Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing

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Equilibrium and Non-Equilibrium Thermodynamics of
Natural Gas Processing

• Measurement and Modelling of Absorption of Carbon
  Dioxide into Methyldiethanolamine Solutions at
  High Pressures

Ph.D Dissertation Even Solbraa14.February 2003
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What has been done ?

• A high pressure experimental equipment has been
  built and new high pressure experimental data
  are presented
• Equilibrium and kinetic limitations related to
  CO2 removal at high pressures in MDEA
  solutions are identified
• NeqSim - a general simulation program for
  natural gas processing operations has been
  developed. It is based on equilibrium and
  non-equilibrium models developed in this work.
  Many types of processes can now be solved
  effectively using a general non- equilibrium
  two-fluid model

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How are the results used today?

• Capacity and kinetic limits of high pressure
  absorption processes of CO2 in MDEA-solutions
  are estimated
• The simulation program developed is used to
  solve and teach thermodynamics and mass
  transfer processes
• High pressure equilibrium (e.g. dew point) and
  non-equilibrium (e.g. drying) processes are
  solved in an effective way

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Outline
1. Introduction to Natural Gas Processing and
Transport 2. Equilibrium and Non-Equilibrium
Model Development 3. Presentation of the
Simulation Program Developed 4. Modelling and
Regression to Experimental Data 5. Experimental
Work and Results 6. Conclusions
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The Natural Gas Chain
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Natural Gas Processing
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(No Transcript)
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CO2 removal with physical and chemical solvents
Physical Solvent (water)
PCO2
CO2
WaterCO2
Physical Solvents
Chemical Solvents
Chemical Solvent(MDEA)
CO2
xCO2
CO32-
MDEA
Water
HCO3-
CO2
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Two Illustrative and Case Studies
Problem to reach design specification in high
pressure (100 bar) CO2 absorption plant operating
at 70-80C using MDEA
Condensation of Liquid Water in Sub Sea Dry Gas
Pipeline operating between 100-200 bar
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Outline
1. Introduction to Natural Gas Processing and
Transport 2. Equilibrium and Non-Equilibrium
Model Development 3. Presentation of the
Simulation Program Developed 4. Modelling and
Regression to Experimental Data 5. Experimental
Work and Results 6. Conclusions
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The Non-Equilibrium Two Fluid Model
The Non-Equilibrium Two Fluid Model
Closure Relations
Thermodynamic Models
Mass Transfer / Kinetic Models
Physical Property Models
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Weak Electrolyte Calculation Procedure
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Thermodynamic Modelling of Amine Solutions
State of the Art
Polynoms(Kent and Eisenberg, 1976)
Easy and fast- Too simple, no physics
Electrolyte GE-modelsAustgen (1989), Li and
Mather (1994)
Relatively easy and fast- Problematic to add
supercritical components- Low pressure model
Future
Electrolyte Equations of StateFurst and Renon
(1993), this work
Generally applicable - Computational demanding
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Thermodynamic Models
Type of Fluid
Year
Electrolyte
Polar
Polymers
Non-Polar
Debye-Huckel
Empirical models
1950
GE-Models
EoS-Models
1980
EoS-Models
GE-Models
EoS-Models
Empirical models
1990
EoS-Models
EoS-Models
EoS-Models
other
2000
EoS-Models
EoS-Models
EoS-Models
EoS-Models
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Definition and Calculation of Thermodynamic
Equilibrium
Equation of States

• Parameters
• Critical Temperature and Pressure
• Accentric Factor

GE-models

• Molecular Parameters
• Vapour Pressure of Pure Components
• Molar Volumes in solution

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Development of Two New Electrolyte Equations of
State
General Equation of State
Contributions to the Helmholtz Energy
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Development of Two New Electrolyte Equations of
State
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Equations of State Considered
Equations of State
Mixing Rules

• RK (Redlich Kwong, 1949)
• SRK (Soave, 1971)
• PR (Peng and Robinson, 1979)
• ScRK (Scwartzentruber and Renon, 1989)
• CPA (Kontegorgios, 1999)

• no
• Classic (Van der Waals, 1905)
• Huron Vidal (Huron-Vidal, 1979)
• Wong-Sandler (Wong and Sandler, 1993)

Electrolyte Extensions

• Debye-Huckel (Debye-Huckel, 1952)
• MSA (Blum and Høye, 1982)
• Furst and Renon (Furst and Renon, 1993)

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Molecular Terms of Electrolyte Equations of State
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Mixing Rules for Molecular Terms
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Electrolyte Terms
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Evaluation of Electrolyte Terms
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Predictions With the Electrolyte Model
Density of Ionic Solution
Mean Ionic Activity Coefficient
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Non-Equilibrium Modelling
Scientific Work
Simulation Tools
Software
1900 1920 1950 1970 1980 1990 2000
Ficks law for diffusion Fourier law of heat
transfer Kinetic Theory of Gasses Multicomponent
Mass Transfer Non-Equilibrium Thermodynamics Molec
ular Simulation Resistance at Interface
Equilibrium Models
OLGA
Stage Efficiencies
HYSYS
Ficks law
Simple Maxwell Stefan General Maxwell Stefan
ASPEN PLUS
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Generalized Maxwell Stefan Equations
Multicomponent Maxwell Stefan Equation
General model
- Relatively complicated- Need thermodynamic
model
Generalized Driving Force
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The Enhancement Factor
Water MDEACO2HCO3-MDEA
CO2
CO2
Water
?yCO2
?yCO2
?xCO2
?xCO2
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Calculation of the Enhancement Factor
Two Ways to Estimate the Enhancement Factor

• Analytical Expressions (for simple reactions,
  e.g reversible first order reactions)
• Numerical Solutions of Film (for coupled and
  reversible reactions)

analytical
This work
CO2 fraction at chemical equilibrium in liquid
bulk
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The Generalized Non-Equilibrium Two Fluid Model

• Conservation of total mass
• Conservation of components
• Conservation of momentum
• Conservation of energy

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Outline
1. Introduction to Natural Gas Processing and
Transport 2. Equilibrium and Non-Equilibrium
Model Development 3. Presentation of the
Simulation Program Developed 4. Modelling and
Regression to Experimental Data 5. Experimental
Work and Results 6. Conclusions
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NeqSim a General Non-Equilibrium Simulator
General modelling tool for non-equilibrium and
equilibrium processes Based on rigorous
thermodynamic models Fluid mechanics based the
on the one- or two fluid model Implemented in
an object oriented language (Java/Python
object oriented design where everything is an
object) Suitable for being used as a modelling
tool (general parameter fitting routines
implemented) Validated against experimental
data (equilibrium/non-equilibrium)
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NeqSim a General Non-Equilibrium Simulator
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NeqSim - Examples of use

• Multiphase flash calculation
• Construction of phase envelopes
• Weak electrolyte calculations
• Process plant simulation

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Parameter Fitting Routines
Shi-Square Fitting
Minimized using the Levenberg- Marquardt Method
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Outline
1. Introduction to Natural Gas Processing and
Transport 2. Equilibrium and Non-Equilibrium
Model Development 3. Presentation of the
Simulation Program Developed 4. Modelling and
Regression to Experimental Data 5. Experimental
Work and Results 6. Conclusions
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Thermodynamic Properties of Mixtures
ScRK-EOS Huron Vidal CPA-EOS Classic
Mutual solubility of WaterCO2
Mutual solubility of WaterCO2
Freezing points of MDEAWater
Mutual solubility of MethaneWater
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Solubility of CO2 in waterMDEA solutions
Electrolyte ScRK-EoS
20.5 wt MDEA
50 wt MDEA
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High pressure solubility of CO2 and methane in
waterMDEA solutionsElectrolyte ScRK-EoS
Estimated PCO230 wt MDEA
Estimated bubble point pressure30 wt MDEA
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High pressure solubility of methane in
CO2waterMDEA solutionsElectrolyte ScRK-EoS
Estimated methane solubility30 wt MDEA
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Capacity Loss of Amine Solution at 100 bar and 70C
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Outline
1. Introduction to Natural Gas Processing and
Transport 2. Equilibrium and Non-Equilibrium
Model Development 3. Presentation of the
Simulation Program Developed 4. Modelling and
Regression to Experimental Data 5. Experimental
Work and Results 6. Conclusions
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The High-Pressure Wetted Wall Column
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Experiments Done in This Work
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Experimental Results Reference Data CO2 Water
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Experimental Results Reference Data CO2, MDEA
and water
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Conclusions
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Conclusions
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Case 1
Case 1 Problem to reach design specification in
high pressure (100 bar) CO2 absorption plant
operating at 70-80C using MDEA
Case 2 Condensation of Liquid Water in Sub Sea
Dry Gas Pipeline operating between 100-200 bar
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Case 2
Case 2 Condensation of Liquid Water in Sub Sea
Dry Gas Pipeline operating between 100-200 bar
Solubility of water in methane
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Thanks

• Institute for Energy- and Process Technology
• Statoil
• Norwegian Research Council