Reaction submodels for the A6G example simulation

This simulation uses the EQAmmonia reaction submodel from the simulation-specific Model Library.

The EQAmmonia reaction submodel includes only the ammonia synthesis reaction:

The reference condition for heat of reaction data is vapor at 800°F and the heat of reaction is -45.18×103 energy units per mole of nitrogen converted. The equilibrium constant is a function of temperature according to the Arrhenius equation:

where

A is the pre-exponential factor. In the reactor submodel, we enter this value as the EqnA parameter. For this system, we use -32.975.

B is the combined activation energy constant calculated in terms of Rankine. In the reactor submodel, we enter this value as the EqnB parameter. For this system, we use 22930.4.

Because AVEVA Process Simulation performs calculations in terms of the internal units of temperature (K), we include the conversion factor for Rankine to Kelvin (9/5) to ensure that the temperature used in the equation corresponds to the units of measure used to determine the B constant in the Arrhenius equation.

After we calculate the equilibrium constant, we then use the partial pressure expression for the equilibrium constant to determine the equilibrium compositions of the reaction components and the corresponding reaction rates:

where

pi is the partial pressure of component i in psig.

Because the partial pressures must be in terms of psig, the reaction includes an additional equation (Keq2) to convert the partial pressure from internal units of pressure (kPa) to psig. You can open the reaction submodel in the Model Editor and expand the Equations section to view the exact formulation of these equations in the reaction submodel.