The Temperature of Pretreatment on Microstructure Change of Lump Ore and Improvement of Metallurgical Properties

Abstract

Goethite is one of the most common minerals in iron ore, and is the main source of internal crystal water generated during the heating process of lump ore. To address this challenge, three measures are proposed: first, minimizing the decomposition of crystalline water upon the introduction of lump ores into the furnace; second, reducing the heat absorption of water vapor within the furnace; and third, increasing the proportion of lump ores being introduced into the furnace. With this in mind, the lump ore preheating treatment technology is introduced. By preheating the lumps at different temperatures, the influence of pretreatment on the reduction and soft melting of the lumps is studied. The results show that at different preheating temperatures, due to the transformation of FeOOH to Fe2O3, the natural goethite gradually changes from natural granular to spherical at higher preheating temperatures. When the preheating temperature is 400–700 °C, the coexisting phase of goethite and hematite in the pores changes obviously. The metallurgical properties of lump ore change dramatically. When the temperature is lower than 400 °C or higher than 700 °C, almost all goethite in lump ore is transformed into hematite, and the morphology does not change.