Thermodynamic model for calorimetric and phase coexistence properties of coal derived fluids. Annual report

Abstract

On September 1, 1989 work was initiated on a project to extend the available vapor-liquid equilibrium (VLE) model for coal fluids to allow satisfactory predictions of excess enthalpies of coal liquids at high pressures. The available vapor liquid equilibrium model was developed with support from previous grant from DOE-PETC (Grant no. DE-FG22-89PC90541). The current project also involves measurement of some model compound VLE data and chromatographic characterization of coal liquids for distribution of heteroatoms. A computational thermodynamic model for VLE, excess enthalpies and heat capacities of coal derived liquids has been developed. The model uses the modified UNIFAC correlation for the liquid phase. Some unavailable UNIFAC interactions parameters have been regressed from experimental VLE and excess enthalpy data. The computations are carried out using the method of continuous thermodynamics. Mode is used to derive interesting conclusions on the effect of oxygen, nitrogen, and sulfur heteroatoms on the thermodynamic properties of coal liquids. When compared with limited experimental data available for coal liquids the model shows good agreement. Some progress has been made on binary VLE measurements and size exclusion chromatography of coal liquids.