Constant-volume continuous stirred tank reactor

Consider a simple first-order exothermie reaction, A —> B, carried out in a single, constant-volume, continuous stirred-tank reactor (Fig. 3.12), with constant jacket coolant temperature, where r = - k Ca,. 

Case C Constant-Volume Continuous Stirred-Tank Reactor... 

The Ideal Single-Stage, Constant-Volume Continuous Stirred Tank Reactor, CSTR (Pseudohomogeneous L-Phase Reactor Model)... 

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. 

A single continuous stirred tank reactor is used for these reactions. A and B are mixed in equimolar proportions such that each has the concentration C0 in the combined stream fed at a volumetric flowrate v to the reactor. If the rate constants above are kP = kQ = k and the total conversion of B is 0.95, that is the concentration of B in the outflow is 0.05C0, show that the volume of the reactor will be 69 v/kC0 and that the relative yield of P will be 0.82, as for case a in Figure 1.24, Volume 3. 

Let us consider an ideal continuously stirred tank reactor with constant broth volume. The mass balance equation for substrate as a carbon source (Eq. 27), biomass (Eq. 28) and oxygen in the fermentation broth (Eq. 29) can be given for the liquid phase, as follows [65,66] ... 

When N a is the over-all conversion rate per unit volume which depends on the concentration of the reactants according to Na = kanbm, then the total order of conversion is n + m, where n and m are the partial orders of conversion in the reactants A and B, respectively. In a continuous stirred tank reactor the concentration b is constant and the same throughout the reactor, and since we are only interested in the effect on the partial conversion order n we put /cbm = ku so that N a = ha in which a is the average concentration of A in the whole reactor. 

In the following we attempt to describe the acetylcholinesterase/choline acetyltransferase enzyme system inside the neural synaptic cleft in a simple fashion see Figure 4.49. The complete neurocycle of the acetylcholine as a neurotransmitter is simulated in our model as a simple two-enzymes/two-compartments model. Each compartment is described as a constant-flow, constant-volume, isothermal, continuous stirred tank reactor (CSTR). The two compartments (I) and (II) are separated by a nonselective permeable membrane as shown in Figure 4.50. 

If, in the system examined, we can neglect spatial differences in the reactant concentrations, a continuous stirred tank reactor (CSTR) model for a reactor can be used. A set of equations is constructed accounting for the process of the totality of reactions under examination at a constant volume. It is then supplemented by a new factor which accounts for the substance exchange with the ambient medium. As usual, concentration equations are used that are analogues to those for substance quantities since the reaction system volume is assumed to be unchanged... 

Ideal Continuous Stirred Tank Reactor In an ideal CSTR, reactants are fed into and removed from an ideally mixed tank. As a result, the concentration within the tank is uniform and identical to the concentration of the effluent. The mass and energy conservation equations for an ideal constant-volume or constant-density CSTR with constant volumetric feed rate V may be written as... 

In continuous processes, the reactants are added and products are removed at a constant rate from the reactor, so that the volume of reacting material in the reactor (reaction vessel) remains constant. Two types of reactors, either (1) a continuous stirred tank or (2) a pipe reactor, are generally used. A continuous stirred tank reactor is similar to the batch reactor described above. A pipe reactor typically is a piece of tubing arranged in a coil or helix shape that is jacketed in a heat-transfer fluid. Reactants enter one end of the pipe, and the materials are mixed under the turbulent flow and react as they pass through the system. Pipe reactors are well-suited for reactants that do not mix well, because the tiu--bulence in the pipes causes all materials to mix thoroughly. 

Interpretation of reaction rates using stirred flow-through reactors is more straightforward than for batch reactors because solution chemistry remains constant during dissolution. In a continuously stirred tank reactor (CSTR) or a mixed flow reactor (Rimstidt and Dove, 1986) a mineral sample is placed in a reactor of volume Rq and fluid is pumped through at flow rate Q (L T ). Fluid is stirred by a propeller or by agitation. The rate of reaction, r (molm s i), is calculated from the inlet (q) and outlet concentrations (cq) of a component released during dissolution of the mineral ... 

Calculate the reactor size requirements for one continuously stirred tank reactor (CSTR). Also calculate the volume requirements for a cascade composed of two identical CSTRs. Assume isothermal operation at 25°C where the reaction rate constant is equal to 9.92m /(kgmol ks). Reactant concentrations in the feed are each equal to 0.08kgmol/m, and the liquid feed rate is equal to 0.278 m /ks. The desired degree of conversion is 87.5%. 

Assume that you obtained the Cg versus t curve you calculated in part (a) experimentally. Estimate K/ and by plotting the (Cg - Cs)/ln(Cg /Cg) versus f/ln(Cgj,/Cg) curve according to Eq. (2.38). Is tnis approach reliable Chemostat (continuously stirred-tank reactor) runs with various flow rates were carried out. If the inlet substrate concentration is 300 mol/m and the flow rate is 100 cm / min, what is the steady-state substrate concentration of the outlet The reactor volume is 300 cm. Assume that the enzyme concentration in the reactor is constant so that the same kinetic parameters can be used. 

Show that the concentration cA of reactant A in an isothermal continuous stirred tank reactor exhibits first-order dynamics to changes in the inlet composition, cA/. The reaction is irreversible, A - B, and has first-order kinetics (i.e., r = kcA). Furthermore (a) identify the time constant and static gain for the system, (b) derive the transfer function between cA and cA (c) draw the corresponding block diagram, and (d) sketch the qualitative response of cA to a unit pulse change in cAj. The reactor has a volume V, and the inlet and outlet flow rates are equal to F. 

EXAM PLE 2.5. The component balance equation for an irreversible /)th-order. non-isothermal reaction occurring in a constant-volume, variable-throughput continuous stirred-tank reactor (CSTR) is... 

In models for continuous ideal reactors, the continuously stirred tank reactor, CSTR, and the plug flow tube reactor, PFTR, are distinguished. Both are shown schematically in Figure 4-2. Both are characterized by a simultaneous input feed of educts and solvents on one side and a removal of the reaction mixture on the other side with a constant reaction rate. As a consequence, the reaction volume remains constant in both reactors throughout the reaction period. 

For the first criterion, one compares the reactor volumes based on the average residence time for a given extent of reaction or final conversion. The average residence time depends on the reaction kinetics and therefore the reaction rate, which in turn depends on whether the reaction takes place at constant volume or variable volume. In a system at constant volume, one obtains directly a ratio between the volumes, because the average residence time is equal to space time which is defined as the ratio between reactor volume and inlet volumetric flow in the reactor. For the same conversion, the ratio between volumes is proportional. Since the average residence time in a PFR reactor is similar to the reaction time in a batch reactor, we may assume that they have similar behaviors and then we compare only the ideal tubular reactors (PFR — plug flow reactor) to the ideal tank reactors (CSTR—continuous stirred-tank reactor). 

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. 

We want to determine the dynamic response of component A in a continuous stirred tank reactor when the volume of the tank is V (cm ), the inlet and outlet total volumetric flow rate is F (cm /min), the inlet concentration is constant at Co (g mol/cm ), and the initial concentration of component A in the tank is zero. Component A undergoes a first-order reaction in the tank ... 

Fig. 1.8.1 shows schematically a continuous stirred tank reactor of constant volume K w is the constant volumetric flow rate of input and output streams and Uj=(ciy,. ..,c y,Ty) is the input or feed state variables, which are given functions of time. As a result of the mixing, the state variables u=(cj,..., T) have the same values in the reactor and... 

Another continuous operation that is very popular in industry, but is not used very much in the chemical laboratory, is the continuous stirred tank reactor (CSTR) (it is silently assumed that the CSTR is operated in the steady state). The reactants are fed continuously into a well stirred vessel, and a constant product flow leaves the reactor through an exit port that can be located anywhere in the reactor wall. If the reactor contents are indeed well mixed, the reactants entering the vessel are diluted immediately, and the reaction proceeeds at relatively low reactant concentrations. The pr uct flow leaving the reactor must then have the same composition as the reaction mixture. This may appear to be an illogical way of carrying out a chemical reaction, but it has several distinct advantages, at least for reactions that are intrinsically rapid. The most important advantage is the thermal stability, especially in the case of exothermic reactions. Since the reaction proceeds at low reactant concentrations, the reaction rate per unit volume is relatively low, and so is the heat evolution. These are both constant in time. 

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