How to extract iron from limonite?

Limonite is a typical refractory iron ore, which is easy to mud and has poor sorting index. Common limonite beneficiation methods mainly include gravity separation, magnetic separation, flotation and combined process.

01Limonite gravity separation process

We generally use gravity separation to process coarse-grained limonite. In production, most limonite processing plants will use a scrubber-gravity separation process to separate limonite and horse iron. In the first step, we use trommel screen, chute washing machine and washing machine to wash the ore, and then we use heavy media and gravity separation equipment such as jig for ore beneficiation.

02Limonite 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)

03Limonite flotation process

The single flotation method has a better recovery effect on fine-grained iron minerals, but because limonite is easy to form mud, which seriously affects the flotation effect, de-sliming or enhanced sludge dispersion can be considered before flotation.

In production, the flotation process of limonite can use positive flotation or reverse flotation. Research and practice show that reverse flotation is more suitable for limonite upgrading and impurity reduction. In addition, because the limonite particles have loose crystals and large specific surface area, it is easy to adsorb 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 of ore will reduce the sorting index, and the impact of the centralized return of the intermediate ore on the sorting index is smaller than that of the sequential return of the intermediate ore.

04Limonite combined beneficiation process

 (1) Gravity-strong magnetic separation process

Limonite is finely crushed or ground and then washed, screened, classified and deslimed. Coarse particles use gravity separation to obtain concentrate, medium particles use drum magnetic separator, and fine particles and pulp use high gradient magnetic separator.

In order to improve the recovery rate of iron ore, we often regrind and re-select medium ore in the process of gravity separation, which can significantly improve the grade of iron ore concentrate. At the same time, higher recovery rates can be obtained due to the recovery of fine-grained iron minerals and pulp.

(2) Selective flocculation flotation process

When the grinding fineness reaches a certain value, sodium carbonate and water glass are added in the grinding process to make the slurry well dispersed and to selectively flocculate the limonite. 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 method can be used on the basis of selective flocculation to obtain better separation indicators. .

(3) Flocculation-Intensive Magnetic Separation Process

For low-grade, fine-grained limonite, fine grinding is required to help obtain higher-grade iron ore; however, sludge is produced, resulting in lower recovery rates. In this case, flocculation-intensive magnetic separation can be used.