Example of Process Simulation With Excel Including Phase Equilibrium

EXAMPLE OF PROCESS SIMULATION WITH EXCEL INCLUDING PHASE EQUILIBRIUM 

The next modification you will try allows phase equilibrium in the separator where most of the ammonia is condensed. For simplicity, though, you should set the conversion per pass in the reactor to 25 percent Change the separator so that it is a phase separation. The A -values are nitrogen, 4.8 hydrogen, 70 ammonia, 0.051 carbon dioxide, 0.32. (Remember that the symbol K value is used in both chemical reaction equilbria and phase equilibria, but K represents different things in those two cases.) The flow rates of nitrogen and hydrogen into the process are 1 and 3 mol per time unit, respectively, but there is also 0.01 mol per time unit of carbon dioxide. Because of the carbon dioxide, 

Now the separator must satisfy the Rachford-Rice equation, Eq. (3.9)  

Once the value of vf is found that satisfies this equation, the values of mole fraction and molar flow rates are given by Eqs. (3.1)-(3.8)  

In Eqs. (5.8)-(5.10) Zi is the mole fraction of the /th species into the flash unit, Ai, is the A -value for the /th species (often the vapor pressure divided by the total pressure), and v is the fraction of the feed that goes out as vapor (between 0 and 1). 

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