Method for recovering indium metal by carbothermal reduction and volatilization

Abstract

This invention discloses a method for recovering indium metal through carbothermic reduction volatilization, belonging to the field of metal recovery technology in the metallurgical and materials industries. In this invention, indium-containing materials are conveyed to a fuming furnace via a belt conveyor, while hot molten indium-containing slag flows into the fuming furnace for heating via a chute. Powdered coal is carried in by primary air, mixed with secondary air, and then blown into the fuming furnace to generate metal vapor. This vapor volatilizes and, upon contact with tertiary air, generates metal oxide dust. The indium-containing dust is collected by a dust collection device and then sent to the indium leaching process to complete the recovery of indium metal. This invention overcomes the difficulty of indium evaporation of In2O3 by chemically converting it, effectively reducing the residual indium metal in pyrometallurgical slag and significantly improving resource utilization. This invention transforms the difficult-to-recover indium, which was originally retained in the slag, into a volatile form, greatly improving the recovery rate of indium in pyrometallurgical processes and providing an efficient technical path for the resource utilization of indium-containing materials.

Description

Technical Field

[0001] This invention relates to the field of metal recycling technology in the metallurgical and materials industry, and more specifically to a method for recovering indium metal by carbothermic reduction volatilization. Background Technology

[0002] In the process of reducing and volatilizing indium-containing materials in pyrometallurgical processes, indium often exists in the form of indium oxide (In2O3). In2O3 has extremely strong chemical stability and extremely low vapor pressure, and is a typical non-volatile substance, which greatly limits the efficient separation and recovery of indium.

[0003] Hulunbuir Chihong Mining Co., Ltd. is a comprehensive smelting enterprise integrating lead-zinc smelting, slag processing, and valuable metal recovery. Its zinc smelting process uses zinc sulfide concentrate and zinc-containing materials for oxygen pressure leaching. After oxygen pressure leaching, indium metal is concentrated in the leaching residue as oxides, which are stable. The oxygen pressure leaching residue needs to be processed by a pyrometallurgical system to recover valuable metals. Most of the indium metal and its compounds can volatilize into the flue gas for recovery. However, due to the extremely strong chemical stability and extremely low vapor pressure of indium oxide (In₂O₃), it is a typical non-volatile substance, which prevents this portion of indium from volatilizing with other components and ultimately remains in the pyrometallurgical slag. Currently, the indium content in the slag from the pyrometallurgical furnace is as high as 60-150 g / t, causing serious resource waste and restricting the improvement of indium metal recovery efficiency. Based on the above production pain points...

[0004] Therefore, there is an urgent need in the field to provide a method for extracting indium metal by carbothermic reduction volatilization in order to solve the problem of recycling low-grade indium oxide (In2O3) materials. Summary of the Invention

[0005] In view of this, the present invention provides a method for extracting indium metal by carbothermic reduction volatilization, providing an efficient technical path for the resource utilization of indium-containing materials.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for recovering indium metal by carbothermic reduction volatilization, characterized by comprising the following steps: (1) The indium-containing material is conveyed to the fuming furnace via a belt, while the hot molten indium-containing slag (reduction slag) flows into the fuming furnace through a chute for heating; (2) Powdered coal is carried in by primary air, mixed with secondary air and sent to the fuming furnace for smelting to generate metal vapor. After the metal vapor volatilizes and comes into contact with tertiary air, the metal vapor generates metal oxide dust. (3) After recovering the waste heat of the metal oxide dust using a waste heat boiler, the indium-containing dust is collected by a dust collection device and then sent to the indium leaching process to complete the recovery of indium metal.

[0008] In this invention, the primary air, secondary air, and tertiary air are all air. Pulverized coal is used to control the stability inside the furnace. It has no fixed ratio with other raw materials. The pulverized coal is transported into the furnace by the primary air as a power carrier. After being mixed with the secondary air, it is stably stored in the furnace to ensure the stability of the reaction.

[0009] In the scheme of this invention, the carbothermic reduction of indium oxide generates a large amount of CO gas, and the flue gas needs to be treated accordingly; the carbothermic reduction temperature needs to be stably controlled above 1250℃ to ensure the reduction effect.

[0010] This invention employs a carbothermal reduction process to treat indium-containing materials. Through the action of a carbon-based reducing agent, the stable structure of In₂O₃ is broken down and converted into a volatile indium form, promoting the efficient migration of indium into flue gas for enrichment. The carbothermal reduction process for indium oxide (In₂O₃) involves using carbon (coke powder, coal powder, etc.) as a reducing agent, reacting it with In₂O₃ at high temperature. The carbon is oxidized to CO or CO₂, simultaneously generating metallic indium. The specific reaction equations are shown below: Excess carbon, insufficient oxygen: In₂O₃ + 3C → 2In + 3CO↑ (Main reaction) Peroxidizing atmosphere: In₂O₃ + 3 / 2C → 2In + 3 / 2CO₂↑ In In₂O₃, indium has a oxidation state of +3. The essence of the reduction process is that In… 3+ Electron transfer reactions: In 3+ +3e - →In (metallic indium) or 2In 3+ +2e - →2In 2+ In theory, InO can be generated, but In 2+ Poor stability, prone to misclassification into In 3+ And I (metal indium).

[0011] Simultaneously, the elemental zinc produced during the fuming process undergoes a metallothermic reduction reaction with indium oxide (In2O3), as detailed below: In₂O₃ + 3Zn → 2In + 3ZnO Through the above reaction, the structurally stable indium oxide (In2O3) is decomposed into In (metallic indium) and In2O3. 2+ Indium metal is recovered by volatilizing into the dust.

[0012] Furthermore, the heating temperature of the fuming furnace in step (1) is 1250±50℃.

[0013] Furthermore, the primary air intake in step (2) is 8500-9500 m³ / h. 3 / h; The secondary air intake is 15000-16000m³. 3 / h; The volume of the third type of wind is 1500-2000m. 3 / h.

[0014] Furthermore, after the three-stage air blowing process, blowing slag is generated. The blowing slag is quenched in water and then flushed into a water-quenched slag pool. It is then dewatered by a stirring cage slag removal system, conveyed by a high-angle belt to a dry slag bin, and finally transported by truck to a transfer slag yard for storage.

[0015] The present invention provides a high-temperature enhanced reduction volatilization oxidation process. Essentially, a mixture of air and pulverized coal is blown into the molten slag inside the volatilization furnace. The incomplete combustion of pulverized coal generates a large amount of heat and carbon monoxide gas, maintaining a high temperature and a strong reducing atmosphere within the furnace. This causes lead, zinc, and indium in the slag to be reduced from their oxides into metal vapors, which then volatilize and are oxidized again in the upper space of the furnace by air drawn in through the tertiary tuyeres. These metal oxides, in the form of flue gas, are collected as dust after waste heat recovery in a waste heat boiler and then enter a dust collection system. The sulfur-containing flue gas is sent to the sulfuric acid system. The slag produced after carbothermic reduction volatilization is water-quenched and flushed into a water-quenched slag pool. It is then dehydrated by a stirring cage slag removal system, conveyed by a steep-angle conveyor belt to a dry slag bin, and finally transported by truck to a transfer slag yard for storage.

[0016] This invention discloses a method for extracting indium metal by carbothermic reduction volatilization. This method, through the action of a carbon-based reducing agent, effectively breaks down the stable structure of In2O3, converting it into a volatile indium form. This facilitates the efficient migration of difficult-to-recover indium into flue gas for enrichment and recovery, providing an efficient technical path for the resource utilization of indium-containing materials and helping to solve the problem of recovering low-grade indium oxide (In2O3) materials.

[0017] The beneficial effects of this invention are as follows: 1. This invention addresses the issue of the low volatility of In2O3 by overcoming its volatilization barrier through chemical conversion, effectively reducing indium metal residue in pyrometallurgical slag and significantly improving resource utilization.

[0018] 2. This invention can be integrated into existing pyrometallurgical systems without requiring large-scale modifications to production equipment. It is easy to connect with existing lead-zinc smelting and slag processing processes, thus lowering the threshold for industrial application.

[0019] 3. The method of the present invention uses inexpensive carbon-based materials as reducing agents. The raw materials are readily available and the cost is much lower than that of metal reducing agents (such as aluminum and magnesium) or gaseous reducing agents (such as hydrogen), making it suitable for large-scale industrial production.

[0020] 4. This invention transforms the difficult-to-recover indium that was originally retained in the slag into a volatile form, greatly improving the recovery rate of indium in pyrometallurgical processes and providing an efficient technical path for the resource utilization of indium-containing materials.

[0021] 5. When applied to a fuming volatilization furnace, this invention can effectively utilize the metal reducing agent generated during fuming volatilization to further enhance the reduction and volatilization of indium oxide. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of the carbothermic reduction volatilization recovery of indium metal according to the present invention. Detailed Implementation

[0023] 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.

[0024] Example 1 A method for recovering indium metal by carbothermic reduction volatilization (1) Add the indium-containing material and indium-containing slag into the fuming furnace and heat to 1250°C; (2) Powdered coal is introduced via primary air, mixed with secondary air, and then sent to the fuming furnace for smelting to generate metal vapor. After the metal vapor volatilizes and comes into contact with tertiary air, it generates metal oxide dust. Then, it is dehydrated by the stirring cage slag removal system, conveyed by a steep-angle belt to the dry slag bin, and then transported by truck to the transfer slag yard for storage. The primary air intake is 9000 m³. 3 / h, the secondary air inflow is 15500m³ / h. 3 / h, the volume of the third wind is 1750m³. 3 / h; (3) After recovering the waste heat of the metal oxide dust using a waste heat boiler, the indium-containing dust is collected by a dust collection device, and then the indium-containing dust is leached with indium to complete the recovery of indium metal.

[0025] 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 method for recovering indium metal by carbothermic reduction volatilization, characterized in that, Includes the following steps: (1) The indium-containing material is conveyed to the fuming furnace via a belt, while the hot molten indium-containing slag flows into the fuming furnace through a chute for heating; (2) Powdered coal is carried in by primary air, mixed with secondary air and sent to the fuming furnace for smelting to generate metal vapor. After the metal vapor volatilizes and comes into contact with tertiary air, the metal vapor generates metal oxide dust. (3) After recovering the waste heat of the metal oxide dust using a waste heat boiler, the indium-containing dust is collected by a dust collection device and then sent to the indium leaching process to complete the recovery of indium metal.

2. The method for recovering indium metal by carbothermic reduction volatilization according to claim 1, characterized in that, The heating temperature of the fuming furnace in step (1) is 1250±50℃.

3. The method for recovering indium metal by carbothermic reduction volatilization according to claim 1, characterized in that, The primary air volume introduced in step (2) is 8500-9500 m³. 3 / h; The secondary air intake is 15000-16000m³. 3 / h; The volume of the third type of wind is 1500-2000m. 3 / h.

4. The method for recovering indium metal by carbothermic reduction volatilization according to claim 1 or 3, characterized in that, After the three-stage air blowing process, blowing slag is generated. The blowing slag is quenched in water and then flushed into the water-quenched slag pool. It is then dewatered by the stirring cage slag removal system, conveyed by a high-angle belt to the dry slag bin, and transported by truck to the transfer slag yard for storage.

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