Method for recovering valuable metal tungsten and tin from hazardous waste tungsten slag

Abstract

The invention discloses a method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag, and aims to solve the problems that the existing method for recovering the valuable metals from the tungsten slag needs higher temperature and the recovery rate of the valuable metals tungsten and tin needs to be improved. The recovery method comprises the following steps: S1, uniformly stirring and mixing tungsten slag powder with a reducing agent and a vulcanizing agent A; s2, the slag agent mixture in the S1 is placed in a tubular furnace to be subjected to high-temperature reduction treatment; s3, carrying out sulfuric acid leaching treatment on the furnace slag; s4, the acid leaching residues serve as a vulcanizing agent B, and high-temperature reduction treatment and sulfuric acid leaching treatment are repeated for multiple times; and S5, stirring the tungsten-enriched sulfide slag and sodium hydroxide, roasting, performing water leaching on a product to obtain a sodium tungstate solution, and finally performing evaporative crystallization. The valuable metal tin in the hazardous waste tungsten slag is extracted through high-temperature vulcanization reduction. Tin is recovered through sulfuration reduction reaction, sulfide generated by lead and arsenic oxides is separated from scheelite slag and enters smoke dust, iron and manganese oxides are subjected to sulfuration reduction reaction and enter a slag system, and harmless treatment of hazardous wastes is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of resource recovery and utilization, and in particular relates to a process for recovering valuable metals tungsten and tin from tungsten slag hazardous waste. Background Art

[0002] When tungsten ore is decomposed by sodium alkali pressure cooking, tungsten is converted into soluble sodium tungstate and enters the solution. The alkali decomposition pressure cooking slag is obtained by filtration, commonly known as tungsten slag. The iron, manganese, scandium, molybdenum, tantalum, niobium, lead, arsenic and other elements associated with tungsten ore enter the tungsten slag. Tungsten slag contains a variety of harmful elements and was listed in the list of hazardous wastes by the state in 2016 with the hazardous characteristic of "T". If tungsten slag is not managed and disposed of harmlessly, it will cause great pollution to the environment. The tungsten content in tungsten slag continues to decrease with the development of tungsten smelting technology. The tungsten oxide content in the old tungsten slag in stock is as high as 5% or more. The tungsten oxide content in the current new tungsten slag is between 1% and 3%. Compared with the tungsten content in the original ore of only 0.2% to 0.3%, the grade of tungsten slag is more than 10 times higher than that of the original tungsten ore. At the same time, tungsten slag contains the valuable metal element tin, which accounts for about 0.4% to 1.5% of tungsten slag. Therefore, tungsten slag can be used as a secondary resource of tungsten and tin, and has recycling value. Research on the recovery of valuable metals in tungsten slag: on the one hand, it can treat the stockpiled tungsten slag and reduce the impact on the environment; on the other hand, it can alleviate the increasing reduction of mineral resources.

[0003] Some methods for recovering valuable metals from tungsten slag are disclosed in the prior art. For example, Chinese patent CN113737027A discloses a method for recovering valuable metals tungsten, iron and manganese from tungsten-containing slag. After high-temperature reduction and smelting with limestone and carbon reducing agent, tungsten is further reacted with alkaline oxidant under oxygen-rich conditions to form tungstate slag and separated from iron-manganese alloy, and finally leached to obtain sodium tungstate product. However, this method requires secondary high temperature, and the first high temperature reaches 1200-1400°C, which consumes high energy. For example, Chinese patent CN115261627A discloses a method for recovering tin, tungsten and sodium sulfite from scheelite leaching slag. Scheelite slag, sodium sulfate and anthracite materials are reduced and smelted at 1400-1500°C. Tin volatilizes into the flue gas in the form of stannous sulfide, and the reduced slag is further quenched with water and then ball milled and leached to obtain sodium tungstate product. However, this method requires a high temperature, and the maximum tin recovery rate is only 85.84%, and the tungsten metal recovery rate is 78.65%. Summary of the invention

[0004] The present invention aims to solve the problem that the existing method for recovering valuable metals from tungsten slag requires high temperature and the recovery rate of tungsten and tin valuable metals needs to be improved, and provides a method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag, thereby simultaneously realizing the harmless treatment and resource utilization of tungsten slag.

[0005] The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag of the present invention is implemented by the following steps:

[0006] S1. The finely ground and dried tungsten slag powder is thoroughly stirred and mixed with the reducing agent and the vulcanizing agent A to obtain a slag-agent mixture;

[0007] S2, placing the slag-agent mixture in step S1 in the heating zone of the tubular furnace, placing the quartz filter screen at the condensing end of the tubular furnace, starting the heating mode, heating to 800° C. to 1200° C. for high-temperature reduction treatment, cooling to room temperature, and collecting the reduced slag and the tin-containing smoke on the quartz filter screen;

[0008] S3, taking the reduction slag in step S2, crushing it, and then performing sulfuric acid leaching treatment, and filtering the sulfuric acid leaching to obtain acid leaching residue;

[0009] S4, using the acid leaching residue obtained in step S3 as a sulfiding agent B, and then fully mixing it with tungsten slag powder and a reducing agent, cyclically repeating the high temperature reduction treatment of step S2 and the sulfuric acid leaching treatment of step S3 for multiple times, and finally performing a high temperature reduction treatment to obtain tungsten-enriched sulfided slag;

[0010] S5, the tungsten-enriched sulfide slag obtained in step S4 is mixed evenly with sodium hydroxide and then placed in a crucible for roasting at 700° C. The roasted product is filtered after being soaked in water to obtain a sodium tungstate solution, and the filtrate is evaporated and crystallized to obtain sodium tungstate crystals, thereby completing the recovery of valuable metals tungsten and tin from the tungsten slag;

[0011] The reducing agent is carbon particles, carbon powder or activated carbon, and the vulcanizing agent A is calcium sulfate.

[0012] The present invention uses hazardous waste tungsten slag as raw material. In order to achieve the purpose of separating and recovering metallic tin in scheelite slag, high-temperature sulfidation reduction is used to react tin dioxide in scheelite slag to generate low-boiling point stannous sulfide, which is volatilized into flue gas and separated from slag. While the sulfidation reduction reaction recovers tin, other metal oxides also react. Among them, lead and arsenic oxides undergo sulfidation reduction reactions to generate sulfides, which are separated from scheelite slag and also enter the smoke dust, while iron and manganese oxides undergo sulfidation reduction reactions to generate sulfides, which enter the slag system. The high-temperature sulfidation reduction process not only achieves the purpose of recovering tin from tungsten slag, but also performs harmless treatment on scheelite slag, which can achieve the dual effects of resource utilization and environmental protection.

[0013] 2SnO 2 +2CaSO 4 +5C=2SnS↑+2CaO+5CO 2 ↑

[0014] PbO+CaSO 4 +2C=PbS↑+CaO+2CO 2 ↑

[0015] 2As 2 O 3 +4CaSO 4 +9C=4AsS↑+4CaO+9CO 2 ↑

[0016] 2Fe 2 O 3 +4CaSO 4 +9C=4FeS+4CaO+9CO 2 ↑

[0017] 2MnO 2 +2CaSO 4 +5C=2MnS+2CaO+5CO 2 ↑

[0018] The sulfide slag is further leached with sulfuric acid. The iron and manganese compounds in the sulfide slag react with sulfuric acid to become ions and enter the solution, while calcium forms calcium sulfate precipitation. Calcium tungstate is basically insoluble in dilute sulfuric acid. After leaching, tungsten-containing slag with calcium sulfate as the main component is obtained by filtration. Calcium sulfate tungsten-containing slag can replace lime and be recycled in high-temperature sulfidation reduction of scheelite slag. With the increase of the number of cycles, tungsten is enriched in the slag system, and finally sodium tungstate is recovered by alkali decomposition.

[0019] FeO+H 2 SO 4 =H 2 O+FeSO 4

[0020] MnS+H 2 SO 4 =MnSO 4 +H 2 S

[0021] CaO+H 2 SO 4 =CaSO 4 +H 2 O

[0022] FeS+H 2 SO 4 =H 2 S+FeSO 4

[0023] Compared with the prior art, the beneficial effect of the present invention is that valuable metal tin is extracted from hazardous waste tungsten slag by high-temperature sulfidation reduction. Tin is recovered by sulfidation reduction reaction, while lead and arsenic oxides generate sulfides that are separated from scheelite slag and also enter the smoke, while iron and manganese oxides undergo sulfidation reduction reaction to generate sulfides that enter the slag system, thereby achieving harmless treatment of hazardous waste. In addition, the waste slag is recycled after acid leaching treatment, and tungsten enrichment is achieved through multiple cycles. Tungsten can be recovered by further alkaline decomposition of the tungsten enriched slag. The present invention achieves the purpose of recovering tin and tungsten resources in tungsten slag, while harmlessly treating scheelite slag, which can play a dual role of resource utilization and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention is a process flow chart for recovering valuable metals tungsten and tin from hazardous waste tungsten slag. DETAILED DESCRIPTION

[0025] Specific implementation method 1: The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag in this implementation method is implemented according to the following steps:

[0026] S1. The finely ground and dried tungsten slag powder is thoroughly stirred and mixed with the reducing agent and the vulcanizing agent A to obtain a slag-agent mixture;

[0027] S2, placing the slag-agent mixture in step S1 in the heating zone of the tubular furnace, placing the quartz filter screen at the condensing end of the tubular furnace, starting the heating mode, heating to 800° C. to 1200° C. for high-temperature reduction treatment, cooling to room temperature, and collecting the reduced slag and the tin-containing smoke on the quartz filter screen;

[0028] S3, taking the reduction slag in step S2, crushing it, and then performing sulfuric acid leaching treatment, and filtering the sulfuric acid leaching to obtain acid leaching residue;

[0029] S4, using the acid leaching residue obtained in step S3 as a sulfiding agent B, and then fully mixing it with tungsten slag powder and a reducing agent, cyclically repeating the high temperature reduction treatment of step S2 and the sulfuric acid leaching treatment of step S3 for multiple times, and finally performing a high temperature reduction treatment to obtain tungsten-enriched sulfided slag;

[0030] S5, the tungsten-enriched sulfide slag obtained in step S4 is mixed evenly with sodium hydroxide and then placed in a crucible for roasting at 700° C. The roasted product is filtered after being soaked in water to obtain a sodium tungstate solution, and the filtrate is evaporated and crystallized to obtain sodium tungstate crystals, thereby completing the recovery of valuable metals tungsten and tin from the tungsten slag;

[0031] The reducing agent is carbon particles, carbon powder or activated carbon, and the vulcanizing agent A is calcium sulfate.

[0032] This embodiment provides a sulfidation reduction-acid leaching cycle-sodium alkali melting-water leaching-evaporation crystallization process to recover tin and tungsten from scheelite slag. The process is: calcium sulfate, carbon particles and scheelite slag are dried and mixed to obtain a mixed material, and the mixed material is roasted by a high-temperature sulfidation reduction process to obtain stannous sulfide smoke, thereby achieving the separation and enrichment of tin elements. Stannous sulfide dust is sold to tin smelting enterprises as a product. The slag is further reduced by sulfuric acid leaching to generate tungsten-containing acid leaching slag whose main component is calcium sulfate. The tungsten-containing acid leaching slag is used as calcium sulfate for high-temperature sulfidation reduction to achieve the purpose of tungsten enrichment. Finally, the tungsten-enriched slag adopts a sodium hydroxide melting-water leaching-evaporation crystallization process to obtain sodium tungstate crystals.

[0033] This implementation method can recover tin and tungsten in scheelite slag while separating the toxic metal elements lead and arsenic in the scheelite slag, thereby simultaneously realizing resource utilization and harmless treatment of the scheelite slag.

[0034] Specific implementation method 2: The difference between this implementation method and specific implementation method 1 is that the particle size of the finely ground tungsten slag powder in step S1 is 1 to 10 μm.

[0035] Specific embodiment three: The difference between this embodiment and specific embodiment one or two is that in the tungsten slag powder in step S1, the mass fraction of Sn is 0.5% to 1.5%, the mass content of W is 1% to 5%, the mass content of Ca is 10% to 40%, the mass content of Fe is 10% to 30%, the mass content of Mn is 5% to 15%, the mass content of Si is 5% to 10%, the mass content of Nb is 0.5% to 2%, and the mass content of Ta is 1% to 5%.

[0036] Specific embodiment 4: The difference between this embodiment and any one of specific embodiments 1 to 3 is that the mass ratio of tungsten slag powder to reducing agent in step S1 is (1-20):1.

[0037] The optimized mass ratio of tungsten slag powder to reducing agent in this embodiment is (5-10):1.

[0038] Specific embodiment 5: The difference between this embodiment and specific embodiment 4 is that the mass ratio of tungsten slag powder to sulfurizing agent A in step S1 is 100:(4-15).

[0039] Specific implementation method 6: The difference between this implementation method and any one of specific implementation methods 1 to 5 is that the high-temperature reduction treatment time in step S2 is 1 to 3 hours.

[0040] Specific embodiment seven: The difference between this embodiment and specific embodiments one to five is that in the sulfuric acid leaching process in step S3, the reducing slag and sulfuric acid with a mass percentage of 20% are in a liquid-to-solid ratio of 5mL~15mL / g, the leaching temperature is 60~95℃, and the leaching time is 1~4h.

[0041] Specific embodiment eight: This embodiment differs from any one of specific embodiments one to seven in that the mass ratio of the sulfidizing agent B to the tungsten slag in step S4 is (1-2): (1-2).

[0042] Specific embodiment 9: The difference between this embodiment and any one of specific embodiments 1 to 8 is that in step S5, the mass ratio of tungsten-enriched acid leaching residue to sodium hydroxide is 1:(1.1-3), and the mixture is calcined at 700° C. for 2 h.

[0043] Specific implementation method ten: This implementation method is different from specific implementation methods one to nine in that the water immersion temperature in step S5 is 90° C. and the water immersion time is 4 hours.

[0044] Example 1: The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag in this example is implemented according to the following steps:

[0045] S1. Using (white) tungsten slag produced by a tungsten smelter in Hunan as raw material, 100g of finely ground and dried tungsten slag powder, 10g of carbon particles and 4.1g of calcium sulfate were fully stirred and mixed to obtain a slag agent mixture;

[0046] S2. Place the slag-agent mixture in step S1 in the heating zone of a tubular furnace, place the quartz filter screen at the condensing end of the tubular furnace, start the heating mode, heat to 1200° C. for high-temperature reduction treatment for 1 hour, cool to room temperature, and collect the reduced slag and the smoke on the quartz filter screen.

[0047] The obtained slag and smoke enriched with valuable metals were analyzed. After ICP-AES test, it was calculated that the volatilization rate of tin was 90.03%, and the recovery rate was relatively high.

[0048] Example 2: The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag in this example is implemented according to the following steps:

[0049] S1. Using tungsten slag produced by a tungsten smelter in Hunan as raw material, 100g of finely ground and dried tungsten slag powder was fully stirred and mixed with 20g of carbon particles and 4.1g of calcium sulfate to obtain a slag agent mixture;

[0050] S2. Place the slag-agent mixture in step S1 in the heating zone of a tubular furnace, place the quartz filter screen at the condensing end of the tubular furnace, start the heating mode, heat to 1200° C. for high-temperature reduction treatment for 1 hour, cool to room temperature, and collect the reduced slag and the smoke on the quartz filter screen.

[0051] The obtained valuable metal-enriched slag and smoke dust were analyzed. According to ICP-AES test, the main component of the recovered smoke dust was SnS, and the tin content in the smoke dust was 60.62%. According to calculation, the volatilization rate of tin was 96.79%, and the recovery rate was relatively high.

[0052] Example 3: The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag in this example is implemented according to the following steps:

[0053] S1. Using tungsten slag produced by a tungsten smelter in Hunan as raw material, 100g of finely ground and dried tungsten slag powder was fully stirred and mixed with 20g of carbon particles and 4.1g of calcium sulfate to obtain a slag agent mixture;

[0054] S2, placing the slag-agent mixture in step S1 in the heating zone of a tubular furnace, placing a quartz filter screen at the condensing end of the tubular furnace, starting the heating mode, heating to 1200° C. for high-temperature reduction treatment for 1 hour, cooling to room temperature, and collecting the reduced slag and the smoke on the quartz filter screen;

[0055] S3, crushing the reduction slag in step S2, and then leaching it with 20% sulfuric acid at 95°C and a liquid-to-solid ratio of 5 mL / g for 1 h, filtering the sulfuric acid leaching to obtain acid leaching residue, and grinding it to a particle size of more than 98% to pass a 320-mesh sieve;

[0056] S4, using 25g of the acid leaching residue obtained in step S3 as a sulfiding agent B, and then fully mixing it with 50g of scheelite slag powder and 5g of carbon particles, and repeating the high-temperature reduction treatment of step S2 to obtain tungsten-enriched sulfided slag;

[0057] S5. 5 g of tungsten-enriched sulfide slag obtained in step S4 is mixed evenly with 10 g of sodium hydroxide and then put into a crucible for roasting at 700° C. for 2 h. The roasted product is ground and soaked in water at 90° C. for 4 h. The filtrate is evaporated and crystallized to obtain sodium tungstate crystals, thereby completing the recovery of valuable metals tungsten and tin from the tungsten slag.

[0058] The obtained enriched valuable metal dust was analyzed, and the ICP-AES test showed that the volatilization rate of tin was 96.79%, with a high recovery rate. 0.54g of sodium tungstate was collected from 5g of enriched slag, and the average grade of sodium tungstate was 90.05%.

[0059] Example 4: The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag in this example is implemented according to the following steps:

[0060] S1. Using tungsten slag produced by a tungsten smelter in Hunan as raw material, 100g of finely ground and dried tungsten slag powder was fully stirred and mixed with 20g of carbon particles and 4.1g of calcium sulfate to obtain a slag agent mixture;

[0061] S2, placing the slag-agent mixture in step S1 in the heating zone of a tubular furnace, placing a quartz filter screen at the condensing end of the tubular furnace, starting the heating mode, heating to 1200° C. for high-temperature reduction treatment for 1 hour, cooling to room temperature, and collecting the reduced slag and the smoke on the quartz filter screen;

[0062] S3, crushing the reduction slag in step S2, and then leaching it with 20% sulfuric acid at 95°C and a liquid-to-solid ratio of 5 mL / g for 1 h, filtering the sulfuric acid leaching to obtain acid leaching residue, and grinding it to a particle size of more than 98% to pass a 320-mesh sieve;

[0063] S4, using 25g of the acid leaching residue obtained in step S3 as a sulfiding agent B, and then fully mixing it with 50g of scheelite slag powder and 5g of carbon particles, repeating the high-temperature reduction treatment of step S2 and the sulfuric acid leaching treatment of step S3 for 3 times, and finally performing high-temperature reduction treatment (a total of 5 high-temperature reduction treatments were performed in this embodiment) to obtain tungsten-enriched sulfidized slag;

[0064] S5. 5 g of tungsten-enriched sulfide slag obtained in step S4 is mixed evenly with 10 g of sodium hydroxide and then put into a crucible for roasting at 700° C. for 2 h. The roasted product is ground and soaked in water at 90° C. for 4 h to obtain a sodium tungstate solution. The filtrate is evaporated and crystallized to obtain sodium tungstate crystals, thereby completing the recovery of valuable metals tungsten and tin from the tungsten slag.

[0065] The obtained enriched valuable metal dust was analyzed, and the ICP-AES test showed that the volatilization rate of tin was 90.92%, with a high recovery rate. 0.53g of sodium tungstate was collected from 5g of enriched slag, and the grade of sodium tungstate was 91.53%.

Claims

1. A method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag, characterized in that The method for recovering valuable metals tungsten and tin is implemented according to the following steps: S1. The finely ground and dried tungsten slag powder is thoroughly stirred and mixed with the reducing agent and the vulcanizing agent A to obtain a slag-agent mixture; S2, placing the slag-agent mixture in step S1 in the heating zone of the tubular furnace, placing the quartz filter screen at the condensing end of the tubular furnace, starting the heating mode, heating to 800° C. to 1200° C. for high-temperature reduction treatment, cooling to room temperature, and collecting the reduced slag and the tin-containing smoke on the quartz filter screen; S3, taking the reduction slag in step S2, crushing it, and then performing sulfuric acid leaching treatment, and filtering the sulfuric acid leaching to obtain acid leaching residue; S4, using the acid leaching residue obtained in step S3 as a sulfiding agent B, and then fully mixing it with tungsten slag powder and a reducing agent, cyclically repeating the high temperature reduction treatment of step S2 and the sulfuric acid leaching treatment of step S3 for multiple times, and finally performing a high temperature reduction treatment to obtain tungsten-enriched sulfided slag; S5, the tungsten-enriched sulfide slag obtained in step S4 is mixed evenly with sodium hydroxide and then placed in a crucible for roasting at 700° C. The roasted product is filtered after being soaked in water to obtain a sodium tungstate solution, and the filtrate is evaporated and crystallized to obtain sodium tungstate crystals, thereby completing the recovery of valuable metals tungsten and tin from the tungsten slag; The reducing agent is carbon particles, carbon powder or activated carbon, and the vulcanizing agent A is calcium sulfate.

2. The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag according to claim 1, characterized in that The particle size of the finely ground tungsten slag powder in step S1 is 1-10 μm.

3. The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag according to claim 1, characterized in that In the tungsten slag powder in step S1, the mass fraction of Sn is 0.5% to 1.5%, the mass content of W is 1% to 5%, the mass content of Ca is 10% to 40%, the mass content of Fe is 10% to 30%, the mass content of Mn is 5% to 15%, the mass content of Si is 5% to 10%, the mass content of Nb is 0.5% to 2%, and the mass content of Ta is 1% to 5%.

4. The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag according to claim 1, characterized in that In step S1, the mass ratio of tungsten slag powder to reducing agent is (1-20):

1.

5. The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag according to claim 4, characterized in that In step S1, the mass ratio of tungsten slag powder to sulfurizing agent A is 100:(4-15).

6. The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag according to claim 1, characterized in that The high temperature reduction treatment time in step S2 is 1 to 3 hours.

7. The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag according to claim 1, characterized in that In the sulfuric acid leaching process in step S3, the reducing slag and sulfuric acid with a mass percentage of 20% are mixed at a liquid-to-solid ratio of 5 mL to 15 mL / g, the leaching temperature is 60 to 95° C., and the leaching time is 1 to 4 hours.

8. The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag according to claim 1, characterized in that In step S4, the mass ratio of the sulfiding agent B to the tungsten slag is (1-2): (1-2).

9. The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag according to claim 1, characterized in that In step S5, the mass ratio of tungsten-enriched acid leaching residue to sodium hydroxide is 1:(1.1-3), and the residue is roasted at 700° C. for 2 h.

10. The method for recovering valuable metals tungsten and tin from hazardous waste tungsten slag according to claim 1, characterized in that In step S5, the water immersion temperature is 90° C. and the water immersion time is 4 hours.

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