A method and a device for efficiently recovering indium from indium-rich slag

Abstract

The application discloses a method for efficiently recovering indium from indium-rich residue, and comprises the following steps: S1, alkaline leaching; S2, carbon thermal reduction; and S3, vacuum distillation. The process flow is short, and efficient purification and recovery of zinc, lead and indium are realized through reduction and vacuum distillation. The application has strong adaptability to materials, and can treat various types of indium-rich residue.

Description

Technical Field

[0001] This invention relates to the field of valuable metal recycling, specifically a method for efficiently recovering indium from indium-rich slag. Background Technology

[0002] Indium, due to its excellent physicochemical properties, has become one of the most important metallic materials in the modern electronics industry. Indium does not have independent deposits; it is mostly found as a byproduct in minerals such as zinc and lead ores, and can only be recovered as a byproduct during smelting. A relatively complex smelting process is required to separate indium from these minerals. Lead-zinc smelting systems generate a large amount of indium-containing raw materials annually. Zinc oxide produced in lead systems undergoes a three-stage countercurrent leaching process: neutral leaching, low-acid leaching, and high-acid leaching. Indium in the raw materials is mainly concentrated in the weak-acid leaching supernatant. Further neutralization and precipitation yield indium-rich slag, which is rich in indium and other rare and dispersed metals and has high recovery value. Currently, the commonly used indium extraction process involves leaching of indium-rich slag, extraction, back-extraction, displacement, and casting. This process suffers from drawbacks such as a long process flow and high cost.

[0003] Chinese patent application CN104451205A discloses a method for recovering metallic indium from indium-containing materials. The method involves sulfuric acid leaching, solution purification, oxalic acid reduction of ferric iron, extraction, back-extraction, displacement, and casting to obtain indium ingots with an indium content exceeding 99%. While this method can yield high-purity indium ingots, the process is complex and requires a large volume of solution processing. Summary of the Invention

[0004] This invention combines wet and pyrometallurgical processes, employing carbothermal reduction combined with vacuum distillation to recover valuable indium metal from indium-rich slag. This effectively solves the problems of complex process flow and large solution processing volume in existing technologies, and efficiently separates indium from other impurity metals in indium-rich slag, obtaining high-purity indium products.

[0005] The technical solution adopted in this invention is: a method for efficiently recovering indium from indium-rich slag, comprising the following steps: S1, alkaline leaching: the indium-rich slag is crushed and powdered and then subjected to alkaline leaching to dissolve the arsenic in it in the alkali; a sodium hydroxide solution with a concentration of 80~120g / L is added to the indium-rich slag at a liquid-to-solid ratio of (3~5):1, and the mixture is heated and stirred at 50~80℃ for 2~3h, and filtered to obtain arsenic-removed leaching residue, at which point the arsenic leaching rate is greater than 98%;

[0006] S2, Carbothermic Reduction: The arsenic removal leaching residue obtained in S1 is crushed and ground into powder with a particle size of less than 200 mesh. It is then mixed evenly with a carbonaceous reducing agent and sodium acetate in a certain proportion to obtain a mixed powder. This powder is then reduced in an atmosphere furnace at 1200~1350℃ for 2~5 hours to obtain the reduction product. S3, Vacuum Distillation: The reduction product obtained in S2 is vacuum distilled at 1050~1150℃ with a vacuum degree <10 Pa for 2~6 hours, causing zinc, lead, and indium to volatilize and yield crude zinc, crude lead, and crude indium. Because the arsenic removal leaching residue contains lead sulfate, it releases high-energy active sulfur oxides during heating. These oxides then continue to combine with the carbonaceous reducing agent at high temperatures to generate highly reducing carbonyl sulfide compounds, enhancing the reducing power of carbon. Simultaneously, the addition of sodium acetate further promotes the formation of carbonyl sulfide compounds, resulting in a direct recovery rate of zinc, lead, and indium greater than 98%.

[0007] As a further improvement of the present invention, in step S2, the mass ratio of carbonaceous reducing agent: sodium acetate: arsenic removal leaching residue is 20~25:1~3:100.

[0008] As a further improvement of the present invention, the carbonaceous reducing agent is coke powder or graphite powder.

[0009] As a further improvement of the present invention, in S3, vacuum distillation is carried out using a multi-layer disc distillation furnace.

[0010] As a further improvement of the present invention, the bottom of the multi-layer disc-type distillation furnace is a heating zone, and the middle and upper parts are condensation zones. The temperature of the bottom heating zone is 1010~1100℃, the temperature of the middle condensation zone is 650~750℃, the temperature of the upper condensation zone is 250~390℃, and the vacuum degree is <10Pa. Under this vacuum degree, the boiling point of indium is 1000℃, the boiling point of lead is 760℃, and the boiling point of zinc is 400℃. Therefore, with the bottom heating zone temperature set at 1010~1100℃ and the middle temperature zone set at 650~750℃, indium easily changes from a gaseous state to a liquid state and accumulates on the bottom high-purity graphite sleeve, and lead easily changes from a gaseous state to a liquid state and accumulates on the middle high-purity quartz sleeve. With the upper temperature zone set at 250~350℃, zinc easily changes from a gaseous state to a liquid state and accumulates on the upper high-purity quartz sleeve. The vacuum distillation process is carried out in a multi-layer disc-type distillation furnace. The material is loaded into a high-purity graphite crucible. As the temperature rises inside the distillation furnace, low-boiling-point metals gradually volatilize towards the condensation zone. Since the boiling points of zinc, lead, and indium gradually increase, the upper tray of the condensation zone contains zinc, the middle tray contains lead, and the lower tray contains indium. Meanwhile, high-melting-point metals such as copper remain in the crucible.

[0011] As a further improvement of the present invention, the indium-rich slag is the waste residue rich in indium remaining in the wet process, and the indium-rich slag contains 1.3~3.4% indium, 26.1~34.6% zinc, 9.3~11.8% lead, 8.6~9.8% iron, 2.0~2.7% arsenic and 0.4~0.6% copper.

[0012] As a further improvement of the present invention, a recovery device for efficiently recovering indium from indium-rich slag includes a distillation furnace. The top of the distillation furnace is equipped with a vacuum tube. The distillation furnace includes a bottom heating zone, a middle condensation zone, and an upper condensation zone. A high-temperature resistance wire is installed inside the distillation furnace, located in both the heating and condensation zones. A crucible is located at the bottom of the distillation furnace, and stacked sleeves and trays are arranged on top of the crucible, with a top cover on the uppermost tray. The through-holes of adjacent sleeves and trays are staggered. The distillation vessels used are made of high-purity graphite and high-purity quartz. The trays and sleeves are located on top of the crucible and stacked in layers. The sleeves are used for metal condensation, and the trays are used for metal separation.

[0013] As a further improvement of the present invention, the temperature of the bottom heating zone is 1010~1100℃, the temperature of the middle condensing zone is 650~750℃, and the temperature of the upper condensing zone is 250~390℃.

[0014] As a further improvement of the present invention, the crucible is a high-purity graphite crucible, and the bottom sleeve is made of high-purity graphite; the trays and sleeves in the middle and upper parts are made of high-purity quartz. The crucible and bottom sleeve are made of high-purity graphite, which increases the hardness of the distillation vessel and extends its service life. Additionally, the indium-free graphite facilitates collection. The middle and upper trays and sleeves are made of high-purity quartz, which facilitates observation of material distribution, and the lead and zinc are non-stick to the quartz, facilitating their collection.

[0015] The beneficial effects of this invention are as follows: The process flow is short, achieving efficient purification and recovery of zinc, lead, and indium through reduction and vacuum distillation. This invention is highly adaptable to materials and can handle various types of indium-rich slag. Because the wet process retains lead sulfate, it can release high-energy active sulfur oxides during the high-temperature reduction process at the back end. These oxides then combine with carbonaceous reducing agents at high temperatures to generate highly reducing carbonyl sulfide compounds, enhancing the carbon reduction capacity. Simultaneously, the addition of sodium acetate promotes the release of high-energy active sulfur oxides, significantly increasing the direct metal recovery rate and effectively enhancing the recovery capacity of valuable metals. During vacuum distillation, a multi-layer disc distillation process is used, where the evaporated metals are repeatedly distilled and condensed in the trays and sleeves, achieving material separation and improving metal separation efficiency. Furthermore, based on the boiling points and volatility of different metals such as lead, zinc, and indium, highly pure products are gradually separated during distillation, resulting in higher main metal grades. In addition, multi-layer disc distillation can obtain a larger yield of pure separated products within the same time frame using less raw material and energy consumption, significantly reducing reaction temperature and energy consumption. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the present invention.

[0017] Figure 2 This is a schematic diagram of one embodiment of the recycling device disclosed in this invention.

[0018] The diagram shows: 1. Vacuum tube, 2. Top cover, 3. Sleeve, 4. Tray, 5. High-temperature resistance wire, 7. Crucible. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] As shown in the figure, a method for efficiently recovering indium from indium-rich slag includes the following steps:

[0021] S1, Alkaline Leaching: The indium-rich slag is crushed and powdered, and then subjected to alkaline leaching to dissolve the arsenic in the alkali. A sodium hydroxide solution with a concentration of 80-120 g / L is added to the indium-rich slag at a liquid-to-solid ratio of (3-5):1. The mixture is heated at 50-80℃ and stirred for 2-3 hours. The arsenic-removed leaching residue is then obtained by filtration, at which point the arsenic leaching rate is greater than 98%.

[0022] S2, carbothermic reduction: The arsenic removal leaching residue obtained in S1 is crushed and ground into powder with a particle size of less than 200 mesh, and mixed evenly with carbonaceous reducing agent and sodium acetate in a certain proportion to obtain mixed powder, and then reduced in an atmosphere furnace at 1200~1350℃ for 2~5h to obtain reduction product.

[0023] S3, Vacuum distillation: The reduction product obtained in S2 is vacuum distilled at 1050~1150℃ with a vacuum degree of <10Pa for 2~6h to volatilize zinc, lead and indium to obtain crude zinc, crude lead and crude indium.

[0024] Because the wet process retains lead sulfate, it can release highly active sulfur oxides during the high-temperature reduction process at the back end. These oxides then combine with carbonaceous reducing agents at high temperatures to form strongly reducing carbonyl sulfide compounds, enhancing the carbon reduction capacity. Simultaneously, the addition of sodium acetate promotes the release of these highly active sulfur oxides, significantly increasing the direct metal recovery rate and effectively enhancing the recovery of valuable metals. During vacuum distillation, a multi-layer disc distillation process is used, where the evaporated metal is repeatedly distilled and condensed in the trays and sleeves, achieving material separation and improving metal separation efficiency. Furthermore, based on the boiling points and volatility of different metals such as lead, zinc, and indium, highly pure products are gradually separated during distillation, resulting in higher grades of the main metal.

[0025] Example 1: A method for efficiently recovering indium from indium-rich slag, comprising the following steps:

[0026] In this embodiment, the indium-rich slag contains 1.36% indium, 27.2% zinc, 9.3% lead, 9.1% iron, 2.2% arsenic, and 0.4% copper.

[0027] (1) Alkaline leaching: The indium-rich slag is leached with an alkaline solution of 60 g / L sodium hydroxide at a liquid-to-solid ratio of 4:1. After heating and stirring at 60°C for 3 hours, the leaching residue is obtained with an arsenic leaching rate of more than 98.9%.

[0028] (2) Carbothermic reduction: The arsenic removal leaching residue is crushed and ground into powder with a particle size of less than 200 mesh, and mixed evenly with carbonaceous reducing agent and sodium acetate in a certain proportion to obtain a mixed powder. The powder is then reduced in an atmosphere furnace at 1250℃ for 4 hours to obtain the reduction product. The mass ratio of carbonaceous reducing agent to arsenic removal leaching residue is 22:100, and the mass ratio of sodium acetate to arsenic removal leaching residue is 1:100. During the heating and melting process, the atmosphere furnace must maintain a nitrogen atmosphere to protect the reduction product and prevent oxidation.

[0029] (3) Vacuum distillation: The reduction product is vacuum distilled at 1060°C, with a middle temperature of 690°C, an upper temperature of 350°C, a vacuum degree of 6.3 Pa, and a time of 5 h, so that zinc, lead and indium volatilize to obtain crude zinc, crude lead and crude indium.

[0030] Example 2: A method for efficiently recovering indium from indium-rich slag, comprising the following steps:

[0031] In this embodiment, the indium-rich slag contains 1.4% indium, 25.4% zinc, 10.1% lead, 8.7% iron, 2.3% arsenic, and 0.5% copper.

[0032] (1) Alkaline leaching: The indium-rich slag is leached with an alkaline solution of 70 g / L sodium hydroxide at a liquid-to-solid ratio of 5:1. After heating and stirring at 70°C for 2 hours, the leaching residue is obtained with an arsenic leaching rate of more than 98.5%.

[0033] (2) Carbothermic Reduction: The arsenic removal leaching residue is crushed and ground into powder with a particle size of less than 200 mesh, and mixed evenly with carbonaceous reducing agent and sodium acetate in a certain proportion to obtain a mixed powder. This mixed powder is then reduced in an atmosphere furnace at 1300℃ for 3 hours to obtain the reduction product. The mass ratio of carbonaceous reducing agent to arsenic removal leaching residue is 25:100, and the mass ratio of sodium acetate to arsenic removal leaching residue is 1.5:100. During the heating and melting process, the atmosphere furnace must maintain a nitrogen atmosphere to protect the reduction product and prevent oxidation.

[0034] (3) Vacuum distillation: The reduction product is vacuum distilled at 1080°C, with a middle temperature of 700°C, an upper temperature of 380°C, a vacuum degree of 4.8 Pa, and a time of 6 h, so that zinc, lead and indium volatilize to obtain crude zinc, crude lead and crude indium.

[0035] The following table shows the component analysis of each step in Examples 1 and 2.

[0036] Example Product Composition Analysis Table / %

[0037]

[0038] The analysis in the table above shows that the direct recovery rate of indium in the treated indium-rich slag exceeds 95%, the direct recovery rate of lead exceeds 96%, and the direct recovery rate of zinc exceeds 95%, all of which have high direct recovery rates.

[0039] Those skilled in the art should understand that the protection scheme of the present invention is not limited to the above embodiments, and various arrangements, combinations and transformations can be made on the basis of the above embodiments. Without departing from the spirit of the present invention, all transformations made to the present invention fall within the protection scope of the present invention.

Claims

1. A method for efficiently recovering indium from indium-rich slag, characterized in that: Includes the following steps: S1, Alkaline Leaching: The indium-rich slag is crushed and powdered, and then subjected to alkaline leaching to dissolve the arsenic in the alkali. A sodium hydroxide solution with a concentration of 80-120 g / L is added to the indium-rich slag at a liquid-to-solid ratio of (3-5):

1. The mixture is heated at 50-80℃ and stirred for 2-3 hours. The arsenic-removed leaching residue is then obtained by filtration, at which point the arsenic leaching rate is greater than 98%. S2, carbothermic reduction: The arsenic removal leaching residue obtained in S1 is crushed and ground into powder with a particle size of less than 200 mesh, and mixed evenly with carbonaceous reducing agent and sodium acetate in a certain proportion to obtain mixed powder, and then reduced in an atmosphere furnace at 1200~1350℃ for 2~5h to obtain reduction product. S3, Vacuum distillation: The reduction product obtained in S2 is vacuum distilled at 1050~1150℃ with a vacuum degree of <10Pa for 2~6h to volatilize zinc, lead and indium to obtain crude zinc, crude lead and crude indium.

2. The method for efficiently recovering indium from indium-rich slag according to claim 1, characterized in that: In step S2, the mass ratio of carbonaceous reducing agent: sodium acetate: arsenic removal leaching residue is 20~25:1~3:

100.

3. The method for efficiently recovering indium from indium-rich slag according to claim 2, characterized in that: The carbonaceous reducing agent is coke powder or graphite powder.

4. The method for efficiently recovering indium from indium-rich slag according to claim 1, characterized in that: In S3, vacuum distillation is performed using a multi-layer disc-type distillation furnace.

5. A method for efficiently recovering indium from indium-rich slag according to claim 4, characterized in that: The multi-layer disc-type distillation furnace has a heating zone at the bottom, and condensation zones in the middle and upper parts; the temperature of the bottom heating zone is 1010~1100℃, the temperature of the middle condensation zone is 650~750℃, the temperature of the upper condensation zone is 250~390℃, and the vacuum degree is <10Pa.

6. A method for efficiently recovering indium from indium-rich slag according to any one of claims 1 to 5, characterized in that: The indium-rich slag is a waste residue rich in indium remaining from the wet process. The indium-rich slag contains 1.3-3.4% indium, 26.1-34.6% zinc, 9.3-11.8% lead, 8.6-9.8% iron, 2.0-2.7% arsenic, and 0.4-0.6% copper.

7. A recovery apparatus for efficiently recovering indium from indium-rich slag using any one of claims 1 to 6, comprising a distillation furnace, wherein a vacuum tube (1) is provided at the top of the distillation furnace, characterized in that... The distillation furnace includes a heating zone at the bottom, a condensation zone in the middle, and a condensation zone at the top. A high-temperature resistance wire (5) is provided inside the distillation furnace, and the high-temperature resistance wire is located in the heating zone and the condensation zone respectively. A crucible (7) is provided at the bottom of the distillation furnace. A stacked sleeve (3) and a tray (4) are provided on the upper part of the crucible. A top cover (2) is provided on the uppermost tray. The through holes of adjacent sleeves and trays are arranged in a staggered manner.

8. The recycling device according to claim 7, characterized in that... The temperature of the bottom heating zone is 1010~1100℃, the temperature of the middle condensing zone is 650~750℃, and the temperature of the upper condensing zone is 250~390℃.

9. The recycling device according to claim 7, characterized in that... The crucible is a high-purity graphite crucible, with the bottom sleeve made of high-purity graphite and the trays and sleeves in the middle and upper parts made of high-purity quartz.

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