Phase equilibria calculations with a modified redlich‐kwong equation of state

Abstract A modified Redlich‐Kwong equation of state for pure substances in the liquid‐vapour coexisting phase region is suggested in which the fugacity coefficients of the two phases are equated and the resulting relationship is solved by assuming ωb to be temperature dependent while ωa remains constant. A generalised correlation for ωb is found with the acentric factor as a parameter. This approach is compared with the other two possible modifications, i.e. when ωa is a funtion of temperature while ωb is constant, and when both ωa and ωb are temperature dependent. Comparison revealed the excellent attainment of the equilibrium conditions when the proposed method is applied. Predicted volumetric properties and isothermal enthalpy departures of the liquid and vapour as well as the saturation vapour pressures are also compared which reveal the adequacy of the new modification. With the application of the mixing rules, the proposed modified equation is successfully applied to VLE calculations for binary mixtures of different complexities.