Sequencing of reactors

From the topographical viewpoint illustrated in Figure El4.6a the process comprises a set of reactor-separator sections that connect a set of component feeds (specified as source nodes) to component products (specified as destination nodes). Each section is a prescribed sequence of reactors and associated separation units, and sev-... 

Then the best performance of this sequence of reactors can be found by repeatedly using this formula ... 

Fig. 5.5. Construction for the optimal holding times of a sequence of reactors.

If Qr = 0, r = 1,.. . R, so that no heat is added to or removed from the reactor r by direct interchange, we may speak of the sequence of reactors as adiabatic. Then only 2R operating quantities can be chosen, 0, X, and Th+i. This follows from the fact that with Qr = 0 Eqs. (1) and (2) can be solved for c and T, in terms of c +i,Tr+i when only Xr+, and dr are prescribed. The case of an adiabatic sequence with a single reaction admits of an elementary exposition, and this we will now give. 

The Adiabatic Sequence of Reactors with a Single Reaction... 

It is not unreasonable to expect—and we shall prove this in the next section— that in a sequence of reactors the temperature should always be chosen to maximize the reaction rate. If we had to consider a sequence of tanks all of the same holding time we could draw just such a curve as in Fig. 7.23 for the relation... 

Sequences of reactors are discussed by Levenspiel in his text. See also ... 

Program to calculate conversion in a sequence of reactors (both CSTR and PFR) Program to design polymerisation reactor used for chain polymerisation reaction Program to design batch reactor/CSTR/PFR for first-order exothermic reversible reaction following optimal temperature progression policy... 

Program to calculate conversion in a sequence of reactors clear all % INPUT DATA... 

The analysis of multivelocity reactors is carried out by considering a sequence of reactor systems of increasing generality. The systems studied in this section, both bare and reflected, will be limited by the assumption that all cross sections in the core (and reflector) are energy independent. Studies of more general reactors which include energy-dependent cross sections and moderating reflectors are considered in subsequent sections. 

A cascade of stirred tanks (Figure 4.10.18) is the simplest combination of ideal reactors. This configuration is also used in the chemical industry since the principal disadvantage of a single stirred tank can be bypassed, namely, that a CSTR operates with a low concentration requiring a reactor with a large volume (Section 4.10.2.7). Thus it is helpful to use a sequence of reactors where only the last tank is operated at the final concentrations ofthe reactants. Furthermore, a cascade of CSTRs is useful to model real reactors as we will learn in Section 4.10.5. 

This sequence of reactor power operation is explained using a high-temperature (950°C) rise-to-power test carried out on the HTTR (Fujikawa et al., 2004). 

In the sequencing of reactors, one is often asked. Which reactor should go first to give the highest overall conversion Should it be a PFR followed by a CSTR. or two CSTRs, then a PFR, or. .. " The answer is It depends. It depends not only on the shape of the Levenspiei plot iFpJ-rf) versus X, but... 

The six units of the Fukushima Daiichi plant were numbered sequentially 1 through 6. Units 1 through 4 were arranged north to south. Unit 5 was just to the north of Unit 1, and Unit 6 was to the north of Unit 5 (Fig. 7.1). Thus, from the north to south, the sequence of reactor units was 6-5-1-2-3-4. The total linear distance between the northern point of Unit 6 and the most southern tip of Unit 4 was less than 1 mile. All six units were aligned parallel to the coastline and approximately 35-100 m from the water s edge (Anon., 2012b). 

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