MINERAL SEPARATION
configurations enabling multiple passes within one machine.
As the iron ore industry continues to prioritise sustainability, dry magnetic separation offers a practical route to reducing water consumption while maintaining or improving beneficiation performance. Bunting adds:“ Ongoing test work and flowsheet development demonstrate how different magnetic technologies can be applied across particle size ranges to support more efficient and environmentally responsible iron ore processing.”
Eriez and options for hard rock lithium ore
The main hard rock sources of lithium are spodomene, petalite and lepidolite, and Eriez says its DVMF is a good separation option for both lithium producers and users. Producers pulverise lithium before it goes to the user as a very fine powder. Nee San Yap, Senior Global Product Manager- Mining Magnetics at Eriez told IM that DVMF units are placed prior to and after mill processing. As an additional check, many users position the DVMF at the point they receive lithium purchased from their producer.
When it comes to hard rock mining, a best practice among operators is to install equipment to protect crushers and belts. They accomplish this by combining suspended electromagnets( SEs) and metal detectors. The belt magnet removes ferrous material as it passes under a magnet on a belt or vibratory conveyor, while a metal detector detects ferrous metals missed by the SE and all nonferrous metals. This an important preparation procedure as the fine powders move to the DVMF.
He adds:“ DVMFs reduce contamination in lithium dramatically by utilising a highintensity electromagnet and revolutionary flux converging matrix. The DVMF is fed vertically via gravity flow. As the feed material filters through the matrix and exits out the bottom, the matrix captures and holds the magnetic material as the non-magnetic material passes through. The magnetic collection of fine particles requires a highintensity, high-gradient magnetic field. This type of separator utilises a high-intensity electromagnet and flux converging matrix.”
The matrix amplifies the magnetic field and provides high-gradient collection sites for the magnetic material as the feed materials filter through. The canister is attached to dual high-frequency, lowamplitude vibratory drives. These drives deliver a strong vibratory action to the canister assembly which enhances the fluidity of very fine powders, resulting in a smooth and even flow of product through the matrix grid.“ This has proven to be the most effective separation process for hard rock mining lithium applications. Eriez 5,000 gauss strength DVMFs reduce contamination to parts per billion, rather than parts per million. Eriez state-of-the-art DVMFs are fully automated and feature a simplified cooling system. Other highlights include programmable controllers and the ability to handle four to 12-inch diameter sizes.”
The standard filters’ background magnetic field capacities are based on fine powder flow range up to 100 pounds per square inch of cross sectional area of matrix. A 6-inch diameter is capable of treating up to 2,800 pounds per hour of material weighing 400 lbs cu / ft.
The magnetic filters consist of a solenoid electromagnetic coil enclosed in a steel housing. The coil generates a uniform magnetic field throughout the bore of the coil, which represent background magnetic field. A stack of expanded metal discs are packed in the bore and induced by the magnetic field. These expanded metal discs, termed the matrix, provide the vehicle for separation. The matrix amplifies the background magnetic field, produces local regions of extremely high gradient and provides the collection sites for magnetic particle capture.
Utilising a relatively high background magnetic field coupled with an extremely high magnetic field gradient results in a high-intensity high-gradient separator. A matrix type separator substantially improves the capture of fine particles. In a matrix, the material must filter through several layers of highly induced magnetic grids, increasing the probability of capturing more contamination over conventional plate, grate, trap or drum type separators.
Even with relatively large matrix spacing, the material is subject to this filtering effect, resulting in the capture of magnetic material. The dry filters are rated by the magnetic field strength generated in the bore of the solenoid coil with the matrix removed. The background magnetic field, often termed the open bore field, represents the driving force that produces the amplified high magnetic gradient throughout the matrix. Depending on the matrix configuration, it is typically the case that a 5,000 gauss background field will result in an excess of 10,000 gauss in localised regions of the matrix.
Standard model filters generate background magnetic field strengths of 5,000 gauss. The solenoid coils are wound from copper to dissipate heat and operate at relatively cool temperatures. They are oiled-cooled and utilise a heat exchanger where it is cooled with a 10 GPM water flow. The background magnetic field is typically determined through an identification of the magnetic material or by quantitative testing.
Eriez’ experience has established some general guidelines for selection of the proper magnetic field selection.“ The 5,000 gauss unit is perfect for very fine( minus 50 micron to sub-micron) ferromagnetic iron of abrasion, scale or paramagnetic contaminants such as ilmenite or chromite. It is specified when a high-purity product is required and where product specifications call for parts per million( ppm) contaminants levels.”
Again, the DVMF achieves a parts per billion removed performance level. Duty cycles, the operating time of the magnet between cleaning cycles, are typically determined by identifying the amount of magnetic material contained in the feed product. Materials containing up to 2 % contaminant may require very frequent cleaning. In these applications, the duty cycle may approximate 10 to 20 minutes. In this scenario, an automated feeding valve and reject gate are recommended.“ Treating relatively pure materials, which may have only average ppm levels of contamination, allow relatively long duty cycles which can sometimes exceed an hour.”
China’ s Huate Magnet continues to push the envelope
Last August, China’ s Huate Magnet Group, based in Weifang, Shandong Province, achieved what it said was a historic breakthrough at its headquarters, where four cutting-edge magnetic separation systems, including the world’ s first and largest 7-metre intelligent WHIMS, were officially rolled off the production line and delivered to customers. This milestone event has established the company’ s global leadership in the field of ultra-large magnetic separation technology.
The 7-metre WHIMS( model LHGC- 7000) it says is suitable for wet separation of various weakly magnetic metallic ores with a fine particle size of-5 mm( where the-200 mesh fraction accounts for 30-100 %), such as haematite, limonite, manganese, ilmenite, lithium and and the comprehensive utilisation of materials such as alumina red mud. It can also be used for iron reduction and purification of non-metallic ores like quartz, feldspar, nepheline, and kaolin.
The 7 m extra-large intelligent WHIMS has a height of 12.8 m, a rotating ring diameter of 7.088 m, and a weight of 860 t, with a background magnetic field strength of up to 1.8T. Taking Anshan-type lean haematite as an example, its processing capacity reaches more than 1,600 t / h; for non-metallic ores, taking quartz sand as an example, the processing capacity is as high as 900 t / h, which is more than ten times that of the 3-metre diameter WHIMS and more than 20 times that of the 2-metre diameter WHIMS. The energy consumption per ton of ore is 0.1-0.2 kW · h, which significantly reduces the operating cost. In addition, its process
18 International Mining | MARCH 2026