A method for preparing sodium aluminate by using aluminum ash as raw material
By generating sodium aluminate clinker through sintering, and combining steps such as leaching, solid-liquid separation, concentration and crystallization, and washing with condensate, the problems of high impurities and high energy consumption in the preparation of sodium aluminate from aluminum ash have been solved, and the preparation of high-purity sodium aluminate and the improvement of production efficiency have been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUANGDONG YONGBAO ENVIRONMENTAL TECHNOLOGY CO LTD
- Filing Date
- 2026-01-21
- Publication Date
- 2026-05-29
AI Technical Summary
The existing technology for preparing sodium aluminate from aluminum ash has problems such as many impurities and high energy consumption.
Sodium aluminate clinker is produced by sintering, leaching and solid-liquid separation are performed, followed by concentration at high temperature and cooling crystallization to remove soluble impurities, and finally washing and drying. The solid is washed with condensate and the crystallization filtrate is reused. The concentration of the concentrated liquid components is controlled to achieve continuous production.
It effectively removes impurities, improves the purity of sodium aluminate, reduces energy consumption, and achieves increased production efficiency and efficient resource utilization.
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Figure CN122102179A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aluminum ash resource utilization technology, and in particular to a method for preparing sodium aluminate using aluminum ash as a raw material. Background Technology
[0002] Aluminum ash, a major solid waste in the aluminum industry, contains a large amount of recyclable aluminum, which exists in the form of elemental aluminum and aluminum alloys. Currently, it is mainly recycled efficiently through processes such as screening, gravity separation, and pyrometallurgical smelting, and can be used directly as raw material for aluminum processing or as recycled aluminum ingots, thereby reducing the high energy consumption and high pollution of primary aluminum mining and smelting.
[0003] Sodium aluminate is a strongly alkaline inorganic compound with applications in materials preparation, chemical production, and environmental remediation. Currently, the main method for preparing sodium aluminate from aluminum ash involves preparing a sodium aluminate solution from the aluminum ash, followed by evaporation crystallization to obtain the sodium aluminate product. However, in this process, impurities from the solution are mixed into the sodium aluminate product after evaporation, resulting in low purity. Furthermore, the evaporation of the sodium aluminate solution requires a large amount of heat, leading to high costs for the resource utilization of aluminum ash.
[0004] It is evident that existing technologies still need improvement and enhancement. Summary of the Invention
[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing sodium aluminate using aluminum ash as raw material, which aims to solve the technical problems of high impurities and high energy consumption in the preparation of sodium aluminate using aluminum ash in the prior art.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a method for preparing sodium aluminate from aluminum ash, comprising the following steps: S1. Sodium aluminate clinker is produced by reacting harmlessly treated aluminum ash tailings with sodium carbonate or sodium hydroxide through sintering. S2. Soak sodium aluminate clinker in leaching solution at a leaching temperature of 60–170°C, separate solids and liquids, and then finely filter the liquid to obtain fine filtrate. S3. Evaporate and concentrate the fine filtrate at 100-130℃ to obtain a concentrated solution; S4. Crystallize the concentrated solution at 40-80°C, filter it to obtain a crystallized filtrate and sodium aluminate crystals, and use the crystallized filtrate as a leachate after dilution.
[0007] The method for preparing sodium aluminate from aluminum ash as raw material further includes: S5. washing and drying the sodium aluminate crystals to obtain the finished sodium aluminate product.
[0008] The method for preparing sodium aluminate from aluminum ash further includes: S6. mixing the crystallization washing liquid from S5 with the filtrate.
[0009] The method for preparing sodium aluminate from aluminum ash further includes: washing the solid after solid-liquid separation and fine filtration in S2 with the condensate generated during evaporation and concentration in S3 to obtain a solid washing liquid, and using the solid washing liquid to dilute the crystallization filtrate.
[0010] The method for preparing sodium aluminate from aluminum ash further includes: when the concentration of fluoride ions in the crystallization filtrate is greater than 10 ppm, adding calcium oxide in S1 to remove fluoride ions.
[0011] In the method for preparing sodium aluminate from aluminum ash, in step S1, the mass ratio of the leachate to the sodium aluminate clinker is (1-10):1.
[0012] In the method for preparing sodium aluminate from aluminum ash, in step S2, the concentration of alumina in the leachate is 2-10 wt%, and the concentration of sodium oxide is 2-15 wt%.
[0013] In the method for preparing sodium aluminate from aluminum ash, in step S2, the concentration of alumina in the filtrate is 8-25 wt%, and the concentration of sodium oxide is 10-25 wt%.
[0014] In the method for preparing sodium aluminate from aluminum ash, the sodium oxide concentration of the concentrated solution in step S3 is 28-32 wt%.
[0015] Beneficial Effects: This invention provides a method for preparing sodium aluminate from aluminum ash. First, the aluminum ash tailings are converted into sodium aluminate clinker, which is then leached and separated to remove solid impurities. Next, sodium aluminate crystals are obtained through high-temperature concentration and cooling crystallization, effectively removing a large amount of soluble impurities and improving the purity of the sodium aluminate. Compared with existing technologies, this invention eliminates the need to evaporate the sodium aluminate solution to dryness, resulting in lower energy consumption and fewer impurities. Furthermore, the crystallization filtrate can be further reused in the leachate, enabling continuous use of the filtrate and improving production efficiency. Attached Figure Description
[0016] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation
[0017] This invention provides a method for preparing sodium aluminate using aluminum ash as a raw material. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.
[0018] Please see Figure 1 The first aspect of this invention provides a method for preparing sodium aluminate from aluminum ash, comprising the following steps: S1. Sodium aluminate clinker is produced by reacting harmlessly treated aluminum ash tailings with sodium carbonate or sodium hydroxide through sintering. S2. Soak sodium aluminate clinker in leaching solution at a leaching temperature of 60–170°C and a pressure of atmospheric pressure to 0.7 MPa. By increasing the leaching temperature, the solubility of sodium aluminate in the leaching solution can be increased, thereby reducing the amount of leaching solution used, reducing energy consumption in subsequent concentration steps, and improving concentration efficiency. Solid-liquid separation to remove insoluble particulate impurities (such as silicon, iron, etc.). The liquid obtained after solid-liquid separation is further subjected to fine filtration to remove small particulate solid impurities and obtain fine filtrate. S3. The filtrate is concentrated by evaporation at 100-130℃ to increase the solute concentration in the liquid and obtain a concentrated solution. S4. Cooling allows the concentrate to crystallize at 40–80°C for 1–5 hours. After cooling, the solubility of the solute decreases, thus forming sodium aluminate. As for soluble impurities, due to their low concentration, they will not crystallize even after cooling and will remain in the liquid phase, thereby removing most of the soluble impurities. After crystallization, the solution is filtered to obtain a crystallized filtrate and sodium aluminate crystals. The crystallized filtrate is then diluted and used as a leachate.
[0019] Preferably, the method for preparing sodium aluminate from aluminum ash further includes: S5. Washing and drying the sodium aluminate crystals to obtain the finished sodium aluminate product. During washing, a fine filtrate at a temperature of 60–70°C is used.
[0020] Preferably, the method for preparing sodium aluminate from aluminum ash further includes: S6. mixing the crystallization washing solution and the filtrate from S5. During the washing process, in addition to washing away the surface crystallized filtrate, a small amount of sodium aluminate crystals will also redissolve. Therefore, the crystallization washing solution contains a certain concentration of sodium aluminate. Directly mixing the crystallization washing solution and the filtrate before entering the concentration process can improve the aluminum recovery rate and reduce the generation of waste liquid.
[0021] Preferably, the method for preparing sodium aluminate from aluminum ash further includes: washing the solid after solid-liquid separation and fine filtration in S2 with the condensate generated during evaporation and concentration in S3 to obtain a solid washing liquid, and using the solid washing liquid to dilute the crystallization filtrate. In this embodiment, the condensate formed after the water vapor generated during evaporation and concentration has a high temperature. Using this condensate to wash the solid after solid-liquid separation and fine filtration can further dissolve the residual sodium aluminate in the solid. This step not only achieves waterless discharge but also makes full use of heat. Because the temperature of the condensate is high, the temperature of the solid washing liquid is also high, which increases the heat of the system when used to dilute the crystallization filtrate, resulting in less energy consumption when dissolving the sodium aluminate clinker.
[0022] Preferably, the method for preparing sodium aluminate from aluminum ash further includes: when the fluoride ion concentration in the crystallization filtrate is greater than 10 ppm, adding calcium oxide in step S1 to remove the fluoride ions. In this embodiment, by adding calcium oxide, calcium fluoride precipitate can be generated, removing the fluoride ions. This avoids reducing the purity of the product due to excessive impurities during repeated reuse of the crystallization filtrate.
[0023] Preferably, in the method for preparing sodium aluminate from aluminum ash, in step S1, the mass ratio of the leachate to the sodium aluminate clinker is (1-10):1. By controlling the mass ratio of the leachate to the sodium aluminate clinker, it can be ensured that the sodium aluminate is fully dissolved, while preventing the concentration of alumina and sodium oxide in the filtrate from becoming too low, thus reducing energy consumption during the concentration process.
[0024] Preferably, in the method for preparing sodium aluminate from aluminum ash, in step S2, the alumina concentration of the leachate is 2-10 wt%, and the sodium oxide concentration is 2-15 wt%. The leachate is obtained by diluting the crystallization filtrate, and its alumina and sodium oxide concentrations should not be too high, otherwise the sodium aluminate clinker cannot be fully dissolved.
[0025] Preferably, in the method for preparing sodium aluminate from aluminum ash, in step S2, the alumina concentration of the filtrate is 8-25 wt%, and the sodium oxide concentration is 10-25 wt%. The alumina and sodium oxide concentrations of the filtrate should not be too low, otherwise excessive heat will be required during the concentration stage.
[0026] Preferably, in the method for preparing sodium aluminate from aluminum ash, the sodium oxide concentration in the concentrate in step S3 is 28-32 wt%. In this embodiment, by precisely controlling the sodium oxide concentration in the concentrate, sodium aluminate crystals can be stably precipitated during the crystallization stage, and the sodium oxide concentration in the crystallization filtrate can be maintained within a stable range of 29%-30 wt% and approximately 6 wt%, with minimal fluctuations. The advantage is that when diluting the crystallization filtrate into a leachate, it is unnecessary to repeatedly measure the sodium oxide and its concentration, and recalculate the dilution ratio, which is beneficial for continuous production. In this embodiment, even if the aluminum concentration in the sodium aluminate clinker fluctuates significantly, strict control of the sodium oxide concentration in the concentrate ensures that the crystallization filtrate can be directly reused without changing the dilution ratio, resulting in higher production efficiency. When the sodium oxide content in the concentrate is too high or too low, it will cause fluctuations and instability in the alumina content in the crystallization filtrate. This will affect the filtration performance (due to excessive solute content) and cause large fluctuations in the proportion of the crystallization filtrate when it is returned to the dissolution batch, which is not conducive to continuous production.
[0027] The present invention will be further illustrated by the following examples and comparative examples.
[0028] Example 1 A method for preparing sodium aluminate from aluminum ash includes the following steps: S1. Sodium aluminate clinker is produced by reacting harmlessly treated aluminum ash tailings with sodium carbonate through sintering, with the mass ratio of aluminum ash tailings to sodium carbonate being 1:1. S2. Sodium aluminate clinker is soaked in a leaching solution, wherein the concentration of alumina in the leaching solution is 2wt% and the concentration of sodium oxide is 10wt%; the leaching temperature is 80℃ and the leaching pressure is 0.5MPa. After the sodium aluminate clinker is fully dissolved, solid-liquid separation is performed to obtain a first filter cake. The liquid is then subjected to fine filtration to obtain a fine filtrate and a second filter cake. S3.110℃ evaporates and concentrates the fine filtrate until the sodium oxide concentration in the concentrate is 29.4wt% and the alumina concentration is 18.1wt%. The water vapor generated by evaporation and concentration is liquefied and used to wash the filter cake generated in S2 to obtain a solid washing liquid, which is then used to dilute the crystallization filtrate. S4. The concentrated solution is gradually cooled to 45°C over 4 hours to obtain crystals. The solution is then filtered to obtain a crystallized filtrate and sodium aluminate crystals. The concentration of sodium oxide in the crystallized filtrate is 29.6%, and the concentration of alumina is 6.1%. The crystallized filtrate is diluted 3 times and reused as a leachate. S5. The sodium aluminate crystals were washed and dried using a fine filtrate at 60℃ to obtain the finished sodium aluminate product; after drying, the alumina content of the sodium aluminate crystals was 41.2 wt%, and the sodium oxide content was 32.7 wt%. The crystallization washing liquid is mixed with the subsequent filtrate and then concentrated again.
[0029] Example 2 A method for preparing sodium aluminate from aluminum ash includes the following steps: S1. Sodium aluminate clinker is produced by reacting harmlessly treated aluminum ash tailings with sodium carbonate through sintering, with the mass ratio of aluminum ash tailings to sodium carbonate being 1:1. S2. Sodium aluminate clinker is soaked in a leaching solution, wherein the concentration of alumina in the leaching solution is 2wt% and the concentration of sodium oxide is 10wt%; the leaching temperature is 80℃ and the leaching pressure is 0.5MPa. After the sodium aluminate clinker is fully dissolved, solid-liquid separation is performed to obtain a first filter cake. The liquid is then subjected to fine filtration to obtain a fine filtrate and a second filter cake. S3.1 Evaporate and concentrate the fine filtrate at 110℃ until the sodium oxide concentration in the concentrate is 29.8wt% and the aluminum oxide concentration is 23.1wt%. The water vapor generated by evaporation and concentration is liquefied and used to wash the filter cake generated in S2 to obtain a solid washing liquid, which is then used to dilute the crystallization filtrate. S4. The concentrated solution is gradually cooled to 45°C over 4 hours to obtain crystals. The solution is then filtered to obtain a crystallized filtrate and sodium aluminate crystals. The concentration of sodium oxide in the crystallized filtrate is 29.9%, and the concentration of alumina is 6.0%. The crystallized filtrate is diluted 3 times and reused as a leachate. S5. The sodium aluminate crystals were washed and dried using a fine filtrate at 60℃ to obtain the finished sodium aluminate product; after drying, the alumina content of the sodium aluminate crystals was 41.3 wt%, and the sodium oxide content was 32.8 wt%. The crystallization washing liquid is mixed with the subsequent filtrate and then concentrated again.
[0030] Comparative Example 1 A method for preparing sodium aluminate using aluminum ash as raw material differs from Example 1 in that the concentration of sodium oxide in the concentrate is 25.1 wt% and the concentration of aluminum oxide is 18.2 wt%; after crystallization, the concentration of sodium oxide in the crystallization filtrate is 23.4 wt% and the concentration of aluminum oxide is 11.5 wt%.
[0031] Comparative Example 2 A method for preparing sodium aluminate from aluminum ash differs from Example 1 in that the concentration of sodium oxide in the concentrate is 25.1 wt% and the concentration of aluminum oxide is 23.2 wt%; after crystallization, the concentration of sodium oxide in the crystallization filtrate is 22.8 wt% and the concentration of aluminum oxide is 14.5 wt%.
[0032] Comparative Example 3 A method for preparing sodium aluminate from aluminum ash differs from Example 1 in that the concentration of sodium oxide in the concentrate is 34.2 wt% and the concentration of aluminum oxide is 18.1 wt%; after crystallization, the concentration of sodium oxide in the crystallization filtrate is 36.3 wt% and the concentration of aluminum oxide is 5.5 wt%.
[0033] Comparative Example 4 A method for preparing sodium aluminate from aluminum ash differs from Example 1 in that the concentration of sodium oxide in the concentrate is 34.2 wt% and the concentration of aluminum oxide is 23.3 wt%; after crystallization, the concentration of sodium oxide in the crystallization filtrate is 38.1 wt% and the concentration of aluminum oxide is 4.2 wt%.
[0034] The concentrations of sodium oxide and alumina in the crystallization filtrates of Comparative Example 1 and Comparative Example 2 show that when the concentration of sodium oxide in the concentrate is 25.1 wt%, the concentrations of sodium oxide and alumina in the crystallization filtrates of Comparative Example 1 and Comparative Example 2 differ significantly after crystallization. This requires re-measuring the concentration of key components in the crystallization filtrate and adjusting the dilution ratio each time, which is not conducive to continuous production.
[0035] The concentrations of sodium oxide and alumina in the crystallization filtrates of Comparative Examples 3 and 4 show that when the sodium oxide concentration of the concentrate is 34.2 wt%, the concentrations of sodium oxide and alumina in the crystallization filtrates of Comparative Examples 3 and 4 after crystallization are also very different. It is necessary to re-measure the concentration of key components in the crystallization filtrate and adjust the dilution ratio each time, which is not conducive to continuous production.
[0036] The above comparative examples illustrate that in actual production, when the sodium oxide concentration of the concentrate is too high or too low, the sodium oxide and alumina concentrations of the crystallization filtrate are difficult to maintain stable after crystallization, which is not conducive to continuous production.
[0037] In Examples 1 and 2, the sodium oxide concentration of the concentrate was controlled at 29.6 wt%. After crystallization, the sodium oxide concentration and alumina concentration of the crystallization filtrate of Examples 1 and 2 were very close, with very little difference. No dilution ratio adjustment was required each time it was reused, which is beneficial for continuous production.
[0038] It is understood that those skilled in the art can make equivalent substitutions or modifications to the technical solution and inventive concept of the present invention, and all such substitutions or modifications should fall within the protection scope of the appended claims.
Claims
1. A method for preparing sodium aluminate from aluminum ash, characterized in that, Includes the following steps: S1. Sodium aluminate clinker is produced by reacting harmlessly treated aluminum ash tailings with alkali through sintering. In particular, the alkali used can be one or more of sodium carbonate and sodium hydroxide used at the same time. S2. Soak sodium aluminate clinker in leaching solution at a leaching temperature of 60–170°C, separate solids and liquids, and then finely filter the liquid to obtain fine filtrate. S3. Evaporate and concentrate the fine filtrate at 100-130℃ to obtain a concentrated solution; S4. Crystallize the concentrated solution at 40-80°C, filter it to obtain a crystallized filtrate and sodium aluminate crystals, and use the crystallized filtrate as a leachate after dilution.
2. The method for preparing sodium aluminate from aluminum ash according to claim 1, characterized in that, Also includes: S5. Wash and dry the sodium aluminate crystals to obtain the finished sodium aluminate product.
3. The method for preparing sodium aluminate from aluminum ash according to claim 2, characterized in that, Also includes: S6. Mix the crystallization washing solution from S5 with the filtrate.
4. The method for preparing sodium aluminate from aluminum ash according to claim 1, characterized in that, Also includes: The solids after solid-liquid separation and fine filtration in S2 are washed with the condensate generated during evaporation and concentration in S3 to obtain a solid washing liquid, which is then used to dilute the crystallization filtrate.
5. The method for preparing sodium aluminate from aluminum ash according to claim 1, characterized in that, Also includes: When the fluoride ion concentration in the crystallization filtrate is greater than 10 ppm, calcium oxide is added to S1 to remove the fluoride ions.
6. The method for preparing sodium aluminate from aluminum ash according to claim 1, characterized in that, In S1, the mass ratio of the leachate to the sodium aluminate clinker is (1-10):
1.
7. The method for preparing sodium aluminate from aluminum ash according to claim 1, characterized in that, In S2, the alumina concentration of the leachate is 2-10 wt%, and the sodium oxide concentration is 2-15 wt%.
8. The method for preparing sodium aluminate from aluminum ash according to claim 1, characterized in that, In step S2, the concentration of alumina in the filtrate is 8–25 wt%, and the concentration of sodium oxide is 10–25 wt%.
9. The method for preparing sodium aluminate from aluminum ash according to claim 1, characterized in that, In S3, the sodium oxide concentration of the concentrate is 28-32 wt%.
10. The method for preparing sodium aluminate from aluminum ash according to claim 9, characterized in that, In S3, the sodium oxide concentration of the concentrate is 29-30 wt%.