A deacidification process for flue gas containing high fluorine and chlorine

Abstract

The present invention relates to a deacidification process for flue gas containing high fluorine and chlorine, and belongs to the technical field of flue gas treatment. This process uses dry deacidification to treat flue gas, and prepares a deacidification agent for the characteristic that flue gas contains a large amount of halogen and fluoride ions. Natural zeolite is modified by sodium hydroxide solution, and the activity of zeolite is enhanced by muffle furnace roasting, and zeolite and lime form a good combination to achieve efficient defluorination. In addition, the particle size of baking soda is refined by grinding, its specific surface area is significantly increased, the contact area and reaction rate with acidic flue gas are increased, and an appropriate amount of polyethylene glycol is added, and its hygroscopicity and film-forming properties are utilized to adsorb and fix the surface moisture of baking soda particles, prevent agglomeration and caking, and at the same time, a protective film is formed on the surface of baking soda particles to enhance its stability and dispersibility. The lime-loaded zeolite is combined with modified baking soda to synergistically remove the halogen and fluoride ions in the acidic flue gas, and achieve efficient defluorination and dehalogenation.

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 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] At present, for such acid-containing flue gas, wet deacidification is mostly used, that is, alkaline solution is sprayed in the deacidification tower or washing tower, and the spraying liquid is sodium hydroxide solution, which produces a lot of high-salt wastewater. The soluble salts in these wastewaters can only be separated from the liquid by evaporation and crystallization desalination. These salts are treated as hazardous wastes for secondary treatment. Dry deacidification technology is a commonly used flue gas purification method. Its advantage is that wastewater is generated during the deacidification process, and the salts produced by deacidification are captured by the bag filter together with dust and excess deacidification agent to form fly ash. In dry deacidification technology, the preparation of deacidification agent is one of the key links. Commonly used deacidification agents include alkaline substances such as sodium hydroxide, lime, and baking soda. However, there are some problems in the use of commonly used deacidification agents. For example, baking soda is easy to combine with moisture in the air to cause deliquescence and cause compaction, which greatly affects the deacidification efficiency; at the same time, baking soda has low defluorination efficiency and poor deacidification effect on flue gas containing high fluorine and chlorine. Therefore, it is necessary to prepare a deacidifying 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:

[0006] A deacidification process for flue gas containing high fluorine and chlorine, the deacidification process flow is as follows:

[0007] 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;

[0008] 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 for deacidification;

[0009] The preparation method of the deacidifying agent is as follows,

[0010] 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;

[0011] 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;

[0012] 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;

[0013] The preparation method of the modified baking soda is as follows:

[0014] 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;

[0015] 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.

[0016] Furthermore, the flue gas temperature in S1 is reduced to 130-180°C.

[0017] Furthermore, the temperature in the dry deacidification reaction tower in S2 is 130-160°C.

[0018] Furthermore, the mass fraction of the sodium hydroxide solution in S1-1 is 10%.

[0019] Furthermore, the mass ratio of powder A to lime in S1-2 is 3:1.

[0020] Furthermore, the calcination time in S1-2 is 1.5 h.

[0021] Furthermore, the powder B and modified baking soda in S1-3 are mixed in a mass ratio of 1:(2-4).

[0022] Furthermore, the bags in the bag filter in S3 are made of temperature-resistant and corrosion-resistant PTFE + coated PTFE bag material.

[0023] Furthermore, the baking soda is placed in a grinder and ground at a rotation speed of 1000 r / min.

[0024] Natural zeolite is a hydrous alkali metal or alkaline earth metal aluminum silicate mineral, which is full of pores and cavities, making it have a large specific surface area. There is a strong attraction between the special crystal structure, which makes the zeolite have excellent adsorption. The natural zeolite is modified by sodium hydroxide solution. Sodium hydroxide will react chemically with the silicate components in the zeolite, etching the zeolite surface, increasing its roughness and the number of pores, thereby significantly increasing the surface area of ​​the zeolite, which not only optimizes the pore structure of the zeolite, but also enhances its adsorption capacity for acidic flue gas.

[0025] At a suitable temperature, calcining zeolite in a muffle furnace can effectively remove impurities in the pores and cavities of zeolite, such as moisture and organic matter, thereby improving the patency and specific surface area of ​​the pores. At the same time, the calcination process can also cause some ions in the zeolite crystal structure to migrate, increase its ion exchange capacity, and further enhance the activity of the zeolite. Before calcination, add an appropriate amount of lime powder and mix evenly. The lime powder reacts with the silicate components on the surface of the zeolite at high temperature, and some lime can enter the pores or cavities of the zeolite and form a good combination with the zeolite. Zeolite uses its strong adsorption capacity to adsorb a large amount of acidic flue gas, while lime uses its good defluorination performance to react with fluoride ions on the surface or pores of zeolite to generate calcium fluoride, thereby achieving the purpose of efficient defluorination. As an efficient adsorption carrier, zeolite can reduce the corrosion of acidic components to subsequent processing equipment and extend its service life; at the same time, zeolite is renewable, and its adsorption performance can be restored through regeneration treatment, so that it can be recycled, which significantly reduces industrial costs.

[0026] The size of baking soda particle size and specific surface area directly affects its contact area and reaction rate with acidic flue gas. Further refining the particle size of baking soda by grinding method, grinding commercial baking soda powder particles into fine particles below 300 mesh is a more effective deacidification agent, which can significantly increase its specific surface area, thereby increasing the contact area and reaction opportunity with acidic flue gas, promoting the improvement of deacidification performance, and facilitating air flow to the dry deacidification reaction tower. Since baking soda is prone to deliquescence, resulting in particle agglomeration and hardening, polyethylene glycol has excellent hygroscopicity and film-forming properties, can adsorb and fix the moisture on the surface of baking soda particles, and prevents them from agglomerating and hardening. Therefore, an appropriate amount of polyethylene glycol is added to baking soda during the grinding process, and polyethylene glycol can form a protective film on the surface of baking soda particles to enhance its stability and dispersibility. The modified baking soda powder of the present invention adds 1% to 3% polyethylene glycol.

[0027] The lime-loaded zeolite is combined with modified baking soda to prepare a deacidifying agent after grinding in a grinder, and then screened with 300 meshes to ensure the fine particle size and low water content of the deacidifying agent. The lime-loaded zeolite is combined with modified baking soda to give full play to the synergistic effect of the two, and the dry deacidification process is adopted to effectively remove acidic gases and fluorides in flue gas. The present invention utilizes modified zeolite and lime, that is, the strong adsorption capacity of zeolite is utilized to adsorb a large amount of halogens and fluoride ions in acidic flue gas. At the same time, the lime loaded on the zeolite can also react with fluoride ions to generate calcium fluoride, thereby realizing efficient defluorination. Baking soda utilizes its alkaline characteristics to react with acidic flue gas to further remove halogens and fluoride ions. This combination not only improves the dehalogenation and defluorination performance, but also realizes the environmental and social benefits of energy conservation and emission reduction, while improving the economic benefits of the operating enterprise, and has excellent practicality.

[0028] The bag filter uses heat-resistant and corrosion-resistant PTFE + coated PTFE bag material, which has excellent chemical corrosion resistance and can effectively resist the erosion of corrosive components in flue gas under high temperature environment, thus extending the service life of the bag. The PTFE bag filter also has good filtration efficiency and can effectively filter out tiny particles. Its surface is smooth and dust is not easy to adhere to, so it has low filtration resistance, which helps to reduce the energy consumption of the dust removal system while maintaining high energy-efficient filtration efficiency. In addition, since the PTFE surface is not easy to adhere to dust, the cleaning process is smoother, the cleaning frequency is reduced, and maintenance is relatively simple. Only regular cleaning is required to effectively prevent the reduction of dust removal accuracy and extend the service life.

[0029] Beneficial effects of the present invention:

[0030] (1) The natural zeolite is modified by sodium hydroxide solution, which significantly optimizes the pore structure of the zeolite and enhances the zeolite's 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. The lime reacts with the silicate components on the surface of the zeolite at high temperature, and part of the lime can enter the pores or cavities of the zeolite and form a good combination with the zeolite. Zeolite uses its strong adsorption capacity to adsorb 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.

[0031] (2) The particle size of baking soda is refined by grinding, which increases its specific surface area, significantly improves the contact and reaction efficiency with acidic flue gas, and strengthens the deacidification ability. The addition of an appropriate amount of polyethylene glycol stabilizes the baking soda and enhances its dispersibility through moisture absorption and film formation. Combined with lime-loaded zeolite, the strong adsorption force of zeolite is used to capture halogen and fluoride ions, while baking soda and lime exert their alkalinity and reaction activity to efficiently remove these harmful ions. DETAILED DESCRIPTION

[0032] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0033] Example 1

[0034] A deacidification process for flue gas containing high fluorine and chlorine, the deacidification process flow is as follows:

[0035] S1: Pass the incineration flue gas into the flue gas quenching tower, spray atomized cooling water, and quickly reduce the flue gas temperature to 155 ℃ within 1.0 s, and control the cooling water to not condense in the tower;

[0036] S2: The flue gas after rapid cooling enters the dry deacidification reaction tower. The temperature in 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 for deacidification.

[0037] The preparation method of the deacidifying agent is as follows,

[0038] 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;

[0039] S1-2: Powder A and lime powder were mixed evenly in a mass ratio of 3:1, and placed in a muffle furnace for calcination at a temperature of 500 °C for 1.5 h, and cooled to room temperature at a rate of 5 °C / min to obtain powder B;

[0040] S1-3: Powder B and modified baking soda were mixed in a mass ratio of 1:3, 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;

[0041] The preparation method of the modified baking soda is as follows:

[0042] The baking soda was placed in a grinder and ground, and 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;

[0043] S3: The flue gas after deacidification in the dry deacidification reaction tower is further purified by the bag filter. The bag is made of heat-resistant and corrosion-resistant PTFE + coated PTFE bag material, which captures dust and excess deacidification agent in the flue gas and further removes 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.

[0044] Example 2

[0045] A deacidification process for flue gas containing high fluorine and chlorine, the deacidification process flow is as follows:

[0046] S1: Pass the incineration flue gas into the flue gas quenching tower, spray atomized cooling water, and quickly reduce the flue gas temperature to 130 ℃ within 1.0 s, and control the cooling water to not condense in the tower;

[0047] S2: The flue gas after rapid cooling enters the dry deacidification reaction tower. The temperature in 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 for deacidification.

[0048] The preparation method of the deacidifying agent is as follows,

[0049] 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;

[0050] S1-2: Powder A and lime were mixed in a mass ratio of 3:1, and the mixture was placed in a muffle furnace for calcination at a temperature of 400 °C for 1.5 h, and then cooled to room temperature at a rate of 5 °C / min to obtain powder B;

[0051] 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;

[0052] The preparation method of the modified baking soda is as follows:

[0053] The baking soda was placed in a grinder and ground, and 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;

[0054] S3: The flue gas after deacidification in the dry deacidification reaction tower is further purified by the bag filter. The bag is made of heat-resistant and corrosion-resistant PTFE + coated PTFE bag material, which captures dust and excess deacidification agent in the flue gas and further removes 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.

[0055] Example 3

[0056] A deacidification process for flue gas containing high fluorine and chlorine, the deacidification process flow is as follows:

[0057] S1: Pass the incineration flue gas into the flue gas quenching tower, spray atomized cooling water, and quickly reduce the flue gas temperature to 180 ℃ within 1.0 s, and control the cooling water to not condense in the tower;

[0058] S2: The flue gas after rapid cooling enters the dry deacidification reaction tower. The temperature in 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 for deacidification.

[0059] The preparation method of the deacidifying agent is as follows,

[0060] 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;

[0061] S1-2: Powder A and lime powder were mixed evenly in a mass ratio of 3:1, placed in a muffle furnace for calcination at a temperature of 600 °C for 1.5 h, and cooled to room temperature at a rate of 5 °C / min to obtain powder B;

[0062] S1-3: Powder B and modified baking soda were mixed in a mass ratio of 1:4, 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;

[0063] The preparation method of the modified baking soda is as follows:

[0064] The baking soda was placed in a grinder and ground, and 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;

[0065] S3: The flue gas after deacidification in the dry deacidification reaction tower is further purified by the bag filter. The bag is made of heat-resistant and corrosion-resistant PTFE + coated PTFE bag material, which captures dust and excess deacidification agent in the flue gas and further removes 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.

[0066] Comparative Example 1

[0067] In the preparation of the deacidifying agent, baking soda is not modified, and the remaining steps are consistent with those in Example 1.

[0068] Comparative Example 2

[0069] The preparation of the deacidifying agent does not include step S1-1, and the remaining steps are the same as those in Example 1.

[0070] Comparative Example 3

[0071] The preparation of the deacidifying agent does not involve the muffle furnace calcination step, and the remaining steps are consistent with those of Example 1.

[0072] Deacidification performance test:

[0073] The dehalogenation efficiency and defluorination efficiency in the examples and comparative examples were determined by ion chromatography, and the experimental data are recorded in the following table:

[0074]

[0075] 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.

[0076] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall 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 and 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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