A method for treating vanadium-nitrogen alloy smelting tail gas

Abstract

This application belongs to the technical field of vanadium-nitrogen alloy smelting tail gas treatment, and relates to a method for treating vanadium-nitrogen alloy smelting tail gas. The invention employs a polyimide composite membrane modified with a silane coupling agent (ZIF-8) to separate nitrogen and carbon-containing gases from the vanadium-nitrogen alloy smelting tail gas. A eutectic ionic liquid is used as an adsorbent to further remove carbon dioxide from the carbon-containing gases, resulting in tail gas rich in carbon monoxide. The nitrogen obtained from membrane separation is pressurized and transported to an electric kiln for secondary utilization as a gas medium. The heat generated from the combustion of the carbon monoxide-rich tail gas can be used for raw material preheating, improving the resource utilization rate of the vanadium-nitrogen alloy smelting tail gas.

Description

Technical Field

[0001] This invention relates to the field of vanadium-nitrogen alloy smelting tail gas treatment technology, and in particular to a method for treating vanadium-nitrogen alloy smelting tail gas. Background Technology

[0002] Vanadium-nitrogen alloys are important steel alloying additives that can strengthen steel through grain refinement and precipitation, effectively improving its overall mechanical properties such as wear resistance, strength, toughness, and thermal fatigue resistance. The high-temperature reduction method in electric kilns is one of the production methods for vanadium-nitrogen alloys. The gas medium in the main kiln gas zone is high-purity nitrogen. Because the graphite materials used in the kiln cavity are easily oxidized at high temperatures, and the product needs to be sintered in an oxygen-free atmosphere, pure nitrogen must be introduced for atmosphere protection. Therefore, the smelting tail gas from the electric kiln preparation of vanadium-nitrogen alloys contains a large amount of nitrogen and some carbon-containing gases, such as carbon monoxide and carbon dioxide. Direct emission or simple treatment would not only waste resources but also cause environmental pollution. Therefore, it is necessary to efficiently separate and recycle the smelting tail gas generated by the high-temperature reduction method of electric kilns for vanadium-nitrogen alloy production.

[0003] Currently, the mainstream technical approaches for treating carbon and nitrogen-containing industrial exhaust gases include direct emission or emission after simple combustion, physical adsorption and pressure swing adsorption, etc. These methods have problems such as low resource recovery rate, high energy consumption, high operating cost and poor separation effect. Therefore, it is necessary to modify the existing vanadium-nitrogen alloy smelting exhaust gas treatment methods to improve the resource utilization rate of nitrogen. Summary of the Invention

[0004] This invention aims to provide a method for treating tail gas from vanadium-nitrogen alloy smelting. The invention employs a polyimide composite membrane to separate and capture nitrogen from the tail gas. It utilizes a silane coupling agent to modify the polar amino groups in ZIF-8, forming a dipole-induced dipole interaction with the non-polar nitrogen. The amino groups then interact with the Zn in the ZIF-8 framework. 2+ Coordination is formed, regulating the electronic environment of the ZIF-8 microporous surface, making the inner wall of the micropores weakly polar, further enhancing the adsorption capacity for nitrogen, thereby separating nitrogen and carbon-containing tail gas. A eutectic ionic liquid is used as the adsorbent to remove carbon dioxide from the carbon-containing tail gas. In the eutectic ionic liquid, the anion of choline alanine ionic liquid contains amino and carboxyl bifunctional groups, which can chemically adsorb carbon dioxide. Multiple hydroxyl groups of the polyol can physically adsorb carbon dioxide through van der Waals forces and hydrogen bonds. Before chemical adsorption reaches saturation, carbon dioxide is captured in advance and transferred to the active sites of amino and carboxyl groups, improving the overall adsorption rate. Finally, the obtained nitrogen is transported to an electric kiln for secondary use, and the separated carbon monoxide is burned to generate heat for preheating the raw materials, achieving comprehensive resource utilization and reducing energy waste.

[0005] To achieve the above objectives, the present invention provides a method for treating tail gas from vanadium-nitrogen alloy smelting, comprising the following steps:

[0006] S1. The smelting tail gas after cooling and bag dust removal is dehydrated, and nitrogen and carbon-containing tail gas are separated by a polyimide composite membrane.

[0007] S2. Carbon-containing exhaust gas is passed through a eutectic ionic liquid to obtain exhaust gas rich in carbon monoxide.

[0008] S3. Collect the nitrogen gas from S1 and pass it into the electric kiln; pass the tail gas rich in carbon monoxide from S2 into the combustion system to preheat the raw materials.

[0009] Preferably, in step S1, the cooling temperature is 40~50℃; and the dust content of the smelting tail gas after bag filter dust removal is <5mg / m³.

[0010] Preferably, the adsorbent used for dehydration is activated alumina and 3A molecular sieve, the dehydration temperature is 25~35℃, and the dehydration pressure is 0.10~0.15MPa.

[0011] Preferably, during the separation of nitrogen and carbon-containing tail gas by the polyimide composite membrane, the membrane module operating temperature is 35~50℃, the membrane module operating pressure is 0.3~0.5MPa, and the permeate side pressure is 0.1~0.15MPa.

[0012] Preferably, in step S1, the method for preparing the polyimide composite film includes:

[0013] B1. Dissolve zinc salt in deionized water to obtain zinc salt solution. Dissolve 2-methylimidazole in deionized water to obtain 2-methylimidazole solution. Add all of the zinc salt solution to the 2-methylimidazole solution while stirring. React, collect the precipitate by centrifugation, wash, and dry to obtain ZIF-8.

[0014] B2. Disperse the silane coupling agent in anhydrous toluene, add deionized water, stir to obtain a hydrolysate, add ZIF-8, react under inert gas protection, collect the solid by centrifugation, wash, dry, and obtain modified ZIF-8.

[0015] B3. Disperse the modified ZIF-8 in N-methylpyrrolidone, sonicate to obtain a suspension, add polyimide powder, stir, degas, and obtain a casting solution;

[0016] B4. Coat a liquid film on a glass plate to obtain a liquid film with a thickness of 100~200μm. Immerse the glass plate with the liquid film in a non-solvent bath to obtain the primary film.

[0017] B5. Immerse the nascent membrane in deionized water and anneal it to obtain a polyimide composite membrane.

[0018] Preferably, in B1, the zinc salt is zinc nitrate hexahydrate and / or zinc acetate; the mass-to-volume ratio of zinc salt to deionized water in the zinc salt solution is (1.15~1.2) g: 40 mL; the mass-to-volume ratio of 2-methylimidazole solution to deionized water in the 2-methylimidazole solution is (3.2~3.5) g: 40 mL; the reaction temperature is 25~30℃, and the reaction time is 1~4 h; the drying temperature is 60~80℃, and the drying time is 12~20 h.

[0019] Preferably, in B2, the silane coupling agent is 3-aminopropyltriethoxysilane and / or 3-aminopropyltrimethoxysilane; the volume-to-mass ratio of the silane coupling agent, anhydrous toluene, deionized water, and ZIF-8 is (2~5) mL : (100~120) mL : (0.5~1.5) mL : (5~10) g; the stirring temperature is 40~50℃, and the stirring time is 1~2 h; the reaction temperature is 60~70℃, and the reaction time is 4~6 h; the drying temperature is 60~80℃, and the drying time is 12~20 h.

[0020] Preferably, in B3, the mass-to-volume ratio of the modified ZIF-8, polyimide powder, and N-methylpyrrolidone is 1g:(8~12)g:(40~45)mL; the ultrasonic treatment power is 150~200W, the ultrasonic treatment time is 15~20min, and the ultrasonic treatment temperature is 25~30℃; the stirring temperature is 40~50℃, and the stirring time is 12~16h; the degassing operation is as follows: the reaction system is placed in a vacuum drying oven with a vacuum degree of -0.08~-0.09MPa and left to stand for 30~45min, the system is treated with ultrasound at 25℃ and 200W for 10~15min, then placed in a vacuum drying oven with a vacuum degree of -0.08~-0.09MPa and left to stand for 15~20min, and finally left to stand in a constant temperature environment of 25℃ for 2~4h.

[0021] Preferably, in B4, the non-solvent bath comprises N-methylpyrrolidone and deionized water, and the mass ratio of N-methylpyrrolidone to deionized water is 1:(0.5~2.5); in B5, the soaking time is 20~24h; the annealing temperature is 180~200℃, and the annealing time is 20~30min.

[0022] Preferably, in step S2, the process using the eutectic ionic liquid is carried out inside an adsorption tower, where the pressure is 0.4~0.6 MPa and the temperature is 25~40℃; the eutectic ionic liquid is prepared by a method comprising:

[0023] A1. Under ice bath conditions, add choline hydroxide aqueous solution to alanine aqueous solution, react, distill under reduced pressure, and dry to obtain choline alanine ionic liquid.

[0024] A2. Add the polyol to the choline alanine ionic liquid and stir to obtain a eutectic ionic liquid.

[0025] Preferably, in A1, the mass-to-volume ratio of alanine to deionized water in the alanine aqueous solution is (10~15) g: (100) mL; the mass-to-volume ratio of choline hydroxide to deionized water in the choline hydroxide aqueous solution is 1 g: (1.2~1.5) mL; the mass ratio of choline hydroxide aqueous solution to alanine is (1.36~1.44): 1; the reaction temperature is 60~80℃, and the reaction time is 30~60 min; the vacuum distillation temperature is 50~70℃; and the drying temperature is 60~80℃, and the drying time is 12~24 h.

[0026] Preferably, in A2, the polyol is any one or more of ethylene glycol, glycerol, and polyethylene glycol 400; the mass ratio of the choline alanine ionic liquid to the polyol is 1:(1.29~4.18); the stirring temperature is 60~80℃, and the stirring time is 2~4h.

[0027] Preferably, in step S3, the nitrogen collection process is carried out in a buffer tank with a pressure of 0.01~0.05MPa; the collected nitrogen is pressurized to 0.05~0.1MPa and then introduced into the electric kiln; the operating temperature of the combustion system is 800~1000℃.

[0028] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0029] This invention utilizes a polyimide composite membrane to separate and capture nitrogen gas from the tail gas of vanadium-nitrogen alloy smelting, and then transports it to an electric kiln for secondary utilization. The polyimide composite membrane incorporates ZIF-8 modified with an amino-containing silane coupling agent. The amino groups of the aminosiloxane form hydrogen bonds with the imide rings in the polyimide molecular chain, preventing ZIF-8 from agglomerating in the polyimide matrix and ensuring uniform micropore distribution, forming continuous sieving channels. The polyimide molecular chain contains numerous polar imide rings, which induce instantaneous dipoles in nitrogen molecules, forming dipole-induced dipole interactions. This allows nitrogen to diffuse within the polyimide film, but the separation efficiency is low; therefore, the modified ZIF-8 is added. IF-8 and ZIF-8 have regular microporous structures. When unmodified, the polarity of the inner wall of the pores is weak, resulting in limited adsorption capacity for nitrogen. After modification with silane coupling agents, the siloxane segments grafted onto the inner wall of the ZIF-8 pores widen the micropores, making them closer to the kinetic diameter of nitrogen. Nitrogen can more easily enter the pores and be adsorbed, while carbon monoxide molecules, being larger, are blocked and have difficulty entering the pores, thus achieving separation of the two. The weak hydrophobicity of siloxanes reduces the interference of residual moisture on the inner wall of the pores on adsorption, avoids competition between moisture and nitrogen for adsorption sites, and maintains adsorption stability.

[0030] This invention employs a eutectic ionic liquid as an adsorbent to remove carbon dioxide from carbon-containing exhaust gases. This eutectic ionic liquid is obtained by compounding a polyol and a choline-alanine ionic liquid, with the choline-alanine ionic liquid acting as the primary chemical adsorption agent and the polyol as the secondary agent, synergistically improving the efficiency of carbon dioxide removal from carbon-containing exhaust gases. The choline-alanine ionic liquid is the functional core of the eutectic ionic liquid that specifically interacts with carbon dioxide. In its molecular structure, the cation is a choline cation and the anion is an alanine anion, where the amino group of the alanine anion is the key active site for chemical adsorption of carbon dioxide. Carbon dioxide undergoes a nucleophilic addition reaction with the lone pair electrons of the amino group in the alanine anion to form a carbamate. Multiple hydroxyl groups in the polyol can physically adsorb carbon dioxide through van der Waals forces and hydrogen bonds. The negatively charged oxygen in the hydroxyl group forms a dipole-dipole interaction with the positively charged carbon in the carbon dioxide molecule, and the hydrogen in the hydroxyl group forms a weak hydrogen bond with the oxygen in the carbon dioxide molecule. Physical adsorption is relatively weak. Before chemisorption reaches saturation, physical adsorption can capture carbon dioxide in advance and transfer it to the amino active site, increasing the overall adsorption rate. Therefore, the presence of physical adsorption makes the total adsorption capacity of the eutectic ionic liquid higher than that of a single-component eutectic ionic liquid. However, carbon monoxide in carbon-containing tail gas is a neutral molecule with no electron acceptor; therefore, the eutectic ionic liquid has no adsorption effect on carbon monoxide. Attached Figure Description

[0031] Figure 1 This is a detailed process flow diagram for treating the tail gas from vanadium-nitrogen alloy smelting.

[0032] Figure 2 This is a flowchart illustrating the preparation process of a polyimide composite film. Detailed Implementation

[0033] The technical solution of the present invention will be described in detail below through specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations on the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0034] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0035] Example 1

[0036] like Figure 1 As shown, a eutectic ionic liquid is prepared by means of:

[0037] A1. Under ice bath conditions, add 144g of choline hydroxide aqueous solution (prepared by dissolving 10g of alanine in 100mL of deionized water, weighing 100g) to 100g of alanine aqueous solution (prepared by dissolving 10g of alanine in 120mL of deionized water, weighing 144g). React at 60℃ for 60min, distill under reduced pressure at 50℃, and dry at 60℃ for 24h to obtain choline alanine ionic liquid.

[0038] A2. Add 129g of ethylene glycol to 100g of choline alanine ionic liquid and stir at 60℃ for 4h to obtain a eutectic ionic liquid.

[0039] Example 2

[0040] like Figure 1 As shown, a eutectic ionic liquid is prepared by means of:

[0041] A1. Under ice bath conditions, add 140g of choline hydroxide aqueous solution (prepared by dissolving 12g of alanine in 100mL of deionized water, weighing 100g) to 100g of alanine aqueous solution (prepared by dissolving 100g of choline hydroxide in 135mL of deionized water, weighing 140g). React at 70℃ for 45min, distill under reduced pressure at 60℃, and dry at 70℃ for 18h to obtain choline alanine ionic liquid.

[0042] A2. Add 192g of glycerol to 100g of choline alanine ionic liquid and stir at 70℃ for 3h to obtain a eutectic ionic liquid.

[0043] Example 3

[0044] like Figure 1 As shown, a eutectic ionic liquid is prepared by means of:

[0045] A1. Under ice bath conditions, add 136g of choline hydroxide aqueous solution (prepared by dissolving 15g of alanine in 100ml of deionized water, weighing 100g) to 100g of alanine aqueous solution (prepared by dissolving 100g of choline hydroxide in 150mL of deionized water, weighing 136g). React at 80℃ for 30min, distill under reduced pressure at 70℃, and dry at 80℃ for 12h to obtain choline alanine ionic liquid.

[0046] A2. Add 418g of polyethylene glycol 400 to 100g of choline alanine ionic liquid and stir at 80℃ for 2h to obtain a eutectic ionic liquid.

[0047] Example 4

[0048] like Figure 2 As shown, a polyimide composite film is prepared by means of:

[0049] B1. Dissolve 5.75g of zinc nitrate hexahydrate in 200mL of deionized water to obtain a zinc salt solution. Dissolve 16g of 2-methylimidazole in 200mL of deionized water to obtain a 2-methylimidazole solution. Add the zinc salt solution to the 2-methylimidazole solution with stirring. React at 25℃ for 4h. Collect the precipitate by centrifugation, wash with deionized water, and dry at 60℃ for 20h to obtain ZIF-8.

[0050] B2. Disperse 2 mL of 3-aminopropyltriethoxysilane in 100 mL of anhydrous toluene, add 0.5 mL of deionized water, stir at 40 °C for 2 h to obtain hydrolysate, add 5 g of ZIF-8, react at 60 °C for 6 h under inert gas protection, collect the solid by centrifugation, wash with deionized water, and dry at 60 °C for 20 h to obtain modified ZIF-8.

[0051] B3. Disperse 5g of modified ZIF-8 in 200mL of N-methylpyrrolidone, sonicate at 150W and 30℃ for 20min to obtain a suspension, add 40g of polyimide powder, stir at 40℃ for 16h, place the reaction system in a vacuum drying oven with a vacuum degree of -0.08MPa (gauge pressure), let stand for 45min, treat the system in sonication at 25℃ and 200W for 15min, then place it in a vacuum drying oven with a vacuum degree of -0.08MPa (gauge pressure) for 20min, and finally let it stand in a constant temperature environment of 25℃ for 4h to obtain the casting solution.

[0052] B4. Scrape a film onto a glass plate to obtain a liquid film with a thickness of 150 μm. Immerse the glass plate with the liquid film into a non-solvent bath (prepared from 100 g of N-methylpyrrolidone and 50 g of deionized water) to obtain the nascent film.

[0053] B5. Soak the nascent membrane in deionized water for 24 hours and anneal it at 180°C for 30 minutes to obtain a polyimide composite membrane.

[0054] Example 5

[0055] like Figure 2 As shown, a polyimide composite film is prepared by means of:

[0056] B1. Dissolve 5.9g of zinc acetate in 200mL of deionized water to obtain a zinc salt solution. Dissolve 17g of 2-methylimidazole in 200mL of deionized water to obtain a 2-methylimidazole solution. Add all of the zinc salt solution to the 2-methylimidazole solution with stirring. React at 30℃ for 1h. Collect the precipitate by centrifugation, wash with deionized water, and dry at 70℃ for 16h to obtain ZIF-8.

[0057] B2. Disperse 3.5 mL of 3-aminopropyltrimethoxysilane in 110 mL of anhydrous toluene, add 1 mL of deionized water, stir at 45 °C for 1.5 h to obtain hydrolysate, add 8.25 g of ZIF-8, react at 65 °C for 5 h under inert gas protection, collect the solid by centrifugation, wash with deionized water, and dry at 70 °C for 16 h to obtain modified ZIF-8.

[0058] B3. Disperse 5g of modified ZIF-8 in 225mL of N-methylpyrrolidone, sonicate at 200W and 25℃ for 15min to obtain a suspension, add 50g of polyimide powder, stir at 45℃ for 14h, place the reaction system in a vacuum drying oven with a vacuum degree of -0.09MPa (gauge pressure), let stand for 40min, treat the system in sonication at 25℃ and 200W for 10min, then place it in a vacuum drying oven with a vacuum degree of -0.09MPa (gauge pressure) for 15min, and finally let it stand in a constant temperature environment of 25℃ for 3h to obtain the casting solution.

[0059] B4. Scrape a film onto a glass plate to obtain a liquid film with a thickness of 200 μm. Immerse the glass plate with the liquid film into a non-solvent bath (prepared from 100 g of N-methylpyrrolidone and 100 g of deionized water) to obtain the nascent film.

[0060] B5. Soak the nascent membrane in deionized water for 22 hours and anneal it at 190°C for 25 minutes to obtain a polyimide composite membrane.

[0061] Example 6

[0062] like Figure 2As shown, a polyimide composite film is prepared by means of:

[0063] B1. Dissolve 6g of zinc nitrate hexahydrate in 200mL of deionized water to obtain a zinc salt solution. Dissolve 17.5g of 2-methylimidazole in 200mL of deionized water to obtain a 2-methylimidazole solution. Add all of the zinc salt solution to the 2-methylimidazole solution with stirring. React at 25℃ for 3h. Collect the precipitate by centrifugation, wash with deionized water, and dry at 80℃ for 12h to obtain ZIF-8.

[0064] B2. Disperse 5 mL of 3-aminopropyltriethoxysilane in 120 mL of anhydrous toluene, add 1.5 mL of deionized water, stir at 50 °C for 1 h to obtain hydrolysate, add 12 g of ZIF-8, react at 70 °C for 4 h under inert gas protection, collect the solid by centrifugation, wash with deionized water, and dry at 80 °C for 12 h to obtain modified ZIF-8.

[0065] B3. Disperse 5g of modified ZIF-8 in 225mL of N-methylpyrrolidone, sonicate at 150W and 25℃ for 20min to obtain a suspension, add 60g of polyimide powder, stir at 50℃ for 12h, place the reaction system in a vacuum drying oven with a vacuum degree of -0.09MPa (gauge pressure), let stand for 45min, treat the system in sonication at 25℃ and 200W for 10min, then place it in a vacuum drying oven with a vacuum degree of -0.09MPa (gauge pressure) for 20min, and finally let it stand in a constant temperature environment of 25℃ for 2h to obtain the casting solution.

[0066] B4. Scrape a film onto a glass plate to obtain a liquid film with a thickness of 100 μm. Immerse the glass plate with the liquid film into a non-solvent bath (prepared from 100 g of N-methylpyrrolidone and 250 g of deionized water) to obtain a primary film.

[0067] B5. Soak the nascent membrane in deionized water for 20 hours and anneal it at 200°C for 20 minutes to obtain a polyimide composite membrane.

[0068] Example 7

[0069] like Figure 1 As shown, a method for treating tail gas from vanadium-nitrogen alloy smelting includes the following process:

[0070] S1. The smelting tail gas, cooled to 45°C and with a dust content of <5mg / m³ after bag filter dust removal, is dehydrated using activated alumina and 3A molecular sieve at 30°C and 0.12MPa pressure. The dehydrated gas is then sent to a separation tower, where nitrogen and carbon-containing tail gas are separated using the polyimide composite membrane prepared in Example 4. The membrane module operating temperature is adjusted to 42°C, the pressure is 0.4MPa, and the permeate side pressure is 0.12MPa to obtain nitrogen and carbon-containing tail gas.

[0071] S2. The carbon-containing tail gas is introduced into the adsorption tower, and the pressure of the adsorption tower is adjusted to 0.5 MPa and the temperature is 25°C. The carbon dioxide in the carbon-containing tail gas is adsorbed by the eutectic ionic liquid prepared in Example 1 to obtain tail gas rich in carbon monoxide.

[0072] S3. Collect nitrogen gas from S1 in a buffer tank at a pressure of 0.03 MPa. After pressurizing the collected nitrogen gas to 0.075 MPa, introduce it into the electric kiln for secondary use. In S2, introduce the tail gas rich in carbon monoxide into the combustion system and burn it at 900°C to preheat the raw materials.

[0073] Example 8

[0074] like Figure 1 As shown, a method for treating tail gas from vanadium-nitrogen alloy smelting includes the following process:

[0075] S1. The smelting tail gas, cooled to 40°C and with a dust content of <5mg / m³ after bag filter dust removal, is dehydrated using activated alumina and 3A molecular sieve at 25°C and 0.1MPa pressure. The dehydrated gas is then sent to a separation tower, where nitrogen and carbon-containing tail gas are separated using the polyimide composite membrane prepared in Example 5. The membrane module operating temperature is adjusted to 35°C, the pressure is 0.3MPa, and the permeate side pressure is 0.1MPa to obtain nitrogen and carbon-containing tail gas.

[0076] S2. The carbon-containing tail gas is introduced into the adsorption tower, and the pressure of the adsorption tower is adjusted to 0.4 MPa and the temperature is 30°C. The carbon dioxide in the carbon-containing tail gas is adsorbed by the eutectic ionic liquid prepared in Example 2, and the tail gas rich in carbon monoxide is obtained.

[0077] S3. Collect nitrogen gas from S1 in a buffer tank at a pressure of 0.01 MPa. After pressurizing the collected nitrogen gas to 0.05 MPa, it is introduced into the electric kiln for secondary use. The tail gas rich in carbon monoxide from S2 is introduced into the combustion system and burned at 800°C to preheat the raw materials.

[0078] Example 9

[0079] like Figure 1 As shown, a method for treating tail gas from vanadium-nitrogen alloy smelting includes the following process:

[0080] S1. The smelting tail gas, cooled to 50°C and with a dust content of <5mg / m³ after bag filter dust removal, is dehydrated using activated alumina and 3A molecular sieve at 35°C and 0.15MPa pressure. The dehydrated gas is then sent to a separation tower, where nitrogen and carbon-containing tail gas are separated using the polyimide composite membrane prepared in Example 6. The membrane module operating temperature is adjusted to 50°C, the pressure is 0.5MPa, and the pressure on the permeate side is 0.15MPa, yielding nitrogen and carbon-containing tail gas.

[0081] S2. The carbon-containing tail gas is introduced into the adsorption tower, and the pressure of the adsorption tower is adjusted to 0.6 MPa and the temperature to 40°C. The carbon dioxide in the carbon-containing tail gas is adsorbed by the eutectic ionic liquid prepared in Example 3, and the tail gas rich in carbon monoxide is obtained.

[0082] S3. Collect nitrogen gas from S1 in a buffer tank at a pressure of 0.05 MPa. After pressurizing the collected nitrogen gas to 0.1 MPa, it is introduced into the electric kiln for secondary use. The tail gas rich in carbon monoxide from S2 is introduced into the combustion system and burned at 1000℃ to preheat the raw materials.

[0083] Comparative Example 1

[0084] A method for treating tail gas from vanadium-nitrogen alloy smelting differs from that in Example 9 in that, in step S2, the eutectic ionic liquid prepared in Example 3 is not used as the adsorbent; instead, an ethanolamine solution is used as the adsorbent.

[0085] Comparative Example 2

[0086] A method for treating tail gas from vanadium-nitrogen alloy smelting differs from that in Example 9 in that, in step S1, the polyimide composite membrane prepared in Example 6 is not used to separate nitrogen from crude carbon monoxide; instead, a polyimide membrane without modified ZIF-8 is used.

[0087] Performance testing: The components in the carbon monoxide-rich exhaust gas obtained in S2 of Examples 7 to 9 and Comparative Examples 1 to 2 were analyzed and measured. The test items included carbon monoxide content, moisture content, dust content and nitrogen residue. The test results are shown in Table 1.

[0088] Table 1. Determination of carbon monoxide-rich exhaust gas components in Examples 7-9 and Comparative Examples 1-2

[0089]

[0090] According to the data in Table 1, the moisture content in the carbon monoxide-rich exhaust gases obtained in Examples 7-9 and Comparative Examples 1-2 was all below 100 ppm, and the dust content was all below 10 mg / m³. 3 the following.

[0091] In the carbon monoxide-rich tail gas obtained in Examples 7 to 9, the carbon monoxide content was all above 75%, and the nitrogen residue rate was below 5%. In Comparative Example 1, the carbon monoxide content in the carbon monoxide-rich tail gas was 51.83%, which was significantly lower than that in Examples 7 to 9. In Comparative Example 1, ethanolamine solution was used as an adsorbent to remove carbon dioxide from the converter gas. The primary amine in the ethanolamine molecule is the only active center that reacts with carbon dioxide. Adsorption depends on the fluidity of the aqueous solution. Carbon dioxide first dissolves in water and then diffuses to the -NH2 site of the ethanolamine molecule. The mass transfer resistance is greatly affected by water temperature and viscosity. In addition, the ethanolamine aqueous solution has a certain solubility for carbon monoxide, which leads to carbon monoxide loss. The carbon monoxide content in the exhaust gas obtained in Comparative Example 2 was 55.76%, which was significantly lower than that in Examples 7 to 9; the nitrogen residue was as high as 25%, which was significantly lower than that in Examples 7 to 9 and Comparative Example 1. In Comparative Example 2, a polyimide membrane without modified ZIF-8 was used to separate nitrogen and carbon monoxide. The separation efficiency of the polyimide membrane was low. Therefore, some nitrogen was contained on the intercepted side, which led to a decrease in the carbon monoxide content and an increase in the nitrogen residue.

[0092] The embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for treating tail gas from vanadium-nitrogen alloy smelting, characterized in that, Includes the following steps: S1. The smelting tail gas after cooling and bag dust removal is dehydrated, and nitrogen and carbon-containing tail gas are separated by a polyimide composite membrane. S2. Carbon-containing exhaust gas is passed through a eutectic ionic liquid to obtain exhaust gas rich in carbon monoxide. S3. Collect the nitrogen gas in S1 and pass it into the electric kiln; The exhaust gas rich in carbon monoxide from S2 is introduced into the combustion system to preheat the raw materials; The method for preparing the polyimide composite film includes: B1. Dissolve zinc salt in deionized water to obtain zinc salt solution. Dissolve 2-methylimidazole in deionized water to obtain 2-methylimidazole solution. Add all of the zinc salt solution to the 2-methylimidazole solution while stirring. React, collect the precipitate by centrifugation, wash, and dry to obtain ZIF-8. B2. Disperse the silane coupling agent in anhydrous toluene, add deionized water, stir to obtain a hydrolysate, add ZIF-8, react under inert gas protection, collect the solid by centrifugation, wash, dry, and obtain modified ZIF-8. B3. Disperse the modified ZIF-8 in N-methylpyrrolidone, sonicate to obtain a suspension, add polyimide powder, stir, degas, and obtain a casting solution; B4. Coat a liquid film on a glass plate to obtain a liquid film with a thickness of 100~200μm. Immerse the glass plate with the liquid film in a non-solvent bath to obtain the primary film. B5. Immerse the nascent membrane in deionized water and anneal it to obtain a polyimide composite membrane. The preparation method of the eutectic ionic liquid includes: A1. Under ice bath conditions, add choline hydroxide aqueous solution to alanine aqueous solution, react, distill under reduced pressure, and dry to obtain choline alanine ionic liquid. A2. Add the polyol to the choline alanine ionic liquid and stir to obtain a eutectic ionic liquid.

2. The method for treating tail gas from vanadium-nitrogen alloy smelting according to claim 1, characterized in that, In step S1, the cooling temperature is 40~50℃; the dust content of the smelting tail gas after bag filter dust removal is <5mg / m³; the adsorbent used for dehydration is activated alumina and 3A molecular sieve, the dehydration temperature is 25~35℃, and the dehydration pressure is 0.10~0.15MPa; during the separation of nitrogen and carbon-containing tail gas by the polyimide composite membrane, the membrane module operating temperature is 35~50℃, the membrane module operating pressure is 0.3~0.5MPa, and the permeate side pressure is 0.1~0.15MPa.

3. The method for treating tail gas from vanadium-nitrogen alloy smelting according to claim 1, characterized in that, In B1, the zinc salt is zinc nitrate hexahydrate and / or zinc acetate; the mass-to-volume ratio of zinc salt to deionized water in the zinc salt solution is (1.15~1.2) g: 40 mL; the mass-to-volume ratio of 2-methylimidazole solution to deionized water in the 2-methylimidazole solution is (3.2~3.5) g: 40 mL; the reaction temperature is 25~30℃, and the reaction time is 1~4 h; the drying temperature is 60~80℃, and the drying time is 12~20 h.

4. The method for treating tail gas from vanadium-nitrogen alloy smelting according to claim 1, characterized in that, In B2, the silane coupling agent is 3-aminopropyltriethoxysilane and / or 3-aminopropyltrimethoxysilane; the volume-to-mass ratio of the silane coupling agent, anhydrous toluene, deionized water, and ZIF-8 is (2~5) mL : (100~120) mL : (0.5~1.5) mL : (5~10) g; the stirring temperature is 40~50℃, and the stirring time is 1~2 h; the reaction temperature is 60~70℃, and the reaction time is 4~6 h; the drying temperature is 60~80℃, and the drying time is 12~20 h.

5. The method for treating tail gas from vanadium-nitrogen alloy smelting according to claim 1, characterized in that, In B3, the mass-to-volume ratio of the modified ZIF-8, polyimide powder, and N-methylpyrrolidone is 1g:(8~12)g:(40~45)mL; the ultrasonic treatment power is 150~200W, the ultrasonic treatment time is 15~20min, and the ultrasonic treatment temperature is 25~30℃; the stirring temperature is 40~50℃, and the stirring time is 12~16h; the degassing operation is as follows: the reaction system is placed in a vacuum drying oven with a vacuum degree of -0.08~-0.09MPa and left to stand for 30~45min, the system is treated with ultrasound at 25℃ and 200W for 10~15min, then placed in a vacuum drying oven with a vacuum degree of -0.08~-0.09MPa and left to stand for 15~20min, and finally left to stand in a constant temperature environment of 25℃ for 2~4h.

6. The method for treating tail gas from vanadium-nitrogen alloy smelting according to claim 1, characterized in that, In B4, the non-solvent bath comprises N-methylpyrrolidone and deionized water, with a mass ratio of N-methylpyrrolidone to deionized water of 1:(0.5~2.5); in B5, the soaking time is 20~24h; the annealing temperature is 180~200℃, and the annealing time is 20~30min.

7. The method for treating tail gas from vanadium-nitrogen alloy smelting according to claim 1, characterized in that, In step S2, the process using the eutectic ionic liquid is carried out inside an adsorption tower, where the pressure is 0.4~0.6 MPa and the temperature is 25~40℃.

8. The method for treating tail gas from vanadium-nitrogen alloy smelting according to claim 1, characterized in that, In A1, the mass-to-volume ratio of alanine to deionized water in the alanine aqueous solution is (10~15) g: (100) mL; the mass-to-volume ratio of choline hydroxide to deionized water in the choline hydroxide aqueous solution is 1 g: (1.2~1.5) mL; the mass ratio of choline hydroxide aqueous solution to alanine is (1.36~1.44):1; the reaction temperature is 60~80℃, and the reaction time is 30~60 min; the vacuum distillation temperature is 50~70℃; the drying temperature is 60~80℃, and the drying time is 12~24 h; in A2, the polyol is any one or more of ethylene glycol, glycerol, and polyethylene glycol 400; the mass ratio of choline alanine ionic liquid to polyol is 1: (1.29~4.18); the stirring temperature is 60~80℃, and the stirring time is 2~4 h.

9. The method for treating tail gas from vanadium-nitrogen alloy smelting according to claim 1, characterized in that, In step S3, the nitrogen collection process is carried out in a buffer tank with a pressure of 0.01~0.05MPa; the collected nitrogen is pressurized to 0.05~0.1MPa and then introduced into the electric kiln; the operating temperature of the combustion system is 800~1000℃.

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