Method and application of recovering iron from iron ore tailings

Abstract

The present invention discloses a method for recovering iron from iron ore tailings and its use. The method for recovering iron from iron ore tailings comprises the following steps: 1) screening the iron ore tailings and grinding them; 2) combining the 400-mesh particle size product and the grinding product, and performing weak magnetic separation to obtain weak magnetic separation concentrate and weak magnetic separation tailings; wherein the weak magnetic separation concentrate is magnetic iron concentrate; 3) performing strong magnetic separation on the weak magnetic separation tailings to obtain strong magnetic separation concentrate and strong magnetic separation tailings; 4) mixing the strong magnetic separation concentrate with a composition and pressing the mixture into pellets to obtain pellets; wherein the composition is a mixture of carbon material, slaked lime, and carboxymethyl cellulose; 5) roasting the pellets to obtain a roasted product; 6) grinding the roasted product to obtain a reground product; and performing weak magnetic separation on the reground product to obtain reduced iron. The method of the present invention can respectively obtain magnetic iron concentrate and reduced iron product with higher iron grade.

Description

Technical Field

[0001] The present invention relates to a method for recovering iron from iron-separation tailings and its application, and in particular to a method for recovering iron from fine-grained iron-separation tailings and its application. Background Art

[0002] The Bayan Obo mine is a large, multi-metallic ore deposit containing co-existing iron, rare earth elements, niobium, fluorite, and other metals. The ore features fine-grained intergrowths between minerals, a high content of inclusions, and a high concentration of minerals with similar floatability. To obtain high-quality iron concentrate, reverse flotation is typically used to remove fine-grained iron-containing intergrowths and inclusions. The resulting reverse flotation tailings (i.e., iron-separated tailings) still have a relatively high iron grade. However, due to the fine intergrowths, conventional beneficiation methods cannot effectively separate the various minerals in the iron-separated tailings. Currently, the process is primarily stockpiled, resulting in a waste of resources and environmental pollution. The comprehensive utilization of these iron-separated tailings, improving the utilization rate of mineral resources, would be of great practical significance to the sustainable development of mining companies.

[0003] CN104195328A discloses a method for producing iron oxide ore reduction roasting green balls using iron ore dressing tailings, which mainly includes the following process steps: (1) crushing and grinding weakly magnetic iron oxide ore, and pre-discarding some qualified tailings through strong magnetic separation to obtain a coarse concentrate product of iron oxide ore; (2) grading the qualified tailings in step (1) to obtain a fine-grained tailings product; (3) adding fine-grained tailings equivalent to 2-8% of the mass of the coarse concentrate and 1-5% of coal powder to the coarse concentrate, and then mixing the materials; (4) adding water to the mixed materials to form balls, and then roasting them at 550-700°C, and magnetic separation after roasting to obtain an iron concentrate with a grade of 56-60%. The iron grade of the iron concentrate obtained by this method still needs to be improved.

[0004] CN112791847A discloses a method for separating and recovering iron, rare earths, and fluorine from rare earth-containing iron ore tailings. The method involves mixing the rare earth-containing iron ore tailings, additives, and coal powder, briquetting or pelletizing, roasting, and ball milling to produce magnetically separated iron concentrate and tailings. The magnetically separated tailings are then further processed to produce rare earth chloride leachate, calcium fluoride concentrate, and the like. The additives used in this method are one or more of calcium oxide powder, dolomite powder, limestone powder, and calcium carbonate powder. The magnetically separated iron concentrate obtained in this method contains reduced iron products, which hinders subsequent separation.

[0005] CN118002306A discloses a method for cascade recovery of valuable components in low-grade weakly magnetic iron ore resources, comprising the following steps: (1) crushing and screening the low-grade weakly magnetic iron ore to obtain coarse-grained ore and fine-grained ore of preset particle size; (2) pre-enriching the coarse-grained ore and fine-grained ore obtained in step (1), wherein the coarse-grained ore is dry-sorted to obtain dry-sorted coarse concentrate and dry-sorted tailings; and the fine-grained ore is wet-strong magnetically separated to obtain wet-strong magnetic tailings. The method comprises the following steps: (1) selecting a coarse concentrate and a wet-selection tailing; (2) concentrating and filtering the wet-selection coarse concentrate obtained in step (2); combining the wet-selection coarse concentrate with the dry-selection coarse concentrate and then dry-pulverizing the resulting coarse concentrate to obtain a powdery material; (4) magnetizing and roasting the powdery material obtained in step (3) to obtain a roasted ore; and (5) subjecting the roasted ore obtained in step (4) to stage grinding and stage separation to obtain an iron concentrate and an iron-selection tailing. The iron-selection tailing and the wet-selection pre-enriched fine tailing are concentrated and then subjected to cascade recovery of valuable components. The iron concentrate obtained by this method has a TFe grade of less than or equal to 62%, and there is still room for improvement. Summary of the Invention

[0006] One object of the present invention is to provide a method for recovering iron from iron ore tailings. The method of the present invention can produce magnetically separated iron concentrate and reduced iron, respectively, and the iron grade of the magnetically separated iron concentrate and reduced iron obtained is relatively high. Another object of the present invention is to provide a composition for use in treating iron ore tailings to increase the iron grade of the resulting reduced iron.

[0007] The purpose of the present invention is achieved through the following technical solutions.

[0008] In one aspect, the present invention provides a method for recovering iron from iron ore tailings, comprising the following steps:

[0009] 1) Screening the iron ore tailings to obtain a -400 mesh particle size product; grinding the -200 mesh to +400 mesh particle size product to obtain a ground product; wherein the mass percentage of particles with a grinding fineness of -400 mesh in the ground product is greater than or equal to 90%;

[0010] 2) combining the -400 mesh particle size product and the grinding product, and performing weak magnetic separation at a magnetic separation intensity of less than or equal to 0.3 T to obtain weak magnetic separation concentrate and weak magnetic separation tailings; wherein the weak magnetic separation concentrate is the magnetic separation iron concentrate;

[0011] 3) subjecting the weak magnetic separation tailings to strong magnetic separation at a magnetic separation intensity of 0.5 T or more to obtain strong magnetic separation concentrate and strong magnetic separation tailings;

[0012] 4) mixing the high-intensity magnetic separation concentrate with the composition and pressing the mixture into balls to obtain balls; wherein the composition is a mixture of a carbon material, slaked lime and carboxymethyl cellulose, the carbon material is selected from one or more of bituminous coal, activated carbon, lignite and anthracite, the mass ratio of the sum of the mass of the slaked lime and the carboxymethyl cellulose to the carbon material is (0.05-0.1):(0.25-0.35); the mass ratio of the slaked lime to the carboxymethyl cellulose is 1-4:1, and the mass ratio of the high-intensity magnetic separation concentrate to the composition is 1:0.3-1.35;

[0013] 5) calcining the spherical object at 1300-1600° C. to obtain a calcined product;

[0014] 6) Grinding the roasted product to obtain a reground product; and subjecting the reground product to weak magnetic separation at a magnetic separation intensity of less than or equal to 0.3 T to obtain reduced iron.

[0015] According to the method of the present invention, preferably:

[0016] In the iron ore tailings, the TFe grade is greater than or equal to 30wt%, the sum of the contents of magnetite and hematite is greater than or equal to 76wt%, and the content of magnetite is greater than or equal to the content of hematite;

[0017] In the iron-separation tailings, the mass percentage of particles with a particle size of -200 mesh is greater than or equal to 90%.

[0018] According to the method described in the present invention, preferably, in step 2), the weak magnetic separation includes a roughing separation and a fine separation; in the roughing separation, the magnetic separation intensity is 0.15 to 0.3 T, and the pulp concentration is 15 to 40 wt%; in the fine separation, the magnetic separation intensity is 0.1 to 0.2 T, and the pulp concentration is 15 to 30 wt%.

[0019] According to the method of the present invention, preferably, in step 3), the magnetic separation intensity of the strong magnetic separation is 0.5-1.2 T, and the concentration of the magnetic separation pulp is 10-25 wt%.

[0020] According to the method of the present invention, preferably, in step 4), the mass ratio of the high-intensity magnetic separation concentrate to the composition is 1:0.3-0.85.

[0021] According to the method of the present invention, preferably, in step 4), the mass ratio of slaked lime to carboxymethyl cellulose is 1 to 3:1.

[0022] According to the method of the present invention, preferably, in step 5), the roasting time is 1 to 4 hours.

[0023] According to the method of the present invention, preferably, in step 6), the mass percentage of particles with a grinding fineness of -200 mesh in the re-grinded product is greater than 90%.

[0024] According to the method of the present invention, preferably, in step 6), the magnetic separation intensity is 0.12 to 0.2 T, and the magnetic separation pulp concentration is 10 to 25 wt%.

[0025] On the other hand, the present invention also provides a use of a composition in treating iron ore tailings to improve the iron grade of the resulting reduced iron, wherein the composition is a mixture of carbon material, slaked lime and carboxymethyl cellulose, wherein the carbon material is selected from one or more of bituminous coal, activated carbon, lignite and anthracite, and the mass ratio of the sum of the mass of slaked lime and carboxymethyl cellulose to the mass of the carbon material is (0.05-0.1): (0.25-0.35); the mass ratio of slaked lime to carboxymethyl cellulose is 1-4:1; and the use includes the steps as described above.

[0026] The method of the present invention can respectively recover magnetic iron concentrate and reduced iron product from iron-selected tailings, and the iron grade of the obtained magnetic iron concentrate and reduced iron is high. The iron grade of the magnetic iron concentrate is greater than or equal to 65wt%, and the iron grade of the reduced iron is greater than or equal to 90wt%. According to the preferred technical solution of the present invention, the iron-selected tailings are screened and ground to obtain a -400 mesh particle size product, and then weak magnetic separation is performed under specific conditions to obtain a magnetic iron concentrate with a higher iron grade. The weak magnetic tailings obtained by weak magnetic separation are then subjected to strong magnetic separation, mixed with a specific composition and pelletized, roasted, ground, and then weak magnetic separation is performed to obtain a reduced iron product with a higher iron grade. The method of the present invention can improve resource utilization. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0028] method

[0029] The present invention provides a method for recovering iron from iron ore tailings, comprising the following steps: 1) screening and grinding the iron ore tailings; 2) weak magnetic separation; 3) high-intensity magnetic separation; 4) adding a composition and pelletizing; 5) roasting; and 6) obtaining a reduced iron product. Optionally, the method further includes pre-drying the iron ore tailings. This is described in detail below.

[0030] Drying step

[0031] Drying the iron ore tailings. In certain embodiments, the iron ore tailings can be dried naturally. This facilitates subsequent processing.

[0032] In the present invention, the iron-separation tailings are reverse flotation tailings obtained after the fine iron-containing intergrowths and inclusions are removed through a reverse flotation process.

[0033] In the present invention, the TFe grade of the iron ore tailings is 30 wt% or more, preferably 30 to 40 wt%, and more preferably 33 to 40 wt%.

[0034] In the present invention, the main useful minerals in the iron ore tailings are magnetite and hematite. In the iron ore tailings, the sum of the contents of magnetite and hematite is greater than or equal to 76wt%. Preferably, the sum of the mass of magnetite and hematite accounts for 76-90wt% of the mass of the iron ore tailings, more preferably 79-89wt%, and more preferably 80-88wt%. In the iron ore tailings, the content of magnetite is greater than or equal to the content of hematite. Preferably, the mass ratio of magnetite to hematite is 5-8:3-5, more preferably 5.2-7.8:3.2-4.8, and more preferably 5.5-7.6:3.4-4.5.

[0035] In the present invention, the iron ore tailings also contain sulfur, phosphorus, and fluorine. The sulfur content can be 0.6 to 2.2 wt%, preferably 0.7 to 1.8 wt%, and more preferably 0.8 to 1.5 wt%. The phosphorus content can be 0.8 to 3.5 wt%, preferably 1.0 to 2.5 wt%, and more preferably 1.0 to 2.0 wt%. The fluorine content can be 4.5 to 8.5 wt%, preferably 5.0 to 8.0 wt%, and more preferably 5.3 to 7.8 wt%. Conventional magnetic separation methods cannot effectively separate such iron ore tailings into magnetically separated iron concentrate, let alone reduced iron products.

[0036] In the iron ore tailings, the mass percentage of particles with a particle size of -200 mesh is greater than or equal to 90%, preferably greater than or equal to 95%; the mass percentage of particles with a particle size of -400 mesh is greater than 60%, preferably greater than or equal to 64%.

[0037] In the present invention, the mass percentage of the iron ore tailings particles having a particle size of -200 mesh being greater than or equal to 90% has the same meaning as the mass percentage of the iron ore tailings particles having a particle size of -200 mesh accounting for more than 90%.

[0038] Screening and grinding steps of iron ore tailings

[0039] The iron ore tailings are screened to obtain a -400 mesh fraction. The -200 to +400 mesh fraction is then ground to produce a ground product. The mass percentage of the ground product with a -400 mesh fineness is greater than or equal to 90%. This facilitates magnetic separation. The iron in the iron ore tailings is extremely finely embedded, and the iron minerals are intertwined with gangue minerals containing harmful elements such as sulfur, phosphorus, and fluorine. This makes it difficult to obtain a high-grade magnetic iron concentrate using simple magnetic separation methods.

[0040] In the present invention, -400 mesh refers to a particle size of less than or equal to 400 mesh. Similarly, -200 mesh refers to a particle size of less than or equal to 200 mesh. +400 mesh refers to a particle size of greater than or equal to 400 mesh.

[0041] According to one embodiment of the present invention, the air-dried iron ore tailings are sieved with a 200-mesh sieve to obtain a -200-mesh particle size product and a +200-mesh particle size product. The -200-mesh particle size product is sieved with a 400-mesh sieve to obtain a -200-mesh to +400-mesh particle size product and a -400-mesh particle size product. The +200-mesh particle size product is directly discharged into the final tailings. The -200-mesh to +400-mesh particle size product is ground to obtain a ground product; in the ground product, the mass percentage of particles with a grinding fineness of -400 mesh is greater than or equal to 90%.

[0042] In this step, the +200 mesh size products are mainly silicates and iron-containing silicate gangue minerals, which are directly discharged into the final tailings.

[0043] In this step, a vertical mill is used for grinding. The grinding concentration during grinding is 50-75 wt %, preferably 55-72 wt %, and more preferably 55-70 wt %. The ground product comprises particles with a grinding fineness of -400 mesh accounting for at least 90%, i.e., the mass percentage of particles with a grinding fineness of -400 mesh is greater than or equal to 90%, preferably greater than or equal to 92%, and more preferably greater than or equal to 94%.

[0044] Weak magnetic separation steps

[0045] The -400 mesh particle size product and the grinding product are combined and subjected to weak magnetic separation at a magnetic separation intensity of 0.3T or less to obtain weak magnetic separation concentrate and weak magnetic separation tailings; wherein the weak magnetic separation concentrate is magnetic separation iron concentrate. In this way, magnetic separation iron concentrate can be obtained, the main component of which is ferroferric oxide.

[0046] In this step, weak magnetic separation includes a roughing separation and a fine separation.

[0047] In the primary roughing, the magnetic separation intensity may be 0.15 to 0.3 T, preferably 0.15 to 0.25 T, more preferably 0.15 to 0.2 T. The slurry concentration may be 15 to 40 wt%, preferably 20 to 35 wt%, more preferably 20 to 30 wt%.

[0048] In the primary concentration, the magnetic separation intensity may be 0.1 to 0.2 T, preferably 0.12 to 0.18 T, more preferably 0.14 to 0.18 T. The slurry concentration may be 15 to 30 wt%, preferably 16 to 25 wt%, more preferably 17 to 22 wt%.

[0049] The resulting magnetically separated iron concentrate (i.e., weak magnetic separation concentrate) has an iron grade of 65% by weight or greater, preferably greater than 65% by weight. The iron recovery rate of the magnetically separated iron concentrate is 40% to 50%, for example, 41% to 48%. The iron recovery rate of the magnetically separated iron concentrate is calculated as follows: iron content in the magnetically separated iron concentrate / iron content in the iron separation tailings × 100%.

[0050] The weak magnetic separation tailings are further processed to obtain reduced iron products. The method of the present invention can respectively obtain magnetic separation iron concentrate and reduced iron products, and the iron grade of the obtained magnetic separation iron concentrate and reduced iron products is high.

[0051] Strong magnetic separation steps

[0052] The weak magnetic separation tailings are subjected to strong magnetic separation at a magnetic separation intensity of 0.5 T or higher to obtain strong magnetic separation concentrate and strong magnetic separation tailings. This is beneficial to improving the iron grade of the final reduced iron product.

[0053] In the present invention, the magnetic separation intensity of the high-intensity magnetic separation can be 0.5 to 1.2 T, preferably 0.5 to 0.85 T, more preferably 0.60 to 0.85 T, and even more preferably 0.65 to 0.80 T. The concentration of the magnetic separation slurry can be 10 to 25 wt%, preferably 12 to 20 wt%, and more preferably 13 to 18 wt%. The pulse frequency can be 15 to 30 Hz, preferably 18 to 28 Hz, and more preferably 15 to 25 Hz.

[0054] Adding composition and pressing into balls

[0055] The high-intensity magnetic separation concentrate is mixed with a composition and pressed into pellets to obtain pellets; wherein the composition is a mixture of carbon material, slaked lime, and carboxymethyl cellulose, the carbon material being selected from one or more of bituminous coal, activated carbon, lignite, and anthracite, the mass ratio of the sum of the mass of slaked lime and carboxymethyl cellulose to the mass of the carbon material being (0.05-0.1):(0.25-0.35); the mass ratio of slaked lime to carboxymethyl cellulose being 1-4:1, and the mass ratio of the high-intensity magnetic separation concentrate to the composition being 1:0.3-1.35. This is conducive to obtaining a reduced iron product with a higher iron grade.

[0056] In the present invention, the carbon material may be selected from one or more of bituminous coal, activated carbon, lignite and anthracite.

[0057] According to one embodiment of the present invention, the carbon material is anthracite. According to another embodiment of the present invention, the carbon material comprises activated carbon, lignite, and anthracite in a mass ratio of 1:2-3:2-3. According to another embodiment of the present invention, the carbon material comprises bituminous coal and activated carbon in a mass ratio of 1-1.5:1.

[0058] In the present invention, slaked lime is calcium hydroxide, also known as slaked lime. The present invention has found that the iron grade of the obtained reduced iron product can be better improved by using slaked lime in combination with carboxymethyl cellulose and carbon material.

[0059] The mass ratio of slaked lime to carboxymethyl cellulose can be 1 to 4:1, preferably 1 to 3:1. According to one embodiment of the present invention, the mass ratio of slaked lime to carboxymethyl cellulose is 1:1. According to another embodiment of the present invention, the mass ratio of slaked lime to carboxymethyl cellulose is 2:1. According to yet another embodiment of the present invention, the mass ratio of slaked lime to carboxymethyl cellulose is 3:1.

[0060] The mass ratio of the sum of the mass of slaked lime and carboxymethyl cellulose to the mass of the carbon material is (0.05-0.1):(0.25-0.35), preferably (0.05-0.09):(0.25-0.35), and more preferably (0.05-0.08):(0.25-0.35).

[0061] The mass ratio of the high-intensity magnetic separation concentrate to the composition can be 1:0.3-1.35, preferably 1:0.3-1.1, more preferably 1:0.3-0.85, and even more preferably 1:0.33-0.55.

[0062] In the present invention, the high-intensity magnetic separation concentrate and the composite are uniformly mixed and then pressed into pellets to obtain pellets. The pellets have a particle size of 1 to 2 cm. This helps maintain a reducing atmosphere and improves the grade of reduced iron.

[0063] Calcination steps

[0064] The spherical material is roasted at 1300-1600°C to obtain a roasted product, which is conducive to obtaining a reduced iron product with a higher iron grade.

[0065] The roasting temperature can be 1300-1600°C, preferably 1300-1550°C, more preferably 1300-1500°C, for example 1300°C, 1350°C, 1400°C, 1450°C, 1500°C. The roasting time can be 1-4 hours, preferably 1-3 hours, more preferably 1-2 hours. The present invention has found that if the roasting temperature and roasting time are not within the roasting temperature range of the present invention, the iron grade of the reduced iron product will be reduced and the output will also be reduced. Such roasting temperature and roasting time can promote the growth of fine iron mineral particles to facilitate subsequent magnetic separation, and can also remove some harmful elements.

[0066] Steps to obtain reduced iron products

[0067] The roasted product is ground to obtain a reground product; the reground product is subjected to weak magnetic separation at a magnetic separation intensity of less than or equal to 0.3T to obtain reduced iron.

[0068] When grinding the calcined product, a rod mill can be used. The grinding concentration can be 55-70 wt%, preferably 58-68 wt%, and more preferably 60-67 wt%. The mass percentage of particles with a grinding fineness of -200 mesh in the reground product is greater than 90%, preferably greater than or equal to 91%, and can reach greater than or equal to 94%. This facilitates the subsequent magnetic separation.

[0069] The reground ore product is subjected to weak magnetic separation at a magnetic separation intensity of less than or equal to 0.3 T, wherein the magnetic separation intensity is less than or equal to 0.3 T, preferably 0.12-0.2 T, and more preferably 0.15-0.18 T. The concentration of the magnetic separation slurry can be 10-25 wt%, preferably 15-22 wt%, and more preferably 15-20 wt%.

[0070] The resulting reduced iron product is primarily elemental iron, with an iron grade of 90% or higher, and can reach over 92%. The iron recovery rate is 35-40%. The iron recovery rate is calculated as: iron content in the reduced iron / iron content in the iron-separation tailings × 100%.

[0071] In the present invention, the total recovery rate of iron is greater than 80%.Total recovery rate of iron = (amount of iron in magnetic iron concentrate + amount of iron in reduced iron) / amount of iron in iron tailings × 100%.

[0072] use

[0073] The present invention also provides a use of the composition in treating iron ore tailings to improve the iron grade of the obtained reduced iron. The present invention has found that such a composition is beneficial to improving the iron grade of the obtained reduced iron.

[0074] In the present invention, the composition is a mixture of carbon material, slaked lime and carboxymethyl cellulose, the carbon material is selected from one or more of bituminous coal, activated carbon, lignite and anthracite, the mass ratio of the sum of the mass of slaked lime and carboxymethyl cellulose to the carbon material is (0.05-0.1):(0.25-0.35); the mass ratio of slaked lime to carboxymethyl cellulose is 1-4:1; the use comprises the following steps:

[0075] 1) Screening the iron ore tailings to obtain a -400 mesh particle size product; grinding the -200 mesh to +400 mesh particle size product to obtain a ground product; wherein the mass percentage of particles with a grinding fineness of -400 mesh in the ground product is greater than 90%;

[0076] 2) combining the -400 mesh particle size product and the grinding product, and performing weak magnetic separation at a magnetic separation intensity of less than or equal to 0.3 T to obtain weak magnetic separation concentrate and weak magnetic separation tailings; wherein the weak magnetic separation concentrate is the magnetic separation iron concentrate;

[0077] 3) subjecting the weak magnetic separation tailings to strong magnetic separation at a magnetic separation intensity greater than or equal to 0.4 T to obtain strong magnetic separation concentrate and strong magnetic separation tailings;

[0078] 4) mixing the high-intensity magnetic separation concentrate and the composition and pressing the mixture into balls to obtain balls; wherein the mass ratio of the high-intensity magnetic separation concentrate to the composition is 1:0.3-1.35;

[0079] 5) calcining the spherical object at 1300-1600° C. to obtain a calcined product;

[0080] 6) Grinding the roasted product to obtain a reground product; and subjecting the reground product to weak magnetic separation at a magnetic separation intensity of less than or equal to 0.3 T to obtain reduced iron.

[0081] The detailed description is mentioned above and will not be repeated here.

[0082] The test method is described as follows:

[0083] TFe content: tested according to the method described in national standard GB / T 6730.5-2022.

[0084] In the following examples, unless otherwise specified, the content "%" is the mass percentage. The concentration "%" is the mass percentage.

[0085] Example 1

[0086] The iron ore tailings from Baotou Steel's concentrator contain a TFe grade of 36.52%, a sulfur content of 1.02%, a phosphorus content of 1.34%, and a fluorine content of 6.58%. The main useful minerals are magnetite and hematite, which together account for 84.19% of the total weight of the tailings. The mass ratio of magnetite to hematite is 6.6:4.2. The mass percentage of particles with a -200 mesh size is 96.37%, and the mass percentage of particles with a -400 mesh size is 66.53%.

[0087] The iron ore tailings are air-dried; the air-dried tailings are sieved through a 200-mesh sieve to obtain a -200-mesh particle size product and a +200-mesh particle size product. The -200-mesh particle size product is sieved through a 400-mesh sieve to obtain a -200- to +400-mesh particle size product and a -400-mesh particle size product. The +200-mesh particle size product is directly discharged into the final tailings. The -200- to +400-mesh particle size product is ground in a vertical mill at a grinding concentration of 58% to obtain a ground product; the mass percentage of particles with a grinding fineness of -400 mesh in the ground product is 97.50%.

[0088] The -400 mesh fraction and the grinding product obtained above were combined and then subjected to weak magnetic separation using a belt magnetic separator, specifically including a primary roughing and a primary concentrating process, to produce a weak magnetic separation concentrate (i.e., magnetically separated iron concentrate) and weak magnetic separation tailings. During the primary roughing process, the magnetic separation intensity was 0.22T and the pulp concentration was 28%. During the primary concentrating process, the magnetic separation intensity was 0.14T and the pulp concentration was 20%.

[0089] The weak magnetic separation tailings were subjected to strong magnetic separation at a magnetic separation intensity of 0.8 T, a magnetic separation concentration of 15%, and a pulse of 25 Hz to obtain strong magnetic separation concentrate and strong magnetic separation tailings.

[0090] The high-intensity magnetic separation concentrate and a composition (comprising a carbon material, slaked lime, and carboxymethyl cellulose) are uniformly mixed and then pressed into pellets, resulting in approximately 1 cm spheres. The mass ratio of the high-intensity magnetic separation concentrate to the composition is 1:0.35. The mass ratio of the high-intensity magnetic separation concentrate to the carbon material is 1:0.28. The carbon material is composed of activated carbon, lignite, and anthracite in a mass ratio of 1:2:2. The mass ratio of slaked lime to carboxymethyl cellulose is 1:1.

[0091] The spherical object was placed in a graphite crucible, and the crucible was placed in a muffle furnace and calcined at 1500°C for 1 hour. After the calcination, the crucible was taken out and water quenched to obtain a calcined product.

[0092] The roasted product was ground in a rod mill at a grinding concentration of 65% to obtain a reground product, wherein the mass percentage of particles with a grinding fineness of -200 mesh was 91.36%.

[0093] The reground ore product was subjected to weak magnetic separation at a magnetic separation pulp concentration of 15% and a magnetic separation intensity of 0.18T to obtain reduced iron products and magnetic separation tailings.

[0094] The iron grade of the magnetically separated iron concentrate obtained in this embodiment is 66.03%, and the iron recovery rate of the magnetically separated iron concentrate is 43.72%. The iron grade of the reduced iron product obtained in this embodiment is 91.37%, and the iron recovery rate of the reduced iron product is 38.75%.

[0095] The total recovery of iron was 82.45%.

[0096] Example 2

[0097] We provide iron ore tailings from the Baiyun Ore Dressing Branch of Baoshan Mining. The tailings have a TFe grade of 39.44%, a sulfur content of 0.89%, a phosphorus content of 1.16%, and a fluorine content of 5.93%. The main useful minerals are magnetite and hematite, which together account for 86.53% of the tailings' mass. The mass ratio of magnetite to hematite is 7.5:3.4. The tailings contain 98.18% by mass of particles with a -200 mesh size, and 64.57% by mass of particles with a -400 mesh size.

[0098] The iron ore tailings are air-dried; the air-dried tailings are sieved through a 200-mesh sieve to obtain a -200-mesh particle size product and a +200-mesh particle size product. The -200-mesh particle size product is sieved through a 400-mesh sieve to obtain a -200- to +400-mesh particle size product and a -400-mesh particle size product. The +200-mesh particle size product is directly discharged into the final tailings. The -200- to +400-mesh particle size product is ground in a vertical mill at a grinding concentration of 63% to obtain a ground product; the mass percentage of particles with a grinding fineness of -400 mesh in the ground product is 95.24%.

[0099] The -400 mesh fraction and the grinding product obtained above were combined and then subjected to weak magnetic separation using a belt magnetic separator, specifically including a primary roughing and a primary concentrating process, to produce a weak magnetic separation concentrate (i.e., magnetically separated iron concentrate) and weak magnetic separation tailings. During the primary roughing process, the magnetic separation intensity was 0.2T and the pulp concentration was 25%. During the primary concentrating process, the magnetic separation intensity was 0.15T and the pulp concentration was 22%.

[0100] The weak magnetic separation tailings were subjected to strong magnetic separation at a magnetic separation intensity of 0.65T, a magnetic separation concentration of 13%, and a pulse of 20Hz to obtain strong magnetic separation concentrate and strong magnetic separation tailings.

[0101] The high-intensity magnetic separation concentrate and a composition (comprising a carbon material, slaked lime, and carboxymethyl cellulose) were uniformly mixed and then pressed into pellets, resulting in pellets with a particle size of approximately 1.5 cm. The mass ratio of the high-intensity magnetic separation concentrate to the composition was 1:0.33. The mass ratio of the high-intensity magnetic separation concentrate to the carbon material was 1:0.25. The carbon material consisted of bituminous coal and activated carbon in a mass ratio of 1:1. The mass ratio of slaked lime to carboxymethyl cellulose was 3:1.

[0102] The spherical object was placed in a graphite crucible, and the crucible was placed in a muffle furnace and calcined at 1450° C. for 1.5 h. After the calcination, the crucible was taken out and water quenched to obtain a calcined product.

[0103] The roasted product was ground in a rod mill at a grinding concentration of 60% to obtain a reground product, wherein the mass percentage of particles with a grinding fineness of -200 mesh was 94.31%.

[0104] The reground ore product was subjected to weak magnetic separation at a magnetic separation pulp concentration of 18% and a magnetic separation intensity of 0.16T to obtain reduced iron products and magnetic separation tailings.

[0105] The iron grade of the magnetically separated iron concentrate obtained in this embodiment is 65.93%, and the iron recovery rate of the magnetically separated iron concentrate is 47.73%. The iron grade of the reduced iron product obtained in this embodiment is 92.11%, and the iron recovery rate of the reduced iron product is 35.41%.

[0106] The total recovery of iron was 83.14%.

[0107] Example 3

[0108] Baosteel Walter's iron ore tailings contain a TFe grade of 33.61%, a sulfur content of 1.15%, a phosphorus content of 1.62%, and a fluorine content of 7.34%. The main useful minerals are magnetite and hematite, which together account for 80.19% of the tailings' mass, with a magnetite-to-hematite ratio of 5.5:4.5. The tailings contain 95.72% by mass of particles with a -200 mesh size, and 64.59% by mass of particles with a -400 mesh size.

[0109] The iron ore tailings are air-dried; the air-dried tailings are sieved through a 200-mesh sieve to obtain a -200-mesh particle size product and a +200-mesh particle size product. The -200-mesh particle size product is sieved through a 400-mesh sieve to obtain a -200- to +400-mesh particle size product and a -400-mesh particle size product. The +200-mesh particle size product is directly discharged into the final tailings. The -200- to +400-mesh particle size product is ground in a vertical mill at a grinding concentration of 70% to obtain a ground product; the mass percentage of particles with a grinding fineness of -400 mesh in the ground product is 94.98%.

[0110] The -400 mesh fraction and the grinding product obtained above were combined and then subjected to weak magnetic separation using a belt magnetic separator, specifically including a primary roughing and a primary concentrating process, to produce a weak magnetic separation concentrate (i.e., magnetically separated iron concentrate) and weak magnetic separation tailings. During the primary roughing process, the magnetic separation intensity was 0.25T and the pulp concentration was 20%. During the primary concentrating process, the magnetic separation intensity was 0.16T and the pulp concentration was 18%.

[0111] The weak magnetic separation tailings were subjected to strong magnetic separation at a magnetic separation intensity of 0.75T, a magnetic separation concentration of 13%, and a pulse of 18Hz to obtain strong magnetic separation concentrate and strong magnetic separation tailings.

[0112] The high-intensity magnetic separation concentrate and a composition (consisting of a carbon material, slaked lime, and carboxymethyl cellulose) are uniformly mixed and then pressed into pellets to produce pellets with a particle size of approximately 1 cm. The mass ratio of the high-intensity magnetic separation concentrate to the composition is 1:0.40. The mass ratio of the high-intensity magnetic separation concentrate to the carbon material is 1:0.35. The carbon material is anthracite. The mass ratio of slaked lime to carboxymethyl cellulose is 2:1.

[0113] The spherical object was placed in a graphite crucible, and the crucible was placed in a muffle furnace and calcined at 1300°C for 2 hours. After the calcination, the crucible was taken out and water quenched to obtain a calcined product.

[0114] The roasted product was ground in a rod mill at a grinding concentration of 62.5% to obtain a reground product, wherein the mass percentage of particles with a grinding fineness of -200 mesh was 93.88%.

[0115] The reground ore product was subjected to weak magnetic separation at a magnetic separation pulp concentration of 20% and a magnetic separation intensity of 0.15T to obtain reduced iron products and magnetic separation tailings.

[0116] The iron grade of the magnetically separated iron concentrate obtained in this embodiment is 65.06%, and the iron recovery rate of the magnetically separated iron concentrate is 41.41%. The iron grade of the reduced iron product obtained in this embodiment is 90.48%, and the iron recovery rate of the reduced iron product is 39.51%.

[0117] The total recovery rate of iron was 80.92%.

[0118] Comparative Example 1

[0119] The only difference from Example 1 is that slaked lime and carboxymethyl cellulose are replaced by bentonite.

[0120] Comparative Example 2

[0121] The only difference from Example 1 is that the calcination temperature is 1200°C.

[0122] Table 1

[0123]

[0124] As can be seen from the table, the method of the present invention can recover magnetically separated iron concentrate and reduced iron from the iron ore tailings, wherein the iron grade of the magnetically separated iron concentrate can reach above 65 wt%, and the iron grade of the reduced iron can reach above 90 wt%. Comparing Example 1 of the present invention with Comparative Examples 1 and 2, it can be seen that the iron recovery rate and iron grade of the reduced iron of the present invention are significantly improved.

[0125] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A method for recovering magnetically separated iron concentrate and obtaining reduced iron from iron ore tailings, characterized in that: The following steps are involved: 1) Screening the iron ore tailings to obtain a -400 mesh particle size product; and grinding the particle size product of -200 mesh to +400 mesh to obtain a grinding product; In the grinding product, the mass percentage of particles with a grinding fineness of -400 mesh is greater than or equal to 90%; Wherein, in the iron ore tailings, the TFe grade is greater than or equal to 30wt% and less than 40wt%, the sum of the contents of magnetite and hematite is greater than or equal to 76wt%, and the content of magnetite is greater than or equal to the content of hematite; 2) combining the -400 mesh particle size product and the grinding product, and performing weak magnetic separation to obtain weak magnetic separation concentrate and weak magnetic separation tailings; wherein the weak magnetic separation includes a primary roughing separation and a primary cleaning separation; in the primary roughing separation, the magnetic separation intensity is 0.2 to 0.25 T, and the slurry concentration is 15 to 30 wt%; in the primary cleaning separation, the magnetic separation intensity is 0.1 to 0.18 T, and the slurry concentration is 15 to 25 wt%; Wherein, the weak magnetic separation concentrate is magnetic separation iron concentrate; the main component of the magnetic separation iron concentrate is ferroferric oxide; the iron grade of the magnetic separation iron concentrate is greater than or equal to 65wt%; 3) subjecting the weak magnetic separation tailings to strong magnetic separation at a magnetic separation intensity of 0.5 to 1.2 T and a magnetic separation slurry concentration of 10 to 25 wt% to obtain strong magnetic separation concentrate and strong magnetic separation tailings; 4) mixing the high-intensity magnetic separation concentrate with the composition and pressing the mixture into balls to obtain balls; wherein the composition is a mixture of a carbon material, slaked lime and carboxymethyl cellulose, the carbon material is selected from one or more of bituminous coal, activated carbon, lignite and anthracite, the mass ratio of the sum of the mass of the slaked lime and the carboxymethyl cellulose to the carbon material is (0.05-0.08):(0.25-0.35); the mass ratio of the slaked lime to the carboxymethyl cellulose is 1-4:1, and the mass ratio of the high-intensity magnetic separation concentrate to the composition is 1:0.3-0.55; 5) calcining the spherical material at 1300-1600° C. for 1-4 hours to obtain a calcined product; 6) Grinding the roasted product to obtain a reground product; performing weak magnetic separation on the reground product at a magnetic separation intensity of 0.12 to 0.2 T and a magnetic separation slurry concentration of 10 to 25 wt% to obtain reduced iron.

2. The method according to claim 1, wherein: In the iron-separation tailings, the mass percentage of particles with a particle size of -200 mesh is greater than or equal to 90%.

3. The method according to claim 1, characterized in that In step 4), the mass ratio of the high-intensity magnetic separation concentrate to the composition is 1:0.33-0.

55.

4. The method according to claim 1, wherein In step 4), the mass ratio of slaked lime to carboxymethyl cellulose is 1 to 3:

1.

5. The method according to claim 1, wherein In step 6), the mass percentage of particles with a grinding fineness of -200 mesh in the re-grinded product is greater than 90%.

6. A composition for treating iron ore tailings to improve the iron grade of the obtained reduced iron, characterized in that: The composition is a mixture of carbon material, slaked lime and carboxymethyl cellulose, the carbon material is selected from one or more of bituminous coal, activated carbon, lignite and anthracite, the mass ratio of the sum of the mass of slaked lime and carboxymethyl cellulose to the mass of the carbon material is (0.05-0.08):(0.25-0.35); the mass ratio of slaked lime to carboxymethyl cellulose is 1-4:1; the use includes the steps as described in claim 1.

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