Select thermodynamic models for process simulation
A Practical Guide to a Three Steps Methodology

Table of Contents

Chapter 1: Introduction

1 1 Identify the right physics in process simulation

1 2 What is a thermodynamic method?

1 2 1 The physical model

1 2 2 The algorithm

1 2 3 The data: properties or parameters?

1 2 4 Conclusions

1 3 Criteria for problem analysis

1 3 1 What property is given/requested?

1 3 2 What are the mixture components?

1 3 3 Where are the process conditions located with respect to the phase envelope?

1 4 Conclusions

Reference List

Chapter 2: From Fundamentals to Properties

2 1 Properties, states and phases

2 1 1 Properties

2 1 1 1 Volume
2 1 1 2 Pressure
2 1 1 3 Temperature
2 1 1 4 Entropy
2 1 1 5 Energies

2 1 2 Thermodynamic state

2 1 3 Gibbs’ phase rule, or how to read a phase diagram

2 1 3 1 Pure component application
2 1 3 2 Binary systems
2 1 3 3 Three phases Txy or Pxy diagrams
2 1 3 4 Ternary mixtures
2 1 3 5 Multicomponent system

2 1 4 Duhem’s phase rule (theorem)

2 2 Property computation

2 2 1 Some fundamental relationships

2 2 1 1 System properties
2 2 1 2 Phase properties
2 2 1 3 Mixture
2 2 1 4 Property of a pure component in a phase

2 2 2 Calculation of single phase “thermodynamic” properties

2 2 2 1 Residual approach (equations of state)
2 2 2 2 The excess approach (activity coefficients)

2 2 3 Phase equilibrium

2 2 3 1 Some basic principles for phase calculations
2 2 3 2 Practical applications of phase equilibrium

2 2 4 Chemical equilibrium

2 2 4 1 Basic principles for chemical equilibrium calculations
2 2 4 2 Model requirements for chemical equilibrium

Reference List

Chapter 3: From Components to Models

3 1 Pure Components: properties and parameters

3 1 1 Pure component properties and parameters

3 1 1 1 Physical properties as model parameters
3 1 1 2 Temperature dependent physical properties

3 1 2 Types of component

3 1 2 1 Database components
3 1 2 2 Non-database components (group contribution)
3 1 2 3 Petroleum fluid components

3 1 3 Screening methods for pure component property data

3 1 3 1 Internal check
3 1 3 2 External check

3 2 Mixtures: properties and parameters

3 2 1 Vapour-liquid equilibrium data

3 2 1 1 TPx (isobaric or isothermal)
3 2 1 2 Gas solubility
3 2 1 3 TPxy (isobaric or isothermal)

3 2 2 Liquid-liquid equilibrium data

3 3 Data fitting

3 3 1 General guidelines

3 3 1 1 Choosing the model
3 3 1 2 The parameters to be adjusted
3 3 1 3 The data
3 3 1 4 The objective function
3 3 1 5 The weighting factor
3 3 1 6 The initial values
3 3 1 7 Optimisation algorithm
3 3 1 8 The resulting uncertainties on the parameters

3 3 2 Detailed examples

3 3 2 1 Vapour pressure fit 3 3 2 2 VLE fit

3 3 3 Conclusion

3 4 Models for the mixture properties

3 4 1 Prediction of some phase diagrams using the infinite dilution activity coefficients 160

3 4 1 1 Positive and negative deviations from ideality
3 4 1 2 Azeotropy
3 4 1 3 Liquid-liquid equilibria
3 4 1 4 Conclusion

3 4 2 Activity models, or how the molecular structure affects the non-ideal behaviour 171

3 4 2 1 Enthalpic vs entropic contributions
3 4 2 2 Enthalpic deviation from ideality
3 4 2 3 Entropic deviation from ideality (athermal solutions)
3 4 2 4 Mixed enthalpic and entropic deviation from ideality
3 4 2 5 Electrolyte models
3 4 2 6 Conclusion on activity coefficient models

3 4 3 Equations of State, EoS (all fluid phases)

3 4 3 1 Introduction on the use of equations of state
3 4 3 2 Molecular basis for Equations of State
3 4 3 3 Virial equations of state
3 4 3 4 The cubic equations of state
3 4 3 5 The SAFT family equations of state
3 4 3 6 The lattice fluid equations of state
3 4 3 7 Conclusions for equations of state

3 4 4 Phase-specific models

3 4 4 1 Pure solid phases
3 4 4 2 Hydrates
3 4 4 3 Properties at infinite dilution
3 4 4 4 Gases in hydrocarbons: Grayson and Streed

3 5 What are the key components concentration range?

3 5 1 Phase appearance or phase envelope calculations

3 5 1 1 Vapour-Liquid Equilibrium (VLE) calculations
3 5 1 2 Liquid-Liquid Equilibrium (LLE) calculations
3 5 1 3 Liquid-Solid Equilibrium (LSE) calculations

3 5 2 Distribution coefficients calculation

3 5 2 1 Simple distillation
3 5 2 2 Azeotropic distillation
3 5 2 3 Impurities

Reference List

Chapter 4: From Phases to Method (Models) Selection

4 1 Single phase properties

4 1 1 PVT plot

4 1 2 Enthalpy and entropy plots

4 1 3 Derived properties

4 1 3 1 Heat capacities
4 1 3 2 Joule Thomson coefficient
4 1 3 3 Speed of sound

4 1 4 Model recommendations

4 1 4 1 Use of the one-fluid approximation
4 1 4 2 Use of mixing rules and excess properties

4 2 Phase equilibrium behaviour of industrially significant mixtures 264

4 2 1 Phase equilibrium classification

4 2 1 1 Fluid phases equilibrium
4 2 1 2 Fluid-solid equilibrium

4 2 2 Phase equilibrium in organic (hydrocarbon) mixtures

4 2 2 1 Vapour-liquid equilibrium in organic mixtures
4 2 2 2 Liquid-liquid in organic mixtures
4 2 2 3 Fluid-solid equilibrium in organic mixtures
4 2 2 4 Asphaltene precipitation

4 2 3 Phase equilibrium in presence of H2 or other supercritical gases

4 2 4 Phase equilibrium in presence of an aqueous phase

4 2 4 1 Fluid phase equilibrium
4 2 4 2 Solubilities
4 2 4 3 Fluid-Solid phase equilibrium (ice and hydrates)

4 2 5 Phase equilibrium in presence of CO2/H2S

4 2 5 1 CO2 and H2S with hydrocarbons at high pressures
4 2 5 2 CO2 and H2S solubilities in liquid hydrocarbons
4 2 5 3 Phase equilibria of industrial solvents with CO2 and H2S 310

4 2 6 Phase equilibrium in the presence of molecules containing heteroatoms (e g oxygenated)

4 2 6 1 Polar interactions
4 2 6 2 Hydrogen bonds: auto-association
4 2 6 3 Effect of cross-association

4 2 7 Other systems of industrial interest

4 2 7 1 Polymers
4 2 7 2 Ionic liquids

4 3 Conclusions: how to choose a model

4 3 1 The right questions

4 3 1 1 What is the property of interest?
4 3 1 2 What is the fluid composition?
4 3 1 3 What are pressure and temperature conditions of the process? 326

4 3 2 Decision Tree

Reference List

Chapter 5 - Case Studies

5 1 Problem Solving Procedure

5 1 1 Evaluation of the most appropriate model(s)

5 1 1 1 Properties required
5 1 1 2 Fluid composition
5 1 1 3 Representative phases

5 1 2 Search for the most significant physical data

5 1 3 Evaluation of the result

5 2 Review of major process problems

5 2 1 Flash separations

5 2 2 Simple distillation (continuous or batch)

5 2 3 Close volatility distillation

5 2 4 Extractive distillation

5 2 5 Azeotropic distillation

5 2 6 Liquid-liquid decant vessel

5 2 7 Stripping (vapour-liquid extraction)

5 2 8 Natural gas liquefaction

5 2 9 Gas treatment (physical)

5 2 10 Liquid-liquid extraction

5 2 11 Supercritical extraction

5 2 12 Crystallisation

5 2 13 Flow assurance

5 2 14 “Kinetically controlled” reactions

5 2 15 Reactive equilibrium

5 2 16 Reactive phase equilibrium

Reference List