VIRTUAL APPLICATIONS USING A WEB PLATFORM TO …chem.engr.utc.edu/Webres/Dist/ECE06007.pdf · A WEB PLATFORM TO TEACH CHEMICAL ENGINEERING: THE DISTILLATION CASE ... simulation of

VIRTUAL APPLICATIONS USINGA WEB PLATFORM TO TEACH CHEMICALENGINEERING: THE DISTILLATION CASE

A. C. Rafael1, F. Bernardo1, L. M. Ferreira1,�, M. G. Rasteiro1 and J. C. Teixeira2

1Department of Chemical Engineering, University of Coimbra, Polo II - Pinhal de Marrocos, Coimbra,

Portugal.2Mathematics Department, University of Coimbra, Largo D. Dinis, Coimbra, Portugal

Abstract: The question we will address here is how to integrate computational tools, namely themore modern and interactive ones, in the teaching of Chemical Engineers by means of the WorldWide Web. The case study presented concerns the development of a web application for thesimulation of multicomponent distillation columns running at steady state condition using theMATLAB WebServer. The application allows a remote user to login into a web site, choose sev-eral operating parameters and perform on-line simulations. In short, we believe that the introduc-tion of this new perspective of teaching chemical engineering can result in ample benefits,leading students to a better and wider understanding of the processes involved.

Keywords: distillation; MATLAB; unit operations; virtual teaching; Web platform.

INTRODUCTION

Computers are, nowadays, a widespreadteaching tool for engineering courses. In fact,with the increase of computational capacity,computers can easily be used to explore thenew world of the virtual applications. Duringthe last years, computer packages developedto extend traditional lecture-based courseshave increased in number, and computerapplications can now be used to demonstrateengineering processes that are unreachablethrough traditional laboratory experiments.As a result of the growing concern with the

learning outcomes of students when studyingengineering subjects, the integration of thenew information technologies in classroomcontext has been faced as one of the manypossibilities to enhance the capacity of thestudents to approach complex engineeringproblems. With the evolution of computergraphical capacities new pedagogical waysare open.One of the problems often faced by stu-

dents is the difficulty of associating concepts,given in the classroom, with the adequatephysical models (Clement, 1982). Educationaltools based on immersive graphics, like theones available through virtual reality technol-ogies, are becoming more and more recog-nized as useful to help the students formingcorrect conceptual models (Dede, 1995). Infact, if adequately monitored by the teachers,

they enable performing ‘experiments’ in dis-tinct situations and, as a consequence, under-standing through experience how the processreacts to different conditions, and relate thatto the prevailing physical phenomena andconcepts. Furthermore, the application ofprocess simulators on chemical engineeringeducation has gained considerable import-ance, allowing an increased teaching effective-ness with significant cost reductions. The useof simulators gives the students the possibilityof performing a greater number of experiments(simulated) in a shorter time than in the case oflaboratory experiments. Commercial simu-lators are often used in chemical engineeringteaching, however, those simulators, likeAspen or HySys, for instance, often come as‘black boxes’ making it difficult for the studentto understand the complexity of the mathemat-ical models necessary to describe chemicalprocesses. On the other hand, the applicationof realistic models in simulators is essentialto understand how the process reacts tochanges in operating conditions, feed charac-teristics, and so on.Considering that engineering is a ‘hands

on’ profession, it is desirable to allow theaccess of the students to experiences withreal processes, to achieve an education ofquality. However, laboratorial equipment isextremely costly requiring, in general, theexistence of several teaching modules toaccommodate all students in one single

Vol 2 (D0) 2007 1–9

�Correspondence to:Dr L. M. Ferreira, Departmentof Chemical Engineering,University of Coimbra,Polo II - Pinhal de Marrocos,3030-290 Coimbra, Portugal.E-mail: [email protected]

DOI 10.1205/ece06007

0000–0000/07/$00.00

Education for ChemicalEngineers

Trans IChemE:Part D, Month2007

# 2007 Institutionof ChemicalEngineers

class, with the consequent cost increase. Therefore, thescheduling of laboratory time can be a difficult task, moreso with the new trend of working adults that return to the uni-versity in part-time. Some of the previous problems can besolved applying the concept of interactive distance learning.This concept includes the access to remote computers thatfacilitate the learning according to the individual capacity ofeach student. Moreover, Internet supplies a real time connec-tion eliminating time and space restrictions; it allows theaccess to education at any time, from any place. Besides,due to the multi-task and multi-user nature of the softwarepackages, several students can benefit from the software atthe same time (Palanki and Kolavennu, 2003).

˙In this context,

the development of virtual laboratories presents a widepotential to enable the access of the students to experimentsthat are either unreachable or very difficult to implement in thelaboratory.Recent advances on informatics software technology are

bringing the virtual laboratories to the reach of educationalbudgets and to students themselves. The advances of inter-net and the turn out of new tools such as VRML (virtual realitymodelling language) and XML (extra markup language) havefacilitated the development of educational and laboratorialsystems based on virtual reality with relatively low costs.Therefore, the development of real contents and of standar-dized virtual educational systems (how to teach ‘virtually’)that satisfy the needs of each specific domain, has deservedan increasing attention in engineering disciplines (Shin et al.,2000).However, one needs to be aware of some dangers in the

use of virtual laboratories as teaching aids. In fact, studentshave to be carefully monitored in their tasks, so that usingthe tool just to produce ‘numbers’ ignoring the analysis ofthe simulated situations, based on conceptual models, isavoided. Moreover, it is our opinion that virtual laboratoriescan never substitute, completely, real laboratory work. It isessential that students go on receiving education in exper-imental work, though this may be directed to simple experi-mental set ups aimed at the evaluation of the physical andchemical phenomena common to chemical processes.In the case of Unit Operations, a fundamental subject in

Chemical Engineering, virtual laboratories will enable over-coming many obstacles in the traditional teaching of this sub-ject at laboratory level: limitations of time and space, safetyrisks and resources reduction. Our goal is to develop a setof computational programs for chemical processes simulationusing remote access capabilities, by means of the Internet. Inthe work to be reported here, we have chosen the simulationof multicomponent distillation systems, using the MATLABcomputational tool. The reasons that took us to select thedistillation process are as follows:

. Distillation is one of the more common unit operations inthe chemical industry accounting for 10% of the energyspent in chemical processes.

. In process simulators the distillation unit is one of the moredetailed and better known processes, being a typicalexample of the use of the equilibrium stage model (Biegleret al., 1997). The design of multicomponent distillationcolumns is a complex problem that involves iterative pro-cedures based on tedious calculations of a high numberof equations and variables. This problem is a goodexample to be solved by a computational tool. This

strategy leads the students to a better understanding ofthe cause–effect relationships between the process para-meters and, thus, allows an easier perception of thephysical phenomena behind distillation.

METHODOLOGY

The Computational Platform---MATLAB

MATLAB (MathWorks, Inc.) is a high level programminglanguage that functions under an interactive environmentwith hundred of intrinsic functions for calculus, graphics andanimations. This platform has got a package, the MATLABWebServer, which allows the use of MATLAB’s graphics,calculations and animations in HTML applications. Theseapplications are a combination of MATLAB files (M-files),HTML code and graphics. It is required to the developmentof this type of applications the knowledge of the two program-ming languages MATLAB and HTML.The MATLAB WebServer allows creating MATLAB appli-

cations that use the web capacities for sending data toMATLAB to perform calculations and to show the results onthe web browser. The MATLAB WebServer depends on thenetwork data-communication protocol TCP/IP between theMATLAB and the user’s system. In a normal configuration,the web browser runs in the user’s computer while theMATLAB, the MATLAB WebServer (matlabserver) and theweb provider (http) run in another machine, the server.

Developing the Virtual Application:Distillation Case

The application was designed to be used in tutorial classesas well as to be used by students when studying at home or inthe university campus. The main characteristics of the appli-cation developed are: to allow the remote access to severalusers; to allow performing different simulations of the unit oper-ation for a large range of operation conditions; the final user,student or teacher, does not need to have MATLAB installedin his own machine or to know about the computationallanguage, since the application runs in one single remotemachine—the server. In terms of security the access to thesystem files can be restricted, to prevent non-authorizedaccess to the source code and to the MATLAB’s commandline.Basically, the development of the application involved the

following steps:

(1) Creating of the HTML documents to collect the data inputfrom the user and to show the results.

(2) Listing the application name and configuration settingsassociated to the configuration file matweb.conf.

(3) Writing the M-file in MATLAB which performs the follow-ing steps:(a) receives the data input from the HTML input form;(b) performs the calculations and generates the graphics;(c) places the output data (results) on a MATLAB

structure;(d) calls a MATLAB function, htmlrep, to place the output

data on the output HTML file.

To the normal user, the application displays a web pagethat allows performing the simulation of a distillation columnin steady state and studying its behaviour, visualizing the

Trans IChemE, Part D, Education for Chemical Engineers, 2007, 2(D0): 1–9

2 RAFAEL et al.

design results by means of graphics and numeric tables.It was developed to allow easy operation by the user andeasiness for exporting data. It includes a database with 18entries chosen from the most common components in indus-trial applications (see Table 1), such as cyclic aromatic com-pounds, volatile hydrocarbons, alcohol compounds andwater. The thermodynamic parameters required to describethe non-ideal liquid state by applying the UNIFAC modelare also included. The maximum number of components inthe feed mixture is five, in order to prevent extremely highcalculation times and to diminish the possibility of formingcomplex mixtures, as for example azeotropic mixtures, andof obtaining impossible thermodynamic conditions.The application presents two simulation options:

(a) Firstly, to run the short-cut methods Fenske–Under-wood–Gillilland–Kirkbride (FUGK) (Douglas, 1988;Henley et al., 1981) to obtain the first estimates of thenumber of equilibrium stages, location of the feed plateand limiting operation conditions (minimum number ofequilibrium stages and minimum reflux ratio). After that,the application runs the rigorous design method ofWang–Henke (Monroy-Loperena, 2003), which solvesmaterial and energy balances combined with equilibriumrelations, for all the stages in the column. The inputvalues for the solution of the Wang–Henke method arethe results from the previous run (FUGK). In order tosolve the system of equations the program builds Nmatrixes of material balances, N being the number ofstages.

(b) To run exclusively the rigorous design method of Wang–Henke. In this case the user must insert a larger numberof input data, since in option (a) that data was suppliedby the short-cut methods.

Both options allow the user to select which components torecover in each product (top or bottom), the thermodynamicmodel for the liquid phase (ideality or non-ideality) and thetolerances for the convergence of the numerical schemesused.

Using the Virtual Application

The virtual application developed has been used in thecourse of Unit Operations (7th semester of the ChemicalEngineering degree at Coimbra University) during the lasttwo school years. Distillation is one of the chapters in thiscourse. Traditionally, students have to use computationaltools in this course, namely MATHEMATICA or MATLAB, tosolve design problems (Rasteiro et al., 2005).The distillation virtual laboratory is mainly directed to the

study of the design of the more complex cases, where multi-component feeds have to be treated.We will now describe the application in more detail, to give

the reader an idea of the features available.The virtual application has got two main sections as can be

seen in the flowsheet in Figure 1: the concepts and modellingstrategy and the simulation page.Once in the simulation page the user is led through the

data input steps, without permission to pass to the followingstep before having completed the previous step, as shownin Figure 2. The input page includes the following steps:

(1) defining the composition of the feed stream (the next stepwill only appear when the sum of the molar fractions is 1);

(2) defining simulation option A or B (FUGKþWang Henkeor just Wang Henke);

(3) defining the input data for the selected simulation option.

On a didactic perspective the suggestion is to execute simu-lation option (A) (running both short-cut and rigorousmethods)and then, after analysing the results, to execute the simulationoption (B) (running only the Wang–Henke method) in order tooptimize the operation conditions of the column (to obtain lessperturbations in the feed stage and/or less energy expendi-ture) and compare the results of both methods.The application has an invalid input detection system, to

prevent the introduction of illegal characters or unrealisticphysical conditions (such as molar fractions higher than 1or negative values), that sends error messages to the user,explaining the invalid situation. It allows going back to theprevious step or even to change the data introduced in the

Table 1. Database of chemical components.

Normal boilingpoint, Tb K21

Criticaltemperature, Tc K21

Critical pressure,Pc bar21

Acentricfactor, w

Temperaturerange, K

Methane 111.66 190.56 45.99 0.0115 354–506Ethene 169.41 282.34 50.41 0.0862 311–600Ethane 184.55 305.32 48.72 0.0994 337–600Propene 225.46 364.90 46.00 0.141 396–600Propane 231.11 369.83 42.48 0.152 405–600n-Butane 272.65 425.12 37.96 0.200 455–600Pentane 309.22 469.70 33.70 0.252 498–600Methanol 337.85 512.50 80.84 0.566 490–600Hexane 341.88 507.60 30.25 0.301 167–490Ethanol 351.44 514.00 61.37 0.644 133–481Benzene 353.24 562.05 48.95 0.210 159–523Propanol 370.35 536.80 51.69 0.620 142–4992-Butanol 372.70 536.20 42.02 0.577 160–506Water 373.15 647.13 220.55 0.345 116–600Methilcyclohexane 374.08 572.10 34.80 0.236 176–540Toluene 383.78 591.75 41.08 0.264 176–560Butanol 390.81 563.00 44.14 0.589 160–532Acetic acid 391.05 591.95 57.86 0.467 151–550


VIRTUAL APPLICATIONS USING A WEB PLATFORM TO TEACH CHEMICAL ENGINEERING 3

Figure 1. Flowsheet of the distillation virtual application.

Figure 2. Input window (adapted from window in Portuguese).


4 RAFAEL et al.

same step. Each step of the input form has a help button withseveral instructions and suggestions.After concluding the introduction of all the input data

required, the simulation can start (the simulation time cantake a few seconds or several minutes depending on thecomplexity of the feed mixture). If any of the numericalmethods does not converge, error messages are given onthe browser. The results’ page has got buttons leading tothe graphical representation of the results (temperature,pressure, flow rate and molar fractions profiles in the distilla-tion column) and also to tables with the numerical results ofeach method, as shown in Figure 3. Some numerical outputs

are immediately presented on the distillation column scheme(Figure 3).The results can be exported in several formats. The graphi-

cal images of the profiles can be stored in PS format (PostScript file) or in JPEG format. To visualize the list of numericvalues, the user has the button ‘List’. Those lists can also besaved in txt format. In a similar way, the input and outputnumerical data from each simulation option can be visualizedand stored. In general, the application allows the student todesign the equipment for the feed to be separated, for alarge range of operation conditions, in a short time. Bydoing so, the student can visualize easily the effect of the

Figure 3. Output windows (in Portuguese).

Table 2. Summary of the operating conditions tested for the separation of a benzene/water/toluene feed.

Feed

CaseBenzene(mole %)

Water(mole %)

Toluene(mole %)

Flow rate(Kmoles h21) Temp. RR/Rmin P (bar) Benzene rec. (%) Toluene rec. (%)

1 55 5 40 500 Sat. 1.3 1 98 952 55 5 40 500 Sat. 1.5 1 98 953 55 5 40 500 Sat. 1.3 0.8 98 954 55 5 40 500 Sat. 1.3 1 99 985 55 10 40 500 Sat. 1.3 1 98 956 60 0.0 40 500 Sat. 1.3 1 98 957 55 5 40 500 Cold 1.3 1 98 95



operating conditions on the design and performance of distil-lation equipment.The theory page complements the simulation page and

was constructed in order to help students to get the correctunderstanding of the distillation principles. This page pre-sents the fundamentals of distillation including the underlyingphysical principles, along with descriptions of the numericalmethods used to perform the simulations within this appli-cation, and also a list of bibliographical references. This

leads the user to better understand and analyse the resultsobtained.

RESULTS AND DISCUSSION

This application has been used in the classroom, for thefirst time, during the school year 2004/2005 in the courseof Mass Transfer Operations (Unit Operations II) at CoimbraUniversity, with around 90 students. The application was first

Table 3. Simulated results for a distillation column for the separation of a benzene/water/toluene feed.

Distillate comp. (mole %) Residue comp. (mole %)

Case Benzene Water Toluene Benzene Water Toluene D (Kmoles h21) B (Kmoles h21) RR N NF Qc (Kw) QB (Kw)

1 94.0 2.3 3.7 2.2 8.6 89.2 287.2 212.8 1.24 18 9 19 970 17 9182 94.0 2.4 3.6 2.2 8.5 89.3 287.2 212.8 1.43 16 8 21 692 19 6303 94.5 2.0 3.5 2.1 9.0 90.0 285.6 214.3 1.22 17 9 19 427 17 5864 96.9 1.9 1.2 2.4 8.9 88.7 278.1 221.9 1.52 20 12 21 656 19 5125 89.6 5.5 4.8 2.3 15.4 82.3 270.5 229.5 1.31 18 9 19 803 18 0726 97.4 0.0 2.6 1.8 0.0 98.2 304.0 196.0 1.23 18 10 20 578 18 1087 94.2 2.3 3.4 1.9 8.6 89.5 287.0 213.0 1.3 18 9 20 471 18 391

Figure 4. Output of the distillation virtual laboratory for case 1 (benzene/water/toluene feed). (a) Column scheme; (b)–(f) temperature, flowratesand composition profiles; (g) results table.


6 RAFAEL et al.

introduced in a tutorial class. The main features of the appli-cation were presented and its potentialities were exploited byperforming simulations of some case-studies. The influenceon the design of the column of changing such parametersas feed temperature; operating pressure; reflux ratio; purityof the products, and so on, was exploited. This allowed abetter visualization of the influence of operating conditionson the dimensioning of a distillation column. The resultswere discussed with the students in the class.As referred, the students had already been exposed in

tutorial classes to the use of computational tools to solvesmall design problems. In previous years we have beenusing MATHEMATICA for that purpose (Rasteiro et al.,

2005) though, more recently, since 2004/2005, we startedusing MATLAB. We start first with a class in the computersroom recalling the facilities of MATLAB, where students(15–18 per class) are organized in groups of three, andthen they go on using MATLAB to solve vapor/liquid equili-brium problems and simplified binary distillation designproblems.It is only when we move to more complex multicomponent

distillation problems that the ‘Virtual Laboratory for Distilla-tion’ is introduced only after the basic notions have beengiven in the theory lectures. After the first introductory ses-sion on the Virtual Laboratory in the lecture class, with allthe students present, the students will also have to use thetool in the tutorials (around 20 students per class) to solve

Figure 4. Continued

Figure 4. Continued



some design problems which are discussed among them-selves and with the teachers.After the first sessions, the students have free access to

the application in the computer rooms, and even fromhome, and can use it as a tool to better understand distillationprinciples. Moreover, the students can also use the virtualapplication to test their own computational programs, basedon the Matlab software, to simulate the distillation of multi-component mixtures. This project has been proposed to thestudents for quite sometime, in the aforementioned course,as project work, though it is possible that, in the nearfuture, in the new curriculum that is being designed to fulfillwith the Bologna Declaration, the project work will becomeoptional, since it is necessary to compromise to give timeto other subjects that are becoming important in ChemicalEngineering, like, for instance, the bio-fields. In this case,the need for virtual applications like the ‘Distillation VirtualLaboratory’, that allows the students to contact with morecomplex and realistic engineering problems, on their own,will become altogether more imperative.

Simulation Examples

In this section an example of a distillation design problemsolved using the virtual laboratory, will be presented, tobetter illustrate the capabilities of this application.Table 2 summarizes the problem formulation. The objective

is to separate a benzene/toluene mixture, where water ispresent as an impurity, in order to obtain a distillate rich inbenzene and a residue rich in toluene. The column isequipped with a total condenser and a partial reboiler andthe reflux has been assumed saturated.The effect, on the column design, of changing the reflux

ratio, recovery of the two main components (benzene and

toluene), operating pressure and percentage of the impurityin the feed stream, has been studied.Table 2 summarizes the different conditions tested and

Table 3 gives the simulation results obtained. In Figure 4we present the outputs obtained with the virtual applicationdeveloped (temperature profile, both liquid and vapor flowrate profiles, composition profiles and table results usingboth the FUGK and the rigorous Wang–Henke methods),just for case 1 in Table 2.In Tables 2 and 3 and in Figure 4 the variables have the fol-

lowing mean: RR is the reflux ratio; D, B, L, V and F are thedistillate, residue, liquid, vapour and feed flowrates, respect-ively; LK and HK are the light and heavy keys, respectively;NT is the total number of stages, NF is the feed stage, P isthe operating pressure, Qc is the heat removed in the con-denser and QR is the heat supplied in the reboiler.This example shows clearly how the student can easily see

the implications on the column design of changing the differ-ent operating parameters. These results can be used in theclass room to provoke discussion among the differentgroups. This discussion will then be directed by the teacherto the fundamentals of distillation (vapour/liquid equilibrium,mass and energy transfer principles).

Assessing the Use of the Applicationin the Classroom

After this first year of using the ‘Virtual Laboratory’ the gen-eral opinion of the students was quite positive. The studentsstressed both the benefits to the understanding of distillation

Figure 4. Continued

Figure 4. Continued


8 RAFAEL et al.

fundaments and to an easier development of each group dis-tillation project. These opinions were collected in an oral dis-cussion with each group, no formal survey having beenconducted. It must also be mentioned that the overall passrate in the course on Mass Transfer Operations increasedfrom the usual average of 60%, in previous years, to 85%in 2004/2005 and to 70% in 2005/2006 (Chemical Engineer-ing students).

CONCLUSIONS

The application here presented refers to a Web-basedinteractive virtual system to integrate, in the teaching ofChemical Engineering, the new technologies and compu-tational tools. We believe that there are several benefits onthe use of these applications: it stimulates the students to for-mulate new operation conditions for the simulation of processunits and surpasses several obstacles on performing labora-torial experiments.The computational tool selected, MATLAB WebServer,

allows the application to be employed in class context andto be used by students as a tool in individual study.Regarding the distillation case study, this application allows

the students to learn actively and to acquire knowledge byinteracting with the system, by means of the Internet, withouttime and space restrictions. They can combine an infinity ofinput parameters, each student carrying out different simu-lations. In addition, the students can study and visualize theeffect of changes in the process parameters and initial con-ditions on the distillation column design and performance.The students can repeat the simulation several times and dis-cuss the results among them, what can lead them to higherlevels of understanding about the distillation process. Thus,

the application offers a good environment to illustrate awide range of situations and to stimulate discussion amongthe students. Moreover, it allows an easy graphical represen-tation of the column profiles and of the numerical results,which then become more perceptive to students.

REFERENCESBiegler, L., Grossman, I. and Westerberg, 1997, Systematic Methods

of Chemical Process Q1Design (Prentice Hall, Englewood Cliffs,USA).

Clement, J., 1982, Student’s preconceptions in introductory mech-anics, Am J Phys, 50: 66.

Dede, C., 1995, The evolution of constructivist learning environ-ments: Immersion in distributed virtual worlds, Educational Tech-nology, 35: 46.

Douglas, J., 1988, Conceptual Design of Chemical Processes(McGraw-Hill, New York, NY, USA).

Henley, E., Seader, E. and Rasmussen, 1981, Equilibrium-StageSeparation Operations in Chemical Q2Engineering (John-Wiley &Sons, New York, NY, USA).

Monroy-Loperena, R., 2003, Simulations of multicomponent multi-stage vapour-liquid separations. An improved algorithm using theWang-Henke tridiagonal matrix method, Ind Eng Chem Res,42(1): 175.

Palanki, S. and Kolavennu, S., 2003, Simulation of control of a CSTRprocess, Int J Eng Ed, 19(3): 398.

Rasteiro, M.G., Bernardo, F.P. and Saraiva P.M., 2005, Using MTHE-MATICA to teach process units: A distillation case study, Che EngEducation, Spring: 116.

Shin, D., Yoon, E., Sang, J. and Lee, E., 2000, Web-based interactivevirtual laboratory system for unit operations and process systemsengineering education, Computers & Chemical Engineering, 24:1381.

The manuscript was received 3 March 2006 and accepted forpublication after revision 27 November 2006.



ECE06007Queries

A. C.Rafael, F.Bernardo, L.M. Ferreira, M.G. Rasteiro and J.C. Teixeira

Q1 Inital for Westerberg?

Q2 Initial for Rasmussen?

Documents

VIRTUAL APPLICATIONS USING A WEB PLATFORM TO …chem.engr.utc.edu/Webres/Dist/ECE06007.pdf · A WEB PLATFORM TO TEACH CHEMICAL ENGINEERING: THE DISTILLATION CASE ... simulation of