(462d) Design and Optimization of a Fusel Oil Separation System Using a Dividing Wall Column

Design and optimization of a fusel oil separation system using a dividing wall column

 José de Jesús Mendoza Pedroza, Alvaro Orjuela, Juan Gabriel Segovia H,

Fusel oil is a mixture of alcohols obtained as a side stream during distillation of fermentation-derived ethanol with yields around 1 to 10 liters per thousand liters of fuel ethanol. According with GC-MS characterization, sugarcane derived fusel oil is mainly composed of isoamyl alcohol, ethanol, water, with minor concentrations of n-butanol, isobutanol and other alcohols, acids, and esters. Currently fusel oil is used as fuel in steam boilers in the ethanol biorefinery, or mixed back with anhydrous ethanol and sold as fuel. However fusel alcohols can be transformed in higher added-value products such as esters for the fragrances and flavors industries.

Conventional separation of fusel oils is accomplished in batch distillation systems using different cuts where water and ethanol are removed first. After lights removal, isoamyl alcohol is distilled from top obtaining a 95% w/w product while a dark brown liquid is removed from the reboiler. This process is energy intensive and operating costs represent a major fraction of the final costs.

In this direction, this work describes the design and optimization of a novel continuous distillation system including a dividing wall column. Thermodynamics of phase equilibria were validated by regression of binary and ternary equilibrium data reports with a NRTL-HOC activity-based model. The method used for the optimization corresponds to a stochastic differential evolution and a tabu list, setting the objective function to minimize energy consumption and the purity of product streams. This optimization was implemented by connecting Aspen Plus^TM and Visual Basic^TM (included in EXCEL^TM). A preliminary design and optimization was developed including only the three major components: isoamyl alcohol (66% mol), ethanol (16 % mol) and water (18% mol). In a subsequent stage n-butanol, isobutanol and heavy compounds were included in the fusel oil feed stream. In both cases, a reduction in energy consumption of around 20 to 30% with respect to conventional continuous distillation was observed.