A double-layer composite ceramic fiber filter tube with functions of flue gas dust removal, nitrous oxide removal, and dioxin removal, and its preparation method.

Abstract

This invention discloses a double-layer composite ceramic fiber filter tube with functions of flue gas dust removal, nitrous oxide removal, and dioxin removal, and its preparation method. The ceramic fiber tube consists of an outer filter layer and an inner catalyst layer. The ceramic fiber tube provided by this invention has high dust removal efficiency at 150℃~400℃, high nitrous oxide removal efficiency, and high dioxin removal efficiency. The preparation process is simple and has few steps. The active components are uniformly dispersed on the carrier, with adjustable loading and high bonding strength. This material can achieve integrated treatment of dust, nitrous oxide, and dioxins, efficiently simplifying the treatment process of industrial exhaust gas purification and reducing flue gas treatment costs.

Description

Technical Field

[0001] This invention relates to a double-layer composite ceramic fiber filter tube with functions of flue gas dust removal, nitrous oxide removal, and dioxin removal, and its preparation method, belonging to the field of industrial flue gas nitrous oxide removal and dust purification. Background Technology

[0002] NO x Dioxins are one of the main sources of air pollution, posing a significant threat to human health and the ecological environment. They are a collective term for two classes of tricyclic aromatic organic compounds and are among the most potent carcinogens discovered to date. Excessive intake by humans produces irreversible teratogenic, carcinogenic, and mutagenic effects. Industrial flue gas has a complex composition, including dust, heavy metals, and SO2. x NO x Along with dioxins, these pollutants have become significant factors restricting the green development of industries. In recent years, environmental protection laws and regulations have been gradually improved, emission standards for conventional pollutants have become more stringent, and trace pollutants such as dioxins have also been included in the monitoring scope. At the same time, industrial N2O emission sources are diverse, with high emission concentrations and large total flue gas volumes, and they also interact with other nitrogen oxides (NOx). x Dust and carbon dioxide (CO2) share a common origin and are a key component of the national strategy for coordinated pollution reduction and carbon emission control. Currently, these pollutants are typically controlled using separate removal methods, resulting in large footprints and high treatment costs for factory flue gas treatment equipment. Therefore, research and development of a multifunctional ceramic filter capable of simultaneously removing dust, nitrous oxide, and dioxins is needed. This allows for the removal of these three pollutants as the flue gas passes through the ceramic fiber tube, significantly reducing equipment and operating costs.

[0003] Among existing ceramic filter patents, patent CN202210232049.4 involves adding a catalyst active slurry to a ceramic fiber tube precursor mixture and mixing it evenly. Finally, a mold is used to form a semi-finished ceramic fiber tube catalyst. This semi-finished product is then dried and calcined to obtain an integrated ceramic fiber tube SCR denitrification catalyst. Patent CN202110095966.8 designs a ceramic fiber catalytic filter tube and dust collector, including a ceramic fiber tube, a catalyst coating, and a honeycomb carrier, possessing the ability to catalytically oxidize organic pollutants. Patent CN202211432617.1 uses an external molding process to produce ceramic fiber tubes with an outermost ceramic membrane, which can block the impact of dust and desulfurizing agents on the surface of the ceramic fiber tube, improving its service life. However, the designs of the above patents only target single pollutants and cannot achieve the synergistic removal of multiple pollutants, failing to fundamentally solve the problems of long processes, high investment, and high operating costs in existing purification processes.

[0004] Patent CN201920981497.8 describes a desulfurization, denitrification, and dust removal composite pipe obtained by spraying a denitrification catalyst slurry onto the inner surface of a ceramic fiber tube using a spray gun. Patent CN202210933049.7 describes immersing a ceramic fiber tube in a prepared mixture, followed by sintering and furnace cooling to obtain a dust removal fiber tube, achieving integrated dust removal and denitrification. Currently, methods for loading catalysts onto ceramic filters mainly include impregnation, sol-gel methods, and coating methods. While the ceramic filters prepared using these methods have achieved certain results, they still suffer from drawbacks such as uneven catalyst dispersion, easy detachment, and low efficiency in removing nitrous oxide and dioxins. Furthermore, the ceramic fiber tube forming and catalytic active component loading are carried out in separate steps, resulting in a long overall preparation process and low efficiency. Summary of the Invention

[0005] The purpose of this invention is to address the current status and problems of industrial flue gas dust removal and purification, and to propose a double-layer composite ceramic fiber filter tube with functions of flue gas dust removal, nitrous oxide removal, and dioxin removal. Another purpose of this invention is to provide a method for preparing the above-mentioned double-layer composite ceramic fiber tube.

[0006] A double-layer composite ceramic fiber tube with functions of flue gas dust removal, nitrous oxide removal, and dioxin removal is provided. The ceramic fiber tube consists of an outer filter layer and an inner catalyst layer. The thickness ratio of the outer filter layer to the inner catalyst layer is 1-10:1-10. The active component is loaded in the inner catalyst layer. Based on the mass of the ceramic fiber in the inner catalyst layer, the mass percentage of the catalytic active component is 1-10%.

[0007] In the technical solution of this invention: the ceramic fiber slurry corresponding to the outer filter layer and the inner catalyst layer of the ceramic fiber tube is composed of ceramic fiber, inorganic binder, surfactant and deionized water, and the mass ratio is (5~10):(1~2):(0.1~0.5):(100~200).

[0008] In the technical solution of this invention: based on the mass of the ceramic fiber in the inner catalyst layer, the mass percentage of the catalytic active component is 2-8%.

[0009] In the technical solution of this invention, the mass ratio of cerium oxide: manganese oxide: holmium trioxide: tin oxide in the active components is (5-10): (5-10): (2-5): (1-2).

[0010] A method for preparing the above-mentioned double-layer composite ceramic fiber tube, wherein the method for preparing the ceramic fiber tube is as follows:

[0011] (1) Ceramic fiber pretreatment

[0012] Ceramic fibers are sheared and ball-milled to obtain short ceramic fibers with different aspect ratios.

[0013] (2) Preparation of slurry for outer filter layer

[0014] Ceramic fibers with an aspect ratio of 500 to 1000, inorganic binders, and surfactants are added to deionized water and stirred to obtain an outer filter layer slurry.

[0015] (3) Preparation of inner catalyst layer slurry

[0016] Ceramic fibers with an aspect ratio of 100 to 500, inorganic binders, surfactants, and cerium salts, manganese salts, holmium salts, and tin salts are added to deionized water and stirred to obtain an inner catalyst layer slurry.

[0017] (4) Inner catalyst layer forming

[0018] The ceramic fiber tube forming mold is immersed in the inner catalyst layer slurry, and the inner catalyst layer is obtained after rotary negative pressure filtration and drying.

[0019] (5) Forming of outer filter layer

[0020] The dried mold with the inner catalyst layer is immersed in the slurry of the outer filter layer, and the outer catalyst layer is obtained after rotary negative pressure filtration and drying.

[0021] (6) Calcination and molding of ceramic fiber tubes

[0022] The ceramic fiber tubes formed by vacuum filtration are placed in a tube furnace for high-temperature calcination, and after natural cooling, a double-layer composite ceramic fiber tube is obtained.

[0023] In the above preparation method: the ceramic fiber mentioned in step (1) is one of aluminum silicate fiber, alumina fiber, zirconium oxide fiber, mullite fiber, and zirconium-containing aluminum silicate fiber, with a fiber diameter of 5 to 15 μm and an aspect ratio of 100 to 1000 after ball milling pretreatment.

[0024] In the above preparation method: the cerium salt mentioned in step (3) is cerium nitrate hexahydrate or cerium chloride heptahydrate; the manganese salt is manganese sulfate monohydrate or manganese chloride tetrahydrate or manganese nitrate hexahydrate; the holmium salt is holmium nitrate pentahydrate; and the tin salt is anhydrous stannous chloride.

[0025] In the above preparation method: the inorganic binder mentioned in steps (2) and (3) is one of water glass or aluminum dihydrogen phosphate; the surfactant mentioned in steps (2) and (3) is one of sodium carboxymethyl cellulose, hydroxypropyl cellulose, or polyvinyl alcohol.

[0026] In the above preparation method: the rotational speed of the rotary filtration in steps (4) and (5) is 50-200 r / min, and the filtration pressure is 0.05 MPa to 0.1 MPa;

[0027] The drying temperature in steps (4) and (5) is 100-150℃, and the drying time is 2-4 hours.

[0028] The calcination temperature in step (6) is 1200-1500℃ and the calcination time is 2-8h.

[0029] The present invention relates to the application of the double-layer composite ceramic fiber tube in the removal of nitrous oxide and dioxins from industrial flue gas.

[0030] The catalytic experimental conditions and results of this invention: using Figure 1 The apparatus was used to test the effect of ceramic fiber tubes on nitrous oxide and dioxin removal, with chlorobenzene (CB) as a dioxin simulant. Laboratory gas mixtures were used to simulate flue gas, with the following inlet components: N₂O (500 ppm), NH₃ (1000 ppm), O₂ (11 vol.%), CB (500 ppm), and the remainder being N₂. The total gas flow rate was 1000 mL / min. The ceramic fiber tubes were fixed inside quartz tubes with an outer diameter of 30 mm and placed in a tube furnace. The test temperature was 150–400 °C. A Laoying 3021 portable carbon emission monitor was used to measure the N₂O concentration, and a GC-112N gas chromatograph was used to measure the CB concentration.

[0031] The beneficial effects of this invention are:

[0032] Given that the purification of multiple pollutants (N2O, dust, dioxins, etc.) in industrial flue gas generally employs separate removal methods, resulting in large footprints and high treatment costs for factory flue gas treatment equipment. Furthermore, existing methods for loading catalysts onto ceramic filters (impregnation, coating, etc.) suffer from drawbacks such as long preparation processes, low efficiency, uneven catalyst dispersion within the ceramic filter, easy detachment, and low efficiency in removing nitrous oxide and dioxins. Therefore, this invention innovatively develops a double-layer composite ceramic fiber tube capable of simultaneously removing dust, nitrous oxide, and dioxins. This allows for the removal of these three pollutants as the flue gas passes through the ceramic fiber tube, achieving both catalytic active component loading and ceramic fiber tube forming in one step, significantly reducing equipment and operating costs.

[0033] The main basis is that the double-layer composite ceramic fiber tubes prepared using different aspect ratios have a large aspect ratio in the outer filter layer, resulting in high strength after mixing and molding with binders and modifiers. This effectively intercepts flue gas dust while maintaining a long service life. The inner catalyst layer has a small aspect ratio in the fibers, resulting in a large specific surface area, easy loading of active components, high loading strength, and strong adsorption of pollutants. The composite oxide composed of cerium oxide, manganese oxide, holmium oxide, and tin oxide has excellent redox properties, enabling efficient removal of N2O and dioxins. At the same time, dioxins can easily poison the catalyst, and the high concentration of active oxygen on the surface of the composite oxide effectively enhances the inner catalyst layer's resistance to dioxin poisoning. The successful application of this invention not only achieves the synergistic removal of dust, nitrous oxide, and dioxins, but also improves the production efficiency of ceramic fiber filter tubes, thus bringing significant economic, environmental, and social benefits. Attached Figure Description

[0034] Figure 1 This is a simplified diagram of a ceramic fiber tube N2O and CB synergistic catalytic performance testing device.

[0035] Among them: 1. N2; 2. O2; 3. NH3 (1%); 4. N2O (1%); 5. Pressure reducing valve; 6. Flow meter; 7. Micro-injection pump; 8. Chlorobenzene; 9. Oil bath; 10. Mixing chamber; 11. Tube furnace; 12. Quartz sleeve; 13. Ceramic fiber tube; 14. Three-way valve; 15. Flue gas analyzer; 16. Gas chromatograph.

[0036] Figure 2 The graphs show the performance of ceramic fiber tubes prepared in Examples 1-3 and Comparative Examples 1-3 in removing N2O.

[0037] Figure 3 The graph shows the performance of ceramic fiber tubes prepared in Examples 1-3 and Comparative Examples 1-3 in removing CB. Detailed Implementation

[0038] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto:

[0039] Example 1

[0040] I. Preparation of Ceramic Fiber Tubes

[0041] (1) Ceramic fiber pretreatment

[0042] Zirconia fibers were sheared and ball-milled to obtain ceramic short fibers with different aspect ratios.

[0043] (2) Preparation of slurry for outer filter layer

[0044] Add 500g of zirconium oxide fiber (length-to-diameter ratio of 500-1000), 100g of aluminum dihydrogen phosphate, and 50g of polyvinyl alcohol to 20kg of deionized water and stir to obtain the outer filter layer slurry.

[0045] (3) Preparation of inner catalyst layer slurry

[0046] Based on the mass of the ceramic fiber in the inner catalyst layer, the mass percentage of the catalytic active component is 2%. 50g of zirconium oxide fiber (aspect ratio 100–500), 10g of aluminum dihydrogen phosphate, 5g of polyvinyl alcohol, 1.031g of cerium chloride heptahydrate, 0.786g of manganese nitrate hexahydrate, 0.533g of holmium nitrate pentahydrate, and 0.060g of anhydrous stannous chloride were added to 2kg of deionized water and stirred to obtain the inner catalyst layer slurry. The mass ratio of cerium oxide:manganese oxide:holmium trioxide:tin oxide in the active component was 10:5:2:1.

[0047] (4) Inner catalyst layer forming

[0048] The ceramic fiber tube forming mold is immersed in the inner catalyst layer slurry. The inner catalyst layer semi-finished product is formed by negative pressure filtration under the conditions of 100 r / min rotation speed and 0.05 MPa filtration pressure. Then, the inner catalyst layer is obtained by drying in an oven at 120℃ for 3 h.

[0049] (5) Forming of outer filter layer

[0050] The dried mold with the inner catalyst layer was immersed in the outer filter layer slurry. The outer filter layer semi-finished product was formed by negative pressure filtration under the conditions of 100 r / min rotation speed and 0.05 MPa filtration pressure. Then, the outer catalyst layer was obtained by drying in an oven at 120℃ for 3 h.

[0051] (6) Calcination and molding of ceramic fiber tubes

[0052] The ceramic fiber tube formed by vacuum filtration is placed in a tube furnace and calcined at 1200℃ for 6 hours. After natural cooling, a double-layer composite ceramic fiber tube is obtained, with the thickness ratio of the outer filter layer to the inner catalyst layer being 1:1.

[0053] II. Activity Test Results

[0054] use Figure 1The apparatus was used to test the effect of ceramic fiber tubes on nitrous oxide and dioxin removal, using chlorobenzene (CB) as a dioxin simulant. Laboratory gas was used to simulate flue gas, with the following inlet components: N₂O (500 ppm), NH₃ (1000 ppm), O₂ (11 vol.%), CB (500 ppm), and the remainder being N₂. The total gas flow rate was 1000 mL / min. The ceramic fiber tube was fixed inside a quartz tube with an outer diameter of 30 mm and placed in a tube furnace. The test temperature was 150–400 °C. A Laoying 3021 portable carbon emission monitor was used to measure the N₂O concentration, and a GC-112N gas chromatograph was used to measure the CB concentration. Figure 2 and Figure 3 As shown, the test results indicate that the N2O removal rate was 100% and the CB removal rate was 80.2% after 10 minutes at 150℃.

[0055] Example 2

[0056] I. Preparation of Ceramic Fiber Tubes

[0057] (1) Ceramic fiber pretreatment

[0058] Alumina fibers were sheared and ball-milled to obtain ceramic short fibers with different aspect ratios.

[0059] (2) Preparation of slurry for outer filter layer

[0060] Add 500g of alumina fiber (length-to-diameter ratio of 500-1000), 50g of water glass, and 25g of hydroxypropyl cellulose to 5kg of deionized water and stir to obtain the outer filter layer slurry.

[0061] (3) Preparation of inner catalyst layer slurry

[0062] Based on the mass of the ceramic fiber in the inner catalyst layer, the mass percentage of the catalytic active component was 4%. 125g of alumina fiber (aspect ratio 100–500), 12.5g of water glass, 6.25g of hydroxypropyl cellulose, 4.672g of cerium nitrate hexahydrate, 4.216g of manganese chloride tetrahydrate, 2.073g of holmium nitrate pentahydrate, and 0.466g of anhydrous stannous chloride were added to 1.25kg of deionized water and stirred to obtain the inner catalyst layer slurry. The mass ratio of cerium oxide:manganese oxide:holmium trioxide:tin oxide in the active component was 8:5:3:2.

[0063] (4) Inner catalyst layer forming

[0064] The ceramic fiber tube forming mold is immersed in the inner catalyst layer slurry. The inner catalyst layer semi-finished product is formed by negative pressure filtration under the conditions of 200 r / min rotation speed and 0.08 MPa filtration pressure. Then, the inner catalyst layer is obtained by drying in an oven at 100℃ for 4 h.

[0065] (5) Forming of outer filter layer

[0066] The dried mold with the inner catalyst layer was immersed in the outer filter layer slurry. The outer filter layer semi-finished product was formed by negative pressure filtration under the conditions of 200 r / min rotation speed and 0.08 MPa filtration pressure. Then, the outer catalyst layer was obtained by drying in an oven at 100℃ for 4 h.

[0067] (6) Calcination and molding of ceramic fiber tubes

[0068] The ceramic fiber tube formed by vacuum filtration is placed in a tube furnace and calcined at 1500℃ for 2 hours. After natural cooling, a double-layer composite ceramic fiber tube is obtained, with the thickness ratio of the outer filter layer to the inner catalyst layer being 1:1.

[0069] II. Activity Test Results

[0070] use Figure 1 The apparatus was used to test the effect of ceramic fiber tubes on nitrous oxide and dioxin removal, using chlorobenzene (CB) as a dioxin simulant. Laboratory gas was used to simulate flue gas, with the following inlet components: N₂O (500 ppm), NH₃ (1000 ppm), O₂ (11 vol.%), CB (500 ppm), and the remainder being N₂. The total gas flow rate was 1000 mL / min. The ceramic fiber tube was fixed inside a quartz tube with an outer diameter of 30 mm and placed in a tube furnace. The test temperature was 150–400 °C. A Laoying 3021 portable carbon emission monitor was used to measure the N₂O concentration, and a GC-112N gas chromatograph was used to measure the CB concentration. Figure 2 and Figure 3 As shown, the test results indicate that the N2O removal rate was 94.5% and the CB removal rate was 83.4% after 10 minutes at 150℃.

[0071] Example 3

[0072] I. Preparation of Ceramic Fiber Tubes

[0073] (1) Ceramic fiber pretreatment

[0074] Alumina silicate fibers were sheared and ball-milled to obtain short ceramic fibers with different aspect ratios.

[0075] (2) Preparation of slurry for outer filter layer

[0076] Add 500g of aluminosilicate fiber (length-to-diameter ratio of 500-1000), 100g of water glass, and 10g of sodium carboxymethyl cellulose to 10kg of deionized water and stir to obtain the outer filter layer slurry.

[0077] (3) Preparation of inner catalyst layer slurry

[0078] Based on the mass of the ceramic fiber in the inner catalyst layer, the mass percentage of the catalytic active component was 8%. 125g of aluminosilicate fiber (aspect ratio 100–500), 25g of water glass, 2.5g of sodium carboxymethyl cellulose, 14.016g of cerium nitrate hexahydrate, 5.400g of manganese sulfate monohydrate, 2.487g of holmium nitrate pentahydrate, and 0.699g of anhydrous stannous chloride were added to 2.5kg of deionized water and stirred to obtain the inner catalyst layer slurry. The mass ratio of cerium oxide:manganese oxide:holmium trioxide:tin oxide in the active component was 10:5:5:2.

[0079] (4) Inner catalyst layer forming

[0080] The ceramic fiber tube forming mold is immersed in the inner catalyst layer slurry. The inner catalyst layer semi-finished product is formed by negative pressure filtration under the conditions of 50 r / min rotation speed and 0.1 MPa filtration pressure. Then, the inner catalyst layer is obtained by drying in an oven at 150℃ for 2 h.

[0081] (5) Forming of outer filter layer

[0082] The dried mold with the inner catalyst layer was immersed in the outer filter layer slurry. The outer filter layer semi-finished product was formed by negative pressure filtration under the conditions of 50 r / min rotation speed and 0.1 MPa filtration pressure. Then, the outer catalyst layer was obtained by drying in an oven at 150℃ for 2 h.

[0083] (6) Calcination and molding of ceramic fiber tubes

[0084] The ceramic fiber tube formed by vacuum filtration is placed in a tube furnace and calcined at 1200℃ for 8 hours. After natural cooling, a double-layer composite ceramic fiber tube is obtained, with the thickness ratio of the outer filter layer to the inner catalyst layer being 1:1.

[0085] II. Activity Test Results

[0086] use Figure 1 The apparatus was used to test the effect of ceramic fiber tubes on nitrous oxide and dioxin removal, using chlorobenzene (CB) as a dioxin simulant. Laboratory gas was used to simulate flue gas, with the following inlet components: N₂O (500 ppm), NH₃ (1000 ppm), O₂ (11 vol.%), CB (500 ppm), and the remainder being N₂. The total gas flow rate was 1000 mL / min. The ceramic fiber tube was fixed inside a quartz tube with an outer diameter of 30 mm and placed in a tube furnace. The test temperature was 150–400 °C. A Laoying 3021 portable carbon emission monitor was used to measure the N₂O concentration, and a GC-112N gas chromatograph was used to measure the CB concentration. Figure 2 and Figure 3 As shown, the test results indicate that the removal rate of N2O after 10 minutes at 150℃ was 97.3%, and the removal rate of CB was 81.5%.

[0087] Comparative Example 1

[0088] I. Preparation of Ceramic Fiber Tubes

[0089] (1) Preparation of inner catalyst layer slurry

[0090] No cerium salt, manganese salt, holmium salt, or tin salt are added during the preparation of the inner catalyst layer slurry; otherwise, it is the same as in Example 1.

[0091] II. Activity Test Results

[0092] use Figure 1 The apparatus was used to test the effect of ceramic fiber tubes on nitrous oxide and dioxin removal, using chlorobenzene (CB) as a dioxin simulant. Laboratory gas was used to simulate flue gas, with the following inlet components: N₂O (500 ppm), NH₃ (1000 ppm), O₂ (11 vol.%), CB (500 ppm), and the remainder being N₂. The total gas flow rate was 1000 mL / min. The ceramic fiber tube was fixed inside a quartz tube with an outer diameter of 30 mm and placed in a tube furnace. The test temperature was 150–400 °C. A Laoying 3021 portable carbon emission monitor was used to measure the N₂O concentration, and a GC-112N gas chromatograph was used to measure the CB concentration. Figure 2 and Figure 3 As shown, the catalytic performance drops sharply because the inner catalyst layer is not loaded with composite oxide active components. The test results show that the removal rates of N2O and CB are almost 0 in the temperature range of 150 to 400℃.

[0093] Comparative Example 2

[0094] I. Preparation of Ceramic Fiber Tubes

[0095] (1) Preparation of inner catalyst layer slurry

[0096] The alumina fibers were selected (with an aspect ratio of 500 to 1000), and other aspects were the same as in Example 2.

[0097] II. Activity Test Results

[0098] use Figure 1 The apparatus was used to test the effect of ceramic fiber tubes on nitrous oxide and dioxin removal, using chlorobenzene (CB) as a dioxin simulant. Laboratory gas was used to simulate flue gas, with the following inlet components: N₂O (500 ppm), NH₃ (1000 ppm), O₂ (11 vol.%), CB (500 ppm), and the remainder being N₂. The total gas flow rate was 1000 mL / min. The ceramic fiber tube was fixed inside a quartz tube with an outer diameter of 30 mm and placed in a tube furnace. The test temperature was 150–400 °C. A Laoying 3021 portable carbon emission monitor was used to measure the N₂O concentration, and a GC-112N gas chromatograph was used to measure the CB concentration. Figure 2 and Figure 3 As shown, the alumina fibers in the inner catalyst layer are selected with a large aspect ratio, resulting in insufficient loading intensity of the catalytic active components and uneven loading, which leads to a decrease in catalytic performance. The test results show that the N2O removal rate is 12.3% and the CB removal rate is 12.5% ​​after 10 min at 150℃.

[0099] Comparative Example 3

[0100] I. Preparation of Ceramic Fiber Tubes

[0101] (1) Preparation of slurry for outer filter layer and inner catalyst layer

[0102] Sodium carboxymethyl cellulose was not added during the preparation of the slurry for the outer filter layer and inner catalyst layer; otherwise, it was the same as in Example 3.

[0103] II. Activity Test Results

[0104] use Figure 1 The apparatus was used to test the effect of ceramic fiber tubes on nitrous oxide and dioxin removal, using chlorobenzene (CB) as a dioxin simulant. Laboratory gas was used to simulate flue gas, with the following inlet components: N₂O (500 ppm), NH₃ (1000 ppm), O₂ (11 vol.%), CB (500 ppm), and the remainder being N₂. The total gas flow rate was 1000 mL / min. The ceramic fiber tube was fixed inside a quartz tube with an outer diameter of 30 mm and placed in a tube furnace. The test temperature was 150–400 °C. A Laoying 3021 portable carbon emission monitor was used to measure the N₂O concentration, and a GC-112N gas chromatograph was used to measure the CB concentration. Figure 2 and Figure 3 As shown, the lack of sodium carboxymethyl cellulose as a surfactant resulted in poor binding between the active component and the aluminosilicate fiber, leading to a decrease in catalytic performance. The test results showed that the N2O removal rate was 23.5% and the CB removal rate was 15.8% after 10 minutes at 150℃.

Claims

1. A double-layer composite ceramic fiber tube with functions of flue gas dust removal, nitrous oxide removal, and dioxin removal, characterized in that: The ceramic fiber tube consists of an outer filter layer and an inner catalyst layer. The thickness ratio of the outer filter layer to the inner catalyst layer is 1-10:1-10. The active component is loaded in the inner catalyst layer. Based on the mass of the ceramic fiber in the inner catalyst layer, the mass percentage of the active component is 1-10%. The mass ratio of cerium oxide:manganese oxide:holmium trioxide:tin oxide in the active component is (5-10):(5-10):(2-5):(1-2). The preparation method of the double-layer composite ceramic fiber tube is as follows: (1) Ceramic fiber pretreatment Ceramic fibers are sheared and ball-milled to obtain short ceramic fibers with different aspect ratios. (2) Preparation of slurry for outer filter layer Ceramic fibers with an aspect ratio of 500 to 1000, inorganic binders, and surfactants are added to deionized water and stirred to obtain an outer filter layer slurry. (3) Preparation of inner catalyst layer slurry Ceramic fibers with an aspect ratio of 100 to 500, inorganic binders, surfactants, and cerium salts, manganese salts, holmium salts, and tin salts are added to deionized water and stirred to obtain an inner catalyst layer slurry. (4) Inner catalyst layer forming The ceramic fiber tube forming mold is immersed in the inner catalyst layer slurry, and the inner catalyst layer is obtained after rotary negative pressure filtration and drying. (5) Forming of outer filter layer The dried mold with the inner catalyst layer is immersed in the slurry of the outer filter layer, and the outer catalyst layer is obtained after rotary negative pressure filtration and drying. (6) Calcination and molding of ceramic fiber tubes The ceramic fiber tubes formed by vacuum filtration are placed in a tube furnace for high-temperature calcination, and after natural cooling, a double-layer composite ceramic fiber tube is obtained.

2. The double-layer composite ceramic fiber tube with flue gas dust removal, nitrous oxide removal, and dioxin removal functions according to claim 1, characterized in that: The ceramic fiber slurry corresponding to the outer filter layer and the inner catalyst layer of the ceramic fiber tube consists of ceramic fiber, inorganic binder, surfactant and deionized water, with a mass ratio of (5-10):(1-2):(0.1-0.5):(100-200).

3. The double-layer composite ceramic fiber tube with flue gas dust removal, nitrous oxide removal, and dioxin removal functions according to claim 1, characterized in that: Based on the quality of the ceramic fiber in the inner catalyst layer, the mass percentage of the active component is 2-8%.

4. The double-layer composite ceramic fiber tube with flue gas dust removal, nitrous oxide removal, and dioxin removal functions according to claim 1, characterized in that: The ceramic fiber mentioned in step (1) is one of aluminum silicate fiber, alumina fiber, zirconium oxide fiber, mullite fiber, or zirconium-containing aluminum silicate fiber. The fiber diameter is 5-15 μm, and the aspect ratio is 100-1000 after ball milling pretreatment.

5. The double-layer composite ceramic fiber tube with flue gas dust removal, nitrous oxide removal, and dioxin removal functions according to claim 1, characterized in that: The cerium salt mentioned in step (3) is cerium nitrate hexahydrate or cerium chloride heptahydrate; the manganese salt is manganese sulfate monohydrate or manganese chloride tetrahydrate or manganese nitrate hexahydrate; the holmium salt is holmium nitrate pentahydrate; and the tin salt is anhydrous stannous chloride.

6. The double-layer composite ceramic fiber tube with flue gas dust removal, nitrous oxide removal, and dioxin removal functions according to claim 1, characterized in that: The inorganic binder mentioned in steps (2) and (3) is one of water glass or aluminum dihydrogen phosphate; the surfactant mentioned in steps (2) and (3) is one of sodium carboxymethyl cellulose, hydroxypropyl cellulose, or polyvinyl alcohol.

7. The double-layer composite ceramic fiber tube with flue gas dust removal, nitrous oxide removal, and dioxin removal functions according to claim 1, characterized in that: In steps (4) and (5), the rotational speed of the rotary filtration is 50~200 r / min, and the filtration pressure is 0.05MPa~0.1MPa; The drying temperature in steps (4) and (5) is 100-150℃, and the drying time is 2-4 hours. The calcination temperature in step (6) is 1200-1500℃ and the calcination time is 2-8h.

8. The application of the double-layer composite ceramic fiber tube with flue gas dust removal, nitrous oxide removal, and dioxin removal functions as described in claim 1 in the removal of nitrous oxide and dioxins in industrial flue gas.

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