ABSTRACT
In this work, the production of
biodiesel via reactive distillation process has been modelled and simulated
with the aid of ChemCAD for both steady state and dynamics. Also, the control
of the process has been carried out using MATLAB/Simulink. In order to achieve
this aim, dynamics data showing the response of biodiesel mole fraction in the
column bottoms (controlled variable) to a change in reboiler duty (manipulated
variable) and reflux ratio (selected disturbance variable) were extracted from
the ChemCAD dynamic simulation of the developed process model and used to
obtain the first-order-plus-dead-time transfer function relation between
biodiesel mole fraction in the column bottoms, reboiler duty and reflux ratio
with the aid of MATLAB. The open loop simulation was done by applying steps to
the input variables (reboiler duty and reflux ratio). Furthermore, the
set-point tracking and disturbance rejection control of the system were carried
out using a PID controller tuned with Zeigler- Nichols, Cohen-Coon and
trial-and-error techniques. It was observed that the controller parameters
obtained by Zeigler-Nichols and Cohen-Coon tuning were not able to achieve the
set-point tracking control of the system, and this necessitated the use of
trial-and-error technique that was used to obtain the controller parameters
used to handle the system in the desired manner for set-point tracking of
maintaining the mole fraction of biodiesel at 0.9. Nonetheless, Zeigler-Nichols
and Cohen-Coon tuning techniques were sufficient to successfully tune the
process controller to carry out the disturbance rejection of the process.
However, it was observed that the performance of Cohen-Coon tuning technique
was better than that of Zeigler-Nichols tuning technique in the disturbance
rejection control simulation as it had lower Integral Square Error and lower
Integral Absolute Error values. It has, thus, been discovered that biodiesel
could be produced in high purity via reactive distillation process, and the
system could be efficiently handled to behave as desired using PID control
system.
CHAPTER ONE
1.0
INTRODUCTION
1.1
Background of Study
Due to an increased demand of energy
by the world population and the non-renewability of crude oil, the development
of renewable energy generation techniques for future generations has gained
great importance over the century (Madhu et al., 2012). One of these renewable
energy has been identified to be biodiesel.
Biodiesel is a renewable, non-toxic,
biodegradable substitute for diesel produced from crude oil. Generally, it is
produced by transesterification of vegetable oils and animal fat by short
chained aliphatic alcohols. Commercially, the production of biodiesel from
vegetable oils and fats still have various drawbacks. Both batch and continuous
processes utilize almost 100% excess alcohol than the stoichiometric molar
requirement (3:1) in order to drive the transesterification reaction to
completion and produce the maximum amount of biodiesel per unit consumption of
oil (Kiss et al., 2008). At the end of the process, unreacted alcohol
must be recovered by a separate distillation column. The use of a separate
distillation column for alcohol recovery increases capital as well as operating
cost. Therefore, there is the need to develop alternative means for the
commercial production of biodiesel which minimizes cost without reducing the
yield and quality of biodiesel produced. Reactive distillation is one of such
alternative means.
Reactive distillation combines
separation and reaction into a single vessel to minimize operation and
equipment costs (Kiss et al., 2008). In this process, the products formed are
removed as soon as they are formed. This characteristic makes it possible to
overcome the equilibrium thermodynamics of a reaction, reaching high conversion
and selectivity. Thus, it is particularly effective for reversible reactions
such as the transesterification of vegetable oil and fats to biodiesel (He et
al, 2006). However, the combination of reaction and separation into a single
unit that resulted in many complexities of the process has made its dynamics
and control study of this process a challenge to Process Engineers.
Dynamics in chemical engineering is
the study of how process variables vary with time. As all real-life process
variables vary with time, it is therefore important to study the dynamics of
the biodiesel production process. Control is the external intervention needed
to guarantee the satisfaction of operational requirements such as safety,
production specifications, environmental regulations, operational constraints,
economics (Stephanopoulos, 1984). Since the structure of biodiesel reactive
distillation process is complex, due the need to maximize mass and energy raw
materials, there is therefore need to develop a suitable control system for the
process.
This research project is aimed at
providing an outlook at the dynamics of biodiesel production by reactive distillation
and developing a control system for the process by means of CHEMCAD and MATLAB
modelling and simulation.
1.2 Research Problem Statement
Biodiesel is a valuable renewable fuel
that can supplement and replace petroleum diesel in diesel engines. However,
its cost of production by the reversible transesterification of vegetable oil
and fats with alcohol by conventional means to achieve high purity of the
product is relatively high. This high cost is a big problem that needs to be
solved through provision of an alternative, novel, route and development of a
reliable control method to make the process behave efficiently.
1.3 Aim and Objectives
The aim of this project is to model,
simulate and control a reactive distillation process used for the production of
biodiesel from the transesterification reaction between triolein and methanol.
This aim would be achieved by realizing the following objectives:
• developing and simulating the
ChemCAD steady-state model of the process,
• converting the steady-state model
into a dynamic type to generate dynamic data,
• using the generated dynamic data to
develop the process transfer functions with the aid of MATLAB,
• using the transfer function model of
the process to obtain the tuning parameters of a PID controller,
• applying the PID controller to make
the mole fraction of the biodiesel be at the desired set-point value.
1.4 Scope
This work is limited to employing
ChemCAD and MATLAB to develop a model, simulate the model and carry out the
open-loop and closed-loop simulations of the model for a reactive distillation
used for biodiesel production from the transesterification reaction between
triolein and methanol.
TOPIC: MODELLING, SIMULATION AND CONTROL OF THE REACTIVE DISTILLATION OF BIODIESEL PRODUCTION
Chapters: 1 - 5
Delivery: Email
Delivery: Email
Number of Pages: 78
Price: 3000 NGN
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