A multi-stage deep iron removal method for zinc hydrometallurgy oxygen pressure leaching solution

Abstract

The application discloses a kind of zinc hydrometallurgy oxygen pressure leaching solution multistage depth iron removal methods, belong to metal material regeneration technical field, the present application will be removed before liquid first mineralization and sink iron, then spray-hydrolysis iron removal again.The scheme of the present application realizes the closed loop of "iron conversion-depth removal-resource recovery".Compared with traditional hematite method, there is no harsh high temperature and high pressure condition, iron conversion efficiency and iron slag grade are significantly improved;Compared with traditional neutralization iron removal method, reagent consumption and slag rate are greatly reduced, and residual iron deep removal is realized;Compared with existing mineralization and sink iron technology, spray-hydrolysis iron removal process is added to solve the problem of residual iron removal, and process parameters are optimized to realize iron resource recovery and energy consumption optimization, and the overall technical scheme has significant non-obviousness, which provides an efficient, economical, clean and stable solution for wet zinc smelting iron removal process.

Description

Technical Field

[0001] This invention relates to the field of metal material recycling technology, specifically to a multi-stage deep iron removal method using oxygen pressure leaching solution in zinc hydrometallurgy. Background Technology

[0002] In hydrometallurgical zinc smelting, iron separation and resource utilization are key bottlenecks restricting the industry's clean and efficient development. Currently, the "two-stage oxygen-enriched pressure direct leaching" hydrometallurgical process used in zinc smelting achieves preliminary iron separation to some extent, but still suffers from the following prominent problems: First, the process produces a large leaching slag rate (60-70% from zinc concentrate) and low iron grade (less than 30%), making it difficult to achieve iron resource utilization and resulting in iron resource waste; second, a large amount of leaching slag interferes with subsequent sulfur flotation processes, affecting separation efficiency and increasing the cost of lead system slag treatment; furthermore, controlling reaction conditions during iron precipitation is difficult and energy consumption is high, restricting the overall economic efficiency and stability of the process.

[0003] To overcome the aforementioned problems, the industry has begun exploring external iron removal technology in oxygen pressure reactors. Currently, the commonly used jaundice and goethite processes produce iron slag with low iron and high zinc content, large slag volume, and poor stability, still requiring pyrometallurgical treatment to achieve zinc recovery and iron slag harmlessness. While the hematite process can yield high-grade iron slag, it is difficult to operate efficiently in the high-zinc, high-acid hydrometallurgical zinc smelting solutions, exhibiting limitations such as low iron conversion efficiency, harsh process conditions (temperature 180–220℃, pressure 1.8–2.0 MPa), and high energy consumption. Furthermore, changes in slag shape after external iron removal in the oxygen pressure reactor can affect the stability of the oxygen pressure reactor system.

[0004] Existing methods face challenges in the conversion and recovery of iron from high-zinc-content sulfuric acid solutions. The traditional hematite method is ill-suited to high-zinc, high-acid solution systems, resulting in low iron conversion efficiency and hindering the efficient generation of α-Fe₂O₃ and the resource recovery of iron. Another challenge is the efficient and deep removal of residual iron from high-acid solutions. Even after iron precipitation, the solution still contains 2-3 g / L of ferric iron. Traditional neutralization methods for iron removal in such high-acid systems suffer from high neutralizing agent consumption (400-450 kg / t zinc flakes), high slag ratio (200%-300% from neutralizing agent to intermediate leaching slag), and difficulties in liquid-solid separation, making it difficult to achieve deep iron purification.

[0005] Therefore, developing a fully hydrometallurgical zinc-iron resource recovery process suitable for high-zinc, high-acid systems to achieve clean and efficient iron recycling has become a technical challenge that the industry urgently needs to overcome. Summary of the Invention

[0006] In view of this, the present invention provides a multi-stage deep iron removal method for oxygen pressure leaching solution in zinc hydrometallurgy. The multi-stage deep iron removal process of the present invention refers to a scheme in which the pre-iron removal solution undergoes a synergistic iron removal process of mineralization, spraying, and hydrolysis. This achieves deep iron removal through mineralization and spraying after the valuable metals have been recovered from the oxygen pressure leaching solution.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A multi-stage deep iron removal method using oxygen pressure leaching solution in zinc hydrometallurgy, characterized by comprising the following steps: (1) Mineralized iron deposits: The iron, acid, and zinc contents in the pre-iron removal liquid to be treated are tested and the acid content is adjusted to 5-15 g / L. Then, medium-pressure steam is introduced into the pre-iron removal liquid to raise the temperature, and an oxidant is introduced to mineralize and precipitate iron. The resulting slurry is then separated into liquid and solid in a thickening tank. The supernatant obtained from the separation (containing ≤3.0 g / L of iron) is transported to the next stage of spray-water de-iron removal operation, and the underflow enters a centrifuge for centrifugation and washing to obtain iron concentrate. (2) Spray-hydration iron removal: Neutralizing agent and oxidizing agent are added to the supernatant of mineralized iron precipitate for spray iron removal operation. The resulting slurry overflows to the water-hydration iron removal operation section for hydrolysis treatment. The resulting hydrolyzed slurry is sent to the thickening tank for liquid-solid separation. The supernatant (containing iron <20mg / L) and underflow are separated. Then the underflow is filtered, slurried, and washed to form intermediate leaching residue, which is sent to the next operation.

[0009] This invention addresses the challenge of iron conversion in high-zinc, high-acid systems by developing a medium-temperature mineralization iron precipitation technology. This technology successfully achieves the efficient generation of α-Fe₂O₃ with an iron grade exceeding 50%, enabling the resource recovery of iron. This technology significantly reduces leaching slag rate, minimizes the loss of valuable metals and subsequent treatment costs, and improves the overall economic and environmental benefits of the process. Regarding the difficulty in removing residual iron from the solution after medium-temperature mineralization iron precipitation, traditional neutralization methods suffer from limitations such as large slag volume and difficulty in clarification. This invention, through process optimization, achieves deep purification and efficient separation of iron in high-acid systems, reducing iron content while minimizing impurity interference and ensuring stable operation of subsequent processes.

[0010] This invention addresses the unique characteristics of high-zinc, high-acid systems by innovatively designing a synergistic "mineralization-spraying-hydrolysis" process, achieving a closed loop of "iron conversion-deep removal-resource recovery." Compared to the traditional hematite method, it eliminates the need for stringent high-temperature and high-pressure conditions, significantly improving iron conversion efficiency and slag grade. Compared to the traditional neutralization iron removal method, it drastically reduces reagent consumption and slag ratio, achieving deep removal of residual iron. Compared to existing mineralization iron precipitation technologies, the addition of a spraying-hydrolysis iron removal step solves the problem of residual iron removal, while optimizing process parameters to achieve resource recovery of iron and energy consumption optimization. The overall technical solution exhibits significant non-obviousness, providing an efficient, economical, clean, and stable solution for iron removal in hydrometallurgical zinc smelting.

[0011] This invention offers significant environmental benefits: the method can greatly reduce the generation of leaching residue and neutralization residue, thereby reducing the environmental pressure caused by waste residue stockpiling and disposal; the resource-based recovery of iron resources avoids the environmental costs associated with the harmless treatment of iron slag; the reduction in reagent consumption and energy consumption reduces pollutant emissions, meeting the needs of the non-ferrous metal smelting industry for green and low-carbon transformation, and achieving a win-win situation for both economic and environmental benefits.

[0012] The present invention boasts outstanding economic advantages: In this invention, the spray-water iron removal process requires no additional heating, reducing steam consumption to 0 t / t·zinc sheet, and controlling steam consumption for heating the mineralized iron deposit at 0.8-1.5 t / t·zinc sheet, resulting in a significant reduction in overall energy consumption compared to traditional processes. Simultaneously, the present invention reduces reagent consumption; the dosage of neutralizing agents and oxidizing agents is significantly reduced after optimization, lowering the slag ratio. This saves 150-200 yuan per ton of zinc sheet, resulting in annual cost savings of tens of millions of yuan. Furthermore, it eliminates the need for large-scale modifications to existing production systems, exhibiting strong process adaptability, low modification costs, and rapid implementation.

[0013] Furthermore, the iron content in step (1) is 10-15 g / L, the acid content is 5-15 g / L, and the zinc content is 120-165 g / L.

[0014] Furthermore, the oxidant mentioned in step (1) is oxygen.

[0015] Furthermore, in step (1), the oxidant flow rate is 2-5 Nm³ / m³·mineralized iron precipitation liquid; The medium-pressure steam is introduced at a pressure of 0.8-1.6 MPa and at a rate of 0.10-0.20 t / m³·pre-mineralization iron precipitation liquid.

[0016] Furthermore, in step (1), the reaction temperature for mineralizing iron is 130-170℃ and the reaction pressure is 0.7-0.8MPa.

[0017] Furthermore, the neutralizing agent mentioned in step (2) is zinc calcined sand, high-purity zinc oxide powder, or zinc oxide powder; The amount of zinc metal consumed in the neutralizing agent is 280-380 kg / t of zinc sheet. In this invention, 280-380 kg of neutralizing agent zinc metal is required to produce one ton of zinc sheet, and 10-11 m³ of mineralized iron supernatant is used to produce one ton of zinc sheet.

[0018] Furthermore, the oxidant mentioned in step (2) is oxygen or air; Among them, the oxygen consumption is 6-10 Nm³ / t·zinc sheet (based on the zinc content in the supernatant of the mineralized iron precipitate), and the air consumption is 70-85 m³ / t·zinc sheet (based on the zinc content in the supernatant of the mineralized iron precipitate).

[0019] Furthermore, the temperature during the spray iron removal operation in step (2) is 80-90℃, and the pH value is 2.8-3.2; The temperature of the iron removal process is 80-90℃, the pH value is 4.8-5.2, and the iron removal time is 1-2 hours.

[0020] Preferably, the pH value needs to be controlled between 4.8 and 5.0, the operating temperature between 80 and 85°C, and the iron content of the solution is less than 20 mg / L.

[0021] The beneficial effects of this invention are as follows: This invention, through a "mineralization-spraying-hydrolysis synergistic iron removal process," precisely solves the two core technical challenges of iron removal in existing wet zinc smelting oxygen pressure leaching solutions. It also addresses many derivative problems of traditional processes, demonstrating significant advantages over existing technologies, as detailed below: 1. Solving the problem of iron conversion and recovery in high-zinc, high-acid systems: This invention abandons the limitations of the traditional hematite method and, through a medium-temperature mineralization precipitation process, precisely controls core parameters such as temperature and pressure, combined with high-purity oxygen oxidation, successfully achieves the efficient generation of α-Fe2O3, producing iron concentrate with an iron content >50%. This completely solves the pain points of low iron conversion efficiency, low iron slag grade (less than 30%), and inability to recover resources in traditional processes, realizing the clean and efficient recovery of iron resources, turning waste into treasure, and improving resource utilization.

[0022] 2. Significantly improved resource utilization: The iron concentrate in this invention has a grade of over 50%, which can be directly used as an iron-containing raw material for resource utilization, completely changing the current situation of iron resource waste in traditional processes; at the same time, this invention also significantly reduces the oxygen pressure leaching slag rate from 60-70% to 35-40%, reducing the entrainment loss of valuable metals (such as zinc), improving the recovery rate of valuable metals, and eliminating the interference of a large amount of leaching slag on the subsequent sulfur flotation process, improving separation efficiency and reducing the slag treatment cost of lead system.

[0023] 3. Strong Process Stability and Adaptability: This invention, through multiple case studies, has demonstrated stable and efficient iron conversion and deep removal in oxygen pressure leaching solutions with high zinc, high acid, and varying iron contents, adapting to different operating conditions. The process involves coordinated operation of each step with controllable parameters, avoiding the problems of difficult-to-control reaction conditions and unstable operation inherent in traditional processes. It also overcomes the limitations of the hematite process, which requires harsh conditions (high temperature and high pressure). Iron precipitation only requires 130-170℃ and 0.7-0.8MPa, reducing operational difficulty and equipment wear, thus ensuring the stable operation of the entire hydrometallurgical zinc smelting system.

[0024] 4. Solving the Challenge of Deep Removal of Residual Iron in High-Acid Systems: For the 2-3 g / L of trivalent iron residue in the solution after iron precipitation, a spray-hydrolysis synergistic process is employed. No additional heating is required (utilizing the temperature of the supernatant from the iron precipitation at 80-90℃). By precisely controlling the pH value and oxidant ratio, the iron content in the solution is reduced to below 20 mg / L, achieving deep iron purification. Compared to traditional neutralization iron removal methods, neutralizing agent consumption is reduced from 400-450 kg / t zinc flakes to 280-380 kg / t zinc flakes, and the slag rate is reduced from 200%-300% to 75-110 t / t neutralizing agent. Simultaneously, the problem of difficult liquid-solid separation is solved, significantly reducing reagent consumption and waste disposal costs. Attached Figure Description

[0025] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1 (1) Iron mineralization: The pre-iron removal liquid (containing 12 g / L iron, 10 g / L acid, and 140 g / L zinc) was treated, with the temperature controlled at 155℃ and the pressure at 0.75 MPa. Oxygen with a purity >99% was used as the oxidant, with a consumption of 45 Nm³ / t·zinc sheet; medium-pressure steam at a pressure of 1.5 MPa was used for heating, with a consumption of 1.1 t / t·zinc sheet. After the iron mineralization reaction was completed, the slurry was separated into liquid and solid in a thickening tank. The supernatant contained 2.5 g / L iron and was transported to the spray-water iron removal section. The underflow was separated and washed by a centrifuge to produce iron concentrate containing 53% iron, and the oxygen pressure leaching residue rate was 38%.

[0028] (2) Spray-hydration iron removal: The supernatant of the mineralized iron precipitate (its own temperature is 85℃) is used, and no additional heating is required. The temperature is controlled at 85℃ and pH value at 3.0 during the spray iron removal stage, and the temperature is controlled at 82℃ and pH value at 5.0 during the hydration iron removal stage. The slurry formed during the spray iron removal operation overflows to the hydration iron removal section. Zinc roasted sand is used as a neutralizing agent, with a zinc metal consumption of 320 kg / t·zinc sheet; oxygen with a purity of >99% (consumption of 40 Nm³ / t·zinc sheet) and air (consumption of 78 Nm³ / t·zinc sheet) are used as oxidants. After the slurry formed after hydration iron removal is separated into liquid and solid in the thickening tank, the supernatant contains 15 mg / L of iron and is sent to the purification section; after underflow filtration, pulping, and washing, the intermediate leaching residue is produced and sent to the high acid leaching section. The spray-hydration iron removal slag rate is 90 t / t·neutralizing agent.

[0029] Overall results: Calculations show that the valve stem iron conversion efficiency of Example 1 is over 98%, and the iron concentrate grade is 53%, which can be directly utilized as a resource; the iron content of the solution after spray-water iron removal is 11 mg / L, which meets the requirements for deep purification; the oxygen pressure leaching slag rate is reduced by 20-30% compared with the traditional process, and the neutralizing agent consumption is reduced by 100 kg / t zinc sheet compared with the traditional neutralization iron removal method, which greatly improves the economic efficiency and environmental protection of the process.

[0030] Example 2 (2) Iron mineralization: The pre-iron removal liquid (containing 15 g / L iron, 15 g / L acid, and 165 g / L zinc) was treated, with the temperature controlled at 170℃ and the pressure at 0.8 MPa. Oxygen with a purity >99% was used as the oxidant, with a consumption of 50 Nm³ / t·zinc sheet; medium-pressure steam at a pressure of 1.6 MPa was used for heating, with a consumption of 1.4 t / t·zinc sheet. After the iron mineralization reaction was completed, the slurry was separated into liquid and solid in a thickening tank. The supernatant contained 2.8 g / L iron and was transported to the spray-water iron removal section. The underflow was separated and washed by a centrifuge to produce iron concentrate containing 54% iron, and the oxygen pressure leaching residue rate was 39%.

[0031] (2) Spray-hydration iron removal: The supernatant of the mineralized iron precipitate (its own temperature is 90℃) is used, and no additional heating is required. The temperature is controlled at 83℃ and pH value at 3.2 during the spray iron removal stage, and the temperature is controlled at 80℃ and pH value at 5.2 during the hydration iron removal stage. The slurry formed by the spray iron removal operation overflows to the hydration iron removal operation section. High-purity zinc oxide powder is used as a neutralizing agent, with a zinc metal consumption of 340 kg / t·zinc sheet; oxygen with a purity of >99% (consumption of 80 Nm³ / t·zinc sheet) and air (consumption of 85 Nm³ / t·zinc sheet) are used as oxidants. After the slurry formed by hydration iron removal is separated into liquid and solid in the thickening tank, the supernatant contains 15 mg / L of iron and is sent to the purification section; after underflow filtration, pulping, and washing, the intermediate leaching residue is produced and sent to the high acid leaching operation section. The spray-hydration iron removal slag rate is 105 t / t·neutralizing agent.

[0032] Overall Results: Calculations show that the iron conversion efficiency of Example 2 is over 97.5%, the iron concentrate grade is 54%, and the iron resource recovery effect is significant. After iron removal by spraying and water, the solution contains 15 mg / L of iron, which meets the requirements for deep purification. It can still operate stably under high iron and high acid conditions. The neutralizing agent consumption is reduced by 120 kg / t of zinc flakes compared with the traditional neutralization iron removal method, effectively solving the problem of residual iron removal in high acid systems.

[0033] Example 3 (1) Iron mineralization: The pre-iron removal liquid (containing 10 g / L iron, 5 g / L acid, and 120 g / L zinc) was treated, with the temperature controlled at 140℃ and the pressure at 0.7 MPa. Oxygen with a purity >99% was used as the oxidant, with a consumption of 40 Nm³ / t·zinc sheet; medium-pressure steam at a pressure of 0.8 MPa was used for heating, with a consumption of 0.8 t / t·zinc sheet. After the iron mineralization reaction was completed, the slurry was separated into liquid and solid in a thickening tank. The supernatant contained 2.2 g / L iron and was transported to the spray-water iron removal section. The underflow was separated and washed by a centrifuge to produce iron concentrate containing 50% iron, and the oxygen pressure leaching residue rate was 35%.

[0034] (2) Spray-hydration iron removal: The supernatant of the mineralized iron precipitate (its own temperature is 80℃) is used, and no additional heating is required. The temperature is controlled at 83℃ and pH value at 2.8 during the spray iron removal stage, and the temperature is controlled at 80℃ and pH value at 4.8 during the hydration iron removal stage. The slurry formed by the spray iron removal operation overflows to the hydration iron removal operation section. A neutralizing agent of zinc roasted sand and high-purity zinc oxide powder (ratio 1:1) is used, with a zinc metal consumption of 280 kg / t·zinc sheet; oxygen with a purity of >99% (consumption of 6 Nm³ / t·zinc sheet) and air (consumption of 70 Nm³ / t·zinc sheet) are used as oxidants. After the slurry formed by hydration iron removal is separated into liquid and solid in the thickening tank, the supernatant contains 10 mg / L of iron and is sent to the purification section; after underflow filtration, pulping, and washing, the intermediate leaching residue is produced and sent to the high acid leaching operation section. The spray-hydration iron removal slag rate is 80 t / t·neutralizing agent.

[0035] Overall results: Calculations show that the iron conversion efficiency in Example 3 is over 98.5%, the iron concentrate grade is 50%, and iron resource recovery is achieved; the iron content in the solution after spray-water de-ironization is 10mg / L, reaching the deep purification standard; the oxygen pressure leaching slag rate is reduced by 30% compared with the traditional process, and the neutralizing agent consumption is reduced by 220kg / t·zinc sheet compared with the traditional neutralization iron removal method. Energy consumption and reagent consumption are further optimized, and the process economy is outstanding.

[0036] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A multi-stage deep iron removal method using oxygen pressure leaching solution in zinc hydrometallurgy, characterized in that, Includes the following steps: (1) Mineralized iron deposits: The iron, acid, and zinc content in the pre-iron removal liquid to be treated is tested and the acid content is adjusted to 5-15 g / L. Then, medium-pressure steam is introduced into the pre-iron removal liquid to raise the temperature, and an oxidant is introduced to oxidize ferrous iron to ferric iron for mineralization and precipitation. The resulting slurry is then separated into liquid and solid in a thickening tank. The supernatant obtained from the separation is sent to the next stage of spray-water de-iron removal operation, and the underflow enters a centrifuge for centrifugation and washing to obtain iron concentrate. (2) Spray-hydration iron removal: Neutralizing agent and oxidizing agent are added to the supernatant of mineralized iron precipitate for spray iron removal operation. The resulting slurry overflows to the water-hydration iron removal operation section for hydrolysis treatment. The resulting hydrolyzed slurry is sent to the thickening tank for liquid-solid separation. The supernatant and underflow are separated. Then the underflow is filtered, pulped and washed to form intermediate leaching residue and sent to the next operation. The supernatant is sent to the next operation.

2. The multi-stage deep iron removal method for oxygen pressure leaching solution in zinc hydrometallurgy according to claim 1, characterized in that, The iron content in step (1) is 10-15 g / L, the acid content is 5-15 g / L, and the zinc content is 120-165 g / L.

3. The multi-stage deep iron removal method for oxygen pressure leaching solution in zinc hydrometallurgy according to claim 2, characterized in that, The oxidant mentioned in step (1) is oxygen.

4. The multi-stage deep iron removal method for oxygen pressure leaching solution in zinc hydrometallurgy according to claim 3, characterized in that, The oxidant flow rate in step (1) is 2-5 Nm³ / m³·pre-mineralization iron precipitation solution; The medium-pressure steam is introduced at a pressure of 0.8-1.6 MPa and at a rate of 0.10-0.20 t / m³·pre-mineralization iron precipitation liquid.

5. The multi-stage deep iron removal method for oxygen pressure leaching solution in zinc hydrometallurgy according to claim 4, characterized in that, In step (1), the reaction temperature for mineralizing iron is 130-170℃, the reaction pressure is 0.7-0.8MPa, the reaction time for mineralizing iron is 1-3h, and the mineralized iron slurry overflows into the thickening tank for thickening.

6. The multi-stage deep iron removal method for oxygen pressure leaching solution in zinc hydrometallurgy according to claim 4, characterized in that, The neutralizing agent mentioned in step (2) is zinc calcined sand, high-purity zinc oxide powder, or zinc oxide powder; The amount of zinc metal consumed in the neutralizing agent is 280-380 kg / t zinc sheet.

7. The multi-stage deep iron removal method for oxygen pressure leaching solution in zinc hydrometallurgy according to claim 4, characterized in that, The oxidant mentioned in step (2) is oxygen or air; Among them, the oxygen consumption is 6-10 Nm³ / t·zinc sheet, and the air consumption is 70-85 m³ / t·zinc sheet.

8. The multi-stage deep iron removal method for oxygen pressure leaching solution in zinc hydrometallurgy according to claim 4, characterized in that, The temperature during the spray iron removal operation in step (2) is 80-90℃, and the pH value is 2.8-3.2; The temperature of the iron removal process is 80-90℃, the pH value is 4.8-5.2, and the iron removal time is 1-2 hours.

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