Fly ash recycling flue gas deacidification system and method

Abstract

The application discloses a fly ash recycling flue gas deacidification system and method, and belongs to the field of flue gas deacidification technology. The fly ash recycling flue gas deacidification system comprises fly ash pretreatment units, a collaborative grinding and activation unit and a fly ash grading back spraying unit which are sequentially connected. The collaborative grinding and activation unit comprises a raw material mixing device for mixing fly ash, calcium-based materials and heavy metal stabilizers to form a mixture, and a grinding device for grinding and activating the mixture. The fly ash grading back spraying unit comprises an activated ash bin, a metering device and a pneumatic conveying and spraying device which are sequentially connected. The fly ash recycling flue gas deacidification system of the application realizes the recycling of fly ash through the connection of the fly ash pretreatment unit, the collaborative grinding and activation unit and the fly ash grading back spraying unit.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and flue gas purification technology, and in particular to a fly ash recycling flue gas deacidification system and method. Background Technology

[0002] Reusing fly ash from waste incineration as a deacidifying agent is a key strategy for achieving "waste treatment with waste" and reducing environmental costs. However, the engineering application of this technology faces systemic challenges: chloride salts in raw fly ash can easily cause corrosion inside the furnace; its composition fluctuates greatly, and its alkaline activity is low, resulting in poor direct utilization efficiency; heavy metals pose a risk of volatilization at high temperatures. In addition, there is a lack of efficient coordination between the various process units from fly ash collection and treatment to precise reuse, making it difficult to form a stable and complete system.

[0003] Existing solutions mostly focus on localized process improvements, failing to provide a complete technical solution from a system integration perspective that can simultaneously address activity enhancement, safety risk control, and seamless integration with existing flue gas purification facilities. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a fly ash reuse flue gas deacidification system and a fly ash reuse flue gas deacidification method.

[0005] The technical solution adopted by the present invention to solve its technical problem is: to provide a fly ash reuse flue gas desulfurization system, including a fly ash pretreatment unit for washing, dechlorinating and drying fly ash, a co-grinding and activation unit connected to the fly ash pretreatment unit for grinding and activating fly ash, and a fly ash grading and re-spraying unit connected to the co-grinding and activation unit for metering and diverting the ground and activated fly ash. The co-grinding and activation unit includes a raw material mixing device for mixing fly ash with calcium-based materials and heavy metal stabilizers to form a mixture, and a grinding device for grinding and activating the mixture. The fly ash grading and re-spraying unit includes an activated ash silo, a metering feeding device, and a pneumatic conveying and spraying device connected in sequence.

[0006] Preferably, the fly ash pretreatment unit outputs fly ash with a moisture content of 8% to 15%.

[0007] Preferably, the raw material mixing device is a stirring mixing device; the grinding device is a stirring grinding device or a planetary grinding device.

[0008] Preferably, the fly ash pretreatment unit includes a fly ash storage silo, a pulping tank, a multi-stage countercurrent washing device, a solid-liquid separation device, and a drying device connected in sequence; the drying device is connected to the raw material mixing device.

[0009] Preferably, the heavy metal stabilizer includes at least one of calcium dihydrogen phosphate, calcium phosphate, and silicate, and its addition amount is 3%-5% of the total dry basis mass of fly ash, calcium supplementary materials, and heavy metal stabilizer.

[0010] Preferably, the highly active stabilized fly ash output by the synergistic grinding and activation unit has an effective calcium oxide content of not less than 35%, a particle size D50 of 10 μm to 15 μm, and a specific surface area of ​​10 m². 2 / g~20m 2 / g.

[0011] Preferably, the grinding device is a closed-loop grinding system.

[0012] This invention also provides a method for desulfurizing fly ash-recycled flue gas, comprising the following steps: S1. Fly ash pretreatment: The raw fly ash is dechlorinated and dried to obtain fly ash with a moisture content of 8% to 15%. S2, Co-grinding and activation: The fly ash obtained in step S1 is mixed with supplemented calcium-based materials and heavy metal stabilizers and mechanically ground and activated to form highly active stabilized fly ash. S3. Staged Re-spraying Utilization: The highly active stabilized fly ash obtained in step S2 is diverted and transported to the 850℃~900℃ temperature zone of the waste incinerator and the semi-dry reaction tower for re-spraying utilization to facilitate acid removal.

[0013] Preferably, the heavy metal stabilizer includes at least one of calcium dihydrogen phosphate, calcium phosphate, and silicate, and its addition amount is 3%-5% of the total dry basis mass of fly ash, calcium supplementary materials, and heavy metal stabilizer.

[0014] Preferably, the highly active stabilized fly ash has an effective calcium oxide content of not less than 35%, a particle size D50 of 10 μm to 15 μm, and a specific surface area of ​​10 m². 2 / g~20m 2 / g.

[0015] The beneficial effects of this invention are as follows: By connecting the fly ash pretreatment unit, the co-grinding and activation unit, and the fly ash staged re-spraying unit, fly ash is recycled as a resource, constructing a complete and coherent industrial system from "waste" to "agent" to "use." Each unit has a clearly defined function and is closely integrated, solving the problems of fragmented processes and unstable operation in previous technologies. The proposed co-grinding and activation process integrates multiple functions, resulting in a short process flow and high efficiency. Clearly defined pretreatment indicators (moisture content 8%-15%) and final product indicators (CaO≥35%, D50=10-15μm) ensure the reliability of the process and the stability of product performance, laying the foundation for large-scale engineering applications. Stabilization treatment at the system's front end eliminates environmental risks, and staged re-spraying maximizes deacidification efficiency, achieving a balance between environmental and economic benefits. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1 This is a connection diagram of a fly ash recycling flue gas deacidification system according to an embodiment of the present invention. Detailed Implementation

[0017] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0018] like Figure 1 As shown, an embodiment of the fly ash reuse flue gas desulfurization system of the present invention includes a fly ash pretreatment unit 10, a co-grinding and activation unit 20, and a fly ash grading and re-spraying unit 30 connected in sequence.

[0019] The fly ash pretreatment unit 10 is used to wash, dechlorinate, and dry the original fly ash, outputting fly ash with a moisture content of 8% to 15%; the co-grinding and activation unit 20 is used to grind and activate the pretreated fly ash; and the fly ash grading and re-spraying unit 30 is used to meter and divert the ground and activated fly ash to achieve fly ash reuse.

[0020] The raw fly ash first enters the fly ash pretreatment unit 10, where it undergoes three-stage countercurrent water washing and dechlorination (to reduce the water-soluble chloride content to below 1.5%) and drying treatment, stabilizing the fly ash moisture content at around 10% (range 8%–15%), creating optimal material conditions for subsequent grinding. Specifically, the fly ash pretreatment unit 10 may include a fly ash storage silo 11, a pulping tank 12, a multi-stage countercurrent water washing device 13, a solid-liquid separation device 14, and a drying device 15 connected in sequence. The fly ash storage silo 11 is used to receive and store the raw fly ash and sends it to the pulping tank 12, where the fly ash is mixed with water. The multi-stage countercurrent water washing device 13 performs three-stage countercurrent water washing and dechlorination, and after completion, it is conveyed to the solid-liquid separation device 14 for solid-liquid separation. The separated solid is then sent to the drying device 15 for drying treatment.

[0021] Among them, the solid-liquid separation device 14 is preferably a plate and frame filter press solid-liquid separation device; the drying device 15 is preferably a paddle dryer.

[0022] The drying device 15 of the fly ash pretreatment unit 10 is connected to the co-grinding and activation unit 20. Fly ash that has undergone pretreatment and reached the required moisture content enters the co-grinding and activation unit 20 from the drying device 15. The co-grinding and activation unit 20 specifically includes a raw material mixing device 21 and a grinding device 22. The drying device 15 of the fly ash pretreatment unit 10 is connected to the raw material mixing device 21 to deliver the pretreated fly ash to the raw material mixing device 21. The raw material mixing device 21 is used to mix fly ash with calcium-based materials (including quicklime powder) and heavy metal stabilizers to form a mixture. The grinding device 22 receives the mixture from the raw material mixing device 21 and grinds and activates the mixture.

[0023] The raw material mixing device 21 can be a stirring mixing device; the grinding device 22 can be a stirring grinding device or a planetary grinding device.

[0024] The heavy metal stabilizer includes at least one of calcium dihydrogen phosphate, calcium phosphate, and silicate, and its addition amount is 3% to 5% of the total dry basis mass of fly ash, calcium supplementary materials, and heavy metal stabilizer.

[0025] In the co-grinding activation unit 20, fly ash, supplemented quicklime powder, and 3%–5% (by dry weight) of calcium dihydrogen phosphate stabilizer are premixed in the raw material mixing device 21 and then fed into the grinding device 22. The mixture is co-grinded to a particle size D50 of 10 μm–15 μm and a specific surface area increased to 10 m². 2 / g~20m 2 / g, this process not only refines the particles, but also achieves molecular-level mixing of the components and in-situ stabilization of heavy metals, producing highly active stabilized fly ash with an effective CaO content of not less than 35%.

[0026] The grinding device 22 is preferably a closed-loop circulation grinding system to avoid dust from flying.

[0027] The highly active stabilized fly ash finally enters the fly ash classification and re-injection unit 30. The fly ash classification and re-injection unit 30 may further include an activation ash bin 31, a metering feeder 32, and a pneumatic conveying and injection device 33 connected in sequence. The highly active stabilized fly ash enters the fly ash classification and re-injection unit 30, is first stored in the activation ash bin 31, and then, after being regulated by the metering feeder 32, is conveyed by the pneumatic conveying and injection device 33 to the flue gas system for recycling (reuse). Depending on the reuse requirements, it can be divided into two or more independent conveying paths.

[0028] In one embodiment, the pneumatic conveying jet device 33 delivers gas in two independent paths. One path delivers the gas to the high-temperature zone (approximately 900°C) at the top of the incinerator 40 (e.g., a waste incinerator), where it rapidly achieves preliminary deacidification (primarily HCl removal) at high temperatures. The other path delivers the gas to the inlet flue of the semi-dry reaction tower 50, where it works in conjunction with lime slurry at a lower temperature (140°C–160°C) to complete deep desulfurization and deacidification. The delivery ratio of the two paths can be optimized and adjusted online according to actual flue gas parameters. After purification, the flue gas passes through a bag filter 60 to collect solid products, achieving ultra-low emissions. The dust collected by the bag filter 60 can also be returned to the fly ash pretreatment unit 10 for further recycling, improving resource utilization.

[0029] refer to Figure 1 An embodiment of the fly ash reuse flue gas desulfurization method of the present invention may include the following steps: S1. Fly ash pretreatment: The raw fly ash (hereinafter referred to as raw ash) is washed with water to remove chlorine and dried to obtain fly ash with a moisture content of 8% to 15%.

[0030] Fly ash pretreatment is achieved using the fly ash pretreatment unit 10 of the fly ash recycling flue gas desulfurization system. Specifically, the raw fly ash first enters the fly ash pretreatment unit 10, where it undergoes three-stage countercurrent water washing and dechlorination (to reduce the water-soluble chloride content to below 1.5%) and drying treatment, stabilizing the fly ash moisture content at 8% to 15%, thus creating optimal material conditions for subsequent grinding.

[0031] S2, Co-grinding and activation: The fly ash obtained in step S1 is mixed with supplemented calcium-based materials and heavy metal stabilizers and mechanically ground and activated to form highly active stabilized fly ash.

[0032] The heavy metal stabilizer includes at least one of calcium dihydrogen phosphate, calcium phosphate, and silicate, and its addition amount is 3% to 5% of the total dry basis mass of fly ash, calcium supplementary materials, and heavy metal stabilizer.

[0033] Highly active stabilized fly ash has an effective calcium oxide content of no less than 35%, a particle size D50 of 10μm to 15μm, and a specific surface area of ​​10m². 2 / g~20m 2 / g.

[0034] The co-grinding activation is achieved using the co-grinding activation unit 20 of the fly ash recycling flue gas deacidification system.

[0035] The drying device 15 of the fly ash pretreatment unit 10 is connected to the co-grinding and activation unit 20. Fly ash that has undergone pretreatment and reached the required moisture content enters the co-grinding and activation unit 20 from the drying device 15. The co-grinding and activation unit 20 specifically includes a raw material mixing device 21 and a grinding device 22. The drying device 15 of the fly ash pretreatment unit 10 is connected to the raw material mixing device 21 to deliver the pretreated fly ash to the raw material mixing device 21. The raw material mixing device 21 is used to mix fly ash with calcium-based materials (including quicklime powder) and heavy metal stabilizers to form a mixture. The grinding device 22 receives the mixture from the raw material mixing device 21 and grinds and activates the mixture.

[0036] In the co-grinding activation unit 20, fly ash, supplemented quicklime powder, and 3%–5% (by dry weight) of calcium dihydrogen phosphate stabilizer are premixed in the raw material mixing device 21 and then fed into the grinding device 22. The mixture is co-grinded to a particle size D50 of 10 μm–15 μm and a specific surface area increased to 10 m². 2 / g~20m 2 This process not only refines the particles but also achieves molecular-level mixing of the components and in-situ stabilization of heavy metals, producing highly active stabilized fly ash with an effective CaO content of approximately 38%. The highly active stabilized fly ash output from the co-grinding and activation unit has an effective calcium oxide content of no less than 35%, a particle size D50 of 10μm to 15μm, and a specific surface area of ​​10m². 2 / g~20m 2 / g.

[0037] S3. Staged Re-spraying Utilization: The highly active stabilized fly ash obtained in step S2 is diverted and transported to the upper high-temperature zone (850℃~900℃ temperature zone) in the incinerator and the semi-dry reaction tower for re-spraying utilization to facilitate acid removal.

[0038] The graded re-injection is achieved using the fly ash graded re-injection unit 30 of the fly ash recycling flue gas desulfurization system.

[0039] Specifically, the highly active stabilized fly ash enters the fly ash grading and re-spraying unit 30, is first stored in the activation ash bin 31, then is regulated by the metering feeder 32, and then transported and recovered by the pneumatic conveying and spraying device 33.

[0040] The pneumatic conveying and injection device 33 can be independently conveyed in two paths. One path conveys the gas to the high-temperature zone (approximately 900°C) at the top of the incinerator 40 (such as a waste incinerator), where it rapidly achieves preliminary deacidification (mainly HCl removal) at high temperatures. The other path conveys the gas to the inlet flue of the semi-dry reaction tower 50, where it works in conjunction with lime slurry at a lower temperature (140°C–160°C) to complete deep desulfurization and deacidification. The conveying ratio of the two paths can be optimized and adjusted online according to actual flue gas parameters. After purification, the flue gas passes through a bag filter 60 to collect solid products, achieving ultra-low emissions. The dust collected by the bag filter 60 can also be returned to the fly ash pretreatment unit 10 for further recycling, improving resource utilization.

[0041] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A fly ash recycling flue gas desulfurization system, characterized in that, It includes a fly ash pretreatment unit for washing, dechlorinating and drying fly ash, a co-grinding and activation unit for grinding and activating fly ash, and a fly ash grading and re-spraying unit for metering and diverting the ground and activated fly ash. The co-grinding and activation unit includes a raw material mixing device for mixing fly ash with calcium-based materials and heavy metal stabilizers to form a mixture, and a grinding device for grinding and activating the mixture. The fly ash grading and re-spraying unit includes an activated ash silo, a metering feeding device, and a pneumatic conveying and spraying device connected in sequence.

2. The fly ash reuse flue gas desulfurization system according to claim 1, characterized in that, The fly ash pretreatment unit outputs fly ash with a moisture content of 8% to 15%.

3. The fly ash reuse flue gas desulfurization system according to claim 1, characterized in that, The raw material mixing device is a stirring type mixing device; the grinding device is a stirring type grinding device or a planetary type grinding device.

4. The fly ash reuse flue gas desulfurization system according to claim 1, characterized in that, The fly ash pretreatment unit includes a fly ash storage silo, a pulping tank, a multi-stage countercurrent washing device, a solid-liquid separation device, and a drying device connected in sequence; the drying device is connected to the raw material mixing device.

5. The fly ash reuse flue gas desulfurization system according to claim 1, characterized in that, The heavy metal stabilizer includes at least one of calcium dihydrogen phosphate, calcium phosphate, and silicate, and its addition amount is 3% to 5% of the total dry basis mass of fly ash, calcium supplementary materials, and heavy metal stabilizer.

6. The fly ash reuse flue gas desulfurization system according to claim 1, characterized in that, The highly active stabilized fly ash output by the synergistic grinding and activation unit has an effective calcium oxide content of not less than 35%, a particle size D50 of 10μm to 15μm, and a specific surface area of ​​10m². 2 / g~20m 2 / g.

7. The fly ash reuse flue gas desulfurization system according to claim 1, characterized in that, The grinding device is a closed-loop grinding system.

8. A method for desulfurizing fly ash-recycled flue gas, characterized in that, Includes the following steps: S1. Fly ash pretreatment: The raw fly ash is washed with water to remove chlorine and dried to obtain fly ash with a moisture content of 8% to 15%. S2, Co-grinding and activation: The fly ash obtained in step S1 is mixed with supplemented calcium-based materials and heavy metal stabilizers and mechanically ground and activated to form highly active stabilized fly ash. S3. Staged Re-spraying Utilization: The highly active stabilized fly ash obtained in step S2 is diverted and transported to the 850℃~900℃ temperature zone of the waste incinerator and the semi-dry reaction tower for re-spraying utilization to facilitate acid removal.

9. The method for desulfurizing fly ash-recycled flue gas according to claim 8, characterized in that, The heavy metal stabilizer includes at least one of calcium dihydrogen phosphate, calcium phosphate, and silicate, and its addition amount is 3% to 5% of the total dry basis mass of fly ash, calcium supplementary materials, and heavy metal stabilizer.

10. The method for desulfurizing fly ash-recycled flue gas according to claim 8, characterized in that, The highly active stabilized fly ash has an effective calcium oxide content of not less than 35%, a particle size D50 of 10μm to 15μm, and a specific surface area of ​​10m². 2 / g~20m 2 / g.

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