A process for carbon fixation in steel slag

Abstract

The present invention relates to the technical field of steel slag carbon fixation, and specifically to a process method for steel slag carbon fixation, comprising the following steps: S1: collecting and screening steel slag, and collecting and performing denitration and desulfurization purification treatment on flue gas at the same time; S2: preparing a carbon dioxide gas-liquid-solid three-phase reaction device, and adding an absorption liquid; S3: introducing steel slag and flue gas into the carbon dioxide gas-liquid-solid three-phase reaction device at the same time; S4: performing solid-liquid separation on the mixture after the reaction, and performing single or multiple grinding to obtain steel slag powder, mixing the flue gas with the steel slag powder and adding a catalyst for secondary carbon fixation reaction; S5: the flue gas after the reaction in S4 is discharged into the atmosphere after dust removal, and the steel slag powder is collected. Through the synergistic effect of the two reaction devices of the carbon dioxide gas-liquid-solid three-phase reactor and the carbon dioxide gas-solid two-phase reactor, and the addition of a special catalyst, the carbon fixation efficiency is improved and the cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steel slag carbon fixation, and in particular to a process method for steel slag carbon fixation. Background Art

[0002] As global climate change and environmental problems become increasingly severe, reducing greenhouse gas emissions has become a global consensus. It is particularly important to find and develop effective carbon dioxide capture, utilization and storage (CCUS) technologies. As one of the main by-products of the steel industry, steel slag is produced in huge quantities every year. It contains a large amount of alkali metal oxides such as CaO and MgO. These components are natural reactants that react with carbon dioxide and have potential carbon fixation value. Steel slag can generally be used directly as a building material, but when used as a cement admixture, the amount used is limited and high-energy grinding is required. When used as concrete aggregate, due to its high activity and high content of free calcium oxide (CaO) that is easy to expand, it is easy to cause concrete strength to decrease or even crack. In addition, the use of alkaline solid waste as building materials also faces pain points such as excessive heavy metal leaching. Carbon dioxide mineralization technology uses carbon dioxide to react with alkaline components such as CaO in solid waste to generate carbonates, which can not only achieve carbon dioxide emissions reduction, but also reduce alkali and detoxify alkaline solid waste, which is conducive to subsequent utilization. It is an important waste reduction and carbon reduction synergistic efficiency technology, and is an effective technical choice for low-carbon transformation in industries such as steel.

[0003] However, traditional steel slag treatment methods often ignore its carbon fixation potential and treat it as waste, which not only causes a waste of resources but also may cause environmental problems. Although studies have attempted to use steel slag for the mineralization and fixation of carbon dioxide, there has been no good solution for how to achieve efficient, rapid and low-cost carbon fixation reactions. This is mainly because although the carbon dioxide mineralization reaction is a thermodynamic reduction process, it can theoretically proceed spontaneously. However, from a kinetic point of view, the carbon dioxide mineralization reaction is an extremely slow process. The reaction process involves a gas-liquid-solid three-phase system, including three key steps: carbon dioxide dissolution, dissolution of calcium-based minerals in alkaline solid waste and release of calcium ions, and precipitation reaction to form insoluble carbonates. The reaction rate is restricted by factors such as the low solubility of calcium-based minerals in water, the slow gas-liquid mass transfer rate of carbon dioxide, and the low solubility of carbon dioxide.

[0004] Carbon dioxide mineralization technology can be realized by two routes, direct method and indirect method. Direct carbon dioxide mineralization refers to the mineralization reaction of high-purity carbon dioxide with alkaline solid waste in a single reaction device. The direct method process is simple, but there is a key bottleneck problem of low reaction rate. The mass transfer rate between the gas-liquid-solid three phases during the reaction is low and the mass transfer area is small, resulting in a long residence time of the slurry during the reaction, large equipment investment, and low production efficiency. Indirect carbon dioxide mineralization usually includes two steps of leaching and mineralization. In the leaching stage, an acid leaching aid is introduced to accelerate the dissolution of the active mineral phase in the solid waste, and then the calcium-rich leachate is used to absorb carbon dioxide to achieve calcium carbonate preparation and separation, but there are also bottleneck problems such as difficult regeneration of leaching aids and low carbon dioxide utilization. Existing technologies often have problems such as low reaction efficiency, high cost, and complex operation, and it is difficult to achieve large-scale industrial application. For example, the capture of carbon dioxide using steel slag proposed in CN117244503A "A Carbon Dioxide Circulation Treatment System and Method" requires the reaction pressure to be increased to more than 1MPa, resulting in an increase in energy consumption. The steel slag carbon capture technology proposed in Patent C118341252A "Carbon dioxide capture device and process based on steel slag capture and grinding effect" has a too slow reaction rate, which takes more than 5 minutes, and the proportion of catalyst is high, resulting in high operating costs.

[0005] In view of the above problems, the present invention proposes a new steel slag carbon fixation method and process. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the present invention provides a process for carbon fixation in steel slag, which can effectively solve the problems of low efficiency, high cost and complex operation of carbon dioxide mineralization in the prior art.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: The present invention provides a process for carbon fixation in steel slag, comprising the following steps: S1: Collect and screen the steel slag, and collect and denitrate and desulfurize the flue gas; S2: prepare a carbon dioxide gas-liquid-solid three-phase reaction device and add an absorption liquid therein; S3: introducing the screened steel slag and the purified flue gas into a carbon dioxide gas-liquid-solid three-phase reaction device at the same time; S4: preparing a carbon dioxide gas-solid two-phase reactor, performing solid-liquid separation on the mixture after the reaction of the carbon dioxide gas-liquid-solid three-phase reaction device, and grinding it once or multiple times to obtain steel slag powder, introducing the purified flue gas and the steel slag powder into the carbon dioxide gas-solid two-phase reactor, mixing them, and adding a catalyst to perform a secondary carbon fixation reaction; S5: The flue gas after the reaction in S4 is discharged into the atmosphere after dust removal, and the steel slag powder is collected.

[0008] Furthermore, the absorption liquid is composed of one or more of monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, 2-amino-2-methyl-1-propanol, amino acid salt, potassium carbonate, potassium hydroxide, and sodium hydroxide aqueous solution.

[0009] Furthermore, the catalyst is composed of one or more components of a mixture of MgO, CaO, Al-Mg hydrotalcite, La2O3, ZnO, CeO2, sodium carbonate, sodium silicate, sodium sulfate, asbestos, and clay substances.

[0010] Furthermore, the carbon dioxide gas-liquid-solid three-phase reaction device is externally connected to an impurity pump, the impurity pump is externally connected to a liquid-solid separation device, the liquid-solid separation device is connected to an absorption liquid tank, and the absorption liquid tank is in communication with the carbon dioxide gas-liquid-solid three-phase reaction device.

[0011] Furthermore, a stirrer is provided in the carbon dioxide gas-liquid-solid three-phase reaction device.

[0012] Furthermore, the absorption liquid tank is connected to a dryer, and the dryer separates the precipitate in the absorption liquid tank.

[0013] Furthermore, the carbon dioxide gas-liquid-solid three-phase reaction device is connected to a liquid replenishing tank, and the liquid replenishing tank is used to control the gas-liquid flow ratio in the carbon dioxide gas-liquid-solid three-phase reaction device to be between 10:1 and 1000:1.

[0014] Compared with the known prior art, the technical solution provided by the present invention has the following beneficial effects: Through the synergistic effect of the two reaction devices, the carbon dioxide gas-liquid-solid three-phase reactor and the carbon dioxide gas-solid two-phase reactor, and the addition of special catalysts, the carbon fixation efficiency is significantly improved and the cost is reduced, providing a new technical path for the subsequent resource utilization of steel slag and carbon dioxide emission reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 is a process flow chart of the present invention; Figure 2 This is a process flow chart of removing carbon dioxide after the gas-solid two-phase reactor in the present invention; Figure 3 It is the process flow chart of Example 4; Figure 4 It is the process flow chart of Example 5; Figure 5 The present invention is a flow chart of the method.

[0017] The numbers in the figure represent: 1. primary screening machine; 2. secondary screening machine; 3. carbon dioxide gas-liquid-solid three-phase reaction device; 4. impurity pump; 5. liquid-solid separation device; 6. first liquid pump; 7. absorption liquid tank; 8. second liquid pump; 9. dryer; 10. replenishing liquid tank; 11. third liquid pump; 12. condenser; 13. desulfurization and denitrification tower; 14. primary booster fan; 15. flue gas cooler; 16. bypass; 17. secondary booster fan; 18. catalyst bin; 19. fourth liquid pump; 20. mixer; 21. primary mill; 22. secondary mill; 23. carbon dioxide gas-solid two-phase reactor; 24. dust collector; 25. slag powder bin. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] The present invention will be further described below in conjunction with the embodiments.

[0020] A process for carbon fixation in steel slag comprises the following steps: S1: Collect and screen the steel slag, and collect and denitrate and desulfurize the flue gas; S2: preparing a carbon dioxide gas-liquid-solid three-phase reaction device 3, and adding an absorption liquid therein; S3: introducing the screened steel slag and the purified flue gas into the carbon dioxide gas-liquid-solid three-phase reaction device 3 at the same time; S4: prepare a carbon dioxide gas-solid two-phase reactor 23, perform solid-liquid separation on the mixture after the reaction of the carbon dioxide gas-liquid-solid three-phase reaction device 3, and grind it once or multiple times to obtain steel slag powder, introduce the purified flue gas and the steel slag powder into the carbon dioxide gas-solid two-phase reactor 23, mix them, and add a catalyst to perform a secondary carbon fixation reaction; S5: The flue gas after the reaction in S4 is discharged into the atmosphere after dust removal, and the steel slag powder is collected.

[0021] The catalyst comprises one or more components of a mixture of MgO, CaO, Al-Mg hydrotalcite, La2O3, ZnO, CeO2, sodium carbonate, sodium silicate, sodium sulfate, asbestos, clay and the like.

[0022] The carbon dioxide gas-liquid-solid three-phase reaction device 3 is externally connected to an impurity pump 4, the impurity pump 4 is externally connected to a liquid-solid separation device 5, the liquid-solid separation device 5 is connected to an absorption liquid tank 7, and the absorption liquid tank 7 is connected to the carbon dioxide gas-liquid-solid three-phase reaction device 3.

[0023] like Figure 5 As shown, it is a method flow chart of the present method, in which it is worth noting that the carbon dioxide gas-liquid-solid three-phase reaction device 3 and the carbon dioxide gas-solid two-phase reactor 23 work simultaneously, which can improve the reaction efficiency.

[0024] The carbon dioxide gas-liquid-solid three-phase reaction device 3 is provided with a stirrer.

[0025] The absorption liquid tank 7 is connected to a dryer 9 , and the dryer 9 separates the precipitate in the absorption liquid tank 7 .

[0026] The carbon dioxide gas-liquid-solid three-phase reaction device 3 is connected to a liquid replenishing tank 10, and the liquid replenishing tank 10 is used to control the gas-liquid flow ratio in the carbon dioxide gas-liquid-solid three-phase reaction device 3 to be between 10:1 and 1000:1.

[0027] In this technology, the steel slag is first screened. First, the particles with a size larger than 10 mm are screened out through the primary screening as aggregates, and the particles smaller than 10 mm are screened for the second time. The secondary screening will determine a screening value Y in mm based on the consideration of the carbon fixation amount and the carbon fixation cost. When the particles are larger than the particle size Y, they will enter the primary mill 21, and the particles with a particle size smaller than Y will enter the carbon dioxide gas-liquid-solid three-phase reaction device for reaction. The carbon dioxide gas-liquid-solid three-phase reaction device is a carbon dioxide gas-liquid-solid three-phase reaction device at normal pressure. The range of Y is 0.1-10, preferably between 0.5-2.

[0028] like Figure 1 As shown, the steel slag needs to be screened at two stages, that is, a primary screening machine 1 and a secondary screening machine 2 are arranged before the carbon dioxide gas-liquid-solid three-phase reaction device 3 .

[0029] At the same time, the flue gas usually has a carbon dioxide content of 10%-20%. After desulfurization, denitration and dust removal, as shown in the figure, the flue gas is first purified in the desulfurization and denitration tower 13, and then sent to the flue gas cooler 15 through the primary booster fan 14 to cool to a temperature of about 40°C. A bypass 16 is set before the flue gas enters the carbon dioxide gas-liquid-solid three-phase reaction device 3, one way of flue gas enters the carbon dioxide gas-liquid-solid three-phase reaction device 3 from the bottom, and the other way is sent to the carbon dioxide gas-solid two-phase reactor 23 through the secondary booster fan 17.

[0030] The stirrer in the carbon dioxide gas-liquid-solid three-phase reaction device 3 rotates at a certain speed to ensure that the steel slag particles do not sink to the bottom. The flue gas enters the carbon dioxide gas-liquid-solid three-phase reaction device 3. Since a certain volume of carbon dioxide absorption liquid is installed inside the reactor, the carbon dioxide gas molecules in the flue gas dissolve in the absorption liquid and react with the absorbent, and are transferred to the absorbent to become carbonate, bicarbonate, carbamate and other ions. These ions then react with calcium ions and magnesium ions on the surface of the steel slag particles to form calcium carbonate, magnesium carbonate and other substances, thereby realizing the transfer of carbon dioxide from the gas phase to the solid phase.

[0031] At the bottom of the carbon dioxide gas-liquid-solid three-phase reaction device 3, there is an impurity pump 4, which can pump the absorption liquid containing steel slag particles out of the reactor at a constant flow rate. After the absorption liquid containing steel slag particles comes out of the pump, it passes through a liquid-solid separation device 5 to separate the steel slag particles and the absorption liquid, and the absorption liquid is partially pumped back to the absorption liquid tank 7 at the top of the reactor. In the absorption liquid tank 7, part of the calcium ions impregnated by the absorption liquid react with the carbonate ions in the absorption liquid to form a milky calcium carbonate precipitate. After the partial precipitation, nano calcium carbonate is obtained, and the nano calcium carbonate is separated from the bottom of the absorption liquid tank 7 at a fixed time and sent to the dryer 9 to obtain a nano calcium carbonate product.

[0032] The absorption liquid is then pumped from the middle of the absorption liquid tank 7 into the reactor to circulate. Considering that part of the absorption liquid is entrained by the steel slag particles, there is also a replenishment tank 10 on the top. The liquid level of the carbon dioxide gas-liquid-solid three-phase reaction device 3 must be controlled at a certain height. When the liquid level of the reactor is lower than the set height, the replenishment tank 10 is opened for replenishment. At the bottom of the replenishment tank 10, a third liquid pump 11 is used to pump the liquid to the top of the carbon dioxide gas-liquid-solid three-phase reaction device 3.

[0033] A first liquid pump 6 is arranged between the liquid-solid separation device 5 and the absorption liquid tank 7, a second liquid pump 8 is arranged between the absorption liquid tank 7 and the carbon dioxide gas-liquid-solid three-phase reaction device 3, and a third liquid pump 11 is arranged between the replenishing liquid tank 10 and the carbon dioxide gas-liquid-solid three-phase reaction device 3.

[0034] The carbon dioxide flue gas after the reaction is discharged from the top of the carbon dioxide gas-liquid-solid three-phase reaction device 3, and then condenses and refluxes part of the absorption liquid through the condenser 12 into the carbon dioxide gas-liquid-solid three-phase reaction device 3, and finally discharged into the atmosphere.

[0035] The gas-liquid flow ratio of the reaction device is between 10:1 and 1000:1, preferably 100:1 to 500:1. The volume ratio of particles in the liquid is not higher than 30%, preferably 10%-20%. The carbon dioxide load of the absorption liquid in the carbon dioxide gas-liquid-solid three-phase reaction device 3 is greater than 0.1 molCO 2 / mol absorbent. The residence time of the slag particles in the reaction device is greater than 5s, preferably between 5-60s. The temperature of the carbon dioxide flue gas entering the reaction device is 30-60°C.

[0036] The wet slag particles separated by the liquid-solid separation device 5 are mixed with the slag particles separated by the secondary screener, and then conveyed to the mill through a belt for fine grinding to form slag powder. The fine grinding process can be carried out through two mills (primary mill 21 and secondary mill 22) and finally ground to a specific surface area of ​​300m 2 / kg or more, it can also be directly ground to a specific gravity of 300m 2 / kg or more. Figure 1 , Figure 2 and Figure 4 The primary mill 21 and the secondary mill 22 grind to a specific surface area of ​​300 m 2 / kg and above. The steel slag powder is then sent to the carbon dioxide gas-solid two-phase reactor 23 to react with the flue gas sent by the secondary booster fan 17. During the reaction, a small amount of catalyst is added to the carbon dioxide gas-solid two-phase reactor 23 through the catalyst bin 18 to accelerate the carbon fixation reaction process. The flue gas after the reaction is then discharged into the atmosphere after passing through the dust collector 24. The steel slag powder after the reaction and carbon fixation is then sent to the steel slag powder bin 25 for storage.

[0037] The wet steel slag particles separated by the liquid-solid separation device 5 entrain a small amount of absorption liquid components in the carbon dioxide gas-liquid-solid three-phase reaction device 3 and migrate to the carbon dioxide gas-solid two-phase reactor 23, and then react synergistically with the catalyst added in the catalyst bin 18, further accelerating the gas-solid absorption reaction of carbon dioxide and steel slag powder in the carbon dioxide gas-solid two-phase reactor 23.

[0038] The specific surface area of ​​the steel slag powder in the carbon dioxide gas-solid two-phase reactor 23 is greater than 300m 2 / kg, preferably 300-400m 2 The residence time of the steel slag powder in the carbon dioxide gas-solid two-phase reactor 23 is greater than 60 seconds, preferably 60-300 seconds.

[0039] A fourth liquid pump 19 is provided between the catalyst chamber 18 and the carbon dioxide gas-solid two-phase reactor 23 or the secondary mill 22 .

[0040] The components of the absorption liquid are one or more aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), methyldiethanolamine (MDEA), 2-amino-2-methyl-1-propanol (AMP), amino acid salts, potassium carbonate, potassium hydroxide, sodium hydroxide, etc.

[0041] The catalyst is composed of one or more of a mixture of MgO, CaO, Al-Mg hydrotalcite, La2O3, ZnO, CeO2, sodium carbonate, sodium silicate, sodium sulfate, asbestos, clay and the like.

[0042] It is preferred that the secondary mill 22 in the original process be transformed into a carbon dioxide gas-solid two-phase reactor 23, that is, during the slag grinding process, a certain flow of flue gas and catalyst are introduced to achieve the same mineralization reaction of carbon dioxide, thus eliminating the carbon dioxide gas-solid two-phase reactor 23 in the original process. Figure 2 and Figure 3 shown.

[0043] Several different embodiments are introduced below. These embodiments have different processes and operating parameters, but all achieve good carbon fixation effects. The composition of the steel slag is as follows:

[0044] Embodiment 1: In this embodiment, after secondary screening, particles larger than 2 mm are directly fed into the mill, and steel slag particles smaller than 2 mm are fed into the carbon dioxide gas-liquid-solid three-phase reaction device 3. The amount of steel slag particles in this part is 100 kg / h. In the carbon dioxide gas-liquid-solid three-phase reaction device 3, 30 w.t.% MEA-PZ aqueous solution is used as the absorption liquid, and the liquid flow rate is 0.5 m 3 / h. The average reaction temperature is controlled at 50°C, the carbon dioxide concentration in the flue gas is 15% v / v, the flue gas temperature entering the carbon dioxide gas-liquid-solid three-phase reaction device 3 is controlled at 45°C, and the flue gas flow rate of this part is 400m 3 After the reaction is completed, the wet slag particles are separated from the absorption liquid, mixed with slag particles larger than 2 mm, and then enter the primary mill 21 and the secondary mill 22 for grinding treatment, and finally grind to 300 mm 2 The fine steel slag powder then enters the carbon dioxide gas-solid two-phase reactor 23 for gas-solid reaction. During this process, the flue gas flow rate is 5000m 3 / h, the residence time is 1200kg / h of continuous slag powder input, 24kg / h of added carbon fixation catalyst, and the ratio of catalyst to slag powder is 2%. Through the above two carbon fixation reactions, the carbon fixation ratio of slag powder can reach 15% kgCO 2 / kg steel slag, and 0.75kg / d of nano calcium carbonate product is obtained.

[0045] Embodiment 2: In this embodiment, after secondary screening, particles larger than 2 mm are directly fed into the mill, and steel slag particles smaller than 2 mm are fed into the carbon dioxide gas-liquid-solid three-phase reaction device 3. The amount of steel slag particles in this part is 100 kg / h. In the carbon dioxide gas-liquid-solid three-phase reaction device 3, 30 w.t.% MEA-PZ aqueous solution is used as the absorption liquid, and the liquid flow rate is 0.5 m 3 / h. The average reaction temperature is controlled at 50°C, the carbon dioxide concentration in the flue gas is 15% v / v, the flue gas temperature entering the carbon dioxide gas-liquid-solid three-phase reaction device 3 is controlled at 45°C, and the flue gas flow rate of this part is 200m 3 After the reaction is completed, the wet slag particles are separated from the absorption liquid, mixed with slag particles larger than 2 mm, and then enter the primary mill 21 and the secondary mill 22 for grinding treatment, and finally grind to 300 mm 2 The fine steel slag powder then enters the carbon dioxide gas-solid two-phase reactor 23 for gas-solid reaction. During this process, the flue gas flow rate is 5000m 3 / h, the residence time is 1200kg / h of continuous steel slag powder, 12kg / h of added carbon fixation catalyst, and 1% of catalyst to steel slag powder. Through the above two carbon fixation reactions, the carbon fixation ratio of steel slag powder can reach 11% kg carbon dioxide / kg steel slag, and 0.5kg / d of nano calcium carbonate products can be obtained.

[0046] Embodiment 3: In this embodiment, after secondary screening, particles larger than 2 mm are directly fed into the mill, and steel slag particles smaller than 2 mm are fed into the carbon dioxide gas-liquid-solid three-phase reaction device 3. The amount of steel slag particles in this part is 100 kg / h. In the carbon dioxide gas-liquid-solid three-phase reaction device 3, 35 w.t.% NaOH-PZ aqueous solution is used as the absorption liquid, and the liquid flow rate is 0.35 m 3 / h. The average reaction temperature is controlled at 50°C, the carbon dioxide concentration in the flue gas is 15% v / v, the flue gas temperature entering the carbon dioxide gas-liquid-solid three-phase reaction device 3 is controlled at 45°C, and the flue gas flow rate of this part is 300 m 3 After the reaction is completed, the wet slag particles are separated from the absorption liquid, mixed with slag particles larger than 2 mm, and then enter the primary mill 21 and the secondary mill 22 for grinding treatment, and finally grind to 350 mm 2 The fine steel slag powder then enters the carbon dioxide gas-solid two-phase reactor 23 for gas-solid reaction. During this process, the flue gas flow rate is 3000m 3 / h, the continuous intake of steel slag powder is 1200kg / h, the amount of carbon fixation catalyst added is 24kg / h, and the ratio of catalyst to steel slag powder is 2%. Through the above two carbon fixation reactions, the carbon fixation ratio of steel slag powder can reach 14% kg carbon dioxide / kg steel slag, and 0.65kg / d of nano calcium carbonate products are obtained.

[0047] Embodiment 4: In this embodiment, after secondary screening, particles larger than 2 mm are directly fed into the mill, and steel slag particles smaller than 2 mm are fed into the carbon dioxide gas-liquid-solid three-phase reaction device 3. The amount of steel slag particles in this part is 100 kg / h. In the carbon dioxide gas-liquid-solid three-phase reaction device 3, 30 w.t.% MEA-PZ aqueous solution is used as the absorption liquid, and the liquid flow rate is 0.5 m 3 / h. The average reaction temperature is controlled at 50°C, the carbon dioxide concentration in the flue gas is 15% v / v, the flue gas temperature entering the carbon dioxide gas-liquid-solid three-phase reaction device 3 is controlled at 45°C, and the flue gas flow rate of this part is 200m 3 / h. The reaction time in the carbon dioxide gas-liquid-solid three-phase reaction device 3 is 20s. After the reaction is completed, the wet slag particles are separated from the absorption liquid, mixed with the slag particles larger than 2mm, and then enter the ball mill for grinding. In this embodiment, it is directly ground to 300m by a ball mill (i.e., a single secondary mill 22). 2 The fine steel slag powder then enters the carbon dioxide gas-solid two-phase reactor 23 for gas-solid reaction. During this process, the flue gas flow rate is 5000m 3 / h, the continuous intake of steel slag powder is 1200kg / h, the amount of carbon fixation catalyst added is 12kg / h, and the ratio of catalyst to steel slag powder is 1%. Through the above two carbon fixation reactions, the average carbon fixation ratio of steel slag powder can reach 13.5% kgCO 2 / kg steel slag, and 0.5kg / d of nano calcium carbonate product is obtained.

[0048] It is worth noting that Figure 3 The process flow diagram of Example 4 shows only a secondary mill 22 .

[0049] Embodiment 5: In this embodiment, after secondary screening, particles larger than 1 mm are directly fed into the primary mill 21 (which is a roller press) and ground to 50 mm. 2 / kg ratio of coarse powder, steel slag particles less than 1mm enter the carbon dioxide gas-liquid-solid three-phase reaction device 3, the amount of steel slag particles in this part is 40kg / h. In the carbon dioxide gas-liquid-solid three-phase reaction device 3, we use 30w.t.% MEA-PZ aqueous solution as the absorption liquid, and the liquid flow rate is 0.25m 3 / h. The average reaction temperature is controlled at 50°C, the carbon dioxide concentration in the flue gas is 15% v / v, the flue gas temperature entering the carbon dioxide gas-liquid-solid three-phase reaction device 3 is controlled at 45°C, and the flue gas flow rate of this part is 100m 3 / h. The reaction time in the carbon dioxide gas-liquid-solid three-phase reaction device is 15s. After the reaction is completed, the wet slag particles are separated from the absorption liquid, and then mixed with the coarse slag powder from the primary mill 21, and then enter the secondary mill 22 (ball mill) for grinding to reach 300m 2 The fine steel slag powder then enters the carbon dioxide gas-solid two-phase reactor 23 for gas-solid reaction. During this process, the flue gas flow rate is 5000m 3 / h, the continuous intake of steel slag powder is 1200kg / h, the amount of carbon fixation catalyst added is 12kg / h, and the ratio of catalyst to steel slag powder is 1%. Through the above two carbon fixation reactions, the average carbon fixation ratio of steel slag powder can reach 11% kgCO 2 / kg steel slag, and 0.4kg / d of nano calcium carbonate product is obtained.

[0050] It is worth noting that Figure 4 In the process flow diagram of Example 5 shown, the mixer 20 is placed after the primary mill 21.

[0051] Embodiment 6: In this embodiment, we further simplify the process, and we use the secondary mill 22 as a gas-solid reactor. After screening, particles larger than 2 mm directly enter the primary mill 21. Steel slag particles smaller than 2 mm enter the carbon dioxide gas-liquid-solid three-phase reaction device 3, and the amount of steel slag particles in this part is 100 kg / h. In the carbon dioxide gas-liquid-solid three-phase reaction device 3, we use 35w.t.% MEA-AMP aqueous solution as the absorption liquid, and the liquid flow rate is 0.5m 3 / h. The average reaction temperature is controlled to be 50°C, the concentration of carbon dioxide in the flue gas is 15% v / v, the flue gas temperature entering the carbon dioxide gas-liquid-solid three-phase reaction device 3 is controlled to be below 50°C, and the flue gas flow rate of this part is 200 m3 / h. After the reaction is completed, the steel slag particles are mixed with the steel slag particles larger than 2mm and first enter the primary mill 21 for powder grinding treatment to a specific surface area of ​​50m 2 / kg, the treated steel slag powder enters the secondary mill 22 for grinding, at which time the steel slag powder is further ground to 300m 2 / kg, and a gas-solid reaction is carried out in the secondary mill 22. During this process, the flue gas flow rate is 1000m 3 / h, the continuous intake of steel slag powder is 1200kg / h, the amount of carbon fixation catalyst added is 12kg / h, and the ratio of catalyst to steel slag powder is 1%. Through the above two carbon fixation reactions, the average carbon fixation ratio of steel slag powder can reach 10% kgCO2 / kg steel slag, and 0.5kg / d of nano calcium carbonate product is obtained.

[0052] In the above embodiments, the steel slag can achieve a carbon fixation efficiency of more than 10%, that is, 1 ton of steel slag can fix and mineralize 100kg of carbon dioxide. And the mineralized steel slag completely solves its stability problem and can be used in the production of some low-carbon cementitious materials. The obtained nano calcium carbonate has a particle size of , and has a high added value.

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for carbon fixation in steel slag, characterized in that: The following steps are involved: S1: Collect and screen the steel slag, and collect and denitrate and desulfurize the flue gas; S2: preparing a carbon dioxide gas-liquid-solid three-phase reaction device (3) and adding an absorption liquid thereto; S3: introducing the screened steel slag and the purified flue gas into the carbon dioxide gas-liquid-solid three-phase reaction device (3) at the same time; S4: preparing a carbon dioxide gas-solid two-phase reactor (23), performing solid-liquid separation on the mixture after the reaction in the carbon dioxide gas-liquid-solid three-phase reaction device (3), and grinding once or multiple times to obtain steel slag powder, introducing the purified flue gas and the steel slag powder into the carbon dioxide gas-solid two-phase reactor (23), mixing, and adding a catalyst to perform a secondary carbon fixation reaction; S5: The flue gas after the reaction in S4 is discharged into the atmosphere after dust removal, and the steel slag powder is collected.

2. The process for carbon fixation in steel slag according to claim 1, characterized in that: The absorption liquid comprises one or more components of monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, 2-amino-2-methyl-1-propanol, amino acid salt, potassium carbonate, potassium hydroxide, and sodium hydroxide aqueous solution.

3. The process for carbon fixation in steel slag according to claim 1, characterized in that: The catalyst comprises one or more components of a mixture of MgO, CaO, Al-Mg hydrotalcite, La2O3, ZnO, CeO2, sodium carbonate, sodium silicate, sodium sulfate, asbestos, and clay.

4. The process for carbon fixation in steel slag according to claim 1, characterized in that: The carbon dioxide gas-liquid-solid three-phase reaction device (3) is externally connected to an impurity pump (4), the impurity pump (4) is externally connected to a liquid-solid separation device (5), the liquid-solid separation device (5) is connected to an absorption liquid tank (7), and the absorption liquid tank (7) is in communication with the carbon dioxide gas-liquid-solid three-phase reaction device (3).

5. The process for carbon fixation in steel slag according to claim 1, characterized in that: The carbon dioxide gas-liquid-solid three-phase reaction device (3) is provided with a stirrer.

6. The process for carbon fixation in steel slag according to claim 1, characterized in that: The absorption liquid tank (7) is connected to a dryer (9), and the dryer (9) separates the precipitate in the absorption liquid tank (7).

7. The process for carbon fixation in steel slag according to claim 1, characterized in that: The carbon dioxide gas-liquid-solid three-phase reaction device (3) is connected to a liquid replenishing tank (10), and the liquid replenishing tank (10) is used to control the gas-liquid flow ratio in the carbon dioxide gas-liquid-solid three-phase reaction device (3) to be between 10:1 and 1000:1.

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