WO2021148944A1

WO2021148944A1 - Dry magnetic separator for separating super fine iron ore from gangue

Info

Publication number: WO2021148944A1
Application number: PCT/IB2021/050388
Authority: WO
Inventors: Mostafa NAGHIZADEH; Hamid Reza RAHDAR; Behnam MOSLEHI; Shahrooz JAFARI
Original assignee: Naghizadeh Mostafa; Rahdar Hamid Reza; Moslehi Behnam; Jafari Shahrooz
Priority date: 2020-01-22
Filing date: 2021-01-19
Publication date: 2021-07-29

Abstract

This invention substitutes previous methods with magnetic separators by removing water from the process of separating super fine iron ore from gangue. In this method, through floating the iron powder evenly in the air and passing it by the side of the rotating magnetic disk, the iron particles are attached to the plate and separated from the dust particles. Then the attached super fine particles are separated from the magnetic disk and become the output of the device, if necessary, this process can be done several times with different amounts of magnet to get the best result. This method has many advantages such as less energy consumption, environmental safety, less investment cost, more accuracy than the previous methods.

Description

Title of Invention : Dry Magnetic separator for separating super fine iron ore from gangue

Technical Field

[0001] Technical background of this invention is involved with the processing excavated iron ore from iron ore mines.

Background Art

[0002] One of the most significant inventions and creations in the area of dry processing is the method used by Brazilian Newsteel Company which a factory was established and started its operation with capacity of 300.000 tons in 2018 by this company applying this method. The said method is based on separation of various fractions of iron ore and feeding them separately to angled band separators (21 degree) with magnetic level of 210 degree. This method has demonstrated appropriate and acceptable results for the iron ore with freedom degree of about 300 micron; however for the iron ores with high involvement of wastes and freedom degree of less than this amount, it has had no ideal function. Moreover, it has no efficiency for hematite iron ore with oxide degree of 14<Feo.

[0003] An invention has been patented with the USPTO under number US4248700 called TRANSIT MATERIALS SEPARATOR, which discloses a method for this purpose.

[0004] A materials separator apparatus comprising a stacked array of horizontally oriented and vertically spaced separator stages, which may be interconnected by a material conductor disposed for receiving commingled materials from an upper stage and feeding it to an input portion of a lower stage, each stage including a vibrating, endless belt supported for carrying a stream of commingled materials longitudinally over a steady-state magnetic array of spatially alternating, oppositely polarized magnets disposed substantially parallel to one another and extended transversely at an oblique angle to the stream whereby electrically conductive items of nonferromagnetic material passing over the magnetic array are deflected laterally out of the stream, the materials remaining in the stream may be discharged from the belt by passing them over a roller which may be magnetized for segregating dielectric nonferromagnetic material from ferromagnetic material.

[0005] In this invention, the vibration of the belt is used to distance the particles and then the electromagnetic force is used to separate the iron particles from the gangue, which is completely different from the claimed method.

Technical Problem

[0006] In the beneficiation and processing industries of iron ore, after grinding iron ore, the main issue is separating grinded iron ore from wastes. No iron ore could be found in pure form in the nature, and they are in the form of ferriferous minerals together with other elements which are called wastes in processing expressions.

[0007] In traditional methods, iron ores were grinded primarily up to 10 mm, then iron and wastes were separated by traditional magnetic separators while these methods have no maximum retrieval and efficiency and waste part of energy. In modern systems to separate iron mineral correctly from wastes with the highest percentage of retrieval, it is required to be smashed up to maximum required amount which is called freedom degree, and become micronized powder (less than 100 micron) (this action is made in various mills), then iron and wastes shall be separated.

[0008] The technical problem of this operation is appeared when dimension and granulation of iron ore and waste reaches less than 5 mm, the common method of dry magnetic separation has no efficiency and upon smashing iron ore and wastes more and more, the problem gets worse; since when the dimensions of small particles get tinier, special surface is increased, thus contact surface among the particles is enhanced and electro-static and electro-magnetic forces made waste particles are attracted by the iron ore particles due to the same force, and make a node. When one intends to separate iron ore from wastes using a magnetic field, such nodes are so troublesome, and it causes wastes to be attracted to magnetic field together with iron ore particles.

[0009] To solve this problem, some methods have been developed as wet separators in which first a contagious solution is mixed with water and iron ore powder, then this slurry is separated in wet separators. This method and its relevant equipment had desirable results in the area of processing; however it consumes high amount of water and brings out some environmental limitations. Regarding the location of many mines in dry regions and limitations in water resources, it is required to make and develop dry methods for execution of this separation (without using water). On the other hand, existing methods apply chemicals such as sodium, methyl isobutyl carbonyl and fatty acids which are harmful to the environment.

Solution to Problem

[0010] In this invention, to solve the problem of the contact surface between particles and the existence of electrostatic and electromagnetic forces, super fine iron ore is first floated in the air stream. The resulting mixture is then directed into a dry magnetic separator. The output of the device has two separate channels. The gangue enters the dust separator from the air. The output of the product also enters directly into the product storage tank.

[0011] There is a circular disk inside the magnetic separator housing. The space on this disk is divided into three equal sectors, in each part a number of holes are created with a special pattern at a distance from the center. There is a magnet inside these holes.

[0012] On both sides of this disk there is a space for the rotation of the flow of super fine iron ore suspended in the air. At the bottom of the chamber and at the location of the product outlet channel, a separating blade is installed. This blade has the task of separating the iron ore that is attached to the magnets installed on the disk, and after separation, these particles fall into the tank under the machine due to gravity and are collected there.

[0013] Similar to the blade retaining column, a symmetrical column with blades attached to the blade column in the center is inserted to reduce airflow into the product chamber. Iron ore gangue, which do not have the property of magnetic absorption, are suspended in the air stream from the opposite side of the inlet and out of its special channel. In order to reach the iron grade of the product suitable for use in pelletizing, the output product of the primary separation chamber enters another similar chamber, with the difference that in the second separation chamber, the amount of magnet on the disks is less than the first disk.

[0014] Also, due to the fact that the magnetic adsorption properties of super fine iron ore differ based on the chemical structure and minerals that make it up, some iron ore particles may be present in the gangue effluent. Therefore, these materials enter the third separation chamber. This chamber is quite similar to the original chamber, with the difference that here the amount of magnetic absorption of the magnets mounted on the disk is different due to the dilution and complete separation of the iron from the gangue.

[0015] The output product of the third chamber is combined with the initial input feed to the first chamber and its gangue output will enter the separating cyclones. The cyclone is a funnel-like chamber in which the flow pressure is reduced and the tailings suspended in the air fall into the lower reservoir due to their gravitational force and air is expelled from the upper part.

Advantageous Effects of Invention

[0016] In the present dry magnetic separation method, mostly gravity and centrifugal forces are regarded, that it has little effect on tiny particles so as efficiency of separation operation is decreased greatly and it becomes uneconomical. Thus, the common systems and even the inventions during the last years have no proper efficiency in micronized powder with dimension of less than 100 micron. Moreover, upon decreasing amount of FEO, it is not practically appropriate for separation; however, the claimed device in this invention has appropriate performance in all the aforesaid cases.

[0017] Other advantages of using this device compared to existing methods are as follows:

[0018] 1. It obviates the needs to consume water

[0019] 2. No wastewater production and therefore no environmental pollution

[0020] 3. No need for pumps and drying steps and other available steps resulting in less energy consumption

[0021] 4. More efficiency and high operation speed of the device [0022] 5. Less investment cost to set up the system

[0023] 6. The possibility of extracting iron ore from the gangue by old methods

[0024] 7. There is no needs to chemicals in the extraction process

[0025] 8. More accuracy in the extraction process

Brief Description of Drawings

[0026] Figure 1 : General shape, introduction and method of placing separation system

[0027] Figure 2: Magnetic disc and arrangement of cylindrical magnets

[0028] Figure 3: Internal shape of dry separator and placement of magnetic disc and separating blades in it

[0029] Figure 4: Location of electro-gearbox and transferring rotation through chain and gear to magnetic disc shaft

[0030] Figure 5: Operation cycle of magnetic separators in circuit

Description of Embodiments

[0031] In this invention to solve problem of contact level between particles and electro-static and electro-magnetic forces among levels, first micronized powder are floated in air flow. Hence, as demonstrated in figure 1 , air flow is produced by a blower to a tube and micronized powder is fed by rotary valve through input airflow to the device. Then, the mixture is directed to magnetic separator. As it could be seen, magnetic separator includes one cubic case with one input duct and input flow enters to the device by a pipe after passing through a LR 3D elbow (to decrease pressure drop more and more).

[0032] The egress of device has two separated ducts for withdrawal of wastes and for exiting the product, respectively. The output of wastes, like the entrance, passes through a LR 3D elbow and enters a separator of dusts from air. As it was demonstrated in figure 2, the space on this disc is divided to three equal parts with angle of 120 degree. Finally, the gangue is dumped into the gangue tank (10). The output of product also directly enters a reservoir of product. [0033] Inside this magnetic separator, there is circle-like disc (11). As it is shown in figure 2, the space on this disc is divided to three equal parts with angel of 120 degree, and 16 holes have been made, with special model. The cylindrical magnets are placed inside these holes with gauss of 1300. After installation of magnetic insulation, amount of gauss on both side disc reachesl 100 on insulator’s surface. (Amount of gauss shall be in proportionate with type of iron ore and feo.)

[0034] As it is demonstrated in figure 3, there is a space of rotating powder suspended on air on both sides of this disc(14). In lower part of case and in output place of product exit, there is a separating blade with length and angle of 10 degree in relation to output tube. This blade is to separate the iron ore installed on magnets on the disc, and after separation, these particles will fall inside the storage due to gravity, and gathered there.

[0035] Like the maintenance column of blades, one symmetrical column with blades stuck to column of blades is installed to decrease air flow to the case of product.

[0036] Iron ore waste has no magnetic characteristic, and exit as suspended in the air from the other side of the entrance from its own special duct.

[0037] Driving force for rotating disc by an adjustable speed electro-gearbox is supplied (Figure 4). In this system, 5-KW electromotor is connected to a 1-15 gearbox, and to decrease spinning more, 10^*10 output gear is transferred by a chain to 10^*30 gear connected to 40-mm shaft of separator which is driving force of magnetic disc. To maintain the disc sin the desired location and inside the case, two ordinary UCP bearings are used on the maintenance bases of device. Finally, with the said structure, the spinning speed of disc could be observed up to 20 rpm. It should be mentioned that such spinning may be changed in proportionate with the kind of iron ore.

[0038] Given the necessity for upgrading iron product to more than 65% to be used in pelletizing, the output product of the first separating case enters case with exactly similar dimensions (5), sizes and performance mechanism, with this difference that in the second separation case, amount of gauss of magnets on discs are designed to be less than first disc and about 600 to 900 gauss. [0039] Moreover, regarding the magnetic attraction of particles of iron micronized powder, they differ based on their compromising chemical and minerals structure, and there may be some part of iron ore particles in output flow of wastes so that by repeating the separation step, we absorb these particles. Thus, these materials enter the third magnetic separator (5). This case is so similar to the first separator, with this difference that due to full separation of iron from waste, amount of attraction of magnets installed on disc is about 2000-2300 gauss. The output product of the third separator is mixed with the primary feed of the first one, and its waste output will enter separating cyclone. The said cyclone is a funnel like case in which flow is decreased and waste particles floating on air are fallen to the storage below and air could go out from its upper part.

[0040] As for several cycles for separation, the proposed process is specified in Figure 5. The micronized powder enters the device from the tank (3) and in the first step enters the first magnetic separator (5a). The product of the first separator (22a) enters the second separator (5b) and the product of the second separator (22b) will be the final product of the device. But the tail of the first separator (22c) will enter the third separator (5c) and the tail of the third separator (22d) will be directed to the dust separator from the air (9). The tail of the second separator (22e) enters the third separator (5c) and the product of the third separator (22f) enters the first separator (5a) for re-separation. In this way, the highest extraction efficiency will be achieved in this system.

Examples

[0041] By applying this device, we can separate the powder resulting from grinding and milling the iron ore excavated from mines and use it as a feed for agglomeration factories to produce iron ore pellets. This device can be used in two ways. First, the powder obtained from the crushing and milling operations of iron ore extracted from mines and produced as feed for agglomeration factories to produce iron ore pellets by this machine. Also in this machine, raw iron ore can be used directly after crushing. On the other hand, this device can be used to extract iron ore in dried gangue of old methods.

Industrial Applicability [0042] This device may be used as a substitute magnetic separator in all factories producing iron ore concentrate using water. In these devices, different grades of super fine are turned into mud after mixing with water and the separation operation is performed, which the claimed device substitute it. In addition, in case of developing required substructures and adding two stages of dry grinding to production line, many traditional workshops of producing granular iron can use this device to produce concentrate to benefit from a maximum retrieval.

Claims

[Claim 1] Dry Magnetic separator for separating super fine iron ore from gangue comprising: a. Air fan b. Rotary valve c. Transmission pipes d. Magnetic separator e. Cyclone f. Inlet feed tanks, super fine iron ore and gangue

[Claim 2] According to claim 1 , the fan transfers air into the pipe and the iron powder is sucked into the pipe from the tank, which rotates evenly, causing the iron powder to suck and float evenly inside the pipes.

[Claim 3] According to claim 1 , the magnetic separator consists of a circular disk with holes drilled in it where the magnet is located, and this disk is connected to the body of the magnetic separator by a shaft, and the shaft is chained to It is a connected motor that causes the magnetic plate to rotate.

[Claim 4] According to claims 1 to 3, super fine iron ore enters the magnetic separator through pipes and passes around a disk with a spinning magnet, and iron ore particles adhere to the magnets.

[Claim 5] According to claims 1 to 4, the disk of the magnetic separator has a separating blade in one direction, which is responsible for separating the iron ore that is attached to the magnets, and after separating these particles due to the force of gravity into the tank below. The device falls and collects there and the gangue particles come out of the other side of the magnetic separator.

[Claim 6] According to claims 1 to 5, depending on the need and type of super fine iron, it is possible to repeat the entry of particles into the magnetic separator several times to complete the extraction, in which case the material output from the first separator enters the second separator. And the output of the second separator will be the final product.

[Claim 7] According to claim 6, the gangue of the first separator and the gangue of the second separator enter the third separator and the material output from the third separator returns to the first separator and the gangue of the third separator enters the cyclone dust separator.