed into the system at the same rate as polymer is withdrawn. The heat problem is somewhat diminished because of the constant removal of heated products and the addition of nonheated reactants. 

Figure 3-1 The continuous stirred tank reactor (CSTR) of volume V with inlet molar flow rate Fja and outlet molar flow rate F ...

This expression enhances the fact that the heat release rate is a function of the conversion and will therefore vary with time in discontinuous reactors or during storage. In a batch reaction, there is no steady state. It is constant in the Continuous Stirred Tank Reactor (CSTR) and is a function of the location in the tubular reactor (see Chapter 8). The heat release rate is... 

Yet who would have thought the old man to have had so much hlood in him This title, given by Prof. Rutherford Aris and his collaborator W.W. Farr to their recent paper [Chem. Eng. Sci., 41 (1986) 1385], is a phrase used by Lady Macbeth (Macbeth, V, 1, 42-44). Fierce, isn t it Apparently, they mean it to imply that traditional theoretical problems in the dynamics of chemical reactions, in particular the known problem of the dynamics of the continuous stirred tank reactor (CSTR), are far from being exhausted. Novel mathematical approaches provide new results oriented to physico-chemical comprehension. This current trend is confirmed by the present volume. 

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. 

In the following section the two commonly preferred laboratory reactors — the plug flow reactor and the continuous stirred tank reactor (CSTR) — are discussed. 

An example of the latter type is the continuous stirred tank reactor (CSTR), which is essentially an STR into which the reactants are added continuously with the partially reacted material removed at the same rate. >3 in... 

One type of reactor which can be useful for kinetic measurements is the continuous stirred tank reactor (CSTR). The kinetic model is identical with that for the recirculation reactor and the designs are based on the reactors used for homogeneous reactions. Carberry et have described a CSTR which... 

One type of continuous operation is the continuously stirred tank reactor (CSTR, Figure 13.2a), in which the reactants are continuously fed to the first vessel, and the vessel contents overflow into the successive vessels. This principle allows for good mixing and isolates the contents in the second and subsequent vessels from contact with reagents entering the first vessel. In principle the... 

The reactor models considering complete mixing may be subdivided into batch and continuous types. In the continuous stirred tank reactor (CSTR) models, an entering fluid is assumed to be instantaneously mixed with the existing contents of the reactor so that it loses its identity. This type of reactor operates at uniform concentration and temperature levels. For this reason the species mass balances and the temperature equation may be written for the entire reactor volume, not only over a differential volume element. Under steady-state conditions, the species mass and heat balances reduce to algebraic equations. 

This mole balance is named the continuous stirred tank reactor (CSTR) model. 

A mixed-flow reactor (MFR), also known as the continuous stirred tank reactor (CSTR), is fuUy mixed at the molecular level, and the composition of the exiting stream is identical to that within the reactor. In this case, the material balance of Equation (11.12) is applied for the entire reactor and not just for a differential element as in a PFR. No integration is needed the eqnation becomes... 

With respect to benzaldehyde, (R)-oxynitrilase exhibits saturation kinetics (Michaelis Menten kinetics, see Sect. 7.4.2.1) and a maximum reaction rate is reached above a concentration of about 5 mmol L 1. The chemical reaction presents a linear increase of the reaction rate with increasing benzaldehyde concentration, representing first order kinetics, when the concentration of HCN is kept constant (see Fig. 7-13). As a consequence the enzymatic reaction becomes more dominating at lower concentrations of the substrate benzaldehyde (for HCN as substrate the same kinetic behavior occurs, data not shown). Accordingly an enzyme reactor would be suitable that works under minimum average substrate concentrations. These requirements are satisfied by the continuous stirred tank reactor (CSTR). In Sect. 7.5.2.1 this aspect of enzyme reaction engineering will be discussed further. 

After a certain time a steady state will be reached within the reactor, meaning that concentrations of substrates and products do not change. Typical continuous reactors are the plug flow reactor (PFR) and the continuous stirred tank reactor (CSTR). A comparison of these different reactor types is given in Fig. 7-22. 

The continuous stirred tank reactor (CSTR) in the steady state exhibits constant concentrations as a function of both time and position. The exit stream from this reactor has the same composition as the fluid within the reactor the CSTR is also a well-mixed reactor. 

Continuous flow reactors are almost always operated at steady state. We will consider three types the continuous stirred tank reactor (CSTR). the plug flow reactor (PFR). and the packed bed reactor (PBR). Detailed descriptions of these reactors can be found in both the Professional Reference Shelf (PRS) for Chapter 1 and in the Visual Encyclopedia of Equipinent on the CD-ROM,... 

Figure 7.1c and d show two types of the steady-state flow reactors with a continuous supply of reactants and continuous removal of product(s). Figure 7.1c shows the continuous stirred-tank reactor (CSTR) in which the reactor contents are perfectly mixed and uniform throughout the reactor. Thus, the composition of the outlet flow is constant, and the same as that in the reactor. Figure 7.Id shows the plug flow reactor (PFR). Plug flow is the idealized flow, with a uniform fluid velocity across the entire flow channel, and with no mixing in the axial and radial...

The continuous stirred tank reactor (CSTR) adds a further degree of sophistication and is generally preferred to single batch operations for the larger scale or more frequent manufacture of products due to lower operating costs and overall investment. In practice, mechanical or hydraulic agitation is required to achieve uniform composition and temperature. 

Numerical simulations and analyses were performed for both the continuous stirred-tank reactor (CSTR) and the plug-flow reactor (PER). A comparison between the microkinetic model predictions for an isothermal PFR and the experimental results [13], is presented in Fig. 2 for the following conditions commercial low temperature shift Cu catalyst loading of 0.14 g/cm total feed flow rate of 236 cm (STP) min residence time r = 1.8 s feed composition of H20(10%), CO(10%), C02(0%), H2(0%) and N2(balance). As can be seen, the model can satisfactorily reproduce the main features of the WGSR on Cu LTS catalyst without any further fine-tuning, e.g., coverage dependence of the activation energy, etc, which is remarkable and provides proof of the adequacy of the... 

In this contribution, we present computer analyses of several selected temperature-programmed desorption (TPD) and temperature-programmed surface reaction (TPSR) experiments in a microreactor flow system operating under atmospheric pressure. The continuous stirred tank reactor (CSTR) and plug flow reactor (PFR) models have been applied for the design equation as... 

The continuous-stirred-tank reactor (CSTR) is shown in Figure 1.3. Reactants and products flow into and out of the reactor continuously, and the contents of the reactor are assumed to be well mixed. The well-mixed assumption can be realized more easily for liquids than gases, so CSTRs are often used for liquid-phase reactions. The fluid composition and temperature undergo a step change when passing from the feed stream into the interior of the reactor the composition and temperature of the effluent stream are identical to those of the reactor. 

The continuous-stirred-tank reactor (CSTR) is also a well-stirred reactor so there are no concentration gradients anywhere in the reactor volume. We again consider the entire reactor contents to be the reactor volume element as in Figure 4.13, and V = Vr, Since the reactor is well stirred, the relations in Equations 4.3 and 4.4 apply to the CSTR also. The difference between the CSTR and batch reactor is the flow streams shown in figure 4,13. We denote the feed... 

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