Method for preparing large-particle sodium bicarbonate from sodium sulfate

Abstract

The invention discloses a method for preparing large-particle sodium bicarbonate from sodium sulfate. The method comprises the following steps: pretreating raw materials; dynamically adjusting reaction conditions; establishing a raw material database; carrying out multistage continuous crystallization reaction; heat integration and waste heat recovery; the alkali medium is recycled; the temperature gradient design is simplified; double salt crystal separation and resource utilization, and bicarbonate radical concentration control; strengthening double salt separation by a membrane separation technology; and carrying out solid-liquid separation and product collection. In a sodium sulfate raw material dissolving stage, sodium carbonate or sodium bicarbonate is added to adjust the concentration of carbonate in a solution, so that the concentration is stabilized in a target range, ATR FT-IR is used for carrying out in-situ real-time quantitative analysis on carbonate ions in an aqueous solution, carbonate is automatically supplemented through feedback control, and the content of carbonate ions in the aqueous solution is determined. A plate heat exchanger is installed in a multi-stage reaction device, waste heat of previous-stage reaction liquid is utilized to preheat next-stage reaction liquid, and heat in mother liquor is recovered by adopting a vacuum evaporation technology in salting-out crystallization.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, specifically a method for preparing large-particle sodium bicarbonate from sodium sulfate. Background Technology

[0002] Sodium bicarbonate is an important industrial and daily chemical product. It is generally produced from sodium chloride via the Solvay process or a combined alkali production process. Sodium sulfate is a basic chemical raw material derived from sodium sulfate minerals and chemical byproducts. Currently, the production of sodium sulfate far exceeds the demand. If sodium sulfate could replace sodium chloride as a raw material for the production of sodium bicarbonate, it would have significant economic and environmental benefits.

[0003] The ideal method for preparing sodium bicarbonate from sodium sulfate is to react it with ammonium bicarbonate via solution metathesis. However, the conversion rate of sodium sulfate metathesis reaction is low, the utilization rate of sodium sulfate is less than 60%, and it is impossible to obtain pure ammonium sulfate, resulting in high costs and hindering the development and application of this technology.

[0004] CN118479496B discloses a method for preparing large-particle sodium bicarbonate from sodium sulfate. The method includes: continuously crystallizing a saturated sodium sulfate solution containing carbonate ions with ammonium bicarbonate, introducing carbon dioxide during the reaction, and separating the solid and liquid phases after the reaction to obtain large-particle sodium bicarbonate. This invention uses a saturated sodium sulfate solution containing carbonate ions as raw material, and through a continuous crystallization reaction, controls the nucleation of sodium bicarbonate by carbon dioxide, enabling the preparation of large-particle sodium bicarbonate with a D50 particle size greater than 200 μm. The product has high purity, and the total alkali content of the sodium bicarbonate product can reach over 98.0%. Simultaneously, it yields recyclable sodium sulfate raw material and pure double salt, achieving high raw material utilization. Furthermore, existing methods for preparing large-particle sodium bicarbonate from sodium sulfate have the following disadvantages in use:

[0005] (1) Existing methods for preparing large-particle sodium bicarbonate from sodium sulfate have certain requirements on the purity of the saturated sodium sulfate solution, especially the carbonate content, which may affect the final quality and yield of the product.

[0006] (2) Existing methods for preparing large-particle sodium bicarbonate from sodium sulfate require a multi-stage temperature gradient that requires gradual cooling (e.g., 55℃→35℃), which requires continuous cooling and has low energy efficiency. High-temperature reaction (e.g., 55℃) and low-temperature salting-out steps may increase additional energy consumption. Salting-out crystallization requires the addition of an alkaline medium (e.g., ammonia or sodium hydroxide), which increases reagent consumption and subsequent processing costs.

[0007] (3) Existing methods for preparing large-particle sodium bicarbonate from sodium sulfate require separation of double salt crystals (such as Na2SO4·(NH4)2SO4·4H2O), which may increase subsequent purification steps. Improper control of bicarbonate concentration during salting-out crystallization can lead to secondary precipitation of sodium bicarbonate, affecting the cycle efficiency. Summary of the Invention

[0008] The technical problem to be solved by this invention is to overcome the above-mentioned technical defects and provide a method for preparing large-particle sodium bicarbonate from sodium sulfate.

[0009] To solve the above problems, the technical solution of the present invention includes the following steps:

[0010] S1. Raw material pretreatment: During the sodium sulfate raw material dissolution stage, sodium carbonate or sodium bicarbonate is added to adjust the carbonate concentration in the solution to 0.5-1.5 mol / L; Attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) is used to perform in-situ real-time quantitative analysis of carbonate ions in the aqueous solution, and carbonate is automatically replenished through a feedback control system; When there are many impurities in the raw material, a filtration or adsorption step is added to remove impurity ions.

[0011] S2. Dynamically adjust reaction conditions, and dynamically adjust the addition ratio of ammonium bicarbonate and carbon dioxide according to the actual concentration of carbonate in the raw materials.

[0012] S3. Establish a raw material database, record the impurity content of different batches of sodium sulfate, and predict the optimal combination of reaction parameters through machine learning algorithms;

[0013] S4. Multi-stage continuous crystallization reaction, wherein the treated saturated sodium sulfate solution is subjected to a multi-stage continuous crystallization reaction with ammonium bicarbonate, and carbon dioxide is introduced during the reaction to form microbubbles.

[0014] S5. Heat integration and waste heat recovery: Plate heat exchangers are installed in the multi-stage reaction device to preheat the next stage reaction liquid using the waste heat of the previous stage reaction liquid; in the salting-out crystallization step, vacuum evaporation technology is used to recover the heat in the mother liquor.

[0015] S6. Alkali medium recycling: calcium hydroxide is added to the mother liquor of salting out crystallization, which reacts with ammonium sulfate to generate ammonia and calcium sulfate precipitate. The ammonia is recovered by distillation and returned to the reaction system. Electrodialysis technology is used to separate sodium ions and sulfate ions in the mother liquor to realize the recycling of alkaline medium.

[0016] S7. Simplify the temperature gradient design. The optimal number of temperature gradient levels and temperature difference are determined experimentally. A segmented temperature-controlled reactor is adopted, with each reaction segment independently controlled in temperature.

[0017] S8. Separation and resource utilization of double salt crystals and control of bicarbonate concentration: The separated double salt is reacted with lime milk to generate calcium sulfate and ammonia water. The ammonia water is returned to the salting-out step for recycling. An online pH meter and ion-selective electrode are installed in the salting-out crystallization tank to monitor the bicarbonate concentration in real time and dynamically adjust it to the target range by automatically adding dilute sulfuric acid or sodium hydroxide.

[0018] S9. Membrane separation technology enhances the separation of complex salts. The ceramic ultrafiltration membrane is used to perform solid-liquid separation on the salting-out mother liquor, retaining complex salt crystals, and washing and drying the complex salt crystals.

[0019] S10. Solid-liquid separation and product collection: After the reaction is completed, solid-liquid separation is performed to obtain large-particle sodium bicarbonate and sodium bicarbonate mother liquor; the sodium bicarbonate mother liquor is mixed with sodium sulfate for salting out and crystallization; after solid-liquid separation, double salt crystals and a recycled sodium sulfate saturated solution containing carbonate ions are obtained.

[0020] Furthermore, the composition of the complex salt crystal is Na2SO4·(NH4)2SO4·4H2O, and solid-liquid separation is achieved by membrane separation technology or centrifugal separation in the salting-out crystallization step.

[0021] Furthermore, in step S4, ammonium bicarbonate and carbon dioxide are added independently to at least two stages of reactors, and the initial introduction time of carbon dioxide is no earlier than the addition time of ammonium bicarbonate.

[0022] Furthermore, in the salting-out crystallization step, the concentration of bicarbonate and the pH value of the solution are monitored and adjusted in real time using an online pH meter and attenuated total reflectance Fourier transform infrared spectroscopy (ATRFT-IR). The amount of alkaline medium added is dynamically controlled. When the concentration of bicarbonate is too high, dilute sulfuric acid is added dropwise to carry out the reaction. When the concentration of bicarbonate is too low, sodium hydroxide is added dropwise to carry out the reaction.

[0023] Furthermore, in step S1, the diameter of the microbubbles is 100-1000 μm, preferably 200-600 μm, and the rate of carbon dioxide introduction is 0.5-2.0 L / min per liter of solution.

[0024] Furthermore, the alkaline medium is at least one of ammonia, sodium hydroxide, or potassium hydroxide, and its addition amount is 0.1-1.0 times the concentration of bicarbonate in the solution.

[0025] Furthermore, the reaction apparatus for the multi-stage continuous crystallization reaction is at least one of a DTB crystallizer, an FC crystallizer, or a stirred tank reactor.

[0026] Furthermore, the D50 particle size of the large-particle sodium bicarbonate is 250-500 μm, and the total alkali content of the product is ≥98.0%.

[0027] Furthermore, in the membrane separation technology enhanced by the double salt separation step, a ceramic ultrafiltration membrane with a suitable pore size is selected to ensure effective retention of double salt crystals, and the filtrate is recycled to reduce waste; the retained double salt crystals are washed multiple times until the required purity is achieved.

[0028] The advantages of this invention compared to existing technologies are:

[0029] 1. This invention provides a method for preparing large-particle sodium bicarbonate from sodium sulfate. In the sodium sulfate raw material dissolution stage, sodium carbonate or sodium bicarbonate is added to adjust the carbonate concentration in the solution and stabilize it within the target range (e.g., 0.5-1.5 mol / L). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) is used to perform in-situ real-time quantitative analysis of carbonate ions in the aqueous solution. Carbonate is automatically replenished through feedback control. When there are many impurities in the raw material, a filtration or adsorption step is added to remove impurity ions.

[0030] 2. This invention provides a method for preparing large-particle sodium bicarbonate from sodium sulfate. A plate heat exchanger is installed in a multi-stage reaction apparatus to preheat the next stage reaction liquid using the residual heat from the previous stage reaction liquid. For example, the heat from the outlet liquid of stage 1 (55°C) is transferred to the inlet liquid of stage 2 (50°C). In the salting-out crystallization step, vacuum evaporation technology is used to recover heat from the mother liquor for preheating subsequent reaction liquids.

[0031] 3. This invention provides a method for preparing large-particle sodium bicarbonate from sodium sulfate, wherein the separated double salt (Na2SO4·(NH4)2SO4·4H2O) is reacted with lime milk (Ca(OH)2) to generate calcium sulfate (CaSO4) and ammonia water (NH3·H2O), and the ammonia water is returned to the salting-out step for recycling. Attached Figure Description

[0032] Figure 1 This is a flowchart of a method for preparing large-particle sodium bicarbonate from sodium sulfate according to the present invention. Detailed Implementation

[0033] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses consistent with some aspects of this disclosure as detailed in the appended claims.

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, this embodiment proposes a method for preparing large-particle sodium bicarbonate from sodium sulfate, including the following steps:

[0036] S1. Raw material pretreatment: During the sodium sulfate raw material dissolution stage, sodium carbonate or sodium bicarbonate is added to adjust the carbonate concentration in the solution to 0.5-1.5 mol / L; the carbonate content in the solution is monitored in real time using an online ion chromatograph or conductivity sensor, and carbonate is automatically replenished through a feedback control system; when there are many impurities in the raw material, a filtration or adsorption step is added to remove impurity ions.

[0037] S2. Dynamically adjust reaction conditions, and dynamically adjust the addition ratio of ammonium bicarbonate and carbon dioxide according to the actual concentration of carbonate in the raw materials.

[0038] S3. Establish a raw material database, record the impurity content of different batches of sodium sulfate, and predict the optimal combination of reaction parameters through machine learning algorithms;

[0039] S4. Multi-stage continuous crystallization reaction: The treated saturated sodium sulfate solution is subjected to a multi-stage continuous crystallization reaction with ammonium bicarbonate. Carbon dioxide is introduced during the reaction to form microbubbles.

[0040] S5. Heat integration and waste heat recovery: Plate heat exchangers are installed in the multi-stage reaction unit to preheat the next stage reaction liquid with the waste heat of the previous stage reaction liquid; in the salting-out crystallization step, vacuum evaporation technology is used to recover the heat in the mother liquor.

[0041] S6. Alkali medium recycling: Calcium hydroxide is added to the mother liquor of salting out crystallization, which reacts with ammonium sulfate to generate ammonia and calcium sulfate precipitate. Ammonia is recovered by distillation and returned to the reaction system. Sodium ions and sulfate ions in the mother liquor are separated by electrodialysis technology to realize the recycling of alkaline medium.

[0042] S7. Simplify the temperature gradient design, determine the optimal number of temperature gradient levels and temperature difference through experiments, and adopt a segmented temperature-controlled reactor with independent temperature control for each reaction segment;

[0043] S8. Separation and resource utilization of double salt crystals and control of bicarbonate concentration: The separated double salt is reacted with lime milk to generate calcium sulfate and ammonia. The ammonia is returned to the salting-out step for recycling. An online pH meter and ion-selective electrode are installed in the salting-out crystallization tank to monitor the bicarbonate concentration in real time and dynamically adjust it to the target range by automatically adding dilute sulfuric acid or sodium hydroxide.

[0044] S9. Membrane separation technology enhances the separation of complex salts. A ceramic ultrafiltration membrane is used to perform solid-liquid separation on the salting-out mother liquor, retaining complex salt crystals, and washing and drying the complex salt crystals.

[0045] S10. Solid-liquid separation and product collection: After the reaction is completed, solid-liquid separation is performed to obtain large-particle sodium bicarbonate and sodium bicarbonate mother liquor; the sodium bicarbonate mother liquor is mixed with sodium sulfate for salting out and crystallization, and after solid-liquid separation, double salt crystals and a recycled sodium sulfate saturated solution containing carbonate ions are obtained.

[0046] Furthermore, in step S1, the diameter of the microbubbles is 100-1000 μm, preferably 200-600 μm, and the rate of carbon dioxide introduction is 0.5-2.0 L / min per liter of solution.

[0047] Furthermore, the multi-stage continuous crystallization reaction has 3-5 stages, and along the material flow direction, the reaction temperature of each stage forms a decreasing temperature gradient, the temperature difference between adjacent stages is 2-4℃, the final discharge temperature is 25-45℃, and the supersaturation of sodium bicarbonate in the solution is controlled at 5-20g / kg during the reaction.

[0048] Furthermore, the alkaline medium is at least one of ammonia, sodium hydroxide, or potassium hydroxide, and its addition amount is 0.1-1.0 times the concentration of bicarbonate in the solution.

[0049] Furthermore, the composition of the double salt crystal is Na2SO4·(NH4)2SO4·4H2O, and solid-liquid separation is achieved by membrane separation technology or centrifugation in the salting-out crystallization step.

[0050] Furthermore, the reaction apparatus for the multi-stage continuous crystallization reaction is at least one of a DTB-type crystallizer, an FC-type crystallizer, or a stirred tank reactor.

[0051] Furthermore, in step S4, ammonium bicarbonate and carbon dioxide are added independently to at least two stages of reactors, and the initial introduction time of carbon dioxide is no earlier than the addition time of ammonium bicarbonate.

[0052] Furthermore, the D50 particle size of the large-particle sodium bicarbonate is 250-500 μm, and the total alkali content of the product is ≥98.0%.

[0053] Furthermore, during the salting-out crystallization step, the bicarbonate concentration is monitored and adjusted in real time using an online pH meter and an ion-selective electrode, and the amount of alkaline medium added is dynamically controlled. When the bicarbonate concentration is too high, dilute sulfuric acid is added dropwise to carry out the reaction; when the bicarbonate concentration is too low, sodium hydroxide is added dropwise to carry out the reaction.

[0054] Furthermore, in the membrane separation technology enhanced by the double salt separation step, a ceramic ultrafiltration membrane with a suitable pore size is selected to ensure effective retention of double salt crystals, allowing the filtrate to be recycled and reducing waste; the retained double salt crystals are washed multiple times until the required purity is achieved.

[0055] refer to Figure 1As shown, the specific implementation process is as follows: Sodium sulfate raw material is dissolved in deionized water and stirred until completely dissolved to form an initial sodium sulfate solution. Sodium carbonate (Na₂CO₃) or sodium bicarbonate (NaHCO₃) is added to the solution to adjust the carbonate concentration to 0.5-1.5 mol / L. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) is used for in-situ real-time quantitative analysis of carbonate ions in the aqueous solution. Carbonate is automatically replenished through a feedback control system. If impurity ions (such as Ca²⁺) in the raw material are present... 2+ Mg 2+ If the content exceeds 10 ppm, an additional pretreatment step is added to remove organic impurities by adsorption with activated carbon (addition amount: 1-3% of solution volume), and then the activated carbon and insoluble impurities are removed by filtration with a ceramic membrane with a pore size of 0.2 μm.

[0056] Based on the online monitoring of carbonate concentration, the dosage of ammonium bicarbonate (NH4HCO3) is dynamically adjusted to ensure that the carbonate concentration is 1 mol / L. Simultaneously, the carbon dioxide (CO2) introduction rate is adjusted to a range of 0.5-2.0 L / min (per liter of solution).

[0057] Establish a raw material database to record the impurity content (such as Ca) of each batch of sodium sulfate. 2+ Mg 2+ Cl - The algorithm takes raw material impurity data as input and corresponding reaction parameters (temperature, pH, supersaturation) as input, and outputs the optimal combination of reaction parameters (such as temperature gradient, CO2 injection rate). Through iterative optimization, the prediction error is controlled within ±5%.

[0058] The pretreated saturated sodium sulfate solution is mixed with ammonium bicarbonate and fed into a 3-5 stage series reactor (such as a DTB crystallizer). CO2 is introduced to form microbubbles with a diameter of 200-600 μm at a rate of 1.0 L / min (per liter of solution). The temperature gradient is controlled at 3℃ per stage (e.g., 55℃→52℃→49℃→46℃→43℃). The final discharge temperature is 35℃. The supersaturation of sodium bicarbonate in the solution is maintained at 10-15 g / kg to prevent explosive nucleation.

[0059] Plate heat exchangers (heat exchange efficiency ≥85%) are installed at the outlet of each reactor stage to preheat the inlet liquid of the next stage (from 25°C to 50°C) using the residual heat (55°C) of the previous stage reaction liquid. The salting-out mother liquor recovers heat through a vacuum evaporator (operating pressure -0.08MPa, temperature 60°C) and is used to preheat the reaction liquid.

[0060] Calcium hydroxide (Ca(OH)2) is added to the salting-out mother liquor at a molar ratio of 1:1. The reaction produces ammonia (NH3) and calcium sulfate (CaSO4). The ammonia is recovered by distillation in a column (80℃), condensed, and returned to the salting-out step for recycling, achieving a recovery rate ≥90%. An electrodialysis device (voltage 20V, current density 50A / m³) is used. 2 Separating Na from the mother liquor + and SO4 2- The recovered NaOH solution (10% concentration) can be used to adjust the carbonate concentration.

[0061] The optimal temperature gradient was determined to be 3℃ / stage through experiments, and the total number of stages was reduced to 4 (originally 5-10 stages). A segmented temperature-controlled reactor was adopted, with each stage independently controlled (error ±0.5℃).

[0062] Double salt (Na₂SO₄·(NH₄)₂SO₄·4H₂O) reacts with lime milk (Ca(OH)₂) in a 2:3 molar ratio to produce CaSO₄ and NH₃·H₂O. In-situ real-time quantitative analysis of bicarbonate ions in the aqueous solution is performed using an online pH meter (accuracy ±0.1) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR). The pH value of the salting-out mother liquor is monitored in real time. When HCO₃ - When the concentration exceeds 60 g / L, dilute sulfuric acid (10% concentration) is automatically added to adjust; when it is below 5 g / L, NaOH solution (5% concentration) is added.

[0063] The salting-out mother liquor was filtered through a ceramic ultrafiltration membrane (pore size 0.1 μm, flux 50 L / m³). 2 ·h) Filter to retain the double salt crystals. Return the filtrate to the reaction system. Wash the double salt crystals three times with deionized water (the washing liquid volume is twice the crystal volume). After drying (temperature 60℃, time 4h), the purity is ≥98.0%.

[0064] After the reaction, the slurry was separated by centrifugation (4000 rpm, 15 min) to obtain large-particle sodium bicarbonate (D50 particle size 300 μm, total alkali content 98.0%). The mother liquor was mixed with sodium sulfate and then fed into a salting-out crystallization tank. The temperature was controlled at 40℃ and the stirring speed at 200 rpm to separate the double salt crystals (purity 95%) and the recycled sodium sulfate saturated solution (carbonate concentration 1.0 mol / L).

[0065] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0066] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0067] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for preparing large-particle sodium bicarbonate from sodium sulfate, characterized in that, Includes the following steps: S1. Raw material pretreatment: During the sodium sulfate raw material dissolution stage, sodium carbonate or sodium bicarbonate is added to adjust the carbonate concentration in the solution to 0.5-1.5 mol / L; Attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) is used to perform in-situ real-time quantitative analysis of carbonate ions in the aqueous solution, and carbonate is automatically replenished through a feedback control system. When there are many impurities in the raw material, a filtration or adsorption step is added to remove impurity ions. S2. Dynamically adjust reaction conditions, and dynamically adjust the addition ratio of ammonium bicarbonate and carbon dioxide according to the actual concentration of carbonate in the raw materials. S3. Establish a raw material database, record the impurity content of different batches of sodium sulfate, and predict the optimal combination of reaction parameters through machine learning algorithms; S4. Multi-stage continuous crystallization reaction, wherein the treated saturated sodium sulfate solution is subjected to a multi-stage continuous crystallization reaction with ammonium bicarbonate, and carbon dioxide is introduced during the reaction to form microbubbles. S5. Heat integration and waste heat recovery: Plate heat exchangers are installed in the multi-stage reaction device to preheat the next stage reaction liquid using the waste heat of the previous stage reaction liquid; in the salting-out crystallization step, vacuum evaporation technology is used to recover the heat in the mother liquor. S6. Alkali medium recycling: calcium hydroxide is added to the mother liquor of salting out crystallization, which reacts with ammonium sulfate to generate ammonia and calcium sulfate precipitate. The ammonia is recovered by distillation and returned to the reaction system. Electrodialysis technology is used to separate sodium ions and sulfate ions in the mother liquor to realize the recycling of alkaline medium. S7. Simplify the temperature gradient design. The optimal number of temperature gradient levels and temperature difference are determined experimentally. A segmented temperature-controlled reactor is adopted, with each reaction segment independently controlled in temperature. S8. Separation and resource utilization of double salt crystals and control of bicarbonate concentration: The separated double salt is reacted with lime milk to generate calcium sulfate and ammonia water. The ammonia water is returned to the salting-out step for recycling. An online pH meter is installed in the salting-out crystallization tank, and attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR) is used to perform in-situ real-time quantitative analysis of bicarbonate ions in the aqueous solution, monitor the bicarbonate concentration in real time, and dynamically adjust it to the target range by automatically adding dilute sulfuric acid or sodium hydroxide. S9. Membrane separation technology enhances the separation of complex salts. The ceramic ultrafiltration membrane is used to perform solid-liquid separation on the salting-out mother liquor, retaining complex salt crystals, and washing and drying the complex salt crystals. S10. Solid-liquid separation and product collection: After the reaction is completed, solid-liquid separation is performed to obtain large-particle sodium bicarbonate and sodium bicarbonate mother liquor. The sodium bicarbonate mother liquor is mixed with sodium sulfate for salting out and crystallization. After solid-liquid separation, double salt crystals and a recycled sodium sulfate saturated solution containing carbonate ions are obtained.

2. The method for preparing large-particle sodium bicarbonate from sodium sulfate according to claim 1, characterized in that: In step S1, the diameter of the microbubbles is 100-1000 μm, preferably 200-600 μm, and the rate of carbon dioxide introduction is 0.5-2.0 L / min per liter of solution.

3. The method for preparing large-particle sodium bicarbonate from sodium sulfate according to claim 1, characterized in that: The multi-stage continuous crystallization reaction has 3-5 stages, and along the material flow direction, the reaction temperature of each stage forms a decreasing temperature gradient, with a temperature difference of 2-4℃ between adjacent stages. The final discharge temperature is 25-45℃, and the supersaturation of sodium bicarbonate in the solution is controlled to be 5-20 g / kg during the reaction.

4. The method for preparing large-particle sodium bicarbonate from sodium sulfate according to claim 1, characterized in that: The alkaline medium is at least one of ammonia, sodium hydroxide, or potassium hydroxide, and its addition amount is 0.1-1.0 times the concentration of bicarbonate in the solution.

5. The method for preparing large-particle sodium bicarbonate from sodium sulfate according to claim 1, characterized in that: The composition of the complex salt crystal is Na2SO4·(NH4)2SO4·4H2O, and solid-liquid separation is achieved by membrane separation technology or centrifugation in the salting-out crystallization step.

6. The method for preparing large-particle sodium bicarbonate from sodium sulfate according to claim 1, characterized in that: The reaction apparatus for the multi-stage continuous crystallization reaction is at least one of a DTB crystallizer, an FC crystallizer, or a stirred tank reactor.

7. The method for preparing large-particle sodium bicarbonate from sodium sulfate according to claim 1, characterized in that: In step S4, ammonium bicarbonate and carbon dioxide are added independently to at least two stages of reactors, and the initial introduction time of carbon dioxide is no earlier than the addition time of ammonium bicarbonate.

8. The method for preparing large-particle sodium bicarbonate from sodium sulfate according to claim 1, characterized in that: The large-particle sodium bicarbonate has a D50 particle size of 250-500 μm and a total alkali content of ≥98.0%.

9. The method for preparing large-particle sodium bicarbonate from sodium sulfate according to claim 1, characterized in that: In the salting-out crystallization step, the concentration of bicarbonate and the pH value of the solution are monitored and adjusted in real time using an online pH meter and attenuated total reflectance Fourier transform infrared spectroscopy (ATR FT-IR). The amount of alkaline medium added is dynamically controlled. When the concentration of bicarbonate is too high, dilute sulfuric acid is added dropwise to carry out the reaction. When the concentration of bicarbonate is too low, sodium hydroxide is added dropwise to carry out the reaction.

10. The method for preparing large-particle sodium bicarbonate from sodium sulfate according to claim 1, characterized in that: In the enhanced complex salt separation step of the membrane separation technology, a ceramic ultrafiltration membrane with a suitable pore size is selected to ensure effective retention of complex salt crystals, and the filtrate is recycled to reduce waste; the retained complex salt crystals are washed multiple times until the required purity is achieved.

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