Effect of Cooling Condition and Oxidation of P-concentrated Slag on Phosphorus Dissolution Behavior

It is expected that phosphorus-concentrated slag produced by using the pyro-reaction between high phosphorus hot metal, which was prepared by the reduction of usual steelmaking slag with a small amount of hot metal, and oxidizing slag can become an important phosphorus resource instead of phosphate rock. For separating phosphorus from the phosphorus-concentrated slag, the citric acid leaching method has been reported to be available. In this study, the effects of cooling condition and oxidation treatment of phosphorus-concentrated slag on the dissolution behaviors of phosphorus and other elements were discussed. Compared to slow-cooled slag, CO2 blowing-quenched slag did not affect dissolution of phosphorus but decreased dissolution of iron. Oxidation treatment increased the dissolution ratio of phosphorus by about twice and decreased that of iron by one-sixth. It was confirmed by the microscopic analysis of the mineral phases in these slags that the concentration of SiO2 and FeO solid-solved in 3CaO center dot P2O5 (C3P) phase increased by slow cooling, and they precipitated as fine Fe2O3-SiO2 compound in C3P phase by oxidation. Furthermore, the dissolution behavior of SiO2 and FeO solid-solved in C3P phase was investigated. Experimental results showed that the C3P-2CaO center dot SiO2 dissolved easily and the C3P-3FeO center dot P2O5 dissolved hardly. From those experimental findings, it was presumed that the change in dissolution behavior due to slag cooling conditions and oxidation treatment were attributed to the concentration of SiO2 and FeO in C3P phase.

Automated summary

It is possible to utilize phosphorus-concentrated slag produced from the pyro-reaction between high phosphorus hot metal and oxidizing slag as a substitute for phosphate rock. The citric acid leaching method can be used to separate phosphorus from the phosphorus-concentrated slag. This study evaluated the effects of cooling condition and oxidation treatment on the dissolution behaviors of phosphorus and other elements in the slag.