Method for preparing desulfurizer with coral reef-like porous structure from alkaline sludge of circulating water of power plant and application thereof

Abstract

The present application belongs to the field of power plant industrial solid waste resource utilization and flue gas purification technology, and particularly relates to a method for preparing a coral reef-like porous structure desulfurizer from power plant circulating water alkaline sludge and application. The method for preparing a coral reef-like porous structure desulfurizer from power plant circulating water alkaline sludge disclosed in the present application comprises the following raw materials: alkaline sludge: 60-90%, acid activator: 3-10%, structure regulator: 0.5-5%, exogenous calcium supplement: 0-15%, and the balance is water, and the alkaline sludge is calculated by dry mass. In the present application, alkaline sludge is used as the core raw material, and the sludge itself is reacted with the acid activator to generate gas, and the structure regulator is used to construct a three-dimensional network structure with a through "coral reef-like" multi-level pore in situ. Not only is the internal waste of the power plant recycled, but also the unique pore structure provides a large specific surface area and excellent mass transfer performance, and the desulfurizer has the characteristics of high desulfurization efficiency, good mechanical strength and low cost.

Description

Technical Field

[0001] This invention belongs to the field of power plant industrial solid waste resource utilization and flue gas purification technology, specifically relating to a method and application of preparing a coral reef-shaped porous desulfurizing agent from alkaline sludge in power plant circulating water. Background Technology

[0002] Power plant circulating cooling water and wastewater treatment commonly employ the sodium hydroxide-sodium carbonate dual-alkali process for hardening removal, which generates a large amount of alkaline sludge, primarily composed of carbonates and hydroxides. Currently, this type of sludge, after dewatering, is generally treated as solid waste and disposed of through landfills, not only occupying land but also wasting the alkaline substances and mineral resources it contains.

[0003] Flue gas from power plant boilers requires desulfurization agents (such as limestone, whose main component is calcium carbonate) for purification. Currently, the most widely used and technologically mature desulfurization process in the world is the wet limestone-gypsum process, which can achieve a desulfurization efficiency of over 95%. Its main principle is the absorption of acidic gases by the alkaline absorbent calcium carbonate in limestone and the action of water. In the process, prepared limestone slurry is sprayed upwards from the bottom of the absorption tower, forming countless tiny droplets. The flue gas flows upwards and comes into countercurrent contact with the downward-sprayed slurry, mixing thoroughly. The SO2 in the flue gas neutralizes and oxidizes with the alkaline substances in the slurry, ultimately producing gypsum (CaSO4·2H2O).

[0004] Alkaline sludge is rich in substances such as calcium carbonate. If it can be developed into a desulfurizing agent, it can achieve "waste treatment with waste" and create significant environmental benefits. However, directly using this sludge for desulfurization has fatal flaws: the particles are too small, with low porosity, small specific surface area, and low reactivity. Traditional granulation methods further exacerbate its mass transfer resistance, resulting in desulfurization efficiency that cannot meet industrial requirements.

[0005] Therefore, the preparation of desulfurizing agents with high porosity reaction sites through alkaline sludge modification has become an urgent problem to be solved. Summary of the Invention

[0006] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose a method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water.

[0007] 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.

[0008] The advantages and technical effects of the method for preparing a coral reef-like porous desulfurizing agent from alkaline sludge in power plant circulating water according to embodiments of the present invention are as follows: 1. In the embodiments of the present invention, alkaline sludge is used as the core raw material, with little or no reliance on exogenous pore-forming agents. An acidic activator reacts with some CaCO3 in the sludge to generate CO2, which then reacts with metal hydroxides (generating water and promoting gelation). The generated gas is captured by a structure regulator, forming stable, interconnected foam pores in situ. This pore structure intertwines with the amorphous silica-alumina gel of the sludge itself, forming a robust and porous morphology similar to a coral reef; 2. In the embodiments of the present invention, 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 dioxide (m² / g) far exceeds that of ordinary dried sludge, resulting in a significant increase in desulfurization reaction rate and sulfur capacity. 3. In the embodiments of this invention, the concept of circular economy is perfectly aligned, using water treatment waste (alkaline 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. 4. 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.

[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 comes from the power plant's circulating cooling water treatment process or wastewater treatment process.

[0010] In some embodiments, 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.

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

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

[0013] In some embodiments, 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) Molding and curing: The foam slurry is injected into the mold and allowed to stand and 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.

[0014] The advantages and technical effects of the method for preparing coral reef-like porous desulfurizer from alkaline sludge in power plant circulating water according to embodiments of the present invention are as follows: 1. The method of the present invention utilizes potential binding components such as silicon and aluminum in alkaline sludge 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℃). This process causes the amorphous Si-O and Al-O bonds to break and dissolve, forming the skeleton of the desulfurizer; 2. The method of the present invention uses the skeleton network constructed in the first stage as a medium, and utilizes the reaction between the components in the alkaline sludge and the acidic activator to generate a gas template, forming a multi-level pore structure with macro-mesoporous hierarchy in situ; under high-speed shear, the acidic activator is added by atomization, causing the acid droplets to react with carbonate-rich... When the gel slurry comes into contact with the material, micro-CO2 bubbles are generated in a controllable manner. These bubbles are captured by a viscoelastic gel network, forming interconnected primary macropores. At the bubble / slurry interface, due to surface tension, silica-alumina gel particles, metal hydroxide colloids, etc., self-assemble and arrange themselves to form 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 of the gel and fixing the foam structure at this moment. 3. In the method of this embodiment, the molded wet blank 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) to form an "egg-box" shaped three-dimensional network, which greatly enhances the strength and stability of the gel skeleton.

[0015] In some embodiments, 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 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) Molding and curing: The foam slurry is injected into the mold and allowed to stand and 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 is water, by weight percentage, wherein the basic sludge is based on dry weight. 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. The acidic activator includes at least one of dilute hydrochloric acid, dilute sulfuric acid, or citric acid solution, and the concentration of hydrogen ions in the acidic activator is not greater than 0.02 mol / L; The structure modifier includes at least one of sodium carboxymethyl cellulose or sodium alginate; The method 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.

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 exogenous calcium supplement includes at least one of carbide slag, quicklime, or cement.

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, 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.

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, In step (4), the temperature for static curing is 20~60℃, and the time for static curing is 6~24h.

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, 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℃.

6. The application of the desulfurizing agent prepared by the method according to any one of claims 1 to 5 in flue gas purification.

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