Multistage adiabatic reactors

9 Design of adiabatic reactors (a) with cold shot cooling (b) with interchanger cooling between beds. 

Taking our cue from the optimal stirred tank sequence, we shall number the stages from the end to the beginning as in Fig. 8.10. The inlet conditions to reactor n are denoted by T and the exit by T,. Then in any one stage T — is constant for stage n 

10 Multibed adiabatic reactor with interstage cooling 

For TV stages a suitable sequence of decisions would be as follows. 

Actually in working out an optimal design it pays to make the decisions in precisely the reverse order. This is in keeping with our experience with stirred tanks where it was desirable to work from the end to the beginning. 

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Equation (6.14) is used for the temperature of gas in the tubes of the intermediate heat exchanger used in the multistage adiabatic reactor system. Heat is transferred from the hot gas to saturated water on the shell side generating steam at temperature Tst. The overall heat transfer coefficient Uux is constant and is equal to 0.227 kJ s-1 m-2 K-1. The heat transfer area per volume Ahx/Vhx is 157 m2/m3 ... 

MULTISTAGE ADIABATIC REACTOR SYSTEM WITH INTERSTAGE COOLING 299... 

Figure 6.16 shows results for a 20% increase in recycle flow FR. The production rate is changed by only 10%, which is less than observed for the single adiabatic reactor. Thus the recycle flowrate is not an effective manipulating variable for changing the production rate in this multistage adiabatic reactor system with intermediate cooling. 

The development of reactors in which the heat exchange surfaces are integrated in the fixed bed occurred in parallel with the development of multistage adiabatic reactors with intermediate heating or cooling. Here the main aim is to supply or remove the heat of reaction as close as possible to the reaction site. 

UOP s Oleflex process uses multistage adiabatic reactors with CCR. 

Important commercial reactions that are carried out in multistage adiabatic reactors include 1) the oxidation of SO2 to SO3 over a vanadium pentoxide catalyst, which is the key step in sulfuric acid manufacture, and 2) the silver-catalyzed oxidation of methanol to... 

The scheme of commercial methane synthesis includes a multistage reaction system and recycle of product gas. Adiabatic reactors connected with waste heat boilers are used to remove the heat in the form of high pressure steam. In designing the pilot plants, major emphasis was placed on the design of the catalytic reactor system. Thermodynamic parameters (composition of feed gas, temperature, temperature rise, pressure, etc.) as well as hydrodynamic parameters (bed depth, linear velocity, catalyst pellet size, etc.) are identical to those in a commercial methana-tion plant. This permits direct upscaling of test results to commercial size reactors because radial gradients are not present in an adiabatic shift reactor. 

Figures 6.5-6.8 show the control structures used for the four alternative tubular reactor systems. In Figures 6.6 and 6.7 (the multistage adiabatic systems with interstage...

Fig.3.3a-d. Various types of methanol synthesis reactors, (a) Cold gas quench (b) cooling by evaporation - multistage, adiabatic (c) cooling by evaporation - tubular, near isothermal (d) liquid entrained system using heat carrier liquid... 

The most important fixed-bed designs are the nonisothermal, nonadiabatic, fixed- (or packed)-bed reactor (NINA-PBR) (also called the multitubular or heat-exchanger-type reactor), and the single or multistage adiabatic fixed-bed reactor (A-PBR), and it is important at the outset to note the difference between the approaches and the design of these two operational categories. 

This is a reversible, exothermic reaction carried out adiabatically in a multistage, fixed-bed reactor with axial flow of fluid and interstage heat transfer for temperature adjustment see Figure 1.4. The catalyst is promoted V205. 

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