Steam Reforming and Water-gas Shift Reaction

1 Introduction All of the examples up to this point have approached construction of the AR for various systems under different conditions. In the initial chapters of the book, we investigated lower dimensional systems under constant density, isothermal operation in concentration space. We have slowly relaxed many of these assumptions throughout the course of the book. In this final example, we wish to show how the constmction of the AR for a more realistic system might be addressed. 

In Section 9.2.7, the stoichiometric subspace for the CH4 steam reforming reaction was computed. In reality, the system of equations given involves the CH4 reforming reaction, as well as the water-gas shift reaction. Both of these reactions are important, for instance, in Fischer-Tropsch synthesis reactors (Anderson et al., 1984 Dry, 2002). It follows that it would be useful to understand the limits of achievability for this system. 

In this section, the AR for the CH4 steam reforming and water-gas shift reaction will be investigated. This system involves two independent reactions involving five components. Ordinarily, generation of the AR for this system would involve the construction of a two-dimensional AR. For this example, the interest will also be in understanding the minimum reactor volume achievable. Reactions of all components occur in the gas phase under nonisothermal conditions. The ideal gas equation of state is hence not a suitable one for this system. Instead, the Peng-Robinson equation of state shall be employed for this purpose. 

in this example, the goal is to determine the AR for a nonisothermal, variable density system, involving a 

The following discussion is merely shown to demonstrate how one might go about approaching a non-ideal system. The specific kinetics and equations of state used are shown for illustrative purposes alone, and are not indicative of how these reactions are carried out in reality. We ultimately want to demonstrate that even when the system is fairly complex, given realistic data and operating assumptions, the ideas discussed earlier may still be employed to compute the AR. 

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The remaining feed is catalytically reformed via the steam reforming and water-gas shift reactions ... 

CO2 hydrogenation, ammonia synthesis, hydrogenation of unsaturated organics, methane reforming, hydrogenolysis of saturated hydrocarbons, and wet oxidation of pollutants in waste waters have been tested, the main reactions taking place in the auto-exhaust converters have received special attention. Such is the case of CO and hydrocarbon oxidations, NO reduction, steam reforming, and water-gas shift reaction. 

TABLE 9.1 Rate Constant for Methane Steam Reforming and Water-Gas Shift Reactions... 

Therefore, the product gas from CPO at high conversions will be close to the thermod5mamic equilibriiun of the steam reforming and water-gas-shift reactions [242]. For adiabatic operation, the exit... 

Increasing the inert gas flow on the retenate side increased the driving force for the steam reforming and water-gas shift reactions due to the thermodynamic equilibrium of methane steam reforming and water-gas shift. Consequently, conversion increased. While increasing pressure decreases (equilibrium) conversion in conventional methane steam reformers, conversion could be increased at elevated pressure in a membrane reactor under certain conditions. In a similar way, the water-gas shift reaction is pushed in a favourable dhection in a membrane reactor, while the reaction is pressure independent in a conventional reactor (see Section 3.10.1). 

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