A method for separating iron oxide from silica sand by stepwise magnetic separation

Abstract

The application discloses a method for grading magnetic separation of iron oxide and silica sand, and belongs to the technical field of black metal ore dressing. According to the differences in physical and chemical properties of main minerals in medium-quality iron ore, such as magnetite, iron oxide, quartz and the like, including metal content, embedded particle size, Mohs hardness, specific magnetization, settling velocity, single liberation degree and the like, suitable grinding fineness, classification fineness, desliming particle size, magnetic field strength, magnetic separation equipment, separation medium, magnetic separation pulsation and the like are selected, and a combined ore dressing process, such as crushing and grinding, weak magnetic separation of iron, medium magnetic separation of iron, strong magnetic separation of iron, classification, strong magnetic separation of iron, desliming, strong magnetic purification and the like, can separate high-quality iron concentrate, high-quality silica sand concentrate, building material raw materials and other industrial products, improves the recovery rate of iron minerals, and the comprehensive utilization rate of minerals reaches 100%, tail water produced by solid-liquid separation can be recycled after precipitation and clarification, double-zero emission of tailings and tail water is realized, green environmental protection is achieved, and the method is suitable for large-scale production and application.

Description

Technical Field

[0001] This invention relates to the field of ferrous metal ore beneficiation technology, specifically to a method for separating iron oxide and silica sand by stepwise magnetic separation. Background Technology

[0002] Ferrous metal ores mainly include iron ore, manganese ore, and chromium ore, with iron ore being the most typical ferrous metal ore. At present, in the process of smelting iron ore, high-quality lumpy iron ore with a TFe grade of >63% can be directly smelted in the furnace, while medium-quality granular iron oxide ore with a TFe grade of 45-60% still needs to go through mineral processing to obtain qualified iron concentrate products.

[0003] The main metallic minerals in some medium-quality iron ores are iron oxide ores and a small amount of magnetite. The proportion of single magnetite is relatively small. The main gangue minerals are silicates such as quartz. The content of impurity minerals such as sulfur and phosphorus is low. The particle size is generally -40mm, the total iron (TFe) content is 45-55%, and the quartz (SiO2) content is 20-30%. The proportion of magnetite in iron minerals is generally 3-6%. Most of the iron-bearing minerals are iron oxide ores such as hematite, specularite, and limonite. The degree of oxidation of iron oxide ores is relatively high.

[0004] Conventional beneficiation processes for iron oxide ore include magnetic separation, flotation, gravity separation, roasting-magnetic separation combined, magnetic separation-flotation combined, and gravity separation-magnetic separation-flotation combined. Among these, flotation, gravity separation, and roasting-magnetic separation are traditional beneficiation methods, all of which suffer from drawbacks such as high reagent costs, low beneficiation indexes, high production costs, long process flow, heavy environmental pollution, and low economic benefits. Magnetic separation utilizes the characteristics of magnetite in iron oxide ore having a high specific magnetic susceptibility, iron oxide ore having a low specific magnetic susceptibility, and quartz being a non-magnetic non-metallic mineral. It employs a conventional beneficiation process of grinding-weak magnetic separation-strong magnetic separation, but generally suffers from production and technical difficulties such as high iron content in tailings, significant metal loss, low economic benefits, and insufficient comprehensive utilization rate.

[0005] In view of this, in order to solve the technical problems existing in the current medium-quality iron ore beneficiation process, it is an urgent problem to develop and design a staged, step-by-step separation method for high-quality iron concentrate, high-quality silica sand concentrate, building material raw materials and other industrial products, improve the recovery rate of iron minerals, ensure the stability of beneficiation indicators and actual production, achieve 100% comprehensive utilization of minerals, be green and environmentally friendly, and suitable for large-scale production applications. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for separating iron oxide and silica sand using a stepped magnetic separation process. This method employs a combination of crushing and grinding, weak magnetic separation, medium magnetic separation, strong magnetic removal, grading, strong magnetic separation, desliming, and strong magnetic purification processes for medium-quality iron ore. This process can separate high-quality iron concentrate, premium silica sand concentrate, building material raw materials, and other industrial products, improving the recovery rate of iron ore and achieving 100% comprehensive mineral utilization. The tailings water generated during solid-liquid separation can be returned to each operating section for recycling after sedimentation and clarification, achieving zero discharge of tailings and tailings water. This green and environmentally friendly method is suitable for large-scale production applications.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides a method for separating iron oxide and silica sand by stepwise magnetic separation, comprising the following steps: S1: Crushing and grinding operation: crushing and / or grinding the raw ore to obtain a fine product; S2: Weak magnetic separation operation: The fine product is subjected to a first stage of magnetic separation under a first magnetic field strength to obtain a first magnetic material and a first non-magnetic material, wherein the first magnetic material is magnetite, which meets the quality standard of first-grade iron concentrate, and the first magnetic material is discharged into the first concentrate sedimentation tank. S3: Medium magnetic separation of iron: The first non-magnetic material is subjected to a second stage of magnetic separation under a second magnetic field strength to obtain a second magnetic material and a second non-magnetic material. The second magnetic material is iron oxide ore, which meets the quality standard of grade II iron concentrate. The second magnetic material is discharged into the first concentrate sedimentation tank. The second non-magnetic material is subjected to a third stage of magnetic separation under a third magnetic field strength to obtain a third magnetic material and a third non-magnetic material. The third magnetic material is iron oxide concentrate, which meets the quality standard of grade III iron concentrate. The third magnetic material is discharged into the first concentrate sedimentation tank. S4: Strong magnetic separation operation: The third non-magnetic material is subjected to a fourth magnetic separation operation under a fourth magnetic field strength to obtain a fourth magnetic material and a fourth non-magnetic material. The fourth magnetic material is a low-quality mixed coarse concentrate, mainly consisting of intergrowth and fine-grained iron-bearing minerals; the fourth non-magnetic material is iron tailings, mainly consisting of silica sand, fine mudstone and a small amount of intergrowth or fine-grained iron oxide. S5: Grading operation: The fourth magnetic material is graded to obtain coarse and fine products, wherein the coarse product is an iron-silicon intergrowth, and the coarse product is returned to the crushing and grinding operation in step S1. S6: Strong magnetic separation of iron: The fine-particle product is subjected to the fifth stage of magnetic separation under the fifth magnetic field strength to obtain the fifth magnetic material and the fifth non-magnetic material. The fifth magnetic material is iron oxide ore, which meets the quality standard of grade III iron concentrate. The fifth magnetic material is discharged into the first concentrate sedimentation tank, and the fifth non-magnetic material is discharged into the tailings sedimentation tank. S7: Desliming operation: The fourth non-magnetic material is deslimed to obtain medium-grained product and fine mud product. The medium-grained product is mainly silica sand and a small amount of iron oxide in the form of intergrowths and inclusions. The fine mud product is mainly fine-grained iron oxide, iron silicate, silicate and other minerals, which have no mineral processing value. The fine mud product is discharged into the tailings sedimentation pond. S8: Strong magnetic purification operation: The medium-particle product is subjected to a sixth-stage magnetic separation operation under a sixth magnetic field strength to obtain a sixth magnetic material and a sixth non-magnetic material. The sixth magnetic material is iron-containing impurities and iron-silicon intergrowths, and the sixth magnetic material is discharged into the tailings sedimentation tank. The sixth non-magnetic material is silica sand, and the sixth non-magnetic material is discharged into the second concentrate sedimentation tank. S9: Solid-liquid separation operation: The products in the first concentrate sedimentation tank, the second concentrate sedimentation tank, and the tailings sedimentation tank are subjected to solid-liquid separation operation respectively. The separated solids are iron concentrate, silica sand concentrate, and total tailings. The separated tailings water can be returned to each operation section for recycling after clarification.

[0008] As a preferred technical solution, in step S1, the raw ore is crushed to a particle size of -12mm by a hammer crusher, mixed with a slurry concentration of 67%, and then ground by a ball mill. And / or, the fineness of the fine product is set to -0.074mm, accounting for 60-65%.

[0009] As a preferred technical solution, in step S2, a drum magnetic separator is used to perform the first stage of magnetic separation, and the strength of the first magnetic field is set to 0.25~0.35T.

[0010] As a preferred technical solution, in step S3, a vertical ring high gradient magnetic separator is used to perform the second stage magnetic separation operation and the third stage magnetic separation operation. The magnetic separation medium used is a high permeability stainless steel rod with a diameter of Φ1~3mm, the pulsation is set to 20~25Hz, the second magnetic field strength is set to 0.65~0.75T, and the third magnetic field strength is set to 0.85~0.95T.

[0011] As a preferred technical solution, in step S4, a vertical ring high gradient magnetic separator is used to perform the fourth stage of magnetic separation. The magnetic separation medium used is a high permeability stainless steel rod with a diameter of Φ0.5~2.5mm, the pulsation is set to 3~5Hz, and the strength of the fourth magnetic field is set to 1.6~1.8T.

[0012] As a preferred technical solution, in step S5, a hydrocyclone is used to perform the grading operation, the particle size of the coarse product is set to +0.10mm, and the particle size of the fine product is set to -0.10mm.

[0013] As a preferred technical solution, in step S6, a plate magnetic separator is used to perform the fifth stage of magnetic separation, and the strength of the fifth magnetic field is set to 1.3 to 1.4T.

[0014] As a preferred technical solution, in step S7, a hydrocyclone is used to perform the desliming operation, the particle size of the medium-sized product is set to +0.015mm, and the particle size of the fine mud product is set to -0.015mm.

[0015] As a preferred technical solution, in step S8, an electromagnetic slurry high gradient magnetic separator is used to perform the sixth stage of magnetic separation. The magnetic separation medium used is a diamond-shaped high-permeability stainless steel mesh with a specification of 3×6mm, and the strength of the sixth magnetic field is set to 1.9~2.0T.

[0016] As a preferred technical solution, in step S9, the product in the first concentrate sedimentation tank is subjected to solid-liquid separation using a plate and frame filter press; the product in the second concentrate sedimentation tank is subjected to solid-liquid separation using a disc filter press; and the product in the tailings sedimentation tank is subjected to solid-liquid separation using a plate and frame filter press.

[0017] The beneficial effects of this invention are as follows: 1. This invention adopts a synergistic process of "cascade magnetic separation + graded regrinding + deep iron removal and silica sand purification". For medium-quality iron ore, it selects reasonable crushing and grinding, weak magnetic separation, medium magnetic separation, strong magnetic removal, grading, strong magnetic separation, desliming, and strong magnetic purification combined mineral processing processes. It can separate high-quality iron concentrate, high-quality silica sand concentrate, building material raw materials and other industrial products, improve the recovery rate of iron minerals, and achieve a 100% comprehensive utilization rate of minerals. The tailwater generated by solid-liquid separation can be returned to each operation section for recycling after sedimentation and clarification, realizing zero discharge of tailings and tailwater, which is green and environmentally friendly and suitable for large-scale production applications.

[0018] 2. This invention uses a combination of mature industrial equipment such as hammer crusher, ball mill, drum magnetic separator, vertical ring high gradient magnetic separator, hydrocyclone, plate magnetic separator, electromagnetic slurry magnetic separator, disc filter, and plate and frame filter press. The entire mineral processing flow adopts a purely physical process to achieve separation, which will not generate any pollution.

[0019] 3. Based on the differences in the metal content, particle size, Mohs hardness, specific magnetic susceptibility, settling velocity, and degree of liberation of the main valuable minerals such as magnetite, iron oxide, and quartz in medium-quality iron ore, this invention selects appropriate grinding fineness, classification fineness, desliming particle size, magnetic field strength, magnetic separation equipment, separation media, and magnetic separation pulsation conditions to optimize the separation of minerals such as strongly magnetic magnetite, weakly magnetic iron oxide, fine-grained iron oxide, coarse-grained intergrowths, fine-grained clay, and granular quartz silica sand under different conditions. This achieves effective separation and enrichment of various minerals, ensuring the maximization of beneficiation indicators for each product and the benefits for the beneficiation plant.

[0020] 4. This invention employs weak magnetic separation to preferentially select high-quality magnetite, uses two medium magnetic separation processes to effectively separate weakly magnetic iron oxide ores, and employs strong magnetic removal to select intergrowths and fine-grained iron-containing minerals. The corresponding magnetic field strength increases in stages, and the staged magnetic separation process can ensure the stability of beneficiation indicators and actual production. Each operation section adopts a scientific and reasonable combination configuration, which is suitable for large-scale production applications.

[0021] 5. This invention classifies the fourth magnetic material obtained from strong magnetic iron removal. The coarse product (coarse-grade intergrowth) is returned to the grinding process for dissociation, which can improve the recovery rate of iron ore. The fine product is processed by a plate magnetic separator with a rare earth material neodymium iron boron magnetic system and a high field strength, which can more effectively capture and recover fine iron oxide particles, further improving the metal recovery rate. The fourth non-magnetic material obtained from strong magnetic iron removal is deslimed. The medium-sized product is processed by an electromagnetic slurry magnetic separator with a higher magnetic field gradient and a suitable steel mesh medium, which can deeply magnetize and recover fine-grained iron-silicon intergrowths and mottled scattered iron oxide on the surface of silica sand, thereby obtaining high-quality silica sand products, which can significantly increase the economic benefits of enterprises. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of one embodiment of a method for separating iron oxide and silica sand by step magnetic separation according to the present invention. Detailed Implementation

[0023] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0024] Please refer to Figure 1 Table 1 shows an example of a method for separating iron oxide and silica sand using a stepped magnetic separation provided by this invention at a mineral processing plant in Jiangsu Province.

[0025] Previously, the concentrator used the conventional "grinding-weak magnetic separation-strong magnetic separation" process to process imported raw ore from Brazil. The raw ore was a medium-quality iron ore, which had production and technical difficulties such as high iron content in the tailings, large metal loss, low economic benefits, and insufficient comprehensive utilization.

[0026] Extensive research revealed that this medium-quality iron ore has a grain size of -40mm, a total iron (TFe) content of 50-56%, a magnetic iron (MFe) content of 3-6%, and its main iron-bearing minerals are hematite, specularite, limonite, and a small amount of magnetite. Iron silicate minerals are relatively few, and iron oxide minerals account for 85-90%. The main gangue minerals are quartz and a small amount of feldspar. The content of harmful impurities such as sulfur and phosphorus is low. The ore has a low proportion of magnetic iron and a high proportion of iron oxide, classifying it as an iron oxide ore based on its oxidation degree. Microscopic observation shows that magnetite is black and coarsely embedded, hematite is red and granular, specularite has a black and shiny platy structure, limonite is dark brown, has low hardness, and is easily muddied, and quartz has a translucent granular structure with relatively high hardness. The minerals exhibit edge embedding, which facilitates the liberation of individual minerals. The magnetite in this medium-quality iron ore is strongly magnetic, the iron oxide minerals are weakly magnetic, and the quartz is non-magnetic, indicating a relatively simple mineral composition.

[0027] In summary, this type of high-silicon iron ore is easy to beneficiate. Under the premise of ensuring beneficiation indicators, adopting a scientific and reasonable beneficiation process to comprehensively recover iron and silicon, maximize production efficiency, save energy and reduce consumption, improve quality and reduce emissions, has become a technical and production problem that beneficiation plants urgently need to solve.

[0028] The present invention specifically includes the following steps: S1: Crushing and grinding operation: Medium-quality iron ore with a particle size of -40mm is crushed to -12mm in a hammer crusher, mixed with a slurry of 67% concentration, and then ground in a wet ball mill to a fineness of -0.074mm, accounting for 60-65% of the total fineness. This is the fine product. Crushing to -12mm in the crushing process creates micro-cracks inside the medium-quality iron ore under high pressure, which can significantly improve the degree of liberation between magnetite, iron oxide, and quartz, and effectively reduce the production cost of subsequent grinding operations. The grinding process uses shearing and grinding to grind the finely embedded magnetite and iron oxide to a fineness of -0.074mm, which ensures sufficient liberation, which is beneficial to the improvement of subsequent beneficiation indicators, and avoids over-grinding and mudding, which affects the quality of silica sand.

[0029] In other embodiments, the raw ore may only undergo crushing or grinding operations, with the fineness of the product obtained meeting the subsequent mineral processing indicators.

[0030] S2: Weak magnetic separation operation: After the fine product is prepared into a slurry with a 30% slurry concentration, it enters a drum magnetic separator for the first stage of magnetic separation under the first magnetic field strength of 0.25-0.35T. Under this specific magnetic separation condition, the first magnetic material and the first non-magnetic material can be obtained. The first magnetic material is magnetite with a TFe grade of 67-68%, which meets the quality standard of first-grade iron concentrate. The first magnetic material is discharged into the first concentrate sedimentation tank. The weak magnetic separation operation is based on the specific magnetic susceptibility of the magnetite contained in the fine product. A drum magnetic separator with a low magnetic field strength can effectively separate this part of the magnetite.

[0031] S3: Medium magnetic separation operation: The first non-magnetic material is fed into a vertical ring high gradient magnetic separator for a second stage of magnetic separation under a second magnetic field strength of 0.65-0.75T. The magnetic separation medium used is a high-permeability stainless steel rod with a diameter of 1-3mm, and the pulsation is set to 20-25Hz. Under these specific magnetic separation conditions, a second magnetic material and a second non-magnetic material can be obtained. The second magnetic material is iron oxide ore with a TFe grade of 63-64%, which meets the quality standard of grade II iron concentrate. The second magnetic material is discharged into the first concentrate sedimentation tank. The second non-magnetic material is fed into a vertical ring high-gradient magnetic separator for a third-stage magnetic separation under a third magnetic field strength of 0.85–0.95T. The magnetic separation medium used is a high-permeability stainless steel rod with a diameter of 1–3 mm, and the pulsation is set to 20–25 Hz. Under these specific magnetic separation conditions, a third magnetic material and a third non-magnetic material can be obtained. The third magnetic material is iron oxide concentrate with a TFe grade of 61–62%, meeting the quality standard of grade III iron concentrate. The third magnetic material is discharged into the first concentrate sedimentation tank. Based on the specific magnetic susceptibility of iron oxide ore, the two medium-magnetic separation operations use a vertical ring high-gradient magnetic separator with a medium magnetic field strength under specific magnetic separation medium and specific pulsation conditions to effectively separate weakly magnetic iron oxide ore.

[0032] S4: Strong magnetic iron removal operation: The third non-magnetic material is fed into a vertical ring high-gradient magnetic separator for fourth-stage magnetic separation under a fourth magnetic field strength of 1.6–1.8T. The magnetic separation medium is a high-permeability stainless steel rod with a diameter of 0.5–2.5 mm, and the pulsation is set to 3–5 Hz. Under these specific magnetic separation conditions, a fourth magnetic material and a fourth non-magnetic material can be obtained. The fourth magnetic material is a low-quality mixed rough concentrate with a TFe grade of 36–40%, mainly consisting of intergrowths and fine-grained iron-bearing minerals. The fourth non-magnetic material is iron tailings with a TFe content of 10–12%, mainly composed of silicon. The minerals consist of sand, fine mud, and a small amount of intergrowth or fine-grained iron oxide. The strong magnetic separation operation utilizes the extremely weak magnetic properties of impurities such as iron, manganese, and chromium contained in the third non-magnetic material. A vertical ring high-gradient magnetic separator with a high magnetic field strength is selected under specific magnetic separation media and specific pulsation conditions to effectively separate iron-containing minerals. Furthermore, the magnetic separation intensity increases sequentially from weak magnetic separation to medium magnetic separation to strong magnetic separation, forming a staged, tiered magnetic separation operation. Each operation section adopts a scientifically and rationally combined configuration, enabling the sequential separation of various iron-containing minerals and ensuring the stability of beneficiation indicators and actual production.

[0033] S5: Tiered Operations: The fourth magnetic material is fed into a hydrocyclone for classification, yielding coarse products with a particle size of +0.10 mm and fine products with a particle size of -0.10 mm. The coarse product consists of iron-silicon intergrowths and is returned to step S1 for crushing and grinding to achieve individual liberation of iron minerals and silicate minerals. The classification process is precisely controlled with 0.10 mm as the critical classification particle size based on the differences in physicochemical properties of the embedded particle size, which is highly matched with the embedding characteristics of iron minerals and silicate gangues. The obtained +0.10 mm coarse product does not achieve sufficient individual liberation of iron minerals and is mostly iron-silicon intergrowths, so it must be returned for regrinding. The obtained -0.10 mm fine product has achieved sufficient liberation and can be directly entered into the subsequent high-intensity magnetic separation process.

[0034] S6: Strong magnetic separation operation: The fine-grained product is fed into a plate magnetic separator for the fifth stage of magnetic separation under a fifth magnetic field strength of 1.3–1.4T. Under these specific magnetic separation conditions, fifth magnetic and fifth non-magnetic materials can be obtained. The fifth magnetic material is iron oxide ore (fine-grained iron oxide) with a TFe content of 60–61%, meeting the quality standard of grade III iron concentrate, and is discharged into the first concentrate settling tank. The fifth non-magnetic material has a TFe content of 15–20% and is discharged into the tailings settling tank. The high-intensity magnetic separation of iron is based on the specific magnetic susceptibility of the fine-grained iron oxide in the fine-grained product and the embedding characteristics of the fine-grained iron oxide. A plate magnetic separator with a higher magnetic field strength is selected to efficiently recover this portion of fine-grained iron oxide, reduce metal loss, and improve the total iron recovery rate.

[0035] S7: Desliming operation: The fourth non-magnetic material is fed into a hydrocyclone for desliming, yielding medium-sized products (+0.015mm) and fine-sized products (-0.015mm). The medium-sized product mainly consists of silica sand and a small amount of iron oxide in the form of intergrowths and inclusions. The fine-sized product mainly consists of fine-grained iron oxide, ferrosilicon, silicates, and other minerals, which have no mineral processing value and are discharged into the tailings sedimentation pond. The desliming operation is based on the differences in mineral particle size and settling characteristics, with a strict critical desliming particle size of 0.015mm for precise classification. The -0.015mm fine-sized product is mostly composed of overly fine clay minerals (fine-grained clay), which are not only difficult to sort and have low recovery value, but also easily interfere with subsequent beneficiation operations and should be removed in advance. The +0.015mm medium-sized product retains the main valuable intergrowths and qualified silica sand components, which can be further recycled in subsequent strong magnetic purification operations, thereby improving the overall sorting efficiency and product purity.

[0036] S8: Strong magnetic purification operation: The medium-sized particles are fed into an electromagnetic slurry high-gradient magnetic separator for sixth-stage magnetic separation under a sixth magnetic field strength of 1.9–2.0T. The magnetic separation medium used is a 3×6mm rhomboid high-permeability stainless steel mesh. Under these specific magnetic separation conditions, sixth-stage magnetic and sixth-stage non-magnetic materials are obtained. The sixth-stage magnetic material consists of iron-containing impurities and iron-silicon intergrowths, and is discharged into the tailings sedimentation tank. The sixth-stage non-magnetic material contains 99.10–99.30% SiO2. Silica sand (granular silica sand), the sixth non-magnetic material, is discharged into the second concentrate sedimentation tank; the strong magnetic purification operation is based on the difference in specific magnetic susceptibility and embedding characteristics between the fine-grained iron-silicon intergrowths in the medium-grained product and the mottled and scattered iron oxide on the surface of silica sand and the silica sand. An electromagnetic slurry high-gradient magnetic separator with ultra-high magnetic field strength is selected. Under specific magnetic separation medium conditions, iron and silicon mineral impurities can be deeply removed, and high-purity silica sand can be retained to the maximum extent, so as to achieve efficient separation and purification of iron impurities and iron-silicon intergrowths from silica sand.

[0037] S9: Solid-liquid separation operation: The product in the first concentrate settling tank is subjected to solid-liquid separation using a plate and frame filter press. The separated solids are iron concentrate with a TFe content of 64-65%, meeting the quality standard for grade II iron concentrate. The product in the second concentrate settling tank is subjected to solid-liquid separation using a disc filter press. The separated solids are silica sand concentrate with a SiO2 content of 99.10-99.30% and a TFe content of 0.10-0.15%, meeting the quality standard for silica sand used in glass and chemical industries. The product in the tailings settling tank is subjected to solid-liquid separation using a plate and frame filter press. The separated solids are total tailings with a TFe content of 15-20% and a SiO2 content of 70-75%, which can be used as aggregate for concrete, brick making, and aerated concrete block raw materials. The separated tailings water can be returned to each working section for recycling after clarification.

[0038] Table 1. Beneficiation parameters for separating iron oxide and silica sand using a tiered magnetic separation process.

[0039] Addressing previous production technology and process issues, this ore processing plant employs a tiered magnetic separation process provided by this invention to separate iron oxide and silica sand. This process yields a high-quality iron concentrate with a TFe content of 64.35%, used as a premium raw material for iron and steel smelting; a high-quality silica sand concentrate with a SiO2 content of 99.28%, used as a raw material for glass and chemicals; and a mixed ferrosilicon tailings, used as a building material. The comprehensive mineral utilization rate reaches 100%, and the iron recovery rate is 10-15% higher than that of the conventional "grinding-weak magnetic separation-strong magnetic separation" ore processing process.

[0040] It should be noted that in this embodiment, each working section of the mineral processing adopts a green, environmentally friendly, and pollution-free physical mineral processing technology. The resulting iron concentrate, silica sand, building material raw materials, and other industrial products all generate industrial value. The filtered water produced by the solid-liquid separation operation can be returned to each working section for recycling after clarification, achieving zero discharge of tailings and tailings.

[0041] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for separating iron oxide and silica sand by stepwise magnetic separation, characterized in that, Includes the following steps: S1: Crushing and grinding operation: crushing and / or grinding the raw ore to obtain a fine product; S2: Weak magnetic separation operation: The fine product is subjected to the first stage of magnetic separation under the first magnetic field strength to obtain the first magnetic material and the first non-magnetic material. The first magnetic material is discharged into the first concentrate sedimentation tank. S3: Medium magnetic separation of iron: The first non-magnetic material is subjected to a second stage of magnetic separation under a second magnetic field strength to obtain a second magnetic material and a second non-magnetic material. The second magnetic material is discharged into the first concentrate sedimentation tank. The second non-magnetic material is subjected to a third-stage magnetic separation operation under a third magnetic field strength to obtain a third magnetic material and a third non-magnetic material. The third magnetic material is then discharged into the first concentrate sedimentation tank. S4: Strong magnetic iron removal operation: The third non-magnetic material is subjected to the fourth stage of magnetic separation under the fourth magnetic field strength to obtain the fourth magnetic material and the fourth non-magnetic material; S5: Grading operation: The fourth magnetic material is graded to obtain coarse and fine products. The coarse product is returned to the crushing and grinding operation in step S1. S6: Strong magnetic separation of iron: The fine-particle product is subjected to the fifth stage of magnetic separation under the fifth magnetic field strength to obtain the fifth magnetic material and the fifth non-magnetic material. The fifth magnetic material is discharged into the first concentrate sedimentation tank and the fifth non-magnetic material is discharged into the tailings sedimentation tank. S7: Desliming operation: The fourth non-magnetic material is deslimed to obtain medium-grained product and fine mud product, and the fine mud product is discharged into the tailings sedimentation tank. S8: Strong magnetic purification operation: The medium-particle product is subjected to a sixth-stage magnetic separation operation under a sixth magnetic field strength to obtain a sixth magnetic material and a sixth non-magnetic material. The sixth magnetic material is discharged into the tailings sedimentation tank and the sixth non-magnetic material is discharged into the second concentrate sedimentation tank. S9: Solid-liquid separation operation: The products in the first concentrate sedimentation tank, the second concentrate sedimentation tank, and the tailings sedimentation tank are subjected to solid-liquid separation operation respectively. The separated solids are iron concentrate, silica sand concentrate, and total tailings. The separated tailings water can be returned to each operation section for recycling after clarification.

2. The method for separating iron oxide and silica sand by stepwise magnetic separation according to claim 1, characterized in that, In step S1, the raw ore is crushed to a particle size of -12mm by a hammer crusher, mixed with a slurry concentration of 67%, and then ground by a ball mill. And / or, the fineness of the fine product is set to -0.074mm, accounting for 60-65%.

3. The method for separating iron oxide and silica sand by stepwise magnetic separation according to claim 2, characterized in that, In step S2, a drum magnetic separator is used to perform the first stage of magnetic separation, and the strength of the first magnetic field is set to 0.25 to 0.35T.

4. The method for separating iron oxide and silica sand by stepwise magnetic separation according to claim 3, characterized in that, In step S3, a vertical ring high gradient magnetic separator is used to perform the second stage magnetic separation operation and the third stage magnetic separation operation. The magnetic separation medium is a high permeability stainless steel rod with a diameter of Φ1~3mm, the pulsation is set to 20~25Hz, the second magnetic field strength is set to 0.65~0.75T, and the third magnetic field strength is set to 0.85~0.95T.

5. The method for separating iron oxide and silica sand by stepwise magnetic separation according to claim 4, characterized in that, In step S4, a vertical ring high gradient magnetic separator is used to perform the fourth stage of magnetic separation. The magnetic separation medium used is a high permeability stainless steel rod with a diameter of Φ0.5 to 2.5 mm, the pulsation is set to 3 to 5 Hz, and the strength of the fourth magnetic field is set to 1.6 to 1.8 T.

6. The method for separating iron oxide and silica sand by stepwise magnetic separation according to claim 5, characterized in that, In step S5, a hydrocyclone is used to perform the grading operation, with the particle size of the coarse product set to +0.10 mm and the particle size of the fine product set to -0.10 mm.

7. The method for separating iron oxide and silica sand by stepwise magnetic separation according to claim 6, characterized in that, In step S6, a plate magnetic separator is used to perform the fifth stage of magnetic separation, and the strength of the fifth magnetic field is set to 1.3 to 1.4 T.

8. The method for separating iron oxide and silica sand by stepwise magnetic separation according to claim 7, characterized in that, In step S7, a hydrocyclone is used to perform the desliming operation, the particle size of the medium-sized product is set to +0.015mm, and the particle size of the fine mud product is set to -0.015mm.

9. The method for separating iron oxide and silica sand by stepwise magnetic separation according to claim 8, characterized in that, In step S8, the sixth stage of magnetic separation is performed using an electromagnetic slurry high gradient magnetic separator. The magnetic separation medium used is a diamond-shaped high-permeability stainless steel mesh with a specification of 3×6mm, and the strength of the sixth magnetic field is set to 1.9~2.0T.

10. The method for separating iron oxide and silica sand by stepwise magnetic separation according to claim 9, characterized in that, In step S9, the product in the first concentrate sedimentation tank is separated into solid and liquid using a plate and frame filter press; the product in the second concentrate sedimentation tank is separated into solid and liquid using a disc filter press; and the product in the tailings sedimentation tank is separated into solid and liquid using a plate and frame filter press.

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