Beneficiation Technology and Equipment Application of Limonite

2025-12-12

Limonite is a kind of weakly magnetic iron oxide ore with relatively low hardness (ranging from 1 to 4 on the Mohs scale) and a density of approximately 3.3–4.0 g/cm³. It features a complex ore structure, high susceptibility to argillation, and is often associated with gangue minerals such as quartz. From the perspective of industrial production practice, high-grade limonite (with a raw ore grade of over 50%) can be directly used as a sintering blending material for blast furnace ironmaking. In contrast, low-grade limonite (with a raw ore grade of 30–45%) has a relatively low resource utilization rate.

However, its grade can be significantly improved through beneficiation treatment. For instance, after processing via the combined "calcination-magnetic separation" process, the grade of iron concentrate can generally be increased by 8–10 percentage points, achieving efficient resource utilization[2].

Beneficiation Technology and Equipment Application of Limonite2

Beneficiation Technology and Equipment Application of Limonite3

Firstly, the mined raw ore undergoes primary crushing in a jaw crusher. During the crushing process, water washing is required due to the high mud content of the ore. After primary crushing, the material is sent to an impact crusher for secondary and fine crushing. Finally, classification is carried out using a circular vibrating screen to obtain three particle size fractions: 0–8 mm, 8–25 mm, and +25 mm. Materials larger than 25 mm are returned to the impact crusher for re-crushing, realizing the preliminary dissociation of gangue minerals. The core equipment selected includes jaw crushers and impact crushers, and the particle size of the crushed products must meet the requirements of subsequent washing and separation processes. To meet the needs of subsequent processes such as magnetic separation, a Ball Mill is adopted for grinding treatment. The crushed ore is further ground by the ball mill, and the grinding concentration and fineness should be adjusted according to the separation process.

Given the high mud content of limonite after grinding, ore washing and desliming serve as crucial auxiliary steps, mainly using trommel scrubbers and trough washers. After washing, a spiral classifier is used in conjunction, which cleans and classifies the ore mixture by leveraging the difference in sedimentation velocity of solid particles in liquid due to varying specific gravities. Ore particles that do not meet the requirements are returned to the ball mill for re-grinding; the trommel scrubber also has a classification function simultaneously. Removing the argillaceous coatings on the ore surface can improve the efficiency of subsequent separation.

After the fine materials are classified by the spiral classifier, the mixed ore is fed into a magnetic separator, which separates magnetic substances through magnetic and mechanical forces by virtue of the difference in specific magnetic susceptibility. After preliminary magnetic separation, the mineral particles can be sent to a flotation machine for further separation. The qualified ore pulp is transferred to a mixing tank and fully stirred with reagents, then subjected to high-energy flotation in the flotation machine to obtain high-grade iron concentrate pulp. For subsequent treatment, if the grade of the iron concentrate pulp obtained by flotation fails to meet the standard, a secondary flotation cleaning can be conducted.

The flotation machine is also used for the secondary flotation cleaning, and it is necessary to adjust the reagent dosage and flotation parameters. The separated products (concentrate and tailings) contain a large amount of water and need to undergo multi-stage dehydration and drying treatment. In the concentration stage, a thickener is used for high-efficiency concentration and sedimentation to remove most of the free water. In the filtration stage, appropriate filtration equipment, such as the TS series dewatering screen, is selected according to the material properties. In the drying stage, a dryer is used to complete the final dehydration, resulting in dry iron concentrate powder that meets the requirements for storage and smelting[5].

For tailings with high residual iron grade, secondary separation can be performed to recover some iron minerals, thereby improving resource utilization efficiency. Tailings that cannot be recovered must meet the environmental protection discharge standards and can be used for filling mining areas, manufacturing building materials, etc., realizing the resource utilization of tailings and reducing environmental pressure.
For complex or low-grade limonite resources, the mainstream combined processes include gravity-magnetic separation, magnetic-flotation separation, and calcination-magnetic separation[4].

Conclusion

The beneficiation of limonite requires formulating differentiated schemes based on ore grade and properties. The pretreatment is centered on crushing, grinding, and ore washing & desliming to ensure that the materials meet the separation requirements. The core separation processes mainly include gravity separation, high-intensity magnetic separation, flotation, and combined processes. Among them, gravity separation is preferred for ores with coarse-grained dissemination, flotation is suitable for fine-grained ores, and combined processes such as calcination-magnetic separation are recommended for low-grade refractory ores. The entire process needs to focus on the optimization of process parameters and quality monitoring, while strengthening the resource utilization of tailings^[3].

Prospect

Beneficiation Technology and Equipment Application of Limonite4

The core development direction of beneficiation technology in the future will focus on efficient resource utilization and green development. It will prioritize breaking through the separation technology of low-grade and complex associated limonite resources, promote the research, development and application of intelligent and large-scale equipment, improve the comprehensive utilization system of tailings, and realize the high-quality development of the limonite beneficiation industry^[1].