Resource utilization method of asbestos tailings

Abstract

The invention belongs to the field of metallurgy, and discloses a resource utilization method of asbestos tailings, which comprises the following steps: carrying out first ore grinding treatment on the asbestos tailings; carrying out first magnetic separation on a product obtained by the first ore grinding treatment to obtain first magnetic separation iron-containing middlings and first magnetic separation tailings; the first magnetic separation tailings and concentrated sulfuric acid are subjected to first mixing, and clinker is obtained; the clinker and a leaching agent are subjected to second mixing, and leaching ore pulp is obtained; second magnetic separation is conducted on the leached ore pulp, so that second magnetic separation iron-containing middlings, a first solution and second magnetic separation tailings are obtained, and the first solution comprises the magnesium element; and performing first crystallization on the first solution to obtain a first crystal isolate and a first crystal separation liquid, the first crystal isolate comprising magnesium sulfate. The technical problems that in the background technology, the leaching rate of iron, magnesium and the like is low, and energy consumption is high can be solved or relieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgy, and particularly relates to a method for resource utilization of asbestos tailings. Background Art

[0002] Asbestos tailings are mineral residues generated during the beneficiation process of asbestos ore. The main component of asbestos tailings is serpentine, and it also contains non-serpentine group minerals such as brucite, chlorite, magnetite, quartz, and talc. The existing asbestos reserves are relatively large, but the grade of asbestos ore is not high, only 2% - 3%. For every 1 ton of asbestos produced, hundreds of tons of asbestos tailings will be generated. The main components in asbestos ore tailings are magnesium and silicon, and at the same time, it contains a small amount of iron, nickel, etc. Recovering metals from asbestos is one of the important ways for the resource utilization of asbestos tailings.

[0003] Currently, in the methods for resource utilization of valuable elements such as iron, nickel, and magnesium in asbestos tailings: direct magnetic separation is used to recover iron, but the recovery rate of iron in this method is relatively low, and the utilization of magnesium cannot be achieved; the method of calcining and roasting asbestos tailings - acid solution leaching is used to recover valuable elements from asbestos tailings. Although the leaching rate of magnesium in this method is high, the tailings need to be activated by high-temperature calcination or roasting methods, with high energy consumption; directly using sulfuric acid to leach magnesium from the tailings, but the leaching rate of magnesium in this method is low. Summary of the Invention

[0004] To solve the problems existing in the prior art, the purpose of the present invention is to provide a method for resource utilization of asbestos tailings, which can solve or alleviate the technical problems of low leaching rates of iron, magnesium, etc. and high energy consumption mentioned in the background art.

[0005] To achieve the above purpose, the technical scheme adopted by the present invention is as follows: A method for resource utilization of asbestos tailings, including the following processes: Perform first grinding treatment on asbestos tailings; Perform first magnetic separation on the product obtained from the first grinding treatment to obtain first magnetic separation iron-containing middlings and first magnetic separation tailings; Mix the first magnetic separation tailings with concentrated sulfuric acid for the first time to obtain clinker; Mix the clinker with a leaching agent for the second time to obtain leaching pulp; Perform second magnetic separation on the leaching pulp to obtain second magnetic separation iron-containing middlings, a first solution, and second magnetic separation tailings, and the first solution contains magnesium element; Perform first crystallization on the first solution to obtain a first crystallization separation product and a first crystallization separation liquid, and the first crystallization separation product includes magnesium sulfate.

[0006] Preferably, the particle size of the asbestos tailings after the first grinding treatment (i.e., the product obtained from the first grinding treatment) is 200 - 300 mesh.

[0007] Preferably, the first magnetic separation includes a first-stage dry magnetic separation and a second-stage dry magnetic separation carried out in sequence.

[0008] Preferably, the magnetic field intensity of the first-stage dry magnetic separation is 70 - 120 kA / m.

[0009] Preferably, the magnetic field intensity of the second-stage dry magnetic separation is 60 - 100 kA / m.

[0010] Preferably, after the first-stage dry magnetic separation and before the second-stage dry magnetic separation, a second grinding treatment is also included for the product obtained from the first-stage magnetic separation.

[0011] Preferably, the particle size of the product obtained from the second grinding treatment is 300 - 500 mesh.

[0012] Preferably, the conditions for obtaining the clinker by mixing the first magnetic separation tailings with concentrated sulfuric acid include that the molar ratio of concentrated sulfuric acid to magnesium element in the first magnetic separation tailings in the first mixing is (3 - 8)∶1.

[0013] Preferably, the temperature of the first mixing is 180 - 220 °C.

[0014] Preferably, the time of the first mixing is 1 - 6 h.

[0015] Preferably, the leaching agent includes water, sulfuric acid, ammonia water, hydrochloric acid or nitric acid.

[0016] Preferably, the mass ratio of the leaching agent to the clinker is (4 - 10)∶1.

[0017] Preferably, the mixing of the clinker and the leaching agent is carried out under stirring conditions, wherein the stirring time is 0.5 - 2 h and the stirring temperature is 25 °C - 100 °C.

[0018] Preferably, the second magnetic separation is a wet magnetic separation, and the magnetic field intensity of the second magnetic separation is 63 - 84 kA.

[0019] Preferably, before the first crystallization of the first solution, it also includes: mixing the first solution and the first magnetic separation tailings to obtain a second solution; mixing the second solution with a precipitant to obtain a third solution, and the third solution includes magnesium element; carrying out the first crystallization on the third solution.

[0020] Preferably, the volume ratio of the first solution to the volume mass of the first magnetic separation tailings is (5 - 10)∶1 L / kg.

[0021] Preferably, the first solution and the first magnetic separation tailings are mixed for 0.5 to 3 hours.

[0022] Preferably, the precipitant includes at least one of ammonium sulfide, ammonium bisulfide, sodium sulfide, and sodium bisulfide.

[0023] Preferably, the molar ratio of the precipitant to the total amount of iron and nickel in the second solution is (1-1.5):1.

[0024] Preferably, the first crystallization is performed at 15-18° C. for 0.5-3 h.

[0025] Preferably, the method further comprises subjecting the first crystallization separation liquid to a second crystallization treatment; the second crystallization is performed by standing at 1-5° C. for 0.5-3 h.

[0026] The resource utilization method of asbestos tailings of the present invention comprises the following steps: crushing the asbestos tailings through a first grinding process, which is beneficial to the preliminary dissociation of serpentine in the asbestos tailings and enables the serpentine to be dissociated from magnetite to a large extent; performing a first magnetic separation on the crushed asbestos tailings, which can reduce the amount of iron entering the solution in the subsequent leaching process, so that the first magnetic separation can obtain a higher iron recovery rate, and at the same time, the asbestos tailings have a smaller particle size, and the tailings after the first magnetic separation have a small particle size, which is helpful to improve the subsequent activation effect and the magnesium leaching rate in the leaching process; using concentrated sulfuric acid to mix with the first magnetic separation tailings and heating to obtain clinker, and using concentrated sulfuric acid to directly mix with the asbestos tailings can effectively destroy the hydroxyl groups in the serpentine, so that the serpentine is easier to decompose, and heating can The magnesium silicate in the serpentine reacts chemically with the concentrated sulfuric acid, converts the magnesium silicate into a material that is easily soluble in water, activates the solubility of magnesium in the magnesium silicate, mixes the concentrated sulfuric acid with the asbestos tailings and heats them, and the mixed material contains almost no water, so the heating process can reduce heat consumption; the clinker is leached, and the leaching conditions are relatively mild and can be carried out at room temperature, thereby reducing the energy consumption of the leaching process; the slurry obtained after the clinker is leached is subjected to a second magnetic separation, and the serpentine structure in the asbestos tailings is further destroyed after the asbestos tailings particles are matured and leached, and the magnetite wrapped in the serpentine can be released; the second magnetic separation is used to further recover the magnetite in the solid particles in the slurry, so that the recovery rate of iron in the asbestos tailings is further improved. The first solution containing the magnesium element is then subjected to the first crystallization and the second crystallization in sequence, and the first crystallization product is magnesium sulfate, and the second crystallization product is ammonium sulfate. As a result, the process is highly operable and low in cost, and the added concentrated sulfuric acid is fully utilized (such as obtaining magnesium sulfate). BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the several views denote the same or similar components or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings merely depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0028] Figure 1 is the XRD pattern of asbestos tailings provided by an embodiment of the present application; Figure 2 is the XRD pattern of the clinker of Embodiment 1 of the present application; Figure 3 is the XRD pattern of the leaching residue of Embodiment 1 of the present application. Detailed Embodiments

[0029] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as limiting the present application. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and do not necessarily need to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0031] In the present application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the distribution of the optional numerical values within the numerical interval is considered continuous and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When providing multiple numerical ranges to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in the present application should be understood to include any and all sub-ranges subsumed therein. The "numerical values" in the numerical interval can be any quantitative values, such as numbers, percentages, ratios, etc. The "numerical interval" allows for a broad inclusion of quantitative intervals such as percentage intervals, ratio intervals, ratio value intervals, etc.

[0032] Due to the symbiotic replacement of iron and serpentine in asbestos tailings, when recovering iron by magnetic separation, serpentine cannot be fully destroyed, resulting in a low recovery rate of iron. When precipitating iron from the solution obtained after leaching iron with an acid solution, the goethite method is commonly used. Due to the strong adsorption of goethite, a large amount of magnesium ions will be adsorbed on iron hydroxide during the precipitation of iron, resulting in a large loss of magnesium ions in the solution.

[0033] Accordingly, the present invention provides a method for resource utilization of asbestos tailings, comprising the following steps: (1) Perform a first grinding treatment on the asbestos tailings; (2) Perform a first magnetic separation on the product obtained from the crushing treatment to obtain a first magnetic separation iron-containing concentrate and a first magnetic separation tailings; (3) Mix the first magnetic separation tailings with concentrated sulfuric acid for the first time to obtain a clinker; (4) Mix the clinker with a leaching agent for the second time to obtain a leaching pulp; (5) Perform a second magnetic separation on the leaching pulp to obtain a second magnetic separation iron-containing concentrate, a first solution containing magnesium element, and a second magnetic separation tailings; (6) Perform a first crystallization treatment on the first solution to obtain a first crystallization separation product and a first crystallization separation liquid, wherein the first crystallization separation product comprises magnesium sulfate.

[0034] According to an embodiment of the present application, in step (1), a first grinding treatment is performed on the asbestos tailings. In this step, by performing the first grinding treatment on the asbestos tailings, magnetite that is easy to dissociate in the asbestos tailings can be dissociated from the asbestos tailings, which helps to obtain a higher iron recovery rate in the first magnetic separation. At the same time, it provides raw materials with small particle size and high activity for the subsequent activation step of the magnetic separation tailings, improving the activation effect of the subsequent ripening step on the material.

[0035] In some embodiments, the first grinding treatment includes a crushing treatment and a fine grinding treatment performed in sequence. The crushing treatment can crush the larger asbestos tailings blocks, and the fine grinding treatment further finely grinds the product obtained from the crushing, which is beneficial to separating the finely ground minerals that have reached monomer dissociation during the subsequent first magnetic separation process, thereby improving the iron recovery rate during the first magnetic separation.

[0036] Optionally, the particle size of the asbestos tailings after the first grinding treatment is 200-300 mesh.

[0037] According to an embodiment of the present application, a first magnetic separation is performed on the product obtained from the first grinding treatment to obtain a first magnetic separation iron-containing concentrate and a first magnetic separation tailings. In this step, by the first magnetic separation, magnetite dissociated from serpentine in the asbestos tailings after the first grinding treatment can be recovered, and thus the first magnetic separation iron-containing concentrate is obtained.

[0038] Optionally, the iron grade in the first magnetic separation intermediate iron ore containing iron can reach 15% - 30%.

[0039] In some embodiments, the first magnetic separation includes a first-stage dry magnetic separation and a second-stage dry magnetic separation carried out in sequence. The two-stage magnetic separation process can further improve the recovery rate of iron in the asbestos tailings.

[0040] Optionally, the magnetic separation intensity of the first magnetic separation is 70 - 120 kA / m, such as 70 kA / m, 90 kA / m, 100 kA / m, 120 kA / m.

[0041] Optionally, the magnetic separation intensity of the second magnetic separation is 60 - 100 kA / m, such as 60 kA / m, 70 kA / m, 90 kA / m, 100 kA / m.

[0042] In some embodiments, after the first-stage dry magnetic separation and before the second-stage dry magnetic separation, a second grinding treatment is further included for the product obtained from the first-stage magnetic separation. Further grinding and second-stage dry magnetic separation treatment are performed on the intermediate iron ore containing iron obtained from the first-stage dry magnetic separation, which can improve the iron grade in the obtained intermediate iron ore containing iron, and thus iron concentrate with an iron grade greater than or equal to 60% can be obtained.

[0043] Optionally, the particle size of the product obtained from the second grinding treatment is 300 - 500 mesh.

[0044] As an example, the product obtained from the first grinding treatment is subjected to the first-stage magnetic separation of minerals with a magnetic field intensity of 70 - 120 kA / m. After the first-stage magnetic separation, the first magnetic separation intermediate iron ore containing iron is obtained, and the iron grade in the intermediate iron ore containing iron reaches 15% - 30%. Then, the first magnetic separation intermediate iron ore containing iron is subjected to a second grinding treatment, and the ground minerals are subjected to the second-stage dry magnetic separation with a magnetic field intensity of 60 - 100 kA / m. In this way, the iron grade in the magnetic separation concentrate (iron concentrate) can reach more than 60%.

[0045] According to the embodiments of the present application, in step (3), the first magnetic separation tailings are mixed with concentrated sulfuric acid for the first time to obtain a clinker. In this step, serpentine is a mineral with a layered structure and is composed of layered silicate minerals. These silicate minerals have a shape similar to tiles and are stacked on top of each other to form a layered structure. Concentrated sulfuric acid can provide a large amount of H + , and a strong H + concentration gradient is formed between the high-concentration H + and serpentine. At the same time, the size of H + is small, and H + can penetrate into the layered gaps of serpentine, destroying the layered structure of serpentine and promoting the decomposition of the serpentine structure. The magnesium in serpentine gradually turns into hydrated magnesium sulfate, and its possible reaction is as follows:

[0046] In some embodiments, the molar ratio of the concentrated sulfuric acid to the magnesium element in the first magnetic separation tailings is (3-8):1, such as 3:1, 4:1, 5:1, 8:1. In this way, as the amount of acid added increases, the structure of serpentine can be more thoroughly destroyed, and macroscopically, the activation effect is improved to increase the leaching rate of magnesium.

[0047] In some embodiments, the time for mixing the first magnetic separation tailings with concentrated sulfuric acid is 1-6 h, such as 1 h, 2 h, 3 h, 4 h, 5 h, 6 h. In this way, a sufficiently long activation time can ensure that H + penetrates more fully into the crystal structure of serpentine to achieve the effect of fully destroying the serpentine structure.

[0048] In some embodiments, the temperature for mixing the first magnetic separation tailings with concentrated sulfuric acid is 180-220 °C, such as 180 °C, 190 °C, 210 °C, 220 °C. Thus, the foregoing temperature range is conducive to the progress of the diffusion reaction, thereby further enhancing the activation effect.

[0049] According to the embodiments of the present application, in step (4), the clinker is secondarily mixed with a leaching agent to obtain a leached pulp. In this step, the clinker is mixed with the leaching agent so that valuable elements (such as magnesium and nickel) in the clinker are leached into the solution. Optionally, the leaching agent includes one or any combination of water, sulfuric acid, ammonia water, hydrochloric acid, and nitric acid.

[0050] As an example, the leaching agent is water.

[0051] In some embodiments, the mass ratio of the leaching agent to the clinker is (4-10):1, such as 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1.

[0052] In some embodiments, the mixing of the clinker and the leaching agent is carried out under stirring conditions, the stirring time is 0.5-2 h, and the stirring temperature is 20 °C - 100 °C. In this way, the diffusion rate of magnesium from the solid phase to the liquid phase can be increased, the leaching rate of magnesium can be enhanced, and the leaching time can be shortened.

[0053] According to the embodiments of the present application, in step (5), the leached pulp is secondarily magnetically separated to obtain a second magnetically separated iron-containing concentrate, a first solution, and a second magnetically separated tailings, and the first solution contains magnesium element. In this step, the second magnetic separation can extract the iron-containing substances in the leached pulp.

[0054] Optionally, the magnetic field intensity of the second magnetic separation is 63-84 kA, such as 63 kA, 68 kA, 75 kA, 84 kA.

[0055] In some embodiments, the second magnetic separation of the leaching pulp further includes solid-liquid separation of the pulp after the second magnetic separation to obtain a first solution and tailings of the second magnetic separation. The first solution contains magnesium element, and the tailings of the second magnetic separation include silicon dioxide and silicic acid, and the tailings of the second magnetic separation can be used to prepare white carbon black or other silicon compounds.

[0056] According to an embodiment of the present application, in step (6), the first solution is subjected to a first crystallization treatment to obtain a first crystallization separation and a first crystallization separation liquid, and the first crystallization separation includes magnesium sulfate.

[0057] In this step, magnesium sulfate is obtained by crystallization treatment, and the operation is simple and easy.

[0058] In some embodiments, before the first solution is subjected to the first crystallization treatment, it further includes: (6-1) mixing the first solution and the first magnetic separation tailings to obtain a second solution; (6-2) mixing the second solution with a precipitant to obtain a third solution. In this way, the content of magnesium element in the third solution is greater than that in the second solution which is greater than that in the first solution. The first magnetic separation magnesium-containing tailings obtained by the first magnetic separation are used as a neutralizing agent for the first solution. Using this raw material as a neutralizing agent can, on the one hand, partially leach the magnesium in this raw material and increase the magnesium content in the first solution, and on the other hand, it can increase the pH of the first solution, which is beneficial to reducing the loss of the sulfide precipitant caused by the formation of hydrogen sulfide by sulfur ions and hydrogen ions in the first solution during subsequent sulfide precipitation; adding a precipitant to the neutralized first solution (second solution) and stirring well to form precipitates of dissolved nickel and iron ions in the solution in the form of sulfides. After solid-liquid separation of the solution after sulfide precipitation, a purified magnesium sulfate solution is obtained, and the magnesium sulfate solution is subjected to cooling crystallization treatment.

[0059] In some embodiments, in (6-1), the first solution and the first magnetic separation tailings are mixed to obtain a second solution, and the second solution contains magnesium element. In this process, adding the first magnetic separation tailings to the first solution can dissolve some easily soluble magnesium in the first magnetic separation tailings with sulfuric acid in the first solution. On the one hand, it increases the pH of the first solution, which is beneficial to reducing the consumption of sulfides during the subsequent removal of iron and nickel in the solution by sulfide precipitation, and on the other hand, it can increase the magnesium content in the solution.

[0060] Optionally, the volume ratio of the first solution to the mass of the first magnetic separation tailings is (5-10):1 L / kg, such as 5:1 L / kg, 7:1 L / kg, 10:1 L / kg.

[0061] Optionally, the mixing time of the first solution and the first magnetic separation tailings is 0.5 to 3 h, such as 0.5 h, 1 h, 2 h, 3 h.

[0062] In some embodiments, (6-2) the second solution is mixed with a precipitating agent. During this process, the precipitating agent can react with iron ions and nickel ions in the second solution to precipitate in the form of iron sulfide or nickel sulfide, and then through solid-liquid separation, a third solution is obtained. This third solution contains a relatively high amount of magnesium ions and a relatively low content of impurities such as iron and nickel.

[0063] Optionally, the precipitating agent includes one or any combination of ammonium sulfide, ammonium hydrosulfide, sodium sulfide, and sodium hydrosulfide.

[0064] Optionally, the molar ratio of ammonium sulfide to the total amount of iron and nickel elements in the second solution is (1 to 1.5):1, such as 1:1, 1:1.1, 1:1.2.

[0065] Optionally, the first-stage crystallization is carried out by standing still at 15 to 18 °C for 0.5 to 3 h. Magnesium sulfate crystals are obtained by the first crystallization treatment, and the solution obtained after solid-liquid separation of the crystallized magnesium sulfate continues the second crystallization treatment.

[0066] In some embodiments, it further includes performing a second crystallization treatment on the first crystallization separation liquid.

[0067] Optionally, the second crystallization is carried out by standing still at 3 to 5 °C for 0.5 to 3 h. Ammonium sulfate crystals are cryogenically crystallized, and after solid-liquid separation after the second-stage cryogenic crystallization, a crystallization mother liquor with less magnesium and ammonium ions can be obtained, and this substance can be used as a raw material for step (3) to facilitate the recycling of ammonium, magnesium, sulfate ions, and water in the solution and avoid the discharge of such water.

[0068] Next, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited only to the embodiments set forth herein.

[0069] In the following examples and comparative examples, the components in the asbestos tailings are shown in Table 1, and the phase structure is shown in Figure 1 .

[0070] Table 1

[0071] Example 1 The method for resource utilization of asbestos tailings in this example includes the following steps: S1. After grinding the asbestos tailings (the first grinding treatment) to a particle size of 250 mesh, the iron in the finely ground tailings is selected as iron-containing middlings (the first magnetic separation iron-containing middlings) by the first magnetic separation method. The first magnetic separation includes the first-stage dry magnetic separation and the second-stage dry magnetic separation carried out in sequence. The magnetic field intensity of the first-stage dry magnetic separation is 95.49 kA / m. The product obtained from the first-stage dry magnetic separation (the first-stage dry magnetic separation iron-containing middlings) is further ground to a particle size of 400 mesh for the second-stage dry magnetic separation to obtain the first magnetic separation iron-containing middlings. The magnetic field intensity of the second-stage magnetic separation is 84 kA / m.

[0072] After the first-stage magnetic separation, the iron grade in the first-stage magnetic separation iron-containing middlings is 21%, and the iron recovery rate is 82%. After the second-stage magnetic separation, the grade of the iron concentrate obtained from the second-stage magnetic separation is 60%, and the iron recovery rate is 75%. The total magnetic separation recovery rate of iron is 61.5%.

[0073] S2. The remaining tailings after magnetic separation (the first magnetic separation tailings) are used as raw materials for extracting magnesium. The tailings powder is mixed with concentrated sulfuric acid in a certain proportion (the molar ratio of concentrated sulfuric acid to magnesium element in the first magnetic separation tailings is 5:1), stirred evenly, and then the mixed material is kept at a temperature of 200 °C for 3 h. The material after the heat preservation is used as the raw material for the next leaching. Here, the material after heating and heat preservation is called the clinker. Figure 2 This is the XRD pattern of the clinker in this embodiment. It can be seen that the magnesium in the asbestos tailings is transformed from magnesium hydrosilicate into water-soluble sulfate, and the silicon phase disappears, indicating that the silicon is transformed from the original magnesium silicate into an amorphous silicon compound.

[0074] S3. The clinker obtained in S2 is mixed with water in a certain proportion to adjust the pulp (the mass ratio of water to the clinker is 5:1). The pulp after adjustment is stirred and leached for 1 h, and the leached pulp is obtained after the leaching ends.

[0075] S4. The leached pulp obtained in S3 is subjected to the second magnetic separation by the wet magnetic separation method. The undissolved metal solid compounds such as iron and nickel in the pulp are magnetically separated into iron- and nickel-containing minerals. The magnetic field intensity of the second magnetic separation is 75 kA.

[0076] For the second magnetic separation iron-containing minerals and leached residue obtained after the second magnetic separation, the iron recovery rate into the second magnetic separation iron-containing middlings during the second magnetic separation is 32%. The magnesium leaching rate is calculated based on the magnesium content in the leached residue after the second magnetic separation, and the magnesium leaching rate is 92%. Figure 3 This is the XRD pattern of the leached residue in this embodiment. It can be seen that it is basically a flat peak, indicating that it is mainly amorphous phase material, and the detectable silicon phase is hydrous silicic acid.

[0077] S5. The pulp after magnetic separation in S4 is subjected to solid-liquid separation, and the obtained liquid is a solution containing magnesium sulfate, and the solid is a silicon-containing solid.

[0078] S6. Add a certain amount of the selected iron tailings obtained from S1 to the magnesium sulfate-containing solution obtained from S5, and stir and leach for 2 h. After the leaching is completed, perform solid-liquid separation to obtain a magnesium sulfate solution, and use the solid residue as the raw material for S2. The volume ratio of the first solution to the volume mass of the first magnetic separation tailings is 8:1 L / kg.

[0079] S7. Add ammonium sulfide to the magnesium sulfate solution obtained from S6 to precipitate nickel, iron ions, etc. in the magnesium sulfate solution in the form of iron sulfide and nickel sulfide. After the precipitation, perform solid-liquid separation to obtain a magnesium sulfate solution free of iron and nickel ions. This magnesium sulfate solution is herein referred to as the refined magnesium sulfate solution. The molar ratio of ammonium sulfide to the total amount of iron and nickel elements in the second solution is 1.2:1.

[0080] After sulfide precipitation, the iron and nickel concentrations in the solution are 18 mg / L and 12 mg / L respectively.

[0081] S8. Perform two-stage freezing crystallization on the refined magnesium sulfate solution obtained from S7. In the first-stage crystallization, magnesium sulfate crystals are obtained. After the magnesium sulfate is crystallized out, the solution obtained by solid-liquid separation is then subjected to second-stage freezing crystallization to crystallize out ammonium sulfate crystals. After the second-stage freezing crystallization, perform solid-liquid separation, and the separated solution is returned as a raw material to S3. The first-stage crystallization is carried out by standing still at 17 °C for 2 h; the second-stage crystallization is carried out by standing still at 4 °C for 2 h.

[0082] The magnesium sulfate crystallized out in the first-stage cooling crystallization is magnesium sulfate heptahydrate, and the ammonium sulfate crystals are crystallized out in the second-stage cooling crystallization.

[0083] Example 2 In this example, the asbestos tailings are treated in the same manner as in Example 1, except that in S1 of this example: the asbestos tailings are ground (first grinding treatment) to a particle size of 200 mesh.

[0084] Example 3 In this example, the asbestos tailings are treated in the same manner as in Example 1, except that in S1 of this example: the asbestos tailings are ground (first grinding treatment) to a particle size of 300 mesh.

[0085] Example 4 In this example, the asbestos tailings are treated in the same manner as in Example 1, except that in S2 of this example: the remaining tailings after magnetic separation (the first magnetic separation tailings) are used as the raw material for extracting magnesium. The tailings powder is mixed with concentrated sulfuric acid in a certain proportion (the molar ratio of concentrated sulfuric acid to the magnesium element in the first magnetic separation tailings is 3:1), stirred evenly, and then the mixed material is kept at a temperature of 200 °C for 3 h. The material after the heat preservation is used as the raw material for the next leaching step. Herein, the material after heating and heat preservation is referred to as the clinker.

[0086] Example 5 This example treats the asbestos tailings in the same manner as in Example 1. The difference is that in step S2 of this example: the remaining tailings after magnetic separation (the first magnetic separation tailings) are used as the raw material for extracting magnesium. The tailings powder is mixed with concentrated sulfuric acid in a certain proportion (the molar ratio of concentrated sulfuric acid to magnesium element in the first magnetic separation tailings is 8:1), stirred evenly, and then the mixed material is kept at a temperature of 200 °C for 3 h. The material after the heat preservation is used as the raw material for the next leaching step. Here, the material after heating and heat preservation is called the clinker.

[0087] Example 6 This example treats the asbestos tailings in the same manner as in Example 1. The difference is that in step S3 of this example: the clinker obtained in S2 is mixed with water in a certain proportion to make pulp (the mass ratio of water to the clinker is 4:1). The pulp after making pulp is stirred and leached for 1 h, and the leached pulp is obtained after the leaching ends.

[0088] Example 7 This example treats the asbestos tailings in the same manner as in Example 1. The difference is that in step S3 of this example: the clinker obtained in S2 is mixed with water in a certain proportion to make pulp (the mass ratio of water to the clinker is 10:1). The pulp after making pulp is stirred and leached for 1 h, and the leached pulp is obtained after the leaching ends.

[0089] Example 8 This example treats the asbestos tailings in the same manner as in Example 1. The difference is that in step S6 of this example: a certain amount of the iron - selected tailings obtained in S1 is added to the magnesium sulfate - containing solution obtained in S5 and stirred and leached for 2 h. After the leaching ends, solid - liquid separation is carried out to obtain the magnesium sulfate solution, and the solid residue is used as the ingredient for S2, where the volume ratio of the first solution to the mass of the first magnetic separation tailings is 5:1 L / kg.

[0090] Example 9 This example treats the asbestos tailings in the same manner as in Example 1. The difference is that in step S6 of this example: a certain amount of the iron - selected tailings obtained in S1 is added to the magnesium sulfate - containing solution obtained in S5 and stirred and leached for 2 h. After the leaching ends, solid - liquid separation is carried out to obtain the magnesium sulfate solution, and the solid residue is used as the ingredient for S2, where the volume ratio of the first solution to the mass of the first magnetic separation tailings is 10:1 L / kg.

[0091] Example 10 This embodiment processes the asbestos tailings in the same manner as in Embodiment 1, except that in step S7 of this embodiment: ammonium sulfide is added to the magnesium sulfate solution obtained in S6, so that nickel, iron ions, etc. contained in the magnesium sulfate solution precipitate in the form of iron sulfide and nickel sulfide. After solid-liquid separation of the precipitate, a magnesium sulfate solution free of iron and nickel ions is obtained. This magnesium sulfate solution is hereinafter referred to as the refined magnesium sulfate solution. The molar ratio of ammonium sulfide to the total amount of iron and nickel elements in the second solution is 1:1.

[0092] Embodiment 11 This embodiment processes the asbestos tailings in the same manner as in Embodiment 1, except that in step S7 of this embodiment: ammonium sulfide is added to the magnesium sulfate solution obtained in S6, so that nickel, iron ions, etc. contained in the magnesium sulfate solution precipitate in the form of iron sulfide and nickel sulfide. After solid-liquid separation of the precipitate, a magnesium sulfate solution free of iron and nickel ions is obtained. This magnesium sulfate solution is hereinafter referred to as the refined magnesium sulfate solution. The molar ratio of ammonium sulfide to the total amount of iron and nickel elements in the second solution is 1.5:1.

[0093] Comparative Example 1 This comparative example processes the asbestos tailings in the same manner as in Embodiment 1, except that in step S1 of this comparative example: the iron in the asbestos tailings is selected as iron concentrate (the first magnetic separation iron-containing middlings) by the first magnetic separation method. The first magnetic separation includes the first-stage magnetic separation and the second-stage magnetic separation carried out in sequence; the magnetic field intensity of the first-stage magnetic separation is 95.49 kA / m; the magnetic field intensity of the second-stage magnetic separation is 84 kA / m.

[0094] Conclusion: Since the particle sizes of the asbestos tailings are different, and some of the tailings have a particle size of more than 10 cm, without grinding and dissociating the minerals, the magnetic separation has basically no effect.

[0095] Comparative Example 2 This comparative example processes the asbestos tailings in the same manner as in Embodiment 1, except that in this comparative example, S3 is not carried out.

[0096] Conclusion: Without leaching the clinker, magnesium cannot be extracted, and the final result can only be to recover the iron in the tailings.

[0097] Comparative Example 3 This comparative example processes the asbestos tailings in the same manner as in Embodiment 1, except that in this comparative example, S4 is not carried out, and in S5, the leached pulp obtained in S3 is subjected to solid-liquid separation, and the obtained liquid is a magnesium sulfate-containing solution, and the solid is a silicon dioxide-containing solid.

[0098] Conclusion: Without the second magnetic separation, iron, magnesium, etc. that are not dissolved into the solution during the leaching process will enter the leaching residue, resulting in an increase in the iron and magnesium content in the leaching residue. The high iron and magnesium content in the residue not only causes waste of iron and magnesium resources, but also brings impurity elements such as iron and nickel to the subsequent resource utilization of silicon compounds, increasing the difficulty of resource utilization of silicon compounds.

[0099] The above-mentioned examples and comparative examples were tested as follows, and the specific results are shown in Table 2.

[0100] Table 2

[0101] The recovery rate of iron and the leaching rate of magnesium were both tested with reference to the standard (HG / T 3575-2006).

[0102] The calculation method of the leaching rate of magnesium is: η / % = 100% - m 2 / m 1 *100%, where: m 1 is the mass of magnesium oxide (g) in the tailings of the first magnetic separation, and m 2 is the magnesium oxide content in the leaching residue.

[0103] The calculation method of the recovery rate of iron is: η / % = 100% - m 4 / m 3 *100%, where: m 3 is the mass of iron oxide (g) in the tailings of the first magnetic separation, and m 4 is the mass of iron oxide (g) in the leaching residue.

[0104] The purity test method of magnesium sulfate is: detect the magnesium oxide content in magnesium sulfate, and calculate the purity of magnesium sulfate heptahydrate according to the molecular weight of magnesium sulfate heptahydrate.

[0105] It can be seen from Table 2 above that by comparing Examples 1-11 and Comparative Examples 1-3, it can be known that the finer the grinding particle size during the first grinding, the higher the recovery rate of iron in the first magnetic separation. After the tailings of the first magnetic separation are finely ground and then leached after ripening, the leaching rate of magnesium is high. At the same time, most of the iron in the tailings of the first magnetic separation will enter the leaching solution during leaching, and the recovery rate of iron during the second magnetic separation will decrease; when the amount of the tailings of the first magnetic separation added to the leaching solution decreases, the consumption of sulfide during the sulfide precipitation of iron and nickel in the leaching solution will increase. Without changing the addition amount of sulfide, the purity of the obtained magnesium sulfate will decrease. The larger the liquid-solid ratio during the leaching of the clinker, the higher the leaching rate of magnesium can be increased.

[0106] It should also be noted that the "some embodiments", "other embodiments", "embodiments", etc. mentioned in this application refer to the specific features, structures or characteristics described in connection with the embodiment being included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in connection with any one embodiment, it is intended that the implementation of such feature, structure or characteristic in combination with other embodiments also falls within the scope of this application.

[0107] In the above embodiments, the descriptions of each embodiment have their own emphases. For parts not detailed in a certain embodiment, reference may be made to the relevant descriptions of other embodiments.

[0108] It should also be noted that the above are only the preferred embodiments of this application, and do not limit the scope of patent protection of this application. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, shall similarly be included in the scope of patent protection of this application.

Claims

1. A method for resource utilization of asbestos tailings, characterized in that: The process includes the following: First grinding treatment of asbestos tailings; Performing a first magnetic separation on the product obtained from the first ore grinding process to obtain a first magnetically separated iron-containing middling ore and a first magnetically separated tailings; The first magnetic separation tailings are first mixed with concentrated sulfuric acid to obtain clinker; The clinker is mixed with a leaching agent for a second time to obtain a leached slurry; Performing a second magnetic separation on the leached slurry to obtain a second magnetically separated iron-containing middling, a first solution and a second magnetically separated tailings, wherein the first solution includes magnesium; The first solution is subjected to a first crystallization to obtain a first crystal separated product and a first crystal separated liquid, wherein the first crystal separated product includes magnesium sulfate.

2. The resource utilization method of asbestos tailings according to claim 1, characterized in that: The particle size of the product obtained by the first grinding treatment is 200-300 meshes.

3. The resource utilization method of asbestos tailings according to claim 1, characterized in that: The first magnetic separation includes a first stage dry magnetic separation and a second stage dry magnetic separation performed sequentially; The magnetic field strength of the first stage dry magnetic separation is 70~120kA / m; The magnetic field strength of the second stage dry magnetic separation is 60~100kA / m.

4. The resource utilization method of asbestos tailings according to claim 3, characterized in that: After the first stage of dry magnetic separation and before the second stage of dry magnetic separation, the method further comprises subjecting the first stage of magnetic separation to a second grinding treatment; The particle size of the product obtained by the second grinding treatment is 300-500 mesh.

5. The resource utilization method of asbestos tailings according to claim 1, characterized in that: The conditions for first mixing the first magnetic separation tailings with concentrated sulfuric acid to obtain clinker include: The molar ratio of concentrated sulfuric acid to the magnesium element in the first magnetic separation tailings is (3-8):1; Temperature is 180~220℃; The time is 1~6h.

6. The resource utilization method of asbestos tailings according to claim 1, characterized in that: The leaching agent includes water, sulfuric acid, ammonia water, hydrochloric acid or nitric acid; The mass ratio of the leaching agent to the clinker is (4-10):1; The mixing of the clinker and the leaching agent is carried out under stirring conditions, wherein the stirring time is 0.5-2h and the stirring temperature is 25°C-100°C.

7. The resource utilization method of asbestos tailings according to claim 1, characterized in that: The second magnetic separation is wet magnetic separation, and the magnetic field strength of the second magnetic separation is 63~84kA.

8. The resource utilization method of asbestos tailings according to claim 1, characterized in that: Before performing the first crystallization on the first solution, the method further comprises: Mixing the first solution and the first magnetic separation tailings to obtain a second solution; mixing the second solution with a precipitant to obtain a third solution, wherein the third solution includes magnesium; The third solution is subjected to a first crystallization.

9. The resource utilization method of asbestos tailings according to claim 8, characterized in that: The volume mass ratio of the first solution to the first magnetic separation tailings is (5-10): 1 L / kg; The first solution and the first magnetic separation tailings are mixed for 0.5 to 3 hours; The precipitant comprises at least one of ammonium sulfide, ammonium bisulfide, sodium sulfide and sodium bisulfide; The molar ratio of the precipitant to the total amount of the iron element and the nickel element in the second solution is (1-1.5):1; The first crystallization is performed by standing at 15-18° C. for 0.5-3 h.

10. The resource utilization method of asbestos tailings according to claim 8, characterized in that: It also includes performing a second crystallization treatment on the first crystallization separation liquid; The second crystallization is performed by standing at 1-5° C. for 0.5-3 h.

Images