Method for decreasing reducibility of indium-containing zinc oxide dust and improving indium leaching rate

Abstract

A method for decreasing the reducibility of indium-containing zinc oxide dust and improving an indium leaching rate. When smelting the hot slag of lead-containing zinc in a side-blow reduction furnace, pulverized coal and limestone are added, and the oxidation atmosphere in the furnace is enhanced by means of three instances of air supply, such that zinc metal is oxidized into zinc oxide, and the reducibility of the produced indium-containing zinc oxide dust is decreased, thereby obtaining indium-containing zinc oxide dust and water-quenched residue. The indium-containing zinc oxide dust is mixed with an acidic solution containing Fe3+ at a liquid-solid ratio of 7-7.25 : 1 for oxidative neutral leaching, so that indium metal in the dust is oxidized and enters a neutrally leached residue to obtain an indium-containing neutrally leached residue and a zinc sulfate solution. The indium-containing neutrally leached residue is mixed with a sulfuric acid solution at a liquid-solid ratio of 3-4 : 1 for high-acid leaching to obtain an indium-containing solution and a lead residue. The indium-containing solution is allowed to enter an indium recovery system, and extraction, refining and electrolysis are performed to obtain a sponge indium.

Description

A method to reduce the reducing properties of indium-containing zinc oxide dust and improve indium leaching rate Technical Field

[0001] This invention belongs to the field of metal smelting technology, specifically relating to a method for reducing the reducing properties of indium-containing zinc oxide dust and increasing the indium leaching rate. Background Technology

[0002] Currently, the zinc oxide dust produced by the side-blown reduction furnace in the lead smelting system has a high zinc and indium content. This indium-containing dust needs to be returned to the zinc smelting system for neutral leaching to recover zinc and high-acid leaching to recover indium. However, this indium-containing zinc oxide dust has a high reducing power, with high zinc and indium metal content, reaching up to 27% zinc. During the high-acid leaching of indium from the zinc oxide dust, the leached indium is reduced again by the reducing metals in the zinc oxide dust, resulting in indium metal entering the slag and preventing indium metal from being leached out, thus reducing the indium leaching rate and directly affecting the indium recovery rate. Therefore, in order to reduce the reducing power of zinc oxide dust and improve the indium leaching rate, this invention proposes a method to reduce the zinc and indium metal content in zinc oxide dust in stages. The side-blown reduction stage reduces the zinc metal content, and the neutral leaching stage reduces the indium metal content, thereby reducing the reducing power of the zinc oxide dust and achieving a significant improvement in the indium leaching rate. Technical solutions

[0003] The purpose of this invention is to provide a method for reducing the reducing properties of indium-containing zinc oxide dust and increasing the indium leaching rate.

[0004] The objective of this invention is achieved as follows: the method for reducing the reducing properties of indium-containing zinc oxide dust and increasing the indium leaching rate includes the following steps:

[0005] Step 1: Side-blown reduction stage. When smelting lead-zinc hot slag in a side-blown reduction furnace, pulverized coal and limestone are added. The oxidizing atmosphere in the furnace is increased by three air supply cycles, which oxidizes metallic zinc into zinc oxide and reduces the reducing power of the indium-containing zinc oxide dust produced, resulting in indium-containing zinc oxide dust and water-quenched slag.

[0006] Step 2: Neutral oxidative leaching stage, indium-containing zinc oxide dust is mixed with Fe-containing... 3+ An acidic solution is mixed with a liquid-solid ratio of 7~7.25:1 and subjected to oxidative neutral leaching, which oxidizes the metallic indium in the flue dust into the intermediate leaching residue, resulting in an indium-containing intermediate leaching residue and a zinc sulfate solution.

[0007] Step 3: High acid leaching stage. The indium-containing leaching residue is mixed with sulfuric acid solution at a liquid-to-solid ratio of 3-4:1 and subjected to high acid leaching to obtain indium-containing solution and lead slag.

[0008] Step 4: Indium recovery stage, the indium-containing solution is introduced into the indium recovery system, and after extraction, refining and electrolysis, sponge indium is obtained. Beneficial effects

[0009] Compared with existing technologies, the technical solution of this invention has outstanding substantive features and significant progress in the following aspects: The method achieves staged reduction of the reducibility of indium-containing zinc oxide dust. After four steps of treatment, the indium content in lead slag is reduced from 500-800 g / t to 30-40 g / t, and the indium leaching rate is increased to 90-95%. This provides technical support for the comprehensive recovery of valuable metals from secondary resources in enterprises, effectively reduces the circulation of indium metal in the system, improves the primary recovery rate of indium, and realizes the release of indium production capacity. Attached Figure Description

[0010] Figure 1 is a flowchart of the method described in this invention. Embodiments of the present invention

[0011] The present invention will be further described below, but this is not intended to limit the invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the scope of protection of the present invention.

[0012] The method for reducing the reducing properties of indium-containing zinc oxide dust and increasing the indium leaching rate includes the following steps:

[0013] Step 1: Side-blown reduction stage. When smelting lead-zinc hot slag in a side-blown reduction furnace, pulverized coal and limestone are added. The oxidizing atmosphere in the furnace is increased by three air supply cycles, which oxidizes metallic zinc into zinc oxide and reduces the reducing power of the indium-containing zinc oxide dust produced, resulting in indium-containing zinc oxide dust and water-quenched slag.

[0014] Step 2: Neutral oxidative leaching stage, indium-containing zinc oxide dust is mixed with Fe-containing... 3+ An acidic solution is mixed with a liquid-solid ratio of 7~7.25:1 and subjected to oxidative neutral leaching, which oxidizes the metallic indium in the flue dust into the intermediate leaching residue, resulting in an indium-containing intermediate leaching residue and a zinc sulfate solution.

[0015] Step 3: High acid leaching stage. The indium-containing leaching residue is mixed with sulfuric acid solution at a liquid-to-solid ratio of 3-4:1 and subjected to high acid leaching to obtain indium-containing solution and lead slag.

[0016] Step 4: Indium recovery stage, the indium-containing solution is introduced into the indium recovery system, and after extraction, refining and electrolysis, sponge indium is obtained.

[0017] The lead-zinc hot slag mentioned in step 1 contains 8-15% zinc, 1.5-3% lead, 25-27% iron, 19-21% silicon dioxide, and 8-10% calcium oxide, and is added at a rate of 8-10 t / h.

[0018] The three-stage air supply mentioned in step 1 refers to: a primary air supply of 6500~9500 Nm³ / h, a secondary air supply of 15500~16000 Nm³ / h, and a tertiary air supply of 3000~6000 Nm³ / h. This three-stage air supply maintains an oxygen content of 800~900 m³ / h within the furnace.

[0019] The amount of pulverized coal added in step 1 is 5~7 t / h. The pulverized coal has a fixed carbon content ≥75%, ash content ≤25%, volatile matter ≤26%, particle size with a sieve undersize ratio of >80% passing through a 160-mesh sieve, and moisture content ≤2%.

[0020] The amount of limestone added in step 1 is 0.5~2 t / h. During smelting, maintain SiO2 / Fe = 0.9~1.25 and CaO / SiO2 = 0.2~0.6.

[0021] The temperature of the molten pool in the side-blown reduction furnace described in step 1 is 1300~1350℃.

[0022] The zinc oxide dust containing indium mentioned in step 1 contains 55-60% zinc, of which 4-5% is metallic zinc, 10-15% lead, and 1500-3000 g / t of indium.

[0023] The Fe-containing component mentioned in step 2 3+ The acidic solution contains 76.5~77.5 g / L of acid and Fe. 3+ 14~15g / l.

[0024] The reaction time for the oxidative neutral leaching in step 2 is 1 hour, the temperature is 25~30℃, the liquid-to-solid ratio is preferably 7.1~7.2:1, and the pH value at the reaction endpoint is 2.3~2.8.

[0025] The acidity of the sulfuric acid solution mentioned in step 3 is 180~200 g / t.

[0026] The reaction time for the high acid leaching in step 3 is 2-3 hours, the temperature is 80-95℃, and the liquid-to-solid ratio is preferably 3.5:1.

[0027] Example 1

[0028] A method for reducing the reducing properties of indium-containing zinc oxide dust and increasing indium leaching rate includes the following steps:

[0029] Step 1: In the side-blown reduction stage, lead-zinc hot slag containing 8% zinc, 1.5% lead, 25% iron, 19% silicon dioxide, and 8% calcium oxide is added to the side-blown reduction furnace at a rate of 8 t / h for smelting. Simultaneously, pulverized coal is added at a rate of 7 t / h, and limestone at a rate of 1 t / h, maintaining SiO2 / Fe = 1 and CaO / SiO2 = 0.4 during smelting. The primary air supply is 6500 Nm³ / h, the secondary air supply is 15500 Nm³ / h, and the tertiary air supply is 3000 Nm³ / h, maintaining an oxygen content of 800 m³ / h in the furnace. The molten pool temperature in the side-blown reduction furnace is maintained at 1300℃. The resulting indium-containing zinc oxide dust contains 60% zinc (4.5% metallic zinc), 12% lead, and 2500 g / t of indium.

[0030] Step 2: Neutral oxidative leaching stage, indium-containing zinc oxide dust is mixed with acid containing 76.5 g / L and Fe... 3+ An acidic solution of 14 g / L was mixed at a liquid-to-solid ratio of 7.1:1 and subjected to oxidative neutral leaching for 1 hour at a temperature of 25°C. The pH value at the end of the reaction was 2.3, and the solution contained 0.2 mg / L of indium. This process oxidized the metallic indium in the flue dust and allowed it to enter the intermediate leaching residue, resulting in an indium-containing intermediate leaching residue and a zinc sulfate solution. The zinc sulfate solution was then returned to the zinc recovery system.

[0031] Step 3: High-acid leaching stage. The indium-containing leaching residue is mixed with a sulfuric acid solution with an acidity of 180 g / t at a liquid-to-solid ratio of 3:1 for high-acid leaching. The reaction time is 2 hours and the temperature is 80℃. Indium-containing solution and lead slag are obtained.

[0032] Step 4: Indium recovery stage, the indium-containing solution enters the indium recovery system, where it undergoes extraction, refining, and electrolysis to obtain sponge indium. The lead slag is returned to the lead recovery system. After these four steps, the indium content in the lead slag decreases from 500 g / t to 30 g / t, and the indium leaching rate reaches 90%.

[0033] Example 2

[0034] A method for reducing the reducing properties of indium-containing zinc oxide dust and increasing indium leaching rate includes the following steps:

[0035] Step 1: In the side-blown reduction stage, lead-zinc hot slag containing 10% zinc, 2% lead, 26% iron, 20% silicon dioxide, and 9% calcium oxide is added to the side-blown reduction furnace at a rate of 9 t / h for smelting. Simultaneously, pulverized coal is added at a rate of 5 t / h, and limestone at a rate of 0.5 t / h, maintaining SiO2 / Fe = 0.9 and CaO / SiO2 = 0.2 during smelting. The primary air supply is 8000 Nm³ / h, the secondary air supply during the reaction is 15800 Nm³ / h, and the tertiary air supply is 5000 Nm³ / h, maintaining an oxygen content of 850 m³ / h in the furnace. The molten pool temperature in the side-blown reduction furnace is maintained at 1320℃. The resulting indium-containing zinc oxide dust contains 55% zinc (4% metallic zinc), 10% lead, and 1500 g / t of indium.

[0036] Step 2: Neutral oxidative leaching stage, indium-containing zinc oxide dust is mixed with acid containing 77g / l and Fe... 3+ An acidic solution of 14.5 g / L was mixed at a liquid-to-solid ratio of 7.2:1 and subjected to oxidative neutral leaching for 1 hour at a temperature of 26°C. The pH value at the end of the reaction was 2.5, and the solution contained 0.21 mg / L of indium. This process oxidized the metallic indium in the flue dust and allowed it to enter the intermediate leaching residue, resulting in an indium-containing intermediate leaching residue and a zinc sulfate solution. The zinc sulfate solution was then returned to the zinc recovery system.

[0037] Step 3: High-acid leaching stage. The indium-containing leaching residue is mixed with a sulfuric acid solution with an acidity of 190 g / t at a liquid-to-solid ratio of 3.5:1 for high-acid leaching. The reaction time is 2.5 h and the temperature is 85 °C. Indium-containing solution and lead slag are obtained.

[0038] Step 4: Indium recovery stage, the indium-containing solution enters the indium recovery system, where it undergoes extraction, refining, and electrolysis to obtain sponge indium. The lead slag is returned to the lead recovery system. After these four steps, the indium content in the lead slag decreases from 700 g / t to 35 g / t, and the indium leaching rate reaches 92%.

[0039] Example 3

[0040] A method for reducing the reducing properties of indium-containing zinc oxide dust and increasing indium leaching rate includes the following steps:

[0041] Step 1: In the side-blown reduction stage, lead-zinc hot slag containing 15% zinc, 3% lead, 27% iron, 21% silicon dioxide, and 10% calcium oxide is added to the side-blown reduction furnace at a rate of 10 t / h for smelting. Simultaneously, pulverized coal is added at a rate of 6 t / h and limestone at a rate of 2 t / h, maintaining the SiO2 / Fe ratio at 1.25 and the CaO / SiO2 ratio at 0.6 during smelting. The primary air supply is 9500 Nm³ / h, the secondary air supply is 16000 Nm³ / h, and the tertiary air supply is 6000 Nm³ / h, maintaining an oxygen content of 900 m³ / h in the furnace. The molten pool temperature in the side-blown reduction furnace is maintained at 1350℃. The resulting indium-containing zinc oxide dust contains 60% zinc (5% metallic zinc), 15% lead, and 3000 g / t of indium.

[0042] Step 2: Neutral oxidative leaching stage, indium-containing zinc oxide dust is mixed with acid containing 77.5 g / L and Fe... 3+ A 15 g / L acidic solution was mixed at a liquid-to-solid ratio of 7.25:1 and subjected to oxidative neutral leaching for 1 hour at a temperature of 30°C. The pH value at the reaction endpoint was 2.8, and the solution contained 0.25 mg / L of indium. This process oxidized the metallic indium in the flue dust, causing it to enter the intermediate leaching residue, resulting in an indium-containing intermediate leaching residue and a zinc sulfate solution. The zinc sulfate solution was then returned to the zinc recovery system.

[0043] Step 3: High-acid leaching stage. The indium-containing leaching residue is mixed with a sulfuric acid solution with an acidity of 200 g / t at a liquid-to-solid ratio of 4:1 for high-acid leaching. The reaction time is 3 hours and the temperature is 95℃. Indium-containing solution and lead slag are obtained.

[0044] Step 4: Indium recovery stage, the indium-containing solution enters the indium recovery system, where it undergoes extraction, refining, and electrolysis to obtain sponge indium. The lead slag is returned to the lead recovery system. After these four steps, the indium content in the lead slag is reduced from 800 g / t to 40 g / t, and the indium leaching rate reaches 95%.

[0045] The working principle and process of this invention:

[0046] In the side-blown reduction stage, lead-zinc hot slag containing 8-15% zinc, 1.5-3% lead, 25-27% iron, 19-21% silicon dioxide, and 8-10% calcium oxide is continuously added to the side-blown reduction furnace at a rate of 8-10 t / h. Primary air, pulverized coal, limestone, secondary air, and tertiary air are supplied to the side-blown reduction furnace; 5-7 t / h of pulverized coal is supplied, the primary air supply is 6500-9500 Nm³ / h, the secondary air supply is 15500-16000 Nm³ / h to promote fuel combustion and maintain the molten pool temperature, which is controlled at 1300-1350℃, and the tertiary air supply is 3000-6000 Nm³ / h. The tertiary air supply ensures that the reducing metals such as zinc and lead volatilized from the molten pool are oxidized into zinc oxide, etc., and zinc oxide, lead oxide, indium oxide, etc., enter the produced flue dust. During this process, the supply volume of tertiary air is strictly controlled, ensuring an air supply volume of 3000-6000 Nm³ / h and an oxygen content of 800-900 m³ / h in the furnace, thereby reducing the metallic zinc in the zinc oxide dust produced by the side-blown reduction furnace to below 5%; the amount of limestone added is 0.5-2 t / h, maintaining SiO2 / Fe = 0.9-1.25 and CaO / SiO2 = 0.2-0.6 during smelting.

[0047] The reaction principle of the side-blown reduction stage:

[0048] Side-blown reduction furnace smelting is a high-temperature enhanced reduction and volatilization oxidation process. In essence, a mixture of air and pulverized coal is blown into the molten slag inside the side-blown reduction furnace. The combustion of pulverized coal generates a large amount of heat and carbon monoxide gas, which keeps the furnace at a high temperature and a certain reducing atmosphere. This causes the lead and zinc in the slag to be reduced from their oxides into metal vapors and volatilized. The vapors are then oxidized again in the upper space of the furnace by air drawn in from the tertiary tuyeres into lead oxide and zinc oxide. The lead in the slag may also volatilize in the form of lead oxide or lead sulfide. All these metal oxides are produced in the form of zinc oxide dust.

[0049] Combustion reaction of carbon in pulverized coal:

[0050] 2C + O2 = 2CO

[0051] C + O₂ = CO₂

[0052] CO2 + C = 2CO

[0053] CO + O2 = CO2

[0054] Reactions of metal salts:

[0055] 2ZnSO4 = 2ZnO + 2SO2↑ + O2

[0056] Reduction reactions of metal oxides:

[0057] PbO + CO = Pb + CO2↑

[0058] 2PbO + C = 2Pb + CO2↑

[0059] ZnO + CO = Zn + CO2↑

[0060] 2ZnO + C = 2Zn + CO2↑

[0061] Oxidation reaction of metal gas in the upper part of the side-blown reduction furnace:

[0062] 2Pb + O₂ = 2PbO

[0063] 2Zn + O2 = 2ZnO

[0064] By strictly controlling the oxidizing atmosphere of the metal gas in the upper part of the furnace, metallic zinc is oxidized into zinc oxide.

[0065] The zinc oxide dust containing indium produced during the neutral oxidative leaching stage and the side-blown reduction stage is mixed with acid containing 76.5–77.5 g / L and Fe. 3+ Oxidative leaching is performed using an acidic solution with a concentration of 14–15 g / L, a liquid-to-solid ratio of 7–7.25:1, a reaction time of 1 hour, a temperature of 25–30 °C, and a final pH of 2.3–2.8. The solution contains 0.20–0.25 mg / L of indium. The zinc sulfate solution produced after leaching is returned to the zinc recovery system, and the indium-containing leaching residue produced after leaching enters the high-acid leaching stage.

[0066] The reaction principle of the neutral leaching stage: Indium-containing zinc oxide dust enters the neutral leaching stage, where zinc is leached out, and at the same time, metallic indium in the zinc oxide dust is oxidized into high-valence indium and hydrolyzed into the neutral leaching residue.

[0067] The reaction of zinc oxide entering the solution:

[0068] ZnO + H₂SO₄ = ZnSO₄ + H₂O

[0069] The oxidation reaction of metallic indium in zinc oxide dust:

[0070] In+Fe 3+ =In 3+ +Fe 2+

[0071] In 3+ +3OH - =In(OH)3

[0072] In the high-acid leaching stage, the indium-containing leaching residue from the neutral oxidative leaching stage enters the high-acid leaching stage. The acidity of the sulfuric acid solution is 180–200 g / t, the liquid-to-solid ratio is 3–4:1, the reaction time is 2–3 hours, and the temperature is 80–95℃. The indium-containing solution after high-acid leaching enters the indium recovery system, and the leached lead slag is returned to the lead recovery system. The indium content in the lead slag decreases from 500–800 g / t to 30–40 g / t, and the indium leaching rate increases to 90–95%.

[0073] The reaction principle of the high acid leaching stage: Indium-containing intermediate leaching residue enters the high acid leaching stage, and indium enters the solution in the form of indium sulfate. The indium-containing solution enters the indium recovery stage, while other valuable metals such as lead and copper enter the lead slag. The lead slag is returned to the lead system for further recovery of valuable metals such as lead and copper.

[0074] The reaction of indium entering the solution:

[0075] In₂O₃ + 3H₂SO₄ = In₂(SO₄)₃ + 3H₂O

[0076] 2In(OH)3+3H2SO4=In2(SO4)3+3H2O.

Claims

1. A method for reducing the reducibility of indium-containing zinc oxide fumes to increase the leaching rate of indium, characterized by The method comprises the following steps: Step 1: side-blown reduction stage, when smelting lead-zinc hot slag by a side-blown reduction furnace, adding pulverized coal and limestone, improving the oxidation atmosphere in the furnace by three times of air supply, oxidizing zinc into zinc oxide, reducing the reducibility of the produced indium-containing zinc oxide dust, and obtaining indium-containing zinc oxide dust and water-quenched slag; Step 2: Oxidative neutral leaching stage, the indium-containing zinc oxide dust is mixed with the Fe 3+ containing acidic solution at a liquid-solid ratio of 7-7.25:1 to perform oxidative neutral leaching, so that the indium in the dust is oxidized into the neutral leaching residue, and indium-containing neutral leaching residue and zinc sulfate solution are obtained; Step 3: high-acid leaching stage, mixing indium-containing leaching residue with sulfuric acid solution according to a liquid-solid ratio of 3-4:1, and performing high-acid leaching to obtain indium-containing solution and lead residue; Step 4: indium recovery stage, making the indium-containing solution enter an indium recovery system, and obtaining sponge indium after extraction, refining and electrolysis.

2. The method of reducing the reducibility of indium-containing zinc oxide fume to increase the leaching rate of indium according to claim 1, characterized by The lead-zinc hot slag in step 1 contains 8-15% zinc, 1.5-3% lead, 25-27% iron, 19-21% silicon dioxide and 8-10% calcium oxide, and the adding amount is 8-10 t / h.

3. The method of reducing the reducibility of indium-containing zinc oxide fume to increase the leaching rate of indium according to claim 1, characterized by The three times of air supply in step 1 refers to: the first air supply amount is 6500-9500 Nm³ / h, the second air supply amount is 15500-16000 Nm³ / h, and the third air supply amount is 3000-6000 Nm³ / h.

4. The method of reducing the reducibility of indium-containing zinc oxide fume and increasing the indium leaching rate according to claim 3, characterized in that The three times of air supply in step 1 makes the oxygen content in the furnace be 800-900 m³ / h.

5. The method of reducing the reducibility of indium-containing zinc oxide fume and increasing the indium leaching rate according to claim 1, characterized in that The indium-containing zinc oxide dust in step 1 contains 55-60% zinc, of which 4-5% is metallic zinc, 10-15% is lead, and 1500-3000 g / t is indium.

6. The method of reducing the reducibility of indium-containing zinc oxide fume and increasing the leaching rate of indium according to claim 1, characterized in that The acid solution containing Fe 3+ contains 76.5-77.5 g / l acid, contains Fe 3+ 14-15 g / l.

7. The method of reducing the reducibility of indium-containing zinc oxide fume and increasing the leaching rate of indium according to claim 1, characterized in that The reaction time of the oxidative neutral leaching in step 2 is 1 h, the temperature is 25-30°C, and the liquid-solid ratio is 7.1-7.2:

1.

8. The method of reducing the reducibility of indium-containing zinc oxide fume and increasing the leaching rate of indium according to claim 1, characterized by The pH value of the reaction end point of the oxidative neutral leaching in step 2 is 2.3-2.

8.

9. The method of reducing the reducibility of indium-containing zinc oxide fume to increase indium leaching rate according to claim 1, characterized in that The acidity of the sulfuric acid solution in step 3 is 180-200 g / t.

10. The method of reducing the reducibility of indium-containing zinc oxide fume and increasing the leaching rate of indium according to claim 1, characterized in that The reaction time of the high-acid leaching in step 3 is 2-3 h, the temperature is 80-95°C, and the liquid-solid ratio is 3.5:1.

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