Hematite beneficiation process | Iron ore beneficiation

Hematite is a weakly magnetic iron ore with better floatability and wider distribution than magnetite. It is one of the important raw materials for iron extraction. Its composition is complex. In addition to containing a small amount of magnetite, the impurity embedded in hematite has uneven particle size and high content of fines, so extraction of iron from hematite requires some beneficiation methods.

The process flow of hematite iron extraction is: crushing, grinding, extraction (flotation, magnetic separation, gravity separation, etc.), drying.

First stage crushing and screening of hematite

First, the raw hematite ore is evenly sent to the jaw crusher through the vibrating feeder for coarse crushing, and then sent to the cone crusher for fine crushing. Next, the ore is screened by a vibrating screen. The particles that meet the requirements are sent to be crushed, and the rest are returned to the cone crusher for further crushing.

Second stage grinding of hematite

The finely divided hematite is sent to a ball mill for grinding, and then classified into different particle sizes by a spiral classifier. Qualified ore goes to the next process, and unqualified ore continues to be finely ground.

The third stage extracts iron from hematite

According to the size of the embedded ore, hematite can be divided into coarse-grained hematite, medium-grained hematite and fine-grained hematite.

Coarse-grained hematite refers to iron ore with an embedded particle size of 2 mm or more. This type of hematite can easily extract iron by gravity and magnetic separation.

Medium-grained hematite refers to iron ore with embedded particle size between 0.02-2mm. This type of hematite is also relatively easy to choose, mainly using gravity separation, magnetic separation and magnetic roasting.

Fine-grained hematite refers to iron ore with embedded particle size less than 0.02mm. From the genesis of the deposit, this type of hematite is mostly sedimentary iron ore. The ore composition is complex and difficult to choose. At present, the combined processes of weak magnetic separation - strong magnetic separation, magnetic separation - flotation, magnetic baking - flotation, heavy magnetic separation - flotation and so on are used.

Hematite flotation separation

      Flotation separation is mainly used to extract iron from fine and granular hematite. If it is difficult to recover fine ore particles smaller than 10μm by other methods, flotation separation method can be used.

      At present, froth flotation is commonly used. The principle is to grind the hematite into a slurry with water in the flotation machine, and then stir and aerate to generate a large number of dispersed bubbles. Part of the floatable minerals are attached to the air bubbles and float to the surface of the slurry to form foam (concentrate), while the non-floating gangue (tailings) remain in the slurry to achieve iron extraction from hematite.

      According to the value of the mineralized foam, the hematite flotation process is divided into hematite positive flotation and hematite reverse flotation.

Hematite positive flotation: the use of anionic collectors (fatty acids or hydrocarbyl sulfates and petroleum sulfonates) to carry out flotation process in weakly alkaline or weakly acidic pulp. Sodium carbonate is used to disperse sludge and precipitate multivalent harmful metal ions.

Hematite Reverse Flotation: It uses anionic or cationic collectors. The cationic collector uses sodium carbonate to adjust the pH of the pulp to 8-9, uses starch, dextrin, etc. to inhibit iron minerals, and then uses amine collectors (ether amine, aliphatic amine) to flotate quartz gangue. Whereas anionic collectors use sodium hydroxide or sodium hydroxide and sodium carbonate to adjust the pH of the pulp above 11, starch and dextrin to inhibit hematite, calcium chloride to activate quartz, and then a collector (fatty acid) ) to capture quartz gangue.

Fourth stage drying of hematite

After extraction, hematite needs to be concentrated with a thickener to remove water, and then dried with a dryer. Ultimate quality iron