Method for recovering valuable metal tin from waste tire powder high-temperature reduction tungsten slag

Abstract

The application discloses a method for recovering valuable metal tin from waste tire powder high-temperature reduced tungsten slag, and aims at solving the problems of low Sn content in the tungsten slag and low tin recovery rate.The method for recovering valuable metal tin comprises the following steps: firstly, white tungsten slag powder, SiO2 and waste tire powder after fine grinding and drying are fully stirred and uniformly mixed to obtain a slag agent mixture;secondly, the slag agent mixture is placed in a crucible, and then the slag agent mixture and the crucible are placed in a heating zone of a tubular furnace, and the pre-burning is activated at a temperature of 600-800 DEG C under the condition of no gas; and thirdly, high-temperature reduction reaction is carried out on the pre-burning product at a temperature of 1000 DEG C-1200 DEG C.The application adopts the tubular furnace high-temperature oxygen-free condition to pyrolyze the waste tire powder to generate reducing gas and sulfide gas, the reducing gas reduces the tin element into stannous oxide or tin element under the oxygen-free condition, the sulfide gas further makes the tin element generate low-boiling-point stannous sulfide and volatilize into flue gas, and the separation and enrichment of the tin element are realized.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling technology, specifically relating to a method for recovering valuable metals from waste tire powder by high-temperature reduction of tungsten slag. Background Technology

[0002] Tin is an indispensable metallic material in national economic construction, with wide applications in many fields, especially in the electronics and materials industries. With the increasing depletion of primary tin ore resources, the reserves of exploitable metallic tin resources are declining year by year. Therefore, the comprehensive recovery of tin from the waste slag generated during the smelting process is of great significance. Tungsten smelting produces a large amount of tungsten slag; for every 1 ton of WO3 produced, approximately 0.8 tons of tungsten slag are generated, resulting in approximately 70,000 tons of tungsten slag stockpiled annually. Tungsten slag contains the valuable metallic element tin, accounting for approximately 0.4-1.5% of the slag. Therefore, tungsten slag can serve as a secondary resource for tin and has recycling value. Research on tin recovery from tungsten slag can, on the one hand, treat stockpiled tungsten slag and reduce environmental impact; on the other hand, it can alleviate the increasing scarcity of tin concentrate.

[0003] Currently, the main methods for tin recovery include direct reduction, chlorination volatilization, and sulfide volatilization. Direct reduction involves adding a carbonaceous reducing agent to the material and reducing it at high temperature to prepare the corresponding metal, alloy, or carbide. Chlorination volatilization involves adding a chlorinating agent (calcium chloride, ammonium chloride, sodium chloride, etc.) and a reducing agent to the tin-containing material, mixing them thoroughly, and then roasting them at high temperature. This causes the tin and other non-ferrous metals in the material to volatilize as chlorides, and the tin-containing chloride dust is then recovered in a dust collection system. Sulfide volatilization, under roasting conditions, uses coke powder, anthracite, etc., as reducing agents, and pyrite, elemental sulfur, gypsum, etc., as sulfiding agents to convert the difficult-to-separate cassiterite (SnO2) in tin-containing iron ore into easily volatile SnS, and then recovering the tin from the dust. Theory and practice have proven that sulfide volatilization is the most effective and advanced technology for processing low-grade tin resources. For example, Chinese patent CN115261627A discloses a method for recovering tin, tungsten, and sodium sulfite from scheelite leaching residue. This method involves high-temperature reduction smelting of scheelite slag, sodium sulfate, and anthracite at 1500℃. Tin volatilizes into the flue gas in the form of stannous sulfide, achieving a tin recovery rate of 85%. Chinese patent CN113999978A discloses a method for recovering valuable metals from tungsten slag. This method involves ball milling tungsten slag and carbonaceous materials, followed by high-temperature reduction at 1400-1700℃ to obtain a ferrotungsten-tin alloy. The ferrotungsten-tin alloy is then vacuum distilled to obtain ferrotungsten alloy and tin.

[0004] Waste tires are a common type of waste, with an annual output exceeding 10 million tons. They are primarily composed of natural rubber, synthetic rubber, sulfur, and carbon black. "Black pollution" has long been a global environmental concern, causing alarming levels of pollution. Currently, pyrolysis is the best method for disposing of waste tires. However, the high sulfur content in the pyrolysis products of waste tires prevents their direct application. When waste tire powder is used as a vulcanizing agent, the carbon black and sulfur in the waste tires can simultaneously play a role in reduction and vulcanization throughout the process. To date, there are no reports of using waste tire powder as both a vulcanizing and reducing agent to recover valuable tin from tungsten slag through vulcanization and reduction. Summary of the Invention

[0005] This invention addresses the problems of high cost of reducing and sulfiding agents used in the sulfidation volatilization method for tin recovery, low Sn content in tungsten slag, and low tin recovery rate. It provides a method for high-temperature reduction of tungsten slag from waste tire powder to recover valuable tin metal, which can achieve tin metal recovery and simultaneously realize the harmless and resource-based treatment of tungsten slag and waste tire powder.

[0006] The method for recovering valuable tin from waste tire powder by high-temperature reduction of tungsten slag according to the present invention is implemented according to the following steps:

[0007] 1. Mix 88%–94% finely ground and dried scheelite slag powder, 1%–2% SiO2 and 5%–10% waste tire powder thoroughly according to the mass percentage to obtain a slag-agent mixture.

[0008] 2. Place the slag-agent mixture in a crucible, and then place it together in the heating zone of a tube furnace. Place the filter screen at the condenser end of the tube furnace and activate and pre-calcine at a temperature of 600-800℃ for 20-30 minutes under no gas flow conditions to obtain the pre-calcined product.

[0009] 3. The pre-calcined product is subjected to a high-temperature reduction reaction at a temperature of 1000℃~1200℃. After cooling to room temperature, the crucible is removed, and the smoke and dust on the filter screen are collected, thereby completing the recovery of valuable metal tin.

[0010] This invention uses hazardous tungsten slag as raw material. Under high-temperature pyrolysis of waste tire powder, valuable tin metal is reduced to tin sulfide, which volatilizes and enters the flue gas. The tin sulfide dust is then sold as a product to tin smelting enterprises, achieving the recovery of metallic tin. Waste tire powder is first decomposed into CO, CO2, H2, H2S, SO2, and COS under high-temperature, oxygen-deficient conditions of 600–800℃. The reducing gases CO and CO2 can then reduce Fe3O4, CaO, MnO2, and SnO2 in the tungsten slag under high-temperature, oxygen-free conditions of 1000–1200℃. The reduced Sn(l) reacts with SO2(g) and H2S(g) generated from the pyrolysis of waste tire rubber to form SnS(g), which enters the flue gas. Meanwhile, CaS, FeS, and MnS generated from Fe3O4, CaO, and MnO2, along with the additive SiO2, enter the slag system. Therefore, waste tire powder can simultaneously act as a vulcanizing agent and a reducing agent under high-temperature pyrolysis. The oxidation reaction equations for tungsten slag and waste tire powder during the high-temperature reduction process in a tubular furnace are as follows:

[0011] SnO₂ + 2CO = Sn + 2CO₂↑

[0012] SnO₂ + CO = SnO + CO₂↑

[0013] SnO₂ + 2H₂ = Sn + 2H₂O↑

[0014] Sn + H₂S = SnS↑ + H₂↑

[0015] SnO + H₂S = SnS↑ + H₂O↑

[0016] SnO₂ + SO₂ + 4CO = SnS↑ + 4CO₂↑

[0017] 2CaO + 2SO₂ + 6CO = 2CaS + 6CO₂↑

[0018] Fe3O4+3SO2+10CO=3FeS+10CO2↑

[0019] MnO₂ + SO₂ + 4CO = MnS + 4CO₂↑

[0020] Compared with existing technologies, the method for recovering valuable tin from waste tire powder by high-temperature reduction of tungsten slag in this invention has the following advantages:

[0021] Based on the characteristics of tungsten slag (high melting point, low Sn content in slag powder), and waste tire powder (containing carbon and sulfur), a tubular furnace was used to first pyrolyze the waste tire powder under high-temperature, oxygen-deficient conditions to generate reducing and sulfide gases. The reducing gases, under oxygen-free conditions, reduce tin to stannous oxide or elemental tin. The sulfide gases further reduce tin to low-boiling-point stannous sulfide, which then volatilizes into the flue gas, achieving the separation and enrichment of tin. The stannous sulfide dust is sold as a product to tin smelting enterprises. This invention not only solves the problem of environmental pollution and harm to human health caused by tungsten slag and waste tire powder as solid waste, but also effectively recovers the valuable tin resources they contain, resulting in considerable economic benefits and responding to the development of a resource-saving and environmentally friendly society. Attached Figure Description

[0022] Figure 1 This is a photograph of the slag-removing agent mixture in the examples;

[0023] Figure 2 The image shows the product of the slag-agent mixture after high-temperature reduction reaction in the example. Detailed Implementation

[0024] Specific Implementation Method 1: The method for recovering valuable tin from waste tire powder by high-temperature reduction of tungsten slag in this implementation method is carried out according to the following steps:

[0025] 1. Mix 88%–94% finely ground and dried scheelite slag powder, 1%–2% SiO2 and 5%–10% waste tire powder thoroughly according to the mass percentage to obtain a slag-agent mixture.

[0026] 2. Place the slag-agent mixture in a crucible, and then place it together in the heating zone of a tube furnace. Place the filter screen at the condenser end of the tube furnace and activate and pre-calcine at a temperature of 600-800℃ for 20-30 minutes under no gas flow conditions to obtain the pre-calcined product.

[0027] 3. The pre-calcined product is subjected to a high-temperature reduction reaction at a temperature of 1000℃~1200℃. After cooling to room temperature, the crucible is removed, and the smoke and dust on the filter screen are collected, thereby completing the recovery of valuable metal tin.

[0028] Specific Implementation Method Two: The difference between this implementation method and Specific Implementation Method One is that the particle size of the finely ground scheelite slag powder in step one is 1 to 10 μm.

[0029] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the particle size of the waste tire powder in step 1 is 0.2 to 0.5 mm.

[0030] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the scheelite slag powder mentioned in step one contains Sn with a mass fraction of 0.5% to 1.5%, W with a mass fraction of 1% to 5%, Ca with a mass fraction of 10% to 40%, Fe with a mass fraction of 10% to 30%, Mn with a mass fraction of 5% to 15%, Si with a mass fraction of 5% to 10%, Nb with a mass fraction of 0.5% to 2%, and Ta with a mass fraction of 1% to 5%.

[0031] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the waste tire powder mentioned in Step One has a carbon content of 75% to 85%, a hydrogen content of 5% to 10%, an oxygen content of 5% to 10%, a sulfur content of 0.5% to 3%, and a nitrogen content of 0.5% to 3%.

[0032] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that in step one, 90% to 92% of finely ground and dried scheelite slag powder, 1% to 2% of SiO2, and 8% to 10% of waste tire powder are thoroughly mixed according to their mass percentages.

[0033] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the filter screen in step two is a quartz filter screen.

[0034] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that step two involves activation and pre-firing at 600°C for 30 minutes.

[0035] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the high-temperature reduction reaction time in step three is 1 to 3 hours.

[0036] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that step 3 involves a high-temperature reduction reaction at 1000-1100°C for 1 hour.

[0037] Example 1: The method for recovering valuable tin from waste tire powder by high-temperature reduction of tungsten slag in this example is implemented according to the following steps:

[0038] 1. Using tungsten slag from a tungsten smelter in Hunan and waste tire powder from a rubber recycling company in Hebei as raw materials, the original tungsten slag was dried, finely ground and sieved. 100g of finely ground and dried scheelite slag powder, 1g of SiO2 and 10g of waste tire powder with a particle size of 0.25mm were thoroughly mixed to obtain a slag-agent mixture.

[0039] 2. Place the slag-agent mixture in a graphite crucible, and then place it together in the heating zone of a tube furnace. Place the filter screen at the condenser end of the tube furnace, start the heating mode, and activate and pre-calcine for 30 minutes at a temperature of 600℃ without gas flow to obtain the pre-calcined product.

[0040] 3. The pre-calcined product is subjected to a high-temperature reduction reaction at 1000℃ for 1 hour. After cooling to room temperature, the slag in the graphite crucible is removed, and the smoke and dust on the filter screen are collected, thus completing the recovery of valuable metal tin.

[0041] The slag and dust enriched with valuable metals were analyzed. According to ICP-AES testing, the tin volatility was 65.82%, indicating a high recovery rate.

[0042] Example 2: The method for recovering valuable tin from waste tire powder by high-temperature reduction of tungsten slag in this example is implemented according to the following steps:

[0043] 1. Using tungsten slag from a tungsten smelter in Hunan and waste tire powder from a rubber recycling company in Hebei as raw materials, the original tungsten slag was dried, finely ground and sieved. 100g of finely ground and dried scheelite slag powder, 2g of SiO2 and 5g of waste tire powder with a particle size of 0.25mm were thoroughly mixed to obtain a slag-agent mixture.

[0044] 2. High-temperature sulfidation and volatilization: The slag-agent mixture is placed in a graphite crucible and then placed together in the heating zone of a tube furnace. The filter screen is placed at the condenser end of the tube furnace. The heating mode is started, and the product is activated and pre-calcined at 700℃ for 30 minutes without gas flow to obtain the pre-calcined product.

[0045] 3. The pre-calcined product is subjected to a high-temperature reduction reaction at 1000℃ for 1 hour. After cooling to room temperature, the slag in the graphite crucible is removed, and the smoke and dust on the filter screen are collected, thus completing the recovery of valuable metal tin.

[0046] Analysis of the slag and dust enriched with valuable metals was performed. According to ICP-AES testing, the volatility of tin was calculated to be 49.17%, indicating a low recovery rate.

[0047] Example 3: The method for recovering valuable tin from waste tire powder by high-temperature reduction of tungsten slag in this example is implemented according to the following steps:

[0048] 1. Using tungsten slag from a tungsten smelter in Hunan and waste tire powder from a rubber recycling company in Hebei as raw materials, the original tungsten slag was dried, finely ground and sieved. 100g of finely ground and dried scheelite slag powder, 1g of SiO2 and 10g of waste tire powder with a particle size of 0.25mm were thoroughly mixed to obtain a slag-agent mixture.

[0049] 2. Place the slag-agent mixture in a graphite crucible, and then place it together in the heating zone of a tube furnace. Place the filter screen at the condenser end of the tube furnace, start the heating mode, and activate and pre-calcine at 800℃ without gas flow for 30 minutes to obtain the pre-calcined product.

[0050] 3. The pre-calcined product is subjected to a high-temperature reduction reaction at 1100℃ for 1 hour. After cooling to room temperature, the slag in the graphite crucible is removed, and the smoke and dust on the filter screen are collected, thus completing the recovery of valuable metal tin.

[0051] Analysis of the slag and dust enriched with valuable metals, performed by ICP-AES testing, showed that the tin volatilization rate reached 95.47%, indicating a high recovery rate. Despite a relatively low high-temperature reduction reaction temperature, the tin volatilization rate still reached 95.47%. The sulfiding agent used in this invention is waste tire powder, which reacts more readily than existing sodium sulfate to form sulfides, further undergoing sulfidation and reduction to generate tin sulfide, which then volatilizes.

[0052] This invention involves drying and mixing tungsten slag and waste tire powder to obtain a mixture, which is then calcined using a high-temperature reduction process to obtain tin sulfide dust, achieving the separation and enrichment of tin. The tin sulfide dust is sold as a product to tin smelting enterprises.

[0053] This invention eliminates the need for additional reducing agents, sulfiding agents, or other auxiliary raw materials. While reducing costs, it can recover the valuable element tin from tungsten slag. It also solves the problem of tungsten slag and waste tire powder polluting the environment and harming human health as solid wastes in one step. The process is simple and has high economic benefits.

Claims

1. A method for recovering valuable metallic tin from waste tire powder by high-temperature reduction of tungsten slag, characterized in that... The method for recovering valuable tin from waste tire powder by high-temperature reduction of tungsten slag is implemented through the following steps:

1. Mix 88%–94% finely ground and dried scheelite slag powder, 1%–2% SiO2 and 5%–10% waste tire powder thoroughly according to the mass percentage to obtain a slag-agent mixture.

2. Place the slag-agent mixture in a crucible, and then place it together in the heating zone of a tube furnace. Place the filter screen at the condenser end of the tube furnace, and activate and pre-calcine at a temperature of 600-800℃ for 20-30 minutes under no gas flow conditions to obtain the pre-calcined product.

3. The pre-calcined product is subjected to a high-temperature reduction reaction at 1100℃ for 1 hour. After cooling to room temperature, the crucible is removed and the smoke and dust on the filter screen are collected, thus completing the recovery of valuable metal tin. In the waste tire powder mentioned in step one, the mass fraction of carbon is 75% to 85%, the mass fraction of hydrogen is 5% to 10%, the mass fraction of oxygen is 5% to 10%, the mass fraction of sulfur is 0.5% to 3%, and the mass fraction of nitrogen is 0.5% to 3%.

2. The method for recovering valuable metallic tin from waste tire powder by high-temperature reduction of tungsten slag according to claim 1, characterized in that... The particle size of the finely ground scheelite slag powder in step one is 1–10 μm.

3. The method for recovering valuable metallic tin from waste tire powder by high-temperature reduction of tungsten slag according to claim 1, characterized in that... In step one, the particle size of the waste tire powder is 0.2~0.5mm.

4. The method for recovering valuable metallic tin from waste tire powder by high-temperature reduction of tungsten slag according to claim 1, characterized in that... In the scheelite powder mentioned in step one, the mass fraction of Sn is 0.5%–1.5%, the mass content of W is 1%–5%, the mass content of Ca is 10%–40%, the mass content of Fe is 10%–30%, the mass content of Mn is 5%–15%, the mass content of Si is 5%–10%, the mass content of Nb is 0.5%–2%, and the mass content of Ta is 1%–5%.

5. The method for recovering valuable metallic tin from waste tire powder by high-temperature reduction of tungsten slag according to claim 1, characterized in that... In step one, 90%–92% of finely ground and dried scheelite slag powder, 1%–2% of SiO2 and 8%–10% of waste tire powder are thoroughly mixed according to their mass percentages.

6. The method for recovering valuable metallic tin from waste tire powder by high-temperature reduction of tungsten slag according to claim 1, characterized in that... The filter screen used in step two is a quartz filter screen.

7. The method for recovering valuable metallic tin from waste tire powder by high-temperature reduction of tungsten slag according to claim 1, characterized in that... In step two, the activation and pre-firing are carried out at a temperature of 600℃ for 30 minutes.

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