Romanian International Conference on Chemistry and Chemical Engineering – RICCCE XIV
Phase Equilibria Database and Calculation Program for Pure Component Systems and
Mixtures
Dan Geană ∗ , Liviu Rus
Department of Applied Physical Chemistry and Electrochemistry, Polytechnic University of
Bucharest, 1 Polizu Street, 011061 Bucharest, Romania
Abstract
The importance and role of phase equilibria are related to plant design, safety, reliability,
operation in chemical and biochemical engineering. For an effective and efficient utilization
of large amounts of phase equilibrium data in chemical and biochemical engineering, an
intelligent database program for phase equilibrium (PHEQ) data management and application
was developed. PHEQ program enables the extraction of data and results so that the timeconsuming data management, data processing and analysis are avoided. Furthermore,
calculation programs of phase equilibrium based on the most reliable models were
implemented. PHEQ Windows allows users to set up problems and to carry out calculations
in a simple and rapid manner. It provides access to all PHEQ facilities and can produce output
as text files, graphics or Excel worksheets.
Introduction
Phase equilibria software has been developed in our laboratory since long time. The first
calculation programs were written in 1984, and used for pressure-volume-temperature (PVT)
and phase equilibria calculations with the general cubic equation of state.1
In 1995, the calculation programs, rewritten in FORTRAN 77, and running under Windows
95, were coupled with databases. The software for binary vapor-liquid equilibria calculations,
called VLE 95, was used in our department and in other research groups, by doctorands and
students both as learning and research tool. Special programs coupled with corresponding data
bases were used for calculations.
A project (called PHEQ – Phase Equilibria Database and Calculation Programs) was started to
develop software using modern features of the last Windows programs (2000, Me and XP),
∗
d_geana@chim.upb.ro
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databases applications (MS Access, Visual Basics), and Fortran programming (Compaq
Visual Fortran Compilator).
The first product of the PHEQ project, is a software package to manage a database for pure
component, binary and ternary/multicomponent VLE experimental data which can be
supplied by the user, and the application programs for correlation and/or prediction of phase
behaviour of the three types of systems. Graphical output is integrated in the software, in
order to provide plots of phase diagrams, and tools to export calculated and experimental
information to other software like Word or Excel. The database software was programmed
under Visual Basic 6.0. Special programs coupled with corresponding data bases were
implemented for calculations of pure-component properties by equations of state2,3 (LVV1
and LVV1DT). For binary phase equilibria systems a series of programs were developed,
based on GE models (GAMMA, UNIFAC) for low pressures or on EOS at high-pressures4,5
(GEOSK2, HVID). Other programs were developed for calculations of ternary systems and
three-phase equilibria6 (GEOSPH3), as well as for critical lines calculation of mixtures
(CRIMIX). All calculation programs are Compaq Visual Fortran 6.6 compiled Windows
versions.
Database and application program PHEQ
Fig. 1 shows the main screen of intelligent database program developed in this project. An
intelligent data base program written in Visual Basic 6.0 has been constructed under fully
compatibility with Windows XP for the continuous upgrade version and the effective
interface with users. The Pentium 4 PC was used to build and run the database program and
applications. Fig. 2 shows the initial screen image for the pure component data base and
applications (called TERMOD1) where we can pick up all the related information, applicable
code and associated data managment. A toolbar serves as a foundation for the higher levels
convenient access to the database, interactive and automated data set selection and
calculations. This software may be used in relation to MS-Office (Word, Excel, PowerPoint
and Access). Basically, the software MS Access is used for the implementation of the
database as shown in the Fig. 3. Tables, queries and forms are the main parts of the database.
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Fig.1. Main screen of PHEQ database program
Fig.2. Screen image for the pure component data base and applications (TERMOD1)
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Fig. 3. Access database used by the PHEQ program
The database form for binary VLE data (called VLE2) is shown in Fig. 4. Using the sorted
VLE data, it can be used to analyze and visualize the data and to offer the support for
application of VLE models.
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Fig.4. Screen image for the binary VLE database and applications (VLE2)
Fig.5. Database form for ternary VLE data and calculations (VLE3)
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Fig. 6. Enthalpy-pressure diagram of CO2 in PHEQ program. Points are literature data, and
lines are calculations with GEOS3C EOS.
Fig. 5 shows database form for ternary VLE data (called VLE3). An example of the results
analysis is shown in Fig. 6, for the calculation of enthalpy-pressure diagram of CO2. Fig. 7
shows another example of the output of PHEQ program, for a binary P-X-Y phase diagram of
the high-pressure ethane-butane system. The Fig. 8 presents a graphic output of a ternary VLE
diagram of the high-pressure methane-butane-decane system at 344.15 K and 27.58 bar.
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Fig. 7. Binary P-X-Y phase diagram of the ethane-butane system at 323.15 K. Symbols are
experimental data and lines are calculations by GEOS3C equation of state
The calculation of different problems of phase equilibria is the main task in applications of the
PHEQ package. Several equations of state have been evaluated to determine their accuracy in
predicting and correlation of phase equilibria. GEOS, as a general cubic equation of state was
used in computer programs, allowing the particular specification of many popular cubic forms
like Soave-Redlich-Kwong EOS (SRK), Peng-Robinson EOS (PR). Non-cubic equations of
state are also implemented in computer codes, like PHSGEOS a perturbed hard-sphere
model7.
Concluding remarks
The PHEQ software is an intelligent Windows-based package for the management of large
amounts of phase equilibrium data, involving three types of systems (pure components, binary
mixtures and ternary/multicomponent mixtures) and calculation programs for the correlation
and/or prediction of phase behavior of the above systems. The project enables to develop the
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program at three software levels: the intelligent user friendly interface, calculation programs
for phase equilibria problems, implementing the new models (our and from the literature), and
the data base with the considered types of systems.
Phase equilibrium data and applications can be easily added for subsequent operation of
PHEQ program. PHEQ program enables the prompt extraction of data and facilities for
analysis of calculation results.
Fig.8. Graphic output of a ternary VLE diagram of the high-pressure methane-butane-decane
system at 344.15 K and 27.58 bar
Furthermore, development of the software in Visual Basic.Net is intended, as well as new
calculation programs to integrate the last models and algorithms appeared in literature.
Several similar packages are available. A program, called PE (Phase Equilibria) was
developed at Technical University Hamburg-Harburg, since 1985, in the group of the
professor Gerd Brunner.8 The last free versions, after 1998, run on PC under Windows 98,
NT, Me, XP. Another program9, called MULTIFLASH is commercially available, by the firm
INFOCHEM, Computer Services Ltd, UK. A third package10, called COSMOTHERM, is
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commercially available, by the firm COSMOlogic GMBH, De. More or less elaborated
programs for phase equilibria calculations can be found on many sites in Internet.
References
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4. V. Feroiu, D. Geană,
Fluid Phase Equilib. 1996, 120(1-2), 1 – 10.
5. D. Geană, V. Feroiu, Ind. Eng. Chem. Res., 1998, 37, 1173 – 1180.
6. M. Drescher, O. Seidel, D. Geană, J. Supercrit. Fluids 2002, 23(2), 103 – 111.
7. D. Geană, Proc. Rom. Acad., Series B, 2003, 5(1-2), 3 – 10.
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H. Utz Vlg., München, 1998.
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Equilibrium Modelling, Equilibrium Prediction, Flash Routines, hydrates, waxes,
asphaltenes modelling, www.infochem.uk, 2004.
10. A. Klamt, F. Eckert, Fluid Phase Equilibria, 2000, 172, 43-72.
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