Preparation method and preparation device of sodium bicarbonate and gypsum

Abstract

The present invention relates to a method and an apparatus for preparing sodium bicarbonate and gypsum, the method comprising: a step of adding carbon dioxide (CO2) and ammonia (NH3) to a sodium sulfate solution to prepare sodium bicarbonate; a step of adding a calcium (Ca)-containing substance to the first filtrate generated in the step of preparing sodium bicarbonate to prepare and recover first gypsum (CaSO4); a step of adding sodium carbonate (Na2CO3) to the second filtrate generated in the step of preparing and recovering the first gypsum to precipitate calcium carbonate (CaCO3) so as to remove a Ca substance and then recover ammonia; and a step of mixing the first gypsum with the waste liquid generated in the ammonia recovery step and then adding sulfuric acid to prepare second gypsum having a purity higher than that of the first gypsum. According to the invention, the problem of scaling caused by calcium can be solved, and the preparation cost of sodium bicarbonate and gypsum can be reduced.

Description

Technical Field

[0001] This invention relates to a method and apparatus for preparing sodium bicarbonate and gypsum. Background Technology

[0002] Sulfur oxides (SOx) are not only a major cause of acid rain, but also harmful gases that can cause respiratory diseases after being absorbed by the human body. Currently, with industrial development, the emission of sulfur oxides from various factories, thermal power plants, and incinerators is increasing. In order to minimize sulfur oxide emissions, various desulfurization methods are applied on-site.

[0003] Currently, sodium bicarbonate (NaHCO3) is being used as an adsorbent in sintering plants of iron smelting plants to remove sulfur oxides. In order to meet increasingly stringent environmental regulations, the use of sodium bicarbonate is also on the rise.

[0004] When importing industrial sodium bicarbonate from overseas, there is a problem that the import price of sodium bicarbonate can fluctuate significantly depending on the overseas economic situation. In addition, the reaction of using sodium bicarbonate to remove sulfur oxides produces carbon dioxide and sodium sulfate (Na2SO4), which are currently being directly landfilled, causing disposal costs and secondary environmental problems.

[0005] If a process for preparing sodium bicarbonate and gypsum using sodium sulfate is adopted, it can solve a number of problems such as waste reduction, carbon neutrality, and stable raw material supply through internal recycling of sodium bicarbonate. Therefore, the development of this technology is urgent. Summary of the Invention

[0006] (a) Technical problems to be solved The method for preparing sodium bicarbonate and gypsum of the present invention aims to remove calcium carbonate (CaCO3) from the filtrate by adding sodium carbonate (Na2CO3) to precipitate calcium carbonate (CaCO3), thereby solving the problem of equipment scaling caused by calcium and removing calcium ions (CaCO3) from the filtrate. 2+ The concentration was reduced to an operable level.

[0007] (II) Technical Solution A method for preparing sodium bicarbonate and gypsum according to a specific embodiment of the present invention includes: a step of adding carbon dioxide (CO2) and ammonia (NH3) to a sodium sulfate solution to prepare sodium bicarbonate; a step of adding a calcium-containing (Ca) substance to a first filtrate produced in the step of preparing sodium bicarbonate to prepare and recover a first gypsum (CaSO4); and a step of adding sodium carbonate (Na2CO3) to a second filtrate produced in the step of preparing and recovering the first gypsum to precipitate calcium carbonate (CaCO3) and remove calcium ions (Ca2CO3). 2+The steps include: recovering ammonia; and mixing the first gypsum with sulfuric acid in the waste liquid generated during the ammonia recovery step to prepare a second gypsum with a higher purity than the first gypsum.

[0008] The sodium sulfate solution may be prepared by a step of forming a sodium sulfate solution from a raw material containing sodium sulfate (Na2SO4).

[0009] The recovered ammonia can be added back into the sodium sulfate solution during the step of preparing sodium bicarbonate.

[0010] The second filtrate may contain calcium at a concentration of 40 ppm to 1000 ppm based on the total concentration of the second filtrate.

[0011] The sodium carbonate may be added to the second filtrate at a rate of 0.1% to 10% by weight, based on the total weight of the second filtrate.

[0012] The calcium-containing substance may be quicklime (CaO).

[0013] According to another specific embodiment of the present invention, the method for preparing sodium bicarbonate and gypsum may further include, after the step of preparing the second gypsum, adding sodium carbonate (Na2CO3) to the fourth filtrate produced in the step of preparing the second gypsum to precipitate calcium carbonate (CaCO3) and remove the Ca substance.

[0014] An apparatus for preparing sodium bicarbonate and gypsum according to another specific embodiment of the present invention comprises: a sodium bicarbonate preparation machine, which receives a sodium sulfate solution, carbon dioxide (CO2), and ammonia (NH3) to prepare sodium bicarbonate; a first gypsum preparation machine, which receives a first filtrate and a calcium (Ca)-containing substance generated in the sodium bicarbonate preparation machine to prepare a first gypsum (CaSO4); and an ammonia recovery machine, which receives a second filtrate and sodium carbonate (Na2CO3) generated in the first gypsum preparation machine to precipitate calcium carbonate (CaCO3) to remove calcium ions (Ca2CO3). 2+ The process involves: 1) recovering ammonia; and 2) a second gypsum preparation machine, which receives the waste liquid generated in the ammonia recovery machine and the first gypsum, mixes them, and then receives sulfuric acid to prepare a second gypsum with a higher purity than the first gypsum.

[0015] (III) Beneficial Effects The method for preparing sodium bicarbonate and gypsum according to the present invention can solve the scaling problem caused by calcium.

[0016] Furthermore, the preparation method of sodium bicarbonate and gypsum according to the present invention can reduce the preparation cost of sodium bicarbonate and gypsum. Attached Figure Description

[0017] Figure 1 This is a flowchart schematically illustrating a method for preparing sodium bicarbonate and gypsum according to one embodiment of the present invention.

[0018] Figure 2 (a) shows the XRD analysis results of the solid phase generated in the preparation method of sodium bicarbonate and gypsum according to one embodiment of the present invention.

[0019] Figure 2 (b) shows the XRD analysis results of the solid phase generated in the preparation method of sodium bicarbonate and gypsum according to one embodiment of the present invention. Best practice

[0020] Hereinafter, preferred embodiments of the present invention will be described with reference to various embodiments. However, embodiments of the present invention can be modified in many other forms, and the scope of the present invention is not limited to the embodiments described below.

[0021] One aspect of the present invention relates to a method for preparing sodium bicarbonate and gypsum.

[0022] The exhaust gas from the sintering plant of the ironmaking plant contains sulfur oxides (SOx). The reaction formula for removing sulfur oxides (SOx) with sodium bicarbonate (NaHCO3) is shown in Formula 1 below.

[0023] [Formula 1] 2NaHCO3(s)+SO2(g)+1 / 2O2(g)→Na2SO4(s)+2CO2(g)+H2O(g) In desulfurization processes using sodium bicarbonate, as shown in Formula 1, carbon dioxide is emitted. Furthermore, the reaction involving the removal of sulfur oxides using sodium bicarbonate produces sodium sulfate (Na₂SO₄). Sodium sulfate is composed of sodium and sulfate, thus sodium can be used to produce sodium bicarbonate, and sulfate can be used to produce gypsum (CaSO₄).

[0024] Sodium bicarbonate can be produced by dissolving sodium sulfate in water and then reacting it with carbon dioxide and ammonia. Calcium-containing substances can be added to the wastewater produced to produce gypsum.

[0025] The desulfurization waste generated in the sintering plant of an ironmaking plant contains calcium (Ca). Specifically, the sodium sulfate waste generated in the sintering plant contains approximately 3% by weight of calcium. The sodium bicarbonate production equipment also contains calcium ions (Ca) in the filtrate. 2+ Scale buildup on the equipment walls can hinder normal operation. Therefore, to improve process efficiency, it is necessary to reduce the calcium ion concentration in the solution before adding the filtrate to the equipment. 2+) concentration. Especially in wastewater treatment processes involving ammonia recovery and evaporation concentration, it is necessary to reduce the calcium ion (Ca) concentration in the filtrate before adding it to the equipment. 2+ Smooth operation can only be achieved when the concentration is reduced to below 120 ppm.

[0026] Table 1 shows the calcium ion solubility (g / 100mL H2O) of calcium chloride (CaCl2), calcium sulfate (CaSO4), and calcium carbonate (CaCO3) in the form of calcium ion (g / 100mL H2O) according to temperature.

[0027] [Table 1] Table 1 confirms that calcium ions (Ca) 2+ When in its calcium carbonate (CaCO3) form, it has low solubility and is therefore prone to precipitation. Therefore, it can be precipitated by adding substances containing carbonate ions (CO3). 2- And substances with high solubility can induce Ca 2+ (aqueous solution (aq.)) + CO3 2- (aq.) a CaCO3(s) reaction.

[0028] Figure 1 This is a schematic diagram illustrating a hydrogen production apparatus according to one embodiment of the present invention. Hereinafter, reference will be made to... Figure 1 The present invention will now be described in more detail.

[0029] The method for preparing sodium bicarbonate and gypsum of the present invention includes: a step of adding carbon dioxide (CO2) and ammonia to a sodium sulfate solution to prepare sodium bicarbonate; a step of adding a calcium-containing (Ca) substance to a first filtrate produced in the step of preparing sodium bicarbonate to prepare and recover a first gypsum (CaSO4); and a step of adding sodium carbonate (Na2CO3) to a second filtrate produced in the step of preparing and recovering the first gypsum to precipitate calcium carbonate (CaCO3) and remove calcium ions (Ca2CO3). 2+ The steps include: recovering ammonia; and mixing the first gypsum with sulfuric acid in the waste liquid generated during the ammonia recovery step to prepare the second gypsum.

[0030] According to the method for preparing sodium bicarbonate and gypsum of the present invention, calcium ions (Ca) can be... 2+ The concentration of sodium bicarbonate and gypsum is reduced to an operable level. Therefore, the preparation cost of sodium bicarbonate and gypsum can be reduced through stable operation.

[0031] The method for preparing sodium bicarbonate and gypsum of the present invention includes the step of adding carbon dioxide (CO2) and ammonia to a sodium sulfate solution to prepare sodium bicarbonate.

[0032] The sodium sulfate solution can be prepared by a step of forming a sodium sulfate solution from a raw material containing sodium sulfate (Na2SO4).

[0033] The raw material containing sodium sulfate can be, for example, desulfurization waste. A mixture can be prepared by dissolving the sodium sulfate-containing raw material in a leaching agent and stirring. The leaching agent can be water. The mixture can be stirred to perform solid / liquid separation, thereby obtaining solid desulfurization waste (primary waste) and a sodium sulfate solution.

[0034] The first gypsum is low-purity gypsum, and the second gypsum is high-purity gypsum with a higher purity than the first gypsum.

[0035] The method for preparing sodium bicarbonate and gypsum according to the present invention includes the step of adding carbon dioxide and ammonia to the sodium sulfate solution to prepare sodium bicarbonate.

[0036] The method for preparing sodium bicarbonate and gypsum according to the present invention includes the step of adding a calcium-containing substance to the first filtrate produced in the step of preparing sodium bicarbonate to prepare and recover the first gypsum. The calcium-containing substance may be quicklime (CaO).

[0037] The method for preparing sodium bicarbonate and gypsum of the present invention includes adding sodium carbonate (Na2CO3) to the second filtrate generated in the step of preparing and recovering the first gypsum to precipitate calcium carbonate (CaCO3) and remove calcium ions (Ca). 2+ The subsequent ammonia recovery step.

[0038] The method for preparing sodium bicarbonate and gypsum of the present invention includes a step of mixing the first gypsum with the waste liquid generated in the ammonia recovery step and then adding sulfuric acid to prepare a second gypsum with a higher purity than the first gypsum.

[0039] The form in which calcium is formed varies depending on the pH. Below pH 6, calcium ions mainly exist as calcium sulfate (CaSO4) or calcium chloride (CaCl2). Above pH 6, they exist as calcium carbonate (CaCO3). Above pH 12, they can also exist as slaked lime (Ca(OH)2). The pH of desulfurization waste is generally 9, dropping to between 7 and 8 after sodium bicarbonate production. To recover ammonia, calcium-containing substances (CaO and Ca(OH)2, etc.) need to be added to raise the pH above 11. Therefore, CO32-containing substances are added... 2- When the substance is present, the calcium carbonate (CaCO3) production reaction occurs very well. Although there are various substances containing CO3... 2- While sodium bicarbonate and gypsum are substances, sodium carbonate (Na2CO3), which can be produced by heating sodium bicarbonate in a process, can be used to optimize operating costs in the production of sodium bicarbonate and gypsum.

[0040] The method for preparing sodium bicarbonate and gypsum of the present invention allows the ammonia recovered in the ammonia recovery step to be reintroduced into the sodium sulfate solution in the sodium bicarbonate preparation step. This allows for the recycling of ammonia without waste, thereby preventing environmental pollution and reducing the cost of sodium bicarbonate preparation.

[0041] The second filtrate may contain calcium of about 40 ppm to 1000 ppm based on the total concentration of the second filtrate.

[0042] The method for preparing sodium bicarbonate and gypsum of the present invention involves adding sodium carbonate (Na2CO3) to the second filtrate remaining after gypsum recovery. The sodium carbonate (Na2CO3) is added at approximately 0.1% to 10% by weight of the total weight of the second filtrate to precipitate calcium carbonate (CaCO3) and remove calcium ions (Ca). 2+ ).

[0043] The method for preparing sodium bicarbonate and gypsum of the present invention may further include, after the ammonia recovery step, the addition of sulfuric acid (H2SO4) to the remaining filtrate after ammonia recovery from the waste liquid to form gypsum and then recovering it.

[0044] The method for preparing sodium bicarbonate and gypsum of the present invention may further include adding sodium carbonate (Na2CO3) to the fourth filtrate produced in the step of preparing the second gypsum to precipitate calcium carbonate (CaCO3) and remove calcium ions (Ca). 2+ The steps are as follows.

[0045] The method for preparing sodium bicarbonate and gypsum of the present invention involves the removal of calcium ions (Ca). 2+ Following the steps described above, a wastewater treatment step may be further included. This wastewater treatment step allows the discharge of wastewater from which secondary waste has been removed.

[0046] Another aspect of the invention relates to an apparatus for preparing sodium bicarbonate and gypsum.

[0047] The apparatus for preparing sodium bicarbonate and gypsum according to the present invention comprises: a sodium bicarbonate preparation machine, wherein the sodium bicarbonate preparation machine receives sodium sulfate solution, carbon dioxide (CO2), and ammonia (NH3) to prepare sodium bicarbonate; a first gypsum preparation machine, wherein the first gypsum preparation machine receives a first filtrate and calcium (Ca)-containing substances generated in the sodium bicarbonate preparation machine to prepare first gypsum (CaSO4); and an ammonia recovery machine, wherein the ammonia recovery machine receives a second filtrate and sodium carbonate (Na2CO3) generated in the first gypsum preparation machine to precipitate calcium carbonate (CaCO3) to remove calcium ions (Ca2CO3). 2+The process involves: 1) recovering ammonia; and 2) a second gypsum preparation machine, which receives the waste liquid generated in the ammonia recovery machine and the first gypsum, mixes them, and then receives sulfuric acid to prepare a second gypsum with a higher purity than the first gypsum. Detailed Implementation

[0048] Example The present invention will now be described in more detail through embodiments. These embodiments are intended to illustrate the invention more specifically, but are not intended to limit the invention.

[0049] Example 1 Steps for preparing sodium bicarbonate Add 100g of desulfurization waste and 200mL of water, and stir at 40°C for 1 hour to prepare a mixture. After stirring, perform solid / liquid separation on the mixture to obtain solid desulfurization waste (primary waste) and sodium sulfate solution.

[0050] Repeat the preparation of sodium sulfate solution until 370g of sodium sulfate solution is obtained.

[0051] 70 g of a 25% to 30% by weight ammonia solution and 48.5 g of carbon dioxide were added to 370 g of the produced sodium sulfate solution, and the reaction was carried out at 40°C and 7 bar for 4 hours to obtain a slurry containing sodium bicarbonate. The slurry containing sodium bicarbonate was subjected to solid / liquid separation to obtain a first filtrate and sodium bicarbonate.

[0052] Steps for preparing the first gypsum Add 250g of 25% by weight quicklime (CaO) slurry to the first filtrate and stir for 1 hour. After stirring, perform solid / liquid separation to prepare and recover the second filtrate and the first gypsum.

[0053] Ammonia recovery steps Add 0.5g of sodium carbonate (Na2CO3) to 100g of the recovered second filtrate, and stir at room temperature for 30 minutes to perform solid / liquid separation, thereby recovering the third filtrate and the first solid phase.

[0054] The recovered third filtrate is heated to 80°C and aerated with inert gas to recover ammonia (NH3) from the filtrate.

[0055] Steps for preparing the second gypsum The waste liquid from aeration to remove NH3 was mixed again with 100g of the first gypsum, and then 85g of a 30% by weight sulfuric acid aqueous solution was slowly added and stirred for 1 hour to form a slurry. The slurry was then subjected to solid / liquid separation to recover the fourth filtrate and the second gypsum. 0.5g of sodium carbonate (Na2CO3) was added to 100g of the recovered fourth filtrate, and the mixture was stirred at room temperature for 30 minutes, followed by solid / liquid separation to recover the fifth filtrate and the second solid phase.

[0056] Add 90g of a 30% hydrochloric acid aqueous solution to lower the pH of the fifth filtrate to below 6. Then, add 0.5g of sodium carbonate (Na₂CO₃) to 100g of the recovered sixth filtrate and stir at room temperature for 30 minutes. The calcium ions (Ca) in the sixth filtrate... 2+ The concentrations of calcium ions (Ca) are shown in Table 4. 2+ The concentration analysis method is the same as the measurement method for the third filtrate.

[0057] Examples 2 to 5 Sodium bicarbonate and gypsum were prepared using the same method as in Example 1, except that 1g, 3g, 5g, and 10g of sodium carbonate (Na2CO3) were added, respectively.

[0058] Comparative Example 1 Sodium bicarbonate and gypsum were prepared using the same method as in Example 1, except that sodium carbonate (Na2CO3) was not added.

[0059] Experimental Example The calcium ions (Ca) in the third filtrate of Examples 1 to 5 and Comparative Example 1 were compared. 2+ The concentration changes of calcium ions (Ca) are shown in Table 2. 2+ The concentration was measured using ion chromatography (IC).

[0060] The XRD analysis results of the first solid phase of Examples 1 to 5 and Comparative Example 1 are shown in the figure. Figure 2 In (a), it can be confirmed that when an excess of sodium carbonate (Na2CO3) is added, the solid phase will contain unreacted Na2CO3 and other impurities, rather than CaCO3.

[0061] [Table 2] The calcium ions (Ca) recovered from the fifth filtrate of Examples 1 to 5 and Comparative Example 1 2+ The concentration changes of the recovered second solid phase and the XRD analysis results are shown in Table 3 and . Figure 2 In (b), calcium ions (Ca) 2+The concentration analysis method is the same as that used for the third filtrate and the first solid phase.

[0062] [Table 3] Tables 2 and 3 confirm that as the amount of sodium carbonate (Na₂CO₃) added increases, the calcium ions (CaO) in the third and sixth filtrates increase. 2+ The concentration of calcium ions (Ca) decreased. The sixth filtrate of Examples 1 to 5 and Comparative Example 1 showed a decrease in the concentration of calcium ions (Ca). 2+ The concentrations of ) are shown in Table 4.

[0063] [Table 4] The analysis results in Table 4 confirm that, due to the low pH, the calcium ions (Ca) in the seventh filtrate... 2+ The concentration of ) did not decrease.

[0064] 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.

Claims

1. A method for preparing sodium bicarbonate and gypsum, comprising: The steps for preparing sodium bicarbonate by adding carbon dioxide (CO2) and ammonia (NH3) to a sodium sulfate solution; The step of adding a calcium (Ca)-containing substance to the first filtrate produced in the step of preparing sodium bicarbonate to prepare and recover the first gypsum (CaSO4); Sodium carbonate (Na₂CO₃) is added to the second filtrate produced in the step of preparing and recovering the first gypsum to precipitate calcium carbonate (CaCO₃) and remove calcium ions (Ca). 2+ The subsequent ammonia recovery step; as well as The step involves mixing the first gypsum with the waste liquid generated in the ammonia recovery step, and then adding sulfuric acid to prepare a second gypsum with a higher purity than the first gypsum.

2. The method for preparing sodium bicarbonate and gypsum according to claim 1, wherein, The sodium sulfate solution is prepared by a step of forming a sodium sulfate solution from a raw material containing sodium sulfate (Na2SO4).

3. The method for preparing sodium bicarbonate and gypsum according to claim 1, wherein, The recovered ammonia is added back into the sodium sulfate solution during the sodium bicarbonate preparation step.

4. The method for preparing sodium bicarbonate and gypsum according to claim 1, wherein, The second filtrate contains calcium at a concentration of 40 ppm to 1000 ppm based on the total concentration of the second filtrate.

5. The method for preparing sodium bicarbonate and gypsum according to claim 1, wherein, The sodium carbonate is added to the second filtrate at a rate of 0.1% to 10% by weight, based on the total weight of the second filtrate.

6. The method for preparing sodium bicarbonate and gypsum according to claim 1, wherein, The calcium-containing substance is quicklime (CaO).

7. The method for preparing sodium bicarbonate and gypsum according to claim 1, wherein, Following the step of preparing the second gypsum, the method further includes adding sodium carbonate (Na2CO3) to the fourth filtrate produced in the step of preparing the second gypsum to precipitate calcium carbonate (CaCO3) and remove the Ca substances.

8. An apparatus for preparing sodium bicarbonate and gypsum, comprising: A sodium bicarbonate preparation machine, wherein the sodium bicarbonate preparation machine receives sodium sulfate solution, carbon dioxide (CO2) and ammonia (NH3) to prepare sodium bicarbonate; A first gypsum preparation machine receives a first filtrate and a calcium (Ca)-containing substance produced in the sodium bicarbonate preparation machine to prepare a first gypsum (CaSO4). An ammonia recovery machine receives the second filtrate and sodium carbonate (Na₂CO₃) produced in the first gypsum preparation machine to precipitate calcium carbonate (CaCO₃) in order to remove calcium ions (Ca). 2+ Then, the ammonia is recovered. as well as The second gypsum preparation machine receives the waste liquid generated in the ammonia recovery machine and the first gypsum, mixes them, and then receives sulfuric acid to prepare a second gypsum with a higher purity than the first gypsum.

Images