The Function of Ca(OH)2 and Na2CO3 as Additive on the Reduction of High-Phosphorus Oolitic Hematite-coal Mixed Pellets

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A process with coal-based direct reduction followed by magnetic separation is presented for recovering metallic iron from high-phosphorus oolitic hematite in this study. Ca(OH)2 and Na2CO3 were used as additives in the reduction roasting. A Direct Reduction Iron (DRI) with 93.28 mass% Fe, and 0.07 mass% P can be obtained at a recovery percentage of 92.30 mass% under optimal conditions. The mechanisms of Ca(OH)2 and Na2CO3 were investigated by XRD and SEM with EDS. It showed that fluorapatite was reduced to P smelt into metallic iron without additives while the hematite was reduced. The addition of Ca(OH)2 can not only inhibit the reduction of fluorapatite but also promote the reduction of hematite. Na2CO3 can promote the separation of iron from slag, meanwhile it may also inhibit the reduction of fluorapatite at the presence of 15 mass% Ca(OH)2. Under optimal conditions, phosphorus remained as fluorapatite in the slag and can be removed by grinding and magnetic separation.