Steel slag micro-powder prepared through carbonization treatment of high-concentration CO2 tail gas and waste flue gas and application of steel slag micro-powder

Abstract

The invention discloses steel slag micro-powder prepared through carbonization treatment of high-concentration CO2 tail gas and waste flue gas and application of the steel slag micro-powder. Steel slag particles are subjected to crushing and grinding treatment and then ground to obtain steel slag micro-powder, and the steel slag micro-powder is dried; the steel slag powder and water are subjected to burdening mixing, and a steel slag mixture is obtained; and finally, conveying the steel slag mixture into an elevator in a flow control state, lifting the steel slag mixture into a mixed suspension carbonization system by the elevator, introducing high-concentration CO2 tail gas and waste flue gas, and continuously performing full interface contact with the fully dispersed steel slag micro powder in a suspension state. Through continuous carbonization reaction, free calcium oxide in the steel slag micro-powder can be basically eliminated, and the stability of the carbonized steel slag micro-powder is ensured to meet the standard requirement.

Description

Technical Field

[0001] The present invention belongs to the resource utilization of solid waste building materials, and particularly relates to a method for preparing steel slag fine powder by carbonization treatment of high-concentration CO2 tail gas and waste flue gas and its application. Background Art

[0002] Steel slag is a by-product generated during the steelmaking process, and its output accounts for 15% - 20% of the total steel output. The cumulative stockpile of steel slag in China exceeds 1.1 billion tons, and its comprehensive utilization rate is less than 30%. A large amount of steel slag is landfilled or stacked outdoors, which not only occupies land resources, but also seriously affects the natural environment and poses a serious threat to human health due to the high alkalinity of steel slag and the easy leaching of harmful metals. Therefore, it is urgent to develop new technologies for the environmental protection and resource utilization of steel slag.

[0003] During the application of steel slag in building materials, there are two serious problems. First, the content of free calcium oxide (f-CaO) and magnesium oxide (f-MgO) in steel slag is relatively high, which makes the steel slag prone to expansion and cracking, and the volume stability is poor. As a result, problems such as concrete surface popping and cracking will occur when steel slag is used in building materials. Second, the main low-activity phase in steel slag is γ-dicalcium silicate, and its hydration activity is extremely low.

[0004] The patent with the publication number CN115340306A discloses a method for preparing carbonized steel slag by using a rotating packed bed with high gravity to capture carbon dioxide. The carbon dioxide concentration is 3 - 99.99%, the carbon dioxide gas flow rate is 0.33 - 0.99 m 3 / min, the mixed slurry flow rate is 0.33 - 0.56 m3 / h, and the gravity created by the rotating packed bed with high gravity is 10 - 100G to obtain a carbonized steel slag slurry. The patent with the publication number CN114538867A discloses a method for preparing a cement-based material by using a carbonized steel slag slurry. The steel slag and water are mixed according to a solid-liquid ratio of 0.15 - 0.45 in an open stirrer to obtain a slurry, and the slurry is heated. The temperature during stirring is controlled at 20 - 80°C, carbon dioxide gas is introduced and high-speed stirring is maintained. The stirring time of the steel slag slurry is 40 - 120 min, the stirring speed is 800 - 1200 rpm / min, the carbon dioxide concentration is 10 - 99.99%, and the gas flow rate is 1 - 9 L / min to obtain a carbonized steel slag slurry. In the above technologies, due to the relatively large solid-liquid ratio, the treated carbonized steel slag slurry needs to be filtered, dried and ground, with many steps, and the activity of the treated steel slag is not significantly improved. Summary of the Invention

[0005] Objective of the Invention: The technical problem to be solved by the present invention is to provide a method for carbonizing steel slag with low cost, low resources, environmental friendliness and simple process in view of the deficiencies of the prior art, to improve the volume stability problem of steel slag, expand the application range of steel slag, and further improve the resource utilization rate of steel slag.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing steel slag micropowder by carbonizing treatment with high-concentration CO2 tail gas and waste flue gas, comprising the following steps: (1) Crushing, iron separation and grinding of steel slag particles to obtain steel slag powder, and drying; (2) Mixing the steel slag powder obtained in step (1) with water and an admixture to obtain a steel slag mixture; (3) Sending the steel slag mixture obtained in step (2) to a mixed suspension carbonization system through a hoist, introducing the tail gas of high-concentration CO2 and waste flue gas, and allowing it to continuously make full interfacial contact and continuous carbonization reaction with the steel slag mixture in a suspended state, thus obtaining the product.

[0007] Specifically, in step (1), the steel slag particles are selected from at least one of converter slag, open-hearth slag and electric furnace steel slag.

[0008] Specifically, in step (1), the steel slag particles are crushed by a roller press, then the iron filings in the steel slag particles are removed by magnetic separation, and then sent to a ball mill for grinding to 200 meshes to obtain steel slag micropowder, and dried at 100-105 °C for 8-10 hours.

[0009] Preferably, in step (2), the dosage of the steel slag powder is 100 parts by mass, the dosage of water is 2-4 parts by mass, and the dosage of the admixture is 2-3 parts by mass.

[0010] Preferably, the admixture is an aqueous solution of dilute sulfuric acid or an aqueous solution of dilute nitric acid, and the concentration is 0.01-0.1 mol / L.

[0011] Specifically, in step (2), the mixed suspension carbonization system is composed of a material hoisting device, a three-stage cyclone suspension device, a carbonization and air-drying system and a dust collection device, wherein the three-stage cyclone suspension device can be but is not limited to a CLT / A type cyclone.

[0012] Specifically, in the mixed suspension carbonization system, introducing the tail gas of high-concentration CO2 and waste flue gas raises the pressure of the system to 0.5-1 MPa, so as to fully disperse and suspend the steel slag mixture particles in the system.

[0013] Preferably, the temperature in the hybrid suspension carbonization system is maintained at 50-60°C, and the carbonization reaction time is 5-10 hours. Through continuous carbonization reaction, the free calcium oxide in the steel slag can be fully decomposed, ensuring that the soundness of the carbonized steel slag meets the standard requirements. The exhaust gas after carbonization in the system is treated by a dust collector and discharged after meeting the international emission requirements.

[0014] In the present invention, the steel slag reacts with high-concentration CO2 tail gas and waste flue gas through carbonization. The steel slag can be continuously carbonized for production, and the output of carbonized steel slag per unit time is high.

[0015] The CO2 gas is in a flowing state in the suspension carbonization system, and the steel slag mixture makes full interfacial contact in the suspended state. At the same time, the loss of CO2 can be reduced, and the utilization efficiency of CO2 in the CO2 tail gas and waste flue gas can be improved. The impact on the environment is reduced, the practical application and promotion of CO2 emission reduction technology are promoted, and the environmental protection benefits and sustainability of CO2 utilization technology are enhanced.

[0016] Preferably, in the tail gas and waste flue gas introduced into the hybrid suspension carbonization system, the volume concentration of CO2 is 25%-30%.

[0017] Furthermore, the steel slag micro-powder prepared by the above preparation method is also within the protection scope of the present invention.

[0018] Furthermore, the present invention also claims the application of the above steel slag micro-powder as a admixture to replace cement clinker in the preparation of cementitious materials. Beneficial effects

[0019] (1) The present invention contains calcium minerals such as free CaO and calcium silicate, which have high carbonization reaction activity in a CO2-rich environment. The steel slag that forms calcium carbonate and amorphous SiO2 after carbonization can solve problems such as poor volume stability and low activity, making it an effective way to utilize steel slag. A dense carbonized layer can be formed on the surface of the carbonized steel slag, which can make the carbonized steel slag have high particle strength and be used as concrete aggregate. The carbonized steel slag after the carbonization reaction can solve problems such as poor volume stability and low activity, making its wide use possible. At the same time, the carbonized steel slag powder can have certain activity and replace part of the cement as a blending material and admixture.

[0020] (2) The present invention uses high-concentration CO2 tail gas and waste flue gas to carbonize steel slag. Utilizing the characteristics of the suspension carbonization system, the steel slag makes full interfacial contact with CO2 gas in the suspension carbonization system and undergoes continuous carbonization reaction. The three-stage cyclone suspension device fully disperses and evenly suspends the steel slag micro-powder, and sprays a specific proportion of fine water mist to form a weak acid environment, enabling CO2 to quickly penetrate into the steel slag. The carbonization reaction rate between the high-concentration CO2 tail gas and waste flue gas and the steel slag is fast and the efficiency is high.

[0021] Although there are also solutions for carbonating steel slag with carbon dioxide in the prior art, usually gaseous carbon dioxide is used to carbonate steel slag, and the liquid-solid ratio is relatively large, resulting in a slow carbonation rate and a long carbonation time. However, the present invention uses a suspension carbonation system for treatment, which can effectively improve the carbonation rate and greatly shorten the carbonation time.

[0022] (3) The present invention uses high-concentration CO2 tail gas and waste flue gas to carbonate steel slag, greatly improving problems such as the soundness of steel slag. CO2 fully carbonates with free calcium oxide and free magnesium oxide in the steel slag to form thermodynamically stable calcium carbonate and magnesium carbonate. Moreover, CO2 also undergoes a carbonation reaction with calcium silicate in the steel slag to form calcium carbonate and amorphous SiO2. Both products improve the hydration activity of the steel slag and enhance its reaction activity. The carbonation reaction equations are shown in (1 - 3): 。

[0023] The nano-calcium carbonate formed by the carbonation reaction can fill the pores and matrix of the cement-based material, increasing the density of the matrix and providing more nucleation sites for cement hydration, promoting the formation of hydration products (such as C-S-H), and improving the compressive strength of the carbonated steel slag cement-based material. The carbonated steel slag of the present invention has a high activity index, greatly improving the problem of low gelling property of steel slag. The activity index of the carbonated steel slag cement mortar can be as high as over 75% compared with that of the PI42.5 cement mortar.

[0024] (4) By using high-concentration CO2 tail gas and waste flue gas to carbonate steel slag, the present invention produces carbonated steel slag with good soundness, which can be used in building materials, such as as a cement concrete admixture, for preparing carbonated steel slag cementitious materials, and for producing carbonated steel slag products, etc., improving the application prospect of steel slag in building materials and having wide practical application significance. The present invention uses the carbonation process of high-concentration CO2 tail gas and waste flue gas to prepare carbonated steel slag, which can utilize both the industrial solid waste steel slag and the waste gas, realizing the sustainable utilization of steel slag resources, reducing its environmental pollution, and reducing the pressure on the ecological environment.

[0025] (5) The present invention is conducive to promoting the utilization of CO2 and realizes the resource utilization of carbon dioxide in the field of building materials. To a certain extent, it not only alleviates the problems of land resource waste and ecological environment caused by the large-scale stacking of steel slag, but also reduces the CO2 emission problem. It can also be used as a substitute material for traditional cement to prepare concrete materials, thereby improving the utilization rate of steel slag, promoting the realization of carbon neutrality and the resource utilization of solid waste, and thus promoting the development of green building materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The following further specifically describes the present invention in conjunction with the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0027] Figure 1 XRD patterns of carbonated and uncarbonated steel slag under the conditions of temperature of 50 °C, pressure of 0.5 MPa, liquid-solid ratios of 0.02 and 0.04, and carbonation for 6 h in the carbonation suspension system in Example 1.

[0028] Figure 2 Histogram of compressive strength of each group of the control group and the group with 30% carbonated steel slag under the carbonation conditions of Example 1.

[0029] Figure 3 XRD patterns of carbonated and uncarbonated steel slag under the conditions of temperature of 60 °C, pressure of 0.5 MPa, liquid-solid ratios of 0.02 and 0.04, and carbonation for 6 h in the carbonation suspension system in Example 2.

[0030] Figure 4 Histogram of compressive strength of each group of the control group and the group with 30% carbonated steel slag under the carbonation conditions of Example 2.

[0031] Figure 5 XRD patterns of carbonated and uncarbonated steel slag under the conditions of temperature of 60 °C, pressure of 1 MPa, liquid-solid ratios of 0.02 and 0.04, and carbonation for 6 h in the carbonation suspension system in Example 3.

[0032] Figure 6 Histogram of compressive strength of each group of the control group and the group with 30% carbonated steel slag under the carbonation conditions of Example 3. Detailed implementation manners

[0033] The present invention can be better understood according to the following examples. Example 1

[0034] The steel slag selected in this Example 1 is the steel slag of Maanshan Iron & Steel Co., Ltd., and the main chemical components are shown in Table 1. Tap water is selected as water.

[0035] Table 1 Chemical composition of the steel slag of Maanshan Iron & Steel used in Example 1 (wt.%) .

[0036] This Example 1 includes the following steps: (1) The steel slag particles are subjected to crushing - iron separation - ball milling treatment, and then ground to 200 meshes to obtain steel slag powder. The steel slag fine powder is dried at 105 °C for 8 - 10 hours.

[0037] (2) The steel slag powder, water and admixture are proportioned and mixed according to the mass parts: 100 parts of steel slag powder, 2 and 4 parts of water, and 2 parts of dilute sulfuric acid to obtain a steel slag mixture, which are respectively denoted as Example 1 CS-L / S(0.02) and Example 1 CS-L / S(0.04); (3) Feed the steel slag mixture from step (2) to the hybrid suspension carbonation system, introduce the tail gas and waste flue gas with high-concentration CO2, increase the pressure to 0.5 MPa, raise the temperature to 50 °C, and carry out carbonation reaction with the steel slag mixture for 6 h; (4) Dry the carbonated steel slag sample from step (3) at 105 °C for 6 hours, and then grind it to 200 mesh to preferably obtain carbonated steel slag fine powder.

[0038] To verify the suspension carbonation effect of the present invention, 100 parts of steel slag powder, 2 parts of water, and 2 parts of dilute sulfuric acid are proportioned and mixed, denoted as Comparative Example 1 CS-L / S(0.02) and Comparative Example 1 CS-L / S(0.04), and sent to a conventional carbon dioxide reactor, introduce carbon dioxide gas with a concentration of 100%, increase the pressure to 0.5 MPa, raise the temperature to 50 °C, and carry out carbonation reaction with the steel slag mixture for 6 h.

[0039] Table 2 shows the comparison of the carbonation degree of the conventional carbonated steel slag and the suspension carbonated steel slag in Example 1 under the same conditions. The carbonation degree of the steel slag is expressed by the carbonation weight gain rate and the free calcium oxide content. The carbonation weight gain rate is calculated according to the following formula (4), and the calculation accuracy is accurate to 0.1%.

[0040] ; In the formula: M is the carbonation weight gain rate of the carbonated steel slag, %; M0 is the mass of the steel slag before carbonation, in g, and M1 is the mass of the steel slag after carbonation, in g. The free calcium oxide content in the steel slag is determined according to the ethylene glycol substitution method in the national standard GB / T 176-2017 "Methods of Chemical Analysis of Cement".

[0041] It is found by comparison that the carbonation weight gain rate of the steel slag in the suspension carbonation system is larger than that of the conventional carbonation, and the reduction of the free calcium oxide content in the steel slag is more obvious compared with the conventional carbonation, indicating that under the same carbonation conditions, the carbonation rate in the suspension carbonation system is faster and the carbonation degree is deeper.

[0042] Table 2 shows the carbonation degree (%) of the conventional carbonated steel slag and the suspension carbonated steel slag under the same conditions 。

[0043] To verify the performance effect of the steel slag of the present invention, a comparative example (SS) is set up, where SS is the steel slag without carbonation treatment, and the compressive strength and volume stability of Example 1 (CS-L / S(0.02), CS-L / S(0.04)) and Comparative Example SS are compared. The difference between the preparation processes of the comparative example and Example 1 is as follows: (1) A comparative sample of cement mortar was prepared using 450 g of ordinary Portland cement, 1350 g of standard sand, and 225 g of water. For Example 1 group of cement mortar, 135 g of carbonized steel slag powder, 315 g of ordinary Portland cement, 1350 g of standard sand, and 225 g of water were used. For the comparative group of cement mortar, 135 g of uncarbonized steel slag powder, 315 g of ordinary Portland cement, 1350 g of standard sand, and 225 g of water were used.

[0044] (2) The preparation and activity test of cement mortar were carried out with reference to GB / T 17671–2021 "Test Method for Strength of Cement Mortar (ISO Method)" and GB / T 51003–2014 "Technical Specification for Application of Mineral Admixtures".

[0045] (3) Carbonized steel slag powder (CS-L / S(0.02) and CS-L / S(0.04)) was selected, and cement paste with a water-cement ratio of 0.3 was prepared with a steel slag content of 30% as Example 1. At the same time, uncarbonized steel slag powder (SS) was selected as the comparative group. The carbonized steel slag powder, cement, and pure water were added to a cement mortar mixer and stirred at low speed for 2 min and then at high speed for 2 min to obtain the paste.

[0046] (4) According to GB / T 1346–2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement", a boiling test was carried out on the paste specimens placed in Le Chatelier molds to determine the volume soundness of free calcium oxide. When the average increase distance of the Le Chatelier mold pointer after boiling the specimens does not exceed 5 mm, the volume soundness is considered qualified. Then, specimens of 25 × 25 × 280 mm were prepared using molds, and an autoclave test was carried out according to GB / T 750–2024 "Test Method for Autoclave Soundness of Cement" to determine the volume soundness of free magnesium oxide. When the autoclave expansion rate does not exceed 0.5%, the volume soundness is considered qualified. The test results are shown in Table 3.

[0047] In the suspension carbonization system, at a temperature of 50 °C, a pressure of 0.5 MPa, liquid-solid ratios of 0.02 and 0.04, and carbonization for 6 h, the XRD patterns of carbonized steel slag are as Figure 1 shown. The column charts of the compressive strengths of the control group and the groups with 30% carbonized steel slag are as Figure 2 shown. It can be seen that the strength of the carbonized steel slag experimental group is significantly improved compared to that of the uncarbonized steel slag group. The activities are increased by 20.02% and 20.17% respectively compared to the uncarbonized steel slag group, and the 28-day activities are increased by 10.24% and 8.42% respectively compared to the uncarbonized steel slag group. Among them, the activity of carbonized steel slag with a liquid-solid ratio of 0.02 is the highest.

[0048] Table 3 shows the volume soundness test results of Example 1 and the comparative group. . Example 2

[0049] In Example 2, the steel slag selected is the steel slag of Maanshan Iron & Steel Co., Ltd. The main chemical components are shown in Table 4, and the water selected is tap water.

[0050] Table 4 Chemical composition of the steel slag of Maanshan Iron & Steel used in Example 2 (wt.%) 。

[0051] Example 2 includes the following steps: (1) The steel slag particles are subjected to crushing - iron separation - ball milling treatment, and then ground to 200 mesh to obtain steel slag powder. The steel slag fine powder is dried at 105°C for 8 - 10 hours.

[0052] (2) The steel slag powder, water and admixture are proportioned and mixed by mass: 100 parts of steel slag powder, 2 - 4 parts of water, and 2 parts of dilute sulfuric acid to obtain a steel slag mixture, denoted as Example 2 CS - L / S(0.02) and Example 2 CS - L / S(0.04) respectively; (3) The steel slag mixture in step (2) is sent to the hybrid suspension carbonation system by a hoist, and the tail gas and waste flue gas with high - concentration CO2 are introduced. The pressure is increased to 0.5 MPa and the temperature is raised to 60°C, and carbonation reaction is carried out with the steel slag mixture for 6 h; (4) The carbonated steel slag sample in step (3) is dried at 105°C for 6 hours, and then ground to 200 mesh to preferably obtain carbonated steel slag fine powder.

[0053] To verify the suspension carbonation effect of the present invention, 100 parts of steel slag powder, 2 and 4 parts of water, and 2 parts of dilute sulfuric acid are proportioned and mixed, denoted as Comparative Example 2 CS - L / S(0.02) and Comparative Example 2 CS - L / S(0.04), and sent to a conventional carbon dioxide reaction kettle. Carbon dioxide gas with a concentration of 100% is introduced, the pressure is increased to 0.5 MPa, the temperature is raised to 60°C, and carbonation reaction is carried out with the steel slag mixture for 6 h.

[0054] Table 5 shows the comparison of the carbonation degree of the conventional carbonated steel slag and the suspension - carbonated steel slag in Example 2 under the same conditions. The carbonation degree of the steel slag is expressed by the carbonation weight - gain rate and the free calcium oxide content. The carbonation weight - gain rate is calculated according to the following formula (4), and the calculation accuracy is accurate to 0.1%.

[0055] ; Where: M is the carbonation weight - gain rate of the carbonated steel slag, %; M0 is the mass of the steel slag before carbonation, in g, and M1 is the mass of the steel slag after carbonation, in g. The free calcium oxide content in the steel slag is determined according to the ethylene glycol substitution method in the national standard GB / T176 - 2017 "Methods of Chemical Analysis of Cement".

[0056] It was found by comparison that the carbonation weight gain rate of steel slag in the suspended carbonation system is larger than that in conventional carbonation, and the content of free calcium oxide in steel slag is reduced more significantly compared with conventional carbonation, indicating that under the same carbonation conditions, the carbonation rate in the suspended carbonation system is faster and the degree of carbonation is deeper.

[0057] Table 5 shows the carbonation degree (%) of conventional carbonated steel slag and suspended carbonated steel slag under the same conditions. 。

[0058] To verify the technical effects of the present invention, a comparative example (SS) was set up, and the compressive strength and volume stability of Example 2 (CS-L / S(0.02), CS-L / S(0.04)) and Comparative Example SS were compared. The difference in the preparation process between the comparative example and Example 2 is as follows: (1) Prepare a cement mortar comparison sample using 450 g of ordinary Portland cement, 1350 g of standard sand, and 225 g of water. Prepare the cement mortar Example 2 group using 135 g of carbonated steel slag micro-powder, 315 g of ordinary Portland cement, 1350 g of standard sand, and 225 g of water. Prepare the cement mortar comparative example group using 135 g of uncarbonated steel slag micro-powder, 315 g of ordinary Portland cement, 1350 g of standard sand, and 225 g of water.

[0059] (2) The preparation and activity test of cement mortar refer to GB / T 17671–2021 "Test Method for Cement Mortar Strength (ISO Method)" and GB / T 51003–2014 "Technical Specification for Application of Mineral Admixtures" for implementation.

[0060] (3) Select carbonated steel slag micro-powder (CS-L / S(0.02) and CS-L / S(0.04)), and prepare a cement paste with a water-cement ratio of 0.3 with a steel slag content of 30% as Example 2. At the same time, select uncarbonated steel slag micro-powder (SS) as the comparative example group. Add the carbonated steel slag micro-powder, cement, and pure water into a cement mortar mixer, stir at low speed for 2 min and then at high speed for 2 min to obtain the paste.

[0061] (4) According to GB / T 1346–2011 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement", perform a boiling test on the paste specimen placed in the Le Chatelier mold to determine the volume stability of free calcium oxide. When the average increase distance of the Le Chatelier mold pointer after the specimen is boiled does not exceed 5 mm, it is considered that the volume stability is qualified. Then use a mold to prepare a specimen of 25 × 25 × 280 mm, and perform an autoclave test according to GB / T 750–2024 "Test Method for Autoclave Soundness of Cement" to determine the volume stability of free magnesium oxide. When the autoclave expansion rate does not exceed 0.5%, it is considered that the volume stability is qualified. The test results are shown in Table 6.

[0062] In the suspension carbonization system, the temperature is 60 °C, the pressure is 0.5 MPa, the liquid-solid ratio is 0.02 and 0.04, and the XRD pattern of the carbonized steel slag after 6 h of carbonization is as Figure 3 shown. The bar charts of the compressive strength of the control group and each group doped with 30% carbonized steel slag are as Figure 4 shown. It can be seen that the strength of the experimental group of carbonized steel slag is significantly improved compared with that of the uncarbonized steel slag group. The activities are increased by 22.78% and 19.69% respectively compared with the uncarbonized steel slag group, and the 28-day activities are increased by 13.16% and 8.27% respectively compared with the uncarbonized steel slag group. Among them, the activity of the carbonized steel slag with a liquid-solid ratio of 0.02 is the highest.

[0063] Table 6 shows the volume stability test results of Example 2 and the comparative example group . Example 3

[0064] The steel slag selected in this Example 3 is the steel slag of Maanshan Iron & Steel Co., Ltd. The main chemical components are shown in Table 7, and the water selected is tap water.

[0065] Table 7 Chemical composition (wt.%) of the Maanshan Iron & Steel slag used in Example 3 .

[0066] This Example 3 includes the following steps: (1) Crush - iron separation - ball mill the steel slag particles, and then grind them to 200 meshes to obtain steel slag powder. The steel slag fine powder is dried at 105 °C for 8 - 10 hours.

[0067] (2) Mix the steel slag powder, water and admixture according to the mass parts: 100 parts of steel slag powder, 2 - 4 parts of water, and 2 parts of dilute sulfuric acid, and mix them to obtain a steel slag mixture, which are respectively denoted as Example 3 CS-L / S(0.02) and Example 3 CS-L / S(0.04); (3) Send the steel slag mixture in step (2) to the hybrid suspension carbonization system by a hoist, introduce the tail gas and waste flue gas with high-concentration CO2, boost the pressure to 1 MPa, and raise the temperature to 60 °C. The high-concentration CO2 tail gas and waste flue gas react with the steel slag mixture for 6 h; (4) Dry the carbonized steel slag sample in step (3) at 105 °C for 6 hours, and then grind it to 200 meshes to preferably obtain carbonized steel slag fine powder.

[0068] To verify the suspension carbonization effect of the present invention, 100 parts of steel slag powder, 24 parts of water, and 2 parts of dilute sulfuric acid were proportioned and mixed, denoted as Comparative Example 3 CS-L / S(0.02) and Comparative Example 3 CS-L / S(0.04), and sent to a conventional carbon dioxide reactor. Carbon dioxide gas with a concentration of 100% was introduced, the pressure was increased to 1 MPa, the temperature was raised to 60 °C, and the carbonization reaction with the steel slag mixture was carried out for 6 h.

[0069] Table 8 shows the comparison of the carbonization degrees of conventional carbonized steel slag and suspended carbonized steel slag in Example 3 under the same conditions. The carbonization degree of the steel slag is expressed by the carbonization weight gain rate and the free calcium oxide content. The carbonization weight gain rate is calculated according to the following formula (4), and the calculation accuracy is accurate to 0.1%.

[0070] ; In the formula: M is the carbonization weight gain rate of the carbonized steel slag, %; M0 is the mass of the steel slag before carbonization, in g, and M1 is the mass of the steel slag after carbonization, in g. The free calcium oxide content in the steel slag is determined according to the ethylene glycol substitution method in the national standard GB / T 176-2017 "Methods of Chemical Analysis of Cement".

[0071] It was found by comparison that the carbonization weight gain rate of the steel slag in the suspension carbonization system is larger than that of the conventional carbonization, and the reduction of the free calcium oxide content in the steel slag compared with the conventional carbonization is more obvious, indicating that under the same carbonization conditions, the carbonization rate in the suspension carbonization system is faster and the carbonization degree is deeper.

[0072] Table 8 shows the carbonization degrees (%) of conventional carbonized steel slag and suspended carbonized steel slag under the same conditions 。

[0073] To verify the technical effect of the present invention, a comparative example (SS) was set, and the compressive strength and volume stability of Example 3 (CS-L / S(0.02), CS-L / S(0.04)) and Comparative Example SS were compared. The difference between the preparation processes of the comparative example and Example 3 is as follows: (1) 450 g of ordinary Portland cement, 1350 g of standard sand, and 225 g of water were used to prepare a cement mortar comparison sample. 135 g of carbonized steel slag powder, 315 g of ordinary Portland cement, 1350 g of standard sand, and 225 g of water were used to prepare the cement mortar Example 3 group. 135 g of uncarbonized steel slag powder, 315 g of ordinary Portland cement, 1350 g of standard sand, and 225 g of water were used to prepare the cement mortar comparative example group.

[0074] (2) The preparation and activity test of the cement mortar refer to GB / T 17671–2021 "Test Methods for the Strength of Cement Mortar (ISO Method)" and GB / T 51003–2014 "Technical Specification for the Application of Mineral Admixtures" for implementation.

[0075] (3) Carbonized steel slag powder (CS-L / S (0.02) and CS-L / S (0.04)) was selected, and a cement paste with a water-cement ratio of 0.3 was prepared according to the steel slag content of 30% as Example 2, and uncarbonized steel slag powder (SS) was selected as the comparative example group. Carbonized steel slag powder, cement and pure water were added to a cement mortar mixer, stirred at low speed for 2 minutes and then at high speed for 2 minutes to obtain a paste.

[0076] (4) According to GB / T 1346-2011 "Test Method for Water Consumption, Setting Time and Stability of Cement Standard Consistency", the pure slurry sample placed in the Redger clamp was boiled to determine the volume stability of free calcium oxide. When the average increase distance of the Redger clamp pointer after the specimen is boiled does not exceed 5mm, the volume stability is considered to be qualified. Then use the mold to prepare a 25 × 25 × 280mm sample, and perform an autoclave test according to GB / T 750-2024 "Test Method for Autoclave Stability of Cement" to determine the volume stability of free magnesium oxide. When the autoclave expansion rate does not exceed 0.5%, the volume stability is considered to be qualified. The test results are shown in Table 9.

[0077] In the suspension carbonization system, the temperature is 60℃, the pressure is 0.5MPa, the liquid-solid ratio is 0.02 and 0.04, and the XRD spectrum of the carbonized slag after carbonization for 6h is as follows: Figure 5 The compressive strength bar graphs of the control group and the groups mixed with 30% carbonized steel slag are shown in Figure 6 As shown. It can be seen that the strength of the carbonized steel slag experimental group is significantly improved compared with the uncarbonized steel slag group. Compared with the uncarbonized steel slag group, the activity is increased by 21.16% and 16.25%, respectively. Compared with the uncarbonized steel slag group, the 28d activity is increased by 7.84% and 5.83%, respectively. Among them, the carbonized steel slag with a liquid-to-solid ratio of 0.02 has the highest activity.

[0078] Table 9 shows the volume stability test results of Example 3 and the comparative example group .

[0079] The present invention provides a method and idea for preparing steel slag powder and its application by carbonization treatment of high-concentration CO2 tail gas and waste flue gas. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A method for preparing steel slag powder by carbonization treatment of high-concentration CO2 tail gas and waste flue gas, characterized in that: The steps include: (1) Crushing, iron selection and grinding of steel slag particles to obtain steel slag powder, and drying; (2) mixing the steel slag powder obtained in step (1) with water and an admixture to obtain a steel slag mixture; (3) The steel slag mixture obtained in step (2) is sent to a mixed suspension carbonization system through an elevator, and high-concentration CO2 tail gas and waste flue gas are introduced to allow them to continuously undergo sufficient interface contact and continuous carbonization reaction with the steel slag mixture in a suspended state to obtain the product.

2. The method for preparing steel slag powder by carbonization treatment of high-concentration CO2 tail gas and waste flue gas according to claim 1, characterized in that: In step (1), the steel slag particles are selected from at least one of converter slag, open-hearth slag and electric furnace slag.

3. The method for preparing steel slag powder by carbonization treatment of high-concentration CO2 tail gas and waste flue gas according to claim 1, characterized in that: In step (1), the steel slag particles are crushed by a roller press, and then the iron filings in the steel slag particles are removed by magnetic separation. The steel slag particles are then sent to a ball mill for grinding to 200 mesh to obtain steel slag powder, which is then dried at 100-105°C for 8-10 hours.

4. The method for preparing steel slag powder by carbonization treatment of high-concentration CO2 tail gas and waste flue gas according to claim 1, characterized in that: In step (2), the amount of steel slag powder is 100 parts by mass, the amount of water is 2-4 parts by mass, and the amount of admixture is 2-3 parts by mass; the admixture is a dilute sulfuric acid aqueous solution or a dilute nitric acid aqueous solution, and the concentration is 0.01-0.1 mol / L.

5. The method for preparing steel slag powder by carbonization treatment of high-concentration CO2 tail gas and waste flue gas according to claim 1, characterized in that: In step (2), the mixed suspension carbonization system is composed of a material lifting device, a three-stage cyclone suspension device, a carbonization air drying system and a dust collecting device, wherein the model of the three-stage cyclone suspension device is CLT / A type.

6. The method for preparing steel slag powder by carbonization treatment of high-concentration CO2 tail gas and waste flue gas according to claim 5, characterized in that: In the mixed suspension carbonization system, high-concentration CO2 tail gas and waste flue gas are introduced to increase the system pressure to 0.5-1 MPa, so that the steel slag mixture particles are fully dispersed and suspended in the system.

7. The method for preparing steel slag powder by carbonization treatment of high-concentration CO2 tail gas and waste flue gas according to claim 5, characterized in that: The temperature in the mixed suspension carbonization system is maintained at 50-60° C., and the carbonization reaction time is 5-10 hours.

8. The method for preparing steel slag powder by carbonization treatment of high-concentration CO2 tail gas and waste flue gas according to claim 5, characterized in that: The volume concentration of CO2 in the tail gas and waste flue gas introduced into the mixed suspension carbonization system is 25%~30%.

9. The steel slag powder prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the steel slag powder according to claim 9 as an admixture to replace cement clinker in preparing cementitious materials.

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