Mineral processing technology for efficiently recovering iron from magnetite tailings

Abstract

The invention relates to an efficient beneficiation process for recycling iron from iron tailings, which comprises the following steps of: feeding magnetite tailing pulp into a tailing recycling machine, feeding concentrate of the recycling machine into a first-section magnetic separator, and feeding concentrate of the first-section magnetic separator into a concentration magnetic separator; directly feeding concentrate of the concentration magnetic separator into a tower mill, feeding discharged ore of the tower mill into a swirler, and returning settled sand of the swirler to the tower mill to form closed-circuit ore grinding; overflow of the cyclone is fed into a second-stage magnetic separator, second-stage magnetic separator concentrate with the grade being 38% or above is obtained, and the second-stage magnetic separator concentrate is fed into a moxa sand mill; ore discharged by the moxa sand mill is fed into a third-section magnetic separator, concentrate of the third-section magnetic separator is fed into a fourth-section magnetic separator, concentrate of the fourth-section magnetic separator is fed into an elutriator, the concentrate of the elutriator is final concentrate, and the grade reaches 66% or above; the elutriator returns to the first section, the second section, the second section, the third section and the fourth section, and tailings of the magnetic separators are converged into comprehensive tailings. By optimizing the technological process, the concentrate grade is improved by more than 2%, and meanwhile, the tailing grade is reduced by 0.3%.

Description

Technical Field

[0001] The invention belongs to the technical field of iron ore dressing technology, and in particular relates to a dressing technology for efficiently recovering iron from magnetite tailings. Background Art

[0002] The beneficiation of magnetite mainly adopts the process of stage grinding-single magnetic separation-fine screening and re-grinding. With the acceleration of the mining process of domestic ore resources, the magnetite ore selected is becoming poorer, the crystal size is becoming finer, and the embedding degree is becoming more and more complex. Therefore, the loss of magnetic iron in the selection process is also increasing. On the one hand, the loss of magnetic iron causes low metal recovery rate, waste of magnetic iron resources, and reduced economic benefits; on the other hand, it increases the amount of tailings, shortens the service life of the tailings pond, and causes environmental pollution.

[0003] The relationship between iron minerals and gangue minerals in magnetic tailings is complex. They mainly exist in the form of poor intergrowth of iron minerals, and there are also a small amount of fine-grained monomer iron minerals. Generally, fine grinding and multiple concentrations are required to obtain a high-grade concentrate. At present, the re-selection of magnetite magnetic tailings mostly uses disc recovery machines and magnetic separators to recover magnetic minerals in the tailings, and the recovered coarse concentrates are subjected to grinding-cyclone classification, screening and separation.

[0004] The problems are: 1. Since most of the magnetic iron in the tailings is a poor intergrowth that is difficult to grind and select, in the conventional grinding and separation process, most of the magnetic iron content in the particles is low, so the overall specific gravity of the particles is small. Since the cyclone classification is classified by specific gravity, during the classification process, some of the magnetite poor intergrowths in the coarse concentrate will directly enter the cyclone classification overflow and skip the grinding process, resulting in under-grinding of some intergrowths. This part of the poor intergrowth will cause metal loss and low metal recovery rate when entering the magnetic separation tailings; it will cause low concentrate grade when entering the magnetic separation concentrate.

[0005] 2. Some magnetite tailings recovery processes use high-frequency vibrating fine screens to screen the grinding products, re-grind and re-select the products on the screen, and select the products under the screen in order to obtain high-grade concentrates and high recovery rates. However, most magnetite tailings have fine particle sizes, which require finer sieve holes, generally below 45 microns. In production, sieves below 45 microns have low opening rates and screening efficiency, require a large number of equipment, and have high production and maintenance costs. Second, the amount on the screen is large, the screen holes are easily blocked, and there are a large number of fine particles on the screen that should enter the screen below. Third, the amount on the screen is unstable, which makes production control difficult and the concentrate indicators unstable.

[0006] 3. The grinding particle size is not fine enough, and the dissociation degree of the grinding product is not enough, resulting in low concentrate grade, high tailings grade, and high production cost. The particle size of the coarse concentrate of magnetic tailings is generally fine, most of which are above 50% of -200 mesh. It is generally believed that the feed particle size and discharge particle size are between -200 mesh 30% and 90% respectively, which are suitable for ball milling. The feed particle size and discharge particle size are between -200 mesh 30% and -320 mesh 90% respectively, which are suitable for tower milling. The feed particle size is above -400 mesh 90%, which is suitable for super mills such as Aisha mills. Magnetic tailings re-grinding generally needs to be ground to more than 90% of -500 mesh to fully dissociate, so as to obtain high-grade concentrate and higher metal recovery rate.

[0007] Chinese Patent No. 201811098588.3 discloses "An Anshan-type lean magnetite tailings efficient recovery and reselection process" adopts a large-angle, countercurrent medium magnetic field magnetic separator to replace the original disc recovery machine for a roughing process, and the roughing concentrate adopts a long cylinder mill and a cyclone for a first grinding and classification, the first grinding discharge product returns to the first roughing magnetic separator, the first classification overflow with a particle size of 90% of -200 mesh is fed to the second magnetic separator, the second magnetic separator concentrate is fed to the second cyclone for classification, the classified sand is fed to the tower mill for second grinding, the tower mill discharge returns to the second magnetic separation, the second classification overflow with a particle size of more than 90% of -400 mesh is fed to the final magnetic separation, and the final magnetic separation consists of a three-stage magnetic separator, an electromagnetic concentration magnetic separator, and a sweeping magnetic separator. Among them, the magnetic system wrap angle of the magnetic separator is 240°~260°, and the average field strength on the surface of the barrel of the magnetic separator sweeping zone is above 380mT. The large wrap angle, high field strength magnetic system and countercurrent bottom box ensure that the magnetic iron content of the tailings is below 0.8%, reducing the loss of metal. The existing problems are: 1. The feed particle size of the first stage grinding reaches more than 50% of -200 mesh, and the overflow particle size of the first stage classification reaches 90% of -200 mesh. The feed and discharge particle sizes are fine, and the ball mill is used for grinding, and the grinding cost is high. 2. When the cyclone is used as a matching classification equipment for the ball mill and tower mill, the slurry is first fed into the cyclone, the cyclone sand is fed into the ball mill or tower mill, and the cyclone overflow enters the next process. At the same time, due to the light specific gravity, some lean conjoined bodies will directly overflow from the cyclone into the next process without entering the mill, and will not play a role in improving the degree of dissociation. They will directly enter the separation operation, resulting in low concentrate grade and metal recovery rate. 3. The second stage grinding adopts a tower mill. The tower mill has a large volume, and the grinding medium is mainly in the lower layer. The lower layer has a good grinding effect, and the upper layer has a large settling area. Due to the high concentration of the slurry and the large buoyancy, the iron minerals with a large specific gravity are more likely to sink to the lower layer and form over-grinding; the lean intergrowth particles are easy to float on the upper layer of the tower mill, making it difficult to grind and easier to enter the tower mill to discharge. Therefore, the over-grinding and under-grinding situation is aggravated. At the same time, when the iron mineral grinding particle size of the tower mill exceeds 90% of -400 mesh, the grinding time and energy consumption increase rapidly; to obtain high-quality iron concentrate, the iron tailings often need to be ground to more than 90% of -400 mesh.

[0008] Chinese patent 201010187615.1 discloses a "new process for the recovery of iron tailings in Anshan", which uses a recovery machine to recover magnetic tailings. After the recovery machine concentrate is concentrated by a magnetic dewatering tank, the dewatering tank concentrate is fed to a vibrating fine screen, the underscreen is fed to a magnetic separator for selection, and the magnetic separator concentrate is fed to a centrifuge. The centrifuge concentrate is used as the final concentrate, and the recovery machine tailings, dewatering tank tailings, fine screen, magnetic separator tailings and centrifuge tailings are used as the final tailings. The process is simple, does not require grinding, and has low cost. However, the magnetic tailings do not improve the degree of dissociation through grinding, and can only recover a small amount of fine-grained iron minerals that have been well dissociated, so the final concentrate grade and metal recovery rate are low.

[0009] Chinese patent 201310326795.0 discloses a "process for selecting iron concentrate from lean magnetite tailings", in which the recovery machine concentrate passes through a pre-selection magnetic separator, the pre-selection magnetic separator concentrate is fed into a closed-circuit grinding consisting of a primary cyclone and a first-stage ball mill, the first-stage classification overflow passes through the second-stage magnetic separation, and the magnetic separation concentrate is fed into the second-stage tower mill, and the second-stage tower mill discharge is fed into the third, fourth and fifth-stage magnetic separation for separation, and the pre-selection tailings, second, third, fourth and fifth-stage magnetic separation tailings are used as the final tailings. The use of ball mills and cyclones for first-stage grinding classification in this patent is consistent with the above-mentioned patent issues and will not be repeated. The second-stage magnetic separation concentrate is directly fed into the tower mill, and the optimal grinding concentration of the tower mill is 70%. In actual production, the concentration of the second-stage magnetic separation concentrate is difficult to reach more than 60%, which will result in low tower mill grinding efficiency and high grinding cost; at the same time, the tower mill discharge has not been inspected and classified, and is prone to coarseness, resulting in high subsequent magnetic separation tailings and low metal recovery rate. Summary of the invention

[0010] The purpose of the present invention is to provide an efficient ore dressing process for recovering iron from iron tailings, which can improve the grade of iron concentrate and metal recovery rate, improve resource utilization and reduce ore dressing costs.

[0011] The objective of the present invention is achieved through the following technical solutions: The invention discloses an efficient beneficiation process for recovering iron from iron tailings, characterized in that it comprises the following steps: 1) Feed the magnetite tailings slurry with a total iron grade of 6-15% into the tailings recovery machine to obtain a recovery machine concentrate with a grade of 10-20%; 2) Feed the recovery machine concentrate with a grade of 10-20% into a first-stage magnetic separator, and obtain a first-stage magnetic separator concentrate with a grade of 15-25% and feed it into a concentration magnetic separator; 3) The concentrate from the concentrated magnetic separator is directly fed into the tower mill, and the tailings from the recovery machine, the first stage magnetic separator, and the concentrated magnetic separator enter the comprehensive tailings. The tower mill discharge is fed into the cyclone, and the cyclone sand is returned to the tower mill to form a closed-circuit grinding; 4) After the overflow particle size of the cyclone reaches 90% of -200 mesh to 95% of -320 mesh, it is fed into the second-stage magnetic separator to obtain the second-stage magnetic separator concentrate with a grade of more than 38%, and the concentration of the second-stage magnetic separator concentrate is controlled at 40% to 55% and then directly fed into the sand mill; 5) The particle size of the ore discharged from the sand mill reaches more than 90% of -400 mesh, and is fed into the three-stage magnetic separator to obtain a three-stage magnetic separator concentrate with a grade of more than 60%; 6) The three-stage magnetic separator concentrate is fed into the four-stage magnetic separator to obtain the four-stage magnetic separator concentrate with a grade of more than 64%; the four-stage magnetic separator concentrate is fed into the panning machine, and the panning machine produces the final concentrate with a grade of more than 66%; the panning machine returns to the two-stage magnetic separator, and the tailings of the two-stage magnetic separator, the three-stage magnetic separator and the four-stage magnetic separator are merged into the comprehensive tailings.

[0012] The maximum magnetic field strength of the second-stage magnetic separator, the second-stage magnetic separator tailings, the third-stage magnetic separator tailings and the fourth-stage magnetic separator of the magnetic separator is 400mT.

[0013] The advantages of the present invention are: By optimizing the first-stage tower mill grinding and classification, the second-stage argon sand mill grinding and magnetic separation process, the dissociation degree of the grinding product was improved. Compared with the two-stage tower mill cyclone classification-stage magnetic separation process for tailings re-selection, the test results show that when the beneficiation cost is the same, the concentrate grade is increased by more than 2 percentage points, and the tailings grade is reduced by 0.3 percentage points. Beneficial effects specific plan The first-stage magnetic separator concentrate recovered from the magnetic separation tailings is mainly composed of lean intergrowths with low dissociation degree, which requires fine grinding. The traditional method of first classification and then grinding often causes a large number of medium and fine particles to directly enter the classification overflow and bypass the grinding. The lean intergrowths bypassing the grinding will lead to the classification overflow dissociation degree not being improved, thereby reducing the grade of the second-stage magnetic separation concentrate and improving the grade of the second-stage magnetic separation tailings. In the present invention, the concentrate recovered by the first-stage magnetic separator is not directly fed into the cyclone, but is concentrated by a concentrating magnetic separator. The concentrate of the concentrating magnetic separator is directly fed into a first-stage tower mill from the bottom. The concentration of the first-stage magnetic separator is about 60%, and the sand concentration of the cyclone is about 75%. The sand ratio is generally 250%. Therefore, the comprehensive feeding concentration of the tower mill is about 70%. In the optimal grinding concentration range of the tower mill, the grinding effect can reach the best. The first-stage magnetic concentrate is directly fed into the tower mill, which reduces the feed amount of the cyclone and reduces the production cost of the cyclone feed pump. The cyclone feed is completely composed of the tower mill discharge, and the feed particle size is finer and more uniform, which optimizes the cyclone feed particle size composition and improves the classification efficiency.

[0014] The second-stage magnetic separation concentrate is ground with an Ai sand mill, ① avoiding the reverse enrichment of the cyclone and the overflow of lean intergrowths from the cyclone directly into the next stage of operation, resulting in insufficient grinding (the principle is the same as above). ② The Ai sand mill has the advantages of high grinding efficiency, classification while grinding, uniform grinding particle size, and no need for external classification equipment, which simplifies the process flow. ③ The Ai sand mill is more suitable for fine-grained grinding, and the particle size of the grinding product can be finer, which can make the final concentrate grade higher; at the same time, for grinding particles above 90% of 400 mesh, the Ai sand mill has lower power consumption and ball consumption, saving grinding costs. ④ The feed concentration of the Ai sand mill is generally 45-55%, which is suitable for direct feeding of the second magnetic concentrate without further concentration, simplifying the process flow.

[0015] The tailings from the washing machine are returned to the second-stage magnetic separator and then to the sand mill for grinding, which improves the dissociation degree of the electromagnetic tailings and ultimately improves the metal recovery rate. In the current production process, the electromagnetic tailings are often fed into the second-stage cyclone. Since it is the overflow of the cyclone, most of the particles in it will directly enter the overflow of the cyclone, thus forming a closed loop. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0017] The present invention will be further described below in conjunction with the accompanying drawings.

[0018] like Figure 1 As shown, an efficient beneficiation process for recovering iron from iron tailings of the present invention is characterized by comprising the following steps: 1) Feed the magnetite tailings slurry with a total iron grade of 6-15% into the tailings recovery machine to obtain a recovery machine concentrate with a grade of 10-20%; 2) Feed the recovery machine concentrate with a grade of 10-20% into a first-stage magnetic separator, and obtain a first-stage magnetic separator concentrate with a grade of 15-25% and feed it into a concentration magnetic separator; 3) The concentrate from the concentrated magnetic separator is directly fed into the tower mill, and the tailings from the recovery machine, the first stage magnetic separator, and the concentrated magnetic separator enter the comprehensive tailings. The tower mill discharge is fed into the cyclone, and the cyclone sand is returned to the tower mill to form a closed-circuit grinding; 4) After the overflow particle size of the cyclone reaches 90% of -200 mesh to 95% of -320 mesh, it is fed into the second-stage magnetic separator to obtain the second-stage magnetic separator concentrate with a grade of more than 38%, and the concentration of the second-stage magnetic separator concentrate is controlled at 40% to 55% and then directly fed into the sand mill; 5) The particle size of the ore discharged from the sand mill reaches more than 90% of -400 mesh, and is fed into the three-stage magnetic separator to obtain a three-stage magnetic separator concentrate with a grade of more than 60%; 6) The three-stage magnetic separator concentrate is fed into the four-stage magnetic separator to obtain the four-stage magnetic separator concentrate with a grade of more than 64%; the four-stage magnetic separator concentrate is fed into the panning machine, and the panning machine produces the final concentrate with a grade of more than 66%; the panning machine returns to the two-stage magnetic separator, and the tailings of the two-stage magnetic separator, the three-stage magnetic separator and the four-stage magnetic separator are merged into the comprehensive tailings.

[0019] The maximum magnetic field strength of the two-stage magnetic separator, the two-stage magnetic separator tailings, the three-stage magnetic separator tailings and the four-stage magnetic separator of the magnetic separator described in the present invention is 400mT.

[0020] The present invention adopts a first-stage tower mill grinding and classification, a second-stage argon sand mill grinding and a magnetic separation process, which effectively improves the dissociation degree of the grinding product; the concentrate grade is increased by more than 2 percentage points compared with the prior art, and the tailings grade is reduced by 0.3 percentage points.

Claims

1. An efficient beneficiation process for recovering iron from iron tailings, characterized in that: The following steps are involved: 1) Feed the magnetite tailings slurry with a total iron grade of 6-15% into the tailings recovery machine to obtain a recovery machine concentrate with a grade of 10-20%; 2) Feed the recovery machine concentrate with a grade of 10-20% into a first-stage magnetic separator, and obtain a first-stage magnetic separator concentrate with a grade of 15-25% and feed it into a concentration magnetic separator; 3) The concentrate from the concentrated magnetic separator is directly fed into the tower mill, and the tailings from the recovery machine, the first stage magnetic separator, and the concentrated magnetic separator enter the comprehensive tailings. The tower mill discharge is fed into the cyclone, and the cyclone sand is returned to the tower mill to form a closed-circuit grinding; 4) After the overflow particle size of the cyclone reaches 90% of -200 mesh to 95% of -320 mesh, it is fed into the second-stage magnetic separator to obtain the second-stage magnetic separator concentrate with a grade of more than 38%, and the concentration of the second-stage magnetic separator concentrate is controlled at 40% to 55% and then directly fed into the sand mill; 5) The particle size of the ore discharged from the sand mill reaches more than 90% of -400 mesh, and is fed into the three-stage magnetic separator to obtain a three-stage magnetic separator concentrate with a grade of more than 60%; 6) The three-stage magnetic separator concentrate is fed into the four-stage magnetic separator to obtain the four-stage magnetic separator concentrate with a grade of more than 64%; the four-stage magnetic separator concentrate is fed into the panning machine, and the panning machine produces the final concentrate with a grade of more than 66%; the panning machine returns to the two-stage magnetic separator, and the tailings of the two-stage magnetic separator, the three-stage magnetic separator and the four-stage magnetic separator are merged into the comprehensive tailings.

2. The efficient iron tailings iron recovery beneficiation process according to claim 1, characterized in that: The maximum magnetic field strength of the two-stage magnetic separator, the two-stage magnetic separator tailings, the three-stage magnetic separator tailings and the four-stage magnetic separator of the magnetic separator is 400mT.

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