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Introduction of computational thermodynamics (CTD)

Introduction of computational thermodynamics (CTD). 477415S Thermodynamic and process modelling in process metallurgy and mineral processing. Goals of this lecture. To give a brief theoretical background for the course of computational thermodynamics What is computational thermodynamics, CTD?

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Introduction of computational thermodynamics (CTD)

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  1. Introduction of computational thermodynamics (CTD) 477415S Thermodynamic and process modelling in process metallurgy and mineral processing

  2. Goals of this lecture To give a brief theoretical background for the course of computational thermodynamics • What is computational thermodynamics, CTD? • How to define chemical equilibria with CTD? To give an overview on CTD software • Introduction to CTD software used in metallurgy • Introduction to HSC Practical arrangements concerning the course

  3. Contents Introduction: Modelling in general Thermodynamic modelling • Computational thermodynamics • Determination of chemical equilibria with optimisation method • Databases • Applications of CTD • Common problems and mistakes CTD software used in metallurgy • Emphasis on the HSC Chemistry • History, Structure & Data flows, Modules, Databases, Syntax, Interface Practical arrangements in this course

  4. Introduction:A few words about modelling in general A model is a representation of something in the real world • May be very simple or very complicated • Usually simplified and idealized in order to be more easily constructed, used, understood and interpreted Scientific modelling • Simplified and idealized representation of physical systems • Helps to understand, define, quantify, visualize or simulate • Always need for validation! Simulation is an implementation of a model • Steady state (certain point in time, e.g. equilibrium) • Dynamic Model types • Theoretical models: Logic/mathematical causalities • Empirical models: Experimental data fitted for math. functions • Semi-empirical models: commonly calibration of theoretical model with experimental data Figure: Visuri V-V: PhD thesis, University of Oulu, 2017. Reproduced from Sargent RG: Proc. 1988 Winter Simulation Conf. San Diego, USA, pp. 33-39.

  5. Introduction:Model types Theoretical models • Based on fundamental physical, mathematical or logical causalities • e.g. physical chemistry, reaction kinetics, heat transfer, fluid flow mechanics, etc. • As few simplifications and empirical calibration as possible • Usually large validation range and good extrapolation • Use requires understanding of the modelled phenomena Empirical models • Based on experimental data fitted to certain mathematical functions by finding suitable model structure/parameters • A lot of data required for model construction/validation • Usually valid only in the context for which it was created • ”Black box” – does not require theoretical understanding • Usually faster to create Semi-empirical models • Easier and faster to create than theoretical models • Give more information and more easily extrapolated than empirical models Physical water model built to study and visualise the flows inside the AOD process. Figure: Fabritius T: PhD thesis, University of Oulu, 2003.

  6. Modelling of chemical equilibria What is (chemical) equilibrium? • A state in which no changes take place as a function of time (unless conditions are externally changed) • i.e. no spontaneous changes/reactions What is a spontaneous reaction/phenomenon? • A change in which no external energy/work is required • On the contrary: energy is released for other use Connection: Equilibrium – Spontaneity • Spontaneous reactions lead into equilibrium • i.e. equilibrium is not reached as long as energy is released in reactions – For infinitesimal changes in equilibrium energy is neither released nor needed Equilibrium can be determined by determining the energy changes for the phenomena/ reactions within the studied system • For mathematical modelling, equations for this energy are required Figure: Atkins PW: Physical chemistry. 6th ed. Oxford. Oxford University Press. 1988. 1014 p.

  7. Modelling of chemical equilibria In order to determine chemical equilibrium computationally, an energy function is needed • Internal energy (U) represents all the energy contained in the material/system/body itself (excludes external energies such as kinetic energy and potential energy) • When phenomena with volumetric changes occur within a system that stays in constant pressure: • Either expansion or compression takes place • Energy is needed for expansion against external pressure • Entalphy/Heat content (H) represents internal energy from which the work against external pressure is subtracted • H = U + pV • Usability of energy is decreased to increase in entropy (S) • Free energy (F or G) represents the energy that can be used for ”useful work” (i.e. spontaneous reactions/changes) • G = H – TS • Helmholz free energy (F) for constant volume systems • Gibbs free energy (G) for constant pressure systems To model chemical equilbria is to determine changes for Gibbs free energy Josiah Willard Gibbs (1839 – 1903) Images: Wikipedia.

  8. Optimisation/ Minimsation method Modelling of chemical equilibria In order to determine chemical equilibrium computationally, an energy function is needed • Internal energy (U) represents all the energy contained in the material/system/body itself (excludes external energies such as kinetic energy and potential energy) • When phenomena with volumetric changes occur within a system that stays in constant pressure: • Either expansion or compression takes place • Energy is needed for expansion against external pressure • Entalphy/Heat content (H) represents internal energy from which the work against external pressure is subtracted • H = U + pV • Usability of energy is decreased to increase in entropy (S) • Free energy (F or G) represents the energy that can be used for ”useful work” (i.e. spontaneous reactions/changes) • G = H – TS • Helmholz free energy (F) for constant volume systems • Gibbs free energy (G) for constant pressure systems To model chemical equilbria is to determine changes for Gibbs free energy Using equilibrium constant (K) GSystem= (GPhase) GPhase= (GComponent)  Finding min(GSystem) For individual chemical reactions. Not considered in this course. 477401A Thermodynamic equilibria 477417S High temperature chemistry Gibbs free energy G = H - TS Entalphy H =  CP dT Entropy S =  CP/T dT Heat capacity as a function of T e.g. Kelley equation CP = a + bT + cT2 + dT-2

  9. Modelling of chemical equilibria Using equilibrium constant • Each chemical reaction is studied individually • Chemical reactions must be known • Easy to calculate • Not suitable for more complicated systems Optimisation/minimisation method • For studying several reactions taking place in the same system • Not necessary to know the reactions • Starting point: possible phases + their components + total composition of the system • Calculation with thermodynamic software = Computational Thermodynamics, CTD • Various software developed for different applications and purposes • Software consist of • Minimisation routine • Thermochemical database

  10. Computational thermodynamics User interface of the CTD software is usually relatively easy to use The main challenge in utilisation of the software is: How to define the system properly? • Computational system corresponds the one under consideration • Definition of • Phases (pure, solutions) • Components • Total composition • Conditions • Models and parameters used • Constants and variables • Software can tell the user if the system definition is not complete, but it cannot tell whether it is meaningful or relevant

  11. Modelling of chemical equilibria with CTD Main principle • Total composition of the system defines the elements available in the system • These elements are ”divided” between possible phases (and their components) in such a way that minimises the Gibbs free energy of the whole system = State of equilbrium • Computations seeks for a global minimum of the Gibbs free energy equation for the whole system • Mathematical equation for Gibbs free energy is needed • G = f(T, p, Xi, Xj, ...) Databases • Data concerning the models and parameters required in the computations • H0, S0, CP=f(T), ai=f(T,P,Xi,Xj,...) • Usually separate DB for pure substances and solutions • Some open, some closed • Software seeks the required information from the DB automatically

  12. Modelling of chemical equilibria with CTD Main principle – Example Results Total composition (initial comp.): CO(g) 25 % CO2(g) 25 % H2(g) 25 % H2O(g) 25 % Elements available: C x mol O y mol H z mol Phases existing in the system and compositions of these phases in the equilibrium state in given conditions: 1 Nm3 gas, in which: 23 % H2 23 % CO2 27 % CO 27 % H2O (No soot is formed) System size: 1 Nm3 Conditions: T = 900 C Ptot= 1 bar Possible phases: Gas phase (CO,CO2,H2,H2O) Precipitated soot (= Solid C) Gibbs free energy equation for the system Initial state No need to know the chemical reactions in advance. Database Models, thermodyn. data

  13. Applications of CTD Applications in • Chemistry • Chemical engineering • Pyro- and hydrometallurgy • Mineral processing • Corrosion • Energy • Geology Used in R&D to • Improve old processes • Develop new processes • Search optimal conditions • Reduce ”need” for trial-and-error • Support experimental research Used in education to • Illustrate the application of thermodynamics in practice Figures: Kemppainen, 大野, Iljana, Mattila, Paananen, Heikkinen, 前田, 国友 & ”Fabritius: 高炉内融着帯における酸性ペレットおよびオリビンペレットの軟化挙動”. 鉄と鋼(Tetsu-to-Hagane). 103(2017)4, pp. 175-183.

  14. Applications of CTD Typical application is the estimation phase fractions and compositions for given systems in given conditions • e.g. liquid phase fraction during the AOD process in stainless steelmaking Figures: Heikkinen, Visuri & Fabritius: ”On the heterogeneity of AOD slags in different stages of blowing”. EOSC2018-conference. Taranto, Italy. 10-12 October 2018.

  15. Problems and mistakes with CTD System definition • Specification of practical problem into chemical format • Specification of chemical system (phases, species, ...) • Pure substances vs. solutions/mixtures • Ideal activities vs. non-ideal solutions/mixtures Use of software and database • Missing thermodynamic data • Errors in thermodynamic data • Thermodynamic data used out of its boundaries • Erroneous extrapolation of thermodynamic data • Erroneous syntax Interpretation of the results • Analysis of the results • Inadequate validation of results(if any) • Experiments, literature, phase diagrams, process data • Results applied for a system not limited by equilibrium • Kinetics not taken into account in CTD Source: Outotec. Figure: Jaako J: Report B48, Control Eng. Lab., Univ. of Oulu. 2003. 39 p.

  16. CTD software used in metallurgy ”Chemical equilibrium in complex mixtures” White, Johnson & Dantzig, J Chem Phys (1958) Gibbs-routine (1974) Outokumpu, Kokkola Timo Talonen Solgasmix-routine (1974) University of Umeå Gunnar Eriksson MTDATA (1980s) National Physics Laboratory, London Thermo-Calc (1981) Kungliga Tekniska Högskolan, Stockholm HSC Chemistry (1980) Outokumpu  Outotec Pori FACT (1976) CRCT, École polytechnique, Montreal Others e.g. Pandat, CEQCSI, ... ChemSage (1987) GTT, Aachen FactSage (2001) GTT/CRCT

  17. CTD software used in metallurgy Different software for different purposes

  18. CTD with process simulation tools Process simulation tools in which CTD is included or in which it could be connected • Aspen Plus • Aspen HYSYS • CHEMCAD • PRO/II • FLOWBAT • HSC sim • CFD software such as Fluent • CTD is connected with modelling of • Reaction kinetics • Fluid dynamics • Heat transfer • Physical and chemical properties

  19. HSC Chemistry Developed in Pori, Finland • Outokumpu Research Center, later Outotec • First for internal use only • Tool for R&D projects • Currently a commercial product Originally for equilibrium calculations • Current version 9.9.2 contains several other modules Very good database for pure substances • > 28000 species • Open database Easy user interface • Possibility for AddIn functions http://www.outotec.com/hsc • Tutorial videos found in YouTube (Search for ”HSC”)

  20. 2014 Version 8.0 (1st version for Win7&8) All modules re-written with .NET/C++ HSC Chemistry: History 2002 Version 5.0 (1st version for WinXP) 1992 Version 1.0 (1st version for Win3.1) 1966 First equilibrium calculations with Fortran (Timo Talonen, MSc thesis) 1979 Development of DB begins >20000 lisences 1997 Version 3.0 (1st version for Win95/NT) 2015 Version 9.0 (1st version for Win10) 1983 Modules 2009 Version 7.0 (1st version for WinVista) 1987 Sales to other companies started 1974 Generic equilibrium routine 1999 Version 4.0 (1st version for Win98) 2019 Current version 9.9.2 1970 1980 1990 2000 2010 2020 1993 Starts process engineering studies at UO 1996 First contact with HSC version 2 (Simulation exercise) 1997 Tutor in teaching of HSC 1999  Responsible teacher (CTD, HSC) 2001  Use of CTD and HSC in research 2017  Separate HSC course at UO

  21. HSC Chemistry: History

  22. HSC Chemistry: Structure & Data flows Data flows have been simplified since version 8 • In old versions (until 7), user was required to save the data to files more often Figures: Antti Roine, Outotec.

  23. HSC Chemistry: Structure & Data flows Database file structure • HSC DB (since version 8) can access 3 file formats • .HSC / .HSC8 / .XML • Regardless of the structure, all the files contain same type of information about species Figures: Antti Roine, Outotec.

  24. HSC Chemistry: Modules • Sim – Process simulation • Data – Statistical analysis • Geo – Mineralogical calculations • Map – GPS material stock • Reaction equations • Heat and material balances • Heat loss calculator • Equilibrium calculations • Electrochemical cell equilibria • E-pH (Pourbaix) –diagrams • H, S and CP estimations • H, S, CP and Ellingham diagrams • Stability diagrams (modules Tpp and Lpp) • Water-steam-tables • Formula weights • Conversion – Species to elements • Mineralogy iterations • Periodic chart of elements • Measure units • Aqueous solutions estimator • Numerical data fit

  25. HSC Chemistry: Databases • H, S and CP thermochemical database • Over 28000 species • Water/steam database • Heat conduction database • Heat convection database • Surface radiation database • Gas radiation database • Particle radiation database • Elements database • Measure units database • Minerals database • Over 13000 species • Aqueous solution density database • Aqueous solution activity database

  26. HSC Chemistry: Syntax Chemical formulas of species/compounds must be written in a form that is understood by the database Basic rules • Compound name = Its chemical formula • No need to use superscripts or subscripts • e.g. Na2SO4 • Some compounds are written as combinations of two compounds (connected with ”*”) • e.g. Li2O*Fe3O4 • ”*” is required in the beginning, if the name would otherwise start with number: e.g. *3Al2O3*2SiO2 • Parentheses may be used • e.g. H2Sn(OH)6 • Suffix in the end (in parentheses) specify state, crystal structure and charge of species • e.g. Cu2S(l), O2(g), H(+a), SO4(-2a), SiO2(Q) In more detail during the ”lectures”

  27. HSC Chemistry: Interface Graphic interface • Relatively easy to learn how to use • Different modules used for different purposes All the modules are not covered within this course • The most relevant ones for pyrometallurgists are studied in exercises and assignments during the ”lectures”

  28. 477415S Thermodynamic and process modelling in metallurgy and mineral processing General information • 5 ECTS credits  135 h of work • Autumn semester (Periods I and II) – 2 x 2h/week • Mondays at 10-12 (lecture room varies) • Fridays at 10-12 (lecture room varies) • Some exceptions – Check www-site for details! • http://www.oulu.fi/pyometen/477415s_schedule • Total of 12 x 2h for each part • Teaching in English • Reports may be written in English, Finnish or Swedish Learning outcomes • Students passing the course can use HSC Chemistry -software to investigate the thermodynamic equilibria • These thermodynamic considerations include 1) Equilibrium calculations 2) Mass and heat balances 3) Phase diagrams • They can also use HSC Sim -software to model metallurgical processes • Student will know how to 1) Model flowsheets for various processes 2) Apply simulation in practical problems 3) Run calculation and analyse the results

  29. 477415S Thermodynamic and process modelling in metallurgy and mineral processing Contents • Part I focuses on thermodynamic modelling • How to use HSC Chemistry as well as its modules? • Reaction equations, Equilbrium compositions, Heat & Material balances, H, S, CP, G diagrams, Stability diagrams, Eh-pH diagrams, Measure units, Periodic chart, Species converter) and database • How to define a system? • How to interpret results? • Part II focuses on process simulation • HSC-Sim structure and user interface, toolbar, drawing a flowsheets with HSC Sim, data necessary for building up a simulation, simulation Continuous assessment – No written exam • Assignments for Parts I and II • Adequate participation to ”lectures” in order to do the required assignments • Reports written outside lectures • Work individually or recommendably in pairs • Material available from the course website • http://www.oulu.fi/pyometen/477415s_materials • Search for additional material may be required

  30. Final words http://www.oulu.fi/pyometen/477415s Check information found in the course website • Read documents about exercises and assignments in advance • Check video tutorials (made by Outotec) if necessary Be active during the course • Participate ”lectures” in order to have enough time for assignments • One or two missed lectures are not the end of the world, but frequent absence makes it difficult to keep up with the schedule • Ask for guidance if necessary • Both during as well as outside the ”lectures” • Reserve enough time for writing the report

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