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As one of the earliest and most widely used metals in the world, iron ore is an important raw material for iron and steel production. The beneficiation of iron ore needs a series of processes, including crushing, grinding, magnetic separation, flotation, gravity separation.
At present, the iron ore resources are decreasing day by day. The iron ore resources are featured with more lean ore, less rich ore, more associated ore and complex ore composition. There are a variety of iron ores in nature, mainly including magnetite, haematite, limonite, siderite, so the beneficiation of iron ore needs a suitable process to improve the economic benefit.
Because of the strong magnetism of magnetite, weak magnetic processing technology is the main processing technology, including:
1. Single weak magnetic separation process
The single weak magnetic separation process is suitable for a simple single magnetite, which can be divided into successive grinding - weak magnetic separation process and stage grinding - weak magnetic separation process.
What more, successive grinding - weak magnetic separation process is suitable for the magnetite with coarse grain or high grade. Stage grinding - weak magnetic separation process is suitable the magnetite with fine grain and low grade.
2. Weak magnetic - reverse flotation separation process
Weak magnetic - reverse flotation separation process is mainly used to the beneficiation of iron ore which is difficult to increase the concentrate grade or with many SiO2 impurities. It includes weak magnetic- cation anti - flotation separation process and magnetic - positive anion flotation separation process.
3. Weak magnetic - strong magnetic - flotation separation process
Weak magnetic - strong magnetic - flotation separation process is mainly used to the beneficiation of iron ore with multiple metals and complex iron ore.
Hematite is a kind of weak magnetic ore, whose floatability is better than magnetite. In the early, the beneficiation of iron ore from haematite often adopted the gravity separation process. However, it was difficult to obtain the ideal processing capacity and recovery rate by the gravity separation process. Now, the beneficiation of iron ore from haematite often adopts:
1. Weak magnetic - strong magnetic separation process
Generally, adding the weak magnetic separation before the strong magnetic separation can remove the strong magnetic mineral in the raw ore. Then strong magnetic separation process is used to separate the hematite. This process is also often used to the beneficiation of mixture iron ore of magnetite and hematite.
2. Flotation separation process
Hematite has good floatability, which can be separated by flotation. As the density of iron ore is much higher than that of gangue mineral, so the gangue mineral is more likely to attach to the froth than iron ore. Therefore, reverse flotation is more advantageous than positive flotation for iron ore. But when the magnetite content mixed in hematite is higher, reverse flotation is a more convenient method.
3. Strong magnetic - flotation combined separation
Adopting the strong magnetic separation to remove a part of gangue mineral in the ore, and then send the coarse concentration of strong magnetic separation to the flotation for obtaining the final qualified concentrate.
Limonite is one of the main iron ores, the beneficiation of iron ore from limonite mainly includes:
1. Single beneficiation process
The single beneficiation of iron ore from limonite is mainly used for the limonite with high iron content and good selectivity, which can be divided into a single magnetic separation process and single gravity separation process.
2. Combined beneficiation process
The combined beneficiation process only used for the beneficiation of iron ore from limonite includes magnetization - magnetic separation process, flotation - strong magnetic separation process, gravity separation - strong magnetic separation process, etc., which are used for the treatment of limonite with relatively complex composition.
Siderite is also low-graded and unstable iron ore. The beneficiation of iron ore from siderite often adopts gravity separation and strong magnetic separation process. Of course, different siderite has different separation methods. Single siderite with coarse grain size is suitable to be processed with single gravity separation, single strong magnetic separation and combined process. The siderite with fine grain size is suitable to be processed with roasting magnetic separation, strong magnetic separation, flotation or magnetic separation - flotation combined process. The siderite containing magnetite can be separated by a combined process of weak magnetic separation and gravity separation, strong magnetic separation, or flotation in series, even a more complex process.
It is not difficult to see that, due to the various kinds and complex nature, the beneficiation of iron ore needs to adopt multiple mineral processing processes to obtain the ideal ore processing indicators.