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The mineral structure of high-phosphorus iron ore is complex, mainly oolitic high-phosphorus iron ore. Iron oxides are generally dominated by hematite, and may also include siderite, magnetite, limonite, goethite, etc. Gangue minerals mainly include quartz, phosphate minerals, chlorite, carbonate, etc. The core of oolitic particles is generally hematite or quartz.
High-phosphorus iron ore is a complex and difficult-to-select iron ore in the world, with complex mineral embedding relationships and close iron-phosphorus bonding. The dephosphorization methods of high-phosphorus iron ore are divided into ore dressing, wet method, smelting method and direct reduction method.
Dephosphorization by ore dressing method is a method of grinding the ore to fully dissociate the iron minerals and phosphate minerals, and then performing gravity separation, flotation and magnetic separation for dephosphorization, including reverse flotation, selective flocculation reverse flotation and magnetic separation-reverse flotation and other combined processes.
Among them, it is difficult to achieve efficient dephosphorization through conventional ore dressing. The phosphorus content after dephosphorization is generally above 0.2%, and the iron recovery rate is 50% to 70%. A high dephosphorization rate is generally manifested by the strong phosphorus collection effect of the collector, but a lot of iron is carried out by the tailings during the ore dressing process, resulting in a low iron recovery rate.
Gravity separation is a method of separation based on the difference in mineral density coefficients. Reasonable use of gravity separation can increase iron and reduce silicon, reduce grinding costs and prevent over-grinding. Zhu Jiang used gravity separation to conduct experiments. The phosphorus content after dephosphorization was 0.981%, and the iron recovery rate was low.
Flotation method is divided into positive flotation and reverse flotation according to the different valuable components to be separated. Positive flotation uses anionic collectors to float iron minerals, while reverse flotation uses cationic collectors to float gangue. The flotation process for dephosphorization of high-phosphorus iron ore includes reverse flotation, selective agglomeration-reverse flotation, selective flocculation-desludging-reverse flotation and magnetic separation-reverse flotation.
Magnetic separation is a method of separating iron and phosphorus by using the difference in magnetic permeability of each phase in iron ore. Magnetic separation is simple and low-cost, and is an important method for dephosphorization. However, the difference in magnetic permeability between hematite and apatite in high-phosphorus oolitic hematite is small, so it needs to be finely ground, which will greatly increase the grinding cost, and the dephosphorization effect of a single magnetic separation method is low.
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