Cement kiln bypass dust high-value utilization method and system

Abstract

This invention belongs to the field of energy-saving and environmental protection technology, and discloses a method and system for high-value utilization of cement kiln bypass vent ash, including the following steps: waste heat recovery from bypass vent flue gas via a flue gas heat exchanger; gas-solid separation to obtain solid bypass vent ash; the flue gas is conveyed to a flue gas scrubbing tower for washing; the washing water and bypass vent ash generated from the scrubbing tower are both input into an extraction tower, where the washing water is used to extract calcium ions from the bypass vent ash to obtain a mixed slurry; liquid-solid separation to obtain a calcium-containing solution and water-insoluble impurities; the separated calcium-containing solution is input into a mineralization reaction tower, where the washed flue gas and crystal form control agent are also added, followed by liquid-solid separation and drying to obtain the finished product, aragonite-type calcium carbonate. This invention enhances the recycling value of bypass vent ash and realizes high-value utilization of substances in bypass vent ash.

Description

Technical Field

[0001] This invention belongs to the field of energy conservation and environmental protection technology, specifically relating to a method and system for high-value utilization of cement kiln bypass vent ash. Background Technology

[0002] Because cement kilns co-process waste, sludge, and solid waste with complex compositions, and because the alternative and derivative fuels used in cement kilns have high sulfur and chlorine content, large amounts of alkali, chlorine, and sulfur are released during cement kiln operation and circulate and accumulate within the kiln, easily causing scaling and blockage. To prevent the accumulation of alkali, chlorine, and sulfur in the kiln system, when the sulfur and chlorine content in the hot raw materials reaches a certain level, bypass ventilation technology is needed to release a portion of the flue gas enriched with high concentrations of alkali, chlorine, and sulfur to alleviate this problem.

[0003] The bypass ventilation system releases a portion of high-temperature flue gas (containing some hot raw materials) from the kiln tail flue or other nearby areas. This high-temperature flue gas, at approximately 1000°C, is rapidly mixed with air in a collector box, reducing its temperature to 200-350°C. The hot raw materials are then collected using a cyclone dust collector or baghouse dust collector; this collected hot raw materials are called bypass ventilation ash. Bypass ventilation ash is a complex, high-alkali, high-chlorine material, currently mainly used as a small-scale admixture added to cement. However, its generation is increasing year by year, making comprehensive utilization more difficult.

[0004] While existing technologies exist for absorbing carbon dioxide using bypass vent ash, the resulting product is ordinary calcium carbonate, generally only suitable for use in cementitious materials or desulfurizing agents, resulting in low economic efficiency. This is partly due to the properties of the calcium carbonate produced by existing technologies, and partly due to the presence of impurities such as SiO2, Al2O3, Fe2O3, and K2O in the bypass vent ash. These impurities ultimately limit the product's applicability. Therefore, improving the recycling and treatment technology of bypass vent ash, increasing the utilization value of the recovered product, reducing the impact of impurities on the product, and further recovering and utilizing the valuable portions of the aforementioned impurities have become the technical problems that existing technologies need to solve. Summary of the Invention

[0005] The purpose of this invention is to provide a method for high-value utilization of cement kiln bypass vent ash, which solves the technical problems of low utilization value of recycled products, high susceptibility to impurities, and difficulty in recycling the impurities in existing technologies.

[0006] The method for high-value utilization of cement kiln bypass vent ash includes the following steps: recovering waste heat from the bypass vent flue gas using a flue gas heat exchanger, allowing the waste heat of the bypass vent flue gas to be absorbed into the heat exchange medium; inputting the dust-laden flue gas discharged from the flue gas heat exchanger into a gas-solid separation tower, where gas-solid separation yields solid bypass vent ash; the flue gas separated by the gas-solid separation tower is transported to a flue gas scrubbing tower, where the separated flue gas is scrubbed; the scrubbing water and bypass vent ash generated by the scrubbing tower are both input into an extraction tower, where the scrubbing water is used to extract calcium ions from the bypass vent ash to obtain a mixed slurry; the mixed slurry undergoes liquid-solid separation to obtain a calcium-containing solution and water-insoluble impurities; the separated calcium-containing solution is input into a mineralization reaction tower, and the scrubbed flue gas is also passed into... The mineralization reaction tower is used to add a crystal form control agent to generate aragonite-type calcium carbonate. The liquid-solid mixture after the mineralization reaction is separated into liquid and solid, and the obtained aragonite-type calcium carbonate is dried to obtain the finished product. The remaining solution is sent to a potassium sulfate preparation tower. Ammonia-containing flue gas from the cement kiln denitrification system is introduced into the potassium sulfate preparation tower to react and form a mixed solution. The mixed solution is then fed into a metathesis reaction tower for further reaction. The mixture after the reaction is cooled and crystallized, and potassium sulfate crystals are separated by filtration. The potassium sulfate crystals are dried to obtain the finished product. The remaining ammonium chloride mother liquor after filtration is evaporated and crystallized to obtain solid ammonium chloride. The evaporated water is then recycled and sent to a flue gas scrubbing tower for scrubbing the flue gas.

[0007] Preferably, the temperature of the bypass flue gas entering the flue gas heat exchanger is about 1200°C. After heat exchange, the temperature of the bypass flue gas drops to 200°C to 350°C. The heat exchange medium that absorbs the waste heat of the bypass flue gas is used to dry aragonite-type calcium carbonate and potassium sulfate, as well as to evaporate and crystallize ammonium chloride solution.

[0008] Preferably, the ammonia concentration in the ammonia-containing flue gas is detected using an ammonia analyzer, and the potassium ion concentration in the remaining solution is detected by sampling using a radiometric method. The amount and time of ammonia-containing flue gas introduced are controlled based on the ammonia concentration and potassium ion concentration. The molar ratio between potassium ions and ammonia is 1:1, and the molar ratio between ammonia and sulfuric acid is 2:1.

[0009] Preferably, the washing water and the bypass vent ash are thoroughly stirred in the extraction tower for 2 hours.

[0010] Preferably, in the mineralization reaction tower, the flue gas flow rate is controlled at 60 L / h to 120 L / h, and the mineralization reaction time is controlled at 1 to 2 hours.

[0011] Preferably, the drying temperature in the aragonite drying tower is controlled at 70-90℃, and the drying time is 1-1.5h.

[0012] Preferably, the reaction temperature is controlled at 80℃~100℃ and the reaction time is 30min~60min in the metathesis reaction, and stirring is carried out continuously.

[0013] Preferably, the mixture after the metathesis reaction is cooled to 50°C to 60°C and then transported to a crystallization tank for stirring. After a period of time, a solid-liquid mixture containing potassium sulfate crystals is obtained.

[0014] This invention also provides a high-value utilization system for bypass vent ash from cement kilns, comprising a flue gas scrubbing tower, an extraction tower, a first liquid-solid separation tower, a mineralization reaction tower, a second liquid-solid separation tower, a spheroidal aragonite drying tower, a potassium sulfate preparation tower, a metathesis reaction tower, a crystallization tank, a potassium sulfate drying tower, and an ammonium chloride evaporation tower. The bypass vent gas is input to the gas-solid separation tower. The flue gas outlet of the gas-solid separation tower is connected to the flue gas scrubbing tower. The vent ash outlet of the gas-solid separation tower is connected to the extraction tower. The flue gas outlet of the flue gas scrubbing tower is connected to the mineralization reaction tower. The wash water outlet of the flue gas scrubbing tower is connected to the extraction tower. The outlet of the extraction tower is connected to the first liquid-solid separation tower. The liquid outlet of the first liquid-solid separation tower is connected to... The solid outlet of the first liquid-solid separation tower is connected to the mineralization reaction tower, and the solid outlet of the first liquid-solid separation tower outputs impurities insoluble in water. The outlet of the mineralization reaction tower is connected to the second liquid-solid separation tower, the liquid outlet of the second liquid-solid separation tower is connected to the potassium sulfate preparation tower, and the solid outlet of the second liquid-solid separation tower is connected to the aragonite drying tower. The potassium sulfate preparation tower is also provided with an ammonia inlet for inputting ammonia-containing flue gas. The outlet of the potassium sulfate preparation tower is connected to the metathesis reaction tower, the outlet of the metathesis reaction tower is connected to the crystallization tank, the mother liquor outlet of the crystallization tank is connected to the ammonium chloride evaporation tower, the solid outlet of the crystallization tank is connected to the potassium sulfate drying tower, and the evaporated water outlet of the ammonium chloride evaporation tower is connected to the flue gas scrubbing tower via a pipeline.

[0015] Preferably, the bypass vent gas is input to the gas-solid separation tower via the flue gas heat exchanger. The flue gas heat exchanger is equipped with a heat exchange medium pipeline, and the output part of the heat exchange medium pipeline is respectively connected to the aragonite drying tower, the potassium sulfate drying tower, and the ammonium chloride evaporation tower.

[0016] The present invention has the following advantages: The present invention solves the problem of recycling bypass venting ash. By extracting calcium ions from bypass venting ash, high-value aragonite-type calcium carbonate is prepared. Two commonly used agricultural wastes, potassium sulfate and ammonium chloride, are also generated, which improves the recycling value of bypass venting ash, realizes the high-value utilization of substances in bypass venting ash, and solves the problem of bypass venting ash storage.

[0017] This method uses carbon dioxide from cement kiln flue gas as a carbon source, reducing carbon emissions through absorption and capture. Simultaneously, it also recovers and utilizes ammonia-containing flue gas generated in the cement kiln's denitrification system, directly utilizing escaped ammonia without requiring specialized treatment, thus saving on equipment investment.

[0018] This method utilizes a flue gas heat exchanger, effectively reducing the energy consumption required for flue gas treatment. Furthermore, it recovers some of the waste heat for drying aragonite-type calcium carbonate, potassium sulfate, and ammonium chloride, as well as for the evaporation and crystallization of ammonium chloride mother liquor. This approach significantly reduces energy consumption. With sulfuric acid compensation, this scheme generates two agricultural fertilizers, potassium sulfate and ammonium chloride, achieving effective utilization of potassium salts in the bypass vent ash. The evaporation water generated during the ammonium chloride evaporation and crystallization process can be used to wash the heat-exchanged flue gas, realizing water recycling. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process for a method and system for high-value utilization of cement kiln bypass vent ash according to the present invention.

[0020] The reference numerals in the accompanying drawings of the instruction manual include: 1. Flue gas heat exchanger, 2. Gas-solid separation tower, 3. Flue gas scrubbing tower, 4. Extraction tower, 5. Liquid-solid separation tower one, 6. Mineralization reaction tower, 7. Liquid-solid separation tower two, 8. Potassium sulfate preparation tower, 9. Metathesis reaction tower, 10. Crystallization tank, 11. Ammonium chloride evaporation tower, 12. Aragonite drying tower, 13. Potassium sulfate drying tower. Detailed Implementation

[0021] The following detailed description of the embodiments, with reference to the accompanying drawings, will further illustrate the specific implementation of the present invention, in order to help those skilled in the art to have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention.

[0022] The main chemical composition of the bypass vent ash is shown in Table 1. The main component of the bypass vent ash is CaO. This scheme considers using a deep calcium ion extraction process to extract calcium ions from the bypass vent ash and then using CO2 from the cement kiln flue gas for reaction, controlling the reaction conditions to generate aragonite calcium carbonate. After liquid-solid separation, the heat from the bypass vent flue gas is used to dry the aragonite calcium carbonate, finally obtaining the aragonite calcium carbonate product.

[0023] However, the bypass vent ash also contains many impurities, including SiO2, Al2O3, Fe2O3, K2O, Na2O, and MgO. These impurities significantly affect the preparation of aragonite, resulting in insufficient purity. Therefore, impurities need to be removed during the preparation of aragonite. Furthermore, the reaction conditions for aragonite formation must be strictly controlled to obtain aragonite with high purity. Meanwhile, the bypass vent gas, as the source of bypass vent ash, contains a significant amount of carbon dioxide and small amounts of acidic and harmful gases such as sulfur dioxide. Finally, as shown in Table 1, the K2O content is high, and potassium fertilizer is a valuable agricultural fertilizer. Therefore, if potassium can be recovered from the impurities simultaneously, the value of the recovered product can be further enhanced.

[0024] Table 1. Main chemical composition (%) of bypass vent ash

[0025]

[0026] like Figure 1 As shown, the present invention provides a method for high-value utilization of cement kiln bypass vent ash, comprising the following steps.

[0027] Waste heat is recovered from the bypass vent gas through flue gas heat exchanger 1, allowing the waste heat of the bypass vent gas to be absorbed into the heat exchange medium. The flue gas discharged from flue gas heat exchanger 1 is dust-containing flue gas. The temperature of the bypass vent gas is approximately 1200℃, and after heat exchange, the temperature drops to 200℃~350℃.

[0028] The dust-laden flue gas is fed into the gas-solid separation tower 2 for gas-solid separation to obtain bypass vent ash in solid state. The flue gas separated by the gas-solid separation tower 2 is then transported to the flue gas scrubbing tower 3.

[0029] The flue gas scrubbing tower 3 washes the separated flue gas, removing acidic gases such as chloride ions, sulfur dioxide, and some carbon dioxide, and obtaining an acidic solution with a low pH, which is the washing water.

[0030] Wash water and bypass vent ash are both fed into extraction tower 4 for mixing. Extraction tower 4 thoroughly stirs the mixture for 2 hours, thereby using the wash water to extract calcium ions from the calcium oxide in the bypass vent ash. The corresponding chemical reaction is: CaO + H₂O → Ca(OH)₂. This yields a calcium-containing solution containing calcium hydroxide. Sodium, potassium, and chloride ions from the bypass vent ash also dissolve in this solution. After sufficient reaction time in extraction tower 4, the calcium-containing solution has extracted all calcium ions from the calcium oxide, and the solution is also rich in calcium, potassium, and chloride ions.

[0031] Next, the mixed slurry obtained in extraction tower 4 is sent to liquid-solid separation tower 5. The water-insoluble impurities in the bypass vent ash, such as silicon oxide, aluminum oxide, iron oxide and magnesium oxide, are separated by liquid-solid separation tower 5 and used in cement admixtures. The liquid obtained after separation is a calcium-containing solution.

[0032] The calcium-containing solution after separation is fed into mineralization reaction tower 6, while the scrubbed flue gas is also fed into mineralization reaction tower 6. The calcium-containing solution, as a calcium-rich solution, reacts with the scrubbed flue gas; the main reaction equations are as follows:

[0033] CO2(g)→CO2(l)

[0034] CO2(l) + OH - →H2O(l)+CO3 2-

[0035] Ca 2+ +CO3 2- →CaCO3

[0036] Because the formation conditions for aragonite-type calcium carbonate are quite demanding, the flue gas flow rate should be controlled at 60 L / h to 120 L / h, and the reaction time should be controlled at 1 to 2 hours to ensure the formation of aragonite-type calcium carbonate. During the reaction, a crystal form control agent should be added to regulate the process and ensure the homogeneity of the aragonite-type calcium carbonate. Crystal form control agents are alcohols, acids, and amino acids, such as citric acid and glycine. It should be noted that if the reaction time is too long, the resulting aragonite-type calcium carbonate will remain in water for too long and will transform into calcite-type calcium carbonate; therefore, the reaction time needs to be controlled.

[0037] After the reaction, the mineralization reaction tower 6 conveys the resulting liquid-solid mixture to the liquid-solid separation tower 7 to separate the generated aragonite-type calcium carbonate from the remaining solution rich in K+ and Cl- ions. The separated aragonite-type calcium carbonate is then conveyed to the aragonite drying tower 12, and the remaining solution is conveyed to the potassium sulfate preparation tower 8.

[0038] The aragonite drying tower 12 uses the heat exchange medium from the flue gas heat exchanger 1, which absorbs the residual heat, for drying to obtain the finished aragonite-type calcium carbonate. To prevent the aragonite-type calcium carbonate from decomposing into calcite-type calcium carbonate upon heating, the drying temperature in the aragonite drying tower 12 is controlled at 70-90℃, and the drying time is 1-1.5 hours. Spherical aragonite-type calcium carbonate possesses excellent smoothness, flowability, dispersibility, and wear resistance, and is therefore widely used in rubber, paints, inks, pharmaceuticals, toothpaste, and cosmetics. Therefore, the aragonite-type calcium carbonate produced in this method has high added value, making this method of significant economic value and practical significance.

[0039] Ammonia-containing flue gas from the cement kiln denitrification system is introduced into potassium sulfate preparation tower 8 to react and form a mixed solution. The ammonia concentration in the flue gas is detected using an ammonia analyzer, and the potassium ion concentration in the remaining solution is measured using a radiometric method. Based on the ammonia and potassium ion concentrations, the flow rate and time of the ammonia-containing flue gas are controlled to ensure a 1:1 molar ratio of potassium ions to ammonia. Simultaneously, sulfuric acid is added in a measured amount; the concentration of sulfuric acid is known, and the amount added must ensure a 2:1 molar ratio of ammonia to sulfuric acid. After dissolving in the remaining solution, ammonia reacts with sulfuric acid in the following way: 2NH3·H2O + H2SO4 → (NH4)2SO4 + 2H2O.

[0040] The denitrification system in a cement kiln purifies the flue gas by removing nitrogen and sulfur dioxide. During this process, a large amount of ammonia water is used to remove ammonia from the flue gas. Some unreacted ammonia escapes, resulting in a high ammonia content in the flue gas. Adding ammonia and sulfuric acid in a specific ratio ensures complete reaction in the double displacement reaction that occurs in the next unit.

[0041] The mixed solution formed in the previous unit is fed into the double decomposition reaction tower 9 for reaction. During the reaction, the reaction temperature is controlled at 80℃~100℃, the reaction time is 30min~60min, and stirring is carried out continuously. At this time, the double decomposition reaction will occur in the double decomposition reaction tower 9: 2KCl+(NH4)2SO4→K2SO4+2NH4Cl.

[0042] The mixture after the reaction in the previous unit is cooled to 50℃~60℃ and then transported to crystallization tank 10 for stirring. Potassium sulfate begins to precipitate. After a period of time, a solid-liquid mixture containing potassium sulfate crystals is obtained. The solid-liquid mixture is filtered to obtain potassium sulfate crystals and a mother liquor containing ammonium chloride.

[0043] After potassium sulfate crystals are fed into potassium sulfate drying tower 13, they are dried using a heat exchange medium that absorbs waste heat, ultimately yielding dried potassium sulfate product. The mother liquor is then sent to ammonium chloride evaporation tower 11, where it is evaporated and crystallized using a heat exchange medium that absorbs waste heat, finally yielding solid ammonium chloride. The evaporated water output from the evaporation unit is then recycled to flue gas scrubbing tower 3 for scrubbing the flue gas, achieving recycling.

[0044] Both K2SO4 and NH4Cl are essential fertilizer raw materials for agricultural production. In the production process of this scheme, potassium comes from potassium-containing impurities in the bypass vent ash, while ammonium ions containing nitrogen come from residual ammonia in the flue gas after denitrification in cement plants. Therefore, valuable substances are recovered from waste in the cement production system, and high-value products are obtained, further improving the economic benefits of this method.

[0045] This invention also provides a high-value utilization system for cement kiln bypass vent ash, comprising a gas-solid separation tower 2, a flue gas scrubbing tower 3, an extraction tower 4, a liquid-solid separation tower 5, a mineralization reaction tower 6, a liquid-solid separation tower 7, a spheroidal aragonite drying tower 12, a potassium sulfate preparation tower 8, a metathesis reaction tower 9, a crystallization tank 10, a potassium sulfate drying tower 13, and an ammonium chloride evaporation tower 11. The bypass vent flue gas is input to the gas-solid separation tower 2. The flue gas outlet of the gas-solid separation tower 2 is connected to the flue gas scrubbing tower 3. The vent ash outlet of the gas-solid separation tower 2 is connected to the extraction tower 4. The flue gas outlet of the flue gas scrubbing tower 3 is connected to the mineralization reaction tower 6. The washing water outlet of the flue gas scrubbing tower 3 is connected to the extraction tower 4. The outlet of the extraction tower 4 is connected to the liquid-solid separation tower 5. Tower 5 is a liquid-solid separation tower. Its liquid outlet is connected to the mineralization reaction tower 6, and its solid outlet outputs water-insoluble impurities. The outlet of the mineralization reaction tower 6 is connected to a second liquid-solid separation tower 7, whose liquid outlet is connected to the potassium sulfate preparation tower 8. The solid outlet of the second liquid-solid separation tower 7 is connected to the aragonite drying tower 12. The potassium sulfate preparation tower 8 also has an ammonia inlet for inputting ammonia-containing flue gas. The outlet of the potassium sulfate preparation tower 8 is connected to the metathesis reaction tower 9, whose outlet is connected to the crystallization tank 10. The mother liquor outlet of the crystallization tank 10 is connected to the ammonium chloride evaporation tower 11, and the solid outlet of the crystallization tank 10 is connected to the potassium sulfate drying tower 13. The evaporated water outlet of the ammonium chloride evaporation tower 11 is connected to the flue gas scrubbing tower 3 via a pipeline, thereby recovering the evaporated water to scrub the flue gas, saving water.

[0046] The flue gas outlet connection to the system also includes a flue gas heat exchanger 1. The bypass vent flue gas is input to the gas-solid separation tower 2 via the flue gas heat exchanger 1. The flue gas heat exchanger 1 is equipped with a heat exchange medium pipeline, and the output part of the heat exchange medium pipeline is respectively connected to the aragonite drying tower 12, the potassium sulfate drying tower 13, and the ammonium chloride evaporation tower 11. In this way, the aragonite drying tower 12, the potassium sulfate drying tower 13, and the ammonium chloride evaporation tower 11 can all utilize the heat exchange medium that has absorbed the waste heat of the bypass vent flue gas for heating and drying, thereby reducing the system's energy consumption.

[0047] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A system for high-value utilization of cement kiln bypass vent ash, characterized in that: The system includes a flue gas heat exchanger (1), a gas-solid separation tower (2), a flue gas scrubbing tower (3), an extraction tower (4), a liquid-solid separation tower one (5), a mineralization reaction tower (6), a liquid-solid separation tower two (7), a spheroidal aragonite drying tower (12), a potassium sulfate preparation tower (8), a metathesis reaction tower (9), a crystallization tank (10), a potassium sulfate drying tower (13), and an ammonium chloride evaporation tower (11). Bypass vent gas is fed into the gas-solid separation tower (2). The flue gas outlet of the gas-solid separation tower (2) is connected to the flue gas scrubbing tower (3). The vent ash outlet of the gas-solid separation tower (2) is connected to the extraction tower (4). The flue gas outlet of the flue gas scrubbing tower (3) is connected to the mineralization reaction tower (6). The washing water outlet of the flue gas scrubbing tower (3) is connected to the extraction tower (4). The outlet of the extraction tower (4) is connected to the liquid-solid separation tower one (5). The liquid outlet of the liquid-solid separation tower one (5) is connected to... The solid outlet of the first liquid-solid separation tower (5) is connected to the mineralization reaction tower (6), and the solid outlet of the first liquid-solid separation tower (5) is connected to the water-insoluble impurities. The outlet of the mineralization reaction tower (6) is connected to the second liquid-solid separation tower (7), the liquid outlet of the second liquid-solid separation tower (7) is connected to the potassium sulfate preparation tower (8), the solid outlet of the second liquid-solid separation tower (7) is connected to the aragonite drying tower (12), the potassium sulfate preparation tower (8) is also provided with an ammonia inlet for inputting ammonia-containing flue gas, the outlet of the potassium sulfate preparation tower (8) is connected to the metathesis reaction tower (9), the outlet of the metathesis reaction tower (9) is connected to the crystallization tank (10), the mother liquor outlet of the crystallization tank (10) is connected to the ammonium chloride evaporation tower (11), the solid outlet of the crystallization tank (10) is connected to the potassium sulfate drying tower (13), and the evaporated water outlet of the ammonium chloride evaporation tower (11) is connected to the flue gas scrubbing tower (3) via a pipeline.

2. The high-value utilization system for cement kiln bypass vent ash according to claim 1, characterized in that: The bypass vent gas is fed into the gas-solid separation tower (2) via the flue gas heat exchanger (1). The flue gas heat exchanger (1) is equipped with a heat exchange medium pipeline. The output part of the heat exchange medium pipeline is connected to the aragonite drying tower (12), the potassium sulfate drying tower (13), and the ammonium chloride evaporation tower (11), respectively.

3. A method for high-value utilization of cement kiln bypass vent ash, characterized in that: The system for high-value utilization of cement kiln bypass vent ash according to claim 1 includes the following steps: recovering waste heat from the bypass vent ash through a flue gas heat exchanger (1), allowing the waste heat of the bypass vent ash to be absorbed into the heat exchange medium; inputting the dust-laden flue gas discharged from the flue gas heat exchanger (1) into a gas-solid separation tower (2), and obtaining solid bypass vent ash through gas-solid separation; the flue gas separated by the gas-solid separation tower (2) is transported to a flue gas scrubbing tower (3), and the flue gas scrubbing tower (3) scrubs the separated flue gas; The washing water and bypass vent ash generated by the flue gas scrubbing tower (3) are fed into the extraction tower (4), where the calcium ions in the bypass vent ash are extracted using the washing water to obtain a mixed slurry. The mixed slurry is separated into a calcium-containing solution and water-insoluble impurities by liquid-solid separation. The separated calcium-containing solution is fed into the mineralization reaction tower (6), and the washed flue gas is also fed into the mineralization reaction tower (6). A crystal form control agent is added to the mineralization reaction tower (6) to generate aragonite-type calcium carbonate by mineralization reaction. The liquid-solid mixture after mineralization reaction is separated into liquid and solid, and the obtained aragonite-type calcium carbonate is dried to obtain the finished product of aragonite-type calcium carbonate. The separated residual solution is sent to the potassium sulfate preparation tower (8). The ammonia-containing flue gas output from the cement kiln denitrification system is fed into the potassium sulfate preparation tower (8) to react and form a mixed solution. The mixed solution is then fed into the metathesis reaction tower (9) for reaction. The mixture after reaction is cooled and crystallized and then separated into potassium sulfate crystals by filtration. The potassium sulfate crystals are dried to obtain the finished product of potassium sulfate. The remaining ammonium chloride mother liquor after filtration is evaporated and crystallized to obtain ammonium chloride solid. The evaporated water is then recycled and sent to the flue gas scrubbing tower (3) for scrubbing the flue gas.

4. The method for high-value utilization of cement kiln bypass vent ash according to claim 3, characterized in that: The temperature of the bypass flue gas entering the flue gas heat exchanger (1) is 1200℃. After heat exchange, the temperature of the bypass flue gas drops to 200℃~350℃. The heat exchange medium that absorbs the waste heat of the bypass flue gas is used to dry aragonite-type calcium carbonate and potassium sulfate, as well as to evaporate and crystallize ammonium chloride solution.

5. A method for high-value utilization of cement kiln bypass vent ash according to claim 3, characterized in that: The ammonia concentration in the ammonia-containing flue gas was detected using an ammonia analyzer, and the potassium ion concentration in the remaining solution was detected by sampling using a radiometric method. The amount and time of ammonia-containing flue gas introduced were controlled based on the ammonia and potassium ion concentrations. The molar ratio of potassium ions to ammonia was 1:1, and the molar ratio of ammonia to sulfuric acid was 2:

1.

6. The method for high-value utilization of cement kiln bypass vent ash according to claim 3, characterized in that: The washing water and the bypass venting ash are thoroughly stirred in the extraction tower (4) for 2 hours.

7. A method for high-value utilization of cement kiln bypass vent ash according to claim 3, characterized in that: In the mineralization reaction tower (6), the flue gas flow rate is controlled at 60L / h ~ 120L / h, and the reaction time of the mineralization reaction is controlled at 1~2h.

8. A method for high-value utilization of cement kiln bypass vent ash according to claim 3, characterized in that: The drying temperature in the aragonite drying tower (12) is controlled at 70-90℃, and the drying time is 1-1.5h.

9. A method for high-value utilization of cement kiln bypass vent ash according to claim 3, characterized in that: In the metathesis reaction, the reaction temperature is controlled at 80℃~100℃, the reaction time is 30 min~60 min, and stirring is carried out continuously.

10. A method for high-value utilization of cement kiln bypass vent ash according to claim 3, characterized in that: The mixture after the metathesis reaction is cooled to 50℃~60℃ and then transported to the crystallization tank (10) for stirring. After a period of time, a solid-liquid mixture containing potassium sulfate crystals is obtained.

Images