Beneficiation method for iron ore with uneven distribution of crystal granularity and thickness

Abstract

The invention provides a beneficiation method for iron ore with non-uniform crystal granularity and thickness distribution, and relates to the technical field of mineral engineering, the beneficiation method comprises the following steps: S1, preparing materials; s2, dry separation; s3, an ore grinding and grading process; s4, a first-stage magnetic separation process; s5, performing an independent screening process; s6, a fine selection two-stage elutriation machine process; s7, a moxa sand grinding and regrinding process; and S8, a fine selection three-section elutriation machine process. Aiming at the low-grade magnetic iron ore with non-uniform crystal particle size distribution, coarse and fine grading recovery is realized, the low-grade ore can be treated, the ore grinding cost is reduced, the whole process flow is simple and efficient, industrial production is easy, and the treatment efficiency and the product quality are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of mining engineering, and in particular to a method for beneficiating iron ore with uneven distribution of crystal grain size. Background Art

[0002] my country's iron ore reserves are quite rich, but the average iron grade is only about 34%. Domestic iron ore is mainly lean, and the reserves of rich iron ore that can be directly put into furnace smelting only account for 2.53% of the total reserves. In recent years, the amount of iron ore mined in my country has been decreasing, and the cost of mining and beneficiation in domestic mines is relatively high. Domestic iron ore is usually selected by stage grinding, and the process is basically the same. Minerals form ores with uneven crystal grain size under complex geological conditions. Usually, this unevenly distributed iron ore is used. The commonly used beneficiation process is the stage grinding stage tailings, and the commonly used two-stage or three-stage grinding stage selection process; in this process, the iron minerals that have been dissociated in the monomers are not selected in time, and thus enter the grinding process for circulation, resulting in a waste of grinding energy consumption and affecting the processing capacity of the beneficiation plant. At the same time, the final iron concentrate particle size is too fine, which has an adverse effect on the subsequent pelletizing or sintering process.

[0003] "Experimental Study on New Process for Hematite Ore Dressing" An iron mine in Yunnan is mainly hematite. The particle size of hematite in the ore is extremely uneven. It is possible to obtain part of the concentrate at a coarser particle size. In order to maximize the output of powder ore, the raw ore is divided into two particle sizes: coarse (6mm-0.15mm) and fine (0.15mm-0) for classification and selection. The coarse (6mm-0.15mm) partial beneficiation test conducted by Changsha Mining and Metallurgy Research Institute uses a wet permanent magnetic separator. After one coarse, one fine, and one sweeping middling, the concentrate product with an iron grade of 55% and an operating recovery rate of more than 60% meets the requirements. The Kunming University of Science and Technology conducted an experimental study on the comprehensive utilization of coarse-grained medium ore and fine-grained ore. The new ore dressing process adopted coarse-fine separation, and the coarse-grained medium ore was re-grinded and combined with the fine-grained ore for selection. The coarse concentrate grade obtained by the one-coarse-one-sweep process was 56%, and the operation recovery rate was close to 90%. After the shaking table was selected, the concentrate grade reached 60%, and the recovery rate was close to 80%. However, the document is a process for recovering hematite, which adopts first classification and treatment of different particle sizes. There will be a situation where the fine-grained ore is also separated and not recovered first. Finally, the shaking table is used to improve the product grade, which affects the iron yield.

[0004] "A method for sorting fine-grained hematite with uneven crystal size" uses strong magnetic roughing, centrifuge selection of roughing concentrate, and strong magnetic scavenging of roughing tailings; re-grinding and classification of centrifuge tailings and scavenged concentrates, strong magnetic separation of graded products, centrifuge selection of magnetic concentrates, re-grinding of centrifuge tailings, and centrifuge concentrates as final concentrates. However, this process is suitable for hematite sorting, and the tailings TFe grade is 15%. The centrifuge selection process is low, which limits industrialization.

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

[0006] The purpose of the present invention is to provide a method for beneficiating iron ore with uneven distribution of crystal particle size, which overcomes the problem that the iron ore has uneven crystal particle size, the ore that has reached the dissociation of iron mineral monomers in the beneficiation process is still circulated in the process, resulting in waste of grinding energy consumption, too fine particle size of concentrate products and low grinding processing capacity.

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

[0008] The present invention provides a method for beneficiating iron ore with uneven distribution of crystal grain size, comprising the following steps:

[0009] S1, material preparation; S2, dry separation; S3, grinding and classification process; S4, one-stage magnetic separation process; S5, independent screening process; S6, selected two-stage washing machine process; S7, wormwood grinding and regrinding process; S8, selected three-stage washing machine process.

[0010] Further, based on the above technical solution, in step S1, the material preparation includes: crushing the raw material to obtain a crushed product;

[0011] Wherein, the raw material comprises 55-90% magnetite ore and 10-45% surrounding rock in terms of mass percentage;

[0012] Preferably, the particle sizes of the magnetite ore and surrounding rock are both 0-100 mm;

[0013] Preferably, the particle size of the crushed product is 0-5 mm.

[0014] Further, based on the above technical solution, in step S2, the dry separation includes: dry separation of the crushed product in a dry separation machine to obtain dry separation tailings and dry separation concentrate;

[0015] Among them, the magnetic field strength in the dry separator is 250-270kA / m;

[0016] Dry separation tailings are directly discarded, and dry separation concentrates are finely crushed in a closed circuit to obtain finely crushed ore samples;

[0017] The particle size of the finely crushed ore sample is 0-3mm.

[0018] Further, based on the above technical solution, in step S3, the grinding and classification process includes:

[0019] The finely crushed ore sample is fed into a ball mill for grinding, and the obtained grinding product is classified by a cyclone. The grinding product flowing out through the overflow pipe is used as the feed material for the next process, and the sediment formed at the bottom of the cyclone is returned to the ball mill for feeding;

[0020] Grinding concentration is 60%-75%;

[0021] The degree of dissociation of iron mineral monomers in the grinding product flowing out through the overflow pipe is ≥50%;

[0022] 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 input minerals, the grinding is stopped.

[0023] Further, based on the above technical solution, in step S4, the magnetic separation process includes:

[0024] The grinding product flowing out of the overflow pipe obtained in step S3 is fed into a wet drum magnetic separator to obtain magnetically separated tailings and magnetically separated concentrates;

[0025] The particle size of the grinding product flowing out of the overflow pipe is 0-3mm;

[0026] The working parameters of the wet drum magnetic separator include: magnetic separation concentration of 20%-40%, magnetic field strength of 76-300kA / m.

[0027] Further, based on the above technical solution, in step S5, the independent screening process includes: feeding the magnetic concentrate into a fine screen to obtain an oversize product and an undersize product, feeding the oversize product into an abrasive mill, and using the undersize product as feed for the next process;

[0028] The iron monomer dissociation degree in the undersize product is 60%-80%;

[0029] When the content of minerals with a particle size of -200 mesh in the screened product accounts for 75% to 90% of the total amount of the input minerals, screening is stopped.

[0030] Further, based on the above technical solution, in step S6, the selective two-stage elutriation process includes:

[0031] 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 an abrasive mill, and using the first elutriator concentrate as a final concentrate;

[0032] And / or, 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.

[0033] Further, based on the above technical solution, in step S7, the wormwood mill regrinding process includes: feeding the first elutriator tailings and the screened product into the wormwood mill to obtain the wormwood mill discharge product;

[0034] and / or, the grinding concentration of the moxa grinder is 25%-50%;

[0035] And / or, when the content of minerals with a particle size of -400 mesh in the grinding product accounts for 60% to 80% of the total amount of the input minerals, the grinding is stopped and the grinding time is 60-120s to ensure that the dissociation degree of iron monomers in the ore discharge product of the sand mill is greater than 90%.

[0036] Further, based on the above technical solution, in step S8, the three-stage elutriator process comprises: feeding the ore discharge product of the sand mill into the second elutriator to obtain the second elutriator concentrate and the second elutriator tailings, and the obtained second elutriator concentrate is used as the final concentrate, and the second elutriator tailings is used as the final tailings;

[0037] And / or, 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.

[0038] Furthermore, based on the above technical solution, the average TFe content in the final concentrate is 67-69%, and the total yield is 60-65%.

[0039] The present invention provides a method for beneficiating iron ore with uneven distribution of crystal grain size, which has the following beneficial effects:

[0040] 1. The present invention adopts coarse-fine step recovery based on the uneven and unevenly distributed properties of the raw material magnetic iron crystal particles, and can preferentially obtain coarse-grained qualified products.

[0041] 2. The present invention finely controls the first-stage grinding and classification according to the coarse-grained particle size distribution in the raw material crystals, reduces the materials that have reached monomer dissociation and do not circulate in the grinding and classification process, and improves the processing capacity of the mill.

[0042] 3. The present invention adopts magnetic drum roughing, and the tailings can be directly discarded, reducing the amount of ore entering the subsequent process.

[0043] 4. The present invention adopts fine screening for classification, which further improves the monomer dissociation degree of iron in the product under the screen, provides narrow particle size raw materials for the elutriator, which is beneficial to the elutriator sorting; and the elutriator is used for selection, so that the concentrate has less inclusions.

[0044] 5. The present invention adopts an argon sand mill for grinding, so that the grinding particle size is more uniform.

[0045] 6. The process flow of the present invention is simpler and easy to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 A schematic flow chart of a method for beneficiating iron ore with uneven distribution of crystal grain size provided by the present invention. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0049] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0050] According to a first aspect of the present invention, there is provided a method for beneficiating iron ore with uneven distribution of crystal grain size, comprising the following steps:

[0051] S1, material preparation; S2, dry separation; S3, grinding and classification process; S4, one-stage magnetic separation process; S5, independent screening process; S6, selected two-stage washing machine process; S7, wormwood grinding and regrinding process; S8, selected three-stage washing machine process.

[0052] As an optional embodiment of the present invention, in step S1, the material preparation includes: crushing the raw material to obtain a crushed product;

[0053] Wherein, the raw material comprises, by mass percentage, 55-90% (e.g., 60%, 65%, 70%, 75%, 80%, 85%, etc.) of magnetite ore and 10-45% (e.g., 15%, 20%, 25%, 30%, 35%, 40%, etc.) of surrounding rock;

[0054] Specifically, the magnetite ore raw material to be processed by the present invention contains a small amount of impurity ores such as surrounding rocks. However, the present invention additionally dopes 10-45% of surrounding rocks into the magnetite ore raw material, which has the following advantages:

[0055] (1) Improve the subsequent dry separation effect: The hardness and brittleness of the surrounding rock and magnetite are different, so it is easier to form coarse particles during crushing. After the surrounding rock is added, the particle size distribution of the ore after overall crushing is more uniform, the physical boundary between the magnetite particles and the surrounding rock is clearer, and the existence of intergrowth is reduced, making the separation of magnetic minerals and non-magnetic waste rock more thorough during dry separation;

[0056] (2) Improve the sorting accuracy of the dry separator: After the surrounding rock is added, the crushing parameters can be adjusted to ensure that the magnetite and the surrounding rock are in the optimal sorting particle size range, thereby improving the sorting accuracy;

[0057] (3) Improve the sorting efficiency: After the surrounding rock is added, the proportion of coarse waste rock produced by crushing increases. Since magnetite has high toughness, its particle size is finer after crushing. During dry magnetic separation, coarse non-magnetic surrounding rock is more easily repelled by the magnetic field, while fine magnetite is adsorbed, thereby reducing the entrainment of fine waste rock particles and improving the sorting efficiency.

[0058] (4) Make the sorting more accurate: Pure magnetite ore tends to form magnetic agglomerates (fine-grained magnetite and waste rock bonded together) after crushing, resulting in waste rock being entrained during sorting. However, after being mixed with surrounding rock, the surrounding rock particles act as "isolation media" during the crushing process, reducing the probability of magnetic agglomeration and making the sorting more accurate;

[0059] (5) Increase the processing capacity: Adding surrounding rock can adjust the looseness of the ore pile to avoid equipment blockage or too dense separation layer due to excessive density of pure magnetite. The appropriate proportion of surrounding rock can make the material flow more evenly in the separator, thereby increasing the processing capacity.

[0060] The particle size of the crushed product is 0-5 mm (such as 1 mm, 2 mm, 3 mm, 4 mm, etc.);

[0061] Wherein, the particle sizes of the magnetite ore and surrounding rock are both 0-100 mm.

[0062] The crushing is a two-stage crushing, specifically, large pieces of magnetite ore and surrounding rock are fed to a coarse crusher for coarse crushing, and the magnetite ore after coarse crushing is screened and then transported to a medium crusher or a fine crusher for fine crushing.

[0063] The crushed product is obtained after laboratory crushing, and its particle size is 0-5mm; screening analysis (set sieve analysis) of the sample shows that the raw material crystal particle size is unevenly distributed, and the grade distribution is uneven, which meets the raw material requirements for the process of the present invention.

[0064] As an optional embodiment of the present invention, in step S2, the dry separation includes: dry separation of the crushed product in a dry separation machine to obtain dry separation tailings and dry separation concentrate;

[0065] Among them, the magnetic field strength in the dry separator is 250-270kA / m (such as 255kA / m, 260kA / m, 265kA / m, etc.);

[0066] Dry separation tailings are directly discarded, and dry separation concentrates are finely crushed in a closed circuit to obtain finely crushed ore samples;

[0067] The particle size of the finely crushed ore sample is 0-3mm (such as 1mm, 1.5mm, 2mm, etc.).

[0068] Specifically, the purpose of dry separation in the present invention is to significantly improve the iron grade of the raw materials entering the grinding process by removing low-grade ore and waste rock, thereby improving the subsequent separation efficiency. Dry separation can remove waste rock in advance and greatly reduce the grinding process volume. The reduction in grinding process volume can directly reduce the power consumption and steel consumption of subsequent equipment such as ball mills.

[0069] As an optional embodiment of the present invention, in step S3, the grinding and classification process includes:

[0070] The finely crushed ore sample is fed into a ball mill for grinding, and the obtained grinding product is classified by a cyclone. The grinding product flowing out through the overflow pipe is used as the feed material for the next process, and the sediment formed at the bottom of the cyclone is returned to the ball mill for feeding;

[0071] The grinding concentration is 60%-75% (such as 63%, 65%, 67%, 69%, 70%, 73%, etc.);

[0072] Specifically, the grinding concentration of the ball mill affects the grinding particle size and processing volume, so 60%-75% concentration 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 higher processing efficiency, avoiding problems such as insufficient grinding due to too low concentration or excessive wear and excessive equipment load caused by too high concentration.

[0073] The degree of dissociation of iron mineral monomers in the grinding product flowing out through the overflow pipe is ≥50% (e.g. 55%, 60%, 65%, etc.);

[0074] 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 input minerals (such as 47%, 49%, 51%, 53%, 55%, 57%, 59%, etc.), stop grinding.

[0075] Specifically, the grinding particle size is determined according to the coarse crystal particle size in the raw material. Through reasonable grinding particle size control (by controlling the content of minerals with a particle size of -200 mesh to account for 45% to 60% of the total input minerals), it can ensure that the useful minerals in the ore are fully dissociated, which is convenient for subsequent sorting operations.

[0076] Specifically, the dissociation degree of iron mineral monomers in the ground ore products is statistically observed under a microscope.

[0077] Specifically, the hydrocyclone is a device that performs particle classification by controlling the feeding pressure, and can separate the particles in the slurry according to the particle size. The grinding products (i.e., particles with smaller particle size) flowing out of the hydrocyclone through the overflow pipe are used as the feed for the next process, while the sediment (i.e., particles with larger particle size) formed at the bottom of the hydrocyclone is returned to the feeding port of the ball mill for re-grinding.

[0078] As an optional embodiment of the present invention, in step S4, the magnetic separation process includes:

[0079] The grinding product flowing out of the overflow pipe obtained in step S3 is fed into a wet drum magnetic separator to obtain magnetically separated tailings and magnetically separated concentrates;

[0080] The working parameters of the wet drum magnetic separator include: magnetic separation concentration of 20%-40% (such as 25%, 30%, 35%, etc.), magnetic field strength of 76-300kA / m (such as 100kA / m, 150kA / m, 200kA / m, 250kA / m, etc.).

[0081] Specifically, in step S4 of the present invention, magnetic drum roughing is adopted, and the tailings can be directly discarded, thereby reducing the amount of ore entering the subsequent process.

[0082] Specifically, in a wet drum magnetic separator, ore particles flow through the magnetic field area with the slurry. Magnetic minerals are attracted by the magnetic field and adsorbed on the surface of the magnetic drum. As the magnetic drum rotates, they are brought to an area with weaker magnetic field strength. In this area, the magnetic minerals lose sufficient magnetic support, fall off the magnetic drum, and fall into the concentrate collection device to form magnetic concentrate. Non-magnetic minerals are not affected by the magnetic field and continue to flow with the slurry, and are eventually discharged from the tailings port of the magnetic separator to form magnetic tailings. The magnetic tailings are used as the final tailings and are no longer processed further. The magnetic concentrate is fed into the next process for further processing.

[0083] As an optional embodiment of the present invention, in step S5, the independent screening process includes: feeding the magnetic separation concentrate into a fine screen to obtain an oversize product and an undersize product, the oversize product is fed into an abrasive mill, and the undersize product is used as feed material for the next process;

[0084] The degree of dissociation of iron monomer in the undersize product is 60%-80% (e.g., 65%, 70%, 75%, etc.);

[0085] Specifically, if the iron monomer dissociation degree of the undersize product obtained in step S5 is higher than 80%, a large amount of the oversize product needs to be returned to the previous processing flow for reprocessing. This will not only increase the processing cost, but also may cause increased equipment wear and reduce production efficiency due to repeated processing. If the dissociation degree is less than 60%, it means that a large amount of iron minerals still exist in the form of conjoined bodies, and effective monomer dissociation cannot be achieved, resulting in unqualified products.

[0086] When the content of minerals with a particle size of -200 mesh in the screened product accounts for 75% to 90% of the total amount of the input minerals, screening is stopped.

[0087] Among them, the specifications and combination of fine screen meshes are determined by the coarse particle size of the magnetic separation concentrate. Specifically, the specifications and combination of fine screen meshes are to meet the requirement that 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 input minerals (such as 77%, 80%, 83%, 85%, 87%, etc.).

[0088] Specifically, the independent screening process adopted in step S5 of the present invention is placed after a magnetic separation process in a wet drum magnetic separator in order to obtain narrow particle size materials for use in a washing machine. If it is used before a magnetic separation process, it is usually used to control the grinding particle size. The present invention obtains a grinding product with a particle size of 0-3mm through a grinding and grading process, and the grinding feed particle size is reduced, thereby omitting the screening process before magnetic separation and simplifying the entire process flow.

[0089] As an optional embodiment of the present invention, in step S6, the selective two-stage elutriation process includes:

[0090] 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 an abrasive mill, and using the first elutriator concentrate as a final concentrate;

[0091] And / or, the working parameters of the first washing machine include: magnetic field strength: 3KA / m-50KA / m (such as 10KA / m, 20KA / m, 30KA / m, 40KA / m, etc.); ore feed rate: 0.25-1.5kg / min (such as 0.5kg / min, 0.7kg / min, 1kg / min, 1.3kg / min, etc.); ore feed concentration: 15%-30% (such as 17%, 20%, 23%, 25%, 27%, etc.); rising water flow: 10-30L / min (such as 15L / min, 20L / min, 25L / min, etc.).

[0092] Specifically, after the sorting treatment of the first elutriator, the mineral particles with strong magnetism are attracted by the magnetic field and gathered together to form the first elutriator concentrate; the mineral particles that are not effectively attracted by the magnetic field and the non-magnetic minerals are discharged with the water flow to form the first elutriator tailings. In order to recover the useful minerals in the first elutriator tailings, they can be sent to the abrasive mill for re-grinding. Grinding can further reduce the particle size of the mineral particles, improve the monomer dissociation degree of the useful minerals, and create more favorable conditions for the subsequent sorting process. After the sorting treatment of the first elutriator, the grade and recovery rate of the first elutriator concentrate meet the requirements and can be directly used as the final concentrate.

[0093] As an optional embodiment of the present invention, in step S7, the wormwood sand mill regrinding process includes: feeding the first elutriator tailings and the screened product into the wormwood sand mill to obtain the wormwood sand mill discharge product;

[0094] and / or, the grinding concentration of the moxa grinder is 25%-50% (e.g., 30%, 35%, 40%, 45%, etc.);

[0095] And / or, after the content of minerals with a particle size grade of -400 mesh in the grinding product accounts for 60% to 80% (such as 65%, 70%, 75%, etc.) of the total amount of input minerals, the grinding is stopped and the grinding time is 60-120s (such as 70s, 80s, 90s, 100s, 110s, etc.) to ensure that the degree of dissociation of iron monomers in the ore discharge product of the sand mill is greater than 90%.

[0096] Specifically, if the grinding concentration of the Ai grinding machine is too high (greater than 50%), it will cause the mill to swell. The swelling of the mill means that the material inside the mill is too dense and the fluidity is poor. This will not only increase the operating load of the mill, but also may cause the material inside the mill to be unable to be discharged normally, thereby affecting the overall working efficiency and stability of the mill. In addition, too high a grinding concentration may also lead to increased wear inside the mill and shorten the service life of the equipment; if the Ai grinding machine concentration is too low (less than 25%), the processing capacity of the mill will be significantly reduced because the collision and grinding opportunities of the material inside the mill will be greatly reduced. This will not only reduce the production efficiency of the mill, but more importantly, too low a grinding concentration will cause the media inside the mill (such as grinding balls or grinding rods) to collide with each other in the absence of sufficient material buffering, resulting in severe wear of the media. The increase in media wear will not only further reduce the processing capacity of the mill, but also increase the maintenance cost of the equipment and the frequency of replacing the media, posing a threat to the continuous and stable operation of the production line.

[0097] Specifically, the first elutriation tailings are ground by an Ai sand mill in step S7 of the present invention because the first elutriation tailings have been transformed into fine-grained tailings after the above treatment, and their particle size is small and in an over-crushed state. Tailings in this state have extremely high specific surface area and complex surface properties, which makes conventional grinding equipment, such as ball mills, face many challenges when processing. Specifically, conventional ball mills are often difficult to achieve ideal grinding effects when processing tailings in fine-grained and over-crushed states. Due to the enhanced interaction between particles, fine-grained tailings are prone to agglomeration and adhesion, which not only reduces the grinding efficiency, but also may cause excessive wear of the equipment and increase in energy consumption. In addition, when processing such tailings, the ball mill may also have the problem of over-crushing, further deteriorating the particle size distribution of the tailings and affecting the smooth progress of subsequent processing procedures. In contrast, the Ai sand mill has significant advantages in processing tailings in fine-grained and over-crushed states. The Ai sand mill can effectively grind the tailings without destroying the original particle size distribution of the tailings through special grinding media and grinding mechanism. This equipment not only has higher grinding efficiency, but also can significantly reduce energy consumption and equipment wear, thereby improving the economy and sustainability of the overall treatment.

[0098] Specifically, the dissociation of mineral monomers refers to the fact that during the grinding stage, due to the presence of many inclusions in the magnetic separation equipment, minerals with low dissociation degree are also magnetically separated into the concentrate, thereby 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 market, the present invention introduces the step S7 of the Aisha mill re-grinding process after the second-stage washing process. As a highly efficient ultra-fine crushing equipment, the Aisha mill has a unique grinding mechanism and medium movement mode, which can grind and impact the material more finely without destroying the crystal structure of the mineral, and effectively promote the further dissociation between iron minerals and gangue minerals. Through the re-grinding treatment of the Aisha 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 subsequent processes.

[0099] As an optional embodiment of the present invention, in step S8, the three-stage elutriator process comprises: feeding the ore discharge product of the sand mill 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 final tailings;

[0100] And / or, the working parameters of the second washing machine include: magnetic field strength: 3KA / m-50KA / m (such as 10KA / m, 20KA / m, 30KA / m, 40KA / m, etc.); ore feed rate: 0.25-1.5kg / min (such as 0.5kg / min, 0.7kg / min, 1kg / min, 1.3kg / min, etc.); ore feed concentration: 15%-30% (such as 17%, 20%, 23%, 25%, 27%, etc.); rising water flow: 10-30L / min (such as 15L / min, 20L / min, 25L / min, etc.).

[0101] Specifically, the iron in the magnetic separation tailings and the second panning machine tailings is mainly iron silicate, and the above tailings can be collected and processed for reuse.

[0102] As an optional embodiment of the present invention, the average TFe content in the final concentrate is 67-69%, and the total yield is 60-65%.

[0103] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0104] Example 1

[0105] S1. Material preparation: crush the raw materials into 0-30 mm in two stages to obtain crushed products;

[0106] Wherein, the raw material comprises 75% magnetite ore and 25% surrounding rock by mass percentage;

[0107] S2. The crushed product is dry-selected in a magnetic field strength of 260 kA / m. The TFe content of the dry-selected tailings is 10.20%, and the yield is 89.67%. The TFe content of the dry-selected concentrate is 28.36%. The dry-selected tailings are directly discarded, and the dry-selected concentrate is subjected to a closed-circuit fine crushing process to obtain finely crushed ore samples. The particle size of the finely crushed ore samples is 0-2 mm (laboratory test particle size). Screening and analysis of the samples show that: the crystal particle size of +100 mesh accounts for 70%, and -400 mesh accounts for 10%, which meets the requirements of the process for raw materials.

[0108] S3, grinding and classification process: the finely crushed ore sample is fed into a ball mill with a grinding concentration of 70% for 15 minutes. After the classification and grinding, the minerals with a fineness of -200 mesh account for 50% of the total amount of the fed minerals. The obtained grinding products are classified by a cyclone, and the grinding products flowing out through the overflow pipe are used as feed for the next process. The sediment formed at the bottom of the cyclone is returned to the ball mill for ore feeding;

[0109] S4, one-stage magnetic separation process: the grinding product flowing out of the overflow pipe is fed into a wet drum magnetic separator, the magnetic separation concentration is 35%, the magnetic field strength is 120kA / m, and a magnetic separation concentrate is obtained, wherein the TFe content is 52.08%, the yield is 80.42%, and the TFe content in the magnetic separation tailings is 10.88%, and the mFe content is 0.18%;

[0110] S5. Independent screening process: feed the magnetic concentrate to a 200-mesh fine screen to obtain the oversize product and the undersize product. The oversize product is fed to the sand mill. When the content of minerals with a particle size of -200 mesh in the undersize product accounts for 75% to 90% of the total amount of the fed minerals, the screening is stopped and the undersize product is used as the feed material for the next process. The degree of dissociation of iron monomers in the undersize product is 92%;

[0111] S6, concentrating two-stage elutriator process: feeding the undersize product into the first 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 first elutriator concentrate and the first elutriator tailings, wherein the TFe content of the first elutriator concentrate is 67.42%, and the yield is 87.24%; the TFe content of the first elutriator tailings is 22.05%; the first elutriator tailings are fed into the sand mill, and the first elutriator concentrate is used as the final concentrate;

[0112] S7, regrinding process of sand mill: feed the tailings of the first washing machine and the screen product into the sand mill, the grinding concentration is 30%, and the content of minerals with a particle size of -400 mesh in the grinding product accounts for 60% to 80% of the total amount of the fed minerals, then stop grinding, the grinding time is 90s, and obtain the sand mill discharge product;

[0113] S8, three-stage elutriation process: feed the ore product discharged from the sand mill into the second elutriation machine, the magnetic field strength is 5kA / m, the feed amount is 1.0kg / min, the feed concentration is 20%, the rising water flow is 20L / min, and the second elutriation machine concentrate and the second elutriation machine tailings are obtained, wherein the TFe content in the second elutriation machine concentrate is 67.88%, the yield is 78.82%, the TFe content in the second elutriation machine tailings is 11.18%, and the mFe content is 0.23%. The obtained second elutriation machine concentrate is used as the final concentrate, and the second elutriation machine tailings is used as the final tailings.

[0114] The average TFe content of the iron ore concentrate obtained by this process is 67.53%, and the total yield is 60.50%.

[0115] Example 2

[0116] S1. Material preparation: crush the raw materials into 0-30 mm in two stages to obtain crushed products;

[0117] Wherein, the raw material comprises 65% magnetite ore and 35% surrounding rock by mass percentage;

[0118] S2. The crushed product is dry-selected in a magnetic field strength of 260 kA / m. The TFe content of the dry-selected tailings is 12.20%, and the yield is 79.34%. The TFe content of the dry-selected concentrate is 27.63%. The dry-selected tailings are directly discarded, and the dry-selected concentrate is subjected to a closed-circuit fine crushing process to obtain finely crushed ore samples. The ore sample particle size is 0-2 mm (laboratory test particle size). After analysis: the sample crystal particle size of +100 mesh accounts for 60%, and -400 mesh accounts for 10%, which meets the requirements of the process for raw materials.

[0119] S3, grinding and classification process: the finely crushed ore sample is fed into a ball mill with a grinding concentration of 70% for 18 minutes. After the classification and grinding, the minerals with a fineness of -200 mesh account for 60% of the total amount of the fed minerals. The obtained grinding products are classified by a cyclone, and the grinding products flowing out through the overflow pipe are used as feed for the next process. The sediment formed at the bottom of the cyclone is returned to the ball mill for ore feeding;

[0120] S4, one-stage magnetic separation process: the grinding product flowing out of the overflow pipe is fed into a wet drum magnetic separator, the magnetic separation concentration is 35%, the magnetic field strength is 120kA / m, and a magnetic separation concentrate is obtained, wherein the TFe content is 52.58%, the yield is 79.11%, and the TFe content in the magnetic separation tailings is 9.88%, and the mFe content is 0.15%;

[0121] S5. Independent screening process: feed the magnetic concentrate into a 200-mesh fine screen to obtain the oversize product and the undersize product. The oversize product is fed into the sand mill. When the content of minerals with a particle size of -200 mesh in the undersize product accounts for 75% to 90% of the total amount of the fed minerals, the screening is stopped and the undersize product is used as the feed material for the next process. The iron monomer dissociation degree in the undersize product is 95%;

[0122] S6, concentrating two-stage elutriator process: feeding the undersize product into the first 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 first elutriator concentrate and the first elutriator tailings, wherein the TFe content of the first elutriator concentrate is 67.92%, and the yield is 88.61%; the TFe content of the first elutriator tailings is 20.45%; the first elutriator tailings are fed into the sand mill, and the first elutriator concentrate is used as the final concentrate;

[0123] S7, regrinding process of sand mill: feed the tailings of the first washing machine and the screen product into the sand mill, the grinding concentration is 30%, and the content of minerals with a particle size of -400 mesh in the grinding product accounts for 60% to 80% of the total amount of the fed minerals, then stop grinding, the grinding time is 90s, and obtain the sand mill discharge product;

[0124] S8, three-stage elutriation process: feed the ore product discharged from the sand mill into the second elutriation machine, the magnetic field strength is 5kA / m, the feed amount is 1.0kg / min, the feed concentration is 20%, the rising water flow is 20L / min, and the second elutriation machine concentrate and the second elutriation machine tailings are obtained, wherein the TFe content in the second elutriation machine concentrate is 68.38%, the yield is 88.97%, the TFe content in the second elutriation machine tailings is 10.38%, and the mFe content is 0.22%. The obtained second elutriation machine concentrate is used as the final concentrate, and the second elutriation machine tailings is used as the final tailings.

[0125] The average TFe content of the iron ore concentrate obtained by this process is 68.18%, and the total yield is 64.96%.

[0126] Comparative Example 1

[0127] The main difference between this comparative example and Example 1 is that the ball milling and regrinding process is adopted in step S7, and the other technical parameters and operation steps are the same as those in Example 1, specifically:

[0128] Steps S1-S6 are the same as those in Example 1;

[0129] S7, ball mill regrinding process: feed the first elutriator tailings and the screened product into the ball mill, the grinding concentration is 67%, and the ball mill discharge product is obtained;

[0130] S8, four-stage elutriation process: the ball mill discharge product is fed into the second elutriation machine, the magnetic field strength is 5kA / m, the feed amount is 1.0kg / min, the feed concentration is 20%, the rising water flow is 20L / min, and the second elutriation machine concentrate and the second elutriation machine tailings are obtained, wherein the TFe content in the second elutriation machine concentrate is 65.5%, the TFe content in the second elutriation machine tailings is 13.5%, and the mFe content is 2.2%. The obtained second elutriation machine concentrate is used as the final concentrate, and the second elutriation machine tailings is used as the final tailings. The average TFe content of the iron concentrate obtained by this process is 65.6%, and the total yield is 59.5%.

[0131] Compared with Example 1, this comparative example replaces the argon sand mill regrinding process in step S7 of Example 1 with a ball mill regrinding process. Since the first washing tailings are fine-grained tailings, the interaction between particles is strong and agglomeration and adhesion are prone to occur. When a ball mill is used to process the first washing tailings and the screened products, over-crushing will occur, further aggravating the agglomeration and adhesion problems between particles, resulting in agglomerates in the discharge products entering the second washing machine, affecting the washing effect; and the use of ball milling cannot make the iron monomer dissociation degree in the ball mill discharge products meet the requirements, which ultimately leads to a decrease in the average TFe content in the final concentrate and a decrease in yield.

[0132] Comparative Example 2

[0133] The difference between this comparative example and Example 1 is that the independent screening process in step S5 is cancelled, and the remaining technical parameters and operation steps are the same as those in Example 1, specifically:

[0134] Steps S1-S4 are the same as those in Example 1;

[0135] S5, concentrating two-stage elutriator process: feeding the magnetic separation concentrate into the first elutriator, with a magnetic field strength of 5kA / m, a feed amount of 1.0kg / min, a feed concentration of 20%, and an upward water flow of 20L / min, to obtain the first elutriator concentrate and the first elutriator tailings, wherein the TFe content of the first elutriator concentrate is 65.8%; the TFe content of the first elutriator tailings is 35.4%; the first elutriator tailings are fed into the sand mill, and the first elutriator concentrate is used as the final concentrate;

[0136] S6, wormwood mill regrinding process: feed the tailings of the first elutriator into the wormwood mill, the grinding concentration is 30%, and the content of minerals with a particle size of -400 mesh in the grinding product accounts for 60% to 80% of the total amount of the fed minerals, then stop grinding, the grinding time is 90s, and obtain the wormwood mill discharge product;

[0137] S7, three-stage elutriation process: feed the ore product of the sand mill into the second elutriation machine, the magnetic field strength is 5kA / m, the feed amount is 1.0kg / min, the feed concentration is 20%, the rising water flow is 20L / min, and the second elutriation machine concentrate and the second elutriation machine tailings are obtained, wherein the TFe content in the second elutriation machine concentrate is 65.6%; the TFe content in the second elutriation machine tailings is 12.9%, and the mFe content is 1.8%. The obtained second elutriation machine concentrate is used as the final concentrate, and the second elutriation machine tailings are used as the final tailings.

[0138] The average TFe content of the iron ore concentrate obtained by this process is 65.67%, and the total yield is 58.76%.

[0139] Compared with Example 1, since Comparative Example 2 cancels the independent screening process and directly feeds the magnetic concentrate into the first washing machine, the magnetic concentrate is not screened, and coarse-grained materials will enter the washing machine. It is difficult for the washing machine to separate the iron monomers in the material, resulting in the iron content in the final product being unable to meet the requirements of subsequent processing or market.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, 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 iron ore with uneven distribution of crystal grain size, characterized in that: The steps include: S1, material preparation; S2, dry separation; S3, grinding and classification process; S4, one-stage magnetic separation process; S5, independent screening process; S6, selected two-stage washing machine process; S7, wormwood grinding and regrinding process; S8, selected three-stage washing machine process.

2. The method for beneficiating iron ore with uneven distribution of crystal grain size according to claim 1, characterized in that: In step S1, the material preparation includes: crushing the raw material to obtain a crushed product; Wherein, the raw material comprises 55-90% magnetite ore and 10-45% surrounding rock in terms of mass percentage; Preferably, the particle sizes of the magnetite ore and surrounding rock are both 0-100 mm; Preferably, the particle size of the crushed product is 0-5 mm.

3. The method for beneficiating iron ore with uneven distribution of crystal grain size according to claim 2, characterized in that: In step S2, the dry separation includes: performing dry separation on the crushed product in a dry separation machine to obtain dry separation tailings and dry separation concentrates; Among them, the magnetic field strength in the dry separator is 250-270kA / m; Dry separation tailings are directly discarded, and dry separation concentrates are finely crushed in a closed circuit to obtain finely crushed ore samples; The particle size of the finely crushed ore sample is 0-3mm.

4. The method for beneficiating iron ore with uneven distribution of crystal grain size according to claim 3, characterized in that: In step S3, the grinding and classification process includes: The finely crushed ore sample is fed into a ball mill for grinding, and the obtained grinding product is classified by a cyclone. The grinding product flowing out through the overflow pipe is used as the feed material for the next process, and the sediment formed at the bottom of the cyclone is returned to the ball mill for feeding; Grinding concentration is 60%-75%; The degree of dissociation of iron mineral monomers in the grinding product flowing out through the 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 input minerals, the grinding is stopped.

5. The method for beneficiating iron ore with uneven distribution of crystal grain size according to claim 4, characterized in that: In step S4, the magnetic separation process includes: The grinding product flowing out of the overflow pipe obtained in step S3 is fed into a wet drum magnetic separator to obtain magnetically separated tailings and magnetically separated concentrates; The working parameters of the wet drum magnetic separator include: magnetic separation concentration of 20%-40%, magnetic field strength of 76-300kA / m.

6. The method for beneficiating iron ore with uneven distribution of crystal grain size according to claim 5, characterized in that: In step S5, the independent screening process includes: feeding the magnetic concentrate into a fine screen to obtain an oversize product and an undersize product, the oversize product is fed into an abrasive mill, and the undersize product is used as feed for the next process; 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 screened product accounts for 75% to 90% of the total amount of the input minerals, screening is stopped.

7. The method for beneficiating iron ore with uneven distribution of crystal grain size according to claim 6, characterized in that: In step S6, the selective two-stage elutriation process includes: 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 an abrasive mill, and using the first elutriator concentrate as a final concentrate; And / or, 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 iron ore with uneven distribution of crystal grain size according to claim 7, characterized in that: In step S7, the wormwood mill regrinding process includes: feeding the first elutriator tailings and the screened product into the wormwood mill to obtain the wormwood mill discharge product; and / or, the grinding concentration of the moxa grinder is 25%-50%; And / or, when the content of minerals with a particle size of -400 mesh in the grinding product accounts for 60% to 80% of the total amount of the input minerals, the grinding is stopped and the grinding time is 60-120s to ensure that the dissociation degree of iron monomers in the ore discharge product of the sand mill is greater than 90%.

9. The method for beneficiating iron ore with uneven distribution of crystal grain size according to claim 8, characterized in that: In step S8, the three-stage elutriator process comprises: feeding the ore product discharged from the sand mill 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 final tailings; And / or, 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 iron ore with uneven distribution of crystal grain size according to claim 8, characterized in that: The average TFe content in the final concentrate is 67-69%, and the total yield is 60-65%.

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