Method for directly recovering metallic aluminum through vacuum distillation-vibratory screening of aluminum ash

Abstract

The invention discloses a method for directly recovering metallic aluminum by vacuum distillation-vibratory screening of aluminum ash, which comprises the following steps: (1) adding the aluminum ash into a graphite reactor, then putting the graphite reactor into a closed low-pressure high-temperature reaction furnace for vacuum distillation, cooling to room temperature, and filtering to obtain a filtrate; residues containing powder, particles and blocks and powdery volatile matter impurities are collected; and (2) the residues containing the powder, the particles and the blocks are screened through a vibration screen to obtain particles and block metal and screened fine powder, wherein the particles and the block metal are mainly metal aluminum. According to the method, volatile impurities containing elements such as Zn and the like are separated based on the gasification and volatilization characteristics of different substances in the aluminum ash under the same pressure and temperature, fine metal aluminum particles of the aluminum ash are remelted for nucleation and crystal expansion to form large metal aluminum particles, and then the metal aluminum and powder impurity particles containing elements such as Fe, Si and Ca are separated according to the difference between the particle size and the weight of the metal aluminum and the particle size and the weight of the powder impurity particles. The aluminum ash is efficiently recycled through vibration screening, and the problem of comprehensive recycling of the aluminum ash is solved.

Description

Technical Field

[0001] The invention relates to the technical field of resource conversion and utilization, and in particular to a method for directly recovering metallic aluminum through vacuum distillation-vibration screening of aluminum ash. Background Art

[0002] China's aluminum production accounts for more than 30% of the world's total production. As one of the most commonly used metals, aluminum is widely used in aluminum alloys, automobile manufacturing, conductors, aerospace and other fields. However, aluminum will produce aluminum ash slag that is insoluble in aluminum liquid during the electrolysis and smelting production process. The heavy metals in the aluminum ash will pollute the soil and groundwater, and will also produce toxic gases such as arsenic when it comes into contact with water. In addition, every ton of aluminum produced will produce 100~200 kg of aluminum ash, which is very difficult to recycle. Due to its large production and strong harmfulness, the Ministry of Ecology and Environment has listed aluminum ash as a special hazardous waste in the "National List of Hazardous Wastes".

[0003] At present, aluminum in aluminum ash is mainly extracted through processes such as roasting, pressing, and wet treatment. The roasting method uses salt additives to increase the impurity content in aluminum and reduce the recovery rate of aluminum. At the same time, a large amount of volatile smoke and dust will be produced during the heating process to pollute the environment. The aluminum recovery rate is 51.3%; the pressing method will oxidize aluminum into alumina. During the production process, hot aluminum ash needs to be treated in time to prevent oxidation. It faces problems such as difficult operation and high energy consumption. The aluminum recovery rate is 62.5%; the wet treatment process has an aluminum leaching rate of 87.5%, but chemical reagents need to be added and pressurized leaching is used. There are problems such as high energy consumption, high risk, small equipment processing capacity, and wastewater generation.

[0004] Therefore, it is urgent to explore new ideas and new processes for the effective treatment and recycling of aluminum ash, solve the problem of aluminum ash recycling, and achieve stable, clean and healthy development of the aluminum industry chain. Summary of the invention

[0005] The purpose of the present invention is to provide a method for directly recovering metallic aluminum by vacuum distillation-vibration screening of aluminum ash, so as to solve the above-mentioned difficulties in the recycling and treatment of hazardous waste of aluminum ash and the common problems that the current treatment methods are prone to produce other impurities, require the addition of chemical reagents and have low aluminum recovery rates.

[0006] To achieve the above object, the present invention provides a method for directly recovering metallic aluminum by vacuum distillation-vibration screening of aluminum ash, comprising the following steps: (1) adding aluminum ash into a graphite reactor, and then placing it in a closed low-pressure high-temperature reaction furnace for vacuum distillation, and after cooling to room temperature, collecting residues containing powder, particles and block forms and powdery volatile impurities; (2) The residue containing powder, granules and bulk forms is vibrated and sieved to obtain granules, bulk metals and sieved fine powders, wherein the granules and bulk metals are mainly aluminum.

[0007] Preferably, the powdered volatile impurities are mainly metallic zinc, which is subsequently used to recover the metallic zinc.

[0008] Preferably, the sieved fine powder is mainly iron, silicon and calcium, which is subsequently used as a slag-making agent for steelmaking.

[0009] The graphite reactor is a commonly used vessel in high-temperature smelting processes. The shape and size of the reactor are not specially specified. It has the advantages of good thermal conductivity and high temperature resistance, small thermal expansion coefficient, good strain resistance and strong corrosion resistance.

[0010] There is no special requirement for the vacuum distillation device, and a common closed low-pressure high-temperature reaction furnace can be used. In the embodiment of the present invention, the vacuum distillation device is preferably a closed low-pressure high-temperature reaction furnace.

[0011] There is no special requirement for the vibration device, and a common vibration screening device can be used. In the embodiment of the present invention, the vibration screening device is preferably a three-dimensional vibration screen.

[0012] Preferably, the aluminum ash in step (1) is aluminum ash in the form of fine powder containing aluminum produced in the process of recycling waste lithium-ion batteries, and the impurity elements in the aluminum ash include multiple elements of Fe, Si, Ca, Ti, Ni, Cu, Zn, Ga, V, Sn, and Bi.

[0013] Preferably, the vacuum degree of vacuum distillation in step (1) is 0.001~100Pa.

[0014] Preferably, the temperature of the vacuum distillation in step (1) is 400-1300°C.

[0015] By increasing the temperature, low-melting-point substances can be volatilized more thoroughly, reducing the content of impurity elements in the residue. The remelting effect of fine metal aluminum particles is significant, which is convenient for screening and helps to improve the purity and direct recovery rate of aluminum.

[0016] Preferably, the vacuum distillation time in step (1) is 60 to 240 minutes.

[0017] Preferably, the vibration screening in step (2) uses a three-dimensional vibration screen.

[0018] Preferably, the mesh size of the three-dimensional vibrating screen in step (2) is 100-300 mesh.

[0019] Therefore, the present invention adopts a method for directly recovering metallic aluminum by vacuum distillation-vibration screening of aluminum ash with the above structure, which has the following beneficial effects: (1) The present invention utilizes the differences in the vaporization and volatilization characteristics of different substances at the same pressure and temperature in a low-pressure closed system, and the differences in the particle size and gravity of metal aluminum and powder impurity particles. By controlling the distillation temperature and the insulation time, the aluminum ash is vacuum-distilled at high temperature to obtain residues in the form of powder, particles, blocks, etc. and volatile impurities in the form of powder such as Zn. The fine metal aluminum particles in the remelted aluminum ash are nucleated and crystallized to form larger metal aluminum particles, thereby realizing the first stage of physical separation of metal aluminum and easily vaporized volatile impurities such as Zn in the aluminum ash.

[0020] (2) The present invention vibrates and screens the residues in the form of powder, granules, blocks, etc. obtained by the first stage of physical separation to obtain granular and block-shaped metallic aluminum and sieved fine powders containing impurities such as Fe, Si, and Ca, respectively, thereby realizing the second stage of physical separation of metallic aluminum from volatile impurities such as Fe, Si, and Ca that are difficult to gasify, and finally realizing the direct recovery of metallic aluminum through the full physical process of aluminum ash vacuum distillation-vibration screening. The results show that the direct recovery rate of metallic aluminum is >80% and the purity is >99%.

[0021] (3) In the method provided by the present invention, the raw materials do not need to be pretreated for detoxification, and no auxiliary agents are added in the whole process. Only two physical processes are cleverly combined to not only achieve the separation and purification of metallic aluminum in aluminum ash, but also innovatively propose a new method for extracting metals by a full physical process of vacuum distillation-vibration screening, which has a very broad application prospect.

[0022] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a process flow chart of the present invention; Figure 2 The XRD spectrum of the aluminum ash used in the embodiments of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and a specific operation process, but the present invention is not limited to this embodiment.

[0025] The aluminum ash used in the present invention is a fine powder of aluminum produced in the recycling process of waste lithium-ion batteries. The composition is shown in Table 1 and the phase spectrum (XRD) is shown in Table 1. Figure 2 shown.

[0026]

[0027] Example 1 like Figure 1 As shown, the embodiment of the present invention provides a method for directly recovering metallic aluminum through a full physical process of aluminum ash vacuum distillation-vibration screening, including the following specific steps: S1. Place aluminum ash in a graphite reactor, and perform vacuum high-temperature distillation of the aluminum ash in a closed low-pressure high-temperature reactor. The vacuum degree is 5 Pa, the vacuum distillation temperature is 900 °C, and the vacuum distillation time is 120 min. After cooling to room temperature, collect the residues in the form of powder, particles, blocks, etc. and powdery volatile impurities.

[0028] S2. The residues in the form of powder, granules, blocks, etc. are vibrated and screened using a three-dimensional vibrating screen to obtain granules, block metals and sieved fine powders. The sieve aperture of the three-dimensional vibrating screen is 250 meshes. The metal blocks are tested and the sieved fine powders are recycled.

[0029] Example 1 obtained 13.98 g of product aluminum with a direct yield of 65% and a purity of 97.53%.

[0030] Example 2 like Figure 1 As shown, the embodiment of the present invention provides a method for directly recovering metallic aluminum through a full physical process of aluminum ash vacuum distillation-vibration screening, including the following specific steps: S1. Place aluminum ash in a graphite reactor, and perform vacuum high-temperature distillation of the aluminum ash in a closed low-pressure high-temperature reactor. The vacuum degree is 5 Pa, the vacuum distillation temperature is 1000 °C, and the vacuum distillation time is 120 min. After cooling to room temperature, collect the residues in the form of powder, particles, blocks, etc. and powdery volatile impurities.

[0031] S2. The residues in the form of powder, granules, blocks, etc. are vibrated and screened using a three-dimensional vibrating screen to obtain granules, block metals and sieved fine powders. The sieve aperture of the three-dimensional vibrating screen is 200 meshes. The metal blocks are tested and the sieved fine powders are recycled.

[0032] Example 2 obtained 15.91 g of product aluminum with a direct yield of 74% and a purity of 98.67%.

[0033] Example 3 like Figure 1 As shown, the embodiment of the present invention provides a method for directly recovering metallic aluminum through a full physical process of aluminum ash vacuum distillation-vibration screening, including the following specific steps: S1. Place aluminum ash in a graphite reactor, and perform vacuum high-temperature distillation of the aluminum ash in a closed low-pressure high-temperature reactor. The vacuum degree is 5 Pa, the vacuum distillation temperature is 1100 °C, and the vacuum distillation time is 120 min. After cooling to room temperature, collect the residues in the form of powder, particles, blocks, etc. and powdery volatile impurities.

[0034] S2. The residues in the form of powder, granules, blocks, etc. are vibrated and screened using a three-dimensional vibrating screen to obtain granules, block metals and sieved fine powders. The sieve aperture of the three-dimensional vibrating screen is 150 meshes. The metal blocks are tested and the sieved fine powders are recycled.

[0035] Example 3 obtained 17.22 g of product aluminum with a direct yield of 81% and a purity of 99.89%.

[0036] Comparative Example 1 The difference from Example 3 is that the vacuum degree is 200Pa.

[0037] Comparative Example 2 The difference from Example 3 is that the vacuum distillation temperature is 1500°C.

[0038] Comparative Example 3 The difference from Example 3 is that the vacuum distillation time is 300 min.

[0039] Comparative Example 4 The difference from Example 3 is that the sieve hole diameter of the three-dimensional vibrating screen is 50 meshes.

[0040] The direct aluminum yields of the products of the embodiments and comparative examples are shown in Table 2.

[0041] Table 2 Aluminum direct recovery rate of the embodiments and comparative examples

[0042] Group Product aluminum direct yield / % Example 1 65 Example 2 74 Example 3 81 Comparative Example 1 50 Comparative Example 2 51 Comparative Example 3 55 Comparative Example 4 43 It can be seen from Table 2 that the direct recovery rates of the product aluminum in Examples 1 to 3 are all higher than 60%. In Comparative Example 1, the vacuum degree is changed, and its vacuum degree is higher than the range specified in the present invention. The direct recovery rate of the product aluminum decreases, indicating that the vacuum degree is too high, and some low-boiling-point impurities are difficult to be completely separated, thereby affecting the recovery rate of metallic aluminum. In addition, too high a vacuum degree is not conducive to lowering the melting and boiling points of the metal. Therefore, the aluminum remelting process is not thorough under this vacuum degree, and the high-boiling-point impurity metals cannot be melted and separated from the aluminum liquid, thereby being mixed in the aluminum liquid to reduce the purity of the recovered aluminum.

[0043] In Comparative Example 2, the vacuum distillation temperature is changed, and its vacuum distillation temperature is higher than the range specified in the present invention. As the temperature increases, some high-boiling point impurities including aluminum may also be distilled out, which may lead to a decrease in the recovery rate of metallic aluminum.

[0044] In Comparative Example 3, the vacuum distillation time was changed. The vacuum distillation time was higher than the range specified in the present invention. If the distillation time was too long, aluminum might evaporate gradually, especially when approaching or exceeding its boiling point, which would lead to the loss of metallic aluminum. In addition, as the distillation time was prolonged, some volatile low-boiling-point impurities might also drip back into the aluminum liquid, thereby affecting the purity of the recovered aluminum.

[0045] In Comparative Example 4, the sieve aperture is changed, and the aperture is larger than the range specified by the present invention. In the present invention, as the vacuum distillation temperature increases, it is helpful for the volatilization and aggregation of aluminum to form larger particles or lumps. Therefore, in the present invention, the vacuum distillation temperature and the sieve aperture are positively changed. As the vacuum distillation temperature increases, the sieve aperture becomes larger, which can ensure that more bulk metal is collected, thereby improving the aluminum yield and reducing aluminum loss. This shows that the vacuum distillation temperature and the sieve aperture in the present invention have a certain relationship. In Example 3, the vacuum distillation temperature is 1100°C, and the sieve aperture is 150 mesh at this time, which can collect and screen to obtain the highest aluminum yield. When the sieve aperture is adjusted to 50 mesh in Comparative Example 4, the aperture is greatly increased. During the screening process, part of the bulk metal aluminum is also screened into the fine powder, resulting in aluminum metal loss and a significant decrease in aluminum yield.

[0046] Therefore, the present invention adopts a method of directly recovering metallic aluminum by vacuum distillation-vibration screening of aluminum ash of the above structure. Based on the vaporization and volatilization characteristics of different substances in aluminum ash at the same pressure and temperature, volatile impurities containing elements such as Zn are separated, and fine metallic aluminum particles of the aluminum ash are remelted to form nuclei and crystals to form larger metallic aluminum particles; the difference in particle size and gravity between metallic aluminum particles and powder impurity particles containing elements such as Fe, Si, and Ca is utilized to efficiently recover aluminum ash by vibration screening, so as to solve the problem of comprehensive recycling of aluminum ash. The method of directly recovering metallic aluminum by vacuum distillation-vibration screening in the full physical process of the present invention does not require pretreatment or the addition of any chemical reagents, has a short process flow, is green and low-carbon, does not involve wet methods, does not generate harmful wastewater, has a simple device, is safe and environmentally friendly, and has broad application prospects.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for directly recovering metallic aluminum by vacuum distillation and vibration screening of aluminum ash, characterized in that: The following steps are involved: (1) adding aluminum ash into a graphite reactor, and then placing it in a closed low-pressure high-temperature reaction furnace for vacuum distillation, and after cooling to room temperature, collecting residues containing powder, particles and block forms and powdery volatile impurities; (2) The residue containing powder, granules and bulk forms is vibrated and sieved to obtain granules, bulk metals and sieved fine powders, wherein the granules and bulk metals are mainly aluminum.

2. The method for directly recovering metallic aluminum by vacuum distillation and vibration screening of aluminum ash according to claim 1, characterized in that: The powdered volatile impurities are mainly metallic zinc, which is subsequently used to recover metallic zinc.

3. The method for directly recovering metallic aluminum by vacuum distillation and vibration screening of aluminum ash according to claim 1, characterized in that: The sieved fine powder is mainly iron, silicon and calcium, which is subsequently used as slag-making agent for steelmaking.

4. The method for directly recovering metallic aluminum by vacuum distillation and vibration screening of aluminum ash according to claim 1, characterized in that: The aluminum ash in step (1) is aluminum ash in the form of fine powder containing aluminum produced in the process of recycling waste lithium-ion batteries. The impurity elements in the aluminum ash include multiple elements of Fe, Si, Ca, Ti, Ni, Cu, Zn, Ga, V, Sn, and Bi.

5. The method for directly recovering metallic aluminum by vacuum distillation and vibration screening of aluminum ash according to claim 1, characterized in that: The vacuum degree of vacuum distillation in step (1) is 0.001~100Pa.

6. The method for directly recovering metallic aluminum by vacuum distillation and vibration screening of aluminum ash according to claim 1, characterized in that: The temperature of the vacuum distillation in step (1) is 400-1300°C.

7. The method for directly recovering metallic aluminum by vacuum distillation and vibration screening of aluminum ash according to claim 1, characterized in that: The vacuum distillation time in step (1) is 60 to 240 minutes.

8. The method for directly recovering metallic aluminum by vacuum distillation and vibration screening of aluminum ash according to claim 1, characterized in that: The vibration screening in step (2) uses a three-dimensional vibration screen.

9. The method for directly recovering metallic aluminum by vacuum distillation-vibration screening of aluminum ash according to claim 8, characterized in that: In step (2), the sieve hole diameter of the three-dimensional vibrating screen is 100-300 mesh.

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