Multibed ammonia reactor

The temperature-composition relation in such a multibed adiabatic reactor is illustrated in Fig. 11.3-4 for ammonia synthesis [3]. The F, curve in this diagram represents the equilibrium relation between composition and temperature. The maximum ammonia content that could be obtained in a single adiabatic bed with inlet conditions corresponding to A would be 14 mole % as indicated by point B, and this would theoretically require an infinite amount of catalyst. The five-bed quench converter corresponding to the reaction path ABCDEFGHIJ permits... 

Figure 11.5.e-II Operating diagrams for various types of ammonia synthesis reactors, (a) Multitubular reactor with cocurrent flow, (b) Multitubular reactor with countercurrent flow, (c) Multibed adiabatic reactor (from Fodor [122]). 

This figure clearly illustrates that the range within which multiple steady states can occur is very narrow. It is true that, as Hlavacek and Hofmann calculated, the adiabatic temperature rise is sufficiently high in ammonia, methanol and oxo-synthesis and in ethylene, naphthalene, and o-xylene oxidation. None of the reactions are carried out in adiabatic reactors, however, although multibed adiabatic reactors are sometimes used. According to Beskov (mentioned in Hlavacek and Hofmann) in methanol synthesis the effect of axial mixing would have to be taken into account when Pe < 30. In industrial methanol synthesis reactors Pe is of the order of 600 and more. In ethylene oxidation Pe would have to be smaller than 200 for axial effective transport to be of some importance, but in industrial practice Pe exceeds 2500. Baddour et al. in their simulation of the TVA ammonia synthesis converter found that the axial diffusion of heat altered the steady-state temperature profile by less than 0.6°C. Therefore, the length of... 

Interstage cooling scheme for multibed catalytic reactor for ammonia synthesis process. H. J. Herbort (Uhde Gmbh). DE 3725564 (1989). 

Design of a multibed catalytic reactor for ammonia synthesis process in which each bed is partitioned into two or more zones, alternately a vertical adiabatic... 

Annable was the first to use the Temkin-Pyzhev equation to analyze operating data from industrial ammonia units [38] an adiabatic reactor operating at 245 atm and a multibed quench reactor operating at 300 atm. 

Figure 17.20. Control of temperature in multibed reactors so as to utilize the high rates of reaction at high temperatures and the more favorable equilibrium conversion at lower temperatures, (a) Adiabatic and isothermal reaction lines on the equilibrium diagram for ammonia synthesis, (b) Oxidation of SOz in a four-bed reactor at essentially atmospheric pressure, (c) Methanol synthesis in a four bed reactor by the ICI process at 50 atm not to scale 35% methanol at 250°C, 8.2% at 300°C, equilibrium concentrations.

In the synthesis of ammonia (NH3), a multibed reactor is used. The reaction takes place on an iron catalyst, and ammonia is synthesized from hydrogen and nitrogen. Extraordinary... 

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