Preparation method and application of concrete filler based on secondary aluminum ash

Abstract

The application discloses a preparation method of concrete filling material based on secondary aluminum ash, which comprises the following steps: after secondary aluminum ash is crushed and ground, water and sulfuric acid are added in sequence and stirred, and then filter residue A is obtained after filtration; the filter residue A is mixed with water to obtain slurry, then carbon dioxide is continuously introduced into the slurry and stirred, and then filter residue B is obtained after filtration; the filter residue B is washed with water, calcium hydrogen phosphate, magnesium oxide and zinc oxide are added and uniformly stirred, and then sintering is conducted, and the concrete filling material based on secondary aluminum ash is obtained after crushing after cooling. The harmful components such as aluminum nitride and fluoride in the secondary aluminum ash can be effectively removed, and the porous ceramic filling material with excellent performance is prepared by taking the secondary aluminum ash as a main raw material, so that the heat insulation, durability, sound insulation and other effects of the material can be improved when the material is applied to the building material field.

Description

Technical Field

[0001] This invention belongs to the field of secondary aluminum ash recycling technology, specifically relating to a method for preparing and applying a concrete filler based on secondary aluminum ash. Background Technology

[0002] Secondary aluminum ash is a hazardous waste generated in the aluminum industry, mainly originating from the secondary processing stages of aluminum smelting, processing, or recycling. It primarily contains alumina, aluminum nitride, as well as oxides of iron, silicon, and magnesium, and chlorides and fluorides of potassium, sodium, calcium, and magnesium. Aluminum nitride is one of the main components contributing to the hazardous nature of secondary aluminum ash; it releases ammonia gas upon contact with water, potentially causing explosions or poisoning. How to effectively treat and utilize secondary aluminum ash to achieve resource reuse and reduce environmental pollution is a crucial issue currently facing the aluminum industry.

[0003] Currently, commonly used methods for treating secondary aluminum ash include calcination, hydrolysis, and chemical stabilization. Calcination involves calcining at high temperatures to decompose or transform harmful substances in the secondary aluminum ash into stable oxides, or mixing it with other components and sintering it to produce ceramsite for recycling. However, due to the influence of the secondary aluminum ash composition and process conditions, the quality of the resulting ceramsite is relatively poor, limiting its application areas. Hydrolysis uses water or steam and hydrolysis catalysts to rapidly and thoroughly hydrolyze the secondary aluminum ash, decomposing harmful components such as aluminum nitride. The process is simple and convenient, but the choice and cost of the catalyst may affect the treatment effect, and it requires strict control of hydrolysis conditions. Chemical stabilization involves reacting chemical agents with aluminum nitride to generate stable compounds, or physically encapsulating it to prevent contact with water, but the risk of residual harmful substances remains. Therefore, a truly effective method for recycling and reusing secondary aluminum ash is still lacking. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention discloses a method for preparing concrete filler based on secondary aluminum ash. This method effectively removes harmful components such as aluminum nitride and fluorides from the secondary aluminum ash and uses it as the main raw material to prepare a high-performance porous ceramic filler. When applied to the field of building materials, it can improve the heat insulation, durability, and sound insulation effects of the materials, thereby realizing the effective utilization of secondary aluminum ash waste resources.

[0005] This invention is achieved using the following technical solution: A method for preparing a concrete filler based on secondary aluminum ash, comprising the following steps: (1) Take secondary aluminum ash, crush and grind it, add water and sulfuric acid in sequence and mix them. Then stir and treat it at 60-80℃ for 20-30 minutes. After filtration, filter residue A is obtained. (2) Take the filter residue A obtained in step (1) and mix it with water to obtain a slurry. Then, continuously introduce carbon dioxide into the slurry and stir it at 50-60°C for 30-60 minutes. After filtration, filter residue B is obtained. (3) Take the filter residue B obtained in step (2) and wash it with water 1 to 2 times. Then add dicalcium phosphate, magnesium oxide and zinc oxide and stir to mix evenly. Dry it at 100 to 150°C for 10 to 15 minutes. Then sinter it at 700 to 900°C for 30 to 60 minutes. After cooling, crush it to obtain concrete filler based on secondary aluminum ash.

[0006] This invention first treats secondary aluminum ash with water and sulfuric acid to decompose aluminum nitride, thereby eliminating the risk of NH3. Simultaneously, it dissolves soluble fluorides in the secondary aluminum ash, effectively removing harmful substances such as aluminum nitride and fluorides. Next, water is added to the treated filter residue A to form a slurry, followed by carbon dioxide treatment to further decompose the aluminum nitride in filter residue A, achieving complete decomposition and removal of aluminum nitride from the secondary aluminum ash. Then, the obtained filter residue B is mixed with dicalcium phosphate, magnesium oxide, and zinc oxide, and then subjected to a suitable temperature. Under the action of magnesium oxide and zinc oxide, residual insoluble fluorides react with dicalcium phosphate to form calcium fluorophosphate or calcium magnesium fluorophosphate solid solutions, achieving the immobilization of residual fluorides. Furthermore, zinc ions replace calcium ions in the apatite lattice, improving structural stability. The addition of magnesium oxide and zinc oxide also lowers the sintering temperature.

[0007] The waste gas generated during the stirring process in steps (2) and (3) is mainly ammonia. The waste gas can be adsorbed by phosphoric acid solution, and the recovered ammonia can be used to prepare ammonium phosphate. The wastewater generated can be used to recover soluble fluorides such as sodium fluoride and potassium fluoride.

[0008] Furthermore, in step (1), the secondary aluminum ash is crushed and ground and then passed through a 100-150 mesh sieve, and then water and sulfuric acid are added in sequence for mixing.

[0009] Furthermore, in step (1), the weight ratio of the secondary aluminum ash, water and sulfuric acid is 100:(100-200):(5-8).

[0010] Furthermore, the stirring process described in step (1) is carried out at a speed of 80 to 100 r / min; the stirring process described in step (2) is carried out at a speed of 200 to 300 r / min.

[0011] Furthermore, in step (2), the weight ratio of the filter residue A to water is 1:(3-5). By controlling the solid-liquid ratio, it is ensured that the residual aluminum nitride can be completely decomposed and the soluble fluorides can be dissolved and removed.

[0012] Furthermore, in step (2), carbon dioxide is continuously introduced into the slurry to adjust its pH to 5-6. Introducing carbon dioxide to adjust the slurry to be slightly acidic is beneficial for the decomposition and removal of residual aluminum nitride.

[0013] Furthermore, in step (3), the weight ratio of the filter residue B, dicalcium phosphate, magnesium oxide and zinc oxide is 100:(5-8):(1-3):(0.5-0.6).

[0014] Furthermore, in step (3), the temperature is increased to 700-900°C at a rate of 5-8°C / min for sintering. By controlling the heating rate, the activation of insoluble fluorides (such as calcium fluoride) is promoted, thereby increasing their reaction with calcium hydrogen phosphate to form stable fluorapatite.

[0015] Furthermore, in step (3), calcium hydrogen phosphate, magnesium oxide, zinc oxide, binder and sintering aid are added to filter residue B and stirred until uniform before sintering. The weight ratio of filter residue B, binder and sintering aid is (60-70):(10-15):(3-8). The binder includes kaolin and bentonite, and the amount of kaolin used is 1.5-2.5 times that of bentonite by weight. The sintering aid includes silicon dioxide and quartz.

[0016] The application of concrete filler based on secondary aluminum ash involves mixing it with silicate cement to prepare lightweight concrete, and the weight of the concrete filler based on secondary aluminum ash accounts for 20-30% of the weight of the lightweight concrete.

[0017] Compared with existing technologies, this technical solution has the following advantages: 1. This invention recycles secondary aluminum ash to prepare filler for concrete. It not only realizes the recycling of secondary aluminum ash waste resources, but also pre-treats the secondary aluminum ash to remove harmful substances such as aluminum nitride and fluorides. This allows the secondary aluminum ash to effectively improve the performance of concrete when used as filler, which is conducive to the promotion and application of secondary aluminum ash filler and truly realizes the upgrade from "industrial waste" to "high-performance building material".

[0018] 2. In this invention, water and an appropriate amount of sulfuric acid are first added to the secondary aluminum ash for treatment to promote the decomposition of aluminum nitride in the secondary aluminum ash. This not only removes harmful aluminum nitride, but also allows the ammonia gas generated during the treatment process to be recovered and reused. Then, in order to completely remove aluminum nitride and soluble fluorides, carbon dioxide is introduced into the slurry of the treated secondary aluminum ash for further treatment. By stirring the slurry, the residual aluminum nitride is exposed and decomposed. This also reduces the amount of sulfuric acid used, reduces equipment wear and waste acid treatment costs, and avoids the introduction of excessive sulfate ions that may have an adverse effect on subsequent processes.

[0019] 3. In this invention, dicalcium phosphate, magnesium oxide, zinc oxide, and other additives are added to secondary aluminum ash and then sintered after uniform mixing. This allows insoluble fluorides (such as calcium fluoride) that are difficult to remove from the secondary aluminum ash to react with dicalcium phosphate to form stable fluorapatite. This not only achieves the curing of fluorides but can also be used as a filler in concrete to improve the mechanical properties and durability of concrete. Detailed Implementation

[0020] The present invention is further illustrated by the following examples, but these are not intended to limit the invention. Specific experimental conditions and methods not specified in the following examples are generally conventional methods well known to those skilled in the art.

[0021] Example 1: A method for preparing concrete filler based on secondary aluminum ash, comprising the following steps: (1) Take secondary aluminum ash, crush and grind it and pass it through a 120-mesh sieve. Then add water and sulfuric acid in sequence and mix them. Then stir and treat it for 25 minutes at 70℃ and 90r / min. After filtration, filter residue A is obtained. The weight ratio of the secondary aluminum ash, water and sulfuric acid is 100:200:6. (2) Take the filter residue A obtained in step (1) and mix it with water to obtain a slurry. Then, continuously introduce carbon dioxide into the slurry to adjust the pH value of the slurry to 5.5, and stir it for 45 minutes at 55°C and a speed of 250 r / min. After filtration, filter residue B is obtained. The weight ratio of filter residue A to water is 1:4. (3) Take the filter residue B obtained in step (2) and wash it twice with water. Then add dicalcium phosphate, magnesium oxide and zinc oxide and stir to mix evenly. Dry it at 120℃ for 12 min. Then heat it to 800℃ at a rate of 6℃ / min and sinter for 45 min. After cooling, crush it to obtain concrete filler based on secondary aluminum ash. The weight ratio of filter residue B, dicalcium phosphate, magnesium oxide and zinc oxide is 100:6:2:0.58.

[0022] Example 2: A method for preparing concrete filler based on secondary aluminum ash, comprising the following steps: (1) Take secondary aluminum ash, crush and grind it and pass it through a 100-mesh sieve. Then add water and sulfuric acid in sequence and mix them. Then stir and treat it for 30 minutes at 60℃ and speed of 80r / min. After filtration, filter residue A is obtained. The weight ratio of the secondary aluminum ash, water and sulfuric acid is 100:100:5. (2) Take the filter residue A obtained in step (1) and mix it with water to obtain a slurry. Then, continuously introduce carbon dioxide into the slurry to adjust the pH value of the slurry to 5 and stir it for 60 minutes at 50°C and a speed of 200 r / min. After filtration, filter residue B is obtained. The weight ratio of filter residue A to water is 1:3. (3) Take the filter residue B obtained in step (2) and wash it with water once. Then add dicalcium phosphate, magnesium oxide, zinc oxide, binder and sintering aid and stir to mix evenly. Dry it at 100℃ for 15 min. Then heat it to 700℃ at a rate of 5℃ / min and sinter for 60 min. After cooling, crush it to obtain concrete filler based on secondary aluminum ash. The weight ratio of filter residue B, dicalcium phosphate, magnesium oxide and zinc oxide is 100:5:1:0.5. The weight ratio of filter residue B, binder and sintering aid is 60:10:3. The binder includes kaolin and bentonite. By weight, the amount of kaolin is 1.5 times that of bentonite. The sintering aid includes silicon dioxide and quartz.

[0023] Example 3: A method for preparing concrete filler based on secondary aluminum ash, comprising the following steps: (1) Take secondary aluminum ash, crush and grind it and pass it through a 120-mesh sieve. Then add water and sulfuric acid in sequence and mix them. Then stir and treat it for 25 minutes at 75℃ and a speed of 90r / min. After filtration, filter residue A is obtained. The weight ratio of the secondary aluminum ash, water and sulfuric acid is 100:180:6. (2) Take the filter residue A obtained in step (1) and mix it with water to obtain a slurry. Then, continuously introduce carbon dioxide into the slurry to adjust the pH value of the slurry to 5.5, and stir it for 45 minutes at 58°C and a speed of 250 r / min. After filtration, filter residue B is obtained. The weight ratio of filter residue A to water is 1:4.5. (3) Take the filter residue B obtained in step (2) and wash it twice with water. Then add dicalcium phosphate, magnesium oxide, zinc oxide, binder and sintering aid and stir to mix evenly. Dry it at 135℃ for 12 min. Then heat it to 850℃ at a rate of 7℃ / min and sinter for 50 min. After cooling, crush it to obtain concrete filler based on secondary aluminum ash. The weight ratio of filter residue B, dicalcium phosphate, magnesium oxide and zinc oxide is 100:6:2.5:0.52. The weight ratio of filter residue B, binder and sintering aid is 65:12:6. The binder includes kaolin and bentonite. By weight, the amount of kaolin is twice that of bentonite. The sintering aid includes silicon dioxide and quartz.

[0024] Example 4: A method for preparing concrete filler based on secondary aluminum ash, comprising the following steps: (1) Take secondary aluminum ash, crush and grind it and pass it through a 150-mesh sieve. Then add water and sulfuric acid in sequence and mix them. Then stir and treat it for 20 minutes at 80℃ and speed of 100r / min. After filtration, filter residue A is obtained. The weight ratio of the secondary aluminum ash, water and sulfuric acid is 100:200:8. (2) Take the filter residue A obtained in step (1) and mix it with water to obtain a slurry. Then, continuously introduce carbon dioxide into the slurry to adjust the pH value of the slurry to 6, and stir it for 30 minutes at 60°C and a speed of 300 r / min. After filtration, filter residue B is obtained. The weight ratio of filter residue A to water is 1:5. (3) Take the filter residue B obtained in step (2) and wash it with water once. Then add dicalcium phosphate, magnesium oxide, zinc oxide, binder and sintering aid and stir to mix evenly. Dry it at 150°C for 10 min and then sinter it at 900°C for 30 min at a rate of 8°C / min to obtain sintered material. The weight ratio of filter residue B, dicalcium phosphate, magnesium oxide and zinc oxide is 100:8:3:0.6. The weight ratio of filter residue B, binder and sintering aid is 70:15:8. The binder includes kaolin and bentonite, and the amount of kaolin is 2.5 times that of bentonite by weight. The sintering aid includes silicon dioxide and quartz.

[0025] Comparative Example 1: A method for preparing a concrete filler based on secondary aluminum ash, comprising the following steps: (1) Take secondary aluminum ash, crush and grind it and pass it through a 120-mesh sieve. Then add water and sulfuric acid in sequence and mix them. Adjust the pH to 5.5. Then stir and treat it for 60 minutes at 80℃ and 100r / min. After filtration, filter residue A is obtained. The weight ratio of the secondary aluminum ash, water and sulfuric acid is 100:300:8. (2) Take the filter residue A obtained in step (1) and wash it with water twice. Then add dicalcium phosphate, magnesium oxide and zinc oxide and stir to mix evenly. Dry it at 120℃ for 12 min. Then heat it to 800℃ at a rate of 6℃ / min and sinter for 45 min. After cooling, crush it to obtain concrete filler based on secondary aluminum ash. The weight ratio of filter residue B, dicalcium phosphate, magnesium oxide and zinc oxide is 100:6:2:0.58.

[0026] Comparative Example 2: A method for preparing a concrete filler based on secondary aluminum ash, comprising the following steps: (1) Take secondary aluminum ash, crush and grind it and pass it through a 120-mesh sieve. Then add water and sulfuric acid in sequence and mix them. Then stir and treat it for 25 minutes at 70℃ and 90r / min. After filtration, filter residue A is obtained. The weight ratio of the secondary aluminum ash, water and sulfuric acid is 100:200:6. (2) Take the filter residue A obtained in step (1) and mix it with water to obtain a slurry. Then, continuously introduce carbon dioxide into the slurry to adjust the pH value of the slurry to 5.5, and stir it for 45 minutes at 55°C and a speed of 250 r / min. After filtration, filter residue B is obtained. The weight ratio of filter residue A to water is 1:4. (3) Take the filter residue B obtained in step (2) and wash it twice with water. Then add dicalcium phosphate and stir to mix evenly. Dry it at 120℃ for 12 min. Then heat it to 800℃ at a rate of 6℃ / min and sinter for 45 min. After cooling, crush it to obtain concrete filler based on secondary aluminum ash.

[0027] Experimental Example 1: Concrete filler based on secondary aluminate was prepared according to the preparation methods described in Examples 1-4 and Comparative Examples 1-2, and then mixed with silicate cement to prepare lightweight concrete. The concrete was tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test results are shown in Table 1. The lightweight concrete included the following raw materials in parts by weight: 35 parts silicate cement, 25 parts concrete filler based on secondary aluminate, 20 parts sand, 5 parts vitrified microspheres, 5 parts fly ash, 1 part redispersible latex powder, 0.5 parts water-reducing agent, and 8.5 parts water. The performance of the lightweight concrete was then tested.

[0028] Table 1 Performance test results of concrete blocks prepared by different methods Example 1 152.3 22.6 Example 2 154.8 22.9 Example 3 155.6 23.8 Example 4 155.2 23.6 Comparative Example 1 138.3 18.4 Comparative Example 2 149.7 21.9 Experimental Example 2: Concrete filler based on secondary aluminum ash was prepared according to the preparation method described in Example 3, and lightweight concrete was prepared by mixing it with silicate cement in different proportions. The raw material composition of the lightweight concrete is shown in Table 2. In this experimental example, six different raw material composition proportions were tested and recorded as Experiment 1 to 6. The performance test results of the lightweight concrete prepared by the raw material composition of Experiment 1 to 6 are shown in Table 3.

[0029] Table 2 Raw material proportions for lightweight concrete

[0030] Table 3 Performance test results of lightweight concrete with different mix proportions Experiment 1 151.2 22.1 Experiment 2 152.9 22.5 Experiment 3 154.6 23.1 Experiment 4 155.6 23.8 Experiment 5 155.3 23.7 Experiment 6 154.2 23.1 Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing concrete filler based on secondary aluminum ash, characterized in that: Includes the following steps: (1) Take secondary aluminum ash, crush and grind it, add water and sulfuric acid in sequence and mix them. Then stir it at 60-80℃ and 80-100r / min for 20-30min. After filtration, filter residue A is obtained. (2) Take the filter residue A obtained in step (1) and mix it with water to obtain a slurry. Then, continuously introduce carbon dioxide into the slurry to adjust the pH value of the slurry to 5-6, and stir it at 50-60℃ and a speed of 200-300r / min for 30-60min. After filtration, filter residue B is obtained. The weight ratio of filter residue A to water is 1:(3-5). (3) Take the filter residue B obtained in step (2) and wash it with water 1 to 2 times. Then add dicalcium phosphate, magnesium oxide, zinc oxide, binder and sintering aid and stir to mix evenly. Dry it at 100 to 150°C for 10 to 15 minutes, then sinter it at 700 to 900°C for 30 to 60 minutes. After cooling, crush it to obtain concrete filler based on secondary aluminum ash. The weight ratio of filter residue B, dicalcium phosphate, magnesium oxide, and zinc oxide is 100:(5-8):(1-3):(0.5-0.6); the weight ratio of filter residue B, binder, and sintering aid is (60-70):(10-15):(3-8); the binder includes kaolin and bentonite, and the amount of kaolin used is 1.5-2.5 times that of bentonite by weight; the sintering aid includes silica and quartz.

2. The method for preparing concrete filler based on secondary aluminum ash according to claim 1, characterized in that: In step (1), the secondary aluminum ash is crushed and ground and then passed through a 100-150 mesh sieve, and then water and sulfuric acid are added in sequence for mixing.

3. The method for preparing concrete filler based on secondary aluminum ash according to claim 1, characterized in that: In step (1), the weight ratio of the secondary aluminum ash, water and sulfuric acid is 100:(100-200):(5-8).

4. The method for preparing concrete filler based on secondary aluminum ash according to claim 1, characterized in that: In step (3), the temperature is increased to 700-900℃ at a rate of 5-8℃ / min for sintering.

5. The application of the concrete filler based on secondary aluminum ash obtained by the preparation method according to any one of claims 1 to 4, characterized in that: Lightweight concrete is prepared by mixing the secondary aluminum ash-based concrete filler with silicate cement, wherein the weight of the secondary aluminum ash-based concrete filler accounts for 20-30% of the weight of the lightweight concrete.

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