In the programs, we perform flash calculations of a mixture of hydrocarbons (ethane, propane, n-butane and n-pentane) using the Rachford-Rice equation. The phi-phi method, based on the SRK equation of state, is used to compute the equilibrium constants. We also find the True Vapor Pressure. All results are in agreement with those given by HYSYS 3.2 as well as the thesis of Privat from the Ecole Nationale Supérieure des Industries Chimiques de Nancy under the supervision of J-P Corriou.
A paper on the SRK EOS is available at these links: