STUDY ON PHOSPHORUS REMOVAL OF HIGH-PHOSPHORUS OOLITIC HEMATITE BY COAL-BASED DIRECT REDUCTION AND MAGNETIC SEPARATION

摘要

In this article, mineralogical phase changes and structural changes of iron oxides and phosphorus-bearing minerals during the direct reduction roasting process were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). It has been found that the reduction of hematite follows the following general pathway: Fe_2O_3 -> Fe_3O_4 -> FeO -> Fe. The last step of the reduction process contains two side reactions: either FeO -> Fe_2SiO_4 ->Fe or FeO -> FeAl_2O_4 -> Fe depending on the micro mineralogical makeup of the ore. In the reduction process of FeO ^ Fe, oolitic structure was destroyed completely and fluorapatite was diffused into gangue while metallic phase is coarsening at temperatures below 1200℃. Therefore, the separation of phosphorus-bearing gangue and metallic iron can he achieved by wet grinding and magnetic separation, and low phosphorus content metallic iron powder can be obtained. However, when the temperature reached 1250° C and beyond, some of the fluorapatite was reduced to elemental P and diffused into the metallic iron phase, making the P content higher in the metallic iron powder.