A method for co-preparing building materials from solid waste and carbon dioxide in the steel industry

Abstract

This invention relates to the field of CO4B, specifically to a method for the co-production of building materials from steel industry solid waste and carbon dioxide. The method uses steel industry solid waste as raw material, obtains a billet by controlling the molding process, and then conducts a mineralization reaction in a closed environment with carbon dioxide flue gas to obtain the finished building material. This invention addresses the problems of existing steel slag products, such as high density, limited application scenarios, low net emission reduction, and low mineralization degree. It proposes a method for preparing building materials by co-producing steel industry solid waste and carbon dioxide. By changing the molding method, optimizing the raw material formula, and related processes, the density of the test block is controlled to ensure mineralization efficiency. Simultaneously, the self-heating generated during the mineralization process is rationally utilized to improve the carbon sequestration effect of the mineralized product.

Description

Technical Field

[0001] This invention relates to the field of CO4B, specifically to a method for the co-production of building materials from solid waste in the steel industry and carbon dioxide. Background Technology

[0002] With the development of my country's steel industry, steel slag production has increased rapidly. The large-scale stockpiling of steel slag not only wastes resources but also causes significant environmental pollution. While steel slag possesses certain cementitious activity and can be used as a low-grade "cement," its high content of free CaO and MgO leads to stability issues in the preparation of cementitious materials. Furthermore, the high density of steel slag itself results in high-strength products after use, limiting its application scenarios. Overall, the resource utilization rate of steel slag in my country is relatively low. In addition to steel slag emissions, production also generates substantial carbon dioxide emissions, with CO2 concentrations ranging from 10% to 30% in these exhaust gases. Utilizing CO2 from these exhaust gases is one of the effective technical measures for reducing emissions in steel enterprises. Mineralization technology, as a key technology for addressing carbon emissions at their source, can meet the goal of absorbing large amounts of solid waste from the steel industry and co-treating emitted carbon dioxide, making it the best solution under the current circumstances.

[0003] Steel slag contains a large amount of active dicalcium silicate and tricalcium silicate, which can be used as a mineralization raw material. Through mineralization technology, it reacts with carbon dioxide, not only fixing a large amount of carbon dioxide generated by the steel industry and reducing carbon emissions, but also producing building materials that generate good economic benefits. However, the mineralization reaction is greatly affected by process conditions such as gas partial pressure and temperature within the system. Patent CN114163205A describes a steel slag-based carbonization material, its preparation method, and its application. A mixture is obtained by adding dry slag, quartz sand tailings, fly ash, stone powder, mineral powder, silica fume, and desulfurized gypsum to steel slag. This mixture is then pressed into bricks under a pressure of 8-30 MPa. Most of the raw materials need to be ball-milled, and the use of high molding pressure and small raw material particle size ensures the strength and carbon fixation efficiency of the test blocks. Patent CN112266204B describes a high-strength all-steel slag block with enhanced carbon dioxide curing effect and its preparation method. The molding pressure is 5-15 MPa. The strength of the test block is guaranteed by using only steel slag, and the particle size of the steel slag is controlled within 5-75 micrometers, thereby ensuring that the density of the test block is maintained at 1650-1850 kg / m³. 3 The process and raw material costs are relatively high. While the above factors can be addressed by adjusting molding pressure and raw material particle size to improve the degree of mineralization, the resulting product has a high density and limited application scenarios. Furthermore, the mineralization reaction requires a certain temperature, which further increases the carbon emissions of the entire process and is not conducive to net carbon reduction. Summary of the Invention

[0004] Therefore, this invention addresses the problems of existing steel slag products, such as high density, limited application scenarios, low net emission reduction, and low mineralization degree. It proposes a method for preparing building materials by co-producing solid waste and carbon dioxide from the steel industry. By changing the molding method and adjusting related processes, the density of the test block is controlled to ensure mineralization efficiency. At the same time, the self-heating generated during the mineralization process is rationally utilized to improve the carbon fixation rate and strength of the mineralized product.

[0005] This invention provides a method for the co-production of building materials from steel industry solid waste and carbon dioxide. The method uses steel industry solid waste as raw material, obtains a billet by controlling the composition of the raw material and the forming method, and carries out a mineralization reaction in a closed environment containing carbon dioxide gas to obtain the finished building material.

[0006] As a preferred technical solution, the method for co-preparing building materials from solid waste and carbon dioxide in the steel industry specifically includes the following steps:

[0007] (1) Mix calcium-containing solid waste and silicon-aluminum solid waste to obtain mixed solid waste. Then, send the mixed solid waste and water into a mixing system and mix them evenly to obtain a mixture.

[0008] (2) The mixture is fed into the powder mixing system and stirred until the mixture is uniformly mixed to obtain the powder mixture;

[0009] (3) The powder mixture is fed into the digestion system and digested for 20-60 minutes to obtain the digested material;

[0010] (4) The digested material is fed into a vibration molding system to prepare a blank;

[0011] (5) The billet is fed into the reactor at a certain filling rate, and carbon dioxide gas is introduced to carry out the mineralization reaction for a certain period of time to obtain the finished building material.

[0012] As a preferred technical solution, the mass percentage of each component in the mixture in step (1) is: 15-70% calcium-containing solid waste, 15-80% silicon-aluminum solid waste, and 5-30% water; preferably, the mass percentage of each component in the mixture in step (1) is: 25%-45% calcium-containing solid waste, 35%-65% silicon-aluminum solid waste, and 10-20% water; more preferably, the water-to-binder ratio (mass ratio of water to solid waste) in the mixture in step (1) is 0.1-0.2:1.

[0013] Preferably, the calcium-containing solid waste can be one or more of steel slag, ore slag, magnesium slag, waste lime, waste cement, etc.; preferably, the siliceous aluminous solid waste can be one or more of recycled aggregate, phosphogypsum, construction waste, yellow phosphorus slag, fly ash, smelting slag, red mud; preferably, the siliceous aluminous solid waste can be one or two of coarse aggregate and fine aggregate according to particle size distribution; more preferably, the siliceous aluminous solid waste includes coarse aggregate and fine aggregate according to particle size distribution;

[0014] As a preferred technical solution, the mass ratio of coarse aggregate to fine aggregate is (0.5-1.5):(0.6-1.7); preferably, the mass ratio of coarse aggregate to fine aggregate is (0.6-1.3):(0.7-1.5); and even more preferably, the mass ratio of coarse aggregate to fine aggregate is (0.7-1.2):(0.8-1.4).

[0015] The coarse aggregate has a particle size of 0.05-7 mm, preferably 1-6 mm; the fine aggregate has a particle size of 0.05-0.6 mm, preferably 0.075-0.5 mm.

[0016] As a preferred technical solution, the vibration frequency of the vibration molding system in step (4) is 1200-4200 times / min; preferably, the vibration frequency of the vibration molding system in step (4) is 1800-3800 times / min; preferably, the vibration frequency is 2400-3600 times / min; and more preferably, the vibration frequency is 2800-3200 times / min.

[0017] As a preferred technical solution, the vibration molding time of the vibration molding system in step (4) is 2-30s; preferably, the vibration molding time is 5-20s.

[0018] The method provided by this invention, through the control of gradation and molding process, can reduce the density of the product, making the product more widely applicable; on the other hand, it increases the porosity of gas entering the block, improves the degree of mineralization, enhances product performance, reduces the amount of steel slag used, reduces the cost of resource utilization, and synergistically treats carbon dioxide to produce building materials with good carbon fixation performance and excellent physical properties, which is conducive to the promotion and application of this process in the steel industry.

[0019] Based on the present invention, the solid waste raw materials in the steel industry include calcium-containing solid waste, coarse aggregate of silicon-aluminum solid waste, and fine aggregate of silicon-aluminum solid waste with different particle sizes. The green body is prepared by a vibration molding system. By controlling the vibration molding time and frequency, solid waste raw materials with different particle sizes are interlocked, the density of the green body is regulated, and the diffusion rate of carbon dioxide is increased, thereby ensuring mineralization efficiency. At the same time, the self-heating generated during the mineralization process is rationally utilized to improve the carbon fixation rate and strength of the mineralized product.

[0020] As a preferred technical solution, the filling rate (V / V) of the preform in the reactor in step (5) is 10-50%.

[0021] As a preferred technical solution, the filling rate (V / V) of the preform in the reactor in step (5) is 30-40%.

[0022] As a preferred technical solution, the ventilation rate of carbon dioxide gas in step (5) is 70-130 m. 3 / min;

[0023] As a preferred technical solution, in step (5), the volume of carbon dioxide gas introduced into the reactor before the mineralization reaction accounts for one-third of the reactor volume;

[0024] As a preferred technical solution, the mineralization reaction time in step (5) is 2-8 hours; the pressure of the mineralization reaction is 0.1-1.2 MPa.

[0025] As a preferred technical solution, the source of carbon dioxide gas in step (5) is one or more of the following: flue gas emitted from coal chemical plants, flue gas from coal-fired power plants, flue gas from lime kilns, flue gas from steel plants, flue gas from chemical plants, flue gas from cement plants, and gas after carbon capture and analysis; preferably, the volume fraction of carbon dioxide in the carbon dioxide gas in step (5) is 5%-95%.

[0026] Beneficial effects:

[0027] 1. This invention addresses the problems of high density, limited application scenarios, low net emission reduction, and low mineralization degree of existing steel slag products. It proposes a method for preparing building materials by co-producing solid waste and carbon dioxide from the steel industry. The density of the test block is controlled by changing the molding method, optimizing the raw material formula and related processes, thereby ensuring mineralization efficiency. At the same time, the self-heating generated during the mineralization process is rationally utilized to improve the carbon fixation effect of the mineralized product.

[0028] 2. The method provided by this invention reduces the density of the product by adjusting the gradation of coarse and fine raw materials and the molding process. On the one hand, this results in a product with low density and wide application. On the other hand, it increases the porosity of gas entering the block, improves the degree of mineralization, enhances product performance, reduces the amount of steel slag used, lowers the cost of resource utilization, and synergistically treats carbon dioxide to produce building materials with good carbon fixation performance and excellent physical properties. This is conducive to the promotion and application of this process in the steel industry.

[0029] 3. This invention utilizes the carbon dioxide waste gas emitted from solid waste generated in the steel industry, and improves the carbon sequestration effect by using the self-heating of the mineralization reaction, thereby reducing the carbon emissions of the entire process. Through the optimization of related process flows, the energy consumption of the process is reduced, and high-performance building materials are produced, providing an effective carbon net emission reduction path for the steel industry.

[0030] 4. This application proposes using low-concentration carbon dioxide flue gas as the curing gas, and directly using the carbon dioxide-containing flue gas for mineralization curing. Under certain processes, high-quality building materials are produced, effectively realizing the efficient resource utilization of low-concentration carbon dioxide from coal chemical plants, coal-fired power plants, steel plants, etc. The building materials produced by the synergistic mineralization treatment have a total carbon emission that is more than 50% lower than that of traditional silicate cement products. This not only solves the solid waste disposal and carbon emission problems of enterprises such as coal chemical plants, coal-fired power plants, and steel plants, but also plays an important role in promoting the low-carbon development of my country's building materials industry. Detailed Implementation

[0031] In this embodiment of the application: steel slag from a steel enterprise was selected as calcium-containing solid waste with a moisture content of 2.4%. XRF analysis revealed its chemical composition and weight percentage as follows:

[0032] Table 1. Main elemental composition of steel slag

[0033] Elemental composition CaO <![CDATA[Fe2O3]]> <![CDATA[SiO2]]> <![CDATA[Al2O3]]> MgO MnO <![CDATA[P2O5]]> <![CDATA[TiO2]]> LOSS Content (wt%) 38.64 22.43 19.64 6.32 6.73 1.92 1.32 0.79 2.21

[0034] The steel slag is sieved through a standard sieve, as shown in the table below:

[0035] Table 2 Screening results of steel slag

[0036]

[0037] Recycled aggregate from a building materials factory was selected as coarse aggregate from silica-alumina solid waste. Its moisture content was 1.2%. XRF analysis revealed its chemical composition and weight percentage as follows:

[0038] Table 3. Main elemental composition of coarse aggregate

[0039]

[0040] The recycled aggregate, after being sieved through a standard sieve, is shown in the table below:

[0041] Table 4 Screening results of recycled aggregate

[0042]

[0043] Fine sand from a building materials factory was selected as the silica-alumina fine aggregate. Its moisture content was 2.3%. XRF analysis revealed its chemical composition and weight percentage as follows:

[0044] Table 5. Main elemental composition of fine sand

[0045]

[0046] The fine sand, after being sieved through a standard sieve, is shown in the table below:

[0047] Table 6. Screening results of fine sand

[0048]

[0049] The exhaust gas from a salt and steel plant in Hefei was selected, and its gas composition and weight percentage are as follows:

[0050] Table 7. Composition (volume fraction) of exhaust gas from a steel plant in Hefei after capture.

[0051] Gas composition <![CDATA[CO2]]> <![CDATA[N2]]> LOSS Steel exhaust 70.5％ 28.9％ 0.6％

[0052] Example 1

[0053] Embodiment 1 of the present invention provides a method for co-preparing building materials from steel industry solid waste and carbon dioxide. The method uses steel industry solid waste as raw material, obtains a billet by controlling the composition of raw materials and the forming method, and carries out a mineralization reaction in a closed environment containing carbon dioxide gas to obtain finished building materials.

[0054] The method for co-preparing building materials from solid waste and carbon dioxide in the steel industry specifically includes the following steps:

[0055] (1) Mix calcium-containing solid waste and silicon-aluminum solid waste to obtain mixed solid waste. Then, send the mixed solid waste and water into a mixing system and mix them evenly to obtain a mixture.

[0056] (2) The mixture is fed into the powder mixing system and stirred until the mixture is uniformly mixed to obtain the powder mixture;

[0057] (3) The powder mixture is fed into the digestion system and digested for 50 minutes to obtain the digested material;

[0058] (4) The digested material is fed into a vibration molding system to prepare a blank;

[0059] (5) The billet is fed into the reactor by a shuttle car at a certain filling rate. When the pressure in the reactor reaches the set value, the gas is introduced and then the gas is stopped. The mineralization reaction is carried out for a certain time, the gas is exhausted to atmospheric pressure, and the reactor is opened.

[0060] (6) Once the temperature inside the autoclave drops to 50°C, pull out the transfer vehicle. The product is ready as a finished building material without any curing required.

[0061] The mass percentage of each component in the mixture in step (1) is as follows: 30% calcium solid waste, 55% siliceous aluminum solid waste, and 15% water; the siliceous aluminum solid waste includes coarse aggregate and fine aggregate according to particle size distribution; the mass ratio of coarse aggregate to fine aggregate is 1:1.

[0062] The vibration frequency of the vibration molding system in step (4) is 3000 times / min; the vibration molding time of the vibration molding system in step (4) is 15s.

[0063] In step (5), the filling rate (V / V) of the preform in the reactor is 40%.

[0064] The ventilation rate of carbon dioxide gas in step (5) is 100 m. 3 / min.

[0065] In step (5), the volume of carbon dioxide gas introduced into the reactor before the mineralization reaction accounts for one-third of the reactor volume.

[0066] The mineralization reaction in step (5) takes 5 hours and the pressure of the mineralization reaction is 0.4 MPa.

[0067] Example 2

[0068] Example 2 of the present invention provides a method for co-preparing building materials from solid waste in the steel industry and carbon dioxide. The specific implementation method is the same as that in Example 1, except that the mass percentage of each component in the mixture in step (1) is: 45% calcium solid waste, 45% siliceous aluminum solid waste, and 10% water; the siliceous aluminum solid waste includes coarse aggregate and fine aggregate according to the particle size distribution; the mass ratio of coarse aggregate to fine aggregate is 1.5:1.

[0069] Example 3

[0070] Example 3 of the present invention provides a method for co-preparing building materials from solid waste in the steel industry and carbon dioxide. The specific implementation method is the same as that in Example 1, except that the mass percentage of each component in the mixture in step (1) is: 25% calcium solid waste, 60% siliceous aluminum solid waste, and 15% water; the siliceous aluminum solid waste includes coarse aggregate and fine aggregate according to the particle size distribution; the mass ratio of coarse aggregate to fine aggregate is 0.8:1.7.

[0071] Example 4

[0072] Example 4 of the present invention provides a method for co-preparing building materials from solid waste in the steel industry and carbon dioxide. The specific implementation method is the same as that in Example 1, except that all the silicon-aluminate solid waste is coarse aggregate.

[0073] Example 5

[0074] Example 5 of the present invention provides a method for co-preparing building materials from solid waste in the steel industry and carbon dioxide. The specific implementation method is the same as that in Example 1, except that all the silicon-aluminate solid waste is fine aggregate.

[0075] Example 6

[0076] Example 6 of the present invention provides a method for co-preparing building materials from solid waste in the steel industry and carbon dioxide. The specific implementation method is the same as that in Example 1, except that the mass percentage of each component in the mixture in step (1) is: 70% calcium-containing solid waste, 15% silicon-aluminum solid waste, and 15% water.

[0077] Example 7

[0078] Example 7 of the present invention provides a method for co-preparing building materials from solid waste in the steel industry and carbon dioxide. The specific implementation method is the same as that in Example 1, except that the mass percentage of each component in the mixture in step (1) is: 15% calcium-containing solid waste, 70% silicon-aluminum solid waste, and 15% water.

[0079] Example 8

[0080] Example 8 of the present invention provides a method for co-preparing building materials from solid waste and carbon dioxide in the steel industry. The specific implementation method is the same as that in Example 1, except that the vibration frequency of the vibration molding system in step (4) is 2800 times / min and the vibration molding time of the vibration molding system in step (4) is 20s.

[0081] Example 9

[0082] Example 9 of the present invention provides a method for co-preparing building materials from solid waste and carbon dioxide in the steel industry. The specific implementation method is the same as that in Example 1, except that the vibration frequency of the vibration molding system in step (4) is 3200 times / min and the vibration molding time of the vibration molding system in step (4) is 10s.

[0083] Example 10

[0084] Example 10 of the present invention provides a method for co-preparing building materials from solid waste and carbon dioxide in the steel industry. The specific implementation method is the same as that in Example 1, except that the vibration frequency of the vibration molding system in step (4) is 1000 times / min and the vibration molding time of the vibration molding system in step (4) is 30s.

[0085] Example 11

[0086] Example 11 of the present invention provides a method for co-preparing building materials from solid waste and carbon dioxide in the steel industry. The specific implementation method is the same as that in Example 1, except that the vibration frequency of the vibration molding system in step (4) is 5000 times / min and the vibration molding time of the vibration molding system in step (4) is 3s.

[0087] Example 12

[0088] Example 12 of the present invention provides a method for co-preparing building materials from solid waste and carbon dioxide in the steel industry. The specific implementation method is the same as that in Example 1, except that the vibration frequency of the vibration molding system in step (4) is 3000 times / min and the vibration molding time of the vibration molding system in step (4) is 40s.

[0089] Example 13

[0090] Example 13 of the present invention provides a method for the co-preparation of building materials from solid waste and carbon dioxide in the steel industry. The specific implementation method is the same as that in Example 1, except that the filling rate (V / V) of the blank in the reactor in step (5) is 10%.

[0091] Example 14

[0092] Example 14 of the present invention provides a method for the co-production of building materials from solid waste and carbon dioxide in the steel industry. The specific implementation method is the same as that in Example 1, except that the filling rate (V / V) of the blank in the reactor in step (5) is 20%.

[0093] Example 15

[0094] Example 15 of the present invention provides a method for co-preparing building materials from solid waste and carbon dioxide in the steel industry. The specific implementation method is the same as that in Example 1, except that the filling rate (V / V) of the blank in the reactor in step (5) is 30%.

[0095] Example 16

[0096] Example 16 of the present invention provides a method for the co-preparation of building materials from solid waste and carbon dioxide in the steel industry. The specific implementation method is the same as that in Example 1, except that the filling rate (V / V) of the blank in the reactor in step (5) is 50%.

[0097] Example 17

[0098] Embodiment 17 of the present invention provides a method for co-preparing building materials from solid waste in the steel industry and carbon dioxide. The specific implementation method is the same as in Embodiment 1, except that the method for co-preparing building materials from solid waste in the steel industry and carbon dioxide specifically includes the following steps:

[0099] (1) Mix calcium-containing solid waste and silicon-aluminum solid waste to obtain mixed solid waste. Then, send the mixed solid waste and water into a mixing system and mix them evenly to obtain a mixture.

[0100] (2) The mixture is fed into the powder mixing system and stirred until the mixture is uniformly mixed to obtain the powder mixture;

[0101] (3) The powder-mixed material is pressed into a blank by controlling the molding pressure to 10MPa in the static pressure molding system.

[0102] (4) The billet is transported into the reactor by a shuttle car, the reactor door is closed, the carbon dioxide inlet valve is opened, and carbon dioxide gas is introduced until the pressure in the reactor reaches the set value. Then the gas is stopped, the mineralization reaction is carried out for a certain time, the gas is exhausted to atmospheric pressure, and the reactor is opened.

[0103] (5) Once the temperature inside the autoclave drops to 50°C, pull out the transfer vehicle. The product is ready as a finished building material without any curing required.

[0104] Performance testing methods

[0105] 1. Weight Gain Rate: The weight gain rate of the finished building materials prepared in the examples and comparative examples was tested, and the performance test results are shown in Table 1. In this invention, the weight gain rate is expressed as the weight gain rate of the test block (finished building material); the change in mass before and after CO2 curing was determined by the mass weighing method, and the calculation method of the weight gain rate is as follows:

[0106]

[0107] Where ω is the apparent weight gain rate.

[0108] m0 is the dry weight after CO2 compression.

[0109] m1 represents the mass of the specimen after CO2 curing (mass after drying).

[0110] The specific steps are as follows:

[0111] (1) The moisture content w1 of the digested raw material was measured, and the mass of the brick was weighed after pressing. The corresponding dry basis mass m0 in the test block was calculated based on the moisture content after digestion.

[0112] (2) After the mineralization of the test block is completed, the test block is dried to constant weight and its dry basis mass is measured as m1.

[0113] (3) The weight gain rate of the corresponding test block can be obtained by using the above formula.

[0114] The mass was measured using a PTY-B5000 electronic balance with a range of 5 kg and a linear error of ±0.04 g.

[0115] 2. Compressive strength test: Referring to GBT4111-2013 "Test methods for concrete blocks and bricks", the finished bricks prepared in the examples and comparative examples were naturally air-dried for 24 hours to obtain specimens. The compressive strength of the specimens was tested, and the performance test results are shown in Table 1.

[0116] (1) Experimental Procedure

[0117] 1) Measure the length and width of the connection surface or pressure surface of each specimen twice, and take the average value of each, accurate to 1 mm.

[0118] 2) Place 10 specimens flat in the center of the pressure plate and apply the load perpendicular to the pressure surface. The loading should be uniform and stable, without any impact or vibration. The loading rate is (5 ± 0.5) kN / s until the specimen fails. Record the maximum failure load F (in N) for each specimen.

[0119] (2) Calculation of test results: Calculate the compressive strength of 10 specimens according to the following formula, accurate to 0.1MPa.

[0120]

[0121] In the formula f mc —Compressive strength (MPa);

[0122] F—Maximum destructive load (N);

[0123] L—Length (mm) of the pressure-bearing surface (connection surface);

[0124] B—Width of the pressure-bearing surface (connection surface) (mm).

[0125] Calculate the average compressive strength of the three specimens. If the difference between the measured values ​​and their average value is no greater than 15%, then the average value is used as the compressive strength. If any value differs from the average value by more than 15%, this value should be discarded, and the average value should be calculated using the remaining values.

[0126] Table 8

[0127] Example Weight gain rate (%) Compressive strength (MPa) 1 9.73 18.85 2 8.91 17.26 3 6.32 13.47 4 8.97 7.74 5 5.21 7.31 6 7.31 8.74 7 4.21 5.37 8 9.14 18.31 9 8.98 18.54 10 7.75 10.32 11 7.41 12.67 12 6.71 10.42 13 6.41 9.73 14 7.21 11.91 15 8.27 15.37 16 6.17 11.35 17 5.42 12.57

[0128] As shown in Table 8, the building materials prepared according to the formulation of this application in Examples 1-3 have a weight gain rate of over 6.32% and a compressive strength of over 13.47 MPa, indicating that the building materials prepared according to the formulation and method of this application have good carbon sequestration effect and high strength. In Example 3, due to the low content of calcium-containing solid waste and relatively low degree of mineralization, the weight gain rate and compressive strength are relatively low.

[0129] Example 4: Using only coarse silica raw materials, the system lacked fine aggregates, resulting in lower strength of the bonded specimens. Simultaneously, the system had high porosity, and while the carbon fixation rate was not significantly affected, the compressive strength decreased rapidly. Example 5: Using only fine silica raw materials, on the one hand, easily blocked the carbon dioxide diffusion channels in the specimens, leading to a rapid decrease in carbon fixation rate; on the other hand, due to the lack of support from coarse aggregates, the strength improvement after mineralization was limited, resulting in lower compressive strength of the specimens.

[0130] Example 6: Excessive calcium content disrupted the optimal aggregate composition of the system. On one hand, the molded specimens exhibited lower strength; on the other hand, the excessive calcium content led to an excessively high mineralization rate and system temperature. The rapid mineralization reaction occurred on the surface, sealing the external pores of the product and preventing carbon dioxide from penetrating. This reduced the degree of mineralization, resulting in a lower weight gain and reduced product strength. Example 7: Insufficient calcium content reduced the probability of contact between carbon dioxide and calcium elements, leading to a lower mineralization rate and degree of mineralization in the specimens. This resulted in a lower carbon fixation rate and a decrease in compressive strength.

[0131] Example 8 used a vibration frequency of 2800 times / min and a vibration time of 20 seconds, while Example 9 used a vibration frequency of 3200 times / min and a vibration time of 10 seconds. Both examples showed high weight gain and compressive strength, indicating that the corresponding vibration parameters help obtain a green body with uniform component distribution and appropriate density, which is beneficial for subsequent mineralization reactions. Example 10 used a vibration frequency of 1000 times / min and a vibration time of 30 seconds. Although the vibration time was increased after reducing the vibration frequency, the vibration force was too small due to the low vibration frequency. Despite the increased vibration time, the overall effect was not good, resulting in heavy materials accumulating at the bottom and light materials accumulating at the top. The brick body was relatively loose and not dense. Although the degree of mineralization reaction was high and the weight gain of the test block increased, the internal structural strength distribution of the test block was uneven, and the compressive strength of the product after the reaction was low. Example 11 used a vibration frequency of 5000 times / min and a vibration time of 3 seconds. The vibration frequency was too high, resulting in a large excitation force. Although reducing the vibration time did not make the green body too dense, the low vibration time led to poor dispersion of the components within the specimen, uneven distribution of mineralizable substances and pores, and a decrease in the mineralization degree and compressive strength of the specimen. Example 12, at a more optimal vibration frequency, resulted in a higher density of the specimen. Moreover, the excessively long vibration time caused stratification of coarse and fine particles, resulting in an uneven distribution of coarse and fine particles within the specimen. The blockage of pores in the specimen led to a lower degree of mineralization. At the same time, the uneven strength distribution of the specimen resulted in a decrease in the compressive strength of the specimen.

[0132] In Examples 13 and 14, the filling rates of the preforms in the reactor were low, at 10% and 20% respectively. The resulting building materials exhibited low weight gain and compressive strength, indicating that a low filling rate is detrimental to the mineralization reaction. In Example 15, with a filling rate of 30%, the resulting building materials showed superior weight gain and compressive strength. In Example 16, with a filling rate reaching 50%, the weight gain and compressive strength of the resulting building materials decreased significantly. This was mainly because the higher filling rate led to a higher degree of mineralization in the initial stage of the reaction, causing the reactor to heat up quickly to a certain temperature, thus increasing the mineralization reaction rate. The sample block rapidly mineralized on the surface, forming a dense sealing layer that prevented carbon dioxide from diffusing into the interior of the sample block, resulting in a decrease in the degree of mineralization and a significant decrease in compressive strength. This demonstrates that a filling rate of 30-40% resulted in building materials with superior carbon fixation and compressive strength.

[0133] In Example 17, the compression molding method was used. The density of the compressed test block was too high, which blocked the channels for carbon dioxide diffusion. Carbon dioxide could not diffuse into the interior of the test block, thus limiting the occurrence of the mineralization reaction in the system. The degree of mineralization of the test block was reduced. Even if the compaction strength of the test block was high, the low degree of internal mineralization resulted in a low degree of connection between particles, which in turn reduced the compressive strength of the test block.

Claims

1. A method for co-preparing building materials from solid waste and carbon dioxide in the steel industry, characterized in that, The method specifically includes the following steps: (1) Mix calcium-containing solid waste and silicon-aluminum solid waste to obtain mixed solid waste. Then, send the mixed solid waste and water into a mixing system and mix them evenly to obtain a mixture. (2) The mixture is fed into the powder mixing system and stirred until the mixture is uniformly mixed to obtain the powder mixture; (3) The powder mixture is fed into the digestion system and digested for 20-60 minutes to obtain the digested material; (4) The digested material is fed into a vibration molding system to prepare a blank; (5) The billet is fed into the reactor at a certain filling rate, and carbon dioxide gas is introduced to mineralize for a certain time to obtain finished building materials. The self-heating generated during the mineralization process is used to improve the carbon fixation rate and strength of the mineralized products. The mass percentages of each component in the mixture in step (1) are: 25-45% calcium-containing solid waste, 35-60% silicon-aluminum solid waste, and 10-20% water. The mass ratio of water to solid waste in the mixture is 0.1-0.2:

1. The calcium-containing solid waste is steel slag. The vibration frequency of the vibration molding system in step (4) is 1200-4200 times / min, and the vibration molding time of the vibration molding system in step (4) is 2-30s. In step (5), the filling rate (V / V) of the preform in the reactor is 30-40%. The silicon-aluminate solid waste includes coarse aggregate and fine aggregate according to particle size distribution, and the mass ratio of coarse aggregate to fine aggregate is 0.5-1.5:0.6-1.7; The coarse aggregate is recycled aggregate, and the fine aggregate is fine sand; The coarse aggregate has a particle size of 0.5-7 mm; the fine aggregate has a particle size of 0.05-0.6 mm. In step (5), the ventilation rate of carbon dioxide gas is 70-130 m / s. 3 / min; the mineralization reaction time in step (5) is 2-8 hours; the pressure of the mineralization reaction is 0.1-1.2MPa.

2. The method for co-preparing building materials from solid waste and carbon dioxide in the steel industry according to claim 1, characterized in that, The vibration frequency of the vibration molding system in step (4) is 2400-3600 times / min, and the vibration molding time of the vibration molding system in step (4) is 5-20s.

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