Method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized fly ash

Abstract

The invention belongs to the technical field of sodium bicarbonate preparation, and particularly relates to a method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized fly ash, which comprises the following steps: step 1, adding water into desulfurized fly ash for dissolving, and filtering to obtain a treatment solution; 2, the treatment liquid reacts with carbon dioxide gas in a carbonization tower for carbonization, and carbonization liquid is obtained; 3, ammonium bicarbonate is added into the carbonized solution for a reaction, and a sodium bicarbonate solid product is obtained after a filter cake is washed and dried; step 4, adding sulfuric acid into the filtrate obtained in the step 3 to adjust the pH value, and diluting to obtain a diluent; and 5, preparing sodium bicarbonate by using a bipolar membrane electrodialysis device. The sodium bicarbonate solid product is obtained through the double decomposition reaction of the desulfurized fly ash treatment liquid and ammonium bicarbonate, and the cyclic utilization of ammonia in the process is realized through the bipolar membrane electrodialysis equipment, so that the treatment problem of mother liquor after double decomposition is solved, the cost for treating hazardous waste desulfurized fly ash is greatly reduced, and the economic benefit is increased. And the purchase cost of the desulfurizing agent is also saved.

Description

Technical Field

[0001] The invention relates to the technical field of sodium bicarbonate preparation, and in particular to a method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash. Background Art

[0002] Sodium bicarbonate is an important chemical raw material, which is widely used in the fields of intermediates for the preparation of soda ash, surface cleaners, acid neutralizers for industrial waste gas, food additives, fire extinguisher powders and flue gas desulfurizers. At present, the main production method of sodium bicarbonate is the carbonization of soda ash or natural alkali. Several major alkali plants in my country, such as Tianjin Alkali Plant, Qingdao Alkali Industry Company and Hubei Chemical Plant, all adopt this method. In addition, Solvay also uses sodium chloride as raw material to produce large-particle active sodium bicarbonate products with high activity through special processes. With the substantial increase in the demand for sodium bicarbonate in industrial production, new production methods are needed. In the steel industry, many steel mills use sodium bicarbonate as a flue gas desulfurizer. The desulfurization process produces a large amount of desulfurization ash, the main components of which are sodium sulfate and insoluble impurities, and also contain a small amount of sodium carbonate, sodium bicarbonate and sodium chloride. The desulfurization ash has complex composition, low economic value and huge quantity, and is mostly treated as solid hazardous waste. Since its main components are soluble salts, it will pollute soil and water sources after being washed by rainwater. If sodium bicarbonate can be prepared using sodium sulfate as raw material, it will not only reduce the cost of hazardous waste treatment and desulfurization agent purchase, but also bring significant environmental benefits.

[0003] At present, sodium sulfate is used to prepare sodium bicarbonate through a double decomposition reaction between sodium sulfate solution and ammonium bicarbonate or ammonia and carbon dioxide. Scientists have developed a circulating alkali production method by imitating the Solvay process. The process of this method is to carbonize the mirabilite solution and ammonia water in a carbonization tower to produce sodium bicarbonate, and then filter and wash to separate the sodium bicarbonate. This method has obvious disadvantages: the conversion rate of double decomposition is low, and the utilization rate of sodium ions is not high, only about 64%. At the same time, the separation of the by-product ammonium sulfate is difficult. Direct evaporation of sodium sulfate-ammonium sulfate mother liquor will produce complex salts that are difficult to separate, and it is difficult to directly obtain relatively pure ammonium sulfate. The key to the technology of preparing sodium bicarbonate from sulfuric acid is to improve the utilization rate of sodium ions and the separation of sodium sulfate-ammonium sulfate mother liquor. CN102198953A discloses a method for preparing sodium bicarbonate by double decomposition, wherein sodium sulfate and ammonium bicarbonate are used as raw materials, sodium bicarbonate is obtained by double decomposition reaction, the separated mother liquor is subjected to high temperature deammoniation, evaporated and concentrated at 130°C to obtain sodium sulfate crystals, the separated mother liquor is cooled and crystallized to obtain a double salt of sodium sulfate and ammonium sulfate, and the mother liquor is evaporated and crystallized to obtain an ammonium sulfate product. The method has a long process, undergoes multiple high temperature, cooling and other processes, has a large evaporation depth, a large material circulation volume, and the utilization rate of sodium ions and sulfate ions needs to be improved.

[0004] CN111039304A discloses a method for preparing sodium bicarbonate and co-producing sulfuric acid by double decomposition, wherein any one of diammonium hydrogen phosphate, ammonium formate or ammonium nitrate or a mixture of at least two of them is reacted with sodium sulfate to generate the first target product ammonium sulfate and sodium salt, and then the ammonium sulfate crystals and sodium salt solution are obtained by evaporation and crystallization, and the sodium salt solution is further added with ammonium bicarbonate (or carbon dioxide + ammonia) to react to generate the second target product sodium bicarbonate. This method can effectively promote the double decomposition reaction, and avoids the operation of repeated heating and cooling of mother liquor separation, which can greatly reduce the process energy consumption, but the process consumes a large amount of reagents and the equipment occupies a large area.

[0005] In addition, some researchers have developed a new green process of ethanolamine anti-solvent crystallization to solve the problem of separating sodium sulfate and ammonium sulfate mother liquor. This process first evaporates and concentrates the filtered mother liquor to obtain some sodium sulfate solids. The filtered filtrate is added to the ethanolamine anti-solvent crystallizer. At 80°C, ethanolamine acts to crystallize solid sodium sulfate. After the filtered filtrate is cooled and crystallized, solid ammonium sulfate can be obtained. This method can effectively separate sodium sulfate and ammonium sulfate mother liquor, but sodium sulfate and ammonium sulfate will carry ethanolamine, which will affect the purity of the product. In addition, the energy consumption of heating first and then cooling will also cause high energy consumption.

[0006] Regarding how to improve the utilization rate of sodium ions, CN101544385 discloses a method for co-producing soda ash and calcium sulfate using mirabilite and organic amine as raw materials. The outstanding advantage of this method is that the conversion rate can reach more than 90%, but organic amines have a high boiling point and high viscosity, and the energy consumption for evaporation recovery is relatively high. In addition, sodium bicarbonate and calcium sulfate are entrained by organic amines, which affects the purity of the products.

[0007] In summary, the problems of complex process, low raw material utilization rate and high production cost in the technology of preparing sodium bicarbonate from sodium sulfate need to be urgently solved. Summary of the invention

[0008] 1. Technical issues to be solved

[0009] The purpose of the present invention is to solve the problems of complex process, low raw material utilization and high production cost in the prior art of preparing sodium bicarbonate from sodium acid, and to propose a method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash.

[0010] 2. Technical solution

[0011] In order to achieve the above object, the present invention adopts the following technical solutions:

[0012] A method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash, comprising the following steps:

[0013] Step 1: Dissolve the desulfurized ash in water and filter to obtain the treated liquid;

[0014] Step 2: reacting the treated liquid obtained in step 1 with carbon dioxide gas in a carbonization tower to carbonize the treated liquid to obtain a carbonized liquid;

[0015] Step 3: adding ammonium bicarbonate to the carbonized liquid, filtering after a period of reaction to obtain a filtrate and a filter cake, and washing and drying the filter cake to obtain a sodium bicarbonate solid product;

[0016] Step 4: adding sulfuric acid to the filtrate obtained in step 3, adjusting the pH of the solution, and diluting the solution to obtain a diluted solution;

[0017] Step 5: Add sodium sulfate solution to the polar chamber water tank of the bipolar membrane electrodialysis equipment, add sodium hydroxide solution to the alkali chamber water tank, add the diluent obtained in step 4 to the salt chamber water tank, add sulfuric acid solution to the acid chamber water tank, start the circulation pump, transport the solutions in each water tank to the corresponding compartment, then turn on the DC power supply to start the circulation pump, transport the solutions in each water tank to the corresponding compartment, and then turn on the DC power supply; the obtained alkali solution is circulated to step 2 for carbonization, and the acid solution is circulated to step 4 for pH adjustment.

[0018] Preferably, the pH of the treatment liquid in step 1 is 8-11.5 and does not contain solid particles.

[0019] Preferably, the desulfurized ash in step 1 is produced by a desulfurization process using sodium bicarbonate as a desulfurizing agent, the main component of which is sodium sulfate, and the salt concentration of the treatment liquid is 100-400 g / L.

[0020] Preferably, the carbonization process in step 2 is achieved using a falling film absorption tower.

[0021] Preferably, the reaction temperature in step 3 is 25-45°C, and the raw material ratio n(Na + ):n(HCO3 - ) is 1:0.8-1:1.2.

[0022] Preferably, the pH value of the solution after adjustment in step 4 is 3-5, and the concentration of the diluted solution is 50-150 g / L.

[0023] Preferably, in step 5, the concentration of the sodium sulfate solution in the cathode chamber water tank is 0.01-0.5 mol / L, the concentration of the sulfuric acid solution in the acid chamber water tank is 0.01-0.5 mol / L, and the concentration of the sodium hydroxide solution in the alkali chamber water tank is 0.01-0.5 mol / L.

[0024] Preferably, in step 5, the solution in the water tank circulates back and forth between the water tank and the membrane stack to perform electrodialysis until the conductivity in the salt chamber water tank drops below 7 mS / cm, and the power is turned off.

[0025] Preferably, step 5 is carried out under constant current conditions with a current density of 40-70 mA / cm 2 The range of temperature is 15-35℃.

[0026] The present invention also proposes a bipolar membrane electrodialysis device for converting desulfurized ash to prepare sodium bicarbonate, comprising a voltage-stabilized DC power supply, a bipolar membrane stack, an electrode chamber water tank, an alkali chamber water tank, a salt chamber water tank and an acid chamber water tank, wherein the output end of the voltage-stabilized DC power supply is connected to the input end of the bipolar membrane stack, and the output end of the bipolar membrane stack is respectively connected to the input ends of the electrode chamber water tank, the alkali chamber water tank, the salt chamber water tank and the acid chamber water tank, and a pump, a valve and a flow meter are provided between the output ends of the electrode chamber water tank, the alkali chamber water tank, the salt chamber water tank and the acid chamber water tank and the input end of the bipolar membrane stack.

[0027] 3. Beneficial effects

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] (1) In the present invention, a sodium bicarbonate solid product is obtained by a double decomposition reaction of a desulfurization ash treatment liquid and ammonium bicarbonate, and ammonia is recycled in the process by a bipolar membrane electrodialysis device, thereby solving the problem of treating the mother liquor after double decomposition, which not only greatly reduces the cost of treating hazardous waste desulfurization ash, but also saves the cost of purchasing a desulfurizer.

[0030] (2) In the present invention, the purity of the product of the preparation method can reach more than 95%, and the preparation method processes the mother liquor through bipolar membrane electrodialysis, which greatly reduces energy consumption; no additional reagents are added in the overall process, which greatly saves the cost of reagents; the overall process flow is short, and the required equipment occupies a small area. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of an electrodialysis device for converting desulfurized ash into sodium bicarbonate proposed by the present invention;

[0032] Figure 2 The present invention provides a schematic flow chart of a method for preparing sodium bicarbonate by electrodialysis conversion of desulfurization ash.

[0033] In the figure: 1- stabilized DC power supply; 2- electrodialysis membrane stack; 3- flow meter; 4- valve; 5- pump; 6- pole chamber water tank; 7- sodium bicarbonate water tank; 8- ammonium bicarbonate water tank; 9- ammonium sulfate water tank; 10- sodium sulfate water tank. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0035] Embodiment 1:

[0036] Reference Figure 1 A bipolar membrane electrodialysis device for converting desulfurized ash into sodium bicarbonate comprises a voltage-stabilized DC power supply 1, a bipolar membrane stack 2, an electrode chamber water tank 6, an alkali chamber water tank 7, a salt chamber water tank 8 and an acid chamber water tank 9. The output end of the voltage-stabilized DC power supply 1 is connected to the input end of the bipolar membrane stack 2. The output end of the bipolar membrane stack 2 is respectively connected to the input ends of the electrode chamber water tank 6, the alkali chamber water tank 7, the salt chamber water tank 8 and the acid chamber water tank 9. A pump 5, a valve 4 and a flowmeter 3 are arranged between the output ends of the electrode chamber water tank 6, the alkali chamber water tank 7, the salt chamber water tank 8 and the acid chamber water tank 9 and the input end of the bipolar membrane stack 2.

[0037] Reference Figure 2 , a method for preparing sodium bicarbonate by desulfurization ash double decomposition-bipolar membrane electrodialysis coupling process conversion, comprising the following steps:

[0038] Step 1: Dissolve the desulfurized ash in water and filter to obtain the treated liquid;

[0039] Step 2: reacting the treated liquid with carbon dioxide gas in a carbonization tower for carbonization;

[0040] Step 3: adding ammonium bicarbonate to the carbonized liquid in step 2, filtering after a period of reaction, washing and drying the filter cake to obtain a sodium bicarbonate solid product;

[0041] Step 4: adding sulfuric acid to the filtrate obtained in step 3, adjusting the pH of the solution, and diluting the solution to obtain a diluted solution;

[0042] Step 5: Add sodium sulfate solution to the polar chamber water tank 6 of the bipolar membrane electrodialysis equipment, add sodium hydroxide solution to the alkali chamber water tank 7, add the diluent obtained in step 4 to the salt chamber water tank 8, add sulfuric acid solution to the acid chamber water tank 9, start the circulation pump 5, transport the solution in each water tank to the corresponding compartment, then turn on the DC power supply to start the circulation pump, transport the solution in each water tank to the corresponding compartment, and then turn on the DC power supply 1. The obtained alkali solution is circulated to step 2 for carbonization, and the acid solution is circulated to step 4 for pH adjustment.

[0043] In this embodiment, a sodium bicarbonate solid product is obtained by a double decomposition reaction of a desulfurization ash treatment liquid and ammonium bicarbonate, and ammonia is recycled in the process by a bipolar membrane electrodialysis device, thereby solving the problem of handling the mother liquor after double decomposition. This not only greatly reduces the cost of handling hazardous waste desulfurization ash, but also saves the cost of purchasing desulfurizers.

[0044] In this embodiment, the purity of the product of this method can reach more than 95%. The method processes the mother liquor through bipolar membrane electrodialysis, which greatly reduces energy consumption; no additional reagents are added in the overall process, which greatly saves reagent costs; and the equipment required for the overall process occupies a small area.

[0045] Embodiment 2:

[0046] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0047] In this embodiment, a method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash comprises the following steps:

[0048] Step 1: Dissolve the desulfurized ash in water and filter to obtain a treated liquid with a salt concentration of 300 g / L and a pH of 8-11.5 without solid particles;

[0049] Step 2: reacting the treated liquid with carbon dioxide gas in a falling film absorption tower for carbonization;

[0050] Step 3: Add ammonium bicarbonate to the carbonized liquid in step 2, with a raw material ratio of n(Na + ):n(HCO3 - ) is 1:1, the reaction temperature is 30°C, the reaction is performed for 90 minutes and filtered, and the filter cake is washed and dried to obtain a sodium bicarbonate solid product;

[0051] Step 4: adding sulfuric acid to the filtrate obtained in step 3, adjusting the pH of the solution to 3, and diluting to obtain a diluted solution with a concentration of 70 g / L;

[0052] Step 5: Add 0.5 mol / L sodium sulfate solution to the polar chamber water tank 6 of the bipolar membrane electrodialysis equipment, add 0.05 mol / L sodium hydroxide solution to the alkali chamber water tank 7, add the dilution solution with a concentration of 70 g / L obtained in step 4 to the salt chamber water tank 8, add 0.05 mol / L sulfuric acid solution to the acid chamber water tank 9, start the circulation pump 5, transport the solutions in each water tank to the corresponding compartment, then turn on the DC power supply, and set the current density to 50 mA / cm 2 , start the circulation pump to transfer the solution in each water tank to the corresponding compartment, then turn on the DC power supply 1, and end the experiment when the conductivity of the solution in the salt chamber water tank 8 drops to 7mS / cm. The obtained alkali solution is circulated to step 2 for carbonization, and the acid solution is circulated to step 4 for pH adjustment.

[0053] Embodiment 3:

[0054] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0055] In this embodiment, the reaction temperature in step 3 is 35°C, and the raw material ratio is n(Na + ):n(HCO3 - ) is 1:1; the dilution concentration is 70g / L, the bipolar membrane device uses BP-2 bipolar membrane, AHT anion exchange membrane, CEM cation exchange membrane, and the effective membrane area is 0.105m 2 ; The circulation flow rate of each compartment is 140L / h, and the temperature is 25℃; the experiment is terminated when the conductivity of the solution in the salt chamber water tank drops below 7mS / cm.

[0056] Embodiment 4:

[0057] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0058] In this embodiment, the reaction temperature in step 3 is 40°C, and the raw material ratio is n(Na + ):n(HCO3 - ) is 1:1; the dilution concentration is 70g / L, the bipolar membrane device uses BP-2 bipolar membrane, AHT anion exchange membrane, CEM cation exchange membrane, and the effective membrane area is 0.105m 2 ; The circulation flow rate of each compartment is 140L / h, and the temperature is 25℃; the experiment is terminated when the conductivity of the solution in the salt chamber water tank drops below 7mS / cm.

[0059] Embodiment 5:

[0060] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0061] In this embodiment, the reaction temperature in step 3 is 45°C, and the raw material ratio is n(Na + ):n(HCO3 - ) is 1:1; the dilution concentration is 70g / L, the bipolar membrane device uses BP-2 bipolar membrane, AHT anion exchange membrane, CEM cation exchange membrane, and the effective membrane area is 0.105m 2 ; The circulation flow rate of each compartment is 140L / h, and the temperature is 25℃; the experiment is terminated when the conductivity of the solution in the salt chamber water tank drops below 7mS / cm.

[0062] Comparative Example 1:

[0063] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0064] In this embodiment, the reaction temperature in step 3 is 35°C, except that the raw material ratio n(Na + ):n(HCO3 - ) is 1:1.05. The concentration of the dilution added to the salt chamber water tank in step 5 is 70g / L, and the applied current density is 50mA / cm 2 .

[0065] Comparative Example 2:

[0066] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0067] In this embodiment, the reaction temperature in step 3 is 35°C, except that the raw material ratio n(Na + ):n(HCO3 - ) is 1:1.1. The concentration of the dilution added to the salt chamber water tank in step 5 is 70g / L, and the applied current density is 50mA / cm 2 .

[0068] Comparative Example 3:

[0069] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0070] In this embodiment, the reaction temperature in step 3 is 35°C, except that the raw material ratio n(Na + ):n(HCO3 - ) is 1:1.15. The dilution concentration added to the salt chamber water tank in step 5 is 70g / L, and the applied current density is 50mA / cm 2 .

[0071] Comparative Example 4:

[0072] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0073] In this embodiment, the reaction temperature in step 3 is 35°C, and the raw material ratio is n(Na + ):n(HCO3 - ) is 1:1.05. The dilution concentration added to the salt chamber water tank in step 5 is 70g / L, except that the applied current density is 40mA / cm 2 .

[0074] Comparative Example 5:

[0075] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0076] In this embodiment, the reaction temperature in step 3 is 35°C, and the raw material ratio is n(Na + ):n(HCO3 - ) is 1:1.05. The concentration of the dilution added to the salt chamber water tank in step 5 is 70g / L, except that the applied current density is 60mA / cm 2 .

[0077] Comparative Example 6:

[0078] It has the implementation content of the above-mentioned embodiment, wherein the specific implementation of the above-mentioned embodiment can refer to the above description, and the embodiment here will not be repeated in detail; and in the embodiment of the present application, it is different from the above-mentioned embodiment in that:

[0079] In this embodiment, the reaction temperature in step 3 is 35°C, and the raw material ratio is n(Na + ):n(HCO3 - ) is 1:1.05. The concentration of the dilution added to the salt chamber water tank in step 5 is 70g / L, except that the applied current density is 70mA / cm 2 .

[0080] According to the process control parameters of the above embodiment, the process indicators after the system runs continuously and stably are shown in Table 1:

[0081] Table 1 Process indicators and results

[0082]

[0083] In this embodiment, it can be seen from the table that under the optimal conditions, the primary utilization rate of sodium ions can reach more than 70%, and the purity of the prepared sodium bicarbonate is more than 94%. For the mother liquor produced by double decomposition, bipolar membrane electrodialysis can effectively recover the sodium ions and ammonia in the mother liquor for recycling. It can be seen that the method provided by the present invention can well realize the resource utilization of desulfurization ash, and the whole process is simple to operate, without adding external agents, and the process is clean, with significant economic and environmental effects.

[0084] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A bipolar membrane electrodialysis device for converting desulfurized ash into sodium bicarbonate, comprising a voltage-stabilized DC power supply (1), a bipolar membrane stack (2), an electrode chamber water tank (6), an alkali chamber water tank (7), a salt chamber water tank (8) and an acid chamber water tank (9), characterized in that: The output end of the voltage-stabilized DC power supply (1) is connected to the input end of the bipolar membrane stack (2), and the output end of the bipolar membrane stack (2) is respectively connected to the input ends of the polar chamber water tank (6), the alkali chamber water tank (7), the salt chamber water tank (8) and the acid chamber water tank (9), and a pump (5), a valve (4) and a flow meter (3) are provided between the output ends of the polar chamber water tank (6), the alkali chamber water tank (7), the salt chamber water tank (8) and the acid chamber water tank (9) and the input end of the bipolar membrane stack (2).

2. A method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash using the bipolar membrane electrodialysis device of claim 1, characterized in that: The following steps are involved: Step 1: Dissolve the desulfurized ash in water and filter to obtain the treated liquid; Step 2: reacting the treated liquid obtained in step 1 with carbon dioxide gas in a carbonization tower to carbonize the treated liquid to obtain a carbonized liquid; Step 3: adding ammonium bicarbonate to the carbonized liquid, filtering after a period of reaction to obtain a filtrate and a filter cake, and washing and drying the filter cake to obtain a sodium bicarbonate solid product; Step 4: adding sulfuric acid to the filtrate obtained in step 3, adjusting the pH of the solution, and diluting the solution to obtain a diluted solution; Step 5: adding sodium sulfate solution to the polar chamber water tank (6) of the bipolar membrane electrodialysis device, adding sodium hydroxide solution to the alkali chamber water tank (7), adding the diluent obtained in step 4 to the salt chamber water tank (8), adding sulfuric acid solution to the acid chamber water tank (9), turning on the circulation pump (5), transferring the solutions in each water tank to the corresponding compartment, then turning on the DC power supply to start the circulation pump, transferring the solutions in each water tank to the corresponding compartment, and then turning on the DC power supply (1); the obtained alkali solution is circulated to step 2 for carbonization, and the acid solution is circulated to step 4 for pH adjustment.

3. The method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash according to claim 2, characterized in that: The pH of the treatment liquid in step 1 is 8-11.5 and does not contain solid particles.

4. The method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash according to claim 2, characterized in that: The desulfurized ash in step 1 is produced by a desulfurization process using sodium bicarbonate as a desulfurizing agent, the main component of which is sodium sulfate, and the salt concentration of the treatment liquid is 100-400 g / L.

5. The method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash according to claim 2, characterized in that: The carbonization process in step 2 is achieved by using a falling film absorption tower.

6. The method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash according to claim 2, characterized in that: The reaction temperature in step 3 is 25-45°C, and the raw material ratio is n(Na + ):n(HCO3 - ) is 1:0.8-1:1.

2.

7. The method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash according to claim 2, characterized in that: The pH value of the solution after adjustment in step 4 is 3-5, and the concentration of the diluted solution is 50-150 g / L.

8. The method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash according to claim 2, characterized in that: In step 5, the concentration of the sodium sulfate solution in the cathode chamber water tank (6) is 0.01-0.5 mol / L, the concentration of the sulfuric acid solution in the acid chamber water tank (9) is 0.01-0.5 mol / L, and the concentration of the sodium hydroxide solution in the alkali chamber water tank (7) is 0.01-0.5 mol / L.

9. The method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash according to claim 2, characterized in that: In step 5, the solution in the water tank circulates back and forth between the water tank and the membrane stack to perform electrodialysis until the conductivity in the salt chamber water tank (8) drops below 7 mS / cm, and the power is turned off.

10. The method for preparing sodium bicarbonate by electrodialysis conversion of desulfurized ash according to claim 2, characterized in that: The step 5 is carried out under constant current conditions with a current density of 40-70 mA / cm 2 The range of temperature is 15-35℃.

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