Dephosphorization of High-Phosphorus Oolitic Iron Ore By Prereduction with Carbon Monoxide Followed By Smelting

The study aims to develop an effective method for selective reduction of iron from high-phosphorus oolitic ore, enabling the subsequent separation of low-phosphorus metallic iron and high-phosphorus slag. The approach involves fluxing the ore with calcium oxide (CaO) to stabilize phosphorus and facilitate its removal.

The oolitic iron ore was fluxed with CaO to achieve a basicity of 2.0, then subjected to oxidative roasting at 1200 °C in a Nabertherm muffle furnace to convert iron phosphates into stable calcium phosphates. Solid-phase reduction was performed in a laboratory Tamman furnace at 1000 °C under a CO atmosphere. Final smelting was conducted at 1600 °C in a vertical Nabertherm furnace to achieve liquid-phase separation of metal and slag. X-ray diffraction and micro-X-ray spectral analysis were used for phase characterization.

CO selectively reduced iron to metallic form in both fluxed and non-fluxed samples, while phosphorus remained in the oxide phase. In fluxed samples, phosphorus was primarily present as calcium and aluminum phosphates, and iron was fully metallized. In non-fluxed samples, partial iron reduction occurred with residual phosphorus in iron, calcium, and aluminum phosphates. Upon smelting, non-fluxed ore formed a single melt with 0.1 wt.% phosphorus, whereas fluxed samples yielded separate metal and slag phases, with 0.3 wt.% phosphorus retained in the slag.

The results confirm that fluxing promotes the formation of stable calcium phosphates, preventing phosphorus reduction and enabling efficient Fe–P separation. The selective reduction of iron by CO was kinetically controlled and did not reduce phosphorus compounds. Compared to non-fluxed treatment, fluxing significantly improves the separation of phosphorus into slag during smelting.

This study demonstrates a two-stage process for effective dephosphorization of high-phosphorus oolitic iron ores. Key contributions include the identification of phosphorus stabilization mechanisms via CaO fluxing, successful selective reduction of iron by CO, and development of a method for producing low-phosphorous metal and high-phosphorous slag. The approach offers a promising route for processing refractory iron ores.