A method for resourceful treatment of sodium chloride waste salt

Abstract

The application provides a resourceful treatment method of sodium chloride waste salt, and belongs to the field of sodium chloride waste salt treatment. The method comprises the following steps: preparing a first saturated sodium chloride solution by using sodium chloride waste salt; introducing ammonia into the saturated sodium chloride solution to obtain a saturated ammonia salt aqueous solution; introducing carbon dioxide into the saturated ammonia salt aqueous solution to obtain a first mixed slurry; performing solid-liquid separation on the first mixed slurry to obtain a NaHCO3 product and a first filtrate; adding sodium chloride waste salt into the first filtrate to obtain a second saturated sodium chloride solution; introducing ammonia into the second saturated sodium chloride solution to obtain a saturated mixed solution; performing cooling crystallization on the saturated mixed solution to obtain a second mixed slurry; performing solid-liquid separation on the second mixed slurry to obtain an NH4Cl product and a second filtrate; and recycling the second filtrate to prepare the first saturated sodium chloride solution to form a closed cycle. Thus, a new resourceful treatment method of sodium chloride waste salt is provided.

Description

Technical Field

[0001] This application relates to the field of sodium chloride waste salt treatment technology, and in particular to a method for the resource-based treatment of sodium chloride waste salt. Background Technology

[0002] With the continuous improvement of domestic industrialization, many industries such as printing and dyeing, pharmaceuticals, petrochemicals, and coal chemicals generate large amounts of high-salinity wastewater during production. This high-salinity wastewater contains soluble inorganic salt ions and organic substances, including soluble inorganic salt ions such as sodium (Na₂O₃). + Cl - SO4 2- Ca 2+ The inorganic salts in high-salinity wastewater are mainly toxic and harmful organic compounds. Most companies treat high-salinity wastewater using traditional methods, extracting inorganic salts from the wastewater through evaporation and crystallization. However, the extracted waste salts increase the company's treatment budget and pose certain challenges to both the environment and the company itself.

[0003] Currently, the annual output of waste salt in China exceeds 20 million tons, mainly from the treatment of high-salinity wastewater and waste salt residue generated as a byproduct of chemical production. The composition of waste salt varies depending on the enterprise, ranging from waste salt primarily composed of a single salt to mixed waste salt and impurity salts. One type of waste salt, primarily composed of sodium chloride, mainly comes from production facilities of hydrazine hydrate, furanophenol, and glyphosate. These facilities generate 4-5 tons, 0.67 tons, and 1.1-1.4 tons of sodium chloride residue for every ton of product produced, respectively. Taking glyphosate as an example, China accounts for 80% of global glyphosate production, generating 1 million tons of sodium chloride residue annually. With the increasing market demand for related chemicals, the total reserves of waste salt are also constantly increasing, significantly impacting enterprise development and environmental governance. Summary of the Invention

[0004] This application provides a method for the resource-based treatment of sodium chloride waste salt to solve the following technical problem: providing a new method for the resource-based treatment of sodium chloride waste salt.

[0005] This application provides a method for the resource recovery treatment of sodium chloride waste salt, the method using an airlift circulating reactor, the method comprising:

[0006] Prepare a first saturated sodium chloride solution from waste sodium chloride salt;

[0007] Under the first set conditions, ammonia gas is introduced into the saturated sodium chloride solution to obtain a saturated ammonium salt aqueous solution;

[0008] Carbon dioxide is bubbled into the saturated ammonium salt aqueous solution to react and generate NaHCO3 precipitate, thus obtaining the first mixed slurry;

[0009] The first mixed slurry was subjected to solid-liquid separation to obtain NaHCO3 product and first filtrate;

[0010] Add waste sodium chloride to the first filtrate to obtain a second saturated sodium chloride solution;

[0011] Under the second set conditions, ammonia gas is introduced into the second saturated sodium chloride solution to reduce the NH4+ in the first filtrate. + and Cl - The mixture is in a supersaturated state, resulting in a saturated mixture.

[0012] The saturated mixture is cooled and crystallized to precipitate NH4Cl, resulting in a second mixed slurry.

[0013] The second mixed slurry was subjected to solid-liquid separation to obtain NH4Cl product and a second filtrate; and

[0014] The second filtrate is recycled to prepare a first saturated sodium chloride solution, forming a closed loop.

[0015] Optionally, the height-to-diameter ratio of the airlift circulating reactor is 4 to 9, and the inner-outer diameter ratio of the airlift circulating reactor is 0.4 to 0.8.

[0016] Optionally, the airlift circulating reactor includes a guide tube, a cylinder, and a gas distributor; wherein,

[0017] The height ratio of the guide tube to the cylinder body is 0.5 to 0.7, the opening diameter of the gas distributor is 3 mm to 5 mm, and the opening degree of the enlarged section of the gas distributor is 30°C to 60°C.

[0018] Optionally, the mass concentration of sodium chloride in the first saturated sodium chloride solution is 24.5% to 26.5%.

[0019] Optionally, the molar concentration of ammonia in the saturated ammonia salt solution is 5.0 mol / L to 6.0 mol / L.

[0020] Optionally, the first set conditions include: the ammonia temperature is 5℃~10℃; and / or

[0021] The second set conditions include: the ammonia temperature is 20℃~30℃.

[0022] Optionally, the mass concentration of sodium chloride in the second saturated sodium chloride solution is 22% to 24%.

[0023] Optionally, the concentration of ammonia in the saturated mixture is 4.5 mol / L to 5.5 mol / L.

[0024] Optionally, the reaction temperature for generating NaHCO3 precipitate is 20℃~30℃.

[0025] Optionally, the cooling and crystallization temperature is 5°C to 15°C.

[0026] The technical solutions provided in this application have the following advantages compared with the prior art:

[0027] This application provides a method for the resource utilization of sodium chloride waste salt. The method uses an airlift circulating reactor and includes: preparing a first saturated sodium chloride solution from the sodium chloride waste salt; under first set conditions, introducing ammonia gas into the saturated sodium chloride solution to obtain a saturated ammonium salt aqueous solution; introducing carbon dioxide into the saturated ammonium salt aqueous solution to react and generate NaHCO3 precipitate, obtaining a first mixed slurry; performing solid-liquid separation on the first mixed slurry to obtain NaHCO3 product and a first filtrate; adding sodium chloride waste salt to the first filtrate to obtain a second saturated sodium chloride solution; and under second set conditions, introducing ammonia gas into the second saturated sodium chloride solution to reduce the NH4+ in the first filtrate. + and Cl - The solution is in a supersaturated state, resulting in a saturated mixture. This saturated mixture is then cooled and crystallized to precipitate NH4Cl, yielding a second mixed slurry. The second mixed slurry undergoes solid-liquid separation to obtain an NH4Cl product and a second filtrate. The second filtrate is then recycled to prepare a first saturated sodium chloride solution, forming a closed-loop system. On one hand, considering the characteristics of sodium chloride waste salt, an airlift circulating reactor is used, which enhances the reaction process, improves the mass transfer between gas and liquid, reduces reaction time, and increases efficiency. On the other hand, the resource utilization of sodium chloride waste salt ultimately yields sodium bicarbonate and ammonium chloride products with good purity and high yield, which is environmentally friendly. Furthermore, the recycling of the second filtrate to prepare the first saturated sodium chloride solution forms a closed-loop system, reducing wastewater discharge and resource waste, and achieving resource recovery and reuse. This provides a new method for the resource-based treatment of sodium chloride waste salt. Attached Figure Description

[0028] 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.

[0029] 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.

[0030] Figure 1 A flowchart illustrating a method for the resource recovery of sodium chloride waste salt provided in this application embodiment;

[0031] Figure 2 A schematic diagram illustrating a method for the resource recovery of sodium chloride waste salt provided in an embodiment of this application;

[0032] Figure 3 This is a schematic diagram of the structure of the airlift circulating reactor provided in the embodiments of this application;

[0033] Figure 4 This is a velocity cloud diagram of an airlift circulating reactor provided in Embodiment 1 of this application;

[0034] Figure label:

[0035] 1-Airlift circulating reactor; 2-Flow guide tube; 3-Gas distributor; 4-Three-way valve; 5-Tail gas receiving device; 6-Rotameter; 7-CO2 and NH3 gas cylinders; 8-Dissolved oxygen meter. Detailed Implementation

[0036] 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.

[0037] 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 rigid 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. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0038] Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" 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 single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation," such as parts by weight or parts by mass, indicates the proportional relationship between components. In the proportional relationships discussed in this article, parameters described by proportion should be understood as the first term of the proportion in the order of description, while the proportion figure should be understood as the second term. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figure in the proportion in the order of description, i.e., the mass of substance A : the mass of substance B : the mass of substance C = 1:2:3.

[0039] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0040] Figure 1 A schematic flowchart illustrating a method for the resource recovery of sodium chloride waste salt provided in this application embodiment; Figure 2 This is a schematic diagram of a method for the resource utilization of sodium chloride waste salt provided in an embodiment of this application.

[0041] like Figure 1 and Figure 2 As shown in the embodiment of this application, a method for the resource recovery of sodium chloride waste salt is provided. The method uses an airlift circulating reactor and includes:

[0042] S1. Prepare a first saturated sodium chloride solution from the waste sodium chloride salt;

[0043] By preparing a saturated solution, sufficient solute can be ensured to participate in the reaction in subsequent steps, which also facilitates the mixing and reaction of the gas and liquid phases in the airlift circulating reactor.

[0044] Figure 3 This is a schematic diagram of the structure of the airlift circulating reactor provided in the embodiments of this application.

[0045] like Figure 3 As shown, in some embodiments, the height-to-diameter ratio of the airlift circulating reactor is 4 to 9, and the inner-outer diameter ratio of the airlift circulating reactor is 0.4 to 0.8.

[0046] An airlift circulating reactor is a gas-powered reactor whose structure mainly consists of a bottom gas inlet pipe, a reactor shell, an upper gas outlet pipe, and an internal annular plate or guide tube. Based on structural characteristics, airlift circulating reactors can be divided into two main categories: internal circulating reactors and external circulating reactors. In an internal circulating reactor, gas enters the reactor through a central guide tube, forming an upward flow, while liquid forms a downward flow at the periphery, achieving a circulating flow of two-phase or three-phase gas-liquid mixtures. The working principle of an airlift circulating reactor is that gas enters the rising zone of the reactor through an aeration device at the bottom, forming a two-phase or three-phase mixture. The presence of the gas phase reduces the density of the rising zone, creating a density difference with the falling zone, which drives the liquid phase in the falling zone to enter the rising zone from the bottom of the falling zone. Simultaneously, the gas phase in the rising zone carries the liquid phase upward, forming a circulating flow of two-phase or three-phase gas-liquid mixtures within the reactor.

[0047] A height-to-diameter ratio of 4–9 results in a relatively high reactor height, which facilitates thorough mixing of gas and liquid, improving reaction efficiency. Simultaneously, a higher height-to-diameter ratio increases the gas-liquid contact area within the reactor, thereby increasing the mass transfer rate and promoting the reaction. A diameter-to-inner diameter ratio of 0.4–0.8 results in a more rational reactor structure, which is beneficial for fluid circulation and mixing. Furthermore, an appropriate diameter-to-inner diameter ratio enhances the structural stability of the reactor, preventing deformation or damage due to excessive fluid pressure. In addition, a reasonable diameter-to-inner diameter ratio makes the reactor easier to operate and maintain, reducing operating costs. For example, the height-to-diameter ratio of an airlift circulating reactor can be 4, 5, 6, 7, 8, or 9, while the diameter-to-inner diameter ratio can be 0.4, 0.5, 0.6, 0.7, or 0.8.

[0048] In some embodiments, the airlift circulating reactor includes a guide tube, a cylinder, and a gas distributor; wherein,

[0049] The height ratio of the guide tube to the cylinder body is 0.5 to 0.7, the opening diameter of the gas distributor is 3 mm to 5 mm, and the opening degree of the enlarged section of the gas distributor is 30°C to 60°C.

[0050] Limiting the height ratio of the guide tube to the reactor body to 0.5–0.7 creates an effective fluid circulation path, improving mixing efficiency. A suitable guide tube height also optimizes mass transfer within the reactor, leading to a more complete reaction. Furthermore, optimizing the guide tube height ratio reduces reactor energy consumption and improves overall operating efficiency. Limiting the gas distributor's orifice diameter to 3mm–5mm ensures more uniform gas distribution within the reactor, preventing excessively high or low local gas concentrations. Uniform gas distribution improves gas utilization, resulting in a more efficient reaction. It also prevents gas distributor blockage, ensuring stable reactor operation. Limiting the gas distributor's enlarged section's flare opening to 30°–60° effectively guides gas flow, allowing for smoother gas entry into the reactor. This reduces bubble coalescence, increases bubble dispersion, and enhances gas-liquid mixing. Additionally, the optimized flare opening improves mass transfer efficiency, leading to a more complete and efficient reaction. For example, the height ratio of the guide tube to the cylinder body can be 0.5, 0.55, 0.6, 0.65, 0.7, etc., the opening diameter of the gas distributor can be 3mm, 3.5mm, 4mm, 4.5mm, 5mm, etc., and the opening degree of the enlarged section of the gas distributor can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, etc.

[0051] In this embodiment, an airlift circulating reactor is employed. This gas-liquid reactor is specifically designed for the resource recovery of sodium chloride waste salt, ensuring the high efficiency and targeted nature of the reaction process. This customized design helps maximize the utilization of sodium chloride waste salt while reducing unnecessary energy consumption and waste generation. Simultaneously, by optimizing the reactor's structure and operating conditions, the mass transfer capacity between gas and liquid is significantly improved. This means more thorough contact between reactants, a faster reaction rate, thereby reducing reaction time and improving efficiency. Furthermore, the reactor design not only improves mass transfer capacity but may also enhance the reaction process through other means (such as increased stirring and optimized temperature control), further improving processing efficiency and product quality.

[0052] Compared to traditional batch reactors, this gas-liquid reactor allows the reaction to occur without external pressure. This not only reduces energy consumption but also increases the safety of the reactor system, avoiding potential safety hazards caused by high-pressure operation. Furthermore, the airtightness of traditional batch reactors significantly impacts the reaction process; poor airtightness can drastically reduce product yield and purity. Since the gas-liquid reactor of this invention does not require pressurization, the issue of reactor airtightness does not need to be overly considered, which simplifies reactor design and operation and reduces maintenance costs. In addition, the absence of pressurization and reduced consideration of airtightness make this gas-liquid reactor exhibit higher safety and reliability in the resource recovery of sodium chloride waste salt. This helps ensure the continuity and stability of production, improving overall economic efficiency.

[0053] In summary, this gas-liquid reactor demonstrates significant advantages in the resource recovery of sodium chloride waste, not only improving processing efficiency and product quality but also reducing energy consumption and safety risks. These characteristics make this reactor a promising candidate for application in the resource utilization of sodium chloride waste.

[0054] In some embodiments, the mass concentration of sodium chloride in the first saturated sodium chloride solution is 24.5% to 26.5%.

[0055] Sodium chloride is saturated within this concentration range, which is conducive to the full conduct of chemical reactions. In the resource recovery process of waste sodium chloride, this concentration range ensures sufficient contact and reaction between reactants, thereby improving the efficiency of the chemical reaction. For example, the mass concentration of sodium chloride in the first saturated sodium chloride solution can be 24.5%, 24.6%, 24.7%, 24.9%, 25%, 25.3%, 25.6%, 26%, 26.5%, etc.

[0056] S2. Under the first set conditions, ammonia gas is introduced into the saturated sodium chloride solution to obtain a saturated ammonium salt aqueous solution.

[0057] After ammonia gas is introduced, it dissolves in a saturated sodium chloride solution to form an aqueous solution of ammonium salts. In this process, ammonia, as an alkaline gas, together with chloride and sodium ions in the solution, constitutes the reaction environment, providing the conditions for the subsequent introduction of carbon dioxide to produce sodium bicarbonate. Simultaneously, the efficient mixing capability of the airlift circulating reactor contributes to the uniform distribution of ammonia gas in the solution.

[0058] In some embodiments, the molar concentration of ammonia in the saturated ammonia salt solution is 5.0 mol / L to 6.0 mol / L.

[0059] Limit ammonia (NH4) +A molar concentration of ammonia of 5.0 mol / L to 6.0 mol / L is beneficial for accelerating the reaction with carbon dioxide and sodium chloride, thereby increasing the rate of sodium bicarbonate formation. Simultaneously, an appropriate ammonia concentration helps reduce side reactions and avoid the formation of unnecessary impurities. This contributes to obtaining higher purity sodium bicarbonate and the final sodium carbonate product. For example, the molar concentration of ammonia in saturated ammonia brine can be 5.0 mol / L, 5.2 mol / L, 5.4 mol / L, 5.6 mol / L, 5.8 mol / L, 6.0 mol / L, etc.

[0060] In some embodiments, the first set condition includes: the ammonia temperature is 5°C to 10°C.

[0061] At lower ammonia inlet temperatures (5°C–10°C), the solubility of ammonia increases, which is beneficial for its dissolution in saturated sodium chloride solution. This facilitates the formation of higher concentrations of ammonium salt aqueous solutions, providing more favorable conditions for subsequent reactions. For example, the ammonia inlet temperature can be 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, etc.

[0062] S3. Carbon dioxide is introduced into the saturated ammonium salt aqueous solution to react and generate NaHCO3 precipitate, thus obtaining the first mixed slurry;

[0063] When carbon dioxide is passed into a saturated aqueous solution of ammonium salts, it reacts with ammonium ions and carbonate ions (generated by the reaction of ammonia and carbon dioxide in water) to form sodium bicarbonate precipitate. This step is one of the key steps in resource recovery, converting waste sodium chloride into valuable sodium bicarbonate through a chemical reaction. The specific reaction equation can be expressed as: NaCl + NH3 + CO2 + H2O → NaHCO3↓ + NH4Cl.

[0064] In some embodiments, the reaction temperature for generating NaHCO3 precipitate is 20°C to 30°C.

[0065] Within a temperature range of 20℃ to 30℃, the reactants exhibit moderate reactivity, which is conducive to accelerating the chemical reaction rate. This means that more NaHCO3 precipitate can be generated in a shorter time, thereby improving production efficiency. Simultaneously, an appropriate reaction temperature helps reduce side reactions and avoids the formation of unnecessary impurities. At 20℃ to 30℃, the reaction process can be controlled more effectively, ensuring that the generated NaHCO3 precipitate has high purity. This is crucial for subsequent product processing and utilization. For example, the reaction temperature for generating NaHCO3 precipitate can be 20℃, 22℃, 24℃, 26℃, 28℃, 30℃, etc.

[0066] S4. The first mixed slurry is subjected to solid-liquid separation to obtain NaHCO3 product and first filtrate;

[0067] The solid-liquid separation step separates the generated sodium bicarbonate precipitate from the reaction solution to obtain pure sodium bicarbonate product. Simultaneously, the first filtrate contains unreacted ammonia and sodium chloride, providing raw materials for recycling in subsequent steps.

[0068] S5. Add sodium chloride waste salt to the first filtrate to obtain a second saturated sodium chloride solution;

[0069] The first filtrate is mixed again with waste sodium chloride to form a second saturated sodium chloride solution. Adding waste sodium chloride increases the concentration of chloride ions in the solution, creating conditions for the precipitation of ammonium chloride in subsequent steps.

[0070] In some embodiments, the mass concentration of sodium chloride in the second saturated sodium chloride solution is 22% to 24%.

[0071] An appropriate sodium chloride concentration can provide sufficient chloride ions to combine with ammonium ions to form ammonium chloride. For example, the mass concentration of sodium chloride in the second saturated sodium chloride solution can be 22%, 22.5%, 23%, 23.5%, 24%, etc.

[0072] S6. Under the second set conditions, ammonia gas is introduced into the second saturated sodium chloride solution to reduce the NH4+ in the first filtrate. + and Cl - The mixture is in a supersaturated state, resulting in a saturated mixture.

[0073] After ammonia gas is introduced again, the concentrations of ammonium and chloride ions in the solution increase, reaching a supersaturated state. This step prepares for the subsequent precipitation of ammonium chloride by adjusting the reaction conditions to ensure its smooth precipitation.

[0074] In some embodiments, the concentration of ammonia in the saturated mixture is 4.5 mol / L to 5.5 mol / L.

[0075] The concentration of ammonia is 4.5 mol / L to 5.5 mol / L, and the concentration of ammonium ions (NH4+) in the solution is... + A moderate concentration is beneficial for the reaction with chloride ions (Cl). - Ammonium chloride (NH4Cl) is formed by the combination of ammonium and chloride ions. When both ammonium and chloride ion concentrations reach a supersaturated state, ammonium chloride will precipitate more easily from the solution, thereby improving the precipitation efficiency. For example, the concentration of ammonia in the saturated mixture can be 4.5 mol / L, 4.6 mol / L, 4.7 mol / L, 4.8 mol / L, 4.9 mol / L, 5.2 mol / L, 5.4 mol / L, 5.5 mol / L, etc.

[0076] In some embodiments, the second set condition is: the ammonia temperature is 20°C to 30°C.

[0077] In the resource recovery treatment of sodium chloride waste salt, when using an airlift circulating reactor, the ammonia inlet temperature differs between the first and second set conditions. The chemical reaction rate varies at different temperatures. The selection of the ammonia inlet temperature needs to consider the balance between reaction rate and product purity. Under the first set condition, a lower ammonia inlet temperature (5℃~10℃) is favorable for certain reactions, such as the dissolution of ammonia in brine and initial reactions. Under the second set condition, a slightly higher ammonia inlet temperature (20℃~30℃) is more favorable for subsequent reactions, such as the combination of ammonium and chloride ions and the precipitation of ammonium chloride. Simultaneously, temperature also has a significant impact on the thermodynamic equilibrium of the chemical reaction. In the first stage, a lower temperature may help maintain the stability of the reaction system and avoid unnecessary side reactions. In the second stage, a slightly higher temperature may favor the reaction towards the formation of ammonium chloride, thereby improving the precipitation efficiency of ammonium chloride. For example, the second ammonia inlet temperature could be 20℃, 22℃, 24℃, 26℃, 28℃, 30℃, etc.

[0078] S7. Cool the saturated mixture to crystallize and precipitate NH4Cl to obtain a second mixed slurry;

[0079] The cooling crystallization step utilizes the property that the solubility of ammonium chloride decreases with decreasing temperature, causing ammonium chloride to precipitate from the saturated mixture. NH 4 The solubility of Cl is less than that of NaCl, which makes NH... 4 Cl precipitates preferentially.

[0080] In some embodiments, the cooling and crystallization temperature is 5°C to 15°C.

[0081] Within a temperature range of 5℃ to 15℃, the solubility of ammonium chloride changes significantly, allowing it to precipitate rapidly from the solution. This faster precipitation rate helps shorten the production cycle and improve production efficiency. Meanwhile, the solubility changes of other potential impurities (such as sodium chloride) are relatively small, making them less likely to precipitate along with the ammonium chloride. This helps ensure that the precipitated ammonium chloride has high purity. For example, the cooling and crystallization temperatures can be 5℃, 7℃, 9℃, 11℃, 13℃, 15℃, etc.

[0082] S8. The second mixed slurry is subjected to solid-liquid separation to obtain NH4Cl product and a second filtrate; and

[0083] The precipitated ammonium chloride is separated from the reaction solution to obtain pure ammonium chloride product. Meanwhile, the separated second filtrate can be recycled for preparing a first saturated sodium chloride solution or subjected to other treatments.

[0084] S9. The second filtrate is recycled to prepare a first saturated sodium chloride solution, forming a closed loop.

[0085] The second filtrate contains NaCl, NaHCO3, NH4Cl, and ammonia. Recycling the second filtrate can reduce wastewater discharge and resource waste. By reusing the second filtrate to prepare the first saturated sodium chloride solution, a closed-loop system can be formed, improving resource utilization efficiency.

[0086] Meanwhile, after multiple cycles, the second filtrate contains high levels of NaHCO3 and NH4Cl, which can be evaporated to obtain high-purity sodium carbonate.

[0087] This method for the resource recovery of sodium chloride waste salt, employing an airlift circulating reactor, has significant advantages, as detailed below:

[0088] (1) High-efficiency reaction and mixing: The airlift circulating reactor uses gas as a power source to achieve high-efficiency mixing and circulation of gas-liquid two-phase or gas-liquid-solid three-phase reactions, thereby improving reaction efficiency. The reactor's height-to-diameter ratio, inner-outer diameter ratio, the height ratio of the guide tube to the cylinder, and the design of the gas distributor have all been optimized to further enhance the mixing effect and mass transfer rate of the fluid.

[0089] (2) Optimization of reaction conditions: By precisely controlling the ammonia inlet temperature and the reaction temperature, the rate of chemical reaction and the purity of products were optimized. Different temperature conditions were used at different reaction stages to balance the reaction rate and product purity, ensuring efficient and high-quality production of sodium bicarbonate and ammonium chloride.

[0090] (3) Improving product purity and yield: The precipitation processes of ammonium chloride and sodium bicarbonate both utilize the property that solubility changes with temperature, achieving efficient precipitation through cooling crystallization. Simultaneously, strict control of reaction conditions reduces side reactions and ensures high product purity. Furthermore, higher reaction efficiency and product purity contribute to improved overall yield and reduced production costs.

[0091] (4) Closed-loop circulation and resource recovery: The second filtrate is recycled to prepare the first saturated sodium chloride solution, forming a closed-loop system that reduces wastewater discharge and resource waste. At the same time, high-purity sodium carbonate and ammonium chloride are recovered from the recycling process, further improving resource utilization efficiency.

[0092] (5) Reduced energy consumption and safety risks: The airlift circulating reactor can react without the need for external pressure, thus reducing energy consumption. At the same time, the reactor design does not require much consideration of airtightness issues, simplifying design and operation and reducing maintenance costs. In addition, the characteristics of not requiring pressurization and having less consideration for airtightness issues make this reactor exhibit higher safety and reliability in the resource recovery treatment of sodium chloride waste salt.

[0093] (6) Broad application prospects: This method is not only applicable to the resource recovery of sodium chloride waste salt, but may also be extended to the treatment of other types of waste salt. At the same time, by optimizing reaction conditions and reactor design, this method is expected to achieve efficient resource recovery while reducing environmental pollution and production costs.

[0094] In summary, this method for the resource-based treatment of sodium chloride waste salt demonstrates significant advantages in terms of reaction efficiency, product purity, resource recovery, energy consumption reduction, and safety, and has broad application prospects and important environmental significance.

[0095] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to industry standards. If there is no corresponding industry standard, then common international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0096] Example 1

[0097] A method for the resource utilization of waste sodium chloride includes the following steps:

[0098] (1) Prepare a saturated sodium chloride solution by adding water to sodium chloride waste salt. The concentration of the saturated sodium chloride solution is 24.5%. The solution is pumped into an airlift circulating reactor using a metering pump. The height-to-diameter ratio of the airlift circulating reactor is 4, the inner-to-outer diameter ratio is 0.4, the height ratio of the guide tube to the cylinder is 0.5, the opening diameter of the gas distributor is 3 mm, and the opening of the bell mouth of the expansion section is 30°. Ammonia gas is introduced into the saturated sodium chloride solution to form a saturated ammonium salt aqueous solution. The concentration of ammonia in the saturated ammonium salt aqueous solution is 5.0 mol / L. Carbon dioxide is then introduced into the saturated ammonium salt aqueous solution. The reaction temperature is controlled at 20°C to generate NaHCO3 precipitate. After filtration, drying, and purification, NaHCO3 product is obtained.

[0099] (2) Continue adding sodium chloride waste salt to the filtrate to resaturate the solution. The sodium chloride concentration in the saturated solution is 22%. Then, ammonia gas is introduced to reduce the NH4+ concentration in the solution. 4+ Ions, Cl -The ions were in a supersaturated state, and the concentration of ammonia in the saturated solution was 4.5 mol / L. The obtained filtrate was cooled and crystallized at 15℃. At this time, the solubility of NH4Cl was less than that of NaCl, so NH4Cl was preferentially precipitated. After filtration, drying, and purification, the final product was NH4Cl.

[0100] (3) In step (2), the filtrate contains NaCl and NaHCO3. 3、 NH4Cl and ammonia, etc., are reused in step (1) by adding sodium chloride waste salt to prepare a saturated solution. The above steps are repeated to achieve resource recycling.

[0101] The final NaHCO3 product had a purity of 98.2% and a yield of 92.0%, while the ammonium chloride product had a purity of 99.5% and a yield of 91.2%.

[0102] Figure 4 This is a velocity contour plot of the airlift circulating reactor provided in Embodiment 1 of this application. Figure 4 It can be seen that the fluid flow velocity inside the reactor is uniform.

[0103] Example 2

[0104] A method for the resource utilization of waste sodium chloride includes the following steps:

[0105] (1) Prepare a saturated sodium chloride solution by adding water to sodium chloride waste salt. The concentration of the saturated sodium chloride solution is 25.5%. The solution is pumped into an airlift circulating reactor using a metering pump. The height-to-diameter ratio of the airlift circulating reactor is 5, the inner-to-outer diameter ratio is 0.5, the height ratio of the guide tube to the cylinder is 0.6, the opening diameter of the gas distributor is 4 mm, and the opening of the bell mouth of the expansion section is 45°. Ammonia gas is introduced into the saturated sodium chloride solution to form a saturated ammonium salt aqueous solution. The concentration of ammonia in the saturated ammonium salt aqueous solution is 5.5 mol / L. Carbon dioxide is then introduced into the saturated ammonium salt aqueous solution, and the reaction temperature is controlled at 25°C to generate NaHCO3 precipitate. After filtration, drying, and purification, NaHCO3 product is obtained.

[0106] (2) Continue adding sodium chloride waste salt to the filtrate to resaturate the solution. The sodium chloride concentration in the saturated solution is 23%. Then, ammonia gas is introduced to reduce the NH4+ concentration in the solution. 4+ Ions, Cl - The ions were in a supersaturated state, and the concentration of ammonia in the saturated solution was 5.0 mol / L. The obtained filtrate was cooled and crystallized at 10℃. At this time, the solubility of NH4Cl was less than that of NaCl, so NH4Cl was preferentially precipitated. After filtration, drying, and purification, the final product was NH4Cl.

[0107] (3) In step (2), the filtrate contains NaCl and NaHCO3.3、 NH4Cl and ammonia, etc., are reused in step (1) by adding sodium chloride waste salt to prepare a saturated solution. The above steps are repeated to achieve resource recycling.

[0108] The final NaHCO3 product had a purity of 98.4% and a yield of 92.5%, while the ammonium chloride product had a purity of 99.6% and a yield of 92.1%.

[0109] Example 3

[0110] A method for the resource utilization of waste sodium chloride includes the following steps:

[0111] (1) Prepare a saturated sodium chloride solution by adding water to sodium chloride waste salt. The concentration of the saturated sodium chloride solution is 26.5%. The solution is pumped into an airlift circulating reactor using a metering pump. The height-to-diameter ratio of the airlift circulating reactor is 7, the inner-to-outer diameter ratio is 0.6, the height ratio of the guide tube to the cylinder is 0.7, the opening diameter of the gas distributor is 3 mm, and the opening of the bell mouth of the expansion section is 30°. Ammonia gas is introduced into the saturated sodium chloride solution to form a saturated ammonium salt aqueous solution. The concentration of ammonia in the saturated ammonium salt aqueous solution is 6.0 mol / L. Carbon dioxide is then introduced into the saturated ammonium salt aqueous solution, and the reaction temperature is controlled at 30°C to generate NaHCO3 precipitate. After filtration, drying, and purification, NaHCO3 product is obtained.

[0112] (2) Continue adding sodium chloride waste salt to the filtrate to resaturate the solution. The sodium chloride concentration in the saturated solution is 24%. Then, ammonia gas is introduced to reduce the NH4+ concentration in the solution. 4+ Ions, Cl - The ions were in a supersaturated state, and the concentration of ammonia in the saturated solution was 5.5 mol / L. The obtained filtrate was cooled and crystallized at 5℃. At this time, the solubility of NH4Cl was less than that of NaCl, so NH4Cl precipitated preferentially. After filtration, drying, and purification, the final product was NH4Cl.

[0113] (3) In step (2), the filtrate contains NaCl and NaHCO3. 3、 NH4Cl and ammonia, etc., are reused in step (1) by adding sodium chloride waste salt to prepare a saturated solution. The above steps are repeated to achieve resource recycling.

[0114] The final NaHCO3 product had a purity of 99.0% and a yield of 94.0%, while the ammonium chloride product had a purity of 99.9% and a yield of 93.2%.

[0115] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0116] In this embodiment of the application, a gas-liquid reactor for resource-based treatment of sodium chloride waste salt is designed to address the characteristics of sodium chloride waste salt. The reactor is enhanced during the reaction process, and the mass transfer capacity between gas and liquid is improved, thereby reducing the reaction time and increasing work efficiency.

[0117] In this embodiment, compared to a traditional batch reactor, the reaction can occur without external pressure, increasing the safety of the reactor system. The airtightness of a traditional batch reactor also significantly affects the reaction process; poor airtightness can greatly reduce product yield and purity. However, the gas-liquid reactor of this invention does not require pressurization, thus eliminating the need to consider the reactor's airtightness.

[0118] In this embodiment, waste sodium chloride is utilized to obtain sodium bicarbonate and ammonium chloride products with good purity and high yield, which is environmentally friendly.

[0119] In the embodiments of this application, the purity of the final NaHCO3 product is >98.0%, the yield is >90.0%, and the purity of the ammonium chloride product is >98.0%, the yield is >90.0%.

[0120] 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 herein.

Claims

1. A method for the resource recovery treatment of sodium chloride waste salt, the method using an airlift circulating reactor, the method comprising: Prepare a first saturated sodium chloride solution from waste sodium chloride salt; Under the first set conditions, ammonia gas is introduced into the saturated sodium chloride solution to obtain a saturated ammonium salt aqueous solution; Carbon dioxide is bubbled into the saturated ammonium salt aqueous solution to react and generate NaHCO3 precipitate, thus obtaining the first mixed slurry; The first mixed slurry was subjected to solid-liquid separation to obtain NaHCO3 product and first filtrate; Add waste sodium chloride to the first filtrate to obtain a second saturated sodium chloride solution; Under the second set conditions, ammonia gas is introduced into the second saturated sodium chloride solution to reduce the NH4+ in the first filtrate. + and Cl - The mixture is in a supersaturated state, resulting in a saturated mixture. The saturated mixture is cooled and crystallized to precipitate NH4Cl, resulting in a second mixed slurry. The second mixed slurry was subjected to solid-liquid separation to obtain NH4Cl product and second filtrate; as well as The second filtrate is recycled to prepare a first saturated sodium chloride solution, forming a closed loop.

2. The method according to claim 1, characterized in that, The height-to-diameter ratio of the airlift circulating reactor is 4 to 9, and the inner-outer diameter ratio of the airlift circulating reactor is 0.4 to 0.

8.

3. The method according to claim 2, characterized in that, The airlift circulating reactor includes a guide tube, a cylinder, and a gas distributor; wherein... The height ratio of the guide tube to the cylinder body is 0.5 to 0.7, the opening diameter of the gas distributor is 3 mm to 5 mm, and the opening degree of the enlarged section of the gas distributor is 30°C to 60°C.

4. The method according to claim 1, characterized in that, The mass concentration of sodium chloride in the first saturated sodium chloride solution is 24.5% to 26.5%.

5. The method according to claim 1, characterized in that, The molar concentration of ammonia in the saturated ammonia salt solution is 5.0 mol / L to 6.0 mol / L.

6. The method according to claim 1, characterized in that, The first set conditions include: the ammonia temperature is 5℃~10℃; and / or, The second set conditions include: the ammonia temperature is 20℃~30℃.

7. The method according to claim 1, characterized in that, The mass concentration of sodium chloride in the second saturated sodium chloride solution is 22% to 24%.

8. The method according to claim 1, characterized in that, The concentration of ammonia in the saturated mixture is 4.5 mol / L to 5.5 mol / L.

9. The method according to claim 1, characterized in that, The reaction temperature for generating NaHCO3 precipitate is 20℃~30℃.

10. The method according to claim 1, characterized in that, The cooling and crystallization temperature is 5℃~15℃.

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