Separation and recovery of phosphorus from steelmaking slags with the aid of strong magnetic field

In order to make sure the great potential of steelmaking slag as a new phosphorus resource, domestic phosphorus material flow in Japan including iron and steel industry has been investigated based on the statistical data on 2002. It has been demonstrated that phosphorus in the steelmaking slag is almost equivalent with that in the imported phosphate rock in the view points of the amount and the concentration. Phosphorus exists mainly in the form of calcium-phosphate or its solid solution with calcium-silicate rather than the FetO rich liquid phase in the slag and exhibits remarkable segregation in the solidified slag. If the strong magnetic field is applied to the crushed slag, precipitated calcium-phosphate solution phase can be separated from FetO matrix phase due to the large difference of each magnetic property. It has also been indicated by the Waste Input-Output model that the phosphorus recovery from steelmaking slag by the new process proposed in the present work has great environmental and economical benefits.