悬浮磁化焙烧——氧化冷却过程中磁赤铁矿生成规律

Formation of Maghemite in Suspension Magnetization Roasting-Oxidation Cooling Process

悬浮磁化焙烧—磁选已在难选铁矿石的开发中实现工业应用,焙烧产物的冷却过程是影响磁选指标的重要因素。空气氧化冷却可以将焙烧产物中的部分磁铁矿氧化成强磁性磁赤铁矿,同时可以回收氧化过程释放的潜热,具有广阔的应用前景。对酒钢铁矿石进行了悬浮磁化焙烧—氧化冷却试验。结果表明,氧化温度、氧化时间和空气流量对氧化过程及磁选指标影响显著。最佳的氧化条件为氧化温度300℃、氧化时间5 min、空气流量500 mL/min。在最佳条件下,氧化冷却产物中磁赤铁矿含量为17.74%,磁选精矿铁品位为55.34%、铁回收率为90.31%。焙烧产物的氧化冷却过程按两条路径同时进行,一是Fe_(3)O_(4)→α—Fe_(2)O_(3),二是Fe_(3)O_(4)→γ—Fe_(2)O_(3)→α—Fe_(2)O_(3);氧化温度高于300℃时,磁铁矿主要被氧化为赤铁矿。因此,焙烧产物在氧化冷却时,应先在N_(2)中冷却至300℃,再经空气氧化冷却至室温,以获得较高的磁赤铁矿含量。

Suspension magnetization roasting-magnetic separation has been industrially applied in the development of refractory iron ore,and the cooling process of roasted product is an important factor affecting the magnetic separation indexes.Air oxidation cooling can oxidize part of the magnetite in the roasted product into strong magnetic maghemite,and at the same time the latent heat released by the oxidation process can be recovered,which has broad application prospects.The suspension magnetization roasting and oxidation cooling experiments were carried out on Jiugang iron ore,and the results showed that:oxidation temperature,oxidation time and air flow rate have significant effects on the oxidation process and magnetic separation indexes.The best oxidation conditions are:oxidation temperature 300℃,oxidation time 5 min,air flow rate 500 mL/min.Under the best conditions,the maghemite content in the oxidation cooling product is 17.74%,the iron grade of the magnetic separation concentrate is 55.34%,and the iron recovery is 90.31%.The oxidation cooling process of the roasted product is carried out simultaneously in two paths,one is Fe_(3)O_(4)→α-Fe_(2)O_(3),and the other is Fe_(3)O_(4)→γ-Fe_(2)O_(3)→α-Fe_(2)O_(3).When the oxidation temperature is higher than 300℃,magnetite is mainly oxidized to hematite.Therefore,when the roasted product is cooled under oxidization atmosphere,the roasted product should first be cooled to 300℃in N_(2),and then cooled to room temperature in air to obtain a higher maghemite content.