Constant-volume continuous stirred tank

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

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,. 

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%. 

Forney et al. [85] were among the first authors to study the potential advantages of the liquid-liquid extraction using a Taylor-vortex column. In the column, the power input is evenly distributed throughout the entire volume of the contactor, and the rotor and tank stirrers are roughly equal in diameter [74]. The maximum shear is one to two orders of magnitude lower than in a continuously stirred contactor. This leads to a between 10-fold and 100-fold increase in the area inside the continuously stirred tank that is exposed to constant maximum shear. 

There are two different ways of operating a continuous stirred-tank fermentor, namely chemostat and turbidostat. In the chemostat, the flow rate of the feed medium and the liquid volume in the fermentor are kept constant. The rate of cell growth will then adjusts itself to the substrate concentration, which depends on the feed rate and substrate consumption by the growing cells. In the turbidostat the liquid volume in the fermentor and the liquid turbidity, which varies with the cell concentration, are kept constant by adjusting the liquid flow rate. Whereas, turbidostat operation requires a device to monitor the cell concentration (e.g., an optical sensor) and a control system for the flow rate, chemostat is much simpler to operate and hence is far more commonly used for continuous fermentation. The characteristics of the continuous stirred-tank fermentor (CSTF), when operated as a chemostat, is discussed in Chapter 12. 

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... 

---