ABSTRACT
In this work, a reactive distillation
process for the production of a fuel additive has been modelled, simulated and
controlled using proportional-integral-derivative (PID) control method. The
fuel additive considered was isopropyl alcohol that was produced from the
reaction occurring between propylene and water, with diisopropyl ether as a
side product. In accomplishing the work, the ChemCAD model of the process was
first developed using SCDS Distillation Column #1 and the fluid package
employed was UNIFAC property model. The ChemCAD column had 15 stages where the
feed stream for water was the 6th stage and the one propylene was the 10th
stage; the section of the column between the two feed streams was the reaction
section of the column. After simulating the developed ChemCAD model to
convergence, it was converted to dynamic type from which the dynamic responses
of the system were generated and used with the aid of MATLAB to develop
transfer function model having the reboiler duty, the reflux ratio and the
temperature of the bottom product as the input variable, the disturbance and
the output variables of the process, respectively. The obtained transfer
function of the model was used to develop both open-loop and closed-loop
Simulink models for the process that were used to carry out the open-loop and
the closed-loop simulations of the process. The closed-loop simulation was
carried out with the desire of achieving a fuel additive product with a mole
fraction of 0.97. This was accomplished using a PID controller applied
inferentially via the product temperature and tuned by trial-and-error
technique. It was observed from the results obtained that isopropyl alcohol
could be produced successfully from a reaction between propylene and water
using reactive distillation suppressing the associated side reaction. It was
also found out that it is possible to control the mole fraction of isopropyl
alcohol inferentially using bottom temperature because temperature and mole fraction
have been found to be dependent on each other. Finally, it has has been shown
that a reactive distillation has been controlled to give high purity of
isopropyl alcohol of approximately 0.97 mole fraction as the bottom product in
the developed reactive distillation column using the PID controller with
trial-and-error tuning technique.
CHAPTER ONE
1.0
INTRODUCTION
1.1
Background of Study
Agreeing to statistics that has been
provided from U.S Energy Information Administration in 2007 annual report on
rapid increase of demand for petroleum and gas production. World demand for oil
is projected to increase by 37% over 2006 levels by 2030. It is because the oil
is widely used in many industries such as transportation, manufacturing,
polymers, shipment and others. Transportation consumes major amount of the
energy and increase year by year. This growth has largely come from new demand
for personal-use vehicles powered by internal combustion engines. There is endless
need to reduce carbon emissions and problems encountered with biodiesel blends,
such as fuel system corrosion, increased fuel foaming and water separation.
Fuel additives are compounds put together to increase the quality and
efficiency of the fuels used in motor vehicles through treatments. Cars and
trucks are predicted to cause the highest demand in the transportation
approaching to 75%. In other to reduce the consumption of fuel as well
as improvement of gas produced during combustion, isopropyl alcohol (IPA) is
used as an additive in the fuel.
IPA is used in gasoline blending as an
octane enhancer to improve hydrocarbon combustion efficiency. It is primarily
produced by combining water and propene in a hydration reaction. It is also
produced by hydrogenating acetone. In the conventional process, separate system
between reactor and separation units are used. This technology features a
two-stage reactor system of which the first reactor is operated in a recycle
mode. With this method, a slight expansion of the catalyst bed is achieved
which ensures very uniform concentration profiles within the reactor and can
avoid hot spot formation. Undesired side reactions, such as the formation of
diisopropyl ether (DIPE) also can be minimized.
Nowadays, the search for a novel
method to replace the conventional one has been a major interest both in
industry and academia. This novel method is learnt to give high conversion of
fuel additives economically (Giwa and Giwa, S.O., 2013), and it is know as
“reactive distillation”. Reactive distillation is a process in which the
chemical reactor is also the still (an apparatus used to distill liquid
mixtures by heating to selectively boil and then cooling to condense the
vapor). Separation of the product from the reaction mixture does not need a
separate distillation step, which saves energy (for heating) and materials.
Furthermore, reactive distillation is
a process that combines chemical reactions and physical separations into a
single unit operation. This process, as a whole, is not a new concept as the
first patent dates back to 1920. The initial publications on this process dealt
with homogeneous self-catalyzed reactions such as esterifications and
hydrolysis, but heterogeneous catalysis in reactive distillation is a more
recent development. While the concept existed much earlier, the first real-
world of the system implementation of reactive distillation took place only in
the 1980s.
The relatively large amount of new
interest in reactive distillation is due to the numerous advantages it has over
typical distillation. It can enhance reaction rates, increased conversion,
enhanced reaction selectivity. Also, heat integration benefits and reduced
operating costs are part of the benefits associated with reactive distillation.
All these factors contribute to the growing commercial importance of reactive
distillation.
However, since heat transfer, mass
transfer, and reactions are all occurring simultaneously, the dynamics which
can be exhibited by catalytic distillation columns can be considerably more
complex than found in regular columns. These results in an increase in the
complexity of process operations and the control structure installed to
regulate the process.
1.2 Problem statement
The conventional method of isopropyl
alcohol (a fuel additive) production is not only ineffective in handling the
side reaction involved in the process but also very costly because many pieces
of equipment (reactors, separators, etc) are required by it. The inefficiency
of this process to suppress those side reactions as well as its high cost are
the major problems identified it and to which solutions must to be proffered.
One approach of solving this problem is by developing a control algorithm that
will be able to make the process behave as desired.
1.3 Aim and Objectives
The aim of this project to carry out
proportional-derivative-integral (PID) control of a reactive distillation
process for fuel additive (isopropyl alcohol) production. In order to achieve
this aim, the following objectives are set:
•
developing ChemCAD model of the process,
•
simulating the developed ChemCAD process model for both steady-state and
dynamics to generate dynamic response data,
•
developing the process transfer functions with the aid of MATLAB using the
generated data,
•
developing the Simulink mode of the process using the developed transfer
function,
•
carrying out the open-loop simulation of the transfer function in Simulink
environment, and
•
applying an appropriate method to tune the controller and simulating the
control system of the process for both servo and regulatory cases.
TOPIC: MODELLING, SIMULATION AND CONTROL OF A REACTIVE DISTILLATION PROCESS FOR FUEL ADDITIVE PRODUCTION
Chapters: 1 - 5
Delivery: Email
Delivery: Email
Number of Pages: 55
Price: 3000 NGN
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