Measurement of Process Conditions Present in Pilot Scale Iron Ore Sintering

Abstract

An improved experimental technique has been developed to measure, concurrently, the oxygen partial pressures and temperatures within a pilot scale iron ore sinter pot as a function of time. The measurements and thermodynamic calculations have demonstrated that the oxygen partial pressure at peak bed temperature and during cooling can be oxidising or reducing relative to hematite. Examples of typical microstructures and phase assemblages observed in product sinters are presented. Potential mechanisms of hematite and magnetite formation at sub-liquidus and sub-solidus conditions are demonstrated. The relative impacts of changes to coke rate and draft pressure drop on the process conditions and proportions of the phases formed in the sinter have been measured. Increasing coke rate was shown to result in a faster sinter heating rates, higher peak bed temperatures and times at peak temperature. Higher draft pressures across the sinter bed resulted in faster sinter heating rates and shorter times at peak temperature.

Effect of Cooling Rate on the Controlled Solidification of “Fe₂O₃”–CaO–SiO₂ Liquids in Air in Synthetic Iron Ore Sinter

“…The bulk composition of the oxide mixture, 72.74 wt% Fe 2 O 3 , 6.11 wt% SiO 2 and 21.14 wt% CaO (CaO/SiO 2 ratio of 3.46 wt/wt), was selected as this was predicted to form SFC, Fe 2 O 3 and C 2 S on equilibrium cooling of the liquid in air. 9) For this bulk oxide composition, the liquidus temperature is estimated to be 1 568 K (1 295°C). Constant cooling rates between 2 K/s and 0.01 K/s were selected.…”

“…The controlled cooling rates achievable with the new experimental technique are within the range of cooling rates measured in industrial iron ore sintering. 9) An oxide pellet (0.1 g, 6 mm diameter) and substrate (70/30 Pt/Rh wire, 0.5 mm diameter) is heated and cooled in air in an electrically heated vertical tube furnace (alumina reaction tube, 38 mm OD 30 mm ID). The sample is suspended vertically within the reaction tube in the furnace with an alumina rod.…”

Effects of the Bulk Fe₂O₃ Concentration on the Controlled Solidification of “Fe₂O₃”–CaO–SiO₂ Liquids in Air

“…The controlled cooling rates achievable with the new experimental technique are within the range of cooling rates measured in industrial iron ore sintering. 5) A pelletised oxide powder mixture (0.1 g, 6 mm diameter) supported on a substrate (70/30 Pt/Rh wire, 0.5 mm diameter) is heated and cooled in air in an electrically heated vertical tube furnace (alumina reaction tube, 38 mm OD 30 mm ID). The sample is vertically suspended within the reaction tube in the furnace from an alumina rod.…”

“…The experiments were performed in air, as the effective oxygen partial pressures present in sinter on cooling from the peak bed temperatures to the solidus (approximately 1 200°C) in iron ore sinter pot tests has been measured to be close to 0.21 atm 5) and phase equilibria data is available for the "Fe 2 O 3 "-CaO-SiO 2 system in air. 6) Samples were cooled from 1 623 K to 1 073 K at 2 K/s, with the cooling rate selected as this is typical of that encountered in industrial iron ore sintering processes.…”

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“…Sintering of iron ore has been extensively investigated to get better insight into the process [1][2][3][4][5], including study of the use of pellets, sinter, and nut coke charges [6][7][8], thermodynamic analysis [9,10], and measurements and characterization [11,12].…”