A method and apparatus for defluorination of electroslag remelting waste gas

Abstract

This invention belongs to the field of electroslag remelting waste gas treatment technology, and specifically relates to a method and apparatus for defluorination of electroslag remelting waste gas. The method involves spraying a defluorination spray solution during the defluorination process; the defluorination spray solution comprises, by mass percentage: active MgO: 3%-6%; Al2(SO4)3: 1%-2.5%; Na2S2O8: 0.5%-1.5%; microcrystalline cellulose: 0.1%-0.3%; deionized water: balance. This invention features high defluorination efficiency, stable operation, and strong adaptability.

Description

Technical Field

[0001] This invention belongs to the field of electroslag remelting waste gas treatment technology, and specifically relates to a method and apparatus for defluorination of electroslag remelting waste gas. Background Technology

[0002] Electroslag remelting (ESR) technology, a key metallurgical process for improving the performance of special steels and high-end alloys, generates large quantities of highly toxic and corrosive fluorine-containing waste gases, primarily hydrogen fluoride, during its smelting process due to the use of fluorine-containing fluxes such as fluorite. Improper handling poses a serious threat to the atmospheric environment, production equipment, and human health. Currently, alkaline solution spraying remains the mainstream technology for treating such waste gases. However, traditional sodium hydroxide or sodium carbonate absorbent solutions have significant limitations in practical applications: their reaction product, sodium fluoride, easily combines with calcium and magnesium ions in the circulation system to form a hard calcium fluoride scale layer, causing blockage of packed towers, efficiency reduction, and frequent shutdowns for maintenance—a long-standing technical pain point in the industry. Furthermore, traditional formulations have limited functionality, insufficient ability to synergistically remove odorous gases such as phosphine and trace organic matter that may coexist in the waste gas, and fail to address the issue of fluorine resource recovery.

[0003] Currently, the most common treatment method in the industry is to use alkaline spray scrubbing towers, with sodium hydroxide (NaOH) or sodium carbonate (Na2CO3) solutions as the commonly used scrubbing liquid. While this method effectively neutralizes HF, it has a significant drawback: calcium ions (CaO) in the waste gas or process water... 2+ ) will react with the fluoride ions (F) generated in the reaction - The combination of these substances forms a very hard and highly adhesive calcium fluoride (CaF2) scale. This scale can clog spray heads, coat packing materials, and adhere to tower walls and pipes, leading to increased system pressure drop, decreased mass transfer efficiency, and accelerated equipment corrosion. Frequent shutdowns for cleaning and maintenance are necessary, severely impacting production continuity and economic efficiency.

[0004] Regarding the waste gas and dust generated during electroslag remelting, the existing patent CN202311850198.8 describes an electroslag remelting waste gas treatment device. This device primarily uses physical methods to treat the waste gas, aiming to purify the air and protect the environment. However, this waste gas treatment device generally suffers from low treatment efficiency, high operating costs, difficulty in replacement, and complex equipment. Furthermore, it may generate secondary pollution during the treatment process. The filter element in the waste gas treatment device is a consumable and requires continuous replacement. The insertion of the stirring rod into the filter element complicates the replacement process, and the equipment shutdown during replacement disrupts normal production procedures. Moreover, fluoride removal is a core technological bottleneck in green production in electroslag metallurgy, directly impacting environmental compliance and industrial sustainability. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method and apparatus for defluorination of electroslag remelting waste gas with high defluorination efficiency, stable operation and strong adaptability.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A method for defluorinating electroslag remelting waste gas includes a defluorinating spray solution used for spraying treatment during the defluorination process. The defluorinating spray solution comprises, by mass percentage: active MgO: 3%-6%; Al2(SO4)3: 1%-2.5%; Na2S2O8: 0.5%-1.5%; microcrystalline cellulose: 0.1%-0.3%; and deionized water: balance.

[0008] The preparation method of the defluoridation spray liquid includes the following steps:

[0009] 1) Magnesium oxide pre-slurrying and activation: Add 60-70% of the total amount of deionized water to the reactor, and slowly add active MgO powder while stirring. The feeding time is 10-15 minutes. Continue stirring after feeding to form a uniform magnesium oxide suspension.

[0010] 2) Preparation and stepwise blending of aluminum sulfate solution: Dissolve Al2(SO4)3 in 15-20% of the total amount of the formula with deionized water at a temperature of 40-50°C and stir until completely transparent. Slowly add the prepared aluminum sulfate solution to the magnesium oxide suspension obtained in step 1), and control the addition time to 15-20 minutes to form a magnesium-aluminum mixture.

[0011] 3) Low-temperature dissolution and introduction of sodium persulfate: Using the remaining deionized water, dissolve Na2S2O8 at a temperature below 30°C, and add the obtained sodium persulfate solution to the magnesium-aluminum mixture and mix thoroughly.

[0012] 4) Dispersion and stabilization of microcrystalline cellulose: Under high-speed shearing at a stirring speed of 1000-1500 rpm, microcrystalline cellulose is slowly added to the mixture in step 3) and dispersed for 10-15 minutes until the system is homogeneous and free of lumps; then the speed is adjusted to 200-300 rpm and stirring is continued for 60-80 minutes to obtain the finished product.

[0013] Step 1) Before adding the active MgO powder, the stirring speed is 200-300 rpm. After the addition is complete, the stirring speed is increased to 400-500 rpm and the stirring is continued for 30-40 minutes.

[0014] Step 2) Stirring speed 400-500 rpm.

[0015] A defluorination device for electroslag remelting waste gas includes a reaction chamber shell and a spray chamber. The reaction chamber shell is a cylindrical sealed cavity with a spray chamber connected to its left end and an exhaust port at its right end. The spray chamber is a cylindrical tube structure with an air inlet and an air outlet at its left and right ends, respectively. A spray head for spraying the defluorination spray liquid is installed at the top of the spray chamber. A drain outlet is provided at the bottom. Inside the reaction chamber shell, a primary filter element, a secondary filter element, an air guide fan, and a tertiary filter element are arranged sequentially along the airflow direction. The air guide fan is fixed on a circular support. A metal contact is provided below the circular support to connect to a power source outside the tank. A filter screen made of multiple layers of stacked stainless steel wires is also provided on the right side of the tertiary filter element.

[0016] The gas outlet is conical and communicates with the interior of the reaction chamber shell.

[0017] The filler material of the primary filter element is limestone.

[0018] The filler material of the secondary filter element is zeolite.

[0019] The filler material of the three-stage filter element is activated carbon.

[0020] Compared with existing technologies, the beneficial effects of this invention are:

[0021] 1. In terms of formulation, the spray solution of this invention is a defluorination and resource recovery spray solution based on magnesium-aluminum cycle and reaction enhancement. This invention completely abandons the traditional sodium alkali method and innovatively constructs a multi-effect synergistic system of "magnesium-aluminum mineral fixation-free radical oxidation-physical mass transfer enhancement". Among them, active magnesium oxide, as a slow-release alkali source, achieves efficient defluorination and avoids drastic pH fluctuations in the system; aluminum sulfate induces the formation of a stable magnesium-aluminum-fluoride mineral phase, fundamentally eliminating the formation of calcium fluoride scale and creating conditions for fluoride resource recovery; the sulfate free radicals generated by sodium persulfate activation can simultaneously degrade phosphine, organic matter and other co-pollutants; microcrystalline cellulose greatly enhances the gas-liquid mass transfer process.

[0022] 2. This invention introduces an advanced oxidation process and employs a synergistic system of environmentally friendly physical synergists.

[0023] Transforming "neutralization" into "mineral fixation": transforming the problem of soluble NaF into a stable, resource-available (Mg-Al-F) mineral problem.

[0024] Transforming "single fluoride removal" into "oxidation-precipitation synergistic treatment": a single system simultaneously addresses multiple pollutants, including fluoride, odor, and organic pollutants.

[0025] Transforming "chemical scale prevention" into "physical-chemical synergistic scale prevention": By regulating product morphology and enhancing mass transfer, the physical basis of scale formation is fundamentally eliminated.

[0026] 3. Regarding the preparation method, this invention employs a strict feeding sequence: MgO → Al2(SO4)3 → Na2S2O8 → cellulose, ensuring a gradient in the chemical reaction and effective retention of functional components. Pre-slurry activation of MgO and maturation treatment of the mixture are crucial for stimulating its reactivity and achieving synergistic effects between components, which cannot be achieved through simple mixing. The final product is a stable, multifunctional gas-liquid-solid three-phase reaction system, rather than a simple solution. The solid phase (MgO, microcrystalline cellulose) is the core component for achieving efficient mass transfer, deep defluorination, and scale prevention.

[0027] 4. The electroslag remelting waste gas defluorination treatment device has low manufacturing cost, a sophisticated layout, a compact structure, and convenient maintenance. It effectively meets the defluorination process requirements while recovering energy from the waste gas. It has low requirements for raw materials, a long catalyst replacement cycle, and is easy to disassemble and maintain. It is suitable for various waste gas energy recovery and defluorination / denitrification processes. It boasts high defluorination efficiency; even with high-concentration, complex waste gas, the device can stably suppress the outlet fluoride concentration to below 5.0 mg / m³, with a removal rate consistently exceeding 98%. Attached Figure Description

[0028] Figure 1 This is a structural diagram of the electroslag remelting waste gas defluorination device of the present invention.

[0029] In the diagram: 1. Reaction chamber shell; 2. Spray chamber; 3. Air inlet; 4. Air outlet; 5. Primary filter element; 6. Secondary filter element; 7. Air guide fan; 8. Tertiary filter element; 9. Filter screen; 10. Metal contact; 11. Drain outlet; 12. Exhaust outlet; 13. Spray head; 14. Circular bracket. Detailed Implementation

[0030] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. The reference to "embodiment" herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0031] A method for defluorinating electroslag remelting waste gas, wherein a defluorinating spray solution is used for spray treatment during the defluorination process; the defluorinating spray solution comprises, by mass percentage: 3%-6% active magnesium oxide (MgO); 1%-2.5% aluminum sulfate (Al2(SO4)3); 0.5%-1.5% sodium persulfate (Na2S2O8); 0.1%-0.3% microcrystalline cellulose; and the balance being deionized water.

[0032] Active magnesium oxide suspension (MgO) is the main defluorinating agent; aluminum sulfate (Al2(SO4)3) is a reaction promoter and product regulator; sodium persulfate (Na2S2O8) is a free radical catalytic oxidant; and microcrystalline cellulose is a physical mass transfer enhancer.

[0033] (1) Activated magnesium oxide (MgO) - core defluorinating agent and pH buffer source

[0034] Instead of the traditional strong alkali (NaOH), a weakly alkaline MgO suspension is used. It reacts with HF to produce magnesium fluoride (MgF2): MgO + 2HF → MgF2↓ + H2O.

[0035] Technical benefits: Slow-release effect: MgO has low solubility in water and can slowly release OH⁻, so that the local pH of the liquid surface will not be too high at an instant, avoiding the rapid absorption of CO2 and the formation of carbonate scale, and making the system pH more stable.

[0036] Product advantages: The generated MgF2 is an extremely insoluble precipitate (Ksp=5.16×10⁻¹¹), with strong reaction driving force and thorough defluorination. Its loose crystal structure, in a flocculent form, does not easily form a hard, dense scale layer on the equipment surface and is easily discharged with the liquid flow.

[0037] Providing a matrix for subsequent reactions: The generated MgF2 is a precursor for the subsequent reaction with aluminum agents to form stable minerals.

[0038] (2) Aluminum sulfate (Al2(SO4)3) - reaction promoter and product regulator

[0039] Introducing AI 3+ It is not used as a simple coagulant, but rather undergoes a solid-phase transformation reaction with MgF2 to induce the formation of a more stable and easier-to-separate and recoverable magnesium aluminum fluoride mineral phase (similar to MgAlF5).

[0040] Technical benefits: Product stabilization and resource utilization: MgF2 + Al 3+ →(Mg-Al-F) complex. This mineral phase is extremely chemically stable, enabling the immobilization and resource utilization of fluorine, and providing the possibility for subsequent hydrometallurgical recovery of fluorine and aluminum resources from waste residue, turning waste into treasure.

[0041] Synergistic defluorination: Al 3+It can also form complexes with F⁻ (such as AlF3) to further purify trace amounts of fluorine.

[0042] Breaking through the passivation layer: For the possible presence of metal fluoride passivation layers, Al 3+ It has an erosive effect, which can destroy its structure and maintain the surface activity of the filler.

[0043] (3) Sodium persulfate (Na2S2O8) - free radical catalytic oxidant

[0044] Introducing the concept of advanced oxidation technology. Persulfates react with transition metal ions (such as Fe2+, which may be carried in exhaust gases). 2+ Activated by heat or other means, it produces strongly oxidizing sulfate free radicals (SO4· ... - ).

[0045] Technical efficacy: Collaborative governance: SO4· - It can non-selectively oxidize and decompose organic matter, CO, and odorous substances such as PH3 and H2S that may coexist in waste gas, achieving synergistic removal of multiple pollutants within the same spray unit. SO4· - +Pollutants→CO2+ H2O +SO4² - .

[0046] Sterilization and preservation: Effectively kills microorganisms in the circulating water system and prevents the growth of biological slime.

[0047] (4) Microcrystalline cellulose - physical mass transfer enhancer

[0048] It abandons chemical surfactants and uses natural polymer materials. After being dispersed in water, it forms a network of countless micron-sized flexible fibers.

[0049] Technical benefits: "Solid-gas" mass transfer bridge: These microfibers can attach to the surface of the packing material, greatly increasing the contact interface between the gas, liquid and solid phases, and acting like a "bridge" to more efficiently "pull" HF molecules into the liquid phase for reaction.

[0050] Nucleus induction: It provides a large number of crystallization sites for precipitates such as MgF2, which promotes the precipitation of crystals in a smaller and more uniform form, and completely avoids the problem of a few crystal nuclei growing into hard scale.

[0051] Environmentally friendly: natural, biodegradable, non-toxic, and with no risk of secondary pollution.

[0052] The method for preparing the spray liquid includes:

[0053] 1) Magnesium oxide pre-slurrying and activation: Add 60-70% of the total amount of deionized water to the reactor, stir at 200-300 rpm, slowly add active MgO powder, and add the powder over 10-15 minutes; after the addition is complete, increase the stirring speed to 400-500 rpm and continue stirring for 30-40 minutes to form a uniform suspension.

[0054] Key control point: This step aims to fully wet and disperse the MgO particles to form a stable magnesium oxide suspension, providing a large specific surface area for subsequent reactions.

[0055] 2) Preparation and stepwise blending of aluminum sulfate solution: Dissolve Al2(SO4)3 in 15-20% of the total amount of the formula in deionized water at 40-50°C, and stir at 400-500 rpm until completely transparent; slowly add the prepared aluminum sulfate solution dropwise to the magnesium oxide suspension obtained in step 1), and control the dropwise addition time to 15-20 minutes to form a magnesium-aluminum mixture;

[0056] Key control point: Slow dripping can make Al 3+ It undergoes a preliminary and mild interaction with the surface of MgO particles, initially constructing a "magnesium-aluminum" reactive center, thus avoiding the generation of excessive aluminum hydroxide colloid due to excessively high local concentration.

[0057] 3) Low-temperature dissolution and introduction of sodium persulfate: Using the remaining deionized water, dissolve Na2S2O8 at a temperature below 30°C; add the prepared sodium persulfate solution to the reaction vessel and mix thoroughly with the magnesium-aluminum mixture;

[0058] Key control point: Low-temperature water is used to prevent sodium persulfate from being activated and decomposed prematurely at higher temperatures, ensuring that it efficiently generates sulfate free radicals when it encounters high-temperature exhaust gas in the spray tower.

[0059] 4) Dispersion and stabilization of microcrystalline cellulose: Under high-speed shear at a stirring speed of 1000-1500 rpm, microcrystalline cellulose is slowly added to the mixed solution in step 3), and dispersed under high-speed shear for 10-15 minutes until the system is homogeneous and free of lumps; then the stirring speed is adjusted to 200-300 rpm, and stirring is continued for 60-80 minutes to obtain the finished product, with the pH value stabilized between 8.5 and 9.5.

[0060] Key control points: High-speed shearing ensures sufficient depolymerization and dispersion of microcrystalline cellulose, forming a stable three-dimensional network structure. The maturation process allows for full interaction among the components, enabling the system to reach a stable state and achieve optimal performance.

[0061] The resulting product is a suspension with a slightly opalescent appearance and uniform texture.

[0062] like Figure 1A defluorination device for electroslag remelting waste gas includes a reaction chamber shell 1 and a spray chamber 2. The reaction chamber shell 1 is a cylindrical sealed cavity with the spray chamber 2 connected to its left end and an exhaust port 12 at its right end. The spray chamber 2 is a cylindrical tube structure with an air inlet 3 and an air outlet 4 at its left and right ends, respectively. A spray head 13 for spraying the defluorination spray liquid is installed at the top of the spray chamber 2, and a drain outlet 11 is provided at the bottom. Inside the reaction chamber shell 1, a primary filter element 5, a secondary filter element 6, an air guide fan 7, and a tertiary filter element 8 are arranged sequentially along the airflow direction. The air guide fan 7 is fixed on a circular bracket 14, and a metal contact 10 is provided below the circular bracket 14 to connect to an external power source. A filter screen 9 made of multiple layers of stainless steel wire is also provided on the right side of the tertiary filter element 8.

[0063] The gas outlet is conical and communicates with the interior of the reaction chamber shell 1. This is used to increase the gas pressure.

[0064] The filler for the primary filter element 5 is limestone.

[0065] The filler material of the secondary filter element 6 is zeolite.

[0066] The filler for the three-stage filter element 8 is activated carbon.

[0067] Work process:

[0068] The exhaust gas first enters the spray chamber 2, where a defluorination spray solution is sprayed through the spray head 13. The fluorides in the exhaust gas react chemically with the spray solution, forming insoluble fluoride precipitates. Subsequently, the exhaust gas passes sequentially through a primary filter element 5, a secondary filter element 6, and a tertiary filter element 7 to further remove residual fluorides and other harmful substances. Finally, after passing through the filter screen 9, the purified gas is discharged into the atmosphere through the exhaust port 12.

[0069] 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.

[0070] Example:

[0071] A defluorination device for electroslag remelting waste gas includes a reaction chamber shell 1 and a spray chamber 2. The reaction chamber shell 1 is a cylindrical sealed cavity, with the spray chamber 2 connected to its left end and an exhaust port 12 at its right end. The spray chamber 2 is a cylindrical tube structure, with an air inlet 3 and an air outlet 4 at its left and right ends, respectively. The air outlet 4 is a constricting cone shape and communicates with the interior of the reaction chamber shell 1. A spray head 13 for spraying the defluorination spray liquid is installed at the top of the spray chamber 2; a drain outlet 11 is provided at the bottom. Inside the reaction chamber shell 1, a primary filter element 5, a secondary filter element 6, an air guide fan 7, and a tertiary filter element 8 are arranged sequentially along the airflow direction. The primary filter element 5, secondary filter element 6, and tertiary filter element 8 have the same structure, which is a disc structure. The outer ring is made of polypropylene; metal mesh is fixed on both sides; and filler is added in the middle of the metal mesh. The filler of the primary filter element 5 is limestone. The filler of the secondary filter element 6 is zeolite. The filler of the tertiary filter element 8 is activated carbon.

[0072] The air guide fan 7 is fixed on the annular bracket 14. A metal contact 10 is provided below the annular bracket 14 to connect to the power supply outside the tank. A multi-layer stainless steel wire filter screen 9 is also provided on the right side of the three-stage filter element 8. A booster fan is provided in front of the air inlet 3 of the spray chamber 2.

[0073] Example 1

[0074] The preparation method of the defluoridation spray solution includes the following steps:

[0075] 1) Components by mass percentage: 4% MgO; 2% Al2(SO4)3; 1% Na2S2O8; 0.2% microcrystalline cellulose; balance: deionized water. Active magnesium oxide (MgO, industrial grade, purity ≥85%), aluminum sulfate (Al2(SO4)3·18H2O, industrial grade), sodium persulfate (Na2S2O8, industrial grade).

[0076] 2) Add 68% of the total amount of deionized water to the reactor, stir at 260 rpm, slowly add active MgO powder, and add the powder over 10 minutes. After the powder is added, increase the stirring speed to 450 rpm and continue stirring for 30 minutes to form a uniform suspension.

[0077] 3) Preparation and stepwise blending of aluminum sulfate solution: Dissolve Al2(SO4)3 in 20% of the total amount of the formula in deionized water at 45°C and stir until completely transparent; Under stirring at 400 rpm, slowly add the aluminum sulfate solution dropwise to the magnesium oxide suspension obtained in step 1), and control the dropwise addition time to 15 minutes.

[0078] 4) Low-temperature dissolution and introduction of sodium persulfate: Dissolve Na2S2O8 in the remaining deionized water at 28°C; add the sodium persulfate solution to the reaction vessel and mix thoroughly with the magnesium-aluminum mixture;

[0079] 5) Dispersion and stabilization of microcrystalline cellulose: Microcrystalline cellulose was slowly added to the reactor under high-speed shear at 1200 rpm and dispersed under high-speed shear for 12 minutes until the system was homogeneous and free of lumps; then the speed was adjusted to 220 rpm and stirring was continued for at least 70 minutes to obtain the finished product; the pH value of the spray liquid was measured and the pH value was 9.0.

[0080] Example 2

[0081] The preparation method of the defluoridation spray solution includes the following steps:

[0082] 1) Components by mass percentage: 5% MgO; 2.5% Al2(SO4)3; 1.5% Na2S2O8; 0.25% microcrystalline cellulose; balance: deionized water. Activated magnesium oxide (MgO, industrial grade, purity ≥85%), aluminum sulfate (Al2(SO4)3·18H2O, industrial grade), sodium persulfate (Na2S2O8, industrial grade).

[0083] 2) Add 70% of the total amount of deionized water to the reactor and stir at 280 rpm. Slowly add the active MgO powder over 12 minutes. After the addition is complete, increase the stirring speed to 420 rpm and continue stirring for 40 minutes to form a uniform suspension.

[0084] 3) Preparation and stepwise blending of aluminum sulfate solution: Dissolve Al2(SO4)3 in 18% of the total amount of the formula in deionized water at 45°C and stir until completely transparent; slowly add the aluminum sulfate solution dropwise to the magnesium oxide suspension obtained in step 1) while stirring at 410 rpm, and control the addition time to 16 minutes.

[0085] 4) Low-temperature dissolution and introduction of sodium persulfate: Dissolve Na2S2O8 in the remaining deionized water at a temperature of 28°C; add the sodium persulfate solution to the reaction vessel and mix it thoroughly with the magnesium-aluminum mixture.

[0086] 5) Dispersion and stabilization of microcrystalline cellulose: Microcrystalline cellulose was slowly added to the reactor under high-speed shear at 1300 rpm and dispersed under high-speed shear for 15 minutes until the system was homogeneous and free of lumps; then the speed was adjusted to 220 rpm and stirring was continued for at least 60 minutes to obtain the finished product. The pH value of the spray liquid was measured and found to be 9.2.

[0087] Example 3

[0088] The preparation method of the defluoridation spray solution includes the following steps:

[0089] 1) Components by mass percentage: 3% MgO; 1% Al2(SO4)3; 0.5% Na2S2O8; 0.15% microcrystalline cellulose; balance: deionized water. Active magnesium oxide (MgO, industrial grade, purity ≥85%), aluminum sulfate (Al2(SO4)3·18H2O, industrial grade), sodium persulfate (Na2S2O8, industrial grade).

[0090] 2) Add 65% of the total amount of deionized water to the reactor and stir at 300 rpm. Slowly add the active MgO powder over 12 minutes. After the addition is complete, increase the stirring speed to 460 rpm and continue stirring for 30 minutes to form a uniform suspension.

[0091] 3) Preparation and stepwise blending of aluminum sulfate solution: Dissolve Al2(SO4)3 in 20% of the total amount of the formula in deionized water at 40°C and stir until completely transparent; slowly add the aluminum sulfate solution to the magnesium oxide suspension obtained in step (1) while stirring at 450 rpm, and control the addition time to 15 minutes.

[0092] 4) Low-temperature dissolution and introduction of sodium persulfate: Dissolve Na2S2O8 in the remaining deionized water at 30°C; add the sodium persulfate solution to the reaction vessel and mix it thoroughly with the magnesium-aluminum mixture.

[0093] 5) Dispersion and stabilization of microcrystalline cellulose: Microcrystalline cellulose was slowly added to the reactor under high-speed shear at 1300 rpm and dispersed under high-speed shear for 15 minutes until the system was homogeneous and free of lumps; then the speed was adjusted to 220 rpm and stirring was continued for at least 65 minutes to obtain the finished product; the pH value of the spray liquid was measured and found to be 8.9.

[0094] Application Example 1:

[0095] Application Background: The original NaOH spray system suffered from severe scaling in the high-hardness water of northern regions, making it unable to consistently meet discharge standards.

[0096]

[0097] Comparison of usage effects and test data:

[0098]

[0099] Conclusion: This invention not only completely solves the scaling problem, but also achieves deep and stable emission of fluorides in compliance with standards, and has synergistic deodorization capabilities.

[0100] Application Example 2:

[0101] Application background: The odor of PH3 is disturbing residents, and there is a desire to recycle harmful fluorinated waste.

[0102]

[0103] Comparison of usage effects and test data:

[0104]

[0105] Conclusion: This solution has transformed the "cost center" into a "potential profit center," eliminating odors while pioneering a new model for the recycling of fluorine resources.

[0106] Application Example 3:

[0107] Application background: Unable to afford high maintenance costs and environmental risks.

[0108]

[0109] Comparison of usage effects and test data:

[0110]

[0111] Conclusion: This invention provides the most worry-free and economical solution for achieving emission standards, with its stability, low maintenance, and operational safety, eliminating the biggest concerns about environmental operation.

[0112] This invention abandons the traditional strong alkali route and constructs a multifunctional synergistic system with activated magnesium oxide as the core, aluminum sulfate as the promoter, sodium persulfate as the catalytic oxidant, and microcrystalline cellulose as the physical synergist. This formula not only achieves a highly efficient and scale-free defluorination process through a novel reaction pathway, but also possesses the potential to oxidize and decompose multiple synergistic pollutants and realize the resource recovery of fluorine.

[0113] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for removing fluoride from electroslag remelting waste gas, characterized in that, In the process of defluorination of electroslag remelting waste gas, a defluorination spray solution is used for spray treatment; the defluorination spray solution comprises, by mass percentage: active MgO: 3%-6%; Al2(SO4)3: 1%-2.5%; Na2S2O8: 0.5%-1.5%; microcrystalline cellulose: 0.1%-0.3%; deionized water: balance; The preparation method of the defluoridation spray liquid includes the following steps: 1) Magnesium oxide pre-slurrying and activation: Add 60-70% of the total amount of deionized water to the reactor, and slowly add active MgO powder while stirring. The feeding time is 10-15 minutes. Continue stirring after feeding to form a uniform magnesium oxide suspension. 2) Preparation and stepwise blending of aluminum sulfate solution: Dissolve Al2(SO4)3 in 15-20% of the total amount of the formula with deionized water at a temperature of 40-50°C and stir until completely transparent. Slowly add the prepared aluminum sulfate solution to the magnesium oxide suspension obtained in step 1), and control the addition time to 15-20 minutes to form a magnesium-aluminum mixture. 3) Low-temperature dissolution and introduction of sodium persulfate: Using the remaining deionized water, dissolve Na2S2O8 at a temperature below 30°C, and add the obtained sodium persulfate solution to the magnesium-aluminum mixture and mix thoroughly. 4) Dispersion and stabilization of microcrystalline cellulose: Under high-speed shearing at a stirring speed of 1000-1500 rpm, microcrystalline cellulose is slowly added to the mixture in step 3) and dispersed for 10-15 minutes until the system is homogeneous and free of lumps; then the speed is adjusted to 200-300 rpm and stirring is continued for 60-80 minutes to obtain the finished product.

2. The method for defluorinating electroslag remelting waste gas according to claim 1, characterized in that, Step 1) Before adding the active MgO powder, the stirring speed is 200-300 rpm. After the addition is complete, the stirring speed is increased to 400-500 rpm and the stirring is continued for 30-40 minutes.

3. The method for removing fluoride from electroslag remelting waste gas according to claim 1, characterized in that, Step 2) Stirring speed 400-500 rpm.

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