Deacidification treatment process for flue gas containing high fluorine and chlorine

Abstract

The invention relates to a deacidification treatment process for flue gas containing high fluorine and chlorine, and belongs to the technical field of flue gas treatment. According to the process, the flue gas is treated by adopting dry deacidification, and a novel deacidification agent is prepared aiming at the characteristic that the flue gas contains a large amount of halogen and fluorine ions. Natural zeolite is subjected to modification treatment by adopting a sodium hydroxide solution, the activity of the zeolite is enhanced by roasting in a muffle furnace, and the zeolite and lime are well combined, so that efficient defluorination is realized. In addition, the particle size of the baking soda is refined through a grinding method, the specific surface area of the baking soda is remarkably increased, the contact area and the reaction rate with acid smoke are increased, a proper amount of polyethylene glycol is added, moisture on the surfaces of baking soda particles is adsorbed and fixed through the hygroscopicity and the film-forming property of the polyethylene glycol, agglomeration and hardening are prevented, and meanwhile protective films are formed on the surfaces of the baking soda particles. The stability and the dispersity are enhanced. The zeolite loaded with lime is combined with modified baking soda to synergistically remove halogen and fluorine ions in the acidic flue gas, so that efficient defluorination and dehalogenation are realized.

Description

Technical Field

[0001] The invention belongs to the technical field of flue gas treatment and relates to a deacidification treatment process for flue gas containing high levels of fluorine and chlorine. Background Art

[0002] The flue gas from hazardous waste incineration systems usually contains high concentrations of HCl, SO2, a small amount of HF and other acidic substances. These acidic substances have a significant pollution impact on the atmospheric environment. Therefore, it is particularly important to purify this type of flue gas.

[0003] Currently, wet deacidification is mostly used to treat this type of acidic flue gas. This involves spraying alkaline solutions in deacidification towers or scrubbers with sodium hydroxide solution, generating high-salt wastewater. The soluble salts in this wastewater can only be separated from the liquid through evaporative crystallization, and these impurities are then treated as hazardous waste for secondary treatment. Dry deacidification is a commonly used flue gas purification method. Its advantage is that during the deacidification process, impurities generated by deacidification are captured by bag filters along with dust and excess deacidifiers as fly ash. The preparation of deacidifiers is a key step in dry deacidification. Commonly used deacidifiers include alkaline substances such as sodium hydroxide, lime, and baking soda. However, these commonly used deacidifiers present several challenges. For example, baking soda readily reacts with moisture in the air, causing deliquescence and hardening, significantly impacting deacidification efficiency. Furthermore, baking soda has low defluorination efficiency, making it less effective for flue gas containing high levels of fluorine and chlorine. Therefore, it is very necessary to prepare a deacidification agent with good reactivity and stability in a flue gas environment. Summary of the Invention

[0004] The object of the present invention is to provide a deacidification process for flue gas containing high fluorine and chlorine, which has the characteristics of high deacidification efficiency.

[0005] The purpose of the present invention can be achieved through the following technical solutions: A deacidification process for flue gas containing high fluorine and chlorine, the deacidification process flow is as follows: S1: The incineration flue gas is passed into the flue gas quenching tower and sprayed with atomized cooling water to rapidly reduce the flue gas temperature to below 200°C within 1.0 s, and the cooling water is controlled to prevent condensation in the tower; S2: The flue gas after rapid cooling enters the dry deacidification reaction tower, and the deacidification agent is added to the dry deacidification reaction tower by air flow conveying to react with HCl, SO2, and HF acidic substances in the flue gas to deacidify; The preparation method of the deacidifying agent is as follows: S1-1: 10 parts by weight of natural zeolite was added to 90 parts by weight of sodium hydroxide solution, stirred for 24 hours, washed three times with deionized water equal in mass to the zeolite, and dried in a vacuum drying oven at 60°C for 12 hours to obtain powder A; S1-2: Powder A and lime powder are mixed evenly, placed in a muffle furnace and calcined at a temperature of 400-600°C, and cooled to room temperature at a rate of 5°C / min to obtain powder B; S1-3: Powder B and modified baking soda were mixed, placed in a grinder and ground for 30 min at a grinding speed of 800 r / min, and sieved through 300 mesh to obtain the deacidifying agent; The preparation method of the modified baking soda is as follows: Grinding baking soda in a grinder for 10 min, adding 1-3 wt% polyethylene glycol, and continuing to grind for 20 min to obtain the modified baking soda; S3: The flue gas after deacidification in the dry deacidification reaction tower is further purified by the bag dust collector to capture dust and excess deacidifying agent in the flue gas, and further remove residual acidic substances at the bag dust collector interface. The purified flue gas meets the emission standards and is discharged from above the filter bag support plate.

[0006] Furthermore, the flue gas temperature in S1 is reduced to 130-180°C.

[0007] Furthermore, the temperature in the dry deacidification reaction tower in S2 is 130-160°C.

[0008] Furthermore, the mass fraction of the sodium hydroxide solution in S1-1 is 10%.

[0009] Furthermore, the mass ratio of powder A to lime in S1-2 is 3:1.

[0010] Furthermore, the calcination time in S1-2 is 1.5 h.

[0011] Furthermore, the powder B and modified baking soda in S1-3 are mixed in a mass ratio of 1:(2-4).

[0012] Furthermore, the bags in the bag filter in S3 are made of heat-resistant and corrosion-resistant PTFE + coated PTFE bag material.

[0013] Furthermore, the baking soda is placed in a grinder and ground at a rotation speed of 1000 r / min.

[0014] Natural zeolite is a hydrous aluminosilicate mineral of alkali or alkaline earth metals. Its interior is filled with pores and cavities, resulting in a large specific surface area. The strong attraction between the unique crystal structure gives zeolite excellent adsorption properties. Modifying natural zeolite with a sodium hydroxide solution chemically reacts with the silicate components in the zeolite, etching the zeolite surface, increasing its roughness and the number of pores. This significantly increases the zeolite's surface area, optimizing its pore structure and enhancing its adsorption capacity for acidic flue gases.

[0015] Calcination of zeolite in a muffle furnace at an appropriate temperature effectively removes impurities such as moisture and organic matter from the zeolite's pores and cavities, thereby improving pore patency and specific surface area. The calcination process also causes some ions in the zeolite's crystal structure to migrate, increasing its ion exchange capacity and further enhancing the zeolite's activity. Before calcination, an appropriate amount of lime powder is added and mixed evenly. At high temperatures, the lime powder reacts with the silicate components on the zeolite's surface, allowing some of the lime to enter the zeolite's pores and cavities, forming a good bond with the zeolite. Zeolite utilizes its strong adsorption capacity to absorb large amounts of acidic flue gas, while lime, with its excellent defluorination properties, reacts with fluoride ions on the zeolite's surface and within its pores to form calcium fluoride, achieving efficient defluorination. As a highly efficient adsorption carrier, zeolite reduces acidic corrosion on subsequent processing equipment, extending its service life. Furthermore, zeolite is recyclable, restoring its adsorption properties through regeneration, enabling recycling and significantly reducing industrial costs.

[0016] The particle size and specific surface area of ​​baking soda directly affect its contact area with acidic flue gas and its reaction rate. Further refining the baking soda particle size by grinding, grinding commercially available baking soda powder into fine particles below 300 mesh, is a more effective deacidification agent. This can significantly increase its specific surface area, thereby increasing the contact area with acidic flue gas and the reaction opportunity, promoting improved deacidification performance, and facilitating airflow to the dry deacidification reaction tower. Because baking soda is prone to deliquesce, causing particles to agglomerate and compact, polyethylene glycol has excellent hygroscopicity and film-forming properties, which can absorb and fix moisture on the surface of baking soda particles, preventing them from agglomerating and compacting. Therefore, an appropriate amount of polyethylene glycol is added to the baking soda during the grinding process. The polyethylene glycol can form a protective film on the surface of the baking soda particles, enhancing their stability and dispersibility. The modified baking soda powder of the present invention contains 1% to 3% polyethylene glycol.

[0017] A deacidifying agent is prepared by combining lime-loaded zeolite with modified baking soda after grinding in a grinder. The deacidifying agent is then screened through a 300-mesh screen to ensure fine particle size and low moisture content. Combining lime-loaded zeolite with modified baking soda can fully leverage their synergistic effects, effectively removing acidic gases and fluorides from flue gas using a dry deacidification process. The present invention utilizes modified zeolite and lime, leveraging the zeolite's powerful adsorption capacity to absorb large amounts of halogens and fluoride ions from acidic flue gas. Simultaneously, the lime loaded on the zeolite reacts with fluoride ions to form calcium fluoride, achieving efficient defluorination. The baking soda, utilizing its alkaline properties, reacts with the acidic flue gas, further removing halogens and fluoride ions. This combination not only improves dehalogenation and defluorination performance, but also achieves the environmental and social benefits of energy conservation and emission reduction, while also increasing the economic efficiency of the operating company, resulting in excellent practicality.

[0018] The bag filter utilizes heat-resistant and corrosion-resistant PTFE + coated PTFE bag material, which offers excellent chemical resistance. It can effectively resist the erosion of corrosive components in flue gas even in high-temperature environments, extending the service life of the bag. The PTFE bag filter also has excellent filtration efficiency, effectively filtering out tiny particles. Its smooth surface is less prone to dust adhesion, resulting in low filtration resistance, which helps reduce the energy consumption of the dust collection system while maintaining high energy-efficient filtration efficiency. Furthermore, because the PTFE surface is less prone to dust adhesion, the cleaning process is smoother, reducing cleaning frequency and making maintenance relatively simple. Regular cleaning is sufficient to effectively prevent degradation of dust collection accuracy and extend service life.

[0019] Beneficial effects of the present invention: (1) Modification of natural zeolite with sodium hydroxide solution significantly optimizes the pore structure of the zeolite and enhances its adsorption capacity for acidic flue gas. The zeolite is calcined in a muffle furnace to remove the water adsorbed in the zeolite, further increasing the specific surface area and adsorption activity of the zeolite. Lime reacts with the silicate components on the surface of the zeolite at high temperature, and some of the lime can enter the pores or cavities of the zeolite, forming a good bond with the zeolite. Zeolite uses its strong adsorption capacity to absorb a large amount of acidic flue gas, while lime uses its good defluorination performance to react with fluoride ions on the surface or in the pores of the zeolite to generate calcium fluoride, achieving the purpose of efficient defluorination.

[0020] (2) By grinding, the baking soda particle size is refined, increasing its specific surface area, significantly improving its contact and reaction efficiency with acidic flue gas and enhancing its deacidification ability. Adding an appropriate amount of polyethylene glycol stabilizes the baking soda through moisture absorption and film formation, enhancing its dispersibility. Combined with lime-loaded zeolite, the strong adsorption capacity of the zeolite is utilized to capture halogen and fluoride ions, while the baking soda and lime exert their alkalinity and reactivity to efficiently remove these harmful ions. DETAILED DESCRIPTION

[0021] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0022] Example 1 A deacidification process for flue gas containing high fluorine and chlorine, the deacidification process flow is as follows: S1: The incineration flue gas is passed into the flue gas quenching tower and sprayed with atomized cooling water to rapidly reduce the flue gas temperature to 155°C within 1.0 s, and control is made to prevent cooling water condensation in the tower; S2: After rapid cooling, the flue gas enters the dry deacidification reaction tower. The temperature inside the dry deacidification reaction tower is 145°C. The deacidification agent is added to the dry deacidification reaction tower by air flow conveying to react with HCl, SO2, and HF acidic substances in the flue gas to remove the acid; The preparation method of the deacidifying agent is as follows: S1-1: 10 parts by weight of natural zeolite was added to 90 parts by weight of sodium hydroxide solution, stirred for 24 hours, washed three times with deionized water equal in mass to the zeolite, and dried in a vacuum drying oven at 60°C for 12 hours to obtain powder A; S1-2: Powder A and lime powder were mixed in a mass ratio of 3:1, and the mixture was placed in a muffle furnace and calcined at 500°C for 1.5 h. The mixture was then cooled to room temperature at a rate of 5°C / min to obtain powder B. S1-3: Powder B and modified baking soda were mixed in a mass ratio of 1:3, and ground in a grinder for 30 min at a grinding speed of 800 r / min. The mixture was sieved through 300 mesh to obtain the deacidifying agent; The preparation method of the modified baking soda is as follows: The baking soda was placed in a grinder and ground. After grinding for 10 min, 2 wt% polyethylene glycol was added and the grinding was continued for 20 min at a grinding speed of 1000 r / min to obtain the modified baking soda. S3: The flue gas after deacidification in the dry deacidification reaction tower is further purified by the bag dust collector. The bag is made of heat-resistant and corrosion-resistant PTFE + coated PTFE bag material, which captures dust and excess deacidifying agent in the flue gas and further removes residual acidic substances at the bag dust collector interface. The purified flue gas meets the emission standards and is discharged from above the filter bag support plate.

[0023] Example 2 A deacidification process for flue gas containing high fluorine and chlorine, the deacidification process flow is as follows: S1: The incineration flue gas is passed into the flue gas quenching tower and sprayed with atomized cooling water to rapidly reduce the flue gas temperature to 130°C within 1.0 s, and control is made so that no cooling water condensation occurs in the tower; S2: The flue gas after rapid cooling enters the dry deacidification reaction tower. The temperature inside the dry deacidification reaction tower is 130°C. The deacidification agent is added to the dry deacidification reaction tower by air flow conveying to react with HCl, SO2, and HF acidic substances in the flue gas to remove the acid; The preparation method of the deacidifying agent is as follows: S1-1: 10 parts by weight of natural zeolite was added to 90 parts by weight of sodium hydroxide solution, stirred for 24 hours, washed three times with deionized water equal in mass to the zeolite, and dried in a vacuum drying oven at 60°C for 12 hours to obtain powder A; S1-2: Powder A and lime were mixed in a mass ratio of 3:1, placed in a muffle furnace and calcined at 400°C for 1.5 h, and cooled to room temperature at a rate of 5°C / min to obtain powder B. S1-3: Powder B and modified baking soda were mixed in a mass ratio of 1:2, ground in a grinder for 30 min at a grinding speed of 800 r / min, and sieved through 300 mesh to obtain the deacidifying agent; The preparation method of the modified baking soda is as follows: The baking soda was placed in a grinder and ground. After grinding for 10 min, 1 wt% polyethylene glycol was added and the grinding was continued for 20 min at a grinding speed of 1000 r / min to obtain the modified baking soda. S3: The flue gas after deacidification in the dry deacidification reaction tower is further purified by the bag dust collector. The bag is made of heat-resistant and corrosion-resistant PTFE + coated PTFE bag material, which captures dust and excess deacidifying agent in the flue gas and further removes residual acidic substances at the bag dust collector interface. The purified flue gas meets the emission standards and is discharged from above the filter bag support plate.

[0024] Example 3 A deacidification process for flue gas containing high fluorine and chlorine, the deacidification process flow is as follows: S1: The incineration flue gas is passed into the flue gas quenching tower and sprayed with atomized cooling water to rapidly reduce the flue gas temperature to 180°C within 1.0 s, and control is made so that no cooling water condensation occurs in the tower; S2: After rapid cooling, the flue gas enters the dry deacidification reaction tower. The temperature inside the dry deacidification reaction tower is 160°C. The deacidification agent is added to the dry deacidification reaction tower by air flow conveying to react with HCl, SO2, and HF acidic substances in the flue gas to remove the acid; The preparation method of the deacidifying agent is as follows: S1-1: 10 parts by weight of natural zeolite was added to 90 parts by weight of sodium hydroxide solution, stirred for 24 hours, washed three times with deionized water equal in mass to the zeolite, and dried in a vacuum drying oven at 60°C for 12 hours to obtain powder A; S1-2: Powder A and lime powder were mixed in a mass ratio of 3:1, and the mixture was calcined in a muffle furnace at 600°C for 1.5 h. The mixture was then cooled to room temperature at a rate of 5°C / min to obtain powder B. S1-3: Powder B and modified baking soda were mixed in a mass ratio of 1:4, and the mixture was ground in a grinder at a speed of 800 r / min for 30 min, and sieved through 300 mesh to obtain the deacidifying agent; The preparation method of the modified baking soda is as follows: The baking soda was placed in a grinder and ground. After grinding for 10 min, 3 wt% polyethylene glycol was added and the grinding was continued for 20 min at a grinding speed of 1000 r / min to obtain the modified baking soda. S3: The flue gas after deacidification in the dry deacidification reaction tower is further purified by the bag dust collector. The bag is made of heat-resistant and corrosion-resistant PTFE + coated PTFE bag material, which captures dust and excess deacidifying agent in the flue gas and further removes residual acidic substances at the bag dust collector interface. The purified flue gas meets the emission standards and is discharged from above the filter bag support plate.

[0025] Comparative Example 1 In the preparation of the deacidifying agent, baking soda is not modified, and the remaining steps are consistent with those in Example 1.

[0026] Comparative Example 2 The preparation of the deacidifying agent does not include step S1-1, and the remaining steps are the same as those in Example 1.

[0027] Comparative Example 3 The preparation of the deacidifying agent does not involve the muffle furnace calcination step, and the remaining steps are the same as those in Example 1.

[0028] Deacidification performance test: The dehalogenation efficiency and defluorination efficiency in the examples and comparative examples were determined by ion chromatography. The experimental data are recorded in the following table:

[0029] It can be seen from the data of the examples and comparative examples that the deacidification agent prepared by the present invention has excellent flue gas deacidification efficiency.

[0030] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A deacidification process for flue gas containing high fluorine and chlorine, characterized in that: The deacidification process is as follows: S1: The incineration flue gas is passed into the flue gas quenching tower, and atomized cooling water is sprayed in to rapidly reduce the flue gas temperature. The flue gas temperature drops below 200°C within 1.0 s, and it is controlled that no cooling water condenses in the tower; S2: The flue gas after rapid cooling enters the dry deacidification reaction tower, and the deacidification agent is added to the dry deacidification reaction tower by air flow conveying to react with HCl, HF, SO2 acidic substances in the flue gas for deacidification; The preparation method of the deacidifying agent is as follows, S1-1: 10 parts by weight of natural zeolite was added to 90 parts by weight of sodium hydroxide solution, stirred for 24 hours, washed three times with deionized water of the same mass as the zeolite, and then dried in a vacuum drying oven at 60°C for 12 hours to obtain powder A; S1-2: Powder A and lime powder are mixed evenly, placed in a muffle furnace for calcination at a temperature of 400-600 °C, and cooled to room temperature at a rate of 5 °C / min to obtain powder B; S1-3: Powder B and modified baking soda were mixed, placed in a grinder and ground for 30 min at a grinding speed of 800 r / min, and sieved through 300 mesh to obtain the deacidifying agent; The preparation method of the modified baking soda is as follows: Grinding baking soda in a grinder, adding 1-3 wt% polyethylene glycol after grinding for 10 min, and continuing grinding for 20 min to obtain the modified baking soda; S3: The flue gas after deacidification in the dry deacidification reaction tower is further purified by the bag filter to capture dust and excess deacidification agent in the flue gas, and further remove residual acidic substances at the interface of the bag filter. The purified flue gas meets the emission standards and is discharged from above the filter bag support plate.

2. The deacidification process for high-fluorine and chlorine-containing flue gas according to claim 1, characterized in that: The flue gas temperature in S1 is reduced to 130-180°C.

3. The deacidification process for high-fluorine and chlorine-containing flue gas according to claim 1, characterized in that: The temperature in the dry deacidification reaction tower in S2 is 130-160°C.

4. The deacidification process for high-fluorine and chlorine-containing flue gas according to claim 1, characterized in that: The mass fraction of the sodium hydroxide solution in the S1-1 is 10%.

5. The deacidification process for high-fluorine and chlorine-containing flue gas according to claim 1, characterized in that: The mass ratio of powder A to lime in S1-2 is 3:

1.

6. The deacidification process for high-fluorine and chlorine-containing flue gas according to claim 1, characterized in that: The calcination time in S1-2 is 1.5 h.

7. The deacidification process for high-fluorine and chlorine-containing flue gas according to claim 1, characterized in that: In the S1-3, powder B and modified baking soda are mixed in a mass ratio of 1:(2-4).

8. The deacidification process for high-fluorine and chlorine-containing flue gas according to claim 1, characterized in that: The bags in the bag filter in S3 are made of heat-resistant and corrosion-resistant PTFE + coated PTFE bag material.

9. The deacidification process for high-fluorine and chlorine-containing flue gas according to claim 1, characterized in that: The baking soda is placed in a grinder and ground at a rotation speed of 1000 r / min.

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