Method for efficiently separating powdery lean magnetite through magnetic roller

Abstract

The invention discloses a method for efficiently separating powdery lean magnetite through a magnetic roller, and belongs to the technical field of mineral processing. The method comprises the following steps: firstly, carrying out aggregate dispersion on mineral aggregates before selection, and dispersing aggregates by utilizing shearing force generated by vibration; and then the feeding material layer of the thinning magnetic roller is quantitatively and rapidly conveyed, so that secondary aggregates are prevented from being formed. According to the method, through collaborative optimization of three elements of high-frequency vibration of loose materials, high ore feeding speed and high weak magnetic field intensity, the bottlenecks of traditional fine ore dry magnetic separation in the aspects of material dispersity, separation dynamics and poor magnetic mineral recovery efficiency are broken through; accurate capture is achieved, separation is enhanced, the magnetic iron grade of separation tailings is reduced, and the tailing throwing rate of separation is increased.

Description

Technical Field

[0001] The invention relates to a method for efficiently separating powdered lean magnetite with a magnetic drum, belonging to the technical field of mineral processing. Background Art

[0002] Lean magnetite ore accounts for the vast majority of my country's magnetite resources, with low iron grade, especially magnetic iron grade is even lower, generally between 8% and 20%, and the embedded particle size of magnetite minerals is fine. Even if the crushed ore particle size reaches 0.074mm, there are still intergrowths of magnetite minerals and gangue minerals, which makes accurate sorting difficult. Moreover, in lean magnetite ore, the gangue minerals contained are mostly silicate minerals with poor grindability, which will increase grinding energy consumption and steel consumption, thereby increasing production costs; although more than 15% of the tailings are discarded by dry separation after medium crushing, there are still about 9% gangue minerals in the final crushed material. In the existing process, a magnetic drum is added for dry separation of fine ore before entering the mill, but the sorting effect is poor. If the tailing amount of the magnetic drum is increased, the magnetite mineral content in the tailings will increase, resulting in a waste of resources. The reasons are analyzed as follows: 1. When the particle size of the selected material is 0-12mm, the content of fine ore with a size of 0-5mm is as high as more than 50%. Although it is dry material, the proportion of fine ore is large, and the surface electrostatic adsorption ability between the fine ore particles is strong. In addition, the feeding layer of the magnetic drum is thick, which aggravates the magnetic agglomeration and inclusion of magnetite ore particles and gangue particles, and worsens the separation effect.

[0003] 2. The magnetic field strength of the original magnetic drum is low, less than 300kA / m, especially the magnetic field strength at 50mm radially outward from the magnetic drum surface is less than 40kA / m. In order to increase the tailing rate of the magnetic drum, the centrifugal force on the ore particles must be increased. Due to the low magnetic field strength of the original magnetic drum, the magnetic field adsorption force on a certain degree of conjoined ore particles of magnetite minerals is low, which will cause these conjoined ore particles to be easily thrown out of the magnetic field and become magnetic drum separation tailings, resulting in a high magnetic iron grade in the separation tailings and a reduced recovery rate of magnetic minerals. If the centrifugal force is reduced to maintain resource utilization, the throwing distance of the gangue will be reduced, the boundary between the separation concentrate and the tailings will be unclear, and it will be difficult to separate different separation products. In addition, it is difficult for the gangue to overcome the micro-surface adsorption between it and the magnetite ore particles or be mixed in the separation zone, reducing the separation efficiency.

[0004] 3. Since the ore materials entering the mill are all finely crushed and screened products, which contain a large amount of powdered ore, the characteristics of the ore materials and the production process determine that it is difficult to adopt wet pre-selection operations. The agglomerates formed between the fine particles in the powdered ore due to electrostatic adsorption and other reasons make it difficult to sort them efficiently.

[0005] Therefore, studying a method for efficiently separating powdered lean magnetite using a magnetic drum is of great significance for improving the utilization rate of lean magnetite resources, improving the grindability of the ore and reducing production costs. Summary of the Invention

[0006] The present invention aims to provide a method for efficiently sorting powdered lean magnetite by a magnetic drum. By applying a pretreatment technology under the synergistic effect of vibration dispersion and high-speed ore feeding thinning material layer and a precise capture and enhanced sorting technology under the synergistic effect of high-speed ore feeding and a high-weak magnetic field, the magnetic drum can efficiently sort powdered lean magnetite, further reducing the amount of gangue mixed in the ore entering the mill. The method is suitable for the pre-selection of powdered dry lean magnetite before entering the mill. While effectively reducing the magnetic mineral content of the tailings in the dry magnetic separation, the tailing rate of non-magnetic minerals is increased, which is beneficial to reducing the grinding amount, improving the grindability of the ore, and reducing production costs.

[0007] The present invention utilizes a pretreatment technology that synergizes vibration dispersion and high-speed ore feeding to thin the material layer, as well as a precise capture and enhanced sorting technology that synergizes high-speed ore feeding and a high-weak magnetic field, achieving efficient sorting of powdered, lean magnetite ore before magnetic drum milling. First, the synergistic effects of vibration dispersion and high-speed ore feeding thin the material layer on the magnetic drum feed cause previously bonded powdered ore particles to become discrete for sorting, reducing mutual adsorption between particles and the secondary adsorption during conveying that forms aggregates, hindering sorting. The principle is to utilize the shear force generated by vibration to eliminate the electrostatic adsorption between powdered, lean magnetite ore particles, breaking up aggregates and loosening the powdered ore, increasing the proportion of individual ore particles. Second, the high-speed feeding of the magnetic drum thins the material layer on the belt conveyor, minimizing secondary agglomeration during magnetic drum sorting. This technical approach creates optimal sorting conditions for the magnetic drum to fully discard gangue minerals and recover magnetite ore. Third, the synergistic effect of high-speed feeding of the magnetic drum and high-weak magnetic field can accurately capture and enhance sorting. The main function is to increase the throwing distance of gangue minerals, clarify the boundary between the magnetic drum sorting concentrate and tailings, and prevent the secondary mixing of the concentrate and tailings after sorting. At the same time, it can also make the extremely poor conjoined bodies of magnetite minerals that have no recovery value break free from the magnetic field force and enter the sorting tailings, thereby increasing the tailing rate; and the magnetite conjoined bodies with low magnetite content but worthy of recycling are captured with a higher weak magnetic field to improve resource utilization; the principle is that the magnetic field strength of the magnetic drum needs to be designed according to the magnetic susceptibility coefficient of the pre-recovered magnetite conjoined bodies so that the magnetic drum can capture the conjoined bodies, and at the same time, the high feeding speed will throw the extremely poor conjoined bodies and gangue that have no recovery value away from the magnetic drum at a long distance.

[0008] The present invention provides a method for efficiently sorting powdered lean magnetite using a magnetic drum, comprising the following steps: first, agglomerates of the ore before selection are dispersed, and the agglomerates are dispersed using the shear force generated by vibration; then, the feed layer of the magnetic drum is quantitatively and rapidly transported to thin the ore to prevent the formation of secondary agglomerates; the above operations enhance the ability to capture valuable lean intergrown ore particles and enhance the centrifugal force for unusable extremely lean intergrown ore particles to break free from the magnetic field adsorption, thereby enhancing the ability of unusable extremely lean intergrown ore particles and gangue particles to be thrown away from the magnetic drum, and clearly defining the dividing line between the sorted concentrate and the tailings.

[0009] The method for efficiently separating powdered lean magnetite with a magnetic drum specifically comprises the following steps: Step 1: Front-end deagglomeration: Use vibration energy to destroy the adhesion and electrostatic adsorption between ore particles before sorting, forcibly expose the magnetite ore particles and gangue particles, and reduce the difficulty of sorting. Replace the swing feeder above the magnetic drum feeding belt with a vibrating feeder. Feed the powder ore in the silo into the vibrating feeder first. Under the premise of keeping the total feeding amount unchanged, use multiple vibrating feeders to feed the ore, and reduce the feeding amount of a single vibrating feeder. In this way, the ore particles that are squeezed and stuck together in the silo can be dispersed after being fully vibrated and deagglomerated by the vibrating feeder, and then fall into the belt conveyor with increased speed to be fed to the magnetic drum for sorting; prevent the ore from being piled up and sticking together for the second time, which will affect the sorting effect; Step 2: Mid-end thinning: The loose ore materials that have been vibrated and deagglomerated at the front end will fall into the feeding belt conveyor of the magnetic drum. In order to prevent the secondary agglomeration of the ore particles due to the excessive thickness of the conveying material layer, the conveying speed of the belt conveyor is increased to thin the material layer and build a thin layer sorting state. This can also reduce the mechanical inclusions caused by magnetic interference, and is conducive to increasing the effective range of the magnetic field to prevent the escape of magnetite ore. Step 3: High centrifugal force and magnetic field adaptation at the back end: The process of thinning the material layer at the middle end correspondingly increases the centrifugal force during the mineral separation process. Although the centrifugal force can make the boundary of the separation product clear, the increase in centrifugal force will inevitably lead to the ejection of some valuable poor intergrowth ore particles from the magnetic field, resulting in the loss of magnetite minerals. A higher magnetic field strength is required to firmly adsorb and drag the easily escaped valuable intergrowth ore particles to the separation concentrate area, thereby increasing the recovery rate of magnetite minerals and reducing the magnetic iron grade of the separation tailings.

[0010] Based on the installation dimensions of the on-site magnetic drum facilities, this invention modeled and determined the feed rate required for the drum to eject gangue minerals, increasing the separation feed rate from 1.5 m / s to 2.5 m / s. The magnetic field strength of the drum was designed based on the specific magnetic susceptibility of valuable, poorly intergrown ore particles. The magnetic field strength was set to a maximum of 400 kA / m at the radial magnetic surface of the drum, and 70 kA / m 50 mm radially outward from the drum surface.

[0011] Preferably, the above process steps are described as follows: Step 1: Change the original swing feeder to an electromagnetic vibrating feeder. The ore in the storage bin is vibrated by the electric vibrating feeder to loosen the ore and then fed to the magnetic drum for sorting via a speeded-up belt conveyor.

[0012] In step two, the thickness of the material layer on the belt conveyor is controlled within 5mm to achieve thin and uniform feeding, preventing the reduction of looseness caused by an overly thick material layer. By replacing the conventional motor of the magnetic drum feed belt conveyor with a variable frequency motor and adjusting the frequency to control the belt speed above 2.5m / s, the feeding speed can be increased and the centrifugal force of the powdered ore particles can be enhanced. At the same time, the feeding layer of the magnetic drum can be thinned, allowing the discrete gangue ore particles to be fully exposed.

[0013] Step three redesigned the magnetic drum's magnetic field, shortening the pole spacing from the conventional 30mm to 15mm. This increased the magnetic field strength at a distance radially outward from the drum surface, specifically at the topmost layer of the material. The original magnetic field strength at a distance of 50mm radially outward from the drum surface was measured at 40kA / m. This increased to 70kA / m with the pole spacing shortened to 15mm. This improved the ability to attract magnetic ore particles, particularly fine-grained magnetite and ore particles with magnetite content exceeding 1 / 9, preventing these particles from becoming tailings in the sorting process due to increased centrifugal force.

[0014] Beneficial effects of the present invention: (1) The present invention starts from the essential influence of the characteristics of the sorted ore and the sorting behavior on the sorting effect, grasps the essential factors that affect the poor effect of magnetic drum sorting of powdered lean magnetite, and reverses the situation of poor magnetic drum sorting effect by adopting targeted, simple and effective technical means; specifically, the collaborative pretreatment technology of vibrating loose materials and thinning the material layer with high-speed ore feeding creates favorable conditions for efficient magnetic drum sorting; the high-speed ore feeding and high-weak magnetic field collaborative precise capture and enhanced sorting technology lays the foundation for efficient magnetic drum sorting.

[0015] (2) The present invention does not require additional process configurations. Compared with similar technologies, it adopts a multi-stage sorting process to improve the pre-selection efficiency of powdered lean magnetite before entering the mill, and the production process is simple. DETAILED DESCRIPTION

[0016] The present invention is further illustrated below by way of examples, but is not limited to the following examples. Example

[0017] Taking the production of a mining company as an example, the company's ore is Anshan-type metamorphic sedimentary rock-poor magnetite ore. The gangue minerals are mainly silicate minerals, which are difficult to grind. The crushed powdered ore (particle size 0-12mm) is sorted and discarded with a magnetic drum before grinding, which is beneficial to improving the grinding efficiency of the ball mill and reducing production costs. Experimental testing shows that more than 9.0% of the powdered ore before the ore enters the mill is gangue (hereinafter referred to as tailings). However, in actual production, the amount of tailings discarded by the magnetic drum before grinding is less than 4%, and the magnetic iron grade of the tailings is as high as 2.50%, which is a poor sorting effect. If the amount of tailings discarded by the magnetic drum is increased, the content of magnetite minerals in the tailings will increase, resulting in a waste of resources.

[0018] After analyzing the above situation, this embodiment intends to solve the following technical problems: 1. In the past, there was a problem of insufficient sorting due to the agglomeration of mineral materials.

[0019] When magnetic drums are used to separate powdered lean magnetite ore, the dense agglomerates formed by the surface adsorption of the ore particles and the mutual wrapping between the magnetite particles and the gangue particles are the main reasons for the low separation efficiency of the magnetic drums for separating powdered lean magnetite ore.

[0020] This embodiment uses vibration pretreatment for deagglomeration before sorting. Directed vibration is used to apply shear force to the preselected ore to destroy the bonding force between the ore particles, so that the rate of independent state of magnetite ore particles and gangue particles is increased to ≥80%.

[0021] 2. The problem of low recovery rate caused by the magnetic shielding effect of thick material layer in previous processes.

[0022] In the past, the thickness of the magnetic drum selection layer was greater than 10 cm, and the magnetic interference between the ore particles formed a magnetic shield, making it difficult to effectively capture the poor intergrowth ore particles and the magnetite ore particles wrapped by the gangue particles.

[0023] This embodiment adopts high-speed ore feeding. Under the condition of the same ore feeding amount, the separation material layer is reduced to less than 5 cm. High-speed thinning material layer separation can improve the magnetic field penetration by more than 50%, greatly reduce the loss rate of lean intergrowth ore, and effectively control the magnetic iron grade of tailings in dry magnetic separation of fine ore.

[0024] 3. The previous process had the problem of poor ability to capture magnetite-poor conjoined bodies due to low and weak magnetic field strength.

[0025] Due to their low content of magnetite minerals, the overall specific magnetic susceptibility of magnetite's lean intergrowths is low, making them less attractive for capture in weak magnetic fields. This makes them more likely to escape the magnetic field and enter the tailings, especially during high centrifugal force tailings removal. This reduces recovery and increases the magnetic iron grade of the tailings. Therefore, when strengthening and clarifying the boundary between the concentrate and tailings products—in other words, increasing the feed rate and thus the centrifugal force on the ore particles—it is necessary to simultaneously increase the magnetic field strength of the weak magnetic field to enhance the capture of magnetite's lean intergrowths. This reduces the probability of tailings discarding of magnetite's lean intergrowths, increases resource recovery, and lowers the magnetic iron grade of the sorted tailings.

[0026] The vibration loosening pretreatment and high-speed ore feeding thinning material layer synergistic technology before dry magnetic separation of powdered ore in this embodiment, as well as the high-speed ore feeding and high-weak magnetic field synergistic precise capture and enhanced sorting technology effectively solve the problem of low sorting efficiency when magnetic drums are used to sort powdered lean magnetite, and achieve an increase in the tailing rate and controllable tailing magnetic grade of the sorted tailings.

[0027] The specific implementation process is as follows: Step 1: Based on the installation dimensions of the on-site magnetic drum facilities, a model was developed to determine the feed rate required for the drum to remove the gangue minerals. The magnetic field strength of the drum was designed based on the specific magnetic susceptibility of the valuable and poor intergrowth ore particles.

[0028] Build a mathematical model: Detailed description: A method for efficiently separating powdered lean magnetite using a magnetic drum. The key is to eliminate the adsorption force between powdered ore particles through a certain vibration force, so that the magnetite ore and its intergrowth ore and gangue particles are in a highly loose state. A certain high feed rate thins the magnetic drum feed layer to a certain extent, effectively preventing the secondary adhesion and mutual adsorption between the ore particles to form agglomerates again. At the same time, under the synergistic effect of appropriate high-weak magnetic field strength and high centrifugal force, the powdered magnetite ore and gangue are effectively separated. Therefore, it is necessary to establish a scientific mathematical model to determine the reasonable vibration force, feed rate and magnetic field strength, the three important parameters and the synergistic relationship between them. Including: 1. Magnetic drum feeding speed modeling The goal is to quantify the minimum feed rate required for gangue particles to be ejected from the magnetic field so that the dry separation tailings can be ejected from the separation area, clearly separating the boundary between concentrate and tailings, and facilitating the precise separation of concentrate and tailings.

[0029] The magnetic drum feeding belt conveyor is installed horizontally. Gangue particles move horizontally after leaving the upper end of the magnetic drum (the starting point). The equation of horizontal motion with the starting point as the origin is χ = υt and Based on this, a mathematical model of the velocity required for throwing gangue into the tailings area is established: , m / s In the formula, υ represents the outer diameter linear velocity of the magnetic drum during operation, that is, the feed speed during magnetic drum sorting; χ represents the horizontal distance of the tailings from leaving the magnetic drum to falling onto the sorting plate; y represents the vertical distance of the tailings from leaving the magnetic drum to falling onto the sorting plate; g represents the acceleration of gravity; t represents the time required for the tailings to leave the magnetic drum and fall onto the sorting plate.

[0030] The on-site installation parameters of the separation plate for separating the concentrate and tailings separated by the magnetic drum are: the horizontal distance between the separation plate and the vertical center line of the magnetic pulley is χ = 900mm, and the vertical distance between the top of the separation plate and the starting point is y = 700mm. Gravitational acceleration g = 9.8m / s 2 , then the critical feed rate of the separator to separate the gangue into the tailings area can be calculated .

[0031] The mathematical model shows that if the magnetic drum feed speed is less than 2.38m / s, the horizontal drop distance of the gangue minerals will be less than 900mm, and some gangue minerals will fall onto the sorting plate or into the sorting concentrate area. This will lead to an unclear boundary between the sorting concentrate and tailings, and the sorting tailings will easily mix with the sorting concentrate, seriously affecting the sorting effect. It was determined that the sorting feed speed was increased from the original 1.5m / s to 2.5m / s.

[0032] The feed speed was increased to 2.5 m / s, 1 m / s higher than the original speed. The effective ore transport width b of the magnetic drum feeder belt was 400 mm, and the required sorting capacity was 80 tons per hour. The average material layer thickness was 18.52 mm. For ore particles 0 to 5 mm in size, there was a problem of mutual compression, which prevented the ore particles from being fully exposed before sorting. After the speed was increased, the average material layer thickness was 11.11 mm. The thinner material layer was more conducive to exposing mineral particles 0 to 5 mm in size, creating favorable conditions for fully capturing magnetite ore particles to prevent their escape, reducing gangue inclusions, and increasing the amount of tailings discarded during sorting.

[0033] The effect of increasing the feed rate on the separation indexes was verified under the conditions of non-vibrating feeding, maximum field strength of 300kA / m at the surface of the radial magnetic system of the magnetic drum and feed rate of 80t / h, as shown in Table 1.

[0034] Table 1

[0035] As can be seen from the values ​​in Table 1, increasing the feed speed of the magnetic drum significantly improves the tailing rate, but also increases the magnetic iron grade of the tailings. However, increasing the speed thins the separation layer, making it easier for the ore particles to be separated as individual particles and clarifying the boundary between the concentrate and tailings. Therefore, the increase in the magnetic iron grade of the tailings is much smaller than the increase in the tailing rate.

[0036] 2. Vibration loose pretreatment modeling The goal was to quantify the extent to which vibration frequencies affect bulkiness of the ore material and to test their impact on magnetic drum sorting operations.

[0037] Reference vibration energy E 振动 Relationship with vibration frequency f And looseness S and vibration energy E 振动 The relationship A mathematical model between looseness S and vibration frequency is established, namely: ,%, Where, is the initial looseness, and the initial value of the test is 15%; A is the amplitude of the vibrating feeder, and the value provided by the manufacturer is 5mm; is the ore characteristic coefficient, and the value of poor magnetite ore is 0.3; The efficiency coefficient of vibration on looseness improvement is related to the dry powdered lean magnetite ore and the vibrating feeder used. In this embodiment, the calibrated value is 10.5.

[0038] Then, the mathematical model of looseness and vibration frequency can be simplified as: , % When the maximum field strength at the radial magnetic surface of the magnetic drum is 300kA / m and the feed speed is 2.5m / s, the influence of vibration frequency and looseness on the separation effect of the magnetic drum is verified, as shown in Table 2.

[0039] Table 2

[0040] The data in Table 2 show that vibration can loosen the ore, which improves the separation efficiency of the magnetic drum. The separation tailing rate increases, and the magnetic iron grade of the tailings decreases significantly. When the vibration frequency exceeds 45 Hz, the separation efficiency no longer improves.

[0041] 3. Modeling of the effect of weak magnetic field strength on the capture ability of magnetite-poor conjoined bodies A weak magnetic field is commonly used to separate magnetite ores. However, the specific magnetic susceptibility and magnetic induction intensity of magnetite ores vary with the magnetite mineral content. In poor magnetite ores, where magnetite minerals are embedded in uneven particle sizes, intergrown particles with varying magnetite mineral contents are inevitable after crushing. This requires determining the strength of the weak magnetic field based on the level of pre-captured intergrown particles to prevent magnetite from escaping during the separation process.

[0042] The feeding speed determines the magnitude of the centrifugal force on the ore particles. If the magnetic attraction of the magnetic field to the magnetite ore is smaller than the centrifugal force, they will escape and become sorting tailings, resulting in a high magnetic iron grade in the tailings and a poor sorting effect.

[0043] The purpose of the modeling is to determine the minimum magnetic field strength required to prevent the escape of valuable magnetite conjoined bodies.

[0044] First, when determining that the magnetic iron grade of the sorting tailings can be controlled at ≤1% when using magnetic drums to sort powdered lean magnetite, the basis for this is that according to the ore rock identification standard, conjoined ore with a magnetic iron grade of ≤8% is considered waste rock. Based on this, a mathematical model for the proportion of magnetite minerals that allow conjoined ore in tailings from magnetic drum sorting is established: , where x is the mass ratio of magnetite mineral in a conjoined ore particle, and Q is the mass of a conjoined ore particle.

[0045] That is, the mass proportion of magnetite minerals in the conjoined ore in the sorting tailings , that is, the mass proportion of magnetite minerals in magnetite ore All conjoined ores should be recycled.

[0046] According to the positive correlation between the specific magnetic susceptibility of magnetite intergrowth and the volume or mass proportion of magnetite minerals, when the proportion of magnetite minerals is less than 1 / 9, the specific magnetic susceptibility of the intergrowth ore is:

[0047] The magnetic induction intensity B≈0.5T is tested for the minerals with a magnetite content of 1 / 9 of the total mass of the conjoined minerals. In this way, the ore with a magnetic mineral content of more than 1 / 9 of the total mass of the conjoined minerals is prevented from being sorted into tailings. The surface magnetic field intensity of the magnetic drum should meet the following requirements:

[0048] The ability of magnetic field strength to control the magnetic iron grade of tailings in magnetic drum separation was verified under the condition of no vibration of loose materials and a feeding speed of 2.5m / s, as shown in Table 3.

[0049] Table 3

[0050] The data in Table 3 demonstrates that the synergistic effect of high feed rate and strong weak magnetic field allows the magnetic drum to effectively control the magnetic grade of the sorted tailings to no more than 1%, while increasing the tailing rejection rate. This confirms that the synergistic effect of high feed rate and strong weak magnetic field facilitates the magnetic drum to achieve precise capture and enhanced sorting.

[0051] 4. Magnetic drum separation operating parameter settings: Maximum magnetic field strength at the radial magnetic surface of the magnetic drum is 400 kA / m, magnetic field strength 50 mm radially outward from the drum surface is 70 kA / m, feed speed is 2.50 m / s, and vibration frequency of the vibrating feeder is 45 Hz. Sorting indicators are shown in Table 4 below.

[0052] Table 4

[0053] It can be seen from Table 4 that the separation tailing rate of the magnetic drum is significantly improved, with an increase of more than 100%, and the magnetic iron grade of the separated tailings is stable within 1%.

[0054] The second step is to design a specific implementation plan for this example based on the results of the above modeling, including the following: pretreatment technology using the synergistic effects of vibration dispersion and high-speed ore feeding to thin the material layer, and the comprehensive application of precise capture and enhanced sorting technology using the synergistic effects of high-speed ore feeding and a strong weak magnetic field; The specific implementation process is:

[0055] 1. The original pendulum feeder was replaced with an electromagnetic vibrating feeder. The ore in the storage silo is vibrated by the electric vibrating feeder to loosen the ore, and then fed to the magnetic drum for sorting via a speeded belt conveyor. The thickness of the material layer on the belt conveyor is controlled within 5mm, achieving thin and uniform feeding, and preventing the looseness of the material layer caused by excessive thickness.

[0056] 2. Replace the ordinary motor of the magnetic drum feeding belt conveyor with a variable frequency motor. By adjusting the frequency conversion, the belt speed of the belt conveyor can be controlled at above 2.5m / s, which can increase the feeding speed and improve the centrifugal force of the powdered ore particles. At the same time, the feeding material layer of the magnetic drum can be thinned, allowing the discrete gangue ore particles to be fully exposed.

[0057] 3. The magnetic field of the magnetic drum has been redesigned, with the magnetic pole spacing shortened from the conventional 30mm to 15mm. The maximum magnetic field intensity on the radial magnetic surface of the magnetic drum has been increased from 300kA / m to 400kA / m, and the magnetic field intensity 50mm radially outward from the drum surface has been increased from 40kA / m to 70kA / m. This enhances the adsorption of fine-grained magnetite and ore particles with a magnetite content greater than 1 / 9, preventing them from becoming tailings in the sorting process due to increased centrifugal force.

[0058] The statistics of relevant indicators before and after implementation are shown in Table 5 below.

[0059] Table 5

[0060] As can be seen from Table 5, the application of the technical solution of the present invention increases the pre-grinding magnetic drum separation tailing rate from 3.51% to 7.23%, reduces the magnetic iron grade of the sorted tailings from 2.1% to 0.67%, and increases the magnetic iron grade of the ore entering the mill from 16.68% to 17.45%. The grindability of the ore is improved, and the annual amount of waste rock entering the mill is reduced by 313,900 tons, reducing production costs while increasing resource utilization. This demonstrates that the present invention achieves efficient separation by optimizing the operating conditions for magnetic drum separation of powdered lean magnetite by changing magnetic drum separation parameters. While controlling the magnetic iron grade of the tailings to less than 1%, the amount of tailings separated approaches its content before separation.

[0061] By changing the state of the sorting material and the parameters of relevant process equipment, the present invention significantly improves the effect of magnetic drum sorting of powdered lean magnetite, not only greatly increases the tailing volume of the sorting tailings, but also greatly reduces its magnetic iron grade; improves the grade of the ore entering the mill, which is beneficial to the company's cost reduction and efficiency improvement; and has great value for promotion and application.

[0062] Although the embodiments of the present invention have been shown and described above, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for efficiently separating powdered poor magnetite using a magnetic drum, characterized in that: The following steps are involved: First, the ore aggregates before selection are dispersed, and the shear force generated by vibration is used to disperse the agglomerates; then, the feed layer of the magnetic drum is quantitatively and quickly transported to thin it to prevent the formation of secondary agglomerates; the above operations enhance the capture ability of valuable lean intergrowth ore particles and enhance the centrifugal force of unusable extremely lean intergrowth ore particles to break free from the magnetic field adsorption, thereby enhancing the ability of unusable extremely lean intergrowth ore particles and gangue particles to be thrown away from the magnetic drum, and clarifying the separation boundary between the selected concentrate and tailings.

2. The method for efficiently separating powdered lean magnetite using a magnetic drum according to claim 1, characterized in that: The specific steps include: Step 1: Front-end deagglomeration: Replace the swing feeder above the magnetic drum feeding belt with a vibrating feeder. The powdered ore in the silo is first fed into the vibrating feeder. The powdered ore is fully vibrated and deagglomerated before falling into the belt conveyor. Step 2: Mid-end thinning: The loose ore materials that have been vibrated and deagglomerated at the front end will fall into the feeding belt conveyor of the magnetic drum. In order to prevent the secondary agglomeration of the ore particles due to the excessive thickness of the conveying material layer, the conveying speed of the belt conveyor is increased to thin the material layer and build a thin layer sorting state. This can also reduce the mechanical inclusions caused by magnetic interference, and is conducive to increasing the effective range of the magnetic field to prevent the escape of magnetite ore. Step 3: High centrifugal force and magnetic field adaptation at the back end: A higher magnetic field strength is required to firmly adsorb and drag the easily escaped valuable conjoined ore particles to the separation concentrate area, thereby increasing the recovery rate of magnetite minerals and reducing the magnetic iron grade of the separation tailings.

3. The method for efficiently separating powdered lean magnetite using a magnetic drum according to claim 2, characterized in that: Under the premise of keeping the total feeding amount unchanged, multiple vibrating feeders are used to feed the ore, thus reducing the feeding amount of a single vibrating feeder.

4. The method for efficiently separating powdered lean magnetite using a magnetic drum according to claim 2, wherein: The thickness of the material layer on the belt conveyor is controlled within 5mm to achieve uniform feeding of thin layers and prevent the reduction of looseness caused by excessively thick material layers.

5. The method for efficiently separating powdered lean magnetite using a magnetic drum according to claim 2, characterized in that: The feeding belt of the magnetic drum is connected to the frequency conversion motor. By adjusting the frequency conversion, the belt speed of the belt is controlled to be above 2.5m / s, thereby increasing the feeding speed and improving the centrifugal force of the powdered ore particles.

6. The method for efficiently separating powdered lean magnetite using a magnetic drum according to claim 2, characterized in that: The magnetic field of the magnetic drum is set, and the magnetic pole spacing is shortened from the conventional 30mm to 15mm, which increases the magnetic field strength at a long distance radially outward from the surface of the magnetic drum, that is, increases the magnetic field strength at the top layer of the material layer.

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