Magnetic separation of phosphorus enriched phase from multiphase dephosphorization slag

Abstract

The authors have found that phosphorus exhibits remarkable segregation in the exhausted actual hot metal pretreatment slag (dephosphorization slag) and it exists as 3CaO • P2O5-2CaO SiO2 solid solution together with FeO-CaO-SiO2 matrix. Since their magnetic properties are significantly different, it is possible to separate them with the aid of superconducting strong magnetic field. In order to investigate effects of magnetic field strength, particle size of slag and so on, the experiment of the magnetic separation has been carried out by using simulated dephosphorization slag (18.1 Fe,O-45.9CaO-20.3SiO2-6.6 P2O 5-2.5MnO-5.5MgO in mass%) and super conducting magnet with 0.5 to 2.5 T. At stronger magnetic field, the quality of the recovered slag becomes better due to smaller contamination of Fe1O matrix phase while its quantity becomes worse and the amount of recovered slag is smaller. However, the quantity of the recovered slag can be improved by repeating the magnetic separation procedure. In the present experiment, about 65% of phosphorus enriched slag can be recovered with less than 10% of Fe,O matrix phase contamination at the condition of 0.5 T, particle size of smaller than 35 ¿im and water/slag ratio of 32 with single procedure. P2O5 content in the recovered slag is very close to that in the phosphorus enriched phase in the initial slag and Fe,O content is markedly decreased with magnetic separation. :.