Analysis of Model Behavior

Our objective in this section is to study the steady-state and transient effects of various parameters, operating conditions, and modeling assumptions on the predicted behavior of the reactor. These studies will allow us to form 

The numerical values of the parameters used for this analysis are based on published results of packed bed analyses. Typical values of the major parameters are shown in Table III.10 

Two sets of typical operating conditions are used for the simulations presented. These are shown in Table IV and will be referred to as standard type I or II conditions. Type I corresponds to operation at moderate to high temperatures, pressures, and flow rates with relatively low inlet CO and H2 concentrations and small amounts of inlet CH4, C02, and HzO either from recycle or from the upstream process. Type II is based on conditions for the industrial use of methanation in synthetic natural gas production. Note that the inlet methane concentration is much higher than in type I. 

10 Effective thermal conductivities and heat transfer coefficients are given by De Wasch and Froment (1971) for the solid and gas phases in a heterogeneous packed bed model. Representative values for Peclet numbers in a packed bed reactor are given by Carberry (1976) and Mears (1976). Values for Peclet numbers from 0.5 to 200 were used throughout the simulations. 

The real power of the model developed in this work lies in the transient or dynamic simulations such as those necessary for control system design. The model we have developed can be used to simulate the effects on the reactor of various process disturbances and input changes. Under normal reactor operating conditions, step or pulse changes in inlet gas temperatures, concentrations, or velocity or changes in cooling rates can significantly affect 

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