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The Equilib module – Regular Features

The Equilib module – Regular Features. Equilib calculates the conditions for multiphase, multicomponent equilibria, with a wide variety of tabular and graphical output modes, under a large range of constraints. Equilib accesses both compound and solution databases. Table of contents.

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The Equilib module – Regular Features

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  1. The Equilib module – Regular Features • Equilibcalculates the conditions for multiphase, multicomponent equilibria, with a wide variety of tabular and graphical output modes, under a large range of constraints. • Equilib accesses both compound and solution databases. Table of contents Section 1 Table of Contents Section 2Opening the Equilib Module Section 3From stoichiometric reactions to complex equilibria Section 4Simple equilibrium case (Mg+3Cu2O+2Fe3C+Ar) Section 5Additional output using the LIST window Section 6HELP with right mouse button Section 7Constant volume calculation (SiI4 decomposition) Section 8Constant pressure in steps (MgO+Si) Section 9Non-ideal gas (boiling point of water) (continued) Equilib 1.1

  2. The Equilib module Table of contents(continued) Section 10Adiabatic combustion, use of the «A» parameter (CH4 + O2) Section 11 Fixed activity calculation (FeS under O2 partial pressure) Section 12Setting up an ideal liquid and adding activity coefficientsA part of the Cu-Cr System Section 13Standard equilibrium: aqueous solutionLeaching arsenic-bearing copper concentrate Section 14Standard equilibrium: non-ideal solution Fe-Mn-Si-C Section 15Adding slag: An explanation on SlagA, SlagB, Slag? Section 16Standard case: Desulphurisation of steel adding CaSi Section 17Standard case: Pitzer aqueous with NaCl Section 18Heterogeneous equilibria and the phase rule Section 19Compound species selection-FactSage 6.4 Equilib 1.2

  3. The Equilib module Click on Equilib in the main FactSage window. Equilib 2

  4. Using Reaction and Equilibmodules to identify the most probable reaction What are the products of the following chemical reaction at 25°C: Mg + 3 Cu2O + 2 Fe3C + Ar ? We will assume that only pure stoichiometric compounds can be formed and we will ignore kinetic considerations. Using the Reaction program, we see (on the following page) there are many possibilities. For example: 1MgO + 6 Cu + 4.5 Fe + 2 C + 0.5 Fe3O4 + Ar 2MgO + 6 Cu + 4.667 Fe + 2 C + 0.667 Fe2O3 + Ar 3MgCO3 + 6 Cu + 6 Fe + 1 C +Ar 46 Cu + 4.667 Fe + 2 C + 0.667 MgFe2O4 + 0.333 MgO + Ar etc… According to the Reaction program, reaction 1 has the most negative Gibbs energy change. Hence, according to thermodynamic laws, this is the most probable reaction. By the method of Gibbs energy minimization, in a single calculation module Equilib identifies this most probable reaction. Equilib 3.1

  5. Reaction module: 4 possible isothermal isobaric reactions and 4 values of DG Reaction 1 Reaction 2 Reaction 3 Reaction 4 MostnegativeDG DG1» -670 kJ DG2» -659 kJ DG3 » -621 kJ DG4 » -668 kJ Equilib 3.2

  6. Gibbs Energy Minimization Where, Equilib determines the combination of ni, Piand Xiwhich minimizes the total Gibbs energy G of the system. In the present example the equilibrium products are an ideal gas and pure solid compounds Equilib 3.3

  7. Reactants window – entering a new reaction Equilibhas 4 windows: Reactantswindow Add a New Reactant Reactants window Menu window Reaction Table List window Results window Open 1st entry: Click on New Reaction All calculations shown here use the FACT compound and solution databases and are stored in FactSage - click on: File > Directories… > Slide Show Examples … 2nd entry:Define the reactants. List of compound and solution databases initial conditionscheckbox is not selected Press «Next» to go to the Menu window Equilib 4.1

  8. Menu window – possible products, final T and P, and calculating the equilibrium Menuwindow Summary of the Reactants. Save Open New Reaction 3rd entry:Selection of compound products: ideal gas phase and pure solids. 4th entry:Final conditions: 25°C, 1 atm. 5th. Pressto calculate equilibrium. Equilib 4.2

  9. Results window – FACTformat output. The equilibrium products: Cu, Fe, C, MgO, Fe3O4 and Ar satisfy the mass balance and minimize the Gibbs energy. Results window 1 mol (39.948g) of product ideal gas at 1 atm: mainly Ar. These are mole fractions Xi , in an ideal gas: Pi = Xi × Ptotal or P(CO2)eq = 0.17814 x 10-19 atm. Note thepure stable stoichiometricsolids: activity = 1.0 6 mol Cu(s1) 4.5 mol Fe(s1) 2 mol C(s1) [graphite] 1 mol MgO(s1) Solids beyond this point are not formed: 0 moland activity < 1.0They are ordered with regard to activity. 0.5 mol Fe3O4(s1) Equilib 4.3

  10. Results window – ChemSage format output Menu bar:Output>Format >ChemSage Format Final conditions Amount of reactants Product gases: gasfugacitiesare calculated Product: stable purestoichiometricsolids Equilib 4.4

  11. List window – manipulating the results Final conditions List window Click on List Window Display of gas fugacities, for example:fCO2=1.7814×10-20 atm. In an ideal gas, the fugacity is equal to the partial pressure. Hence: PCO2= XCO2× PT =fCO2=1.7814 × 10-20 atm choice of phases: and Sorry – diamond is not formedadiamond< 1 solid GAS format and ordered with respect to moles Equilib 5.1

  12. List window – distributionformat For example,Fe is distributed in:a gas phase: 0% as Fe(g) 2 solid phases: 75% as Fe(s) and 25% as Fe3O4(s) 3. Scroll 1. Select distributionformat 2. Press Refresh Equilib 5.2

  13. List window – thermodynamic data format Selection: 1. Show: pure solid phases 2. Format:thermodynamic data «Absolute» values of Gibbs energy G°. DG°for the reaction: 3 Fe(s) + C(s)=Fe3C(s) is given by: DG°= G°Fe3C - [ 3G°Fe + G°C ] = -7594.9 - [ 3(-8133.5) + (-1711.4)] = 18517 J/mol 3. And press Refresh 4. To obtain the thermodynamic data format Equilib 5.3

  14. Comparison of Gibbs energy values obtained by the Reaction and the Equilibprograms … Specify the phase of each reactant at 25ºC and 1 atm pressure… Thermodynamic functions:DH,DG,DV,DS,DU,DA and Prod V. The value ofDG is the same as the Reaction program (Reaction 1, page 3) Select the initial conditions A spontaneous isobaric isothermal chemical reaction takes place (DG<0)and the reaction is exothermic: DH = - 693.3 kJ Equilib 5.4

  15. Reactants window – Help > More information... Menu bar:Help >More information... « Point to a frame heading or input box and then click the mouse right button. » Equilib 6.1

  16. Reactants or Menu window - Help > Directory of examples... Reactants or Menu window menu bar:Help >Directory of examples... If you want to Change Directory then go to File>Directory> [Select a directory] or press on View Short description of the example Equilib 6.2

  17. The mouse right button - Reactants Click with the mouse right button Equilib 6.4

  18. Help: – the mouse right button Click with the mouse right button in the enclosed areas: header or input box and information boxes will appear. 1. Massinfo 2. Massunits 3. Speciesinfo 4. Speciesaccess to ViewData 5. Phase 6. Temperatureinfo 7. Temperatureunits 8. Pressureinfo 9. Pressureunits 10. Stream numberinfo 11. Datainfo 12. Databases info 1 3 5 6 8 10 11 2 4 7 9 12 Equilib 6.5

  19. Help – Example of mouse right button, Mass: 1. Header and 2. Input Box 1 Conversion of mass units Selection of mass units 2 Default setting for masses Equilib 6.6

  20. Units window: T,P, Energy, Mass and Volume Reactants Menu bar:Units > Move the arrow through the frames to see the conversion factors. Equilib 6.7

  21. Homogeneous GaseousEquilibria Reacting H2S with Cl2 Products selection: idealgas solution phase Product T= 1500 K and P=2 atm Press «Calculate» Drop-down menu for extensive property Equilib 6.8

  22. H2S + Cl2 = Results window, FACTFormat Output Total pressurePtotal= 2.0 atm Mole fractionXHCl= 0.65092 ÞPHCl= XHCl × Ptotal= 1.30184 atm Equilib 6.9

  23. List window – Help > …and go to the next slide “+” denotes species or phase is selectedas a possible product. Other options are available. Click right button for more … Point to a frame heading or input box, a message box appears and then click the mouse right button Equilib 6.10

  24. Help – Another example of the use of the mouse right button 1 2 3 Click mouse right button to custom select species for gas species Click mouse right button for extended menu on H2S(g) To get all the information you need about the extended menu Equilib 6.11

  25. Simple heterogeneous equilibrium: thermal decomposition of SiI4 Species selection for the thermal decomposition of SiI4: an ideal solution gas phase and puresolids are selected as possible products. To view a list of the species selected before computation and specify a pure solid Si phase instead of 3 puresolids, click themouse right buttonat a«Compound species»input boxor press the«ListWindow» button Computations are at 1400 Kfor two fixed volumes: 1000 and 10000 litres. Equilib 7.1

  26. Customselectionof product species:a short-cut 1.Click with mouse right button. 2.Select a species: Click on its + column or press {Ins} or {Del} to add or remove it. For a group of species, drag the mouse first and then press {Ins} or {Del}. 4.*Acustomselectionfor the solid phase 3. Press «OK» Equilib 7.2

  27. The Selection Window You can also double click on the column header to sort the list. Add columns to the list filled with the data you have requested or calculated. Note: Your last selection becomes a default setting. Equilib 7.3

  28. Results window – 1400 K,1000 L for SiI4 First tab [page 1/2] (selected): 0.2281 atm Fixed volume: 1000 L Second tab: 3.529E-02 atm [page 2/2] Equilib 7.4

  29. Decomposition of SiI4at lower vapor pressures V =1000 L T = 1400 K, P = 0.22813 atm 0 mol (no Si(s) formed) activity < 1 V =10000 L T = 1400 K, P = 0.03529 atm 0.25082 mol Si(s) formed activity = 1 Equilib 7.5

  30. Effect of Pressure on Simple Heterogeneous Equilibria: Radiation Baffles Pidgeon Process for the Productionof Magnesium: Apparatus Schema Ni - Cr Alloy Retort Water-cooled vacuum connection also condenses alkalis Mg(Ca)O + Fe - Si Heated to 1423 K for Mg Reduction Mg condensed on removable sleeve Equilibrium Mg partial pressure developed at the hot end of the retort Final Conditions:twodifferent pressures and onetemperatureresult in 2calculations Equilib 8.1

  31. Reacting MgO with Si at 1 atm – no reaction 0 mol of gas, however XMg= 1.0876×10-3 and Ptotal= 1 atm, hence PMgeq= 1.0876×10-3 atm Reactants Products SPgas species= 1.0969×10-3 atm No reaction takes place because the pressure (1 atm)is toohigh for thegas phase Note:Unit activity but0 mol.i.e. it is«thermodynamically ready»to form. Equilib 8.2

  32. MgO and Si reaction at a reduced total pressure Coexistingphases The gas phase is stable under a reduced total pressure.XMg= 0.99151and Ptotal= 0.001 atm, hence PMgeq= 9.91×10-4 atm Gas phase:numbers are mole fractions Compare the formation of the gas phase here at 10-3 atm with the previous page where pressure is 1 atm. Refer to the next page for the distribution of elements in the products. Equilib 8.3

  33. Pidgeon Process for the Production of Magnesium:Results Radiation Baffles Ni - Cr Alloy Retort Mg(Ca)O + Fe - Si Heated to 1423 K for Mg Reduction Water-cooled vacuum connection also condenses alkalis T = 1423 K Ptotal= 0.001 atm Mg(g)condenseson water-cooled removable sleeve Equilib 8.4

  34. Boiling Point of Water: Ideal Gas Calculation Settings • Products: • aliquidphase; • anideal gasphase Final Conditions: T = 0°Cand150°C; P= 1atm; and anytransitionpoint in the temperature interval Equilib 9.1

  35. Boiling Point of Water: Ideal Gas Calculation;Results: Tb(water) = 100.35°C The asterisk in front ofT = 100.35°Cindicates the calculated value … Compare the final volume of the phase … for the equilibrium temperature betweenH2O(g)[ideal gas phase]andH2O(L1)[i.e., theidealboiling point] Equilib 9.2

  36. Boiling Point of Water: Real Gas Calculation Settings • Products: • aliquidphase; • anreal gasphase Final Conditions: T = 0°Cand150°C; P= 1atm; and anytransitionpoint in the temperature interval Possible selection of solution species (the box Show and the radio button all are checked). Equilib 9.3

  37. Boiling Point of Water, Real Gas Calculation Results Tb = 100°C [ChemSage Output] The asterisk in front ofT = 100°Cindicates the calculated value … Compare the final volume of the phase … for the equilibrium temperature betweenH2O(g)[real gas phase]andH2O(L1)[i.e., therealboiling point] Equilib 9.4

  38. Adiabatic Reaction between CH4 andO2– Specifying an Extensive Property, DH=0 • Possible products are: • an ideal gas phase; • pure liquids and • pure solids. Select «Initial Conditions» with the checkbox. For an adiabatic reaction, set DH=0. Equilib 10.1

  39. Equilibrium Products and Final T of the Adiabatic Reaction between CH4 and O2 ProductT is 3053 K. Clearly a very high temperature. It can be used for flame spectroscopic applications. No condensed phases Note: DH=0; DS is a maximum for specified input conditions Equilib 10.2

  40. Fixing the activity of a component in the equilibrium state In the following four slides is shown how the Equilib module can be used in order to perform calculations which do not use an amount of a substance but rather its chemical potential, here the partial pressure of a gas species. As an example FeS is considered in a gas atmosphere with a given O2 partial pressure. Equilib 11.0

  41. Fixing the Activity of a Species O2(g) in the Product Equilibrium FeS and O2 To view a list of the species selected before computation, press the «List Window» button. Note: 1.8 molO2 1. To fix the activity of a species asO2(g),click the mouse right button on the name of the phase containing the species you want (in this case, the gas phase). Click mouse right button to custom select species for gas species. A right click in the «compound species» frame will provide you some information Equilib 11.1

  42. Fixing the Activity of a Species 2. Click themouse right buttonin the first column of the line containingO2(g) species, a context menu opens… 3. Select «activity» in the sub-menu «aActivity» to open a dialog box 4. Fix the activity (or partial pressure) of the species;Press «OK». Equilib 11.2

  43. Activity of O2(g) in the product equilibrium FeS and O2: Custom activity details 5. Partial pressure ofO2is fixed:PO2 = 1 × 10-2 atm Press «OK» to returntoMenu Window 6. The «Customsolutions» frame indicates: 1 fixed activity …For more information, press «Details» 7. Press « Calculate >> » Equilib 11.3

  44. Activity of a Species O2(g) in the Product Equilibrium FeS and O2 : Resultswindow 0.03709 mol O2must be added to the reactants in order to have the final equilibrium partial pressure for O2 i.e. FeS + 1.83709O2 as reactants PO2= 0.01atm Products Equilib 11.4

  45. Assembling an ideal liquid and adding activity coefficients In the following 16 slides is shown how in the Equilib module two pure liquid components are used to describe a custom defined liquid solution. First ideal mixing is assumed, then a comparison with the known phase diagram is used to derive activity coefficients via the Reaction module. Finally the activity coefficients are applied in complex equilibrium calculations using the Equilib module. Equilib 12.0

  46. Setting up of an idealliquid solution of Cu and Cr 1.In order to define the components of an ideal liquid solution, click the mouse right button on the name of the phase containing the species you want (in this case, liquid). Click mouse right button to custom select species for liquid species. Equilib 12.1

  47. Setting up of an idealliquid solution of Cu and Cr 2. Click themouse right buttonin the first column (+) of the line containingCr(liq)species – an extended menu appears. Click mouse right button for extended menu on Cr(liq). 3.Click on «Ideal Solution #1» in sub-menu«Ideal Solution»toselectCr(liq)as the firstcomponent. 4.Repeat steps 2 and 3 to selectCu(liq)as the second componentof Ideal Solution #1. Equilib 12.2

  48. LiquidCu-Cralloy assuming idealmixing ofCuandCr 6. Press «OK» to return to the Menu Window where the «Custom Solutions» label box indicates: 1 ideal solution …For more information, press «Details» 5. Cr(liq) and Cu(liq) are the components of «IdealSolution #1» 7. Set Final Conditions and press «Calculate >>» Equilib 12.3

  49. Results window – assumption of Cr(liq) - Cu(liq)ideal mixing. ChemSage format Idealsolution phase: liquid#1 Numbers are mole fractionsXCr(liq) = 0.4XCu(liq) = 0.6 FACT format Equilib 12.4

  50. List window – assumption of Cr(liq) - Cu(liq)ideal mixing Idealsolution, henceXCu(liq) = aCu(liq)= 0.6XCr(liq) = aCr(liq)= 0.4 • List Window • check Show, Species «selected»; • select: • Format «mole» and Order «code». Option Show «properties» checked According to the phase diagram (next page): XCr(liq) = 0.01837 at 1373.15K (1100°C). Hence, the assumption of an ideal solution is not very good in this example. Equilib 12.5

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