Effects of CaO and Na₂CO₃ on the reduction of high silicon iron ores

Abstract

The effects of CaO and Na₂CO₃ on the reduction of high silicon iron ores at 1 250 °C were studied. The experimental results showed that the metallization rate was significantly hindered by the addition of CaO and Na₂CO₃, particularly at the early stage of roasting, compared to the rate without additives. In the absence of additives, iron oxides were quickly reduced to metallic iron, and fayalite was difficult to form. When CaO and Na₂CO₃ were added, the low reducible iron-containing silicate compounds formed and melted, subsequently retarding the metallization process. The inhibition of Na₂CO₃ was more noticeable than that of CaO, and higher Na₂CO₃ doses resulted in stronger inhibition of the increased metallization rate. However, when Na₂CO₃ was added prior to CaO, the liquid phase formed, which facilitated the growth of the metallic phase. To reinforce the separation of the metallic phase and slag, an appropriate amount of liquid phase generated during the reduction is necessary. It was shown that when 10% CaO and 10% Na₂CO₃ were added, a high metallization rate and larger metallic iron particles were obtained, thus further decreasing the required Na₂CO₃ dosage.

Keywords

high silicon iron ores / metallization rate / liquid phase / metallic iron / growth

References

[1] Chen H L, Shen W G, Shan L L, et al. Situation of Discharge and Comprehensive Utilization of Iron Tailings Domestic and Abroad[J]. Concr., 2012, 2: 88-91.

[2] Li J, Ni W, Fan D C, et al. Process Mineralogy Research on Iron Tailings from Qidashan[J]. Metal Mine., 2014, 451: 158-162.

[3] Bai S J, Wen S M, Liu D W, et al. Beneficiation of High Phosphorus Limonite Ore by Sodium-carbonate-added Carbothermic Reduction[J]. ISIJ Int., 2012, 52(10): 1757-1763.

[4] Bai S J, Wen S M, Liu D W, et al. Catalyzing Carbothermic Reduction of Siderite Ore with High Content of Phosphorus by Adding Sodium Carbonate[J]. ISIJ Int., 2011, 51(10): 1601-1607.

[5] Zhu D Q, Chun T J, Pan J, et al. Recovery of Iron from High-Iron Red Mud by Reduction Roasting With Adding Sodium Salt[J]. J. Iron Steel Res. Int., 2012, 19(8): 1-5.

[6] Yu W, Sun T C, Liu Z G, et al. Effects of Particle Sizes of Iron Ore and Coal on the Strength and Reduction of High Phosphorus Oolitic Hematite-coal Composite Briquettes[J]. ISIJ Int., 2014, 54(1): 56-62.

[7] Yu W, Sun T C, Kou J, et al. The Function of Ca(OH)₂ and Na₂CO₃ as Additive on the Reduction of High-Phosphorus Oolitic Hematite-coal Mixed Pellets[J]. ISIJ Int., 2013, 53(3): 427-433.

[8] Zhu D Q, Chun T J, Pan J, et al. Upgrading and Dephosphorization of Western Australian Iron Ore Using Deduction Roasting by Adding Sodium Carbonate[J]. Int. J. Miner. Metall. Mater., 2013, 20(6): 505-513.

[9] Basumallick A. Influence of CaO and Na₂CO₃ as Additive on the Reduction of Hematite-Lignite Mixed Pellets[J]. ISIJ Int., 1995, 35(10): 1050-1053.

[10] Sun Y S, Han Y X, Gao P, et al. Recovery of Iron from High Phosphorus Oolitic Iron Ore Using Coal-based Reduction Followed by Magnetic Separation[J]. Int. J. Miner. Metall. Mater., 2013, 20(5): 411-419.

[11] Wren A W, Coughlan A, Smale K E, et al. Fabrication of CaO-NaOSiO₂/TiO₂ Scaffolds for Surgical Applications[J]. J. Mater. Sci. Mater. Med., 2012, 23(12): 2881-2891.

[12] Silva A C, Castanho S R H. Silicate Gasses Obtained from Fine Silica Powder Modified with Galvanic Waste Addition[J]. J. Non-Cryst. Solids., 2004, 348: 211-217.

[13] Morey G W. Data of Deochemistry, 1964 Washington: United States Government Printing Office.

[14] Pan W, Ma Z J, Zhao Z X, et al. Effect of Na₂O on the Reduction of Fe₂O₃ Compacts with CO/CO₂[J]. Metall. Mater. Trans., B, 2012, 43(6): 1326-1337.

[15] Jozwiak W K, Kaczmarek E, Maniecki T P, et al. Reduction Behavior of Iron Oxides in Hydrogen and Carbon Monoxide Atmospheres[J]. Appl. Catal. A-Gen., 2007, 326(1): 17-27.

[16] Huang Z C, Cai L B, Zhang Y B, et al. Reduction of Iron Oxides of Red Mud Reinforced by Na₂CO₃ and CaF₂[J]. J. Cent. South Univ.(Sci Technol.)., 2010, 41(03): 838-843.

[17] Li G H, Zhang S H, Rao M J, et al. Effects of Sodium Salts on Reduction Roasting and Fe-P Separation of High-phosphorus Oolitic Hematite Ore[J]. Int. J. Miner. Process., 2013, 124: 26-34.

[18] Nadiv S, Weissberger S, Lin I J, et al. Diffusion Mechanisms and Reactions During Reduction of Oolitic Iron-Oxide Mineral[J]. J. Mater. Sci., 1988, 23(3): 1050-1055.

[19] Weissberger S, Zimmels Y, Lin I J. Mechanism of Growth of Metallic Phase in Direct Reduction of Iron Bearing Oolites[J]. Metall. Trans. B, 1986, 17(3): 433-442.

[20] Chen J, Lin W M. Noncoking Ironmaking, 2014 Beijing: Chemical Industry Press.

[21] Hu W T, Wang H J, Liu X W, et al. Monomer Dissociation Characteristics and Selective Recovery Technology of Microfine Iron Particles[J]. J. Univ. Sci. Technol B, 2013, 35(11): 1424-1430.