Low-cost continuous carbon sequestration method for dry ash storage of thermal power plants

Abstract

The application provides a low-cost continuous carbon sequestration method for a dry ash storage of a thermal power plant, comprising the following steps: performing in-situ modification on an original dry ash storage of the thermal power plant to achieve sealing, and sealingly conveying dry fly ash after dust removal of the power plant to the modified dry ash storage; introducing low-concentration flue gas of the power plant after trace humidification as a gas-solid reaction medium, and simultaneously applying microwave activation and fluidization stirring to the dry fly ash; performing first-stage pre-mineralization on the dry fly ash in a first-stage pre-mineralization bin, and then performing second-stage deep mineralization on the dry fly ash in a second-stage deep mineralization bin, so as to continuously and gradiently sequestrate carbon dioxide of the dry fly ash, and return uncompletely reacted fly ash to the first-stage pre-mineralization bin for reaction again; and returning residual flue gas after the mineralization reaction to an original dust removal system of the power plant through a closed loop pipeline for unified dust removal and purification. One technical effect of the application is that zero wastewater, zero dust, low energy consumption, continuous CO2 mineralization and sealing can be realized, and the activity of the mineralized ash can be accurately controlled, and high-value building material resource utilization of the product can be realized.

Description

Technical Field

[0001] This invention belongs to the technical field of carbon dioxide (CO2) mineralization and storage in flue gas of thermal power plants and the resource utilization of fly ash. Specifically, it relates to a low-cost, continuous carbon fixation method for dry ash silos in thermal power plants, and more particularly to a method that relies on the existing dry ash silos in thermal power plants for in-situ closed modification, and achieves continuous mineralization and carbon fixation of fly ash and flue gas CO2 under low temperature and normal pressure conditions to produce highly active building material admixtures. Background Technology

[0002] Currently, fly ash CO2 mineralization and carbon sequestration technologies are mainly divided into two categories: wet mineralization and traditional dry mineralization. Both mainstream technologies have significant shortcomings in engineering implementation, which seriously restricts the large-scale promotion of low-carbon retrofitting of existing thermal power units.

[0003] Specifically, the main drawbacks of the wet mineralization process are: First, high water consumption and severe secondary pollution. Wet mineralization relies heavily on industrial water for pulping, resulting in large water resource consumption; the reaction process generates a large amount of secondary wastewater, and wastewater treatment procedures are cumbersome and costly, making it unsuitable for the technological upgrading of thermal power plants in water-scarce areas. Second, high infrastructure investment and large land area. The wet process requires a separate mineralization reaction workshop and specialized reaction equipment, resulting in large civil engineering works, extensive equipment footprint, and high new infrastructure investment, making it extremely unsuitable for the technological upgrading of existing power plants. Furthermore, environmental issues are prominent. The transfer of fly ash and the wet pulping process are prone to dust emission and slurry leakage, leading to low overall carbon sequestration and treatment benefits.

[0004] The main drawbacks of traditional dry mineralization processes are twofold: First, they are subject to harsh operating conditions and extremely high energy consumption. To ensure efficient gas-solid mineralization reactions, traditional dry mineralization processes generally rely on high-temperature, high-pressure reaction conditions, resulting in extremely high system energy consumption. They require specialized heating and pressurization equipment, making them unsuitable for the conventional low-temperature, normal-pressure conditions of existing thermal power plants. This leads to significant modification difficulties, high operating costs, and challenges in achieving continuous and stable industrial operation. Furthermore, the reactions are uneven, and the carbon fixation rate is low. Existing dry carbon fixation systems lack staged reactions and material recycling designs, resulting in uneven fly ash mineralization reactions, low carbon fixation rates, and the inability to reuse unreacted fly ash, leading to substantial raw material waste. Second, the lack of closed-loop flue gas treatment and the tendency for emissions are significant. The absence of closed-loop flue gas treatment during the mineralization process easily leads to environmental problems such as dust emissions and flue gas escape, making it impossible to achieve near-zero emissions throughout the process. Moreover, the products exhibit unstable activity and low added value. Existing mineralization technologies only focus on CO2 sequestration and have not achieved high-value resource utilization of fly ash products. The activity of mineralized ash is unstable and cannot be directly used on a large scale in the building materials field, resulting in low added value of carbon sequestration technology.

[0005] In addition, especially for water-scarce areas and suburban thermal power plants, where water resources are scarce, land resources in the plant area are limited, and environmental protection controls are strict, traditional wet and dry carbon sequestration technologies, which are high in water consumption, large in land area, and high in energy consumption, are completely unsuitable.

[0006] In summary, existing technologies generally suffer from drawbacks such as high energy consumption, high retrofit costs, large water consumption, poor environmental performance, and low product utilization. There is an urgent need for a simple and low-cost carbon sequestration technology that requires zero additional land occupation, has low energy and water consumption, operates continuously, and allows for high-value utilization of products, in order to fill the technological gap in the dry-process simple and low-carbon technical retrofitting of existing power plants and carbon sequestration of thermal power plants in water-scarce areas. Summary of the Invention

[0007] This invention aims to solve at least one of the technical problems existing in the prior art by providing a new technical solution for a low-cost, continuous carbon sequestration method for dry ash silos in thermal power plants. It is a low-cost, water-saving carbon sequestration technology system specifically designed for existing thermal power plants, featuring a simplified dry process retrofit. It utilizes the existing dry ash silos in thermal power plants for in-situ, closed-loop retrofitting, eliminating the need for new plant buildings and independent reaction equipment. Under low-temperature and normal-pressure conditions, it achieves a highly efficient gas-solid mineralization reaction between fly ash and flue gas CO2. Through an integrated process including microwave activation, fluidized bed stirring enhancement, staged dual-compartment reaction, material recycling, closed-loop flue gas dust removal, and trace amounts of recycled water humidification, it achieves zero wastewater, zero dust, low energy consumption, and continuous CO2 mineralization and storage. Simultaneously, it precisely controls the activity of the mineralized ash, enabling the high-value building material resource utilization of the product.

[0008] According to a first aspect of the present invention, a low-cost, continuous carbon sequestration method for a dry ash silo in a thermal power plant is provided, comprising the following steps: Step S1: In-situ sealed modification and sealed ash conveying of the dry ash silo. The existing dry ash silo of the thermal power plant is modified to be sealed in situ, and the dry fly ash after dust removal from the power plant is conveyed to the modified dry ash silo in a sealed manner.

[0009] Specifically, the existing mature dry ash storage equipment in the power plant is completely renovated in a closed and modular manner, sealing the open structure of the ash storage and equipping it with closed ash conveying and closed flue gas introduction devices. There is no need to add new civil engineering plants or build independent reaction workshops, completely eliminating the high infrastructure investment of traditional carbon sequestration processes, minimizing the cost of low-carbon transformation of existing power plants, and adapting to thermal power scenarios with limited land resources in various plant areas.

[0010] Step S2, Low-temperature and ambient-pressure microwave fluidized coupled dry mineralization. Low-concentration flue gas from a power plant, slightly humidified, is introduced as the gas-solid reaction medium. Under low-temperature and ambient-pressure conditions, microwave activation and fluidized stirring are simultaneously applied to the dry fly ash to activate the activity of calcium and magnesium minerals within the fly ash and enhance gas-solid contact, causing the fly ash to undergo a mineralization reaction with CO2 in the flue gas to generate stable carbonates.

[0011] Specifically, the traditional high-temperature, high-pressure dry reaction process is abandoned in favor of a low-temperature, normal-pressure reaction mode. Dry fly ash from the power plant, after dust removal, is transported in a sealed container to the modified ash silo. Low-concentration flue gas from the power plant, with a small amount of humidified ash, is introduced, using a small amount of water vapor as the gas-solid reaction medium. An integrated fluidized bed agitator and microwave-assisted activation device are used. Microwave action activates the free calcium and magnesium minerals within the fly ash, and combined with fluidized bed agitation to enhance gas-solid contact, efficiently triggering the mineralization reaction between fly ash and CO2 at normal temperature and pressure. This generates stable calcium carbonate and silica-alumina composite carbonates, achieving permanent CO2 sequestration.

[0012] Step S3, graded continuous gradient carbon fixation. The dry ash silo is divided into a primary pre-mineralization silo and a secondary deep mineralization silo. The dry fly ash first undergoes primary pre-mineralization in the primary pre-mineralization silo, and then undergoes secondary deep mineralization in the secondary deep mineralization silo, so as to carry out continuous gradient carbon fixation of the dry fly ash. The incompletely reacted fly ash is returned to the primary pre-mineralization silo for further reaction, so as to obtain continuous discharge of mineralized ash.

[0013] Specifically, the sealed ash silo is divided into a two-stage structure: a primary pre-mineralization chamber and a secondary deep mineralization chamber, constructing a continuous gradient carbon fixation process. Fly ash first enters the primary pre-mineralization chamber to complete the initial mineralization reaction, weakening the surface inert components; then it enters the secondary deep mineralization chamber for deep mineralization and carbon fixation; incompletely reacted fly ash is recycled back to the primary pre-mineralization chamber for secondary reaction through a reflux system, completely solving the problems of uneven mineralization reaction and low raw material utilization in traditional dry processes, ensuring continuous, large-scale, and stable carbon fixation production.

[0014] Step S4, closed-loop dust removal of flue gas. The residual flue gas after the mineralization reaction is returned to the power plant's existing dust removal system for unified dust removal and purification through a closed-loop pipeline.

[0015] Specifically, the residual flue gas after the mineralization reaction is returned to the power plant's original dust removal system through a closed-loop pipeline for unified dust removal and purification treatment. The entire process is dust-free and flue gas-free, completely solving the dust pollution problem of dry fly ash treatment.

[0016] Regarding the water used for micro-humidification of the reaction medium: The water used for micro-humidification of the flue gas in step S2 is taken from the reclaimed water of the power plant. All the water required for micro-humidification of the reaction is taken from the reclaimed water of the power plant. There is no industrial water consumption or discharge of production wastewater throughout the process, and the water consumption is extremely low, which is perfectly suited to the low-carbon transformation needs of thermal power plants in water-scarce areas.

[0017] Regarding the precise control of mineralized ash activity and high-value resource utilization: By adjusting the microwave activation power, flue gas humidification amount and mineralization residence time in a coordinated manner, the carbonate content and material activity of the obtained mineralized ash are controlled to produce highly active calcium carbonate-silica-alumina composite ash slag, which can be used as a low-carbon building material admixture for cement preparation or roadbed building materials.

[0018] Specifically, by precisely controlling the microwave activation power, flue gas humidification amount, and mineralization residence time, the composition and activity of the mineralization products are stably controlled, and highly active calcium carbonate-silica aluminum composite ash is prepared. The product has uniform performance and strong stability, and can be directly used as a low-carbon building material admixture. It can be applied on a large scale in cement preparation, roadbed building materials and other fields, realizing the triple benefits of carbon sequestration, solid waste disposal and high-value utilization of building materials.

[0019] Preferably, the dry ash silo is equipped with a fluidizing agitator and a microwave-assisted activation device; the microwave-assisted activation device activates the free calcium and magnesium minerals inside the fly ash at low temperature and normal pressure; the fluidizing agitator fluidizes the fly ash to enhance gas-solid contact.

[0020] Preferably, in step S2, the microwave activation power, flue gas moisture content, and fluidization velocity are synergistically adjusted according to the mineralization reaction rate and carbon fixation rate.

[0021] Preferably, the microwave activation power is 10 kW.

[0022] Preferably, the moisture content of the flue gas after micro-humidification is 6%.

[0023] Preferably, the fluidization velocity is 1.5 m / s; and the microwave activation power, flue gas moisture content, and fluidization velocity are synergistically adjusted according to the mineralization reaction rate and carbon fixation rate.

[0024] Preferably, the residence time for primary premineralization is 30 min, the residence time for secondary deep mineralization is 40 min, and the total residence time for graded mineralization is 70 min; the residence time for primary premineralization is shorter than the residence time for secondary deep mineralization.

[0025] Preferably, the proportion of incompletely reacted fly ash returned to the primary pre-mineralization bin is 40% of the discharge.

[0026] One technical advantage of this invention is that: In this embodiment, the low-cost continuous carbon sequestration method for dry ash silos in thermal power plants relies on the in-situ sealed renovation of the existing dry ash silos in the power plant to construct a simple and low-cost carbon sequestration technology system with low temperature and normal pressure, low water consumption, zero additional land occupation, continuous carbon sequestration, and high-value utilization of products. This fills the technological gap in the dry-process simple and low-carbon technical renovation of existing power plants and the carbon sequestration of thermal power plants in water-scarce areas. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a low-cost, continuous carbon sequestration method for a dry ash silo in a thermal power plant, according to an embodiment of the present invention. Detailed Implementation

[0028] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0029] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0030] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0031] Example 1 This embodiment provides a low-cost, continuous carbon sequestration method for dry ash silos in thermal power plants, the process flow of which is as follows: Figure 1 As shown, it includes the following steps: Step S1 involves making the existing dry ash silo in the thermal power plant a sealed, in-situ modification, and then conveying the dry fly ash after dust removal from the power plant to the modified dry ash silo in a sealed manner.

[0032] Step S2 involves introducing slightly humidified low-concentration flue gas from the power plant as the gas-solid reaction medium, and simultaneously applying microwave activation and fluidized agitation to the dry fly ash under low-temperature and normal-pressure conditions. The microwave-assisted activation device activates the free calcium and magnesium minerals within the fly ash at low temperature and normal pressure; the fluidized agitation device fluidizes the fly ash to enhance gas-solid contact; the fly ash reacts with CO2 in the flue gas to form stable carbonates (calcium carbonate and silica-alumina composite carbonates). The water used for slight humidification is taken from the power plant's wastewater.

[0033] Step S3, graded continuous gradient carbon fixation: The dry ash silo is divided into a primary pre-mineralization bin and a secondary deep mineralization bin. The dry fly ash first undergoes primary pre-mineralization (preliminary mineralization, weakening of surface inert components) in the primary pre-mineralization bin, and then undergoes secondary deep mineralization (deep carbon fixation) in the secondary deep mineralization bin, achieving continuous gradient carbon fixation; the fly ash discharged from the secondary deep mineralization bin that has not fully reacted is returned to the primary pre-mineralization bin for further reaction, resulting in continuous discharge of mineralized ash.

[0034] Step S4, closed-loop dust removal of flue gas: The residual flue gas after the mineralization reaction is returned to the power plant's original dust removal system through a closed-loop pipeline for unified dust removal and purification, so as to achieve no dust discharge and no flue gas escape throughout the process.

[0035] In the above embodiments, the low-cost continuous carbon sequestration method for dry ash silos in thermal power plants has the following technical advantages: 1. Low renovation cost and zero additional land occupation. This invention relies on the existing dry ash storage of thermal power plants for in-situ sealed renovation, without the need to build new independent reaction plants and special reaction equipment. It fundamentally eliminates the high civil engineering and equipment investment of traditional wet and dry mineralization methods, and is suitable for existing power plants with tight land resources and low-carbon technological transformation of thermal power plants in water-scarce areas.

[0036] 2. Low energy consumption and suitable for conventional power plant operating conditions. This invention completes the mineralization reaction of fly ash and flue gas CO2 at low temperature and normal pressure, eliminating the high temperature and high pressure conditions of traditional dry methods. It does not require special heating and pressurization equipment, significantly reducing system energy consumption and enabling continuous and stable industrial operation.

[0037] 3. Low water consumption and no secondary wastewater. This invention uses only a small amount of humidified flue gas as the gas-solid reaction medium to replace wet pulping, resulting in extremely low water consumption and no secondary wastewater generation, thus overcoming the problems of high water consumption and wastewater treatment in wet mineralization.

[0038] 4. High carbon fixation rate and uniform reaction. Microwave activation efficiently stimulates the activity of calcium and magnesium minerals inside fly ash, and fluidized stirring enhances the full contact between gas and solid. The coupling of the two enables the mineralization reaction at room temperature and pressure to generate stable carbonates efficiently and uniformly, achieving permanent CO2 sequestration.

[0039] 5. Continuous operation and high raw material utilization. The graded gradient reaction of primary pre-mineralization and secondary deep mineralization, the recirculation and re-reaction of incompletely reacted fly ash, and continuous discharge work together to overcome the defects of uneven reaction, low carbon fixation rate, and raw material waste in traditional dry processes, and achieve continuous, large-scale, and stable carbon fixation production.

[0040] 6. Near-zero emissions and environmentally friendly. The residual flue gas from mineralization is returned to the power plant's existing dust removal system through a closed-loop pipeline for unified purification, with no dust emissions or flue gas escape throughout the process; the existing dust removal system is reused and no new dust removal equipment is required.

[0041] In summary, the synergistic effect of the aforementioned technical features enables continuous, high-carbon-fixing-rate, and near-zero-emission mineralization and storage of fly ash and flue gas CO2 from thermal power plants without requiring new infrastructure or land occupation, relying on high temperatures and pressures, or generating secondary wastewater. This demonstrates outstanding substantive characteristics and significant technological advancements. The optimal process parameters for this embodiment are: microwave activation power 10 kW, flue gas moisture content 6%, fluidization velocity 1.5 m / s, primary pre-mineralization residence time 30 min, secondary deep mineralization residence time 40 min, and reflux ratio 40%. The basis for the values ​​of each parameter and the optimization process are described in Examples 2 to 5.

[0042] Example 2: Microwave activation power difference comparison (core factor: mineral activation efficiency and energy consumption matching degree).

[0043] This embodiment investigates the effect of microwave activation power on mineralization. With fixed flue gas humidification moisture content of 6%, fluidization velocity of 1.5 m / s, total residence time for staged mineralization of 70 min (30 min for primary pre-mineralization and 40 min for secondary deep mineralization), and material recirculation ratio of 40%, five microwave activation power gradients were set: 0 kW, 5 kW, 10 kW, 15 kW, and 20 kW.

[0044] The experimental results show that: 0 kW (without microwave activation): Fly ash has low calcium and magnesium mineral activity, extremely slow gas-solid reaction rate, and low CO2 mineralization rate. 5 kW: Insufficient activation, limited improvement in mineral activity; 10 kW: The inert components of fly ash are effectively activated, the mineralization reaction rate and carbon fixation rate are greatly improved, and the energy consumption cost-effectiveness is optimal. 15 kW and 20 kW (high power): Local overheating and sintering of fly ash are likely to occur, mineral structure is damaged, the activity of mineralized ash decreases, and system energy consumption increases significantly, resulting in a significant reduction in economic efficiency.

[0045] In summary, the optimal microwave activation power is 10 kW.

[0046] Example 3: Differential comparison of flue gas humidification moisture content (core factors: reaction medium and water-saving balance).

[0047] This embodiment investigates the effect of flue gas humidification moisture content on mineralization. The optimal microwave activation power was fixed at 10 kW, fluidization velocity at 1.5 m / s, total residence time for staged mineralization at 70 min (30 min for primary pre-mineralization and 40 min for secondary deep mineralization), and reflux ratio at 40%. Five flue gas humidification moisture content gradients were set: 2%, 4%, 6%, 8%, and 10%.

[0048] The experimental results show that: 2% and 4% (low moisture content): insufficient hydroxyl groups in the reaction medium, incomplete gas-solid mineralization reaction, and low carbon fixation efficiency; 6%: Provides sufficient reaction medium, achieves peak mineralization efficiency, leaves no excess water residue, and generates no wastewater throughout the process; 8% or 10% (high moisture content): Excessive humidity inside the ash silo makes fly ash prone to moisture absorption, caking, and agglomeration, hindering gas-solid contact, resulting in decreased mineralization uniformity, and increasing the system's dehumidification energy consumption.

[0049] In summary, the optimal humidification moisture content for flue gas is 6%. The humidification water is taken from the power plant's reclaimed water, and there is no industrial water consumption or discharge of production wastewater throughout the entire process.

[0050] Example 4: Comparison of fluidized air velocity differences in ash silos (core factor: uniformity of gas-solid contact).

[0051] This embodiment investigates the effect of fluidization velocity in the ash silo on the mineralization effect. With fixed microwave activation power of 10 kW, flue gas humidification moisture content of 6%, total residence time for staged mineralization of 70 min (30 min for primary pre-mineralization and 40 min for secondary deep mineralization), and a recirculation ratio of 40%, five fluidization velocity gradients were set: 0.5 m / s, 1.0 m / s, 1.5 m / s, 2.0 m / s, and 2.5 m / s.

[0052] The experimental results show that: 0.5 m / s, 1.0 m / s (low wind speed): insufficient fluidization of fly ash, material accumulation, serious local dead corners, uneven gas-solid contact, and large differences in mineralization effect; 1.5 m / s: Fly ash is completely and uniformly fluidized, with no accumulation or escape, the gas-solid mass transfer efficiency is optimal, and the mineralization uniformity is the highest. 2.0 m / s, 2.5 m / s (high wind speed): Fine-grained fly ash is easily carried away by flue gas and escapes, increasing material loss and reducing system stability.

[0053] In summary, the optimal fluidization velocity is 1.5 m / s.

[0054] Example 5: Comparative Study of Differentiated Retention Time in Graded Mineralization (Core Factors: Carbon Sequestration Adequacy and Production Capacity Balance).

[0055] This embodiment investigates the effect of different residence time combinations in staged mineralization on the mineralization effect. A complete set of optimal static parameters was fixed (microwave activation power 10 kW, flue gas humidification moisture content 6%, fluidization velocity 1.5 m / s, recirculation ratio 40%), and five combinations of staged residence times were set: pre-mineralization 20 min + deep mineralization 30 min, pre-mineralization 30 min + deep mineralization 40 min, pre-mineralization 40 min + deep mineralization 50 min, pre-mineralization 50 min + deep mineralization 60 min, and pre-mineralization 60 min + deep mineralization 70 min.

[0056] The experimental results show that: Short residence time combinations (e.g., pre-mineralization 20 min + deep mineralization 30 min): fly ash mineralization is incomplete, carbonate content is low, and product activity is insufficient. Pre-mineralization for 30 min + deep mineralization for 40 min (total residence time 70 min): sufficient mineralization, stable product performance, and optimal matching of production capacity and carbon sequestration efficiency; Excessively long residence time combinations: No carbon fixation gain effect, but instead reduce the continuous output capacity of the system and affect the efficiency of large-scale operation.

[0057] In summary, the optimal residence time for each stage is 30 min for primary pre-mineralization and 40 min for secondary deep mineralization (total residence time 70 min), with the residence time for primary pre-mineralization being shorter than that for secondary deep mineralization.

[0058] It should be noted that this application enables precise control of the activity of mineralized ash and high-value resource utilization. Specifically, by adjusting the microwave activation power, flue gas humidification rate, and mineralization residence time in a coordinated manner, the carbonate content and material activity of the resulting mineralized ash are controlled. Under the optimal parameter combination determined in Examples 2-5 (microwave activation power 10 kW, flue gas humidification moisture content 6%, fluidization velocity 1.5 m / s, primary pre-mineralization for 30 min and secondary deep mineralization for 40 min, reflux ratio 40%), fly ash is fully and uniformly mineralized, yielding highly active calcium carbonate-alumina silicate composite ash. Moreover, the resulting mineralized ash exhibits uniform performance and strong stability, and can be directly used as a low-carbon building material admixture for large-scale application in cement preparation, roadbed construction materials, and other fields. This invention thus achieves a triple benefit: carbon sequestration (permanent CO2 storage), solid waste disposal (fly ash utilization), and high-value utilization in building materials.

[0059] Furthermore, this application achieves closed-loop dust removal of flue gas and zero wastewater reuse. Specifically, the residual flue gas after the mineralization reaction is returned to the power plant's existing dust removal system through a closed-loop pipeline for unified dust removal and purification treatment. The entire process is dust-free and flue gas-free, achieving near-zero emissions. The trace amounts of humidification water required for the reaction are all taken from the power plant's reclaimed water, with no industrial water consumption or production wastewater discharge throughout the process. Water consumption is extremely low, making it suitable for the low-carbon retrofitting needs of thermal power plants in water-scarce areas.

[0060] It should be noted that the specific values ​​given in the above embodiments, such as microwave activation power of 10 kW, flue gas humidification moisture content of 6%, fluidization velocity of 1.5 m / s, primary pre-mineralization residence time of 30 min, secondary deep mineralization residence time of 40 min, total residence time of 70 min, and reflux ratio of 40%, are all optimal values ​​determined through differentiated control experiments. These values ​​are intended to enable those skilled in the art to implement the present invention and do not constitute an undue limitation on the scope of protection of the claims. Those skilled in the art can make appropriate adjustments to the parameters based on actual operating conditions such as fly ash source, flue gas CO2 concentration, and production capacity requirements, which are still within the scope of protection of the present invention.

[0061] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A low-cost, continuous carbon sequestration method for dry ash silos in thermal power plants, characterized in that, Includes the following steps: Step S1: The existing dry ash silo of the thermal power plant is modified to be sealed in situ, and the dry fly ash after dust removal of the power plant is transported in a sealed manner to the modified dry ash silo. Step S2: Introduce low-concentration flue gas from the power plant that has been slightly humidified as a gas-solid reaction medium, and simultaneously apply microwave activation and fluidized stirring to the dry fly ash under low temperature and normal pressure conditions to activate the activity of calcium and magnesium minerals inside the fly ash and enhance gas-solid contact, so that the fly ash and CO2 in the flue gas can undergo a mineralization reaction to generate stable carbonates. Step S3: Divide the interior of the dry ash silo into a primary pre-mineralization silo and a secondary deep mineralization silo. The dry fly ash first undergoes primary pre-mineralization in the primary pre-mineralization silo and then undergoes secondary deep mineralization in the secondary deep mineralization silo to continuously and gradually fix carbon in the dry fly ash. The incompletely reacted fly ash is then returned to the primary pre-mineralization silo for further reaction, resulting in continuous discharge of mineralized ash. Step S4: The residual flue gas after the mineralization reaction is returned to the power plant's original dust removal system for unified dust removal and purification through a closed-loop pipeline.

2. The carbon fixation method according to claim 1, characterized in that, In step S2, the dry ash silo is equipped with a fluidizing and stirring device and a microwave-assisted activation device. The microwave-assisted activation device activates the free calcium and magnesium minerals inside the fly ash at low temperature and normal pressure. The fluidizing and stirring device fluidizes the fly ash to enhance gas-solid contact.

3. The carbon fixation method according to claim 1, characterized in that, In step S2, the microwave activation power is 10kW.

4. The carbon fixation method according to claim 3, characterized in that, In step S2, the moisture content of the flue gas after micro-humidification is 6%.

5. The carbon fixation method according to claim 4, characterized in that, In step S2, the fluidization velocity is 1.5 m / s; and the microwave activation power, flue gas moisture content, and fluidization velocity are synergistically adjusted according to the mineralization reaction rate and carbon fixation rate.

6. The carbon fixation method according to claim 1, characterized in that, In step S3, the residence time for primary pre-mineralization is 30 minutes, and the residence time for primary pre-mineralization is shorter than the residence time for secondary deep mineralization.

7. The carbon fixation method according to claim 6, characterized in that, In step S3, the residence time for secondary deep mineralization is 40 minutes.

8. The carbon fixation method according to claim 7, characterized in that, In step S3, the proportion of incompletely reacted fly ash returned to the primary pre-mineralization stage is 40% of the output.

9. The carbon fixation method according to claim 1, characterized in that, By adjusting the microwave activation power, flue gas humidification amount, and mineralization residence time in a coordinated manner, the carbonate content and material activity of the resulting mineralized ash are controlled, and highly active calcium carbonate-silica-alumina composite ash is produced. This ash can then be used as a low-carbon building material admixture in cement preparation or roadbed construction materials.

10. The carbon fixation method according to claim 1, characterized in that, The water used for micro-humidification of the flue gas in step S2 is taken from the wastewater of the power plant.

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