Method for preparing sodium bicarbonate using sodium sulfate and pH regulator

Abstract

The present invention relates to a method for preparing sodium bicarbonate using sodium sulfate and a pH adjusting agent, and more particularly, to a method for preparing sodium bicarbonate, comprising the steps of: forming an alkaline sodium sulfate solution containing sodium sulfate (Na2SO4) and a pH adjusting agent; and adding carbon dioxide and ammonia to the alkaline sodium sulfate solution to produce sodium bicarbonate (NaHCO3).

Description

Preparation method of sodium bicarbonate using sodium sulfate and pH adjuster Technical Field

[0001] This invention relates to a method for preparing sodium bicarbonate using sodium sulfate and a pH adjuster, and more specifically, to a method for increasing the yield of sodium bicarbonate while reducing the amount of ammonia used by increasing the solubility of carbon dioxide. Background Technology

[0002] Sodium bicarbonate (NaHCO3) is a compound produced by the reaction of sodium (Na) with carbon dioxide (CO2). It is white at room temperature and is widely used industrially as a remover for sulfur oxides emitted as waste gas. In medicine, it is used as an antacid and a raw material for detergents. Soda ash (sodium carbonate, lime, Na2CO3) is produced by heating sodium bicarbonate. It is used in glass manufacturing and can also be used together with sodium bicarbonate as a raw material in the manufacture of soaps or detergents.

[0003] The most widely used method for preparing sodium bicarbonate and soda ash is the Solvay process. The Solvay process involves dissolving salt (sodium chloride, NaCl) in water to create a brine, then dissolving ammonia and carbon dioxide to prepare sodium bicarbonate, and finally reheating the sodium bicarbonate to produce soda ash. The Solvay process includes the following steps: the carbon dioxide used in the Solvay process is generated during the decomposition of lime (calcium carbonate, CaCO3). The resulting quicklime (calcium oxide, CaO) reacts with the waste liquid remaining after sodium bicarbonate production to produce calcium chloride.

[0004] Furthermore, with increased focus on the environment and carbon neutrality, the production of sodium sulfate (sodium sulfate, Na₂SO₄) is rising recently. Sodium bicarbonate can be used to remove sulfur oxides (SO₄) emitted from chimneys. x Sodium sulfate is produced by the reaction of sulfur oxides contained in the exhaust gas with sodium bicarbonate, as shown in the following formula.

[0005] 2NaHCO3(s) + SO2(g) + 1 / 2O2(g) When sulfur oxides (Na₂SO₄(s) + 2CO₂(g) + H₂O(g)) are released into the atmosphere, they contribute to acid rain and may act as precursors to ultrafine particulate matter. Therefore, relevant regulations are being strengthened. For this reason, the use of sodium bicarbonate in production sites that emit sulfur oxides is also increasing, leading to a corresponding increase in sodium sulfate production.

[0006] Furthermore, the global demand for carbon neutrality is increasing in order to mitigate climate change. To achieve carbon neutrality, reducing carbon dioxide emissions from transportation is crucial. To meet this goal, the adoption of electric vehicles is rapidly increasing, and the production of secondary batteries used in these vehicles is also growing dramatically. The production of secondary batteries requires processes for producing lithium, nickel, precursors, etc., and the recycling of waste batteries is also important. These processes require extracting lithium, nickel, and other substances from ores or waste batteries, and the necessary processes for this extraction include the use of caustic soda and sulfuric acid. In processes using caustic soda and sulfuric acid, sodium sulfate is inevitably produced as a byproduct. For this reason, with the strengthening of global environmental regulations and the expansion of the secondary battery business, the production of sodium sulfate is also increasing significantly, leading to a substantial increase in the problem of disposing of the large amounts of sodium sulfate generated.

[0007] This sodium sulfate contains sodium, so developing a process to produce sodium bicarbonate and soda ash from sodium sulfate could be an excellent alternative to addressing increasingly stringent environmental regulations and the large amounts of sodium sulfate generated during the production of secondary battery materials. However, sodium sulfate solution has chemical properties different from existing brine solutions. The most significant difference is the type of anion dissolved in the solution; salts form chloride ions, while sodium sulfate contains sulfate ions. Furthermore, the sodium sulfate produced after removing sulfur oxides and in the secondary battery material production process has different impurities and impurity levels compared to the brine solutions used in the existing Solvay process. Therefore, there is an urgent need to utilize sodium sulfate solution with these characteristics to improve the sodium bicarbonate and soda ash processes. Summary of the Invention

[0008] (I) Technical problem to be solved One aspect of the present invention provides a method for preparing sodium bicarbonate, which can reduce the amount of ammonia added to the carbonation reaction and increase the amount of dissolved CO2, thereby achieving the effect of improving the yield of sodium bicarbonate.

[0009] (II) Technical Solution According to one aspect of the present invention, a method for preparing sodium bicarbonate is provided, comprising the following steps: forming an alkaline sodium sulfate solution containing sodium sulfate (Na2SO4) and a pH adjuster; and adding carbon dioxide and ammonia to the alkaline sodium sulfate solution to generate sodium bicarbonate (NaHCO3).

[0010] (III) Beneficial Effects According to the present invention, the method for preparing sodium bicarbonate using sodium sulfate solution involves mixing a pH adjuster into a sodium sulfate solution to form an alkaline sodium sulfate solution. This increases the solubility of carbon dioxide added for the carbonation reaction, thereby reducing the amount of ammonia used in the sodium bicarbonate production process and increasing the yield of sodium bicarbonate. Therefore, an improvement in the efficiency of the sodium bicarbonate production process using sodium sulfate is expected. Attached Figure Description

[0011] Figure 1 schematically illustrates an exemplary process flow diagram of the present invention.

[0012] Figure 2(a) and Figure 2(b) are graphs showing the change in sodium bicarbonate yield depending on the amount of Na2CO3 and NaOH added.

[0013] Figure 3 shows the change in sodium bicarbonate yield based on Na2CO3 content and ammonia addition.

[0014] Figure 4 is a flowchart schematically illustrating an exemplary apparatus for the preparation method of sodium bicarbonate using sodium sulfate and a pH adjuster that can be used in this invention. Preferred Embodiment

[0015] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention can be modified in many other ways, and the scope of the present invention is not limited to the embodiments described below.

[0016] The method for preparing sodium bicarbonate of the present invention utilizes sodium sulfate (Na2SO4) to form an alkaline sodium sulfate solution containing a pH adjuster, thereby increasing the solubility of carbon dioxide, which not only reduces the amount of ammonia used but also increases the yield of sodium bicarbonate.

[0017] More specifically, the method for preparing sodium bicarbonate according to the present invention includes the following steps: forming an alkaline sodium sulfate solution containing sodium sulfate (Na2SO4) and a pH adjuster; and adding carbon dioxide and ammonia to the alkaline sodium sulfate solution to generate sodium bicarbonate (NaHCO3).

[0018] Figure 1 schematically illustrates an exemplary process flow diagram of the present invention, which includes a step 100 of mixing sodium sulfate (Na2SO4) 101 and pH adjuster 102 by stirring or the like to form an alkaline sodium sulfate solution, and a carbonation step 200, in which sodium bicarbonate 201 is generated. Subsequently, an ammonia recovery process 300 can be performed, and the ammonia 301 recovered in the ammonia recovery process can be added to the carbonation step. The remaining waste liquid can be treated as wastewater 302.

[0019] Furthermore, the sodium sulfate solution can be obtained by dissolving sodium sulfate-containing substances (e.g., desulfurization byproducts, etc.) in a leaching agent, and can be obtained using a substance with a sodium sulfate content of 50% by weight (wt%) or more. For example, sodium sulfate-containing waste can be a solution containing sulfur oxides (SO₄). x The waste gas containing sodium bicarbonate is generated through desulfurization treatment with sodium bicarbonate, or it can be waste generated as a byproduct of lithium production plants. For example, it can be generated from waste gas produced by combustion in thermal power plants, factories, incinerators, etc., or from waste gas treated by electrostatic precipitators in iron sintering plants, through desulfurization treatment with sodium bicarbonate. The sodium sulfate-containing waste may leach and contain heavy metals such as lead (Pb) and zinc (Zn), and is characterized by high content of alkaline components such as sodium (Na), potassium (K), and calcium (Ca), as well as high content of chlorine (Cl). Sodium bicarbonate used as a desulfurizing agent is mostly related to SO₂. x The reaction transforms the waste into sodium sulfate, and also contains some insoluble gangue components found in the exhaust gas. Specifically, the main crystalline phases constituting the desulfurization waste are sodium sulfate, sodium chloride and potassium chloride, sodium carbonate, calcium sulfate and calcium carbonate, etc., and also contain iron oxides. Among the main crystalline phases of the desulfurization dust aqueous solution, sodium sulfate, sodium chloride, and potassium chloride are components with high water solubility; therefore, they can be dissolved in water to prepare an alkaline desulfurization dust aqueous solution. As described above, the sodium sulfate-containing substance of the present invention can be a desulfurization byproduct.

[0020] The leaching agent is not particularly limited as long as it can come into contact with a substance containing sodium sulfate and leach out sodium ions. For example, it can be selected from one or more of water and ammonia, such as water.

[0021] More specifically, in this case, for the recovery of sodium sulfate from sodium sulfate-containing waste in the form of a sodium sulfate solution containing sodium ions, the ratio of sodium sulfate-containing waste to leaching agent is crucial. When the leaching agent ratio is too low, the sodium sulfate waste is not completely dissolved, resulting in a large amount of residue and a reduced sodium recovery rate. The leaching agent ratio that prevents sodium sulfate loss as residue is 1.2 parts by weight or more relative to 1 part by weight of sodium sulfate waste. Preferably, 1.4 to 3 parts by weight, for example 2 to 3 parts by weight, of leaching agent are mixed relative to 1 part by weight of sodium sulfate waste. When the leaching agent exceeds this range and is excessively contained, even if carbon dioxide is subsequently dissolved in the sodium-containing solution, it will not precipitate as sodium bicarbonate. Therefore, the content of sodium bicarbonate flowing out in the dissolved state is high, leading to a reduced sodium bicarbonate recovery rate.

[0022] Regarding the step of forming an alkaline sodium sulfate solution containing the sodium sulfate (Na₂SO₄) and a pH adjuster, the sodium sulfate solution containing sodium (Na₂SO₄) is prepared by adding sodium sulfate (Na₂SO₄) to the solution. +When carbon dioxide is dissolved in the raw materials, sodium bicarbonate, which has the lowest solubility, precipitates first. Since carbon dioxide is an acidic gas, the solution needs to be alkaline for it to dissolve. However, when sodium sulfate is dissolved in water, the pH is neutral (~7), making carbon dioxide difficult to dissolve. Therefore, this invention can achieve a highly efficient reaction by forming an alkaline sodium sulfate solution containing sodium sulfate (Na₂SO₄) and a pH adjuster.

[0023] Therefore, any highly alkaline substance can serve as a pH adjuster in the sodium bicarbonate production process. However, considering the purity and yield of sodium bicarbonate, the pH adjuster of this invention can be Na+. + The series of pH adjusters can be sodium salts with a pH of 9 to 12. More specifically, the pH adjuster of the present invention can be Na... + The series of alkaline substances can be at least one selected from sodium hydroxide (NaOH, pH=13), sodium carbonate (Na2CO3, pH=11.7), and sodium bicarbonate. In particular, the sodium carbonate can be generated by heating sodium bicarbonate (NaHCO3), thus having the advantage of being supplied through internal circulation.

[0024] Alternatively, an aqueous ammonia solution can be added to an alkaline sodium sulfate solution to form a mixture, and then the carbon dioxide can be added to the mixture.

[0025] In the method for preparing sodium bicarbonate of the present invention, the contents of sodium sulfate (Na2SO4), pH adjuster, ammonia and water in each step can be based on the weight of the mixture after mixing them, adding 10% to 30% sodium sulfate (Na2SO4), 1% to 20% pH adjuster, 3% to 15% ammonia and the balance water. For example, 17% to 26% sodium sulfate (Na2SO4), 1% to 17% pH adjuster, 3.5% to 10% ammonia and the balance water can be added.

[0026] The pH adjuster not only regulates the pH but also serves to prepare bicarbonate derivatives of sodium bicarbonate. When the pH adjuster is caustic soda, the ammonia content can be 2% to 10% by weight, based on the weight of the mixture of sodium sulfate (Na₂SO₄), pH adjuster, ammonia, and water. When the pH adjuster is sodium carbonate (Na₂CO₃), the ammonia content can be 5% to 10% by weight, based on the weight of the mixture of sodium sulfate (Na₂SO₄), pH adjuster, ammonia, and water. Using a pH adjuster outside the scope of this invention may reduce the purity and yield of sodium bicarbonate.

[0027] The pH of the alkaline sodium sulfate solution thus obtained can be greater than 7 to 14, for example, pH can be between 8 and 13.

[0028] The method for preparing sodium bicarbonate according to the present invention further includes the step of adding an aqueous solution of carbon dioxide and ammonia to the alkaline sodium sulfate solution to generate sodium bicarbonate (NaHCO3).

[0029] When the step of forming the alkaline sodium sulfate solution is distinguished from the step of generating sodium bicarbonate (NaHCO3) as described in this invention, the generation of impurities can be reduced, thereby producing sodium bicarbonate with high purity and high yield.

[0030] Carbon dioxide is an acidic gas and is therefore readily soluble in sodium sulfate solution. However, when sodium bicarbonate is prepared using only carbon dioxide and sodium sulfate solution, the pH continuously decreases, thus reducing the yield of sodium bicarbonate production. This invention improves the yield of sodium bicarbonate by mixing ammonia, which acts as a pH buffer, into sodium sulfate. Therefore, the ammonia is mixed with the sodium sulfate solution, for example, in the form of an aqueous ammonia solution.

[0031] Normally, to dissolve ammonia in solutions such as water, gaseous ammonia needs to be aerated in the aqueous solution. However, when ammonia is aerated in an aqueous solution, the pH rises further, and in alkaline aqueous solutions, ammonia exists as NH3 rather than NH4. + Ammonia exists in a certain state, thus exhibiting a tendency to dissociate easily outside the water. Therefore, aeration alone cannot adequately dissolve ammonia. Consequently, to prepare high-concentration ammonia solutions, it is common practice to increase the pressure of the equipment used to dissolve ammonia.

[0032] Therefore, for example, in order to fully dissolve ammonia in sodium leachate using sodium sulfate-containing waste, ammonia can be mixed in the form of ammonia water instead of being injected in gaseous form, but the form of ammonia is not particularly restricted.

[0033] Based on the total weight of the sodium sulfate solution and the ammonia solution, the content of the ammonia solution can be from 15% to 35% by weight, for example, from 32% to 33% by weight. When the pH adjuster is outside the scope of this invention, the purity and yield of sodium bicarbonate may be reduced.

[0034] Additionally, the sodium sulfate solution is mixed with ammonia to make the ammonia (NH3) / sodium (Na) ratio... + The molar ratio of ammonia (NH3) to sodium (Na2) is 0.9 to 1.8, for example, 1.2 to 1.6. + When the molar ratio of sodium bicarbonate exceeds the scope of this invention, the purity and yield of sodium bicarbonate may be reduced. In this case, when excess ammonia is added to dissolve carbon dioxide, the ammonia reacts with carbon dioxide to form a solid of ammonium carbonate ((NH4)2CO3), which may reduce the purity of sodium bicarbonate.

[0035] When using an ammonia solution, the ammonia solution may be 25-30% by weight, and the content of the ammonia solution may be 32% to 35% by weight, based on the total weight of sodium sulfate (Na2SO4), pH adjuster and ammonia solution.

[0036] The sodium sulfate solution can react with carbon dioxide and ammonia to produce solid sodium bicarbonate through a carbonation reaction according to Formula 1 below.

[0037] Na₂SO₄ + 2CO₂ + 2NH₃ + 2H₂O The Gibbs free energy of the reaction NaHCO3+(NH4)2SO4 (1) as shown in Equation 1 above is -851.0 kJ / mol, which is negative, indicating that the reaction to produce sodium bicarbonate can occur spontaneously. Furthermore, this reaction is exothermic, thus having the advantage of minimal additional energy consumption during the formation of sodium bicarbonate.

[0038] The reaction pressure of the carbonation reactor that produces the carbonation reaction can be 1-10 standard atmospheres (atm), and the reaction temperature can be below 80°C. When the pressure of the carbonation reactor is greater than 10 standard atmospheres, although sufficient carbon dioxide can be dissolved, the energy required for the carbonation reactor is high, which reduces the economic efficiency of the final products, namely sodium bicarbonate and gypsum.

[0039] Furthermore, the carbonation reaction time varies depending on the method of carbon dioxide injection. The carbon dioxide of this invention can be injected in gaseous form, allowing for aeration times of up to 4 hours. However, the optimized pressure and reaction time can vary depending on the reactor size / space / conditions.

[0040] The steps can be carried out at temperatures above 25°C and below 100°C. When the temperature exceeds this range, the solubility of sodium sulfate tends to decrease, which may reduce the yield.

[0041] The carbon dioxide described in this invention may be selected from one or more of the following: pure carbon dioxide, FINEX offgas (FOG), FINEX tail gas (FTG), blast furnace gas (BFG), converter gas, waste gas from coal-fired power plants, waste gas from gas-fired power plants, waste gas from incinerators, waste gas from glass melting, waste gas from thermal equipment, waste gas from petrochemical processes, process gases from petrochemical processes, pre-combustion waste gas, and waste gas from gasifiers. Furthermore, the carbon dioxide may be concentrated using one or more methods selected from the wet amine process, the PSA process, and the membrane separation process.

[0042] The sodium sulfate (Na2SO4) solution that can be used in this invention can be, for example, a 30% to 35% sodium sulfate aqueous solution, sodium carbonate (Na2CO3) can be, for example, a 30% to 35% sodium sulfate aqueous solution, and NaOH can be a 50% to 60% aqueous solution, but is not limited thereto.

[0043] Furthermore, the process may include a sodium bicarbonate washing step, where the more water used for washing, the higher the purity of the resulting sodium bicarbonate. The washing solution used may be, for example, selected from one or more of water, aqueous sodium solution, and aqueous ammonia solution, and the solution used for washing may be reused as a leaching agent.

[0044] Furthermore, the sodium bicarbonate washed with water may further include a sodium bicarbonate drying and crushing step. In this case, the drying temperature is preferably below 50°C, for example, 20°C to 50°C, preferably 40°C to 50°C. When the drying temperature exceeds 50°C, the sodium bicarbonate may decompose back into sodium carbonate; therefore, it is preferable to carry out the drying at a temperature above the freezing point of the washing solution. Additionally, the crushing can be performed using a ball mill or a cutter mill, but is not limited to these methods.

[0045] Furthermore, the method for preparing sodium bicarbonate of the present invention may further include the step of adding a calcium-containing substance to the filtrate remaining after recovering the sodium bicarbonate to generate gypsum. That is, the filtrate discharged after the carbonation reaction contains a large amount of sulfate ions (SO42-). 2- Therefore, in order to prepare gypsum from the sulfate ions contained in the filtrate, a calcium-containing substance can be added. At this point, the molar ratio of calcium ions to sulfate ions (Ca...) is... 2+ :SO4 2- The preferred ratio is 1:1.0-1.3. When the sulfate ion ratio exceeds 1.3, the purity of gypsum decreases. When the sulfate ion ratio is below 1.0, the pH of the filtrate is too low, which leads to the problem that ammonia cannot be fully recovered in the ammonia stripping step.

[0046] The calcium-containing substance may be selected from one or more of the following: waste cement, waste concrete, fly ash, fly ash, steelmaking slag, quicklime (CaO), calcium chloride (CaCl2), wollastonite, limestone, olivine, serpentine, asbestos, and deinking ash.

[0047] Furthermore, the method for preparing sodium bicarbonate of the present invention may further include an ammonia recovery step of heating the filtrate remaining after recovering the gypsum to recover ammonia.

[0048] The pH of the ammonia recovery step is preferably maintained above 8.0. When the pH of the ammonia recovery step is below 8.0, the ammonia recovery rate decreases. Furthermore, the ammonia recovery step involves heating the remaining filtrate, preferably at a temperature of 50°C or higher. When the temperature of the filtrate is below 50°C, the ammonia recovery rate decreases.

[0049] The recovered ammonia can be reused in gaseous form or by being reprocessed into ammonia water.

[0050] Figure 4 of the present invention illustrates an exemplary apparatus for the preparation method of sodium bicarbonate using sodium sulfate and a pH adjuster, which can be used in the present invention. As shown in Figure 4, the apparatus may include a stirring device S1, a carbonation device S2, and an ammonia recovery device S3. In the stirring device S1, a step of forming an alkaline sodium sulfate solution containing sodium sulfate (Na2SO4) and a pH adjuster can be performed. In the carbonation device S2, a step of adding carbon dioxide and ammonia to the alkaline sodium sulfate solution to generate sodium bicarbonate (NaHCO3) can be performed. Then, in the ammonia recovery device S3, a step of adding a calcium-containing substance to the filtrate remaining after recovering the sodium bicarbonate to generate gypsum, followed by heating the filtrate remaining after recovering the gypsum to recover ammonia, can be performed.

[0051] The present invention will now be described in more detail through specific embodiments. These embodiments are merely examples to aid in understanding the invention, and the scope of the invention is not limited thereto. Detailed Implementation

[0052] Example 1. Preparation of sodium bicarbonate and gypsum using sodium sulfate and pH adjuster. In Example 1, 200g of water was added to 100g of sodium sulfate (Na2SO4), and the mixture was stirred at 40°C for 1 hour to prepare a sodium sulfate solution with a concentration of 33% by weight.

[0053] Add 200g of water to 100g of sodium carbonate (Na2CO3) at the same ratio, and stir at 40°C for 1 hour to prepare a 33% by weight sodium carbonate solution.

[0054] Add 100g of water to 100g of solid NaOH and stir for 1 hour to prepare a 50% by weight NaOH solution.

[0055] To 80g of the sodium sulfate solution prepared above, 33% by weight of sodium carbonate and 50% by weight of NaOH were added, as shown in Table 1 below. The mixture was then placed in a reactor, followed by the addition of 25% by weight of ammonia. Carbon dioxide was further injected into the reactor at 7 bar via bubbling, and the reaction was carried out at 40°C for 8 hours. The sodium bicarbonate slurry discharged after the reaction was completed underwent solid-liquid separation. The resulting sodium bicarbonate was dried in an oven at 50°C for at least 12 hours, and then the mass was measured to confirm the yield.

[0056] The sodium bicarbonate yield is calculated based on the amount of sodium sulfate and sodium carbonate added, and the Na content of the produced sodium bicarbonate. + Calculations were performed using moles as the baseline. The purity of sodium bicarbonate was measured by X-ray diffraction (XRD) and inductively coupled plasma mass spectrometry (ICP-MS). The yield and purity results for sodium bicarbonate are shown in Table 1 and Figure 2 below.

[0057] The results, as shown in Table 1 below, confirm that even with the addition of the same amount of ammonia, the yield of sodium bicarbonate increases with the addition of Na₂CO₃ and NaOH. Furthermore, it can be confirmed that the yield of sodium bicarbonate is even higher when using NaOH with a higher pH.

[0058] [Table 1] Purity and yield of sodium bicarbonate based on the amount of sodium carbonate and NaOH added. However, as can be confirmed by Table 1, although the yield of sodium bicarbonate increases with the increase of sodium carbonate or NaOH, it does not increase to more than 80%.

[0059] Experimental Example 1 prepared a 33 wt% solution of Glauber's salt, sodium carbonate, and NaOH using the same process as in Preparation Example 1. The prepared solution was added to the reactor along with 25 wt% ammonia solution, as shown in Table 2 below. The reaction, drying, purity, and yield measurement conditions were the same as in Preparation Example 1. The yield and purity results for sodium bicarbonate are shown in Table 2.

[0060] As shown in Table 2 and Figure 3, when a certain amount of sodium carbonate is added and then ammonia is added, the yield of sodium bicarbonate, which no longer increases due to the addition of sodium carbonate and / or NaOH, is further improved, and the purity of sodium bicarbonate is also maintained at a certain value.

[0061] In addition, more than 90% of the ammonia used can be recovered in the actual process. Therefore, by adding a certain amount of soda ash and increasing the amount of ammonia added, the purity and yield of sodium bicarbonate can be effectively improved.

[0062] [Table 2] Purity and yield of sodium bicarbonate based on the amount of sodium carbonate and ammonia added. In addition, in actual processes, more than 90% of ammonia can be recovered and reused through stripper. Experimental results confirm that even when using the same amount of ammonia, the yield can be increased by more than 70% by adding a small amount of NaOH and Na2CO3.

[0063] The embodiments of the present invention have been described in detail above, but the scope of the present invention is not limited thereto. Various modifications and variations can be made without departing from the technical concept of the present invention as set forth in the claims, which will be obvious to those skilled in the art.

[0064] [Explanation of reference numerals in the attached diagram] 100: Sodium sulfate solution formed by stirring, etc.; 101: Glauber's salt; 102: pH adjuster; 200: Carbonation reactor; 201: Sodium bicarbonate; 300: Ammonia recovery; 301: Ammonia; 302: Wastewater

Claims

1. A method for preparing sodium bicarbonate, comprising the following steps: An alkaline sodium sulfate solution containing sodium sulfate (Na2SO4) and a pH adjuster is formed; and carbon dioxide and ammonia are added to the alkaline sodium sulfate solution to generate sodium bicarbonate (NaHCO3).

2. The method for preparing sodium bicarbonate according to claim 1, wherein, The pH adjuster is at least one sodium salt selected from sodium carbonate (Na2CO3), caustic soda, and sodium bicarbonate, with a pH of 9 to 12.

3. The method for preparing sodium bicarbonate according to claim 1, wherein, An aqueous solution of ammonia is added to an alkaline sodium sulfate solution to form a mixture, and then the carbon dioxide is added to the mixture.

4. The method for preparing sodium bicarbonate according to claim 3, wherein, The contents of sodium sulfate (Na2SO4), pH adjuster, ammonia and water are based on the weight of the mixture after they are mixed, with 10% to 30% by weight of sodium sulfate (Na2SO4), 1% to 20% by weight of pH adjuster, 3% to 15% by weight of ammonia and the balance being water.

5. The method for preparing sodium bicarbonate according to claim 3, wherein, When the pH adjuster is caustic soda, the ammonia content is 1% to 10% by weight, based on the weight of the mixture of sodium sulfate (Na2SO4), pH adjuster, ammonia and water.

6. The method for preparing sodium bicarbonate according to claim 3, wherein, When the pH adjuster is sodium carbonate (Na2CO3), the ammonia content is 5% to 10% by weight, based on the weight of the mixture of sodium sulfate (Na2SO4), pH adjuster, ammonia and water.

7. The method for preparing sodium bicarbonate according to claim 1, wherein, The preparation method further includes the step of adding a calcium-containing substance to the filtrate remaining after recovering the sodium bicarbonate to generate gypsum.

8. The method for preparing sodium bicarbonate according to claim 7, wherein, The preparation method further includes an ammonia recovery step, which involves heating the remaining filtrate after recovering the gypsum to recover ammonia.

9. The method for preparing sodium bicarbonate according to claim 1, wherein, The sodium sulfate solution is mixed with the ammonia solution to make the ammonia (NH3) / sodium (Na) ratio equal. + The ratio is 0.9 to 1.

8.

10. The method for preparing sodium bicarbonate according to claim 1, wherein, The carbon dioxide was injected in gaseous form.

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