Fusel Oil Separation Process

Fusel Oil Separation Process

Natalia Montoya¹, Fernando Córdoba¹, Carlos Trujillo², Iván Gil¹, Gerardo Rodríguez¹,

¹Grupo de Procesos Químicos y Bioquímicos, Department of Chemical and Environmental Engineering. Universidad Nacional de Colombia, Sede Bogotá.

²Laboratorio de Catálisis Heterogénea. Department of Chemistry. Universidad Nacional de Colombia, Sede Bogotá.

Abstract

Fusel Oil is a by-product from the production of bioethanol composed by alcohols from C₂ to C₅, water and some heavy and volatile components, in low concentrations. In Colombia, for 2012, 730000 liters per year of raw fusel oil are expected to be produced, considering that about 1 liter of Fusel Oil is produced by each 1000 liters of ethanol. The Isoamyl alcohol is the main component in the Fusel Oil (present in around 80% to 90% mass composition), for that reason a separation process for purifying this valuable alcohol is presented. According to literature reports Fusel Oil is composed mainly by ethanol, isoamyl alcohol, water and heavy components. In this study, a stream containing these substances was used to represent the Fusel Oil to be separated.

The process simulation was done on Aspen Plus^® process simulator using NRTL as a property package. The simulated process involves three main steps and is showed in Fig. 1. The first one corresponds to neutralizing the minor organic acids present in Fusel Oil using a diluted solution of sodium hydroxide in excess. The second step consists on separating the Alcohols and Water from the heavy components and the third one involves purifying of the Isoamyl Alcohol.

In the case of the second step, neutralized Fusel Oil is passed through a distillation column to draw off the lighter components at the top and separate the heavy components (above 124°C at 560 mmHg) at the bottom. The design specification is set to 99,9% mass recovery of heavy components. The column has 14 equilibrium stages, including reboiler and condenser, and the feed is located at stage 8.

In the third step the lighters components are fed into a stripper. A mix of ethanol, water and isoamyl alcohol is obtained at the top. This stream is passed through a condenser and then into a liquid-liquid phase separator for extracting the aqueous phase and recirculate the organic phase to the column. The Isoamyl alcohol is separated at the bottom. The design specification is set for obtaining a mass purity of 99,8% of Isoamyl alcohol. The stripper has 4 stages, including reboiler.  

The distillation column and the stripper were also designed using a non-equilibrium approach. Results for the distillation column showed that 13 ft height and 3 in diameter column packed with Sulzer Nutter ring is able to manage a volumetric flow of 2000 liters per day of Fusel Oil. In the case of the stripper a 10 ft height and 3 in diameter column packed with Sulzer Nutter ring is necessary to perform the process. The overall recovery at the process is 99,4% of Isoamyl Alcohol with respect to the Isoamyl Alcohol present in the initial Fusel Oil.  

Figure 1. Scheme of Fusel Oil separation process

Keywords: Isoamyl Alcohol, Process Simulation, Aspen Plus, Fuel Ethanol.