A method for co-production of ammonium sulfate by regenerating sodium-based desulfurizer with desulfurized ash

Abstract

This invention discloses a method for regenerating sodium-based desulfurizing agents and co-producing ammonium sulfate using desulfurization ash, belonging to the field of solid waste resource utilization. The method involves heating sodium-based desulfurization ash into a pulp, then adding calcium-based desulfurization ash and a bisphenol complexing agent to undergo a multiphase causticization reaction. The resulting strongly alkaline pulp is directly aerated and oxidized to eliminate impurities, followed by solid-liquid separation. The liquid phase undergoes segmented carbonization to precipitate high-purity sodium bicarbonate, achieving the regeneration and recycling of the complexing agent. The solid tailings are then co-produced as ammonium sulfate and calcium carbonate through ammonium bicarbonate carbonation. This invention introduces a bisphenol complexing agent into a mixed system of sodium-based and calcium-based desulfurization ash, cleverly utilizing its weak acidity and complexing effect to effectively promote the in-situ causticization reaction of sodium sulfate and calcium hydroxide in the desulfurization ash. This method overcomes the problem that sodium sulfate is difficult to directly convert with lime under conventional conditions, achieving efficient conversion of sodium salts without the need for purchased alkali agents or calcium sources, significantly reducing reagent consumption and treatment costs.

Description

Technical Field

[0001] This invention belongs to the field of industrial solid waste resource utilization technology, specifically involving a resource utilization method for the co-processing of sodium-based desulfurization ash and calcium-based desulfurization ash, in-situ alkali production to regenerate sodium-based desulfurizing agent and produce ammonium sulfate and calcium carbonate. It is particularly suitable for the harmless treatment and high-value utilization of desulfurization waste residue in the steel, coking, and building materials industries. Background Technology

[0002] The mainstream flue gas desulfurization technologies in industries such as steel, coking, and building materials mainly include sodium bicarbonate desulfurization and dry calcium oxide desulfurization. These two processes generate large quantities of sodium-based and calcium-based desulfurization ash, respectively, during operation. This type of desulfurization ash waste has a complex composition, typically containing 30%–40% sulfites, sulfates, and unreacted alkali agents. It suffers from problems such as unstable raw material characteristics, slow hydration reactions, easy volume expansion, and the release of sulfur dioxide at high temperatures, causing secondary pollution. Currently, the vast majority of desulfurization waste is difficult to utilize in large quantities and is still mainly stored and landfilled, significantly consuming land resources and polluting the environment. The industry urgently needs to address its harmless treatment and high-value utilization.

[0003] Currently, most publicly available technologies for the resource utilization of desulfurization ash are limited to the disposal of single solid wastes and have obvious shortcomings. For example, for calcium-based desulfurization ash, patent CN202010755523.2 proposes to use an electromagnetic induction external heating rotary kiln to convert calcium sulfite into calcium sulfate. This technology only focuses on the single oxidation of calcium-based desulfurization ash and fails to coordinate with the treatment of sodium-based desulfurization ash, thus failing to achieve high-value co-production of sodium, sulfur, and calcium resources. For sodium-based desulfurization ash, existing patents such as CN202610052879.7 and CN202310633203.3 only prepare desulfurizing agents or sodium sulfate through steps such as dissolution, oxidation, and carbonization. These methods generally suffer from high reagent consumption and incomplete impurity removal. Some processes (such as CN202410275759.4 and CN202410275773.4) use acid dissolution, defluorination, and evaporation crystallization to prepare sodium sulfate, which is not only lengthy and energy-intensive but also produces products with extremely low added value. Other technologies aimed at improving impurity removal (such as CN202411629701.1 and CN202311319513.4), while introducing electrocoagulation and bipolar membrane methods, result in large equipment investments and high operating costs, making large-scale promotion difficult. Regarding resource utilization, current disposal methods also suffer from significant low-value disposal issues. For example, patents CN202311597985.6 and CN202510601252.8 use desulfurization ash for steel slag modification or building materials. These methods not only have a low desulfurization ash content, but also directly bury the valuable elements in the desulfurization ash, making it impossible to achieve high-value recovery of sodium and sulfur resources, resulting in extremely poor economic benefits.

[0004] To address the issues of single-processing and low-value disposal, the industry has hoped to achieve in-situ synergistic reactions between sodium-based and calcium-based desulfurization ash, aiming to directly convert sodium salts using the alkaline calcium source inherent in the calcium-based desulfurization ash. However, none of the currently available technologies have truly realized this vision. This is because sodium-based desulfurization ash contains a large amount of sodium sulfate (Na2SO4), which, due to chemical thermodynamic equilibrium, is extremely difficult to causticize with lime under normal conditions. This results in a very incomplete synergistic reaction, requiring companies to purchase large quantities of calcium sources and alkali agents externally to meet standards. This not only incurs high reagent costs but also results in low solid waste disposal capacity, completely deviating from the original intention of "treating waste with waste."

[0005] Furthermore, the interference from impurities such as calcium sulfite in the complex dual solid waste system is another core challenge limiting the high-value co-production of desulfurization ash. If the traditional model of first separating solid and liquid and then treating them separately is adopted, not only is the mother liquor circulation complex, but the sulfite conversion efficiency is also low. In summary, how to overcome the thermodynamic barrier of sodium sulfate causticization in desulfurization ash to achieve extremely high sodium salt regeneration conversion, how to cleverly overcome the interference of sulfite impurities, and how to abandon the purchase of external acid and alkali reagents and construct an integrated co-production process with closed-loop circulation of mother liquor and wastewater have become urgent technical bottlenecks in the field of desulfurization ash resource utilization. Summary of the Invention

[0006] To address the aforementioned issues, this invention involves heating sodium-based desulfurization ash into a pulp, then adding calcium-based desulfurization ash and a bisphenol complexing agent to conduct a multiphase causticization reaction. The resulting strongly alkaline pulp is directly aerated and oxidized to eliminate impurities, followed by solid-liquid separation. The liquid phase undergoes segmented carbonization to precipitate high-purity sodium bicarbonate, achieving the regeneration and recycling of the complexing agent. The solid tailings are then carbonized with ammonium bicarbonate to co-produce ammonium sulfate and calcium carbonate.

[0007] Specifically, the present invention provides a method for regenerating sodium-based desulfurizing agent and co-producing ammonium sulfate using desulfurization ash, which includes the following steps: S1, heating and dissolving: mixing sodium-based desulfurization ash with water to form a slurry and heating it; S2. Multiphase Alkali Production and In-situ Causticization: Calcium-based desulfurization ash and bisphenol complexing agent are added to the slurry of S1, and a multiphase reaction is carried out under heating conditions. The carbonates and sulfates in the sodium-based desulfurization ash react with the calcium-containing compounds in the calcium-based desulfurization ash. The bisphenol complexing agent participates in the reaction and promotes the causticization of sodium sulfate in the desulfurization ash, generating a strongly alkaline multiphase mixture containing sodium hydroxide, calcium carbonate, and calcium sulfate. The bisphenol complexing agent is converted into easily soluble sodium bisphenolate and dissolved in the liquid phase. The amount of calcium-based desulfurization ash added is determined based on the amount of sodium-based desulfurization ash added and the amount of sodium ions in the sodium carbonate (NaHCO3+Na2CO3) to determine the amount of alkaline calcium ions required for the chemical reaction: 2NaHCO3+Ca(OH)2→2NaOH+CaCO3+CO2↑+H2O, Na2CO3+Ca(OH)2→2NaOH+CaCO3. Thus, the amount of calcium-based desulfurization ash added can be determined. Similarly, the amount of alkaline calcium ions required for the chemical reaction can be determined: Na₂SO₄ + Ca(OH)₂ + 2H₂O → 2NaOH + CaSO₄•2H₂O. Finally, the amount of calcium-based desulfurization ash to be added can be determined from this. The sum of the two is the corresponding amount of calcium-based desulfurization ash to be added.

[0008] The specific operation method is as follows: based on the total mass of sulfate and sodium sulfite ions in sodium-based desulfurization ash and the total mass of calcium ions of calcium oxide and calcium hydroxide in calcium-based desulfurization ash, add sodium-based desulfurization ash to the sodium-based desulfurization ash solution at a mass ratio of Na:Ca=23:20~22, and add bisphenol A at the same time. The amount added is 2.85 times the theoretical amount of NaOH generated in the reaction system, added all at once.

[0009] S3, Strongly Alkaline Slurry Aeration Oxidation: Without solid-liquid separation, oxygen-containing gas is directly introduced into the strongly alkaline multiphase mixture after the S2 reaction for aeration oxidation, oxidizing calcium sulfite in the system to calcium sulfate; wherein, the air supply is calculated by calculating the oxidation oxygen demand based on the content of sodium sulfite and calcium sulfite in the desulfurization ash and then converting it into air volume.

[0010] S4. Segmented carbonization preparation of sodium bicarbonate and regeneration of complexing agent: The mixture after oxidation in S3 is subjected to a first solid-liquid separation to obtain a first solid product and a first liquid mother liquor containing sodium hydroxide and sodium bisphenol salt; a carbon dioxide-containing gas is introduced into the first liquid mother liquor to carry out a carbonization reaction. By adjusting the pH value of the reaction system, the sodium bisphenol salt is converted into an insoluble bisphenol complexing agent and precipitated, and sodium bicarbonate is crystallized and precipitated; the precipitated bisphenol complexing agent and sodium bicarbonate are separated and collected separately to obtain sodium bicarbonate product, and the recovered bisphenol complexing agent is recycled back to step S2; S5. Preparation of ammonium sulfate and calcium carbonate from tailings: The first solid product is slurried with water, and ammonium bicarbonate is added as a carbonizing agent to react. After the reaction, a second solid-liquid separation is performed to obtain a solid calcium carbonate product and an ammonium sulfate solution. The ammonium sulfate solution is concentrated, evaporated, and crystallized to obtain the ammonium sulfate product. Preferably, in step S1, the solution is heated to a temperature of 70-90℃; and / or, in step S2, the temperature of the multiphase reaction is 70-90℃, the reaction time is 60-90 min, and the pH value at the reaction endpoint is controlled at 12.0-13.5.

[0011] Preferably, in step S2, the bisphenol complexing agent is a weakly acidic organic compound having a bisphenol structure; more preferably, the bisphenol complexing agent is selected from one or more of bisphenol A, bisphenol S, and bisphenol F.

[0012] Preferably, in step S2, the amount of calcium-based desulfurization ash added is calculated based on the amount of sodium-based desulfurization ash added; specifically, the calculation is based on: calculating the first molar amount of alkaline calcium ions required based on the total molar amount of sodium ions in sodium carbonate in sodium-based desulfurization ash; and / or, calculating the second molar amount of alkaline calcium ions required based on the total molar amount of sodium ions in sulfate and sulfite in sodium-based desulfurization ash; and using the sum of the first molar amount and the second molar amount as the basis for the total mass of calcium ions introduced into calcium oxide and calcium hydroxide in calcium-based desulfurization ash.

[0013] Preferably, in step S3, compressed air is supplied using a Roots blower as the oxygen-containing gas; and / or, the gas supply pressure for the aeration oxidation is 85-110 kPa; and / or, the reaction time for the aeration oxidation is 20-40 min; and / or, the gas supply volume of the oxygen-containing gas is determined as 2-4 times the theoretical oxygen demand calculated based on the sulfite content in the desulfurization ash.

[0014] Preferably, in step S4, the temperature of the first liquid mother liquor carbonization reaction is 30-50℃; and / or, the time of the first liquid mother liquor carbonization reaction is 40-60 min; and / or, the final pH value of the first liquid mother liquor carbonization reaction is controlled at 8.0~9.5.

[0015] Preferably, in step S4, the sodium bicarbonate and the bisphenol complexing agent are separated by utilizing the difference in solubility of the two in different solvents or at different temperatures; and / or, the sodium bicarbonate obtained after separation is fed into a vacuum dryer and vacuum dried at a temperature of 50~60°C for 40~60 minutes to obtain sodium bicarbonate product; and / or, the sodium bicarbonate obtained after separation is fed into a flash dryer and flash evaporated at a temperature of 110~120°C for 40~60 minutes to obtain sodium bicarbonate product; and / or, the carbonization mother liquor generated after separating sodium bicarbonate is recycled in a closed loop to the multiphase reactor process.

[0016] Preferably, in step S5, the reaction temperature of the first solid product with ammonium bicarbonate is 60-80℃, and the reaction condition is atmospheric pressure; and / or, the reaction time of the first solid product with ammonium bicarbonate is 35-55 min; and / or, the final pH value of the reaction between the first solid product and ammonium bicarbonate is controlled at 6.0-8.0.

[0017] Preferably, the evaporation condensate generated in the concentration and evaporation process of step S5 is recycled back to the heating and dissolving process of step S1 as pulping water; and / or, the crystallization mother liquor generated by centrifugation and dehydration in the crystallization and purification process of step S5 is recycled back to the multiphase reactor process of step S2.

[0018] Preferably, the carbon dioxide-containing gas used in step S4 has a carbon dioxide concentration of ≥40%; and / or, the carbon dioxide-containing gas originates from purified flue gas enriched and purified by kilns or boilers at the industrial site, or is purchased liquid carbon dioxide.

[0019] Compared with the prior art, the present invention has the following beneficial effects: First, this invention introduces a bisphenol complexing agent into a mixed system of sodium-based and calcium-based desulfurization ash. By cleverly utilizing its weak acidity and complexing effect, it effectively promotes the in-situ causticization reaction between sodium sulfate and calcium hydroxide in the desulfurization ash. This method overcomes the problem of sodium sulfate being difficult to directly convert with lime under conventional conditions, achieving efficient conversion of sodium salts without the need for externally purchased alkali agents or calcium sources, significantly reducing reagent consumption and processing costs.

[0020] Secondly, addressing the abundant and highly unstable calcium sulfite impurities in desulfurization waste residue, this invention breaks away from the conventional approach of "solid-liquid separation followed by separate oxidation," innovatively employing a process sequence of "causticization for alkali production—direct aeration of the raw slurry." Utilizing the highly concentrated sodium hydroxide produced in the multiphase alkali production step to create a strongly alkaline liquid phase environment (pH 12-13), the mass transfer efficiency and reaction kinetics of calcium sulfite oxidation in the system are greatly accelerated, completely converting it into stable calcium sulfate. This not only eliminates the interference of impurities on the purity of subsequent liquid-phase carbonization but also removes obstacles to the synthesis of high-quality ammonium sulfate from the tailings.

[0021] Furthermore, this invention ingeniously integrates the complete processes of desulfurizer regeneration, impurity removal, and tailings fertilizer production, constructing a highly integrated closed-loop recycling system. Specifically, the segmented carbonization process enables the bisphenol complexing agent to achieve efficient regeneration and recycling through an automatic "dissolution-precipitation" mechanism; all wastewater generated from ammonium sulfate concentration and evaporation is recycled back to the front-end pulping stage; and the carbonization mother liquor generated during separation is entirely returned to the multiphase reactor. The entire process is short, with no wastewater discharge, eliminating the complex purification units such as acid dissolution, bipolar membranes, and electrodialysis found in traditional processes. This significantly reduces equipment investment by over 60%, truly achieving high economic efficiency in both green, low-carbon, and engineering applications.

[0022] Finally, thanks to the aforementioned synergistic conversion and in-situ impurity removal mechanisms, this invention completely transforms two types of difficult-to-utilize polluting desulfurization solid wastes into commodities with high economic value. The final sodium bicarbonate obtained has a purity of ≥98.0% and can be directly reused as a high-quality desulfurizing agent; the co-produced ammonium sulfate has a purity of ≥99.0%, meeting fertilizer-grade or industrial-grade standards; and the tailings are converted into ordinary calcium carbonate powder. The overall process achieves the ultimate extraction of valuable components from the solid waste, with sodium recovery rates ≥98%, sulfur recovery rates ≥99%, and calcium recovery rates ≥95%. The comprehensive utilization rate of the two wastes reaches over 95%, achieving unexpected synergistic resource recovery effects. Attached Figure Description

[0023] Figure 1 The process flow diagram provided by this invention is for the co-production of ammonium sulfate using sodium-based desulfurizing agent regenerated from desulfurization ash. Detailed Implementation

[0024] Example 1 1. Raw material composition: Sodium-based desulfurization ash, with the following mass fractions: NaHCO3 17.3%, Na2CO3 22.7%, Na2SO3 18.6%, Na2SO4 38.9%, processing capacity 1000 kg / h. Calcium-based desulfurization ash, with the following mass fractions: CaO 12.4%, Ca(OH)2 27.2%, CaSO3 17.1%, CaSO4 40.6%, processing capacity 1400 kg / h. Complexing agent: Bisphenol A, industrial grade, dosage 1150 kg (initial addition, subsequent recycling and regeneration, and very small supplementary additions). Ammonium bicarbonate: fertilizer grade, dosage 1700 kg / h. Carbon dioxide: from the lime kiln on-site, enriched and purified, CO2 concentration 55%, dosage 375 Nm³ / h.

[0025] 2. Process Steps: S1. Heating and Dissolving: Add 1000 kg of sodium-based desulfurization ash and 5000 kg of water to a reaction vessel to make a slurry. Heat the solution to reach and maintain a temperature of 80°C. S2. Multiphase Alkali Production and In-situ Causticization: Mix the above slurry with 1400 kg of calcium-based desulfurization ash and 1150 kg of bisphenol A in a multiphase reactor. Perform a multiphase synergistic reaction at atmospheric pressure and 80°C for 75 min. Control the pH value at the final reaction point to 13 to obtain a strongly alkaline multiphase mixture. S3. Strongly Alkaline Slurry Aeration and Oxidation: Without solid-liquid separation, directly introduce the above reaction product (slurry) into the aeration tank. Use a Roots blower to supply compressed air at a flow rate of 880 Nm³ and a pressure of 100 kPa for aeration and oxidation for 30 min. S4. Segmented Carbonation Preparation of Sodium Bicarbonate and Regeneration of Complexing Agent: The liquid mother liquor obtained from pressure filtration 1 is introduced into carbonation reactor 1 and 55% CO2 gas is introduced. The reaction temperature is 35℃, and segmented carbonization separation is carried out under normal pressure using a pH gradient: In the first stage, CO2 is introduced to lower the pH value of the system to 9.8. The free precipitated bisphenol A solid is recovered by filtration and directly returned to the S2 process for recycling. In the second stage, CO2 is continued to be introduced into the remaining filtrate, and the cumulative reaction time reaches 50 minutes. The final pH value of the reaction is controlled to be 8.5, and a large amount of NaHCO3 precipitate is precipitated. After separation by pressure filtration 2, the separated filter cake enters a vacuum dryer. At a temperature of 60℃, vacuum drying for 50 minutes yields 1200 kg of high-purity NaHCO3 product; filtrate 2 is returned to the S2 multiphase reaction process in a closed loop. S5. Preparation of Ammonium Sulfate and Calcium Carbonate from Tailings: The solid filter cake obtained from pressure filtration 1 is slurried with water and then fed into carbonation reactor 2. 1700 kg of ammonium bicarbonate (NH4HCO3) is added as a carbonizing agent. The reaction is carried out at atmospheric pressure and 65℃ for 45 min, and the final pH value is controlled to be 7. The reaction products are separated by pressure filtration 3. The liquid phase is purified, concentrated, evaporated, crystallized, and centrifuged to obtain 1430 kg of (NH4)2SO4 product. The evaporated condensate and crystallization mother liquor generated in the process are recycled to processes S1 and S2 in a closed loop, respectively. The solid filter cake is dried to obtain 1400 kg of CaCO3 powder product.

[0026] 3. Purity Testing and Recovery Rate Determination: Tested according to national standards (GB / T 1606-2008 and GB / T 535-2020), the purity of the NaHCO3 product obtained in this example is 98.3%, and the purity of the (NH4)2SO4 product is 99.1%. Based on the overall material balance of the system, the sodium recovery rate in this example is 98.6%, the sulfur recovery rate is 99.2%, and the calcium recovery rate is 95.8%, with the comprehensive utilization rate of both wastes consistently above 95%.

[0027] Example 2 1. Raw material composition: Sodium-based desulfurization ash, with the following mass fractions: NaHCO3 16.7%, Na2CO3 21.8%, Na2SO3 19.2%, Na2SO4 39.1%, processing capacity 1500 kg / h. Calcium-based desulfurization ash, with the following mass fractions: CaO 12.6%, Ca(OH)2 26.9%, CaSO3 16.8%, CaSO4 40.9%, processing capacity 2050 kg / h. Complexing agent: Bisphenol A, industrial grade, dosage 1720 kg. Ammonium bicarbonate: fertilizer grade, dosage 2500 kg / h. Carbon dioxide: from on-site boiler flue gas enriched and purified, CO2 concentration 45%, dosage 1250 Nm³ / h.

[0028] 2. Process Steps: S1. Heating and Dissolving: Add 1500 kg of sodium-based desulfurization ash and 7500 kg of water to a reaction vessel to make a slurry. Heat the solution to reach and maintain a temperature of 80°C. S2. Multiphase Alkali Production and In-situ Causticization: Mix the above slurry with 2050 kg of calcium-based desulfurization ash and 1720 kg of bisphenol A in a multiphase reactor. Perform a multiphase synergistic reaction at atmospheric pressure and 80°C for 75 min. Control the pH value at the final reaction point to 13 to obtain a strongly alkaline multiphase mixture. S3. Strongly Alkaline Slurry Aeration and Oxidation: Without solid-liquid separation, directly introduce the above reaction product (slurry) into the aeration tank. Use a Roots blower to supply compressed air at a flow rate of 1400 Nm³ and a pressure of 100 kPa for aeration and oxidation for 30 min. S4. Segmented Carbonation Preparation of Sodium Bicarbonate and Regeneration of Complexing Agent: The liquid mother liquor obtained from pressure filtration 1 is introduced into carbonation reactor 1 and 45% CO2 gas is introduced. The reaction temperature is 35℃, and segmented carbonization separation is carried out under atmospheric pressure using a pH gradient: In the first stage, CO2 is introduced to lower the pH value of the system to 9.8. The free precipitated bisphenol A solid is recovered by filtration and directly returned to the S2 process for recycling. In the second stage, CO2 is continued to be introduced into the remaining filtrate, and the cumulative reaction time reaches 50 minutes. The final pH value of the reaction is controlled to be 8.5, and a large amount of NaHCO3 precipitate is precipitated. After separation by pressure filtration 2, the separated filter cake enters a flash dryer and is flash-dried at 120℃ for 50 minutes to obtain 1795 kg of high-purity NaHCO3 product. Filtrate 2 is returned to the S2 multiphase reaction process in a closed loop. S5. Preparation of Ammonium Sulfate and Calcium Carbonate from Tailings: The solid filter cake obtained from pressure filtration 1 is slurried with water and then fed into carbonation reactor 2. 2500 kg of ammonium bicarbonate (NH4HCO3) is added as a carbonizing agent. The reaction is carried out at atmospheric pressure and 65℃ for 45 min, and the final pH value is controlled to be 7. The reaction products are separated by pressure filtration 3. The liquid phase is purified, concentrated, evaporated, crystallized, and centrifuged to obtain 2130 kg of (NH4)2SO4 product. The evaporated condensate and crystallization mother liquor generated in the process are recycled to processes S1 and S2 in a closed loop, respectively. The solid filter cake is dried to obtain 2150 kg of CaCO3 powder product.

[0029] 3. Purity detection and recovery rate determination: According to the sampling and testing according to the above-mentioned relevant standards, the purity of the NaHCO3 product obtained in this embodiment is 98.4%, and the purity of the (NH4)2SO4 product is 99.2%. After material balance calculation of the whole process, the sodium element recovery rate is 98.5%, the sulfur element recovery rate is 99.3%, the calcium element recovery rate is 96.1%, and the comprehensive utilization rate of solid waste is greater than 95%.

[0030] Example 3 1. Raw material composition: Sodium-based desulfurization ash, with the following mass fractions: NaHCO3 15.4%, Na2CO3 21.6%, Na2SO3 20.3%, Na2SO4 39.7%, processing capacity 2000 kg / h. Calcium-based desulfurization ash, with the following mass fractions: CaO 12.2%, Ca(OH)2 28.1%, CaSO3 16.4%, CaSO4 40.4%, processing capacity 2750 kg / h. Complexing agent: Bisphenol A, industrial grade, dosage 2280 kg. Ammonium bicarbonate: fertilizer grade, dosage 3380 kg / h. Carbon dioxide: purchased liquid CO2 vaporized, CO2 concentration 95%, dosage 775 Nm³ / h.

[0031] 2. Process Steps: S1. Heating and Dissolving: Add 2000 kg of sodium-based desulfurization ash and 10000 kg of water to a reaction vessel to make a slurry. Heat the solution to reach and maintain a temperature of 80°C. S2. Multiphase Alkali Production and In-situ Causticization: Mix the above slurry with 2750 kg of calcium-based desulfurization ash and 2280 kg of bisphenol A in a multiphase reactor. Perform a multiphase synergistic reaction at atmospheric pressure and 80°C for 75 min. Control the pH value at the final reaction point to 13 to obtain a strongly alkaline multiphase mixture. S3. Strongly Alkaline Slurry Aeration and Oxidation: Without solid-liquid separation, directly introduce the above reaction product (slurry) into the aeration tank. Use a Roots blower to supply compressed air at a flow rate of 1800 Nm³ and a pressure of 100 kPa for aeration and oxidation for 30 min. S4. Segmented Carbonation Preparation of Sodium Bicarbonate and Regeneration of Complexing Agent: The liquid mother liquor obtained from pressure filtration 1 is introduced into carbonation reactor 1 and 95% CO2 gas is introduced. The reaction temperature is 35℃, and segmented carbonization separation is carried out under atmospheric pressure using a pH gradient: In the first stage, CO2 is introduced to lower the pH value of the system to 9.8. The free precipitated bisphenol A solid is recovered by filtration and directly returned to the S2 process for recycling. In the second stage, CO2 is continued to be introduced into the remaining filtrate, and the cumulative reaction time reaches 50 minutes. The final pH value of the reaction is controlled to be 8.5, and a large amount of NaHCO3 precipitate is precipitated. After separation by pressure filtration 2, the separated filter cake enters a flash dryer and is flash-dried at 120℃ for 50 minutes to obtain 1795 kg of high-purity NaHCO3 product. Filtrate 2 is returned to the S2 multiphase reaction process in a closed loop. S5. Preparation of Ammonium Sulfate and Calcium Carbonate from Tailings: The solid filter cake obtained from pressure filtration 1 is slurried with water and then fed into carbonation reactor 2. 3380 kg of ammonium bicarbonate (NH4HCO3) is added as a carbonizing agent. The reaction is carried out at atmospheric pressure and 65℃ for 45 min, and the final pH value is controlled to be 7. The reaction products are separated by pressure filtration 3. The liquid phase is purified, concentrated, evaporated, crystallized, and centrifuged to obtain 2850 kg of (NH4)2SO4 product. The evaporated condensate and crystallization mother liquor generated in the process are recycled to processes S1 and S2 in a closed loop, respectively. The solid filter cake is dried to obtain 2850 kg of CaCO3 powder product.

[0032] 3. Purity detection and recovery rate determination: According to the sampling and testing according to the relevant standards mentioned above, the purity of the NaHCO3 product obtained in this embodiment is 98.5%, and the purity of the (NH4)2SO4 product is 99.4%. After material balance calculation of the whole process, the sodium element recovery rate is 98.8%, the sulfur element recovery rate is 99.5%, the calcium element recovery rate is 96.4%, and the comprehensive utilization rate of solid waste in the system reaches over 95%.

Claims

1. A method for co-producing ammonium sulfate using desulfurization ash to regenerate sodium-based desulfurizing agent, characterized in that, Includes the following steps: S1. Heating and dissolving: Sodium-based desulfurization ash is mixed with water to form a slurry, and then heated; S2, Multiphase Alkali Production and In-situ Causticization: Calcium-based desulfurization ash and bisphenol complexing agent are added to the slurry of S1, and a multiphase reaction is carried out under heating conditions; the carbonates and sulfates in the sodium-based desulfurization ash react with the calcium-containing compounds in the calcium-based desulfurization ash, wherein the bisphenol complexing agent participates in the reaction and promotes the causticization of sodium sulfate in the desulfurization ash, generating a strongly alkaline multiphase mixture containing sodium hydroxide, calcium carbonate, and calcium sulfate, and the bisphenol complexing agent is converted into easily soluble sodium bisphenolate dissolved in the liquid phase; S3, Strong Alkaline Slurry Aeration Oxidation: Without solid-liquid separation, oxygen-containing gas is directly introduced into the strong alkaline multiphase mixture after the S2 reaction for aeration oxidation, oxidizing calcium sulfite in the system to calcium sulfate. S4. Segmented carbonization preparation of sodium bicarbonate and regeneration of complexing agent: The mixture after oxidation in S3 is subjected to a first solid-liquid separation to obtain a first solid product and a first liquid mother liquor containing sodium hydroxide and sodium bisphenol salt; a carbon dioxide-containing gas is introduced into the first liquid mother liquor to carry out a carbonization reaction. By adjusting the pH value of the reaction system, the sodium bisphenol salt is converted into an insoluble bisphenol complexing agent and precipitated, and sodium bicarbonate is crystallized and precipitated; the precipitated bisphenol complexing agent and sodium bicarbonate are separated and collected separately to obtain sodium bicarbonate product, and the recovered bisphenol complexing agent is recycled back to step S2; S5. Preparation of ammonium sulfate and calcium carbonate from tailings: The first solid product is slurried with water, and ammonium bicarbonate is added as a carbonizing agent to react. After the reaction is completed, a second solid-liquid separation is performed to obtain a calcium carbonate solid product and an ammonium sulfate solution. The ammonium sulfate solution is concentrated, evaporated, crystallized and purified to obtain the ammonium sulfate product.

2. The method according to claim 1, characterized in that, In step S1, the solution is heated to a temperature of 70-90℃; and / or, in step S2, the temperature of the multiphase reaction is 70-90℃, the reaction time is 60-90 min, and the pH value at the reaction endpoint is controlled at 12.0-13.

5.

3. The method according to claim 1, characterized in that, In step S2, the bisphenol complexing agent is a weakly acidic organic compound having a bisphenol structure; preferably, the bisphenol complexing agent is selected from one or more of bisphenol A, bisphenol S and bisphenol F.

4. The method according to claim 1, characterized in that, In step S2, the amount of calcium-based desulfurization ash added is calculated based on the amount of sodium-based desulfurization ash added. Specifically, the calculation is based on: calculating the first molar amount of alkaline calcium ions required based on the total molar amount of sodium ions in sodium carbonate in sodium-based desulfurization ash; and / or calculating the second molar amount of alkaline calcium ions required based on the total molar amount of sodium ions in sulfate and sulfite in sodium-based desulfurization ash; and using the sum of the first molar amount and the second molar amount as the basis for the total mass of calcium ions introduced into calcium oxide and calcium hydroxide in calcium-based desulfurization ash.

5. The method according to claim 1, characterized in that, In step S3, compressed air is supplied using a Roots blower as the oxygen-containing gas; and / or, the gas supply pressure for the aeration oxidation is 85-110 kPa; and / or, the reaction time for the aeration oxidation is 20-40 min; and / or, the gas supply volume of the oxygen-containing gas is determined as 2-4 times the theoretical oxygen demand calculated based on the sulfite content in the desulfurization ash.

6. The method according to claim 1, characterized in that, In step S4, the temperature of the first liquid mother liquor carbonization reaction is 30-50℃; and / or, the time of the first liquid mother liquor carbonization reaction is 40-60 min; and / or, the final pH value of the first liquid mother liquor carbonization reaction is controlled at 8.0~9.

5.

7. The method according to claim 1, characterized in that, In step S4, the sodium bicarbonate and the bisphenol complexing agent are separated by utilizing their differences in solubility in different solvents or at different temperatures; and / or, the sodium bicarbonate obtained after separation is fed into a vacuum dryer and vacuum dried at 50-60°C for 40-60 minutes to obtain sodium bicarbonate product; and / or, the sodium bicarbonate obtained after separation is fed into a flash dryer and flash evaporated at 110-120°C for 40-60 minutes to obtain sodium bicarbonate product; and / or, the carbonation mother liquor generated after separating sodium bicarbonate is recycled in a closed loop to the multiphase reactor process.

8. The method according to claim 1, characterized in that, In step S5, the reaction temperature of the first solid product with ammonium bicarbonate is 60-80℃, and the reaction condition is atmospheric pressure; and / or, the reaction time of the first solid product with ammonium bicarbonate is 35-55 min; and / or, the final pH value of the reaction between the first solid product and ammonium bicarbonate is controlled at 6.0~8.

0.

9. The method according to claim 1, characterized in that, The evaporation condensate generated in the concentration and evaporation process of step S5 is recycled back to the heating and dissolving process of step S1 as pulping water; and / or, the crystallization mother liquor generated by centrifugation and dehydration in the crystallization and purification process of step S5 is recycled back to the multiphase reactor process of step S2.

10. The method according to claim 1, characterized in that, The carbon dioxide-containing gas used in step S4 has a carbon dioxide concentration of ≥40%; and / or the carbon dioxide-containing gas originates from purified flue gas enriched and purified by kilns or boilers at industrial sites, or is purchased liquid carbon dioxide.

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