A method for mineralizing CO2 from flue gas using coking ammonia water and desulfurized gypsum
By mixing and reacting coking ammonia with desulfurized gypsum and purifying it through ethanol crystallization, the problem of impurities in coking ammonia was solved, enabling the preparation of high-purity calcium carbonate and ammonium sulfate, supporting industrial applications and the circular economy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GANSU RUNYUAN ENVIRONMENTAL RESOURCES TECH CO LTD
- Filing Date
- 2026-03-31
- Publication Date
- 2026-06-19
AI Technical Summary
The existing technology for desulfurization gypsum mineralization flue gas CO2 process using commercial concentrated ammonia water as raw material has poor economic efficiency, and the composition of impurities in coking ammonia water is prone to fluctuation, resulting in difficulties in controlling the reaction process and insufficient product purity.
High-purity calcium carbonate and ammonium sulfate products were prepared by mixing coking ammonia water with desulfurized gypsum, controlling the pH value at the end of the mineralization reaction, removing impurities by evaporation, and using ethanol for synergistic crystallization purification.
It achieves efficient substitution of coking ammonia water, reduces raw material costs, and obtains desulfurizing agents and high-purity ammonium sulfate products that can replace limestone, supporting industrial applications and circular economy models.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of industrial flue gas treatment and solid waste resource utilization technology, specifically involving a method for mineralizing CO2 from flue gas using coking ammonia water and desulfurized gypsum. Background Technology
[0002] CO2 capture, utilization, and storage has become a research hotspot. Mineralization technology, due to its ability to convert CO2 into thermodynamically stable carbonates for permanent carbon sequestration, exhibits enormous industrial potential. Mineralization raw materials include natural ores and industrial solid waste. Among these, CO2 mineralization technology using industrial solid waste as raw material offers the dual benefits of carbon emission reduction and solid waste resource utilization, making it a key pathway to achieving a circular economy and green, low-carbon development.
[0003] Desulfurized gypsum is a major calcium-based solid waste from coal-fired power plants, primarily composed of calcium sulfate dihydrate with a theoretical CaO content of 32.5%, making it an ideal mineralization raw material. Currently, existing technologies are exploring processes for mineralizing flue gas CO2 with desulfurized gypsum using ammonia as the reaction medium. For example, patent CN118125485A mixes desulfurized gypsum with water to obtain a mixture, then adds ammonia and serine as the reaction medium and additive, respectively, to prepare aragonite-type calcium carbonate and ammonium sulfate fertilizer. Patent CN116212607A discloses a system and method for accelerating the direct mineralization of flue gas CO2 by desulfurized gypsum, using ammonia to absorb CO2 from the desulfurized flue gas to obtain an ammonium carbonate absorbent; the absorbent is then mixed with a pretreated suspension of desulfurized gypsum and ammonia to carry out a mineralization reaction, obtaining a mixture of calcium carbonate and ammonium sulfate. However, these existing technologies mostly use commercially available concentrated ammonia as raw material, resulting in significant economic problems and failing to meet the economic requirements for large-scale industrial applications.
[0004] The residual ammonia water produced as a byproduct of coal coking processes accounts for approximately 10% of the total coal charged into the furnace. Taking an annual coke production of 3.5 million tons as an example, the residual ammonia water production exceeds 500,000 tons per year, and the concentrated ammonia water obtained after further ammonia stripping is approximately 50,000 tons per year. Without affecting the stable operation of the coking process, replacing commercial ammonia water with the concentrated ammonia water obtained after stripping the residual ammonia water as the reaction medium could significantly improve the economics of the desulfurized gypsum CO2 mineralization technology. However, this concentrated ammonia water contains impurities such as sulfides, cyanides, and phenols, and its composition is prone to fluctuation, making the reaction process difficult to control and resulting in insufficient product purity. Summary of the Invention
[0005] The purpose of this invention is to provide a method for mineralizing CO2 from flue gas using coking ammonia water and desulfurized gypsum, in order to solve the above-mentioned problems.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: 1. A method for mineralizing CO2 from flue gas using coking ammonia and desulfurized gypsum, characterized by comprising the following steps: S1. Slurry preparation and mineralization reaction: Desulfurized gypsum is mixed with coking ammonia water to obtain a slurry. The mass ratio of desulfurized gypsum to coking ammonia water is 1:6-10. The slurry is then contacted with CO2-containing flue gas in a reactor to carry out a mineralization reaction until the pH value of the slurry stabilizes at 6.5-7.5, resulting in a reaction suspension. S2, Solid-liquid separation: The reaction suspension obtained in S1 was subjected to solid-liquid separation to obtain a solid rich in calcium carbonate and a mother liquor rich in ammonium sulfate. S3. Recycling of solid calcium carbonate: The solid obtained from S2 is washed and then used as a desulfurizing agent in the flue gas desulfurization system. S4. Ammonium sulfate recovery and purification: The mother liquor obtained from S2 is evaporated and concentrated to obtain concentrated mother liquor. Then, anhydrous ethanol is added to the concentrated mother liquor to precipitate crude ammonium sulfate. After dissolving the crude ammonium sulfate in water, the crude ammonium sulfate solution is evaporated, concentrated, cooled, crystallized, and separated into solid and liquid components to obtain ammonium sulfate mother liquor and ammonium sulfate solid. The ammonium sulfate solid is dried to obtain the ammonium sulfate product.
[0007] To further realize the present invention, the coking ammonia water mentioned in S1 is concentrated ammonia water after ammonia stripping treatment.
[0008] To further realize the present invention, the CO2-containing flue gas mentioned in S1 is the desulfurized flue gas from a coal-fired power plant, wherein the volume fraction of CO2 is 10%-30%.
[0009] To further realize the present invention, the reaction temperature of the mineralization reaction in S1 is 30℃-60℃, and the reaction pressure is 0.1MPa-0.3MPa.
[0010] To further realize the present invention, the reactor described in S1 is a stirred tank reactor or a spray tower reactor.
[0011] To further realize the present invention, the amount of anhydrous ethanol added in S4 is 5%-25% of the volume of the concentrated mother liquor.
[0012] To further realize the present invention, the evaporation and concentration of the mother liquor in S4 is carried out by vacuum evaporation at a temperature of 60℃-80℃, and the concentration is carried out to 20%-50% of the original mother liquor volume.
[0013] To further realize the present invention, the evaporation and concentration of the crude ammonium sulfate solution in S4 is carried out by vacuum evaporation at a temperature of 60℃-80℃ until a crystal film appears.
[0014] To further realize the present invention, the cooling crystallization described in S4 is cooled to 30°C.
[0015] To further realize the present invention, the steam generated in the evaporation and concentration of the mother liquor in S1 is condensed to obtain condensate and the ammonium sulfate mother liquor obtained in S4 is returned to the wastewater treatment system.
[0016] The advantages of this invention compared to the prior art are as follows: This invention can directly mineralize CO2 from flue gas using desulfurization gypsum with complex coking concentrated ammonia water as the reaction medium. By controlling the pH value at the end of the mineralization reaction and removing volatile impurities by evaporation, and by using ethanol to induce crystallization and purification, the invention solves the problems of difficult mineralization process control and insufficient product purity, and finally obtains calcium carbonate and ammonium sulfate products for flue gas desulfurization that can replace limestone.
[0017] This invention breaks through the conventional understanding in the field that impurities in coking ammonia water severely interfere with the reaction and pollute the products. Through a specific process combination, it achieves a direct replacement of high-cost commercial ammonia water in the gypsum mineralization process, significantly reducing raw material costs. Simultaneously, the resulting calcium carbonate-rich solid directly replaces limestone as a desulfurizing agent in power plants for on-site disposal and closed-loop recycling. This eliminates the need for limestone procurement, transportation, and the energy-intensive ball milling process; while the refined ammonium sulfate is exported as a product. This lays an economic foundation for the large-scale industrial application of the technology and serves as a model of circular economy, demonstrating significant environmental benefits. Attached Figure Description
[0018] Figure 1 This is a process flow diagram of the method described in this invention; Figure 2 This is a SEM image of the calcium carbonate-rich solid in this invention; Figure 3 The XRD pattern of the calcium carbonate-rich solid obtained from the mineralization reaction in this invention is shown. Figure 4 This is the XRD pattern of the ammonium sulfate product in this invention. Detailed Implementation
[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0020] like Figure 1 As shown, a method for mineralizing CO2 from flue gas using coking ammonia water and desulfurized gypsum includes the following steps: S1. Slurry preparation and mineralization reaction: Desulfurized gypsum is mixed with coking ammonia water to obtain a slurry. The coking ammonia water is concentrated ammonia water after ammonia stripping treatment. The mass ratio of desulfurized gypsum to coking ammonia water is 1:6-10. The slurry is then contacted with CO2-containing flue gas in a stirred tank reactor or a spray tower reactor to carry out a mineralization reaction. The reaction temperature of the mineralization reaction is 30℃-60℃, and the reaction pressure is 0.1MPa-0.3MPa, until the pH value of the slurry stabilizes at 6.5-7.5, resulting in a reaction suspension. In this step, the CO2-containing flue gas is the desulfurized flue gas from a coal-fired power plant, with a CO2 volume fraction of 10%-30%. S2, Solid-liquid separation: The reaction suspension obtained in S1 was subjected to solid-liquid separation to obtain a solid rich in calcium carbonate and a mother liquor rich in ammonium sulfate. S3. Recycling of solid calcium carbonate: The solid obtained from S2 is washed and then used as a desulfurizing agent in the flue gas desulfurization system. S4. Ammonium sulfate recovery and purification: The mother liquor obtained from S2 is evaporated and concentrated to obtain a concentrated mother liquor. Then, anhydrous ethanol is added to the concentrated mother liquor to precipitate crude ammonium sulfate. The amount of anhydrous ethanol added is 5%-25% of the volume of the concentrated mother liquor. After dissolving the crude ammonium sulfate in water, the crude ammonium sulfate solution is evaporated and concentrated. Then, it is cooled and crystallized to 30°C. Solid-liquid separation is performed to obtain ammonium sulfate mother liquor and ammonium sulfate solid. The ammonium sulfate solid is dried to obtain the ammonium sulfate product.
[0021] In S4, the mother liquor is concentrated by vacuum evaporation at a temperature of 60℃-80℃, and concentrated to 20%-50% of the original mother liquor volume.
[0022] The crude ammonium sulfate solution in S4 was concentrated by vacuum evaporation at a temperature of 60℃-80℃ until a crystalline film appeared.
[0023] The steam generated during the evaporation and concentration of the mother liquor in S1 is condensed to obtain condensate, and the ammonium sulfate mother liquor obtained in S4 is returned to the wastewater treatment system.
[0024] The main components of the desulfurized gypsum used in the following examples are shown in Table 1. The residual ammonia water used has a total ammonia content of 4.5-7.5 g / L, an oil content of 0.1-0.5 g / L, an H2S content of 0.5-1.5 g / L, an HCN content of 0.1-0.25 g / L, and a salt content of 1.5-2.5 g / L (mainly ammonium salts, including: NH4Cl, (NH4)2SO4, NH4CNS, and NH4NO3, etc.), with a density of approximately 1180 kg / m³. 3 After ammonia is distilled using sodium hydroxide, the ammonia concentration in the resulting concentrated ammonia solution increases to over 18%, and the tar content is ≤50 mg / L.
[0025] Table 1. Main element content of desulfurized gypsum (calculated as oxides) Example 1: (1) Slurry preparation and mineralization reaction: Weigh 100 g of desulfurized gypsum and mix it thoroughly with 600 g of coking concentrated ammonia in a stirred tank reactor. Simulated desulfurized flue gas (CO2 volume fraction 15%) is continuously introduced in a bubbling manner. The reaction temperature is controlled at 60 ℃ and the reaction pressure at 0.3 MPa. The slurry pH value is continuously monitored online. After about 180 minutes of reaction, the pH value stabilizes at 6.8. The flue gas is then introduced and the reaction suspension is obtained.
[0026] (2) Solid-liquid separation: The reaction suspension is separated by vacuum filtration to obtain a wet solid rich in calcium carbonate and a mother liquor rich in ammonium sulfate.
[0027] (3) Recycling of calcium carbonate solids: Wash the above solids 2-3 times with deionized water, dry them at 80 ℃ to constant weight, and then perform SEM (Selenium Microscopy). Figure 2 ) and XRD analysis ( Figure 3 The main components are a mixture of calcite and aragonite, with a calcium carbonate content of 91.4%. When this product was used in a simulated flue gas desulfurization experiment, its desulfurization efficiency was comparable to that of commercially available limestone.
[0028] (4) Ammonium sulfate recovery and refining: a. Take 200 mL of the ammonium sulfate-rich mother liquor obtained in step (2), evaporate it under reduced pressure at 80 ℃ and 80 kPa, and concentrate it to 40% of the original volume (about 80 mL) to obtain a first-concentrated mother liquor.
[0029] b. Using a peristaltic pump, 20% (16 mL) of anhydrous ethanol was slowly added dropwise to the concentrated mother liquor, resulting in the precipitation of a large amount of crystals. The product was then filtered to obtain crude ammonium sulfate.
[0030] c. Dissolve the crude ammonium sulfate completely in deionized water, and then evaporate it under reduced pressure at 80 °C and 80 kPa MPa until a dense crystalline film forms on the liquid surface.
[0031] d. The solution was naturally cooled to 30 °C, aged at this temperature for 1 hour, and then filtered. The resulting crystals were dried at 60 °C to constant weight to obtain the ammonium sulfate product, the XRD of which is shown in Figure 1. Figure 4 As shown. Testing revealed that the product purity is greater than 97%.
[0032] Example 2: The steps are the same as in Example 1, with the main difference being the following parameters: the mass ratio of desulfurized gypsum to coking ammonia water is 1:10, the simulated flue gas CO2 volume fraction is 25%, and the reaction temperature is 40°C. oC, reaction pressure 0.2 MPa, pH value stabilized at 7.5 at the reaction endpoint.
[0033] The evaporation and concentration are carried out under reduced pressure at a temperature of 60℃-80℃, and the concentration is reduced to 20%-50% of the original mother liquor volume.
[0034] During ammonium sulfate recovery, the mother liquor is evaporated under reduced pressure at a temperature of 60°C and concentrated to 20% of the original mother liquor volume. The amount of ethanol added is 10% of the concentrated mother liquor volume.
[0035] The vacuum evaporation temperature of the crude ammonium sulfate solution is 80℃.
[0036] The final calcium carbonate product had a purity of 90.5%, and the ammonium sulfate product had a purity greater than 98%.
[0037] Example 3: The steps are the same as in Example 1, with the main difference being the following parameters: the mass ratio of desulfurized gypsum to coking ammonia water is 1:8, the simulated flue gas CO2 volume fraction is 30%, and the reaction temperature is 30°C. o C, reaction pressure 0.1 MPa, pH value stabilized at 6.5 at the reaction endpoint.
[0038] During ammonium sulfate recovery, the mother liquor is evaporated under reduced pressure at a temperature of 70°C and concentrated to 30% of the original mother liquor volume. The amount of ethanol added is 25% of the concentrated mother liquor volume.
[0039] The vacuum evaporation temperature of the crude ammonium sulfate solution is 70℃.
[0040] The final calcium carbonate product had a purity of 90.1%, and the ammonium sulfate product had a purity greater than 98%.
[0041] Example 4: The steps are the same as in Example 1, with the main difference being the following parameters: the mass ratio of desulfurized gypsum to coking ammonia water is 1:9, the simulated flue gas CO2 volume fraction is 10%, and the reaction temperature is 50°C. o C, reaction pressure 0.2 MPa, pH value stabilized at 7.0 at the reaction endpoint.
[0042] During ammonium sulfate recovery, the mother liquor is evaporated under reduced pressure at a temperature of 60°C and concentrated to 50% of the original mother liquor volume. The amount of ethanol added is 5% of the volume of the concentrated mother liquor.
[0043] The vacuum evaporation temperature of the crude ammonium sulfate solution is 60℃.
[0044] The final calcium carbonate product had a purity of 91.2%, and the ammonium sulfate product had a purity greater than 98%.
Claims
1. A method for mineralizing flue gas CO2 with coked ammonia water and desulfurized gypsum, characterized by Includes the following steps: S1. Slurry preparation and mineralization reaction: Desulfurized gypsum is mixed with coking ammonia water to obtain a slurry. The mass ratio of desulfurized gypsum to coking ammonia water is 1:6-10. The slurry is then contacted with CO2-containing flue gas in a reactor to carry out a mineralization reaction until the pH value of the slurry stabilizes at 6.5-7.5, resulting in a reaction suspension. S2, Solid-liquid separation: The reaction suspension obtained in S1 was subjected to solid-liquid separation to obtain a solid rich in calcium carbonate and a mother liquor rich in ammonium sulfate. S3. Recycling of solid calcium carbonate: The solid obtained from S2 is washed and then used as a desulfurizing agent in the flue gas desulfurization system. S4. Ammonium sulfate recovery and purification: The mother liquor obtained from S2 is evaporated and concentrated to obtain concentrated mother liquor. Then, anhydrous ethanol is added to the concentrated mother liquor to precipitate crude ammonium sulfate. After dissolving the crude ammonium sulfate in water, the crude ammonium sulfate solution is evaporated, concentrated, cooled, crystallized, and separated into solid and liquid components to obtain ammonium sulfate mother liquor and ammonium sulfate solid. The ammonium sulfate solid is dried to obtain the ammonium sulfate product.
2. The method for mineralizing flue gas CO2 with coked ammonia water and desulfurized gypsum according to claim 1, characterized in that: The coking ammonia water mentioned in S1 is concentrated ammonia water after ammonia stripping treatment.
3. The method for mineralizing flue gas CO2 with coked ammonia water and desulfurized gypsum according to claim 1 or 2, characterized in that: The CO2-containing flue gas mentioned in S1 is the desulfurized flue gas from a coal-fired power plant, wherein the volume fraction of CO2 is 10%-30%.
4. The method for mineralizing flue gas CO2 with coked ammonia water and desulfurized gypsum according to claim 3, characterized by: The mineralization reaction described in S1 has a reaction temperature of 30℃-60℃ and a reaction pressure of 0.1MPa-0.3MPa.
5. The method for mineralizing flue gas CO2 with coked ammonia water and desulfurized gypsum according to claim 4, characterized by: The reactor described in S1 is a stirred tank reactor or a spray tower reactor.
6. The method for mineralizing flue gas CO2 with coked ammonia water and desulfurized gypsum according to claim 5, characterized by: The amount of anhydrous ethanol added in S4 is 5%-25% of the volume of the concentrated mother liquor.
7. The method for mineralizing flue gas CO2 with coked ammonia water and desulfurized gypsum according to claim 6, characterized by: The evaporation and concentration of the mother liquor described in S4 is carried out by vacuum evaporation at a temperature of 60℃-80℃, concentrating it to 20%-50% of the original mother liquor volume.
8. The method for mineralizing flue gas CO2 with coked ammonia water and desulfurized gypsum according to claim 6, characterized by: The crude ammonium sulfate solution described in S4 is concentrated by vacuum evaporation at a temperature of 60℃-80℃ until a crystalline film appears.
9. The method for mineralizing flue gas CO2 with coked ammonia water and desulfurized gypsum according to claim 6, characterized by: The cooling crystallization described in S4 is cooled to 30°C.
10. The method for mineralizing CO2 from flue gas using coking ammonia water and desulfurized gypsum as described in claim 6, characterized in that: The steam generated during the evaporation and concentration of the mother liquor in S1 is condensed to obtain condensate, and the ammonium sulfate mother liquor obtained in S4 is returned to the wastewater treatment system.