Comprehensive utilization method of high-magnesium aluminum ash

Abstract

The invention discloses a method for comprehensively utilizing high-magnesium aluminum ash, and belongs to the technical field of solid waste resource utilization. The method comprises the following steps: mixing high-magnesium aluminum ash and limestone according to a specific molar ratio, and calcining at a high temperature to obtain a high-activity clinker taking 12CaO. 7Al2O3 and magnesium oxide as main components; the clinker is subjected to primary acid pickling, and a high-aluminum raw material and filtrate are obtained; carrying out secondary acid leaching on the high-aluminum raw material, putting the high-aluminum raw material into hydrochloric acid in batches for reaction, and filtering to obtain polyaluminum chloride and high-silicon slag; and performing calcium chloride purification on the primary pickling filtrate, adjusting the pH value, filtering to obtain liquid calcium chloride and magnesium hydroxide filter residues, and further treating to obtain industrial-grade calcium chloride and magnesium hydroxide products. According to the method, resource utilization of the high-magnesium aluminum ash is achieved, three valuable chemical products including polyaluminum chloride, calcium chloride and magnesium hydroxide can be obtained at the same time, and good economic benefits and environmental benefits are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid waste resource utilization, and particularly relates to a comprehensive utilization method of high-magnesium aluminum ash. BACKGROUND

[0002] Primary aluminum ash is derived from various aspects of the aluminum industry, including aluminum electrolysis, aluminum remelting, and aluminum alloy production. Secondary aluminum ash is the product after extracting aluminum from primary aluminum ash. Due to the wide source of primary aluminum ash, the composition of secondary aluminum ash is often complex, making it difficult to adopt a unified comprehensive utilization method. The utilization methods of secondary aluminum ash include producing calcium aluminate powder for water treatment agents, calcium aluminate for steelmaking desulfurizer, refractory materials, aluminum sulfate, and polyaluminum chloride.

[0003] Currently, some existing patents have disclosed methods for comprehensive utilization of high-magnesium aluminum ash. Chinese Patent CN109928414B discloses a method for synchronously preparing calcium aluminate-based steelmaking desulfurizer by sintering and removing impurities from aluminum ash. Chinese Patent CN112607758B discloses a method for preparing calcium aluminate by co-treating high-magnesium aluminum ash and fly ash. In this method, high-magnesium aluminum ash, fly ash, and quicklime are wet ball-milled, and the ball-milled materials are sequentially subjected to washing, solid-liquid separation, and calcination to obtain calcium aluminate products. Although this method can treat high-magnesium aluminum ash, it mainly focuses on the utilization of aluminum components, and the recovery and utilization efficiency of magnesium components is low. Moreover, the process flow is complex. In the above patents, calcium aluminate is used for steelmaking desulfurizer, and does not involve the separation and extraction of valuable elements.

[0004] The main problems existing in the prior art are: magnesium in aluminum ash exists in the form of magnesium oxide, magnesium chloride, and magnesium aluminate spinel, and magnesium aluminate spinel exists in most aluminum ash. The magnesium and aluminum in the spinel phase have low activity and are difficult to extract by ordinary acid method or alkali method. It is difficult to utilize. The production of steelmaking desulfurizer from aluminum ash has requirements for the content of magnesium and silicon in the raw material, otherwise it cannot meet the use standard; the production of water treatment agent calcium aluminate from aluminum ash has strict requirements for the aluminum content of the raw material, and high-impurity aluminum ash is difficult to produce qualified products; the production of refractory materials from aluminum ash needs to strictly limit the composition of aluminum ash or perform complex impurity removal steps. Especially for high-magnesium aluminum ash, the existing technology is difficult to simultaneously achieve efficient recovery and utilization of aluminum, magnesium, and other valuable components, the process flow is complex, the economic benefit is not high, and secondary pollution is easy to occur. SUMMARY

[0005] In order to solve the technical problem of difficult extraction and utilization of magnesium elements in aluminum ash and achieve efficient separation and comprehensive utilization of valuable components in high-magnesium aluminum ash, a method for comprehensive utilization of high-magnesium aluminum ash is provided.

[0006] The technical problem this invention aims to solve is that magnesium in aluminum ash exists in phases such as magnesium oxide, magnesium chloride, and magnesium aluminum spinel, with magnesium aluminum spinel being present in most aluminum ash. The magnesium in the spinel phase has low reactivity with aluminum, making it difficult to extract using ordinary acid or alkali methods, thus hindering its utilization. The production of steelmaking desulfurizing agents from aluminum ash requires specific magnesium and silicon content in the raw materials; otherwise, the standards cannot be met. The production of calcium aluminate, a water treatment agent from aluminum ash, requires strict control over the aluminum content of the raw materials; high-impurity aluminum ash makes it difficult to produce qualified products. The production of refractory materials from aluminum ash necessitates strict control over the aluminum ash composition or complex impurity removal steps.

[0007] The technical solution adopted by this invention to solve its technical problem is: to provide a method for comprehensive utilization of high magnesium-aluminum ash, comprising the following steps:

[0008] S1, High-temperature calcination activation

[0009] High magnesium aluminum ash and limestone are mixed in a certain proportion to obtain a uniform mixture, which is then calcined at high temperature. After calcination, the mixture is cooled and ground to obtain a highly active clinker with 12CaO·7Al2O3 and magnesium oxide as the main components.

[0010] S2, First pickling

[0011] The highly active clinker obtained by calcination is leached with a primary pickling solution under stirring. After the primary pickling is completed, the pH of the slurry is adjusted to above 5.0 using lime milk with a mass concentration of 10-30% and then filtered. After filtration, high-alumina raw material and filtrate are obtained. The high-alumina raw material is washed with clean water 1-5 times under stirring. The washing solution and filtrate of the high-alumina raw material are recovered and used to prepare the primary pickling solution.

[0012] S3, Secondary Acid Immersion

[0013] The high-alumina raw material, after being washed with clean water, is leached with hydrochloric acid while being stirred. The high-alumina raw material is added to the hydrochloric acid in two batches. The first batch consists of 50-70% of the high-alumina raw material washed with clean water, and the addition temperature is greater than 70℃. After reacting for 10-60 minutes, the second batch consists of the remaining high-alumina raw material washed with clean water, and the addition temperature is greater than 90℃. After the second batch is added, the reaction is carried out for 30-100 minutes. After the second acid leaching, the mixture is immediately filtered to obtain polyaluminum chloride and high-silica slag. The high-silica slag is washed with water 1-3 times. The washing liquid can be recycled for the preparation of acid for the second acid leaching.

[0014] S4, calcium chloride purification

[0015] After repeated leaching, the filtrate obtained from the first acid washing process enriches calcium and magnesium. The pH is adjusted to 8.5-9.0 with 10-30% lime milk, and the mixture is filtered to obtain liquid calcium chloride and magnesium hydroxide filter residue. The magnesium hydroxide filter residue is washed with water and stirred. The liquid calcium chloride is evaporated, concentrated, and crystallized to obtain calcium chloride. The purity of both calcium chloride and washed magnesium hydroxide meets the requirements of industrial-grade products.

[0016] As a preferred embodiment, the high magnesium aluminum ash and limestone in step S1 are mixed in the proportion of Al2O3, SiO2 and CaO, wherein the molar ratio of the corresponding components is nCaO:(12 / 7nAl2O3+2nSiO2)=0.8~1.2.

[0017] As a preferred embodiment, the high-temperature calcination temperature in step S1 is 1050–1400°C, and the calcination time is 30–240 min.

[0018] As a preferred embodiment, in step S2, the liquid-to-solid ratio of the primary pickling solution and the highly active clinker is 8:1 to 20:1, the acidity of the primary pickling solution is 3 to 10%, the primary pickling time is 10 to 80 minutes, the temperature is 15 to 90°C, and the stirring speed is controlled at 40 to 200 rpm / min; the liquid-to-solid ratio of the clean water washing is 10:1 to 20:1, the washing temperature is 15 to 90°C, the stirring speed is controlled at 40 to 200 rpm / min, and the stirring time is 10 to 80 minutes.

[0019] As a preferred embodiment, the primary pickling solution described in step S2 can be prepared by mixing water, high-alumina raw material washing solution, or primary pickling filtrate with hydrochloric acid.

[0020] As a preferred embodiment, the solid-liquid ratio of the high-alumina raw material to hydrochloric acid in step S3 is 2.5:1 to 6:1, the concentration of the hydrochloric acid is 8 to 31%, the secondary acid leaching temperature is 95℃ to 105℃, the secondary acid leaching time is 30 to 120 min, and the stirring speed is controlled at 40 to 200 rpm / min.

[0021] As a preferred embodiment, the concentration of the liquid calcium chloride in step S4 is 10-20%;

[0022] The liquid-to-solid ratio of the water used for stirring and washing is 2:1 to 10:1. The washing is performed 1 to 3 times, the washing temperature is 5 to 90°C, the stirring speed is 40 to 200 rpm / min, and the stirring time is 10 to 80 min.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This invention achieves the purpose of fully activating α-Al2O3 and magnesium aluminum spinel in aluminum ash by adjusting the calcination ratio, making them easier to dissolve.

[0025] 2. This invention controls the acidity of calcined high-activity clinker and performs two leaching processes to separate valuable components. In the first acid wash, the amount of hydrochloric acid used is controlled, or the pH is adjusted later to achieve a final pH of 5.0–6.5, fully dissolving calcium and magnesium and causing aluminum to form an amorphous aluminum hydroxide precipitate that enters the filter residue. Calcium and magnesium are thus separated. After multiple cycles of enrichment of the filtrate, the pH is adjusted to 8.5–9.0, precipitating magnesium hydroxide and separating calcium and magnesium. The resulting calcium chloride and magnesium hydroxide both meet the corresponding industrial product quality requirements.

[0026] 3. The high-alumina raw material obtained by a single acid pickling process has higher alumina activity than ordinary aluminum hydroxide, reacts faster with hydrochloric acid, shortens the preparation time, and can produce polyaluminum chloride with higher basicity in one step without the need for high-pressure equipment. Compared with ordinary two-step polyaluminum chloride, the resulting polyaluminum chloride has a lower calcium oxide content and better resistance to deliquescence when used to produce solid polyaluminum chloride.

[0027] 4. After separating the valuable components from the aluminum ash, the resulting filter residue is a high-silica material that can be used to produce cement, prepare refractory bricks, etc.

[0028] 5. This invention extracts valuable components from high-magnesium aluminum ash to produce industrial products that meet quality standards, thereby achieving the goal of resource utilization.

[0029] 6. Valuable components in high-magnesium aluminum ash are extracted separately from aluminum ash to produce industrial products that meet quality standards, achieving the goal of resource utilization and solving the problem of the difficulty in comprehensive utilization of high-magnesium aluminum ash. Attached Figure Description

[0030] Figure 1 This is a process flow diagram of the present invention;

[0031] Figure 2 The XRD pattern of the highly active clinker of Example 1 of the present invention;

[0032] Figure 3 The image shows the XRD pattern of the highly active clinker from Example 4 of this invention. Detailed Implementation

[0033] The following examples are intended to further illustrate the present invention, but not to limit the scope of protection of the claims of the present invention.

[0034] Example 1:

[0035] A method for comprehensive utilization of high magnesium-aluminum ash, comprising the following steps:

[0036] S1. Take 200g of No. 1 aluminum ash and 306.7g of limestone, mix them evenly, and calcine them at a temperature of 1300℃ for 1 hour. After cooling, grind them to obtain highly active clinker.

[0037] S2. Take 350g of the highly active clinker obtained in step S1, leach it with 5.5% dilute hydrochloric acid by stirring, with a liquid-to-solid ratio of 12:1, a temperature of 50℃, a stirring speed of 200rpm / min, leach for 30min, and then separate the solid and liquid to obtain high-alumina raw material and filtrate 1.

[0038] S3. The calcium oxide content in the above filtrate 1 is 3.45%, the magnesium oxide content is 0.37%, and the aluminum oxide content is 0.3%. After the filtrate 1 is recovered, a primary pickling solution is prepared to replace dilute hydrochloric acid for primary pickling.

[0039] S4. Wash the high-alumina raw material from step S2 twice with water, and then perform a second acid leaching with 790 mL of 14% hydrochloric acid. The second acid leaching temperature is 95℃, and the reaction is carried out with stirring at 80 rpm for 80 min. Filter while hot. The resulting liquid polyaluminum chloride has an alumina concentration of 11.73% and a basicity of 64.28%.

[0040] S5. The high-silica slag, after secondary acid leaching, is washed twice with water at room temperature to obtain the cleaned high-silica slag. The dry slag weighs only 7.3g, accounting for 2.09% of the highly active clinker.

[0041] Example 2:

[0042] A method for comprehensive utilization of high magnesium-aluminum ash, comprising the following steps:

[0043] S1. Take 200g of No. 2 aluminum ash and 360g of limestone, mix them evenly, and calcine them at a temperature of 1400℃ for 0.5h. After cooling, grind them to obtain highly active clinker.

[0044] S2. Prepare a primary pickling solution using filtrate 1 from Example 1. The primary pickling solution is prepared by mixing water, high-alumina raw material washing solution or filtrate 1 from the primary pickling solution with hydrochloric acid. The primary pickling solution contains 2.54% calcium oxide, 0.27% magnesium oxide, 0.22% aluminum oxide, and 10% HCl.

[0045] S3. Take 350g of the highly active clinker from step S1, leach it with the pickling solution prepared in step S2, with a liquid-to-solid ratio of 8:1, leach at 15℃ for 80min, stirring at 80rpm / min, adjust the pH to 5.06 with 25% lime milk, and separate the solid and liquid to obtain high-alumina raw material and filtrate 2.

[0046] S4. Filtrate 2 has a calcium oxide content of 6.37%, a magnesium oxide content of 0.63%, and an aluminum oxide content of 0.35%. After filtrate 2 is recovered, it is prepared for primary acid washing.

[0047] S5. Wash the high-alumina raw material from step S3 three times with water, and then perform a second acid leaching with 560 mL of 31% hydrochloric acid. Heat the hydrochloric acid solution to 70°C, add half of the washed high-alumina raw material while stirring at 120 rpm / min, and react for 20 min. Heat the hydrochloric acid solution to 105°C, add the other half of the washed high-alumina raw material, and continue stirring for 100 min. Filter while hot. The resulting liquid polyaluminum chloride has an alumina concentration of 15.17% and a basicity of 39.76%.

[0048] S6. The high-silica slag, after secondary acid leaching, is washed twice with water at room temperature to obtain the washed high-silica slag. The dry slag weighs 14.54g, accounting for 4.16% of the high-activity clinker.

[0049] Example 3:

[0050] A method for comprehensive utilization of high magnesium-aluminum ash, comprising the following steps:

[0051] S1. Take 200g of No. 3 aluminum ash and 277g of limestone, mix them evenly, and calcine them at a temperature of 1250℃ for 1.5h. After cooling, grind them to obtain highly active clinker.

[0052] S2. Prepare a primary pickling solution using the primary pickling filtrate from multiple cycles, with a calcium oxide content of 10.79%, a magnesium oxide content of 1.13%, an aluminum oxide content of 0.27%, and an HCl concentration of 4%.

[0053] S3. Take 350g of the high-activity clinker from step S1, leach it with the pickling solution from step S2, with a liquid-to-solid ratio of 16:1, a temperature of 60℃, a stirring speed of 120rpm / min, leach for 20min, and then separate the solid and liquid to obtain high-alumina raw material and filtrate 3.

[0054] S4. The filtrate 3 from step S3 has a calcium oxide content of 13.98%, a magnesium oxide content of 1.64%, and an aluminum oxide content of 0.31%. After filtrate 3 is recovered, it is prepared for primary acid washing.

[0055] S5. Wash the high-alumina raw material from step S3 three times with water, and then perform a second acid leaching with 1300 mL of 8% hydrochloric acid. The temperature is 105℃, and the reaction is carried out with stirring at 100 rpm for 30 min. Filter while hot. The resulting liquid polyaluminum chloride has an alumina concentration of 7.23% and a basicity of 68.11%.

[0056] S6. The high-silica slag, after secondary acid leaching, is washed twice with water at room temperature to obtain the cleaned high-silica slag. The dry slag weighs 26.94g, accounting for 7.7% of the high-activity clinker.

[0057] Example 4:

[0058] A method for comprehensive utilization of high-magnesium aluminum ash is carried out according to the following steps:

[0059] S1. Take 200g of No. 4 aluminum ash and 243g of limestone, mix them evenly, and calcine them at a temperature of 1050℃ for 4 hours. After cooling, grind them to obtain highly active clinker.

[0060] S2. Prepare a primary pickling solution using the primary pickling filtrate from multiple cycles, with a calcium oxide content of 15.24%, a magnesium oxide content of 1.74%, an aluminum oxide content of 0.26%, and an HCl concentration of 3%.

[0061] S3. Take 350g of the high-activity clinker from step S1, leach it with the pickling solution from step S2, with a liquid-to-solid ratio of 20:1, a temperature of 90℃, a stirring speed of 180rpm / min, leach for 10min, adjust the pH to 5.12 with 22% lime milk, separate the solid and liquid, and obtain high-alumina raw material and filtrate 4.

[0062] S4. The filtrate 4 from step S3 has a calcium oxide content of 18.23%, a magnesium oxide content of 1.98%, and an aluminum oxide content of 0.23%. The pH is adjusted to 9 with 25% lime milk, and the solution is filtered to obtain magnesium hydroxide filter residue and filtrate 5. The magnesium hydroxide filter residue has a purity of 98%, and filtrate 5 has a calcium oxide content of 18.12%, both meeting the corresponding industrial product quality standards.

[0063] S5. The above high-alumina raw material was washed three times with water and then subjected to a second acid leaching with 920 mL of 9% hydrochloric acid. The reaction was carried out at 100℃ and 150 rpm for 60 min with stirring. The mixture was then filtered while hot. The resulting liquid polyaluminum chloride had an alumina concentration of 10.34% and a basicity of 68.26%.

[0064] S6. Wash the secondary acid leaching residue twice with water at room temperature to obtain high-silica slag. The dry slag weighs 35g, accounting for 10% of the high-activity clinker.

[0065] Table 1 Main components of each aluminum ash in the above embodiments

[0066]

[0067] Table 2. High-silica slag composition (XRF analysis) in the above embodiments.

[0068]

[0069] As can be seen from Tables 1 and 2, the above steps achieved comprehensive utilization of high-magnesium aluminum ash, yielding valuable products such as polyaluminum chloride, calcium chloride, and magnesium hydroxide. Taking Example 1 as an example, the dry residue of the secondary acid leaching residue weighed only 7.3g, accounting for 2.09% of the highly active clinker, demonstrating efficient utilization of the high-magnesium aluminum ash.

[0070] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for comprehensive utilization of high-magnesium aluminum ash, characterized in that, The comprehensive utilization method includes the following steps: S1, High-temperature calcination activation High magnesium aluminum ash and limestone are mixed in a certain proportion to obtain a uniform mixture, which is then calcined at high temperature. After calcination, the mixture is cooled and ground to obtain a highly active clinker with 12CaO·7Al2O3 and magnesium oxide as the main components. S2, First pickling The highly active clinker obtained by calcination is leached with a primary pickling solution under stirring. After the primary pickling is completed, the pH of the slurry is adjusted to above 5.0 using lime milk with a mass concentration of 10-30% and then filtered. After filtration, high-alumina raw material and filtrate are obtained. The high-alumina raw material is washed with clean water 1-5 times under stirring. The washing solution and filtrate of the high-alumina raw material are recovered and used to prepare the primary pickling solution. S3, Secondary Acid Immersion The high-alumina raw material, after being washed with clean water, is leached with hydrochloric acid while being stirred. The high-alumina raw material is added to the hydrochloric acid in two batches. The first batch consists of 50-70% of the high-alumina raw material washed with clean water, and the addition temperature is greater than 70℃. After reacting for 10-60 minutes, the second batch consists of the remaining high-alumina raw material washed with clean water, and the addition temperature is greater than 90℃. After the second batch is added, the reaction is carried out for 30-100 minutes. After the second acid leaching, the mixture is immediately filtered to obtain polyaluminum chloride and high-silica slag. The high-silica slag is washed with water 1-3 times. The washing liquid can be recycled for the preparation of acid for the second acid leaching. S4, calcium chloride purification After multiple leaching cycles, the filtrate obtained from the first acid wash is enriched with calcium and magnesium. The pH is adjusted to 8.5-9.0 with 10-30% lime milk, and the residue is filtered to obtain liquid calcium chloride and magnesium hydroxide. The magnesium hydroxide residue is washed with water and stirred. The liquid calcium chloride is evaporated, concentrated, and crystallized to obtain calcium chloride. The purity of both calcium chloride and washed magnesium hydroxide meets the key indicators of industrial-grade products: magnesium oxide content >93% and calcium oxide content <1.0% in magnesium hydroxide; effective calcium chloride content >74% and total magnesium impurity content <0.50%.

2. The method for comprehensive utilization of high-magnesium aluminum ash according to claim 1, characterized in that, The high magnesium aluminum ash and limestone in step S1 are mixed according to the ratio of Al2O3, SiO2 and CaO, wherein the molar ratio of the corresponding components is nCaO: (12 / 7nAl2O3+2nSiO2)=0.8~1.

2.

3. The method for comprehensive utilization of high-magnesium aluminum ash according to claim 1, characterized in that, The high-temperature calcination temperature in step S1 is 1050–1400°C, and the calcination time is 30–240 min.

4. The method for comprehensive utilization of high-magnesium aluminum ash according to claim 1, characterized in that, In step S2, the liquid-solid ratio of the primary pickling solution and the highly active clinker is 8:1 to 20:1, the acidity of the primary pickling solution is 3 to 10%, the primary pickling time is 10 to 80 minutes, the temperature is 15 to 90°C, and the stirring speed is controlled at 40 to 200 rpm / min. The liquid-to-solid ratio of the clean water washing solution is 10:1 to 20:1, the washing temperature is 15 to 90°C, the stirring speed is controlled at 40 to 200 rpm / min, and the stirring time is 10 to 80 min.

5. The method for comprehensive utilization of high-magnesium aluminum ash according to claim 1, characterized in that, The pickling solution described in step S2 can be prepared by mixing water, high-alumina raw material washing solution or pickling filtrate with hydrochloric acid.

6. The method for comprehensive utilization of high-magnesium aluminum ash according to claim 1, characterized in that, In step S3, the solid-liquid ratio of the high-alumina raw material to hydrochloric acid is 2.5:1 to 6:1, the concentration of the hydrochloric acid is 8 to 31%, the secondary acid leaching temperature is 95℃ to 105℃, the secondary acid leaching time is 30 to 120 min, and the stirring speed is controlled at 40 to 200 rpm / min.

7. The method for comprehensive utilization of high-magnesium aluminum ash according to claim 1, characterized in that, The concentration of the liquid calcium chloride in step S4 is 10-20%; The liquid-to-solid ratio of the water used for stirring and washing is 2:1 to 10:

1. The washing is performed 1 to 3 times, the washing temperature is 5 to 90°C, the stirring speed is 40 to 200 rpm / min, and the stirring time is 10 to 80 min.

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