Influence of Al₂O₃ modification on phosphorus enrichment in P bearing steelmaking slag

Abstract

In order to effect enrichment of phosphorus in converter slag, phosphorus enrichment was researched by Al₂O₃ melting modification, the Al₂O₃ modification process is discussed according to the thermodynamic analysis, and phosphorus rich phase was separated from experimental slag by magnetic separation. The results show that gehlenite (Ca₂Al₂SiO₇) and high phosphorus solid solution (n′C₂S–C₃P) are generated by the continuous reaction of n2CaO.SiO₂–3CaO.P₂O₅ (nC₂S–C₃P) solid solution precipitated in the slag with Al₂O₃ at 1623K. The early precipitated solid solution (nC₂S–C₃P) is reduced with increasing content of Al₂O₃, and even disappeared. If the addition of Al₂O₃ is increased or excess in the slag, the high phosphorus solid solution (n′C₂S–C₃P) that was generated by the above mentioned reaction will continue to react with Al₂O₃ to produce gehlenite, then the phosphorus content in the phosphorus rich phase is increased. Through magnetic separation the amount of non-magnetic substance of no. 2 slag after modification is raised 26·88% compared to the original slag, the distribution ratio of P₂O₅ is raised from 0·96 to 4·61, and the amount of separated non-magnetic substance is 68·47% of the total no. 2 slag, 84·57% of the phosphorus in slag is entered into collected non-magnetic substance, thereby most phosphorus element was recycled.

Keywords:

• P bearing steelmaking slag
• nC₂S–C₃P solid solution
• Al₂O₃ melting modification
• Enrichment
• Magnetic separating

Acknowledgements

The authors would like to thank Australian Hamersley Iron Ore Company for the financial support. The great help from Rio Trading (Shanghai) Company Limited is really appreciated.