Separation of FeO and P<sub>2</sub>O<sub>5</sub> from Steelmaking Slag Utilizing Capillary Action

Abstract

The recoverability of FeO and P resources from steelmaking slag was investigated using a novel mechanical approach involving capillary action. After determining the phase relationship of the CaO–FeO–SiO2–P2O5 system with the coexisting 2CaO·SiO2 and MgO phases, it was found that P2O5 was concentrated in the 2CaO·SiO2 phase and was also distributed in the liquid phase. Due to the density difference of the FeO rich liquid phase and P2O5 containing 2CaO·SiO2 phase, the P2O5 concentration in the upper part of the sample was 2.2–3.6 times higher than that of the lower part. Also, the FeO concentration in the upper part of the sample was nearly half of that in the lower part. To improve the efficiency of the separation of the solid 2CaO·SiO2 phase and FeO rich liquid phase in steelmaking, capillary action was used to facilitate penetration into sintered CaO. Once the liquid phase had penetrated the CaO sinter, it was found that that the solid 2CaO·SiO2 phase and FeO rich phase could be effectively separated. When a sintered CaO sphere was added to a mixture of the solid 2CaO·SiO2 phase and FeO rich liquid phase, it was possible to recover 87% of the P2O5 and 90% of the FeO from steelmaking slag. The recovered CaO sinter, which includes a FeO rich liquid phase, may be used as Fe source or a dephosphorization agent, and the 2CaO·SiO2 phase, which includes P2O5, may be used as P source.