CSTR - Continuous Stirred-Tank Cascade

A system of three continuous stirred-tank reactors is used to carry out the first-order isothermal reaction 

Component balances for the three tanks give Tank 1 

The program is formulated with all three tanks having an equal volume, V. 

CONTINUOUS STIRRED TANK REACTOR CASCADE (CSTR) 

Study the effect of varying the residence time, x, and the rate constant values. 

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Figure 3.30. Basic reactor concept and concentration-versus>time and concentration-versus-space profiles. DCSTR, discontinuous stirred tank reactor SCSTR, semicon-tinuous stirred tank reactor CSTR, continuous stirred tank reactor CPFR, continuous plug flow reactor NCSTR, a cascade of N stirred vessels.

Fig. 2.7 Definition sketch showing common modes of operation for reactors, (a) Simple-batch reactor, (b) Single-pass reactor, (c) Batch-recirculation reactor, (d) Cascade of n identical reactors. PFR, plug flow reactor CSTR, continuously stirred tank reactor.

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. 

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. 

Sulfonation of p-nitrotoluene (PNT) is performed in a cascade of Continuous Stirred Tank Reactors (CSTR). The process is started by placing a quantity of converted mass in the first stage of the cascade, a 400-liter reactor, and heating to 85 °C with jacket steam (150°C). PNT melt and Oleum are then dosed in simultaneously (exothermal reaction). When 110°C is reached, cooling is switched on automatically. On the day of the accident, a rapid increase in pressure took place at 102 °C. The lid of the reactor burst open and the reaction mass, which was decomposing, flowed out like lava, causing considerable damage. 

Classical chemical reaction engineering provides mathematical concepts to describe the ideal (and real) mass balances and reaction kinetics of commonly used reactor types that include discontinuous batch, mixed flow, plug flow, batch recirculation systems and staged or cascade reactor configurations (Levenspiel, 1996). Mixed flow reactors are sometimes referred to as continuously stirred tank reactors (CSTRs). The different reactor types are shown schematically in Fig. 8-1. All these reactor types and configurations are amenable to photochemical reaction engineering. 

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%. 

Figure 1.2 Continuous reactors (a) tubular reactor, (b) continuous stirred-tank reactor (CSTR), and (c) cascade of CSTRs.

For the physicochemical interpretation of Eq. (8.10), representing a cascade of thin active catalyst zones, it makes sense to compare this equation with the equation for a cascade of imaginary continuous stirred-tank reactors (CSTRs). Each imaginary CSTR in this cascade is assumed to have the same conversion as a unitary reactor consisting of one active zone and a... 

There are seven main sulphonation reactor systems used world-wide for SOs/air sulphonation for which there is proven practical and documented experience The Ballestra Sulphurex continuous stirred tank reactor (CSTR) cascade, the Ballestra Sulphurex F (a multitube falling-film reactor (MT-FFR)) the Chemithon falling-film reactor (FFR), the Chemithon Jet Impact Reactor, the MM falling-film reactor (FFR), the Mazzoni Sulpho film reactor (a multitube falling-film reactor) and the Japanese T-0 FFR reactor system. 

Ideal reactors have idealized flow patterns. Four cases are important, the uniformly mixed batch reactor, the plug flow reactor (PFR), the continuous stirred tank reactor (CSTR), and a cascade of CSTRs. Real reactors are arbitrarily complicated, but can be regarded as composed of elements of ideal reactors. Modeling is possible, if we know how to account for non-ideal flow. 

It follows from calculations in the proceeding section that the necessa reactor volume of a continuous stirred tank reactor (CSTR) needed to obtain a high degree of conversion is relatively large. A so-called "cascade of CSTR s (a number of CSTR s in series) can be a practical alternative. Let us assume that we replace one CSTR with volume V by a series of n equal CSTR s that have the same total volume. The mean residence time in each reactor is then x/n. We can calculate the relative degree of conversion in each consecutive reactor, for any reaction order, with eq. (3.49), where X is replaced by x/n. We find then for... 

Another example of a cascade process is where the conversion of a chemical reaction in a continuous stirred-tank reactor (CSTR)is very lowsuch that thecontinuousoverflowfrom one can be fed into another reactor for further reaction and conversion. Where there are many CSTRs in series, the operation approximates to that of a plug flow reactor. 

The bioreactor has been introduced in general terms in the previous section. In this section the basic bioreactor concepts, i.e., the batch, the fed-batch, the continuous-flow stirred-tank reactor (CSTR), the cascade of CSTRs and the plug-flow reactor, will be described. 

The cascade consists of a series of ideal continuously operated stirred tank reactors, CSTR, connected one after the other. The outlet function of one CSTR is... 

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