Application of Magnetic Separation Pre-Selection Technology in Lean Iron Ore Beneficiation

01What is ore pre-selection?

The purpose of ore pre-selection is to sort minerals based on the differences between target minerals and gangue minerals before sorting. Pre-selection operations are mainly used to process ores with a high dilution rate of raw ores, or ores where the target minerals can be dissociated from the gangue minerals during the crushing process. After the pre-selection operation, waste rock accounting for 30-60% of the original ore can be thrown away, which can greatly reduce the energy consumption of the equipment in the grinding operation.

02Magnetic separation and pre-selection technology for lean iron ore

The pre-selection operation of lean iron ore is mainly carried out using magnetic separation technology, and the main purpose is to discard the tailings. When the throughput of the grinding operation remains unchanged, the use of pre-tailing operation can improve the iron grade of the selected ore, reduce production costs and increase the concentrate output of the ore dressing plant. Magnetic pre-selection operations can improve the utilization rate of lean iron ore, extend the service life of mines, and can also alleviate the problem of insufficient tailings storage capacity. Magnetic separation technology has been widely used in the pre-selection and tailing process of strong magnetic magnetite. With the continuous development of magnetic materials and magnetic separation equipment, magnetic separation pre-selection technology has been widely used in low-grade fine-grained magnetite and weak magnetic materials. The application of lean hematite in beneficiation work is also becoming more and more important.

03Particle size reduction on magnetic separation pre-selection of lean iron ore

To a certain extent, the reduction of iron ore crushing particle size can effectively improve the working efficiency of the grinding system, and can also facilitate the pre-selection process of lean iron ore. As mining depth increases, the grade of iron in the selected raw ore decreases, which directly leads to a decrease in the grade of iron in the concentrate and an increase in production costs. A hydraulic cone crusher is used for the crushing process, and the final crushed product particle size is reduced from the original -30mm to -15mrn, accounting for more than 95%, and then a magnetic pulley is added to dry magnetic separation of the final crushed product. The pre-selected concentrate has a higher iron grade. Raw ore can be increased by 3 to 4 percentage points, and the tailing yield can be over 8%.

High-pressure roller mills have also been successfully used in magnetite concentrators, and the pre-selection technology of high-pressure roller mill ultra-fine crushing and magnetic separation pre-selection and tailings has gradually been formed. One of the main reasons is that the high-pressure roller mill has a large crushing ratio, the crushed products have a high content of fine particles, many micro-cracks, and good mineral dissociation properties. Another key reason is that the iron-poor iron after being ultrafinely crushed by the high-pressure roller mill The effect of ore pre-selection and tailing is good, especially in the pre-selection operation of fine-grained impregnated iron ore.

The application of high-efficiency grinding technology can effectively reduce the selected particle size of lean iron ore. After pre-selection, the selected grade of ore can be improved and the amount of grinding input can be reduced, maximizing the realization of more crushing and less grinding, and early throwing.

04Magnetic separation Pre-selection of strong magnetic lean magnetite ore

The pre-selection process of lean magnetite ore is generally designed after medium crushing or fine crushing. However, with the continuous improvement of magnetic material performance and the continuous improvement of magnetic system design methods, the pre-selection particle size range of magnet ore continues to expand, which can not only reduce the risk of mining operations. For boundary grades, it is also possible to carry out large-grained pre-selection and tailing directly after the coarse crushing operation.

When pre-selecting extremely lean magnetite ores with finer particle sizes, the ores generally need to be finely crushed to -3mm or even finer, which places higher requirements on the pre-selection magnetic separation equipment. On the one hand, it is necessary to ensure that the magnetic separation equipment has a high magnetic field strength to prevent the loss of fine-grained strong magnetic ores. On the other hand, it is necessary to cause more magnetic tumbling of the ores during the sorting process to discard low-grade tailings.

05Magnetic separation pre-selection of weak magnetic lean hematite ore

As one of the difficult-to-select iron ores, weakly magnetic hematite ore has an average beneficiation cost that is more than 50% higher than that of the easily-selected highly magnetic magnetite. Therefore, for the beneficiation of weakly magnetic lean hematite ore, the research on reducing the cost of beneficiation through the application of magnetic pre-selection technology is of great significance.

An efficient grinding process is used to reduce the selected particle size of poor hematite ore, and a permanent magnet drum magnetic separator with medium magnetic field strength and a high gradient magnetic separator are used in combination to pre-select and polish strong magnetic magnet ore and weak magnetic hematite ore respectively. Finally, these measures can achieve efficient pre-selection of poor hematite ore.

The above is the application of magnetic separation and pre-selection technology in the mineral processing process of lean iron ore resources. From the above, it can be seen that the gangue minerals in the ore can be effectively removed through magnetic separation and pre-selection technology and the quality of the concentrate can be improved. Magnetic pre-selection technology can not only improve the utilization efficiency of ore resources, but also reduce the burden and cost of the subsequent mineral processing process, so this technology can be widely used in mineral processing plants.