A process for the simultaneous treatment of carbon monoxide and nitrogen oxides in sintering flue gas

Abstract

The present application relates to the technical field of sintering flue gas treatment, and discloses a synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas, which comprises the following steps: first, the sintering flue gas is subjected to a carbon monoxide removal process by a regenerative oxidation process, and then is introduced into a denitration system with built-in catalysts, and is subjected to catalytic treatment by the catalysts and then is discharged; wherein the catalysts are supported manganese-based catalysts, and the raw materials of the supported manganese-based catalysts comprise the following components in parts by weight: acid-treated multi-walled carbon nanotubes 9-11 parts, sodium alkyl benzene sulfonate 30-35 parts, carboxymethyl chitosan 4-8 parts, manganese source 4-6 parts, rare earth compound 1-2 parts, and urea 35-40 parts. Through the above technical solution, the problem of insufficient catalytic efficiency of the supported catalysts in the related art is solved.

Description

Technical Field

[0001] This invention relates to the field of sintering flue gas treatment technology, specifically to a synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas. Background Technology

[0002] Sintering flue gas is one of the main air pollutants generated during the steel industry production process. It contains a large amount of carbon monoxide and nitrogen oxides. Direct emission of these gases can cause serious harm to the ecological environment and human health. Therefore, the synergistic and efficient removal of carbon monoxide and nitrogen oxides has become a key technological requirement for the control of sintering flue gas pollution.

[0003] In existing technologies, carbon monoxide in sintering flue gas can be effectively removed through high-temperature combustion. However, in the denitrification process, while commonly used vanadium-titanium catalysts exhibit some activity in selective catalytic reduction, they generally suffer from insufficient denitrification efficiency, making it difficult to meet the requirements for removing nitrogen oxides from sintering flue gas. Therefore, to further improve the catalytic effect of catalysts, supported catalysts are often used in existing related technologies for the removal of nitrogen oxides. However, for supported catalysts, traditional preparation methods such as impregnation and mechanical mixing often lead to poor dispersion of active components on the support surface and severe particle agglomeration. This reduces the effective exposure of active sites and restricts the improvement of catalytic efficiency. Summary of the Invention

[0004] This invention proposes a synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas, which solves the problem of insufficient catalytic efficiency of supported catalysts in related technologies.

[0005] The technical solution of the present invention is as follows:

[0006] This invention proposes a synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas, comprising the following steps: the sintering flue gas first undergoes a regenerative oxidation process to remove carbon monoxide, and then enters a denitrification system with a built-in catalyst. After catalytic treatment by the catalyst, it is discharged. The catalyst is a supported manganese-based catalyst, and the raw materials of the supported manganese-based catalyst include the following components in parts by weight: 9-11 parts of acid-treated multi-walled carbon nanotubes, 30-35 parts of sodium alkylbenzene sulfonate, 4-8 parts of carboxymethyl chitosan, 4-6 parts of manganese source, 1-2 parts of rare earth compound, and 35-40 parts of urea.

[0007] As a further technical solution, the sodium alkylbenzene sulfonate is composed of sodium dodecylbenzene sulfonate and sodium hexadecylbenzene sulfonate.

[0008] In this invention, a synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas is described. The supported manganese-based catalyst contains sodium alkylbenzenesulfonate composed of sodium dodecylbenzenesulfonate and sodium hexadecylbenzenesulfonate. Based on the synergistic effect of their different carbon chain lengths, a more stable dispersion system can be constructed. The short-chain component facilitates rapid adsorption and wetting, while the long-chain component provides stronger steric hindrance. The combination of the two not only significantly improves the stability of the multi-walled carbon nanotube suspension and effectively prevents its aggregation, but also provides more diverse and uniformly distributed adsorption sites for the metal active components. This ultimately ensures the high dispersion of the active centers on the support, resulting in a catalyst with superior catalytic performance.

[0009] As a further technical solution, the mass ratio of sodium dodecylbenzenesulfonate and sodium hexadecylbenzenesulfonate is 2 to 5:1, for example, it can be 2:1, 3:1, 4:1, or 5:1, preferably 5:1.

[0010] As a further technical solution, the manganese source includes one or two of manganese nitrate hexahydrate and manganese acetate tetrahydrate.

[0011] As a further technical solution, the rare earth compounds include cerium nitrate hexahydrate and lanthanum nitrate hexahydrate.

[0012] In this invention, a synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas utilizes cerium nitrate hexahydrate and lanthanum nitrate hexahydrate as composite rare earth components in a supported manganese-based catalyst, leveraging the synergistic effect between cerium and lanthanum. Cerium possesses variable valence states and oxygen vacancy regulation capabilities, which can be utilized in the Ce... 3+ and Ce 4+ The conversion occurs between the two elements, which promotes the regeneration and cycling of active oxygen species. This effectively regulates the redox cycle on the catalyst surface and significantly improves the conversion rate of nitrogen oxides. The introduction of lanthanum further enhances the adsorption capacity of nitrogen oxide molecules. The synergistic effect of the two elements enhances the selective catalytic reduction activity and reaction stability of the catalyst, thereby significantly strengthening the removal efficiency of nitrogen oxides from sintering flue gas.

[0013] As a further technical solution, the mass ratio of cerium nitrate hexahydrate to lanthanum nitrate hexahydrate is 1:0.2~0.5, for example, it can be 1:0.2, 1:0.3, 1:0.4, 1:0.5, preferably 1:0.4.

[0014] As a further technical solution, the preparation method of the acid-treated multi-walled carbon nanotubes is as follows: multi-walled carbon nanotubes are added to an aqueous nitric acid solution, refluxed, cooled to room temperature, filtered, washed, and dried to obtain acid-treated multi-walled carbon nanotubes.

[0015] As a further technical solution, the reflux is performed at 120°C for 5 hours.

[0016] As a further technical solution, the preparation method of the supported manganese-based catalyst is as follows:

[0017] S1. After dispersing the sodium alkylbenzene sulfonate and carboxymethyl chitosan evenly in water, add the acid-treated multi-walled carbon nanotubes and mix evenly to obtain a suspension;

[0018] S2. After dispersing manganese source, rare earth compound and urea evenly in water, add the suspension and mix evenly. Then reflux and cool to room temperature. After filtration, washing, drying and calcination, a supported manganese-based catalyst is obtained.

[0019] As a further technical solution, in step S2, the reflux is performed at 100°C for 8 hours.

[0020] As a further technical solution, in step S2, the calcination is divided into two stages: the first stage is to raise the temperature from room temperature to 300-350°C at a heating rate of 1-5°C / min and calcinate at a constant temperature for 1 hour; the second stage is to continue to raise the temperature to 450-500°C at a heating rate of 1-5°C / min and calcinate at a constant temperature for 5 hours.

[0021] As a further technical solution, the calcination is carried out under inert gas protection.

[0022] The working principle and beneficial effects of this invention are as follows:

[0023] This invention proposes a synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas. The supported manganese-based catalyst in the denitrification system comprises sodium alkylbenzene sulfonate and carboxymethyl chitosan as raw materials. Sodium alkylbenzene sulfonate possesses both hydrophilic and hydrophobic groups. The benzene ring structure of its hydrophobic group can form π-π conjugated bonds with the surface of acid-treated multi-walled carbon nanotubes (MWCNTs), resulting in uniform modification of the MWCNT surface. This significantly improves the dispersibility and suspension stability of the acid-treated MWCNTs in water, while simultaneously providing a source of manganese and gold from the dissociation of rare earth compounds. The cations provide adsorption sites; while carboxymethyl chitosan molecules contain active groups such as carboxyl, hydroxyl, and amino groups. On the one hand, they can form hydrogen bonds with oxygen-containing functional groups on the surface of acid-treated multi-walled carbon nanotubes through hydroxyl and amino groups. On the other hand, active groups such as carboxyl, hydroxyl, and amino groups can also form complexes with the above-mentioned metal cations, ensuring uniform distribution of metal components. Under the synergistic effect of the two, the phenomenon of poor dispersion and severe particle agglomeration of active components on the carrier surface is solved, providing a guarantee for the uniform loading and binding of metal active components, thereby improving the catalytic denitrification efficiency of nitrogen oxides in sintering flue gas. Detailed Implementation

[0024] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] In the following embodiments and comparative examples:

[0026] The nitric acid aqueous solution is a nitric acid aqueous solution with a mass concentration of 65%.

[0027] Carboxymethyl chitosan, manufacturer: Xi'an Shouhe Biotechnology Co., Ltd.

[0028] Multi-walled carbon nanotubes, diameter: 8-15nm, length: 3-12μm.

[0029] Example 1

[0030] A process for the synergistic treatment of carbon monoxide and nitrogen oxides in sintering flue gas includes the following steps:

[0031] The sintering flue gas first undergoes a regenerative oxidation process to remove carbon monoxide, and then enters a denitrification system with a built-in catalyst. After being catalytically treated by the catalyst, it is discharged.

[0032] The catalyst is a supported manganese-based catalyst. The raw materials for the supported manganese-based catalyst include the following components in parts by weight: 9 parts of acid-treated multi-walled carbon nanotubes, 30 parts of sodium alkylbenzene sulfonate, 4 parts of carboxymethyl chitosan, 4 parts of manganese nitrate hexahydrate, 1 part of cerium nitrate hexahydrate, and 35 parts of urea. The sodium alkylbenzene sulfonate is composed of sodium dodecylbenzene sulfonate and sodium hexadecylbenzene sulfonate in a mass ratio of 2:1.

[0033] The preparation method of acid-treated multi-walled carbon nanotubes is as follows: multi-walled carbon nanotubes are added to nitric acid aqueous solution, refluxed at 120℃ for 5h, cooled to room temperature, filtered, washed with water until neutral, washed with anhydrous ethanol, and dried to obtain acid-treated multi-walled carbon nanotubes, wherein the mass-volume ratio of multi-walled carbon nanotubes to nitric acid aqueous solution is 1g:100mL.

[0034] The preparation method of the supported manganese-based catalyst is as follows:

[0035] S1. After dispersing sodium alkylbenzene sulfonate and carboxymethyl chitosan evenly in water, acid-treated multi-walled carbon nanotubes are added and mixed evenly to obtain an acid-treated multi-walled carbon nanotube suspension, wherein the mass ratio of sodium alkylbenzene sulfonate and carboxymethyl chitosan to water is 1g:50mL.

[0036] S2. Manganese nitrate hexahydrate, cerium nitrate hexahydrate, and urea were added to water (the mass ratio of manganese nitrate hexahydrate, cerium nitrate hexahydrate, and urea to water was 1 g: 45 mL) and dispersed evenly. Then, an acid-treated multi-walled carbon nanotube suspension was added and mixed evenly. The mixture was refluxed at 100°C for 8 hours, cooled to room temperature, filtered, washed, and dried. Under nitrogen protection, the temperature was first increased to 300°C at a rate of 5°C / min and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 450°C at a rate of 5°C / min and calcined at a constant temperature for 5 hours to obtain a supported manganese-based catalyst.

[0037] Example 2

[0038] A process for the synergistic treatment of carbon monoxide and nitrogen oxides in sintering flue gas includes the following steps:

[0039] The sintering flue gas first undergoes a regenerative oxidation process to remove carbon monoxide, and then enters a denitrification system with a built-in catalyst. After being catalytically treated by the catalyst, it is discharged.

[0040] The catalyst is a supported manganese-based catalyst. The raw materials for the supported manganese-based catalyst include the following components in parts by weight: 10 parts of acid-treated multi-walled carbon nanotubes, 32 parts of sodium alkylbenzene sulfonate, 6 parts of carboxymethyl chitosan, 5 parts of manganese nitrate hexahydrate, 1.5 parts of cerium nitrate hexahydrate, and 37 parts of urea. The sodium alkylbenzene sulfonate is composed of sodium dodecylbenzene sulfonate and sodium hexadecylbenzene sulfonate in a mass ratio of 2:1.

[0041] The preparation method of acid-treated multi-walled carbon nanotubes is as follows: multi-walled carbon nanotubes are added to nitric acid aqueous solution, refluxed at 120℃ for 5h, cooled to room temperature, filtered, washed with water until neutral, washed with anhydrous ethanol, and dried to obtain acid-treated multi-walled carbon nanotubes, wherein the mass-volume ratio of multi-walled carbon nanotubes to nitric acid aqueous solution is 1g:100mL.

[0042] The preparation method of the supported manganese-based catalyst is as follows:

[0043] S1. After dispersing sodium alkylbenzene sulfonate and carboxymethyl chitosan evenly in water, acid-treated multi-walled carbon nanotubes are added and mixed evenly to obtain an acid-treated multi-walled carbon nanotube suspension, wherein the mass ratio of sodium alkylbenzene sulfonate and carboxymethyl chitosan to water is 1g:50mL.

[0044] S2. Manganese nitrate hexahydrate, cerium nitrate hexahydrate, and urea were added to water (the mass ratio of manganese nitrate hexahydrate, cerium nitrate hexahydrate, and urea to water was 1 g: 45 mL) and dispersed evenly. Then, an acid-treated multi-walled carbon nanotube suspension was added and mixed evenly. The mixture was refluxed at 100°C for 8 hours, cooled to room temperature, filtered, washed, and dried. Under nitrogen protection, the temperature was first increased to 350°C at a rate of 5°C / min and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 500°C at a rate of 5°C / min and calcined at a constant temperature for 5 hours to obtain a supported manganese-based catalyst.

[0045] Example 3

[0046] A process for the synergistic treatment of carbon monoxide and nitrogen oxides in sintering flue gas includes the following steps:

[0047] The sintering flue gas first undergoes a regenerative oxidation process to remove carbon monoxide, and then enters a denitrification system with a built-in catalyst. After being catalytically treated by the catalyst, it is discharged.

[0048] The catalyst is a supported manganese-based catalyst. The raw materials for the supported manganese-based catalyst include the following components in parts by weight: 11 parts of acid-treated multi-walled carbon nanotubes, 35 parts of sodium alkylbenzene sulfonate, 8 parts of carboxymethyl chitosan, 6 parts of manganese nitrate hexahydrate, 2 parts of cerium nitrate hexahydrate, and 40 parts of urea. The sodium alkylbenzene sulfonate is composed of sodium dodecylbenzene sulfonate and sodium hexadecylbenzene sulfonate in a mass ratio of 2:1.

[0049] The preparation method of acid-treated multi-walled carbon nanotubes is as follows: multi-walled carbon nanotubes are added to nitric acid aqueous solution, refluxed at 120℃ for 5h, cooled to room temperature, filtered, washed with water until neutral, washed with anhydrous ethanol, and dried to obtain acid-treated multi-walled carbon nanotubes, wherein the mass-volume ratio of multi-walled carbon nanotubes to nitric acid aqueous solution is 1g:100mL.

[0050] The preparation method of the supported manganese-based catalyst is as follows:

[0051] S1. After dispersing sodium alkylbenzene sulfonate and carboxymethyl chitosan evenly in water, acid-treated multi-walled carbon nanotubes are added and mixed evenly to obtain an acid-treated multi-walled carbon nanotube suspension, wherein the mass ratio of sodium alkylbenzene sulfonate and carboxymethyl chitosan to water is 1g:50mL.

[0052] S2. Manganese nitrate hexahydrate, cerium nitrate hexahydrate, and urea were added to water (the mass ratio of manganese nitrate hexahydrate, cerium nitrate hexahydrate, and urea to water was 1 g: 45 mL) and dispersed evenly. Then, an acid-treated multi-walled carbon nanotube suspension was added and mixed evenly. The mixture was refluxed at 100°C for 8 hours, cooled to room temperature, filtered, washed, and dried. Under nitrogen protection, the temperature was first increased to 300°C at a rate of 5°C / min and calcined at a constant temperature for 1 hour. Then, the temperature was increased to 450°C at a rate of 5°C / min and calcined at a constant temperature for 5 hours to obtain a supported manganese-based catalyst.

[0053] Example 4

[0054] The only difference between this embodiment and Embodiment 2 is that in this embodiment, sodium alkylbenzene sulfonate is composed of sodium dodecylbenzene sulfonate and sodium hexadecylbenzene sulfonate in a mass ratio of 4:1.

[0055] Example 5

[0056] The only difference between this embodiment and Embodiment 2 is that in this embodiment, sodium alkylbenzene sulfonate is composed of sodium dodecylbenzene sulfonate and sodium hexadecylbenzene sulfonate in a mass ratio of 5:1.

[0057] Example 6

[0058] The only difference between this embodiment and Embodiment 2 is that in this embodiment, cerium nitrate hexahydrate is replaced with equal amounts of cerium nitrate hexahydrate and lanthanum nitrate hexahydrate in a mass ratio of 1:0.2.

[0059] Example 7

[0060] The only difference between this embodiment and Embodiment 2 is that in this embodiment, cerium nitrate hexahydrate is replaced with equal amounts of cerium nitrate hexahydrate and lanthanum nitrate hexahydrate in a mass ratio of 1:0.4.

[0061] Example 8

[0062] The only difference between this embodiment and Embodiment 2 is that in this embodiment, cerium nitrate hexahydrate is replaced with equal amounts of cerium nitrate hexahydrate and lanthanum nitrate hexahydrate in a mass ratio of 1:0.5.

[0063] Comparative Example 1

[0064] The only difference between this comparative example and Example 2 is that the sodium alkylbenzene sulfonate in this comparative example is sodium dodecylbenzene sulfonate.

[0065] Comparative Example 2

[0066] The only difference between this comparative example and Example 2 is that the sodium alkylbenzene sulfonate in this comparative example is only sodium hexadecylbenzene sulfonate.

[0067] Comparative Example 3

[0068] The only difference between this comparative example and Example 2 is that carboxymethyl chitosan is replaced with equal amounts of sodium dodecylbenzenesulfonate and sodium hexadecylbenzenesulfonate in a mass ratio of 2:1.

[0069] Experimental Example

[0070] The supported manganese-based catalysts prepared in Examples 1-8 and Comparative Examples 1-3 were tested according to the following methods:

[0071] Denitrification rate: at a space velocity of 5000 h⁻¹ -1 Nitrogen oxide concentration 500 mg / m³ 3 The denitrification efficiency of the catalyst was tested under the condition of a reaction temperature of 300℃.

[0072] Denitrification rate (%) = (Nitrogen oxide concentration in initial sintering flue gas - Nitrogen oxide concentration in post-catalytic sintering flue gas) / Nitrogen oxide concentration in initial sintering flue gas × 100%;

[0073] Table 1. Denitrification rates of supported manganese-based catalysts in Examples 1-5 and Comparative Examples 1-3

[0074]

[0075] The denitration rates of the supported manganese-based catalysts prepared in Examples 1-5 were all higher than those in Comparative Examples 1-3, indicating that the present invention improved the denitration rate of the supported manganese-based catalyst by adding sodium dodecylbenzenesulfonate and sodium hexadecylbenzenesulfonate in combination with carboxymethyl chitosan.

[0076] Table 2. Denitrification rates of supported manganese-based catalysts in Examples 2, 6-8

[0077]

[0078] The denitration rates of the supported manganese-based catalysts prepared in Examples 6-8 were higher than those in Example 2, indicating that the present invention improved the denitration rate of the supported manganese-based catalyst by adding cerium nitrate hexahydrate and lanthanum nitrate hexahydrate in a compound.

[0079] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for the synergistic treatment of carbon monoxide and nitrogen oxides in sintering flue gas, characterized in that, Includes the following steps: The sintering flue gas first undergoes a regenerative oxidation process to remove carbon monoxide, and then enters a denitrification system with an embedded catalyst. After being catalytically treated by the catalyst, it is discharged. The catalyst is a supported manganese-based catalyst, and the raw materials of the supported manganese-based catalyst include the following components in parts by weight: 9-11 parts of acid-treated multi-walled carbon nanotubes, 30-35 parts of sodium alkylbenzene sulfonate, 4-8 parts of carboxymethyl chitosan, 4-6 parts of manganese source, 1-2 parts of rare earth compound, and 35-40 parts of urea. The sodium alkylbenzene sulfonate is composed of sodium dodecylbenzene sulfonate and sodium hexadecylbenzene sulfonate; The mass ratio of sodium dodecylbenzenesulfonate to sodium hexadecylbenzenesulfonate is 2~5:1; The rare earth compounds include cerium nitrate hexahydrate and lanthanum nitrate hexahydrate.

2. The synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas according to claim 1, characterized in that, The manganese source includes one or both of manganese nitrate hexahydrate and manganese acetate tetrahydrate.

3. The synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas according to claim 1, characterized in that, The mass ratio of cerium nitrate hexahydrate to lanthanum nitrate hexahydrate is 1:0.2~0.

5.

4. The synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas according to claim 1, characterized in that, The preparation method of the acid-treated multi-walled carbon nanotubes is as follows: multi-walled carbon nanotubes are added to an aqueous nitric acid solution, refluxed, cooled to room temperature, filtered, washed, and dried to obtain acid-treated multi-walled carbon nanotubes.

5. The synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas according to claim 1, characterized in that, The preparation method of the supported manganese-based catalyst is as follows: S1. After dispersing the sodium alkylbenzene sulfonate and carboxymethyl chitosan evenly in water, add the acid-treated multi-walled carbon nanotubes and mix evenly to obtain a suspension; S2. After dispersing manganese source, rare earth compound and urea evenly in water, add the suspension and mix evenly. Then reflux and cool to room temperature. After filtration, washing, drying and calcination, a supported manganese-based catalyst is obtained.

6. The synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas according to claim 5, characterized in that, In step S2, the calcination is divided into two stages: the first stage is to raise the temperature from room temperature to 300-350°C at a heating rate of 1-5°C / min and calcinate at a constant temperature for 1 hour; the second stage is to continue to raise the temperature to 450-500°C at a heating rate of 1-5°C / min and calcinate at a constant temperature for 5 hours.

7. The synergistic treatment process for carbon monoxide and nitrogen oxides in sintering flue gas according to claim 6, characterized in that, The calcination is carried out under inert gas protection.

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