How to extract iron from limonite?

Limonite is a typical difficult-to-process iron ore, which is easy to mix with mud and has poor sorting indicators. Common limonite beneficiation methods mainly include gravity separation, magnetic separation, flotation and combined processes. 

01 Limonite Gravity Separation Process

We generally use gravity separation to treat coarse-grained limonite. In production, most limonite processing plants will use a washing-gravity separation process to separate limonite and limonite. In the first step, we use drum screens, chute washers and washers to wash the ore, and then we use gravity separation equipment such as heavy media and jigs for beneficiation.

02 Limonite Magnetic Separation Process

Differences in iron content lead to differences in magnetism. Generally, strong magnetic separation is used to separate limonite, but this method is not suitable for recovering fine-grained limonite (-20um iron minerals)

03 Limonite Flotation Process

Single flotation method has a good recovery effect on fine-grained iron minerals, but because limonite is easy to mud, it seriously affects the flotation effect. Desludging or enhanced sludge dispersion can be considered before flotation.

In production, the flotation process of limonite can adopt positive flotation or reverse flotation. Research and practice have shown that reverse flotation is more suitable for improving the quality and reducing impurities of limonite. In addition, due to the loose crystallization and large specific surface area of limonite particles, it is easy to absorb and consume a large amount of reagents during the flotation process. Therefore, the flotation process of multi-stage dosing and multi-stage separation should be adopted for limonite beneficiation. The closed-circuit flotation process formed by the return ore will reduce the sorting index, and the concentrated return of the medium ore has less impact on the sorting index than the sequential return of the medium ore.

04 Limonite Combined Beneficiation Process

(1) Gravity Separation-Strong Magnetic Separation Process

After fine crushing or grinding, limonite is washed, screened, graded and desludged. Coarse particles are separated by gravity to obtain concentrate, medium particles are separated by drum magnetic separator, and fine particles and slurry are separated by high gradient magnetic separator.

In order to improve the recovery rate of iron ore, we often re-grind and re-separate the medium ore during the gravity separation process, which can significantly improve the grade of iron concentrate. At the same time, due to the recovery of fine-grained iron ore and slurry, a higher recovery rate can be obtained. 

(2) Selective flocculation flotation process

When the grinding fineness reaches a certain value, sodium carbonate and water glass are added during the grinding process to make the slurry well dispersed and the limonite selectively flocculated. However, sometimes a single flocculation method cannot remove a large amount of coarse-grained gangue minerals, and it is still difficult to improve the grade of limonite concentrate. Therefore, flotation can be used on the basis of selective flocculation to obtain better separation indicators. .

(3) Flocculation-strong magnetic separation process

For low-grade, fine-grained limonite, fine grinding is required to help obtain higher-grade iron ore; but at the same time, sludge will be produced, resulting in a lower recovery rate. In this case, flocculation-strong magnetic separation can be used.