Selective Reduction of Iron and Phosphorus from Oolitic Ore
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ctive Reduction of Iron and Phosphorus from Oolitic Ore S. P. Salikhova, *, B. Suleimena, **, and V. E. Roshchina, *** a
South Ural State University, Chelyabinsk, 454080 Russia *e-mail: [email protected] **e-mail: [email protected] ***e-mail: [email protected]
Received December 13, 2019; revised January 24, 2020; accepted January 24, 2020
Abstract—The possibility of selective solid-phase reduction of iron from oolitic ore has been experimentally confirmed. Solid phase reduction was carried out at temperatures of 850 and 1000°C in a CO atmosphere and in a mixture with solid carbon. Distribution of iron and phosphorus was investigated with a scanning electron microscope. It was found that at a temperature of 1000°C a minimum amount of phosphorus (up to 0.3%) is transformed into the metallic phase upon reduction with carbon monoxide. Upon reduction in a mixture of ore with carbon, the phosphorus content in the metal phase reaches 1.0–1.3% even at a temperature of 850°C. Thermodynamic modeling of the processes occurring during reductive roasting of oolitic ore was carried out depending on temperature (1000–1400 K) and amount of carbon in the system. It is shown that reduction temperature and degree of phosphorus reduction vary depending on the ratio of CO and CO2 in the gas phase. At temperatures below 892°C, phosphorus is not reduced, and all iron is in the metal phase. With an increase in the amount of carbon in the system, phosphorus appears in the metal phase. With an excess of carbon in the system, all phosphorus is in the metal phase at a temperature of 892°С. Thus, with a certain amount of carbon in the system and, correspondingly, with a certain ratio of CO and CO2 in the gas phase, selective reduction of iron is possible without phosphorus reduction even at a temperature of 1100°С. Comparison of experimental results with results of thermodynamic calculation confirms the possibility of selective reduction of iron without phosphorus reduction only by carbon monoxide. Keywords: oolitic ore, selective reduction, metallization, phosphorus reduction, reduction degree, reduction temperature, thermodynamic modeling DOI: 10.3103/S0967091220070128
INTRODUCTION Development of iron recovery technology from oolitic phosphorus-bearing rocks is a relevant problem due to their huge global reserves [1]. Some examples include the Lisakovsk (1.6 billion tons) and Ayat deposits (more than 10 billion tons) in Kazakhstan [2, 3]. The proved reserves of oolitic rocks in China correspond to nearly 10% of the global reserves of iron ore [4]. The Bakcharsk deposit (28.7 billion tons) is one of the largest deposits of iron ore in Russia and the world [5]. The genesis of most of these rocks determines the high (up to 0.9 wt % and higher) phosphorus content in oolites. Phosphorus is nearly completely transformed into cast iron upon blast-furnace smelting. The elimination of phosphorus from cast iron in ladles or steel-making units requires increased consumption of materials and time. The maximum phosphorus content in iron-ore conce
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