Multi-crushing and less-grinding beneficiation method for low-grade iron ore with non-uniform crystal particle size distribution

Abstract

The invention provides a multi-crushing and less-grinding beneficiation method for low-grade iron ore with uneven crystal particle size and thickness distribution, and relates to the technical field of mineral engineering, the method comprises the following steps: S1, preparing materials; s2, a high-pressure rolling process; s3, an ore grinding and grading process; s4, a second-stage magnetic separation process; s5, performing an independent screening process; s6, a fine selection three-section elutriation machine process; s7, performing a second-stage grading process; s8, a moxa sand grinding and regrinding process; s9, a fine selection four-section elutriation machine process; and S10, performing a three-stage magnetic separation process. Aiming at the low-grade magnetic iron ore with non-uniform crystal granularity distribution, the method realizes coarse and fine grading recovery, can treat the low-grade ore, reduces the ore grinding cost, improves the treatment capacity of a mill, is more environment-friendly in the enrichment process, improves the iron monomer dissociation degree, provides high-quality raw materials for fine selection, ensures the purity of concentrate and the uniform ore grinding granularity, and improves the ore quality. The whole technological process is simple and efficient, industrial production is easy, and the treatment efficiency and the product quality are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of mining engineering, and in particular to a beneficiation method for low-grade iron ore with uneven distribution of crystal grain sizes, which involves multi-crushing and less grinding. Background Art

[0002] The reserves of iron ore in China are quite abundant, but the average iron grade is only about 34%. The domestic iron ore mainly consists of lean ore, and the reserved reserves of rich iron ore that can be directly smelted in the furnace only account for 2.53% of the total reserves. In recent years, the iron ore mining volume in China has been continuously decreasing, the mining and beneficiation costs of domestic mines are relatively high, and the domestic iron ore usually adopts stage grinding and stage separation, and the processes are basically the same. Minerals form ores with uneven crystal grain sizes under complex geological conditions. Usually, this kind of iron ore with uneven distribution is utilized, and the commonly used beneficiation process is stage grinding and stage tailing discarding, and commonly used two-stage or three-stage grinding and separation processes; in this process, the monomer-dissociated iron minerals are not selected in time, thus entering the grinding process for circulation, resulting in waste of grinding energy consumption and affecting the throughput of the concentrator. At the same time, the particle size of the final iron concentrate is too fine, which has an adverse effect on the subsequent pelletizing or sintering process.

[0003] "Experimental Research on a New Beneficiation Process for Hematite Ore" In a certain iron ore in Yunnan, the particle sizes of hematite in the hematite ore are extremely uneven. In order to maximize the production of fine ore, the raw ore is divided into two particle sizes: coarse particles (6 mm - 0.15 mm) and fine particles (0.15 mm - 0) for classified beneficiation. The beneficiation test research on the coarse particle part (6 mm - 0.15 mm) conducted by the Changsha Research Institute of Mining and Metallurgy uses a wet permanent magnetic high-intensity magnetic separator. After one roughing, one cleaning, one scavenging, and re-selection of the middlings, a concentrate with an iron grade of 55% and an operation recovery rate of over 60% is obtained, and the concentrate product meets the requirements. The experimental research on the comprehensive utilization of the coarse particle middlings and the fine particle size conducted by Kunming University of Science and Technology adopts a new beneficiation process of rough and fine separation, in which the coarse particle middlings are reground and then combined with the fine particle size for beneficiation. The process adopts a one-roughing and one-scavenging flow, and the obtained rough concentrate grade is 56%, and the operation recovery rate is close to 90%. After tabling concentration, the obtained concentrate grade can reach 60%, and the recovery rate is close to 80%. However, this literature is about the process of recovering hematite. By first classifying and treating different particle sizes, there will be a situation where the monomer dissociation in the fine particle size is not recovered first. Finally, tabling is used to improve the product grade, which affects the iron recovery rate.

[0004] "A Beneficiation Method for Fine-Grained Hematite with Uneven Crystal Grain Sizes" Through rough separation by high-intensity magnetic separation, centrifugal concentration of the rough separation concentrate, strong magnetic scavenging of the rough separation tailings; the tailings of the centrifuge and the scavenging concentrate are reground and classified, the classified products are subjected to high-intensity magnetic separation, the magnetic separation concentrate is centrifugally concentrated, the tailings of the centrifuge are reground, and the centrifuge concentrate is used as the final concentrate. However, this process is suitable for the separation of hematite. The TFe grade of the tailings is 15%, and the treatment capacity of the centrifugal concentration is relatively low, which limits industrialization.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The object of the present invention is to provide a beneficiation method for low-grade iron ore with uneven particle size distribution of crystal grains, which overcomes the problems of uneven particle size of crystal grains of low-grade iron ore, the ore that has reached monomer dissociation of iron minerals still circulating in the process during beneficiation, resulting in waste of grinding energy consumption, too fine particle size of concentrate products, and low grinding throughput.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A beneficiation method for low-grade iron ore with uneven particle size distribution of crystal grains provided by the present invention includes the following steps: S1. Preparation of materials; S2. High-pressure roll grinding or dry separation process; S3. Grinding and classification process; S4. Second-stage magnetic separation process; S5. Independent screening process; S6. Fine selection three-stage elutriator process; S7. Second-stage classification process; S8. Aisha grinding re-grinding process; S9. Fine selection four-stage elutriator process; S10. Third-stage magnetic separation process.

[0009] Further, on the basis of the above technical solution, the material preparation includes: crushing magnetite ore to obtain a crushed product;

[0010] The particle size of the crushed product is 0-100 mm;

[0011] The content of TFe in the magnetite ore is less than 25%.

[0012] Further, on the basis of the above technical solution, the high-pressure roll grinding process includes: feeding the crushed product into a high-pressure roll grinding closed-circuit process for crushing to obtain a finely crushed ore sample, and feeding the finely crushed ore sample into a first wet drum magnetic separator to obtain a first magnetic separation tailing and a first magnetic separation concentrate;

[0013] The particle size of the finely crushed ore sample is 0-3 mm;

[0014] The working parameters of the first wet drum magnetic separator include: magnetic separation concentration of 20%-40%, magnetic field intensity of 76-300 kA / m.

[0015] Further, on the basis of the above technical solution, the grinding and classification process includes: feeding the first magnetic separation concentrate into a ball mill for grinding, and the obtained grinding product is classified by a first cyclone, and the grinding product flowing out through the first overflow pipe is used as the feed for the next process, and the first sand deposit formed at the bottom of the first cyclone returns to the ball mill for feeding;

[0016] The concentration of the ball mill grinding is 60%-75%;

[0017] The monomer dissociation degree of iron minerals in the grinding product flowing out through the first overflow pipe is ≥ 50%;

[0018] When the content of minerals with a particle size grade of -200 mesh in the grinding product accounts for 45% - 60% of the total amount of the first magnetic separation concentrate fed in, stop grinding.

[0019] Further, on the basis of the above technical solution, the secondary magnetic separation process includes: feeding the grinding product flowing out through the first overflow pipe into a second wet drum magnetic separator to obtain a second magnetic separation tailing and a second magnetic separation concentrate;

[0020] The monomer dissociation degree in the second magnetic separation concentrate is 55% - 70%;

[0021] The operating parameters of the second wet drum magnetic separator include: magnetic separation concentration of 20% - 40%, magnetic field intensity of 72 - 168 kA / m.

[0022] Further, on the basis of the above technical solution, the independent screening process includes: feeding the second magnetic separation concentrate into a fine screen to obtain an oversize product and an undersize product, feeding the oversize product into a second cyclone, and feeding the undersize product into a first elutriator;

[0023] The iron monomer dissociation degree in the undersize product is 60% - 80%;

[0024] When the content of minerals with a particle size of -200 mesh in the undersize product accounts for 75% - 90% of the total amount of the second magnetic separation concentrate fed in, stop screening.

[0025] Further, on the basis of the above technical solution, the three-stage elutriator beneficiation process includes: feeding the undersize product into a first elutriator to obtain a first elutriator concentrate and a first elutriator tailing, feeding the first elutriator tailing into a second cyclone, and taking the first elutriator concentrate as the final concentrate;

[0026] The operating parameters of the first elutriator include: magnetic field intensity of 3 kA / m - 50 kA / m; feed rate of 0.25 - 1.5 kg / min; feed concentration of 15% - 30%; upward water flow of 10 - 30 L / min.

[0027] Further, on the basis of the above technical solution, the secondary classification process includes: feeding the first elutriator tailing and the oversize product into a second cyclone to obtain a grinding product flowing out through a second overflow pipe and a second sand deposit; feeding the grinding product flowing out through the second overflow pipe into a second elutriator;

[0028] The regrinding process of the sand grinding mill includes: feeding the second sand deposit formed at the bottom of the second cyclone into a sand grinding mill for grinding to obtain a discharge product of the sand grinding mill;

[0029] The grinding concentration of the sand grinding mill is 25% - 50%;

[0030] After the content of minerals with a particle size grade of -400 mesh in the discharged product of the AI sand mill accounts for 60% - 80% of the total amount of fed minerals, stop grinding, and the grinding time is 60 - 120 s;

[0031] The degree of monomer dissociation of iron in the discharged product of the AI sand mill is greater than 90%.

[0032] Further, on the basis of the above technical solution, the four-stage elutriator process for concentration includes: feeding the discharged product of the AI sand mill and the ground product flowing out of the second overflow pipe into the second elutriator to obtain the concentrate of the second elutriator and the tailings of the second elutriator. The obtained concentrate of the second elutriator is used as the final concentrate, and the tailings of the second elutriator are used as the feed for the next process;

[0033] The operating parameters of the second elutriator include: magnetic field strength: 3 kA / m - 50 kA / m; feed rate: 0.25 - 1.5 kg / min; feed concentration: 15% - 30%; upward water flow: 10 - 30 L / min;

[0034] The average TFe content in the final concentrate is 60 - 69%, and the total recovery rate is 65 - 67%.

[0035] Further, on the basis of the above technical solution, the three-stage magnetic separation process includes: feeding the tailings of the second elutriator into the third wet drum magnetic separator to obtain the tailings of the third magnetic separation and the concentrate of the third magnetic separation; the concentrate of the third magnetic separation is returned to the AI grinder for grinding, and the tailings of the third magnetic separation are used as the final tailings;

[0036] The degree of monomer dissociation in the concentrate of the third magnetic separation is 75 - 85%;

[0037] The operating parameters of the third wet drum magnetic separator include: magnetic separation concentration of 20% - 40%, and magnetic field strength of 72 - 168 kA / m.

[0038] A beneficiation method for low-grade iron ore with uneven crystal grain size distribution, which is provided by the present invention, has the following beneficial effects:

[0039] 1. According to the properties of the raw material with uneven and non-uniform crystal grain sizes of magnetic iron, the present invention adopts step-by-step recovery of coarse and fine particles, and can preferentially obtain qualified products of coarse particle sizes.

[0040] 2. The present invention can process low-grade magnetite ores with a TFe content of less than 25%, and has a wide processing range.

[0041] 3. By introducing the high-pressure roller grinding technology, the present invention realizes "more crushing and less grinding" of ores, not only significantly reducing the grinding cost, but also ensuring that the crystal grain size of the raw materials remains unchanged during the processing. In actual production operations, the feed particle size range of the high-pressure roller grinding is 0 - 100 mm, and after high-pressure roller grinding, it is effectively reduced to 0 - 3 mm. This change directly leads to a significant increase in the content of the fine particle level. Due to the reduction of the feed particle size, the grinding time required for the final product to meet the same particle size requirements is also significantly reduced, thereby further improving the production efficiency.

[0042] 4. The present invention finely controls the first-stage grinding classification according to the particle size distribution of the coarse particle fraction in the raw material crystallization, reducing the recycling of the materials that have reached monomer dissociation in the grinding classification process and improving the processing capacity of the mill.

[0043] 5. The present invention uses a magnetic drum for rough selection, and the tailings can be directly discarded, reducing the amount of ore entering the subsequent process;

[0044] 6. The present invention uses fine screening classification, further improving the monomer dissociation degree of iron in the undersize product, providing narrow particle size raw materials for the elutriator, which is beneficial to the separation of the elutriator;

[0045] 7. The present invention uses an elutriator for beneficiation, and the concentrate has less impurity;

[0046] 8. The present invention uses an Aisha mill for grinding, and the grinding particle size is more uniform.

[0047] 9. The process flow of the present invention is simpler and easier to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0049] Figure 1 It is a schematic flow chart of a beneficiation method for low-grade iron ore with uneven coarse and fine distribution of crystal grain size provided in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] To make the objectives, technical solutions and advantages of the present invention clearer, the following will, in conjunction with the embodiments of the present invention, clearly and completely describe the technical solutions in the embodiments of the present invention. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. The process parameters without specific conditions noted in the following embodiments are usually in accordance with conventional conditions.

[0051] In the ranges disclosed in the present invention, the endpoints and any values of the ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0052] According to the first aspect of the present invention, as Figure 1 shown, a beneficiation method for low-grade iron ore with uneven coarse and fine crystal grain size distribution and multi-crushing and less grinding is provided, including the following steps: S1. Preparation of materials; S2. High-pressure roller grinding or dry separation process; S3. Grinding and classification process; S4. Two-stage magnetic separation process; S5. Independent screening process; S6. Refining three-stage elutriator process; S7. Two-stage classification process; S8. Aisha grinding and re-grinding process; S9. Refining four-stage elutriator process; S10. Three-stage magnetic separation process.

[0053] As an optional implementation manner of the present invention, the preparation of materials includes: crushing magnetite ore to obtain a crushed product;

[0054] The particle size of the crushed product is 0 - 100 mm (such as 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, etc.);

[0055] Among them, the TFe content in the magnetite ore is less than 25% (such as 23%, 21%, 19%, etc.).

[0056] The crushing is three-stage one-closed-circuit crushing. Specifically, large pieces of magnetite ore are fed into a coarse crusher for coarse crushing. After the coarse-crushed magnetite ore is screened, it is transported to a fine crusher for fine crushing. The finely crushed ore is screened again. The ore that meets the particle size requirements enters the grinding stage, while the ore that does not meet the requirements is returned to the fine crushing section for re-crushing.

[0057] The particle size of the crushed product is 0 - 100 mm. Through screening analysis (nest sieve analysis) of the sample, it can be known that the crystal grain size of the oversize product with a size of +100 mesh accounts for 60 - 75% of the total sample amount, and the crystal grain size of the undersize product with a size of -400 mesh accounts for 10 - 15% of the total sample amount. The raw material has uneven distribution of crystal grain size and uneven grade distribution, meeting the requirements of the raw materials for the process of the present invention.

[0058] As an optional implementation mode of the present invention, the high-pressure roller grinding process includes: feeding the crushed product into a closed-circuit high-pressure roller grinding process for crushing to obtain a finely crushed ore sample, and feeding the finely crushed ore sample into a first wet drum magnetic separator to obtain a first magnetic separation tailing and a first magnetic separation concentrate;

[0059] The particle size of the finely crushed ore sample is 0 - 3 mm (such as 1 mm, 1.5 mm, 2 mm, etc.);

[0060] The operating parameters of the first wet drum magnetic separator include: magnetic separation concentration of 20% - 40% (such as 25%, 30%, 35%, etc.), and magnetic field intensity of 76 - 300 kA / m (such as 100 kA / m, 150 kA / m, 200 kA / m, 250 kA / m, etc.).

[0061] Specifically, by using the high-pressure roller grinding technology, "more crushing and less grinding" of the ore is realized, which not only greatly reduces the grinding cost, but also ensures that the crystal grain size of the raw material remains unchanged during the processing. In actual production operation, the feeding particle size range of the high-pressure roller grinding is 0 - 100 mm, and after high-pressure roller grinding, it is effectively reduced to 0 - 3 mm. This change directly leads to a significant increase in the content of the fine particle level. Due to the reduction of the feeding particle size, the grinding time required for the final product to reach the same particle size requirement is also greatly reduced, thereby further improving the production efficiency.

[0062] Specifically, in step S2 of the present invention, magnetic roller rough selection is adopted, and the first magnetic separation tailing can be directly discarded to reduce the amount of ore entering the subsequent process.

[0063] Specifically, in the first wet drum magnetic separator, the ore particles flow through the magnetic field area with the pulp. The magnetic minerals are attracted by the magnetic field, adsorbed on the surface of the magnetic drum, and are carried to the area with a weaker magnetic field intensity as the magnetic drum rotates. In this area, the magnetic minerals lose sufficient magnetic force support, fall off from the magnetic drum, and fall into the concentrate collection device to form a magnetic separation concentrate. The non-magnetic minerals are not affected by the magnetic field, continue to flow with the pulp, and finally are discharged from the tailing port of the magnetic separator to form a magnetic separation tailing. The magnetic separation tailing is used as the final tailing and is not further processed. The magnetic separation concentrate is fed into the next process operation for further processing.

[0064] As an alternative embodiment of the present invention, the grinding and classification process includes: feeding the first magnetic separation concentrate into a ball mill for grinding, and classifying the obtained grinding product through a first hydrocyclone. The grinding product flowing out through the first overflow pipe is used as the feed for the next process, and the first sand deposit formed at the bottom of the first hydrocyclone returns to the ball mill for feeding;

[0065] The concentration of the ball mill grinding is 60%-75% (such as 63%, 65%, 67%, 69%, 70%, 73%, etc.);

[0066] Specifically, the grinding concentration of the ball mill affects the grinding particle size and throughput. Therefore, the concentration condition of 60%-75% is the best, which can not only ensure that the ore particles are effectively and evenly ground to meet the expected particle size requirements, but also maintain the stable operation of the mill at a high processing efficiency, avoiding problems such as insufficient grinding caused by too low concentration or excessive wear and excessive equipment load caused by too high concentration.

[0067] The monomer dissociation degree of the iron minerals in the grinding product flowing out through the first overflow pipe is ≥50% (such as 55%, 60%, 65%, etc.);

[0068] When the content of minerals with a particle size grade of -200 mesh in the grinding product accounts for 45%-60% (such as 47%, 49%, 51%, 53%, 55%, 57%, 59%, etc.) of the total amount of the first magnetic separation concentrate fed in, stop grinding.

[0069] Specifically, the grinding particle size is determined according to the particle size of the crystalline coarse particle grade in the raw material. By reasonably controlling the grinding particle size (by controlling the content of minerals with a particle size grade of -200 mesh to account for 45%-60% of the total amount of minerals fed in), it can ensure that the useful minerals in the ore are fully dissociated, facilitating subsequent separation operations.

[0070] Specifically, the monomer dissociation degree of the iron minerals in the grinding product is observed and statistically analyzed under a microscope.

[0071] Specifically, a hydrocyclone is a device for classifying particles by controlling the feed pressure, which can separate the particles in the pulp according to the particle size. The grinding product (i.e., the particles with a smaller particle size) flowing out through the overflow pipe of the hydrocyclone is used as the feed for the next process, while the sand deposit (i.e., the particles with a larger particle size) formed at the bottom of the hydrocyclone returns to the feed port of the ball mill for re-grinding.

[0072] As an alternative embodiment of the present invention, the second-stage magnetic separation process includes: feeding the grinding product flowing out through the first overflow pipe into a second wet drum magnetic separator to obtain a second magnetic separation tailing and a second magnetic separation concentrate;

[0073] The monomer dissociation degree in the second magnetic separation concentrate is 55% - 70% (such as 60%, 63%, 65%, 67%, etc.).

[0074] As an optional embodiment of the present invention, the operating parameters of the second wet drum magnetic separator include: the magnetic separation concentration is 20% - 40% (such as 25%, 30%, 35%, etc.), and the magnetic field intensity is 72 - 168 kA / m (such as 100 kA / m, 150 kA / m, 200 kA / m, 250 kA / m, etc.).

[0075] Specifically, the operating mode of the second wet drum magnetic separator is the same as that of the first wet drum magnetic separator.

[0076] Specifically, the iron in the first magnetic separation tailings and the second magnetic separation tailings is mainly iron silicate. After collecting and processing the above tailings, they can be reused. The magnetic separation - grinding process of the present invention first uses magnetic separation technology. Based on the difference in mineral magnetism, the part of the tailings with a lower iron content is separated first. This step not only effectively reduces the processing volume in the subsequent grinding process, that is, reduces the amount of ore fed into the mill, but also significantly improves the grade of the ore entering the grinding stage by removing low - grade ores. Due to the reduction of the treatment of low - grade ores, the energy consumption and abrasive consumption in the grinding process are also reduced, thus significantly reducing the grinding cost.

[0077] As an optional embodiment of the present invention, the independent screening process includes: feeding the second magnetic separation concentrate into a fine screen to obtain an over - screen product and an under - screen product; feeding the over - screen product into a second cyclone, and feeding the under - screen product into a first elutriator.

[0078] The monomer dissociation degree of iron in the under - screen product is 60% - 80% (such as 65%, 70%, 75%, etc.).

[0079] Specifically, if the monomer dissociation degree of the under - screen product obtained in step S5 is higher than 80%, a large amount of the over - screen product needs to be returned to the previous processing flow for re - processing. This will not only increase the processing cost, but also may lead to increased equipment wear due to repeated processing, reducing the production efficiency. If the dissociation degree is less than 60%, it means that a large amount of iron minerals still exist in the form of intergrowths and effective monomer dissociation has not been achieved, resulting in unqualified products.

[0080] When the content of minerals with a particle size of - 200 mesh in the under - screen product accounts for 75% - 90% (such as 77%, 80%, 83%, 85%, 87%, etc.) of the total amount of the second magnetic separation concentrate fed in, stop screening.

[0081] Among them, the specifications and combination methods of the fine screen mesh are determined by the crystal grain size of the magnetic separation concentrate, specifically, the specifications and combination methods of the fine screen mesh are to meet the requirement that the content of minerals with a particle size of -200 mesh in the undersize product accounts for 75% - 90% of the total minerals fed in.

[0082] Specifically, in the present invention, the independent screening process adopted in step S5 is placed after the first-stage magnetic separation process and the second-stage magnetic separation process in the first wet drum magnetic separator to obtain narrow-sized materials for use in the elutriator. If it is used before the first-stage magnetic separation process and the second-stage magnetic separation process, it is usually to control the grinding particle size. The present invention adopts a high-pressure roll grinding closed-circuit process to obtain a fine crushed ore sample with a particle size of 0 - 3 mm. The grinding feed particle size is reduced, the screening process before magnetic separation is omitted, and the whole process flow is simplified.

[0083] As an optional implementation mode of the present invention, the three-stage elutriation process of the concentration includes: feeding the undersize product into the first elutriator to obtain the concentrate of the first elutriator and the tailings of the first elutriator. The tailings of the first elutriator are fed into the second cyclone, and the concentrate of the first elutriator is used as the final concentrate.

[0084] As an optional mode of the present invention, the operating parameters of the first elutriator include: magnetic field intensity: 3 KA / m - 50 KA / m (such as 10 KA / m, 20 KA / m, 30 KA / m, 40 KA / m, etc.); feed rate: 0.25 - 1.5 kg / min (such as 0.5 kg / min, 0.7 kg / min, 1 kg / min, 1.3 kg / min, etc.); feed concentration: 15% - 30% (such as 17%, 20%, 23%, 25%, 27%, etc.); upward water flow: 10 - 30 L / min (such as 15 L / min, 20 L / min, 25 L / min, etc.).

[0085] Specifically, after the separation treatment by the first elutriator, the mineral particles with stronger magnetism are attracted by the magnetic field and aggregated together to form the concentrate of the first elutriator; the mineral particles that cannot be effectively attracted by the magnetic field and the non-magnetic minerals are discharged with the water flow to form the tailings of the first elutriator. In order to recover the useful minerals in the tailings of the first elutriator, they can be fed into the second cyclone, and after classification treatment, they are fed into the Aisha mill for re-grinding treatment. Through grinding, the particle size of the mineral particles can be further reduced, the monomer dissociation degree of the useful minerals can be improved, and more favorable conditions can be created for the subsequent separation process. After the separation treatment by the first elutriator, the grade and recovery rate of the concentrate of the first elutriator both meet the requirements and can be directly used as the final concentrate.

[0086] As an alternative embodiment of the present invention, the two-stage classification process includes: feeding the tailings of the first elutriator and the oversize product into a second cyclone to obtain the grinding product flowing out of the second overflow pipe and the second sand deposit; feeding the grinding product flowing out of the second overflow pipe into a second elutriator;

[0087] Specifically, the purpose of setting the two-stage classification process in the present invention is to reduce the content of fine particle size, reduce the content of fine particle size for the AI sand mill, reduce energy consumption and increase the processing capacity.

[0088] The regrinding process of the AI sand mill includes: feeding the second sand deposit formed at the bottom of the second cyclone into the AI sand mill for grinding to obtain the discharge product of the AI sand mill;

[0089] Specifically, mineral monomer dissociation means that in the grinding stage, due to more inclusions in the magnetic separation equipment, minerals with low dissociation degree are also magnetically separated into the concentrate, thus affecting the element grade in the concentrate. In order to make the iron content and grade in the obtained product meet the requirements of subsequent processing or the market, the regrinding process of the AI sand mill in step S8 is introduced after the elutriation process and the classification process in the present invention. As an efficient ultrafine grinding equipment, the AI sand mill has a unique grinding mechanism and medium movement mode, which can finely grind and impact the material without damaging the crystal structure of the mineral, effectively promoting the further dissociation between iron minerals and gangue minerals. Through the regrinding treatment of the AI sand mill, not only can the monomer dissociation degree of iron minerals be significantly improved, but also the particle size distribution of the material can be optimized, providing more favorable conditions for the subsequent process.

[0090] As an alternative mode of the present invention, the grinding concentration of the AI grinding mill is 25%-50% (such as 30%, 35%, 40%, 45%, etc.);

[0091] As an alternative mode of the present invention, when the content of minerals with a particle size grade of -400 mesh in the discharge product of the AI sand mill accounts for 60%-80% (such as 65%, 70%, 75%, etc.) of the total amount of the fed minerals (including the second sand deposit and / or the third magnetic separation concentrate), stop grinding, and the grinding time is 60-120 s (such as 70 s, 80 s, 90 s, 100 s, 110 s, etc.), so as to ensure that the monomer dissociation degree of iron in the discharge product of the AI sand mill is greater than 90%.

[0092] Specifically, if the grinding concentration of the Aimei grinder is too high (greater than 50%), it will cause the grinder to become bloated. The bloated grinder means that the materials inside the grinder are too dense and the fluidity becomes poor. This will not only increase the operating load of the grinder, but also may cause the materials inside the grinder to be unable to be discharged normally, thus affecting the overall working efficiency and stability of the grinder. In addition, too high a grinding concentration may also lead to increased wear inside the grinder and shorten the service life of the equipment. If the grinding concentration of the Aimei grinder is too low (less than 25%), the throughput of the grinder will be significantly reduced because the chances of collision and grinding of the materials inside the grinder are greatly reduced. This will not only reduce the production efficiency of the grinder, but more importantly, too low a grinding concentration will cause the media (such as grinding balls or grinding rods) inside the grinder to collide with each other in the absence of sufficient material buffer, resulting in serious media wear. The aggravation of media wear will not only further reduce the processing capacity of the grinder, but also increase the equipment maintenance cost and the frequency of replacing the media, posing a threat to the continuous and stable operation of the production line.

[0093] Specifically, in step S8 of the present invention, the Aimei sand mill is used to grind the second tailings and / or the third magnetic separation concentrate because after the above treatment, the particle size of the second tailings and / or the third magnetic separation concentrate is fine and in an over-crushed state. Minerals in this state have an extremely high specific surface area and complex surface properties, making it challenging for conventional grinding equipment, such as ball mills, to handle. Specifically, when a conventional ball mill processes fine-grained and over-crushed minerals, it is often difficult to achieve an ideal grinding effect. Due to the enhanced interaction between particles, fine-grained minerals are prone to agglomeration and adhesion phenomena, which will not only reduce the grinding efficiency, but may also lead to excessive wear of the equipment and an increase in energy consumption. In addition, when the ball mill processes such minerals, there may also be a problem of over-crushing, further deteriorating the particle size distribution of the tailings and affecting the smooth progress of subsequent treatment processes. In contrast, the Aimei sand mill has significant advantages in processing fine-grained and over-crushed minerals. Through special grinding media and grinding mechanisms, the Aimei sand mill can effectively grind such minerals without destroying the original particle size distribution. This equipment not only has a higher grinding efficiency, but can also significantly reduce energy consumption and equipment wear, thus improving the overall processing economy and sustainability.

[0094] As an optional implementation mode of the present invention, the four-stage elutriator process for beneficiation includes: the four-stage elutriator process for beneficiation: feeding the discharge product of the Aimei sand mill and the grinding product flowing out of the second overflow pipe into the second elutriator to obtain the concentrate of the second elutriator and the tailings of the second elutriator. The obtained concentrate of the second elutriator is used as the final concentrate, and the tailings of the second elutriator are used as the feed for the next process;

[0095] As an alternative embodiment of the present invention, the operating parameters of the second elutriator include: magnetic field strength: 3 kA / m - 50 kA / m (such as 10 kA / m, 20 kA / m, 30 kA / m, 40 kA / m, etc.); ore feeding rate: 0.25 - 1.5 kg / min (such as 0.5 kg / min, 0.7 kg / min, 1 kg / min, 1.3 kg / min, etc.); ore feeding concentration: 15% - 30% (such as 17%, 20%, 23%, 25%, 27%, etc.); upward water flow: 10 - 30 L / min (such as 15 L / min, 20 L / min, 25 L / min, etc.).

[0096] As an alternative embodiment of the present invention, the average TFe content in the final concentrate (the concentrate of the first elutriator and the second elutriator) is 67 - 69%, and the total recovery rate is 60 - 67%.

[0097] As an alternative embodiment of the present invention, the three-stage magnetic separation process includes: feeding the tailings of the second elutriator into a third wet drum magnetic separator to obtain the third magnetic separation tailings and the third magnetic separation concentrate; returning the third magnetic separation concentrate to the A mill for grinding, and using the third magnetic separation tailings as the final tailings;

[0098] The degree of monomer dissociation in the third magnetic separation concentrate is 75 - 85% (such as 77%, 80%, 81%, 83%, etc.);

[0099] The operating parameters of the third wet drum magnetic separator include: magnetic separation concentration of 20% - 40% (such as 25%, 30%, 35%, etc.), and magnetic field strength of 72 - 168 kA / m (such as 100 kA / m, 150 kA / m, 200 kA / m, 250 kA / m, etc.).

[0100] Specifically, the purpose of the three-stage magnetic separation process of the present invention is to further recover iron in the tailings of the elutriator.

[0101] The present invention will be further described in detail below with specific examples and comparative examples.

[0102] For the method for measuring the TFe content in the magnetite ore raw material in the examples, refer to "GB / T6730.5 - 2007".

[0103] Example 1

[0104] As Figure 1 shown, a beneficiation method for low-grade iron ore with uneven crystal grain size distribution and more crushing and less grinding is provided, including the following steps:

[0105] S1. Preparation of materials: The TFe content in the magnetite ore raw material is 24.35%. After three-stage one-closed-circuit crushing, a crushed product is obtained, and the particle size of the crushed product is 0 - 30 mm;

[0106] S2. High-pressure roller grinding process: Feed the crushed product into the closed circuit of high-pressure roller grinding and crush it into a fine crushed ore sample of 0 - 2 mm. Through screening analysis of the sample, it can be known that the crystal grain size of the oversize product with +100 mesh accounts for 75% of the total sample amount, and the crystal grain size of the undersize product with -400 mesh accounts for 15% of the total sample amount. The raw material has uneven distribution of crystal grain size and uneven grade distribution, meeting the requirements of this process for the raw material. Feed the fine crushed ore sample into the first wet drum magnetic separator with a magnetic field intensity of 240 kA / m and a magnetic separation concentration of 30% to obtain the first magnetic separation tailings and the first magnetic separation concentrate. The TFe content in the first magnetic separation tailings is 8.23%, the recovery rate is 91.72%, and the yield is 75.65%; the TFe content in the first magnetic separation concentrate is 29.54%. The first magnetic separation tailings are directly discarded, and the first magnetic separation concentrate is ground;

[0107] S3. Grinding and classification process: Feed the first magnetic separation concentrate into the ball mill with a grinding concentration of 70% and grind for 15 minutes. After classification grinding, the minerals with a particle size grade of -200 mesh account for 55% of the total amount of the first magnetic separation concentrate fed. The obtained grinding product is classified by the first hydrocyclone, and the grinding product flowing out through the first overflow pipe is used as the feed for the next process. The first sand deposit formed at the bottom of the first hydrocyclone returns to the ball mill for feeding;

[0108] S4. Second-stage magnetic separation process: Feed the grinding product flowing out from the first overflow pipe into the second wet drum magnetic separator with a magnetic separation concentration of 35% and a magnetic field intensity of 120 kA / m to obtain the second magnetic separation concentrate and the second magnetic separation tailings. The TFe content in the second magnetic separation concentrate is 56.15%, the recovery rate is 79.88%, the TFe content in the second magnetic separation tailings is 10.25%, and the mFe content is 0.13%;

[0109] S5. Independent screening process: Feed the second magnetic separation concentrate into a 200-mesh fine screen to obtain the oversize product and the undersize product. Feed the oversize product into the second hydrocyclone. When the content of minerals with a particle size of -200 mesh in the undersize product accounts for 75% - 90% of the total amount of the second magnetic separation concentrate fed, stop screening, and the undersize product is used as the feed for the next process;

[0110] S6. Three-stage elutriator beneficiation process: Feed the undersize product into the first elutriator with a magnetic field intensity of 5 kA / m, a feed rate of 1.0 kg / min, a feed concentration of 20%, and an upward water flow of 20 L / min to obtain the first elutriator concentrate and the first elutriator tailings. The TFe content in the first elutriator concentrate is 68.37%, and the recovery rate is 88.44%; the TFe content in the first elutriator tailings is 31.85%. The first elutriator tailings are fed into the second hydrocyclone, and the first elutriator concentrate is used as the final concentrate;

[0111] S7. Two-stage classification process: Feed the tailings of the first elutriator and the oversize product into the second cyclone to obtain the grinding product flowing out of the second overflow pipe and the second sand deposit; Feed the grinding product flowing out of the second overflow pipe into the second elutriator;

[0112] S8. Re-grinding process with IsaMill: Feed the second sand deposit formed at the bottom of the second cyclone into the IsaMill, with a grinding concentration of 30%. Stop grinding when the content of minerals with a particle size grade of -400 mesh in the discharge product of the IsaMill accounts for 60% - 80% of the total minerals fed in, and the grinding time is 90 s to obtain the discharge product of the IsaMill;

[0113] S9. Four-stage elutriator process for beneficiation: Feed the discharge product of the IsaMill and the grinding product flowing out of the second overflow pipe into the second elutriator, with a magnetic field strength of 5 kA / m, a feed rate of 1.0 kg / min, a feed concentration of 20%, and an upward water flow of 20 L / min to obtain the concentrate of the second elutriator and the tailings of the second elutriator. Among them, the TFe content in the concentrate of the second elutriator is 67.88%, and the recovery rate is 78.82%. The TFe content in the tailings of the second elutriator is 11.34%, and the mFe content is 0.15%. The concentrate obtained from the second elutriator is used as the final concentrate, and the tailings of the second elutriator are used as the feed for the next process.

[0114] S10. Three-stage magnetic separation process: Feed the tailings of the second elutriator into the third wet drum magnetic separator, with a magnetic field strength of 240 kA / m and a magnetic separation concentration of 30% to obtain the tailings of the third magnetic separation and the concentrate of the third magnetic separation; The TFe content in the tailings of the third magnetic separation is 9.5%; The TFe content in the concentrate of the third magnetic separation is 55%; The concentrate of the third magnetic separation is returned to the IsaMill for grinding, and the tailings of the third magnetic separation are used as the final tailings.

[0115] The average TFe content of the final iron concentrate (the concentrate of the first elutriator and the concentrate of the second elutriator) obtained by this process is 68.15%, and the total recovery rate is 64.59%.

[0116] Example 2

[0117] S1. Feed preparation: The TFe content in the magnetite ore raw material is 24.32%. After three-stage one-closed-circuit crushing, the crushed product is obtained, and the particle size of the crushed product is 0 - 30 mm;

[0118] S2. High-pressure roller grinding process: Feed the crushed products into the closed-circuit high-pressure roller mill and crush them into fine crushed ore samples with a particle size of 0 - 2 mm. Through screening analysis of the samples, it can be known that: the crystal grain size of the oversize product with a mesh size of +100 accounts for 60% of the total sample amount, and the crystal grain size of the undersize product with a mesh size of -400 accounts for 10% of the total sample amount. The raw material has uneven distribution of crystal grain size and uneven grade distribution, meeting the requirements of this process for raw materials. Feed the fine crushed ore samples into the first wet drum magnetic separator with a magnetic field intensity of 240 kA / m and a magnetic separation concentration of 30% to obtain the first magnetic separation tailings and the first magnetic separation concentrate. Among them, the TFe content is 9.54%, the recovery rate is 89.60%, and the yield is 72.93%; the TFe content in the first magnetic separation concentrate is 30.52%; the first magnetic separation tailings are directly discarded, and the first magnetic separation concentrate is ground;

[0119] S3. Grinding and classification process: Feed the first magnetic separation concentrate into the ball mill with a grinding concentration of 70% and grind for 18 minutes. After classification grinding, the minerals with a particle size grade of -200 mesh account for 60% of the total amount of the first magnetic separation concentrate fed. The obtained grinding products are classified by the first hydrocyclone. The grinding products flowing out through the first overflow pipe are used as the feed for the next process, and the first sand deposit formed at the bottom of the first hydrocyclone returns to the ball mill for feeding;

[0120] S4. Second-stage magnetic separation process: Feed the grinding products flowing out through the first overflow pipe into the second wet drum magnetic separator with a magnetic separation concentration of 30% and a magnetic field intensity of 120 kA / m to obtain the second magnetic separation concentrate and the second magnetic separation tailings. Among them, the TFe content is 57.42%, the recovery rate is 82.57%, the TFe content in the second magnetic separation tailings is 9.54%, and the mFe content is 0.12%;

[0121] S5. Independent screening process: Feed the second magnetic separation concentrate into a -200 mesh fine screen to obtain the oversize product and the undersize product. Feed the oversize product into the second hydrocyclone. When the content of minerals with a particle size of -200 mesh in the undersize product accounts for 75% - 90% of the total amount of the second magnetic separation concentrate fed, stop screening, and the undersize product is used as the feed for the next process;

[0122] S6. Process of the first three-stage elutriator for beneficiation: Feed the undersize product into the first elutriator with a magnetic field intensity of 5 kA / m, a feed rate of 1.0 kg / min, a feed concentration of 20%, and an upward water flow of 15 L / min to obtain the first elutriator concentrate and the first elutriator tailings. Among them, the TFe content of the first elutriator concentrate is 68.71%, and the recovery rate is 88.93%; the TFe content of the first elutriator tailings is 30.85%; the first elutriator tailings are fed into the second hydrocyclone, and the first elutriator concentrate is used as the final concentrate;

[0123] S7. Two-stage classification process: Feed the tailings of the first elutriator and the oversize product into the second cyclone to obtain the ground product flowing out of the second overflow pipe and the second sand deposit; Feed the ground product flowing out of the second overflow pipe into the second elutriator;

[0124] S8. Re-grinding process with IsaMill: Feed the second sand deposit formed at the bottom of the second cyclone into the IsaMill, with a grinding concentration of 30%. Stop grinding after the content of minerals with a particle size grade of -400 mesh in the discharged product of the IsaMill accounts for 60% - 80% of the total minerals fed in, and the grinding time is 90 s to obtain the discharged product of the IsaMill;

[0125] S9. Four-stage elutriator process for beneficiation: Feed the discharged product of the IsaMill and the ground product flowing out of the second overflow pipe into the second elutriator, with a magnetic field intensity of 10 kA / m, a feed rate of 1.0 kg / min, a feed concentration of 20%, and an upward water flow of 10 L / min to obtain the concentrate of the second elutriator and the tailings of the second elutriator. Among them, the TFe content in the concentrate of the second elutriator is 68.12%, and the recovery rate is 91.84%; the TFe content in the tailings of the second elutriator is 10.24%, and the mFe content is 0.19%. The concentrate obtained from the second elutriator is used as the final concentrate, and the tailings of the second elutriator are used as the feed for the next process.

[0126] S10. Three-stage magnetic separation process: Feed the tailings of the second elutriator into the third wet drum magnetic separator, with a magnetic field intensity of 240 kA / m and a magnetic separation concentration of 30% to obtain the tailings of the third magnetic separation and the concentrate of the third magnetic separation; the TFe content in the tailings of the third magnetic separation is 9.80%; the TFe content in the concentrate of the third magnetic separation is 57%; the concentrate of the third magnetic separation is returned to the IsaMill for grinding, and the tailings of the third magnetic separation are used as the final tailings.

[0127] The average TFe content of the final iron concentrate (the concentrate of the first elutriator and the concentrate of the second elutriator) obtained by this process is 68.34%, and the total recovery rate is 65.39%.

[0128] Example 3

[0129] S1. Preparation of materials: The TFe content in the magnetite ore raw material is 22.52%. After three-stage one-closed-circuit crushing, the crushed product is obtained, and the particle size of the crushed product is 0 - 30 mm;

[0130] S2. High-pressure roller grinding process: Feed the crushed products into the closed-circuit high-pressure roller mill and crush them into fine ore samples with a particle size of 0 - 2 mm. Screening analysis of the samples shows that the crystal grain size of the oversize product with a mesh size of +100 is 60% of the total sample amount, and the crystal grain size of the undersize product with a mesh size of -400 is 10% of the total sample amount. The raw material has uneven distribution of crystal grain size and grade, meeting the requirements of this process for the raw material. Feed the fine ore samples into the first wet drum magnetic separator with a magnetic field intensity of 240 kA / m and a magnetic separation concentration of 35% to obtain the first magnetic separation tailings and the first magnetic separation concentrate. The TFe content in the first magnetic separation tailings is 10.31%, the recovery rate is 72.93%, and the yield is 88.24%; the TFe content in the first magnetic separation concentrate is 28.71%. The first magnetic separation tailings are directly discarded, and the first magnetic separation concentrate is ground;

[0131] S3. Grinding and classification process: Feed the first magnetic separation concentrate into the ball mill with a grinding concentration of 67% and grind for 18 minutes. After classification grinding, the minerals with a particle size grade of -200 mesh account for 70% of the total amount of the first magnetic separation concentrate fed. The obtained grinding products are classified by the first hydrocyclone. The grinding products flowing out through the first overflow pipe are used as the feed for the next process, and the first sand deposit formed at the bottom of the first hydrocyclone returns to the ball mill for feeding;

[0132] S4. Second-stage magnetic separation process: Feed the grinding products flowing out of the first overflow pipe into the second wet drum magnetic separator with a magnetic separation concentration of 35% and a magnetic field intensity of 120 kA / m to obtain the second magnetic separation concentrate and the second magnetic separation tailings. The TFe content in the second magnetic separation concentrate is 55.95%, the recovery rate is 78.39%, the TFe content in the second magnetic separation tailings is 10.38%, and the mFe content is 0.14%;

[0133] S5. Independent screening process: Feed the second magnetic separation concentrate into a -200 mesh fine screen to obtain the oversize product and the undersize product. Feed the oversize product into the second hydrocyclone. When the content of minerals with a particle size of -200 mesh in the undersize product accounts for 75% - 90% of the total amount of the second magnetic separation concentrate fed, stop screening, and the undersize product is used as the feed for the next process;

[0134] S6. Three-stage elutriator beneficiation process: Feed the undersize product into the first elutriator with a magnetic field intensity of 10 kA / m, a feed rate of 0.8 kg / min, a feed concentration of 20%, and an upward water flow of 15 L / min to obtain the first elutriator concentrate and the first elutriator tailings. The TFe content in the first elutriator concentrate is 67.46%, and the recovery rate is 87.52%; the TFe content in the first elutriator tailings is 31.32%. The first elutriator tailings are fed into the second hydrocyclone, and the first elutriator concentrate is used as the final concentrate;

[0135] S7. Two-stage classification process: Feed the tailings of the first elutriator and the oversize product into the second cyclone to obtain the grinding product flowing out of the second overflow pipe and the second underflow; Feed the grinding product flowing out of the second overflow pipe into the second elutriator;

[0136] S8. Re-grinding process with an IsaMill: Feed the second underflow formed at the bottom of the second cyclone into the IsaMill, with a grinding concentration of 25%. Stop grinding when the content of minerals with a particle size grade of -400 mesh in the discharged product of the IsaMill accounts for 60% - 80% of the total minerals fed in. The grinding time is 100 s to obtain the discharged product of the IsaMill;

[0137] S9. Four-stage elutriator process for beneficiation: Feed the discharged product of the IsaMill and the grinding product flowing out of the second overflow pipe into the second elutriator, with a magnetic field intensity of 10 kA / m, a feed rate of 1.0 kg / min, a feed concentration of 20%, and an upward water flow of 10 L / min to obtain the concentrate of the second elutriator and the tailings of the second elutriator. Among them, the TFe content in the concentrate of the second elutriator is 66.79%, and the recovery rate is 92.02%. The TFe content in the tailings of the second elutriator is 11.04%, and the mFe content is 0.15%. The concentrate obtained from the second elutriator is used as the final concentrate, and the tailings of the second elutriator are used as the feed for the next process.

[0138] S10. Three-stage magnetic separation process: Feed the tailings of the second elutriator into the third wet drum magnetic separator, with a magnetic field intensity of 240 kA / m and a magnetic separation concentration of 30% to obtain the tailings of the third magnetic separation and the concentrate of the third magnetic separation; The TFe content in the tailings of the third magnetic separation is 10.2%; The TFe content in the concentrate of the third magnetic separation is 59.0%; The concentrate of the third magnetic separation is returned to the IsaMill for grinding, and the tailings of the third magnetic separation are used as the final tailings.

[0139] The average TFe content of the final iron concentrate (the concentrate of the first elutriator and the concentrate of the second elutriator) obtained by this process is 67.04%, and the total recovery rate is 65.78%.

[0140] Comparative Example 1

[0141] The main difference between this comparative example and Example 1 is that the ball mill re-grinding process is adopted in step S8, and the other technical parameters and operation steps are the same as those in Example 1. Specifically:

[0142] Steps S1 - S7 are the same as those in Example 1;

[0143] S8. Ball mill re-grinding process: Feed the second underflow formed at the bottom of the second cyclone into the ball mill, with a ball milling time of 60 s and a grinding concentration of 67% to obtain the discharged product of the ball mill;

[0144] S9. Four-stage selective elutriator process: Feed the ore discharge product of the ball mill and the ground product flowing out of the second overflow pipe into the second elutriator. The magnetic field strength is 5 kA / m, the feed rate is 1.0 kg / min, the feed concentration is 20%, and the upward water flow is 20 L / min to obtain the concentrate of the second elutriator and the tailings of the second elutriator. Among them, the TFe content in the concentrate of the second elutriator is 65.34%, and the recovery rate is 88.49%. The TFe content in the tailings of the second elutriator is 11.58%, and the mFe content is 0.19%. The concentrate obtained from the second elutriator is used as the final concentrate, and the tailings of the second elutriator are used as the feed for the next process.

[0145] S10. Three-stage magnetic separation process: Feed the tailings of the second elutriator into the third wet drum magnetic separator. The magnetic field strength is 240 kA / m, and the magnetic separation concentration is 30% to obtain the tailings of the third magnetic separation and the concentrate of the third magnetic separation; the TFe content in the tailings of the third magnetic separation is 10.24%; the TFe content in the concentrate of the third magnetic separation is 58.0%; the concentrate of the third magnetic separation is returned to the ball mill for grinding, and the tailings of the third magnetic separation are used as the final tailings.

[0146] The average TFe content of the final iron concentrate (the concentrate of the first elutriator and the concentrate of the second elutriator) obtained by this process is 65.51%, and the total recovery rate is 59.70%.

[0147] Compared with Example 1, in this comparative example, since the Aisha regrinding process in step S8 of Example 1 is replaced by a ball mill regrinding process, since the second sand deposit formed at the bottom of the second hydrocyclone is fine-grained tailings, the interaction between particles is strong, and agglomeration and adhesion are likely to occur. When using a ball mill to process the second sand deposit formed at the bottom of the second hydrocyclone, the problem of over-grinding will occur, further exacerbating the problem of agglomeration and adhesion between particles, resulting in agglomerates in the ore discharge product entering the second elutriator, affecting the elutriation effect; and using ball mill grinding cannot make the degree of dissociation of iron monomers in the ore discharge product of the ball mill meet the requirements, so ultimately the average TFe content in the final concentrate decreases and the recovery rate decreases.

[0148] Comparative Example 2

[0149] The difference between this comparative example and Example 1 is that the independent screening process in step S5 is cancelled, and the rest of the technical parameters and operation steps are the same as those in Example 1. Specifically:

[0150] Steps S1 - S4 are the same as those in Example 1;

[0151] S5. Process of the three-stage elutriator for selection: Feed the second magnetic separation concentrate into the first elutriator, with a magnetic field intensity of 5 kA / m, a feed rate of 1.0 kg / min, a feed concentration of 20%, and an upward water flow of 20 L / min, to obtain the concentrate of the first elutriator and the tailings of the first elutriator. Among them, the TFe content of the concentrate of the first elutriator is 65.83%, and the recovery rate is 88.54%; the TFe content of the tailings of the first elutriator is 11.35%; the tailings of the first elutriator are fed into the second hydrocyclone, and the concentrate of the first elutriator is used as the final concentrate.

[0152] S6. Two-stage classification process: Feed the tailings of the first elutriator into the second hydrocyclone to obtain the grinding product flowing out of the second overflow pipe and the second sand deposit; Feed the grinding product flowing out of the second overflow pipe into the second elutriator.

[0153] S7. Re-grinding process of the Aisha mill: Feed the second sand deposit formed at the bottom of the second hydrocyclone into the Aisha mill, with a grinding concentration of 30%. After the content of minerals with a particle size grade of -400 mesh in the discharge product of the Aisha mill accounts for 60% - 80% of the total amount of fed minerals, stop grinding, and the grinding time is 90 s to obtain the discharge product of the Aisha mill.

[0154] S8. Process of the four-stage elutriator for selection: Feed the discharge product of the Aisha mill and the grinding product flowing out of the second overflow pipe into the second elutriator, with a magnetic field intensity of 10 kA / m, a feed rate of 1.0 kg / min, a feed concentration of 20%, and an upward water flow of 10 L / min, to obtain the concentrate of the second elutriator and the tailings of the second elutriator. Among them, the TFe content in the concentrate of the second elutriator is 68.12%, and the recovery rate is 91.84%; the TFe content in the tailings of the second elutriator is 10.24%, and the mFe content is 0.19%. The obtained concentrate of the second elutriator is used as the final concentrate, and the tailings of the second elutriator are used as the feed for the next process.

[0155] S9. Three-stage magnetic separation process: Feed the tailings of the second elutriator into the third wet drum magnetic separator, with a magnetic field intensity of 240 kA / m and a magnetic separation concentration of 30%, to obtain the tailings of the third magnetic separation and the concentrate of the third magnetic separation; the TFe content in the tailings of the third magnetic separation is 9.8%; the TFe content in the concentrate of the third magnetic separation is 57.0%; the concentrate of the third magnetic separation is returned to the Aisha mill for grinding, and the tailings of the third magnetic separation are used as the final tailings.

[0156] The average TFe content of the final iron concentrate (the concentrate of the first elutriator and the concentrate of the second elutriator) obtained by this process is 65.96%, and the total recovery rate is 60.13%.

[0157] Compared with Example 1, in this comparative example, since the independent screening process was cancelled in Comparative Example 2 and the concentrate of the second-stage magnetic separation was directly fed into the first elutriator, the concentrate of the second-stage magnetic separation was not screened, and coarse-grained materials would enter the elutriator. It was very difficult for the elutriator to dissociate the monomeric iron in the materials, resulting in the iron content in the finally obtained product not meeting the requirements of subsequent processing or the market.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding, characterized in that: The method comprises the following steps: S1, material preparation; S2, high pressure roller grinding process; S3, grinding and classification process; S4, two-stage magnetic separation process; S5, independent screening process; S6, three-stage selection washing machine process; S7, two-stage classification process; S8, sand grinding and regrinding process; S9, four-stage selection washing machine process; S10, three-stage magnetic separation process.

2. The method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding according to claim 1, characterized in that: The material preparation includes: crushing the magnetite ore to obtain a crushed product; The particle size of the crushed product is 0-100 mm; The TFe content in the magnetite ore is less than 25%.

3. The method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding according to claim 2, characterized in that: The high pressure roller mill process comprises: feeding the crushed product into a high pressure roller mill closed circuit process for crushing to obtain a finely crushed ore sample; feeding the finely crushed ore sample into a first wet drum magnetic separator to obtain a first magnetically separated tailings and a first magnetically separated concentrate; The particle size of the finely crushed ore sample is 0-3 mm; The working parameters of the first wet drum magnetic separator include: magnetic separation concentration of 20%-40%, magnetic field strength of 76-300 kA / m.

4. The method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding according to claim 3, characterized in that: The grinding and classification process comprises: feeding the first magnetic separation concentrate into a ball mill for grinding, the obtained grinding product is classified through a first cyclone, the grinding product flowing out through a first overflow pipe is used as feed for the next process, and the first sediment formed at the bottom of the first cyclone is returned to the ball mill for feeding; The concentration of ball mill grinding is 60%-75%; The degree of dissociation of iron mineral monomers in the grinding product flowing out through the first overflow pipe is ≥50%; When the content of minerals with a particle size of -200 mesh in the grinding product accounts for 45% to 60% of the total amount of the first magnetic separation concentrate fed, grinding is stopped.

5. The method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding according to claim 4, characterized in that: The two-stage magnetic separation process comprises: feeding the grinding product flowing out of the first overflow pipe into a second wet drum magnetic separator to obtain second magnetic separation tailings and second magnetic separation concentrate; The monomer dissociation degree in the second magnetic separation concentrate is 55% to 70%; The working parameters of the second wet drum magnetic separator include: magnetic separation concentration of 20%-40%, magnetic field strength of 72-168 kA / m.

6. The method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding according to claim 5, characterized in that: The independent screening process comprises: feeding the second magnetic separation concentrate into a fine screen to obtain an oversize product and an undersize product, the oversize product is fed into a second cyclone, and the undersize product is fed into a first elutriator; The iron monomer dissociation degree in the undersize product is 60%-80%; When the content of minerals with a particle size of -200 mesh in the underscreen product accounts for 75% to 90% of the total amount of concentrate fed to the second magnetic separation, screening is stopped.

7. The method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding according to claim 6, characterized in that: The three-stage elutriator process comprises: feeding the undersize product into a first elutriator to obtain a first elutriator concentrate and a first elutriator tailings, feeding the first elutriator tailings into a second cyclone, and using the first elutriator concentrate as the final concentrate; The working parameters of the first elutriator include: magnetic field strength: 3KA / m-50KA / m; ore feed rate: 0.25-1.5kg / min; ore feed concentration: 15%-30%; rising water flow: 10-30L / min.

8. The method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding according to claim 7, characterized in that: The two-stage classification process includes: feeding the tailings and the overscreen product of the first elutriator into the second cyclone to obtain the grinding product and the second sediment flowing out of the second overflow pipe; feeding the grinding product flowing out of the second overflow pipe into the second elutriator; The Aisha grinding regrinding process comprises: feeding the second sediment formed at the bottom of the second cyclone into the Aisha grinding machine for grinding to obtain the Aisha grinding ore discharge product; The grinding concentration of the moxa grinder is 25%-50%; When the content of minerals with a particle size of -400 mesh in the ore discharge product of the sand mill accounts for 60% to 80% of the total amount of the input minerals, the grinding is stopped and the grinding time is 60-120s; The iron monomer dissociation degree in the wormwood mill ore product is greater than 90%.

9. The method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding according to claim 8, characterized in that: The four-stage elutriator process comprises: feeding the ore discharge product of the sand mill and the grinding product flowing out of the second overflow pipe into the second elutriator to obtain the second elutriator concentrate and the second elutriator tailings, the obtained second elutriator concentrate is used as the final concentrate, and the second elutriator tailings is used as the feed material for the next step; The working parameters of the second elutriator include: magnetic field strength: 3KA / m-50KA / m; ore feed rate: 0.25-1.5kg / min; ore feed concentration: 15%-30%; rising water flow: 10-30L / min.

10. The method for beneficiating low-grade iron ore with uneven distribution of crystal grain size by more crushing and less grinding according to claim 9, characterized in that: The three-stage magnetic separation process includes: feeding the tailings of the second elutriator into the third wet drum magnetic separator to obtain the third magnetic separation tailings and the third magnetic separation concentrate; the third magnetic separation concentrate returns to the grinding machine for grinding, and the third magnetic separation tailings are used as the final tailings; The monomer dissociation degree in the third magnetic separation concentrate is 75-85%; The working parameters of the third wet drum magnetic separator include: magnetic separation concentration of 20%-40%, and magnetic field strength of 72-168 kA / m.

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