Recycling and silicon elementary substance recycling method based on hydrogen production through hydrolysis of waste aluminum-silicon alloy

Abstract

The invention discloses a recycling and silicon elementary substance recycling method based on waste aluminum-silicon alloy hydrolysis hydrogen production. Aluminum-silicon alloys such as ZL102 and the like are widely applied in many fields due to excellent processability and corrosion resistance of the aluminum-silicon alloys, however, a large amount of waste aluminum alloys are generated due to large-amount application of the aluminum-silicon alloys, and how to recycle the aluminum-silicon alloys is a key technical problem of improving energy utilization. The high-silicon aluminum alloy and the low-melting-point metal are combined to prepare the novel aluminum-based alloy used in the field of hydrolysis hydrogen production, the hydrogen production efficiency can reach 92.4% at most by regulating and controlling the content of the low-melting-point metal, and the hydrogen production rate can reach 396 ml / (min.g); the problems that a traditional waste aluminum recycling technology is complex in process and high in energy consumption, and a large amount of aluminum needs to be diluted to be utilized in a preserve mode are effectively solved, and a new recycling way is provided. Meanwhile, the monatomic silicon is separated and recovered by adopting an acid pickling method, the recovery rate is 97.6%, and the purity of the monatomic silicon can reach 94.3%.

Description

Technical Field

[0001] This invention belongs to the field of aluminum-silicon alloy recycling and resource utilization and hydrolysis hydrogen production, specifically involving a method for the recycling of online hydrogen production materials prepared from aluminum-silicon alloys and the separation and recovery of elemental silicon from the remaining products after hydrolysis. Background Technology

[0002] Aluminum-silicon alloys are widely used, such as the ZL102 alloy, which boasts excellent casting and welding properties, no tendency for hot cracking or porosity, and high airtightness. It also has advantages such as low density and good corrosion resistance, allowing it to be used in corrosive environments such as the atmosphere and seawater, and can withstand the corrosion of concentrated nitric acid and hydrogen peroxide in industrial environments to a certain extent. Therefore, this type of aluminum-silicon alloy is widely used in ship parts, engine covers, and corrosion-resistant components. Currently, the use and replacement of related parts result in a large amount of waste aluminum-silicon alloys, making effective recycling crucial for improving resource utilization. Traditional aluminum-silicon alloy recycling requires pretreatment, smelting, refining and composition control, casting, and post-treatment. While existing recycling processes play an important role in resource reuse, they suffer from drawbacks such as low melting efficiency, high energy consumption, and high costs due to technological limitations and inefficient processes. Furthermore, the recovery rate of the high-content elemental silicon is low. In addition, to maintain the alloy's reusability, existing recycling methods generally require adding large amounts of pure aluminum to dilute the content of other elements to meet the application standards for structural components or building materials. Therefore, it is necessary to find new ways to recycle waste aluminum-silicon alloys to achieve cost-effective and full utilization of resources.

[0003] Meanwhile, as a key energy component in the current energy transition, finding safe, convenient, and low-cost technologies for the production, storage, and transportation of hydrogen is one of the urgent problems to be solved in the process of accelerating the promotion and application of hydrogen energy. Besides its application as a structural component, aluminum is also an ideal energy carrier. Aluminum can spontaneously hydrolyze with water to produce high-purity hydrogen and release a large amount of heat. However, the reaction is easily hindered by the alumina film formed on the surface of aluminum during hydrolysis. Current research has shown that low-melting-point metals such as gallium, indium, and tin can effectively activate aluminum, and aluminum alloys prepared with aluminum can allow the hydrolysis process to continue. Furthermore, the method of preparing aluminum-based hydrolysis hydrogen production materials through molten casting is simple and suitable for large-scale production. Therefore, using waste aluminum-silicon alloys in the field of hydrolysis hydrogen production can greatly improve energy utilization and reduce recycling costs. Although previous reports have disclosed Al-Ga-In-Sn-Si pentagonal hydrolysis hydrogen production alloy materials containing Si, their hydrogen production performance decreases significantly after the Si content exceeds 4 wt.%, making them unsuitable for the reuse of high-silicon aluminum-silicon alloys.

[0004] Therefore, this invention combines aluminum-silicon alloy with low-melting-point metals, and prepares a new type of aluminum alloy by controlling the total amount of low-melting-point metals and designing the element ratios. This achieves a hydrogen production efficiency of over 90%, ensuring the hydrogen production performance of the alloy through hydrolysis. This allows waste aluminum to be converted into hydrogen energy for utilization. At the same time, the residual silicon element after hydrolysis is separated and recovered by acid washing, resulting in a silicon product with a purity close to the requirements of industrial crude silicon. Summary of the Invention

[0005] The purpose of this invention is to provide a novel method for recycling waste aluminum-silicon alloys. This method involves preparing a new aluminum-based alloy by melting and casting the aluminum-silicon alloy with a low-melting-point metal at high temperature. Subsequently, hydrogen is obtained in a high yield through the hydrolysis of Al. Simultaneously, the remaining products after hydrolysis undergo a series of separation and recycling processes to obtain high-purity elemental silicon.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A novel aluminum alloy is prepared by combining an aluminum-silicon alloy with certain amounts of low-melting-point metals gallium, indium, and tin. High-purity hydrogen is obtained through the hydrolysis of the aluminum alloy. Subsequently, the remaining products after hydrolysis are acid-washed and separated to obtain high-purity silicon. The process includes the following steps:

[0008] Step 1: Grind the aluminum-silicon alloy to remove the surface oxide layer, weigh it, and simultaneously weigh a certain mass of three low-melting-point metals, Ga, In, and Sn, and place them together with the aluminum-silicon alloy in a crucible. The content of the aluminum-silicon alloy varies from 80% to 95%, and the total content of the low-melting-point metals gallium, indium, and tin varies from 5% to 20%, with a mass ratio of gallium, indium, and tin of 4.9:1.5:1. Specifically, the content of gallium varies from 6.8% to 13.8%, the content of indium varies from 2.1% to 4.3%, and the content of tin varies from 1% to 2%.

[0009] Step 2: Place the crucible containing the metal in a box-type atmosphere stirring furnace, and fill the furnace with inert gas (nitrogen, argon, etc.) by vacuuming and venting. Melt the metal in a temperature range of 750 ℃ ​​- 850 ℃ and hold it at that temperature for at least 1 hour.

[0010] Step 3: After the heat preservation is completed, stir the molten metal for 5-15 minutes to ensure the uniform distribution of each element. Then, pour the molten metal into a pre-heat-treated mold at a temperature of 200℃-350℃ for casting. After the prepared alloy cools to room temperature, seal and store it.

[0011] Step 4: Take a certain mass of the above alloy, put it into the hydrogen production device, and collect the generated hydrogen gas by hydrolysis at a certain temperature.

[0012] Step 5: After the hydrolysis is complete, collect the hydrolysis residue containing aluminum water reaction byproducts, elemental silicon, and other alloying elements, and dry it to obtain solid hydrolysis residue.

[0013] Step 6: Mix the collected remaining product with a hydrochloric acid solution with a concentration of not less than 20 wt.% and stir thoroughly.

[0014] Step 7: Dilute, filter, and dry the mixed solution to obtain elemental silicon.

[0015] Furthermore, the aluminum-silicon alloy used as a raw material in this invention is an aluminum-silicon alloy of grade ZL102.

[0016] Furthermore, the technical solution described in this invention is also applicable to aluminum-silicon alloys with other silicon contents.

[0017] Furthermore, the average hydrogen production rate was calculated based on hydrogen production data corresponding to the range of 10% to 90% of the maximum hydrogen production.

[0018] Furthermore, the recovery rate of elemental silicon is calculated according to the following formula:

[0019] Silicon recovery rate = Mass of final recovered product / Mass of silicon fed into the reactor

[0020] Furthermore, the purity of elemental silicon is represented by the percentage of silicon mass relative to the total mass calculated from the energy dispersive spectroscopy (EDS) results during elemental analysis.

[0021] Furthermore, other acid solutions similar to hydrochloric acid are also suitable for the pickling step.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) It provides a new recycling method and a new direction for the utilization of waste aluminum alloys. At the same time, it can utilize waste aluminum alloys with high silicon content, which solves the problem of increased energy consumption and carbon emissions caused by adding pure aluminum for dilution when the silicon content is high in the existing technology.

[0024] (2) The hydrogen production material obtained by sintering aluminum-silicon alloy with low-melting-point metal has a high hydrogen production rate and efficiency, realizing the high-efficiency reuse of aluminum resources. It also meets the technical requirements for online hydrogen supply and can solve the safety hazards in the traditional hydrogen energy transportation process.

[0025] (3) The silicon element in the aluminum-silicon alloy was successfully separated and recovered in the form of elemental silicon, with a recovery rate of 97.6% and a purity of 94.3% after recovery, which is close to the purity requirements of industrial crude silicon, providing a new path for the production of elemental silicon.

[0026] (4) The hydrolysis process converts Al into Al(OH)3, which indirectly achieves the purification of Al element. Pure aluminum can be obtained again through methods such as calcination. Attached Figure Description

[0027] Figure 1 Hydrogen production performance curves of hydrogen-producing alloys via hydrolysis

[0028] Figure 2 XRD pattern of the final recycled product of alloy in Example 2

[0029] Figure 3 XRD pattern of the final recycled product of alloy in Example 3

[0030] Figure 4 SEM and EDS images of the final recycled product of the alloy in Example 2.

[0031] Figure 5 SEM and EDS images of the final recycled product of the alloy in Example 3. Detailed Implementation

[0032] Example 1

[0033] The present invention provides a method for preparing aluminum-based hydrolysis hydrogen production materials using low-melting-point metals and aluminum-silicon alloys, specifically comprising the following steps:

[0034] Weigh 20 g of ZL102 aluminum-silicon alloy (surface polished), along with 1.4667 g of gallium, 0.4556 g of indium, and 0.3 g of tin. Place the weighed metal materials in an alumina crucible, then place it in a box-type atmosphere stirring furnace. After filling the furnace with nitrogen, heat the furnace to 800°C at a rate of 11°C / min, and then hold it at this temperature for 1 hour to ensure all metal and alloy materials are in a molten state. After holding at this temperature, stir the molten alloy for 10 minutes. Finally, pour the alloy into a mold preheated to 300°C. After the alloy cools to room temperature, seal and store it.

[0035] Example 2

[0036] The present invention provides a method for preparing aluminum-based online hydrogen production materials using low-melting-point metals and aluminum-silicon alloys, specifically comprising the following steps:

[0037] Weigh 20 g of ZL102 aluminum-silicon alloy (surface polished), 2.3294 g of gallium, 0.7235 g of indium, and 0.4765 g of tin. Place the weighed metal materials in an alumina crucible, then place it in a box-type atmosphere stirring furnace. After filling the furnace with nitrogen, heat the furnace to 800°C at a rate of 11°C / min, and then hold it at this temperature for 1 hour to ensure that all metal and alloy materials are in a molten state. After holding at this temperature, stir the molten alloy for 10 minutes, and finally cast the alloy into a mold preheated to 300°C. After the alloy cools to room temperature, seal and store it.

[0038] Example 3

[0039] The present invention provides a method for preparing aluminum-based online hydrogen production materials using low-melting-point metals and aluminum-silicon alloys, specifically comprising the following steps:

[0040] Weigh 20 g of ZL102 aluminum-silicon alloy (surface polished), along with 3.3 g of gallium, 1.025 g of indium, and 0.675 g of tin. Place the weighed metal materials in an alumina crucible, then place it in a box-type atmosphere stirring furnace. Fill the furnace with nitrogen and heat it to 800°C at a rate of 11°C / min. Hold the furnace at this temperature for 1 hour to ensure all metal and alloy materials are molten. After holding, stir the molten alloy for 10 minutes. Finally, pour the alloy into a mold preheated to 300°C. After cooling to room temperature, seal and store the alloy.

[0041] Example 4

[0042] To evaluate the hydrogen production performance of the novel alloys prepared in Examples 1-3, the following hydrogen production performance test was conducted using the water displacement method. 0.3 g of each alloy prepared in Examples 1-3 was placed in a hydrogen production apparatus, and the hydrolysis reaction temperature provided by the water bath was set to 60 °C. As hydrogen gas was produced, an equal amount of water was displaced from the conical flask. A balance used to measure the water displacement was connected to a computer via a serial port. The computer recorded the water displacement value five times per second, allowing analysis of the alloy's hydrogen production efficiency and average hydrogen production rate. The test results are attached. Figure 1As shown in Table 1, the results indicate that the hydrogen production performance of the alloy significantly improves with increasing proportion of low-melting-point metals, demonstrating the effectiveness of the aluminum-silicon alloy recycling method described in this invention. Specifically, the hydrogen production efficiency of the alloy in Example 1 is 39.9%, and the average hydrogen production rate under this alloy composition is very slow, with a reaction time exceeding 200 min and an average hydrogen production rate of only 4 ml / (min·g). The total hydrogen production efficiency of Example 2 is 74.4%, with an average hydrogen production rate increasing to 48 ml / (min·g). The hydrogen production efficiency of the alloy in Example 3 is 92.4%, with an average hydrogen production rate as high as 396 ml / (min·g). It can be observed that the hydrogen production efficiency of the alloy gradually increases with increasing low-melting-point metal content, and the hydrogen production rate also increases accordingly. The alloy exhibits optimal hydrogen production performance when the mass proportion of low-melting-point metals increases to 20%. This indicates that in the alloy preparation process, to ensure superior hydrolysis hydrogen production performance, the mass proportion of low-melting-point metals should be greater than 15%.

[0043] Table 1 Hydrogen production performance of Examples 1-3 at 60°C

[0044]

[0045] Example 5

[0046] Once the hydrolysis reaction in Example 4 is completely completed, i.e., when the hydrogen production device no longer continuously discharges water, the remaining products from the reaction in the hydrogen production device are collected, and the silicon is separated and recovered. Because the hydrogen production efficiency of the alloy prepared in Example 1 is too low, further silicon separation and recovery operations are not considered. The specific operation is as follows:

[0047] The remaining product after the complete hydrolysis reaction of the alloy corresponding to Example 2 in Example 4 was collected and dried in a drying oven at 80 °C for 24 h to obtain solid product (1). 20 ml of 20 wt.% hydrochloric acid solution was added to product (1) for acid washing to remove Al(OH)3 generated by the hydrolysis reaction and unreacted Al. A magnetic rotor was added to the mixed solution and stirred at 120 r / min for 24 h. After acid washing, the acid-washed material was removed from the stirring device, diluted with 500 ml of RO water, and filtered for 8 h. After complete filtration, it was dried in a drying oven at 80 °C for 24 h to obtain recovered product (3). Product (3) was weighed and recorded as 0.0296 g. Theoretically, the mass of elemental silicon in 0.3 g alloy sample is 0.0306 g, so the preliminary recovery rate was calculated to be 96.7%.

[0048] Example 6

[0049] The remaining product after the complete hydrolysis reaction of the alloy corresponding to Example 3 in Example 4 was collected and dried in a drying oven at 80 °C for 24 h to obtain solid product (2), which was weighed and recorded. 20 ml of 20 wt.% hydrochloric acid solution was added to product (2) for acid washing to remove Al(OH)3 generated by the hydrolysis reaction and unreacted Al. A magnetic rotor was added to the mixed solution and stirred at 120 r / min for 24 h. After separation, 500 ml of RO water was added for dilution and filtration was performed for 8 h. After complete filtration, the product (4) was dried in a drying oven at 80 °C for 24 h to obtain product (4). Product (4) was weighed and recorded as 0.0281 g. Theoretically, the mass of elemental silicon in 0.3 g alloy sample is 0.0288 g, so the preliminary recovery rate was calculated to be 97.6%.

[0050] The XRD patterns, SEM, and EDS images of products (3) and (4) are shown in the attached figures. XRD testing confirmed that silicon in the final products obtained after acid washing exists entirely in the form of elemental silicon. Table 2 shows the molar mass percentages of each element obtained from EDS testing. Based on the data and the relative atomic masses of each element, the purity of silicon in product (3) is calculated to be 82.5%, and the purity of silicon in product (4) is 94.3%. This purity range is very close to the purity standard of industrial crude silicon. Furthermore, Example 6, as a preferred embodiment, shows that the content percentage of other elements using the recovery method of this invention is less than 1%, further demonstrating the effectiveness of the method disclosed in this invention.

[0051] Table 2. Molar mass ratios of each element in the final recovered products of Examples 5-6

[0052]

Claims

1. A method for the recycling and recovery of elemental silicon based on hydrogen production from the hydrolysis of waste aluminum-silicon alloys, characterized in that: The process includes the following steps: alloy preparation and silicon recovery. (1) Place the surface-polished aluminum-silicon alloy and a certain amount of metal gallium, indium and tin together in a crucible and place it in a vacuum box-type atmosphere stirring furnace. After evacuating the stirring furnace, fill the furnace with nitrogen as a protective gas. After the furnace is filled with nitrogen, heat it to 750 ℃ ​​- 850 ℃ at a heating rate of 10-15 ℃ / min and hold it for 30-90 min to melt all the metals into a molten state. (2) After stirring the molten metal thoroughly for 5-15 min, pour it into a mold preheated to 200-350 ℃ and solidify it into an alloy ingot. After the prepared alloy cools to room temperature, seal and store it. (3) The alloy is hydrolyzed in a hydrolysis device to produce hydrogen that can be used directly, thus realizing the efficient reuse of waste aluminum resources; (4) Collect the remaining product after complete hydrolysis and dry it at 70-90 °C for at least 24 h to obtain a solid product; (5) Add excess hydrochloric acid with a mass concentration of 20% to the solid hydrolysis residue and stir for 24 h to remove aluminum hydroxide produced during the hydrolysis process. After the acid washing is completed, add at least 500 ml of pure water to dilute the mixed solution and filter for 8-10 h. Dry the product obtained after filtration at 70-90 °C for at least 24 h to obtain the recovered elemental silicon.

2. The method for regeneration and utilization of hydrogen produced by hydrolysis of waste aluminum-silicon alloy and the recovery of elemental silicon according to claim 1, characterized in that: The silicon content in the aluminum-silicon alloy used as raw material is 5%-13%, and the aluminum content is 87%-95%.

3. The method for regeneration and utilization of hydrogen produced by hydrolysis of waste aluminum-silicon alloy and recovery of elemental silicon according to claim 2, characterized in that: The aluminum-silicon alloy is a ZL102 alloy with a silicon content of 10%-13% and an aluminum content of 87%-90%.

4. The method for regeneration and utilization of hydrogen produced by hydrolysis of waste aluminum-silicon alloy and the recovery of elemental silicon according to claim 1, characterized in that: The aluminum-silicon alloy content in the hydrogen production alloy is 80%-95%, and the total content of metallic gallium, indium, and tin is 5%-20%.

5. The method for regeneration and utilization of hydrogen produced by hydrolysis of waste aluminum-silicon alloy and the recovery of elemental silicon according to claim 4, characterized in that: The aluminum-silicon alloy content is 90%, 85%, or 80%, and the total content of gallium, indium, and tin is 5%, 15%, or 20%.

6. The method for regeneration and utilization of hydrogen produced by hydrolysis of waste aluminum-silicon alloy and the recovery of elemental silicon according to claim 4, characterized in that: The mass ratio of gallium, indium, and tin is 4.9:1.5:1, and the content of metallic gallium is 6.8% - 13.8%, the content of metallic indium is 2.1% - 4.3%, and the content of metallic tin is 1% - 2%.

7. The method for regeneration and utilization of hydrogen produced by hydrolysis of waste aluminum-silicon alloy and the recovery of elemental silicon according to claim 6, characterized in that: The content of gallium is 6.87%, 10.3% or 13.73%; the content of indium is 2.13%, 3.2% or 4.27%; and the content of indium is 1%, 1.5% or 2%.

8. The method for regeneration and utilization of hydrogen produced by hydrolysis of waste aluminum-silicon alloy and the recovery of elemental silicon according to claim 1, characterized in that: The heating rate during alloy preparation was 11 ℃ / min, the holding temperature was 800 ℃, the holding time was 60 min, the stirring time was 10 min, and the preheating temperature of the casting mold was 300 ℃.

9. The method for regeneration and utilization of hydrogen produced by hydrolysis of waste aluminum-silicon alloy and the recovery of elemental silicon according to claim 1, characterized in that: During the recovery of elemental silicon, the drying temperature was 80 ℃ twice, the drying time was 24 h, and the filtration time was 8 h.

10. The method for regeneration and recovery of elemental silicon based on hydrogen production by hydrolysis of waste aluminum-silicon alloy according to claim 1, characterized in that: The hydrolysis hydrogen production performance of the novel aluminum-based alloy prepared by combining low-melting-point metals and aluminum-silicon alloys is significantly improved with the increase of the total amount of low-melting-point metals. When the total content of low-melting-point metals reaches more than 20%, the hydrogen production efficiency can reach more than 90%, the average hydrogen production rate can reach more than 390 ml / min, and the recovery rate of silicon elemental is more than 95%, and the purity can reach more than 94%.

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