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.