Effect of Na2CO3 and CaCO3 on coreduction roasting of blast furnace dust and high-phosphorus oolitic hematite

Abstract

Iron was recovered from blast furnace dust and high-phosphorus oolitic hematite in the presence of Na2CO3 and CaCO3 additives. The functions of Na2CO3 and CaCO3 during the coreduction roasting process were investigated by XRD and SEM-EDS analyses. Results indicate that these additives not only hinder the reduction of fluorapatite, CaCO3 also decreases the P content of direct reduced iron (DRI) by increasing the reduction alkalinity. P remains as fluorapatite in the slag, which can be removed by grinding and magnetic separation under optimal conditions. The Na2CO3 promotes hematite reduction and improves the iron recovery (eFe) by replacing the FeO from fayalite, which results in quick growth and aggregation of metallic iron and improvement of eFe in DRI. A DRI with 91.88 mass% Fe, and 0.065 mass% P can be achieved at a recovery of 87.86 mass% under the optimal condition.