Method for recovering iron from iron separation tailings and application

Abstract

The invention discloses a method for recovering iron from iron separation tailings and application. The method for recovering iron from the iron separation tailings comprises the following steps: 1) screening and grinding the iron separation tailings; (2) the-400-mesh product and the ore grinding product are combined, low-intensity magnetic separation is conducted, and low-intensity magnetic separation concentrate and low-intensity magnetic separation tailings are obtained; wherein the low-intensity magnetic separation concentrate is magnetic separation iron ore concentrate; (3) the low-intensity magnetic separation tailings are subjected to high-intensity magnetic separation, and high-intensity magnetic separation concentrates and high-intensity magnetic separation tailings are obtained; (4) the strong magnetic separation concentrate and the composition are mixed and pressed into balls, and spherical objects are obtained; wherein the composition is a mixture of a carbon substance, slaked lime and carboxymethylcellulose, 5) roasting the spherical substance to obtain a roasted product, 6) grinding the roasted product to obtain a reground product, and carrying out low intensity magnetic separation on the reground product to obtain the reduced iron.

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 micro-particle iron-separation tailings and its application. Background Art

[0002] As a super-large multi-metal co-existing deposit of iron, rare earth, niobium, fluorite, etc., the Bayan Obo Mine has fine interpenetration between minerals in the ore, high inclusion content, and many minerals with similar floatability. In order to obtain high-quality iron concentrate, the reverse flotation process is generally used to remove fine iron-containing interpenetration and inclusions. The iron grade of the obtained reverse flotation tailings (i.e., iron-selected tailings) is still relatively high, but due to the fine interpenetration, the conventional beneficiation method cannot effectively separate several minerals in the iron-selected tailings. At present, it is mainly stored, which not only causes waste of resources, but also pollutes the environment. If the iron-selected tailings can be used for comprehensive resource utilization and the utilization rate of mineral resources can be improved, it will have important practical significance for the sustainable development of mining enterprises.

[0003] CN104195328A discloses a method for making iron oxide ore reduction roasting green balls using iron ore tailings, which mainly includes the following process steps: (1) crushing and grinding weakly magnetic iron oxide ore, discarding part of qualified tailings in advance through strong magnetic separation, and obtaining 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 make balls, and then roasting 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 earth and fluorine from iron ore tailings containing rare earths. The method comprises mixing iron ore tailings containing rare earths, additives and coal powder, briquetting or pelletizing, roasting, ball milling and magnetic separation to obtain magnetic iron concentrate and magnetic tailings; the magnetic tailings are further processed to obtain rare earth chloride leaching solution, calcium fluoride concentrate and the like. The additives used in the method are one or more of calcium oxide powder, dolomite powder, limestone powder and calcium carbonate powder. The magnetic iron concentrate obtained in the method contains reduced iron products, which is not conducive to subsequent separation.

[0005] CN118002306A discloses a method for stepwise 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-selected tailing; (2) concentrating and filtering the wet-selected coarse concentrate obtained in step (2), combining the obtained wet-selected coarse concentrate with the dry-selected coarse concentrate, and then dry-milling the coarse concentrate to obtain a powdery material; (3) magnetizing and roasting the powdery material obtained in step (2) to obtain a roasted ore; and (4) performing stage grinding and stage separation on the roasted ore obtained in step (4) to obtain an iron concentrate and an iron-selected tailing, and the iron-selected tailing and the wet-selected pre-enriched fine tailing are concentrated and then the valuable components are recovered in stages. The TFe grade of the iron concentrate obtained by the method is 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-separation tailings. The method of the present invention can obtain magnetically separated iron concentrate and reduced iron, respectively, and the iron grade of the obtained magnetically separated iron concentrate and the iron grade of the reduced iron are high. Another object of the present invention is to provide a use of a composition in treating iron-separation tailings to improve the iron grade of the obtained 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: 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 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%; 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 magnetic separation iron concentrate; 3) The weak magnetic separation tailings are subjected to strong magnetic separation at a magnetic separation intensity greater than or equal to 0.5 T 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 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 (0.05-0.1):(0.25-0.35); the mass ratio of slaked lime to 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; 5) calcining the spherical material at 1300-1600° C. to obtain a calcined product; 6) Grinding the roasted product to obtain a re-ground product; performing weak magnetic separation on the re-ground product at a magnetic separation intensity of less than or equal to 0.3 T to obtain reduced iron.

[0009] According to the method of the present invention, preferably: 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; In the iron-separation tailings, the mass percentage of particles with a particle size of -200 mesh is greater than or equal to 90%.

[0010] 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 0.15-0.3T, and the pulp concentration is 15-40wt%; in the fine separation, the magnetic separation intensity is 0.1-0.2T, and the pulp concentration is 15-30wt%.

[0011] 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 10-25wt%.

[0012] 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.

[0013] 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.

[0014] According to the method of the present invention, preferably, in step 5), the calcination time is 1 to 4 hours.

[0015] According to the method of the present invention, preferably, in step 6), in the re-grinding product, the mass percentage of particles with a grinding fineness of -200 mesh is greater than 90%.

[0016] According to the method of the present invention, preferably, in step 6), the magnetic separation intensity is 0.12-0.2 T, and the magnetic separation slurry concentration is 10-25 wt%.

[0017] 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 obtained reduced iron, wherein 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, 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; the use comprises the steps as described above.

[0018] The method of the present invention can recover magnetic iron concentrate and reduced iron product from iron-selected tailings, respectively, and the iron grade of the obtained magnetic iron concentrate and the iron grade of reduced iron are 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 scheme of the present invention, the iron-selected tailings are screened and ground to obtain a particle size product of -400 mesh, and then weak magnetic separation is performed under specific conditions to obtain a magnetic iron concentrate with a higher iron grade. Then the weak magnetic tailings obtained by weak magnetic separation are subjected to strong magnetic separation, mixed with a specific composition and pressed into balls, 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

[0019] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0020] method The present invention provides a method for recovering iron from iron ore tailings, comprising the following steps: 1) screening and grinding of the iron ore tailings; 2) weak magnetic separation; 3) strong magnetic separation; 4) adding a composition and pressing into balls; 5) roasting; 6) obtaining a reduced iron product. Optionally, the method further comprises drying the iron ore tailings in advance. The method is described in detail below.

[0021] Drying Steps Drying the iron ore tailings. In certain embodiments, the iron ore tailings can be dried naturally. This facilitates subsequent processing.

[0022] In the present invention, the iron-separation tailings are reverse flotation tailings obtained after the fine iron-containing intergrowths and inclusions are removed by a reverse flotation process.

[0023] 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%.

[0024] In the present invention, the main useful minerals in the iron-selected tailings are magnetite and hematite. In the iron-selected 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-selected tailings, more preferably 79-89wt%, and more preferably 80-88wt%. In the iron-selected 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.

[0025] In the present invention, the iron ore tailings also contain sulfur, phosphorus and fluorine elements. The sulfur content can be 0.6-2.2wt%, preferably 0.7-1.8wt%, and more preferably 0.8-1.5wt%. The phosphorus content can be 0.8-3.5wt%, preferably 1.0-2.5wt%, and more preferably 1.0-2.0wt%. The fluorine content can be 4.5-8.5wt%, preferably 5.0-8.0wt%, and more preferably 5.3-7.8wt%. Such iron ore tailings cannot be separated well to obtain magnetically selected iron concentrate by conventional magnetic separation methods, and it is even more impossible to obtain reduced iron products.

[0026] 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%.

[0027] In the present invention, the mass percentage of particles with a particle size of -200 mesh in the iron-separation tailings being greater than or equal to 90% has the same meaning as the mass percentage of particles with a particle size of -200 mesh in the iron-separation tailings accounting for more than 90%.

[0028] Screening and grinding steps for iron ore tailings The iron ore tailings are screened to obtain a -400 mesh particle size product; the -200 mesh to +400 mesh particle size product is ground 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%. This is conducive to the next step of magnetic separation. The iron in the iron ore tailings is extremely fine, and the iron minerals are interbred with gangue minerals containing harmful elements such as sulfur, phosphorus, and fluorine. It is difficult to obtain a magnetically separated iron concentrate with a higher iron grade using a simple magnetic separation method.

[0029] In the present invention, -400 mesh means the particle size is less than or equal to 400 mesh. Similarly, -200 mesh means the particle size is less than or equal to 200 mesh. +400 mesh means the particle size is greater than or equal to 400 mesh.

[0030] According to one embodiment of the present invention, the 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 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%.

[0031] In this step, the +200 mesh size products are mainly silicate and iron-containing silicate gangue minerals, which are directly discharged into the final tailings.

[0032] In this step, a vertical mill is used for grinding. The grinding concentration during grinding is 50-75wt%, preferably 55-72wt%, and more preferably 55-70wt%. In the grinding product, particles with a grinding fineness of -400 mesh account for more than 90%, that is, 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%.

[0033] Weak magnetic separation steps The -400 mesh particle size product and the grinding product are combined, and weak magnetic separation is performed at a magnetic separation intensity of less than or equal to 0.3T 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, and the main component is ferroferric oxide.

[0034] In this step, weak magnetic separation includes a roughing separation and a fine separation.

[0035] 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%.

[0036] 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%.

[0037] The iron grade of the obtained magnetic iron concentrate (i.e., weak magnetic concentrate) is greater than or equal to 65wt%, preferably greater than 65wt%. The iron recovery rate of the magnetic iron concentrate is 40% to 50%, for example, 41 to 48%. The iron recovery rate of the magnetic iron concentrate = the amount of iron in the magnetic iron concentrate / the amount of iron in the iron tailings × 100%.

[0038] The weak magnetic separation tailings are further processed to obtain reduced iron products. The method of the present invention can obtain magnetic separation iron concentrate and reduced iron products respectively, and the iron grade of the obtained magnetic separation iron concentrate and reduced iron products is high.

[0039] Strong magnetic separation steps The weak magnetic separation tailings are subjected to strong magnetic separation at a magnetic separation intensity greater than or equal to 0.5 T to obtain strong magnetic separation concentrate and strong magnetic separation tailings, which is conducive to improving the iron grade of the final reduced iron product.

[0040] In the present invention, the magnetic separation intensity of the strong magnetic separation can be 0.5-1.2 T, preferably 0.5-0.85 T, more preferably 0.60-0.85 T, and more preferably 0.65-0.80 T. The concentration of the magnetic separation pulp can be 10-25wt%, preferably 12-20wt%, and more preferably 13-18wt%. The pulse is 15-30Hz, preferably 18-28Hz, and more preferably 15-25Hz.

[0041] Adding composition and pressing into balls The high-intensity magnetic separation concentrate is mixed with the composition and pressed into balls to obtain a spherical object; wherein 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 (0.05-0.1): (0.25-0.35); the mass ratio of slaked lime to 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. This is conducive to obtaining a reduced iron product with a higher iron grade.

[0042] In the present invention, the carbon material may be selected from one or more of bituminous coal, activated carbon, lignite and anthracite.

[0043] According to one embodiment of the present invention, the carbon material is anthracite. According to another embodiment of the present invention, the carbon material is composed of activated carbon, lignite and anthracite, and the mass ratio of the three is 1: 2-3:2-3. According to another embodiment of the present invention, the carbon material is composed of bituminous coal and activated carbon, and the mass ratio of the two is 1-1.5:1.

[0044] In the present invention, slaked lime is calcium hydroxide, also known as slaked lime. The present invention finds 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.

[0045] The mass ratio of slaked lime to carboxymethyl cellulose can be 1 to 4:1, preferably 1 to 3:1. According to one specific embodiment of the present invention, the mass ratio of slaked lime to carboxymethyl cellulose is 1:1. According to another specific embodiment of the present invention, the mass ratio of slaked lime to carboxymethyl cellulose is 2:1. According to yet another specific embodiment of the present invention, the mass ratio of slaked lime to carboxymethyl cellulose is 3:1.

[0046] 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).

[0047] 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.

[0048] In the present invention, the high-intensity magnetic separation concentrate and the composite are uniformly mixed and then pressed into balls to obtain spherical objects. The particle size of the spherical objects is 1 to 2 cm. This is conducive to maintaining a reducing atmosphere and improving the grade of reduced iron.

[0049] Calcination steps The spherical object 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.

[0050] 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 1-4h, preferably 1-3h, more preferably 1-2h. The present invention finds 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 decrease and the output will also decrease. 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.

[0051] Steps to obtain reduced iron products 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 0.3 T to obtain reduced iron.

[0052] When the roasted product is ground, a rod mill can be used for grinding. The grinding concentration can be 55-70wt%, preferably 58-68wt%, and more preferably 60-67wt%. In the re-ground product, the mass percentage of particles with a grinding fineness of -200 mesh is greater than 90%, preferably greater than or equal to 91%, and can reach greater than or equal to 94%. This is conducive to the next step of magnetic separation.

[0053] The reground product is subjected to weak magnetic separation at a magnetic separation intensity of 0.3 T or less, the magnetic separation intensity is 0.3 T or less, preferably 0.12 to 0.2 T, more preferably 0.15 to 0.18 T. The concentration of the magnetic separation slurry can be 10 to 25 wt%, preferably 15 to 22 wt%, more preferably 15 to 20 wt%.

[0054] The obtained reduced iron product is mainly iron, and the iron grade of the reduced iron is greater than or equal to 90%, and can reach more than 92%. The iron recovery rate of the reduced iron is 35-40%. The iron recovery rate of the reduced iron = the amount of iron in the reduced iron / the amount of iron in the iron tailings × 100%.

[0055] In the present invention, the total recovery rate of iron is greater than 80%. The 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%.

[0056] use 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 finds that such a composition is beneficial to improving the iron grade of the obtained reduced iron.

[0057] 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 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; the use comprises the following steps: 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 grinding product; in the grinding product, the mass percentage of particles with a grinding fineness of -400 mesh is greater than 90%; 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 magnetic separation iron concentrate; 3) The weak magnetic separation tailings are subjected to strong magnetic separation at a magnetic separation intensity greater than or equal to 0.4T 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 mass ratio of the high-intensity magnetic separation concentrate to the composition is 1:0.3-1.35; 5) calcining the spherical material at 1300-1600° C. to obtain a calcined product; 6) Grinding the roasted product to obtain a re-ground product; performing weak magnetic separation on the re-ground product at a magnetic separation intensity of less than or equal to 0.3 T to obtain reduced iron.

[0058] Please refer to the above for detailed description and will not be repeated here.

[0059] The test method is described as follows: TFe content: tested according to the method described in national standard GB / T 6730.5-2022.

[0060] In the following examples, unless otherwise specified, the content "%" is the mass percentage content. The concentration "%" is the mass percentage concentration.

[0061] Example 1 Provide iron ore tailings from Baotou Iron & Steel Ore Dressing Plant, of which TFe grade is 36.52%, sulfur content is 1.02%, phosphorus content is 1.34%, fluorine content is 6.58%, and the main useful minerals are magnetite and hematite, the sum of the mass of the two accounts for 84.19% of the mass of the iron ore tailings, and the mass ratio of magnetite to hematite is 6.6:4.2. The mass percentage of particles with a particle size of -200 mesh in the iron ore tailings is 96.37%, and the mass percentage of particles with a particle size of -400 mesh is 66.53%.

[0062] The iron-separation tailings are dried; the dried iron-separation 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 with a vertical mill at a grinding concentration of 58% to obtain a grinding product; in the grinding product, the mass percentage of particles with a grinding fineness of -400 mesh is 97.50%.

[0063] The above-obtained -400 mesh particle size product and the grinding product are combined, and then weak magnetic separation is carried out using a belt magnetic separator, specifically including a roughing separation and a concentrating separation, to obtain a weak magnetic separation concentrate (i.e., magnetic iron concentrate) and a weak magnetic separation tailing. In the roughing separation, the magnetic separation intensity is 0.22T, and the pulp concentration is 28%. In the concentrating separation, the magnetic separation intensity is 0.14T, and the pulp concentration is 20%.

[0064] 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 concentrate and strong magnetic tailings.

[0065] The strong magnetic concentrate and the composition (composed of carbonaceous material, slaked lime, and carboxymethyl cellulose) are mixed evenly and then pressed into balls to obtain spheres with a particle size of about 1 cm. The mass ratio of the strong magnetic concentrate to the composition is 1:0.35. The mass ratio of the strong magnetic concentrate to the carbonaceous material is 1:0.28. The carbonaceous 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.

[0066] 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.

[0067] The roasted product was ground by a rod mill at a grinding concentration of 65% to obtain a re-ground product. In the re-ground product, the mass percentage of particles with a grinding fineness of -200 mesh was 91.36%.

[0068] The regrinding product was subjected to weak magnetic separation at a magnetic separation slurry concentration of 15% and a magnetic separation intensity of 0.18T to obtain reduced iron products and magnetic separation tailings.

[0069] 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%.

[0070] The total recovery rate of iron was 82.45%.

[0071] Example 2 The iron ore tailings of Baoshan Mining Baiyun Ore Dressing Branch are provided, among which the TFe grade is 39.44%, the sulfur content is 0.89%, the phosphorus content is 1.16%, and the fluorine content is 5.93%. The main useful minerals are magnetite and hematite, and the sum of the mass of the two accounts for 86.53% of the mass of the iron ore tailings. The mass ratio of magnetite to hematite is 7.5:3.4. The mass percentage of particles with a tailing size of -200 mesh in the iron ore tailings is 98.18%, and the mass percentage of particles with a size of -400 mesh is 64.57%.

[0072] The iron-separation tailings are dried; the dried iron-separation 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 with a vertical mill at a grinding concentration of 63% to obtain a grinding product; in the grinding product, the mass percentage of particles with a grinding fineness of -400 mesh is 95.24%.

[0073] The above-obtained -400 mesh particle size product and the grinding product are combined, and then weak magnetic separation is carried out using a belt magnetic separator, specifically including a roughing separation and a concentrating separation, to obtain a weak magnetic separation concentrate (i.e., magnetic iron concentrate) and a weak magnetic separation tailing. In the roughing separation, the magnetic separation intensity is 0.2T, and the pulp concentration is 25%. In the concentrating separation, the magnetic separation intensity is 0.15T, and the pulp concentration is 22%.

[0074] 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 concentrate and strong magnetic tailings.

[0075] The strong magnetic concentrate and the composition (composed of carbonaceous material, slaked lime, and carboxymethyl cellulose) are mixed evenly and then pressed into balls to obtain spheres with a particle size of about 1.5 cm. The mass ratio of the strong magnetic concentrate to the composition is 1:0.33. The mass ratio of the strong magnetic concentrate to the carbonaceous material is 1:0.25. The carbonaceous material is composed of bituminous coal and activated carbon in a mass ratio of 1:1. The mass ratio of slaked lime to carboxymethyl cellulose is 3:1.

[0076] 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 hours. After the calcination, the crucible was taken out and water quenched to obtain a calcined product.

[0077] The roasted product was ground by a rod mill at a grinding concentration of 60% to obtain a re-ground product. In the re-ground product, the mass percentage of particles with a grinding fineness of -200 mesh was 94.31%.

[0078] The regrinding product was subjected to weak magnetic separation at a magnetic separation slurry concentration of 18% and a magnetic separation intensity of 0.16T to obtain reduced iron products and magnetic separation tailings.

[0079] Among them, 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%.

[0080] The total recovery rate of iron was 83.14%.

[0081] Example 3 The iron ore tailings of Baosteel Walter are provided, of which the TFe grade is 33.61%, the sulfur content is 1.15%, the phosphorus content is 1.62%, and the fluorine content is 7.34%. The main useful minerals are magnetite and hematite, and the sum of the mass of the two accounts for 80.19% of the mass of the iron ore tailings. The mass ratio of magnetite to hematite is 5.5:4.5. The mass percentage of particles with a particle size of -200 mesh in the iron ore tailings is 95.72%, and the mass percentage of particles with a particle size of -400 mesh is 64.59%.

[0082] The iron-separation tailings are dried; the dried iron-separation 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 with a vertical mill at a grinding concentration of 70% to obtain a grinding product; in the grinding product, the mass percentage of particles with a grinding fineness of -400 mesh is 94.98%.

[0083] The above-obtained -400 mesh particle size product and the grinding product are combined, and then weak magnetic separation is carried out using a belt magnetic separator, specifically including a roughing separation and a concentrating separation, to obtain a weak magnetic separation concentrate (i.e., magnetic iron concentrate) and a weak magnetic separation tailing. In the roughing separation, the magnetic separation intensity is 0.25T, and the pulp concentration is 20%. In the concentrating separation, the magnetic separation intensity is 0.16T, and the pulp concentration is 18%.

[0084] 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 concentrate and strong magnetic tailings.

[0085] The strong magnetic concentrate and the composition (composed of carbonaceous material, slaked lime and carboxymethyl cellulose) are mixed evenly and then pressed into balls to obtain spheres with a particle size of about 1 cm. The mass ratio of the strong magnetic concentrate to the composition is 1:0.40. The mass ratio of the strong magnetic concentrate to the carbonaceous material is 1:0.35. The carbonaceous material is anthracite. The mass ratio of slaked lime to carboxymethyl cellulose is 2:1.

[0086] 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.

[0087] The roasted product was ground by a rod mill at a grinding concentration of 62.5% to obtain a reground product, in which the mass percentage of particles with a grinding fineness of -200 mesh was 93.88%.

[0088] The regrinding product is subjected to weak magnetic separation at a magnetic separation slurry concentration of 20% and a magnetic separation intensity of 0.15T to obtain reduced iron products and magnetic separation tailings.

[0089] Among them, the iron grade of the magnetic iron concentrate obtained in this embodiment is 65.06%, and the iron recovery rate of the magnetic 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%.

[0090] The total recovery rate of iron was 80.92%.

[0091] Comparative Example 1 The only difference from Example 1 is that slaked lime and carboxymethyl cellulose are replaced by bentonite.

[0092] Comparative Example 2 The only difference from Example 1 is that the calcination temperature is 1200°C.

[0093]

[0094] As can be seen from the table, the method of the present invention can recover magnetic iron concentrate and reduced iron from the iron tailings, wherein the iron grade of the magnetic iron concentrate can reach more than 65wt%, and the iron grade of the reduced iron can reach more than 90wt%. Comparing Example 1 of the present invention with Comparative Example 1 and Comparative Example 2, it can be seen that the iron recovery rate and the iron grade of the reduced iron of the present invention are significantly improved.

[0095] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be thought of by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for recovering 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 products of -200 mesh to +400 mesh to obtain grinding products; In the grinding product, the mass percentage of particles with a grinding fineness of -400 mesh is greater than or equal to 90%; 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 magnetic separation iron concentrate; 3) The weak magnetic separation tailings are subjected to strong magnetic separation at a magnetic separation intensity greater than or equal to 0.5 T 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 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 (0.05-0.1):(0.25-0.35); the mass ratio of slaked lime to 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; 5) calcining the spherical material at 1300-1600° C. to obtain a calcined product; 6) Grinding the roasted product to obtain a re-ground product; performing weak magnetic separation on the re-ground product at a magnetic separation intensity of less than or equal to 0.3 T to obtain reduced iron.

2. The method according to claim 1, characterized in that: 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; 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 2), the weak magnetic separation includes a roughing separation and a fine separation; in the roughing separation, the magnetic separation intensity is 0.15-0.3T, and the pulp concentration is 15-40wt%; in the fine separation, the magnetic separation intensity is 0.1-0.2T, and the pulp concentration is 15-30wt%.

4. The method according to claim 1, characterized in that In step 3), the magnetic separation intensity of the strong magnetic separation is 0.5-1.2T, and the concentration of the magnetic separation pulp is 10-25wt%.

5. The method according to claim 1, characterized in that In step 4), the mass ratio of the high-intensity magnetic separation concentrate to the composite material is 1:0.3-0.

85.

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

1.

7. The method according to claim 1, characterized in that In step 5), the calcination time is 1 to 4 hours.

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

9. The method according to any one of claims 1 to 8, characterized in that: In step 6), the magnetic separation intensity is 0.12-0.2T, and the magnetic separation slurry concentration is 10-25wt%.

10. Use of 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 (0.05-0.1):(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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