A process for the co-production of pseudoboehmite and soft water

Abstract

The application relates to the technical field of pseudo-boehmite preparation, in particular to a method for co-producing pseudo-boehmite and soft water. The method comprises the following steps: carbonation and neutralization reaction of carbon dioxide gas into a sodium aluminate solution, first aging treatment and filtration, to obtain first solid-phase materials and first liquid-phase materials; the first solid-phase materials are sequentially subjected to washing and drying, to obtain first pseudo-boehmite; aluminum sulfate and the sodium aluminate solution are subjected to parallel neutralization treatment, to obtain second neutralization slurry; the second neutralization slurry and the first liquid-phase materials are mixed, to obtain mixed slurry; the mixed slurry is subjected to second aging treatment and filtration, to obtain second solid-phase materials and second liquid-phase materials; the second solid-phase materials are washed, to obtain second pseudo-boehmite; the second liquid-phase materials are subjected to membrane separation, to obtain soft water. The method realizes significant reduction of the concentration of alkaline substances in waste water by integrating the process and recycling waste liquid, and consumes the alkaline substances generated in the previous stage by subsequent reactions.

Description

Technical Field

[0001] This application relates to the field of boehmite preparation technology, and more particularly to a method for co-producing boehmite and soft water. Background Technology

[0002] Pseudobosite is crucial in industrial applications such as catalyst supports and binders. Currently, pseudoboehmite is generally produced through the carbonization process. However, the carbonization process consumes a large amount of washing water, which contains a large amount of alkaline substances (sodium carbonate / potassium, sodium bicarbonate / potassium, sodium hydroxide / potassium). This washing wastewater is difficult to treat using nanofiltration membrane separation systems, making it difficult to achieve soft water recycling.

[0003] To address this issue, current methods rely on evaporators to extract the soft water component. However, the high alkaline content in the washing wastewater increases the load on the evaporator and energy consumption, while also limiting the production of pseudoboehmite. Therefore, reducing the concentration of alkaline substances in the washing wastewater is crucial for alleviating the evaporator load and achieving energy savings and increased production. Summary of the Invention

[0004] This application provides a method for co-producing pseudoboehmite and soft water to solve the following technical problem: how to reduce the concentration of alkaline substances in the washing wastewater of the carbonization process.

[0005] In a first aspect, embodiments of this application provide a method for co-producing pseudoboehmite and soft water, the method comprising:

[0006] Carbon dioxide gas is passed into sodium aluminate solution to carry out a carbonization and neutralization reaction, resulting in the first neutralized slurry.

[0007] The first neutralized slurry is subjected to a first aging treatment to obtain a first aged slurry;

[0008] The first aging slurry is filtered to obtain a first solid phase material and a first liquid phase material;

[0009] The first solid material was washed and dried sequentially to obtain the first pseudoboehmite;

[0010] Aluminum sulfate and sodium aluminate solution are subjected to co-current neutralization treatment to obtain a second neutralized slurry;

[0011] The second neutralized slurry and the first liquid phase material are mixed to obtain a mixed slurry;

[0012] The mixed slurry is subjected to a second aging treatment to obtain a second aged slurry;

[0013] The second aging slurry is filtered to obtain a second solid phase material and a second liquid phase material;

[0014] The second solid material was washed to obtain the second pseudoboehmite;

[0015] The second liquid phase material is subjected to membrane separation to obtain soft water.

[0016] Optionally, the carbonization neutralization reaction is carried out at a temperature of 25°C to 60°C for a time of 10 min to 15 min; and / or

[0017] The temperature of the parallel flow neutralization process is 40°C to 90°C.

[0018] Optionally, the pH of the first neutralized slurry is 9.5 to 12.5.

[0019] Optionally, the pH of the second neutralized slurry is 4.5 to 7.0.

[0020] Optionally, the temperature of the first aging treatment is 70°C to 80°C, and the duration of the first aging treatment is 3.5h to 4.5h.

[0021] Optionally, the temperature of the second aging treatment is 60°C to 95°C, and the duration of the second aging treatment is 1 hour to 4 hours.

[0022] Optionally, the volume V1 of the second neutralized slurry and the volume V2 of the first liquid phase material satisfy: V1:V2 = (4:1) to (1:2).

[0023] Optionally, the alumina mass concentration of the second neutralizing slurry is from 50 g / L to 150 g / L.

[0024] Optionally, the mass concentration of the alkaline substance in the second liquid phase material is from 2.97 g / L to 4.57 g / L; and / or

[0025] The conductivity of the soft water is from 15 μS / cm to 30 μS / cm.

[0026] Optionally, the crystallinity of the first pseudoboehmite is 72.8% to 79.6%; and / or

[0027] The crystallinity of the second pseudoboehmite is 51.8% to 53.1%.

[0028] The technical solutions provided in this application have the following advantages compared with the prior art:

[0029] This application provides a method for co-producing pseudoboehmite and soft water. The method uses a carbonization neutralization reaction of carbon dioxide and sodium aluminate solution, followed by a first aging treatment, to obtain a first aged slurry containing alkaline substances. Filtering the first aged slurry yields not only a first solid phase material but also a first liquid phase material containing alkaline substances. This first liquid phase material can serve as an alkaline auxiliary agent in the co-current neutralization treatment of aluminum sulfate and the sodium aluminate solution. A second neutralization slurry can consume alkaline substances such as sodium carbonate in the first liquid phase material, thereby reducing the concentration of alkaline substances in the mixed slurry. This avoids the direct discharge of high-concentration alkaline wastewater and effectively reduces the concentration of alkaline substances in the washing wastewater from the carbonization process. Attached Figure Description

[0030] 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.

[0031] 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.

[0032] Figure 1 This is a schematic diagram of a method for co-producing pseudoboehmite and soft water, provided as an embodiment of this application. Detailed Implementation

[0033] 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.

[0034] The range descriptions used in this application, such as numerical ranges and proportional ranges, include all possible sub-ranges and single numerical values ​​within that range. For example, the range descriptions of "1 to 6" or "1 to 6" cover all sub-ranges (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6) between 1 and 6. Unless otherwise specified, the terms "comprising" and others used herein mean "including but not limited to"; relational terms such as "first" and "second" are used only to distinguish different entities or operations and do not imply an actual order or relationship; "and / or" indicates that multiple situations can exist individually or simultaneously; expressions such as "at least one," "multiple," and "at least one" refer to any combination of the corresponding objects, including combinations of single or multiple objects. The proportional relationships involved in this document, such as mass ratios and molar ratios, should be understood as the correspondence between the first and second terms of a proportional formula, according to the order of description. The raw materials, reagents, instruments, and equipment used herein can all be obtained by purchasing from the market or by existing methods.

[0035] It should be noted that, regarding the prior art described in the background section, the inventors have also discovered that the neutralization method for preparing boehmite requires the addition of an alkaline additive to increase the pH of the system, ensuring the pH of the reaction system is within a suitable range to promote the growth and formation of boehmite crystals. If the washing wastewater from the carbonization method could be used as an alkaline additive to replace the alkaline additive used in the neutralization method, not only could the alkalinity of the washing wastewater be reduced, but the preparation cost of boehmite by the neutralization method could also be improved. However, directly using washing wastewater to replace alkaline additives (such as sodium aluminate) makes it difficult to guarantee the production capacity of boehmite per unit volume.

[0036] Figure 1 An exemplary schematic diagram of a method for co-producing pseudoboehmite and soft water according to an embodiment of this application is shown;

[0037] like Figure 1 As shown in the embodiment of this application, a method for co-producing pseudoboehmite and soft water is provided, the method comprising:

[0038] S1. Carbon dioxide gas is passed into sodium aluminate solution to carry out carbonization and neutralization reaction, and the first neutralized slurry is obtained;

[0039] S2. The first neutralized slurry is subjected to a first aging treatment to obtain a first aged slurry;

[0040] S3. Filter the first aging slurry to obtain a first solid phase material and a first liquid phase material;

[0041] S4. The first solid material is washed and dried sequentially to obtain the first pseudoboehmite;

[0042] S5. The aluminum sulfate and the sodium aluminate solution are subjected to co-current neutralization treatment to obtain a second neutralized slurry;

[0043] S6. Mix the second neutralized slurry and the first liquid phase material to obtain a mixed slurry;

[0044] S7. The mixed slurry is subjected to a second aging treatment to obtain a second aged slurry;

[0045] S8. Filter the second aging slurry to obtain a second solid phase material and a second liquid phase material;

[0046] S9. The second solid material is washed to obtain the second pseudoboehmite;

[0047] S10. The second liquid phase material is subjected to membrane separation to obtain soft water.

[0048] It should be noted that this carbonization and neutralization reaction can be carried out under stirring conditions.

[0049] It should be noted that this parallel flow neutralization process can be carried out using a peristaltic pump.

[0050] It should be noted that the flow rate of the carbon dioxide gas can be from 30 L / min to 50 L / min, and the introduction time of the carbon dioxide can be from 10 min to 15 min.

[0051] It should be noted that the method for co-producing pseudoboehmite and soft water provided in this application embodiment recycles alkaline waste liquid (first liquid phase material) as raw material for subsequent neutralization reactions, significantly reducing the concentration of alkaline substances in the final discharged waste liquid (second liquid phase material). Its core mechanism is as follows:

[0052] 1. The first process generates waste liquid containing alkaline substances:

[0053] CO2 is passed into a sodium aluminate solution (NaAlO2) to carry out a carbonization and neutralization reaction:

[0054] 2NaAlO2+CO2+3H2O→2Al(OH)3↓+Na2CO3;

[0055] After the reaction, filtration yielded the first pseudoboehmite (Al(OH)3 or its dehydrated form) and the first liquid phase material.

[0056] Key point: The main components of the first liquid phase material are the Na2CO3 (sodium carbonate) solution generated by the reaction, as well as residual potassium carbonate, sodium / potassium bicarbonate, and sodium / potassium hydroxide. This is the main source of wastewater in the traditional carbonation method, and the concentration is relatively high.

[0057] 2. The second process consumes sodium carbonate:

[0058] Aluminum sulfate (Al2(SO4)3) and sodium aluminate (NaAlO2) were subjected to a co-current neutralization reaction:

[0059] Al2(SO4)3+6NaAlO2+12H2O→8Al(OH)3↓+3Na2SO4;

[0060] Theoretically, this co-current neutralization process should produce Al(OH)3 precipitate and Na2SO4 (sodium sulfate) solution.

[0061] Key point: After obtaining the second neutralized slurry, the first liquid phase material rich in Na2CO3 is immediately added to the second neutralized slurry to form a mixed slurry.

[0062] 3. The key reaction in the mixed slurry – the consumption of alkaline substances:

[0063] The mixed slurry contains:

[0064] Newly formed Al(OH)3 colloid (from the aluminum sulfate / sodium aluminate reaction);

[0065] Unreacted Al2(SO4)3 and / or NaAlO2 (depending on neutralization point control);

[0066] Added Na2CO3;

[0067] The generated Na2SO4.

[0068] In these materials, Na2CO3 will react with Al2(SO4)3 present in the mixed slurry:

[0069] 3Na2CO3+Al2(SO4)3+3H2O→2Al(OH)3↓+Na2SO4+3CO2↑;

[0070] or,

[0071] Na2CO3 will react with unreacted Al 3+ (From Al2(SO4)3) reacts to form aluminum carbonate, which is extremely unstable and hydrolyzes instantaneously.

[0072] Al 3+ +CO3 2- →Al2(CO3)3 (instantaneous)→2Al(OH)3↓+3CO2↑.

[0073] 4. Result - The concentration of alkaline substances decreased significantly:

[0074] During the second aging process of the mixed slurry, the above reaction occurs, transforming the Na2CO3 originally present in the first liquid phase material into:

[0075] Additional Al(OH)3 precipitate (becomes part of the second pseudoboehmite, increasing product yield);

[0076] Volatile CO2 gas (may escape or be recovered);

[0077] And Na2SO4.

[0078] Therefore, the second liquid phase material obtained after the second aging treatment and filtration exhibits the following characteristics:

[0079] The concentration of Na2CO3 was greatly consumed and reduced;

[0080] The main solute was changed to Na2SO4 (sodium sulfate), which is more chemically stable and easier to handle.

[0081] 5. Final processing:

[0082] The second liquid phase material (mainly containing Na2SO4) is further processed through membrane separation (e.g., reverse osmosis) to obtain soft water. At this point, the difficulty and cost of treating the Na2SO4 solution are far lower than those of treating a high-concentration Na2CO3 solution.

[0083] Therefore, the method for co-producing boehmite and soft water provided in this application embodiment is key to reducing the concentration of alkaline substances in carbonation washing wastewater by introducing the waste liquid (first liquid phase material) containing high concentration of sodium carbonate generated in the carbonation neutralization reaction section as a resource into the co-current neutralization treatment section of aluminum sulfate / sodium aluminate. In this subsequent neutralization / aging environment, sodium carbonate undergoes a metathesis reaction with aluminum sulfate, effectively converting into second boehmite and relatively harmless sodium sulfate, thereby realizing the consumption and conversion of sodium carbonate within the system and avoiding the direct discharge of high-concentration sodium carbonate wastewater. This not only reduces the difficulty and cost of wastewater treatment (ultimately only a solution mainly composed of sodium sulfate needs to be treated), but also improves the overall utilization rate of aluminum resources (recovering more aluminum hydroxide products). Essentially, this method achieves a significant reduction in the concentration of sodium carbonate in wastewater by consuming the alkaline substances (sodium carbonate) generated in the previous stage through process integration and waste liquid resource utilization in subsequent reactions.

[0084] In some optional embodiments, the carbonization neutralization reaction is carried out at a temperature of 25°C to 60°C for a duration of 10 min to 15 min; and / or

[0085] The temperature of the parallel flow neutralization process is 40°C to 90°C.

[0086] In these embodiments, a carbonization neutralization reaction at a temperature of 25°C to 60°C and a time of 10 min to 15 min can promote a sufficient reaction between carbon dioxide and sodium aluminate solution to form a first neutralization slurry containing alkaline substances. This is beneficial for obtaining a first liquid phase material containing alkaline substances in the subsequent process. This first liquid phase material can act as an alkaline additive to facilitate the transformation of the second neutralization slurry into pseudo-boehmite and effectively reduce the content of alkaline substances such as sodium carbonate in the first liquid phase material.

[0087] The temperature for the carbonization and neutralization reaction can be 25°C, 30°C, 40°C, 50°C, or 60°C.

[0088] The carbonization and neutralization reaction can take 10 min, 11 min, 12 min, 14 min, or 15 min.

[0089] In some alternative implementations, the pH of the first neutralized slurry is 9.5 to 12.5.

[0090] In these embodiments, the first neutralization slurry with a pH of 9.5 to 12.5 can make the first neutralization slurry contain a certain amount of alkaline substances, which is beneficial to the subsequent reaction between the first liquid phase material and the second neutralization slurry, and promotes the transformation of the second neutralization slurry into pseudoboehmite, so as to effectively reduce the content of alkaline substances in the first liquid phase material.

[0091] The pH of the first neutralizing slurry can be 9.5, 10.0, 10.5, 11.0, 11.5, 12.0, or 12.5.

[0092] It should be noted that if the pH of the first neutralizing slurry is less than 9.5, the crystallinity of the first pseudoboehmite will be too low, and the content of alkaline substances in the first liquid phase material will be insufficient, making it difficult to serve as an alkaline reagent for the subsequent second neutralizing slurry. If the pH of the first neutralizing slurry is greater than 12.5, gibbsite impurities will directly appear in the first pseudoboehmite, and the gibbsite impurities in the subsequent second pseudoboehmite will also increase, affecting the gibbsite impurities in the final pseudoboehmite.

[0093] In some alternative embodiments, the pH of the second neutralized slurry is 4.5 to 7.0.

[0094] In these embodiments, the second neutralization slurry with a pH of 4.5 to 7.0 can promote the presence of sufficient Al(OH)3 colloids in the second neutralization slurry, which is beneficial for the subsequent reaction between the second neutralization slurry and the first liquid phase material. This effectively reduces the content of alkaline substances such as sodium carbonate in the first liquid phase material, which is beneficial for obtaining soft water products.

[0095] The pH of the second neutralizing slurry can be 4.5, 5.0, 5.5, 6.0, 6.5 or 7.0.

[0096] It should be noted that if the pH of the second neutralization slurry is less than 4.5, it will be difficult for alumina compounds to precipitate from the second neutralization slurry, affecting the yield of the second pseudoboehmite. If the pH of the second neutralization slurry is greater than 7.0, it will reduce the consumption of alkaline substances in the first liquid phase material consumed by the subsequent second neutralization slurry, so that the content of alkaline substances in the first liquid phase material is still at a high level, which is difficult to meet the separation requirements of nanofiltration membrane.

[0097] In some alternative embodiments, the temperature of the first aging treatment is 70°C to 80°C, and the duration of the first aging treatment is 3.5h to 4.5h.

[0098] In these embodiments, a first aging treatment at a temperature of 70°C to 80°C for a duration of 3.5h to 4.5h can promote the formation of pseudoboehmite from the aluminum glue component of the first neutralized slurry, which is beneficial for the subsequent molding of the first pseudoboehmite product.

[0099] The temperature for the first aging treatment can be 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃ or 80℃.

[0100] The duration of the first aging treatment can be 3.5h, 3.6h, 3.7h, 3.8h, 3.9h, 4.0h, 4.1h, 4.2h, 4.3h, 4.4h or 4.5h.

[0101] In some alternative embodiments, the temperature of the second aging treatment is 60°C to 95°C, and the duration of the second aging treatment is 1 hour to 4 hours.

[0102] In these embodiments, a second aging treatment at a temperature of 60°C to 95°C for a duration of 1 hour to 4 hours can further consume the alkaline substances in the mixed slurry and convert these alkaline substances into sodium sulfate, which facilitates subsequent membrane separation to obtain soft water.

[0103] The temperature for the second aging treatment can be 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, or 95℃.

[0104] The duration of the second aging treatment can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours.

[0105] It should be noted that when the temperature of the second aging treatment is below 60°C, the aging effect of the second aging treatment is low, and the alkaline substances in the mixed slurry are difficult to react fully with the second neutralized slurry, resulting in a low crystallinity of the final second pseudoboehmite product. Furthermore, the content of alkaline substances in the second liquid phase material remains at a high level, making it difficult to meet the separation requirements of nanofiltration membranes. When the temperature of the second aging treatment is above 95°C, the mixed slurry is prone to boiling, leading to an excessively fast evaporation rate. Consequently, the solid content of the second solid phase material is difficult to control, affecting the crystallinity of the second pseudoboehmite product.

[0106] If the duration of the second aging treatment is less than 1 hour, the aging effect of the second aging treatment will be too low, and the alkaline substances in the mixed slurry will not be able to react fully with the second neutralized slurry. This will result in a low crystallinity of the final second boehmite, and the content of alkaline substances in the second liquid phase material will still be at a high level, making it difficult to meet the separation requirements of the nanofiltration membrane. If the duration of the second aging treatment is greater than 4 hours, the second aging treatment will be over-aged, resulting in the appearance of trihydrate crystal impurities in the second boehmite. This will not only prolong the production time of boehmite and soft water, but also reduce the production efficiency of boehmite.

[0107] In some alternative embodiments, the volume V1 of the second neutralized slurry and the volume V2 of the first liquid phase material satisfy: V1:V2 = (4:1) to (1:2).

[0108] In these embodiments, the second neutralizing slurry and the first liquid phase material with a volume ratio of (4:1) to (1:2) can be fully mixed. The subsequent second aging treatment allows the alkaline substances in the first liquid phase material and the alumina compounds in the second neutralizing slurry to react fully, so that the alkaline substances in the first liquid phase material can be fully consumed by the second neutralizing slurry, effectively reducing the content of alkaline substances in the subsequent soft water.

[0109] The volume V1 of the second neutralizing slurry and the volume V2 of the first liquid phase material satisfy the following ratios: V1:V2 = 4:1, 3.5:1, 3:1, 2.5:1, 2:1, 1.5:1, 1:1 or 1:2.

[0110] It should be noted that when the volume V1 of the second neutralizing slurry and the volume V2 of the first liquid phase material satisfy the ratio V1:V2 < 1:2, this indicates that the addition of too much of the first liquid phase material will cause the mixed slurry to over-age in the second aging process, resulting in the appearance of trihydrate crystal impurities in the second pseudoboehmite. When the volume V1 of the second neutralizing slurry and the volume V2 of the first liquid phase material satisfy the ratio V1:V2 > 4:1, the addition of too little of the second neutralizing slurry will result in a poor aging effect of the mixed slurry in the second aging process, leading to a lower crystallinity of the final second pseudoboehmite.

[0111] In some alternative embodiments, the alumina mass concentration of the second neutralizing slurry is from 50 g / L to 150 g / L.

[0112] In these embodiments, the second neutralizing slurry with an alumina mass concentration of 50 g / L to 150 g / L can have sufficient alumina compounds that can react sufficiently with the alkaline substances in the first liquid phase material to reduce the content of alkaline substances in the first liquid phase material, thereby meeting the requirements of the membrane separation stage.

[0113] The alumina mass concentration of the second neutralizing slurry can be 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, or 150 g / L.

[0114] It should be noted that when the alumina mass concentration of the second neutralizing slurry is less than 50 g / L, the content of alumina compounds in the slurry is low, which is insufficient to meet the production requirements of the second pseudoboehmite product, resulting in low production efficiency and high production cost of the second pseudoboehmite. When the alumina mass concentration of the second neutralizing slurry is greater than 150 g / L, the excessive content of alumina compounds in the slurry will lead to excessive viscosity, resulting in poor mass and heat transfer, thus affecting the yield of the second pseudoboehmite.

[0115] In some optional embodiments, the mass concentration of the alkaline substance in the second liquid phase material is from 2.97 g / L to 4.57 g / L; and / or

[0116] The conductivity of the soft water is from 15 μS / cm to 30 μS / cm.

[0117] In these embodiments, the second liquid phase material with a mass concentration of alkaline substances ranging from 2.97 g / L to 4.57 g / L indicates that the content of alkaline substances in the second liquid phase material is at a low level, which can meet the requirements for membrane separation. Additionally, the soft water with a conductivity of 15 μS / cm to 30 μS / cm indicates that the soft water is relatively pure.

[0118] The mass concentration of the alkaline substance in the second liquid phase material can be 2.97 g / L, 3.00 g / L, 3.50 g / L, 4.00 g / L, 4.50 g / L, or 4.57 g / L.

[0119] The conductivity of this soft water can be 15 μS / cm, 20 μS / cm, 25 μS / cm, or 30 μS / cm.

[0120] In some alternative embodiments, the crystallinity of the first pseudoboehmite is 72.8% to 79.6%; and / or

[0121] The crystallinity of the second pseudoboehmite is 51.8% to 53.1%.

[0122] In these embodiments, the first pseudoboehmite with a crystallinity of 72.8% to 79.6% and the second pseudoboehmite with a crystallinity of 51.8% to 53.1% demonstrate that the method can ultimately obtain pseudoboehmite products with different crystallinities by reducing the content of alkaline substances in the second liquid phase material.

[0123] The crystallinity of the first pseudoboehmite can be 72.8%, 73.0%, 73.5%, 74.0%, 74.5%, 75.0%, 75.5%, 76.0%, 76.5%, 77.0%, 77.5%, 78.0%, 78.5%, 79.0%, 79.5%, or 79.6%.

[0124] The crystallinity of the second pseudoboehmite can be 51.8%, 52.0%, 52.2%, 52.4%, 52.6%, 52.8%, 53.0%, or 53.1%.

[0125] 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 national / industry standards; if there is no corresponding national / industry standard, they are performed according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0126] Example 1

[0127] A sodium aluminate solution with an alumina content of 50 g / L was used as the raw material.

[0128] like Figure 1As shown, a method for co-producing pseudoboehmite and soft water includes:

[0129] S1. Carbon dioxide gas is passed into sodium aluminate solution to carry out carbonization and neutralization reaction, and the first neutralized slurry is obtained;

[0130] S2. The first neutralized slurry is subjected to a first aging treatment to obtain a first aged slurry;

[0131] S3. Filter the first aging slurry to obtain the first solid phase material and the first liquid phase material;

[0132] S4. The first solid material is washed and dried sequentially to obtain the first pseudoboehmite;

[0133] S5. The aluminum sulfate and sodium aluminate solutions are neutralized in parallel to obtain a second neutralized slurry;

[0134] S6. Mix the second neutralized slurry and the first liquid phase material to obtain a mixed slurry;

[0135] S7. The mixed slurry is subjected to a second aging treatment to obtain a second aged slurry;

[0136] S8. Filter the second aging slurry to obtain the second solid phase material and the second liquid phase material;

[0137] S9. Wash the second solid material to obtain the second pseudoboehmite;

[0138] S10. The second liquid phase material is subjected to membrane separation to obtain soft water.

[0139] The carbonization and neutralization reaction was carried out at a temperature of 25°C for 15 minutes.

[0140] The temperature for the parallel flow neutralization process is 40℃.

[0141] The pH of the first neutralized slurry is 11.5.

[0142] The pH of the second neutralized slurry is 4.5.

[0143] The temperature of the first aging treatment is 75℃, and the duration of the first aging treatment is 4.0h.

[0144] The temperature of the second aging treatment is 60℃, and the duration of the second aging treatment is 3 hours.

[0145] The volume V1 of the second neutralizing slurry and the volume V2 of the first liquid phase material satisfy the following condition: V1:V2=8L:2.5L.

[0146] The alumina mass concentration of the second neutralizing slurry is 50 g / L to 150 g / L.

[0147] The mass concentration of alkaline substances in the second liquid phase material is 3.47 g / L.

[0148] Example 2

[0149] Compared to Example 1, the differences in this example are as follows, while the rest are the same:

[0150] The carbonization and neutralization reaction was carried out at a temperature of 30°C for 14 minutes.

[0151] The temperature for the parallel flow neutralization process is 60℃.

[0152] The pH of the first neutralized slurry is 12.5.

[0153] The pH of the second neutralized slurry is 5.5.

[0154] The temperature of the first aging treatment is 75℃, and the duration of the first aging treatment is 4.0h.

[0155] The temperature of the second aging treatment is 70℃, and the duration of the second aging treatment is 2 hours.

[0156] The volume V1 of the second neutralizing slurry and the volume V2 of the first liquid phase material satisfy the following condition: V1:V2=8L:2L.

[0157] The mass concentration of alkaline substances in the second liquid phase material is 2.97 g / L.

[0158] Example 3

[0159] Compared to Example 1, the differences in this example are as follows, while the rest are the same:

[0160] The carbonization and neutralization reaction was carried out at a temperature of 40℃ for 12 minutes.

[0161] The temperature for the parallel flow neutralization process is 80℃.

[0162] The pH of the first neutralized slurry is 10.5.

[0163] The pH of the second neutralized slurry is 6.5.

[0164] The temperature of the first aging treatment is 75℃, and the duration of the first aging treatment is 4.0h.

[0165] The temperature of the second aging treatment is 80℃, and the duration of the second aging treatment is 1 hour.

[0166] The volume V1 of the second neutralizing slurry and the volume V2 of the first liquid phase material satisfy the following condition: V1:V2=8L:6L.

[0167] The mass concentration of alkaline substances in the second liquid phase material is 3.97 g / L.

[0168] Example 4

[0169] Compared to Example 1, the differences in this example are as follows, while the rest are the same:

[0170] The carbonization and neutralization reaction was carried out at a temperature of 60℃ for 11 minutes.

[0171] The temperature for the parallel flow neutralization process is 90℃.

[0172] The pH of the first neutralized slurry is 9.5.

[0173] The pH of the second neutralized slurry is 7.0.

[0174] The temperature of the first aging treatment is 75℃, and the duration of the first aging treatment is 4.0h.

[0175] The temperature of the second aging treatment is 90℃, and the duration of the second aging treatment is 4 hours.

[0176] The volume V1 of the second neutralizing slurry and the volume V2 of the first liquid phase material satisfy: V1:V2=8L:8L.

[0177] The mass concentration of alkaline substances in the second liquid phase material is 4.57 g / L.

[0178] Comparative Example 1

[0179] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same:

[0180] Without subsequent co-current neutralization treatment, the first liquid phase material is directly used as the product.

[0181] The mass concentration of alkaline substances in the second liquid phase material is 46.2 g / L.

[0182] Comparative Example 2

[0183] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same:

[0184] The volume V1 of the second neutralizing slurry and the volume V2 of the first liquid phase material satisfy the following condition: V1:V2=2L:6L.

[0185] The mass concentration of alkaline substances in the second liquid phase material is 1.2 g / L.

[0186] Comparative Example 3

[0187] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same:

[0188] The volume V1 of the second neutralizing slurry and the volume V2 of the first liquid phase material satisfy the following condition: V1:V2=8L:1.6L.

[0189] The mass concentration of alkaline substances in the second liquid phase material is 24.5 g / L.

[0190] Comparative Example 4

[0191] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same:

[0192] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same:

[0193] The second aging treatment was performed at a temperature of 50°C for 6 hours.

[0194] Comparative Example 5

[0195] Compared to Example 1, the differences in this comparative example are as follows, while the rest are the same:

[0196] The second aging treatment was performed at a temperature of 100℃ for 0.5 hours.

[0197] Relevant experimental and effect data:

[0198] The pseudoboehmite products obtained from each embodiment and comparative example, as well as the liquid phase product (soft water) obtained by filtration, were collected and their characteristic data were statistically analyzed. The results are shown in Table 1.

[0199] Table 1. Characteristics of pseudoboehmite products and liquid phase products obtained in each embodiment and comparative example.

[0200]

[0201]

[0202] As shown in Table 1, the method for co-producing boehmite and soft water provided in this application embodiment uses the waste liquid (first liquid phase material) containing high concentration of sodium carbonate generated in the carbonation and neutralization reaction section as a resource, introducing it into the co-current neutralization treatment section of aluminum sulfate / sodium aluminate. In this subsequent neutralization / aging environment, sodium carbonate undergoes a metathesis reaction with aluminum sulfate, effectively converting into second boehmite and relatively harmless sodium sulfate, thereby realizing the consumption and conversion of sodium carbonate within the system and avoiding the direct discharge of high-concentration sodium carbonate wastewater. The core of this method lies in the process integration and waste liquid resource utilization, using subsequent reactions to consume the alkaline substances (sodium carbonate) generated in the previous stage, achieving a significant reduction in the concentration of sodium carbonate in the wastewater, resulting in a final soft water conductivity below 30 μS / cm, and the mass concentration of alkaline substances (calculated as alumina) in the second liquid phase material below 5.0 g / L. It can also produce a first pseudoboehmite with a crystallinity of 72.8% to 79.6% and a second pseudoboehmite with a crystallinity of 51.8% to 53.1%.

[0203] Compared to Example 1, Comparative Example 1 directly uses the first liquid phase material as the product, and its alkaline substance mass concentration is 46.2 g / L. However, the first liquid phase material with high alkalinity is difficult to meet the usage standards of the membrane separation system and cannot obtain soft water product.

[0204] Compared to Example 1, Comparative Example 2 used a larger amount of the first liquid phase material, which made it difficult for the second neutralizing slurry to effectively consume its alkaline content. As a result, the mass concentration of alkaline substances in the second liquid phase material was above 20 g / L, which was insufficient to meet the requirements of membrane separation and thus could not produce soft water. Comparative Example 3 used a larger amount of the second neutralizing slurry, which could effectively reduce the alkaline content of the first liquid phase material. However, excessive second neutralizing slurry would reduce the crystallinity of the second pseudoboehmite and increase the conductivity of the soft water.

[0205] Compared to Example 1, Comparative Example 4 used a lower temperature for the second aging treatment, which resulted in a poorer aging effect on the mixed slurry, affecting the crystallinity of the second pseudoboehmite and increasing the electrical conductivity of the soft water. Comparative Example 5 used a higher temperature for the second aging treatment, which resulted in a faster solidification rate of the mixed slurry, affecting the crystallinity of the second pseudoboehmite. Although it yielded soft water with higher electrical conductivity, the overall energy consumption was higher.

[0206] In summary, the embodiments of this application provide a method for co-producing pseudoboehmite and soft water. This method integrates processes and utilizes waste liquid resources, using subsequent reactions to consume alkaline substances such as sodium carbonate generated in the previous stage, thereby achieving a significant reduction in the concentration of alkaline substances in the wastewater.

[0207] Furthermore, this application provides a method for co-producing boehmite and soft water. This method, while meeting the requirements of carbonation for preparing highly crystalline boehmite and pH control, allows for the regulation of carbon dioxide gas introduction. This ensures that the alkaline content and alumina content of the first liquid phase material meet the needs of alkaline additives, thereby replacing the alkaline additives used in the original neutralization method and reducing the overall cost of soft water treatment. Additionally, by controlling the volume ratio of the first liquid phase material and the second neutralization slurry, as well as the process parameters of the second aging treatment, the alkaline substances in the first liquid phase material react fully with the second neutralization slurry. This not only successfully prepares boehmite with different degrees of crystallinity, achieving diversification of boehmite, but also consumes the alkaline substances produced by the carbonation method, reducing the alkaline content of the second liquid phase material. This allows the second liquid phase material to be converted into high-purity soft water through a membrane separation system, achieving water resource recycling and constructing a green and efficient closed-loop treatment process.

[0208] Furthermore, this application provides a method for co-producing boehmite and soft water. This method can significantly reduce the alkaline content of the second liquid phase material, enabling it to meet the usage standards of membrane separation systems, optimizing the soft water recycling process, and achieving effective utilization and emission reduction of wastewater from the carbonization process. Additionally, this method uses the high-alkaline content first liquid phase material from the carbonization process as an alkaline auxiliary in the neutralization process, reducing the amount of alkaline auxiliaries used, lowering the production cost of boehmite, and improving the production efficiency of both the carbonization and neutralization processes.

[0209] Furthermore, this application provides a method for co-producing boehmite and soft water. This method can also control the aluminum content of the second neutralizing slurry by adjusting the alkaline content of the carbonation process, thereby precisely controlling the crystallinity of the boehmite and improving its performance in industrial applications. Simultaneously, the boehmite obtained by this method generally contains 0.5% or less of gibbsite.

[0210] 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 co-producing pseudoboehmite and soft water, the method comprising: Carbon dioxide gas is passed into sodium aluminate solution to carry out a carbonization and neutralization reaction, resulting in the first neutralized slurry. The first neutralized slurry is subjected to a first aging treatment to obtain a first aged slurry; The first aging slurry is filtered to obtain a first solid phase material and a first liquid phase material; The first solid material was washed and dried sequentially to obtain the first pseudoboehmite; Aluminum sulfate and sodium aluminate solution are subjected to co-current neutralization treatment to obtain a second neutralized slurry; The second neutralized slurry and the first liquid phase material are mixed to obtain a mixed slurry; The mixed slurry is subjected to a second aging treatment to obtain a second aged slurry; The second aging slurry is filtered to obtain a second solid phase material and a second liquid phase material; The second solid material was washed to obtain the second pseudoboehmite; The second liquid phase material is subjected to membrane separation to obtain soft water; The first neutralized slurry has a pH of 9.5 to 12.5, and the second neutralized slurry has a pH of 4.5 to 7.

0. The temperature of the second aging treatment is 60°C to 95°C, and the duration of the second aging treatment is 1 hour to 4 hours; The volume V1 of the second neutralized slurry and the volume V2 of the first liquid phase material satisfy: V1:V2 = (4:1) to (1:2). The alumina mass concentration of the second neutralizing slurry is 50 g / L to 150 g / L.

2. The method of claim 1, wherein, The carbonization neutralization reaction is carried out at a temperature of 25°C to 60°C for a duration of 10 min to 15 min; and / or The temperature of the parallel flow neutralization process is 40°C to 90°C.

3. The method of claim 1, wherein, The temperature of the first aging treatment is 70°C to 80°C, and the duration of the first aging treatment is 3.5h to 4.5h.

4. The method according to claim 1, characterized in that, The mass concentration of the alkaline substance in the second liquid phase material is from 2.97 g / L to 4.57 g / L; and / or The conductivity of the soft water is from 15 μS / cm to 30 μS / cm.

5. The method according to claim 1, characterized in that, The crystallinity of the first pseudoboehmite is 72.8% to 79.6%; and / or The crystallinity of the second pseudoboehmite is 51.8% to 53.1%.

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