Rare earth-charcoal composite modified fly ash adsorbent and method

Abstract

The invention provides a rare earth-charcoal composite modified fly ash adsorbent and a method. The method comprises the following steps: carrying out microwave activation on fly ash of a coal-fired power plant to obtain a porous fly ash matrix; the preparation method comprises the following steps: mixing bamboo charcoal powder with a porous fly ash matrix, adding a starch binder, stirring to prepare paste, and extruding and granulating to obtain composite particles; immersing the composite particles into a rare earth salt solution, and soaking at room temperature to obtain rare earth doped composite particles; and drying the rare earth doped composite particles by using waste heat at the tail of a power plant boiler to obtain the rare earth-charcoal composite modified fly ash adsorbent. The problems that an existing fly ash-based adsorbent is poor in adsorption performance, high in preparation energy consumption and insufficient in regeneration stability are solved.

Description

Technical Field

[0001] This invention belongs to the field of CO2 capture technology, specifically to providing a rare earth-biochar composite modified fly ash adsorbent and method for CO2 capture. Background Technology

[0002] Against the backdrop of addressing global warming, the preparation of CO2 capture and adsorption materials has become a focus of research and industry. With the advancement of industrialization, carbon dioxide emissions are constantly rising, exacerbating the greenhouse effect and causing serious impacts on the ecological environment. To effectively reduce atmospheric CO2 concentration, the optimization and improvement of the performance of adsorption materials, as a core component of CO2 capture technology, is particularly important. Fly ash, a solid waste generated during industrial combustion processes such as coal combustion, is considered a potential high-quality raw material for preparing adsorbents due to its abundant resources and low cost. However, traditional fly ash-based adsorbents have significant shortcomings in adsorption efficiency, energy consumption during preparation, and regeneration stability during long-term use, limiting their widespread application and promotion in the field of CO2 capture.

[0003] While fly ash-based adsorbents are attractive in practical CO2 capture applications due to their readily available raw materials, their actual performance has been less than satisfactory. The primary problem is insufficient adsorption capacity, mainly because the microstructure of fly ash itself is underdeveloped, resulting in a limited specific surface area and consequently, unsatisfactory CO2 adsorption capacity and rate. Secondly, the preparation of these adsorbents often involves high energy consumption, increasing production costs and contradicting current environmental protection principles of energy conservation and emission reduction. Furthermore, the adsorbents exhibit poor regeneration stability after multiple cycles; their adsorption performance significantly declines after several adsorption-desorption processes, affecting the long-term economic viability and reliability of the technology. These problems collectively hinder the further development of fly ash-based adsorbents in the field of CO2 capture.

[0004] To overcome these challenges, existing technologies have adopted a series of innovative strategies. On the one hand, physical or chemical methods are used to modify fly ash, aiming to improve its microstructure, increase porosity and specific surface area, thereby enhancing adsorption performance. For example, acid-base etching, high-temperature activation, or steam treatment are used to optimize the physical properties of fly ash. On the other hand, researchers are also exploring more energy-efficient preparation processes, such as using mechanical mixing, co-precipitation, or sol-gel methods under mild conditions to reduce energy consumption during preparation. In addition, to enhance the regeneration stability of adsorbents, some studies have introduced specific additives or stabilizers, such as rare earth elements (REEs, a class of metallic elements with special physicochemical properties), to improve the structural integrity of the adsorbent and reduce performance loss during regeneration.

[0005] While existing technologies have alleviated the performance bottlenecks of fly ash-based adsorbents to some extent, several problems remain. First, while modification treatments improve adsorption performance, they often lead to more complex preparation processes and increased costs, and some modification methods may cause environmental pollution. Second, while low-energy preparation processes align with the trend of energy conservation and emission reduction, they may compromise on certain key performance indicators of the adsorbent, such as adsorption selectivity and capacity. Furthermore, although the introduction of stabilizers such as rare earth elements improves regeneration stability, the scarcity and high price of rare earth resources limit their feasibility for large-scale applications. Therefore, developing a fly ash-based adsorbent that possesses both high adsorption performance and can be prepared under low-energy conditions, while also exhibiting good regeneration stability, remains a pressing technical challenge in the field of CO2 capture technology. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a rare earth-biochar composite modified fly ash adsorbent and method, which solves the problems of poor adsorption performance, high energy consumption in preparation, and insufficient regeneration stability of existing fly ash-based adsorbents.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a rare earth-biochar composite modified fly ash adsorbent, comprising the following steps: Microwave activation of fly ash from coal-fired power plants yields porous fly ash matrix; Bamboo charcoal powder is mixed with porous fly ash matrix, starch binder is added, and the mixture is stirred into a paste. Then, it is extruded and granulated to obtain composite particles. The composite particles were immersed in a rare earth salt solution and soaked at room temperature to obtain rare earth-doped composite particles. By utilizing the waste heat from the tail end of a power plant boiler to dry the rare earth-doped composite particles, a rare earth-biochar composite modified fly ash adsorbent is obtained.

[0008] Furthermore, the particle size of the fly ash from the coal-fired power plant is <100μm; the specific parameters for microwave activation are: activation for 30min-60min at a power of 500W-800W and a temperature of 300℃-500℃.

[0009] Furthermore, the mass ratio of bamboo charcoal powder to porous fly ash matrix is ​​1:(4-9), the amount of starch binder accounts for 10%-15% of the mass of the mixture of bamboo charcoal powder and porous fly ash matrix, and the particle size of the composite particles is 2mm-5mm.

[0010] Furthermore, the concentration of the rare earth salt solution is 0.5 mol / L-1 mol / L, and the composite particles are soaked in the rare earth salt solution for 2-4 hours, with stirring once or twice during the process.

[0011] Furthermore, the rare earth elements in the rare earth salt solution are one or a mixture of two of cerium and lanthanum.

[0012] Furthermore, the specific parameters for drying the rare earth-doped composite particles using the waste heat from the tail end of the power plant boiler are: drying at 100℃-150℃ for 2-3 hours.

[0013] This invention provides a rare earth-biochar composite modified fly ash adsorbent, which is prepared by the above-mentioned method. The rare earth-biochar composite modified fly ash adsorbent contains 10%-20% bamboo charcoal powder by mass, and the rare earth element doping amount is 1%-5% of the total mass of the rare earth-biochar composite modified fly ash adsorbent.

[0014] Furthermore, the specific surface area of ​​the rare earth-biochar composite modified fly ash adsorbent is 800 m². 2 / g-1000m 2 / g, after 50 regenerations, the adsorption capacity retention rate is ≥90%.

[0015] The present invention also provides a regeneration method for the above-mentioned rare earth-biochar composite modified fly ash adsorbent, which adopts a variable temperature regeneration method, with a regeneration temperature of 150℃-200℃ and a regeneration time of 1h-2h, and the adsorption capacity retention rate after regeneration is ≥90%.

[0016] This invention also provides a method for CO2 capture in a coal-fired power plant, wherein the above-mentioned rare earth-biochar composite modified fly ash adsorbent is filled into a fixed-bed adsorption tower to treat power plant flue gas, with an adsorption temperature of 30℃-80℃ and a flue gas space velocity of 500 h⁻¹. -1 -1000 h -1 CO2 adsorption efficiency ≥85%.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: This invention provides a method for preparing rare earth-biochar composite modified fly ash adsorbent. This method constructs a complete process system encompassing microwave activation, carbon composite granulation, rare earth doping, and waste heat drying. Microwave activation, as a pre-process, utilizes high-frequency microwave energy to disrupt the dense surface structure of fly ash, forming numerous micron- and nano-sized pores, significantly increasing the specific surface area and porosity of the fly ash matrix. Bamboo charcoal powder itself possesses an ultra-high specific surface area and abundant adsorption sites. When mixed with the porous fly ash matrix, it fills the blank areas in the fly ash pores, further increasing the number of adsorption sites and forming a multi-level pore structure of macroscopic pores in fly ash and microscopic pores in bamboo charcoal. The doping of rare earth elements forms active adsorption sites on the pore surface, enhancing the selective adsorption capacity for CO2. The synergistic effect of these three elements completely changes the limited improvement in fly ash adsorption performance achieved by traditional single modification methods (such as activation or doping alone), providing key technical support for increasing the adsorption capacity by 2-3 times compared to unmodified fly ash. By utilizing waste heat from power plant boilers in the drying process, this method breaks away from the traditional modification process's reliance on external heating (such as electric or gas heating) for drying. Power plant waste heat is an industrial byproduct; its non-utilization would result in energy waste. This process converts it into energy for the preparation process, significantly reducing energy consumption in the drying stage and achieving energy recycling. Preliminary calculations show that compared to traditional drying processes, waste heat drying can reduce the overall energy consumption of the preparation process by 40%-60%, significantly reducing production costs and carbon emissions.

[0018] Furthermore, in the microwave activation stage, the specific activation parameters for fly ash particles <100μm were defined: power 500W-800W, temperature 300℃-500℃, and time 30min-60min. This ensures the stable and controllable pore structure of the fly ash matrix and avoids fluctuations in adsorption performance caused by ambiguous parameters. In the preparation of composite particles, the mass ratio of bamboo charcoal to fly ash (1:4-9), the amount of binder (10%-15%), and the particle size (2mm-5mm) were optimized. This not only enhances the synergistic adsorption effect through reasonable proportioning but also makes the particles suitable for filling fixed-bed adsorption towers, balancing performance and application. In the rare earth doping stage, the salt solution concentration (0.5mol / L-1mol / L), soaking time (2h-4h), and number of stirring times were clearly defined to ensure uniform loading of rare earth elements. The rare earth elements were limited to cerium and lanthanum, utilizing their excellent properties to meet the requirements of high efficiency. The waste heat drying parameters (100℃-150℃, 2h-3h) were clearly defined to further implement the low-carbon concept and reduce energy consumption and costs.

[0019] In the rare earth-biochar composite modified fly ash adsorbent prepared by this invention, bamboo charcoal powder accounts for 10%-20%, and rare earth doping amount is 1%-5%. This proportion range ensures that the high specific surface area characteristics of bamboo charcoal are fully utilized, providing sufficient adsorption sites, while the adsorption activity can be controlled by appropriate rare earth doping, ensuring the stability of the adsorbent composition and controllable cost. In terms of performance, the specific surface area is limited to 800 m². 2 / g-1000m 2 / g, this value is much higher than that of traditional fly ash-based adsorbents (usually below 500m). 2 The structure provides a basis for high adsorption capacity ( / g); at the same time, it is specified that the adsorption capacity retention rate is ≥90% after 50 regenerations. The adsorbent of this invention exhibits excellent regeneration stability, which greatly extends the service life of the adsorbent and reduces the replacement frequency and cost in practical applications.

[0020] Furthermore, the rare earth-biochar composite modified fly ash adsorbent prepared by this invention is regenerated using a variable temperature regeneration method, with a regeneration temperature of 150℃-200℃ and a time of 1h-2h. This process is mild, requires no high temperature or high pressure or complex chemical reagents, is easy to operate and has low equipment requirements, making it easy to modify and apply to existing power plant facilities. At the same time, the capacity retention rate after regeneration is ≥90%, and combined with the advantage of rare earth doping reducing urea production by more than 60%, it achieves the dual effects of high-efficiency regeneration and environmental protection with low pollution.

[0021] Furthermore, in practical applications, the rare earth-biochar composite modified fly ash adsorbent prepared by this invention is specifically designed for coal-fired power plant scenarios, where the adsorbent is filled into a fixed-bed adsorption tower, with an adsorption temperature of 30℃-80℃ and a flue gas space velocity of 500 h⁻¹. -1 -1000h -1 These parameters fully cover the actual operating conditions of power plant flue gas (the temperature of power plant flue gas is usually 40℃-60℃, and the space velocity range is 500-1200 h⁻¹). -1 Furthermore, the adsorption efficiency is ≥85%, ensuring that the adsorbent can be directly adapted to the power plant CO2 capture system. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation process of the rare earth-biochar composite modified fly ash adsorbent of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] This invention provides a rare earth-biochar composite modified fly ash adsorbent, which is made from fly ash from coal-fired power plants as a base material, and is subsequently modified by microwave activation, bamboo charcoal composite, and rare earth element doping. The adsorbent contains 10%-20% bamboo charcoal powder by mass, and the rare earth element doping amount is 1%-5% of the total adsorbent mass. The rare earth element is one or a mixture of cerium and lanthanum.

[0025] Testing revealed that the specific surface area of ​​the rare earth-biochar composite modified fly ash adsorbent reached 800 m². 2 / g -1000 m 2 / g, CO2 adsorption capacity is increased by 2 to 3 times compared with unmodified fly ash, and the adsorption capacity retention rate is ≥90% after 50 regenerations.

[0026] like Figure 1 As shown, the present invention also provides a low-energy preparation method for the above-mentioned rare earth-biochar composite modified fly ash adsorbent, comprising the following steps: 1. Fly ash pretreatment: The fly ash from coal-fired power plants is crushed to a particle size of <100μm, sieved, and then placed in a microwave reactor. It is activated for 30min-60min at a power of 500W-800W and a temperature of 300℃-500℃. The microwave energy destroys the dense structure on the surface of the fly ash particles, forming rich pores and obtaining a porous fly ash matrix. 2. Preparation of composite particles: Bamboo charcoal powder and porous fly ash matrix are mixed evenly at a mass ratio of 1:(4-9) to obtain a mixture. The high specific surface area of ​​bamboo charcoal powder can significantly increase the adsorption sites and form a synergistic adsorption effect with the porous fly ash matrix. Add 10%-15% starch binder of the mixture, stir to make a paste, and then extrude and granulate to obtain composite particles with a particle size of 2mm-5mm, which are convenient for filling and use in fixed bed adsorption towers. 3. Rare earth doping modification: The composite particles were immersed in a 0.5 mol / L-1 mol / L rare earth salt solution and soaked at room temperature for 2-4 hours, stirring once or twice during the soaking process to ensure that the rare earth elements were uniformly loaded onto the surface and pores of the composite particles. The rare earth elements not only improve the CO2 adsorption selectivity, but also inhibit the generation of urea during the regeneration process, thus reducing environmental risks. After being removed, the surface solution was drained to obtain rare earth-doped composite particles. 4. Drying and curing: The rare earth-doped composite particles are placed in a power plant waste heat drying device and dried at 100℃-150℃ for 2-3 hours. The waste heat from the tail end of the power plant boiler replaces the traditional high-temperature roasting process, reducing energy consumption by 40%-60%. After cooling to room temperature, a rare earth-biochar composite modified fly ash adsorbent is obtained.

[0027] like Figure 1As shown, this invention also discloses the application of the above-mentioned adsorbent in CO2 capture in coal-fired power plants. The adsorbent is filled into a fixed-bed adsorption tower to treat power plant flue gas, with an adsorption temperature of 30℃-80℃ and a flue gas space velocity of 500 h⁻¹. -1 -1000 h -1 The CO2 adsorption efficiency is ≥85%. The adsorbent after adsorption saturation is regenerated by a variable temperature regeneration method, with a regeneration temperature of 150℃-200℃ and a regeneration time of 1h-2h. The adsorption capacity retention rate after regeneration is ≥90%, and the amount of urea generated during the regeneration process is reduced by more than 60% compared with the adsorbent without rare earth doping.

[0028] In summary, the rare earth-biochar composite modified fly ash adsorbent proposed in this invention uses fly ash from coal-fired power plants as the base material and achieves multiple technological breakthroughs through microwave activation, synergistic modification via carbon composite and rare earth doping. Its specific surface area reaches 800 m². 2 / g-1000 m 2 / g, the CO2 adsorption capacity is increased by 2-3 times compared with unmodified fly ash, and the capacity retention rate exceeds 90% after 50 regenerations. Rare earth doping also reduces urea generation during the regeneration process by more than 60%, balancing high-efficiency adsorption with environmental safety. The preparation process utilizes waste heat from power plants, reducing energy consumption by 40%-60%, which aligns with the low-carbon concept. It is suitable for use with fixed-bed adsorption towers, operating at adsorption temperatures of 30℃-80℃ for 500 h. -1 -1000 h -1 At flue gas space velocity, the adsorption efficiency exceeds 85%, and the variable-temperature regeneration process is simple and easy to implement. This invention not only realizes the resource utilization of fly ash but also provides a low-consumption, high-efficiency, and stable solution for CO2 capture in coal-fired power plants. It has significant practical implications and broad prospects for promoting carbon emission reduction in the power industry and helping to achieve dual-carbon goals.

[0029] Example 1: A rare earth-biochar composite modified fly ash adsorbent, the preparation steps are as follows: 1. Fly ash pretreatment: Take fly ash from a coal-fired power plant (SiO2 content 52%, Al2O3 content 31%), crush it to a particle size <80μm, sieve it and place it in a microwave reactor, activate it for 45min at a power of 600W and a temperature of 400℃ to obtain a porous fly ash matrix. 2. Preparation of composite particles: Bamboo charcoal powder (specific surface area 1200 m²) 2 Mix (g) with porous fly ash matrix at a mass ratio of 1:6, add starch binder accounting for 12% of the mass of the mixture, stir to form a paste, and then extrude and granulate to obtain composite particles with a particle size of 3-4 mm. 3. Rare earth doping modification: The composite particles were immersed in a 0.8 mol / L cerium nitrate solution and soaked at room temperature for 3 hours, stirring twice during the process. After soaking, the surface solution was drained. 4. Drying and curing: The rare earth-doped composite particles were placed in a power plant waste heat drying device and dried at 120°C for 2.5 hours. After cooling to room temperature, the target adsorbent was obtained, in which bamboo charcoal powder accounted for 16.7% of the mass and cerium doping amount was 3% of the total mass of the adsorbent.

[0030] 5. Performance Testing: Specific surface area test: The specific surface area of ​​the adsorbent was determined using the BET method to be 920 m². 2 / g; CO2 adsorption capacity test: Under the conditions of adsorption temperature of 50℃, CO2 volume fraction of 15% and gas flow rate of 50mL / min, the CO2 adsorption capacity was determined by static adsorption method to be 4.2mmol / g, which is 1.8 times higher than that of unmodified fly ash (1.5mmol / g). Regeneration stability test: Using the variable temperature regeneration method, the regeneration temperature was 180℃ and the regeneration time was 1.5h. After 50 adsorption-regeneration cycles, the adsorption capacity retention rate was 93%. Urea production test: The urea content in the regeneration tail gas was determined by high performance liquid chromatography, which reduced it by 68% compared with the adsorbent without rare earth doping; Energy consumption test: The energy consumption of the drying and curing step is 85 kWh / t, which is 59.5% lower than that of the traditional high-temperature calcination process (210 kWh / t).

[0031] Example 2: A rare earth-biochar composite modified fly ash adsorbent, the preparation steps are as follows: 1. Fly ash pretreatment: Take fly ash from a coal-fired power plant (SiO2 content 48%, Al2O3 content 35%), crush it to a particle size <100μm, sieve it and place it in a microwave reactor, activate it for 60 min at a power of 500W and a temperature of 350℃ to obtain a porous fly ash matrix. 2. Preparation of composite particles: Bamboo charcoal powder (specific surface area 1100 m²) 2 Mix (g) with porous fly ash matrix at a mass ratio of 1:4, add starch binder accounting for 10% of the mass of the mixture, stir to form a paste, and then extrude and granulate to obtain composite particles with a particle size of 2-3 mm. 3. Rare earth doping modification: The composite particles were immersed in a 0.5 mol / L lanthanum nitrate solution and soaked at room temperature for 4 hours, stirring once during the soaking period. After soaking, the surface solution was drained. 4. Drying and curing: The rare earth-doped composite particles were placed in a power plant waste heat drying device and dried at 100°C for 3 hours. After cooling to room temperature, the target adsorbent was obtained, in which bamboo charcoal powder accounted for 20% of the mass and lanthanum doping amount was 1% of the total mass of the adsorbent.

[0032] 5. Performance Testing: Specific surface area test: The BET method was used to determine the specific surface area of ​​the adsorbent, which was 850 m². 2 / g; CO2 adsorption capacity test: Under the conditions of adsorption temperature of 30℃, CO2 volume fraction of 12% and gas flow rate of 50mL / min, the CO2 adsorption capacity was determined by static adsorption method to be 3.8mmol / g, which is 1.53 times higher than that of unmodified fly ash (1.5mmol / g). Regeneration stability test: Using the variable temperature regeneration method, the regeneration temperature was 150℃ and the regeneration time was 2h. After 50 adsorption-regeneration cycles, the adsorption capacity retention rate was 91%. Urea production test: The urea content in the regeneration tail gas was determined by high performance liquid chromatography, which reduced it by 62% compared with the adsorbent without rare earth doping; Energy consumption test: The energy consumption of the drying and curing step is 90 kWh / t, which is 55% lower than that of the traditional high-temperature calcination process (200 kWh / t).

[0033] Example 3: A rare earth-biochar composite modified fly ash adsorbent, the preparation steps are as follows: 1. Fly ash pretreatment: Take fly ash from a coal-fired power plant (SiO2 content 50%, Al2O3 content 33%), crush it to a particle size <70μm, sieve it and place it in a microwave reactor, activate it for 40 min at a power of 800W and a temperature of 300℃ to obtain a porous fly ash matrix. 2. Preparation of composite particles: Bamboo charcoal powder (specific surface area 1100 m²) 2 Mix (g) with porous fly ash matrix at a mass ratio of 1:5, add 10% starch binder by mass of the mixture, stir to form a paste, and then extrude and granulate to obtain composite particles with a particle size of 2-3 mm. 3. Rare earth doping modification: The composite particles were immersed in a 0.6 mol / L lanthanum nitrate solution and soaked at room temperature for 2 hours, stirring twice during the soaking process. After soaking, the surface solution was drained. 4. Drying and curing: The rare earth-doped composite particles were placed in a power plant waste heat drying device and dried at 110°C for 3 hours. After cooling to room temperature, the target adsorbent was obtained, in which bamboo charcoal powder accounted for 10% of the mass and lanthanum doping amount was 2.5% of the total mass of the adsorbent.

[0034] 5. Performance Testing: Specific surface area test: The specific surface area of ​​the adsorbent was determined using the BET method to be 880 m². 2 / g; CO2 adsorption capacity test: Under the conditions of adsorption temperature of 45℃, CO2 volume fraction of 10% and gas flow rate of 40mL / min, the CO2 adsorption capacity was determined by static adsorption method to be 3.9mmol / g, which is 1.6 times higher than that of unmodified fly ash (1.5mmol / g). Regeneration stability test: Using the variable temperature regeneration method, the regeneration temperature was 170℃ and the regeneration time was 1 hour. After 45 adsorption-regeneration cycles, the adsorption capacity retention rate was 92%. Urea production test: The urea content in the regeneration tail gas was determined by high performance liquid chromatography, which reduced it by 65% ​​compared with the adsorbent without rare earth doping; Energy consumption test: The energy consumption of the drying and curing step is 80 kWh / t, which is 60% lower than that of the traditional high-temperature calcination process (200 kWh / t).

[0035] Example 4: A rare earth-biochar composite modified fly ash adsorbent, the preparation steps are as follows: 1. Fly ash pretreatment: Take fly ash from a coal-fired power plant (SiO2 content 55%, Al2O3 content 29%), crush it to a particle size <90μm, sieve it and place it in a microwave reactor, activate it for 30 min at a power of 650W and a temperature of 500℃ to obtain a porous fly ash matrix. 2. Preparation of composite particles: Bamboo charcoal powder (specific surface area 1300 m²) 2 Mix (g) with porous fly ash matrix at a mass ratio of 1:9, add 15% starch binder by mass of the mixture, stir to form a paste, and then extrude and granulate to obtain composite particles with a particle size of 4-5 mm. 3. Rare earth doping modification: The composite particles were immersed in a 1 mol / L mixed solution of cerium nitrate and lanthanum nitrate for 3.5 h at room temperature, with stirring twice during the process. After immersion, the surface solution was drained. 4. Drying and curing: The rare earth-doped composite particles were placed in a power plant waste heat drying device and dried at 150°C for 3 hours. After cooling to room temperature, the target adsorbent was obtained, in which bamboo charcoal powder accounted for 14.3% of the mass and cerium and lanthanum elements accounted for 5% of the total mass of the adsorbent.

[0036] 5. Performance Testing: Specific surface area test: The BET method was used to determine the specific surface area of ​​the adsorbent, which was 900 m².2 / g; CO2 adsorption capacity test: Under the conditions of adsorption temperature of 55℃, CO2 volume fraction of 20% and gas flow rate of 60mL / min, the CO2 adsorption capacity was determined by static adsorption method to be 4.5mmol / g, which is 2.0 times higher than that of unmodified fly ash (1.5mmol / g). Regeneration stability test: Using the variable temperature regeneration method, the regeneration temperature was 190℃ and the regeneration time was 2h. After 55 adsorption-regeneration cycles, the adsorption capacity retention rate was 92%. Urea production test: The urea content in the regeneration tail gas was determined by high performance liquid chromatography, which reduced it by 63% compared with the adsorbent without rare earth doping; Energy consumption test: The energy consumption of the drying and curing step is 90 kWh / t, which is 59.1% lower than that of the traditional high-temperature calcination process (220 kWh / t).

[0037] Example 5: The application of a rare earth-biochar composite modified fly ash adsorbent is as follows: 1. Application Testing: The adsorbent prepared in Example 1 was packed into a fixed-bed adsorption tower to treat flue gas from a coal-fired power plant (CO2 volume fraction 13%, temperature 60℃, dust content <10mg / m³). 3 Control the flue gas space velocity to 500 h⁻¹ -1 Adsorption temperature 50℃; 2. Test Results: The CO2 concentration in the outlet flue gas was monitored by an online gas analyzer, and the CO2 adsorption efficiency was calculated to be 88%. After adsorption saturation, a variable temperature regeneration method was used for regeneration. The regeneration temperature was 180℃ and the regeneration time was 1.5h. The adsorption capacity retention rate after regeneration was 92%. During the regeneration process, the urea content in the regenerated tail gas was determined by high performance liquid chromatography, which reduced it by 68% compared with the adsorbent without rare earth doping. After 30 days of continuous operation, the adsorption efficiency remained stable at over 85%.

[0038] Example 6 The application of a rare earth-biochar composite modified fly ash adsorbent is as follows: 1. Application Testing: The adsorbent prepared in Example 1 was packed into a fixed-bed adsorption tower to treat flue gas from a coal-fired power plant (CO2 volume fraction 12%, temperature 30℃, dust content <8mg / m³). 3 Control the flue gas space velocity to 1000 h⁻¹ -1 Adsorption temperature 30℃; 2. Test Results: The CO2 concentration in the outlet flue gas was monitored by an online gas analyzer, and the CO2 adsorption efficiency was calculated to be 86%. After adsorption saturation, a variable temperature regeneration method was used for regeneration. The regeneration temperature was 150℃ and the regeneration time was 1 hour. The adsorption capacity retention rate after regeneration was 91%. During the regeneration process, the urea content in the regenerated tail gas was determined by high performance liquid chromatography, which was 62% lower than that of the adsorbent without rare earth doping. After 30 days of continuous operation, the adsorption efficiency remained stable at over 85%.

[0039] Example 7: The application of a rare earth-biochar composite modified fly ash adsorbent is as follows: 1. Application Testing: The adsorbent prepared in Example 1 was packed into a fixed-bed adsorption tower to treat flue gas from a coal-fired power plant (CO2 volume fraction 14%, temperature 80℃, dust content <12mg / m³). 3 Control the flue gas space velocity to 800 h -1 Adsorption temperature: 80℃; 2. Test Results: The CO2 concentration in the outlet flue gas was monitored by an online gas analyzer, and the CO2 adsorption efficiency was calculated to be 87%. After adsorption saturation, a variable temperature regeneration method was used for regeneration. The regeneration temperature was 200℃ and the regeneration time was 2 hours. The adsorption capacity retention rate after regeneration was 90%. During the regeneration process, the urea content in the regenerated tail gas was determined by high performance liquid chromatography, which reduced it by 68% compared with the adsorbent without rare earth doping. After 30 days of continuous operation, the adsorption efficiency remained stable at over 85%.

[0040] Comparative Example 1: Performance testing of adsorbents without rare earth doping Unmodified fly ash from a coal-fired power plant was pulverized to a particle size <100 μm and directly used as an adsorbent for performance testing. Under adsorption conditions of 50℃, CO2 volume fraction of 13%, and gas flow rate of 50 mL / min, the CO2 adsorption capacity was 1.5 mmol / g. Using a variable-temperature regeneration method (regeneration temperature 180℃, regeneration time 1.5 h), after 50 adsorption-regeneration cycles, the adsorption capacity retention rate was 55%. The urea content in the regenerated tail gas was 120 mg / m³. 3 .

[0041] Comparative Example 2: Performance testing of single-metal doped fly ash adsorbent 1. Preparation: Fly ash from coal-fired power plants was pulverized to a particle size of <100μm, activated in a microwave reactor (power 600W, temperature 400℃, 45min), then immersed in a 0.8mol / L zinc nitrate solution at room temperature for 3h, and dried at 120℃ for 2.5h to obtain a zinc-doped fly ash adsorbent. 2. Performance Testing: Under the conditions of adsorption temperature 50℃, CO2 volume fraction 15%, and gas flow rate 50mL / min, the CO2 adsorption capacity was 2.3mmol / g; after 50 adsorption-regeneration cycles, the adsorption capacity retention rate was 70%; and the urea content in the regeneration tail gas was 105mg / m³. 3 The energy consumption for the drying and curing step is 200 kWh / t.

[0042] The performance data of the adsorbents prepared in Examples 1-7 and Comparative Examples 1-2 are shown in the table below:

[0043] As can be seen from the data in the table, the performance of the rare earth-biochar composite modified fly ash adsorbent is significantly better than that of unmodified fly ash and single zinc-doped adsorbent: In terms of the core CO2 adsorption capacity, the adsorption capacity of the example reaches 3.8-4.5 mmol / g, which is 2.5-3 times that of unmodified fly ash (1.5 mmol / g), and even far inferior to single zinc-doped (2.3 mmol / g); in terms of regeneration stability, the capacity retention rate of the example exceeds 90% after 50 regenerations, far exceeding the 55% of unmodified fly ash and the 70% of zinc-doped fly ash, and rare earth doping effectively extends the cycle life of the adsorbent. At the same time, rare earth modification significantly reduces environmental risks, with urea generation during regeneration reduced by 62%-68% compared to unmodified fly ash, achieving a balance between high efficiency and low carbon emissions.

[0044] The rare earth-biochar composite modified fly ash adsorbent of this invention has an energy consumption of only 85kWh / t-90kWh / t, far lower than the 200kWh / t of single zinc doping. Furthermore, using power plant solid waste fly ash as the base material and combining it with biochar, both raw material and process costs are controllable. In practical applications, the CO2 adsorption efficiency of the embodiments reaches 87%-89%, suitable for 500 h. -1 -800 h -1 With its low flue gas space velocity and adsorption temperature of 30℃-80℃, it covers the common operating conditions required by coal-fired power plants. Overall, the rare earth-biochar composite modified fly ash adsorbent achieves synergy between solid waste resource utilization, efficient carbon capture, and low energy consumption and environmental protection, making it a practical solution for carbon emission reduction in power plants.

Claims

1. A method for preparing a rare earth-biochar composite modified fly ash adsorbent, characterized in that, Includes the following steps: Microwave activation of fly ash from coal-fired power plants yields porous fly ash matrix; Bamboo charcoal powder is mixed with porous fly ash matrix, starch binder is added, and the mixture is stirred into a paste. Then, it is extruded and granulated to obtain composite particles. The composite particles were immersed in a rare earth salt solution and soaked at room temperature to obtain rare earth-doped composite particles. By utilizing the waste heat from the tail end of a power plant boiler to dry the rare earth-doped composite particles, a rare earth-biochar composite modified fly ash adsorbent is obtained.

2. The preparation method of the rare earth-biochar composite modified fly ash adsorbent according to claim 1, characterized in that, The fly ash from the coal-fired power plant has a particle size of <100μm; the specific parameters for microwave activation are: activation for 30min-60min at a power of 500W-800W and a temperature of 300℃-500℃.

3. The preparation method of the rare earth-biochar composite modified fly ash adsorbent according to claim 1, characterized in that, The mass ratio of bamboo charcoal powder to porous fly ash matrix is ​​1:(4-9), and the amount of starch binder accounts for 10%-15% of the mass of the mixture of bamboo charcoal powder and porous fly ash matrix; the particle size of the composite particles is 2mm-5mm.

4. The preparation method of the rare earth-biochar composite modified fly ash adsorbent according to claim 1, characterized in that, The concentration of the rare earth salt solution is 0.5 mol / L-1 mol / L. The composite particles are soaked in the rare earth salt solution for 2-4 hours, and stirred once or twice during the soaking period.

5. The preparation method of a rare earth-biochar composite modified fly ash adsorbent according to claim 4, characterized in that, The rare earth elements in the rare earth salt solution are one or a mixture of two of cerium and lanthanum.

6. The preparation method of a rare earth-biochar composite modified fly ash adsorbent according to claim 1, characterized in that, The specific parameters for drying rare earth-doped composite particles using waste heat from the tail end of a power plant boiler are: drying at 100℃-150℃ for 2-3 hours.

7. A rare earth-biochar composite modified fly ash adsorbent, characterized in that, The rare earth-biochar composite modified fly ash adsorbent is prepared by any one of claims 1 to 6, wherein the mass percentage of bamboo charcoal powder is 10%-20%, and the rare earth element doping amount is 1%-5% of the total mass of the rare earth-biochar composite modified fly ash adsorbent.

8. The rare earth-biochar composite modified fly ash adsorbent according to claim 7, characterized in that, The specific surface area of ​​the rare earth-biochar composite modified fly ash adsorbent is 800 m². 2 / g-1000 m 2 / g, after 50 regenerations, the adsorption capacity retention rate is ≥90%.

9. The regeneration method of the rare earth-biochar composite modified fly ash adsorbent according to claim 7 or 8, characterized in that, The variable temperature regeneration method was adopted, with a regeneration temperature of 150℃-200℃ and a regeneration time of 1h-2h. The adsorption capacity retention rate after regeneration was ≥90%.

10. A method for CO2 capture in a coal-fired power plant, characterized in that, The rare earth-biochar composite modified fly ash adsorbent as described in claim 7 or 8 is filled into a fixed-bed adsorption tower to treat power plant flue gas, with an adsorption temperature of 30℃-80℃ and a flue gas space velocity of 500 h⁻¹. -1 -1000 h -1 CO2 adsorption efficiency ≥85%.

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