A process for recovering valuable metals based on the chlorination volatilization method

Abstract

The present invention discloses a process for recovering valuable metals based on the chlorination volatilization method, belonging to the technical field of valuable metal recovery, and comprising the following steps: S1. Crushing and grinding iron tailings to obtain iron tailings powder, adding the iron tailings powder and a composite chlorinating agent into a mixer, stirring for 0.5 - 1 h to obtain a mixture, adding water to the mixture, stirring evenly, and pelletizing to obtain pellets to be treated; S2. Heating the pellets to be treated in one stage to 800 - 850 °C, holding for 2 h, collecting volatilized dust, then heating in the second stage to 1000 - 1200 °C, holding for 4 h, collecting volatilized dust, and obtaining calcined residues; S3. Cooling the calcined residues to 40 - 60 °C under a nitrogen atmosphere, grinding, and then performing magnetic separation to obtain magnetite. The present invention utilizes a composite chlorinating agent formed by compounding a supported inorganic chlorinating agent and silane-grafted polyvinyl chloride, and through the pelletizing and calcination processes, realizes the efficient volatilization and recovery of zinc and lead in iron tailings.

Description

Technical Field

[0001] The present invention belongs to the technical field of valuable metal recovery, and particularly relates to a process for recovering valuable metals based on the chlorination volatilization method. Background Art

[0002] Chlorination metallurgy is a method of metallurgy through metal oxides, mainly utilizing the characteristics that metal chlorides generally have low melting and boiling points, high volatility, and are easily soluble in water. The commonly used chlorination metallurgy methods in industrial production are: chlorination roasting, chlorination roasting - leaching, chlorination leaching, chlorination segregation, chlorination smelting, and chlorination refining. The method of making metals volatilize in the form of chlorides through chlorination roasting and chlorination refining means is called chlorination volatilization, which is usually used for improving the grade of metal ores, recovering metal waste materials, refining crude metals, etc. The commonly used chlorinating agents in chlorination volatilization are Cl2, HCl, CaCl2, NaCl, and FeCl3, etc., which generally have strong chemical activity and are easy to react with metals and their sulfides, oxides, etc. to form metal chlorides with lower boiling points. According to the differences in the ease of formation and properties of metal chlorides, by controlling conditions such as reaction temperature and vapor pressure of the products, selective chlorination volatilization of metals is achieved.

[0003] Iron tailings contain a large amount of elements such as Fe, Cu, Zn, and In. The large - scale stacking of iron tailings will not only cause great resource waste but also pose a great threat and harm to the environment. In response to this, at present, valuable metal recovery is carried out by treating iron tailings to realize the secondary utilization of waste. Among them, the chlorination volatilization method is the most widely used. Compared with traditional chlorinating agents, waste PVC contains nearly 60% chlorine in its molecules. As a chlorinating agent, it can achieve the advantages of waste utilization and cost saving. However, at present, the temperature for recovering valuable metals by the chlorination volatilization method is relatively high, and PVC begins to decompose to produce hydrogen chloride and chlorine at 300°C - 500°C, resulting in the generated hydrogen chloride and chlorine diffusing into the gas phase in the low - temperature zone and being unable to participate in the chlorination reaction in time in the high - temperature zone. Therefore, the effect of metal chlorination volatilization is not good and the recovery rate is low. Summary of the Invention

[0004] The purpose of the present invention is to provide a process for recovering valuable metals based on the chlorination volatilization method to solve the problem of poor recovery effect of valuable metals in the existing chlorination volatilization process.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A process for recovering valuable metals based on the chlorination volatilization method includes the following steps:

[0007] S1. Crush and grind the iron tailings through a 200 - 400 mesh sieve to obtain iron tailings powder. Add the iron tailings powder and the composite chlorinating agent into a blender and stir at a speed of 60 r / min - 200 r / min for 0.5 h - 1 h to obtain a mixture. Add water to the mixture and stir evenly to obtain a moistened material, and then pelletize it to obtain the pellet to be treated;

[0008] S2. Heat the pellet to be treated in step S1 to 800 °C - 850 °C in one stage, keep it warm for 2 h, collect the zinc - containing dust generated during the volatilization process, and then heat it to 1000 °C - 1200 °C in the second stage, keep it warm for 4 h, collect the lead - containing dust generated during the volatilization process, and obtain the calcined residue;

[0009] S3. Under a nitrogen atmosphere, cool the calcined residue to 40 °C - 60 °C, grind it and then perform magnetic separation to obtain magnetite.

[0010] Furthermore, in S1, the mass ratio of the iron tailings powder to the composite chlorinating agent is 1:0.1 - 1.

[0011] Furthermore, the composite chlorinating agent is composed of a supported inorganic chlorinating agent and silane - grafted polyvinyl chloride compounded.

[0012] Furthermore, the mass ratio of the supported inorganic chlorinating agent to silane - grafted polyvinyl chloride in the composite chlorinating agent is 1:0.5 - 1.

[0013] Furthermore, the supported inorganic chlorinating agent is activated carbon supported chloride salt.

[0014] Furthermore, the chloride salt is at least one of sodium chloride, calcium chloride, ferric chloride, ammonium chloride, and magnesium chloride, preferably calcium chloride.

[0015] Furthermore, the activated carbon is powdered activated carbon, and the particle size of the powdered activated carbon is 200 μm - 400 μm.

[0016] Furthermore, the preparation process of the supported inorganic chlorinating agent is as follows:

[0017] Add the chloride salt into distilled water, stir evenly, then add activated carbon, impregnate at room temperature for 6 h - 10 h, and then dry it to constant weight in an oven at 120 °C to obtain the supported inorganic chlorinating agent.

[0018] Furthermore, in the above - mentioned preparation process, the dosage ratio of the chloride salt, distilled water, and activated carbon is 20 g:100 mL:7 g - 15 g.

[0019] Furthermore, the silane - grafted polyvinyl chloride is methacryloxypropyltriethoxysilane - grafted polyvinyl chloride.

[0020] Furthermore, the preparation process of the silane - grafted polyvinyl chloride is as follows:

[0021] Dissolve polyvinyl chloride in nitrobenzene at room temperature to form a transparent solution, then introduce an initiator and 3-(trimethoxysilyl)propyl methacrylate. Under nitrogen protection, stir and react at 60 °C to 70 °C for 4 h to 5 h. After the reaction, cool to room temperature, add methanol for precipitation. The precipitated product is washed with methanol 3 - 5 times, then methanol is used as the extraction agent for Soxhlet extraction and purification for 2 h. The purified product is dried at 40 °C to constant weight, crushed and passed through a 200-mesh sieve to obtain the silane-grafted polyvinyl chloride.

[0022] Further, in the above preparation process, the dosage ratio of polyvinyl chloride, nitrobenzene, initiator, 3-(trimethoxysilyl)propyl methacrylate and methanol is 5 g : 50 mL to 100 mL : 0.012 g to 0.025 g : 0.2 g to 0.5 g : 500 mL to 1000 mL.

[0023] Further, the initiator is bis(2-phenoxyethyl) peroxydicarbonate (BPPD).

[0024] Further, the iron content in the iron tailings is 20 wt% to 60 wt%, the zinc content is 6 wt% to 15 wt%, and the lead content is 0.01 wt% to 0.5 wt%.

[0025] Further, when adding water in S1, the moisture content in the wetted material should be controlled at 7.5 ± 0.2%.

[0026] Further, pelletizing in S1 is carried out in a φ1000 mm disc pelletizer with a side height of 200 mm, an inclination angle of 45°, a rotation speed of 25 r / min to 40 r / min, and a pelletizing time of 15 min.

[0027] Further, the diameter of the pellets to be processed in S1 is 12 mm to 16 mm.

[0028] Further, air is introduced during the first-stage heating and the second-stage heating in S2, and the introduction rate is 5000 L / (t·min) to 1500 L / (t·min). Introducing air during the first-stage heating and the second-stage heating can keep iron in a high-valence state. At this time, iron is not easily volatilized by chlorination into the flue gas, and the purity of lead and zinc products in the flue gas is relatively higher.

[0029] Further, the nitrogen gas flow rate in S3 is 20 mL / min to 200 mL / min.

[0030] The beneficial effects of the present invention:

[0031] The present invention provides a process for recovering valuable metals based on the chlorination volatilization method. A composite chlorinating agent formed by compounding a supported inorganic chlorinating agent and silane-grafted polyvinyl chloride is used. Through pelletizing and roasting processes, zinc and lead in iron tailings are efficiently volatilized and recovered, solving the problems of low recovery rates of zinc and lead in existing iron tailings and ineffective utilization of iron. The zinc volatilization rate is 89.4 - 94.2%, and the lead volatilization rate is 96.0 - 99.1%, greatly improving the resource utilization rate and realizing the resource utilization of solid waste.

[0032] In the present invention, the supported inorganic chlorinating agent and silane-grafted polyvinyl chloride are used as a composite chlorinating agent, and there is a synergistic effect between them. The supported inorganic chlorinating agent is an activated carbon supported chloride salt. Activated carbon not only has a high specific surface area, but its large cavity structure can accommodate a large amount of chloride salt, giving the chloride salt a large contact area with iron tailings and accelerating the volatilization of valuable metals. At high temperatures, the affinity of activated carbon for oxygen is greater than that of metals for oxygen, weakening the binding force between metals and oxides and making it easier for metals to combine with hydrogen chloride to form metal chlorides, further accelerating the volatilization of valuable metals. The surface of silane-grafted polyvinyl chloride contains a siloxane structure. During the pelletizing process, the silanol bonds generated by the hydrolysis of siloxane can undergo a coupling reaction with iron tailings powder, storing silane-grafted polyvinyl chloride in the pellets. Under high-temperature roasting, silane-grafted polyvinyl chloride decomposes to produce HCl, small molecule hydrocarbons, and silicon dioxide, most of which are confined inside the pellets, reducing the diffusion of hydrogen chloride at low temperatures and helping to improve the chlorination recovery effect. HCl can accelerate the volatilization of valuable metals, and small molecule hydrocarbons are reducing gases such as carbon monoxide and methane. In a reducing atmosphere, the reduction process of zinc and lead can be controlled, enabling metal chlorides to volatilize at high temperatures without being reduced to elemental form. In addition, silicon dioxide can react with the decomposition products of chloride salts (such as calcium chloride) and oxides (such as calcium oxide) to form stable silicates (such as calcium silicate), promoting the reaction of chloride salts to produce hydrogen chloride gas, thereby increasing metal chlorination. In summary, the compound use of the supported inorganic chlorinating agent and silane-grafted polyvinyl chloride in the present invention has excellent volatilization effects and significantly improves the recovery effect of valuable metals in iron tailings. Specific embodiments

[0033] In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present application clearer and more understandable, the following further details the present application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0034] The specific embodiments of the present invention provide a process for recovering valuable metals based on the chlorination volatilization method, including the following steps:

[0035] S1. Crush and grind iron tailings through a 200 - 400 mesh sieve to obtain iron tailings powder. Add the iron tailings powder and a composite chlorinating agent into a blender, and stir at a speed of 60 r / min - 200 r / min for 0.5 h - 1 h to obtain a mixture. Add water to the mixture, stir evenly to obtain a moistened material, and then pelletize to obtain pellets to be treated;

[0036] S2. Heat the pellets to be treated in S1 to 800°C - 850°C in one stage, keep them at this temperature for 2 h, collect the zinc - containing dust generated during the volatilization process, and then heat them to 1000°C - 1200°C in the second stage, keep them at this temperature for 4 h, collect the lead - containing dust generated during the volatilization process, and obtain a calcination residue;

[0037] S3. Under a nitrogen atmosphere, cool the calcination residue to 40°C - 60°C, grind it, and then perform magnetic separation to obtain magnetite.

[0038] In S1, the mass ratio of the iron tailings powder to the composite chlorinating agent is 1:0.1 - 1.

[0039] The composite chlorinating agent is prepared by compounding a supported inorganic chlorinating agent and a silane - grafted polyvinyl chloride.

[0040] In the composite chlorinating agent, the mass ratio of the supported inorganic chlorinating agent to the silane - grafted polyvinyl chloride is 1:0.5 - 1.

[0041] The supported inorganic chlorinating agent is an activated - carbon - supported chloride salt.

[0042] The chloride salt is at least one of sodium chloride, calcium chloride, ferric chloride, ammonium chloride, and magnesium chloride, and preferably calcium chloride.

[0043] The activated carbon is powdered activated carbon, and the particle size of the powdered activated carbon is 200μm - 400μm.

[0044] The preparation process of the supported inorganic chlorinating agent is as follows:

[0045] Add the chloride salt into distilled water, stir evenly, then add activated carbon, impregnate at room temperature for 6 h - 10 h, and then dry in an oven at 120°C to constant weight to obtain the supported inorganic chlorinating agent.

[0046] The dosage ratio of the chloride salt, distilled water, and activated carbon in is 20 g:100 mL:7 g - 15 g.

[0047] The silane - grafted polyvinyl chloride is a methacryloxypropyltriethoxysilane - grafted polyvinyl chloride.

[0048] The preparation process of the silane - grafted polyvinyl chloride is as follows:

[0049] Dissolve polyvinyl chloride in nitrobenzene at room temperature to form a transparent solution, then introduce an initiator and 3-(trimethoxysilyl)propyl methacrylate. Under nitrogen protection, stir and react at 60 °C to 70 °C for 4 h to 5 h. After the reaction is completed, cool to room temperature, add methanol to precipitate, wash the precipitate with methanol 3 - 5 times, then use methanol as an extraction agent and perform Soxhlet extraction and purification for 2 h. Dry the purified product at 40 °C to constant weight, crush it through a 200-mesh sieve to obtain the silane-grafted polyvinyl chloride.

[0050] The dosage ratio of polyvinyl chloride, nitrobenzene, initiator, 3-(trimethoxysilyl)propyl methacrylate and methanol is 5 g : 50 mL to 100 mL : 0.012 g to 0.025 g : 0.2 g to 0.5 g : 500 mL to 1000 mL.

[0051] The initiator is bis(2-phenoxyethyl) peroxydicarbonate (BPPD).

[0052] The iron content in the iron tailings is 20 wt% to 60 wt%, the zinc content is 6 wt% to 15 wt%, and the lead content is 0.01 wt% to 0.5 wt%.

[0053] When adding water in S1, the water content in the wetted material should be controlled at 7.5 ± 0.2%.

[0054] The pelletizing in S1 is carried out in a φ1000 mm disc pelletizer with a side height of 200 mm, an inclination angle of 45°, a rotation speed of 25 r / min to 40 r / min, and a pelletizing time of 15 min.

[0055] The diameter of the pellets to be processed in S1 is 12 mm to 16 mm.

[0056] In S2, air is introduced during the first-stage heating and the second-stage heating processes, and the introduction rate is 5000 L / (t·min) to 1500 L / (t·min).

[0057] The nitrogen gas flow rate in S3 is 20 mL / min to 200 mL / min.

[0058] The technical solutions of the present application are illustrated below through specific examples and comparative examples. In the examples and comparative examples, the iron content in the iron tailings is 20 wt% to 60 wt%, the zinc content is 6 wt% to 15 wt%, and the lead content is 0.01 wt% to 0.5 wt%.

[0059] Preparation Example 1

[0060] The preparation of silane-grafted polyvinyl chloride is as follows:

[0061] Dissolve 5 g of polyvinyl chloride in 50 mL of nitrobenzene at room temperature to form a transparent solution, then introduce 0.012 g of bis(2-phenoxyethyl) peroxydicarbonate and 0.2 g of methacryloxypropyltriethoxysilane. Under nitrogen protection, stir and react at 60 °C for 4 h. After the reaction is completed, cool to room temperature, add 500 mL of methanol to precipitate. Wash the precipitate with methanol three times, then use methanol as the extractant and perform Soxhlet extraction and purification for 2 h. Dry the purified product at 40 °C to constant weight, crush it through a 200-mesh sieve to obtain the silane-grafted polyvinyl chloride.

[0062] Preparation Example 2

[0063] The preparation of silane-grafted polyvinyl chloride is as follows:

[0064] Dissolve 5 g of polyvinyl chloride in 100 mL of nitrobenzene at room temperature to form a transparent solution, then introduce 0.025 g of bis(2-phenoxyethyl) peroxydicarbonate and 0.5 g of methacryloxypropyltriethoxysilane. Under nitrogen protection, stir and react at 70 °C for 5 h. After the reaction is completed, cool to room temperature, add 1000 mL of methanol to precipitate. Wash the precipitate with methanol five times, then use methanol as the extractant and perform Soxhlet extraction and purification for 2 h. Dry the purified product at 40 °C to constant weight, crush it through a 200-mesh sieve to obtain the silane-grafted polyvinyl chloride.

[0065] Example 1

[0066] A process for recovering valuable metals based on the chlorination volatilization method includes the following steps:

[0067] S1. Crush and grind the iron tailings through a 200-mesh sieve to obtain iron tailings powder. Add the iron tailings powder and the composite chlorinating agent to a mixer and stir at a speed of 60 r / min for 0.5 h to obtain a mixture. Add water to the mixture and stir evenly to obtain a wetted material. Control the moisture content of the wetted material to be 7.5 ± 0.2%, and then perform pelletizing to obtain pellets to be treated with a diameter of 12 mm to 16 mm;

[0068] S2. Heat the pellets to be treated in S1 to 800 °C in one stage and hold for 2 h. Collect the zinc-containing dust generated during the volatilization process. Then heat to 1000 °C in the second stage and hold for 4 h. Collect the lead-containing dust generated during the volatilization process and obtain a calcination residue;

[0069] S3. Under a nitrogen atmosphere with a nitrogen flow rate of 20 mL / min, cool the calcination residue to 40 °C, grind it, and then perform magnetic separation to obtain magnetite.

[0070] The mass ratio of the iron tailings powder to the composite chlorinating agent in S1 is 1:0.1.

[0071] The composite chlorinating agent is prepared by compounding a supported inorganic chlorinating agent and the silane-grafted polyvinyl chloride of Preparation Example 1 in a mass ratio of 1:0.5.

[0072] The preparation process of the supported inorganic chlorinating agent is as follows:

[0073] Add 20 g of ferric chloride to 100 mL of distilled water, stir evenly, then add 7 g of activated carbon, impregnate at room temperature for 6 h, and dry in an oven at 120 °C until constant weight to obtain the supported inorganic chlorinating agent.

[0074] The activated carbon is powdered activated carbon, and the particle size of the powdered activated carbon is 200 μm to 400 μm.

[0075] The pelletizing in S1 is carried out in a φ1000 mm and 200 mm high-edge disk pelletizer, with an inclination angle of 45°, a rotation speed of 25 r / min, and a pelletizing time of 15 min.

[0076] In the first-stage heating and the second-stage heating processes in S2, air is introduced at a rate of 1500 L / (t·min).

[0077] Example 2

[0078] A process for recovering valuable metals based on the chlorination volatilization method includes the following steps:

[0079] S1. Crush and grind the iron tailings through a 300-mesh sieve to obtain iron tailings powder. Add the iron tailings powder and the composite chlorinating agent to a mixer, stir at a speed of 100 r / min for 0.8 h to obtain a mixture. Add water to the mixture and stir evenly to obtain a moistened material. Control the moisture content in the moistened material to be 7.5 ± 0.2%, and then carry out pelletizing to obtain pellets to be treated with a diameter of 12 mm to 16 mm;

[0080] S2. Heat the pellets to be treated in S1 to 830 °C in the first stage, hold for 2 h, collect the zinc-containing dust generated during the volatilization process, then heat to 1100 °C in the second stage, hold for 4 h, collect the lead-containing dust generated during the volatilization process, and obtain a calcination residue;

[0081] S3. Under a nitrogen atmosphere with a nitrogen flow rate of 100 mL / min, cool the calcination residue to 50 °C, grind it, and then carry out magnetic separation to obtain magnetite.

[0082] In S1, the mass ratio of the iron tailings powder to the composite chlorinating agent is 1:0.5.

[0083] The composite chlorinating agent is prepared by compounding a supported inorganic chlorinating agent and the silane-grafted polyvinyl chloride of Preparation Example 2 in a mass ratio of 1:0.8.

[0084] The preparation process of the supported inorganic chlorinating agent is as follows:

[0085] Add 20 g of sodium chloride to 100 mL of distilled water. After stirring evenly, add 11 g of activated carbon and impregnate at room temperature for 8 h. Then dry it in an oven at 120 °C until constant weight to obtain the supported inorganic chlorinating agent.

[0086] The activated carbon is powdered activated carbon, and the particle size of the powdered activated carbon is 200 μm to 400 μm.

[0087] The pelletizing in S1 is carried out in a φ1000 mm disc pelletizing machine with a side height of 200 mm, an inclination angle of 45°, a rotation speed of 40 r / min, and a pelletizing time of 15 min.

[0088] In S2, air is introduced during the first-stage heating and the second-stage heating processes, and the introduction rate is 1000 L / (t·min).

[0089] Example 3

[0090] A process for recovering valuable metals based on the chlorination volatilization method, comprising the following steps:

[0091] S1. Crush and grind the iron tailings through a 400-mesh sieve to obtain iron tailings powder. Add the iron tailings powder and the composite chlorinating agent to a mixer and stir at a speed of 200 r / min for 1 h to obtain a mixture. Add water to the mixture and stir evenly to obtain a wetted material. Control the water content in the wetted material to be 7.5 ± 0.2%, and then carry out pelletizing to obtain pellets with a diameter of 12 mm to  16 mm to be treated;

[0092] S2. Heat the pellets to be treated in S1 to 850 °C in the first stage, hold for 2 h, collect the zinc-containing dust generated during the volatilization process, then heat to 1200 °C in the second stage, hold for 4 h, collect the lead-containing dust generated during the volatilization process, and obtain a calcination residue;

[0093] S3. Under a nitrogen atmosphere with a nitrogen flow rate of 200 mL / min, cool the calcination residue to 60 °C, grind it, and then carry out magnetic separation to obtain magnetite.

[0094] In S1, the mass ratio of the iron tailings powder to the composite chlorinating agent is 1:1.

[0095] The composite chlorinating agent is prepared by compounding the supported inorganic chlorinating agent and the silane-grafted polyvinyl chloride of Preparation Example 2 according to a mass ratio of 1:1.

[0096] The preparation process of the supported inorganic chlorinating agent is as follows:

[0097] Add 20 g of calcium chloride to 100 mL of distilled water. After stirring evenly, add 15 g of activated carbon and impregnate at room temperature for 10 h. Then dry it in an oven at 120 °C until constant weight to obtain the supported inorganic chlorinating agent.

[0098] The activated carbon is powdered activated carbon, and the particle size of the powdered activated carbon is 200 μm to 400 μm.

[0099] In S1, pelletizing is carried out in a φ1000 mm disc pelletizer with a side height of 200 mm, an inclination angle of 45°, a rotation speed of 40 r / min, and a pelletizing time of 15 min.

[0100] In S2, air is introduced during the first-stage heating and the second-stage heating processes, and the introduction rate is 1500 L / (t·min).

[0101] Example 4

[0102] A process for recovering valuable metals based on the chlorination volatilization method. Compared with Example 1, the only difference is that "ferric chloride" in Example 1 is replaced with an equal mass of "ammonium chloride".

[0103] Example 5

[0104] A process for recovering valuable metals based on the chlorination volatilization method. Compared with Example 1, the only difference is that "ferric chloride" in Example 1 is replaced with an equal mass of "magnesium chloride".

[0105] Example 6

[0106] A process for recovering valuable metals based on the chlorination volatilization method. Compared with Example 1, the only difference is that the mass ratio of iron tailings powder to the composite chlorinating agent is 1:0.3.

[0107] Example 7

[0108] A process for recovering valuable metals based on the chlorination volatilization method. Compared with Example 1, the only difference is that the mass ratio of iron tailings powder to the composite chlorinating agent is 1:0.8.

[0109] Example 8

[0110] A process for recovering valuable metals based on the chlorination volatilization method. Compared with Example 1, the only difference is that the composite chlorinating agent is prepared by compounding a supported inorganic chlorinating agent and the silane-grafted polyvinyl chloride of Preparation Example 2 in a mass ratio of 1:0.7

[0111] Comparative Example 1

[0112] A process for recovering valuable metals based on the chlorination volatilization method. Compared with Example 3, the only difference is that the supported inorganic chlorinating agent in Example 3 is replaced with a product obtained by stirring 20 g of calcium chloride and 15 g of activated carbon in a blender at 100 r / min for 30 min.

[0113] Comparative Example 2

[0114] A process for recovering valuable metals based on the chlorination volatilization method. Compared with Example 3, the only difference is that the silane-grafted polyvinyl chloride in Example 3 is replaced with polyvinyl chloride that has been pulverized and passed through a 200-mesh molybdenum sieve.

[0115] Comparative Example 3

[0116] A process for recovering valuable metals based on the chlorination volatilization method. Compared with Example 3, the only difference is that the supported inorganic chlorinating agent in Example 3 is removed.

[0117] Comparative Example 4

[0118] A process for recovering valuable metals based on the chlorination volatilization method. Compared with Example 3, the only difference is that the silane-grafted polyvinyl chloride in Example 3 is removed.

[0119] For the processes for recovering valuable metals based on the chlorination volatilization method described in Examples 1 - 8 and Comparative Examples 1 - 4, the removal rates of zinc and lead in the calcination residue were calculated. The calculation formula is:

[0120] Metal volatilization rate (%) = [1 - (c × m) / (C × M)] × 100%, where: C is the metal concentration in the iron tailings (mg / Kg), M is the addition amount of iron tailings (g); c is the metal concentration in the residue after calcination (mg / Kg); m is the mass of the residue after calcination (g);

[0121] The results are shown in Table 1:

[0122] Table 1

[0123]

[0124]

[0125] Analysis of each test data in Table 1 shows that the zinc volatilization rate of the process for recovering valuable metals by chlorination volatilization described in Examples 1-8 is 89.4-94.2%, and the lead volatilization rate is 96.0-99.1%. This indicates that the process provided by the present invention can efficiently recover zinc and lead, solve the problems of low recovery rates of zinc and lead in existing iron tailings and ineffective utilization of iron, greatly improve the resource utilization rate, and realize the resource utilization of solid waste. Specifically, from the test results in Example 3 and Comparative Example 1, it can be seen that the supported inorganic chlorinating agent obtained by mixing calcium chloride and activated carbon has a worse effect compared to the supported inorganic chlorinating agent obtained by impregnation treatment, ultimately resulting in lower zinc and lead volatilization rates. From the test results in Example 3 and Comparative Example 2, it can be seen that when replacing silane-grafted polyvinyl chloride with polyvinyl chloride, due to the lack of coupling effect and the growth of silica as the high-temperature calcination product, the zinc and lead volatilization rates are ultimately lower. From the test results in Example 3 and Comparative Example 3, it can be seen that when using silane-grafted polyvinyl chloride alone as the chlorinating agent, the zinc and lead volatilization rates decrease significantly. From the test results in Example 3 and Comparative Example 4, it can be seen that when using the supported inorganic chlorinating agent alone as the chlorinating agent, the zinc and lead volatilization rates decrease significantly. Therefore, in the present invention, the supported inorganic chlorinating agent and silane-grafted polyvinyl chloride are used as a composite chlorinating agent, and there is a synergistic effect between them to jointly ensure a high volatilization rate of zinc and lead.

[0126] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such process, method, article or device.

[0127] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for recovering valuable metals based on the chlorination volatilization method, characterized in that, It includes the following steps: S1. Crush and grind iron tailings to obtain iron tailings powder. Add the iron tailings powder and a composite chlorinating agent into a blender, stir for 0.5 h to 1 h to obtain a mixture. Add water to the mixture, stir evenly, and form pellets to obtain the pellets to be treated; S2. Heat the pellets to be treated in one stage to 800 - 850 °C, keep the temperature for 2 h, collect the volatile dust, and then heat to 1000 °C - 1200 °C in the second stage, keep the temperature for 4 h, collect the volatile dust, and obtain the calcined residue; S3. Under a nitrogen atmosphere, cool the calcined residue to 40 °C - 60 °C, grind it and then perform magnetic separation to obtain magnetite; The composite chlorinating agent is prepared by compounding a supported inorganic chlorinating agent and silane-grafted polyvinyl chloride; The supported inorganic chlorinating agent is an activated carbon supported chloride salt.

2. The process for recovering valuable metals based on the chlorination volatilization method according to claim 1, characterized in that, In S1, the mass ratio of the iron tailings powder to the composite chlorinating agent is 1:0.1 - 1.

3. A process for recovering valuable metals based on the chlorination volatilization method according to claim 1, characterized in that, In the composite chlorinating agent, the mass ratio of the supported inorganic chlorinating agent to silane-grafted polyvinyl chloride is 1:0.5 - 1.

4. A process for recovering valuable metals based on the chlorination volatilization method according to claim 1, characterized in that, The chloride salt is at least one of sodium chloride, calcium chloride, ferric chloride, ammonium chloride, and magnesium chloride.

5. A process for recovering valuable metals based on the chlorination volatilization method according to claim 1, characterized in that, The silane-grafted polyvinyl chloride is methylacryloxypropyltriethoxysilane-grafted polyvinyl chloride.

6. The process for recovering valuable metals based on the chlorination volatilization method according to claim 1, characterized in that, The preparation process of the silane-grafted polyvinyl chloride is as follows: Dissolve polyvinyl chloride in nitrobenzene at room temperature to form a transparent solution, then introduce an initiator and methylacryloxypropyltriethoxysilane. Under nitrogen protection, stir and react at 60 °C - 70 °C for 4 h to 5 h. After the reaction, cool to room temperature, add methanol to precipitate. Wash the precipitate with methanol 3 - 5 times, then use methanol as an extraction agent and perform Soxhlet extraction and purification for 2 h. Dry the purified product at 40 °C to constant weight, crush it and pass through a 200-mesh sieve to obtain the silane-grafted polyvinyl chloride.

7. A process for recovering valuable metals based on the chlorination volatilization method according to claim 6, characterized in that, The dosage ratio of polyvinyl chloride, nitrobenzene, initiator, methylacryloxypropyltriethoxysilane, and methanol is 5 g:50 mL - 100 mL:0.012 g - 0.025 g:0.2 g - 0.5 g:500 mL - 1000 mL.

8. A process for recovering valuable metals based on the chlorination volatilization method according to claim 6, characterized in that, The initiator is bis(2-phenoxyethyl) peroxydicarbonate.

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