A Fundamental Investigation On Magnetite Concentrate Oxidized Pellets

With the rapid development of steelmaking, domestic high quality magnetite concentrates are becoming increasingly scarce and the properties of iron ore concentrates are complex that resulting the poor ballability problem. How to make full use of the local iron ore resources, especially effective use of local higher grade iron concentrate is a big problem which steel enterprise is facing. Therefore, in-depth study of the mechanism of how the material properties of domestic iron ore concentrates influence the ballability and calcination performance is of great significance to provide a theoretical basis for the promotion of pellet industrial development.In this paper, a same kind of bentonite binder, six domestic magnetite concentrates are adopted as research objects. The influence of iron ore's own inherent characteristics on dynamics ballability, strength of green balls and high temperature oxidation performance have been studied systematically by using the SEM, laser particle size analysis, specific surface area measurement, wetting heat and contact angle measurement, fractal dimension measurement and TGA. Results shows that the drop number is mainly influenced by hydrophilicity and size distribution D75.28,compressive strength of green balls by specific surface area and shock temperature by specific surface area, strength of green balls and moisture content.Study of dynamic ballability showed that dynamic ballability depends largely on the migration rate of capillary water. The growth rate of green balls is affected by particle size and hydrophilicity. When K value is about 0.4～0.5, the pellets grow fastest, With the K value increasing, the growth rate decline instead and the size of green ball become smaller and uniform.The study of oxidation performance of magnetite concentrates at high temperature have showed that the oxidation rate of concentrates is much bigger than the pellets. The oxidation rate of different concentrates has much connection with their particle size and MgO content. The high temperature oxidation of magnetite is controlled by chemical reaction at the initial stage and combination of chemical reaction and gas inner diffusion at later stage. Different iron ore pellets still have different preheating and roasting performance even at the same specific surface area. The FeO and SiO₂ content of raw materials and oxidation rate are the main factors to influence the preheated and fired pellets compressive strength of different concentrate pellets.