Introduction to Chromium Ore Types and Beneficiation Methods

01Chromium ore type

Chromite: It is a magmatic mineral, belonging to the isometric crystal system, with small octahedral crystals, usually in granular and dense block aggregates, black in color, brown in streak, semi-metallic luster, and weakly magnetic.

Chromium-rich crystal stone: Also known as chromite spinel or aluminum chromite, its morphology, physical properties, genesis, occurrence and uses are the same as chromite.

Hard chrome spinel: It has a variety of colors, including black, brown, green, etc., and its morphology, physical properties, genesis, occurrence and uses are also the same as chromite.

02Chromium ore beneficiation method

Chromium ore has high hardness, high specific gravity and diverse mineral composition. Common processes include gravity separation, magnetic separation, flotation and combined beneficiation.

1. Chromium ore gravity separation

Gravity separation is to use the difference in specific gravity between chrome ore and gangue minerals for separation. Under the action of gravity, chrome ore particles with larger specific gravity will settle faster, while gangue mineral particles with smaller specific gravity will settle slower, thus achieving separation. Commonly used gravity separation equipment includes shaking table, jig, spiral chute, etc.

Shaking table: Through the asymmetric reciprocating motion of the bed surface and the flushing effect of the lateral water flow, minerals with different specific gravities are layered on the bed surface and move in different directions, thereby achieving separation. The shaking table has high sorting accuracy and is suitable for processing fine-grained chromium ore.

Jig: The bed layer is loosened by the pulsating water flow up and down, and minerals with different specific gravities are layered according to their specific gravity in the vertical direction, with heavy minerals at the bottom of the bed layer and light minerals at the top of the bed layer, and then discharged separately through the ore discharge device. The jig has a large processing capacity and is suitable for processing coarse and medium-grained chromium ores.

Spiral chute: When the slurry flows in the spiral chute, due to the combined effects of centrifugal force, gravity and friction, minerals with different specific gravities are layered at different positions of the spiral chute, with heavy minerals close to the inner edge of the chute and light minerals close to the outer edge of the chute, thereby achieving separation. The spiral chute has a simple structure, small footprint, and is easy to operate, and is suitable for processing medium and fine-grained chromium ores.

2. Chromium ore magnetic separation method

For chromium ore containing magnetic minerals, magnetic separation can effectively separate chromite and magnetic gangue minerals and improve the grade of chromium ore. Magnetic separation mainly uses the magnetic difference between chromite and gangue minerals for separation. Chromite is a weak magnetic mineral, while some minerals in gangue minerals such as magnetite and hematite are strong magnetic minerals. Under the action of the magnetic field, magnetic minerals will be adsorbed on the magnetic poles of the magnetic separator, while non-magnetic minerals will be discharged, thus achieving separation. Commonly used magnetic separation equipment includes permanent magnetic drum magnetic separator, wet strong magnetic separator, etc.

Permanent magnetic drum magnetic separator: suitable for processing medium and weak magnetic minerals, with the advantages of simple structure, easy operation and large processing capacity.

Wet strong magnetic separator: suitable for processing weak magnetic minerals, with the advantages of high magnetic field strength and good separation effect.

3. Chromium ore flotation method

Using the difference in the physical and chemical properties of the mineral surface, the chromite surface is made hydrophobic by adding flotation agents, thereby separating it from the gangue minerals. Flotation is mostly suitable for the sorting of fine-grained chromium ores, especially for chromium ores with complex symbiotic relationships with gangue minerals and small specific gravity differences. However, the flotation method requires the use of chemical agents, which is costly and has a certain impact on the environment. The commonly used equipment for flotation is mainly mechanical stirring flotation machines and aerated stirring flotation machines.

Mechanical stirring flotation machine: It is an air self-priming flotation machine, which mainly relies on a mechanical agitator (rotor and stator) to achieve aeration and stirring of the slurry. It can self-prime air and slurry, and does not require an external aeration device. The return of the middling ore does not require a pump to transport. The commonly used equipment in hematite beneficiation includes SF type mechanical stirring flotation machine, JJF type mechanical stirring flotation machine, and BF type mechanical stirring flotation machine.

Aerated agitator flotation machine: It is an external air supply flotation machine, which mainly relies on mechanical agitator to stir the slurry and blower to aerate. This type of flotation machine cannot self-absorb air, and when the middling ore returns, it needs to use a lift pump to transport the slurry. In addition, special air supply equipment is also required. The equipment commonly used in hematite beneficiation includes XCF aerated agitator flotation machine, KYF aerated agitator flotation machine and XCF-KYF flotation unit.

4. Combined beneficiation of chromium ore

Due to the complex nature of chromium ore, a single beneficiation method often fails to achieve the ideal beneficiation effect. Therefore, a combined beneficiation method is usually adopted to combine multiple beneficiation methods such as gravity separation, magnetic separation, and flotation to give full play to their respective advantages and improve the recovery rate and grade of chromium ore. It is suitable for various types of chromium ores, especially for ores with complex properties that are difficult to handle with a single beneficiation method.

The above is an introduction to chromium ore types and chromium beneficiation methods. In actual beneficiation plants, due to differences in the properties of chromium ores, the beneficiation process methods are also different. Although the processes are roughly similar, every detail is different. Therefore, it is recommended to conduct beneficiation tests and design suitable chromium beneficiation process methods according to their actual conditions to improve the beneficiation efficiency of chromium, achieve efficient recovery of beneficiation plants, and obtain efficient investment returns.