(428f) 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.