Chemical reactors overall” reaction behavior

In this section, we still restrict ourselves to the consideration of systems where only the overall behavior is of interest, but we extend the analysis to actual chemical reactors. Indeed, the discussion in the previous section was limited to the overall kinetics of multicomponent mixtures seen from the viewpoint of chemical reaction engineering, the discussion was in essence limited to the behavior in isothermal batch reactors, or, equivalently, in isothermal plug flow reactors. In this section, we present a discussion of reactors other than these two equivalent basic ones. The fundamental problem in this area is concisely discussed next for a very simple example. 

In order to simulate the behavior of an industrial membrane reactor, the model described in Sect. 4.2.2, i.e., a two-dimensional pseudo-homogeneous model, is fitted to natural gas steam reforming. Chemical-physical properties of reactions and components involved are taken from literature [17, 18] as functions of temperature, pressure, and mixture composition. The kinetic equations for the reactions scheme composed by 5.1, 5.2 and the overall reaction ... 

The most important part of a chemical process is formed by the chemical reactor. Its selection determines the overall return on investment. Therefore, the appropriate selection of chemical reactors is a topic with various applications. Often, the kinetic equations including the model parameters (activation energy, rate constants, equilibrium constant, etc.) of the reaction system are not known in detail. Only more qualitative information about the behavior of the reaction system is available. Therefore, heuristics can be used to utilize this incomplete set of information in order to propose the best chemical reactor in terms of selectivity, conversion or yield. ... 

Using these methods, the elementary reaction steps that define a fuel s overall combustion can be compiled, generating an overall combustion mechanism. Combustion simulation software, like CHEMKIN, takes as input a fuel s combustion mechanism and other system parameters, along with a reactor model, and simulates a complex combustion environment (Fig. 4). For instance, one of CHEMKIN s applications can simulate the behavior of a flame in a given fuel, providing a wealth of information about flame speed, key intermediates, and dominant reactions. Computational fluid dynamics can be combined with detailed chemical kinetic models to also be able to simulate turbulent flames and macroscopic combustion environments. 

The random movement of the particles causing back-mixing result in an overall reactor behavior that is closer to a CSTR than a plug flow reactor. In many chemical processes, this leads to an increase in the reaction volume and a loss of selectivity. 

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