Preparation method of sodium bicarbonate and gypsum with sodium sulfate for regulating particle size and sodium bicarbonate preparation device

Abstract

The present invention relates to a method for preparing sodium bicarbonate and gypsum using sodium sulfate to adjust the particle size, and a sodium bicarbonate preparation apparatus, and more particularly, to a method for preparing sodium bicarbonate, a method for preparing gypsum, and a reactor for preparing sodium bicarbonate, the method for preparing sodium bicarbonate including the steps of generating a sodium sulfate solution containing sodium ions from a mixture of a leaching agent and a substance containing sodium sulfate, adding carbon dioxide and ammonia to the sodium sulfate solution to generate sodium bicarbonate (NaHCO3), and heating the sodium bicarbonate at a temperature of 60-100°C to adjust the particle size of the sodium bicarbonate, the method for preparing gypsum further including the step of adding a calcium-containing substance to a filtrate remaining after the sodium bicarbonate is recovered in the step of generating sodium bicarbonate to generate gypsum, and the reactor for preparing sodium bicarbonate including a leaching reactor that leaches sodium ions from a substance containing sodium sulfate by a leaching agent to generate a sodium aqueous solution, a carbonation reactor that supplies a carbon dioxide-containing gas or a carbonation solution and an ammonia-containing gas or an ammonia solution to the sodium aqueous solution and generates sodium bicarbonate (NaHCO3) by a reaction, and a particle size reactor that coarsens the particle size of sodium bicarbonate at 60-100°C in a sodium bicarbonate generation aqueous solution.

Description

Technical Field

[0001] This invention relates to a method and related apparatus for preparing sodium bicarbonate and gypsum with adjustable particle size using sodium sulfate. More specifically, it relates to a method and apparatus for preparing sodium bicarbonate and gypsum, which includes a process in the preparation process of sodium bicarbonate that allows for particle size adjustment, thereby enabling the adjustment of the particle size of sodium bicarbonate. Background Technology

[0002] Flue gas desulfurization refers to the removal of sulfur (S), especially sulfur dioxide (SO2), from exhaust gases emitted from iron smelters, thermal power plants, and other similar facilities. With industrial development, the emission of sulfur oxides (SO2) from various factories, thermal power plants, and incinerators has increased significantly. x Harmful gases such as sodium bicarbonate (NaHCO3), activated carbon, and calcium hydroxide (Ca(OH)2) cause serious air pollution and lead to various diseases such as respiratory illnesses, asthma, and lung cancer. Currently, desulfurizing agents used in iron and steel plants include sodium bicarbonate (NaHCO3), activated carbon, and calcium hydroxide (Ca(OH)2). Sodium bicarbonate, in particular, is known to maximize its specific surface area when injected into high-temperature exhaust gas, thus exhibiting excellent adsorption efficiency. However, as a byproduct of desulfurization, sodium sulfate (Na2SO4) waste is generated.

[0003] In recent years, with the increasing popularity of electric vehicles, the demand for lithium, a raw material for rechargeable batteries, is rising. The main byproducts of lithium production are silicon dioxide (SiO2) and sodium sulfate (Na2SO4). It is anticipated that the production of sodium sulfate as a byproduct will also increase in the future as lithium demand grows. Therefore, the development of technologies for recycling sodium sulfate is essential for the widespread adoption of rechargeable batteries.

[0004] Currently, the byproducts generated are dissolved in water and then treated as wastewater or directly landfilled, thus causing both treatment costs and secondary environmental problems. As an effective method for utilizing the byproduct sodium sulfate, one approach is to dissolve sodium sulfate in water and inject carbon dioxide and ammonia to regenerate it into sodium bicarbonate.

[0005] The underlying technology of this method is the Solvay process, which uses concentrated seawater brine to produce sodium bicarbonate as a byproduct during the intermediate process of generating sodium carbonate and calcium chloride. However, the Solvay process does not include the treatment of sulfates (SO42-). 2- The production of sodium sulfate is currently expected to continue to increase. Therefore, there is an urgent need for resource recovery or recycling solutions for byproducts such as sodium sulfate. Summary of the Invention

[0006] (a) Technical problems to be solved One embodiment of the present invention provides a method for preparing sodium bicarbonate with adjustable particle size using a substance containing sodium sulfate.

[0007] Another embodiment of the present invention provides a method for preparing gypsum using sodium bicarbonate with adjustable particle size.

[0008] Another embodiment of the present invention provides an apparatus for preparing sodium bicarbonate with adjustable particle size.

[0009] (II) Technical Solution According to one embodiment of the present invention, a method for preparing sodium bicarbonate is provided, comprising the following steps: generating a sodium sulfate solution containing sodium ions from a mixture of a dissolving agent and a substance containing sodium sulfate; adding carbon dioxide and ammonia to the sodium sulfate solution to generate sodium bicarbonate (NaHCO3); and cooling the sodium bicarbonate at a lower temperature than that used in the step of generating sodium bicarbonate to adjust the particle size of the sodium bicarbonate.

[0010] According to another embodiment of the present invention, a method for preparing gypsum is provided, further comprising the following steps: adding a calcium-containing substance to the filtrate remaining after recovering sodium bicarbonate in the step of generating the sodium bicarbonate, to generate gypsum.

[0011] According to another embodiment of the present invention, a reactor for preparing sodium bicarbonate is provided, comprising: a dissolution reactor, wherein sodium ions are dissolved from a substance containing sodium sulfate by a dissolving agent to generate an aqueous sodium solution; a carbonation reactor, wherein a carbonation reactor supplies the aqueous sodium solution with a gas or carbonation solution containing carbon dioxide and a gas or ammonia solution containing ammonia, and generates sodium bicarbonate (NaHCO3) by reaction; and a particle size distribution reactor, wherein the particle size distribution reactor coarsens the sodium bicarbonate generated aqueous solution at 35-100°C.

[0012] (III) Beneficial Effects According to the present invention, sodium bicarbonate with adjustable particle size can be prepared using minerals containing sodium sulfate, sodium sulfate by-products, and desulfurization waste generated in iron smelters or power plants that contain sodium sulfate. Then, gypsum can be produced using the waste liquid, thereby reducing the landfill costs of waste generated after desulfurization and stably fixing carbon dioxide into carbonates. Therefore, as a CCU technology using carbon dioxide, it has the effect of contributing to carbon neutrality. Attached Figure Description

[0013] Figure 1 This is a schematic diagram illustrating an exemplary process flow of the present invention.

[0014] Figure 2This is a graph showing the yield (corresponding to the curve on the right y-axis) and purity (corresponding to the curve on the left y-axis) of sodium bicarbonate based on the carbonation reaction temperature.

[0015] Figure 3 This is a graph showing the ammonia recovery rate (%) based on the amount of CaO added (mL) in the wastewater discharged after each 100 mL carbonation reaction.

[0016] Figure 4 This is a graph showing the gypsum yield as a percentage of the recovered weight of gypsum relative to the weight of sodium sulfate, based on the amount of quicklime (calcium oxide, CaO) added (mL) per 100 mL of wastewater discharged after the carbonation reaction.

[0017] Figure 5 This is a graph showing the particle size (μm) of sodium bicarbonate produced according to the particle size distribution reactor temperature.

[0018] Figure 6 This is a schematic diagram illustrating an exemplary reactor for preparing sodium bicarbonate according to the present invention. Best practice

[0019] 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.

[0020] This invention relates to a method for preparing sodium bicarbonate (NaHCO3) with adjustable particle size, and a method for preparing gypsum (CaSO4) using the same. The aim is to provide a method for recovering sodium (Na) from substances containing low-purity sodium sulfate, such as waste containing sodium sulfate or natural minerals, to produce sodium bicarbonate, and from SO4... 2- A method and related apparatus for producing high-purity gypsum from waste liquid, thereby reducing landfill costs for waste generated after desulfurization, and for stably fixing carbon dioxide into carbonates to prepare sodium bicarbonate and gypsum.

[0021] The method for preparing sodium bicarbonate according to the present invention includes the following steps: generating a sodium sulfate solution containing sodium ions from a mixture of a dissolving agent and a substance containing sodium sulfate; adding carbon dioxide and ammonia to the sodium sulfate solution to generate sodium bicarbonate (NaHCO3); and cooling the sodium bicarbonate at a lower temperature than that used in the step of generating sodium bicarbonate to adjust the particle size of the sodium bicarbonate.

[0022] Figure 1 This is a schematic diagram illustrating an exemplary process flow of the present invention. The above-mentioned reaction can be carried out through a dissolution reactor 100, a carbonation reactor 200, and a particle size reduction reactor 300.

[0023] More specifically, the step of generating a sodium sulfate solution containing sodium ions from a mixture of leaching agent 101 and a substance containing sodium sulfate, such as sodium sulfate waste 102, can include a solid-liquid separation step that generates and recovers the sodium sulfate solution containing sodium ions from the mixture of leaching agent and sodium sulfate, and discharges waste 103. This reaction can be carried out in a leaching reactor 100.

[0024] The step of generating a sodium sulfate solution containing the sodium ions is a step of generating and recovering a sodium sulfate solution from a sodium sulfate-containing substance using a dissolving agent. Prior to the step of generating the sodium sulfate solution containing the sodium ions, a stirring step of mixing the sodium sulfate-containing substance and the dissolving agent may be further included. The dissolving agent contains almost no sodium ions, therefore a sodium sulfate solution can be readily generated from the sodium sulfate-containing substance.

[0025] The sodium sulfate-containing substance can be waste containing sodium sulfate or natural minerals containing sodium sulfate. For example, sodium sulfate-containing waste can be sulfur oxides (SO₄) x The waste gas containing sodium sulfate 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 produced by sintering plants in iron smelting plants after electrostatic precipitator treatment, through desulfurization treatment with sodium bicarbonate. The waste containing sodium sulfate also contains impurities such as K, Ca, Fe, and Cl in addition to sodium sulfate; therefore, the solid impurities generated after the stirring can be removed in the solid-liquid separation step.

[0026] The solubility of sodium sulfate at room temperature is 28.1 g / 100 mL. Within the temperature range of 5-45℃, the solubility changes drastically with increasing temperature. Therefore, the suitable dissolution temperature for desulfurization waste is between 20-60℃.

[0027] The dissolving agent is not particularly limited as long as it can come into contact with a substance containing sodium sulfate and dissolve sodium sulfate ions; for example, it can be one or more selected from water and ammonia solution.

[0028] The step of adding carbon dioxide, such as carbon dioxide gas 201 and ammonia and / or solution 202, to the sodium sulfate solution to generate sodium bicarbonate (NaHCO3) may include an ammoniation step of adding ammonia to the sodium sulfate solution and a carbonation step of adding carbon dioxide, which may be carried out in a carbonation reactor 200.

[0029] The sodium sulfate solution can react with carbon dioxide and ammonia to produce solid sodium bicarbonate through a carbonation reaction as shown in formula (1).

[0030] Na₂SO₄ + 2CO₂ + 2NH₃ + 2H₂O → 2NaHCO₃ + (NH₄)₂SO₄ (Equation 1) The Gibbs free energy of the reaction that produces calcium carbonate 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.

[0031] The carbonation reactor used for the carbonation reaction can operate at a pressure of 1-10 atmospheres (atm) and at a temperature below 120°C or 80°C. For example, the sodium sulfate solution in the carbonation reactor can be heated to 40-120°C, and carbon dioxide and ammonia can be added to produce sodium bicarbonate (NaHCO3). While a sufficient amount of carbon dioxide can be dissolved when the pressure in the carbonation reactor exceeds 10 atmospheres, the high energy required reduces the economic viability of the final products, sodium bicarbonate and gypsum. The reaction time varies depending on the method of carbon dioxide injection.

[0032] In addition, when the temperature of the carbonation reactor is below 40°C, the purity may be insufficient, and when the temperature of the carbonation reactor is above 120°C, there may be a tendency to reduce the yield.

[0033] When carbon dioxide is injected in gaseous form, the reaction time will vary depending on whether aeration is used; with aeration, the time can be less than 4 hours. However, the optimal pressure and reaction time can vary depending on the size, space, and conditions of the reactor.

[0034] The chemical formula for sodium bicarbonate is NaHCO3. As the amount of bicarbonate ions (HCO3-) in the solution increases... - As the concentration of bicarbonate increases, the production of sodium bicarbonate also increases. The concentration of bicarbonate ions in aqueous solutions of carbonate systems containing carbon dioxide is highest at a pH of 7.5 to 9.0. Therefore, to improve the recovery rate of sodium bicarbonate, it is preferable to maintain the pH of the sodium sulfate solution at 7.5 to 9.0. However, when sufficient carbon dioxide is dissolved in the sodium sulfate solution to produce the aforementioned sodium bicarbonate, the pH of the solution may drop below 7.5. In this case, the concentration of bicarbonate ions (HCO3-) increases. - The sodium bicarbonate is converted into carbonic acid (H₂CO₃), thereby reducing the formation rate of sodium bicarbonate. Therefore, it is preferable to add ammonia to fully dissolve the sodium sulfate solution before adding carbon dioxide, and then add the carbon dioxide.

[0035] The carbon dioxide may be selected from one or more of the following: pure carbon dioxide, FINEX off gas (FOG), FINEX tail gas (FTG), blast furnace gas (BFG), converter gas, coal-fired power plant exhaust gas, gas-fired power plant exhaust gas, incinerator exhaust gas, glass melting exhaust gas, thermal equipment exhaust gas, petrochemical process exhaust gas, petrochemical process gas, pre-combustion exhaust gas, and gasifier exhaust gas. Furthermore, the carbon dioxide may be concentrated using one or more methods selected from the wet amine process, PSA process, and membrane separation process.

[0036] Furthermore, the recovery rate of sodium bicarbonate can be adjusted by regulating the mass ratio of the added sodium sulfate-containing substance to the water used as a dissolving agent. Specifically, to achieve a sodium bicarbonate recovery rate of 50% (Na... + (Molar basis) and above, the mass ratio of the added sodium sulfate-containing substance to the dissolving agent can be 1:1.5 to 1:5, preferably 1:1.75 to 3.0. When the water ratio is less than the above range and too low, the desulfurization waste is not dissolved, resulting in a large amount of residue and a reduced sodium recovery rate. When the water ratio is greater than the above range and too high, the sodium recovery rate increases, but the wastewater treatment cost in subsequent processes becomes higher. Within the scope of the present invention, more than 80% of the sodium contained in the desulfurization waste can be recovered, the amount of undissolved desulfurization waste after separation and drying is less than 10% of the initial addition amount, and the amount of undissolved desulfurization waste decreases as the water volume increases.

[0037] In addition, in order to use Na + Based on a molar concentration of 50 mol% sodium bicarbonate, the ammonia (NH3) / sodium (Na) ratio in the waste solution is recovered. + The molar ratio of ammonia (NH3) to sodium (Na) is preferably 0.8 to 1.3. + When the molar ratio of ammonia (NH3) to sodium (Na) is less than 0.8, the recovery rate of sodium bicarbonate recovered in the second solid-liquid separation step (S5) is less than 50 mol%. + When the molar ratio of sodium bicarbonate is greater than 1.3, the recovery rate of sodium bicarbonate increases, but the purity of sodium bicarbonate may decrease.

[0038] The present invention includes, after the step of heating the sodium sulfate solution to 40-120°C and adding carbon dioxide and ammonia to generate sodium bicarbonate (NaHCO3), a step of cooling the sodium bicarbonate at a lower temperature than the step of generating sodium bicarbonate to adjust the particle size of the sodium bicarbonate.

[0039] The step of adjusting the particle size of the sodium bicarbonate can be carried out in the particle size distribution reactor 300. The temperature of the particle size distribution reactor 300 can be 5-40°C lower than that of the sodium bicarbonate (NaHCO3) generation step, for example, 10-30°C lower. In this case, if the temperature difference is less than 5°C, the particle size adjustment of the sodium bicarbonate may not be successful; if the temperature difference is greater than 40°C, there may be a problem with particle size distribution control failure.

[0040] In addition, the step of adjusting the particle size of the sodium bicarbonate can be carried out at a temperature of 35-100°C, for example, at a temperature of 50-80°C.

[0041] For example, the generated sodium bicarbonate can be processed using a particle size reduction reactor, such as a rotary circulating reactor, to produce sodium bicarbonate 301 with a coarsened particle size after temperature control. The step of adjusting the particle size of the sodium bicarbonate can be to adjust it to 40-250 μm, preferably 50-200 μm. When the particle size of sodium bicarbonate is less than 40 μm, it is difficult to handle due to scattering, and there is a problem of difficulty in adjusting the amount of sodium bicarbonate added in processes using sodium bicarbonate as a raw material.

[0042] At this point, the cooling rate is preferably 2-20°C / hour. When the cooling rate is less than this range, the cooling is slow and particle size adjustment may not be possible. When the cooling rate is greater than this range, crystals form rapidly, leading to problems with particle size distribution control. Furthermore, if the temperature can be reduced at a sufficient cooling rate in the carbonation reactor, the particle size distribution reactor can be omitted.

[0043] In the step of adding carbon dioxide and ammonia to the sodium sulfate solution to generate sodium bicarbonate (NaHCO3), the sodium bicarbonate separated may be prepared using a substance containing sodium sulfate and impurities. Compared to sodium bicarbonate prepared from pure sodium sulfate, the purity of sodium bicarbonate may be lower. Therefore, to improve the purity of sodium bicarbonate, a further sodium bicarbonate washing step can be performed. In this sodium bicarbonate washing step, the greater the amount of water used, the higher the purity of the resulting sodium bicarbonate.

[0044] At this point, water washing can be performed using 0.5-4 parts by weight of water per 1 part by weight of sodium bicarbonate. When the amount of water is less than the above range, the purity improvement may not be sufficient, and when the amount of water is greater than the above range, the recovery rate of sodium bicarbonate may be reduced.

[0045] Furthermore, the sodium bicarbonate washed with water may further include a sodium bicarbonate drying step. When the sodium bicarbonate drying step is carried out at a temperature above 50°C, there is a tendency for the sodium bicarbonate to decompose back into sodium carbonate; therefore, the drying of the sodium bicarbonate is preferably carried out at a temperature below 50°C.

[0046] However, when the final target product is sodium carbonate instead of sodium bicarbonate, the generated sodium bicarbonate can be dried at temperatures above 50°C to obtain sodium carbonate. Furthermore, the solution used in the water washing process to improve the purity of the sodium bicarbonate can be recycled as a dissolving agent.

[0047] According to another embodiment of the present invention, a method for preparing gypsum is provided, which further includes adding a calcium-containing substance 401 to the filtrate remaining after recovering sodium bicarbonate in the step of generating the sodium bicarbonate, to generate gypsum 402. This step can be carried out in a gypsum reactor 400. More specifically, 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, calcium-containing substances can be added.

[0048] 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.

[0049] When a calcium-containing substance is added to a filtrate with a pH optimized to between 7.5 and 9.0 to generate the sodium bicarbonate, the pH of the filtrate rises above 9. When the pH of the filtrate becomes above 9, the residual carbon dioxide in the solution is converted into carbonate ions (CO3-). 2- It exists in the form of ) and therefore the added calcium ions (Ca) 2+ Carbon dioxide reacts with carbonate ions to form calcium carbonate (CaCO3). Furthermore, at high pH conditions, residual carbon dioxide in the solution passes through the hydroxide ions (OH-) in the water. - This forms slaked lime (Ca(OH)2).

[0050] Furthermore, the present invention can be further incorporated into an apparatus equipped with an ammonia recovery reactor 500, which includes an ammonia recovery step in which the filtrate remaining after gypsum recovery in the gypsum generation step is heated to generate ammonia, and the filtrate 501 is discharged. More specifically, the wastewater discharged after the carbonation reaction contains a large amount of ammonia, so it is preferable to recover this ammonia. In this case, to ensure an ammonia recovery rate of 50% or higher, the reactor temperature and pH should be 60°C and pH 8.0 or higher, respectively.

[0051] That is, 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; when the temperature of the heated filtrate is below 60°C, the ammonia recovery rate decreases. For example, the temperature of the ammonia recovery step can be 60-100°C.

[0052] To increase the pH of the waste solution, a prepared quicklime slurry can be added, either in powder form or as a powder. After adding the quicklime slurry, the temperature of the waste solution rises, and ammonia gas will be generated even with simple stirring. However, to shorten the ammonia recovery rate and time, methods such as solution injection can be applied. The ammonia gas generated as described above can be directly injected into the carbonation reactor, or it can be redissolved in water to prepare ammonia solution and then injected into the carbonation reactor.

[0053] At this point, the molar ratio of calcium ions to sulfate ions (Ca... 2+ :SO4 2- The preferred ratio is 1:1.0-1.3. When the sulfate ion ratio is greater than 1.3, the purity of gypsum decreases. When the sulfate ion ratio is less than 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.

[0054] Calcium-containing substances react with water in an exothermic reaction. Therefore, by further including a heat exchanger between the sodium bicarbonate reactor and the ammonia recovery unit to apply heat to the ammonia recovery unit, further energy consumption can be reduced, thereby saving energy in the ammonia recovery step.

[0055] The recovered ammonia can be reused in gaseous form or by being reprocessed into ammonia water.

[0056] 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.

[0057] At this point, the quicklime (CaO) can be added at a volume of 10-50 mL per 100 mL of wastewater discharged after the carbonation reaction.

[0058] According to another embodiment of the present invention, an apparatus is provided that can be used to prepare sodium bicarbonate and gypsum according to the present invention described above. Figure 6 This is a schematic diagram illustrating an exemplary reactor for preparing sodium bicarbonate according to the present invention.

[0059] More specifically, according to the present invention, a reactor for preparing sodium bicarbonate is provided, comprising: a dissolution reactor S1, wherein the dissolution reactor S1 dissolves sodium ions from a substance containing sodium sulfate using a dissolving agent to generate an aqueous sodium solution; a carbonation reactor S2, wherein the carbonation reactor S2 supplies the aqueous sodium solution with a gas or carbonation solution containing carbon dioxide and a gas or ammonia solution containing ammonia, and generates sodium bicarbonate (NaHCO3) through a reaction; and a particle size distribution reactor S3, wherein the particle size distribution reactor S3 coarsens the sodium bicarbonate in the aqueous sodium bicarbonate solution at 35-100°C, for example, 40-80°C.

[0060] The process includes: a step in the dissolution reactor to generate a sodium sulfate solution containing sodium ions from a mixture of a dissolving agent and a substance containing sodium sulfate; a step in the carbonation reactor to supply a sodium aqueous solution with a gas or carbonation solution containing carbon dioxide and a gas or ammonia solution containing ammonia, and to generate sodium bicarbonate (NaHCO3) through a reaction; and a step in the particle size analyzer to cool the sodium bicarbonate at a temperature of 35-100°C to adjust the particle size of the sodium bicarbonate. The sodium bicarbonate aqueous solution can then be passed through the particle size analyzer, for example, through a circulating reactor, at 35-100°C, for example, 40-80°C, for 2-10 hours to coarsen the particle size of the sodium bicarbonate.

[0061] Furthermore, the sodium bicarbonate preparation reactor of the present invention may further include: an ammonia recovery reactor, which generates gaseous ammonia by supplying calcium-containing substances to the filtrate remaining after sodium bicarbonate recovery; and an evaporation and concentration reactor, which supplies the filtrate from the ammonia recovery reactor and generates gypsum by evaporation and concentration.

[0062] At this point, the reactions occurring in each reactor are as described above.

[0063] 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

[0064] Example Example 1: Preparation of sodium bicarbonate Add 100g of desulfurization waste containing sodium sulfate (Na2SO4) as a byproduct of desulfurization treatment and 175mL of water, and stir at 500rpm at 40°C for 1 hour. After stirring, the mixture is filtered to separate the solid and liquid phases to recover the sodium leaching solution.

[0065] Next, to synthesize sodium bicarbonate, 75 mL of sodium dissolution solution and 25 mL of 25% (w / w) ammonia solution were injected into a 300 mL high-pressure reactor. The temperature was maintained at 25 °C, and carbon dioxide gas was injected at 7 bar. At this time, the stirring speed was set to 200 rpm, and the reaction time was 8 hours.

[0066] After the reaction, sodium bicarbonate is formed as a white solid precipitate, which is separated into solid and liquid components by filtration. The sodium bicarbonate obtained as described above is dried at room temperature. During the carbonation reaction, when heated to temperatures above 50°C, sodium bicarbonate decomposes into sodium carbonate, thereby increasing purity and decreasing yield.

[0067] If necessary, a water washing process can be performed to improve the purity of sodium bicarbonate. Additionally, Figure 2 This is a graph showing the yield and purity of sodium bicarbonate according to temperature. More specifically, the carbonation reactor was subjected to reactions at various temperatures of 40°C, 60°C, 80°C, and 100°C, under a CO2 atmosphere and a pressure of 7 bar for 60 minutes. The purity of sodium bicarbonate was confirmed by X-ray diffraction (XRD) analysis and elemental analysis.

[0068] The reaction results of 100g of desulfurization waste are summarized in Table 1 below.

[0069] [Table 1] Example 2: Preparation of gypsum To determine the ammonia recovery rate in the ammonia recovery reactor after gypsum preparation, 100 mL of the carbonated waste solution was placed in the reactor, heated to 80°C, and then 7 M CaO slurry was added. Aeration with nitrogen was then employed.

[0070] Furthermore, the remaining filtrate after recovering the gypsum was evaporated by heating, and ammonia was recovered. The recovery rate of ammonia was confirmed by ion chromatography (IC), and the results are shown in [Figure / Reference]. Figure 3 middle.

[0071] In addition, when the filtrate remaining after gypsum recovery is concentrated by evaporation to recover ammonia, the amount of gypsum generated is measured according to the amount of CaO added. Concentration is then carried out by placing the waste solution after ammonia stripping into a reactor and evaporating it at 80°C. The mass of the final remaining solid is measured, and the resulting gypsum (CaSO4) yield is shown in the figure. Figure 4 middle.

[0072] exist Figure 3 and Figure 4 In the graph, the x-axis represents the volume of quicklime (CaO) produced per 100 mL of filtrate (waste liquid) after carbonation, which is 7 M.

[0073] Experimental Example 1: Particle size of sodium bicarbonate based on reaction temperature In Example 1, to improve particle size, the carbonation reactor was heated to 40-100°C. The sodium bicarbonate solution reacting in the carbonation reactor was then transferred to a particle size reduction reactor to precipitate. This particle size reduction reactor was a circulating reactor, and the temperature of the solution added from the carbonation reactor was adjusted to 60-100°C. In this circulating reactor, a cooling process was performed to facilitate the precipitation of sodium bicarbonate crystals and coarsen the particle size; the temperature of the circulating sodium bicarbonate solution was controlled to be 40-70°C lower than the temperature at which sodium bicarbonate was formed during the carbonation reaction.

[0074] More specifically, the sodium bicarbonate solution was circulated for 60 minutes at various temperatures in the carbonation reactor: 40°C, 60°C, 80°C, and 100°C. After cooling to 40°C in the circulating reactor, the particle size of the sodium bicarbonate passing through was measured, and the results are shown below. Figure 5 The particle size distribution reactor consists of a cooling reactor and an ambient temperature reactor. The sodium bicarbonate solution is added to the ambient temperature reactor and then circulated back to the cooling reactor.

[0075] 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.

[0076] [Explanation of reference numerals in the attached figures] 100: Dissolution reactor 101: Leaching agent; 102: Sodium sulfate waste; 103: Waste 200: Carbonation reactor 201: Gas containing carbon dioxide; 202: Ammonia gas or solution 300: Particle size reduction reactor 301: Sodium bicarbonate 400: Gypsum Reactor 401: Calcium-containing substance; 402: Gypsum 500: Ammonia Recovery Reactor 501: Filtrate

Claims

1. A method for preparing sodium bicarbonate, comprising the following steps: A sodium sulfate solution containing sodium ions is generated from a mixture of a dissolving agent and a substance containing sodium sulfate. The sodium sulfate solution is heated to 40-120°C, and carbon dioxide and ammonia are added to produce sodium bicarbonate (NaHCO3); and The sodium bicarbonate is cooled at a lower temperature than that used in the step of producing sodium bicarbonate to adjust the particle size of the sodium bicarbonate.

2. The method for preparing sodium bicarbonate according to claim 1, wherein, The temperature of the step of adjusting the particle size of the sodium bicarbonate is 5-40°C lower than the temperature of the step of generating sodium bicarbonate (NaHCO3).

3. The method for preparing sodium bicarbonate according to claim 1, wherein, The step of adjusting the particle size of the sodium bicarbonate is carried out at a temperature of 35-75°C.

4. The method for preparing sodium bicarbonate according to claim 1, wherein, The pH of the sodium sulfate solution is between 7.5 and 9.

0.

5. The method for preparing sodium bicarbonate according to claim 1, wherein, The step of adjusting the particle size of the sodium bicarbonate is to adjust the particle size of the sodium bicarbonate to 40-250 μm.

6. The method for preparing sodium bicarbonate according to claim 1, wherein, The preparation method further includes a step of washing the sodium bicarbonate with 0.5-4 parts by weight of water for every 1 part by weight of sodium bicarbonate.

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

8. The method for preparing gypsum according to claim 7, wherein, The pH of the filtrate remaining after recovering sodium bicarbonate in the step of generating the sodium bicarbonate will be adjusted to 7.5 to 9.

0.

9. The method for preparing gypsum according to claim 7, wherein, The preparation method further includes an ammonia recovery step, in which the filtrate remaining after recovering the gypsum in the step of generating the gypsum is heated to above 60°C to generate ammonia.

10. The method for preparing gypsum according to claim 7, wherein, The calcium-containing substance is quicklime (CaO).

11. The method for preparing gypsum according to claim 10, wherein, Add 10-50 mL of quicklime (CaO) to every 100 mL of wastewater discharged after the carbonation reaction.

12. A reactor for preparing sodium bicarbonate, comprising: A dissolution reactor, wherein sodium ions are dissolved from a substance containing sodium sulfate by a dissolving agent to generate an aqueous sodium solution; A carbonation reactor, wherein the carbonation reactor supplies a carbon dioxide-containing gas or carbonation solution and an ammonia-containing gas or ammonia solution to the sodium aqueous solution, and generates sodium bicarbonate (NaHCO3) through a reaction; and A particle size distribution reactor that coarsens the particle size of sodium bicarbonate by generating an aqueous solution of sodium bicarbonate at 35-100°C.

13. The reactor for preparing sodium bicarbonate according to claim 12, wherein, The reactor further comprises an ammonia recovery reactor, which generates gaseous ammonia by supplying calcium-containing substances to the filtrate remaining after the recovery of sodium bicarbonate.

14. The reactor for preparing sodium bicarbonate according to claim 13, wherein, The reactor further comprises an evaporation and concentration reactor, which supplies the filtrate from the ammonia recovery reactor and concentrates it to produce gypsum through evaporation and concentration.

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