| Magnetic roasting technique is one of the most effective operations in the treatment of low-grade siderite ores. Aiming at the disadvantages of traditional magnetic roasting process on high energy consumption, low efficiency and bad roasted quality, suspension calcining process was suggested to dispose siderite.In this paper, the siderite in Daxigou, Shaanxi province was used as the main raw materials, the bonding phenomenon of siderite at high temperature and the feasibility of magnetic roasting siderite by air suspension process at low temperature were investigated. On this basis, magnetic roasting siderite by suspension process at middle-high temperature was conducted. The effects of roasting atmosphere, temperature and time on the roasting indexes were analyzed. The optimical operating parameters for the concentrate of roasted ores with perfect iron grade and iron recovery were obtained. Meanwhile the effect of cooling conditions on the quality of roasted ores was researched, and the feasibility of fast cooling siderite in the air was discussed.The results showed that, roasting siderite in lump state at 950℃ for 1h, the ores began to bond. The ores powder could bond to a piece when it was roasted at 1100℃ for 30min and the bonding intensity was strong, that was, the time when bonding phenomenon occurred was advanced as the temperature became higher. The magnetization effect of suspension roasting at low temperature was not very good. For the siderite with a granularity from 40 to 60 μm, by suspension roasting process, roasted at 750℃ for 3 min in weak-oxidation (air + 5% nitrogen) atmosphere, the concentrate of roasted ores with an iron grade of 58.29% and an iron recovery rate of 80.73% were obtained. The cooling velocity is the most important factor that influences the quality of roasted ores. Fast cooled in the air made the ores skip over the temperature range from 500-400℃ where intense phase change occurred, preserving the magnetism of roasted ores.
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