Fundamental Investigation Of The Pelletization Performance Of Complex Magnetite Concentrates

Abstract:With the rapid development of iron and steel industry and highly increased price of imported iron, the supply of iron ore has restricted the development of iron and steel industry in China, therefore, expanding the supply of iron ore material has become urgent. In this paper, raw properties of six kinds of complex magnetite concentrates, performance of green ball, oxidation characteristics and preheating and roasting behaviors of pellet had been studied, and pellet-making characteristics was revealed to provide theoritical guidance on their utilization.Research indicated that specific surface area, hydrophilicity, size and its composition are major factor that affecting the performance of green ball, magnetite green ball with larger specific surface area, smaller contact angle, higher wetting heat, and wider size composition with proper composition of fine particles had better strength.Green ball of different types of magnetite concentrate dramatically differs in drop number. Before pretreatment, when bentonite dosage is fixed at2.4%, drop number of DYC, PZHC, PTKC green ball is higher than5times per0.5m, while AQC, BTC, NSC is lower than4times per0.5m on average; after the samples is pretreated, when bentonite dosage is fixed at1.2%, of all the green balls are higher than5times per0.5m, DYC and PZHC reaches35times per0.5m.Oxidation characteristics of magnetite dry green ball was essential to roasting performance of pellet. Their is an optimum FeO content for each magnetite preheated pellet that makes its roasted pellet reach a best compressive strength, for each magnetite pellet, the higher the roasting temperature, the lower the FeO content.Since roasting performance differs with each magnetite, the compressive strength reaches above2500N/pellet is easy for roasted pellet made from BTC, NSC and PTKC while hard for those made from AQC, DYC and PZHC. Microstructure analysis on roasted pellets suggested:roasted pellets of BTC and NSC are high in compressive strength for the intimate solid consolidation of new Fe2O3, and PTKC for the emergence of magnesium ferrite and hortonolite, which are good binding phases boosted by B2O3; AQC and DYC was low in compressive strength for the microstructure destruction made by S during its oxidation, and PZHC for the loose solid consolidation of FeTiO3and new Fe2O3.Roasted pellet made from hematite is improved by adding magnetite, and roasted pellet made from magnetite with bad roasting performance is also improved by adding hematite.