Recovery of Phosphorus from Dephosphorization Slag Produced by Duplex High Phosphorus Hot Metal Refining

Phosphate rock is a vital nonrenewable resource. In order to find new source of phosphorus, the recovery of phosphorus from dephosphorization slag produced by duplex steelmaking process (De-P slag in De-P_De-C steelmaking process) was investigated in the present paper. It was demonstrated that the P-rich phase in dephosphorization slag is difficult to recover effectively by magnetic separation as the reason of P enriched phase inlay in the Fe enriched phase in the slag. The relationship between P recovery ratio and magnetic intensity and slag particle size were also obtained. A series of slag modification experiments were designed to investigate the recovery of phosphorus from high P2O5 content dephosphorization slag produced by duplex high phosphorus hot metal refining. It was found that the addition of SiO2, Al2O3 and TiO2 has a positive influence on the P recovery ratio. However, the P recovery ratio and the concentration of P2O5 in unmagnetized slag showed a reciprocal relationship with increasing SiO2 and Al2O3 content. The P recovery ratio was little affected by the addition of FetO and MnO. Furthermore, the P recovery ratio increased under the stirring condition. 74% and 87% P were recovered in the unmagnetized phases with adding 10% SiO2 and Al2O3, respectively. The results demonstrated that most of the phosphorus in the slag could be recovered through slag modification and magnetic separation.