Reduction of Titania-Ferrous Ore by Carbon Monoxide

Abstract

The reduction of titania-ferrous ore (ironsand) containing 57.2 wt% of iron and 7-8 wt% of TiO 2 was investigated in non-isothermal and isothermal reduction experiments using CO-CO 2 -Ar gas mixtures in a laboratory fixed bed reactor. Samples in the course of reduction were characterised using XRD, EPMA and SEM.Two types of particles were identified in ironsand: 1) homogeneous particles of titano-magnetite with cubic spinel structure (a major type); and 2) non-homogeneous particles, characterised by lamellar structure of rhombohedral titano-hematite, exsoluted from the titano-magnetite.Titano-magnetite, which is a magnetite-ulvospinel solid solution (Fe 3 O 3 ) 1Ϫx (Fe 2 TiO 4 ) x , with xϭ0.27Ϯ0.02, was reduced to metallic iron and titanium sub-oxides. Titanium had a strong effect on the mechanism and rate of reduction of iron oxide in ironsand.KEY WORDS: titano-magnetite (Fe 3Ϫx Ti x O 4 ); magnetite (Fe 3 O 4 ); ulvospinel (Fe 2 TiO 4 ); titano-hematite; reduction; carbon monoxide.and then kept at 1 373 K until the completion of the reduction. CO-CO 2 -Ar gas mixture was prepared from highly purified argon, carbon monoxide and chemically pure carbon dioxide using mass flow controllers. The gases were purified before mixing by passing through traps filled with Drierite and 4A molecular sieve to remove moisture. The inlet gas flow rate was maintained at 800 ml/min. The reducing gas was introduced into the reactor from the top and left the reactor through a porous plug at the bottom. The outlet gas was analysed on-line by mass spectrometer.Samples reduced to different extent were analysed by XRD and microprobe spectrometer (EPMA, Cameca SX-50 Probe). The morphology of samples was observed by Field Emission Scanning Electron Microscope (FESEM, HITACHI S-4500). The extent of reduction was calculated as a mass fraction of oxygen in iron oxides removed in the course of reduction. Results and Discussion Phase Characterisation of IronsandThe XRD patterns of ironsand, hematite iron ore and magnetite obtained by partial reduction of the hematite iron ore are shown in Fig. 2. The XRD pattern of ironsand included peaks for magnetite, hematite and traces of maghemite (g-Fe 2 O 3 ). The peaks of Ti-rich phases such as ulvospinel (Fe 2 TiO 4 ), ilmenite (FeTiO 3 ) and rutile (TiO 2 ) were not detected.The EPMA analysis showed that the main phase of the New Zealand ironsand was homogeneous TTM. A small proportion of ironsand exhibited exsolution caused by partial oxidation (weathering) of TTM to TTH, which has the XRD pattern identical to hematite. Homogeneous Titanomagnetite ParticlesParticles with homogeneous TTM phase constituted the bulk of the ironsand. Quantitative elemental analysis across of such particles with a step of 1 micron is shown in Fig. 3. The analysed elements were Fe, Ti, Al, Mg, Si and O. Iron and titanium in the particle were distributed uniformly along the line of analysis with the average compositions of 32.8 at% Fe and 2.98 at% Ti. However, the concentrations of aluminium and magnesium fluctuated in t...

Reduction of the Mixture of Titanomagnetite Ironsand and Hematite Iron Ore Fines by Carbon Monoxide

“…1) With the mixing of 30-75 mass% of the hematite iron ore fines into the ore mixture, the time required for the complete reduction of the iron oxide in the ore mixture could be slightly reduced by about 10 %. However, when the content of the hematite iron ore fines was higher than 75 mass% in the ore mixture, the reduction rate decreased, especially after 80 % reduction achieved.…”

“…1) and 2). The New Zealand ironsand predominantly consists of titanomagnetite (TTM, Fe 3-x Ti x O 4 , with xϭ0.27Ϯ0.02), and contains about 57 mass% of total iron, 1) with the price of about 2/3 of the conventional hematite iron ores.…”

“…It has been reported that the reduction of TTM ironsand is much slower than that of magnetite or hematite iron ores due to the spinel cubic structure and higher thermodynamic stability of TTM phase resulted from the substitution of titanium in the lattice. 1,2,[4][5][6][7] The complete reduction of iron oxides in TTM ironsand by carbon monoxide is possible at high temperatures around 1 373 K, under high reducing potential. 1,4,6,7) Although it has been reported that the preoxidation increases the reducibility of the ironsand, 2,7) the high content of titanium oxide in the ironsand is not preferable for the further ironmaking processes, because the titanium oxides in TTM ironsand form TiN, TiC and TiO, which have very high melting points and, in large amounts, 8) can decrease the sulphide capacity and the viscosity of slags during the processes.…”

Relationship between the Phases, Structure, MgO Migration and the Reduction Performance of the Pre-oxidized Vanadium-titanium Magnetite Ore in a Fluidized Bed

“…4), indicating the FeTiO 3 phase is difficult to be reduced. As reported in some researches, 13,14) the new phase of Fe 2 TiO 4 was generated in the initial stage of the VTM reduction, which was further reduced to FeTiO 3 , and finally was reduced to Fe and TiO 2 . However, no peaks belongs to Fe 2 TiO 4 could be detected due to its low content.…”

Structural Analysis of Sinter with Titanium Addition / Analiza Strukturalna Spieku Z Dodatkiem Tytanu

“…The process is based on the presumption that due to the intensive reduction process within the blast furnace TiO 2 is reduced. Research on this process has shown that the reduced out titanium reacts with carbon and nitrogen and forms TiC, TiN a TiCN [1][2][3][4][5][6].…”