The Basic Research On Magnetizing Roasting-magnetic Separation Of Siderite

With the rapid development of the steel industry, the amount of imported iron ore increased from70million tons in2000to686million tons in2011, an increase of nearly10times. Imported iron ore price increased from26.6dollars per ton in2000to163.8dollars per ton in2011. As China’s steel production capacity increased,60%of iron ore need to import. Siderite resources in China are very rich, but the utilization in iron and steel industry is not high. Rotary kiln is a successful industrial equipment for magnetic roasting process, but it is easy to accretion, and with low operating rate, high production costs. In this paper, scanning electron microscopy, energy dispersive analysis and X-ray diffraction techniques have been used to do the research.The purpose of the research is to provide theoretical guidance to strengthen the magnetic roasting and develop a new siderite roasting technology.Phase transformations and microstructure analysis of roasted ore have been studied. The results show that:whether the siderite roasting in the low-temperature (540℃) or high temperature (800℃), the decomposition rate and transformation rate of inner and outer layers are inconsistent, the decomposition and oxidation of the inner layer is always lagging behind the outer layer.The phase of siderite decompositon course at540℃is FeCO3â†'Fe3O4â†'γ-Fe2O3â†'α-Fe2O3, and the phase of siderite decomposition course at800℃is FeCO3â†'FeOxâ†'Fe3O4â†'γ-Fe2O3â†'α-Fe2O3.The siderite of87%purity have been used to do isothermal kinetics research. The results show that:siderite thermal decomposition reaction mechanism follows the Avrami-Erofeev random nucleation and subsequ-ent growth mechanism (n=1), the activation energy requires for46.17KJ/mol, factor A is23.02.Magnetic susceptibility studies have shown that:the magnetic susceptibility of the roasted ore is not the right indicators to measure the roasting effect, but can be used as the reference index, because Fe3O4and γ-Fe2O3have a strong magnetic field intensity, so magnetic susceptibility of the roasted ore in a wide range can be achieved good magnetic separa-tion indicators.Low-grade siderite of35.43%iron grade have been used to do the magnetizing roasting-magnetic separation process research. The results show that the iron concentrate, assaying63.55%Fe and95.76%iron recovery was obtained under the conditions of grinding fineness of roasted ore at98%passing0.074mm,78%passing0.043mm and magnetic separation at0.19T field intensity, and the roasted ore has been achieved under the roasting conditions of roasting temperature at800℃, roasting time for15min and siderite paticle size between16～10mm in neutral atmosphere. Chemical composition of iron concentrate shows that harmful ingredient is less, quaternary alkalinity is high, belongs to the self-fluxing magnetite concentrate, has a good metallurgical properties.