A method for denitrification of aluminum dross

Abstract

The application relates to the technical field of solid waste recycling, in particular to a method for removing nitrogen from aluminum ash; the aluminum ash contains nitrogen salt and soluble salt; the method comprises the following steps: using an aqueous solution to remove salt from the aluminum ash to obtain a desalted aluminum ash suspension; performing dehydration treatment on the desalted aluminum ash to obtain water-containing aluminum ash with a preset water content; performing nitrogen removal treatment on the water-containing aluminum ash with the preset water content to obtain denitrified aluminum ash; the preset water content is less than or equal to 30%; the desalted aluminum ash suspension is subjected to dehydration treatment to obtain water-containing aluminum ash with a water content less than or equal to 30%; the water-containing aluminum ash with a water content less than or equal to 30% is in a solid-liquid mixed state, so that the efficiency of removing nitrogen from the aluminum ash can be improved.

Description

Technical Field

[0001] This application relates to the field of solid waste recycling technology, and in particular to a method for denitrification of aluminum ash. Background Technology

[0002] Aluminum ash is formed from the slag produced during aluminum electrolysis and smelting, after cooling (or subsequent processing). Furthermore, the aluminum content varies depending on the source of the slag. Based on this aluminum content, aluminum ash can be divided into primary aluminum ash and secondary aluminum ash. Primary aluminum ash is produced during the electrolysis of primary aluminum and casting processes without the addition of salt flux. Its main components are a mixture of metallic aluminum and aluminum oxides, with an aluminum content ranging from 15% to 70%. Secondary aluminum ash refers to the mixture generated after primary aluminum ash is recovered through salt bath treatment or after aluminum alloy refining. Its main components include small amounts of metallic aluminum, alumina, and certain amounts of salts such as NaCl and KCl. Currently, according to actual production statistics, approximately 30 kg to 50 kg of aluminum ash is emitted for every ton of aluminum produced and cast. Due to the environmental hazards of secondary aluminum ash, it is classified as hazardous waste, prompting a change in the treatment methods for secondary aluminum ash. The current treatment model for secondary aluminum ash is to establish a centralized secondary aluminum ash hazardous waste treatment center, and then centrally treat the secondary aluminum ash in the region to achieve efficient, clean, and environmentally friendly disposal and utilization of aluminum ash.

[0003] The harmless and resource-based disposal of aluminum ash first requires the separation of salts from the aluminum ash and the denitrification of aluminum nitride. The separation of salts from aluminum ash and the denitrification of aluminum nitride can be completed before or during resource utilization. Although aluminum ash can be desalted quickly and dissolved rapidly in aqueous solution, the hydrolysis and denitrification conditions for aluminum nitride are relatively harsh and slow. Hydrolysis and denitrification require long-term hydrolysis at high temperatures (generally, to enhance the hydrolysis effect of aluminum nitride, hydrolysis needs to be carried out at above 100°C for more than 2 hours; in addition, the hydrolysis reaction time at room temperature is even longer). Summary of the Invention

[0004] This application provides a method for denitrification of aluminum ash to solve the following technical problem: how to improve the efficiency of denitrification of aluminum ash.

[0005] In a first aspect, this application provides a method for denitrifying aluminum ash, wherein the aluminum ash contains soluble salts and nitrogen salts, the method comprising:

[0006] Aluminum ash is desalinated using an aqueous solution to obtain a desalinated aluminum ash suspension.

[0007] The desalted aluminum ash suspension is dehydrated to obtain aqueous aluminum ash with a preset moisture content;

[0008] The aqueous aluminum ash with a preset moisture content is subjected to denitrification treatment to obtain denitrified aluminum ash;

[0009] Wherein, the preset moisture content is ≤30%;

[0010] Optionally, the temperature of the denitrification treatment is ≤600℃.

[0011] Optionally, the temperature of the denitrification treatment is 100℃~600℃.

[0012] Optionally, the liquid-to-solid ratio of the aqueous solution and the aluminum ash is 0.5 to 2:1.

[0013] Optionally, the temperature of the desalination treatment is 80℃~100℃, and the time of the desalination treatment is 10min~30min.

[0014] Optionally, the desalination process includes desalination using a countercurrent elution method, wherein the countercurrent elution level is ≤3.

[0015] Optionally, the method further includes:

[0016] Aqueous solutions were used to desalinate aluminum ash to obtain desalinated aluminum ash suspension and desalinated tail gas, respectively.

[0017] The desalted aluminum ash suspension is dehydrated to obtain aqueous aluminum ash with a preset moisture content;

[0018] The aqueous aluminum ash with a preset moisture content is subjected to denitrification treatment to obtain denitrified aluminum ash and denitrified tail gas, respectively.

[0019] The desalination tail gas and the denitrification tail gas are cooled by heat exchange, and then ammonia is absorbed by spraying to obtain ammonia water.

[0020] Optionally, the temperature for ammonia absorption is 20℃~30℃, and the time for ammonia absorption is 3s~6s.

[0021] Optionally, the ammonia absorption is carried out using countercurrent absorption, and the countercurrent absorption level is ≤3.

[0022] Optionally, the mass concentration of the ammonia water is 10% to 20%.

[0023] The technical solutions provided in this application have the following advantages compared with the prior art:

[0024] This application provides a method for denitrifying aluminum ash, wherein the aluminum ash contains soluble salts and nitrogen salts. The method includes: desalting the aluminum ash with an aqueous solution to obtain a desalted aluminum ash suspension; dehydrating the desalted aluminum ash to obtain hydrated aluminum ash with a preset moisture content; and denitrifying the hydrated aluminum ash with the preset moisture content to obtain denitrified aluminum ash; wherein the preset moisture content is ≤30%. Aqueous solutions can leach out soluble salts from aluminum ash, separating the soluble salts from the aluminum ash to obtain a desalted aluminum ash suspension. The desalted aluminum ash suspension is then dehydrated to obtain a pre-defined water content of ≤30% for the water-containing aluminum ash. This water-containing aluminum ash exists in a solid-liquid mixed state, containing both aluminum ash solids and water. During the denitrification process, the aluminum ash solids can effectively transfer heat, accelerating water evaporation and rapidly forming sufficient water vapor. On one hand, this sufficient water vapor reacts with the nitrogen salts in the aluminum ash to generate ammonia, thus completing the denitrification of the aluminum ash. On the other hand, the sufficient water vapor can also effectively transfer mass, accelerating the denitrification process and improving the efficiency of aluminum ash denitrification. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic flowchart of a method for denitrifying aluminum ash provided in an embodiment of this application;

[0028] Figure 2 This is a detailed flowchart illustrating a method for denitrifying aluminum ash provided in an embodiment of this application. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range such as 1, 2, 3, 4, 5, and 6, regardless of the range; in addition, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0031] In this document, terms including "comprising" and the like mean "including but not limited to". "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A alone, A and B simultaneously, or B alone; where A and B can be singular or plural. "At least one" means one or more, and "more than one" means two or more. "At least one", "at least one of the following", or similar expressions refer to any combination of these items, including any combination of singular or plural items; for example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this application are commercially available or can be prepared using existing methods.

[0032] It should be noted that the environmental hazards of secondary aluminum ash are mainly reflected in the following three aspects:

[0033] (1) The leaching toxicity of fluoride in secondary aluminum ash exceeds the standard of "Identification Standard for Hazardous Waste" (100 mg / L). In addition, secondary aluminum ash is highly corrosive, and the corrosivity of some secondary aluminum ash exceeds the standard of "Identification Standard for Hazardous Waste" (pH value 12.5). Direct storage of secondary aluminum ash will lead to an increase in the pH value of surrounding groundwater and soil, and will also lead to fluoride pollution of surrounding groundwater and soil.

[0034] (2) Secondary aluminum ash contains aluminum-containing substances such as aluminum nitride, metallic aluminum, and aluminum carbide. These aluminum-containing substances release a large amount of ammonia when they come into contact with water. In addition, the process will also produce flammable and explosive gases such as hydrogen and methane. This makes the direct storage of secondary aluminum ash a potential safety hazard.

[0035] (3) Secondary aluminum ash contains a large amount of soluble salts (such as chlorides and fluorides). The dissolution, leaching and accumulation of these soluble salts can lead to soil salinization and pollution of surrounding groundwater.

[0036] Figure 1 An exemplary schematic diagram of a method for denitrification of aluminum ash provided in an embodiment of this application is shown;

[0037] like Figure 1 As shown in the embodiments of this application, a method for denitrifying aluminum ash is provided, wherein the aluminum ash contains soluble salts and nitrogen salts, and the method includes:

[0038] S1. Desalinate aluminum ash using an aqueous solution to obtain a desalinated aluminum ash suspension;

[0039] S2. The desalinated aluminum ash suspension is dehydrated to obtain aqueous aluminum ash with a preset moisture content;

[0040] S3. The aqueous aluminum ash with a preset moisture content is subjected to denitrification treatment to obtain denitrified aluminum ash;

[0041] Wherein, the preset moisture content is ≤30%;

[0042] In these embodiments, the preset moisture content can be ≤30%. Aluminum ash with a moisture content of ≤30% is in a solid-liquid mixed state. The aluminum ash in the solid-liquid mixed state contains aluminum ash solids and water. During the denitrification process, the aluminum ash solids can have a good heat transfer effect to accelerate the evaporation of water and quickly form sufficient water vapor. On the one hand, sufficient water vapor will react with the nitrogen salts of aluminum ash to generate ammonia gas, thereby completing the denitrification of aluminum ash. On the other hand, sufficient water vapor can have a good mass transfer effect to accelerate the denitrification process, thereby improving the denitrification efficiency of aluminum ash.

[0043] It should be noted that the denitrification treatment can be carried out by drying, and the drying can be carried out using a moving bed furnace, which may include at least one of the following:

[0044] Rotary kilns, fluidized bed furnaces, spray drying towers, fluidized bed roasting furnaces, and multi-hearth furnaces can promote thorough drying, enabling sufficient moisture in the hydrated aluminum ash to form sufficient water vapor. This sufficient water vapor can create a high-temperature environment during the drying process, which can accelerate the reaction of water vapor with nitrogen and aluminum nitride in the aluminum ash to form ammonia, thereby improving the denitrification efficiency of the drying process.

[0045] It should be noted that this desalination process can be carried out under normal pressure using a stirring method.

[0046] It should be noted that this dehydration process can be carried out using multiple filtrations.

[0047] In some optional embodiments, the temperature of the denitrification treatment is ≤600°C;

[0048] In these embodiments, the temperature of the denitrification treatment can be ≤600℃, which can accelerate the heat transfer process of the aluminum ash solid, so as to promote the rapid evaporation of moisture in the water-containing aluminum ash and quickly form sufficient water vapor. On the one hand, sufficient water vapor will react with the nitrogen salts of aluminum ash to generate ammonia, thereby completing the denitrification of aluminum ash. On the other hand, sufficient water vapor can carry out good mass transfer to accelerate the denitrification process and thus improve the denitrification efficiency of aluminum ash.

[0049] In some optional embodiments, the temperature of the denitrification treatment is 100°C to 600°C;

[0050] In these embodiments, the temperature of the denitrification treatment can be 100℃ to 600℃, which can further accelerate the heat transfer process of the aluminum ash solid, so as to promote the rapid evaporation of moisture in the water-containing aluminum ash and quickly form sufficient water vapor. On the one hand, sufficient water vapor will react with the nitrogen salts of aluminum ash to generate ammonia, thereby completing the denitrification of aluminum ash. On the other hand, sufficient water vapor can further carry out good mass transfer to accelerate the denitrification process and thus improve the denitrification efficiency of aluminum ash.

[0051] The drying temperature can be 100℃, 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃ or 600℃.

[0052] In some optional embodiments, the liquid-to-solid ratio of the aqueous solution to the aluminum ash is 0.5 to 2:1;

[0053] In these embodiments, the liquid-to-solid ratio of the aqueous solution and aluminum ash can be 0.5 to 2:1. The aqueous solution can be used to leach the soluble salts of the aluminum ash to separate the soluble salts from the aluminum ash, thereby obtaining a pure desalted aluminum ash aqueous suspension.

[0054] The liquid-to-solid ratio of the aqueous solution and aluminum ash can be 0.5:1, 1.0:1, 1.5:1, or 2:1.

[0055] In some optional embodiments, the temperature of the desalination treatment is 80°C to 100°C, and the time of the desalination treatment is 10 min to 30 min;

[0056] In these embodiments, the temperature of the desalination treatment can be 80°C to 100°C, and the time of the desalination treatment can be 10 min to 30 min, which can promote the aqueous solution to fully leach out the soluble salts of aluminum ash during the desalination treatment, so as to separate the soluble salts from the aluminum ash, thereby obtaining a pure desalted aluminum ash aqueous suspension solution.

[0057] The temperature for the desalination process can be 80℃, 85℃, 90℃, 95℃ or 100℃.

[0058] The desalination treatment time can be 10 min, 15 min, 20 min, 25 min or 30 min.

[0059] In some optional embodiments, the desalination process includes desalination using a countercurrent elution method, wherein the countercurrent elution level is ≤3.

[0060] In these embodiments, the desalination process may include desalination using a countercurrent elution method, and the countercurrent elution level may be ≤3. The countercurrent elution method can promote the aqueous solution to fully leach out the soluble salts of aluminum ash, so as to separate the soluble salts from the aluminum ash, thereby obtaining a pure desalted aluminum ash aqueous suspension.

[0061] Figure 2 A detailed flowchart illustrating a method for denitrification of aluminum ash provided in an embodiment of this application is shown as an example.

[0062] like Figure 2 As shown, in some optional embodiments, the method further includes:

[0063] S101. Aqueous solution is used to desalinate aluminum ash to obtain desalinated aluminum ash suspension and desalinated tail gas, respectively;

[0064] S102. The desalted aluminum ash suspension is dehydrated to obtain aqueous aluminum ash with a preset moisture content;

[0065] S103. The aqueous aluminum ash with a preset moisture content is subjected to denitrification treatment to obtain denitrified aluminum ash and denitrified tail gas, respectively;

[0066] S104. The desalination tail gas and the denitrification tail gas are cooled by heat exchange, and then ammonia is absorbed by spraying to obtain ammonia water;

[0067] In these embodiments, the method may also include heat exchange and cooling of desalination tail gas and denitrification tail gas, and ammonia absorption by spraying, so as to recover and reuse the desalination tail gas and denitrification tail gas generated by desalination treatment, thereby realizing the recovery and reuse of nitrogen element in aluminum ash.

[0068] It should be noted that this spraying method uses an aqueous solution.

[0069] In some optional embodiments, the temperature for ammonia absorption is 20°C to 30°C, and the time for ammonia absorption is 3s to 6s;

[0070] In these embodiments, the temperature for ammonia absorption can be 20°C to 30°C, and the absorption time can be 3s to 6s, which can promote the ammonia absorption process to proceed fully, thereby enabling the recovery and utilization of desalination tail gas generated by desalination treatment and denitrification tail gas generated by denitrification treatment, and thus enabling the full recovery of nitrogen elements from aluminum ash and aluminum nitride.

[0071] The temperature for ammonia absorption can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃.

[0072] The ammonia absorption time can be 3s, 4s, 5s, or 6s.

[0073] In some optional embodiments, the ammonia absorption is carried out using countercurrent absorption, wherein the countercurrent absorption level is ≤3.

[0074] In these embodiments, ammonia absorption can be carried out using countercurrent absorption. The countercurrent absorption level can be ≤3. Countercurrent absorption can be used to ensure that the aqueous solution is fully contacted with the desalination tail gas generated from the desalination treatment and the denitrification tail gas generated from the denitrification treatment, so that the nitrogen element of the desalination tail gas and the denitrification tail gas dissolves in the aqueous solution, thereby fully recovering the nitrogen element of the nitrogen salt of aluminum ash.

[0075] In some optional embodiments, the mass concentration of the ammonia solution is 10% to 20%;

[0076] In these embodiments, the mass concentration of ammonia water can be 10% to 20%, indicating that the method provided in this application can fully recover nitrogen elements from aluminum ash and aluminum nitride.

[0077] The mass concentration of the ammonia water can be 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 26℃, 17℃, 18℃, 19℃ or 20℃.

[0078] The present application is further illustrated below with reference to specific embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards; if no corresponding industry standard exists, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0079] Example 1

[0080] like Figure 2 As shown in the embodiments of this application, a method for denitrifying aluminum ash is provided. The aluminum ash contains aluminum nitride, soluble salts, and nitrogen, including:

[0081] S101. Aqueous solution is used to desalinate aluminum ash to obtain desalinated aluminum ash suspension and desalinated tail gas, respectively;

[0082] S102. The desalted aluminum ash suspension is dehydrated to obtain aqueous aluminum ash with a preset moisture content;

[0083] S103. The aqueous aluminum ash with a preset moisture content is subjected to denitrification treatment to obtain denitrified aluminum ash and denitrified tail gas, respectively;

[0084] S104. The desalination tail gas and denitrification tail gas are cooled by heat exchange, and then ammonia is absorbed by spraying to obtain ammonia water;

[0085] The preset moisture content is 15%.

[0086] The rotary kiln rotates at a speed of 3 r / min;

[0087] The temperature for denitrification is 100℃~200℃.

[0088] The liquid-to-solid ratio of the aqueous solution and aluminum ash is 2:1.

[0089] The desalination temperature was 80℃ and the desalination time was 30 minutes.

[0090] The desalination process includes desalination using countercurrent elution, with three stages of countercurrent elution and each stage lasting 10 minutes.

[0091] The ammonia absorption temperature is 25℃, and the ammonia absorption time is 6s.

[0092] Ammonia absorption is carried out using countercurrent absorption, with one stage of countercurrent absorption and a duration of 6 seconds for each stage.

[0093] The mass concentration of ammonia water is 10%.

[0094] Performance data: With the denitrification rate of denitrified aluminum ash ≥99% as the endpoint of denitrification treatment, the completion time of denitrification treatment was 30 minutes, and the soluble salt removal rate of desalinated aluminum ash was 99.1%, the denitrification rate of denitrified aluminum ash was 99.0%, and the ammonia absorption rate was 98.1%.

[0095] Example 2

[0096] Based on the method disclosed in Example 1, the following modifications are made:

[0097] The preset moisture content is 18%.

[0098] The denitrification process is carried out in a multi-hearth furnace.

[0099] The temperature for denitrification is 200℃~300℃.

[0100] The liquid-to-solid ratio of the aqueous solution and aluminum ash is 1.5:1.

[0101] The desalination temperature was 90℃ and the desalination time was 24 minutes.

[0102] The desalination process includes desalination using countercurrent elution, with two stages of countercurrent elution and each stage lasting 12 minutes.

[0103] The ammonia absorption temperature is 30℃, and the ammonia absorption time is 6s.

[0104] Ammonia absorption is carried out using countercurrent absorption, with three levels of countercurrent absorption and each level lasting 2 seconds.

[0105] The mass concentration of ammonia water is 18%.

[0106] The denitrification rate of denitrified aluminum ash was ≥99% as the endpoint of the denitrification treatment. The final completion time of the denitrification treatment was 15 min, and the soluble salt removal rate of desalinated aluminum ash was 98.5%, the denitrification rate of denitrified aluminum ash was 99.3%, and the ammonia absorption rate was 98.9%.

[0107] Example 3

[0108] Based on the method disclosed in Example 1, the following modifications are made:

[0109] The preset moisture content is 20%.

[0110] The denitrification process is carried out in a fluidized bed roasting furnace.

[0111] The temperature for denitrification is 300℃~400℃.

[0112] The liquid-to-solid ratio of the aqueous solution and aluminum ash is 2.0:1.

[0113] The desalination temperature was 90℃ and the desalination time was 15 minutes.

[0114] The desalination process includes desalination using countercurrent elution, with one stage of countercurrent elution and a time of 15 minutes for each stage.

[0115] The ammonia absorption temperature is 20℃, and the ammonia absorption time is 5s.

[0116] Ammonia absorption is carried out using countercurrent absorption, with one stage of countercurrent absorption and a duration of 5 seconds for each stage.

[0117] The mass concentration of ammonia water is 15%.

[0118] The denitrification rate of denitrified aluminum ash was ≥99% as the endpoint of the denitrification treatment. The final completion time of the denitrification treatment was 5 minutes. The soluble salt removal rate of desalinated aluminum ash was 98.1%, the denitrification rate of denitrified aluminum ash was 99.5%, and the ammonia absorption rate was 98.5%.

[0119] Example 4

[0120] Based on the method disclosed in Example 1, the following modifications are made:

[0121] The preset moisture content is 20%.

[0122] The denitrification process is carried out in a fluidized bed furnace.

[0123] The temperature for denitrification is 400℃~500℃.

[0124] The liquid-to-solid ratio of the aqueous solution and aluminum ash is 0.5:1.

[0125] The desalination temperature was 95℃ and the desalination time was 20 minutes.

[0126] The desalination process includes desalination using countercurrent elution, with two stages of countercurrent elution and each stage lasting 10 minutes.

[0127] The ammonia absorption temperature is 25℃, and the ammonia absorption time is 4s.

[0128] Ammonia absorption is carried out using countercurrent absorption, with two stages of countercurrent absorption and each stage lasting 2 seconds.

[0129] The mass concentration of ammonia water is 16%.

[0130] The denitrification rate of denitrified aluminum ash was ≥99% as the endpoint of the denitrification treatment. The final completion time of the denitrification treatment was 1 minute. The soluble salt removal rate of desalinated aluminum ash was 99.4%, the denitrification rate of denitrified aluminum ash was 99.4%, and the ammonia absorption rate was 98.8%.

[0131] Example 5

[0132] Based on the method disclosed in Example 1, the following modifications are made:

[0133] The preset moisture content is 30%.

[0134] The denitrification process is carried out in a spray drying tower.

[0135] The temperature for denitrification is 500℃~600℃.

[0136] The liquid-to-solid ratio of the aqueous solution and aluminum ash is 1:1.

[0137] The desalination temperature was 100℃ and the desalination time was 10 minutes.

[0138] The desalination process includes desalination using countercurrent elution, with one stage of countercurrent elution and a time of 10 minutes for each stage.

[0139] The ammonia absorption temperature is 20℃, and the ammonia absorption time is 6s.

[0140] Ammonia absorption is carried out using countercurrent absorption, with two levels of countercurrent absorption and each level lasting 3 seconds.

[0141] The mass concentration of ammonia water is 20%.

[0142] The denitrification rate of the denitrified aluminum ash was ≥99% as the endpoint of the denitrification treatment. The final completion time of the denitrification treatment was 0.2 min, and the soluble salt removal rate of the desalinated aluminum ash was 98.2%, the denitrification rate of the denitrified aluminum ash was 99.3%, and the ammonia absorption rate was 99.2%.

[0143] Comparative Example 1

[0144] Based on the method disclosed in Example 1, the following modifications are made:

[0145] The moisture content of the water-containing aluminum ash should be controlled to be greater than 30%.

[0146] The denitrification rate of the denitrified aluminum ash was defined as ≥99% as the endpoint of the denitrification treatment. The final completion time of the denitrification treatment was determined to be 30 minutes. The removal rate of soluble salts from the desalinated aluminum ash was 99.1%, the denitrification rate of the denitrified aluminum ash was 99.1%, and the ammonia absorption rate was 96.3%. This indicates that a moisture content >30% in the water-containing aluminum ash increased the energy consumption of the denitrification treatment and reduced the ammonia absorption rate.

[0147] Comparative Example 2

[0148] Based on the method disclosed in Example 1, the following modifications are made:

[0149] The temperature for denitrification is 80℃.

[0150] The denitrification rate of denitrified aluminum ash was ≥99% as the endpoint of the denitrification treatment. The final completion time of the denitrification treatment was 1500 min. The soluble salt removal rate of desalinated aluminum ash was 99.1%, the denitrification rate of denitrified aluminum ash was 99.0%, and the ammonia absorption rate was 80.9%.

[0151] Comparative Example 3

[0152] Based on the method disclosed in Example 1, the following modifications are made:

[0153] The denitrification treatment temperature is 800℃.

[0154] The denitrification rate of the denitrified aluminum ash was defined as ≥99%, and the final completion time of the denitrification process was determined to be 10 minutes. The removal rate of soluble salts from the desalinated aluminum ash was 99.1%, the denitrification rate of the denitrified aluminum ash was 99.4%, and the ammonia absorption rate was 94.7%. Furthermore, during the decarbonization process, it was observed that some aluminum nitride in the aluminum ash was converted into nitrogen gas, which reduced the efficiency of aluminum nitride conversion to ammonia gas by 3.2%.

[0155] Relevant results and data:

[0156] As can be seen from the data in Comparative Example 3, aluminum nitride can also be denitrified using a high-temperature oxygen-containing method to promote the conversion of aluminum nitride into aluminum oxide. However, the high-temperature oxygen-containing method requires a temperature above 600℃ (in order to obtain a good removal effect, some high-temperature oxygen-containing methods require a temperature of 1000℃ or even higher). At the same time, this high-temperature oxygen-containing method will also generate nitrogen gas during the denitrification process, which will affect the nitrogen absorption effect.

[0157] In summary, the method for denitrifying aluminum ash provided in this application embodiment allows for the leaching of soluble salts from the aluminum ash using an aqueous solution, thereby achieving the separation of soluble salts from the aluminum ash. The desalted aluminum ash suspension is then dehydrated to obtain aqueous aluminum ash with a preset moisture content ≤30%. The aqueous aluminum ash with a moisture content ≤30% is in a solid-liquid mixed state, which can improve the efficiency of aluminum ash denitrification.

[0158] Meanwhile, the method for denitrifying aluminum ash provided in this application embodiment is based on the fact that aluminum nitride in aluminum ash can be hydrolyzed and deaminated in a watery environment to transform into aluminum oxygen-containing compounds. Furthermore, water vapor and liquid water have the same reactivity under normal pressure. When water vapor is generated from water-containing aluminum ash in a solid-liquid mixed state and the water vapor reacts with aluminum nitride, the high temperature environment of the water vapor can increase the reaction rate of hydrolysis and deamination, thereby accelerating the hydrolysis and deamination process. In addition, the embodiment of this application controls the moisture content of the water-containing aluminum ash before drying to ≤30%, which can effectively improve the ammonia absorption rate of aluminum ash and reduce the energy consumption of the overall process.

[0159] In addition, the aluminum ash denitrification method provided in this application has the characteristics of low equipment cost and mild reaction conditions in the desalination and denitrification processes. Furthermore, the denitrification process has a shorter reaction time and lower reaction temperature than the prior art, which not only improves the safety of the denitrification process but also reduces the cost of the denitrification process.

[0160] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed in this application.

Claims

1. A method for denitrifying aluminum ash, wherein the aluminum ash contains soluble salts and nitrogen salts, characterized in that, The method includes: Aqueous solutions were used to desalinate aluminum ash to obtain desalinated aluminum ash suspension and desalinated tail gas, respectively. The desalinated aluminum ash suspension is dehydrated to obtain a water-containing aluminum ash in a solid-liquid mixed state with a preset water content. The aqueous aluminum ash with a preset moisture content is subjected to denitrification treatment to obtain denitrified aluminum ash and denitrification tail gas, respectively. The denitrification treatment temperature is 200℃~600℃, and the denitrification treatment is carried out by drying, which is carried out in any one of rotary kiln, fluidized bed furnace, spray drying tower, fluidized bed roasting furnace and multi-hearth furnace. The desalination tail gas and denitrification tail gas are cooled by heat exchange, and then ammonia is absorbed by spraying to obtain ammonia water. Wherein, the preset moisture content is 15% to 30%, and the liquid-to-solid ratio of the aqueous solution to the aluminum ash is 0.5 to 2:1; The ammonia absorption temperature is 20℃~30℃, and the ammonia absorption time is 3s~6s.

2. The method according to claim 1, characterized in that, The desalination treatment temperature is 80℃~100℃, and the desalination treatment time is 10min~30min.

3. The method according to claim 1, characterized in that, The desalination process includes desalination using a countercurrent elution method, wherein the countercurrent elution level is ≤3.

4. The method according to claim 1, characterized in that, The ammonia absorption is carried out using countercurrent absorption, and the countercurrent absorption level is ≤3.

5. The method according to claim 1, characterized in that, The mass concentration of the ammonia water is 10% to 20%.

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