Three Phase Distillation with the GCA-EoS

FRANCISCO A. SÁNCHEZ

Puerto Varas

Congreso; IX IBEROAMERICAN CONFERENCE ON PHASE EQUILIBRIA AND FLUID PROPERTIES FOR PROCESS DESIGN – EQUIFASE 2012; 2012

Universidad de Concepción

The higher prices of petroleum fuels and environmental issues have increased the interest in biofuels. In contrast with classical refineries, biorefineries have also aqueous mixtures of biofuels and several natural compounds, which must be separated in order to obtain fuel. On the other hand, when this fuels are alkyl compounds the show immiscibility with water that is also usually present in the process because of the product washing units or from the original processed biomass. This leads often to distillation problems where three phases are present.A simple algorithm for three phase distillation was built assuming constant molal overflow[1], and the Schuil and Bool[2] scheme for allowing more than one liquid phase present. They proposed a simple extension of ordinary VL distillation using an average distribution ratio between the vapor and a global liquid phase. The thermodynamic model integrated is the Group Contribution with Association Equation of State (GCA-EoS)[3], which takes account the specific association interactions typically present in mixtures with oxygenated compounds. Moreover, it has been that the GCA-EoS gives reliable prediction of phase equilibria of mixtures of natural compounds, as those present in biorefineries[4][5][6][7]. A methanol recovery distillation column from the work of Espinosa et al.[2] for a biodiesel production plant , has been simulated with the new algorithm. In this unit, methanol is removed from the heavy phase constituted of biodiesel and glycerin using water vapor as stripping agent. A typical simulation result is shown in figure 1, with methyl oleate as the main fatty acid methyl ester (FAME) representing biodiesel.