Use of Process
Simulators for the Unit
Operations Education
of Undergraduate
Chemical Engineers
FABIANO A. N. FERNANDES
Faculdade de Engenharia Quı´mica, Departamento de Processos Quimicos, Universidade Estadual de Campinas,
Caixa Postal 6066, 13083-970, Campinas-SP, Brazil
Received 5 August 2002; accepted 3 September 2002
ABSTRACT: Computer aided design has become extremely popular and its use in
classroom can be very helpful, adding more analysis capabilities to all chemical engineering
areas. Process simulators, such as Hysys and Aspen, are complex tools and students tend to
have doubts when they start using them. This article presents Hyduc, an exercise/tutorial
software, developed to introduce process simulators to undergraduate students and to pro-
vide unit operation courses with realistic exercises involving simulation of chemical processes.
ß 2002 Wiley Periodicals, Inc. Comput Appl Eng Educ 10: 155–160, 2002; Published online in Wiley
InterScience (www.interscience.wiley.com.); DOI 10.1002/cae.10023
Keywords: process simulation; unit operations; education; chemical engineering
INTRODUCTION and the use of these simulators in classroom has been
crescent. Even though, the use of these process simu-
Technological advances in areas linked to engineer- lators has been limited to final industrial design
ing, especially those related to the use of computer- courses and little use is being made in unit operations
aided tools for analysis and development of industrial courses.
processes have been enormous. More and more indus- Experience has shown that letting the students
tries and universities are using process simulators in learn to use process simulators by their own is not a
their projects and researches. Several institutions have good strategy. The first contact can be very frustrating,
bought simulators such as Hysys [1] and Aspen [2], since they do not know how to use them. Simulators
start with an empty flowchart and there are many
options to choose from. Students get lost and they don’t
Correspondence to F. A. N. Fernandes (fabfer@feq.unicamp.br). know if they should start by choosing the components
ß 2002 Wiley Periodicals, Inc. or by adding unit operations to the flowchart.
155
156 FERNANDES
Assigning complex projects to be simulated by plain about expending too much time doing exercises.
students with no or little experience dealing with pro- This second consideration is also because of the
cess simulators can create a lot of confusion. Starting ‘‘baby steps’’ philosophy, i.e., show a little at a time,
by assigning small processes to be simulated is a good making it well understood.
educational choice since it lets the students get used The whole philosophy of the tutorial is ‘‘learning
to the simulation procedures in a progressive way, through doing.’’If the professor only tells the theory,
allowing the necessary time the students need to feel the student may forget it. If the professor involves the
comfortable using the simulator. After a short period, student in an assignment, the student will understand
the use of the simulator becomes natural. it [3]. This is really true, since a lot of times we have
This paper presents Hyduc, an exercise/tutorial seen students just playing with the simulator, moved
software developed to introduce process simulators by simple curiosity to know more about the simulator
to undergraduate students. The idea of developing a capabilities and how some equipment work.
software with a tutorial is to have a permanent tool The software is divided into a tutorial module and
that students can look at when needed. Along with six exercise modules comprising six major catego-
the tutorial, the software provides realistic chemical ries of unit operations: distillation, liquid–liquid ex-
processes exercises that can be used in unit opera- traction, compressor, heat exchanger, and absorption
tion courses. (Fig. 1).
With the exception of the tutorial module, which
does not require a report, the exercises should be
LEARNING THROUGH DOING assessed by a short report, which can be used to
evaluate the students.
Two main considerations were made before creating
the tutorial/exercises software. First of all, the tutorial
would need interesting exercises based on real indus- TUTORIAL MODULE
trial cases in order to attract the students’ attention.
It is well known that students tend to be more inter- The tutorial module shows how to use the process
ested when they know that they are working with simulator. A distillation column is used as an example.
cases they can face in their professional life. Second, The tutorial shows the basic steps that should be
the exercises needed to be very fast forward and less followed when using process simulations: selection of
time consuming. It is also known that students com- a thermodynamic model, selection of the components,
Figure 1 Main menu.
PROCESS SIMULATORS FOR UNDERGRADUATE CHEMICAL ENGINEERS 157
addition of process streams, addition of unit opera- order to push the student harder into thinking about
tions, and the simulation of the process. Texts and the problem and to come up with ideas of how to
figures guide the students in each step of the way, solve them.
using numbered arrows to indicate what should be Several concepts are brought into the students’
done (Figs. 2 and 3). While reading the tutorial, the attention, such as, industrial applications of a par-
student can also follow the steps in the simulator. ticular unit operation, operational cost, influence of
major parameters, analysis of viability, and energy
recovery.
EXERCISES MODULES
Liquid–Liquid Extraction Module
Industrial cases were reviewed and common examples
were transformed into exercises of the tutorial/ This module presents exercises with single stage,
exercise software [4–7]. In each module, the software multiple stages, and column extractors. The exercises
presents an industrial case that needs to be solved. deal with the separation of a water-acetic acid mix-
The tutorial shows how to use Hysys to simulate a ture using benzene or cyclohexane, which can also be
particular unit operation and what steps are requir- repeated in laboratory practices and afterwards have
ed to get the information needed to solve the pro- their results compared (practice and simulation).
blem. An important point is that the software shows The first exercise explores the effect of tempera-
how to use the simulator, but it does not show how to ture on the process since the miscibility of the
solve the problem. This part is left to the students that components changes with temperature (Fig. 4). This
must analyze the process, plan how they are going to effect is later related to the operational cost of the
get the data, and what they are going to do with the system (heating costs), when the recovery of acetic
data. acid in higher temperatures should be analyzed if it is
There is not a particular order that should be economically viable.
followed with the exercises modules and they can be The second exercise illustrates the effect of
used following the structure of the unit operations multiple extraction stages (Fig. 5). Extraction pro-
courses of a particular university. Within the modules, cesses with one and two stages are compared based
the exercises have a crescent level of difficulty in on efficiency and cost. The last exercise deals with
Figure 2 Example of text and figures shown to explain the exercises.
158 FERNANDES
Figure 3 Example of step-by-step teaching of how to use the process simulator (Hysys).
extraction towers, showing the effects of the number of liquid–vapor equilibrium and ending with column
of stages and solvent flow rate. optimization. In a series of five exercises, the students
are driven to simulate short-cut methods to obtain the
initial parameters for the column, and then use these
Distillation Module
information to simulate a more rigorous distillation
Distillation is one of the most important single unit column. This designed column is then optimized and
operation in chemical engineering and as such it forms sized, completing the steps for distillation simulation
the basis of many processes and is an essential part of and design.
many others. It presents a more difficult simulation A water–acetic acid mixture is also used in this
compared with many other unit operations as conver- module since it can be used in comparison with the
gence problems may arise. The distillation module extraction module and also because some universi-
presents all steps required to simulate and design ties run this kind of operation in unit operations
distillation columns beginning with the basic theory lab courses. The simulated system is shown in the
Figure 6.
Short-cut methods can provide valuable informa-
tion to start a rigorous simulation of a distillation
column, so the series of exercises start with the short-
cut methods and the tutorial shows how to use Hysys
Figure 4 Effect of temperature on the binodal curve. Figure 5 Two stage extraction system.
PROCESS SIMULATORS FOR UNDERGRADUATE CHEMICAL ENGINEERS 159
Figure 6 Distillation system.
Figure 7 (a) Benzene production process (reaction zone);
to simulate a short-cut distillation column. The exer- (b) modified benzene production process (reaction zone).
cise asks to recover acetic acid 95% at the bottom of
the column and that a maximum of 5% of the acetic Compressor Module
acid should leave at the top of the column. A second
This module plays with thermodynamics and energy
exercise illustrates the difficulty in making the cor-
requirements of a compression unit. The exercise asks
rect specification for the column. Two forms of
to add intercoolers between the stages of a three stage
column specification are given and should be tested.
compressor as to turn an adiabatic compression into a
The results will show that one form specification
more isothermal compression (Fig. 8). This example
achieves the aimed column performance, while the
shows that the work requirements in isothermal com-
other fails to achieve the aimed condition. This
pression is less then that for adiabatic compression
shows the students that it is not easy to work with
and that is a good reason why cooling is useful in
distillation column simulation and that special atten-
compressors.
tion should be taken toward the correct specification
of the column.
Absorption Module
Heat Exchange Module The absorption module explores the use of absorption
towers as means of product purification (Fig. 9). The
Heat exchange is a very important unit operation in
exercise illustrates the limiting gas–liquid ratio, effect
chemical engineering and as such it is an essential part
of gas and liquid flow rates, changes in the percentage
of many processes. In the software, heat exchangers
of contaminants, and the effect of the number of
are linked together with chemical reactors as a way to
theoretical stages of the tower.
minimize the energy requirements of a process.
The proposed exercise explores the aspects of
energy saving through the insertion of heat exchan- CLASSROOM EXPERIENCE
gers in a process in order to exchange energy between
process streams. The production of benzene by toluene The software has been used in six Brazilian univer-
hydrogenation is used as an example. The exercise sities and one Portuguese university with positive
asks for a change in the process from the one shown
in Figure 7(a) to the process shown in Figure 7(b).
After the changes, the students should analyze how
much energy is being exchanged between streams 1
and 2 and the amount of energy that needs to be
supplied by cold and hot utilities. This exercise is a
good example that can be given to students before
teaching pinch technology, as to motivate them about
the importance of this method. Figure 8 Three stage compressor diagram.
160 FERNANDES
unit operations. The program provides an attractive
way to introduce chemical engineering students to
the analysis of industrial processes and commercial
process simulators. Moreover, the software gives a
good head start for the students to use process simu-
lators in more advanced applications, such as research
and real industrial cases, training students for their
future jobs. The modules are based on fundamental
process models of industrial unit operations using an
available commercial process simulation software.
Figure 9 Absorption process diagram. REFERENCES
[1] HYSYS Process, Version 1.5, AEA Technology Engi-
results. Students showed great satisfaction using the neering Software, Hyprotech Ltd., Calgary, Canada,
software and learned to use Hysys very fast. The 1998.
general degree of knowledge regarding unit opera- [2] Aspen, Version 10.1, Aspen Technology Inc., Cambridge,
tions and its applications has improved. The positive USA, 2000.
experience with this kind of tutorial/exercise soft- [3] B. R. Young, D. P. Mahoney, and W. Y. Svrcek, Real-time
ware and the students’ response has triggered the computer simulation workshops for the process control
extension of the project to other areas of engineering education of undergraduate chemical engineers, Comput
as process control and conceptual design using pro- Appl Eng Educ 9 (2001), 57–62.
cess simulators and other computer aided engineering [4] W. L. McCabe, J. C. Smith, and P. Harriott, Unit Opera-
tions of Chemical Engineering, 5th Edn., McGraw-Hill,
softwares.
New York, 1993.
[5] J. M. Coulson, and J. F. Richardson, Chemical engine-
ering, Butterworth-Heinemann, Oxford, 1991.
CONCLUSIONS [6] R. N. Shreve, Chemical process industries, McGraw-Hill,
New York, 1977.
In this article, we presented a Windows program [7] J. M. Douglas, Conceptual design of chemical processes,
developed for teaching Hysys process simulator and McGraw-Hill, New York, 1988.
BIOGRAPHY
Fabiano Fernandes is a postdoctoral
student at the Universidade Estadual de
Campinas, Campinas, Brazil. He received
his PhD (2002) degree in chemical engi-
neering from the Universidade Estadual de
Campinas. Dr. Fernandes’s teaching inter-
ests center on modeling and simulation,
unit operations, and reactor design. His
research interests center on modeling of
polymerization processes and reactors.
