A process for solidifying CO2 from desulfurization slag

Abstract

This invention relates to the field of carbon dioxide capture and discloses a process for solidifying CO2 from desulfurization slag. The process includes: (1) drying and grinding the SDS desulfurization slag, then reacting it with coke oven gas to obtain a solid product, and mixing the obtained solid product with water to obtain a mixed solution; (2) reacting the mixed solution obtained in step (1) with metallurgical furnace flue gas to obtain a first reaction solution, and then reacting the reacted solution with metallurgical furnace flue gas to obtain a second reaction material; (3) subjecting the reacted material obtained in step (2) to vacuum evaporation and solid-liquid separation, and drying the solid material obtained after solid-liquid separation to obtain sodium bicarbonate. This process achieves synergistic treatment of metallurgical solid waste and CO2 by reconstructing the carbon sequestration and harmless treatment process at the desulfurization site, and converts Na2SO4 and Na2CO3 in the desulfurization slag into the resource-based product NaHCO3.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide capture, and more specifically to a process for solidifying CO2 from desulfurization slag. Background Technology

[0002] Currently, CO2 capture and solidification technologies mainly include saline aquifer and rock layer sequestration technologies, metallurgical solid waste mineralization technologies, and biomass solidification technologies. Among these, steel slag mineralization technology is representative of metallurgical solid waste mineralization technologies, which can achieve both solid waste disposal and CO2 solidification. The cost of carbon sequestration using this type of technology is relatively low, and the solidified product can be sold as a building material raw material.

[0003] However, in the metallurgical solid waste carbon fixation technology (steel slag carbon fixation), the main method is to use the free calcium oxide in steel slag to react with CO2 to generate CaCO3, thereby solidifying CO2. This process route has poor carbon fixation economy because the free calcium oxide content in metallurgical steel slag is low, and the amount of CO2 that can be solidified is relatively small (about 80-100 mg / g). Moreover, the steel slag after carbon fixation is still considered solid waste, and its applicable uses are relatively narrow.

[0004] The invention patent CN116771414B, "A Method for Coordinated CO2 Sequestration and Hydraulic Gas Control in Mines," discloses a method for the coordinated control of CO2 sequestration and hydraulic gas control in coal seams. The method comprises the following steps: perforation, pre-injection, plugging, fracturing, and water injection. This invention introduces hot alkaline water into the pores of the coal seam, pre-injecting sufficient carbon dioxide, thereby partially sealing large pores using the generated precipitate particles. This enables the reuse of treated mine wastewater. The sealed large pores increase the water injection pressure within the coal seam, increasing coal permeability and improving coal seam gas extraction efficiency, recovering high-concentration gas, and reducing the gas content in mine air released into the atmosphere. The unsealed small pores allow for slow wetting of the coal body, reducing dust content in mine air released into the atmosphere, thus constructing a green resource utilization and environmental protection technology system for minerals.

[0005] CN116749348A, "A System and Method for CO2 Sequestration and Utilization in a Concrete Mixing Plant," discloses a system and method for CO2 sequestration and utilization in a concrete mixing plant. The system includes a slurry preparation module, a circulating grinding module, and a storage and application module. The circulating grinding module grinds the composite slurry prepared by the slurry preparation module under CO2-containing gas and a medium ball, and can circulate the CO2-containing gas to achieve continuous production of carbon mineralized slurry. The storage and application module includes a connected storage silo and a mixer. The storage silo receives and stores the carbon mineralized slurry from the slurry silo, and the mixer mixes the carbon mineralized slurry to prepare commercial concrete. This invention continuously peels off the surface of solid waste particles in the composite slurry through liquid-phase grinding mechanical force, and increases CO2 and Ca content through chemical solubilizing components. 2+The diffusion rate is significantly improved, fully releasing the carbonization potential of solid waste and reducing the carbonization time of traditional non-in-situ mineralization reactions from several hours to less than 40 minutes. This invention not only disposes of industrial solid waste but also solidifies CO2 gas, realizing the gelatinous utilization of CO2.

[0006] CN116902981A, "A System and Method for Solidifying CO2 by Adjusting the pH of the System," discloses a system and method for solidifying CO2 by adjusting the pH of the system. The system includes a solid waste raw material input pipeline, an extraction reactor, a CO2 absorption tower, a carbon-rich flue gas input pipeline, and a solid-liquid separator. The solid waste raw material input pipeline is connected to the inlet of the extraction reactor, and the liquid outlet of the extraction reactor is connected to the liquid inlet of the CO2 absorption tower. A gas outlet is provided at the top of the CO2 absorption tower. The carbon-rich flue gas input pipeline is connected to the flue gas inlet on the side of the bottom of the CO2 absorption tower, and the slurry outlet at the bottom of the CO2 absorption tower is connected to the inlet of the solid-liquid separator. The liquid outlet of the solid-liquid separator is connected to the liquid inlet of the extraction reactor. This system and method features a simple process flow, high product economics, and low cost.

[0007] CN116639933A, "A Method for Preparing a Paste for Filling and Solidifying CO2," discloses a method for preparing a paste for filling and solidifying CO2, comprising the following steps: Taking raw materials by weight: 5-25 parts cement, 5-25 parts carbide slag, 25-45 parts fly ash, 25-45 parts coal gangue, and pre-crushed coal gangue; mixing the raw materials; adding water at a solid-to-water mass ratio of 7:3; stirring at a stirring speed of 80-100 r / min; introducing high-purity CO2 into the paste and stirring with a stirrer at a CO2 pressure of 0.1 MPa; stirring speed of 120-160 r / min; and stirring time of 1-2.5 hours. This method prepares a paste with good flowability, solidification performance, and mechanical properties. The prepared paste can be filled into mined-out areas, thereby achieving the goals of supporting mined-out areas, preventing surface subsidence, protecting the ecological environment, rationally utilizing solid waste, and reducing carbon emissions.

[0008] CN113321224B, "A Method for Resource Utilization of Electrolytic Manganese Slag and Solidification of CO2," discloses a method for resource utilization of electrolytic manganese slag and solidification of CO2, comprising the following steps: S100: Grinding electrolytic manganese slag and fly ash into powder and mixing them evenly, pressing the powder into a block mixture; S200: Calcining the block mixture to generate and collect ammonia and SO3 gases respectively. The ammonia is used to prepare ammonia water, and the SO3 is used to prepare sulfuric acid. The residue after calcination is ground into powder; S300: The residue is thoroughly mixed with water to form a slurry, filtered to obtain a first filter residue and a first filtrate, and the first filter residue is dried to obtain a cement admixture; S400: Passing CO2 into the first filtrate obtained in step S300 to obtain a slurry of aragonite calcium carbonate, which is then filtered and dried to obtain aragonite calcium carbonate.

[0009] CN110078463B, "A Production Process for Manufacturing Blocks Using Steel Slag-Curedled CO2," discloses a production process for manufacturing blocks using steel slag-cured CO2, relating to the field of environmental protection technology. The process includes: mixing aluminum ash with water and hydrolyzing it at 80–100°C for 20–30 hours to obtain a solid-liquid mixture and ammonia; filtering, drying, and pulverizing the solid-liquid mixture to obtain a dried product; mixing the dried product, papermaking sludge, and finished calcium aluminate powder to obtain a mixture; adding water to the mixture and placing it in a pelletizing machine to form spherical particles with a diameter of 1–1.5 cm, then firing them at 1200–1350°C for 30–60 minutes to obtain the calcium aluminate powder and CO2; wherein the calcium aluminate powder is used to prepare a water purification agent; and reacting CO2, steel slag, and sand at 200–300°C and 1–1.5 MPa for 3–8 hours to generate the blocks. This invention utilizes CO2 and steel slag generated during the production of water purification agents to produce building blocks, effectively reducing the cost of the produced blocks and providing significant economic, social, and environmental benefits.

[0010] CN116764428A, "An SDS Dry Desulfurization Process for Sodium Bicarbonate Recycling," discloses an SDS dry desulfurization process for sodium bicarbonate recycling. Coke oven flue gas passes through a desulfurization reactor, while pulverized sodium bicarbonate powder is injected simultaneously. After sufficient reaction, the flue gas passes through a bag filter and enters subsequent stages for emission compliance. The solid phase is retained by the bag filter, yielding desulfurization slag. The desulfurization slag mainly contains sodium sulfate, sodium carbonate, and small amounts of sodium chloride and organic matter. The desulfurization slag undergoes catalytic pyrolysis to remove most of the organic pollutants, while simultaneously converting sodium sulfite and sodium bicarbonate completely into sodium sulfate and sodium carbonate. The catalytic pyrolysis products are dissolved and purified to obtain refined brine. A weak acid is added to the refined brine for neutralization, and the brine is then subjected to multi-stage evaporation crystallization and solid-liquid separation to obtain sodium bicarbonate and sodium sulfate, respectively. The sodium bicarbonate is dried to obtain high-purity sodium bicarbonate, which is recycled as a raw material in the SDS dry desulfurization process. The sodium sulfate is sold as a product. The process of this invention has low operating costs and is simple to operate, realizing the concept of high-value recycling of SDS desulfurization slag and carbon emission reduction.

[0011] Currently, there are many methods for CO2 solidification. Among them, many methods utilize metallurgical solid waste as carbon fixation raw materials, such as calcium carbide slag, electrolytic manganese slag, and steel slag, all of which utilize the free calcium oxide within them to react with CO2 for carbon fixation. However, the resource-based products ultimately formed by these technologies are primarily cement and construction raw materials, failing to create resource-based products with broad applications. Summary of the Invention

[0012] The purpose of this invention is to overcome the problems of low solidification rate of CO2 solidification using traditional metallurgical solid waste, inability to combine carbon fixation process with harmless treatment process, and narrow utilization pathways of carbon fixation products in existing technologies. This invention provides a process for solidifying CO2 from desulfurization slag. This process achieves synergistic treatment of metallurgical solid waste and CO2 by reconstructing the carbon fixation and harmless treatment process in desulfurization, and converts Na2SO4 and Na2CO3 in desulfurization slag into resource-based product NaHCO3.

[0013] To achieve the above objectives, the present invention provides a process for solidifying CO2 from desulfurization slag, the process comprising the following steps:

[0014] (1) The SDS desulfurization residue is dried and ground, and then reacted with coke oven gas to obtain a solid product. The obtained solid product is mixed with water to obtain a mixed solution.

[0015] (2) The mixed solution obtained in step (1) is contacted with the flue gas of metallurgical furnace to carry out the first reaction, and the solution after reaction is contacted with the flue gas of metallurgical furnace to carry out the second reaction, and the material after reaction is obtained.

[0016] (3) The reacted material obtained in step (2) is subjected to vacuum evaporation and solid-liquid separation. The solid material obtained after solid-liquid separation is dried to obtain sodium bicarbonate.

[0017] In step (1) of this invention, the SDS desulfurization slag used comes from the by-product (waste desulfurizing agent) of the SDS dry desulfurization system for SO2 treatment of flue gas in metallurgical furnaces and kilns. It belongs to solid hazardous waste. Generally, SDS desulfurization slag contains 50-60wt% Na2CO3 and 30-39wt% Na2SO4, with the remainder being a small amount of dust and miscellaneous salts.

[0018] Furthermore, since a small amount of sodium sulfite and sodium bicarbonate will also be present in the SDS desulfurization slag, a drying process is required to convert the small amount of sodium sulfite and sodium bicarbonate into sodium sulfate and sodium carbonate. In a preferred case, the drying conditions include: a temperature of 200-400℃ (too low a temperature will not convert sodium sulfite into sodium sulfate, and too high a temperature will result in high system energy consumption and affect economic efficiency), and a time of 3-5 hours.

[0019] In step (1) of this invention, after drying the SDS desulfurization slag, it is necessary to grind it. In the preferred case, the particle size of the material is ≤0.2mm, because if the particle size is too large, it will affect the reaction performance of the desulfurization slag in the high-temperature reactor, causing problems such as incomplete conversion.

[0020] The coke oven gas used in this invention is purified clean gas produced in the coking process. It mainly contains 50-60 vol% H2 and 20-30 vol% CH4, and contains small amounts of CO, CO2, N2, O2 and other hydrocarbons.

[0021] In step (1) of this invention, coke oven gas is used as a reducing agent. The coke oven gas is contacted with the SDS desulfurization slag obtained after grinding to carry out a reaction. The reaction is carried out under the condition of a catalyst. This process mainly converts sodium sulfate in the SDS desulfurization slag into sodium sulfide. The chemical reaction equations that occur in the reaction are as follows:

[0022] Na₂SO₄ + 4H₂ → Na₂S + 4H₂O

[0023] In order to ensure that all Na2SO4 in the SDS desulfurization slag can be converted into Na2S, H2 in the coke oven gas needs to be fed in excess according to the above chemical reaction equation, that is, the molar ratio of H2 in the coke oven gas to Na2SO4 in the SDS desulfurization slag should be controlled to be >4:1.

[0024] In step (1) of this invention, the catalyst used in the reaction is an iron-based catalyst, and Fe2O3 is further selected; the reaction conditions include: a temperature of 550-650℃ (too low a temperature will cause the sodium sulfate in the SDS desulfurization slag to not be completely converted into sodium sulfide, and too high a temperature will cause sodium sulfide and sodium sulfate to form eutectic, causing agglomeration and affecting the reaction rate and product purity), and a time of 2-4h.

[0025] In step (1) of this invention, after the reaction is completed, the product is cooled to obtain a solid product. The main components of the solid product are sodium sulfide and sodium carbonate. The purpose of mixing the solid product with water is to completely dissolve the sodium sulfide and sodium carbonate in the water (the amount of water is sufficient to completely dissolve the sodium sulfide and sodium carbonate in the solid product) to obtain a mixed solution containing sodium sulfide and sodium carbonate. Then, in the next step, the mixed solution is contacted with the flue gas of the metallurgical furnace to react (because the gas-liquid reaction rate is much higher than the gas-solid reaction rate, the solid product is mixed with water to obtain a mixed solution, which facilitates the next reaction).

[0026] Further in step (2), the metallurgical furnace flue gas used in this invention is the tail gas produced by the combustion of metallurgical coal gas, which contains 10-20 vol% CO2 and 70-80 vol% N2, as well as trace amounts (ppm level) of SO2 and NO. x .

[0027] In step (2) of this invention, the mixed solution obtained in step (1) is transported to a primary gas-liquid reactor, and then metallurgical furnace flue gas is introduced to allow the mixed solution to contact the metallurgical furnace flue gas for a first reaction, resulting in a reacted solution. Then, the reacted solution is transported to a secondary gas-liquid reactor to contact the metallurgical furnace flue gas, and a certain amount of water is added (the first reaction is a gas-liquid reaction, which will take away some liquid water, and there may be a situation where the water decreases and the solute precipitates, so water needs to be added to ensure that the solute does not precipitate. The specific amount of water added is just enough to ensure that the solute can be completely dissolved and will not precipitate), and a second reaction is carried out (two reactions with metallurgical furnace flue gas can allow the components to be reacted in the mixed solution to be completely reacted), resulting in the reacted material.

[0028] The primary gas-liquid reactor and the secondary gas-liquid reactor used in this invention are both conventional gas-liquid reactors.

[0029] In the first reaction of step (2) of this invention, sodium sulfide in the mixed solution mainly absorbs CO2 in the flue gas of metallurgical furnaces and converts it into sodium bicarbonate. Theoretically, 1 mol of Na2S can absorb 2 mol of CO2. The main reaction equations that occur in the first reaction are as follows:

[0030] Na₂S + 2CO₂ + 2H₂O = 2NaHCO₃ + H₂S

[0031] Furthermore, in the first reaction, in order to absorb as much CO2 as possible from the flue gas of the metallurgical furnace, the CO2 in the flue gas of the metallurgical furnace needs to be fed in excess according to the above chemical reaction equation, that is, the molar ratio of CO2 in the flue gas of the metallurgical furnace to Na2S in the mixed solution obtained in step (1) is controlled to be >2:1.

[0032] The H2S gas produced in the first reaction can be transported through pipelines to the coking Claus process to be used as a raw material for the preparation of high-purity sulfur.

[0033] In the second reaction of step (2) of this invention, sodium carbonate in the solution after the reaction is mainly used to absorb CO2 in the flue gas and convert it into sodium bicarbonate. Theoretically, 1 mol of Na2CO3 can absorb 1 mol of CO2. The main reaction equations that occur in the second reaction are as follows:

[0034] Na₂CO₃ + CO₂ + H₂O = 2NaHCO₃

[0035] Furthermore, in the second reaction, in order to absorb as much CO2 as possible from the flue gas of the metallurgical furnace, the CO2 in the flue gas of the metallurgical furnace needs to be fed in excess according to the above chemical reaction equation, that is, the molar ratio of CO2 in the flue gas of the metallurgical furnace to Na2CO3 in the solution after the reaction is controlled to be >1:1.

[0036] In step (2) of this invention, both the first and second reactions involve an excess of CO2 in the introduced metallurgical furnace flue gas. The liquid is used to capture the CO2 in the metallurgical furnace flue gas. Since the metallurgical furnace flue gas is introduced only once, the reaction will be incomplete. Therefore, the metallurgical furnace flue gas is introduced twice to carry out the first and second reactions respectively, so that the components to be reacted in the mixed solution can fully react to capture the CO2 in the metallurgical furnace flue gas. In the first reaction, Na2S is mainly used to absorb CO2 (the chemical reactivity of Na2S determines that Na2S is preferentially reacted). Some Na2CO3 may participate in the reaction. In the second reaction, Na2CO3 is mainly used to absorb CO2.

[0037] In step (3) of this invention, due to the use of reduced pressure evaporation technology, the sodium bicarbonate product obtained after drying has a high purity.

[0038] Further in step (3), the drying temperature is 40-50℃. When the drying temperature is higher than 50℃, sodium bicarbonate will gradually decompose. Therefore, it is more appropriate to control the drying temperature within the above range.

[0039] In a preferred embodiment, the liquid phase material (waste liquid) obtained after solid-liquid separation in step (3) can be processed by a recovery solution purification system, and a portion of it can be returned to step (1) to be mixed with the solid product to obtain a mixed solution, while the other portion can be returned to step (2) to be used as water to be replenished in the second reaction.

[0040] The sodium bicarbonate product finally obtained in step (3) of this invention can be recycled as a desulfurization raw material for the SDS desulfurization process, or it can be directly sold as a product to further realize resource recycling.

[0041] The use of SDS desulfurization slag, coke oven gas, and metallurgical furnace flue gas in the technical solution of this invention has the following advantages: 1. SDS desulfurization slag is a by-product (a solid hazardous waste) of the SDS desulfurization process. Generally, enterprises outsource its treatment for a fee. The main component of SDS desulfurizer is sodium bicarbonate, and the product after desulfurization is sodium sulfate. Through reaction with CO2, sodium bicarbonate can be produced again, enabling recycling. Furthermore, SDS desulfurizer needs to be purchased separately during the enterprise's desulfurization process. This invention utilizes waste desulfurizer to fix carbon while simultaneously regenerating it, effectively reducing the amount of desulfurizer purchased and treating the desulfurization waste slag—a win-win situation. 2. Coke oven gas is a by-product of iron and steel coking. It is abundant within enterprises and is generally only used as fuel, not fully utilized. Its price is very low within metallurgical enterprises, making it economical. 3. Metallurgical furnace flue gas is waste gas generated during iron and steel smelting. It is waste with no cost and is ubiquitous in the metallurgical industry. This invention further utilizes this waste, while fixing CO2 in the flue gas reduces the enterprise's carbon emissions.

[0042] The technical solution of this invention has the following advantages:

[0043] 1. This invention uses SDS desulfurization slag as a carbon fixation raw material, employing sodium-based carbon fixation. The main components, Na2SO4 and Na2CO3, both participate in the CO2 solidification reaction. While fixing CO2, the desulfurization slag can be harmlessly disposed of, achieving synergistic treatment of metallurgical solid waste and CO2. Compared with traditional metallurgical solid waste carbon fixation processes, it has the advantage of a large amount of solidified CO2. Theoretically, 1 mol of desulfurization slag can solidify 1.5-2 mol of CO2, effectively solving the problems of low CO2 solidification rate in current metallurgical solid waste processes, the inability to combine carbon fixation processes with harmless disposal processes, and the narrow utilization pathways of post-carbon fixation products. This process simultaneously achieves CO2 capture and solidification while treating SDS desulfurization slag and generating resource-based products. It has broad application prospects and significant promotional value.

[0044] 2. This invention fully utilizes resources within the iron and steel metallurgical industry (coke oven gas, metallurgical furnace flue gas) to achieve the harmless treatment of SDS desulfurization slag. It removes sulfur from the SDS desulfurization slag through coke oven gas (H2) and metallurgical furnace flue gas (CO2), and solidifies the CO2 in the flue gas, utilizing downstream supporting processes to realize the resource recovery of sulfur. Simultaneously, it converts Na2SO4 and Na2CO3 from the desulfurization slag into the resource-recovered product NaHCO3, which can be recycled as a desulfurization raw material for the SDS desulfurization process or directly sold as a product. It has wide applications in chemical, pharmaceutical, food, light industry, textile, and other industrial fields, as well as in people's daily lives, achieving a wide range of uses and realizing resource recovery. Attached Figure Description

[0045] Figure 1 It is a process flow chart of the present invention. Detailed Implementation

[0046] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0047] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0048] Example 1

[0049] like Figure 1 The process for solidifying CO2 from desulfurization slag, as shown, includes the following steps:

[0050] (1) The SDS desulfurization slag (containing 59wt% Na2CO3 and 38wt% Na2SO4) was dried at 350℃ for 4 hours. After drying, it was naturally cooled to room temperature and then ground in a grinder until the particle size of the material was ≤0.2mm. Then, 10g of the ground material was sent to a high-temperature reactor and coke oven gas (containing 56vol% H2 and 27vol% CH4) was introduced to make the ground material come into contact with an excess of coke oven gas (i.e., the molar ratio of H2 in the coke oven gas to Na2SO4 in the SDS desulfurization slag was controlled to be >4:1) to react (the reaction was carried out in the presence of the iron catalyst Fe2O3, and the reaction conditions were: temperature 600℃ and time 2h). About 7.98g of solid product was obtained. The obtained solid product was mixed with deionized water at a solid-liquid ratio of 1g / 130mL to completely dissolve Na2S and Na2CO3 in the solid product in the deionized water to obtain a mixed solution.

[0051] (2) The mixed solution obtained in step (1) is sent to the primary reactor and an excess of metallurgical furnace flue gas (containing 20 vol% CO2 and 74 vol% N2, with the molar ratio of CO2 in the metallurgical furnace flue gas to Na2S in the mixed solution obtained in step (1) controlled to be >2:1) is introduced to contact the metallurgical furnace flue gas to carry out the first reaction, and the reacted solution is obtained. The reacted solution is sent to the secondary reactor and deionized water is added to contact the excess metallurgical furnace flue gas (with the molar ratio of CO2 in the metallurgical furnace flue gas to Na2CO3 in the reacted solution controlled to be >1:1) to carry out the second reaction, and the reacted material is obtained.

[0052] (3) The material obtained after the reaction in step (2) is subjected to vacuum evaporation and solid-liquid separation. The solid material obtained after solid-liquid separation is dried at a temperature of 45°C, and finally about 13.84g of high-purity sodium bicarbonate solid is obtained.

[0053] The liquid phase material obtained after solid-liquid separation in step (3) is processed by the recycling and purification system. Part of it is returned to step (1) to be mixed with the solid product to obtain a mixed solution, while the other part is returned to step (2) to be used as deionized water to be replenished in the second reaction.

[0054] Based on mass balance calculations, in this embodiment, if the reaction is complete, the amount of CO2 that can be solidified is 480 mg / g, that is, 1 gram of SDS desulfurization slag can fix 480 milligrams of CO2, which has a good effect on CO2 solidification.

[0055] It should be understood that any parts not described in detail in this specification belong to the prior art.

[0056] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A process for solidifying CO2 from desulfurization slag, characterized in that, The process includes the following steps: (1) The SDS desulfurization residue is dried and ground, and then reacted with coke oven gas to obtain a solid product containing sodium sulfide and sodium carbonate. The obtained solid product is mixed with water to obtain a mixed solution containing sodium sulfide and sodium carbonate. (2) The mixed solution obtained in step (1) is contacted with the flue gas of metallurgical furnace to carry out a first reaction, and a solution after reaction is obtained. The solution after reaction contains sodium bicarbonate and sodium carbonate. The solution after reaction is contacted with the flue gas of metallurgical furnace to carry out a second reaction, and a material after reaction is obtained. The material after reaction is sodium bicarbonate containing impurities. (3) The reacted material obtained in step (2) is subjected to vacuum evaporation and solid-liquid separation. The solid material obtained after solid-liquid separation is dried to obtain sodium bicarbonate.

2. The process for solidifying CO2 from desulfurization slag according to claim 1, characterized in that, In step (1), the SDS desulfurization residue contains 50-60 wt% Na2CO3 and 30-39 wt% Na2SO4.

3. The process for solidifying CO2 from desulfurization slag according to claim 1 or 2, characterized in that, In step (1), the drying conditions include: a temperature of 200-400℃ and a time of 3-5h.

4. The process for solidifying CO2 from desulfurization slag according to claim 1 or 2, characterized in that, In step (1), the material is ground until the particle size is ≤0.2mm.

5. The process for solidifying CO2 from desulfurization slag according to claim 1, characterized in that, In step (1), the coke oven gas contains 50-60 vol% H2 and 20-30 vol% CH4.

6. The process for solidifying CO2 from desulfurization slag according to claim 1 or 5, characterized in that, In step (1), the molar ratio of H2 in coke oven gas to Na2SO4 in SDS desulfurization slag is controlled to be >4:

1.

7. The process for solidifying CO2 from desulfurization slag according to claim 1, characterized in that, In step (1), the reaction is carried out under the condition of a catalyst; The reaction conditions include a temperature of 550-650℃ and a time of 2-4 hours.

8. The process for solidifying CO2 from desulfurization slag according to claim 1, characterized in that, In step (2), the flue gas from the metallurgical furnace contains 10-20 vol% CO2 and 70-80 vol% N2.

9. The process for solidifying CO2 from desulfurization slag according to claim 1 or 8, characterized in that, In step (2), in the first reaction, the molar ratio of CO2 in the flue gas of the metallurgical furnace to Na2S in the mixed solution obtained in step (1) is controlled to be >2:1; In the second reaction, the molar ratio of CO2 in the flue gas of the metallurgical furnace to Na2CO3 in the solution after the reaction is controlled to be >1:

1.

10. The process for solidifying CO2 from desulfurization slag according to claim 1, characterized in that, In step (3), the drying temperature is 40-50°C.

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