A system and method for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater.

Abstract

This application relates to the field of sodium sulfate resource utilization technology, specifically disclosing a system and method for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater. A method for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater includes the following steps: S1: Dissolution: Prepare a solution from sodium sulfate waste salt or high-concentration wastewater; S2: Purification; S3: Carbonation; S4: Separation and drying; S5: Concentration and crystallization: Concentrate the mother liquor I, then add a sodium salt with a solubility greater than that of sodium sulfate and sodium bicarbonate at 0-5℃ to precipitate double salt crystals of sodium sulfate and sodium bicarbonate. After filtration and centrifugation, obtain the double salt product and ammonium sulfate solution. The double salt product is returned to step S3 for reuse; S6: Flash evaporation purification. The method for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater of this application has the advantages of high sodium sulfate utilization rate and high product purity.

Description

Technical Field

[0001] This application relates to the field of sodium sulfate resource utilization technology, and more specifically, it relates to a system and method for the resource utilization of sodium sulfate waste salt or high-concentration wastewater to produce sodium bicarbonate and ammonium sulfate. Background Technology

[0002] In the production processes of industries such as petrochemicals, coal chemicals, pharmaceuticals, lithium carbonate, zinc oxide, chromium salts, flue gas desulfurization, and chemical fibers, large amounts of soda ash and sulfuric acid are used, resulting in a large amount of wastewater or waste salt containing sodium sulfate. Due to strict environmental protection requirements, this sodium sulfate wastewater and waste salt cannot be directly discharged and require further treatment.

[0003] The treatment process for sodium sulfate wastewater or waste salt generally involves evaporation and crystallization to precipitate sodium sulfate products, with the evaporated water then being condensed and reused. However, due to problems such as a saturated sodium sulfate market, low added value, narrow application areas, and poor quality of recycled sodium sulfate products, a large amount of sodium sulfate is generated and stockpiled every year. The stockpiling process is not only labor-intensive and resource-intensive but also easily impacts the ecological environment.

[0004] The resource-based reuse of sodium sulfate is a better way to solve the stockpiling problem. Domestic and international technical personnel have conducted extensive research and development work in this area. For example, based on the soda ash production process, using sodium sulfate to produce soda ash can alleviate the pressure of sodium sulfate stockpiling to a certain extent. Another example is the co-production of sodium bicarbonate and ammonium sulfate from sodium sulfate and ammonium bicarbonate through a carbonation metathesis reaction. Through a process involving two freezing cycles and high-temperature ammonium distillation, the stable production of sodium bicarbonate with a purity of 85%-91% and ammonium sulfate with a nitrogen content of 18%-19.5% has been initially achieved, thus obtaining high-value-added industrial products.

[0005] Currently, the process of preparing sodium bicarbonate and ammonium sulfate by metathesis reaction of ammonium sulfate and ammonium bicarbonate has problems such as high energy consumption, complex process, high impurity content and low utilization rate of sodium and sulfate ions, resulting in the sodium bicarbonate and ammonium sulfate products produced failing to meet market requirements.

[0006] Regarding the above-mentioned issues, Chinese patent application CN111039310A discloses a method for preparing sodium bicarbonate and co-producing ammonium sulfate from sodium sulfate. The method includes carrying out a metathesis reaction of sodium sulfate and ammonium bicarbonate under the action of an accelerator, thereby expanding the crystallization zone of sodium bicarbonate and ammonium sulfate, thus increasing the precipitation rate of sodium bicarbonate and ammonium sulfate, which is beneficial to improving the purity of sodium bicarbonate and sodium sulfate.

[0007] The accelerators used in the above methods can easily introduce new substances into the system, causing a decrease in the purity of sodium bicarbonate and ammonium sulfate products. Summary of the Invention

[0008] To address the issue of low purity in sodium bicarbonate and ammonium sulfate products during the production of sodium bicarbonate from sodium sulfate, this application provides a system and method for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater.

[0009] In a first aspect, this application provides a method for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater, employing the following technical solution:

[0010] A method for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater includes the following steps:

[0011] S1: Dissolution: Prepare a solution by dissolving sodium sulfate waste salt or high-concentration wastewater;

[0012] S2: Purification: Add the impurity removal agent to the solution for heavy metal removal, then add the oxidant for oxidation, and then decolorize and filter to obtain the purified solution;

[0013] S3: Carbonation: Ammonium bicarbonate is added to the purification liquid, and a double decomposition reaction is carried out to obtain a slurry;

[0014] S4: Separation and drying: Centrifuge the slurry to obtain wet sodium bicarbonate and mother liquor I. The wet sodium bicarbonate is dried to obtain dry sodium bicarbonate.

[0015] S5: Concentration and crystallization: Concentrate the mother liquor I, and then add a sodium salt with a solubility greater than that of sodium sulfate and sodium bicarbonate at 0-5℃ to precipitate the double salt crystals of sodium sulfate and sodium bicarbonate. After separation by filtration and centrifugation, the double salt product and ammonium sulfate solution are obtained. The double salt product is returned to step S3 for reuse.

[0016] S6: Flash evaporation purification: The ammonium sulfate solution is concentrated by flash evaporation, cooled, and centrifuged to obtain wet ammonium sulfate and mother liquor II. Mother liquor II is returned to step S5 and mixed with mother liquor I. The wet ammonium sulfate is dried to obtain dry ammonium sulfate.

[0017] By adopting the above technical solution, sodium sulfate waste salt or high-concentration wastewater is first prepared into a solution, thereby separating the soluble components from the insoluble solid components. Then, a purification agent is added to remove heavy metal ions, reducing heavy metal ion pollution. Next, an oxidant is added for oxidation treatment, converting the sodium sulfite in the solution into sodium sulfate, increasing the purity of the sodium sulfate in the solution. After further decolorization and filtration, a relatively pure purified solution is obtained.

[0018] The purified liquid enters the carbonization stage. An appropriate proportion of ammonium bicarbonate is added to the purified liquid, so that sodium sulfate and ammonium bicarbonate undergo a metathesis reaction to generate a slurry containing sodium bicarbonate and ammonium sulfate. The slurry is then centrifuged to separate the wet sodium bicarbonate and mother liquor I. The wet sodium bicarbonate is dried to obtain a high-purity dry sodium bicarbonate.

[0019] The separated mother liquor I contained unreacted sodium sulfate and unseparated sodium bicarbonate components. Direct concentration and crystallization would result in low purity ammonium sulfate. To address this, this application adds a sodium salt with higher solubility than sodium sulfate and sodium bicarbonate to mother liquor I. Under low-temperature conditions of 0-5°C, utilizing the common ion effect of sodium ions, the sodium sulfate and sodium bicarbonate in mother liquor I are crystallized out as a double salt. After centrifugation, a relatively pure ammonium sulfate solution and double salt product are obtained. Furthermore, the double salt product can be reused in the carbonation stage, significantly improving the conversion rate of sodium sulfate and the purity of the sodium bicarbonate product.

[0020] The relatively pure ammonium sulfate solution obtained after centrifugation is concentrated by evaporation, cooled to precipitate ammonium sulfate crystals, and then separated by centrifugation to obtain wet ammonium sulfate and mother liquor II. The wet ammonium sulfate is dried to obtain dry ammonium sulfate with a purity of over 94%. Additionally, the tail gas generated during evaporation and concentration is adsorbed by dilute sulfuric acid to obtain ammonium sulfate recycling liquid. This recycling liquid is returned to the starting point of the process and mixed with the next batch of relatively pure ammonium sulfate solution for the next evaporation and concentration process. The separated mother liquor II is returned to step S5 and mixed with the concentrated mother liquor I for the next batch of crystallization, thereby improving the conversion rate and purity of the ammonium sulfate product.

[0021] This application introduces sodium salt during the freeze crystallization process, and by utilizing the common ion effect and the application of double salts in the carbonization stage, the concentration of ammonium sulfate is greatly increased, while the volume of ammonium sulfate solution is reduced, thereby obtaining a high-purity ammonium sulfate product. The overall energy consumption of the process is also significantly reduced, making it suitable for widespread application.

[0022] Preferably, in step S5, the amount of sodium salt added accounts for 0.1‰-0.15‰ of the mass of mother liquor I.

[0023] By employing the above technical solution, introducing excessive sodium salt during the freeze-crystallization stage does not significantly improve the crystallization-promoting effect; instead, it introduces unnecessary impurities, leading to a decrease in the purity of the ammonium sulfate product. Introducing too little sodium salt reduces the precipitation of sodium sulfate and sodium bicarbonate in mother liquor I, also causing a decrease in the purity of the ammonium sulfate solution. Therefore, optimizing and adjusting the amount of sodium salt added ensures the crystallization-promoting effect without introducing excessive impurities, thereby improving the purity of the ammonium sulfate product.

[0024] Preferably, in step S5, the sodium salt is one or more of sodium nitrate, sodium acetate, and sodium chloride.

[0025] By adopting the above technical solution, the solubility of sodium nitrate, sodium acetate, and sodium chloride at 0-5℃ is greater than that of sodium bicarbonate and ammonium sulfate. Based on the common ion effect, the precipitation of sodium bicarbonate and sodium sulfate can be effectively promoted. Furthermore, the introduction of sodium nitrate, sodium acetate, and sodium chloride will not have an excessive impact on the ammonium sulfate composition, thus ensuring the purity and concentration of the ammonium sulfate solution.

[0026] More preferably, in step S5, the added sodium salt undergoes a modification treatment, which includes the following steps:

[0027] 1) Take 65-80 parts of sodium carboxymethyl cellulose, 35-50 parts of water, 15-20 parts of ethanol, 5-10 parts of alginate, and 3-5 parts of acrylamide and mix them evenly to prepare the coating material;

[0028] 2) Take 150-180 parts of sodium salt, first weigh out 5.5-9% of the total sodium salt mass and add it to the coating material. After dispersing evenly, vacuum dry and grind to obtain the control material;

[0029] 3) Then mix the conditioning material with the remaining sodium salt evenly.

[0030] By employing the above technical solution, sodium carboxymethyl cellulose, alginate, and acrylamide form a cross-linked gel-like coating material in an aqueous system. The coating material has a network cross-linked structure, with hydrophilic groups and alkyl hydrophobic groups arranged in a gradient distribution within the network cross-linked structure, thus forming a hydrophilic-hydrophobic composite layer. This hydrophilic layer, together with water and ethanol, constitutes a "water reservoir" structure. Then, a small portion of sodium salt is added to the coating material and dispersed evenly. The sodium salt dissolves and disperses within the "water reservoir." After vacuum drying, the ethanol and water evaporate rapidly, resulting in a control material with an outer coating layer and an inner porous structure, allowing the sodium salt to be contained within the porous structure.

[0031] During the crystallization stage, after the modified sodium salt is added to the concentrated mother liquor I, the sodium salts, except for the regulator, dissolve rapidly and generate a common ion effect, promoting the precipitation of sodium sulfate and sodium bicarbonate and ensuring the purity of the ammonium sulfate solution. Then, during the crystallization process and subsequent batches, as time progresses, the coating structure of the regulator gradually absorbs water, expands, and dissolves, releasing the sodium salts from the void structure. These sodium salts gradually participate in the crystallization process, and the slow release helps stabilize the crystallization process, reducing the "polarization" and "runaway" phenomena during the crystallization of sodium sulfate and sodium bicarbonate, further improving the purity of the ammonium sulfate solution.

[0032] In addition, after the coating material dissolves, it enters the system and dissociates into carboxymethyl cellulose anions and alginate anions, which can form dynamic bonds with sodium ions. This dynamic bond can be used to introduce a new equilibrium point in the crystallization process, reducing the amount and frequency of sodium salt addition while maintaining the crystallization-promoting effect. At the same time, these anions can be recycled without affecting the system, further improving the purity of the ammonium sulfate product.

[0033] Preferably, in step S5, the endpoint control for concentrating mother liquor I is: the amount of water evaporated accounts for 3 / 10-7 / 20 of the total mass of mother liquor I.

[0034] By adopting the above technical solution, the concentration endpoint of mother liquor I is controlled, so that the concentrations of sodium bicarbonate, sodium sulfate and ammonium sulfate in the concentrated mother liquor I are within a suitable range, which is beneficial to the subsequent common ion precipitation operation, thereby obtaining a higher purity ammonium sulfate solution.

[0035] Preferably, in step S3, the mass ratio of sodium sulfate to ammonium bicarbonate in mother liquor I is 1:(1.05-1.1).

[0036] By adopting the above technical solution, adding too much ammonium bicarbonate during the carbonation stage will increase the subsequent separation pressure of the slurry, while introducing too little ammonium bicarbonate will result in incomplete reaction of sodium sulfate and a decrease in the conversion rate of sodium sulfate. Therefore, optimizing and adjusting the ratio of ammonium bicarbonate to ammonium sulfate is necessary to ensure that all sodium sulfate in the solution reacts, while simultaneously improving the purity of the subsequent sodium bicarbonate and ammonium sulfate products.

[0037] Preferably, in step S6, the concentration endpoint is reached when the amount of water evaporated reaches 1 / 2 to 3 / 5 of the volume of the ammonium sulfate solution.

[0038] By adopting the above technical solution, optimizing and adjusting the concentration endpoint, the precipitation of impurity salt components other than ammonium sulfate is minimized, thereby further improving the purity of the ammonium sulfate product. At the same time, the impact of returning mother liquor II to step S5 on the freeze crystallization system is reduced, thus improving the stability of the entire system.

[0039] Preferably, in step S6, the centrifugal separation factor is 800-1000 and the sieve mesh size is 150-200.

[0040] By adopting the above technical solutions, the centrifugation separation factor and sieve mesh size are tested and screened to reduce the precipitation and doping of impurities and salts, thereby improving the product quality and purity of ammonium sulfate.

[0041] Preferably, in step S4, a saturated sodium bicarbonate solution is used for washing during the centrifugal dehydration process.

[0042] By adopting the above technical solution, during the centrifugation process, a saturated sodium bicarbonate solution is used for rinsing simultaneously to remove the slurry adhering to the surface of the wet sodium bicarbonate particles, significantly improving the purity of the sodium bicarbonate product. The saturated sodium bicarbonate solution introduced during the washing process can be returned to step S3 in step S5 for reuse, without generating wastewater and achieving higher utilization.

[0043] Preferably, the sodium sulfate concentration in the solution is 28-33% by mass.

[0044] By adopting the above technical solution, the mass percentage concentration of sodium sulfate in the solution is optimized and adjusted, so as to obtain a relatively stable system while ensuring the purity of ammonium sulfate and sodium bicarbonate products, and it is not easy for instability to occur in stages such as carbonization, concentration and crystallization.

[0045] Secondly, this application provides a system for the resource-based production of sodium bicarbonate and ammonium sulfate using sodium sulfate waste salt or high-concentration wastewater, employing the following technical solution:

[0046] A system for the resource-based production of sodium bicarbonate and ammonium sulfate using sodium sulfate waste salt or high-concentration wastewater includes a crushing device, a dissolving device, a purification device, a carbonization device, a first centrifuge device, a first concentration device, a cooling device, a freeze crystallization device, a second centrifuge device, a second concentration device, and a third centrifuge device.

[0047] The inlet of the dissolving device is connected to the crushing device, and the outlet is connected to the purification device.

[0048] The liquid outlet of the purification device is connected to the feed inlet of the carbonization device, and the solid outlet of the purification device discharges filter residue.

[0049] The liquid outlet of the carbonization device is connected to the feed inlet of the first centrifuge device, and the solid outlet of the first centrifuge device discharges wet sodium bicarbonate.

[0050] The liquid outlet of the first centrifuge is connected to the feed inlet of the first concentration device, the liquid outlet of the first concentration device is connected to the feed inlet of the cooling device, the liquid outlet of the cooling device is connected to the feed inlet of the freezing crystallization device, the liquid outlet of the freezing crystallization device is connected to the feed inlet of the second centrifuge, and the solid discharge outlet of the second centrifuge discharges the double salt product.

[0051] The liquid outlet of the second centrifuge is connected to the feed inlet of the second concentration device, the liquid outlet of the second concentration device is connected to the feed inlet of the third centrifuge, and the solid outlet of the third centrifuge discharges wet ammonium sulfate.

[0052] In summary, this application has the following beneficial effects:

[0053] 1. This application uses sodium sulfate waste salt or high-concentration wastewater as raw material. After dissolution and purification, it undergoes a carbonization reaction with ammonium bicarbonate to obtain a high-purity sodium bicarbonate product. Furthermore, sodium salt is introduced during the concentration and crystallization stage. Utilizing the sodium common ion effect, a double salt of sodium sulfate and sodium bicarbonate is precipitated and returned to the carbonization stage for reuse. This not only significantly improves the conversion rate of sodium sulfate but also yields a high-purity ammonium sulfate product. The entire process has the advantages of low energy consumption and high sodium sulfate utilization.

[0054] 2. This application improves the purity of sodium bicarbonate and ammonium sulfate products without introducing impurities by controlling the ratio of sodium sulfate and ammonium bicarbonate, as well as the amount of sodium salt added.

[0055] 3. The system of this application uses the above method, and the entire system process is compact and stable. It can process large quantities of sodium sulfate waste salt or high-concentration wastewater intermittently or continuously, while obtaining high-value ammonium sulfate and sodium bicarbonate products, so that sodium sulfate can be well utilized as a resource. Attached Figure Description

[0056] Figure 1 Schematic diagram of purity data for the dried sodium bicarbonate products of Examples 1-9 and Comparative Examples 1-2 of this application.

[0057] Figure 2 : Schematic diagram of the one-step yield of sodium bicarbonate in Examples 1-9 and Comparative Examples 1-2 of this application.

[0058] Figure 3 : Schematic diagram of the residual sodium sulfate content in the dried sodium bicarbonate products of Examples 1-9 and Comparative Examples 1-2 of this application.

[0059] Figure 4 : A schematic diagram showing the content of ammonium sulfate (calculated as nitrogen content) in the dry ammonium sulfate products of Examples 1-9 and Comparative Examples 1-2 of this application.

[0060] Figure 5 : Schematic diagram of the yield of ammonium sulfate in Examples 1-9 and Comparative Examples 1-2 of this application.

[0061] Figure 6 : Schematic diagram of sodium sulfate utilization data in Examples 1-9 and Comparative Examples 1-2 of this application.

[0062] Figure 7 The process flow diagrams of the methods for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater according to Examples 1-9 of this application are shown. Detailed Implementation

[0063] The following combination Figure 7 The present application will be further described in detail with reference to the embodiments.

[0064] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application are all commercially available.

[0065] Example

[0066] Example 1

[0067] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this embodiment includes the following steps:

[0068] S1: Dissolution: Prepare a solution by dissolving sodium sulfate waste salt or high-concentration wastewater or steam condensate. The mass percentage concentration of sodium sulfate in the solution is 25%.

[0069] S2: Purification: Sodium sulfide is added to the solution as a purification agent to remove heavy metals. Then, 27.5% hydrogen peroxide is added as an oxidant for oxidation. Activated carbon is then added for decolorization and filtration to obtain a clear and transparent purified solution. The pH value of the purified solution is controlled within the range of 7-8. The filter residue produced by filtration is further treated to render it harmless.

[0070] S3: Carbonation: Add industrial-grade ammonium bicarbonate to the purification solution, and control the mass ratio of sodium sulfate to added sodium bicarbonate in the purification solution to be 1:1.03. After the double decomposition reaction, a slurry is obtained. The reaction temperature range is controlled at 35℃, the stirring speed is controlled at 50r / min, and the reaction time is controlled at 60min.

[0071] S4: Separation and drying: The slurry is placed in a centrifuge for centrifugation. The centrifugation factor is controlled above 1000 and the sieve mesh of the centrifuge is controlled at 350 mesh to obtain wet sodium bicarbonate and mother liquor I. The wet sodium bicarbonate is dried to obtain dry sodium bicarbonate.

[0072] S5: Concentration and Crystallization: Mother liquor I is concentrated in a negative pressure concentration vessel under the following conditions: vacuum degree controlled at -60-90 kPa, temperature controlled at 80°C. The concentration endpoint is determined by the amount of water evaporated. When the amount of water evaporated is 3 / 10 of the total weight of mother liquor I, the concentrated mother liquor I is obtained. Then, the concentrated mother liquor I is cooled to 35°C and transferred to a cooling crystallization vessel. Sodium acetate is then added to the cooling crystallization vessel at 0°C. The amount of sodium acetate added is 0.05‰ of the mass of mother liquor I. The freezing and heat preservation time is controlled at 90 min, and the refrigerant temperature is controlled at -(10-15)°C. After freezing and crystallization, sodium sulfate and sodium bicarbonate double salt crystals are precipitated. After solid-liquid separation by filtration and centrifugation, the double salt product and ammonium sulfate solution are obtained. The double salt product is returned to the carbonization reaction in step S3 for reuse.

[0073] S6: Flash Evaporation Purification: The ammonium sulfate solution is concentrated by flash evaporation. The flash evaporation concentration process is as follows: the vacuum degree is controlled within the range of 0.06-0.09 MPa, the temperature is 75℃, and the concentration endpoint is determined by the amount of water evaporated, which is 1 / 2 of the volume of the ammonium sulfate solution. The steam generated during the flash evaporation concentration process is condensed and returned to the dissolution process for use. The generated tail gas is absorbed by dilute sulfuric acid and discharged after meeting the standards. The ammonium sulfate circulating liquid generated by absorption is returned to this process and mixed with the ammonium sulfate solution. After being cooled by circulating water, it is transported to a centrifuge for centrifugal dehydration to obtain wet ammonium sulfate and mother liquor II. The centrifugal separation factor is controlled at 800, and the centrifuge screen mesh is controlled at 200 mesh. The obtained mother liquor II is returned to step S5 and mixed with the concentrated mother liquor I. The wet ammonium sulfate is dried to obtain dry ammonium sulfate.

[0074] The system for the resource-based production of sodium bicarbonate and ammonium sulfate using sodium sulfate waste salt or high-concentration wastewater in this embodiment includes a crushing device, a dissolving device, a purification device, a carbonization device, a first centrifuge device, a first concentration device, a cooling device, a cryogenic crystallization device, a second centrifuge device, a second concentration device, and a third centrifuge device.

[0075] The crushing device is a pulverizer, which includes a feed inlet, a crushing chamber, a discharge outlet, and a flue gas dust collector. Sodium sulfate waste salt enters the crushing chamber through the feed inlet for crushing, and the crushed sodium sulfate waste salt particles are discharged through the discharge outlet. The flue gas generated during the crushing process is removed by the flue gas dust collector to avoid pollution.

[0076] The dissolving device is a dissolving tank equipped with a stirring device. The inlet of the dissolving tank is connected to the outlet of the crusher. The crushed sodium sulfate waste salt particles or high-concentration sodium sulfate wastewater are added into the dissolving tank, and steam condensate is added at the same time to mix and stir, so as to prepare a dissolving solution.

[0077] The purification and filtration device is a sedimentation tank. The inlet of the sedimentation tank is connected to the outlet of the dissolving tank. The dissolved solution undergoes sedimentation, impurity removal, oxidation, adsorption, decolorization and filtration in the sedimentation tank to obtain a clear and transparent sodium sulfate solution. The sedimentation tank is equipped with a solid discharge port for discharging filter residue.

[0078] The carbonization device is a reactor equipped with a stirring device and a temperature control device. The inlet of the carbonization device is connected to the outlet of the sedimentation tank. The clear and transparent sodium sulfate solution undergoes a carbonization reaction with ammonium bicarbonate in the reactor to obtain a slurry.

[0079] The first centrifugal device is a centrifuge. The inlet of the centrifuge is connected to the outlet of the reaction vessel. The slurry is centrifuged and separated in the centrifuge to obtain mother liquor I and wet sodium bicarbonate. The wet sodium bicarbonate is discharged through the solid outlet of the centrifuge and then dried by a dryer to obtain dry sodium bicarbonate.

[0080] The first concentration device is a negative pressure concentration vessel. The inlet of the negative pressure concentration vessel is connected to the outlet of the centrifuge. The mother liquor I is concentrated into mother liquor I concentrate.

[0081] The cooling device is a cooling tank. The inlet of the cooling tank is connected to the outlet of the negative pressure concentrator. The cooling tank is equipped with a jacket, and cooling water is circulated in the jacket to cool the mother liquor I concentrate.

[0082] The cryo-crystallization device is a cryo-crystallizer. The inlet of the cryo-crystallizer is connected to the outlet of the cooling tank. The concentrated mother liquor I is cryo-crystallized in the cryo-crystallizer to obtain a cryo-liquid containing sodium sulfate, sodium bicarbonate, and ammonium sulfate solution.

[0083] The second centrifugal device is a centrifuge. The inlet of the centrifuge is connected to the outlet of the cryogenic crystallizer. The cryogenic liquid is centrifuged to separate solids and liquids, resulting in ammonium sulfate solution and sodium sulfate and sodium bicarbonate double salt products. The solids processing port of the centrifuge is connected to the inlet of the dissolving tank, returning the sodium sulfate and sodium bicarbonate double salt products to the dissolving tank for re-dissolution.

[0084] The second concentration device is a vacuum concentration tank. The inlet of the vacuum concentration tank is connected to the outlet of the centrifuge. After the ammonium sulfate solution is concentrated, ammonium sulfate crystals precipitate out, resulting in a mixed solution containing ammonium sulfate crystals. The condensate pipe of the vacuum concentration tank is connected to the dissolving tank to provide condensate to the dissolving tank.

[0085] The third centrifugation device is a centrifuge. The inlet of the centrifuge is connected to the outlet of the vacuum concentrator. After centrifugation, the mixture containing ammonium sulfate crystals is used to obtain wet ammonium sulfate and mother liquor II. The wet ammonium sulfate is discharged through the solid outlet of the centrifuge and then dried by a dryer to obtain dry ammonium sulfate. The outlet of the centrifuge is connected to the inlet of the cryo-crystallizer, and the mother liquor II is returned to the cryo-crystallizer to be mixed with the concentrated mother liquor I for secondary cryo-crystallization and separation of double salt.

[0086] Example 2

[0087] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this embodiment includes the following steps:

[0088] S1: Dissolution: Prepare a solution by dissolving sodium sulfate waste salt or high-concentration wastewater or steam condensate. The mass percentage concentration of sodium sulfate in the solution is 33%.

[0089] S2: Purification: Sodium sulfide is added to the solution as a purification agent to remove heavy metals. Then, 27.5% hydrogen peroxide is added as an oxidant for oxidation. Activated carbon is then added for decolorization and filtration to obtain a clear and transparent purified solution. The pH value of the purified solution is controlled within the range of 7-8. The filter residue produced by filtration is further treated to render it harmless.

[0090] S3: Carbonation: Add industrial-grade ammonium bicarbonate to the purification solution, control the mass ratio of sodium sulfate to added sodium bicarbonate in the purification solution to be 1:1.1, and obtain a slurry after a metathesis reaction. The reaction temperature range is controlled at 40℃, the stirring speed is controlled at 55r / min, and the reaction time is controlled at 50min.

[0091] S4: Separation and drying: The slurry is placed in a centrifuge for centrifugation. The centrifugation factor is controlled above 1000 and the sieve mesh of the centrifuge is controlled at 400 mesh to obtain wet sodium bicarbonate and mother liquor I. The wet sodium bicarbonate is dried to obtain dry sodium bicarbonate.

[0092] S5: Concentration and Crystallization: Mother liquor I is concentrated in a negative pressure concentration vessel under the following conditions: vacuum degree controlled at -60-90 kPa, temperature controlled at 90°C. The concentration endpoint is determined by the amount of water evaporated. When the amount of water evaporated is 7 / 20 of the total weight of mother liquor I, the concentrated mother liquor I is obtained. Then, the concentrated mother liquor I is cooled to 40°C and transferred to a cooling crystallization vessel. Sodium nitrate is added to the cooling crystallization vessel at 5°C. The amount of sodium nitrate added is 0.15‰ of the mass of mother liquor I. The freezing and holding time is controlled at 60 min, and the refrigerant temperature is controlled at -(10-15)°C. After freezing and crystallization, sodium sulfate and sodium bicarbonate double salt crystals are precipitated. After solid-liquid separation by filtration and centrifugation, double salt product and ammonium sulfate solution are obtained. The double salt product is returned to the carbonization reaction in step S3 for reuse.

[0093] S6: Flash Evaporation Purification: The ammonium sulfate solution is concentrated by flash evaporation. The flash evaporation concentration process is as follows: the vacuum degree is controlled within the range of 0.06-0.09 MPa, the temperature is 85℃, and the concentration endpoint is determined by the amount of water evaporated, which is 3 / 5 of the volume of the ammonium sulfate solution. The steam generated during the flash evaporation concentration process is condensed and returned to the dissolution process for use. The generated tail gas is absorbed by dilute sulfuric acid and discharged after meeting the standards. The ammonium sulfate circulating liquid generated by absorption is returned to this process and mixed with the ammonium sulfate solution. After being cooled by circulating water, it is transported to a centrifuge for centrifugal dehydration to obtain wet ammonium sulfate and mother liquor II. The centrifugal separation factor is controlled at 1000, and the centrifuge screen mesh is controlled at 150 mesh. The obtained mother liquor II is returned to step S5 and mixed with the concentrated mother liquor I. The wet ammonium sulfate is dried to obtain dry ammonium sulfate.

[0094] The system used in this embodiment for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 1.

[0095] Example 3

[0096] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this embodiment includes the following steps:

[0097] S1: Dissolution: Prepare a solution by dissolving sodium sulfate waste salt or high-concentration wastewater or steam condensate. The mass percentage concentration of sodium sulfate in the solution is 28%.

[0098] S2: Purification: Sodium sulfide is added to the solution as a purification agent to remove heavy metals. Then, 27.5% hydrogen peroxide is added as an oxidant for oxidation. Activated carbon is then added for decolorization and filtration to obtain a clear and transparent purified solution. The pH value of the purified solution is controlled within the range of 7-8. The filter residue produced by filtration is further treated to render it harmless.

[0099] S3: Carbonation: Add industrial-grade ammonium bicarbonate to the purification solution, and control the mass ratio of sodium sulfate to added sodium bicarbonate in the purification solution to be 1:1.05. After the double decomposition reaction, a slurry is obtained. The reaction temperature range is controlled at 38℃, the stirring speed is controlled at 55r / min, and the reaction time is controlled at 55min.

[0100] S4: Separation and Drying: The slurry is placed in a centrifuge for centrifugation. During centrifugation, it is washed with saturated sodium bicarbonate solution. The amount of saturated sodium bicarbonate solution used is 1 / 20 of the weight of the obtained dry sodium bicarbonate. The centrifugation factor is controlled above 1000, and the mesh size of the centrifuge screen is controlled at 360 mesh to obtain wet sodium bicarbonate and mother liquor I. The wet sodium bicarbonate is dried to obtain dry sodium bicarbonate.

[0101] S5: Concentration and Crystallization: Mother liquor I is concentrated in a negative pressure concentration vessel under the following conditions: vacuum degree controlled at -60-90Kpa, temperature controlled at 85℃. The concentration endpoint is determined by the amount of water evaporated. When the amount of water evaporated is 1 / 3 of the total weight of mother liquor I, the concentrated mother liquor I is obtained. Then, the concentrated mother liquor I is cooled to 35℃ and transferred to a cooling crystallization vessel. Sodium chloride is added to the cooling crystallization vessel at 4℃, with the amount of sodium chloride added being 0.1‰ of the mass of mother liquor I. The freezing and heat preservation time is controlled at 80min, and the refrigerant temperature is controlled at -(10-15)℃. After the freezing and crystallization treatment, sodium sulfate and sodium bicarbonate double salt crystals are precipitated. After solid-liquid separation by filtration and centrifugation, the double salt product and ammonium sulfate solution are obtained. The double salt product is returned to the carbonization reaction in step S3 for reuse.

[0102] S6: Flash Evaporation Purification: The ammonium sulfate solution is concentrated by flash evaporation. The flash evaporation concentration process is as follows: the vacuum degree is controlled within the range of 0.06-0.09 MPa, the temperature is 80℃, and the concentration endpoint is determined by the amount of water evaporated, which is 1 / 2 of the volume of the ammonium sulfate solution. The steam generated during the flash evaporation concentration process is condensed and returned to the dissolution process for use. The generated tail gas is absorbed by dilute sulfuric acid and discharged after meeting the standards. The ammonium sulfate circulating liquid generated by absorption is returned to this process and mixed with the ammonium sulfate solution. After being cooled by circulating water, it is transported to a centrifuge for centrifugal dehydration to obtain wet ammonium sulfate and mother liquor II. The centrifugal separation factor is controlled at 900, and the centrifuge screen mesh is controlled at 180 mesh. The obtained mother liquor II is returned to step S5 and mixed with the concentrated mother liquor I. The wet ammonium sulfate is dried to obtain dry ammonium sulfate.

[0103] The system used in this embodiment for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 1.

[0104] Example 4

[0105] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this embodiment differs from that in Example 3 in that the sodium salt added in step S5 undergoes modification treatment, while the remaining steps are the same as in Example 3.

[0106] The sodium salt added in this embodiment was obtained through the following modification process:

[0107] 1) Accurately weigh 6.5 kg sodium carboxymethyl cellulose, 3.5 kg water, 2 kg ethanol, 0.5 kg alginate and 0.3 kg acrylamide and add them to a mixing tank. Heat the mixture to 65°C and mix it evenly at a stirring speed of 500 rpm / 983 min to obtain the coating material.

[0108] 2) Weigh 15kg of sodium salt, take 825g of sodium salt first, and add the weighed 825g of sodium salt to the coating material at a speed of 50g / min under a stirring speed of 150rpm / min. After the addition is completed, increase the stirring speed to 350rpm / min and continue mixing for 15min. Then place it in a vacuum dryer for vacuum drying and grind it to obtain the control material. The average particle size of the control material is 850μm.

[0109] 3) Mix the conditioning agent with the remaining sodium salt until evenly mixed.

[0110] The system used in this embodiment for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 3.

[0111] Example 5

[0112] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this embodiment differs from that in Example 3 in that the sodium salt added in step S5 undergoes modification treatment, while the remaining steps are the same as in Example 3.

[0113] The sodium salt added in this embodiment was obtained through the following modification process:

[0114] 1) Accurately weigh 8 kg of sodium carboxymethyl cellulose, 5 kg of water, 1.5 kg of ethanol, 1 kg of alginate, and 0.5 kg of acrylamide and add them to a mixing tank. Heat the mixture to 65°C and mix it evenly at a stirring speed of 500 rpm / min to obtain the coating material.

[0115] 2) Weigh 18kg of sodium salt, first take 1.62kg of sodium salt, and add the weighed 1.62kg of sodium salt to the coating material at a stirring speed of 80g / min under a stirring speed of 150rpm / min. After the addition is completed, increase the stirring speed to 350rpm / min and continue mixing for 15min. Then place it in a vacuum dryer for vacuum drying, and then grind it to obtain the conditioning material. The average particle size of the conditioning material is 600μm.

[0116] 3) Mix the conditioning agent with the remaining sodium salt until evenly mixed.

[0117] The system used in this embodiment for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 3.

[0118] Example 6

[0119] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this embodiment differs from that in Example 3 in that the sodium salt added in step S5 undergoes modification treatment, while the remaining steps are the same as in Example 3.

[0120] The sodium salt added in this embodiment was obtained through the following modification process:

[0121] 1) Accurately weigh 7.2 kg sodium carboxymethyl cellulose, 4.6 kg water, 1.75 kg ethanol, 0.83 kg alginate and 0.37 kg acrylamide and add them to a mixing tank. Heat the mixture to 65°C and mix it evenly at a stirring speed of 500 rpm / min to obtain the coating material.

[0122] 2) Weigh 16.5 kg of sodium salt, take 1.25 kg of sodium salt first, and add the weighed 1.25 kg of sodium salt to the coating material at a speed of 75 g / min under a stirring speed of 150 rpm / min. After the addition is completed, increase the stirring speed to 350 rpm / min and continue mixing for 15 min. Then place it in a vacuum dryer for vacuum drying and grind it to obtain the control material. The average particle size of the control material is 730 μm.

[0123] 3) Mix the conditioning agent with the remaining sodium salt until evenly mixed.

[0124] The system used in this embodiment for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 3.

[0125] Example 7

[0126] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this embodiment differs from that in Example 3 in that the sodium salt added in step S5 undergoes modification treatment, while the remaining steps are the same as in Example 3.

[0127] The sodium salt added in this embodiment was obtained through the following modification process:

[0128] 1) Accurately weigh 6.5 kg of sodium carboxymethyl cellulose and 3.5 kg of water and add them to the mixing tank. Heat the mixture to 65°C and mix it evenly with a stirring speed of 500 rpm / min to obtain the coating material.

[0129] 2) Weigh 15kg of sodium salt, take 825g of sodium salt first, and add the weighed 825g of sodium salt to the coating material at a speed of 50g / min under a stirring speed of 150rpm / min. After the addition is completed, increase the stirring speed to 350rpm / min and continue mixing for 15min. Then place it in a vacuum dryer for vacuum drying and grind it to obtain the control material. The average particle size of the control material is 850μm.

[0130] 3) Mix the conditioning agent with the remaining sodium salt until evenly mixed.

[0131] The system used in this embodiment for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 3.

[0132] Example 8

[0133] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this embodiment differs from that in Example 3 in that the sodium salt added in step S5 undergoes modification treatment, while the remaining steps are the same as in Example 3.

[0134] The sodium salt added in this embodiment was obtained through the following modification process:

[0135] 1) Accurately weigh 6.5 kg of gelatin, 3.5 kg of water, 2 kg of ethanol, 0.5 kg of chitosan and 0.3 kg of acrylamide and add them to a mixing tank. Heat the mixture to 65°C and mix it evenly at a stirring speed of 500 rpm / min to obtain the coating material.

[0136] 2) Weigh 15kg of sodium salt, take 825g of sodium salt first, and add the weighed 825g of sodium salt to the coating material at a speed of 50g / min under a stirring speed of 150rpm / min. After the addition is completed, increase the stirring speed to 350rpm / min and continue mixing for 15min. Then place it in a vacuum dryer for vacuum drying and grind it to obtain the control material. The average particle size of the control material is 850μm.

[0137] 3) Mix the conditioning agent with the remaining sodium salt until evenly mixed.

[0138] The system used in this embodiment for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 3.

[0139] Example 9

[0140] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this embodiment differs from that in Example 3 in that the sodium salt added in step S5 undergoes modification treatment, while the remaining steps are the same as in Example 3.

[0141] The sodium salt added in this embodiment was obtained through the following modification process:

[0142] 1) Accurately weigh 6.5 kg sodium carboxymethyl cellulose, 3.5 kg water, 2 kg ethanol, 0.5 kg alginate and 0.3 kg acrylamide and add them to a mixing tank. Heat the mixture to 65°C and mix it evenly at a stirring speed of 500 rpm / min to obtain the coating material.

[0143] 2) Weigh 15kg of sodium salt, take 5kg of sodium salt first, and add the weighed 5kg of sodium salt to the coating material at a speed of 50g / min under a stirring speed of 150rpm / min. After the addition is completed, increase the stirring speed to 350rpm / min and continue mixing for 15min. Then place it in a vacuum dryer for vacuum drying and grind it to obtain the control material. The average particle size of the control material is 850μm.

[0144] 3) Mix the conditioning agent with the remaining sodium salt until evenly mixed.

[0145] The system used in this embodiment for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 3.

[0146] Comparative Example

[0147] Comparative Example 1

[0148] The method for producing sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this comparative example differs from that in Example 1 in that sodium salt is not added during the freezing crystallization stage in step S5, while the remaining steps are the same as in Example 1.

[0149] The system used in this comparative example for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 1.

[0150] Comparative Example 2

[0151] The method for resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater in this comparative example differs from that in Example 1 in that: in step S6, mother liquor II is not returned to step S94.65 to be mixed with mother liquor I, and the remaining steps are the same as in Example 1.

[0152] The system used in this comparative example for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater is the same as that in Example 1.

[0153] Performance testing

[0154] Sodium bicarbonate and ammonium sulfate were produced according to the resource recovery methods for sodium sulfate waste salt or high-concentration wastewater in Examples 1-9 and Comparative Examples 1-2. The purity of the obtained dry sodium bicarbonate was tested, and the data are as follows: Figure 1 As shown; calculate the one-step yield of sodium bicarbonate: One-step yield of sodium bicarbonate = (Actual amount of sodium bicarbonate obtained / Theoretical yield calculated from the double decomposition reaction equation) × 100%, data as follows. Figure 2 As shown; the residual sodium sulfate in the dried sodium bicarbonate was detected, and the data are as follows. Figure 3 As shown; the content of ammonium sulfate (calculated as nitrogen content) in the dried ammonium sulfate product was determined, and the data are as follows. Figure 4 As shown; calculate the yield of ammonium sulfate: Ammonium sulfate yield = (Actual amount of ammonium sulfate obtained / Theoretical yield calculated from the double decomposition reaction equation) × 100%, data as follows. Figure 5 As shown; calculate the utilization rate of sodium sulfate, and use the utilization rate to evaluate the conversion rate of sodium sulfate. The utilization rate of sodium sulfate = (mass of sulfate ions in ammonium sulfate solution / mass of sulfate ions in sodium sulfate solution) × 100%. Data is shown below. Figure 6 As shown.

[0155] Analyze Examples 1-3 and Comparative Examples 1-2 in conjunction with Figure 1-6 It can be seen that by adding an appropriate proportion of ammonium bicarbonate during the carbonization stage, the metathesis reaction is promoted to near-completeness, producing trace amounts of impurity components, which simplifies subsequent separation and results in high product purity. Furthermore, the addition of sodium salt during the freeze-crystallization stage utilizes the effect of sodium ions to promote the precipitation of sodium sulfate and sodium bicarbonate from the ammonium sulfate solution into a double salt product, significantly increasing the concentration and purity of the ammonium sulfate solution. The double salt product is then reused, improving the utilization rate of sodium sulfate. It can be seen that the sodium sulfate utilization rate in Example 3 reaches over 96%, the one-step yield of sodium bicarbonate reaches over 97%, and the purity of the dried sodium bicarbonate product reaches over 98%, with the residual sodium sulfate content in the dried sodium bicarbonate product controlled below 0.5%. In contrast, the sodium sulfate utilization rate in Comparative Example 1 is only 86%, and the one-step yield of sodium bicarbonate is only 83%. Additionally, the ammonium sulfate yield in Example 3 reaches over 94%, and the ammonium sulfate content (based on nitrogen content) in the dried ammonium sulfate product reaches over 20%. In addition, the addition of sodium salt can increase the operating temperature of the freezing crystallization process. Moreover, after sodium sulfate and sodium bicarbonate precipitate, the concentration of ammonium sulfate solution can be increased, thereby reducing the volume of ammonium sulfate solution that needs to be frozen, which can effectively reduce energy consumption. Therefore, compared with the traditional secondary freezing process, it can save about 25-30% of energy consumption.

[0156] Analyze Examples 4-6 and combine them with Figure 4-6 It can be seen that after the sodium salt is modified, a portion of the added sodium salt is contained in the void structure of the control material. During the recycling process, the sodium salt can be continuously released, making the precipitation-promoting effect of the sodium salt stable and continuous during the freezing crystallization stage, thus precipitating more completely and further improving the utilization rate of sodium sulfate and the purity of ammonium sulfate.

[0157] Furthermore, the sodium carboxymethyl cellulose and alginate in the coating material can dissociate into anions. These anions have significant steric hindrance, and through intermolecular forces such as chelation, they can appropriately buffer and regulate the sodium common ion effect during the crystallization process, making the overall crystallization process more stable and complete, and obtaining an ammonium sulfate solution with higher concentration and purity. It can be seen that the ammonium sulfate yield in Example 6 can reach over 97%, and the sodium sulfate utilization rate is over 98%.

[0158] Analyze Examples 3 and 7-9 and combine them with... Figure 1-6It can be seen that in Example 7, using only sodium carboxymethyl cellulose as the coating material component, a complete network cross-linking structure and void structure cannot be formed. The sustained-release effect during the freeze-crystallization stage is poor and unstable, leading to a decrease in the purity of the dried ammonium sulfate product. In Example 8, using gelatin as the coating material component not only fails to provide a good precipitation-promoting effect but also causes instability in the precipitation process. The precipitation of sodium sulfate and sodium bicarbonate is incomplete, and the purity of the dried ammonium sulfate product continuously decreases after repeated use. In Example 9, introducing a large amount of sodium salt into the conditioning material results in an excessively strong sustained-release effect during the freeze-crystallization process. After repeated use, insufficient sodium salt in the early stage and excessive sodium salt in the middle and later stages easily occur, leading to a deterioration in the overall precipitation-promoting effect.

[0159] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for the resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater, characterized in that, Includes the following steps: S1: Dissolution: Prepare a solution by dissolving sodium sulfate waste salt or high-concentration wastewater; S2: Purification: Add the impurity removal agent to the solution for heavy metal removal, then add the oxidant for oxidation, and then decolorize and filter to obtain the purified solution; S3: Carbonation: Ammonium bicarbonate is added to the purification liquid, and a double decomposition reaction is carried out to obtain a slurry; S4: Separation and drying: The slurry is centrifuged to obtain wet sodium bicarbonate and mother liquor I. The wet sodium bicarbonate is dried to obtain dry sodium bicarbonate. S5: Concentration and crystallization: Concentrate the mother liquor I, and then add a sodium salt with a solubility greater than that of sodium sulfate and sodium bicarbonate at 0-5℃ to precipitate the double salt crystals of sodium sulfate and sodium bicarbonate. After separation by filtration and centrifugation, the double salt product and ammonium sulfate solution are obtained. The double salt product is returned to step S3 for reuse. S6: Flash evaporation purification: The ammonium sulfate solution is concentrated by flash evaporation, cooled, and centrifuged to obtain wet ammonium sulfate and mother liquor II. Mother liquor II is returned to step S5 and mixed with mother liquor I. The wet ammonium sulfate is dried to obtain dry ammonium sulfate. The concentration endpoint is defined as the amount of water evaporated reaches 1 / 2 to 3 / 5 of the volume of the ammonium sulfate solution. In step S5, the amount of sodium salt added is 0.1‰-0.15‰ of the mass of mother liquor I; In step S5, the added sodium salt undergoes a modification treatment, which includes the following steps: 1) Take 65-80 parts of sodium carboxymethyl cellulose, 35-50 parts of water, 15-20 parts of ethanol, 5-10 parts of alginate, and 3-5 parts of acrylamide and mix them evenly to prepare the coating material; 2) Take 150-180 parts of sodium salt, first weigh out 5.5-9% of the total sodium salt mass and add it to the coating material. After dispersing evenly, vacuum dry and grind to obtain the control material; 3) Then mix the conditioning material with the remaining sodium salt evenly.

2. The method for resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater according to claim 1, characterized in that, In step S5, the sodium salt is one or more of sodium nitrate, sodium acetate, and sodium chloride.

3. The method for resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater according to claim 1, characterized in that, In step S5, the endpoint control for concentrating mother liquor I is: the amount of water evaporated accounts for 3 / 10-7 / 20 of the total mass of mother liquor I.

4. The method for resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater according to claim 1, characterized in that, In step S6, the centrifugal separation factor is 800-1000, and the sieve mesh size is 150-200 mesh.

5. The method for resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater according to claim 1, characterized in that, In step S4, a saturated sodium bicarbonate solution is used for washing during the centrifugal dehydration process.

6. The method for resource-based production of sodium bicarbonate and ammonium sulfate from sodium sulfate waste salt or high-concentration wastewater according to claim 1, characterized in that, The sodium sulfate concentration in the solution is 28-33% by mass.

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