Ideal Continuous Stirred-Tank Reactor

In an ideal CSTR, the feed mixes instantaneously into the contents of the reactor, and the composition of the effluent stream is exactly the same as the composition of the fluid in the reactor. If a pulse of tracer is injected at t = 0, it will mix instantaneously with the fluid already in the reactor. The concentration of tracer in the reactor at r = 0 is as high as it ever will be. This is because the fluid that enters the reactor at later times does not contain any tracer, and because tracer begins to leave the reactor as soon as it is injected, since the composition of the effluent stream is the same as the composition of the fluid in the reactor. 

The concentration of tracer in the stream leaving the CSTR has a maximum at t = 0, and it declines continuously thereafter. The tracer response curve for an ideal CSTR will resemble the one shown below. 

At this point, we cannot determine, based only on qualitative reasoning, the exact shape of the tracer response curve. That will be developed later in this chapter. 

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The length (height) and the diameter of tank reactor are close to each other or at least of the same order of magnitude. Tank reactors are usually equipped with a stirrer. In an ideal continuous stirred-tank reactor (CSTR), a feed stream is instantaneously mixed with the reaction mixture before molecules of the stream start to react. In reality, small reactors with vigorous stirring where relatively slow reactions occur behave as if they were ideal CSTRs. The... 

Size Comparisons Between Cascades of Ideal Continuous Stirred Tank Reactors and Plug Flow Reactors. In this section the size requirements for CSTR cascades containing different numbers of identical reactors are compared with that for a plug flow reactor used to effect the same change in composition. 

Combinations of Ideal Continuous Stirred Tank Reactors and Plug Flow Reactors... 

REACTOR NETWORKS COMPOSED OF COMBINATIONS OF IDEAL CONTINUOUS STIRRED TANK REACTORS AND PLUG FLOW REACTORS... 

The ideal continuous stirred tank reactor is the easiest type of continuous flow reactor to analyze in design calculations because the temperature and composition of the reactor contents are homogeneous throughout the reactor volume. Consequently, material and energy balances can be written over the entire reactor and the outlet composition and temperature can be taken as representative of the reactor contents. In general the temperatures of the feed and effluent streams will not be equal, and it will be necessary to use both material and energy balances and the temperature-dependent form of the reaction rate expression to determine the conditions at which the reactor operates. 

The next case to be considered is the ideal continuous stirred tank reactor. The key to the derivation of the F(t) curve for this type of reactor is the realization that the assumption of perfect mixing implies that upon entry in the reactor an element of volume can instantaneously appear in any portion of the reactor. Therefore its past or its future history cannot be derived from its position. Furthermore, the prob-... 

Response of ideal continuous stirred tank reactor to step and pulse inputs. 

In an ideal continuous stirred tank reactor, CSTR, the composition and temperature are uniform throughout and the condition of the effluent is the same as that of the tank. When a battery of such vessels is employed in series, the concentration profile is step shaped if the abscissa is total residence time or the stage number. 

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] ... 

On the basis of the considered macroscopic flow pattern, the dominant circulation flows (/ c and Fc/2) subdivide the reactor into three parallel levels, where each level is then divided into Nc/3 equally sized compartments of equal volume Vc = Vr/Nc. Every compartment is modeled as a nonstationary ideal continuous stirred tank reactor, with a main inlet and outlet flow, which connects the given compartment with adjacent compartments on the same level, and secondary exchange flow rates accounting for the turbulent mixing with adjacent compartments laying on the upper and/or lower level (Fig. 7.3). 

Ideal continuous stirred tank reactor (CSTR) behavior is approached when the mean residence time is 5-10 times the length needed to achieve homogeneity, which is accomplished with 500-2,000 revolutions of a properly designed stirrer. 

CSTR Heat capacity at constant pressure Ideal continuous stirred tank reactor kJ/(kg-K) Btu/(lbm°F)... 

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... 

The ideal continuous stirred tank reactor (back-mixed reactor) is free from intrareactor concentration gradients. 

To complete the model of lime dissolution, a discretized particle size distribution is defined, with [x,] being the molar concentration of size fraction i with radius For an ideal continuous stirred tank reactor (CSTR) with residence time T the equation for updating the concentrations of the solid lime size fractions is... 

Ideal continuously stirred tank reactor (CSTR), including single and multiple stages... 

IDEAL CONTINUOUS STIRRED TANK REACTOR (CSTR)... 

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 ... 

Ideal Continuous Stirred Tank Reactor (CSTR). 7-12... 

Example 4-8 An ideal continuous stirred-tank reactor is used for the homogeneous polymerization of monomer M. The volumetric flow rate is O, the volume of the reactor is V, and the density of the reaction solution is invariant with composition. The concentration of monomer in the feed is [M]o. The polymer product is produced by an initiation step and a consecutive series of propagation reactions. The reaction mechanism and rate equations may be described as follows, where is the activated monomer and P2, . . , P are polymer molecules containing n monomer units ... 

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