Coal gasification slag-steel slag-based high-carbon-storage type filling material and preparation method thereof

Abstract

The invention discloses a coal gasification slag-steel slag-based high-carbon-storage type filling material and a preparation method thereof, and belongs to the field of coal-based solid waste resource utilization and carbon emission reduction. The filling material comprises the following components in parts by weight: 100 parts of a cementing material, 10-20 parts of aggregate and 10-20 parts of water. 38 to 52 parts of aggregate; 24 to 40 parts of water; the cementing material comprises the following raw materials: 65-85 parts of coal gasification slag; 15 to 35 parts of steel slag; and 3.0 to 10.5 parts of a composite exciting agent. According to the method, the coal gasification slag can be consumed on a large scale, CO2 is fixed and stored through the carbonization reaction, and stable storage of CO2 is achieved through engineering application of a filling material; the problems of industrial solid waste treatment, carbon emission control, natural resource consumption, environmental pollution and the like are effectively solved, and good environmental protection benefits and practical values are achieved; the invention provides a new technical path for realizing solid waste resource utilization and carbon neutralization targets.

Description

TECHNICAL FIELD

[0001] The present application relates to a coal gasification slag-steel slag-based high carbon storage type filling material and a preparation method thereof, and belongs to the field of coal-based solid waste resource utilization and carbon emission reduction. BACKGROUND

[0002] Coal gasification slag is a kind of solid waste of slag produced by high-temperature gasification of coal. The main chemical composition of coal gasification slag is SiO2 (30%~60%), Al2O3 (10%~30%), Fe2O3 (5%~20%), CaO (5%~20%) and MgO (2%~10%), which is a potential pozzolanic material. Mechanical grinding activation and chemical activation are the main means to improve the pozzolanic activity of coal gasification slag, and are important methods for its use as a cementitious material. Chinese patent CN117069453A discloses a method for preparing a composite activated coal gasification slag-based cementitious filling material based on a response surface method. The patent shows that the surface area of the coal gasification slag ultra-fine powder obtained after grinding by a ball mill is ≥400 m2 / kg, which can be used as a cementitious part for preparing a filling material; but the problem of continuous accumulation and storage of coal gasification slag is still serious, and only using coal gasification slag to prepare a cementitious part of a filling material cannot fully realize its large-scale reuse. 2

[0003] Steel slag is a kind of metallurgical industrial waste produced in the process of steelmaking. The main chemical composition of steel slag is CaO (40%~50%), SiO2 (10%~15%), FeO (5%~15%), Al2O3 (5%~10%) and MgO (5%~10%), which has similar chemical composition and mineral composition to cement. The content of calcium-containing compounds in steel slag is about 35%~45%, and the high calcium content makes steel slag not only a cementitious material but also has good carbon sequestration capacity. Song Jiayi et al. (Song Jiayi, Li Yan, He Wen, et al. Experimental study on CO2 mineralization curing based on composite cementitious material [J]. Energy Engineering, 2021, 41(3):8.) found that the test piece with a mixing ratio of 50% steel slag and 10% fly ash reached the highest carbon sequestration rate and compressive strength when the remaining water-solid ratio w / s was 0.25; the highest carbon sequestration efficiency was 8.77%, which showed that steel slag could be used as a cementitious part of a filling material and had a good carbon sequestration rate, but the cement content was still as high as 40%, which had high emission and high energy consumption.

[0004] In summary, the present application provides a method for preparing a coal gasification slag-steel slag-based high carbon storage type filling material, which can scale up the consumption of coal gasification slag, realize the resource utilization of the solid waste, achieve the purpose of carbon sequestration and storage, and has excellent carbon sequestration and storage performance. It is an important way to realize the green development of bulk solid waste. SUMMARY

[0005] ​In order to realize the resource utilization of solid waste and control carbon emission, the present application provides a preparation method of coal gasification slag-steel slag-based high-carbon storage type filling material.

[0006] The present application provides a coal gasification slag-steel slag-based high-carbon storage type filling material, which comprises cementing material, aggregate and water, and the weight fractions of the components are as follows: Cementing material: 100 parts; Aggregate: 38 parts to 52 parts; Water: 24 parts to 40 parts; The cementing material comprises the following raw materials: Coal gasification slag: 65 parts to 85 parts; Steel slag: 15 parts to 35 parts; Composite activator: 3.0 parts to 10.5 parts.

[0007] Further, the composite activator is a mixture of carbide slag, anhydrous sodium sulfate, desulfurization gypsum and sodium hydroxide, wherein the mass ratio of carbide slag, anhydrous sodium sulfate, desulfurization gypsum and sodium hydroxide is (0.5-2.5):(1.0-3.0):(1.0-3.0):(0.5-2.0); the main component of carbide slag is Ca(OH)2, the main component of desulfurization gypsum is CaSO4·2H2O, and the main component of anhydrous sodium sulfate is Na2SO4, which can provide Ca 2+ , SO4 2- and alkaline environment for the activation reaction of the material, which is beneficial to the activation reaction and carbon storage and sequestration of the material and improves the strength of the material; but the alkalinity provided by them is weak, and after adding NaOH, the pH value of the reaction environment is improved. Under the condition of high pH value, the chemical bonds of some potential active substances in the filling material are more easily broken, so that the reaction activity of these substances is significantly improved, and the hydration reaction is promoted. In the early stage of the reaction, the strong alkalinity can accelerate the reaction, so that the material quickly coagulates; in the later stage of the reaction, through the interaction with other components, the reaction tends to be stable, avoiding the internal structure defects caused by too fast reaction, and ensuring the long-term stability and durability of the filling material.

[0008] Further, the aggregate is composed of coal gasification slag with different particle size ranges, wherein the coal gasification slag with a particle size of 0.83 mm to 6 mm is used as fine aggregate, the coal gasification slag with a particle size of 6 mm to 10 mm is used as medium aggregate, and the coal gasification slag with a particle size of more than 10 mm is used as coarse aggregate, and the mass ratio of the fine aggregate, the medium aggregate and the coarse aggregate is (8-12):(15-20):(15-20).

[0009] The application provides a preparation method of a coal gasification slag-steel slag-based high-carbon-storage type filling material. Step 1: The coal gasification slag and the steel slag are placed into an oven for drying, and the coal gasification slag and the steel slag with a particle size of less than or equal to 0.83 mm are screened out after drying and are subjected to ball milling respectively, and the coal gasification slag and the steel slag after ball milling are screened again to remove impurities and parts with a relatively large particle size, so that the coal gasification slag and the steel slag with a particle size of less than or equal to 0.075 mm are obtained. Step 2: The coal gasification slag with a particle size of more than 0.83 mm is dried, and the coal gasification slag with a particle size ranging from 0.83 mm to 6 mm is screened out as fine aggregate, the coal gasification slag with a particle size ranging from 6 mm to 10 mm is screened out as medium aggregate, and the coal gasification slag with a particle size of more than 10 mm is used as coarse aggregate. Step 3: The carbide slag, anhydrous sodium sulfate, desulfurization gypsum and sodium hydroxide are used as a composite activator to mix and stir with the coal gasification slag and the steel slag ground in step 1, so that a cementitious material is obtained. Step 4: The fine aggregate, the medium aggregate, the coarse aggregate and the cementitious material in step 2 are mixed and stirred according to a proportion, and then water is added for fully stirring, so that the filling material is obtained. Step 5: The filling material is poured and carbonized, and the filling material after pouring is cured, so that the coal gasification slag-steel slag-based high-carbon-storage type filling material is prepared, which can achieve the purpose of carbon sequestration and carbon storage and improve the mechanical properties of the material.

[0010] Further, the oven temperature in step 1 is 115 DEG C, and the drying time is 120 minutes. The rotating speed of the steel ball mill is 550 r / min, and the ball milling time is 80 min.

[0011] Further, the composite activator in step 3 can react with the chemical components in the coal gasification slag and the steel slag in the hydration process to generate hydration products with cementitious properties, so as to enhance the strength and durability of the material. The chemical reaction formula is as follows: Ca(OH)2 + SiO2 + nH2O → CaO·SiO2·(n + 1)H2O; Ca(OH)2+ Al2O3 + nH2O → CaO·Al2O3·(n + 1)H2O; Ca(OH)2+ CaO·SiO2 + nH2O → 2CaO·SiO2·(n + 1)H2O; Ca(OH)2+ CaO·Al2O3 + nH2O → 2CaO·Al2O3·(n + 1)H2O; Na2SO4 + CaO·SiO2→ CaSO4 + Na2SiO3; CaSO4·2H2O + Fe2O3→ CaSO4 + Fe2O3·2H2O; 2NaOH + SiO2→ Na2SiO3 + H2O; 2NaOH + Al2O3 + 3H2O→ 2Na2[Al(OH)4]; 2NaOH + CaO·Al2O3·10H2O→ 2NaAlO2 + Ca(OH)2+ 10H2O.

[0012] Further, after the water is added to prepare the filling material in step 4, the compressive strength and fluidity of the filling material reach an optimal balance. The aggregate matching between different particle sizes optimizes the particle size distribution of the material, the fine aggregate fills the gap between the aggregates, and the material density and stability are improved; the medium aggregate and coarse aggregate provide the main support and skeleton function. This matching not only improves the overall performance of the material, but also enhances its durability and compressive strength.

[0013] Further, the mold used for pouring the filling material in step 5 is a cube with a side length of 40 mm. After pouring, the filling material is first placed in a constant temperature and pressure curing box for pre-curing. The pre-curing time is 1 day to 6 days, the temperature in the curing box during pre-curing is 20°C to 30°C, and the humidity is 90% to 95% RH. After pre-curing, the filling material is placed in a carbonation reaction kettle for carbonation curing. The carbonation curing time is 6 days to 10 days, the carbonation curing atmosphere is power plant flue gas, the CO2 concentration is 12% to 16%, and the curing pressure is 0.2 MPa to 1.8 MPa. After carbonation curing, continue regular curing for 28 days, and the regular curing conditions are the same as pre-curing. After curing, the carbon sequestration capacity of the material can reach 150 kg / t to 200 kg / t, and the coal gasification slag content is about 58% to 78%. During the carbonation curing process, the coal gasification slag is rich in active components such as silicates and aluminates, which will undergo hydration reactions during the cementation process to generate hydration products with cementing properties. The chemical reaction formula is: CaO + H2O→ Ca(OH)2; SiO2+ Ca(OH)2 + H2O→ CaO·SiO2·2H2O; Al2O3 + 2Ca(OH)2 + H2O→ 2CaO·Al2O3·3H2O.

[0014] In addition, in this step, the steel slag contains a large amount of free CaO, Ca(OH)2, NaOH and MgO, which will react with CO2 to form CaCO3, thereby achieving carbon sequestration. The chemical reaction formula is: CaO + H2O → Ca(OH)2; Ca(OH)2 + CO2 → CaCO3 + H2O; 2NaOH + CO2 → Na2CO3 + H2O; MgO + CO2 → MgCO3; CaO·SiO2 + CO2 → CaCO3 + SiO2; MgO·SiO2 + CO2 → MgCO3 + SiO2。

[0015] The chemical composition of coal gasification slag and steel slag is very similar to that of fly ash, and the method for calculating the carbon fixation amount is the same as that of fly ash sample according to Ren Wuan et al (Ren Wuan, Tang Dong, Ju Kai, et al. Fly ash slurry deamination and carbon fixation coupling paste material preparation method construction and performance evaluation [J / OL]. Journal of Coal, 1-15 [2025-05-22].): ; m CO2 The mass of carbon dioxide fixed per kilogram of filling material in a single experiment (g / kg); P is the standard atmospheric pressure, Pa, and is 1.013*10 5 ; V CO2 The total volume of carbon dioxide fixed by the filling material in a single experiment, L; M is the molar mass of CO2, g / mol, and is 44; R is the gas constant, J / (mol·K), and is 8.31; T is the absolute temperature scale, and the experiment is carried out at room temperature of 25℃, and is 298.15; m 充 The mass of filling material used in a single experiment, g; V CO2 can be calculated according to the gas flow and CO2 concentration in the carbonation reactor. The experimental data is brought in and the unit of g / kg is converted to kg / t to obtain the carbon fixation amount of the filling material. The carbon fixation amount of the filling material provided by the present application ranges from 150 kg / t to 200 kg / t.

[0016] The beneficial effects of the present application are: (1) The present application uses fine particle coal gasification slag and steel slag as cementing materials, and coarse particle coal gasification slag as aggregate to prepare carbon storage type filling materials, which has simple preparation process, low cost, can scale up the consumption of coal gasification slag, and realizes the resource utilization of the solid waste; improves the resource utilization of coal gasification slag, and realizes the scale utilization of coal gasification slag, effectively solves the problems of industrial solid waste treatment, carbon emission control, natural resource consumption and environmental pollution, and has good environmental protection benefit and practical value; (2) The present application uses fine particle coal gasification slag and steel slag as cementitious materials, uses coarse particle coal gasification slag as aggregate, and prepares filling materials; the raw material ratio, pre-curing and carbonization curing time are optimized to prepare carbon storage type filling materials with excellent mechanical properties and carbon storage functions; through pre-curing and carbonization curing of the filling materials, carbonization reaction occurs, and the carbon sequestration amount can reach 150 kg / t to 200 kg / t, and through engineering application of the filling materials, carbon is permanently sealed underground; it can be used in the field of mine filling, and provides a new technical path for solid waste resource utilization and realization of carbon neutralization target; (3) In the carbonization curing process, CaO, MgO and other components contained in the coal gasification slag can chemically react with CO2, and the fine particle steel slag as cementitious material contains a large amount of CaO, SiO2, MgO and other components, which increases the carbon sequestration effect; the porosity of the filling material is reduced, and the uniaxial compressive strength, flexural strength and durability are further improved, so that the carbon storage type filling material with excellent mechanical properties and carbon storage functions is prepared, and the purpose of carbon sequestration and storage is achieved; (4) The present application innovatively uses coal gasification slag with different particle sizes to realize resource utilization of the solid waste while large-scale consumption of coal gasification slag; firstly, fine particle coal gasification slag with a particle size of 0.075 mm or less is used as cementitious material, and coal gasification slag with a particle size range of 0.83 mm to 6 mm is used as fine aggregate, coal gasification slag with a particle size range of 6 mm to 10 mm is used as medium aggregate, and coal gasification slag with a particle size greater than 10 mm is used as coarse aggregate; the particle size distribution of the aggregate can improve the strength of the material, and also effectively improve the flowability and pumpability of the material, which can improve the construction efficiency and quality in actual application; the fine aggregate can fill the voids between the coarse aggregate, reduce the porosity, and improve the material density and strength; the medium aggregate is between the fine aggregate and the coarse aggregate, and plays a supporting and supporting role to improve the compressive strength of the material; the coarse aggregate plays a skeleton role, which helps to improve the compressive strength and tensile strength of the material. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a process flow chart of the present application; Figure 2 is the compressive strength of the filling material prepared in Example 1; Figure 3 is the compressive strength of the filling material prepared in Example 2; Figure 4 is the compressive strength of the filling material prepared in Example 3; Figure 5 is the phenolphthalein chart of the filling material before and after carbonization of the comparative example; Figure 6 is the phenolphthalein chart of the filling material before and after carbonization of Example 1; Figure 7The phenolphthalein chart of the filling material of Example 2 before and after carbonization; Figure 8 The phenolphthalein chart of the filling material of Example 3 before and after carbonization; Figure 9 The TG-DTG chart of the filling material of the comparative example after carbon fixation; Figure 10 The TG-DTG chart of the filling material of Example 1 after carbon fixation; Figure 11 The TG-DTG chart of the filling material of Example 2 after carbon fixation; Figure 12 The TG-DTG chart of the filling material of Example 3 after carbon fixation; Figure 13 The XRD spectrum of the filling material of Example 1 before and after carbonization and curing; Figure 14 The XRD spectrum of the filling material of Example 2 before and after carbonization and curing; Figure 15 The XRD spectrum of the filling material of Example 3 before and after carbonization and curing; Figure 16 The FTIR spectrum of the filling material of Example 1 before and after carbonization and curing; Figure 17 The FTIR spectrum of the filling material of Example 2 before and after carbonization and curing; Figure 18 The FTIR spectrum of the filling material of Example 3 before and after carbonization and curing. DETAILED DESCRIPTION

[0018] The present application will be further illustrated by the following comparative examples and examples, but is not limited to the following examples.

[0019] The present application provides a method for preparing carbon storage type filling material, which uses fine particle coal gasification slag and steel slag as cementitious material and coarse particle coal gasification slag as aggregate; the process flow is as shown in Figure 1 The method specifically comprises the following steps: Step 1: dry the coal gasification slag and the steel slag, screen out the coal gasification slag and the steel slag with particle size ≤0.83 mm after drying and respectively perform ball milling, and screen the ball-milled coal gasification slag and steel slag again to remove impurities and parts with relatively large particle size, to obtain coal gasification slag and steel slag with particle size range below 0.075 mm; Step 2: dry the coal gasification slag with particle size >0.83 mm, screen to obtain coal gasification slag with particle size range of 0.83 mm~6 mm as fine aggregate, coal gasification slag with particle size range of 6 mm~10 mm as medium aggregate, and coal gasification slag above 10 mm as coarse aggregate after drying; Step 3: taking carbide slag, anhydrous sodium sulfate, desulfurized gypsum and sodium hydroxide as a composite activator, mixing and stirring the ground coal gasification slag and steel slag in step 1 to obtain a cementitious material; Step 4: selecting the fine aggregate, medium aggregate, coarse aggregate and cementitious material in step 2, mixing and stirring them according to a proportion, then adding water and fully stirring to obtain a filling material; Step 5: pouring the filling material, and curing the poured filling material to achieve the purpose of carbon sequestration and storage, and improve the mechanical properties of the material.

[0020] The following comparative examples are used to prove the superiority of the present application, and the specific embodiments of the present application are introduced through the description of the examples. In the examples, different composite activators are compared.

[0021] Comparative example: Coal gangue from a coal preparation plant and electric furnace steel slag from a steel plant are selected. The main chemical components of the two materials are analyzed by X-ray fluorescence spectroscopy (XRF) and are shown in Table 1.

[0022] Table 1 Main chemical components (wt.%) of the two raw materials in the comparative example

[0023] The steel slag is placed in an oven at 115°C and dried for 120 minutes. After drying, the steel slag is sieved through a 20-mesh sieve to obtain steel slag with a particle size of ≤0.83 mm. The sieved steel slag is placed in a ball mill and ball milled. The ball milled steel slag powder is sieved through a 200-mesh sieve to remove impurities and larger particles, obtaining fine steel slag with a particle size range of ≤0.075 mm.

[0024] The coal gangue is placed in an oven and dried. The dried part of the coal gangue is broken by a jaw crusher, and then sieved through a 20-mesh, 6-mm and 10-mm sieve. The sieved coal gangue with a particle size range of 0.83 mm to 6 mm is used as fine aggregate, the coal gangue with a particle size range of 6 mm to 10 mm is used as medium aggregate, and the coal gangue with a particle size above 10 mm is used as coarse aggregate.

[0025] The carbide slag, sodium sulfate and desulfurized gypsum are used as a composite activator to mix and stir with the fine steel slag with a particle size range of ≤0.075 mm to obtain a cementitious material. The weight fraction of the cementitious material is 100 parts, the fine steel slag in the cementitious part is 95 parts, and the composite activator is 5 parts. In the composite activator, the carbide slag is 1 part, the sodium sulfate is 2 parts, and the desulfurized gypsum is 2 parts.

[0026] Aggregate made from coal gangue is mixed evenly with a cementitious material containing a composite activator and fine-grained steel slag powder, and then water is added in appropriate proportions to prepare the filling material. The mass ratio of cementitious material, aggregate, and water is 4:4:2; and the mass ratio of fine aggregate, medium aggregate, and coarse aggregate in the aggregate is 5:3:2.

[0027] The filling material was poured into a 40mm-per-side cube mold and pre-cured for two days in a constant temperature and pressure curing chamber at 22°C and 95% RH. After pre-curing, the filling material was placed in a carbonization reactor for carbonization curing for three days. The atmosphere used for carbonization curing was power plant flue gas with a CO2 concentration of 14% and a curing pressure of 1.2 MPa. Conventional curing continued for 28 days. Figure 5 The phenolphthalein coating diagram of the filling material without carbonization curing and after carbonization curing is shown in the comparative example. It can reflect the carbonization depth of the specimen. The smaller the purple area, the greater the carbonization depth of the specimen. Figure 5 The carbonization depth is significantly shallower than that of the embodiment, that is, the carbon fixation and storage capacity of the comparative example is weaker.

[0028] The CO2 mass loss in the filling material after high temperature carbon fixation was measured using a thermogravimetric analyzer. Figure 9 As shown, according to the DTG curve, it can be seen that the decomposition temperature of CaCO3 in the heat-activated filling material in the thermometer is approximately 580°C~760°C, and the carbon fixation amount of the filling material after carbonization curing is 98kg / t, which is obviously lower than the carbon fixation amount of the embodiment of the present invention. Example 1

[0029] The coal gasification slag was selected from a coal gasification plant, and the steel slag was selected from an electric furnace slag from a steel mill. The main chemical compositions of the two materials were analyzed by X-ray fluorescence spectroscopy (XRF) and are shown in Table 2.

[0030] Table 2 Main chemical compositions of the two raw materials in Example 1 (wt.%)

[0031] The coal gasification slag and steel slag were dried in an oven at 115°C for 120 minutes. After drying, they were sieved through a 20-mesh sieve to obtain coal gasification slag and steel slag with a particle size of ≤0.83mm. The sieved coal gasification slag and steel slag were respectively placed in a ball mill for ball milling. The ball-milled coal gasification slag powder and steel slag powder were then sieved through a 200-mesh sieve to remove impurities and larger particles, obtaining fine-grained coal gasification slag and steel slag with a particle size of less than 0.075mm.

[0032] The coarse-grained coal gasification slag with particle size > 0.83 mm is dried in an oven, and then screened by using a 20-mesh and 6-mm sieve to obtain the coal gasification slag with particle size ranging from 0.83 mm to 6 mm as fine aggregate, the coal gasification slag with particle size ranging from 6 mm to 10 mm as medium aggregate, and the coal gasification slag with particle size greater than 10 mm as coarse aggregate.

[0033] The fine-grained coal gasification slag and steel slag with particle size less than 0.075 mm are mixed and stirred with calcium carbide slag, sodium sulfate, desulfurization gypsum and sodium hydroxide as a composite activator to obtain a cementitious material. The cementitious material is 100 parts by weight, the fine-grained coal gasification slag is 66 parts by weight, the steel slag is 30 parts by weight, and the composite activator is 4 parts by weight. In the composite activator, the calcium carbide slag is 1 part by weight, the sodium sulfate is 1 part by weight, the desulfurization gypsum is 1 part by weight, and the sodium hydroxide is 1 part by weight.

[0034] The fine aggregate, medium aggregate and coarse aggregate prepared from the coarse-grained coal gasification slag are mixed and stirred with the cementitious material composed of the composite activator, fine-grained coal gasification slag powder and steel slag powder to obtain a filling material. The mass ratio of the cementitious material, aggregate and water is 7:3:2. The mass ratio of the fine aggregate, medium aggregate and coarse aggregate in the aggregate is 10:18:18.

[0035] The filling material is poured into a cubic mold with a side length of 40 mm. The poured filling material is first placed in a constant temperature and pressure curing box for pre-curing for 2 days. The temperature in the curing box is 22℃, and the humidity is 95% RH. After pre-curing, the filling material is placed in a carbonation reaction kettle for carbonation curing. The carbonation curing time is 8 days, the carbonation curing atmosphere is the flue gas discharged from a power plant, the CO2 concentration is 14%, and the curing pressure is 1.2 MPa. After carbonation curing, the filling material is continuously cured for 28 days, and a control group with only conventional curing is set. During the curing period, the hydraulic pressure testing machine is used to test the compressive strength of the carbonation cured and conventionally cured filling materials at 3d, 7d and 28d, respectively. As shown in Figure 2 The 28d compressive strength of the carbonation cured filling material is 21.8 MPa, which is 3.1 MPa higher than that of the filling material without carbonation curing. The pozzolanic activity reaches the requirement. Figure 6 The phenolphthalein coating diagram of the filling material without carbonation curing and with carbonation curing can reflect the carbonation depth of the test piece. The smaller the area of the purple region, the greater the carbonation depth of the test piece.

[0036] The CO2 mass loss in the filling material after high-temperature carbon sequestration is measured by using a thermogravimetric analyzer. As shown in Figure 10 According to the DTG curve, the decomposition temperature of CaCO3 in the filling material in the thermal analyzer is about 565℃~754 ℃. The carbon sequestration amount of the carbonation cured filling material can reach 170 kg / t, and the content of coal gasification slag in the material is 72%.

[0037] Figure 13 and Figure 16 XRD and FTIR spectra of the filling material of the present embodiment before and after activation of carbon sequestration, respectively. The crystal structure, phase composition, etc. of the material can be obtained through the XRD spectrum, and the XRD spectra of the material before and after carbon sequestration can reflect the phase change and crystal structure change thereof during carbon sequestration. Figure 13 It can be reflected that a large amount of calcite crystals and mayenite are generated after carbonation curing of the material. Calcite is a calcium carbonate mineral, and its large amount of production also indicates that the material has superior carbon sequestration and storage performance; mayenite has very high strength, and its large amount of production indicates that the mechanical properties of the material are further improved after carbonation curing. Figure 16 The peak values in the FTIR spectra can indicate the chemical bonds and functional groups present in the material, and the change in the peak values before and after carbonation curing also indicates that the chemical bonds and functional groups in the material have reacted with CO2, and also indicates that the material has the ability of carbon sequestration and storage. Example 2

[0038] The coal gasification slag was selected from the coal gasification slag of a certain coal gasification plant, and the steel slag was selected from the electric furnace steel slag of a certain steel plant. The main chemical components of the two materials were analyzed by X-ray fluorescence spectroscopy (XRF), as shown in Table 3.

[0039] Table 3 Main chemical components (wt.%) of the two raw materials in Example 2

[0040] The coal gasification slag and the steel slag were respectively placed in an oven at 115°C for 120 minutes, and after drying, they were sieved with a 20-mesh sieve to obtain coal gasification slag and steel slag with a particle size of ≤0.83 mm. The sieved coal gasification slag and steel slag were respectively placed in a ball mill for ball milling, and then the ball-milled coal gasification slag powder and steel slag powder were sieved with a 200-mesh sieve to remove impurities and larger particles, thereby obtaining fine coal gasification slag and steel slag with a particle size range of ≤0.075 mm.

[0041] The coarse coal gasification slag with a particle size of >0.83 mm was placed in an oven for drying, and then sieved with a 20-mesh and 6-mm sieve, thereby obtaining coal gasification slag with a particle size range of 0.83 mm-6 mm as fine aggregate, coal gasification slag with a particle size range of 6 mm-10 mm as medium aggregate, and coal gasification slag with a particle size of >10 mm as coarse aggregate.

[0042] A cementitious material is prepared by mixing carbide slag, sodium sulfate, desulfurized gypsum, and sodium hydroxide as a composite activator with ground fine-grained coal gasification slag and steel slag with a particle size range of less than 0.075 mm and stirring them uniformly. The cementitious material comprises 68 parts of fine-grained coal gasification slag, 25 parts of steel slag, and 7 parts of the composite activator, while the composite activator comprises 1.5 parts of carbide slag, 2.5 parts of sodium sulfate, 1.5 parts of desulfurized gypsum, and 1.5 parts of sodium hydroxide, based on a weight ratio of 100 parts.

[0043] Fine aggregate, medium aggregate, and coarse aggregate made from coarse coal gasification slag, along with a cementitious material containing a composite activator, fine coal gasification slag powder, and steel slag powder, are mixed evenly and then water is added in appropriate proportions to prepare the filling material. The mass ratio of cementitious material, aggregate, and water is 7:3:2; and the mass ratio of fine aggregate, medium aggregate, and coarse aggregate in the aggregate is 10:18:18.

[0044] The filling material is poured into a cube mold with a side length of 40mm. The poured filling material is first placed in a constant temperature and constant pressure curing box for pre-curing for 2 days. The temperature in the curing box is 22°C and the humidity is 95% RH. After pre-curing, the filling material is placed in a carbonization reactor for carbonization curing. The carbonization curing time is 6 days. The carbonization curing atmosphere is the flue gas emitted by the power plant, the CO2 concentration is 14%, and the curing pressure is 1.2MPa. After the carbonization curing is completed, conventional curing is continued for 28 days. A control group with only conventional curing is also set up. During the curing period, a hydraulic pressure testing machine is used to perform 3d, 7d, and 28d compressive strength tests on the carbonization-cured and conventionally cured filling materials, respectively. Figure 3 As shown in the figure, the 28d compressive strength of the filling material after mineralization curing is 21.3MPa, which is 2.9MPa higher than the 28d compressive strength of the filling material without carbonization curing, and its pozzolanic activity meets the requirements. Figure 7 This is the phenolphthalein coating diagram of the filling material before and after carbonization curing. It can reflect the carbonization depth of the specimen. The smaller the purple area, the greater the carbonization depth of the specimen.

[0045] The CO2 mass loss in the filling material after high temperature carbon fixation was measured using a thermogravimetric analyzer. Figure 11 As shown in the figure, according to the DTG curve, it can be seen that the decomposition temperature of CaCO3 in the heat activated filling material in the thermometer is approximately 561℃~752℃, the carbon fixation amount of the filling material after carbonization curing can reach 168kg / t, and the gasification slag content in the material is 71%.

[0046] Figure 14 and Figure 17The XRD and FTIR spectra of the filling material of the present embodiment before and after carbonation are shown in FIGS. 1 and 2, respectively. The XRD spectrum can provide information about the crystal structure and phase composition of the material. The XRD spectra of the material before and after carbonation can reflect the phase transition and changes in the crystal structure of the material during carbonation. Figure 14 It can be seen that a large amount of calcite crystals and mayenite are generated after carbonation. Calcite is a calcium carbonate mineral, and its large amount of production also indicates that the material has excellent carbon sequestration and storage performance. Mayenite has high strength, and its large amount of production indicates that the mechanical properties of the material are further improved after carbonation. Figure 17 The peaks in FIG. 2 can indicate the chemical bonds and functional groups present in the material. Changes in the peaks before and after carbonation also indicate that the chemical bonds and functional groups in the material have reacted with CO2, and that the material has the ability to sequester and store carbon. Example 3

[0047] The coal gasification slag was selected from the coal gasification slag of a certain coal gasification plant, and the steel slag was selected from the electric furnace steel slag of a certain steel plant. The main chemical components of the two materials were analyzed by X-ray fluorescence spectroscopy (XRF), as shown in Table 4.

[0048] Table 4 Main chemical components (wt.%) of the two raw materials in Example 3

[0049] The coal gasification slag and the steel slag were placed in an oven at 115°C for 120 minutes. After drying, the sieved coal gasification slag and steel slag with a particle size of ≤0.83 mm were obtained. The sieved coal gasification slag and steel slag were placed in a ball mill for ball milling. The ball-milled coal gasification slag powder and steel slag powder were sieved with a 200-mesh sieve to remove impurities and larger particles, resulting in fine coal gasification slag and steel slag with a particle size range of ≤0.075 mm.

[0050] The coarse coal gasification slag with a particle size of >0.83 mm was placed in an oven for drying, and then sieved with a 20-mesh and 6-mm sieve. The sieved coal gasification slag with a particle size range of 0.83 mm-6 mm was used as fine aggregate, the coal gasification slag with a particle size range of 6 mm-10 mm was used as medium aggregate, and the coal gasification slag with a particle size of >10 mm was used as coarse aggregate.

[0051] The fine coal gasification slag and steel slag with a particle size range of ≤0.075 mm were mixed with calcium carbide slag, sodium sulfate, desulfurization gypsum, and sodium hydroxide as a composite activator to obtain a cementitious material. The weight fraction of the cementitious material was 100 parts, the fine coal gasification slag was 71 parts, the steel slag was 20 parts, and the composite activator was 9 parts. In the composite activator, the calcium carbide slag was 2.5 parts, the sodium sulfate was 2.5 parts, the desulfurization gypsum was 2.5 parts, and the sodium hydroxide was 1.5 parts.

[0052] The fine aggregate, the medium aggregate, the coarse aggregate and the cementitious material containing the composite activator, the fine coal gasification slag powder and the steel slag powder are prepared into the filling material by adding water in proportion after being stirred uniformly. The mass ratio of the cementitious material, the aggregate and the water is 7:3:2. The mass ratio of the fine aggregate, the medium aggregate and the coarse aggregate in the aggregate is 10:18:18.

[0053] The filling material is poured into a cube mold with a side length of 40 mm. The poured filling material is first placed in a constant temperature and pressure curing box for pre-curing for 2 days. The temperature in the curing box is 22°C and the humidity is 95% RH. After pre-curing, the filling material is placed in a carbonization reaction kettle for carbonization curing. The carbonization curing time is 10 days. The carbonization curing atmosphere is the flue gas discharged by a power plant, the CO2concentration of which is 14%, and the curing pressure is 1.2 MPa. After the carbonization curing is completed, the filling material is continuously cured regularly for 28 days. A control group with only regular curing is set. During the curing period, the hydraulic pressure testing machine is used to test the compressive strength of the carbonization cured and regularly cured filling materials at 3d, 7d and 28d, respectively, as shown in FIG. 2. The 28d compressive strength of the carbonization cured filling material is 21.7 MPa, which is 4.1 MPa higher than that of the filling material without carbonization curing. The pozzolanic activity of the filling material reaches the requirement. Figure 4 Figure 8 The phenolphthalein coating diagram of the filling material without carbonization curing and the carbonization cured filling material is shown in FIG. 3. The diagram can reflect the carbonization depth of the test piece. The smaller the area of the purple region, the greater the carbonization depth of the test piece.

[0054] The mass loss of CO2 in the filling material after high-temperature carbon sequestration is measured by using a thermal gravimetric analyzer, as shown in FIG. 4. According to the DTG curve, the decomposition temperature of CaCO3 in the thermal activation filling material in the thermal calorimeter is about 561°C~752 ℃. The carbon sequestration amount of the carbonization cured filling material can reach 168 kg / t, and the content of the coal gasification slag in the material is 71%. Figure 12

[0055] Figure 15 and Figure 18 respectively represent the XRD spectrum and the FTIR spectrum of the filling material of the present embodiment before and after activation and carbon sequestration. The XRD spectrum can obtain the crystal structure, phase composition and other information of the material. The XRD spectra of the material before and after carbon sequestration can reflect the phase change and the change of the crystal structure in the carbon sequestration process. Figure 15 It can be reflected that a large amount of calcite crystals and mayenite are generated after the carbonization curing of the material. Calcite is a calcium carbonate mineral. The large amount of generation of calcite indicates that the material has excellent carbon sequestration and storage performance. Mayenite has very high strength. The large amount of generation of mayenite indicates that the mechanical properties of the material are further improved after the carbonization curing. Figure 18 ​​The peak in the spectrum can indicate the chemical bond and functional group in the material. The change of the peak before and after carbonization indicates that the chemical bond and functional group in the material reacts with CO2, and also indicates that the material has the ability of carbon fixation and storage.

Claims

1. A coal gasification slag-steel slag-based high carbon storage filling material, characterized by: Including cementitious materials, aggregates and water, the weight parts of each component are: Cementitious material: 100 parts; Aggregate: 38~52 parts; Water: 24~40 parts; The gelling material comprises the following raw materials: Coal gasification slag: 65 to 85 parts; Steel slag: 15 to 35 parts; Composite activator: 3.0 to 10.5 parts; The carbon fixation capacity of the filling material reaches 150kg / t~200kg / t.

2. The coal gasification slag-steel slag-based high carbon storage filling material according to claim 1, characterized in that: The composite activator is a mixture of carbide slag, anhydrous sodium sulfate, desulfurized gypsum and sodium hydroxide, wherein the mass ratio of carbide slag, anhydrous sodium sulfate, desulfurized gypsum and sodium hydroxide is: (0.5-2.5): (1.0-3.0): (1.0-3.0): (0.5-2.0).

3. The coal gasification slag-steel slag-based high carbon storage filling material according to claim 1, characterized in that: The aggregate is composed of coal gasification slag with different particle size ranges, wherein the coal gasification slag with a particle size of 0.83 mm to 6 mm is used as fine aggregate, the coal gasification slag with a particle size of 6 mm to 10 mm is used as medium aggregate, and the coal gasification slag with a particle size of more than 10 mm is used as coarse aggregate.

4. The coal gasification slag-steel slag-based high carbon storage filling material according to claim 3, characterized in that: The mass ratio of the fine aggregate, medium aggregate and coarse aggregate is (8-12): (15-20): (15-20).

5. A method for preparing the coal gasification slag-steel slag-based high carbon storage filling material according to any one of claims 1 to 4, characterized in that The steps include: Step 1: Place the coal gasification slag and steel slag in an oven for drying. After drying, screen out the coal gasification slag and steel slag with a particle size of ≤0.83 mm and ball mill them separately. Screen the ball-milled coal gasification slag and steel slag again to remove impurities and larger particles contained therein, obtaining coal gasification slag and steel slag with a particle size range of less than 0.075 mm. Step 2: Dry the coal gasification slag with a particle size greater than 0.83 mm, and screen it after drying to obtain coal gasification slag with a particle size range of 0.83 mm to 6 mm as fine aggregate, coal gasification slag with a particle size of 6 mm to 10 mm as medium aggregate, and coal gasification slag larger than 10 mm as coarse aggregate; Step 3: Carbide slag, anhydrous sodium sulfate, desulfurized gypsum and sodium hydroxide are used as a composite activator, mixed with the coal gasification slag and steel slag ground in step 1, and stirred to obtain a cementitious material; Step 4: Select the fine aggregate, medium aggregate, coarse aggregate and cementitious material in step 2 and mix them in proportion and stir them evenly, then add water and stir them thoroughly to obtain filling material; Step 5: pouring the filling material and curing the poured filling material to obtain a coal gasification slag-steel slag-based high carbon storage filling material.

6. The method for preparing the coal gasification slag-steel slag-based high carbon storage filling material according to claim 5, characterized in that: The oven temperature in step 1 is 115° C., and the drying time is 120 minutes; the speed of the steel ball mill is 550 r / min, and the ball milling time is 80 minutes.

7. The method for preparing the coal gasification slag-steel slag-based high carbon storage filling material according to claim 5, characterized in that: The mold used for pouring the filling material in step 5 is a cube with a side length of 40 mm. The poured filling material is first placed in a constant temperature and pressure curing box for pre-curing, and the pre-curing time is 1 day to 6 days. After pre-curing, the filling material is placed in a carbonization reactor for carbonization curing, and the carbonization curing time is 6 days to 10 days. After the carbonization curing is completed, conventional curing is continued for up to 28 days, and the conventional curing conditions are the same as those for pre-curing.

8. The method for preparing the coal gasification slag-steel slag-based high carbon storage filling material according to claim 7, characterized in that: During pre-curing, the temperature in the curing box is 20℃~30℃ and the humidity is 90%~95% RH.

9. The method for preparing the coal gasification slag-steel slag-based high carbon storage filling material according to claim 7, characterized in that: The atmosphere for carbonization curing is the flue gas emitted by a power plant, with a CO2 concentration of 12%~16% and a curing pressure of 0.2 MPa~1.8 MPa.

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