Enhancement of Pyro-Hydrometallurgical Technology of Dephosphorization of Brown Iron Ore of the Lisakovsk Field by Hot Leaching Method

Abstract

Brown iron ore constitutes about 13% of the global ore reserves and is widespread throughout the world. Brown iron ore is characterized by a significant content of harmful phosphorus (0.7 to 3.0%), which is typically present in the lattice of the main iron ore component in a chemically bound form. Based on the case study of the gravity-magnetic concentrate from the Lisakovsk field, OJSC “VNIIMT” has developed and lab-tested a pyro-hydrometallurgical dephosphorization technology, which can be applied while preparing the concentrate for agglomeration. As established earlier, phosphorus leaching proceeds successfully only after a high-temperature roasting of the gravity-magnetic concentrate, when the hydrated phosphorus-containing component decomposes. Free phosphorus then reacts with sulfuric acid. The main difference of the leaching process was that dephosphorization of the preliminary roasted concentrate with weak aqueous solution of sulfuric acid was performed without cooling it (hot leaching). A fixed-bed roasting was performed in a laboratory muffle furnace. After heating to a specific temperature and soaking for 60 minutes, a crucible containing the sample of the material was removed from the furnace. The roasted material was unloaded in hot condition into a previously prepared weak aqueous solution of sulfuric acid containing 5 wt.% of H2SO4 (solid-to-liquid phase ratio — 1:2). Such ratio prevents the solution from boiling during unloading of the hot concentrate. The pulp was mixed inside the ceramic crucible using an overhead stirrer. It has been established experimentally that hot leaching significantly reduces the duration of dephosphorization (by 3 times or more) compared to leaching under normal conditions. Another important advantage is the possibility of reducing the number of pieces of process equipment industry-wide, since cooling and leaching of the roasted gravity-magnetic concentrate from the Lisakovsk field can be implemented in one apparatus. In this case, reduced duration of the leaching process will enable an increase in productivity of the dephosphorization equipment by 3 times or more.