Method for preparing coral reef-shaped porous structure desulfurizing agent from power plant circulating water alkaline sludge and application of coral reef-shaped porous structure desulfurizing agent

Abstract

The invention belongs to the technical field of power plant industrial solid waste recycling and flue gas purification, and particularly relates to a method for preparing a coral-reef-shaped porous-structure desulfurizing agent from power plant circulating water alkaline sludge and application of the coral-reef-shaped porous-structure desulfurizing agent. The invention discloses a method for preparing a coral reef-shaped porous structure desulfurizing agent from power plant circulating water alkaline sludge, the raw materials comprise, by weight, 60-90% of alkaline sludge, 3-10% of an acid activator, 0.5-5% of a structure conditioning agent, 0-15% of an exogenous calcium supplement agent, and the balance water, and the alkaline sludge is calculated by dry basis mass. According to the invention, the basic sludge is used as a core raw material, the components of the sludge react with the acid activator to generate gas, and the gas cooperates with the structure regulator to construct a three-dimensional network structure with through coral reef-shaped multi-stage pores in situ. According to the present invention, the cyclic utilization of the internal waste of the power plant is achieved, the unique pore structure provides the huge reaction specific surface area and the excellent mass transfer performance, and the characteristics of high desulfurization efficiency, good mechanical strength and low cost are provided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of power plant industrial solid waste resource utilization and flue gas purification, and particularly relates to a method for preparing a coral reef-like porous structure desulfurizer from power plant circulating water alkaline sludge and application thereof. BACKGROUND

[0002] Power plant circulating cooling water and blowdown water treatment generally adopts sodium hydroxide-sodium carbonate double-alkali process to remove hardness, and a large amount of alkaline sludge is formed in the process, mainly being mainly carbonate and hydroxide sludge. At present, the sludge is generally regarded as solid waste for landfill disposal after dewatering, which not only occupies land, but also wastes the contained alkaline substances and mineral resources.

[0003] Power plant boiler flue gas needs to be purified by a desulfurizer (such as limestone, mainly composed of calcium carbonate). At present, the most widely used and most mature technology in the world is the wet limestone-gypsum desulfurization process, which has a desulfurization efficiency of more than 95%. Its main principle is to complete the absorption of acid gas under the action of calcium carbonate alkaline absorbent in limestone and water. In the project, the prepared limestone slurry is sprayed from the lower part of the absorption tower upward to form countless fine droplets, and the flue gas flows upward and contacts with the downwardly sprayed slurry, so that the flue gas and the slurry are fully mixed, and SO2 in the flue gas and the alkaline substances in the slurry are neutralized and oxidized to finally generate gypsum (CaSO4·2H2O).

[0004] The alkaline sludge is rich in calcium carbonate and other substances, and if the alkaline sludge can be developed into a desulfurizer, a huge environmental benefit can be achieved. However, the sludge directly used for desulfurization has fatal defects, i.e. the particles are too small, the porosity is low, the specific surface area is small, and the reaction activity is low. The traditional forming and granulating method will further increase the mass transfer resistance, so that the desulfurization efficiency cannot meet the industrial requirements.

[0005] Therefore, it is an urgent problem to be solved to modify the alkaline sludge to prepare a desulfurizer with high porosity reaction sites. SUMMARY

[0006] The present application aims to at least solve one of the problems in the related art. To this end, the embodiments of the present application propose a method for preparing a coral reef-like porous structure desulfurizer from power plant circulating water alkaline sludge.

[0007] The method for preparing a coral reef-like porous structure desulfurizer from power plant circulating water alkaline sludge according to the embodiments of the present application, the raw materials for preparing the desulfurizer include: alkaline sludge: 60-90 %, acid excitation agent: 3-10 %, structure adjusting agent: 0.5-5 %, and exogenous calcium supplement: 0-15 %, and the balance is water, and the alkaline sludge is calculated in terms of dry mass.

[0008] The method for preparing the desulfurizer with the coral reef-like porous structure from the power plant circulating water alkaline sludge has the following advantages and technical effects: 1. In the embodiment of the present application, the alkaline sludge is used as the core raw material, and an external pore-forming agent is not needed or is needed in a small amount. CO2 is generated by the reaction between the acid excitation agent and part of CaCO3 in the sludge and the metal hydroxide (water is generated and the gelation is promoted), the generated gas is captured by the structure regulator, and stable and through foam holes are formed in situ. The pore structure and the amorphous silica-alumina gel of the sludge are interwoven with each other, and a solid and porous form similar to coral reefs is formed; 2. In the embodiment of the present application, the prepared desulfurizer has a porosity of 60-80% and a specific surface area of 30-60 m² / g, which is much higher than that of ordinary dry sludge, and the desulfurization reaction rate and the sulfur capacity are greatly improved; 3. In the embodiment of the present application, the concept of circular economy is perfectly combined, the waste (alkaline sludge) from the water treatment of the power plant is used to prepare the desulfurizer, and the desulfurizer is used to solve the flue gas treatment problem (flue gas SO2), so that a characteristic material circulation chain in the plant is formed, and the environmental protection and economic significance are great; 4. In the embodiment of the present application, the alkaline sludge can be designed into different forms such as granular and honeycomb, and is suitable for various desulfurization processes such as circulating fluidized bed and fixed bed.

[0009] In some embodiments, the main chemical components of the alkaline sludge include CaCO3, Mg(OH)2, Ca(OH)2, Al(OH)3, Fe(OH)3 and silicate compounds; the pH of the alkaline sludge is 9.5-11.5, and the water content is 40-60%; the alkaline sludge is obtained from the circulating cooling water treatment process or the sewage treatment process of a power plant.

[0010] In some embodiments, the acid excitation agent includes at least one of dilute hydrochloric acid, dilute sulfuric acid or citric acid solution. And / or, the concentration of hydrogen ions in the acid excitation agent is not greater than 0.02 mol / L.

[0011] In some embodiments, the structure regulator includes at least one of carboxymethyl cellulose sodium or sodium alginate.

[0012] In some embodiments, the external calcium supplement includes at least one of carbide slag, slaked lime or cement.

[0013] In some embodiments, the method for preparing the desulfurizer with the coral reef-like porous structure from the power plant circulating water alkaline sludge includes the following steps: (1) sludge conditioning: after the alkaline sludge is homogenized, a weak alkaline solution is added for mixing and stirring, and the water content is adjusted; (2) acid excitation foaming: under high-speed stirring, the acid excitation agent is added to the conditioned sludge in a misting manner, the reaction temperature is controlled to be lower than 50°C, and it is observed that the slurry is obviously expanded and foamed; (3) Structure shaping: adding structure regulator during or after foaming process, and continuing to stir until a stable and uniform foam slurry is formed; (4) Injection molding and solidification: injecting the foam slurry into a mold, and forming a wet blank with preliminary strength after standing and solidification; (5) Curing and drying: curing the wet blank after demolding, atomizing and introducing a solution of multivalent cations into the curing environment, and then performing drying treatment to obtain a finished desulfurizer.

[0014] The method for preparing a coral reef-like porous structure desulfurizer from power plant circulating water basic sludge according to the embodiment of the application has the following advantages and technical effects: 1. The method uses potential bonding components such as silicon and aluminum in the basic sludge to construct a nano-scale initial gel network, which lays a foundation for subsequent formation of solid pore walls; the conditioned sludge is mixed with a weak alkaline solution (such as a NaOH or NaCO3 solution), and stirred under mild heating (60-80°C), which causes the amorphous Si-O and Al-O bonds to break and dissolve, forming the skeleton of the desulfurizer; 2. The method uses the skeleton network constructed in the first stage as a medium, and uses the reaction between the components in the basic sludge and an acidic activator to generate a gas template, thereby forming macro-mesoporous hierarchical pores in situ; under high-speed shearing, the acidic activator is added by atomization, so that the acid droplets come into contact with the gel slurry rich in carbonates, and micro-fine CO2 bubbles are controllably generated; these bubbles are captured by the gel network with viscoelasticity, forming through primary macropores; at the bubble / slush interface, due to the surface tension effect, silicon-aluminum gel particles, metal hydroxide colloids, and the like are self-assembled and arranged, forming dense pore walls around the bubbles; as the reaction proceeds and water evaporates, the nano-pores inherent in these pore walls are preserved and solidified, forming secondary mesopores; meanwhile, the addition of the acid neutralizes part of the alkali, promoting rapid gelation of the gel and fixing the foam structure at this moment; 3. The method places the shaped wet blank in a high-humidity environment, and atomizes and introduces a solution of multivalent cations into the curing environment; the cation ions will ionically crosslink with the molecular chains of the structure regulator (such as sodium alginate), forming an "egg box"-like three-dimensional network, which greatly enhances the strength and stability of the gel skeleton.

[0015] In some embodiments, in step (1), the water content is adjusted to 50-65%. And / or, in step (1), the weak alkaline solution includes a NaCO3 solution, the concentration of the weak alkaline solution is 10-20%, the mass ratio of the basic sludge to the weak alkaline solution is (10-20):1; the temperature of the mixing and stirring is 60-80°C, and the rotation speed of the mixing and stirring is 100-200 rpm. And / or, in step (2), the stirring rate of the high-speed stirring is 1250~1800 rpm; the amount of acid activator added is controlled by online monitoring of pH meter so that the final pH of the slurry is stable between 6.5 and 8.5.

[0016] In some embodiments, in step (4), the temperature for static curing is 20~60 ℃ and the time for static curing is 6~24h.

[0017] In some embodiments, in step (5), the curing treatment is carried out for 1 to 3 days in an environment with a relative humidity >80%, and the polyvalent cation solution includes a CaCl2 solution with a concentration of 5 to 10%. And / or, in step (5), the drying temperature is 80~110 ℃.

[0018] The present invention also provides the application of the above-mentioned desulfurizing agent or the desulfurizing agent prepared by the above-mentioned preparation method in flue gas purification. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the acid-stimulation-self-template foaming reaction during the preparation of the desulfurizing agent in Example 1, and the reaction of the desulfurizing agent in the flue gas purification process. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] The method for preparing a coral reef-like porous desulfurizer from alkaline sludge in power plant circulating water according to an embodiment of the present invention comprises the following raw materials: alkaline sludge: 60-90%, acidic activator: 3-10%, structure regulator: 0.5-5%, exogenous calcium supplement: 0-15%, and the balance being water, by weight percentage, wherein the alkaline sludge is based on dry weight.

[0022] This invention discloses a method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water. Using alkaline sludge as the core raw material, it relies little or no on exogenous pore-forming agents. An acidic activator reacts with some CaCO3 in the sludge to generate CO2, which then reacts with metal hydroxides (producing water and promoting gelation). The generated gas is captured by a structure regulator, forming stable, interconnected foam pores in situ. This porous structure interweaves with the amorphous silica-alumina gel of the sludge itself, forming a robust and porous morphology similar to a coral reef. In this embodiment, the prepared desulfurizing agent has a porosity as high as 60-80% and a specific surface area of ​​30-60 g / m². The concentration of sulfur per cubic meter (m² / g) far exceeds that of ordinary dried sludge, resulting in a significant increase in desulfurization reaction rate and sulfur capacity. In the embodiments of this invention, the concept of circular economy is perfectly aligned, using water treatment waste (basic sludge) from power plants to prepare desulfurizing agents for solving flue gas treatment problems (flue gas SO2), forming a highly distinctive in-plant material recycling chain with significant environmental and economic implications. In the embodiments of this invention, different forms such as granules and honeycomb can be manufactured through mold design, making it suitable for various desulfurization processes such as circulating fluidized bed and fixed bed.

[0023] In some embodiments, preferably, the main chemical components of the alkaline sludge include CaCO3, Mg(OH)2, Ca(OH)2, Al(OH)3, Fe(OH)3 and silicate compounds; the pH of the alkaline sludge is 9.5~11.5 and the water content is 40~60%; the alkaline sludge comes from the power plant's circulating cooling water treatment process or wastewater treatment process.

[0024] In some embodiments, preferably, the acidic activator includes at least one of dilute hydrochloric acid, dilute sulfuric acid, or citric acid solution; And / or, the hydrogen ion concentration in the acidic activator is not greater than 0.02 mol / L.

[0025] In some embodiments, preferably, the structure modifier includes at least one of sodium carboxymethyl cellulose (CMC-Na) or sodium alginate.

[0026] In some embodiments, preferably, the exogenous calcium supplement includes at least one of carbide slag, hydrated lime, or cement. It is added when the CaCO3 content in the basic sludge is below 20% (dry basis) to enhance the effective components of the desulfurizer.

[0027] In some embodiments, preferably, the method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water includes the following steps: (1) Sludge conditioning: After homogenizing the basic sludge, add a weak alkaline solution and mix and stir, and adjust the moisture content; (2) Acid-induced foaming: Under high-speed stirring, acidic activator was added to the conditioned sludge by atomization, and the reaction temperature was controlled below 50℃. The slurry was observed to expand and foam significantly. (3) Structural shaping: Add a structural regulator during or after foaming and continue stirring until a stable and uniform foam slurry is formed; (4) Injection and curing: Inject the foam slurry into the mold and let it stand to cure to form a wet blank with preliminary strength; (5) Curing and drying: After the wet blank is demolded, it is cured and a multivalent cation solution is introduced into the curing environment by atomization. Then it is dried to obtain the finished desulfurizer.

[0028] This invention discloses a method for preparing a coral reef-like porous desulfurizer from alkaline sludge in power plant circulating water. The method utilizes potential binding components in the alkaline sludge, such as silicon and aluminum, to construct an initial nanoscale gel network, laying the foundation for the subsequent formation of robust pore walls. The conditioned sludge is mixed with a weakly alkaline solution (such as NaOH or NaCO3 solution) and stirred under gentle heating (60-80°C). This process breaks and dissolves amorphous Si-O and Al-O bonds, forming the framework of the desulfurizer. Using the framework network constructed in the first stage as a medium, the method generates a gas template through the reaction of components in the alkaline sludge and an acidic activator, forming a multi-level pore structure with macro-mesoporous hierarchy in situ. Under high-speed shear, the acidic activator is added via atomization, allowing acid droplets to contact the carbonate-rich gel slurry, enabling controlled production. Micro-CO2 bubbles are generated and captured by a viscoelastic gel network, forming interconnected primary macropores. At the bubble / slurry interface, due to surface tension, silica-alumina gel particles and metal hydroxide colloids self-assemble and arrange themselves, forming dense pore walls around the bubbles. As the reaction proceeds and water evaporates, the inherent nanopores of these pore walls are retained and solidified, forming secondary mesopores. At the same time, the addition of acid neutralizes some of the alkali, promoting rapid gelation and fixing the foam structure at this moment. In the method of this embodiment, the molded wet preform is placed in a high-humidity environment, and a multivalent cation solution is introduced into the curing environment by atomization. The cations will undergo ionic cross-linking with the molecular chains of the structure regulator (such as sodium alginate), forming an "egg-box" shaped three-dimensional network, which greatly enhances the strength and stability of the gel skeleton.

[0029] In some embodiments, preferably, in step (1), the moisture content is adjusted to 50-65%; And / or, in step (1), the weakly alkaline solution includes a NaCO3 solution, the concentration of the weakly alkaline solution is 10~20%, the mass ratio of the basic sludge to the weakly alkaline solution is (10~20):1; the mixing temperature is 60~80℃, and the mixing speed is 100~200rpm.

[0030] In some embodiments, preferably, in step (2), the stirring rate of the high-speed stirring is 1250~1800 rpm; the dosage of the acidic activator is controlled by online monitoring with a pH meter to stabilize the final pH of the slurry at 6.5~8.5. In this embodiment of the invention, by controlling the final pH of the acidic activator addition, the intensity of the foaming reaction and the gelation process of the slurry are precisely controlled, thereby regulating the size and distribution of pores.

[0031] In some embodiments, preferably, in step (4), the temperature for static curing is 20~60 ℃ and the time for static curing is 6~24h.

[0032] In some embodiments, preferably, in step (5), the curing treatment is carried out for 1 to 3 days in an environment with a relative humidity >80%, and the polyvalent cation solution includes a CaCl2 solution with a concentration of 5 to 10%. And / or, in step (5), the drying temperature is 80~110 ℃.

[0033] The present invention also provides the application of the above-mentioned desulfurizing agent or the desulfurizing agent prepared by the above-mentioned preparation method in flue gas purification.

[0034] The technical solution of the present invention will now be described in detail with reference to specific embodiments and accompanying drawings.

[0035] Example 1 Raw materials: Power plant circulating water pretreatment sludge (dry basis CaCO3 content 25%, pH 11.3, moisture content 50%): 80% (dry basis), dilute hydrochloric acid (hydrogen ion concentration 0.02mol / L): 5%, CMC-Na: 1%, appropriate amount of water for diluting acid and adjusting total slurry consistency.

[0036] Preparation process: (1) Sludge conditioning: Take wet sludge (80% dry basis), stir and homogenize it, then add 15% NaCO3 solution at a mass ratio of 20:1 and stir at 150 rpm at 70℃ to adjust the moisture content to 65%; (2) Acid-induced foaming: Dilute hydrochloric acid is added to the sludge stirred at 1800 rpm by atomization. The pH is monitored by a pH meter and the final pH is controlled to about 7.5. During the process, microbubbles can be seen to be generated and the slurry volume expands to 2 to 3 times the original volume.

[0037] (3) Structural shaping: After the peak of foaming, add CMC solution and continue high-speed stirring for 3-5 minutes to form a stable creamy foam slurry; (4) Injection and curing: Inject the foam slurry into the mold and let it stand and cure for 12 hours at 40°C.

[0038] (5) Curing and drying: After demolding, cure at 90% humidity for 48 hours, and introduce 6% CaCl2 solution into the curing environment by atomization, and then dry in an oven at 100℃ to constant weight.

[0039] In this embodiment, the desulfurizing agent BET has a specific surface area of ​​75 m² / g, a porosity of 82%, and a crushing strength of 8.5 MPa. At a temperature of 175℃, the sulfur dioxide content in the flue gas is 100 mg / m³. 3 Under simulated flue gas conditions, the initial desulfurization efficiency is >99.5%, and the sulfur penetration capacity reaches 0.35 g SO2 / g desulfurizer, which is 8 times that of directly drying sludge.

[0040] Example 2 Raw materials: Power plant circulating water pretreatment sludge (dry basis CaCO3 content 15%, pH 10.9, moisture content 55%): 70% (dry basis), carbide slag (calcium supplement): 10%, 5% aluminum sulfate solution: 8% (equivalent to Al2(SO4)3 dry basis), sodium alginate: 0.5%, carbide slag: 11.5%.

[0041] The preparation method of this embodiment is the same as that of embodiment 1, except that in step (1), the sludge and carbide slag are mixed evenly and then homogenized and conditioned.

[0042] In this embodiment, the desulfurizing agent BET has a specific surface area of ​​63 m². 2 / g; porosity 74%; crushing strength 8.1 MPa; under simulated flue gas conditions, the initial desulfurization efficiency is >98.5%, and the sulfur penetration capacity reaches 0.31 g SO2 / g desulfurizer, which is 6 times that of directly dried sludge.

[0043] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0044] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water, characterized in that, The raw materials for preparing the desulfurizing agent include: basic sludge: 60-90%, acidic activator: 3-10%, structure regulator: 0.5-5%, exogenous calcium supplement: 0-15%, and the balance being water, by weight percentage, wherein the basic sludge is based on dry weight.

2. The method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water according to claim 1, characterized in that, The main chemical components of the alkaline sludge include CaCO3, Mg(OH)2, Ca(OH)2, Al(OH)3, Fe(OH)3 and silicate compounds; the pH of the alkaline sludge is 9.5~11.5 and the water content is 40~60%; the alkaline sludge comes from the power plant's circulating cooling water treatment process or wastewater treatment process.

3. The method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water according to claim 1, characterized in that, The acidic activator includes at least one of dilute hydrochloric acid, dilute sulfuric acid, or citric acid solution; And / or, the concentration of hydrogen ions in the acidic activator is not greater than 0.02 mol / L.

4. The method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water according to claim 1, characterized in that, The structure modifier includes at least one of sodium carboxymethyl cellulose or sodium alginate.

5. The method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water according to claim 1, characterized in that, The exogenous calcium supplement includes at least one of carbide slag, quicklime, or cement.

6. The method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water according to any one of claims 1 to 5, characterized in that, Includes the following steps: (1) Sludge conditioning: After homogenizing the basic sludge, add a weak alkaline solution and mix and stir, and adjust the moisture content; (2) Acid-induced foaming: Under high-speed stirring, acidic activator was added to the conditioned sludge by atomization, and the reaction temperature was controlled below 50℃. The slurry was observed to expand and foam significantly. (3) Structural shaping: Add a structural regulator during or after foaming and continue stirring until a stable and uniform foam slurry is formed; (4) Injection and curing: Inject the foam slurry into the mold and let it stand to cure to form a wet blank with preliminary strength; (5) Curing and drying: After the wet blank is demolded, it is cured and a multivalent cation solution is introduced into the curing environment by atomization. Then it is dried to obtain the finished desulfurizer.

7. The method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water according to claim 6, characterized in that, In step (1), the moisture content is adjusted to 50-65%; And / or, in step (1), the weakly alkaline solution includes a NaCO3 solution, the concentration of the weakly alkaline solution is 10~20%, the mass ratio of the basic sludge to the weakly alkaline solution is (10~20):1; the mixing temperature is 60~80℃, and the mixing speed is 100~200rpm; And / or, in step (2), the stirring rate of the high-speed stirring is 1250~1800 rpm; the amount of acidic activator added is controlled by online monitoring of pH meter so that the final pH of the slurry is stabilized at 6.5~8.

5.

8. The method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water according to claim 6, characterized in that, In step (4), the temperature for static curing is 20~60℃, and the time for static curing is 6~24h.

9. The method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water according to claim 6, characterized in that, In step (5), the curing treatment is carried out in an environment with a relative humidity >80% for 1 to 3 days, and the polyvalent cation solution includes CaCl2 solution with a concentration of 5 to 10%. And / or, in step (5), the drying temperature is 80~110℃.

10. The application of the desulfurizing agent prepared by the method according to any one of claims 1 to 9 in flue gas purification.

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