An activation modification method for preparing flue gas desulfurization adsorbent from ash of a thermal power plant

Abstract

This invention relates to the field of solid waste resource utilization, specifically to an activation and modification method for preparing flue gas desulfurization adsorbents from thermal power plant ash. The method includes: pretreating thermal power plant ash, followed by a five-stage synergistic process of microwave-alkali synergistic lattice activation, acid leaching-hydrothermal synergistic pore-forming, ultrasonic-assisted active component loading, and low-temperature reduction activation. This process yields a flue gas desulfurization adsorbent with high specific surface area, rich hierarchical pore structure, and highly uniform dispersion of active components. This invention uses ash emitted from thermal power plants as raw material, achieving a green circular economy of "treating waste with waste." Through the five-stage synergistic activation mechanism, it solves the problems of insufficient ash activation, inaccurate pore structure control, and insufficient stability of active component loading. The prepared adsorbent has a saturated SO2 adsorption capacity of 120–285 mg / g, and the adsorption capacity retention rate after five regenerations is not less than 88%, demonstrating good prospects for industrial application.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization, specifically to an activation modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash. Background Technology

[0002] Coal-fired power plants produce a large amount of ash and slag (fly ash and bottom ash), and the large amount of ash and slag stockpiles will cause land occupation and environmental pollution. At the same time, SO2 treatment of flue gas from coal-fired power plants mainly relies on limestone-gypsum wet desulfurization, but this technology has high operating costs, difficult by-product disposal, and high carbon emissions.

[0003] Therefore, how to transform the ash residue of thermal power plants into a high-efficiency desulfurization adsorbent and achieve a green cycle of treating waste with waste has become a research goal in the field of resources and environment. Ash residue is rich in components such as SiO2 and Al2O3, which provides the material basis for preparing adsorbents.

[0004] Existing technologies attempt to modify ash slag in the furnace by adding steel slag, rare earth tailings, etc., but mainly improve the performance of building materials rather than desulfurization and adsorption. Another approach uses a combination of alkaline dissolution and hydrothermal reaction to prepare desulfurizing agents, attempting to break the dense silica-alumina glass body in the ash slag from the active components, and to create pores through acid treatment or physical grinding, and then load the active components with metal oxides by impregnation.

[0005] Existing solutions still suffer from three common problems: 1. Insufficient ash activation: Traditional thermal activation is insufficient to effectively break the Si-O-Al network, and alkaline dissolution activation is energy-intensive and lacks sufficient depth, resulting in a limited number of usable active sites and low adsorption capacity. 2. Inadequate pore structure control: Single acid treatment or physical grinding has limited pore-forming effects, making it difficult to achieve both high specific surface area and a suitable microporous-mesoporous hierarchical pore structure for SO2 adsorption. Furthermore, alkali metal residues easily clog pore channels, reducing the effective specific surface area. 3. Insufficient stability of active component loading: The lack of systematic control over the chemical environment of the ash surface and the loading process leads to uneven dispersion of active components, which are prone to agglomeration and loss during multiple adsorption-desorption regeneration cycles, resulting in poor regenerability and short service life. Summary of the Invention

[0006] To address the problems mentioned in the prior art, this invention proposes an activation modification method for preparing flue gas desulfurization adsorbents from thermal power plant ash slag. This method enables precise control of pore structure and stable loading of active components through multi-level synergistic activation modification, thereby solving the technical problems in the background art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: This invention discloses an activation modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash, comprising the following steps: The ash residue from thermal power plants is sequentially dried, crushed, and sieved to obtain ash residue powder. Ash powder and solid alkali activator are mixed in a ratio of 1:(0.3~1.2) to form a material. The material is placed in a microwave reaction chamber for microwave irradiation treatment, which causes the silica-alumina glass in the ash powder to undergo lattice deagglomeration, thus obtaining an alkali-activated product. The alkali-activated product is added to an inorganic acid solution for acid leaching treatment, and the acid leaching filter cake is obtained by solid-liquid separation. The acid leaching filter cake is mixed with water at a ratio of 1:(3-8) to form a slurry. The slurry is transferred to a hydrothermal reactor for hydrothermal crystallization reaction. After the reaction is completed, the product is subjected to solid-liquid separation, washing and drying to obtain an in-situ self-assembled porous carrier. The in-situ self-assembled porous carrier was immersed in an impregnation solution containing a transition metal precursor and subjected to ultrasonic testing. After impregnation, it was dried and calcined to obtain the desulfurization adsorbent precursor. The desulfurization adsorbent precursor is subjected to reduction treatment in a reducing atmosphere to obtain the flue gas desulfurization adsorbent.

[0008] As a further improvement of the present invention, the ash from the thermal power plant is fly ash, bottom ash, or a mixture of fly ash and bottom ash emitted by a coal-fired power plant. The chemical composition of thermal power plant ash is as follows (mass fraction): SiO2: 40%–60%, Al2O3: 20%–35%, CaO: 3%–15%, Fe2O3: 3%–12%, with a loss on ignition of no more than 10%.

[0009] As a further improvement of the present invention, the solid alkali activator is one or a mixture of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate; The microwave irradiation frequency is 915MHz or 2450MHz, the microwave power is 200-800W, and the irradiation time is 5-30min.

[0010] As a further improvement of the present invention, the microwave reaction cavity is equipped with a K-type thermocouple temperature probe and an infrared temperature probe to control the material temperature, wherein the material temperature is 300-750℃.

[0011] As a further improvement of the present invention, the inorganic acid solution is a hydrochloric acid solution or a sulfuric acid solution, the acid concentration is 1.0 to 3.5 mol / L, the acid leaching solution-to-solid mass ratio is 3:1 to 10:1, the acid leaching temperature is 60 to 95°C, and the acid leaching time is 1 to 4 h.

[0012] As a further improvement of the present invention, the temperature of the hydrothermal crystallization reaction is 90-180°C, the reaction pressure is 0.1-1.0 MPa, and the reaction time is 4-24 h; A template agent is also added to the hydrothermal crystallization reaction, which is one or more of tetrapropylammonium bromide, tetraethylammonium hydroxide, or n-butylamine. The amount of template agent added is 0.05 to 0.25 times the molar amount of SiO2 contained in the acid-leaching filter cake on a dry basis.

[0013] As a further improvement of the present invention, the transition metal precursor is one or more of ferric nitrate, copper nitrate, manganese nitrate, cobalt nitrate, and cerium nitrate; The total concentration of transition metal ions in the impregnation solution is 0.1–1.5 mol / L, and the liquid-solid mass ratio of the impregnation solution to the in-situ self-assembled porous support is 2:1–8:1.

[0014] As a further improvement of the present invention, the drying temperature after the impregnation is 80-120°C and the drying time is 6-24 hours; The roasting temperature is 300–550℃, the roasting time is 2–6 hours, and the roasting atmosphere is air or oxygen-deficient atmosphere.

[0015] As a further improvement of the present invention, the reducing atmosphere is a hydrogen-containing reducing atmosphere, which is a mixture of hydrogen and an inert gas, wherein the hydrogen gas fraction is 5% to 50%, and the inert gas is nitrogen or argon; the reduction treatment temperature is 250 to 500°C, and the time is 1 to 6 hours.

[0016] As a further improvement of the present invention, the obtained in-situ self-assembled porous carrier has a specific surface area of ​​180-450 m² / g, a pore volume of 0.15-0.55 cm³ / g, and an average pore diameter of 3.5-16.5 nm. The flue gas desulfurization adsorbent has a saturated adsorption capacity of 120-285 mg / g for SO2 in flue gas, a breakthrough adsorption capacity of 60-165 mg / g, and after five adsorption-desorption cycles, the regeneration adsorption capacity retention rate is not less than 88%.

[0017] Compared with the prior art, the present invention achieves the following technical effects: This invention directly uses the ash and slag emitted by thermal power plants as the sole source of silicon and aluminum, eliminating the need for external pure silicon and aluminum sources or expensive template agents, significantly reducing raw material costs and solving the dual problems of ash and slag stockpiling pollution and flue gas desulfurization requirements. Furthermore, compared to traditional electric heating alkali fusion (requiring 550-700℃, 1-3 hours), this invention employs microwave selective heating in synergy with solid alkali, achieving deep depolymerization of the silicon and aluminum glass at 300-750℃ within 5-30 minutes. Activation time is shortened by more than 80%, and energy consumption is reduced by more than 60%. Comparative experiments show that omitting the microwave-alkali activation step results in a carrier with a specific surface area of ​​only 78 m² / g and an SO2 adsorption capacity of only 43 mg / g, far lower than the performance of this invention.

[0018] Existing methods of single acid treatment or physical grinding for pore formation have limited effectiveness. This invention utilizes the synergy of acid immersion pre-pore formation and hydrothermal in-situ self-assembly to first remove aluminum and alkali metals to form initial mass transfer channels, and then guides the self-assembly of silicon and aluminum species to form an ordered microporous-mesoporous hierarchical structure with a specific surface area of ​​180-450 m² / g. This approach balances the rapid diffusion and high-capacity adsorption of SO2 molecules. When hydrothermal crystallization is omitted, the specific surface area is only 112 m² / g, and there are no ordered channels, resulting in a significant reduction in adsorption efficiency. Secondly, in conventional impregnation methods, the active components mainly adhere to the outer surface and are prone to aggregation and loss. This invention utilizes the ultrasonic cavitation effect to drive the precursor deep into the inner wall of the pores to achieve uniform molecular-level dispersion. Then, low-temperature hydrogen reduction at 250-500℃ (avoiding high-temperature sintering) stabilizes the active components in a low-valence, highly active form. After five adsorption-desorption cycles, the regenerated adsorption capacity retention rate of the obtained adsorbent is no less than 88%, far exceeding the existing technology. Finally, the SO2 saturated adsorption capacity reaches 120-285 mg / g, and the breakthrough adsorption capacity is 60-165 mg / g. Moreover, all five steps are common unit operations in chemical engineering, with mature equipment, mild conditions, and controllable parameters, showing good prospects for industrial application. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall process flow of the present invention. Detailed Implementation

[0020] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0022] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0023] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0024] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0025] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0026] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0028] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0029] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0030] Example 1 Step 1, Raw Material Pretreatment: Take a mixture of fly ash and bottom ash from a coal-fired power plant. Its chemical composition, by mass fraction, is: SiO2 52.3%, Al2O3 28.6%, CaO 8.2%, Fe2O3 5.8%, MgO 1.6%, K2O 1.2%, TiO2 0.9%, with a loss on ignition of 1.4%. Dry the ash from the power plant in a 105℃ forced-air drying oven for 8 hours to constant weight. After coarse crushing using a jaw crusher, grind it using a ball mill. The ground product is sieved through a 100-mesh standard sieve, and the undersize material, i.e., ash powder with a particle size not exceeding 150μm, is collected and sealed for later use.

[0031] In this step, the drying process aims to remove free and adsorbed water from the ash residue, preventing moisture from affecting temperature uniformity and activation efficiency during subsequent high-temperature activation. The grinding and sieving process aims to initially break down the outer shell of some glassy particles in the ash residue through mechanical force, increasing the specific surface area of ​​the particles. Simultaneously, it ensures uniform particle size of the material entering the subsequent microwave activation step, which is beneficial for uniform microwave energy absorption and consistent activation effects. Collecting powder with a particle size no larger than 150 μm is based on experimental verification that within this particle size range, the optimal balance between microwave penetration depth and activation efficiency can be achieved.

[0032] Step 2, Microwave-Alkali Synergistic Lattice Activation: Weigh 100g of the ash powder obtained in step one and grind it thoroughly in a mortar with 50g of solid sodium hydroxide alkali activator (the mass ratio of ash to alkali activator is 1:0.5). Transfer the mixture to a corundum crucible and place it in the center of the cavity of a multimode resonant cavity microwave reactor. Corundum was chosen as the crucible material due to its excellent microwave permeability and high-temperature chemical stability. The microwave reactor operates at a frequency of 2450MHz. The microwave power was set to 500W by adjusting the magnetron output power, and irradiation treatment was performed for 15 minutes.

[0033] The microwave reaction cavity is equipped with a temperature measuring device, specifically including a K-type thermocouple temperature probe and an infrared temperature probe, both protected by a metal shielded sheath and grounded. The K-type thermocouple temperature probe uses an instantaneous intermittent temperature measurement mode, meaning the thermocouple temperature is read the instant the microwave power is cut off to avoid arcing and signal interference caused by electromagnetic induction in the microwave field. The infrared temperature probe continuously monitors the material surface temperature. The data collected by both devices are fused and processed by the control system to serve as the input signal for temperature control. Temperature control is achieved by adjusting the microwave power duty cycle: when the fused temperature approaches the set upper limit, the output power is reduced; when it falls below the lower limit, full power output is restored. In this embodiment, the material temperature is controlled in real-time within the range of 450–550°C.

[0034] Under microwave irradiation, the polar Si-O-Al bonds and OH groups in the ash selectively absorb microwave energy, generating dipole rotation and ion migration, thus efficiently converting microwave energy into heat energy. Simultaneously, under the synergistic effect of the alkaline activator NaOH, the bridging oxygen bonds in the aluminosilicate glass network structure are converted by OH groups. - Ion attack causes breakage, and the Si-O-Al three-dimensional network rapidly depolymerizes, generating soluble sodium silicate and sodium aluminate active intermediates.

[0035] Compared to traditional electric heating alkali fusion (which typically requires calcination in a muffle furnace at 550–700°C for 1–3 hours), microwave heating offers selective heating and volumetric heating from the inside out. Energy acts directly on the chemical bond sites that need to be broken, resulting in a rapid heating rate and a small temperature gradient. This avoids the heat transfer delay and localized overheating problems caused by heat conduction from the outer wall of the crucible to the center, as seen in electric heating. The synergistic effect of microwave and alkali activation reduces the activation time from 1–3 hours using traditional methods to 15 minutes, lowering energy consumption by over 60%, and ensuring more thorough and uniform activation. After irradiation, the product is naturally cooled to room temperature, yielding an alkali-activated product that appears as a dark gray, loose, blocky mass that can be easily crushed into powder by hand.

[0036] Step 3, acid leaching-hydrothermal synergistic pore formation: The alkaline fusion activated product obtained in step two was ground to pass through an 80-mesh sieve and slowly added to a 2.0 mol / L hydrochloric acid solution, with a liquid-to-solid mass ratio of hydrochloric acid solution to activated product of 5:1. The acid leaching process was carried out in a glass reactor equipped with a polytetrafluoroethylene stirrer and a reflux condenser, and the reaction was continuously stirred for 2 hours at a constant temperature of 80°C. During the acid leaching process, the hydrochloric acid selectively reacted with some of the aluminum components and residual alkali metal ions in the alkaline fusion activated product, causing them to enter the liquid phase in the form of soluble chlorides. At the same time, a large number of micron-sized initial channels were formed inside the material, providing mass transfer channels for the subsequent hydrothermal crystallization step.

[0037] After the acid leaching reaction, solid-liquid separation was performed using vacuum filtration to obtain an acid-leached filter cake. The filter cake was repeatedly washed with deionized water until the pH of the washing solution reached 6.5–7.5 and no chloride ions remained as detected by silver nitrate solution. The above acid-leached filter cake was taken, and its dry weight was determined by sampling and measuring the moisture content. Then, based on the dry weight, the acid-leached filter cake and water were mixed at a mass ratio of 1:5 and stirred at 800 rpm for 30 minutes to form a homogeneous slurry. By measuring by dry weight, the influence of filter cake moisture content fluctuations under different filtration conditions on the accuracy of slurry proportioning was eliminated, ensuring the reproducibility of hydrothermal crystallization effects between batches.

[0038] The slurry was transferred into a PTFE-lined stainless steel hydrothermal reactor, with the filling degree controlled at 65%. Tetrapropylammonium bromide, a template agent, was added at a rate 0.10 times the molar amount of SiO2 in the acid-leached filter cake (dry basis). After sealing the reactor, it was placed in a homogeneous reactor, and the temperature was set at 140°C with a heating rate of 3°C / min. At this temperature, the saturated vapor pressure of water in the reactor generated an autogenous pressure of approximately 0.36 MPa, which meets the reaction pressure range of this invention. For hydrothermal conditions requiring higher pressures, pressurization can be achieved by introducing an inert gas into the reactor, such as nitrogen, to raise the reaction system pressure to the target value. The crystallization reaction was continued for 12 hours under these hydrothermal conditions.

[0039] During hydrothermal crystallization, the system undergoes dissolution, migration, condensation, and in-situ self-assembly of silicon-aluminum species: the active silicon-aluminum species generated by acid leaching rearrange in a high-temperature, high-pressure hydrothermal environment, and silicon-oxygen tetrahedra and aluminum-oxygen tetrahedra assemble directionally around the template agent organic molecules, gradually forming an aluminosilicate framework with an ordered microporous-mesoporous hierarchical structure. After the reaction is completed, heating is stopped, and the mixture is allowed to cool naturally to room temperature. The product is then removed from the reactor, separated by vacuum filtration, washed three times with deionized water, and then dried at 105°C for 12 hours to obtain an in-situ self-assembled porous support.

[0040] Step 4, Ultrasonic-assisted loading of active components: The in-situ self-assembled porous carrier obtained in step three was dried, ground, and passed through a 100-mesh sieve. An impregnation solution containing ferric nitrate was prepared, with an iron ion concentration of 0.8 mol / L. The porous carrier was immersed in the impregnation solution at a liquid-to-solid mass ratio of 4:1.

[0041] The impregnation system was placed in an ultrasonic cleaner. The ultrasonic generator was a piezoelectric ceramic type with continuously adjustable output power. The ultrasonic power was set to 150W, the ultrasonic frequency to 40kHz, and the water bath temperature to 50℃, and ultrasonic-assisted impregnation was performed for 60 minutes. During the ultrasonic treatment, the cavitation effect generated by the ultrasonic waves in the impregnation solution formed a large number of microbubbles. The bursting of these microbubbles instantly generated a high-temperature hot spot of approximately 5000K and a high-pressure shock wave of approximately 1000atm, accompanied by a strong microjets effect. These physical effects effectively overcome the capillary resistance and surface tension within the micropores and mesopores of the porous carrier, driving the iron-containing solution to penetrate deep into the internal pore structure of the carrier, promoting the uniform molecular-level adsorption and initial nucleation and anchoring of iron ions on the inner wall of the pores.

[0042] After ultrasonic impregnation, the solid material adsorbed with metal ions was removed and dried at 105℃ for 12 hours to remove free water. After drying, the product was transferred to a muffle furnace and heated to 450℃ at a rate of 5℃ / min in air, then calcined at this temperature for 4 hours. During calcination, ferric nitrate thermally decomposed to generate iron oxide nanoparticles. The molten iron oxide formed initial anchorages on the carrier surface and pore walls through chemical bonding and physical interlocking. After calcination, the material was cooled to room temperature in the furnace to obtain the desulfurization adsorbent precursor.

[0043] Step 5, Low-temperature reduction activation: The desulfurization adsorbent precursor obtained in step four was loaded into a quartz boat and placed in a tube furnace. A mixed gas, consisting of 10% hydrogen and 90% nitrogen by volume, was introduced at a total flow rate of 100 mL / min. The air in the furnace tubes was first purged by passing the gas at room temperature for 30 minutes. Then, the temperature was increased to 350°C at a rate of 5°C / min, and the furnace was subjected to isothermal reduction treatment at this temperature for 3 hours.

[0044] The purpose of low-temperature reduction is to partially reduce the iron oxide (Fe2O3 / Fe3O4) in the precursor into lower-valence iron oxides such as Fe3O4 / FeO, or even zero-valence iron nanoclusters, which have higher desulfurization activity. These reduced iron species have stronger chemisorption capacity and higher reactivity for SO2 molecules. Meanwhile, the reduction temperature of 350℃ is much lower than the temperature required for conventional high-temperature calcination activation (600–800℃), effectively avoiding thermal shrinkage of the pore structure and Ostwald ripening sintering of the active component nanoparticles caused by high temperatures. Furthermore, the oxygen vacancies generated under the reducing atmosphere can form F-center electronic defects in the support framework, further enhancing the Lewis acid-base coordination adsorption capacity for sulfur atoms in SO2.

[0045] After reduction, the product is cooled to room temperature under nitrogen protection and then removed to obtain the final flue gas desulfurization adsorbent, which appears as a brownish-black powder.

[0046] Performance testing: The performance of the flue gas desulfurization adsorbent obtained in this embodiment was tested. Physical structure characterization was performed using an ASAP 2460 fully automated specific surface area and porosity analyzer. Before testing, the sample was degassed at 300℃ for 4 hours. Results showed that the obtained desulfurization adsorbent had a BET specific surface area of ​​312 m² / g, a total pore volume of 0.34 cm³ / g, and an average BJH desorption pore size of 7.8 nm. Compared with the specific surface area of ​​the in-situ self-assembled porous support obtained in step three (measured to be 298 m² / g), the subsequent loading and reduction steps did not cause significant loss of pore structure, indicating that the ultrasonic-assisted loading method and low-temperature reduction strategy played a crucial role in protecting the pore structure.

[0047] The desulfurization performance was evaluated using a fixed-bed adsorption evaluation device: the adsorption tube inner diameter was 10 mm, the adsorbent loading was 1.0 g, the simulated flue gas composition was SO2 concentration of 1000 ppm, O2 volume fraction of 6%, N2 as the balance gas, the total gas flow rate was 200 mL / min, and the adsorption temperature was 80℃. The outlet SO2 concentration was continuously monitored using an online infrared flue gas analyzer. The results showed that the breakthrough adsorption capacity of the adsorbent obtained in this embodiment for SO2 (the cumulative adsorption amount when the outlet concentration reaches 10% of the inlet concentration) was 112 mg / g; after continuing adsorption until complete saturation, the saturated adsorption capacity was measured to be 236 mg / g.

[0048] Regeneration performance test: The saturated adsorbent was thermally desorbed and regenerated at 350℃ under a nitrogen atmosphere for 2 hours. During desorption, the outlet SO2 concentration was monitored using an online infrared flue gas analyzer. Regeneration was considered complete when the outlet SO2 concentration fell below 10 ppm. After regeneration, the adsorption experiment was repeated five times. The results showed that after five cycles of regeneration, the breakthrough adsorption capacity of the adsorbent remained at 101 mg / g, and the regeneration adsorption capacity retention rate was 90.2%, indicating that the adsorbent prepared by the method of this invention has excellent regenerability and structural stability, and the active components did not undergo significant aggregation or loss during multiple cycles.

[0049] Example 2 Step 1, Raw material pretreatment: Take the bottom ash from a coal-fired power plant. Its main chemical components, by mass fraction, are: SiO2 55.6%, Al2O3 26.1%, CaO 9.7%, Fe2O3 4.5%, MgO 1.3%, K2O 0.9%, with a loss on ignition of 1.8%. Process it according to the drying and grinding method in Step 1 of Example 1 and pass it through a 100-mesh sieve.

[0050] Step 2, Microwave-Alkali Synergistic Lattice Activation: Weigh 100g of the bottom slag powder obtained in step one and mix it with 60g of solid sodium carbonate alkali activator (the mass ratio of ash to alkali activator is 1:0.6), grinding them evenly. Place the mixture in a corundum crucible and position it at the center of a single-mode resonant cavity microwave reactor. The single-mode resonant cavity, at a frequency of 2450MHz, can form a highly uniform microwave standing wave field at the center of the cavity, which is beneficial for the precise activation of small batches of samples. The microwave power is set to 400W, and the irradiation treatment time is 18 minutes. A K-type thermocouple temperature probe and an infrared temperature probe with metal shielding and grounding protection are installed inside the cavity. The K-type thermocouple adopts an instantaneous intermittent temperature measurement mode. After fusing the temperature data, the material temperature is controlled at 400-500℃ by adjusting the power duty cycle. After irradiation, the product is cooled to obtain the alkali-activated product.

[0051] In this embodiment, sodium carbonate is used as the alkaline activator. Compared with sodium hydroxide (Example 1), sodium carbonate is less corrosive to the equipment and improves operational safety. However, the irradiation time required to achieve full activation under the same microwave power is slightly longer (from 15 minutes to 18 minutes), and the activation temperature is also slightly lower (from 450-550°C to 400-500°C). This is because sodium carbonate has a weaker alkalinity than sodium hydroxide, requiring a slightly longer reaction time to complete the depolymerization of the aluminosilicate glass.

[0052] Step 3, acid leaching-hydrothermal synergistic pore formation: The alkali-activated product was ground to pass through an 80-mesh sieve and added to a 3.0 mol / L sulfuric acid solution at a liquid-to-solid mass ratio of 6:1. The reaction was carried out at a constant temperature of 85℃ with stirring for 2.5 hours. The advantage of using sulfuric acid instead of hydrochloric acid is that sulfuric acid has lower volatility and a better operating environment. After filtration, the filter cake was repeatedly washed with deionized water until the washing liquid was neutral and sulfate ion detection was negative. The acid-leached filter cake was taken, and its dry weight was determined by moisture content measurement. Based on the dry weight, the acid-leached filter cake and water were mixed at a mass ratio of 1:4 to form a slurry, which was then transferred to a hydrothermal reactor with a filling degree controlled at 60%. Tetraethylammonium hydroxide, a template agent, was added at an amount 0.15 times the molar amount of SiO2 contained in the acid-leached filter cake on a dry weight basis. After sealing, the mixture was crystallized at 150℃ for 10 hours, generating a self-pressure of approximately 0.48 MPa. After the reaction, the mixture was cooled, filtered, washed, and dried to obtain an in-situ self-assembled porous carrier.

[0053] Step 4, Ultrasonic-assisted loading of active components: A mixed solution of manganese nitrate and cerium nitrate was used as the impregnation solution, with a manganese ion concentration of 0.6 mol / L and a cerium ion concentration of 0.2 mol / L (total transition metal ion concentration of 0.8 mol / L), and a liquid-to-solid mass ratio of 3:1. The ultrasonic power was 120 W, the ultrasonic frequency was 28 kHz, the water bath temperature was 60 °C, and the treatment time was 90 minutes. After ultrasonic impregnation, the material was transferred to a muffle furnace and heated to 500 °C at a rate of 5 °C / min under air atmosphere, and then calcined at this temperature for 3 hours to obtain the desulfurization adsorbent precursor.

[0054] In this embodiment, a manganese-cerium bimetallic active component system is used. The introduction of cerium is based on the following principle: cerium ions have Ce³⁺. + / Ce 4+ Its variable valence state cycling ability allows it to form an oxygen-deficient structure of CeO2 / Ce2O3 during calcination and subsequent reduction. This structure can provide additional active oxygen species for SO2 adsorption and oxidation, while also facilitating the interaction between CeO2 and MnO. x The interfacial synergistic effect enhances the dispersibility and catalytic activity of the active components.

[0055] Step 5, Low-temperature reduction activation: The desulfurization adsorbent precursor was loaded into a tubular furnace, and a mixture of 15% H2 / 85% N2 gas was introduced at a flow rate of 100 mL / min. The temperature was increased to 380 °C at a rate of 5 °C / min, and the furnace was kept at this temperature for 2.5 hours for reduction. After reduction, the furnace was cooled under nitrogen protection.

[0056] Performance test results: The obtained flue gas desulfurization adsorbent has a BET specific surface area of ​​276 m² / g, a pore volume of 0.28 cm³ / g, and an average pore size of 9.2 nm. The SO2 breakthrough adsorption capacity is 98 mg / g, and the saturated adsorption capacity is 197 mg / g. After five adsorption-desorption cycles, the regenerated adsorption capacity retention rate is 92.1%.

[0057] Example 3: Step 1, Raw material pretreatment: Take fly ash emitted from a coal-fired power plant. Its main chemical components, by mass fraction, are: SiO2 57.8%, Al2O3 31.2%, CaO 3.4%, Fe2O3 3.2%, MgO 0.9%, K2O 1.7%, and loss on ignition 1.8%. Process it according to the drying and grinding method in Step 1 of Example 1 and pass it through a 100-mesh sieve.

[0058] Step 2, Microwave-Alkali Synergistic Lattice Activation: 100g of fly ash powder was weighed and mixed with 60g of a mixture of potassium hydroxide and sodium hydroxide (40g KOH, 20g NaOH, with a mass ratio of ash to alkali activator of 1:0.6). The mixture was ground evenly and then placed in a multi-mode resonant cavity microwave reactor. The microwave power was set to 600W, and the irradiation treatment lasted for 10 minutes. The same shielded grounded thermocouple and infrared fusion temperature measurement method as in Example 1 was used, and the material temperature was controlled between 550 and 650℃. In the potassium hydroxide-sodium hydroxide mixed alkali activator, the difference in ionic radii between potassium and sodium ions can create a complementary attack effect on the depolymerization of the silica-alumina glass network in the fly ash: the larger potassium ion radius facilitates entry into the network gaps and widens the Si-O-Al bond angle, increasing the OH- ion radius. - The accessibility and bond-breaking efficiency of bridging oxygen bonds are improved; sodium ions, with their smaller radius, have a higher charge density and a faster bond-breaking rate. The synergy of these two factors can further enhance activation efficiency, reducing activation time to 10 minutes.

[0059] Step 3, acid leaching-hydrothermal synergistic pore formation: The alkali-activated product was ground to pass through an 80-mesh sieve and then added to a 2.5 mol / L hydrochloric acid solution at a liquid-to-solid mass ratio of 4:1. The mixture was stirred at 75°C for 3 hours. The mixture was then filtered and washed until neutral and free of chloride ions. The filter cake was taken and mixed with water at a dry weight ratio of 1:6. A template agent, n-butylamine, was added at a ratio of 0.08 times the molar amount of SiO2 in the dry weight of the filter cake. The mixture was transferred to a hydrothermal reactor and hydrothermally crystallized at 120°C for 18 hours at a self-generated pressure of approximately 0.20 MPa. After the reaction, the mixture was cooled, filtered, washed, and dried to obtain an in-situ self-assembled porous support.

[0060] Step 4, Ultrasonic-assisted loading of active components: A mixed solution of copper nitrate and cobalt nitrate was used as the impregnation solution, with a copper ion concentration of 0.5 mol / L and a cobalt ion concentration of 0.3 mol / L, and a liquid-to-solid mass ratio of 5:1. The ultrasonic power was 200 W, the ultrasonic frequency was 40 kHz, the water bath temperature was 45 °C, and the treatment time was 80 minutes. After ultrasonic impregnation, the product was dried at 110 °C for 10 hours, and then calcined in a muffle furnace under air atmosphere at a rate of 5 °C / min to 400 °C for 5 hours.

[0061] Step 5, Low-temperature reduction activation: The desulfurization adsorbent precursor was loaded into a tube furnace, and a 10% H2 / 90% Ar mixed gas was introduced at a flow rate of 80 mL / min. The temperature was increased to 320 °C at a rate of 5 °C / min, and the furnace was kept at this temperature for 4 hours for reduction. After reduction, the furnace was cooled under argon protection.

[0062] Performance test results: The obtained flue gas desulfurization adsorbent has a BET specific surface area of ​​345 m² / g, a pore volume of 0.42 cm³ / g, and an average pore size of 6.5 nm. The SO2 breakthrough adsorption capacity is 131 mg / g, and the saturated adsorption capacity is 278 mg / g. After five adsorption-desorption cycles, the regenerated adsorption capacity retention rate is 89.5%.

[0063] Example 4 (Comparative Experiment): To verify the synergistic value and indivisibility of the steps in the method of this invention, multiple sets of comparative experiments were conducted, using the same raw materials and basic experimental parameters as in Example 1, with only the combination of steps adjusted. The results are summarized below: (1) Step 2, microwave-alkali synergistic activation, was omitted, and the raw material ash was directly subjected to acid leaching-hydrothermal treatment: the specific surface area of ​​the resulting carrier was only 78 m² / g, and the SO2 saturated adsorption capacity was only 43 mg / g. This indicates that microwave-alkali activation is the key step in opening the silica-alumina glass body of the ash and releasing the active silica-alumina components. Without sufficient activation, the subsequent pore-forming effect is extremely limited.

[0064] (2) Omitting hydrothermal crystallization in step three and only performing acid leaching to create pores: the specific surface area of ​​the resulting carrier is 112 m² / g, with no ordered pore structure characteristics, and the SO2 saturated adsorption capacity is only 76 mg / g. This indicates that acid leaching alone can only form irregular pores, and the in-situ self-assembly process of hydrothermal crystallization is indispensable for constructing an ordered hierarchical pore structure.

[0065] (3) Step four, ultrasonic assistance, was omitted, and conventional static impregnation loading was used: the saturated adsorption capacity of the obtained adsorbent for SO2 was 168 mg / g, and the retention rate after five cycles of regeneration was only 62.3%. This shows that ultrasonic assistance makes an irreplaceable contribution to the deep and uniform dispersion of active components. The active components of conventional impregnation loading are mainly attached to the outer surface of the carrier and near the macropore openings, and are easy to agglomerate and fall off during cycle regeneration.

[0066] (4) Step five, low-temperature reduction and activation, was omitted, and the calcined oxide adsorbent was used directly: the SO2 saturated adsorption capacity of the resulting adsorbent was only 118 mg / g, which was only 50% of that in Example 1. This shows that reducing metal oxides to low-valence metals or metastable metal oxides is the key to significantly improving desulfurization performance. The coordination unsaturated active centers generated after reduction enhance the chemical adsorption force and reactivity of SO2.

[0067] The above comparative experiments fully demonstrate that there is a close synergistic relationship among the five steps of the present invention, and each step is a necessary link to achieve the final high-performance desulfurization effect.

[0068] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the scope of the invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0069] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for activating and modifying flue gas desulfurization adsorbents prepared from ash residue of thermal power plants, characterized in that, Includes the following steps: The ash residue from thermal power plants is sequentially dried, crushed, and sieved to obtain ash residue powder. Ash powder and solid alkali activator are mixed in a ratio of 1:(0.3~1.2) to form a material. The material is placed in a microwave reaction chamber for microwave irradiation treatment, which causes the silica-alumina glass in the ash powder to undergo lattice deagglomeration, thus obtaining an alkali-activated product. The alkali-activated product is added to an inorganic acid solution for acid leaching treatment, and acid leaching filter cake is obtained by solid-liquid separation; the acid leaching filter cake is mixed with water at a ratio of 1:(3-8) to form a slurry; The slurry was transferred into a hydrothermal reactor for hydrothermal crystallization reaction. After the reaction was completed, it underwent solid-liquid separation, washing and drying to obtain an in-situ self-assembled porous carrier. The in-situ self-assembled porous carrier was immersed in an impregnation solution containing a transition metal precursor and subjected to ultrasonic testing. After impregnation, it was dried and calcined to obtain the desulfurization adsorbent precursor. The desulfurization adsorbent precursor is subjected to reduction treatment in a reducing atmosphere to obtain the flue gas desulfurization adsorbent.

2. The activation and modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash and slag according to claim 1, characterized in that, The ash and slag from the thermal power plant are fly ash, bottom ash, or a mixture of fly ash and bottom ash emitted by the coal-fired power plant. The chemical composition of thermal power plant ash is as follows (mass fraction): SiO2: 40%–60%, Al2O3: 20%–35%, CaO: 3%–15%, Fe2O3: 3%–12%, with a loss on ignition of no more than 10%.

3. The activation and modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash and slag according to claim 1, characterized in that, The solid alkali activator is one or a mixture of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. The microwave irradiation frequency is 915MHz or 2450MHz, the microwave power is 200-800W, and the irradiation time is 5-30min.

4. The activation and modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash and slag according to claim 1, characterized in that, The microwave reaction cavity is equipped with a K-type thermocouple temperature probe and an infrared temperature probe to control the material temperature, which is 300-750℃.

5. The activation and modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash and slag according to claim 1, characterized in that, The inorganic acid solution is a hydrochloric acid solution or a sulfuric acid solution, with an acid concentration of 1.0–3.5 mol / L, a solid-to-acid mass ratio of 3:1–10:1, an acid leaching temperature of 60–95℃, and an acid leaching time of 1–4 h.

6. The activation and modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash and slag according to claim 1, characterized in that, The hydrothermal crystallization reaction is carried out at a temperature of 90–180°C, a reaction pressure of 0.1–1.0 MPa, and a reaction time of 4–24 h. A template agent is also added to the hydrothermal crystallization reaction, which is one or more of tetrapropylammonium bromide, tetraethylammonium hydroxide, or n-butylamine. The amount of template agent added is 0.05 to 0.25 times the molar amount of SiO2 contained in the acid-leaching filter cake on a dry basis.

7. The activation and modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash and slag according to claim 1, characterized in that, The transition metal precursor is one or more of ferric nitrate, copper nitrate, manganese nitrate, cobalt nitrate, and cerium nitrate. The total concentration of transition metal ions in the impregnation solution is 0.1–1.5 mol / L, and the liquid-solid mass ratio of the impregnation solution to the in-situ self-assembled porous support is 2:1–8:

1.

8. The activation and modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash and slag according to claim 7, characterized in that, The drying temperature after impregnation is 80-120℃, and the drying time is 6-24h; The roasting temperature is 300–550℃, the roasting time is 2–6 hours, and the roasting atmosphere is air or oxygen-deficient atmosphere.

9. The activation and modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash and slag according to claim 1, characterized in that, The reducing atmosphere is a hydrogen-containing reducing atmosphere, which is a mixture of hydrogen and an inert gas, wherein the hydrogen gas fraction is 5% to 50%, and the inert gas is nitrogen or argon; the reduction treatment temperature is 250 to 500°C, and the time is 1 to 6 hours.

10. The activation and modification method for preparing flue gas desulfurization adsorbent from thermal power plant ash and slag according to claim 1, characterized in that, The obtained in-situ self-assembled porous carrier has a specific surface area of ​​180–450 m² / g, a pore volume of 0.15–0.55 cm³ / g, and an average pore size of 3.5–16.5 nm. The flue gas desulfurization adsorbent has a saturated adsorption capacity of 120-285 mg / g for SO2 in flue gas, a breakthrough adsorption capacity of 60-165 mg / g, and after five adsorption-desorption cycles, the regeneration adsorption capacity retention rate is not less than 88%.

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