ABSTRACT
In this work, the modelling,
simulation and optimization of a reactive distillation column for the
production of Fatty Acid Methyl Ester (FAME) has been carried out. The FAME
considered was methyl palmitate, which was produced from an esterification
reaction between palmitic acid and methanol. The reactive distillation column
used was set up in Aspen HYSYS environment using Distillation Column
Sub-Flowsheet and the fluid package employed was Wilson model. The column had
17 stages, excluding the condenser and the reboiler, and it was divided into
seven sections, viz, condenser section, rectifying section, upper feed section,
reaction section, lower feed section, stripping section and reboiler section.
Palmitic acid (fatty acid) entered the column through the upper feed section
while methanol (alcohol) was fed at the lower feed section of the column. The
developed model was simulated to convergence using Sparse Continuation Solver.
Furthermore, the optimizer tool of Aspen HYSYS was used to optimize the process
using three different algorithms (Box, mixed and sequential quadratic
programming). The good convergence obtained from the simulation carried out on
the developed Aspen HYSYS model of the reactive distillation process showed
that Aspen HYSYS has been able to handle this process successfully.
Furthermore, the achievement of the value of the objective function given by
the optimization of the process when the estimated optimum values of reflux
ratio, feed ratio and reboiler duty were used to run the model revealed that
the optimum values obtained were from Aspen HYSYS were theoretically valid.
Therefore, it has been shown that the developed Aspen HYSYS model of this
research work can be used to represent, simulate and optimize a FAME reactive
distillation process successfully.
CHAPTER ONE
1.0
INTRODUCTION
Reactive distillation process has been
given special attention in the past two decades because of its potential for
process intensification for certain types of chemical reactions (Popken et al.,
2001; Murat et al., 2003). Reactive distillation process is a growing
chemical unit operation that involves the integration of a reactor and a
distillation column in one unit i.e. it merges two different unit operations in
a single apparatus. In other words, reactive distillation involves simultaneous
chemical reaction and multi-component distillation. The chemical reaction
usually takes place in the liquid phase or at the surface of a solid catalyst
in contact with the liquid phase (Seader et al., 2006). General
application of reactive distillation is the separation of a close-boiling or
azeotropic mixture (Terril et al., 1985).
The most interesting application
involves combining chemical reactions and separation by distillation in a
single distillation apparatus. The most important benefit of reactive
distillation technology is a reduction in capital investment, because two unit
operations can be carried out in the same device. Such integration leads to
lower costs in pumps, piping and instrumentation. For exothermic reaction, the
reaction heat can be used for vaporization of liquid. This leads to savings of
energy costs by the reduction of reboiler duties. Reactive distillation process
is also advantageous when the reactor product is a mixture of species that can
form several azeotropes with each other. Reactive distillation conditions can
allow the azeotropes to be “reacted away” through reaction. But the combination
of reaction and distillation is only possible if the conditions of both unit
operations can be combined (Taylor and Krishna, 2000).
Reactive distillation can be used with
a variety of chemical reactions e.g. acetylation, aldol condensation,
alkylation, amination, dehydration, esterification, etherification, hydrolysis,
isomerization, oligomerization, transesterification of fatty acids etc.
Fatty acid methyl esters (FAMEs) are a
type of fatty acid ester derived by trans-esterification of fats with methanol.
They are used to produce detergents and biodiesel. Fatty acid esters are
produced by vegetable oils and animal fats trans-esterification with short
chain aliphatic alcohols. This process reduces significantly the vegetable oils
viscosities without affecting its calorific power, thereby, allowing their use
as fuel. Fatty acid methyl esters are typically produced by an alkali-catalyzed
reaction between fats and methanol in the presence of base such as sodium
hydroxide or sodium meth-oxide. The physical properties of Fatty acid esters
are closer to fossil diesel fuel than pure vegetable oils, but the properties
depend on the type of vegetable oil (FAME fact sheet, 2011). A mixture of
different fatty acid methyl esters is commonly referred to as biodiesel, which
is a renewable alternative fuel. Biodiesel is known for being a clean-burning
diesel fuel with minimum negative environmental impacts and potential to
greatly reduce greenhouse gas emissions. It is a biodegradable fuel with
negligible sulfur content and ultra-low sulfur emissions. It has similar
physical properties as fossil diesel fuel, which makes it compatible for
combustion in internal combustion engines and boilers. Biodiesel can be used as
a blending component or a direct replacement for diesel fuel in the diesel
engines. It is defined as a mixture of monoalkyl esters of long chain fatty
acids (FAME) derived from a renewable lipid feedstock, such as vegetable oil or
animal fat. The scarcity of conventional fossil fuels, growing emissions of
combustion- generated pollutants, and their increasing costs will make biomass
sources more attractive (Sensoz et al., 2000). Petroleum-based fuels
have limited reserves concentrated in certain regions of the world. These
sources are on the verge of reaching their peak production. The fossil fuel
resources are shortening day by day. The scarcity of known petroleum reserves
will make renewable energy sources more attractive (Sheehan et al.,
1998).
According to Demirbas, An alternative
fuel to petro-diesel must be technically feasible, economically competitive,
environmentally acceptable and easily available. Biodiesel is one of the
current alternative diesel fuels, which has high heating value a little bit
lower than gasoline (46 MJ/kg), petro-diesel (43 MJ/kg) or petroleum (42
MJ/kg), but higher than coal (32–37 MJ/kg). Biodiesel is also a good lubricant
and can improve the lubrication properties of the diesel fuel blend (Extension,
2010). The production of biodiesel can be simulated using a software package
known as Aspen HYSYS.
Aspen HYSYS is a program that offers a
complete integrated solution to chemical process industries. This software
package can be used in almost every aspect of process engineering from design
stage to cost and profitability analysis. It has a built-in model library for
distillation columns, separators, heat exchangers, reactors etc. custom models
can extend its model library. Aspen HYSYS can interactively change
specifications such as flow sheet configuration, operating conditions and feed
compositions to run new cases and analyze process alternatives. Aspen HYSYS
software allows us to perform a wide range of tasks such as estimating and
regressing physical properties, generating custom graphical and tabular output
results, fitting plant data to simulation models, optimizing process and
interfacing results to spreadsheets.
1.1 Problem Statement
Crude oil has limited reserves and is
the backbone of Nigeria’s economy. Also, it is not a renewable source and
contributes to the unwanted effect to the world environment. Alternative,
renewable, clean and environmentally friendly energy is sought after to support
the availability of crude oil fractions.
1.2 Aim
This research project is aimed at
determining the optimum parameters required for obtaining fatty acid methyl
ester (FAME) of high purity with the aid of Aspen HYSYS.
1.3 Objectives
The objectives of this work are:
To study, simulate and understand
fatty acid methyl ester reactive distillation process using Aspen HYSYS
software package.
To determine optimal parameters for
high purity of the desired product (fatty acid methyl ester).
Chapters: 1 - 5
Delivery: Email
Delivery: Email
Number of Pages: 60
Price: 3000 NGN
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