First Hume-Rothery Seminar on Phase Equilibria and Computational Materials Chemistry The Riverside Centre, Derby January 17th 2017 Modelling Oxide Systems: Slags To Cements J.A. Gisby, J.A.J. Robinson, A.T. Dinsdale, R.H. Davies Hampton Thermodynamics Limited, M. Tyrer Faculty of Engineering, Environment and Computing, Coventry University
Introduction Oxide Modelling Software Used - MTDATA Extraction of Copper, Nickel and Precious Metals Slag-Matte-Alloy-Gas equilibria Establishing an Operating Envelope Producing Pigment Grade TiO 2 Leaching Simulation
Oxide Modelling: Project AIM: To develop a high quality, comprehensive thermodynamic database for oxide (plus sulphur, fluorine) containing systems of industrial interest for use in predictive phase equilibrium calculations Allows calculations directly relevant to industrial processes Calculations can cover temperature and composition ranges outside the scope of hard copy compilations Systems and priorities determined by the sponsors Database validated against plant / process data by sponsors 22 different sponsoring organisations so far Assessment work previously done at NPL coordinated by MIRO, and continuing at Hampton Thermodynamics
Oxide Modelling: Models LIQUID OXIDES, METALS AND MATTES Non-ideally interacting associated species LIQUID OXIDE CuO1/2, FeO, FeO3/2, FeSiO3, Fe2SiO4, SiO2, CaF2 LIQUID METAL / MATTE Cu, CuO, Cu2O, Cu2S, Fe, S CRYSTALLINE SOLUTIONS (for example SPINEL (XY2O4) ) Compound Energy Model: Interactions between ions on different sublattices Sublattice 1 - Tetrahedrally co-ordinated sites (Al+3,Cd+2,Co+2,Cr+3,Cr+2,Cu+2,Cu+,Fe+3,Fe+2,Li+,Mg+2,Mn+2,Ni+2,V+3,Zn+2)1 Sublattice 2 - Octahedrally co-ordinated sites (Al+3,Ca+2,Co+3,Co+2,Cr+3,Cu+2,Fe+3,Fe+2,Li+,Mg+2,Mn+4,Mn+3,Mn+2, Na+,Nb+5,Ni+2,Sn+4,Ti+4,Ti+3,V+3,Zr+4,Va)2 Sublattice 3 - Interstitial sites (Fe+2,Mg+2,Mn+2,Va)2 Sublattice 4 - Anion sites (O-2)4
Oxide Modelling: Coverage
Software: MTDATA Developed at National Physical Laboratory (NPL) Continuing at Hampton Thermodynamics More from Jim Robinson tomorrow
Cu, Ni, Precious Metals: Slag-Matte-Alloy-Gas Equilibria Above: Composition of matte Left: Distribution of Fe and Ni
Cu, Ni, Precious Metals: Slag-Matte-Alloy-Gas Equilibria Composition of matte containing greatest proportion of Ni On cooling, the matte separates into crystalline sulphides and a metallic phase from which precious metals can be extracted via aqueous chemistry
Cu, Ni, Precious Metals: Operating Envelope Cu2O-FeO-Ca2SiO4-Fe2O3 system with 10% Cu2O by mass Liquidus contour calculations used: To identify saturation limits To reduce smelting temperatures Improve fluidity in slag tapping
Cu, Ni, Precious Metals: Operating Envelope Na2O-Fe-O-Al2O3-SiO2 system with 4% Na2O, 6% Al2O3 by mass (natural minority components of flux) 1523 K Operating envelope (region where a homogeneous slag is produced) can also be explored with respect to p(o2) as a variable.
Producing Pigment Grade TiO2 AIM: Refine rutile slag (95% TiO2) by solution in a Na-K-Cl-F molten salt. Allows electro-separation of transition metal impurities OXIDE DATABASE SYSTEM OF INTEREST SALTS DATABASE Na2O-K2O-TiO2 Na-K-Cl-F-Ti-O NaCl-KCl SGTE SUBSTANCE DATABASE Stoichiometric species NaF, KF ASSESSMENT NEEDED NaCl-KCl-NaF-KF Mixed oxide / salt systems
Producing Pigment Grade TiO2 Calculated masses of phases formed as molten (Na,K)F replaces molten (Na,K)Cl used to dissolve TiO2 (4% by mass in the system) at 1100 K. Discolouration found where NaFTiO2 predicted to form. Upper limit for Cl in molten salt solvent established through phase equilibrium calculations
Leaching Simulation C-S-H (CaO-SiO2-H2O) gel is an important binding phase in cements (although generally regarded as metastable) Calculated equilibria between C-S-H and aqueous phases are critical in assessing the resistance to leaching of cements and grouts used in nuclear waste disposal Schematic representation of C-S-H (left) 5 sublattice model used to represent this phase
Leaching Simulation Calculated composition range for C-S-H gel phase at room temperature
Leaching Simulation Flow chart showing sequence of calculations in leaching simulation
Leaching Simulation Calculated results for C-S-H gel with Ca/Si = 2.7 leached with pure water at room temperature Experimental data from Harris, Manning et al., 2002 superimposed (NOT used in modelling C-S-H gel)
Oxide Modelling OXIDE MODELLING: FROM SLAGS TO CEMENTS We have reached CEMENTS. Thank you for your attention.