A flat-ring dry magnetic separation device and method for iron ore

Abstract

This invention addresses the problems of high water consumption, complex processes, and significant environmental pollution associated with existing wet-type flat-ring high-intensity magnetic separators for iron ore. It proposes a dry-type flat-ring magnetic separation method and apparatus for iron ore. The process involves: finely grinding the iron ore and using low-pressure air to create a gas-solid two-phase flow through a powder spray gun. This gas-solid two-phase flow is then introduced from top to bottom into a media box. Under the influence of the magnetic induction intensity of the magnetic poles, the media box generates an induced magnetic field. As the gas-solid two-phase flow passes through the media box, magnetic materials are adsorbed onto the inner surface of the channel under the influence of the induced magnetic field, while non-magnetic materials flow out as tailings from the bottom of the media box. This process separates magnetic and non-magnetic materials in the iron ore, yielding iron concentrate and tailings. This method achieves clean iron ore beneficiation without water, using a dry magnetic separation method, and produces no wastewater or waste gas emissions, thus realizing clean production in the beneficiation process.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical and mineral engineering technology, and relates to a flat-ring dry magnetic separation device and method for iron ore. Background Technology

[0002] High-gradient magnetic separators are commonly used in mineral processing enterprises for iron ore beneficiation. The basic principle of high-gradient magnetic separators is to utilize a medium made of soft magnetic material to generate a high-gradient, strong magnetic force under electromagnetic induction, thereby capturing fine-grained, weakly magnetic minerals. Existing high-gradient magnetic separators can be divided into two categories based on their operating mode: periodic and continuous. Periodic high-gradient magnetic separators can achieve higher magnetic field strength and a larger separation space, but their disadvantage is that they can only operate intermittently. This type of equipment is mainly used in industrial production for the purification of non-metallic minerals and wastewater treatment. Continuous high-gradient magnetic separators were developed specifically for metallic ore beneficiation and have a wider range of applications, such as the separation of fine-grained, weakly magnetic minerals like iron oxide ore, wolframite, manganese ore, ilmenite, and chromite.

[0003] High-intensity magnetic separators can be classified into two categories based on the type of magnet: permanent magnet separators and electromagnetic separators. They can also be classified into dry magnetic separators and wet magnetic separators based on the beneficiation method (dry or wet). High-gradient magnetic separators are a type of high-intensity magnetic separator, generally divided into flat-ring high-intensity magnetic separators and vertical-ring high-intensity magnetic separators. Flat-ring high-intensity magnetic separators are the fastest-growing type of high-intensity magnetic separator, further subdivided into weak-magnetic separators and strong-magnetic separators. High-intensity magnetic separators are suitable for beneficiating weakly magnetic ores or recycling tailings; weak-magnetic separators are suitable for beneficiating strongly magnetic ores.

[0004] Currently, large-scale mineral processing enterprises still mainly use wet high-intensity magnetic separators for mineral processing, while weak magnetic separators require the specific magnetic susceptibility of strongly magnetic minerals to be between 3000 × 10⁻⁶. -6 cm 3 The concentration of [g] or above is suitable for separating strongly magnetic minerals with a particle size of 0–6 mm. The magnetic separation products include both magnetic and non-magnetic materials. Minerals in this category include magnetite and pyrrhotite. Hematite, limonite, and siderite, among others, must be magnetized and roasted before separation.

[0005] The wet-type horizontal ring high-intensity magnetic separator is a continuously operating coarse-grain magnetic separation device, mainly composed of a frame, iron core, sorting disc, excitation coil, magnetic poles, feeding and discharging device, and drive shaft. The machine body support structure uses an iron core magnetic yoke as a support, which reduces both the size and weight of the equipment. The vertical drive shaft is driven to rotate via a reducer, driving the horizontal ring sorting box to rotate between the magnetic poles at a speed of 3-7 rpm / min. The output and concentrate grade of the high-intensity magnetic separator are controlled by adjusting the speed of the speed-regulating motor. Generally, the feed concentration should be less than 20%, with an optimal concentration of around 15%. The feed rate must be controlled within the technical specifications of the magnetic separator, and the feed speed should be relatively stable.

[0006] In the mineral processing of a wet-type horizontal ring magnetic separator, after the media box inside the horizontal annular separator rotates and enters the magnetic field region, finely ground iron ore slurry is added into the media box through the feed inlet. Under the action of the water flow from the feed spray pipe, the mineral particles enter the feed area of ​​the tank in a loose state for separation. Under the action of the magnetic field of the excitation coil, the magnetic mineral particles undergo magnetic aggregation to form "magnetic clusters" or "magnetic chains." These "magnetic clusters" or "magnetic chains" move towards the magnetic poles in the slurry under the action of the magnetic force and are adsorbed onto the surface of the toothed plates of the media box. Subsequently, as the horizontal annular separator rotates, when the media box moves to the non-magnetic region, the magnetic material adsorbed on the surface of the toothed plates is washed away by the pressure water flow from the discharge water pipe and enters the concentrate tank. The non-magnetic materials in the slurry continue to flow downward along the gaps between the toothed plates under the action of the slurry flow and their own gravity, and enter the tailings tank and are discharged out of the tank with the slurry, thus obtaining the tailings. Subsequently, as the horizontal annular sorting box rotates, it enters another non-magnetic field zone, where it begins magnetization in the opposite direction, undergoing the same iron ore sorting process.

[0007] Advantages of wet ring strong magnetic separator: (1) The specific magnetic susceptibility of minerals separated by strong magnetic separator is relatively small, and it has the advantages of large enrichment ratio, strong adaptability, reliable operation and convenient operation and maintenance. (2) The magnetic pole head of the ring strong magnetic separator has a large wrap angle and the outer ring arc of the horizontal ring separation box is long. There is a large space and time from feeding to separation in the magnetic pole area. The magnetic field of the magnetic pole has a large depth and a long contact area and contact time with the fed fine iron ore slurry, thus resulting in a high metal recovery rate. (3) The ring strong magnetic separator has the advantages of simple mechanical structure, reasonable configuration, low space and easy large-scale application. It has been widely promoted and applied in China. (4) The magnetic field strength of the ring strong magnetic separator can reach more than 12000gs. The magnetic field gradient is large, the power consumption is low and the performance is stable. The ring strong magnetic separator is used for the separation of low-grade weak magnetic limonite, which can increase the iron grade of limonite by 5-15% in one go.

[0008] Problems encountered during the use of wet ring magnetic separators: (1) The feeding direction and the washing direction of iron concentrate in the ring magnetic separator are both from top to bottom. Coarse minerals, bark, grass roots and explosive casings in the slurry must pass through the channel of the media box to be washed out. Therefore, the ring magnetic separator has the problem of easy blockage of the media box and large maintenance workload. In addition, the beneficiation index of the ring magnetic separator drops sharply as the blockage in the magnetic medium of the magnetic plate increases, and the working process is very unstable. (2) In order to ensure that the ring magnetic separator can operate normally without blockage, strict measures for slag isolation and coarseness isolation of the feed are required, and the concentrate washing water pressure should be above 0.2MPa. (3) Before use, the toothed plate of the ring magnetic separator should be installed in the media box first, and then the media box should be placed in the horizontal ring separation box. To facilitate the insertion and removal of the media box, the contact between the media box and the separation chamber should not be too tight. This causes the media box to move around in the separation chamber under the action of strong magnetic force, resulting in damage to the media box. (4) The wet magnetic separation process is long, and the subsequent products include concentration, filtration and dewatering, which increases the cost of mineral processing and the investment cost of building a plant. This drawback is particularly prominent in arid and water-scarce areas. (5) The wet magnetic separation process will generate secondary pollution, affecting the quality of groundwater; the tailings are stored in the dam, and daily operation must prevent water leakage and dam failure. In addition to increasing product costs, there are also safety and environmental hazards; the tailings dam occupies a large area, and it is difficult to reclaim it after closure. (6) The iron concentrate produced by wet magnetic separation has a high water content. In cold regions, the storage and transportation of concentrate is difficult during winter production, which leads to some mineral processing plants being forced to stop production in winter, affecting economic benefits.

[0009] Currently, the dry magnetic separation process for iron ore involves dry grinding of ore powder smaller than 3mm to obtain fine powder with a particle size of -200 mesh or higher accounting for 80%. This fine powder is then fed into a dry magnetic separator, where wind-powered magnetic separation is used to separate magnetic and non-magnetic materials. However, the fine powder tends to agglomerate in the magnetic field, containing a large amount of non-magnetic material. During wind-powered magnetic separation, this non-magnetic material is difficult to separate from the magnetic material, resulting in an iron grade in the separated iron concentrate typically around 50%. Furthermore, the separation efficiency is low, hindering its industrial-scale application.

[0010] While the dry process has the aforementioned drawbacks, the product after magnetic separation does not require dewatering, tailings disposal is relatively simple and convenient, and it complies with national environmental protection policies. Furthermore, the disposal cost of the product after magnetic separation is significantly reduced. Secondly, it is beneficial for continuous production in cold regions during winter and for reducing beneficiation costs in arid and water-scarce areas. Therefore, the dry magnetic separation process still possesses irreplaceable advantages. Summary of the Invention

[0011] The purpose of this invention is to provide a dry magnetic separation device and method for iron ore with a flat ring, to solve the above-mentioned problems of wet flat ring high-intensity magnetic separators, improve the grade and metal recovery rate of iron concentrate produced by traditional dry magnetic separation processes, and, based on traditional wet flat ring high-intensity magnetic separator equipment, adopt gas-solid two-phase flow to replace the original slurry, and modify the corresponding equipment to enable the existing flat ring high-intensity magnetic separator to achieve dry magnetic separation, thereby gradually replacing the wet magnetic separation process in the mineral processing field.

[0012] A dry magnetic separator for iron ore with a horizontal ring configuration includes a frame. A power unit is mounted on the top of the frame and is connected to a rotating shaft located in the middle of the frame. A horizontally positioned sorting ring is fixed to the rotating shaft. Permanent magnet systems with magnetic lines of force perpendicular to the axis of the sorting ring are mounted on the left and right sides of the frame. The permanent magnet systems include inner magnetic poles, outer magnetic poles, a magnetic system support, and a metal sealing cover. The inner magnetic poles are located inside the sorting ring, and the outer magnetic poles are located outside the sorting ring. Both the inner and outer magnetic poles are installed within the magnetic system support and form a closed magnetic system through the metal sealing cover mounted on top of the magnetic system support. A feed inlet is located at the top of the metal sealing cover and is in fluid communication with a powder spray gun located outside the frame. The tail of the powder spray gun is connected to a fine grinding hopper and a Roots blower. A concentrate hopper and a tailings collection hood are located at the bottom of the frame. The tailings collection hood is located directly below the permanent magnet system and is in fluid communication with a bag filter located outside the frame. The bottom of the bag filter is connected to the tailings hopper.

[0013] Furthermore, the magnetic pole surfaces of the inner and outer magnetic poles are concentric convex and concave arc surfaces, and an arc-shaped channel for the sorting ring to pass through is left between the inner and outer magnetic poles, thereby forming a sorting space with a uniform background magnetic field.

[0014] Furthermore, the sorting ring includes an inner ring, an outer ring, and multiple media boxes installed between the inner ring and the outer ring. A non-magnetic partition is installed between each media box, and the inner ring is fixedly connected to the rotating shaft.

[0015] Furthermore, the medium box includes a single-sided toothed plate medium and multiple double-sided toothed plate media, the single-sided toothed plate medium and the double-sided toothed plate medium are fixed between non-magnetic separators, and the multiple double-sided toothed plate media are arranged between two single-sided toothed plate media.

[0016] Furthermore, the power unit includes a motor and a reducer, the motor is connected to the reducer, and the reducer is connected to the rotating shaft through gear transmission.

[0017] Furthermore, an exhaust fan is connected to the top of the bag filter, and a circulating air duct is connected between the exhaust fan outlet and the Roots blower inlet, with a valve installed on the circulating air duct.

[0018] The working principle of this invention is as follows: After the powdered iron ore enters the magnetic separation zone in the form of a gas-solid two-phase flow, since the powdered iron ore is highly dispersed in the air, no magnetic agglomeration will occur. In addition to gravity and the inertial force of fluid flow, the magnetic materials in the powdered iron ore are also affected by the magnetic induction force of the magnetic source. As the magnetic materials flow from top to bottom through the medium box channel, they flow towards the surface of the medium box and are adsorbed on the inner surface of the medium box. The non-magnetic materials in the powdered iron ore are only affected by gravity and the inertial force of fluid flow. After flowing from top to bottom through the medium box, they are discharged from the bottom of the medium box, thus realizing the separation of magnetic and non-magnetic materials in the iron ore.

[0019] A method for magnetic separation using a flat-ring dry magnetic separator for iron ore includes the following steps:

[0020] (1) Add 80-90% of iron ore with a particle size of -200 mesh to the fine grinding feed hopper. The iron ore flows into the ore powder spray gun under the action of gravity. Under the action of the low-pressure air blown in by the Roots blower, the iron ore becomes a gas-solid two-phase flow.

[0021] (2) The gas-solid two-phase flow is blown into the medium box through the feed inlets on the left and right sides of the flat ring dry magnetic separator. When the gas-solid two-phase flow flows from top to bottom through the channel of the medium box, the magnetic material in the gas-solid two-phase flow will generate electromagnetic induction under the action of the electromagnetic field and be adsorbed onto the inner surface of the channel of the medium box under the action of electromagnetic induction force. The non-magnetic material in the gas-solid two-phase flow is not affected by the electromagnetic induction force and flows with the air and flows out from the bottom of the medium box as tailings gas-solid two-phase flow.

[0022] (3) The tailing gas-solid two-phase flow on the left and right sides of the flat ring dry magnetic separator is collected by the tailing collection hood and the resulting tailing gas-solid two-phase flow is discharged from the bottom of the flat ring dry magnetic separator.

[0023] (4) When the medium box containing iron concentrate rotates to the non-magnetic area of ​​the horizontal annular sorting ring under the action of the rotating shaft, the iron concentrate will detach from the inner surface of the medium box and flow downward under the action of gravity, and then be collected by the iron concentrate collection hood and sent into the concentrate hopper to obtain iron concentrate.

[0024] (5) The tailings gas-solid two-phase flow flows into the bag filter under the negative pressure of the exhaust fan. The solid and gas in the gas-solid two-phase flow are separated. The collected tailings are transported to the tailings hopper for storage. The discharged low-dust air is pressurized by the exhaust fan and can be discharged or recycled as circulating air.

[0025] (6) The air drawn into the Roots blower can be either recycled air or air drawn from the atmosphere through the intake port.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1) By using low-pressure air to convert finely ground iron ore into a gas-solid two-phase flow, and then introducing the gas-solid two-phase flow into the horizontal annular separation box of the flat-ring high-intensity magnetic separator for dry magnetic separation, magnetic and non-magnetic materials in iron ore can be separated, and iron concentrate and tailings can be obtained in the end.

[0028] 2) Iron ore can be beneficiated by dry magnetic separation using a flat-ring dry magnetic separator without water and with a shorter process.

[0029] 3) When iron ore is beneficiated using the flat ring dry magnetic separator of this invention, there is no wastewater or waste gas discharge, which can realize clean production in the beneficiation process. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the iron ore flat-ring dry magnetic separator of the present invention;

[0031] In Figure 2: a is Figure 1 Schematic diagram of the combination of the sorting ring and permanent magnet system in the China Railway Ore Flat Ring Dry Magnetic Separator, b is... Figure 1 Horizontal sorting ring structure diagram of China Railway Ore Flat Ring Dry Magnetic Separator;

[0032] Figure 3 is a structural diagram of the media box of the iron ore flat-ring dry magnetic separator in Figure 2, where: a is the front view and b is the side view.

[0033] In the diagram, 1-frame, 2-shaft, 3-sorting ring, 31-inner ring, 32-outer ring, 33-medium box, 331-single-sided toothed plate medium, 332-double-sided toothed plate medium, 34-non-magnetic partition, 4-permanent magnet system, 41-inner magnetic pole, 42-outer magnetic pole, 43-magnetic system support, 44-metal sealing cover, 5-feed spray inlet, 6-mineral powder spray gun, 7-fine grinding hopper, 8-Roots blower, 9-concentrate hopper, 10-tailings collection cover, 11-bag filter, 12-tailings hopper, 13-motor, 14-reducer, 15-exhaust fan, 16-circulating air duct, 17-fixing bolt, 18-channel. Detailed Implementation

[0034] The present invention will be further explained below with reference to the accompanying drawings.

[0035] like Figure 1As shown in Figure 2, a horizontal ring dry magnetic separator for iron ore includes a frame 1. A power unit is installed on the top of the frame 1, and the power unit is connected to a rotating shaft 2 located in the middle of the frame 1. A horizontally arranged sorting ring 3 is fixed on the rotating shaft 2. Permanent magnet systems 4 with magnetic lines of force perpendicular to the axis of the sorting ring 3 are arranged on the left and right sides of the frame 1. The permanent magnet system 4 includes an inner magnetic pole 41, an outer magnetic pole 42, a magnetic system support 43, and a metal sealing cover 44. The inner magnetic pole 41 is located inside the sorting ring 3, and the outer magnetic pole 42 is located outside the sorting ring 3. Both the inner magnetic pole 41 and the outer magnetic pole 42 are mounted on... The magnetic system is installed inside the magnetic system support 43 and forms a closed magnetic system through the metal sealing cover 44 installed on the top of the magnetic system support 43; the top of the metal sealing cover 44 is provided with a feed inlet 5, which is in fluid communication with the ore powder spray gun 6 located on the outside of the frame 1; the tail of the ore powder spray gun 6 is connected to the fine grinding feed hopper 7 and the Roots blower 8; the bottom of the frame 1 is provided with a concentrate hopper 9 and a tailings collection cover 10, which is located directly below the permanent magnet system 4 and is in fluid communication with the bag filter 11 located on the outside of the frame 1; the bottom of the bag filter 11 is connected to the tailings hopper 12.

[0036] The inner magnetic pole 41 and the outer magnetic pole 42 have concentric circular convex and concave arc surfaces. An arc-shaped channel for the sorting ring 3 to pass through is left between the inner magnetic pole 41 and the outer magnetic pole 42, thus forming a sorting space with a uniform background magnetic field. Furthermore, excitation coils are wound on the inner magnetic pole 41 and the outer magnetic pole 42. By adjusting the current of the excitation coils, the magnetic induction intensity of the magnetic separation area can be continuously adjusted within the range of 0~14000Gs, thereby enabling this equipment to adapt to dry magnetic separation of iron ore with different magnetic properties.

[0037] The sorting ring 3 includes an inner ring 31, an outer ring 32, and multiple media boxes 33 installed between the inner ring and the outer ring. A non-magnetic partition 34 is installed between each media box. The inner ring 32 is fixedly connected to the rotating shaft 2.

[0038] As shown in Figure 3, the medium box 33 includes a single-sided toothed plate medium 331 and multiple double-sided toothed plate media 332. The single-sided toothed plate medium 331 and the double-sided toothed plate media 332 are fixed between non-magnetic separators 34, and the multiple double-sided toothed plate media 332 are arranged between two single-sided toothed plate media 331. The single-sided toothed plate medium 331 and the double-sided toothed plate media 332 are connected by (double-headed) fixing bolts 17, and a channel 18 for gas-solid two-phase flow is provided between adjacent toothed plate media. The specific structure of the single-sided toothed plate medium 331 and the double-sided toothed plate media 332 can be found in Chinese Utility Model Patent CN201811310898.7.

[0039] The power unit includes a motor 13 and a reducer 14. The motor 13 is connected to the reducer 14, and the reducer 14 is connected to the rotating shaft 2 through gear transmission.

[0040] The top of the bag filter 11 is connected to an exhaust fan 15. A circulating air duct 16 is connected between the air outlet of the exhaust fan 15 and the air inlet of the Roots blower 8. A valve is installed on the circulating air duct 16. In use, the valve on the circulating air duct 16 can be opened to realize air circulation.

[0041] The specific working process of the above-mentioned iron ore flat-ring dry magnetic separator is as follows:

[0042] The iron ore used in this invention is magnetite, magnetized roasted ore, and directly reduced metallized materials, with an iron grade of over 25% and a grinding particle size of -200 mesh accounting for 80-90%.

[0043] (1) Add 80-90% of iron ore with a particle size of -200 mesh to the fine grinding feed hopper. The iron ore flows into the ore powder spray gun under the action of gravity. Under the action of the low-pressure air blown in by the Roots blower, the iron ore becomes a gas-solid two-phase flow.

[0044] (2) The gas-solid two-phase flow is blown into the medium box through the feed inlets on the left and right sides of the flat ring dry magnetic separator. When the gas-solid two-phase flow flows from top to bottom through the channel of the medium box, the magnetic material in the gas-solid two-phase flow will generate electromagnetic induction under the action of the electromagnetic field and be adsorbed onto the inner surface of the channel of the medium box under the action of electromagnetic induction force. The non-magnetic material in the gas-solid two-phase flow is not affected by the electromagnetic induction force and flows with the air and flows out from the bottom of the medium box as tailings gas-solid two-phase flow.

[0045] (3) The tailing gas-solid two-phase flow on the left and right sides of the flat ring dry magnetic separator is collected by the tailing collection hood and the resulting tailing gas-solid two-phase flow is discharged from the bottom of the flat ring dry magnetic separator.

[0046] (4) When the medium box containing iron concentrate rotates to the non-magnetic area of ​​the horizontal annular sorting ring under the action of the rotating shaft, the iron concentrate will detach from the inner surface of the medium box and flow downward under the action of gravity, and then be collected by the iron concentrate collection hood and sent into the concentrate hopper to obtain iron concentrate.

[0047] (5) The tailings gas-solid two-phase flow flows into the bag filter under the negative pressure of the exhaust fan. The solid and gas in the gas-solid two-phase flow are separated. The collected tailings are transported to the tailings hopper for storage. The discharged low-dust air is pressurized by the exhaust fan and can be discharged or recycled as circulating air.

[0048] (6) The air drawn into the Roots blower can be either recycled air or air drawn from the atmosphere through the intake port.

[0049] In summary, this invention enables iron ore beneficiation without water, using a dry magnetic separation method, while eliminating wastewater and waste gas emissions during production, thus achieving clean production in the beneficiation process.

Claims

1. A method for dry magnetic separation of iron ore using a horizontal ring system, characterized in that, A dry magnetic separation device for iron ore using a flat ring is employed. The device includes a frame (1), a power unit is installed on the top of the frame (1), and the power unit is connected to a rotating shaft (2) located in the middle of the frame (1). A horizontally arranged sorting ring (3) is fixed on the rotating shaft (2). Permanent magnet systems (4) with magnetic lines perpendicular to the axis of the sorting ring (3) are arranged on the left and right sides of the frame (1). The permanent magnet system (4) includes an inner magnetic pole (41), an outer magnetic pole (42), a magnetic system support (43), and a metal sealing cover (44). The inner magnetic pole (41) is located inside the sorting ring (3), and the outer magnetic pole (42) is located on the inner side of the sorting ring (3). 2) Located on the outside of the sorting ring (3), the inner magnetic pole (41) and the outer magnetic pole (42) are both installed in the magnetic system support (43) and form a closed magnetic system through the metal sealing cover (44) installed on the top of the magnetic system support (43); the magnetic pole surfaces of the inner magnetic pole (41) and the outer magnetic pole (42) are concentric circular convex and concave arc surfaces, and there is an arc-shaped channel between the inner magnetic pole (41) and the outer magnetic pole (42) through which the sorting ring (3) passes, thereby forming a sorting space with a uniform background magnetic field; the sorting ring (3) includes an inner ring (31), an outer ring (32) and multiple media boxes (33) installed between the inner ring and the outer ring, and a non-magnetic partition (34) is installed between each media box, and the inner ring (31) is fixedly connected to the rotating shaft (2); The media box (33) includes a single-sided toothed plate medium (331) and multiple double-sided toothed plate media (332). The single-sided toothed plate medium (331) and the double-sided toothed plate media (332) are fixed between non-magnetic partitions (34), and multiple double-sided toothed plate media (332) are arranged between two single-sided toothed plate media (331). The top of the metal sealing cover (44) is provided with a feed inlet (5), and the feed inlet (5) is connected to the frame ( 1) The outer side of the ore powder spray gun (6) is in fluid communication, and the tail of the ore powder spray gun (6) is connected to the fine grinding feed hopper (7) and the Roots blower (8); the bottom of the frame (1) is provided with a concentrate hopper (9) and a tailings collection hood (10). The tailings collection hood (10) is located directly below the permanent magnet system (4) and is in fluid communication with the bag filter (11) located on the outside of the frame (1). The bottom of the bag filter (11) is connected to the tailings hopper (12). The method includes the following steps: (1) Add 80-90% of iron ore with a particle size of -200 mesh to the fine grinding feed hopper (7). The iron ore flows into the ore powder spray gun (6) under the action of gravity. Under the action of the low-pressure air blown in by the Roots blower (8), the iron ore becomes a gas-solid two-phase flow. (2) The gas-solid two-phase flow is blown into the medium box (33) through the feed inlet (5) on the left and right sides of the flat ring dry magnetic separator. When the gas-solid two-phase flow flows from top to bottom through the channel of the medium box (33), the magnetic material in the gas-solid two-phase flow will generate electromagnetic induction under the action of the electromagnetic field, and will be adsorbed onto the inner surface of the channel of the medium box (33) under the action of electromagnetic induction force. The non-magnetic material in the gas-solid two-phase flow is not affected by the electromagnetic induction force, and flows with the air and flows out from the bottom of the medium box (33) as tailings gas-solid two-phase flow. (3) The tailing gas-solid two-phase flow on the left and right sides of the flat ring dry magnetic separator is collected by the tailing collection hood (10), and the resulting tailing gas-solid two-phase flow is discharged from the bottom of the flat ring dry magnetic separator. (4) When the medium box (33) adsorbed with iron concentrate rotates to the non-magnetic area of ​​the horizontal annular sorting ring under the rotation of the rotating shaft (2), the iron concentrate will detach from the inner surface of the medium box and flow downward under the action of gravity, and then be collected by the iron concentrate collection hood and sent into the concentrate hopper (9) to obtain iron concentrate. (5) The tailings gas-solid two-phase flow flows into the bag filter (11) under the negative pressure of the exhaust fan (15). The solid and gas in the gas-solid two-phase flow are separated. The collected tailings are transported to the tailings hopper (12) for storage. The low dust air discharged can be discharged after being pressurized by the exhaust fan (15) or recycled as circulating air. (6) The air drawn in by the Roots blower (8) can be either recycled air or air drawn in from the atmosphere through the inlet.

2. The iron ore flat-ring dry magnetic separator as described in claim 1, characterized in that, The power unit includes a motor (13) and a reducer (14). The motor (13) is connected to the reducer (14), and the reducer (14) is connected to the rotating shaft (2) through gear transmission.

3. The iron ore flat-ring dry magnetic separator as described in claim 1, characterized in that, The top of the bag filter (11) is connected to an exhaust fan (15), and a circulating air duct (16) is connected between the air outlet of the exhaust fan (15) and the air inlet of the Roots blower (8). A valve is installed on the circulating air duct (16).

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