Data, analysis and modeling of physical properties for process design of systems involving lipids

• Consistency of measured phase equilibrium data of lipids is considered before regression of model parameters.
• A new thermodynamic consistency test for solid–liquid equilibrium (SLE) data is proposed.
• An activity coefficient model for testing of SLE data is created.
• Regressed model parameters for NRTL, UNIQUAC and UNIFAC models valid for lipids are given.

Pure component and mixture properties are necessary for synthesis, design, and analysis of processes for the production of edible oils, fats, biodiesel, and other lipids. The lack of measured data for these systems makes it necessary to develop reliable predictive models based on limited data. We have systematically collected data for vapor–liquid equilibrium (VLE), solid–liquid equilibrium (SLE) and related pure component properties involving lipid systems as a first step toward developing relevant property models. The established consistency tests to evaluate the VLE data of lipid systems as well as lipid properties are briefly reviewed. For SLE systems, where consistency tests based on the Gibbs–Duhem equation cannot be implemented, a consistency test has been developed. It involves limiting conditions and regression of the parameters for a new thermodynamic model that combines solute activity coefficients in the liquid phase at infinite dilution and a theoretically based term to account for the non-ideality in dilute solutions. This model gives noticeably better descriptions of experimental data in lipid systems than do traditional models. Examination of various objective functions for regressing model parameters showed that some variation of parameter values and differences in accuracy can be found, though they are not large. Some original UNIFAC group contribution parameters for lipids have been revised by fitting to the lipid database.