Table Of Content> OS_X_Noir
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Jean-Charles de HEMPTINNE
Research Engineer, IFP Energies nouvelles
Professor, IFP School
SELECT
THERMODYNAMIC MODELS
FOR PROCESS SIMULATION
A Practical Guide using
a Three Steps Methodology
2012
Editions TECHNIP 25 rue Ginoux, 75015 PARIS, FRANCE
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FROM THE SAME PUBLISHER
•The Geopolitics of Energy
J.P. FAVENNEC
•Heavy Crude Oils. From Geology to Upgrading. An Overview
A.Y. HUC(Ed.)
•Geomechanics Applied to the Petroleum Industry
J.F. NAUROY(Ed.)
•CO Capture
2
Technologies to Reduce Greenhouse Gas Emissions
F. LECOMTE, P.BROUTIN, E. LEBAS
•Corrosion and Degradation of Metallic Materials
Understanding of the Phenomena and Applications in Petroleum
and Process Industries
F. ROPITAL
•Multiphase Production
Pipeline Transport, Pumping and Metering
J. FALCIMAIGNE, S. DECARRE
•A Geoscientist’s Guide to Petrophysics
B. ZINSZNER, F.M. PERRIN
•Acido-Basic Catalysis (2vols.)
Application to Refining and Petrochemistry
C. MARCILLY
•Petroleum Microbiology (2 vols.)
Concepts. Environmental Implications. Industrial Applications
J.P. VANDECASTEELE
•Physico-Chemical Analysis of Industrial Catalysts
A Practical Guide to Characterisation
J. LYNCH
•Chemical Reactors
From Design to Operation
P. TRAMBOUZE, J.P. EUZEN
•Petrochemical Processes (2 vols.)
Technical and Economic Characteristics
A. CHAUVEL, G. LEFEBVRE
•The Technology of Catalytic Oxidations (2vols.)
P. ARPENTINIER, F. CAVANI, F. TRIFIRO
•Marine Oil Spills and Soils Contaminated by Hydrocarbons
C. BOCARD
All rights reserved.
No part of this publication may be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopy, recording, or any information storage and retrieval system, without the
prior written permission of the publisher.
© Editions Technip, Paris, 2012.
Printed in France
ISBN 978-2-7108-0949-4
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Foreword
This user guide is not designed as a thermodynamics textbook. Many very good thermody-
namic handbooks exist for helping teachers in designing a course in a logical, linear fashion
(Elliot & Lira [1], Prausnitz et al. [2], Smith & Van Ness [3], O’Connell [4], Vidal [5]…).
Teachers can use this document as suggested below, but will be disappointed by the lack of
demonstrations, and the non-linear conception of the logic.
This manual is not either a review of the existing thermodynamic models, that would
help developers in understanding and code the most adapted model to their situation. Other
authors have made a significant effort in summarising the models in a logical fashion,
stressing their strengths and weaknesses and providing indications on how they should be
coded, if needed (Poling et al. [6]; Kontogeorgis & Folas [7]; Mollerup & Michelsen [8];
Riazi [9]…). Thermodynamic experts will be disappointed by the lack of completeness, of
numerical parameters and of algorithmic analysis.
Rather, our purpose is to provide a vademecum that should help the practicing engineer
in finding the right questions to answer when faced with a novel type of thermodynamic
problem: when the questions are correctly stated, the answer is half on its way.
The construction of the book, that may seem awkward at first, is designed for this
purpose. It is constructed on three pillars (chapters 2, 3 and 4) that each represent a different
point of view converging to the same goal: the development of an adequate thermodynamic
set of models for an industrial problem. We believe that in order to analyse completely a
physical modelling problem, these three pillars must be correctly mastered (figure 0.1):
1. understanding the fundamental principles,
2. use of the available mathematical models, and
3. knowledge of the system physical (phase) behaviour.
The domain of application that is aimed is petroleum and energy process design. Yet,
readers working in other fields of chemical engineering may also find interesting topics.
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VIII Foreword
Thermodynamics universal equations
Properties
Components Phases
Methods - Models - Data Choice of models in each phase
Figure 0.1
Triangular representation of the fundamental questions in thermodynamic
problem-solving.
BOOK STRUCTURE
The first chapter goes into the details of the philosophy of the approach. The main
messages we want to carry here is:
• A thermodynamic method may contain many different models (as in the image of the
Russian doll); each of which has to be parameterised. The origin of the parameters is
at least as important as the choice of the model.
• The three questions that will help the engineer solve his problem concern the relevant
properties of his process, the type of mixture he has and the phases he might encounter.
The second chapter summarises some of the basic principles of thermodynamics (what
O’Connell [4] calls ‘Always True’). It is written so that most concepts and equations that the
chemical engineer may need are provided in a very concise form. It contains two main
sections:
• How to read and understand a phase diagram, using Gibbs phase rule?
• How are the fundamental thermodynamic principles used for calculating engineering
properties? This results in a rather short presentation of residual properties, excess
properties, and a few algorithmic aspects on phase equilibrium calculation. Chemical
equilibrium is also touched upon.
The third chapter is the heart of this book. Rather than providing an exhaustive list of
thermodynamic models, it emphasises the use of these models, starting from the concept of
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Foreword IX
the fluid composition. In fact, this composition must be regarded as a set of parameters to be
used with the chosen mathematical model. The link between this parameter + equation
combination and the true physical behaviour is performed through a comparison with exper-
imental data. This should explain the construction of the third chapter that has three parts:
• It starts with the description of experimental information: section 1 discusses pure
components; section 2 discusses mixtures. The third section illustrates how this exper-
imental information is used for parameter estimation using data regression.
• In section 4, the actual thermodynamic models are summarised. No effort was made
to be exhaustive (the user is in principle limited to what his process simulator pro-
vides), but it was rather attempted to help the reader make the link between the molec-
ular structure of the fluid phase and the significance of the parameters values.
• In a final, short but important section, the concept of key component is introduced.
The sensitivity of the requested type of information to some parameters may be much
larger than to others. Some guidelines are provided here to help the engineer focus his
attention on the most important parameters (i.e. key components or key binaries).
The fourth chapter puts the modelling issue in the perspective of the true physical
behaviour of a physical system. The phase behaviour depends greatly on the type of mixture
that is considered. This is why a number of important industrial mixtures are discussed. For
each system, some model recommendations are suggested. The discussion is organised in
two main parts:
• First, the property behaviour is discussed through some thermodynamic diagrams. As
phase properties are considered qualitatively independent of the fluid composition,
the example of pure CO is used.
2
• Second, the phase diagrams are analysed in some details. Here, the varying complex-
ity of several types of mixtures is shown.
The true originality of our approach is presented in the final, fifth chapter. It both
concludes the theoretical part of this endeavour (which is the book), and introduces the prac-
tical part that will be proposed on the web. The intention is to publish electronically a
number of case studies that illustrate industrial examples that have been treated at IFP Ener-
gies nouvelles. The solution pattern will follow as closely as possible the approach
suggested in this fifth chapter.
The same final chapter also lists some important industrial processes in order to guide
the engineer in his problem-analysis.
HOW TO READ THE BOOK
As a result of the construction of the book, numerous cross-references are unavoidable. This
may puzzle the reader who wants to start from the beginning and end at the final chapter. We
apologise for this and we have made all our possible to make it readable in various modes.
This has led us to re-state some items in different chapters.
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X Foreword
Mode 1: The teacher
Even though this is not a textbook, the essential features for an advanced thermodynamics
course are available. The main message of this course is condensed in the third chapter of
the book. Nevertheless, several years experience have shown that some basics must be
reviewed in order to make clear the links between the models (chapter 2), and that the
physical picture must continually be kept in mind (chapter 4) in order to avoid that the
student only looks at the mathematical relationships. This is why we suggest trying alter-
nating physical understanding and modelling approach:
1. Discuss single phase properties:
a. We suggest starting with reading diagrams. Section 2.1.3 provides some basics on
the phase diagram, and section 4.1 discusses concretely how the various properties
behave with pressure and temperature for a pure component.
b. Discussion of the diagrams should lead the students to ask himself how these pro-
perties are calculated. This is discussed in section 2.2.2. The definition of the pro-
perties (section 2.1) and the fundamental relationships (section 2.2.1) are available
if needed for detailed questions. At this first stage, it is good to stress the residual
approach and the corresponding states principle, which are essential in most appli-
cations (as an example, we can refer to the Lee-Kesler method, section 3.4.3.3.).
c. Now models have been introduced, it may be worth discussing the parameterisa-
tion of these models (i.e. how does one find the correct parameters considering the
information available on the components). This is presented in section 3.1.
2. Discuss mixture vapour-liquid phase diagrams:
a. Concerning phase diagrams, section 2.1.3 provides the basics of how an isothermal
or an isobaric phase diagram should be read. The starting point should consist in
illustrating Raoult’s law, and, for mixtures with supercritical components, Henry’s
law. The theory of the asymmetric convention is discussed in some length in sec-
tion 2.2.3.1, but it is probably of more use at this point to go to the Rachford-Rice
equation (section 2.2.3.2) in order to allow some simple calculations.
b. Non-ideality can be introduced next, with some example phase diagrams discussed
in section 4.2.1 that goes more into the details of the various types of diagrams (un-
derstanding the significance of three-phase lines is generally not very simple).
3. Equations of state:
a. Now the phase behaviour is understood, it may be of interest to introduce the cal-
culation mode in a more general way (‘always true’) by defining fugacity and fu-
gacity coefficient (sections 2.2.1.2 and 2.2.3.1). The link with the Rachford-Rice
equation, previously seen, becomes then clear.
b. It is now possible to move to the third chapter, and present in some detail the equa-
tions of state. The first step (because most often used) is to illustrate the cubic
equations of state (section 3.4.3.4).
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Foreword XI
4. Activity coefficient models:
a. The models can be introduced in two stages: first, discuss the significance of ex-
cess properties (section 2.2.2.2), then illustrate what is the impact of the activity
coefficient on the phase diagrams (section 3.4.1).
b. At this stage, the list of the activity coefficient models can be shown, as in section
3.4.2.
5. Now that all the basics are laid, the applications can be discussed one by one, with the
model recommendations for each case (section 4.2). If more complex models are needed (as
Huron-Vidal mixing rules or SAFT type equations), they should be introduced in good
order, as referred to in chapter 3.
Mode 2: The student
The student obviously should follow the guidelines of his teacher, but he may find attractive
the fact of finding the main concepts of chemical engineering thermodynamics separated in
the three main chapters:
• Chapter 2 teaches what is ‘always true’. Hence, all concepts and equations presented
in that chapter can be applied in virtually all cases.
• Chapter 3 describes the most important thermodynamic models that can be found in
commercial simulators. It will teach the approximate mathematical relationships that
have been developed over the years for inter- or extrapolating the observed physical
behaviour.
• Chapter 4 may seem of less interest from the student’s point of view, as he is more
often concerned with understanding the mathematical relationships than in viewing
the actual complexity of the real world. Yet, this chapter illustrates that thermodynam-
ics is in fact a physical science and that the numbers that can be generated through the
model equations are to be compared with everyday observations.
Mode 3: The engineer
The book is really designed for the engineer. He should consider this as a working tool,
which he can consult in all directions he wants using the many cross-references.
Most probably, he will start from the end, as he should recognise in the final (fifth) chapter
some concerns he has when designing or upgrading process units. Chapter four should also
help him identify the expected phase behaviour of his system and selecting the adequate model.
Unless he has been guided further in the other chapters through the cross-references, he
could stop at this point. Yet, he may be really concerned with either accuracy or predictive
power, in which case he will have to go to the third chapter which will teach him what experi-
mental data are relevant to his problem and to which parameters it is most sensitive.
The second chapter will most likely be of less interest to him, unless he wants to better
understand how the models are used for calculating the final properties, and what assump-
tions have gone into their choice.
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XII Foreword
CONCLUSION
As a conclusion, we hope that this book will be of use to many process engineers. It has been
designed as a practical guide, and the reader is welcome to contact the main author for
suggesting improvements and practical examples of use. An accompanying website is
available where case studies will be proposed, which may be of help to the process engineer
(http://books.ifpenergiesnouvelles.fr/ebooks/thermodynamics). New case studies will be
added over time, so as to illustrate that the approach proposed in the book is applicable for a
large range of conditions and processes.
Jean-Charles de Hemptinne
Jean-Marie Ledanois
Pascal Mougin
Alain Barreau
REFERENCE LIST
[1] Elliott, J.R. and Lira, C.T. “Introductory Chemical Engineering Thermodynamics”, Prentice
Hall PTR, Upper Saddle River, NJ, 1999.
[2] Prausnitz, J.M., Lichtenthaler, R.N. and Gomes de Azevedo, E. “Molecular Thermodynamics of
Fluid Phase Equilibria”, 3rd Ed., Prentice Hall Int., 1999.
[3] Smith, J.M., Van Ness, H.C. and Abbott, M.M. “Introduction to Chemical Engineering Thermo-
dynamics”, Sixth Edition, McGraw-Hill, Inc., New York, 2001.
[4] O’Connell, J.P. and Haile, J.M. “Thermodynamics: Fundamentals for Applications”, 1st Ed.,
Cambridge University Press, 2005.
[5] Vidal, J. “Thermodynamics: Applications in Chemical Engineering and the Petroleum Industry”,
Editions Technip, Paris, 2003.
[6] Poling, B.E., Prausnitz, J.M. and O’Connell, J.P. “The Properties of Gases and Liquids”,
5th Ed., McGraw-Hill, New York, 2000.
[7] Kontogeorgis, G.M. and Folas, G.K. “Thermodynamic Models for Industrial Applications:
From Classical and Advanced Mixing Rules to Association Theories”, Wiley, 2010.
[8] Michelsen, M.L. and Mollerup, J. “Thermodynamic Models: Fundamental and Computational
Aspects”, 1st Ed., Tie-Line Publications, 2004.
[9] Riazi, M.R. “Characterization and Properties of Petroleum Fluids”, American Society for Test-
ing and Materials, Philadelphia, 2005.
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Preface
In this “Practical Guide to Thermodynamics”, the authors have provided a unique resource
for practitioners, teachers and students for both understanding and use. The presentation has
an orderly presentation of the developments from fundamentals to application case studies,
as well as detailed guidance about specifying thermodynamic property problems and
efficient, effective methods to solve them. The steps from the fundamentals of thermody-
namics to properties, from properties to models, and from models to methods, are explicitly
shown with rigorous derivation and solutions for realistic example situations. Their
problem-solving procedure guides learners and users through the complex set of decisions to
be made in order to achieve maximum accuracy and reliability of the desired results. This
Guide’s contents are far more than a manual; the perceptive user will also gain both
pragmatic skills and valuable confidence to meet the challenges of obtaining thermodynamic
and transport properties, as well as phase and reaction equilibria, in contemporary and future
chemical technologies.
John P. O’Connell, University of Virginia
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Table of Contents
Preface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
Foreword. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VII
Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XIII
Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XV
List of authors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXI
Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XXIII
Chapter 1
INTRODUCTION
1.1 Identify the right physics in process simulation. . . . . . . . . . . . . . . . . . . . . . 2
1.2 What is a thermodynamic method?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.1 The physical model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2.2 The algorithm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.3 The data: properties or parameters? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3 Criteria for problem analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.1 What property is given/requested? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3.1.1 Thermodynamic properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3.1.2 Phase equilibrium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3.1.3 Chemical equilibrium. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.3.2 What are the mixture components?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.3.2.1 What type of components are considered? . . . . . . . . . . . . . . . . . . 13
1.3.2.2 What is the mixture non-ideality? . . . . . . . . . . . . . . . . . . . . . . . . 13
1.3.2.3 What is the key component concentration range? . . . . . . . . . . . . . 15
1.3.3 Where are the process conditions located with respect to the phase envelope?. . 16
1.3.3.1 Nature of the phases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.3.3.2 Pressure- temperature conditions. . . . . . . . . . . . . . . . . . . . . . . . . 17
1.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Reference List. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
