Influence of estimated physical constants and vapor pressure for esters in the methanol/ethanol recovery column for biodiesel production

Abstract

The influence of the estimated values of the physical constants and vapor pressure of esters in a process simulation using the Aspen Hysys was evaluated from the energy parameters of a methanol/ethanol recovery distillation column of a biodiesel production plant. This study was necessary, because in process simulators most of FAMEs and FAEEs are not originally available in the simulator library, due to the lack of experimental data for these components. Accuracy analyses for the values ​​of reboiler temperature and reboiler heat duty of the simulated column were performed from simulations using different predictive models and experimental data. Results demonstrated that small deviations of the vapor pressure can generate considerable errors in the reboiler temperature and reboiler heat duty. In addition, errors can be even greater if vapor pressure is estimated from inaccurate critical constants. Deviations up to 13% were observed for the reboiler temperature and up to 16% for the reboiler heat duty. It is demonstrated that reliable simulations and process design are strongly dependent on the selected physical properties of the esters, specially vapor pressure, which are generated from available experimental data and using group contribution and corresponding states models.