A carbon sequestration treatment method for reducing free calcium oxide in steel slag by using steelmaking waste gas CO2

Abstract

The present application relates to solid waste resource utilization and carbon capture and utilization technical field, disclose a kind of using steelmaking waste gas to reduce the carbon sequestration treatment method of free calcium oxide of steel slag, comprising: steel slag, desulfurization gypsum, papermaking caustic white mud, waste building gypsum board powder and blast furnace water quenching slag are proportioned according to mass ratio, with mine acid wastewater to regulate alkaline slurry, into steelmaking waste gas and carry out wet carbonization disposal;During carbonization disposal, caustic white mud superfine particle is used as heterogeneous nucleation seed to accelerate f-CaO carbonization, three-way cascade supply guarantees uniform formation of ettringite, and mineral powder C-S-H gel is coated paper fiber and is converted into reinforcing phase;Carbonization product is obtained by pressure filtration dewatering and low-temperature drying.The present application realizes permanent mineralization and immobilization of steelmaking waste gas and efficient and complete digestion of f-CaO of steel slag, and multiple types of industrial solid waste and mine acid wastewater are disposed simultaneously, and the product can be used for mine filling and roadbed stabilizing material.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization and carbon capture and utilization technology, and more specifically, it relates to a method for utilizing steelmaking waste gas. Carbon fixation treatment method to reduce free calcium oxide in steel slag. Background Technology

[0002] Steel smelting produces a large amount of steel slag as a byproduct, containing 5%–15% free calcium oxide (f-CaO). f-CaO slowly decomposes and expands in humid environments, resulting in unstable steel slag volume. This makes it unsuitable for direct use as building aggregate or roadbed filler, forcing large quantities of steel slag to be stockpiled for extended periods, leading to resource waste and environmental pressure. The exhaust gases from steelmaking converters and electric arc furnaces also contain... The volume fraction of this waste gas is approximately 15% to 25%. In existing processes, most of this waste gas is released into the atmosphere as exhaust gas, without being utilized for carbon sequestration, and is one of the sources of carbon emissions from steel production. Steel plants also produce large quantities of desulfurization gypsum as a byproduct of flue gas desulfurization. The causticizing process for papermaking alkali recovery continuously generates... The main component is causticized white mud; solid waste from building demolition contains a large amount of waste gypsum board; blast furnace ironmaking produces a large amount of water-quenched slag as a byproduct; and the mining industry continuously discharges waste containing high concentrations of... , and heavy metals ( , , For the acidic wastewater from mines (AMD, pH 2-4), there is a lack of economical and efficient disposal methods for the above-mentioned solid wastes and liquid wastes.

[0003] The existing technology has the following main technical problems: When waste gypsum board is crushed, paper fibers inevitably get mixed in. These paper fibers hydrolyze in an alkaline liquid phase, producing organic acid anions such as acetate and formate, which then react with… Chelation and adsorption Crystal planes, interference Crystallization and the formation of ettringite render waste gypsum board unsuitable for direct use in carbonization systems; existing carbonization systems typically employ a single... The source of the ettringite concentrates its formation at a certain stage, resulting in uneven mineral phases and unstable cementitious strength in the product; in conventional carbonization, a dense layer first forms on the surface of f-CaO. Shell, obstruction Infiltration into f-CaO leads to a low carbonization rate and incomplete decomposition of f-CaO; simultaneously, the scattered and separate treatment of multi-source industrial solid waste and acidic mine wastewater lacks integrated and synergistic approaches, and steelmaking exhaust gas... It has not been utilized for on-site mineralization and carbon sequestration. Summary of the Invention

[0004] This invention provides a method for utilizing steelmaking waste gas A carbon fixation treatment method to reduce free calcium oxide in steel slag, addressing the issue of unstable f-CaO volume in steel slag leading to its inability to be utilized as a resource, and the problems associated with steelmaking waste gas. Technical problems include the lack of carbon sequestration and utilization, and the lack of synergistic and integrated treatment methods for various types of solid waste.

[0005] This invention provides a method for utilizing steelmaking waste gas A carbon fixation method for reducing free calcium oxide in steel slag involves mixing steel slag, desulfurized gypsum, papermaking causticizing mud, waste building gypsum board powder, and blast furnace water-quenched slag in a mass ratio of 100:20-40:5-15:20-35:25-45. A slurry is prepared using acidic mine wastewater as the liquid medium, and the mixture is then introduced into the slurry. Steelmaking waste gas with a volume fraction of 15% to 25% is treated by wet carbonization. During the carbonization process: ultrafine particles in the causticizing white mud used in papermaking Particles, acting as heterogeneous nucleation seeds, reduce Crystallization nucleation energy barrier, causing liquid phase Preferentially attached to seed crystal particles for nucleation and precipitation, maintaining the carbonization reaction channel on the surface of f-CaO particles; Dissolved form in acidic wastewater from mines Fine particles of desulfurized gypsum and coarse particles of waste building gypsum board powder constitute three supply channels: rapid response, medium-speed continuous supply, and slow replenishment, respectively. tiered supply, continuously dissolving aluminum components and liquid phase from steel slag and blast furnace water-quenched slag. Formation of ettringite; The calcium silicate hydrate gel generated from blast furnace water-quenched slag coats paper fibers in waste building gypsum board powder, blocking the release of organic acid anions and integrating the paper fibers into the ettringite matrix. After carbonization, the product is dehydrated by pressure filtration and dried at low temperature to obtain the carbonized product.

[0006] Preferably: the causticizing white mud used in papermaking Content ≥85%, ultrafine The particle size is 1-5 μm, and the amount of causticizing mud used in papermaking is 5%-15% of the mass of steel slag; the residual causticizing mud in papermaking Dissolves in the liquid phase, maintains a high liquid phase pH, and promotes the production of steelmaking exhaust gas. Dissolution in the liquid phase.

[0007] Preferably: the desulfurized gypsum Content ≥85%, particle size 10-50μm; the waste building gypsum board powder is... It is a core component containing a paper lining, and its particle size after mechanical crushing is 0.2–5 mm.

[0008] Preferably, the pH of the acidic mine wastewater is 2-4. Concentration ≥1000 mg / L, containing dissolved form and heavy metals , , The liquid-to-solid mass ratio of the slurry is 0.4 to 0.8.

[0009] Preferably, the specific surface area of ​​the blast furnace water-quenched slag is ≥400 m² / kg; the glassy calcium aluminum silicate phase in the blast furnace water-quenched slag is generated during the f-CaO hydration of the steel slag. Under stimulation, a hydration reaction occurs, forming a calcium-silicon hydrate gel.

[0010] Preferably, the wet carbonization process is carried out at a temperature of 15–40°C and under normal pressure for a time of 2–6 hours.

[0011] Preferably: during the carbonization process, the acidic wastewater from the mine... and As the pH of the system increases, precipitation gradually forms. , And iron carbonate iron phase precipitation, wherein the iron phase precipitation is encapsulated by co-precipitation and surface adsorption. , , It is solidified in the solid phase of the carbonized product.

[0012] Preferably: during the carbonization process, the acidic wastewater from the mine... It reacts with f-CaO in steel slag ( ), accelerates the dissolution of f-CaO, for The formation of ettringite provides ample source.

[0013] Preferably: the carbonization product is... Calcium alum ( The main mineral phases are calcium silicate hydrate gel and iron phase precipitate, forming a multiphase composite cementitious system.

[0014] Preferably, the temperature for low-temperature drying is 40–55°C.

[0015] The beneficial effects of this invention are: in steelmaking waste gas Transformed into a thermodynamically stable form through f-CaO mineralization reaction. ,accomplish The permanent mineralization and sequestration provide an on-site carbon sequestration pathway for steel enterprises; ultrafine The seed crystals maintain the carbonization reaction channels on the surface of f-CaO particles, combined with AMD acid-promoted... Dissolution allows f-CaO to be efficiently and completely converted. This fundamentally eliminates the sources of unstable steel slag volume and significantly expands the scope of steel slag resource utilization; a three-pronged approach: fast, medium, and slow. The sequential gradation ensures uniform and continuous formation of ettringite throughout the entire treatment cycle, resulting in superior product gel strength consistency compared to single-source systems. Blast furnace ore powder CSH gel coating of paper fibers eliminates interference from paper fibers in the carbonization system, allowing waste gypsum board shreds to be directly used in the carbonization treatment system without pre-separation of the paper lining. Simultaneously, the paper fibers are integrated into the ettringite matrix, transforming into a toughening and reinforcing phase in the product, achieving complete resource utilization of waste gypsum board. AMD acid neutralization promotes f-CaO dissolution, and AMD neutralization... The three processes of ettringite formation, AMD iron phase precipitation and solidification of heavy metals are superimposed in the same treatment process; six types of industrial solid waste and waste liquid are simultaneously disposed of in a single wet carbonization process without the need for additional chemical reagents, resulting in low operating costs and providing a highly integrated treatment approach for the integrated and collaborative treatment of solid waste in multiple industries. Attached Figure Description

[0016] Figure 1 This is a comparison curve of the f-CaO residual content changes of sample A (with added causticized white mud seed crystals) and sample B (without added seed crystals, control group) at different carbonization time points in Experiment 1 of this invention. Figure 2 This is a comparison chart of the changes in ettringite content with carbonization time in four groups of samples—S-three-way, S-AMD, S-desulfurized gypsum, and S-waste gypsum board—in Experiment 2 of this invention. Figure 3 This is a bar chart comparing the compressive and flexural strengths of the carbonization products of the three groups of samples S1, S2, and S3 in Experiment 3 of this invention after 28 days of standard curing. Figure 4 This is a field emission scanning electron microscope (FE-SEM) morphology image of the carbonization products in group S3 of Experiment 3 of this invention, showing the growth morphology of CSH gel-coated paper fibers and ettringite crystals on the surface of the coated fibers. Figure 5 This is a bar chart comparing the initial heavy metal concentration of AMD, the leaching concentration of carbonized products in the experimental group, and the limits of GB5085.3-2007 in Experiment 4 of this invention (the vertical axis uses a logarithmic scale). Detailed Implementation

[0017] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0018] Example 1 This embodiment discloses a method for utilizing steelmaking waste gas A method for reducing free calcium oxide in steel slag through carbon fixation includes the following steps: Step 1: Material preparation and slurry mixing 100 parts of steel slag with an f-CaO content of 8% and desulfurization gypsum ( 30 parts of papermaking causticizing mud (90% content, particle size 15-30μm) 10 parts of 88% content, ultrafine particles, particle size 1-3μm, and waste building gypsum board powder (including paper lining, etc.) The core component consists of 25 parts of coarsely crushed ore (0.5–2 mm in diameter) and 35 parts of blast furnace water-quenched slag (mineral powder, specific surface area 430 m² / kg) mixed in a mass ratio of 100:30:10:25:35; and acidic mine wastewater (AMD, pH 3.0) is used as the feedstock. Concentration 2000 mg / L, containing dissolved form 50mg / L 30mg / L and heavy metals 2mg / L 1mg / L 0.5 mg / L) was added to the solid mixture as a liquid medium, and the liquid-to-solid mass ratio of the slurry was controlled at 0.6 to form a homogeneous slurry; during the slurry preparation process, AMD... Reacts with f-CaO ( ), accelerates the initial dissolution and release of f-CaO The alkaline components of steel slag continuously neutralize the acidity of AMD, making the slurry as a whole alkaline (pH about 9.5).

[0019] Step Two: Using steelmaking waste gas as... The source is fed into the slurry for carbonization treatment, and AMD promotes the dissolution of f-CaO and solidifies heavy metals in the iron phase. Will A 20% (by volume) volume fraction of converter steelmaking exhaust gas was continuously fed into the slurry obtained in step one, and wet carbonization was carried out at 25°C and atmospheric pressure (approximately 0.1 MPa) for 4 hours. During the carbonization process, f-CaO continuously hydrated and generated. , thereby ionizing and releasing and exhaust gas Dissolves in alkaline liquid phase to form ( ), with liquid phase Mineralization and carbon fixation reaction occur ( ),Will thermodynamically stable solid Form of permanent mineralization and solidification; AMD and Precipitation forms as the pH of the system increases. , and iron carbonates ( Iron phase precipitation, wherein the iron phase precipitation is achieved through co-precipitation and surface adsorption. , , Solidification within the carbonization product solidifies the heavy metal leaching toxicity. During the aforementioned carbonization process, the technical mechanisms described in steps three, four, and five occur simultaneously.

[0020] Step 3: During the carbonization process, ultrafine causticizing mud for papermaking is used. Particles act as heterogeneous nucleation seeds to accelerate f-CaO carbonization. During the carbonization process, papermaking causticizing mud ( Ultrafine particles with a particle size of 1-3 μm (88% content, 10% of the steel slag mass) The particles adhere to the surface of steel slag f-CaO particles, acting as heterogeneous nucleation seeds for newly formed crystals. Provides a large number of heterogeneous nucleation sites, significantly reducing The nucleation energy barrier required for crystallization makes the liquid phase Preferential nucleation and precipitation on the surface of seed crystal particles, consuming excess in the liquid phase. ,reduce The tendency for localized enrichment and continuous deposition of f-CaO particles on their surface to form a crust maintains the carbonization reaction channels on the f-CaO particle surface, allowing the liquid phase to... Continuous contact with f-CaO accelerates the complete carbonization of all f-CaO particles; residual f-CaO in causticizing mud during papermaking Dissolves in the liquid phase, maintains a high liquid phase pH, and promotes the flow of waste gas. Dissolution in the liquid phase expands the effective carbonization concentration window.

[0021] Step 4: During the carbonization process, three routes tiered supply ensures continuous and uniform formation of ettringite throughout the entire process. During the carbonization process, three different physical forms of... The source is aluminate formed by the dissolution of aluminum components from steel slag and mineral powder. ) and liquid phase The alum-forming reaction continues, producing ettringite (…). Three routes The supply is tiered according to a "fast-medium-slow" time sequence, ensuring a continuous and stable generation of ettringite throughout the carbonization process: the first stage is the dissolved state in AMD. (Concentration 2000 mg / L), it directly participates in the alum-forming reaction in liquid phase, responding rapidly in the early stage of carbonization, providing sufficient nutrients for the early formation of ettringite. The second route involves the continuous and stable dissolution of desulfurized gypsum (fine, uniform powder with a particle size of 15–30 μm, dosage 30 parts) in the liquid phase. The first route provides a sustained medium-term supply for the formation of ettringite; the second route involves the slow dissolution of crushed waste gypsum board powder (coarse particles of 0.5–2 mm, 25 parts). Continuous replenishment during the later stages of carbonization extends the alum formation cycle; the three-stage supply ensures the uniform and continuous formation of ettringite throughout the entire 4-hour treatment cycle, overcoming the challenges of single-stage supply. The source of the product's uneven mineral phase is a problem.

[0022] Step 5: During the carbonization process, blast furnace ore powder CSH gel is used to coat paper fibers and transform them into ettringite reinforcing phase. During the carbonization process, blast furnace water-quenched slag (mineral powder, specific surface area 430 m² / kg, dosage 35% of steel slag mass) is produced during the f-CaO hydration of steel slag. Under alkaline stimulation, the glassy calcium aluminum silicate phase in the mineral powder undergoes a hydration reaction to generate calcium silicate hydrate (CSH gel). The CSH gel nucleates and grows on the surface of paper fibers in waste building gypsum board powder. The interfacial adsorption between the cellulose hydroxyl groups and the surface of the calcium silicate hydrate promotes the bonding between the gel and the fiber surface, forming a dense CSH gel coating layer. This coating layer physically blocks the contact between the organic groups of the paper fibers and the liquid phase, inhibiting the continuous release of organic acid anions such as acetate and formate from the source, eliminating the interference of paper fibers on carbonization crystallization and ettringite formation. The surface of the paper fibers coated with CSH gel serves as a nucleation site for ettringite crystals, which grow along the fiber axis, integrating the paper fibers into the ettringite matrix to form a paper fiber-reinforced ettringite composite product. The paper fibers, through a fiber pull-out energy dissipation mechanism, inhibit crack propagation, giving the product a toughening and strengthening effect. Simultaneously supplement the aluminum source of the system, and coordinate the three routes. Increase the amount of ettringite produced.

[0023] Step Six: After carbonization, the carbonized products are obtained through solid-liquid separation and drying. After 4 hours of carbonization, the slurry was dewatered by pressure filtration, and the resulting solid phase was dried at 50°C to obtain the carbonized product. The carbonized product was then... (Main carbon-fixing phase), ettringite (cementing phase, containing paper fiber reinforcement), CSH gel (stabilized gel phase), iron phase precipitation (heavy metal solidified phase, with...) It is mainly composed of iron carbonates as the main mineral phase, forming a multiphase synergistic composite cementitious system. The product can be directly used as mine filling material and roadbed stabilization material.

[0024] Example 2 This embodiment discloses a method for utilizing steelmaking waste gas under conditions of low material ratio and low carbonization intensity. A method for reducing free calcium oxide in steel slag through carbon fixation includes the following steps: Step 1: Material preparation and slurry mixing 100 parts of steel slag with an f-CaO content of 5% and desulfurization gypsum ( 20 parts of papermaking causticizing mud (86% content, particle size 10-25μm) 5 parts of 87% content, ultrafine particles, particle size 1-2μm, and waste building gypsum board powder (including paper lining, etc.) The core component consists of 20 parts of coarsely crushed ore (0.2–1 mm in diameter) and 25 parts of blast furnace water-quenched slag (mineral powder, specific surface area 400 m² / kg) mixed in a mass ratio of 100:20:5:20:25; and acidic mine wastewater (AMD, pH 2.0) is used as the feedstock. Concentration 1000 mg / L, containing dissolved form 20mg / L 10mg / L and heavy metals 1mg / L 0.5 mg / L Using 0.3 mg / L as the liquid medium, the liquid-to-solid mass ratio of the slurry was controlled at 0.4 to prepare a homogeneous slurry; during the slurry preparation process, AMD... (pH 2.0, strongly acidic) reacts with f-CaO ( This rapidly accelerates the initial dissolution and release of f-CaO. The alkaline components of steel slag continuously neutralize the acidity of AMD, making the slurry as a whole alkaline (pH about 9.0).

[0025] Step Two: Using steelmaking waste gas as... The source is fed into the slurry for carbonization treatment, and AMD promotes the dissolution of f-CaO and solidifies heavy metals in the iron phase. Will A 15% (by volume) volume fraction of converter steelmaking exhaust gas was continuously fed into the slurry obtained in step one, and wet carbonization was carried out at 15°C and atmospheric pressure (approximately 0.1 MPa) for 2 hours. During the carbonization process, f-CaO hydration was released. and exhaust gas (15% by volume) dissolves in an alkaline liquid phase to form , with liquid phase A mineralization and carbon fixation reaction will occur, solid Formal mineralization and solidification; AMD and Precipitation forms as the pH of the system increases. , and Iron phase precipitation, through co-precipitation and surface adsorption , , It is solidified in the solid phase of the carbonization product. During the above carbonization process, the technical mechanisms described in steps three, four, and five occur simultaneously.

[0026] Step 3: During the carbonization process, ultrafine causticizing mud for papermaking is used. Particles act as heterogeneous nucleation seeds to accelerate f-CaO carbonization. During the carbonization process, papermaking causticizing mud ( Ultrafine particles with a particle size of 1-2 μm (content 87%, dosage 5% of steel slag mass) The particles adhere to the surface of steel slag f-CaO particles, acting as heterogeneous nucleation seeds to reduce... Crystallization nucleation energy barrier, causing liquid phase Preferential nucleation and precipitation on the surface of seed crystals maintains the carbonization reaction pathway on the surface of f-CaO particles; residual causticized white mud Dissolves in the liquid phase, maintains the alkalinity of the liquid phase, and promotes the flow of waste gas. Dissolve.

[0027] Step 4: During the carbonization process, three routes tiered supply ensures continuous and uniform formation of ettringite throughout the entire process. During the carbonization process, three routes Supply is tiered according to a "fast-medium-slow" sequence: the first path is AMD medium-solid state. (Concentration 1000 mg / L, which is the lower limit of this method), response in the initial stage of carbonization; the second route is the continuous dissolution of desulfurized gypsum (particle size 10-25 μm, dosage 20 parts) in the liquid phase. The third route involves slowly replenishing the waste gypsum board crushed powder (particle size 0.2–1 mm, dosage 20 parts). The three-stage supply system reacts with the aluminum components throughout the entire 2-hour treatment cycle. It continues to generate ettringite.

[0028] Step 5: During the carbonization process, blast furnace ore powder CSH gel is used to coat paper fibers and transform them into ettringite reinforcing phase. During the carbonization process, blast furnace water-quenched slag (mineral powder, specific surface area 400 m² / kg, dosage 25% of steel slag mass) is used in... CSH gel is generated under alkaline stimulation; the CSH gel nucleates and grows on the surface of paper fibers in waste building gypsum board powder, forming a dense CSH gel coating layer, which physically blocks the contact between the organic groups of paper fibers and the liquid phase, and inhibits the continuous release of organic acid anions such as acetate and formate; the coated paper fibers serve as nucleation sites for ettringite, and ettringite grows along the fiber axis to form a paper fiber reinforced ettringite composite product.

[0029] Step Six: After carbonization, the carbonized products are obtained through solid-liquid separation and drying. After 2 hours of carbonization, the slurry was dewatered by pressure filtration, and the resulting solid phase was dried at 40°C to obtain the carbonized product. The carbonized product was then... The main mineral phases are ettringite (containing paper fiber reinforcement), CSH gel, and iron phase precipitate, forming a multiphase synergistic composite cementitious system. The product can be used as a mine backfill material.

[0030] Example 3 This embodiment discloses a method for utilizing steelmaking waste gas under conditions of high material ratio and high carbonization intensity. A method for reducing free calcium oxide in steel slag through carbon fixation includes the following steps: Step 1: Material preparation and slurry mixing 100 parts of steel slag with an f-CaO content of 15% and desulfurization gypsum ( 40 parts of papermaking causticizing mud (content 92%, particle size 20-50μm) 15 parts of 90% content, ultrafine particles, particle size 3-5μm, and waste building gypsum board powder (including paper lining, etc.) The core component consists of 35 parts of coarsely crushed ore (1-5 mm in diameter) and 45 parts of blast furnace water-quenched slag (mineral powder, specific surface area 500 m² / kg) mixed in a mass ratio of 100:40:15:35:45; and acidic mine wastewater (AMD, pH 4.0) is used as the feedstock. Concentration 3000 mg / L, containing dissolved form 100mg / L 80mg / L and heavy metals 5mg / L 3mg / L The liquid medium is 1.0 mg / L. The liquid-solid mass ratio of the slurry is controlled at 0.8 to form a uniform slurry. The alkaline components of steel slag neutralize the acidity of AMD (pH 4.0), making the slurry as a whole alkaline (pH about 10.2).

[0031] Step Two: Using steelmaking waste gas as... The source is fed into the slurry for carbonization treatment, and AMD promotes the dissolution of f-CaO and solidifies heavy metals in the iron phase. Will Electric arc furnace steelmaking exhaust gas with a volume fraction of 25% was continuously fed into the slurry obtained in step one, and wet carbonization was carried out at a temperature of 40℃ and an atmospheric pressure (approximately 0.1 MPa) for 6 hours. During the carbonization process, f-CaO (content 15%, relatively high amount) hydrated and released a large amount of... and exhaust gas (25% by volume) dissolves in an alkaline liquid phase, producing a large amount of ,and Mineralized carbon sequestration AMD and A large amount of precipitate forms as pH increases. , and Iron phase precipitation, , , It is solidified in the solid phase of the carbonization product. During the above carbonization process, the technical mechanisms described in steps three, four, and five occur simultaneously.

[0032] Step 3: During the carbonization process, ultrafine causticizing mud for papermaking is used. Particles act as heterogeneous nucleation seeds to accelerate f-CaO carbonization. During the carbonization process, papermaking causticizing mud ( Ultrafine particles with a particle size of 3-5 μm (90% content, 15% dosage by weight of steel slag) The particles adhere to the surface of steel slag f-CaO particles, acting as heterogeneous nucleation seeds and significantly reducing [the risk of crystal formation]. The crystallization nucleation energy barrier maintains the carbonization reaction channel on the surface of f-CaO particles, enabling complete carbonization of f-CaO (content 15%, relatively large amount) within a 6-hour treatment cycle; residual causticized white mud Dissolves in the liquid phase, maintains a high liquid phase pH, and promotes the flow of waste gas. Dissolution in the liquid phase.

[0033] Step 4: During the carbonization process, three routes tiered supply ensures continuous and uniform formation of ettringite throughout the entire process. During the carbonization process, three routes Supply is tiered according to a "fast-medium-slow" sequence: the first path is AMD medium-solid state. (Concentration 3000 mg / L, sufficient quantity), it responds rapidly and in large quantities in the early stage of carbonization; the second route is desulfurized gypsum (particle size 20-50 μm, dosage 40 parts), which continuously and stably dissolves a large amount. The medium-term supply is ample; the third route is to slowly replenish the supply with crushed waste gypsum board powder (particle size 1-5mm, dosage 35 parts, largest particle size, slowest dissolution). Towards the later stages of carbonization; the three-stage supply ensures uniform and continuous interaction with the aluminum components throughout the long 6-hour treatment cycle. A large amount of ettringite is generated.

[0034] Step 5: During the carbonization process, blast furnace ore powder CSH gel is used to coat paper fibers and transform them into ettringite reinforcing phase. During the carbonization process, blast furnace water-quenched slag (mineral powder, specific surface area 500 m² / kg, dosage 45% of steel slag mass) is used in... Under alkaline stimulation, a large amount of CSH gel is generated; the CSH gel fully coats the paper fibers in the waste building gypsum board powder, blocking the continuous release of organic acid anions; the coated paper fibers serve as nucleation sites for ettringite, and a large amount of ettringite grows along the fiber axis, forming a paper fiber-reinforced ettringite composite product, giving the product excellent toughening and strengthening effects; a large amount of mineral powder... Significantly supplements the aluminum source of the system, synergistically supporting three pathways. It significantly increases the amount of ettringite produced.

[0035] Step Six: After carbonization, the carbonized products are obtained through solid-liquid separation and drying. After 6 hours of carbonization, the slurry was dewatered by pressure filtration, and the resulting solid phase was dried at 55°C to obtain the carbonized product. The carbonized product was then... (Main carbon-fixed phase), ettringite (cementing phase, containing paper fiber reinforcement), CSH gel (stabilized cementing phase), iron phase precipitation (heavy metal solidified phase, with...) It is mainly composed of iron carbonates as the main mineral phase, forming a multiphase synergistic composite cementitious system. The product can be directly used as mine filling material and roadbed stabilization material.

[0036] Example 4 This embodiment discloses a method for utilizing steelmaking waste gas with high-concentration acidic wastewater from iron and heavy metal mines as the liquid phase medium. A method for reducing free calcium oxide in steel slag through carbon fixation includes the following steps: Step 1: Material preparation and slurry mixing 100 parts of steel slag with an f-CaO content of 10% and desulfurization gypsum ( 25 parts of papermaking causticizing mud (88% content, particle size 15-40μm) 8 parts of 87% content, ultrafine particles, particle size 2-4μm, and waste building gypsum board powder (including paper lining, etc.) The core component consists of 30 parts of coarsely crushed ore (0.5–4 mm in diameter) and 40 parts of blast furnace water-quenched slag (mineral powder, specific surface area 420 m² / kg) mixed in a mass ratio of 100:25:8:30:40; and acidic mine wastewater (AMD, pH 2.5) is used as the feedstock. Concentration 2500 mg / L, containing high concentration of dissolved form 200mg / L 150 mg / L and heavy metals 8mg / L 5mg / L Using 2.0 mg / L as the liquid medium, the liquid-to-solid mass ratio of the slurry was controlled at 0.7 to prepare a homogeneous slurry; during the slurry preparation process, AMD... (pH 2.5) reacts with f-CaO ( This accelerates the dissolution of f-CaO, and the alkaline components of steel slag continuously neutralize the acidity of AMD, making the slurry as a whole alkaline (pH about 9.8).

[0037] Step Two: Using steelmaking waste gas as... The source is fed into the slurry for carbonization treatment, and AMD promotes the dissolution of f-CaO and solidifies heavy metals in the iron phase. Will A converter steelmaking exhaust gas with a volume fraction of 18% was continuously fed into the slurry obtained in step one, and wet carbonization was carried out at a temperature of 20°C and an atmospheric pressure (approximately 0.1 MPa) for 5 hours. During the carbonization process, f-CaO hydration was released. and exhaust gas Dissolves in alkaline liquid phase to form ,and Mineralized carbon sequestration AMD medium to high concentration (200 mg / L) and A large amount of precipitate (150 mg / L) formed as the pH of the system increased. , and Iron phase precipitation, wherein the iron phase precipitate is formed by co-precipitation and surface adsorption to achieve high concentrations of iron phase. (8mg / L) (5mg / L) (2.0 mg / L) is largely solidified in the carbonization product solid phase, significantly reducing the leaching toxicity of heavy metals. During the above carbonization process, the technical mechanisms described in steps three, four, and five occur simultaneously.

[0038] Step 3: During the carbonization process, ultrafine causticizing mud for papermaking is used. Particles act as heterogeneous nucleation seeds to accelerate f-CaO carbonization. During the carbonization process, papermaking causticizing mud ( Ultrafine particles with a particle size of 2-4 μm (87% content, 8% dosage by weight of steel slag) The particles adhere to the surface of steel slag f-CaO particles, acting as heterogeneous nucleation seeds to reduce... Crystallization nucleation energy barrier, causing liquid phase Preferential nucleation and precipitation on the surface of seed crystals maintains the carbonization reaction pathway on the surface of f-CaO particles; residual causticized white mud Dissolves in the liquid phase, maintains the alkalinity of the liquid phase, and promotes the flow of waste gas. Dissolve.

[0039] Step 4: During the carbonization process, three routes tiered supply ensures continuous and uniform formation of ettringite throughout the entire process. During the carbonization process, three routes Supply is tiered according to a "fast-medium-slow" sequence: the first path is AMD medium-solid state. (Concentration 2500 mg / L), with a rapid and large-scale response in the early stage of carbonization; the second route involves the continuous dissolution of desulfurized gypsum (particle size 15-40 μm, dosage 25 parts). The third route involves slowly replenishing the waste gypsum board crushed powder (particle size 0.5–4 mm, dosage 30 parts). The three-stage supply system reacts with the aluminum components throughout the entire 5-hour treatment cycle. The continuous generation of ettringite ensures the uniformity of the mineral phase in the product.

[0040] Step 5: During the carbonization process, blast furnace ore powder CSH gel is used to coat paper fibers and transform them into ettringite reinforcing phase. During the carbonization process, blast furnace water-quenched slag (mineral powder, specific surface area 420 m² / kg, dosage 40% of steel slag mass) is used in... Under alkaline stimulation, a large amount of CSH gel is generated; the CSH gel fully coats the paper fibers in waste building gypsum board powder (30 parts, containing a relatively large amount of paper fibers), physically blocking the continuous release of organic acid anions; the coated paper fibers serve as nucleation sites for ettringite, and ettringite grows along the fiber axis to form a paper fiber-reinforced ettringite composite product; the amount of mineral powder is 40 parts, ensuring sufficient coating of a large number of paper fibers, while supplementing... Aluminum source, synergistically increases the formation of ettringite.

[0041] Step Six: After carbonization, the carbonized products are obtained through solid-liquid separation and drying. After 5 hours of carbonization, the slurry was dewatered by pressure filtration, and the resulting solid phase was dried at 45°C to obtain the carbonized product. The carbonized product was then... The main mineral phases are carbon-fixed phase, ettringite (containing paper fiber reinforcement), CSH gel, and iron phase precipitate (containing a large amount of solidified heavy metals, and the heavy metal leaching toxicity is significantly lower than the concentration before AMD treatment). The product can be directly used as mine backfill material.

[0042] Example 5 This embodiment discloses a method for utilizing steelmaking waste gas to accelerate f-CaO carbonization by enhancing the heterogeneous nucleation seed effect with high dosage of caustic white mud used in papermaking. A method for reducing free calcium oxide in steel slag through carbon fixation includes the following steps: Step 1: Material preparation and slurry mixing 100 parts of steel slag with an f-CaO content of 12% and desulfurization gypsum ( 35 parts of papermaking causticizing mud (89% content, particle size 15-45μm) 12 parts of 92% content, ultrafine particles, particle size 1-4μm, and waste building gypsum board powder (including paper lining, etc.) The core component consists of 22 parts of coarsely crushed particles (0.3–3 mm in diameter) and 30 parts of blast furnace water-quenched slag (mineral powder, specific surface area 460 m² / kg) mixed in a mass ratio of 100:35:12:22:30; and acidic mine wastewater (AMD, pH 3.5) is used as the feedstock. Concentration 1500 mg / L, containing dissolved form 60mg / L 40mg / L and heavy metals 3mg / L 2mg / L The liquid medium is 0.8 mg / L. The liquid-solid mass ratio of the slurry is controlled at 0.5 to form a uniform slurry. The alkaline components of steel slag neutralize the acidity of AMD (pH 3.5), making the slurry as a whole alkaline (pH about 10.0).

[0043] Step Two: Using steelmaking waste gas as... The source is fed into the slurry for carbonization treatment, and AMD promotes the dissolution of f-CaO and solidifies heavy metals in the iron phase. Will The slurry obtained in step one, containing 22% by volume of electric arc furnace steelmaking exhaust gas, was continuously fed into the slurry and subjected to wet carbonization at 30°C and atmospheric pressure (approximately 0.1 MPa) for 3 hours. During the carbonization process, f-CaO (12% content) was released through hydration. and exhaust gas (22% by volume) dissolves in an alkaline liquid phase to form ,and Mineralized carbon sequestration AMD and As pH increases, an iron phase precipitate forms. , , It solidifies into the solid phase of the product. During the carbonization process described above, the technical mechanisms in steps three, four, and five occur simultaneously.

[0044] Step 3: During the carbonization process, ultrafine causticizing mud for papermaking is used. Particles act as heterogeneous nucleation seeds to accelerate f-CaO carbonization. During the carbonization process, papermaking causticizing mud ( With a content of 92% and a dosage of 12% of the steel slag mass (which is considered a relatively high seed content in this method), the ultrafine particles have a particle size of 1–4 μm. A large number of particles adhere to the surface of the steel slag f-CaO particles, forming a new layer. Providing ample heterogeneous nucleation sites significantly reduces the nucleation energy barrier, enabling the liquid phase to... Preferential nucleation and precipitation on the surface of numerous seed crystals, fully maintaining the carbonization reaction channels on the surface of f-CaO particles, achieving efficient and complete carbonization of f-CaO (content 12%) within a relatively short treatment time of 3 hours; high residual content in causticized white mud It dissolves in the liquid phase, maintains a high liquid phase pH (approximately 10.0), and significantly promotes... (22% by volume) Dissolution and absorption in the liquid phase expands the effective carbonization concentration window.

[0045] Step 4: During the carbonization process, three routes tiered supply ensures continuous and uniform formation of ettringite throughout the entire process. During the carbonization process, three routes Supply is tiered according to a "fast-medium-slow" sequence: the first path is AMD medium-solid state. (Concentration 1500 mg / L), response in the initial stage of carbonization; the second route is desulfurized gypsum (particle size 15-45 μm, dosage 35 parts, intermediate stage). (Sufficient supply) Continuous and stable dissolution of large quantities The third route involves slowly replenishing the waste gypsum board crushed powder (particle size 0.3–3 mm, dosage 22 parts). The three-stage supply system ensures uniform and continuous interaction with the aluminum components throughout the entire 3-hour treatment cycle. It forms ettringite.

[0046] Step 5: During the carbonization process, blast furnace ore powder CSH gel is used to coat paper fibers and transform them into ettringite reinforcing phase. During the carbonization process, blast furnace water-quenched slag (mineral powder, specific surface area 460 m² / kg, dosage 30% of steel slag mass) is used in... CSH gel is generated under alkaline stimulation; the CSH gel nucleates and grows on the surface of paper fibers in waste building gypsum board powder, forming a dense CSH gel coating layer, blocking the continuous release of organic acid anions; the coated paper fibers serve as nucleation sites for ettringite crystals, and ettringite grows along the fiber axis, forming a paper fiber-reinforced ettringite composite product, giving the product a toughening effect; in the mineral powder It supplements the source of aluminum and synergistically increases the formation of ettringite.

[0047] Step Six: After carbonization, the carbonized products are obtained through solid-liquid separation and drying. After 3 hours of carbonization, the slurry was dewatered by pressure filtration, and the resulting solid phase was dried at 48°C to obtain the carbonized product. The carbonized product was then... The main mineral phases are ettringite (containing paper fiber reinforcement), CSH gel, and iron phase precipitate, forming a multiphase synergistic composite cementitious system. The product can be directly used as mine filling material and non-load-bearing building filling material.

[0048] Example 6 This embodiment discloses a method for utilizing steelmaking waste gas to dispose of large quantities of waste gypsum board by using a high amount of waste building gypsum board powder. A method for reducing free calcium oxide in steel slag through carbon fixation includes the following steps: Step 1: Material preparation and slurry mixing 100 parts of steel slag with an f-CaO content of 9% and desulfurization gypsum ( 28 parts of papermaking causticizing mud (87% content, particle size 12-42μm) 7 parts of 85% content, ultrafine particles, particle size 2-5μm, and waste building gypsum board powder (including paper lining, etc.) The core component, consisting of 35 parts of coarsely crushed ore (0.8–5 mm in diameter) and 42 parts of blast furnace water-quenched slag (mineral powder, specific surface area 480 m² / kg), was mixed uniformly in a mass ratio of 100:28:7:35:42. The mixture was then prepared using acidic mine wastewater (AMD, pH 3.0). Concentration 1800 mg / L, containing dissolved form 80mg / L 60mg / L and heavy metals 4mg / L 2.5 mg / L Using 1.2 mg / L as the liquid medium, the liquid-to-solid mass ratio of the slurry was controlled at 0.65 to prepare a homogeneous slurry; during the slurry preparation process, AMD... Reacts with f-CaO ( This accelerates the dissolution of f-CaO, and the alkaline components of steel slag continuously neutralize the acidity of AMD, making the slurry as a whole alkaline (pH about 9.6).

[0049] Step Two: Using steelmaking waste gas as... The source is fed into the slurry for carbonization treatment, and AMD promotes the dissolution of f-CaO and solidifies heavy metals in the iron phase. Will Electric arc furnace steelmaking exhaust gas with a volume fraction of 23% was continuously fed into the slurry obtained in step one, and wet carbonization was carried out at a temperature of 35°C and an atmospheric pressure (approximately 0.1 MPa) for 4.5 hours. During the carbonization process, f-CaO hydration and release... and exhaust gas (23% by volume) dissolves in an alkaline liquid phase to form ,and Mineralized carbon sequestration AMD and Precipitation forms as the pH of the system increases. , and Iron phase precipitation, through co-precipitation and surface adsorption , , It is solidified in the solid phase of the carbonization product. During the above carbonization process, the technical mechanisms described in steps three, four, and five occur simultaneously.

[0050] Step 3: During the carbonization process, ultrafine causticizing mud for papermaking is used. Particles act as heterogeneous nucleation seeds to accelerate f-CaO carbonization. During the carbonization process, papermaking causticizing mud ( Ultrafine particles with a particle size of 2-5 μm (content 85%, dosage 7% of steel slag mass) The particles adhere to the surface of steel slag f-CaO particles, acting as heterogeneous nucleation seeds to reduce... The nucleation energy barrier for crystallization maintains the carbonization reaction pathway on the surface of f-CaO particles, accelerating the complete carbonization of f-CaO; residual f-CaO in causticized white mud Dissolves in the liquid phase, promoting the production of waste gas Dissolution in the liquid phase.

[0051] Step 4: During the carbonization process, three routes tiered supply ensures continuous and uniform formation of ettringite throughout the entire process. During the carbonization process, three routes Supply is tiered according to a "fast-medium-slow" sequence: the first path is AMD medium-solid state. (Concentration 1800 mg / L), responds rapidly in the initial stage of carbonization; the second route involves the continuous dissolution of desulfurized gypsum (particle size 12-42 μm, dosage 28 parts). The third route involves slowly and in large quantities replenishing waste gypsum board crushed powder (particle size 0.8–5 mm, dosage 35 parts, which is the largest particle size and highest dosage in this method, resulting in the slowest dissolution). The process continues into the later stages of carbonization, significantly extending the alum-forming cycle; the three-stage supply ensures uniform and continuous generation of ettringite throughout the entire 4.5-hour treatment cycle, with a large amount of waste gypsum board powder slowly releasing [amount missing]. Sufficient alum-forming driving force is maintained in the middle and late stages of carbonization, resulting in a relatively high content of ettringite in the product.

[0052] Step 5: During the carbonization process, blast furnace ore powder CSH gel is used to coat paper fibers and transform them into ettringite reinforcing phase. During the carbonization process, blast furnace water-quenched slag (mineral powder, specific surface area 480 m² / kg, dosage 42% of steel slag mass, which is considered a relatively high mineral powder dosage) is used in... Under alkaline activation, a large amount of CSH gel is generated, which fully coats the waste building gypsum board powder (35 parts, containing a large amount of paper fiber) with a large amount of paper fiber, physically blocking the continuous release of organic acid anions and eliminating the interference of paper fibers on the carbonization system. The large amount of paper fibers coated by CSH gel serves as nucleation sites for ettringite, and a large number of paper fibers are integrated into the ettringite matrix to form an ettringite composite product with abundant paper fiber reinforcement, giving the product a significant toughening and strengthening effect. The high mineral powder content (42 parts) not only ensures the full coating of the large amount of paper fibers, but also supplements a large amount of mineral powder. Aluminum source, coordinated three routes Further increase the amount of ettringite produced.

[0053] Step Six: After carbonization, the carbonized products are obtained through solid-liquid separation and drying.

[0054] After 4.5 hours of carbonization, the slurry was dewatered by pressure filtration, and the resulting solid phase was dried at 52°C to obtain the carbonized product. The carbonized product was then processed as follows: The main mineral phases are carbon-fixed phase, ettringite (containing abundant paper fiber reinforcement, with a relatively high ettringite content), CSH gel, and iron phase precipitation. The product contains a large amount of paper fiber reinforced ettringite, and its mechanical toughness is better than that of the low-waste gypsum board usage scheme. It can be directly used as a mine filling material and roadbed stabilization material.

[0055] Example 7 This embodiment discloses a method for utilizing steelmaking waste gas A method for reducing free calcium oxide in steel slag through carbon fixation includes the following steps: Step 1: Material preparation and slurry mixing 100 parts of steel slag with an f-CaO content of 8% and desulfurization gypsum ( Fine, uniform powder produced as a byproduct of flue gas desulfurization. 30 parts of papermaking causticizing mud (90% content, particle size 15-30μm) 10 parts of 88% content, ultrafine particles, particle size 1-3μm, and waste building gypsum board powder (including paper lining, no need to pre-separate paper fibers). The core component, consisting of coarsely ground, irregularly shaped particles (0.5–2 mm in diameter), was prepared in a mass ratio of 100:30:10:25:35 and mixed uniformly. The mixture was prepared using acidic mine wastewater (AMD, pH 3.0). Concentration 2000 mg / L, containing dissolved form 50mg / L 30mg / L and heavy metals 2mg / L 1mg / L 0.5 mg / L) was added to the solid mixture as a liquid medium, and the liquid-to-solid mass ratio of the slurry was controlled at 0.6 to form a homogeneous slurry; during the slurry preparation process, AMD... Reacts with f-CaO ( Accelerates the initial dissolution and release of f-CaO. f-CaO in steel slag The alkaline components continuously neutralize the acidity of AMD, making the slurry as a whole alkaline (pH about 9.5), providing an alkaline liquid environment for subsequent carbonization treatment.

[0056] Step Two: Using steelmaking waste gas as... The source is fed into the slurry for carbonization treatment, and AMD promotes the dissolution of f-CaO and solidifies heavy metals in the iron phase. Steelmaking waste gas (converter or electric arc furnace waste gas) A 20% (volume fraction) slurry obtained in step one is continuously fed into the mixture, and wet carbonization is carried out at 25°C and atmospheric pressure (approximately 0.1 MPa) for 4 hours. During the carbonization process, f-CaO continuously undergoes a hydration reaction with water. ), Ionization and release in the liquid phase and ( ); exhaust gas Dissolves in an alkaline liquid phase, forming ( ), with liquid phase Mineralization and carbon fixation reaction occur ( ),Will thermodynamically stable solid It is permanently mineralized and preserved.

[0057] AMD and From the slurry preparation stage onwards, precipitation continues to form as the pH of the system increases. , and iron carbonates ( Iron phase precipitation, the above iron phase precipitation is encapsulated by co-precipitation and surface adsorption. , , It is solidified in the solid phase of carbonized products, which greatly reduces the leaching toxicity of heavy metals.

[0058] In the above carbonization process, the f-CaO carbonization and carbon fixation in step three, the continuous generation of ettringite in step four, and the paper fiber coating and reinforcing phase transformation in step five are carried out simultaneously.

[0059] Step 3: During the carbonization process, ultrafine causticizing mud for papermaking is used. Particles act as heterogeneous nucleation seeds to accelerate f-CaO carbonization. During the carbonization process, papermaking causticizing mud ( Ultrafine particles with a particle size of 1–3 μm (content 88%) The particles adhere to the surface of steel slag f-CaO particles and act as heterogeneous nucleation seeds, playing the following roles: Under seedless conditions, f-CaO and Carbonization reaction occurs ( When f-CaO particles are exposed to this process, a continuous and dense layer first forms on their surface. Shell, obstruction Penetration into the interior of f-CaO restricts the advancement of internal carbonization; introduction of ultrafine particles After seeding, the seed crystals adhere to the surface of f-CaO, forming new crystals. Provides a large number of heterogeneous nucleation sites, significantly reducing The nucleation energy barrier required for crystallization in the liquid phase Preferential nucleation and precipitation on the surface of seed crystal particles, consuming excess in the liquid phase. ,reduce The tendency for localized enrichment and continuous deposition of f-CaO particles on their surface to form a shell maintains the carbonization reaction channels on the f-CaO particle surface, thus enabling the liquid phase to... It can continuously contact f-CaO, significantly accelerating the complete carbonization of all f-CaO particles and overcoming The shell hinders the internal carbonization process.

[0060] Residual in causticized white clay Dissolves in the liquid phase, maintains a high liquid phase pH, and further promotes the flow of waste gas. Dissolution in the liquid phase, making the liquid phase The concentration is maintained at a level that allows for continuous reaction with f-CaO. The amount of white mud used is 10% of the steel slag mass to ensure seed crystal effect and avoid excessive alkalinity.

[0061] Step 4: During the carbonization process, three routes tiered supply ensures continuous and uniform formation of ettringite throughout the entire process. During the carbonization process, three different physical forms of... Source: Aluminate formed by the dissolution of aluminum components from steel slag and mineral powder ( ) and liquid phase The alum-forming reaction continues, producing ettringite (…). Three routes The ettringite is continuously and stably generated throughout the entire carbonization process by supplying it in a "fast-medium-slow" tiered manner. First path (rapid response, early carbonization stage): AMD dissolved state It participates directly in the alum-forming reaction in liquid phase without the need for solid-phase dissolution, responding rapidly in the early stages of carbonization and providing sufficient water for the rapid early formation of ettringite. .

[0062] Second route (medium-speed continuous, mid-stage carbonization): Desulfurized gypsum ( Fine, uniform powder with a particle size of 15–30 μm (30 parts) continuously and stably dissolves in the liquid phase. The particles are fine and uniform, and the dissolution rate is stable, providing a medium-term continuous supply for the formation of ettringite.

[0063] Third route (slow replenishment, mid-to-late carbonization stage): Crushed gypsum board from abandoned buildings ( The coarse particles obtained from mechanical crushing have irregular morphology and a particle size of 0.5–2 mm (25 parts used) and exhibit the lowest dissolution rate, releasing slowly and continuously during the later stages of carbonization. This extends the alum-forming cycle.

[0064] Three Roads The sequential gradient originates from the differences in the physical forms of different materials (dissolved state → fine and uniform particles → coarse and irregular particles), ensuring the uniform and continuous formation of ettringite throughout the entire treatment cycle, overcoming the limitations of single-phase processing. The source leads to the concentration of alum formation stages and the uneven mineral phase of the product.

[0065] Step 5: During the carbonization process, blast furnace ore powder CSH gel is used to coat paper fibers and transform them into ettringite reinforcing phase. Paper lining fibers inevitably mix into waste building gypsum board powder. These paper fibers undergo alkaline hydrolysis in an alkaline liquid phase, releasing organic acid anions such as acetate and formate; these organic acid anions react with... Chelation and adsorption Crystal faces interfere with carbonization crystallization and inhibit the formation of ettringite. Blast furnace water-quenched slag (mineral powder) coats paper fibers from waste building gypsum board powder in an alkaline liquid phase through the following process, transforming them into an ettringite reinforcing phase: (1) CSH gel formation: generated by the hydration of mineral powder in steel slag f-CaO Under alkaline activation, the glassy calcium aluminum silicate phase (containing) in the mineral powder , , The main components undergo a hydration reaction to form calcium silicate hydrate (CSH gel). (2) CSH gel coating paper fiber: CSH gel nucleates and grows on the surface of paper fiber. The interfacial adsorption and binding between cellulose hydroxyl groups and the surface of calcium silicate hydrate promotes the binding of gel and fiber surface, forming a dense CSH gel coating layer. The coating layer physically blocks the contact between the organic groups of paper fiber and the liquid phase, inhibiting the continuous release of organic acid anions from the source and eliminating the interference of paper fiber on carbonization crystallization and ettringite formation. (3) Formation of paper fiber reinforced ettringite composite product: The surface of paper fiber coated with CSH gel serves as the nucleation site for ettringite crystals. The ettringite grows along the fiber axis, integrating the paper fiber into the ettringite matrix to form a paper fiber reinforced ettringite composite product. The paper fiber in the ettringite matrix inhibits crack propagation through the fiber pull-out energy dissipation mechanism, giving the ettringite product a toughening and strengthening effect, and transforming the waste gypsum board paper lining that originally interfered with the carbonization system into a beneficial reinforcing component of the product.

[0066] mineral powder The components simultaneously replenish the aluminum source of the system, along with the three-way... Synergistically enhance the formation of ettringite. The amount of mineral powder used is 35% of the mass of steel slag to ensure sufficient formation of CSH gel and effective coating of paper fibers.

[0067] Step Six: After carbonization, the carbonized products are obtained through solid-liquid separation and drying. After carbonization, the slurry was dewatered by pressure filtration, and the resulting solid phase was dried at 50°C to obtain the carbonized product. The carbonized product was then processed as follows: (Main carbon-fixing phase), ettringite (cementing phase, containing paper fiber reinforcement), CSH gel (stabilized gel phase), iron phase precipitation (heavy metal solidified phase, with...) It is mainly composed of iron carbonates as the main mineral phase, forming a multiphase synergistic composite cementitious system; the product can be directly used as mine filling material, roadbed stabilization material and non-load-bearing building filling material.

[0068] Experimental verification Experiment 1 1. Experimental Objective Verification of ultrafine particles in caustic white mud for papermaking Particles (1–3 μm in diameter) can serve as heterogeneous nucleation seeds, effectively reducing The crystallization nucleation energy barrier and the maintenance of carbonization reaction channels on the surface of f-CaO particles significantly accelerate the carbonization rate of steel slag f-CaO, enabling f-CaO to achieve efficient and complete digestion within a 4-hour carbonization cycle. Furthermore, by setting up a control experiment with and without added crystal seeds, the contribution of the crystal seed effect to the carbonization rate and carbonization completeness is quantitatively evaluated.

[0069] 2. Preparation of experimental samples Two sets of experimental samples were set up, and the parameters are as follows.

[0070] Add seed crystal group (sample A): Prepared according to the parameters of Example 1, using 100 parts of steel slag with f-CaO content of 8% as a basis, desulfurized gypsum ( 30 parts of papermaking causticizing mud (90% content, particle size 15-30μm) The following ingredients are uniformly mixed: 10 parts of steel slag powder (88% content, particle size 1-3μm, dosage 10% of steel slag mass), 25 parts of waste building gypsum board powder (particle size 0.5-2mm), and 35 parts of blast furnace water-quenched slag (specific surface area 430m² / kg); with pH 3.0... The AMD-modified slurry had a concentration of 2000 mg / L, a liquid-to-solid mass ratio of 0.6, and a slurry pH of approximately 9.5.

[0071] Group without seed crystals (Sample B, control group): Used equal mass of chemically pure coarse-grained calcite powder (particle size 45–75 μm, used directly without any heat treatment; its specific surface area is much lower than that of causticized white clay ultrafine powder). Except for the use of particles (with negligible density of heterogeneous nucleation sites) to replace causticized white clay, all other raw materials, proportions, and slurry preparation parameters were completely identical to those of sample A. Coarse-grained calcite powder also contained... The residual amount is approximately zero, and its contribution to the liquid phase pH is related to the causticized white mud. The contributions of the components are quite similar (causticized white mud) The content is usually less than 2%, contributing very little to the total alkalinity of this system. Therefore, sample B can be compared with sample A for single-factor effects on seed particle size and nucleation activity, eliminating interference from other components. Note: High-temperature calcination is not used here because... Significant thermal decomposition occurs at 800–850℃. (↑), the generated CaO is produced in large quantities after cooling and reabsorption of water. This will severely alter the alkalinity of the system and disrupt the conditions for single-factor comparison.

[0072] 3. Experimental conditions Carbonization temperature: 25℃; Operating pressure: atmospheric pressure (approximately 0.1 MPa); Gas introduction Volume fraction: 20% (balance is N2), gas flow rate: 1L / min; total carbonization treatment time: 4h; sampling is performed every 0.5h, with each sample weighing approximately 5g.

[0073] 4. Experimental Procedure (1) Prepare sample A and sample B according to the above ratio, place them in a 500mL sealed carbonization reactor, stir continuously with a magnetic stirrer (300r / min), and control the gas flow rate to 1L / min through a mass flow controller, and continuously introduce the gas. 20% by volume of mixed gas ( (N2 was prepared using a gas proportioning apparatus).

[0074] (2) Starting from the start of carbonization, take about 5g of slurry sample from the reactor every 0.5h, immediately add 10mL of anhydrous ethanol to terminate the carbonization reaction, filter the solid phase with a 0.45μm filter membrane, and dry the obtained solid phase in an oven at 40℃ for later use.

[0075] (3) For the dried solid samples at each time point, the f-CaO content was determined by the ethylene glycol monoethyl ether (EGME) method: Weigh about 1g of dried solid sample, add 20mL of ethylene glycol monoethyl ether, stir magnetically for 60min in a constant temperature water bath at 60℃, filter with a 0.45μm filter membrane, take the filtrate and perform potentiometric titration with 0.1mol / L hydrochloric acid standard solution, and calculate the f-CaO content (%).

[0076] (4) Simultaneously, X-ray diffraction (XRD) analysis was performed on the solid samples at each time point, using Cu Kα radiation (λ=0.154056nm), with a scanning range of 5°~70° (2θ) and a step size of 0.02°. The results were calculated using Rietveld full-spectrum refinement. (Calcite, 2θ≈29.4°) mass fraction, to help verify the f-CaO determination results.

[0077] (5) Each experiment was repeated 3 times, and the average of the 3 times was used as the final result. The carbonization rate at each time point was calculated (carbonization rate = (initial f-CaO content - current residual f-CaO content) / initial f-CaO content × 100%).

[0078] 5. Experimental Results Table 1 shows the residual f-CaO content and carbonization rate (average, n=3) of Sample A (with seed crystals) and Sample B (without seed crystals, control) at different carbonization time points: Table 1 Comparison of residual f-CaO content and carbonization rate at different carbonization time points

[0079] Figure 1This is a comparison of the f-CaO residual content curves of samples A and B as a function of carbonization time.

[0080] 6. Analysis and Summary From Table 1 and Figure 1 It can be seen that under the same carbonization conditions (temperature 25℃), Sample A (volume fraction 20%, carbonization time 4h), with added causticized white clay seed crystals, showed a decrease in residual f-CaO content to 0.28% and a carbonization rate of 96.5% after 4h. In contrast, the control group sample B, without seed crystals, still had a residual f-CaO content as high as 2.61% and a carbonization rate of only 67.4% after the same time. The carbonization rate of sample A was particularly significant in the first hour of carbonization, reaching 40.6% after 1 hour, approximately 1.89 times that of sample B (21.5%) at the same time, indicating that the seed crystals began to play a significant accelerating role in the early stages of carbonization.

[0081] The above results prove that the ultrafine causticizing white mud used in papermaking... Particles, acting as heterogeneous nucleation seeds, can effectively reduce... The crystallization nucleation energy barrier maintains the carbonization reaction channel on the surface of f-CaO particles, enabling f-CaO to be efficiently and completely decomposed within a 4-hour carbonization cycle. The carbonization rate is 29.1 percentage points higher than that of the control group (from 67.4% to 96.5%), effectively eliminating the source of unstable steel slag volume.

[0082] Experiment 2 1. Experimental Objective Verify AMD dissolved state Three pathways: (Path 1, rapid response), fine desulfurized gypsum particles (Path 2, medium-speed continuous), and coarse waste building gypsum board particles (Path 3, slow replenishment). A tiered supply model, compared to any single... The source can uniformly and continuously generate more ettringite throughout the entire carbonization process; and by quantifying the mineral phase uniformity of the products of each scheme through the coefficient of variation (CV), it is demonstrated that the temporal complementarity of the three-stage supply is of great importance in ensuring the uniform formation of ettringite.

[0083] 2. Preparation of experimental samples Four groups of experimental samples were set up, each group Despite varying sources, the types and quantities of basic solid raw materials such as steel slag, causticized white mud, and blast furnace slag remain completely consistent to ensure the quality of each group. The sources of aluminum and alkalinity are basically the same, enabling single-factor comparison.

[0084] Three-stage supply group (S-three-stage): Prepared according to the complete parameters of Example 1, namely 100 parts steel slag, 30 parts desulfurized gypsum, 10 parts causticized white mud, 25 parts waste building gypsum board powder, and 35 parts blast furnace slag, with pH 3.0. AMD-modified slurry with a concentration of 2000 mg / L (liquid-to-solid mass ratio of 0.6). Volume fraction 20%, carbonization temperature 25℃, carbonization time 4h.

[0085] Only AMD dissolved state Group (S-AMD): Replace the desulfurized gypsum with an equal mass of chemically pure gypsum. Powder (particle size 10-50 μm, used to supplement equal amounts) The waste gypsum board powder was replaced with an equal mass of inert quartz sand powder (particle size 0.5-2mm, excluding...). The liquid phase still uses pH 3.0. AMD at a concentration of 2000 mg / L (same as S-3), with all other parameters unchanged. This group Derived solely from the dissolved portion (liquid phase) of AMD (After initial heavy consumption, there is no continuous source of solid phase replenishment).

[0086] For the desulfurized gypsum group only (S-desulfurized gypsum): the liquid phase was changed to deionized water with pH 7.0 (excluding dissolved substances). The waste gypsum board powder was replaced with an equal mass of inert quartz sand powder, while the remaining solid raw materials and parameters were the same as those in S-3. It originates solely from the continuous dissolution of desulfurized gypsum particles (particle size 15–30 μm).

[0087] Waste gypsum board only (S-waste gypsum board): The liquid phase is replaced with deionized water at pH 7.0 (excluding dissolved substances). Replace the desulfurized gypsum with an equal mass of chemically pure gypsum. The powder and other solid raw materials and parameters are the same as those in the S-3 circuit. It originates solely from the slow leaching of coarse particles (0.5–2 mm in diameter) from waste gypsum board.

[0088] 3. Experimental conditions Carbonization temperature: 25℃; Operating pressure: atmospheric pressure (approximately 0.1 MPa); Gas introduction Volume fraction: 20%, flow rate: 1L / min; total carbonization time: 4h; sampling is performed every 1h, with each sample weighing approximately 10g.

[0089] 4. Experimental Procedure (1) Prepare four groups of samples, namely S-three-way, S-AMD, S-desulfurized gypsum and S-waste gypsum board, according to the above proportions. Place them in a sealed carbonization reactor and carry out carbonization treatment in the same batch under the same conditions.

[0090] (2) Starting from the start of carbonization, take about 10g of slurry sample from each group of reactors every 1 hour, add anhydrous ethanol immediately to terminate carbonization, filter to separate the solid phase, and dry at 40℃ for later use.

[0091] (3) XRD quantitative analysis was performed on the dried solid samples at each time point (Cu Kα radiation, 2θ range 5°~70°, step size 0.02°), and the mass fraction (wt%) of ettringite (characteristic peak 2θ≈9.1°) was calculated by Rietveld full spectrum refinement. Three samples were repeated for each time point in each group, and the average value was taken.

[0092] (4) Calculate the ettringite formation rate (wt% / h) of each group of samples in each time interval of 0-1h, 1-2h, 2-3h, and 3-4h, and calculate the coefficient of variation (CV = standard deviation / mean × 100%) of the formation rate of each group as an index of the uniformity of the product mineral phase. The smaller the CV value, the more uniform the ettringite formation rate and the more uniform the product mineral phase.

[0093] 5. Experimental Results Table 2 shows the ettringite content (wt%, XRD Rietveld quantification, n=3 average) of the four groups of samples at different carbonization time points: Table 2. Etnacite content in four groups of samples at different carbonization time points

[0094] Table 3. Formation rate (wt% / h) and coefficient of variation of ettringite in four sample groups

[0095] Figure 2 A comparison graph showing the change in ettringite content with carbonization time for four groups of samples.

[0096] 6. Analysis and Summary From Table 2, Table 3 and Figure 2 It can be seen that the S-three-way (three-stage supply) ettringite content reached 23.5 wt% at the end of the 4-hour carbonization cycle, higher than S-AMD (11.3 wt%), S-waste gypsum board (13.2 wt%), and S-desulfurized gypsum (20.5 wt%). Regarding the uniformity of the product mineral phase, S-AMD consumed a large amount of dissolved minerals in the early stages of carbonization. Afterwards, the 1-4 hour period With the supply essentially exhausted, the formation rate of ettringite plummeted from 7.50 wt% / h to 0.30 wt% / h, with a coefficient of variation as high as 110.2%, and the product mineral phases were severely heterogeneous. Due to the excessively low coarse-grained leaching rate of S-waste gypsum board, the driving force for alum formation was severely insufficient in the 0–2h stage, and the formation rate slowly climbed from 0.90 wt% / h to 5.40 wt% / h, with a coefficient of variation of 57.3%. Although the total amount of S-desulfurized gypsum reached 20.5 wt%, it lacked the initial rapid growth provided by AMD. The response and the continuous replenishment provided by waste gypsum board caused the generation rate to rise sharply to 6.70 wt% / h in the 1-2 h stage and then gradually decline, with a relatively high coefficient of variation (CV=29.4%).

[0097] S-Route 3 relies on three routes: fast, medium, and slow. The time sequence is complementary, and the formation rate of ettringite in each time interval fluctuates very little between 4.90 and 6.60 wt% / h, with a coefficient of variation of only 12.8%. The product mineral phase homogeneity is the best among the four groups, and the total ettringite formation is 108.0% and 78.0% higher than that of S-AMD and S-waste gypsum board, respectively.

[0098] The above results prove that the three-way The tiered supply model ensures uniform and continuous formation of ettringite throughout the entire 4-hour carbonization cycle, significantly outperforming any single method in both total quantity and uniformity. Source solution, effectively overcomes single The source leads to the concentration of alum formation stages and the uneven mineral phase of the product.

[0099] Experiment 3 1. Experimental Objective The calcium silicate hydrate (CSH) gel generated by blast furnace water-quenched slag (mineral powder) in an alkaline carbonization system was verified to: (1) effectively coat the paper fibers in waste building gypsum board powder, physically blocking the release of organic acid anions such as acetate and formate from the alkaline hydrolysis of paper fibers, thus eliminating the interference of paper fibers on the carbonization system; (2) make the coated paper fibers serve as nucleation sites for ettringite, integrating the paper fibers into the ettringite matrix to form a paper fiber-reinforced ettringite composite product, significantly improving the mechanical properties of the product. The comprehensive improvement effect of mineral powder on the system was quantitatively evaluated by monitoring the concentration of organic acid anions in liquid phase, testing mechanical properties, and characterizing the morphology using scanning electron microscopy (SEM).

[0100] 2. Experimental sample preparation: Three groups of control samples were set up.

[0101] Excluding waste gypsum board (S1, basic control): 100 parts steel slag, 30 parts desulfurized gypsum, 10 parts causticized white mud, and 35 parts blast furnace slag, with waste building gypsum board powder (25 parts) replaced by an equal mass of inert silica sand to maintain a consistent total solids content; AMD liquid-to-solid mass ratio 0.6. The volume fraction was 20%, the temperature was 25℃, the carbonization time was 4 hours, and the drying temperature was 50℃. This group did not contain paper fibers and served as a baseline control to prevent paper fiber interference.

[0102] Group containing waste gypsum board but excluding mineral powder (S2, paper fiber interference group): 100 parts steel slag, 30 parts desulfurized gypsum, 10 parts causticized white mud, and 25 parts waste building gypsum board powder (including paper lining, particle size 0.5-2mm), in an inert manner of equal mass. Blast furnace slag (35 parts) was replaced with powder (particle size 10-50 μm) to eliminate the contribution of slag powder hydration activity; other parameters were the same as S1. In this group, paper fibers continuously hydrolyzed in the alkaline liquid phase, releasing organic acid anions, which interfered with carbonization and ettringite formation, serving as a control for "unresolved paper fiber interference problem".

[0103] The waste gypsum board containing mineral powder group (S3, this method): prepared according to the complete parameters of Example 1, namely 100 parts steel slag, 30 parts desulfurized gypsum, 10 parts causticized white mud, 25 parts waste building gypsum board powder (particle size 0.5-2mm), and 35 parts blast furnace slag; AMD liquid-to-solid mass ratio 0.6. Volume fraction 20%, temperature 25℃, carbonization time 4h, drying temperature 50℃.

[0104] 3. Experimental conditions Carbonization temperature: 25℃; Operating pressure: atmospheric pressure (approximately 0.1 MPa); Gas introduction Volume fraction: 20%, flow rate: 1L / min; carbonization time: 4h; drying temperature: 50℃.

[0105] 4. Experimental Procedure (1) Prepare three groups of samples, S1, S2, and S3, according to the above ratio, and complete the carbonization treatment for 4 hours under the same carbonization conditions. During carbonization, take about 3 mL of liquid phase sample (filtered through a 0.22 μm filter membrane) every 1 hour, and determine the acetate ion in the liquid phase using ion chromatography (IC). ) and formate ( The concentration (mmol / L) was used to evaluate the extent to which the paper fibers released organic acids through alkaline hydrolysis, and the average value over the 4-hour period was calculated.

[0106] (2) After carbonization treatment, the three groups of slurry were dehydrated by pressure filtration and dried at 50℃. The carbonized product was mixed with standard sand (mass ratio 1:3) and an appropriate amount of distilled water (water-cement ratio 0.50). 40mm×40mm×160mm standard mortar rod specimens were prepared according to GB / T 17671—2021 and cured in a standard curing box at (20±1)℃ and relative humidity ≥95% for 28 days.

[0107] (3) For the specimens after standard curing for 28 days, the flexural strength test (three-point bending, span 100mm, loading rate 50N / s) was carried out according to GB / T 17671—2021. Then, the compressive strength test (force-bearing area 40mm×40mm, loading rate 2400N / s) was carried out on the broken half specimens. Six parallel specimens were prepared for each group, and the average value and standard deviation were taken.

[0108] (4) At the same time, about 5g of carbonization products from groups S2 and S3 were taken, and hydration was terminated by replacing with anhydrous ethanol. The samples were ground to a particle size of <74μm and vacuum dried to prepare SEM samples (sprayed with a gold film of about 2nm thickness). The microstructure of the carbonization products was observed by field emission scanning electron microscopy (FE-SEM) in secondary electron (SE) mode at a magnification of 5000x. The distribution of Si, Ca, Al and S elements in the CSH gel coating interface region was analyzed by energy dispersive spectroscopy (EDS) to verify the coating effect of CSH gel on paper fibers and the growth morphology of ettringite on the fiber surface.

[0109] (5) XRD quantitative analysis of the carbonization products in group S3 was performed to confirm ettringite, Mineral phase composition and relative content of CSH gel.

[0110] 5. Experimental Results Table 4 shows the concentration of organic acid anions in the liquid phase of samples S1, S2, and S3 (average value during the 4-hour carbonization stage), the mechanical properties of the carbonization products after 28 days of standard curing, and the residual f-CaO content. Table 4 Comparison of organic acid anion concentration, mechanical properties, and residual f-CaO content of the three groups of samples

[0111] Figure 3 A bar chart comparing the compressive and flexural strengths of three groups of samples (S1, S2, and S3) after 28 days.

[0112] Figure 4 The image shows the FE-SEM morphology of the carbonized products in group S3, illustrating the growth morphology of CSH gel-coated paper fibers and ettringite crystals on the surface of the coated fibers.

[0113] 6. Analysis and Summary As shown in Table 4, the average total concentration of organic acid anions in the liquid phase of group S2 (including waste gypsum board, excluding mineral powder) reached 4.85 mmol / L, which is much higher than that of S1 (0.12 mmol / L). This proves that paper fibers do indeed undergo continuous alkaline hydrolysis in the alkaline liquid phase, releasing organic acid anions such as acetate and formate.

[0114] The direct consequences of the interference of organic acid anions are reflected in the mechanical properties and carbonization effect: the 28-day compressive strength (12.3 MPa) and flexural strength (2.1 MPa) of group S2 are significantly lower than those of group S1 (18.5 MPa and 3.2 MPa, respectively), and the residual f-CaO content (2.81%) is much higher than that of group S1 (0.52%), which proves that organic acid anions simultaneously inhibit carbonization crystallization and the normal formation of ettringite.

[0115] The total concentration of organic acid anions in the liquid phase of group S3 (this method, containing mineral powder) decreased to 0.38 mmol / L (a 92.2% reduction compared to S2), demonstrating that the CSH gel coating effectively blocked the continuous release of organic acid anions from the source. Meanwhile, the 28-day compressive strength (22.8 MPa) and flexural strength (5.6 MPa) of group S3 not only surpassed those of group S1 (increasing by 23.2% and 75.0% respectively), but the paper fibers also significantly imparted toughness to the product through the fiber pull-out energy dissipation mechanism.

[0116] SEM topography image ( Figure 4 This study visually demonstrates the dense coating layer formed by CSH gel on the surface of paper fibers and the growth morphology of ettringite crystals along the fiber axis, verifying the formation mechanism of the paper fiber-reinforced ettringite composite product. These results prove that by coating paper fibers with CSH gel, blast furnace ore powder achieves the transformation of the paper lining, which originally interfered with the carbonization system, into a reinforcing phase in the product.

[0117] Experiment 4 1. Experimental Objective Verification showed that after introducing acidic wastewater (AMD) from high-speed rail and high-heavy-metal mines into the carbonization treatment system, the AMD... and It can precipitate during the process of increasing the pH of the system. , And iron carbonate iron phase precipitation, and through co-precipitation and surface adsorption mechanisms to encapsulate and absorb iron. , , Heavy metals are efficiently solidified in the solid phase of carbonized products, so that the leaching toxicity of heavy metals in carbonized products meets the corresponding limit requirements of the "Identification Standard for Hazardous Waste - Leaching Toxicity Identification" (GB5085.3-2007).

[0118] 2. Preparation of experimental samples Experimental samples were prepared based on Example 4: 100 parts of steel slag (f-CaO content 10%), desulfurized gypsum ( 25 parts of papermaking causticizing mud (88% content, particle size 15-40μm) The composition consists of 8 parts of waste building gypsum board powder (including paper lining, particle size 0.5-4mm) and 40 parts of blast furnace water-quenched slag (specific surface area 420m² / kg), in a mass ratio of 100:25:8:30:40; with high iron and high heavy metal AMD (pH 2.5). Concentration 2500 mg / L, 200mg / L 150mg / L 8.0 mg / L 5.0 mg / L The medium is liquid (2.0 mg / L), with a liquid-to-solid mass ratio of 0.7. The carbonization process was carried out at a volume fraction of 18%, a carbonization temperature of 20℃, and at atmospheric pressure for 5 hours. After carbonization, the product was dehydrated by pressure filtration and dried at a low temperature of 45℃. Simultaneously, the same amount of deionized water (free of heavy metals) was used. / A blank control group (sample D) was prepared to replace AMD, with all other parameters remaining unchanged, to verify that the heavy metal solidification effect comes from the iron phase precipitation mechanism rather than other physical interception.

[0119] 3. Experimental conditions Carbonization temperature: 20℃; Operating pressure: atmospheric pressure (approximately 0.1 MPa); Gas introduction Volume fraction: 18%, flow rate: 1 L / min; carbonization time: 5 h; drying temperature: 45 ℃; heavy metal leaching test adopted horizontal oscillation method (GB5086.1—1997).

[0120] 4. Experimental Procedure (1) Prepare the experimental group (AMD group) and blank control group (deionized water group) according to the above parameters, perform carbonization treatment for 5 hours, filter and dehydrate, and dry at 45℃ to obtain carbonization products of the experimental group and blank control group respectively.

[0121] (2) Take about 100g of each group of carbonized products and prepare leachate according to GB 5086.1—1997 (horizontal oscillation method): crush the carbonized products to a particle size <9.5mm, add deionized water at a solid-liquid mass ratio of 1:10, place in a horizontal oscillator and oscillate at (30±2)r / min for (18±2)h, filter with a 0.6~0.8μm microporous membrane, collect the leachate, and acidify with high-purity nitric acid (superior grade) to pH<2.

[0122] (3) The concentration of ions in the leachate was determined by inductively coupled plasma mass spectrometry (ICP-MS). , , The total iron concentration (mg / L) was measured; the initial concentrations of the above elements in the AMD stock solution were simultaneously determined as a reference; the curing rate of each element was calculated (curing rate = (initial concentration - leaching concentration) / initial concentration × 100%). Three parallel samples were prepared for each group, and the average value was taken.

[0123] (4) Refer to the limit value of the identification standard for leaching toxicity of hazardous waste in GB 5085.3—2007 to determine the compliance of the leaching concentration of carbonized products in the experimental group.

[0124] (5) XRD analysis was performed on the carbonization products of the experimental group to identify iron phase precipitates (amorphous iron precipitates and their transformed phases FeO(OH) goethite, (Sidestone, etc.) mineral phases; and the iron-rich areas in the product were analyzed by SEM-EDS surface scanning. , , The coexistence of elements was investigated to verify the mechanism of heavy metal precipitation and solidification in the iron phase.

[0125] 5. Experimental Results Table 5 compares the initial heavy metal and iron concentrations in AMD, the leaching concentration of carbonized products in the experimental group, the curing rate, and the limits specified in GB 5085.3—2007. Table 5. Concentrations of heavy metals and iron in AMD before and after carbonization treatment and evaluation of leaching toxicity of carbonization products.

[0126] Figure 5 A bar chart comparing the initial heavy metal concentration in AMD, the leaching concentration of carbonized products in the experimental group, and the limits in GB 5085.3—2007 (the vertical axis is logarithmic).

[0127] 6. Analysis and Summary From Table 5 and Figure 5 It can be seen that after carbonization treatment by this method (parameters of Example 4), the carbonization products contain... , , The leaching concentrations were reduced to 0.12 mg / L, 0.08 mg / L and 0.05 mg / L, respectively, with corresponding curing rates of 98.5%, 98.4% and 97.5%; the total iron leaching concentration was reduced to 0.68 mg / L, with a curing rate of 99.8%. , , The leaching concentrations were all significantly lower than the corresponding limits specified in GB 5085.3—2007. 5.00 mg / L 1.00 mg / L The concentration of carbonized products was 5.00 mg / L, and the leaching toxicity test of the carbonized products was completely qualified, therefore they are not classified as hazardous waste.

[0128] XRD analysis detected amorphous iron precipitate in the carbide products (as shown in the figure). As a precursor, it partially transforms into FeO(OH) goethite phase under drying conditions at 45℃. (Siderite facies) Iron phase precipitation, SEM-EDS surface scanning analysis shows iron phase enrichment areas. , , The coexistence of elements and iron confirms the technical principle of heavy metal solidification through co-precipitation and surface adsorption mechanisms. Blank control group (using deionized water instead of AMD, no...) / No iron phase precipitation was detected in the carbonization products, and its heavy metal retention efficiency was significantly lower than that of the experimental group, further verifying that iron phase precipitation is the core mechanism of heavy metal solidification.

[0129] The above results demonstrate that introducing high-heavy metal AMD from high-speed rail into the carbonization treatment system can efficiently and stably solidify the heavy metals in AMD into the solid phase of the product while achieving carbon fixation, significantly reducing leaching toxicity and realizing the resource transformation of AMD from an environmental burden to an effective component of the carbonization treatment system.

[0130] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A method for utilizing steelmaking waste gas A carbon fixation treatment method for reducing free calcium oxide in steel slag, characterized in that, Steel slag, desulfurized gypsum, papermaking causticizing mud, waste building gypsum board powder, and blast furnace water-quenched slag are mixed in a mass ratio of 100:20-40:5-15:20-35:25-45. A slurry is prepared using acidic mine wastewater as the liquid phase medium and then introduced into the slurry. Steelmaking waste gas with a volume fraction of 15% to 25% is treated by wet carbonization. During the carbonization process: ultrafine particles in the causticizing white mud used in papermaking Particles, acting as heterogeneous nucleation seeds, reduce Crystallization nucleation energy barrier, causing liquid phase Preferentially attached to seed crystal particles for nucleation and precipitation, maintaining the carbonization reaction channel on the surface of f-CaO particles; Dissolved form in acidic wastewater from mines Fine particles of desulfurized gypsum and coarse particles of waste building gypsum board powder constitute three supply channels: rapid response, medium-speed continuous supply, and slow replenishment, respectively. tiered supply, continuously dissolving aluminum components and liquid phase from steel slag and blast furnace water-quenched slag. Formation of ettringite; The calcium silicate hydrate gel generated from blast furnace water-quenched slag coats paper fibers in waste building gypsum board powder, blocking the release of organic acid anions and integrating the paper fibers into the ettringite matrix. After carbonization, the product is dehydrated by pressure filtration and dried at low temperature to obtain the carbonized product.

2. The method according to claim 1, characterized in that, The causticizing white mud used in papermaking Content ≥85%, ultrafine The particle size is 1-5 μm, and the amount of causticizing mud used in papermaking is 5%-15% of the mass of steel slag; the residual causticizing mud in papermaking Dissolves in the liquid phase, promoting the production of steelmaking waste gas Dissolution in the liquid phase.

3. The method according to claim 1, characterized in that, In the desulfurized gypsum Content ≥85%, particle size 10-50μm; the waste building gypsum board powder is... It is a core component containing a paper lining, and its particle size after mechanical crushing is 0.2–5 mm.

4. The method according to claim 1, characterized in that, The pH of the acidic wastewater from the mine is 2–4. Concentration ≥1000 mg / L, containing dissolved form and heavy metals , , The liquid-to-solid mass ratio of the slurry is 0.4 to 0.

8.

5. The method according to claim 1, characterized in that, The specific surface area of ​​the blast furnace water-quenched slag is ≥400 m² / kg; the glassy calcium aluminum silicate phase in the blast furnace water-quenched slag is generated during the f-CaO hydration of steel slag. Under stimulation, a hydration reaction occurs, forming a calcium-silicon hydrate gel.

6. The method according to claim 1, characterized in that, The wet carbonization process is carried out at a temperature of 15–40°C and under normal pressure for a time of 2–6 hours.

7. The method according to claim 4, characterized in that, During the carbonization process, the acidic wastewater from the mine contains and As the pH of the system increases, precipitation gradually forms. , And iron carbonate iron phase precipitation, wherein the iron phase precipitation is encapsulated by co-precipitation and surface adsorption. , , It is solidified in the solid phase of the carbonized product.

8. The method according to claim 4, characterized in that, During the carbonization process, the acidic wastewater from the mine contains It reacts with f-CaO in steel slag, accelerating the dissolution of f-CaO, thus... The formation of ettringite provides ample source.

9. The method according to claim 1, characterized in that, The carbonization products The main mineral phases are ettringite, calcium silicate hydrate gel and iron phase precipitate, forming a multiphase composite cementitious system.

10. The method according to claim 1, characterized in that, The temperature for the low-temperature drying is 40–55°C.

Images