A method for disposing of blast furnace gas or industrial carbon-containing flue gas purification by steel slag carbon sequestration

Abstract

This invention relates to the treatment of blast furnace gas or industrial carbon-containing flue gas, specifically to a method for treating and purifying blast furnace gas or industrial carbon-containing flue gas using steel slag carbonization. This invention aims to solve the problems of high energy consumption in blast furnace gas upgrading, high cost of CO2 capture from industrial carbon-containing flue gas, low resource utilization of steel slag, inability to achieve closed-loop recycling of reagents, and limited process adaptability in existing technologies. It provides a universal, low-energy-consumption, and high-efficiency method for treating carbon-containing flue gas and blast furnace gas using steel slag carbonization, achieving multiple objectives such as blast furnace gas refining and upgrading, efficient CO2 carbonization of industrial carbon-containing flue gas, full utilization of steel slag, closed-loop recycling of calcium ion liquid, and high-value product output. Simultaneously, it achieves synergistic treatment of "waste gas + solid waste," reducing enterprise operating costs and improving environmental and economic benefits.

Description

Technical Field

[0001] This invention belongs to the technical field of low-carbon ironmaking, energy conservation and consumption reduction, metallurgical solid waste resource utilization and industrial carbon capture and utilization in the steel industry. Specifically, it involves an integrated energy-saving and carbon-reducing process method that combines membrane separation and capture of carbon dioxide with steel slag ammonium salt leaching mineralization and carbon fixation. Background Technology

[0002] Blast furnace gas produced in the steel industry is a low-value by-product, with nitrogen accounting for as much as 40% of its original composition. This results in low calorific value and limited utilization efficiency, leading to its frequent direct combustion and significant resource waste. Meanwhile, industrial carbon-containing flue gas from the chemical, energy, and waste incineration industries generally has high nitrogen content and low CO2 concentration; direct emissions would create enormous pressure for carbon reduction. Furthermore, steel slag, rich in calcium oxide and metallic iron, is an excellent source of calcium and iron, but its resource utilization rate is currently low. Large-scale stockpiling not only occupies land resources but also easily causes soil and water pollution.

[0003] In existing technologies, pressure swing adsorption (PSA) is often used for denitrification of blast furnace gas, but this method has high energy consumption and high operating costs. Meanwhile, CO2 capture of industrial carbon-containing flue gas is mainly carried out by amine liquid absorption, which has drawbacks such as high regeneration costs, easy degradation of solvents and secondary pollution.

[0004] In recent years, mineral carbonation (i.e., mineralized carbon fixation) using alkaline solid wastes such as steel slag has become an important research direction for achieving "waste treatment with waste." However, existing steel slag carbon fixation technologies still face many engineering bottlenecks. In direct carbon fixation processes, if carbon-containing flue gas is directly introduced into the steel slag slurry for carbonation, the generated calcium carbonate will quickly adhere to the surface of the steel slag particles, forming a dense passivation layer. This passivation layer severely hinders the further dissolution of calcium ions inside the steel slag, resulting in an overall carbon fixation rate that is usually less than 30%. Furthermore, the reaction products contain a large number of impurities such as iron and silicon, which can only be used for low-end building materials, failing to achieve the high-value resource utilization of steel slag.

[0005] To overcome the aforementioned surface passivation problem, existing technologies have developed an indirect carbon fixation method that first leaches calcium ions with ammonium salts and then introduces carbon-containing gas for carbon fixation. However, due to the poor gas-liquid mass transfer efficiency of traditional stirred reactors, when raw waste gases such as blast furnace gas or industrial carbon-containing flue gas, which are characterized by large flow rates, low CO2 partial pressure, and high inert gas (such as N2) content, are directly introduced, the carbonization reaction becomes extremely slow. This not only results in a long processing cycle but also makes it difficult for the product to meet the quality standards of industrial-grade ultrafine light calcium carbonate.

[0006] To further enhance gas-liquid mass transfer in indirect carbon fixation processes, some existing technologies attempt to introduce centrifugal reactors. While centrifugal equipment boasts high mass transfer efficiency, directly feeding unenriched blast furnace gas or industrial flue gas into the reactor forces companies to configure massive centrifugal reactors with enormous volumes and processing capacities due to the large amounts of inert components such as ineffective nitrogen carried in the gas. This results in extremely high reactive power consumption. More importantly, this single-target CO2 absorption method fails to separate and remove the high nitrogen content in the blast furnace gas. This not only fails to achieve the dual goals of increasing the calorific value and purifying the blast furnace gas, but also leads to extremely poor overall system economic efficiency due to the singular focus on a single processing target.

[0007] In summary, existing processes are mostly designed for single treatment targets, lacking a systematic solution that deeply couples waste gas separation and enrichment, selective leaching and purification of solid waste, and high-gravity enhanced carbonization. Therefore, developing a low-energy, high-efficiency, fully closed-loop reagent-based synergistic treatment process that simultaneously achieves blast furnace gas denitrification and upgrading, efficient carbon fixation of industrial carbon-containing flue gas, and high-value conversion of steel slag is a critical technical challenge that urgently needs to be addressed in this field. Summary of the Invention

[0008] This invention aims to address the problems of high energy consumption in blast furnace gas upgrading, high cost of CO2 capture in industrial carbon-containing flue gas, low resource utilization of steel slag, inability to achieve closed-loop recycling of reagents, and limited process adaptability in existing technologies. It provides a universal, low-energy-consumption, and highly efficient method for treating carbon-containing flue gas and blast furnace gas using steel slag carbonization. This method achieves multiple objectives, including blast furnace gas refining and upgrading, efficient CO2 carbonization in industrial carbon-containing flue gas, full utilization of steel slag, closed-loop recycling of calcium ion liquid, and the production of high-value products. Simultaneously, it achieves synergistic treatment of "waste gas + solid waste," reducing enterprise operating costs and improving environmental and economic benefits.

[0009] Specifically, this invention provides a method for treating and purifying blast furnace gas or industrial carbon-containing flue gas using steel slag carbonization, comprising the following steps: S1 Membrane carbon enrichment: Carbon-containing raw material gas is passed into a membrane separation device for separation to obtain carbon-rich gas, wherein the carbon-containing raw material gas is blast furnace gas or industrial carbon-containing flue gas; S2 Steel slag leaching calcium extraction: Steel slag powder is mixed with a circulating reagent for leaching reaction, wherein the circulating reagent is an aqueous solution of organic or inorganic ammonium salt, and solid-liquid separation is performed after the reaction to obtain a filtrate containing calcium and magnesium ions, an iron-containing filter cake, and ammonia; S3 Hypergravity synergistic carbonization: The carbon-rich gas obtained in S1, the filtrate containing calcium and magnesium ions obtained in S2, and the ammonia are jointly passed into a hypergravity carbonization unit to undergo a carbonization reaction to obtain a light calcium and magnesium carbonate precipitate and a regenerated circulating reagent solution; S4 Closed-loop cycle: The regenerated circulating reagent solution generated in S3 is subjected to solid-liquid separation to obtain solid light calcium magnesium carbonate crude product and regenerated circulating reagent solution; the regenerated circulating reagent solution is refluxed back to the leaching reaction in S2 as the circulating reagent for recycling.

[0010] Preferably, before step S1, the process further includes: performing dust removal pretreatment on the carbon-containing raw material gas; and / or performing cooling pretreatment on the carbon-containing raw material gas to adjust the gas temperature to a suitable operating temperature for the membrane separation device and remove excess water vapor.

[0011] Preferably, in step S1: when the carbon-containing feed gas is blast furnace gas, a polyimide hollow fiber gas separation membrane module is used for treatment. The inlet side operating pressure of the membrane separation device is controlled at 0.2–1.0 MPa, the permeate side is at atmospheric pressure or negative pressure (-0.08–0 MPa), and the operating temperature is 20–50°C.

[0012] Preferably, in step S2: the organic or inorganic ammonium salt is selected from at least one of ammonium bis(2-3)-dimethylamine, ammonium acetate, and ammonium chloride; and / or, the molar concentration of the circulating reagent is 0.5–1.0 mol / L; and / or, the particle size of the steel slag powder is 74–125 μm; and / or, the steel slag powder and the circulating reagent are continuously fed into the leaching reactor at a liquid-to-solid mass ratio of 1:75; and / or, the temperature of the leaching reaction is controlled at 45–55°C, and the reaction time is 45–60 min.

[0013] Preferably, in step S2: the iron-containing filter cake is fed into a magnetic separation unit for magnetic separation to obtain iron concentrate and tailings, respectively; wherein the iron concentrate is used as a raw material for ironmaking; and / or, the tailings are used as building materials after being treated to render them harmless.

[0014] Preferably, an ammonia collection step is further included between S2 and S3: the ammonia generated by the leaching reaction is collected throughout the process using a negative pressure extraction device; and / or, the negative pressure of the negative pressure extraction device is controlled at 15-20 kPa; and / or, all the collected ammonia is sent into the hypergravity carbonization unit of S3 to participate in the carbonization reaction.

[0015] Preferably, the hypergravity-assisted carbonization in S3 satisfies one or more of the following conditions: the hypergravity carbonization unit adopts a hypergravity carbonization reactor with a rotation speed controlled at 800-1200 r / min; and / or, the liquid-to-gas ratio in the reaction system is controlled at 8-12; and / or, the flue gas temperature entering the hypergravity carbonization unit is controlled at 30-35℃.

[0016] Preferably, S4 specifically includes: feeding the output of the supergravity carbonization unit into the pressure filtration separation unit for solid-liquid separation to obtain a solid light calcium magnesium carbonate crude product and a regeneration and recycling reagent solution; and / or, washing, drying, and pulverizing the solid light calcium magnesium carbonate crude product to obtain an industrial-grade light calcium magnesium carbonate product with a particle size of 1 to 10 μm.

[0017] Preferably, step S4 further includes: when the regenerated circulating agent solution is returned to S2, replenishing an amount of initial organic or inorganic ammonium salt agent equal to the amount lost, based on the system agent loss rate, in order to maintain the cyclic balance of the system.

[0018] Preferably, when the carbon-containing raw material gas is blast furnace gas, the method further includes: sending the tail gas discharged after the S3 carbonization reaction into a gas ammonia removal and demisting unit for ammonia removal and demisting treatment.

[0019] Compared with the prior art, the present invention has the following significant advantages: First, this invention innovatively couples membrane carbon enrichment with hypergravity carbonization technology, resulting in high treatment efficiency and significantly reduced energy consumption. It breaks through the limitations of traditional processes that only treat a single type of waste gas, employing a modular design for flexible adaptation to carbon-containing waste gases from multiple industries. The process introduces membrane carbon enrichment to replace the traditional pressure swing adsorption method, significantly reducing denitrification energy consumption by 40% to 60%. Combined with a pipeline leaching reactor, it achieves continuous calcium extraction, with a calcium leaching rate exceeding 85%, and leaching efficiency more than 100% higher than traditional technologies. Simultaneously, the hypergravity reactor constructs a gas-liquid-solid three-phase system, greatly enhancing mass transfer and increasing carbonization efficiency by more than 300% compared to traditional processes, while shortening the reaction time to 15 to 30 minutes, significantly improving the system's treatment capacity and versatility.

[0020] Secondly, the invention achieves multiple benefits synergistically, combining waste gas quality improvement with high-value-added products, which is highly aligned with the national dual-carbon strategy. This invention simultaneously achieves three major goals: blast furnace gas quality improvement, carbon sequestration of industrial carbon-containing flue gas, and full utilization of steel slag. The decarbonized blast furnace gas effectively eliminates ineffective nitrogen and acidic components, significantly increasing its calorific value by 30% to 40%, while the carbon sequestration rate of industrial carbon-containing flue gas reaches over 80%. Simultaneously, the process byproducts include industrial-grade ultrafine lightweight calcium magnesium carbonate with a purity greater than 97.0% and a particle size of 1 to 10 micrometers, as well as iron concentrate with a grade greater than 55%. A single plant can achieve tens of thousands of tons of carbon dioxide sequestration and hundreds of thousands of tons of steel slag utilization annually, perfectly integrating multiple high-value-added economic and environmental benefits.

[0021] Third, a closed-loop recycling system is constructed throughout the entire process, achieving extremely high resource utilization and zero emissions. This invention utilizes waste steel slag as a calcium source, and the ammonia gas generated in the leaching reaction is fully extracted under negative pressure to participate in subsequent carbonization. The regenerated organic or inorganic ammonium salt solution generated by carbonization is directly recycled back to the front end for continued steel slag leaching. The system has an extremely low reagent loss rate, achieving a closed loop with zero reagent discharge. In addition, the purified steel slag tailings are harmlessly treated and used as building material cementitious materials. The entire process has no waste gas, waste liquid, or new solid waste discharge, completely overcoming the disadvantages of traditional amine liquid carbon capture, which is easily degraded and prone to secondary pollution, truly realizing the full resource utilization of waste gas and solid waste.

[0022] Fourth, the industrial equipment used is mature and easy to implement, making the project highly economically feasible and scalable. The hollow fiber gas separation membrane, pipeline leaching reactor, high-gravity reactor, and filter press equipment selected for this system are all mature industrial equipment, eliminating the need for high-risk, high-cost customized development. Equipment procurement costs are low, and construction and modification cycles are short. Since the raw materials for the entire process can be sourced locally and are self-sufficient, combined with the lossless reuse of recycled reagents, the profit from selling high-value-added products, and the potential for additional carbon emission reduction and solid waste resource utilization policy subsidies, the overall operating costs of enterprises are significantly reduced. This provides a highly economically feasible green closed-loop solution for industries such as steel, chemicals, and energy. Attached Figure Description

[0023] Figure 1 This is a process flow diagram for processing blast furnace gas according to the present invention; Figure 2 This is a process flow diagram for treating industrial carbon-containing flue gas according to the present invention. Detailed Implementation

[0024] This invention uses steel slag as the core calcium-containing solid waste raw material and organic or inorganic ammonium salts (such as ammonium adipate, ammonium acetate, ammonium chloride, etc.) as circulating agents. It integrates membrane gas separation, continuous calcium leaching, and high-gravity carbonization technologies to construct a complete closed-loop process system: "raw material gas membrane carbon enrichment → steel slag leaching for calcium and iron extraction → solid-liquid separation and magnetic separation for iron recovery → high-gravity synergistic carbon fixation → calcium salt closed-loop circulation → flue gas carbon fixation." The core process principle is as follows: 1. Membrane carbon enrichment: Utilizing the differences in permeation rates of different gases, CO2 and water in blast furnace gas / industrial carbon-containing flue gas are enriched through membranes.

[0025] 2. A soluble organic or inorganic calcium solution and ammonia gas are prepared using CaO and MgO from steel slag and a circulating reagent. If ammonium adipate is used as the circulating reagent, the main chemical reactions are as follows: CaO + H₂O → Ca(OH)₂ MgO + H₂O → Mg(OH)₂ C6H 16 N2O4+Ca(OH)2→C6H8CaO4+2NH3↑+2H2O C6H 16 N2O4+Mg(OH)2→C6H8MgO4+2NH3↑+H2O 3. After solid-liquid separation of the above reaction products, filtrate and filter cake are obtained. The filtrate is used for decarbonization of blast furnace gas / industrial carbon-containing flue gas. Under the enhanced effect of a hypergravity field, CO2 reacts with C6H8CaO4, C6H8MgO4, and NH3 in the filtrate to form light calcium magnesium carbonate precipitate. The filter cake is iron-containing tailings, which are then subjected to magnetic separation to obtain iron concentrate and tailings. The iron concentrate is used as a raw material for ironmaking, and the tailings can be used as building materials, such as cementitious materials, after harmless treatment, thus achieving full utilization of steel slag. The main chemical reactions are as follows: C6H8CaO4 + CO2 + 2NH3 + H2O → C6H 16 N₂O₄ + CaCO₃↓ C6H8MgO4 + CO2 + 2NH3 + H2O → C6H 16 N₂O₄ + MgCO₃↓ 4. Ammonium salt closed-loop cycle: dilute organic acids C6H regenerated by carbonization reaction 16 The N₂O₄ solution is directly refluxed to the steel slag leaching step, requiring only a small amount of replenishment to maintain system equilibrium. This achieves a closed-loop circulation of reagents with zero outflow, significantly reducing reagent costs. The main chemical reactions are as follows: C6H 16 N2O4+CaO→C6H8CaO4+2NH3↑+H2O C6H 16 N2O4+MgO→C6H8MgO4+2NH3↑+H2O 5. Blast furnace gas purification and upgrading: After decarbonization, other acidic components and moisture in the blast furnace gas are also significantly reduced, thereby realizing its transformation from low-value to high-calorific-value fuel.

[0026] The blast furnace gas treatment process flow of the present invention is as follows: Figure 1 As shown, the industrial carbon-containing flue gas treatment process is as follows: Figure 2 As shown.

[0027] This method adopts a modular design with unified core steps, allowing for flexible adjustment of process parameters based on the target gas (blast furnace gas / industrial carbon-containing flue gas). The specific steps are as follows: Raw gas pretreatment Blast furnace gas or industrial carbon-containing flue gas is introduced into the raw material gas pretreatment unit for dust removal and cooling: dust particles in the raw material gas are removed to prevent clogging of membrane modules and reactors; the gas temperature is adjusted to the appropriate operating temperature of the membrane device, while excess water vapor is removed to prevent condensation and corrosion of subsequent equipment, ensuring the stable operation of the membrane denitrification and carbon enrichment / carbon capture device.

[0028] Membrane-based carbon enrichment The pretreated feed gas is then introduced into a membrane carbon enrichment unit, with the following specific parameters: (1) Blast furnace gas treatment: A polyimide hollow fiber gas separation membrane module is used to separate CO2, H2O and other acidic gases from the blast furnace gas; the blast furnace gas is purified and upgraded. The volume fraction of CO is increased to 35%~40%, the total volume of the gas is reduced, and its calorific value is significantly improved; (2) Industrial carbon-containing flue gas treatment: According to the CO2 removal requirements of the process, a certain amount of clean flue gas is taken and passed through a polyimide hollow fiber gas separation membrane carbon capture device to obtain carbon-rich flue gas with a CO2 concentration of 65~75% and an O2 concentration of 20~25%. Then, by mixing in some untreated clean flue gas, the CO2 volume fraction in the flue gas is made to 40~45%, providing a suitable concentration of CO2 feedstock for the subsequent carbonization reaction.

[0029] Iron extraction by leaching steel slag 1. Steel slag pretreatment: Steel slag from steel plants is crushed and ground to 74-125μm to obtain steel slag powder, which increases the contact area between the steel slag and the circulating reagent solution, thereby improving the calcium solubility and iron recovery rate. 2. Continuous leaching reaction: Steel slag powder is reacted with C6H at a molar concentration of 0.5–1.0 mol / L. 16 N2O4 solution is continuously fed into the leaching reactor at a liquid-to-solid mass ratio of 1:75. A pipeline leaching reactor based on mature aluminum industry technology is preferred. The reactor temperature is controlled at 45-55℃ and the material reaction time is 45-60 min. The reaction produces C6H8CaO4, C6H8MgO4 and NH3 solution and iron-containing tailings.

[0030] 3. After solid-liquid separation of the above reaction products, filtrate and filter cake are obtained. The filtrate is used for decarbonization of blast furnace gas / industrial carbon-containing flue gas. Under the enhanced effect of a hypergravity field, CO2 reacts with C6H8CaO4, C6H8MgO4 and NH3 in the filtrate to produce high-purity light calcium magnesium carbonate precipitate. The filter cake is iron-containing tailings, which are then subjected to magnetic separation to obtain iron concentrate and tailings. The iron concentrate is used as a raw material for ironmaking, and the tailings are used as a cementing material after harmless treatment.

[0031] 4. Ammonia recycling: The NH3 generated by the leaching reaction is collected throughout the process by a negative pressure (15-20 kPa) pumping device. The NH3 recovery rate is ≥98%. All the collected NH3 is sent to the subsequent hypergravity carbonization unit to participate in the carbonization reaction.

[0032] Ammonium adipic acid closed-loop cycle and product purification 1. Pressure Filtration Separation: The effluent from the high-gravity carbonization reactor is fed into the pressure filtration unit for solid-liquid separation, yielding a solid light calcium magnesium carbonate crude product and C6H... 16 N2O4 regeneration solution; 2. Product purification: The crude light calcium magnesium carbonate is washed, dried and then ground to obtain industrial-grade light calcium magnesium carbonate with a purity of ≥99.0% and a particle size of 1~10μm. This product can be sold to rubber, coatings, papermaking, high-end building materials and other fields to achieve high-value utilization. 3. Closed-loop circulation: C6H 16 The N2O4 regenerated solution is directly refluxed to the steel slag leaching step to continue the leaching reaction with the steel slag powder; C6H 16 The N2O4 solution loss rate is ≤0.05%. Only a small amount of ammonium adipate needs to be added according to the actual loss to maintain the circulation balance of the system, realize the closed-loop circulation of the reagent, and ensure that no ammonium salt is discharged throughout the process.

[0033] The present invention will be further described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited to the following embodiments. All equivalent transformations made based on the content of the present invention specification shall fall within the scope of protection of the present invention.

[0034] In this embodiment, the steel slag powder is taken from the converter steel slag of the steel plant, and is crushed and ground to the specified particle size; the ammonium adipate is of industrial grade, and the molar concentration is controlled at 0.5~1.0 mol / L; the membrane carbon enrichment / capture device adopts hollow fiber gas separation membrane, and the ultragravity carbonization reactor adopts a rotating bed structure; the purity of light calcium and magnesium carbonate is detected by XRD method, the calorific value of coal gas is detected by gas calorific value analyzer, the calcium leaching rate is detected by titration method, and the purity of iron concentrate is detected by weighing after magnetic separation.

[0035] Example 1 This embodiment is used for the purification of blast furnace gas in steel slag treatment, such as... Figure 1 As shown, the specific steps are as follows: 1. Raw material pretreatment (1) Blast furnace gas: The original volume composition is CO=30%, CO2=22%, N2=45%, with the remainder being H2, CH4, acidic gases and water vapor. After dust removal and cooling, it is introduced into the carbon-rich system of the polyimide hollow fiber gas separation membrane module to obtain purified and upgraded gas (CO=40%) and high-concentration carbonized gas (CO2=75%). Example 1 processes 10000 Nm of blast furnace gas. 3 / h.

[0036] (2) Steel slag: After crushing and grinding to 100μm, the steel slag powder composition is CaO: 48.35%, SiO2: 17.03%, Fe3O4: 19.4%, MnO: 2.27%, MgO: 6.33%, Al2O3: 4.38%, P2O5: 1.75%, with the remainder being the balance. 11000kg / h of steel slag is utilized.

[0037] 2. Steel slag leaching: Take 1400 kg of steel slag powder and mix it with 1.0 mol / L ammonium adipate solution at a liquid-to-solid mass ratio of 1:75 to prepare 110 m³ of slurry. 3 The material is introduced into a pipeline leaching reactor, with the reaction temperature controlled at 45℃ and the reaction time at 55 minutes. This produces a solution of C6H8CaO4, C6H8MgO4, and NH3, as well as iron-containing tailings. During operation, steel slag powder needs to be continuously added up to approximately 11 tons as calcium and magnesium ions are consumed.

[0038] 3. After solid-liquid separation of the above reaction products, filtrate and filter cake are obtained. The filtrate is used for blast furnace gas decarbonization. CO2 separated from the blast furnace gas undergoes a carbonization reaction with C6H8CaO4, C6H8MgO4, and NH3 in the filtrate under the enhanced effect of the hypergravity field in the carbonization reactor. With the flue gas temperature controlled at 30℃, the rotation speed of the hypergravity carbonization reactor at 900 r / min, and the liquid:gas ratio at 11, a rapid synergistic carbonization reaction occurs, generating light calcium and magnesium carbonate precipitates and C6H8CaO4 and NH3. 16 N2O4 solution. The filter cake is iron-containing tailings, which are obtained by magnetic separation to obtain iron concentrate and tailings. The iron concentrate is used as a raw material for iron smelting, and the tailings are used as a cementing material after being treated to be harmless.

[0039] 4. Ammonia recycling: The NH3 produced by the leaching reaction is collected throughout the process by a negative pressure (15kPa) pumping device, with an NH3 recovery rate of 98.2%. All the collected NH3 is sent to the hypergravity carbonization unit to continue participating in the carbonization reaction.

[0040] 5. Purification and upgrading of blast furnace gas: The other acidic components and moisture in the decarbonized gas are also significantly reduced, thereby realizing the transformation of blast furnace gas from low-value to high-value fuel.

[0041] 6. Results achieved: 6.1 Sequestration of 3.7 tons of carbon; 6.2 11.0 tons of steel slag were disposed of; 6.3 8.7 tons of ultrafine lightweight calcium magnesium carbonate were obtained; 6.4 The blast furnace gas was purified and upgraded, increasing its calorific value by 32%; 2.3 tons of 6.5% iron concentrate, grade ≥55%; 6.6 Building materials and cementitious materials: 2.8 tons.

[0042] Example 2 This embodiment is used for the purification of exhaust gas from industrial kilns in steel slag treatment, such as... Figure 2 As shown, the specific steps are as follows: 1. Raw material pretreatment (1) Industrial boiler flue gas: CO2 volume fraction 15%, N2 volume fraction 65%, after dust removal and cooling, it is fed into the carbon-rich system of polyimide hollow fiber gas separation membrane module, and carbonized flue gas (CO2=40%) is obtained by separation and adjustment; Example 2 treats 10000Nm 3 / h.

[0043] (2) Steel slag: After crushing and grinding to 100μm, the steel slag powder composition is CaO: 48.35%, SiO2: 17.03%, Fe3O4: 19.4%, MnO: 2.27%, MgO: 6.33%, Al2O3: 4.38%, P2O5: 1.75%, with the remainder being the balance. Example 2 utilizes 7500kg / h of steel slag.

[0044] 2. Steel slag leaching: Take 950 kg of steel slag powder and mix it with 1.0 mol / L ammonium adipate solution at a liquid-to-solid mass ratio of 1:75 to prepare 86 m³ of slurry. 3 The material is introduced into a pipeline leaching reactor, with the reaction temperature controlled at 45℃ and the reaction time at 55 minutes. This produces C6H8CaO4, C6H8MgO4, and NH3 solutions, as well as iron-containing tailings. During operation, steel slag powder needs to be continuously added up to approximately 7.5 tons as calcium and magnesium ions are consumed.

[0045] 3. After solid-liquid separation of the above reaction products, filtrate and filter cake are obtained. The filtrate is used for boiler flue gas decarbonization. Under the enhanced effect of a hypergravity field, CO2 in the carbonized flue gas reacts with C6H8CaO4, C6H8MgO4, and NH3 in the filtrate to undergo a carbonization reaction. With the flue gas temperature controlled at 33℃, the hypergravity carbonization reactor rotation speed at 1000 r / min, and the liquid:gas ratio at 11, a rapid synergistic carbonization reaction occurs, generating light calcium and magnesium carbonate precipitates and C6H8MgO4. 16 N2O4 solution. The filter cake is iron-containing tailings, which are obtained by magnetic separation to obtain iron concentrate and tailings. The iron concentrate is used as a raw material for iron smelting, and the tailings are used as a cementing material after being treated to be harmless.

[0046] 4. Ammonia recycling: The NH3 produced by the leaching reaction is collected throughout the process by a negative pressure (18kPa) pumping device, with an NH3 recovery rate of 98.5%. All the collected NH3 is sent to the hypergravity carbonization unit to continue participating in the carbonization reaction.

[0047] 5. Results achieved: 5.1 2.5 tons of carbon sequestration; 5.2 7.5 tons of steel slag were disposed of; 5.3 5.9 tons of ultrafine lightweight calcium magnesium carbonate were obtained; 5.4 1.6 tons of iron concentrate, grade ≥55%; 5.5 Building materials and cementitious materials: 2.0 tons.

[0048] Example 3 This embodiment is used for the purification of flue gas from sintering machines in steel plants using steel slag treatment. The specific steps are as follows: 1. Raw material pretreatment (1) Flue gas: The CO2 volume fraction of the sintering machine is 13.5%, and the N2 volume fraction is 66%. After dust removal and cooling, it is introduced into the carbon-rich system of the polyimide hollow fiber gas separation membrane module, and carbonized flue gas (CO2=45%) is obtained by separation and adjustment; Example 3 treats 10000Nm 3 / h (2) Steel slag: After crushing and grinding to 100μm, the steel slag powder composition is CaO: 48.35%, SiO2: 17.03%, Fe3O4: 19.4%, MnO: 2.27%, MgO: 6.33%, Al2O3: 4.38%, P2O5: 1.75%, with the remainder being the balance. Example 3 utilizes 6000kg / h of steel slag.

[0049] 2. Steel slag leaching: Take 850 kg of steel slag powder and mix it with 1.0 mol / L ammonium adipate solution at a liquid-to-solid mass ratio of 1:75 to prepare a slurry of 68 m³. 3 The material is introduced into a pipeline leaching reactor, with the reaction temperature controlled at 45℃ and the reaction time at 60 minutes. This produces C6H8CaO4, C6H8MgO4, and NH3 solutions, as well as iron-containing tailings. During operation, steel slag powder needs to be continuously added up to approximately 6.0 tons as calcium and magnesium ions are consumed.

[0050] 3. After solid-liquid separation of the above reaction products, filtrate and filter cake are obtained. The filtrate is used for decarbonization of the sintering machine flue gas. Under the enhanced effect of a hypergravity field, CO2 in the carbonized flue gas reacts with C6H8CaO4, C6H8MgO4, and NH3 in the filtrate to undergo a carbonization reaction. With the flue gas temperature controlled at 33℃, the hypergravity carbonization reactor rotation speed at 1000 r / min, and the liquid:gas ratio at 11, a rapid synergistic carbonization reaction occurs, generating light calcium and magnesium carbonate precipitates and C6H8CaO4 and NH3. 16N2O4 solution. The filter cake is iron-containing tailings, which are obtained by magnetic separation to obtain iron concentrate and tailings. The iron concentrate is used as a raw material for iron smelting, and the tailings are used as a cementing material after being treated to be harmless.

[0051] 4. Ammonia recycling: The NH3 produced by the leaching reaction is collected throughout the process by a negative pressure (18kPa) pumping device, with an NH3 recovery rate of 98.7%. All the collected NH3 is sent to the hypergravity carbonization unit to continue participating in the carbonization reaction.

[0052] 5. Results achieved: 5.1 Carbon sequestration: 2.3 tons; 5.2 6.0 tons of steel slag were disposed of; 5.3 tons of ultrafine lightweight calcium magnesium carbonate were obtained; 5.4 tonnes of iron concentrate, grade ≥55%; 5.5 Building materials and cementitious materials: 1.8 tons.

[0053] The method for treating carbon-containing flue gas and blast furnace gas by steel slag carbonization according to the present invention uses mature industrial equipment and has a modular design. It can be flexibly combined according to the actual needs of enterprises to meet the single or combined treatment needs of blast furnace gas and industrial carbon-containing flue gas of different sizes. The construction and renovation cycle is short and the operation and maintenance are simple. Existing technical personnel of steel plants can complete the operation after simple training.

[0054] This method can be implemented directly within the steel plant area, utilizing existing steel slag and blast furnace gas raw materials without additional transportation, which aligns with the actual production needs of the steel industry. At the same time, it can also be adapted to the industrial carbon-containing flue gas treatment needs of industries such as chemical, energy, and waste incineration, achieving the synergistic treatment and resource utilization of "waste gas + solid waste".

[0055] This method simultaneously achieves blast furnace gas upgrading, CO2 carbon fixation in industrial carbon-containing flue gas, full utilization of steel slag, and high-value product output, resulting in significant economic, environmental, 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 application prospects in industries such as steel, chemical, energy, and waste incineration.

Claims

1. A method for disposing of blast furnace gas or industrial carbon-containing flue gas purification by a steel slag carbon sequestration method, characterized by, Includes the following steps: S1 Membrane-based carbon enrichment: Carbon-containing feed gas is passed into a membrane separation device for separation to obtain carbon-rich gas. The carbon-containing feed gas is blast furnace gas or industrial carbon-containing flue gas. S2 Steel slag leaching for calcium extraction: Steel slag powder is mixed with a circulating reagent for leaching reaction. The circulating reagent is an aqueous solution of organic or inorganic ammonium salts. After the reaction, solid-liquid separation is performed to obtain a filtrate containing calcium and magnesium ions, an iron-containing filter cake, and ammonia. S3 Hypergravity-assisted carbon fixation: The carbon-rich gas obtained in S1, the filtrate containing calcium and magnesium ions obtained in S2, and the ammonia are jointly passed into a hypergravity carbonization unit to undergo a carbonization reaction, obtaining a light calcium and magnesium carbonate precipitate and a regenerated circulating reagent solution. S4 Closed-loop circulation: The regenerated circulating reagent solution generated in S3 is subjected to solid-liquid separation to obtain a solid light calcium and magnesium carbonate crude product and a regenerated circulating reagent solution. The regenerated circulating reagent solution is refluxed back into the leaching reaction of S2 and reused as the circulating reagent.

2. The method according to claim 1, characterized in that, Before step S1, the process further includes: performing dust removal pretreatment on the carbon-containing raw material gas; and / or performing cooling pretreatment on the carbon-containing raw material gas to adjust the gas temperature to the suitable operating temperature of the membrane separation device and remove excess water vapor.

3. The method according to claim 1, characterized in that, The process in S1 uses a polyimide hollow fiber gas separation membrane module.

4. The method according to claim 1, characterized in that, In step S2: the organic or inorganic ammonium salt is selected from at least one of ammonium bis(2-3)-carboxylic acid, ammonium acetate, and ammonium chloride; and / or, the molar concentration of the circulating reagent is 0.5–1.0 mol / L; and / or, the particle size of the steel slag powder is 74–125 μm; and / or, the steel slag powder and the circulating reagent are continuously fed into the leaching reactor at a liquid-solid mass ratio of 1:75; and / or, the temperature of the leaching reaction is controlled at 45–55°C, and the reaction time is 45–60 min.

5. The method according to claim 1, characterized in that, In step S2: the iron-containing filter cake is fed into a magnetic separation unit for magnetic separation to obtain iron concentrate and tailings, respectively; wherein the iron concentrate is used as a raw material for ironmaking; and / or the tailings are used as building materials after being treated to be harmless.

6. The method according to claim 1, characterized in that, The process between S2 and S3 also includes an ammonia collection step: using a negative pressure extraction device to collect the ammonia generated during the leaching reaction; and / or, the negative pressure of the extraction device is controlled at 15-20 kPa; and / or, all the collected ammonia is sent into the hypergravity carbonization unit of S3 to participate in the carbonization reaction.

7. The method according to claim 1, characterized in that, The supergravity-assisted carbon fixation in S3 satisfies one or more of the following conditions: the supergravity carbonization unit adopts a supergravity carbonization reactor with a rotation speed controlled at 800-1200 r / min; and / or, the liquid-to-gas ratio in the reaction system is controlled at 8-12; and / or, the flue gas temperature entering the supergravity carbonization unit is controlled at 30-35℃.

8. The method according to claim 1, characterized in that, S4 specifically includes: feeding the output of the supergravity carbonization unit into the pressure filtration separation unit for solid-liquid separation to obtain a solid light calcium magnesium carbonate crude product and a regeneration and recycling reagent solution; and / or, washing, drying, and pulverizing the solid light calcium magnesium carbonate crude product to obtain an industrial-grade light calcium magnesium carbonate product with a particle size of 1 to 10 μm.

9. The method according to claim 1 or 8, characterized in that, S4 further includes: when the regenerated circulating agent solution is returned to S2, an initial organic or inorganic ammonium salt agent of equal amount to the amount lost is added according to the system agent loss rate to maintain the circulation balance of the system.

10. The method according to claim 1, characterized in that, When the carbon-containing raw material gas is blast furnace gas, the method further includes: sending the tail gas discharged after the S3 carbonization reaction into the gas ammonia removal and demisting unit for ammonia removal and demisting treatment.

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