An alternative route of magnetite processing involving the formation of CWF (CaFe3O5/calcio-magnetite) phase in lime-magnetite pellets (LMPs) was proposed in the previous paper. This paper is focused on the isothermal kinetics of the overall reaction, and of CWF formation, at 850, 950 and 1050°C. Different kinetics models were evaluated for the current data, and model-fitting techniques with linear regression analysis was applied. Microstructural analysis was carried out using SEM and EPMA to understand the evolution of product morphology and the reaction mechanism. The time series experiments and characterization results suggested the formation of CWF phase within 5 min of reaction and the formation of C2F (2CaO·Fe2O3) as a transient phase. Kinetic analysis suggested both the overall reaction and CWF formation could be described by Jander model. While there was good evidence for solid-state diffusion-controlled reaction mechanism, further study is required to establish the rate limiting step.
PurohitSRhamdhaniMABrooksGet al.Alternative route for magnetite processing for lower carbon footprint ironmaking through lime-magnetite pellets (LMPs). Ironmak Steelmak. 2019. DOI:10.1080/03019233.2019.1569811.
6.
FotievAAStrelkovVV.Interaction between Fe3O4 with CaCO3 in an inert atmosphere and in air. Zh Neorg Khim. 1979;24:2905–2908.
7.
EvrardOMalamanBJeannotFet al.Mise en évidence de CaFe4O6 et détermination des structures cristallines des ferrites de calcium CaFe2+nO4+n (n = 1, 2, 3): nouvel exemple d’intercroissanc. J Solid State Chem. 1980;35:112–119.
8.
SchenckVRLaymanncAJenckelE.Gleichgewichtsuntersuchungen über die Reduktions-, Oxydations-und Kohlungsvorgänge beim Eisen. XIII. Z Anorg Allg Chem. 1937;235:65–76.
9.
TurkdoganET.Oxygen potentials and phase equilibria in the Fe-Ca-O system. Trans Metall Soc AIME. 1961;221(3):546–553.
10.
BergmanBSongC.Microstructural study of phase equilibria in the Fe-Ca-O system involving CaFe5O7. J Am Ceram Soc. 1989;72(8):1364–1367.
11.
HillertMSellebyMSundmanB.An assessment of the Ca-Fe-O system. Metall Trans A. 1990;21(10):2759–2776.
12.
PhilipsBMuanA.Phase equilibria in the system CaO-iron oxide in air and at 1 atm. O2 pressure. J Am Ceram Soc. 1958;41:445–454.
13.
SchürmannEKraumeG.Phasengleichgewichte des Schnittes FeOn–CaO im Dreistoffsystem FeO–Fe2O3–CaO bei Eisensättigung. Steel Res Int. 1976;47:327–331.
14.
ReeveDAGregoryAG.Modification for the oxygen potential diagram for the system Fe-Ca-O. Trans Inst Min Metall (Sect C). 1967;76:273–277.
15.
HidayatTShishinDDecterovSAet al.Thermodynamic optimization of the Ca-Fe-O system. Metall Mater Trans B. 2016;47(1):256–281.
16.
ScarlettNVYPowncebyMIMadsenICet al.Reaction sequences in the formation of silico-ferrites of calcium and aluminium in iron ore sinter. Metall Mater Trans B. 2004;35(5):929–936.
17.
WebsterNASPowncebyMIMadsenICet al.Silico-ferrite of calcium and aluminium (SFCA) iron ore sinter bonding phases: new insights into their formation during heating and cooling. Metall Mater Trans B. 2012;43(6):1344–1357.
18.
FukuyamaHHossainKNagataK.Solid-state reaction kinetics of the system CaO-FeO. Metall Mater Trans B. 2002;33(2):257–264.
19.
DaiYGuoXZhangJ.Effect of Ca(II)-ion in wüstite on its reduction to iron. Steel Res Int. 2006;77(8):537–541.
20.
FerreiraSCoresARoblaJIet al.The influence of gangue and additives on the divalent iron content of magnetite pellets. Steel Res Int. 2014;85(2):261–272.
21.
ButtonRALundhP-A.Mineralogy and mineral formation in iron ore sinter with addition of magnetite fines. Ironmak Steelmak. 1989;16(3):151–164.
22.
BaleCWBèlisleEChartrandPet al.Factsage thermochemical software and databases, 2010–2016. CALPHAD.2016;54:35–53.
23.
YazawaATakedaY.Equilibrium relations between liquid copper and calcium ferrite slag. Trans Jpn Inst Metals. 1982;23(6):328–333.
24.
ShuvaMAHRhamdhaniMABrooksGAet al.Thermodynamics behaviour of germanium during equilibrium reactions between FeOx–CaO–SiO2–MgO slag and molten copper. Metall Mater Trans B. 2016;47(5):2889–2903.
25.
RietveldHM.A profile refinement method for nuclear and magnetic structures. J Appl Cryst. 1969;2:65–71.
26.
HillRJHowardCJ.Quantitative phase analysis from neutron powder diffraction data using the Rietveld method. J Appl Cryst. 1987;20:467–474.
27.
BrukerAXS. (2013). TOPAS V5: general profile and structure analysis software for powder diffraction data. Version 5.
28.
HarrowfieldIRMacRaeCMWilsonNC.Chemical imaging in electron microprobes. Proceedings of the 27th Annual MAS Meeting, Microbeam Analysis Society; New York; 1993. p. 547–548.
29.
WilsonNCMacRaeCM.An automated hybrid clustering technique applied to spectral data sets. Microsc Microanal. 2005;11(Suppl 2):434CD.
30.
SohnHYSzekelyJ.The effect of reaction order in non-catalytic gas-solid reactions. Can J Chem Eng. 1972;50:674–676.
31.
DoraiswamyLKSharmaMM.Heterogeneous reactions: analysis, examples, and reactor design. New York: Wiley; 1984.
32.
RamachandranPADoraiswamyLK.Modeling of noncatalytic gas-solid reactions. AIChE J. 1982;28(6):881–900.
33.
WenCY.Non-catalytic heterogenerous solid-fluid reaction models. Ind Eng Chem. 1968;60:34.
34.
KhawamAFlanaganDR.Basics and applications of solid-state kinetics: a pharmaceutical perspective. J Pharm Sci. 2006;95(3):472–498.
35.
AhmadSRhamdhaniMAPowncebyMIet al.Sulfidation kinetics of natural chromite ore using H2S gas. Metall Mater Trans B. 2015;46(2):557–567.
36.
JanderW.Reactions in solid state at high temperatures: I. Z Anorg Allg Chem. 1927;163:1–29.
37.
GinstlingAMBrounshteinBI.Concerning the diffusion kinetics of reactions in spherical particles. J Appl Chem USSR (Engl Transl). 1950;23:1327–1338.
38.
FirdausMRhamdhaniMADurandetYet al.High temperature oxidation of rare earth permanent magnets. Part 2 – kinetics. Corros Sci. 2018;133:318–326.
39.
von BogdandyLEngellH-J.The reduction of iron ores: scientific basis and technology. Berlin, Heidelberg: Springer; 2013. p. 101.
40.
LiYFruehanRLucasJet al.The chemical diffusivity of oxygen in liquid iron oxide and a calcium ferrite. Metall Mater Trans B. 2000;31(5):1059–1068.
