Thermodynamic modeling of vapor-liquid equilibrium systems including biodiesel in high and low pressures using cubic equations of state

In the work, vapor-liquid equilibrium (VLE) of pure and binary mixtures of the systems including fatty acid Ethyl or Methyl esters and alcohols is analyzed by two simple cubic equations of state; Cubic-Square-Well (CSW EoS) and the Peng-Robinson (PR EoS). To achieve this purpose, first, the parameters of equations of state for pure systems are optimized using experimental vapor pressure and liquid density. Two models show accepted accuracy, however, the PR EoS with AARD=۱.۰۱% demonstrations better results for pure systems. Then the results of the pure systems are used to correlate the phase behavior of the binary mixtures in low and high pressure using one binary interaction parameter in equilibrium systems. The results for binary fatty acid ester systems show deviations as AARD=۰.۴۵% and AARD=۰.۲۳% for PR and CSW EoSs, respectively. For alcohol+fatty acid ester binary systems the pressure deviations are AARD=۵.۰۴% and AARD=۱۴.۱۴% for PR and CSW EoSs, respectively. Therefore, the results show that the CSW and PR equations of state can be applied to calculate the phase behavior of these types of systems with good accuracy and simplicity, therefore, can be used in designing, modeling, and optimization of the biodiesel units.

کلیدواژه ها:

Biodiesel ، Vapor-liquid Equilibrium ، Cubic-Square-Well (CSW) ، Peng–Robinson (PR) ، Equation of state