Thermodynamics and fluid characterization using trajectory optimization

A straightforward method is proposed to determine interactions parameters for phase equilibrium models based on a relatively small amount of distillation data. The data are collected using the advanced distillation curve method developed by Bruno [1] and [2] where boiling points are measured at true thermodynamic state points. The data are modeled using the trajectory optimization method developed by Satyro and Yarranton [3].The approach was tested on water/alcohol and gasoline/alcohol mixtures. Each mixture was distilled at atmospheric pressure. For the water/alcohol mixtures, the NRTL model was tuned to fit atmospheric distillation data by adjusting the interaction parameters (interaction energies and non-randomness factor). For the gasoline/alcohol mixtures, the gasoline was characterized from a GC hydrocarbon analysis and the advanced Peng–Robinson equation of state was tuned to atmospheric distillation data by adjusting the interaction parameters between the gasoline pseudo-components and the alcohols. The models, tuned only to distillation data, correctly predicted the phase behavior of these non-ideal mixtures including azeotropism. The model is entirely general and can be used to determine interaction parameters for activity coefficient or equation of state based models.