A method for efficiently recovering tungsten from alkali leaching tungsten residue

Abstract

The present application belongs to the technical field of solid waste resource utilization and process closed loop in hydrometallurgy, and specifically discloses a method for efficiently recovering tungsten from alkali leaching tungsten slag. The tungsten slag is first pretreated by grinding through a ball mill, the obtained pretreated slag is subjected to leaching operation, and then the obtained leaching solution is subjected to cyclic pressure boiling. By optimizing pressure boiling parameters such as alkali concentration, temperature and pressure, the insoluble tungsten compounds in the tungsten slag are directionally dissolved, and the tungsten concentration is gradually enriched to match the main process indicators. No additional evaporation and concentration or purification equipment is needed, the industrialization modification difficulty is low, the existing main process equipment can be directly reused, the tungsten recovery rate is high, the main process is well connected, the alkali solution for pressure boiling is recycled, not only the reagent is saved, but also a large amount of alkali-containing wastewater is avoided, which is environmentally friendly and economical. The tungsten recovery rate is greater than or equal to 95% by using the method, the utilization rate of the material liquid is greater than or equal to 90%, solid waste resource utilization and material liquid closed loop utilization are realized, and the method is suitable for industrialization and popularization.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste resource utilization and process closed loop in hydrometallurgy, and specifically discloses a method for efficiently recovering tungsten from alkali leaching tungsten slag. BACKGROUND

[0002] Tungsten is a key strategic metal and is widely used in the fields of aerospace, high-end cutters, electronic information, etc. In the alkali leaching process of hydrometallurgical tungsten smelting, a large amount of tungsten slag will be produced, which usually contains 1-5wt% of tungsten, silicate gangue and other insoluble tungsten compounds such as calcium tungstate that are not completely dissolved. If the tungsten slag is directly stored, not only the tungsten resources will be seriously wasted, but also the soil and groundwater will be polluted due to the storage of solid waste; therefore, the secondary recovery of tungsten slag is a key link for the hydrometallurgical industry to realize efficient utilization of resources.

[0003] The existing technology usually adopts single pressure cooking or acid leaching process to recover tungsten from tungsten slag, which has the following problems: (1) low tungsten recovery rate, the tungsten recovery rate is usually less than 85%, and a large amount of tungsten metal is lost with the tailings; (2) serious waste of liquid, the alkali solution used for pressure cooking is usually used only once, and direct discharge or treatment not only wastes reagents, but also produces a large amount of wastewater containing alkali and tungsten, increasing the environmental protection treatment cost; (3) poor connection of main process, the low-concentration recovery liquid cannot be directly connected to the main process purification and purification process because the tungsten content is much lower than that of the main process leaching liquid, and independent evaporation and concentration or purification equipment needs to be added, resulting in complex process and high investment cost; (4) high energy consumption cost, in order to improve the recovery rate, the existing process usually adopts super-high temperature pressure cooking of more than 200 degrees, which significantly increases the energy consumption and the cost of processing per ton of slag.

[0004] Therefore, it is of great significance to develop a process that can efficiently recover tungsten from tungsten slag, realize recycling and reuse of liquid, and seamlessly connect with the main process, for resource saving, cost reduction and green development of the hydrometallurgical industry. SUMMARY

[0005] In order to solve the problems in the background art, the application discloses a method for efficiently recovering tungsten from alkali leaching tungsten slag, which dissolves the insoluble tungsten compounds and increases the tungsten concentration in the liquid by pretreatment, intensified pressure cooking and three times of liquid circulation enrichment, so that the qualified liquid is directly returned to the main process, forming a closed loop process of solid waste recovery-liquid circulation-main process reuse, improving the tungsten recovery rate and reducing the cost of reagents and energy consumption.

[0006] In order to achieve the above-mentioned application purposes, the application adopts the following technical solutions:

[0007] A method for efficiently recovering tungsten from alkali leaching tungsten slag, comprising the following steps:

[0008] (1) Pretreatment: crushing and grinding the alkali leaching tungsten slag with a tungsten content of 0.5-5wt% produced in the main process of hydrometallurgical tungsten smelting to obtain pretreated slag;

[0009] (2) Leaching: The pretreated residue is added into sodium carbonate lye, and the obtained suspension is sent into a pressure cooking kettle for pressure cooking. After the pressure cooking is completed, filtration is performed to obtain a first leaching solution and a pressure cooked residue;

[0010] (3) Circulating pressure cooking: The first leaching solution is mixed with new tungsten residue at the same liquid-solid ratio as that in step (2) for leaching pressure cooking. After the pressure cooking, filtration is performed to obtain a first circulating leaching solution and a pressure cooked residue. The first circulating leaching solution is mixed with new tungsten residue at the same liquid-solid ratio as that in step (2) for leaching pressure cooking. After the pressure cooking, filtration is performed to obtain a second circulating leaching solution and a pressure cooked residue. The process is repeated to obtain an Nth circulating leaching solution and a pressure cooked residue, wherein N is an integer greater than or equal to 2 and less than or equal to 5.

[0011] (4) Material liquid standard detection and return to main process: The Nth circulating leaching solution is detected. If the tungsten concentration is greater than or equal to 85 g / L, the Nth circulating leaching solution is directly pumped into a tungsten purification process of a hydrometallurgy main process, mixed with the main process leaching solution, and then subjected to subsequent impurity removal and purification processes. If the concentration does not meet the standard, the solution is used as a circulating material liquid for the next round of circulating pressure cooking until the standard is met.

[0012] (5) Harmless treatment of tailings: The pressure cooked residues obtained in steps (2) and (3) are mixed, the pH value is adjusted to 8-9 by adding lime milk, 2-3 wt% calcium dihydrogen phosphate is added as a stabilizer, stirring is performed, and the solidified body is sent into a solidification device to form a block-shaped solidified body after solidification. The heavy metal leaching concentration is detected after solidification. If the concentration meets the standard requirements, the solidified body is safely landfilled or used as a building aggregate auxiliary material.

[0013] Further, in the method for efficiently recovering tungsten from alkali leaching tungsten residue, the liquid-solid ratio of sodium carbonate lye to pretreated residue in step (2) is 3:1-6:1.

[0014] Further, in the method for efficiently recovering tungsten from alkali leaching tungsten residue, the concentration of sodium carbonate lye in step (2) is 130-170 g / L.

[0015] Further, in the method for efficiently recovering tungsten from alkali leaching tungsten residue, the pressure cooking temperature in step (2) is 155-185℃, the pressure is 0.5-0.75 MPa, the stirring rate is 300-500 r / min, and the pressure cooking time is 2-3 h.

[0016] Further, in the method for efficiently recovering tungsten from alkali leaching tungsten residue, in steps (2) and (3), the pressure cooking kettle is equipped with a temperature-pressure linkage control system. During the pressure cooking process, the pressure fluctuation is maintained at ≤±0.05 MPa and the temperature fluctuation is maintained at ≤±4℃ by nitrogen gas supplement. After the pressure cooking is completed, the kettle is cooled at a gradient of 6-9℃ / min to avoid scaling in the kettle.

[0017] Further, in the method for efficiently recovering tungsten from alkali leaching tungsten residue, the concentration of sodium carbonate in the feed liquid is 130-170 g / L before each cycle of pressure boiling, and if the concentration is lower than 130 g / L, solid sodium carbonate is supplemented to the target concentration.

[0018] Further, in the method for efficiently recovering tungsten from alkali leaching tungsten residue, N is equal to 3 in step (3), that is, the pressure boiling is performed three times in step (3).

[0019] Compared with the prior art, the method has the following beneficial effects:

[0020] The method for efficiently recovering tungsten from alkali leaching tungsten residue comprises the following steps: pretreating tungsten residue generated by a main wet metallurgical process through a ball mill, which can significantly increase the specific surface area of the tungsten residue, break the particle agglomeration structure, expose the internal wrapped insoluble tungsten compounds such as calcium tungstate, reduce the mass transfer resistance in the subsequent pressure boiling process, and avoid the insufficient dissolution of tungsten caused by coarse particles; performing leaching operation on the obtained pretreated residue; and performing cycle pressure boiling on the obtained leaching liquid, and optimizing the pressure boiling parameters such as alkali concentration, temperature and pressure to directionally dissolve the insoluble tungsten compounds in the tungsten residue and gradually enrich the tungsten concentration to match the main process index. The method does not need to add evaporation and concentration or purification equipment, has low industrialization modification difficulty, can directly reuse the existing main process equipment, has high tungsten recovery rate, has good main process connection, and the alkali solution for pressure boiling is recycled, which not only saves reagents, but also avoids the generation of a large amount of alkali-containing wastewater, is environmentally friendly and economical, has a tungsten recovery rate of ≥95% by using the method, has a feed liquid recycling rate of ≥90%, realizes solid waste resource utilization and feed liquid closed loop utilization, and is suitable for industrialization promotion. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a process flow chart of the method. DETAILED DESCRIPTION

[0022] In order to better understand the present application, the content of the present application will be further clarified below in combination with examples, but the protection content of the present application is not limited to the following examples. In the following description, a large number of specific details are given in order to provide a more complete understanding of the present application. However, it is obvious to those skilled in the art that the present application can be implemented without one or more of these details. Example 1

[0023] A method for efficiently recovering tungsten from alkali leaching tungsten residue, comprising the following steps:

[0024] Preprocessing: The alkali leaching tungsten slag with 1.5wt% tungsten content produced by the main process of hydrometallurgical tungsten smelting is crushed and ground to obtain pretreated slag. This step can significantly increase the specific surface area of the tungsten slag, break the particle agglomeration structure, expose the internal wrapped insoluble tungsten compounds such as calcium tungstate, reduce the mass transfer resistance in the subsequent pressure cooking process, and avoid the insufficient dissolution of tungsten caused by coarse particles;

[0025] Leaching: The pretreated slag is added to a sodium carbonate solution with a liquid-solid ratio of 3:1. The concentration of the sodium carbonate solution is 150g / L. The obtained suspension is fed into a pressure cooking kettle that is resistant to alkali corrosion, high temperature and pressure, and suitable for strong alkaline pressure cooking environment. The pressure cooking is carried out at a temperature of 175℃, a pressure of 0.65MPa, and a stirring speed of 450r / min for 2h. During this process, sodium carbonate reacts with calcium tungstate in the tungsten slag to form soluble sodium tungstate (CaWO4+ Na2CO3 = Na2WO4+ CaCO3), while silicate gangue does not participate in the reaction. After the pressure cooking, the kettle is cooled at a rate of 6-9℃ / min to avoid scaling. Filtration is performed to obtain the first leaching solution and the pressure cooking residue. The tungsten content in the first leaching solution is 35.2g / L, and the first pressure cooking residue contains a small amount of tungsten that has not been completely dissolved;

[0026] Circulating pressure cooking

[0027] First cycle: The first leaching solution is mixed with new tungsten slag at a liquid-solid ratio of 3:1 for leaching and pressure cooking. The sodium tungstate already contained in the first leaching solution can "induce" the dissolution of insoluble tungsten compounds in the new slag, improving the dissolution efficiency. After 2h of pressure cooking, the first cycle leaching solution and the pressure cooking residue are obtained by filtration. The tungsten content in the first cycle leaching solution is 61.5g / L. The first pressure cooking residue is combined with the current cycle pressure cooking residue and re-cooked to avoid tungsten loss;

[0028] Second cycle: The first leaching solution is mixed with new tungsten slag at a liquid-solid ratio of 3:1 for leaching and pressure cooking. The tungsten concentration in the solution is further increased, which can reduce the dissolution energy barrier of tungsten in the new slag and shorten the reaction time. After 2h of pressure cooking, the second cycle leaching solution with a tungsten content of 75.8g / L and the pressure cooking residue are obtained by filtration;

[0029] Third cycle: The second leaching solution is mixed with new tungsten slag at a liquid-solid ratio of 3:1 for leaching. After 2h of pressure cooking, the third cycle leaching solution with a tungsten content of 90.3g / L and the pressure cooking residue are obtained by filtration. The tungsten content in the third cycle leaching solution meets the standard and is directly returned to the main process. The tungsten recovery rate is 95.6%,

[0030] It should be noted that during the circulating pressure cooking process, if the residual concentration of sodium carbonate in the solution still meets the reaction requirements, i.e. the concentration of sodium carbonate is 130-170g / L, solid sodium carbonate does not need to be supplemented. If the residual concentration of sodium carbonate in the solution cannot meet the reaction requirements, solid sodium carbonate needs to be supplemented to meet the standard.

[0031] Tailings harmless treatment: the obtained pressure cooking slag is mixed, the water content of the pressure cooking slag is ≤25%, the pH value is adjusted to 8-9 by lime milk, 2-3wt% of calcium dihydrogen phosphate is added as a stabilizer, and the reaction is carried out at a stirring rate of 180-220r / min for 1h, then it is sent to a solidification device to form a block-shaped solidified body, after solidification, the heavy metal leaching concentration is detected, and if it meets the standard requirements, it is safely landfilled or used as a building aggregate auxiliary material. Example 2

[0032] A method for efficiently recovering tungsten from alkali leaching tungsten slag, comprising the following steps:

[0033] Pretreatment: the alkali leaching tungsten slag with a tungsten content of 2.1wt% generated by the main process of hydrometallurgical tungsten smelting is crushed and ground to obtain pretreated slag. This step can significantly increase the specific surface area of the tungsten slag, break the particle agglomeration structure, expose the internal wrapped insoluble tungsten compounds such as calcium tungstate, reduce the mass transfer resistance in the subsequent pressure cooking process, and avoid insufficient tungsten dissolution caused by coarse particles;

[0034] Leaching: the pretreated slag is added to a sodium carbonate alkali solution with a liquid-solid ratio of 4:1, and the concentration of the sodium carbonate solution is 135g / L. The obtained suspension is sent to a pressure cooking kettle that is resistant to alkali corrosion, high temperature and high pressure, and suitable for strong alkaline pressure cooking environment. Under the conditions of temperature 160℃, pressure 0.55MPa, and stirring 350r / min, pressure cooking is carried out for 2.2h. During this process, sodium carbonate reacts with calcium tungstate in the tungsten slag to generate soluble sodium tungstate (CaWO4+ Na2CO3 = Na2WO4+ CaCO3), while silicate gangue basically does not participate in the reaction. After pressure cooking, the kettle is cooled at a gradient of 6-9℃ / min to avoid scaling. Filtration is performed to obtain the first leaching solution and pressure cooking slag. The tungsten content in the first leaching solution is 29.5g / L, and the first pressure cooking slag contains a small amount of tungsten that has not been completely dissolved;

[0035] Cyclic pressure cooking

[0036] First cycle: the first leaching solution is mixed with new tungsten slag for leaching and pressure cooking with a liquid-solid ratio of 4:1. The sodium tungstate already contained in the first leaching solution can "induce" the dissolution of insoluble tungsten compounds in the new slag, improving the dissolution efficiency. After pressure cooking for 2-3h, the first cycle leaching solution and pressure cooking slag are obtained after filtration. The tungsten content in the first cycle leaching solution is 59.2g / L. The first pressure cooking slag is combined with the current cycle pressure cooking slag, and re-pressure cooking is performed to avoid tungsten loss;

[0037] Second cycle: the first leaching solution is mixed with new tungsten residue at a liquid-solid ratio of 4:1 for leaching and pressure cooking. At this time, the tungsten concentration in the feed solution is further increased, which can reduce the tungsten dissolution energy barrier in the new residue and shorten the reaction time. After pressure cooking for 2-3 hours, the second cycle leaching solution with a tungsten content of 73.7 g / L and the pressure cooked residue are obtained by filtration;

[0038] Third cycle: the second leaching solution is mixed with new tungsten residue at a liquid-solid ratio of 4:1 for leaching. After pressure cooking for 2-3 hours, the third cycle leaching solution with a tungsten content of 89.7 g / L and the pressure cooked residue are obtained by filtration. The tungsten content in the third cycle leaching solution meets the standard, and it is directly returned to the main process. The tungsten recovery rate is 95.1%,

[0039] It should be noted that during the cycle pressure cooking process, if the residual sodium carbonate concentration in the feed solution still meets the reaction requirements, i.e. the sodium carbonate concentration is 130-170 g / L, solid sodium carbonate does not need to be supplemented. If the residual sodium carbonate concentration in the feed solution cannot meet the reaction requirements, solid sodium carbonate needs to be supplemented to meet the standard;

[0040] Harmless treatment of tailings: the obtained pressure cooked residue is mixed, and the water content of the pressure cooked residue is ≤25%. The pH value is adjusted to 8-9 by lime milk, 2-3wt% of calcium dihydrogen phosphate is added as a stabilizer, and the reaction is carried out at a stirring rate of 180-220 r / min for 1 h. Then it is sent to a solidification device to form a block-shaped solidified body. After solidification, the heavy metal leaching concentration is detected. If it meets the standard requirements, it is safely landfilled or used as a building aggregate auxiliary material. Example 3

[0041] A method for efficiently recovering tungsten from alkali leaching tungsten residue, comprising the following steps:

[0042] Pretreatment: the alkali leaching tungsten residue with a tungsten content of 2.8wt% produced by the main process of hydrometallurgical tungsten smelting is crushed and ground to obtain pretreated residue. This step can significantly increase the specific surface area of the tungsten residue, break the particle agglomeration structure, expose the internal wrapped insoluble tungsten compounds such as calcium tungstate, reduce the mass transfer resistance in the subsequent pressure cooking process, and avoid the insufficient dissolution of tungsten caused by coarse particles;

[0043] Leaching: The pretreated residue is added into sodium carbonate solution with a liquid-solid ratio of 6:1, and the concentration of the sodium carbonate solution is 140 g / L. The obtained suspension is fed into a pressure cooking kettle that is resistant to alkali corrosion, high temperature and pressure, and suitable for strong alkali pressure cooking environment. The pressure cooking is carried out at a temperature of 165℃, a pressure of 0.60 MPa, and a stirring speed of 450 r / min for 2 h. During the process, sodium carbonate reacts with calcium tungstate in the tungsten residue to generate soluble sodium tungstate (CaWO4+ Na2CO3 = Na2WO4+ CaCO3), and silicate gangue basically does not participate in the reaction. After the pressure cooking, the kettle is cooled at a gradient of 6-9℃ / min to avoid scaling in the kettle. Filtration is performed to obtain a first leaching solution and a pressure cooking residue. The tungsten content in the first leaching solution is 28.6 g / L, and the first pressure cooking residue contains a small amount of tungsten that is not completely dissolved.

[0044] Circulating pressure cooking

[0045] First circulation: The first leaching solution is mixed with new tungsten residue for leaching and pressure cooking with a liquid-solid ratio of 6:1. The sodium tungstate already contained in the first leaching solution can "induce" the dissolution of the insoluble tungsten compounds in the new residue, thereby improving the dissolution efficiency. After pressure cooking for 2 h, the first circulation leaching solution and the pressure cooking residue are obtained after filtration. The tungsten content in the first circulation leaching solution is 57.8 g / L. The first pressure cooking residue is combined with the circulating pressure cooking residue, and re-pressure cooking is performed to avoid tungsten loss.

[0046] Second circulation: The first leaching solution is mixed with new tungsten residue for leaching and pressure cooking with a liquid-solid ratio of 6:1. At this time, the tungsten concentration in the feed solution is further increased, which can reduce the dissolution energy barrier of tungsten in the new residue and shorten the reaction time. After pressure cooking for 2 h, the second circulation leaching solution with a tungsten content of 70.6 g / L and the pressure cooking residue are obtained after filtration.

[0047] Third circulation: The second leaching solution is mixed with new tungsten residue for leaching with a liquid-solid ratio of 6:1. After pressure cooking for 2 h, the third circulation leaching solution with a tungsten content of 88.4 g / L and the pressure cooking residue are obtained after filtration. The tungsten content in the third circulation leaching solution meets the standard, and it is directly returned to the main process. The tungsten recovery rate is 95.4%.

[0048] It should be noted that during the circulating pressure cooking process, if the residual concentration of sodium carbonate in the feed solution still meets the reaction requirements, i.e., the concentration of sodium carbonate is 130-170 g / L, solid sodium carbonate does not need to be supplemented. If the residual concentration of sodium carbonate in the feed solution cannot meet the reaction requirements, solid sodium carbonate needs to be supplemented to meet the standard.

[0049] The obtained pressure-cooking slag is mixed, the water content of the pressure-cooking slag is less than or equal to 25%, the pH value is adjusted to 8-9 by using lime milk, 2-3wt% of calcium dihydrogen phosphate is added as a stabilizer, the reaction is carried out under the stirring rate of 180-220r / min for 1h, then the reaction product is sent into a solidification device to form a block-shaped solidified body, after solidification, the heavy metal leaching concentration is detected, and if the heavy metal leaching concentration meets the standard requirement, the solidified body is safely filled or used as a building aggregate auxiliary material.

[0050] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit the present application, and other modifications or equivalent replacements to the technical solutions of the present application made by those skilled in the art should be covered in the scope of claims of the present application as long as they do not deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for efficiently recovering tungsten from alkaline leaching tungsten slag, characterized in that, Includes the following steps: (1) Pretreatment: The alkaline leaching tungsten slag with a tungsten content of 0.5-5wt% produced by the main process of hydrometallurgical tungsten smelting is crushed and ground to obtain pretreated slag; (2) Leaching: The pretreated residue is added to sodium carbonate alkaline solution, and the resulting suspension is sent to a pressure cooker for pressure cooking. After the pressure cooking is completed, the residue is filtered to obtain the first leachate and the pressure cooking residue. (3) Circulating pressure cooking: The first leaching solution and the new tungsten slag are mixed at the same liquid-solid ratio as in step (2) for leaching and pressure cooking. After pressure cooking, the solution is filtered to obtain the first circulating leaching solution and pressure cooking residue. The first circulating leaching solution and the new tungsten slag are mixed at the same liquid-solid ratio as in step (2) for leaching and pressure cooking. After pressure cooking, the solution is filtered to obtain the second circulating leaching solution and pressure cooking residue. The circulating pressure cooking is repeated in this way to obtain the Nth circulating leaching solution and pressure cooking residue, where N is an integer greater than or equal to 2 and less than or equal to 5. (4) Testing of the leaching solution and return to the main process: If the tungsten concentration of the Nth cycle leaching solution is ≥85g / L, the Nth cycle leaching solution is directly pumped into the tungsten purification process of the main hydrometallurgical process and mixed with the main process leaching solution for subsequent impurity removal and purification processes; if it does not meet the standard, it is used as the circulating leaching solution to continue to participate in the next round of circulating pressure cooking until it meets the standard. (5) Harmless treatment of tailings: The pressure cooking residue obtained in steps (2) and (3) is mixed with lime milk to adjust the pH value to 8-9, and 2-3wt% of calcium dihydrogen phosphate is added as a stabilizer. After stirring and solidification, it is sent to the solidification equipment to make a block solidified body. After solidification, the heavy metal leaching concentration is tested. If it meets the standard requirements, it can be safely landfilled or used as building aggregate.

2. The method for efficiently recovering tungsten from alkaline leaching tungsten slag according to claim 1, characterized in that, In step (2), the liquid-solid ratio of sodium carbonate alkali solution and pretreatment residue is 3:1-6:

1.

3. The method for efficiently recovering tungsten from alkaline leaching tungsten slag according to claim 1, characterized in that, The concentration of sodium carbonate solution in step (2) is 130-170 g / L.

4. The method for efficiently recovering tungsten from alkaline leaching tungsten slag according to claim 1, characterized in that, In step (2), the pressure cooking temperature is 155-185℃, the pressure is 0.5-0.75MPa, the stirring rate is 300-500r / min, and the pressure cooking time is 2-3h.

5. The method for efficiently recovering tungsten from alkaline leaching tungsten slag according to claim 1, characterized in that, In steps (2) and (3), the pressure cooker is equipped with a temperature-pressure linkage control system. During the pressure cooking process, nitrogen gas is used to maintain pressure fluctuation ≤ ±0.05MPa and temperature fluctuation ≤ ±4℃. After the pressure cooking is completed, a gradient cooling rate of 6-9℃ / min is adopted to avoid scaling inside the cooker.

6. The method for efficiently recovering tungsten from alkaline leaching tungsten slag according to claim 1, characterized in that, In step (3), the concentration of sodium carbonate in the feed solution needs to be checked before each cycle of pressure cooking. It should be 130-170 g / L. If the concentration is lower than 130 g / L, add solid sodium carbonate to the target concentration.

7. The method for efficiently recovering tungsten from alkaline leaching tungsten slag according to claim 1, characterized in that, In step (3), N equals 3.

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