Research On Process And Mechanism Of Coal Based Reduction And Magnetic Separation Of Siderite

With the rapid development of iron and steel industry, China is faced with a serious problem of raw material shortage, the profit of steelmakers are squeezed by large amount of expensive imported iron ore. Therefore, domestic refractory iron ores like siderite have to be rationally utilized to guarantee the healthy development of iron and steel industry in China. In this paper, siderite from Xinjiang was used as raw samples to set a new way to utilize siderite and launch the research on process and mechanism of coal based direct reduction-magnetic separation of siderite.Coal based direct reduction course of siderite was FeCO3â†'Fe3O4â†'FeOâ†'Fe, for each step of the course, reaction in the inner layer of the ore delayed with that of outer layer. During decomposition and reduction of siderite, the microstructure of ore changed remarkably, tiny holes and interstices initially appeared during the crystal transformation from FeCO3to Fe3O4, when Fe3O4was transformed to FeO, the holes was squeezed and became larger, when FeO was transformed to Fe, the holes was even larger and metallic iron was scattered until the iron grains grew and connected. But the ore stayed integral during the whole course and was less likely to pulverize.Technological experiment of coal-based direct reduction-magnetic separation of siderite was launched in a ratory kiln with siderite and lignite sized from25mm to5mm. The best results was met at roasting temperature at1050℃, roasting time at140min, C/Fe at1.86and desulfurizer dosage at3%. After the roasted product was dryly magnetically separated with field intensity at0.15T, the roasted ore was wetly grinded to85.92%passing0.074mm and separated with field intensity at0.1T, and iron powder with92.06%in Fe content,90.52%in metallization rate,0.16%in S content was prepared,85.94%of Fe was recovered. Since the ore was less likely to pulverize during decomposition and reduction of siderite, the roasted product contains only8.71%of powder, and ring-forming was not found in the rotary kiln.Analysis on final products has shown that residual coal contains50.36%of fixed carbon and was perfect material for semicoke-making, iron powder could be provided to EAF steelmaking, and tailings could be used as raw material for cement-making.