Limonite is a complex and difficult-to-benefit iron ore. Due to its low iron content and complicated ore beneficiation process, it has long faced greater challenges in the field of beneficiation. However, with the gradual reduction of high-grade, easy-to-benefit iron ore resources, efficient limonite ore beneficiation technology has become the main direction of research. In recent years, with the advancement of mineral processing technology, limonite mineral processing technology has gradually made significant progress. This article will introduce several main mineral processing processes of limonite and their development status.
In countries with scarce iron ore resources, the main mining method in the early days was iron-rich limonite, with an iron grade of usually above 50%. For low-grade limonite, a simple crushing, washing and grading process was first used, and it was processed by drum screen washers, trough washers and scrubbers. However, the effect of washing on improving the grade of limonite is limited, usually only 4-5 percentage points, and the tailings grade is still high. In order to further improve the grade of the concentrate, the washing-gravity separation process was gradually adopted in the later period, including heavy medium separation and jigging separation processes, but the recovery effect of fine-grained limonite is poor.
In this process, limonite ore is finely crushed or rod ground, and then washed, screened and deslimed. The coarse-grained fraction is obtained by gravity separation, the intermediate-grained fraction is processed by a roller magnetic separator, and the fine-grained fraction and slime are separated by a high-gradient magnetic separator. In order to improve the recovery rate of iron, gravity concentration of ore may need to be re-grinded and re-selected. This process can not only significantly improve the grade of limonite concentrate, but also effectively recover iron minerals in fine particles and sludge, achieving a high recovery rate.
With the promotion of new high-efficiency strong magnetic separation equipment, the strong magnetic separation process has been widely used in the ore beneficiation of limonite due to its simple and easy operation. However, although the process is easy to operate, the recovery rate of fine-grained limonite (such as minerals less than 20 microns) is low, and the improvement of concentrate quality is limited.
For low-grade, fine-grained limonite, the fine grinding process can help improve the grade of the iron concentrate, but it will also cause the ore to become muddy, affecting the recovery rate. The selective flocculation-strong magnetic separation process can significantly improve the recovery rate of fine-grained limonite through selective dispersion and flocculation control, making up for the shortcomings of the existing strong magnetic separation process in processing fine-grained limonite. The key to the process lies in the selection of flocculants and the control of usage conditions, such as the ore feeding method and the amount of flushing water.
Reduction magnetization roasting-weak magnetic separation is an effective method for processing limonite, but due to its high beneficiation cost, it has not been widely used, especially in China. In some foreign limonite ore beneficiation plant, magnetic roasting technology such as boiling furnace and rotary kiln is used to treat limonite, and good results have been achieved, but the industrial application of this technology is relatively small in China.
The flotation process has attracted much attention for its simple process and good recovery effect on fine-grained limonite. However, limonite is very easy to be muddy, resulting in serious dispersion of ore mud, which affects the flotation effect. This is also one of the reasons why flotation technology is difficult to be applied on a large scale in limonite ore beneficiation. Studies have shown that the reverse flotation process is more suitable for improving the quality and reducing impurities of limonite. In addition, due to the loose structure of limonite particles and large specific surface area, it is easy to absorb a large amount of reagents. It is necessary to adopt a multi-stage "hunger" dosing strategy combined with a closed-circuit flotation process to optimize the selection index.
This process is suitable for low-grade and difficult-to-select limonite, and the process structure is diverse, such as strong magnetic separation combined with flotation process. In flotation operation, cationic reverse flotation process is often used, which has a good effect. This combined process can effectively improve the ore beneficiation efficiency of limonite, but the process is complicated and the process design needs to be adjusted according to the specific limonite ore conditions.
The combined gravity separation, strong magnetic separation and flotation process has been widely used in hematite beneficiation plants, but it is less used in limonite ore beneficiation. The reason may be that the density of limonite is small, resulting in unsatisfactory gravity separation effect. At the same time, the economic value of limonite is relatively low, and the complex process may bring high investment and operating costs.
Although limonite ore beneficiation technology has made some progress, most low-grade or complex and difficult-to-be-selected limonite has not yet been efficiently developed and utilized, or is limited to low-value utilization. Therefore, in the future, it is necessary to further increase technical research efforts and develop economical and efficient ore beneficiation processes for different types of limonite. At the same time, in the process of developing new technologies, economic feasibility studies are also an important link that cannot be ignored. Through the organic combination of technology and economy, the utilization rate of limonite is expected to be further improved.
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