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 Solbraa 14.February 2003

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing 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 CO 2 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

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing How are the results used today? Capacity and kinetic limits of high pressure absorption processes of CO 2 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

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing 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 Outline

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing The Natural Gas Chain

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Natural Gas Processing Natural Gas + CO 2 Natural Gas Lean Amine Rich Amine CO 2 Gas

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Lean Amine Solution Rich Amine Solution Acid Natural Gas Sweet Gas Random and structured packings: Film Flow

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing CO 2 removal with physical and chemical solvents P CO2 x CO2 Physical Solvents Chemical Solvents CO 2 Water+CO 2 Physical Solvent (water): CO 2 Water Chemical Solvent (MDEA): MDEA CO 2 HCO 3 - CO 3 2-

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Two Illustrative and Case Studies Problem to reach design specification in high pressure (100 bar) CO 2 absorption plant operating at 70-80°C using MDEA Condensation of Liquid Water in Sub Sea Dry Gas Pipeline operating between bar 1. Erroneous predictions of water dew-point with standard equations of state in high pressure natural gas systems 1. Almost all models developed are low pressure models (GE-models). 2. High pressure equilibrium and mass transfer data not available 2. Non-equilibrium models for two-phase pipe flow not available

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing 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 Outline

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing The Non-Equilibrium Two Fluid Model Closure Relations Thermodynamic Models Mass Transfer / Kinetic Models Physical Property Models

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Weak Electrolyte Calculation Procedure

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Thermodynamic Modelling of Amine Solutions Polynoms (Kent and Eisenberg, 1976) Electrolyte GE-models Austgen (1989), Li and Mather (1994) State of the Art Future Electrolyte Equations of State Furst and Renon (1993), this work + Easy and fast - Too simple, no physics + Relatively easy and fast - Problematic to add supercritical components - Low pressure model + Generally applicable - Computational demanding

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Thermodynamic Models Type of Fluid Electrolyte Non-Polar PolarPolymers GE-Models EoS-Models EoS-Models 1990 GE-Models Debye- Huckel EoS-Models EoS-Models 2000 Empirical models other EoS-Models EoS-Models Year

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing 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

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Development of Two New Electrolyte Equations of State General Equation of State Contributions to the Helmholtz Energy The Modelling Procedure Find Best Molecular EoS Find Best Electrolyte Terms

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Development of Two New Electrolyte Equations of State

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Equations of State Considered RK(Redlich Kwong, 1949) SRK(Soave, 1971) PR (Peng and Robinson, 1979) ScRK (Scwartzentruber and Renon, 1989) CPA(Kontegorgios, 1999) Equations of StateMixing Rules 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)

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Molecular Terms of Electrolyte Equations of State

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Mixing Rules for Molecular Terms

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Electrolyte Terms

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Evaluation of Electrolyte Terms

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Predictions With the Electrolyte Model Density of Ionic SolutionMean Ionic Activity Coefficient

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Non-Equilibrium Modelling 1900: 1920: 1950: 1970: 1980: 1990: 2000: Fick’s law for diffusion Fourier law of heat transfer Kinetic Theory of Gasses Multicomponent Mass Transfer Non-Equilibrium Thermodynamics Molecular Simulation Resistance at Interface Scientific Work Simulation Tools Equilibrium Models Stage Efficiencies Simple Maxwell Stefan General Maxwell Stefan OLGA Software HYSYS ASPEN PLUS Fick’s law Simple Maxwell Stefan General Maxwell Stefan This work

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Generalized Maxwell Stefan Equations Multicomponent Maxwell Stefan Equation: Generalized Driving Force: + General model - Relatively complicated - Need thermodynamic model

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing The Enhancement Factor CO 2 Water  x CO2  y CO2 CO 2 Water MDEA CO 2 HCO3 - MDEA +  x CO2  y CO2

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing 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) This work: analytical CO 2 fraction at chemical equilibrium in liquid bulk

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing The Generalized Non-Equilibrium Two Fluid Model Conservation of total mass Conservation of components Conservation of momentum Conservation of energy

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing 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 Outline

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing 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)

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing NeqSim – a General Non-Equilibrium Simulator

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing NeqSim - Examples of use Multiphase flash calculation Construction of phase envelopes Weak electrolyte calculations Process plant simulation

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Parameter Fitting Routines Shi-Square Fitting Minimized using the Levenberg- Marquardt Method

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing 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 Outline

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Thermodynamic Properties of Mixtures ScRK-EOS + Huron Vidal CPA-EOS + Classic Mutual solubility of Water+CO 2 : Freezing points of MDEA+Water:Mutual solubility of Methane+Water: Mutual solubility of Water+CO 2 :

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Solubility of CO 2 in water+MDEA solutions Electrolyte ScRK-EoS 20.5 wt % MDEA : 50 wt% MDEA Ref.MDEA (wt%)Temperature (K)Loading range (mol CO 2 /mol amine) Number of points AAD (%) Jou et.al. (1993)35313, Jou et.al. (1982) ,313,343,373, Austgen et.al. (1991) Chakma and Meisen (1987) 19.8, Bahiri (1984) , Kuranov (1996) , 333, 373, Rho et.al. (1997) , 348, Mac Gregor and Mather (1991) Average Deviation 26%

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing High pressure solubility of CO 2 and methane in water+MDEA solutions Electrolyte ScRK-EoS Estimated bubble point pressure 30 wt % MDEA Estimated P CO2 : 30 wt% MDEA

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing High pressure solubility of methane in CO 2 +water+MDEA solutions Electrolyte ScRK-EoS Estimated methane solubility 30 wt % MDEA

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Capacity Loss of Amine Solution at 100 bar and 70C

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing 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 Outline

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing The High-Pressure Wetted Wall Column

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Experiments Done in This Work

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Experimental Results – Reference Data CO 2 +Water

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Experimental Results – Reference Data CO 2, MDEA and water

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Conclusions

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Conclusions

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Case 1: Case 2: Condensation of Liquid Water in Sub Sea Dry Gas Pipeline operating between bar Case 1: Problem to reach design specification in high pressure (100 bar) CO 2 absorption plant operating at 70-80°C using MDEA

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Case 2: Case 2: Condensation of Liquid Water in Sub Sea Dry Gas Pipeline operating between bar Solubility of water in methane:

Equilibrium and Non-Equilibrium Thermodynamics of Natural Gas Processing Thanks Institute for Energy- and Process Technology Statoil Norwegian Research Council