Bauxite ore beneficiation and iron removal process

Commonly used processes for separating iron from bauxite include gravity separation, magnetic separation, flotation, electric separation, flocculation and strong magnetic separation-anion reverse flotation. However, it is difficult to obtain better bauxite concentrate by this conventional method. . Aluminum and iron separation needs to be achieved through magnetizing roasting, direct reduction, Bayer, acid, reduction sintering or calcium aluminate slag smelting.

1. Bauxite magnetization roasting method to remove iron

The magnetization roasting method is used to select aluminum and remove iron. It mainly uses reducing gas (or coal) as a reducing agent to reduce the iron in bauxite into strong magnetite, and then uses magnetic separation to separate the magnet and bauxite. The process is to crush the raw ore to -5mm, add 25% coke amount, and conduct magnetization roasting at a roasting temperature of 780°C and a roasting time of 4.5 hours. After roasting, the minerals are ground and magnetically separated to obtain qualified iron ore concentrate and bauxite concentrate. However, this method suffers large losses and low recovery rate during the magnetic separation process.

2. Iron removal from bauxite by direct reduction method

The direct reduction method selects aluminum and removes iron. It also uses coal or gas as a reducing agent to reduce the iron in the ore into a strong magnet under solid conditions, and then uses magnetic separation to achieve effective separation of iron and bauxite.

However, the iron mineral particles in high-iron bauxite minerals are fine, and the metal magnets generated after direct reduction are difficult to polymerize. Therefore, the magnetic separation effect is poor, and it is ultimately difficult to obtain better aluminum-iron separation.

3. Bauxite acid removal of iron

Aluminum selection and iron removal by acid method utilizes the different abilities of iron and aluminum to dissolve in acid under different conditions, and uses the sequence of evaporation and crystallization of iron and aluminum salt solutions to separate iron and aluminum salt crystals, and then thermally decomposes them to obtain oxidized Aluminum and iron oxide.

Since most silicon compounds are insoluble during the acid dissolution process, iron and aluminum react with acid and dissolve in the liquid, so the acid method is suitable for processing high-silica bauxite. However, the acid method causes serious environmental pollution, it is difficult to recover and recycle the acid liquid, and it requires high equipment.

4. Iron removal from bauxite by reduction sintering method

The reduction sintering method is used to select aluminum and remove iron. It uses the traditional sintering method to produce alumina, and then adds sodium carbonate, calcium carbonate and coal powder to the high-iron and high-silicon bauxite for sintering, so that the bauxite reacts with the sodium carbonate to generate solid aluminum. Sodium acid, silicon minerals react with high-temperature decomposed calcium oxide to form calcium silicate, while iron minerals are reduced to magnetite or metallic iron.