Process for flue gas desulfurization by steel slag

Abstract

The present application relates to the field of metallurgical solid waste resource utilization and industrial flue gas purification, and specifically discloses a process method for flue gas desulfurization by steel slag method, which comprises the following steps: using steel plant solid waste steel slag as a calcium source to prepare organic calcium salt or inorganic calcium salt as a circulating desulfurizer, sequentially preparing a desulfurization liquid, wet flue gas desulfurization, calcium sulfite oxidation separation, desulfurizer regeneration, and steel slag tailing resource utilization, to form a desulfurizer closed loop circulation system. The present application realizes synergistic effect of flue gas desulfurization, steel slag consumption and resource recovery, has stable desulfurization efficiency, far exceeds the low emission standard, and is suitable for wide working condition fluctuation. Using steel slag as a calcium source and desulfurizer closed loop circulation, the raw material and operation cost are greatly reduced, and high purity gypsum and iron concentrate powder can be produced to create income. Steel slag realizes 100% resource utilization, and fundamentally solves the problem of pollution caused by stacking. The process can be directly connected to the existing wet desulfurization equipment, has low modification cost and simple operation and maintenance, greatly reduces the equipment failure rate, and has great industrialization promotion value.

Description

Technical Field

[0001] This invention belongs to the field of synergistic technology of metallurgical solid waste resource utilization and industrial flue gas purification, specifically involving a process method for flue gas desulfurization using steel slag. Background Technology

[0002] As a pillar industry of the national economy, the steel industry generates a large amount of steel slag solid waste during production, with my country's annual steel slag emissions exceeding 100 million tons. Steel slag is rich in 30%–50% CaO, and also contains MgO, iron minerals, and other effective components, making it a natural and inexpensive calcium-based desulfurization raw material with the resource basis to replace traditional desulfurizing agents. However, currently, the comprehensive utilization rate of steel slag in my country is less than 80%. The long-term stockpiling of large amounts of steel slag not only occupies land resources but also causes soil and water pollution due to the leaching of calcium and magnesium alkaline components, becoming a key bottleneck restricting the green development of the steel industry.

[0003] SO2 pollution control in industrial flue gas is a core task of air pollution prevention and control. Wet desulfurization is the mainstream desulfurization technology in industries such as thermal power, steel, chemical, and building materials, with the limestone-gypsum method accounting for over 90% of the market share. Although this technology is mature, it has significant drawbacks: First, it requires the purchase of high-purity limestone and lime as desulfurization raw materials, with a cost exceeding 150 yuan per ton of raw materials. Moreover, the calcium utilization rate in limestone is only 60%~70%, resulting in low resource utilization efficiency. Second, the desulfurization slurry is prone to scaling and clogging, gypsum dewatering is difficult, the system pH fluctuates greatly, and impurities such as chloride ions inhibit desulfurization efficiency, causing the actual desulfurization efficiency to drop from the design value of 95% to below 80%. Third, a solid waste co-utilization system has not been formed, and the purity of the desulfurization by-product gypsum is ≤85%, making it difficult to commercialize and easily generating secondary solid waste.

[0004] In recent years, domestic research on steel slag-based desulfurization technology has made some progress, but existing steel slag-based desulfurization technologies still have core technical bottlenecks: First, the desulfurization slurry is prepared directly from steel slag powder, resulting in low calcium dissolution rate (≤50%), poor stability of the desulfurization liquid, and a significant decrease in desulfurization efficiency when flue gas SO2 concentration fluctuates; second, the process only focuses on the single desulfurization stage, and the iron minerals in the steel slag are not effectively activated and recovered, resulting in an iron resource utilization rate of less than 30% and a low degree of high-value utilization of solid waste; third, a closed-loop recycling system for desulfurizing agents has not been constructed, requiring continuous replenishment of fresh agents to the desulfurization liquid, leading to high operating costs; and fourth, the desulfurization byproduct gypsum cannot be commercialized due to its high impurity content, and there is still a problem of secondary solid waste disposal.

[0005] In summary, neither existing wet desulfurization processes nor steel slag-based desulfurization technologies can simultaneously meet the industrial demands for low cost, high efficiency, stable operation, full utilization of solid waste, and high-value utilization of by-products. Summary of the Invention

[0006] The purpose of this invention is to provide a process for flue gas desulfurization using steel slag, in order to solve the problems mentioned in the background art, such as high raw material costs, unstable desulfurization efficiency, low calcium dissolution rate, lack of iron resource recovery, and lack of closed-loop desulfurization agent circulation in existing wet desulfurization processes.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A process for flue gas desulfurization using steel slag includes preparing organic or inorganic calcium salts as a circulating desulfurizing agent from steel plant solid waste steel slag, and sequentially performing desulfurization liquid preparation, wet flue gas desulfurization, calcium sulfite oxidation and separation, desulfurizing agent regeneration, and resource utilization of steel slag tailings to form a closed-loop desulfurizing agent recycling system; the specific steps are as follows:

[0009] S1. Preparation of calcium adipic acid circulating desulfurization solution: Prepare an aqueous solution with a calcium adipic acid molar concentration of 1 mol / L, control the solution temperature at 50℃~55℃, and stir thoroughly until completely dissolved and homogeneous to obtain the circulating desulfurization solution;

[0010] S2. Desulfurization process of calcium adipic acid circulating desulfurization liquid: The circulating desulfurization liquid is directly sent into the wet desulfurization tower. After being atomized into fine droplets by the spray system, it comes into full counter-current contact with the flue gas containing SO2. The liquid:gas ratio is controlled at 10. The SO2 in the flue gas reacts with the active calcium component in the desulfurization liquid to generate calcium sulfite precipitate, thus completing the flue gas desulfurization and purification. The purified flue gas meets the emission standards.

[0011] S3. Disposal of products after desulfurization reaction: The calcium sulfite slurry generated by the desulfurization reaction is sent to the aeration oxidation tank for aeration oxidation. The oxidized slurry is separated by filter press. The first filter cake is gypsum dihydrate. The first filtrate is sent to the circulating desulfurizing agent regeneration tank after magnesium removal treatment.

[0012] S4. Regeneration of circulating desulfurizing agent:

[0013] S41. The adipic acid solution in the regeneration tank is thoroughly mixed with steel slag powder in a pipeline reactor. The reaction temperature is controlled at 50℃~55℃ and the reaction time is 45~60min to generate soluble calcium adipic acid. At the same time, the acidic solution modifies the ferrite phase in the steel slag into strongly magnetic minerals.

[0014] S42. After the steel slag leaching reaction is completed, the reaction slurry is separated into solid and liquid by a filter press. The second filtrate obtained by filter press is the regeneration circulating desulfurization liquid, which is directly returned to the wet desulfurization tower for continued use. The second filter cake obtained by filter press is the steel slag tailings containing strongly magnetic iron minerals, which is sent to the magnetic separation section for processing.

[0015] S5. Resource utilization of steel slag tailings: After the steel slag tailings separated by the magnetic separation section are subjected to acidification and activation treatment in the early stage, they can be directly used as cement admixtures, concrete aggregates or roadbed backfill materials to realize the full resource utilization of steel slag.

[0016] Preferably, the organic or inorganic calcium salt is one or more of calcium adipic acid, calcium acetate, and calcium chloride.

[0017] Preferably, the organic calcium salt is calcium adipic acid; the calcium adipic acid acts as a desulfurization buffer enhancer, stabilizing the pH of the wet desulfurization system at 5.5~6.5.

[0018] Preferably, the steel slag in step S41 is crushed and ground to a particle size of 74~125μm, the CaO content in the steel slag is ≥30%, and the calcium leaching rate after activation by the pipeline reactor is ≥85%.

[0019] Preferably, the aeration intensity of the aeration oxidation in step S3 is 2~3 m. 3 / (m 2 The oxidation time is 30-40 min, the oxidation rate of calcium sulfite is ≥99%, and the purity of the dihydrate gypsum obtained by pressure filtration is ≥95%.

[0020] Preferably, the tailings in step S5, after acidification and activation treatment, are used as cement admixtures, concrete aggregates, or roadbed backfill materials, thereby realizing the full resource utilization of steel slag.

[0021] The chemical reaction of this invention is as follows:

[0022] C6H 10 CaO4+SO2+H2O→C6H 10 O4+CaSO3↓

[0023] 2CaSO3 + O2 → 2CaSO4

[0024] CaO + H₂O → Ca(OH)₂; C₆H 10 O4 + Ca(OH)2 → C6H8CaO4 + H2O.

[0025] The purpose of this invention is:

[0026] 1. Steel slag from steel plants is used as a substitute for purchased limestone as a calcium source for desulfurization, and organic / inorganic calcium salt circulating desulfurizing agent is prepared, which greatly reduces the cost of desulfurization raw materials and realizes "treating waste with waste";

[0027] 2. Construct a complete closed-loop system of steel slag leaching—desulfurizing agent regeneration—flue gas desulfurization to realize the recycling of desulfurization active components and significantly reduce the operating cost of wet desulfurization;

[0028] 3. Introducing organic / inorganic calcium salts such as calcium adipic acid as circulating desulfurizing agents, which have both desulfurization and pH buffering functions, are suitable for complex wet desulfurization conditions, stabilize the pH value of the system, and ensure that the desulfurization process is continuous, stable and efficient.

[0029] 4. Optimize the leaching and separation sequence of steel slag. Activate the steel slag with an acidic solution to form a soluble organic / inorganic calcium salt solution. After solid-liquid separation, the filtrate is used for desulfurization. The filter cake is separated from the iron and tailings by magnetic separation, realizing the graded and high-value utilization of steel slag.

[0030] 5. The desulfurization byproduct calcium sulfite is oxidized by aeration to produce high-purity calcium sulfate, which can be directly used commercially, with no secondary waste liquid or waste residue discharged throughout the process;

[0031] 6. This method can be directly connected to existing wet desulfurization equipment, requires minimal modification, is highly adaptable, and is suitable for all enterprises using wet desulfurization technology, thus possessing significant value for industrial promotion.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. Excellent desulfurization efficiency and stable operation, with strong compliance with ultra-low emission standards.

[0034] This invention uses calcium adipic acid as the core circulating desulfurizing agent, which combines desulfurization and pH buffering functions, stabilizing the pH of the desulfurization system at 5.5-6.5. This effectively avoids the inhibition of desulfurization efficiency by chloride ions, sulfite ions, and other ions, and the desulfurization tower is free from scaling and clogging problems. The process achieves a stable SO2 removal efficiency of over 99.9%, and the SO2 emission concentration in the purified flue gas is ≤10mg / Nm³. 3 It is far below the national ultra-low emission standard; at the same time, it can adapt to the wide operating condition fluctuation of SO2 concentration in flue gas from 2000 to 8000 mg / Nm³, and the desulfurization efficiency is not affected by changes in operating conditions such as flue gas temperature and sulfur content, and the operation stability is significantly better than traditional processes.

[0035] 2. Raw material and operating costs have been significantly reduced, resulting in outstanding economic benefits.

[0036] By replacing purchased high-purity limestone and lime with steel slag from steel mills as a source of calcium for desulfurization, the process achieves "waste-to-waste" treatment, reducing desulfurization raw material costs by over 60%. This is further supported by national solid waste resource utilization subsidies. The desulfurizing agent forms a complete closed-loop recycling system, with a calcium adipic acid loss rate of ≤0.5%. Only a small amount needs to be replenished to maintain system balance, reducing the operating cost per ton of SO2 removal by 40%–50%, and lowering the overall removal cost from 200–300 yuan for traditional processes to 80–100 yuan. Simultaneously, the process produces high-purity industrial-grade dihydrate gypsum and iron concentrate with a grade ≥55%, which can be directly sold commercially, generating additional economic benefits for enterprises.

[0037] 3. Full disposal of steel slag yields significant environmental benefits and aligns with the dual-carbon strategy.

[0038] The process effectively matches the amount of steel slag processed with the sulfur content of the flue gas. For power plants and steel companies using high-sulfur coal and high-sulfur sinter, it can essentially achieve "zero stockpiling" of steel slag, completely solving the soil and water alkalization pollution problems caused by long-term steel slag stockpiling. Replacing limestone with steel slag as a calcium source reduces the consumption of natural mineral resources and lowers carbon emissions during calcium source preparation, reducing CO2 emissions by over 10,000 tons annually, aligning with the national "dual-carbon" strategy and green development requirements. For power plants and steel companies using high-sulfur coal and high-sulfur sinter, effective control of sulfur emissions significantly expands the range of raw material choices, reduces supply chain risks, and improves product efficiency.

[0039] 4. High-value recycling of steel slag resources yields significant circular economy benefits.

[0040] By activating steel slag with an acidic solution, the calcium and iron components are utilized in a graded and high-value manner, with a calcium leaching rate of ≥85%. The ferrite phase is magnetically modified and then magnetically separated for recovery, resulting in an iron concentrate recovery rate of ≥90%. The recovered iron concentrate can be returned to the ironmaking process for reuse. The steel slag tailings after magnetic separation are acidified and activated, resulting in enhanced cementitious activity, allowing them to be directly used as cement admixtures, concrete aggregates, and other building materials. The desulfurization byproduct, dihydrate gypsum, has a purity of ≥95%, meeting industrial-grade standards, and can replace natural gypsum in the building materials field, significantly improving the efficiency of comprehensive resource utilization.

[0041] 5. Low modification cost and strong industrial scalability.

[0042] This invention can be directly integrated with existing wet desulfurization towers, filter presses, aerated oxidation ponds, and other equipment in enterprises without large-scale modifications. The pipeline reactors and magnetic separators used are all mature industrial equipment, requiring no customized development. The process adopts a modular design, which can be flexibly adjusted according to the scale of flue gas treatment in the enterprise. Furthermore, the process is simple to operate; existing technical personnel can be trained and put into operation and maintenance. It is suitable for all enterprises using wet desulfurization processes, including thermal power, steel, chemical, and building materials industries, and has broad prospects for promotion. Attached Figure Description

[0043] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1:

[0046] A process for flue gas desulfurization using steel slag includes the following steps:

[0047] 1. Steel slag pretreatment: Steel slag from the steel plant converter is crushed and ground to a particle size of 100μm to obtain steel slag powder, the composition of which is CaO: 48.35%, SiO2: 17.03%, Fe3O4: 19.4%, MnO: 2.27%, MgO: 6.33%, Al2O3: 4.38%, P2O5: 1.75%, and the remainder is insoluble impurities;

[0048] 2. Implementation Scenario: Flue gas treatment capacity of 500,000 Nm³ for a coal-fired boiler in a power plant. 3 The flue gas, after dust removal and denitrification, is fed into the existing wet desulfurization tower at a temperature of 55℃ and an SO2 content of 3000 mg / Nm³. 3 The actual flue gas volume treated in this desulfurization operation was 100,000 m³. 3 ;

[0049] 3. Process steps:

[0050] S1. Preparation of calcium adipic acid circulating desulfurization solution: Prepare 5 ml of an aqueous solution with a calcium adipic acid molar concentration of 1 mol / L. 3 The solution temperature is controlled at 52℃, and the solution is stirred thoroughly until completely dissolved to obtain circulating desulfurization liquid;

[0051] S2. Desulfurization process: The circulating desulfurization liquid is sent into the power plant's wet desulfurization tower. After being atomized by the spray system, it comes into countercurrent contact with the flue gas containing SO2. The liquid-to-gas ratio is controlled at 10. The SO2 in the flue gas reacts with the desulfurization liquid to form calcium sulfite precipitate. After purification, the flue gas is discharged after passing the test.

[0052] S3. Product disposal: The calcium sulfite slurry is fed into an aeration oxidation tank with an aeration intensity of 2.5 m. 3 / (m 2 •h), oxidation time 35min, the slurry after oxidation is filtered by a filter press, the filter cake is gypsum dihydrate, and the filtrate is sent to the regeneration tank after magnesium removal;

[0053] S4. Desulfurizing agent regeneration: Adipic acid solution in the regeneration tank and 750 kg of steel slag powder are sent into the pipeline reactor. The reaction temperature is controlled at 52℃ and the reaction time is 50 min. After the reaction is completed, the solid and liquid are separated by a filter press. The filtrate is the regenerated desulfurization liquid and is returned to the desulfurization tower. The filter cake is sent to the magnetic separation section for magnetic separation to recover the ferrous phase.

[0054] S5. Steel slag tailings resource utilization: Steel slag tailings after magnetic separation are directly used as cement admixtures;

[0055] 4. Implementation Results:

[0056] 4.1 SO2 removed: 299.6 kg, SO2 removal efficiency: 99.87%, SO2 emission concentration after purification: 7.8 mg / Nm³ 3 ;

[0057] 4.2 750 kg of steel slag was disposed of, with a calcium leaching rate of 86.2%;

[0058] 4.3 1160 kg of industrial-grade dihydrate gypsum was obtained, with a purity of 95.8%;

[0059] 4.4 Magnetic separation recovered 190 kg of iron concentrate, with an iron concentrate grade of 56.3%;

[0060] 4.5 Produces 200 kg of building material cementitious material, with cementitious activity reaching the national standard S95 slag powder.

[0061] Example 2:

[0062] A process for flue gas desulfurization using steel slag includes the following steps:

[0063] 1. Steel slag pretreatment: Similar to Example 1, the steel slag is crushed and ground to 100μm, and the composition of the steel slag powder is the same as in Example 1;

[0064] 2. Implementation Scenario: A steel plant's sintering machine flue gas treatment capacity of 1 million Nm³ 3 The flue gas, after dust removal and denitrification, is fed into the existing wet desulfurization tower at a temperature of 55℃ and an SO2 content of 5000 mg / Nm³. 3 The actual flue gas volume treated in this desulfurization operation was 100,000 m³. 3 ;

[0065] 3. Process steps:

[0066] S1. Preparation of calcium adipic acid circulating desulfurization solution: Prepare 8.5m of an aqueous solution with a calcium adipic acid molar concentration of 1 mol / L. 3 The solution temperature is controlled at 54℃, and the solution is stirred thoroughly until completely dissolved to obtain circulating desulfurization liquid;

[0067] S2. Desulfurization process: The circulating desulfurization liquid is sent into the steel plant's wet desulfurization tower. After being atomized by the spray system, it comes into countercurrent contact with the flue gas containing SO2. The liquid-to-gas ratio is controlled at 10. The SO2 in the flue gas reacts with the desulfurization liquid to form calcium sulfite precipitate. After purification, the flue gas is discharged after being tested and meeting the standards.

[0068] S3. Product disposal: The calcium sulfite slurry is fed into an aeration oxidation tank with an aeration intensity of 2.8 m. 3 / (m 2 The oxidation time was 38 min. After oxidation, the slurry was filtered by a filter press. The filter cake was gypsum dihydrate. The filtrate was demagnesified and sent to the regeneration tank.

[0069] S4. Desulfurizing agent regeneration: Adipic acid solution in the regeneration tank and 1250 kg steel slag powder are sent into the pipeline reactor. The reaction temperature is controlled at 54℃ and the reaction time is 55 min. After the reaction is completed, the solid and liquid are separated by a filter press. The filtrate is the regenerated desulfurizing liquid and is returned to the desulfurization tower. The filter cake is sent to the magnetic separation section for magnetic separation to recover the ferrous phase.

[0070] S5. Steel slag tailings resource utilization: Steel slag tailings after magnetic separation are directly used as concrete aggregate;

[0071] 4. Implementation Results:

[0072] 4.1 SO2 removal: 499.5 kg, SO2 removal efficiency: 99.90%, SO2 emission concentration after purification: 8.5 mg / Nm³ 3 ;

[0073] 4.2 1250 kg of steel slag was disposed of, with a calcium leaching rate of 85.7%;

[0074] 4.3 1930 kg of industrial-grade dihydrate gypsum was obtained, with a gypsum purity of 96.2%;

[0075] 4.4 Magnetic separation recovered 315 kg of iron concentrate, with an iron concentrate grade of 55.8%;

[0076] 4.5 The output of building material aggregate is 330 kg, which meets the national standard for concrete aggregate.

[0077] The chemical principle of this invention is as follows:

[0078] This invention uses calcium adipic acid, an organic calcium salt, as the core circulating desulfurizing agent. Its core chemical reaction is divided into two parts: the desulfurization reaction and the desulfurizing agent regeneration reaction, as detailed below:

[0079] 1. Desulfurization reaction: Calcium adipic acid reacts with SO2 in industrial flue gas to produce calcium sulfite and adipic acid. Calcium sulfite is further oxidized by aeration to produce calcium sulfate dihydrate (industrial-grade gypsum). The reaction formula is: C6H 10 CaO4+SO2+H2O→C6H 10 O4+CaSO3↓

[0080] 2CaSO3 + O2 → 2CaSO4

[0081] 2. Desulfurizing agent regeneration reaction: The adipic acid generated in the desulfurization reaction neutralizes with the calcium hydroxide dissolved from CaO in the steel slag, regenerating soluble calcium adipic acid, which continues to participate in the desulfurization reaction as a circulating desulfurizing agent. Simultaneously, MgO in the steel slag participates in the reaction without affecting the desulfurization effect. The reaction formula is: CaO + H₂O → Ca(OH)₂; C₆H₂O 10 O4 + Ca(OH)2 → C6H8CaO4 + H2O.

[0082] In summary, the steel slag flue gas desulfurization process described in this invention utilizes mature industrial equipment such as pipeline reactors, magnetic separators, filter presses, and aeration oxidation tanks, requiring no customized development. This results in low equipment procurement costs and simple maintenance. The process adopts a modular design, allowing for flexible adjustments based on the enterprise's flue gas treatment scale. It can also directly connect to the enterprise's existing wet desulfurization equipment, requiring minimal modification and a short modification cycle (≤15 days). Existing technical personnel from steel plants and power plants can complete the process operation and equipment maintenance after simple training.

[0083] This method can be implemented directly within steel plants and power plants, utilizing existing steel slag raw materials without additional transportation. It aligns with the actual production needs of industrial enterprises and is applicable to all enterprises using wet desulfurization processes, including thermal power, steel, chemical, and building materials industries, achieving synergistic integration of "waste gas purification + solid waste disposal + resource recycling".

[0084] This method simultaneously achieves efficient flue gas desulfurization, full utilization of steel slag, recycling of desulfurizing agents, and high-value utilization of by-products, resulting in significant environmental, economic, and social benefits. It aligns with the national development direction of green and low-carbon development and solid waste resource utilization, and has strong industrial promotion value and broad application prospects in the field of industrial flue gas desulfurization.

[0085] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0086] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A process for flue gas desulfurization using steel slag, characterized in that, The process involves preparing organic or inorganic calcium salts from steel plant solid waste slag as a calcium source, which are then used as a circulating desulfurizing agent. This process sequentially includes desulfurization liquid preparation, wet flue gas desulfurization, calcium sulfite oxidation and separation, desulfurizing agent regeneration, and resource utilization of steel slag tailings, forming a closed-loop desulfurizing agent recycling system. The specific steps are as follows: S1. Preparation of calcium adipic acid circulating desulfurization solution: Prepare an aqueous solution with a calcium adipic acid molar concentration of 1 mol / L, control the solution temperature at 50℃~55℃, and stir thoroughly until completely dissolved and homogeneous to obtain the circulating desulfurization solution; S2. Desulfurization process of calcium adipic acid circulating desulfurization liquid: The circulating desulfurization liquid is directly sent into the wet desulfurization tower. After being atomized into fine droplets by the spray system, it comes into full counter-current contact with the flue gas containing SO2. The liquid:gas ratio is controlled at 10. The SO2 in the flue gas reacts with the active calcium component in the desulfurization liquid to generate calcium sulfite precipitate, thus completing the flue gas desulfurization and purification. The purified flue gas meets the emission standards. S3. Disposal of products after desulfurization reaction: The calcium sulfite slurry generated by the desulfurization reaction is sent to the aeration oxidation tank for aeration oxidation. The oxidized slurry is separated by filter press. The first filter cake is gypsum dihydrate. The first filtrate is sent to the circulating desulfurizing agent regeneration tank after magnesium removal treatment. S4. Regeneration of circulating desulfurizing agent: S41. The adipic acid solution in the regeneration tank is thoroughly mixed with steel slag powder in a pipeline reactor. The reaction temperature is controlled at 50℃~55℃ and the reaction time is 45~60min to generate soluble calcium adipic acid. At the same time, the acidic solution modifies the ferrite phase in the steel slag into strongly magnetic minerals. S42. After the steel slag leaching reaction is completed, the reaction slurry is separated into solid and liquid by a filter press. The second filtrate obtained by filter press is the regeneration circulating desulfurization liquid, which is directly returned to the wet desulfurization tower for continued use. The second filter cake obtained by filter press is the steel slag tailings containing strongly magnetic iron minerals, which is sent to the magnetic separation section for processing. S5. Resource utilization of steel slag tailings: After the steel slag tailings separated by the magnetic separation section are subjected to acidification and activation treatment in the early stage, they can be directly used as cement admixtures, concrete aggregates or roadbed backfill materials to realize the full resource utilization of steel slag.

2. The process method for flue gas desulfurization using steel slag according to claim 1, characterized in that: The organic or inorganic calcium salt is one or more of calcium adipic acid, calcium acetate, and calcium chloride.

3. The process method for flue gas desulfurization using steel slag according to claim 1, characterized in that: The organic calcium salt is calcium adipic acid; the calcium adipic acid acts as a desulfurization buffer enhancer, stabilizing the pH of the wet desulfurization system at 5.5~6.

5.

4. The process method for flue gas desulfurization using steel slag according to claim 1, characterized in that: The steel slag mentioned in step S41 is crushed and ground to a particle size of 74~125μm, the CaO content in the steel slag is ≥30%, and the calcium leaching rate after activation by the pipeline reactor is ≥85%.

5. The process method for flue gas desulfurization using steel slag according to claim 1, characterized in that: The aeration intensity for the aeration oxidation described in step S3 is 2~3 m. 3 / (m 2 The oxidation time is 30-40 min, the oxidation rate of calcium sulfite is ≥99%, and the purity of the dihydrate gypsum obtained by pressure filtration is ≥95%.

6. The process method for flue gas desulfurization using steel slag according to claim 1, characterized in that: The tailings described in step S5, after being acidified and activated, can be used as cement admixtures, concrete aggregates, or roadbed backfill materials, thereby realizing the full resource utilization of steel slag.

7. The process method for flue gas desulfurization using steel slag according to any one of claims 1-6, characterized in that, The chemical reaction is as follows: C6H 10 CaO4 + SO2 + H2O → C6H 10 O4 + CaSO3↓ 2CaSO3 + O2 → 2CaSO4 CaO+H2O→Ca(OH)2;C6H 10 O4+Ca(OH)2→C6H8CaO4+H2O。

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