Preparation method of carbon nanotube composite ceramic desulfurizer and low-temperature regeneration method thereof

Abstract

This invention relates to the field of industrial flue gas purification technology, specifically to a method for preparing a carbon nanotube composite ceramic desulfurizer and its low-temperature regeneration method. The invention synthesizes a porous magnesium-aluminum spinel ceramic matrix from steel slag / red mud solid waste, achieving a gradient pore distribution; carbon nanotubes (CNTs) are grown in situ on the matrix surface via Fe-Co-Mo trimetallic catalysis, constructing electron transport channels and high specific surface area active sites; and Joule thermal regeneration is achieved using the CNTs conductive network, overcoming the high energy consumption problem of traditional thermal regeneration. The method of this invention is simple, making the production process more efficient and convenient, and providing feasibility for the large-scale production and use of carbon nanotube-loaded ceramic powder desulfurizers.

Description

Technical Field

[0001] This invention relates to the field of industrial flue gas purification technology, specifically to a method for preparing a carbon nanotube composite ceramic desulfurizer and its low-temperature regeneration method. Background Technology

[0002] The core of industrial flue gas desulfurization technology lies in optimizing the performance of desulfurizing agents. However, existing technologies generally face the challenge of simultaneously improving adsorption capacity, regeneration efficiency, and material lifespan. Traditional calcium-based desulfurizing agents rely on the sulfation reaction between limestone and SO2. Although inexpensive, their sulfur capacity is typically below 40 mg / g, and regeneration requires high-temperature calcination, resulting in energy consumption exceeding 35% of the system's operating cost. Activated carbon-based desulfurizing agents, while boasting a high specific surface area (800-1200 m²), also face challenges. 2 / g) improves sulfur capacity, but its mechanical strength is poor (compression resistance ≤2 MPa), it is highly sensitive to humidity (sulfur capacity decreases by 50% when humidity >5%), and the regeneration process releases CO. x Pollutants, particularly pulverization and secondary pollution, are prominent issues in practical applications. Metal oxide desulfurizers (such as Fe2O3 and CuO) can achieve a sulfur capacity of 60 mg / g under medium-temperature conditions of 300-400℃, but high-temperature sintering easily leads to catalyst agglomeration and deactivation, and regeneration requires strong reducing gases, posing safety risks and operational complexity.

[0003] To address the aforementioned shortcomings, recent research has attempted to improve desulfurizer performance through composite modification, but technological bottlenecks remain unresolved. For example, patent CN111116224A discloses a desulfurizer with red mud waste as the active component, its preparation method, and its application. This desulfurizer is prepared by crushing, batching, granulating, molding, and calcining red mud waste, walnut shell powder, straw fiber, zinc oxide powder, and a molding agent solution. However, its preparation process involves multiple solid-phase mixing and high-temperature treatment, resulting in high process complexity, and it is only suitable for low-concentration H2S desulfurization scenarios. Patent CN114307617A discloses a copper oxide composite desulfurizer, its preparation method, and its application, which involves pretreatment, impregnation, and calcination processes to co-load magnesium oxide and copper oxide onto the surface of a carbon-based material. However, the bottleneck of this method lies in the following: the pretreatment stage requires 8-10 hours of surface oxidation of the carbon-based material with concentrated nitric acid to form oxygen-containing functional groups, resulting in high reaction energy consumption and nitrogen oxide-containing waste acid pollution; the active components rely on high-purity magnesium oxide and copper salts, leading to high raw material costs. Patent CN101590357A discloses a method for preparing desulfurizing agents using waste molecular sieve catalysts, specifically: using waste molecular sieves pretreated with dilute hydrochloric acid as a carrier, mixing it with active components, binders, and water, extruding it into strips, and then heat-treating it. However, this method has significant drawbacks: dilute hydrochloric acid pretreatment can only remove surface deposited metals; residual Ni / V poisons in the internal pores catalyze carbon deposition during desulfurization; and the Cu supported by the equal-volume impregnation method... 2+The decrease in specific surface area of ​​the carrier leads to insufficient dispersion, forming CuO agglomerates and reducing the effective sulfur capacity; structural defects limit its industrial application.

[0004] All of the above technologies face the dual contradiction of resource utilization pathways and active site design. On the one hand, the inherent inertness of waste materials restricts the construction of highly efficient active sites; on the other hand, the heat / mass transfer barriers in the regeneration process also affect the circular economy of materials. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing technologies and provide a method for preparing a carbon nanotube composite ceramic desulfurizer and its low-temperature regeneration method. The core of this invention lies in proposing a ternary synergistic innovation path of "ceramic matrix-catalytic interface-conductive network": a porous magnesium-aluminum spinel ceramic matrix is ​​synthesized from steel slag / red mud solid waste to achieve a gradient pore distribution; using C2H2 as a carbon source, carbon nanotubes (CNTs) are grown in situ on the ceramic matrix surface through Fe-Co-Mo trimetallic catalysis combined with in-situ catalytic pyrolysis and chemical vapor deposition, constructing electron transport channels and high specific surface area active sites; and the CNTs conductive network is used to achieve Joule thermal regeneration, overcoming the high energy consumption problem of traditional thermal regeneration. Compared with existing technologies, the sulfur regeneration temperature of the desulfurizer in this invention is reduced by more than 60%, providing a disruptive solution for medium- and low-temperature flue gas desulfurization.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] This invention provides a method for preparing a carbon nanotube composite ceramic desulfurizing agent, comprising the following steps: Step 1: Using steel slag, red mud, and nano-alumina as raw materials to prepare ceramic powder, the raw materials are ball-milled and then calcined at 800~1200℃ for 1~2 hours in a mixed atmosphere of hydrogen and nitrogen. Step 2: Using ethanol as a dispersant, iron salt, cobalt salt and molybdenum salt are added sequentially, and ultrasonic-assisted stirring is used to obtain a catalyst precursor solution; Step 3: Place the ceramic powder in the catalyst precursor solution, maintain the pressure of 0.08~0.1MPa in the vacuum tank for 0.5~1h, and after restoring to normal pressure, let it stand for 1~2h to ensure that the solution penetrates into the internal micropores; Step 4: Dry the separated powder, then heat-treat it at 650~850℃ for 0.5~1h in a mixed atmosphere of C2H2 and N2, and then heat-treat it at 275~350℃ for 1~3h in an argon atmosphere to obtain the carbon nanotube composite ceramic desulfurizer.

[0008] This invention prepares ceramic powder by compounding steel slag, red mud and nano alumina, uniformly loads Fe-Co-Mo trimetallic catalytic precursor into the ceramic powder by vacuum impregnation, and then grows carbon nanotubes on the surface of the ceramic powder by in-situ catalytic pyrolysis combined with chemical vapor deposition process, thus obtaining carbon nanotube composite ceramic desulfurizer in situ.

[0009] In the above technical solution, further, in step one, the weight parts of each component of the raw material for preparing ceramic powder are: 50-70 parts of steel slag, 20-30 parts of red mud, and 10-20 parts of nano-alumina.

[0010] In the above technical solution, further, the f-CaO content in the steel slag is <3%; The Na2O content in the red mud is <2%.

[0011] In step one, the ball milling time is 4~8 hours, and the ball milling is carried out until D50 = 2~5μm; The volume fraction of hydrogen in the hydrogen and nitrogen mixture is 2.5% to 7.5%.

[0012] In the above technical solution, further, in step two, the total concentration of iron salt and cobalt salt in the catalyst precursor solution is 5wt%~15wt%, and the concentration of molybdenum salt is 0.5wt%~1wt%. The molar ratio of the iron salt to the cobalt salt is (1~2):(2~3); The stirring time is 2 to 6 hours.

[0013] In the above technical solution, further, in step two, the iron salt is one or more of ferric sulfate, ferric chloride, and ferric nitrate; The cobalt salt is one or more of cobalt sulfate, cobalt chloride, and cobalt nitrate; The molybdenum salt is molybdenum chloride.

[0014] In the above technical solution, further, in step four, the drying temperature is 90~120℃ and the drying time is 10~12h; In the C2H2 and N2 mixture, the volume ratio of C2H2 to N2 is 1:(9~10).

[0015] Another aspect of the present invention provides a carbon nanotube composite ceramic desulfurizer prepared by the above-mentioned preparation method, wherein the desulfurizer comprises a porous magnesium aluminum spinel ceramic matrix and carbon nanotubes grown on the surface of the matrix.

[0016] The present invention also provides a low-temperature regeneration method for the above-mentioned carbon nanotube composite ceramic desulfurizer, comprising the following steps: the adsorbed desulfurizer is placed in a conductive crucible, and at 120~220℃, a pulse voltage of 80~100V is applied to both ends of the conductive crucible for 10~40ms, and an inert atmosphere is filled for protection to obtain the regenerated carbon nanotube composite ceramic desulfurizer.

[0017] The beneficial effects of this invention are as follows: 1. The preparation method of this invention involves impregnating a Fe-Co-Mo trimetallic catalyst into the micropores of ceramic powder, and directly growing carbon nanotubes on the surface of the ceramic powder through in-situ catalytic pyrolysis combined with chemical vapor deposition. On the one hand, the carbon nanotubes not only provide a high specific surface area and hydrophobic channels, but also enhance the adsorption capacity for SO2; on the other hand, they achieve chemical bonding and microstructure interlocking between the two phases, thereby improving the interfacial affinity and structural stability of the composite material.

[0018] 2. This invention uses a salt solution of Fe, Co, and Mo as a trimetallic catalyst, which has significant cost advantages. Furthermore, the synergistic effect of Fe, Co, and Mo regulates the electronic structure and optimizes the adsorption energy of intermediates, significantly improving the reaction activity and stability of the catalyst, which is beneficial to the formation of carbon nanotube structures.

[0019] 3. The steel slag and red mud industrial solid waste used in this invention are rich in oxides such as iron, calcium, silicon, and aluminum, and have a porous structure and alkaline surface, which is conducive to the adsorption of acidic SO2. At the same time, nano-alumina is used as an additive, which can adjust the pore structure of the ceramic matrix on the one hand, and improve the specific surface area and thermal stability of the matrix on the other hand. Furthermore, the synergistic effect of steel slag and red mud solid waste results in a hazardous solid waste disposal rate of >65%, significantly reducing the production cost of ceramic powder and thus providing certain economic benefits.

[0020] 4. The carbon nanotube composite ceramic desulfurizer prepared in this invention utilizes an electrothermal heating mechanism to achieve low-temperature desorption of the desulfurizer. It exhibits excellent desorption performance, wide applicability, and low energy consumption requirements. This means that this desulfurizer can play a role in industrial flue gas purification, while also being cost-effective and easy to operate.

[0021] 5. The preparation method of this invention is simple, making the production process more efficient and convenient, and providing feasibility for the large-scale production and use of ceramic powder desulfurizers loaded with carbon nanotubes.

[0022] Therefore, the method of the present invention has a series of positive effects such as high yield, stable properties, and good cyclic adsorption-desorption performance, bringing innovation and progress to the field of industrial flue gas purification. Detailed Implementation

[0023] The following examples are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way.

[0024] Unless otherwise specified, the materials used in the embodiments of the present invention can be obtained commercially or prepared according to conventional methods known to those skilled in the art.

[0025] Example 1 A method for preparing a carbon nanotube composite ceramic desulfurizer includes the following steps: Step 1: Using 70 parts steel slag, 20 parts red mud, and 10 parts nano alumina as raw materials for ceramic powder preparation, the raw materials are ball-milled to D50=5μm for 4 hours and then calcined at 800℃ for 1 hour in a mixed atmosphere of hydrogen and nitrogen (hydrogen gas fraction 5%). Step 2: Using ethanol as a dispersant, iron salt, cobalt salt and molybdenum salt are added sequentially, wherein the total concentration of iron salt and cobalt salt is 5 wt%, the concentration of molybdenum salt is 0.5 wt%, the molar ratio of iron salt and cobalt salt is 1:2, and ultrasonic-assisted stirring is used for 2 hours to obtain the catalyst precursor solution. Step 3: Place the ceramic powder in the catalyst precursor solution, maintain the pressure of 0.08 MPa in the vacuum tank for 1 hour, and then let it stand for 2 hours after restoring the normal pressure to ensure that the solution penetrates into the internal micropores. Step 4: The prepared powder is separated by vacuum filtration, dried at 90℃ for 12h, then heat-treated at 650℃ for 0.5h in a C2H2 and N2 mixed gas atmosphere (volume ratio 1:9), and then heat-treated at 300℃ for 2h in an argon atmosphere to obtain carbon nanotube composite ceramic desulfurizer.

[0026] Low-temperature regeneration process of desulfurizing agent: The adsorbed desulfurizing agent is placed in a conductive crucible, and a pulse voltage (100V / 10ms) is applied to both ends of the conductive crucible at 120℃ and an inert atmosphere is filled for protection to obtain regenerated carbon nanotube composite ceramic desulfurizing agent.

[0027] Example 2 A method for preparing a carbon nanotube composite ceramic desulfurizer includes the following steps: Step 1: Using 60 parts of steel slag, 25 parts of red mud, and 15 parts of nano alumina as raw materials for ceramic powder preparation, the raw materials are ball-milled to D50=4μm for 5 hours and then calcined at 1000℃ for 2 hours in a mixed atmosphere of hydrogen and nitrogen (hydrogen gas fraction 5%). Step 2: Using ethanol as a dispersant, iron salt, cobalt salt and molybdenum salt are added sequentially, wherein the total concentration of iron salt and cobalt salt is 15 wt%, the concentration of molybdenum salt is 1 wt%, and the molar ratio of iron salt to cobalt salt is 1:2. The mixture is stirred with ultrasonic assistance for 4 hours to obtain the catalyst precursor solution. Step 3: Place the ceramic powder in the catalyst precursor solution, maintain the pressure of 0.09 MPa in the vacuum tank for 1 hour, and then let it stand for 2 hours after restoring the normal pressure to ensure that the solution penetrates into the internal micropores. Step 4: The prepared powder is separated by vacuum filtration, dried at 110℃ for 12h, then heat-treated at 750℃ for 0.5h in a C2H2 and N2 mixed gas atmosphere (volume ratio 1:9), and then heat-treated at 300℃ for 2h in an argon atmosphere to obtain carbon nanotube composite ceramic desulfurizer.

[0028] Low-temperature regeneration process of desulfurizing agent: The adsorbed desulfurizing agent is placed in a conductive crucible, and a pulse voltage (80V / 10ms) is applied to both ends of the conductive crucible at 220℃ and an inert atmosphere is filled for protection to obtain regenerated carbon nanotube composite ceramic desulfurizing agent.

[0029] Example 3 A method for preparing a carbon nanotube composite ceramic desulfurizer includes the following steps: Step 1: Using 50 parts of steel slag, 30 parts of red mud, and 20 parts of nano alumina as raw materials for ceramic powder preparation, the raw materials are ball-milled to D50=5μm for 8 hours and then calcined at 1200℃ for 2 hours in a mixed atmosphere of hydrogen and nitrogen (hydrogen gas fraction 5%). Step 2: Using ethanol as a dispersant, iron salt, cobalt salt and molybdenum salt are added sequentially, wherein the total concentration of iron salt and cobalt salt is 10 wt%, the concentration of molybdenum salt is 0.8 wt%, the molar ratio of iron salt and cobalt salt is 1:2, and ultrasonic-assisted stirring is used for 4 hours to obtain the catalyst precursor solution. Step 3: Place the ceramic powder in the catalyst precursor solution, maintain the pressure of 0.1 MPa in the vacuum tank for 1 hour, and then let it stand for 2 hours after restoring the normal pressure to ensure that the solution penetrates into the internal micropores; Step 4: The prepared powder is separated by filtration, dried at 110℃ for 12h, then heat-treated at 850℃ for 0.5h in a C2H2 and N2 mixed gas atmosphere (volume ratio 1:9), and then heat-treated at 300℃ for 3h in an argon atmosphere to obtain carbon nanotube composite ceramic desulfurizer.

[0030] Low-temperature regeneration process of desulfurizing agent: The adsorbed desulfurizing agent is placed in a conductive crucible, and a pulse voltage (100V / 10ms) is applied to both ends of the conductive crucible at 150℃ and an inert atmosphere is filled for protection to obtain regenerated carbon nanotube composite ceramic desulfurizing agent.

[0031] Test Example 1 1. Test conditions: reaction tube diameter 10mm, sample loading amount 2g, reaction bed height-to-diameter ratio = 5:1, temperature 390℃, atmospheric pressure, reaction gas is hydrogen sulfide standard gas (volume concentration 3%, equilibrium gas is nitrogen).

[0032] 2. Test Procedure: Hydrogen sulfide standard gas is passed through the reactor bed at a space velocity of 2000 h⁻¹. 1 When the desulfurizing agent absorbs 5% of the sulfur, the hydrogen sulfide concentration at the reactor outlet is measured. Feeding is stopped when the desulfurizing agent breaks through (hydrogen sulfide concentration at the reactor outlet ≥ 200 ppm). The results of the sulfur breakthrough test are shown in Table 1.

[0033] Table 1

[0034] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon nanotube composite ceramic desulfurizing agent, characterized in that, Includes the following steps: Step 1: Using steel slag, red mud, and nano-alumina as raw materials to prepare ceramic powder, the raw materials are ball-milled and then calcined at 800~1200℃ for 1~2 hours in a mixed atmosphere of hydrogen and nitrogen. Step 2: Using ethanol as a dispersant, iron salt, cobalt salt and molybdenum salt are added sequentially, and ultrasonic-assisted stirring is used to obtain a catalyst precursor solution; Step 3: Place the ceramic powder in the catalyst precursor solution, maintain the pressure of 0.08~0.1MPa in the vacuum tank for 0.5~1h, and after restoring to normal pressure, let it stand for 1~2h to ensure that the solution penetrates into the internal micropores; Step 4: Dry the separated powder, then heat-treat it at 650~850℃ for 0.5~1h in a mixed atmosphere of C2H2 and N2, and then heat-treat it at 275~350℃ for 1~3h in an argon atmosphere to obtain the carbon nanotube composite ceramic desulfurizer.

2. The preparation method of the carbon nanotube composite ceramic desulfurizer according to claim 1, characterized in that, In step one, the weight parts of each component of the raw material for preparing ceramic powder are: 50-70 parts of steel slag, 20-30 parts of red mud, and 10-20 parts of nano-alumina.

3. The preparation method of the carbon nanotube composite ceramic desulfurizer according to claim 1, characterized in that, The steel slag contains less than 3% f-CaO. The Na2O content in the red mud is <2%.

4. The preparation method of the carbon nanotube composite ceramic desulfurizer according to claim 1, characterized in that, In step one, the ball milling time is 4~8 hours, and the ball milling is carried out until D50 = 2~5μm; The volume fraction of hydrogen in the hydrogen and nitrogen mixture is 2.5% to 7.5%.

5. The preparation method of the carbon nanotube composite ceramic desulfurizer according to claim 1, characterized in that, In step two, the total concentration of iron salt and cobalt salt in the catalyst precursor solution is 5wt%~15wt%, and the concentration of molybdenum salt is 0.5wt%~1wt%. The molar ratio of the iron salt to the cobalt salt is (1~2):(2~3); The stirring time is 2 to 6 hours.

6. The preparation method of the carbon nanotube composite ceramic desulfurizer according to claim 1, characterized in that, In step two, the iron salt is one or more of ferric sulfate, ferric chloride, and ferric nitrate; The cobalt salt is one or more of cobalt sulfate, cobalt chloride, and cobalt nitrate; The molybdenum salt is molybdenum chloride.

7. The preparation method of the carbon nanotube composite ceramic desulfurizer according to claim 1, characterized in that, In step four, the drying temperature is 90~120℃ and the drying time is 10~12h; In the C2H2 and N2 mixture, the volume ratio of C2H2 to N2 is 1:(9~10).

8. A carbon nanotube composite ceramic desulfurizer prepared by the preparation method according to any one of claims 1-7, characterized in that, The desulfurizing agent comprises a porous magnesium aluminum spinel ceramic matrix and carbon nanotubes grown on the surface of the matrix.

9. A low-temperature regeneration method for the carbon nanotube composite ceramic desulfurizer according to claim 8, characterized in that, The process includes the following steps: the adsorbed desulfurizing agent is placed in a conductive crucible, and a pulse voltage of 80-100V is applied across both ends of the conductive crucible at 120-220℃ for 10-40ms, and an inert atmosphere is filled for protection to obtain the regenerated carbon nanotube composite ceramic desulfurizing agent.

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