A composite injection material for co-processing hazardous waste in a blast furnace and a preparation method thereof

Abstract

The present application belongs to the field of solid waste resource utilization and metallurgical blast furnace ironmaking technology, and discloses a composite injection material for blast furnace co-processing hazardous waste and a preparation method thereof. First, a plant of the genus acrocephalus is made into a biomass fuel rod, then carbonized under inert atmosphere, and then steel slag micro-powder is sprayed under inert atmosphere to obtain steel slag modified biomass charcoal. Second, waste activated carbon and cold rolling oil sludge are fully mixed in a closed container with low-pressure saturated steam to obtain a mixture A. Finally, the anthracite, the steel slag modified biomass charcoal and the mixture A are mixed and ground to obtain the composite injection material for blast furnace injection. Through targeted raw material screening, pretreatment and precise proportioning, the present application solves the technical difficulties of excessive alkali in biomass charcoal, sulfur residue in waste activated carbon, uneven dispersion of cold rolling oil sludge and high water content, realizes efficient and collaborative recycling of waste activated carbon, biomass charcoal and cold rolling oil sludge, and reduces carbon emissions of blast furnace.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization and blast furnace ironmaking technology in the metallurgical industry, specifically relating to a composite injection material for the co-processing of hazardous waste in blast furnaces and its preparation method. Background Technology

[0002] The steel industry is one of the sectors with the heaviest carbon emission reduction tasks. Blast furnace ironmaking is the carbon-intensive stage in traditional integrated steel production, accounting for over 65% of total carbon emissions. Its carbon reduction effectiveness directly impacts the achievement of the industry's overall carbon reduction goals. Meanwhile, integrated steel enterprises generate large amounts of carbon-containing solid waste during production, such as waste activated carbon from sintering, desulfurization, and denitrification processes, and cold-rolling sludge from cold rolling. Direct stockpiling or simple treatment of such hazardous waste not only wastes carbon resources but also causes environmental problems. To achieve synergistic resource recovery and carbon reduction, related technologies have attempted to use carbon-containing solid waste and biochar as blast furnace fuel; however, existing applications face numerous technical bottlenecks, making efficient synergistic utilization difficult.

[0003] Biochar is widely available, has a high calorific value, and low carbon emission intensity, making it a highly promising low-carbon blast furnace fuel. However, its excessive alkali metal content can easily lead to blast furnace nodule formation. While spent activated carbon possesses a porous structure and a certain calorific value, making it a potential blast furnace fuel, the spent activated carbon produced during sintering desulfurization and denitrification in steel enterprises often contains sulfur residue. Direct use in injection can increase the sulfur content in the blast furnace, reducing the quality of molten iron. Current technologies do not offer effective solutions for controlling and modifying the sulfur content of spent activated carbon. Cold-rolled sludge is rich in recyclable components such as carbon and iron, possessing high resource utilization value. However, it suffers from high moisture content (typically 30%–50%) and complex composition (containing grease, metal scraps, and moisture). When mixed with other fuels, it is prone to uneven dispersion and incomplete combustion, wasting carbon resources and exacerbating furnace condition fluctuations.

[0004] In existing technologies, blast furnace injection technology mainly uses pulverized coal as the injection material, with low attention paid to the co-utilization of carbon-containing solid waste, and lacks precise matching solutions for the characteristics of solid waste and the needs of blast furnace smelting. Even if there are a few attempts to mix two or more carbon-containing solid wastes for injection, they are mostly simple mixing, failing to solve the core technical difficulties of the negative impact of carbon-containing solid waste introduction on blast furnace production. This limits the introduction of carbon-containing solid waste, fails to fully tap the potential for system-level carbon emission reduction, and makes it difficult to simultaneously meet the multiple needs of solid waste resource utilization, process carbon reduction, and blast furnace production. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of existing technologies by providing a composite injection material for the co-processing of hazardous waste in blast furnaces and its preparation method. Through targeted raw material screening, pretreatment and precise proportioning, it solves the technical difficulties of excessive alkali metals in biomass carbon, sulfur residue in waste activated carbon, uneven dispersion and high moisture content of cold-rolled sludge, and achieves efficient co-processing and recycling of waste activated carbon, biomass carbon and cold-rolled sludge, while reducing carbon emissions from blast furnaces.

[0006] To address the technical problem proposed in this invention, this invention provides a method for preparing composite injection material for co-processing hazardous waste in blast furnaces, comprising the following steps: 1) After crushing and drying Miscanthus plants, they are extruded into biomass fuel rods; 2) Carbonize the biomass fuel rods under an inert atmosphere to obtain biochar; then spray steel slag powder onto the surface of the biochar under an inert atmosphere to obtain steel slag modified biochar. 3) Thoroughly mix the waste activated carbon and cold-rolled sludge in a closed container through which low-pressure saturated steam is introduced to obtain mixture A; 4) Anthracite, steel slag modified biochar and mixture A are mixed and ground to obtain composite injection material for use in blast furnace injection.

[0007] In the above scheme, the Miscanthus species are one or more of Miscanthus sinensis, Miscanthus chinensis, and Miscanthus sinensis, with a total cellulose and hemicellulose content of >50%, carbon content ≥45%, alkali metal content ≤3%, and ash content ≤8%, ensuring that the raw materials have good carbonization performance and low pollution characteristics, while guaranteeing a stable source of renewable raw materials.

[0008] In the above scheme, the length of the broken Miscanthus plant is 3-5 mm.

[0009] In the above scheme, the moisture content of the dried Miscanthus plants is 10%~15%.

[0010] In the above scheme, the drying temperature is 110~130℃ and the time is 10~20min.

[0011] In the above scheme, the extrusion pressure is 15~18MPa.

[0012] In the above scheme, the density of the biomass fuel rod is >1200 kg / m³. 3 .

[0013] In the above scheme, the biomass fuel rod is cylindrical, with a diameter of 2-3 cm and a length of 7-9 cm.

[0014] In the above scheme, the inert atmosphere is preferably nitrogen.

[0015] In the above scheme, the carbonization temperature is 380~420℃ and the time is 60~90min.

[0016] In the above scheme, the fixed carbon content of the biochar is ≥60%, and the volatile matter content is ≤20%.

[0017] In the above scheme, the steel slag powder is a powder material obtained by grinding converter smelting waste slag after magnetic separation to remove iron.

[0018] In the above scheme, the surface area of ​​the steel slag powder is 400~500m². 2 / kg, the main components include: CaO 40%~45%, SiO2 10%~15%, TFe 17%~22%, MgO 3%~8%.

[0019] In the above scheme, the spraying amount of the steel slag powder is 0.5% to 1% of the biochar mass.

[0020] In the above scheme, the waste activated carbon is waste granular activated carbon generated during the desulfurization and denitrification process of sintering flue gas in iron and steel enterprises, with a particle size of 0.5~3mm and a specific surface area ≥800 m². 2 / kg, fixed carbon content ≥65%, sulfur content ≤1.2%.

[0021] In the above scheme, the cold-rolled sludge is an oily hazardous solid waste generated by the cold rolling process of steel enterprises, with a water content of 25%~35%, an oil content of 15%~25%, a fixed carbon content of ≥18%, an ash content of ≤30%, and a metal impurity content of ≤5%.

[0022] In the above scheme, the mass ratio of the waste activated carbon to the cold-rolled sludge is (2~3):1.

[0023] In the above scheme, the pressure of the low-pressure saturated steam is 0.25~0.35MPa.

[0024] In the above scheme, the anthracite, steel slag modified biochar and mixture A are mixed in a mass ratio of 83%~89%, 10%~15%, and 1%~2%, respectively.

[0025] In the above scheme, the grinding is carried out to a particle size ≤100 mesh.

[0026] The present invention also provides a composite injection material for co-processing hazardous waste in blast furnaces, which is prepared by the above method.

[0027] In the above scheme, the calorific value of the composite sprayed material is ≥25MJ / kg, the sulfur content is ≤0.5%, and the alkali metal content (total content of Na2O+K2O) is ≤1.5%.

[0028] The main technical concept of this invention is as follows: 1) To address the issues of unstable biomass raw material sources and high transportation and storage costs, Miscanthus species (such as Miscanthus sinensis, Miscanthus jinxianensis, and Miscanthus sinensis) with a wide distribution, low cost, and alkali metal content ≤3% are selected as biochar raw materials to control the introduction of alkali metals at the source. Simultaneously, the raw materials are processed into a density ≥1200 kg / m³ through crushing, drying, and extrusion molding. 3 The cylindrical fuel rods not only significantly reduce the transportation and storage costs of raw materials, but also improve the heat and mass transfer efficiency of the subsequent carbonization process, solving the problem of low carbonization efficiency of loose biomass.

[0029] 2) To address the technical challenge of excessive alkali metals in biomass char that can easily lead to blast furnace nodulation, a low-temperature inert atmosphere carbonization process at 380~420℃ is adopted. Under the premise of ensuring biomass char yield (≥35%) and fixed carbon content (≥60%), the process promotes the full decomposition of cellulose and hemicellulose in Miscanthus plants, effectively removing most of the volatile matter (volatile matter content ≤20%), while reducing the volatilization and enrichment of alkali metals. Furthermore, after carbonization, steel slag powder is sprayed onto the surface of the biomass char. The high calcium content of the steel slag powder forms a stable compound with the alkali metal, achieving solidification and control of the alkali metals, thus reducing the risk of alkali metal pollution when the biomass char is used for blast furnace injection.

[0030] 3) To address the issues of high moisture content, complex composition, and uneven dispersion of cold-rolled sludge, the excellent physical and chemical adsorption properties of waste activated carbon are utilized to achieve primary dispersion of the cold-rolled sludge. Steam is used to remove some sulfur from the waste activated carbon and promote more uniform mixing. Then, the mechanical force of the grinding process is used to achieve secondary homogenization, ensuring uniform composition of the mixture. This solves the core difficulties of easy agglomeration and incomplete combustion when cold-rolled sludge is directly mixed. At the same time, the sulfur residue problem of waste activated carbon is controlled by precise proportioning with low-sulfur anthracite and low-sulfur biochar, ultimately ensuring that the sulfur content of the mixed powder is ≤0.5%, meeting the requirements of blast furnace injection for molten iron quality.

[0031] 4) To address the issue that existing simple mixing and injection of multi-source solid waste cannot meet the needs of blast furnace smelting, based on the strict requirements of blast furnace injection for calorific value, sulfur content, and alkali metal content, the optimal mixing ratio of anthracite, biochar, and mixture A is determined. The calorific value and alkali metal content of the mixed powder are precisely controlled, achieving complementary performance and precise matching of multi-source materials. The entire process requires no additional special equipment or reagents and can be industrialized by relying on the existing blast furnace injection system of steel enterprises, solving the problem of mismatch between the co-utilization of solid waste and the needs of blast furnace smelting in existing technologies.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) This invention breaks through the technical bottleneck of using multi-source carbon-containing solid waste in blast furnace injection: through raw material screening, targeted pretreatment and precise proportioning, it effectively solves the core technical difficulties of excessive alkali metals in biomass carbon, sulfur residue in waste activated carbon and uneven dispersion of cold rolling sludge, avoids problems such as incomplete combustion and furnace condition fluctuation caused by simple mixing, and realizes efficient synergistic resource utilization of waste activated carbon, biomass carbon and cold rolling sludge.

[0033] 2) This invention significantly improves carbon emission reduction efficiency: it uses renewable Miscanthus plants to prepare biochar to replace part of the coal powder, while realizing the recycling of hazardous waste from steel enterprises, reducing carbon emissions from fossil fuel consumption and hazardous waste disposal, and providing a practical and feasible technical path for the low-carbon transformation of the steel industry.

[0034] 3) The invention is economical and practical: the raw materials are selected from cheap and readily available Miscanthus plants and hazardous waste produced by steel enterprises, which reduces the cost of raw materials; the on-site pretreatment process reduces transportation and storage costs, and no new special equipment is required, making it easy to promote industrialization; at the same time, it improves the combustion efficiency of the mixed materials and the stability of blast furnace operation, ensuring the efficiency of ironmaking and the quality of molten iron. Detailed Implementation

[0035] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0036] Example 1 1) The collected Miscanthus plants were crushed on-site to a length of 3mm using a mobile crusher and briquetting machine. The moisture content was reduced to 12% after drying at 110℃ for 20 minutes. Then, they were extruded at 15MPa into cylindrical fuel rods with a diameter of 3cm and a length of 8cm, which increased the density of the raw material to 1250kg / m³. Among them, the collected Miscanthus sinensis plant samples were tested and found to contain 61% total cellulose and hemicellulose, 48% carbon, 2% alkali metals, and 6% ash. 2) The biomass fuel rods were carbonized at 380℃ for 90 minutes under a nitrogen atmosphere to obtain biochar. The fixed carbon content of the biochar was 65% and the volatile matter content was 18%. Then, steel slag powder was sprayed on the surface of the biochar under a nitrogen atmosphere at a spraying amount of 0.5% of the biochar mass to obtain steel slag modified biochar. The steel slag powder used is a powder material obtained by grinding converter smelting waste slag after magnetic separation to remove iron, with a surface area of ​​400 m². 2 / kg, the main components include: CaO 40%, SiO2 12%, TFe 22%, MgO 3%; 3) The waste activated carbon and cold-rolled sludge are thoroughly mixed in a 2:1 ratio in a sealed container with 0.3 MPa saturated steam to obtain mixture A; Among them, the waste activated carbon refers to the waste granular activated carbon generated during the desulfurization and denitrification process of sintering flue gas in iron and steel enterprises, with a particle size of 0.5~3mm and a specific surface area of ​​820m². 2 / kg, with a fixed carbon content of 65% and a sulfur content of 1.2%; Cold-rolled sludge is an oil-containing hazardous solid waste generated during the cold rolling process of steel enterprises. It has a water content of 25%, an oil content of 25%, a fixed carbon content of 25%, an ash content of 30%, and a metallic impurity content of 5%. 4) Mix anthracite, steel slag modified biochar and mixture A at a mass ratio of 83%, 15% and 2%, respectively, and grind them to a particle size of ≤100 mesh to obtain composite injection material for use in blast furnace injection.

[0037] Sampling and testing showed that the composite sprayed material prepared in this embodiment has a calorific value of 25.6 MJ / kg, a sulfur content of 0.5%, and an alkali metal content (total content of Na2O+K2O) of 1.5%.

[0038] Example 2 1) The collected Miscanthus plants were crushed on-site to a length of 5mm using a mobile crusher and briquetting machine. The moisture content was reduced to 15% after drying at 130℃ for 10 minutes. Then, they were extruded at 18MPa into cylindrical fuel rods with a diameter of 2cm and a length of 7cm, which increased the density of the raw material to 1370kg / m³. Among them, samples of Miscanthus sinensis and Reed simonii were collected and tested. The total content of cellulose and hemicellulose was 64%, the carbon content was 50%, the alkali metal content was 2%, and the ash content was 7%. 2) The biomass fuel rods were carbonized at 420℃ for 60 minutes under a nitrogen atmosphere to obtain biochar. The fixed carbon content of the biochar was 63% and the volatile matter content was 20%. Then, steel slag powder was sprayed on the surface of the biochar under a nitrogen atmosphere at a spraying amount of 1% of the biochar mass to obtain steel slag modified biochar. The steel slag powder used is a powder material obtained by grinding converter smelting waste slag after magnetic separation to remove iron, with a surface area of ​​500 m². 2 / kg, the main components include: CaO 45%, SiO2 15%, TFe 17%, MgO 5%; 3) The waste activated carbon and cold-rolled sludge are thoroughly mixed in a 3:1 ratio in a sealed container with 0.25 MPa saturated steam to obtain mixture A; Among them, the waste activated carbon refers to the waste granular activated carbon generated during the desulfurization and denitrification process of sintering flue gas in iron and steel enterprises, with a particle size of 0.5~0.3mm and a specific surface area of ​​800m².2 / kg, with a fixed carbon content of 67% and a sulfur content of 1%; Cold-rolled sludge is an oil-containing hazardous solid waste generated during the cold rolling process of steel enterprises. It has a water content of 35%, an oil content of 20%, a fixed carbon content of 18%, an ash content of 25%, and a metallic impurity content of 4%. 4) Mix anthracite, steel slag modified biochar and mixture A at a mass ratio of 89%, 10% and 1%, respectively, and grind them to a particle size of ≤100 mesh to obtain composite injection material for use in blast furnace injection.

[0039] Sampling and testing showed that the composite sprayed material prepared in this embodiment had a calorific value of 27 MJ / kg, a sulfur content of 0.4%, and an alkali metal content (total content of Na2O+K2O) of 1.2%.

[0040] Example 3 1) The collected Miscanthus plants were crushed on-site to a length of 4mm using a mobile crusher and briquetting machine. The moisture content was reduced to 10% after drying at 120℃ for 20 minutes. Then, they were extruded at 17MPa into cylindrical fuel rods with a diameter of 2cm and a length of 9cm, which increased the density of the raw material to 1210kg / m³. Among them, a mixture of Miscanthus sinensis, Miscanthus jinxianensis and Miscanthus nandi were collected and tested. The total content of cellulose and hemicellulose was 55%, carbon content was 45%, alkali metal content was 3%, and ash content was 8%. 2) The biomass fuel rods were carbonized at 400℃ for 80 minutes under a nitrogen atmosphere to obtain biochar. The fixed carbon content of the biochar was 60% and the volatile matter content was 19%. Then, steel slag powder was sprayed on the surface of the biochar under a nitrogen atmosphere at a spraying amount of 0.8% of the biochar mass to obtain steel slag modified biochar. The steel slag powder used is a powder material obtained by grinding converter smelting waste slag after magnetic separation to remove iron, with a surface area of ​​450 m². 2 / kg, the main components include: CaO 42%, SiO2 10%, TFe 20%, MgO 8%; 3) The waste activated carbon and cold-rolled sludge are thoroughly mixed in a 2:1 ratio in a sealed container with 0.3 MPa saturated steam to obtain mixture A; Among them, the waste activated carbon refers to the waste granular activated carbon generated during the desulfurization and denitrification process of sintering flue gas in iron and steel enterprises, with a particle size of 0.5~0.3mm and a specific surface area of ​​850 m². 2 / kg, with a fixed carbon content of 68% and a sulfur content of 1.1%; Cold-rolled sludge is an oil-containing hazardous solid waste generated during the cold rolling process of steel enterprises. It has a water content of 30%, an oil content of 25%, a fixed carbon content of 23%, an ash content of 29%, and a metallic impurity content of 5%. 4) Mix anthracite, steel slag modified biochar and mixture A at a mass ratio of 85%, 13% and 2%, respectively, and grind them to a particle size of ≤100 mesh to obtain composite injection material for use in blast furnace injection.

[0041] Sampling and testing showed that the composite sprayed material prepared in this embodiment had a calorific value of 25.8 MJ / kg, a sulfur content of 0.45%, and an alkali metal content (total content of Na2O+K2O) of 1.3%.

[0042] Comparative Example 1 Uncarbonized Miscanthus plants were directly used to replace steel slag modified biochar, which was then mixed with anthracite and mixture A (in the same proportions as in Example 1), ground, and injected. It was found that coking at the blast furnace tuyeres worsened, and the potassium and sodium loads at the bottom of the blast furnace increased significantly. Testing showed that the calorific value of the composite injection material prepared in this comparative example decreased to 23.9 MJ / kg, the sulfur content increased to 0.62%, and the alkali metal content reached 2.1%, posing a risk for long-term operation.

[0043] Comparative Example 2 Cold-rolled oily sludge was directly used to replace mixture A, which was mixed with anthracite and steel slag modified biochar (in the same proportion as in Example 1), ground, and then injected. This resulted in blockage of the blast furnace pulverized coal injection system and large fluctuations in furnace temperature. Testing showed that the calorific value of the composite injection material fluctuated around 25.7±4%, severely impacting blast furnace operation.

[0044] The above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations, and any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a composite injection material for co-processing hazardous waste in blast furnaces, characterized in that, Includes the following steps: 1) After crushing and drying Miscanthus plants, they are extruded into biomass fuel rods; 2) Carbonize the biomass fuel rods under an inert atmosphere to obtain biochar; then spray steel slag powder onto the surface of the biochar under an inert atmosphere to obtain steel slag modified biochar. 3) Thoroughly mix the waste activated carbon and cold-rolled sludge in a closed container through which low-pressure saturated steam is introduced to obtain mixture A; 4) Anthracite, steel slag modified biochar and mixture A are mixed and ground to obtain composite injection material for use in blast furnace injection.

2. The method for preparing composite injection material for co-processing hazardous waste in blast furnaces according to claim 1, characterized in that, The *Miscanthus* species are one or more of *Miscanthus sinensis*, *Miscanthus chinensis*, and *Reedia spp.*, with a total cellulose and hemicellulose content >50%, carbon content ≥45%, alkali metal content ≤3%, and ash content ≤8%; the density of the biomass fuel rods is >1200 kg / m³. 3 .

3. The method for preparing composite injection material for co-processing hazardous waste in blast furnaces according to claim 1, characterized in that, The inert atmosphere is preferably nitrogen; the carbonization temperature is 380~420℃ and the time is 60~90min; the fixed carbon content of the biochar is ≥60% and the volatile matter content is ≤20%.

4. The preparation method of the composite injection material for co-processing hazardous waste in blast furnaces according to claim 1, characterized in that, The surface area of ​​the steel slag powder is 400~500m². 2 / kg, the main components include: CaO 40%~45%, SiO2 10%~15%, TFe 17%~22%, MgO 3%~8%; the spraying amount of the steel slag powder is 0.5%~1% of the biochar mass.

5. The preparation method of the composite injection material for co-processing hazardous waste in blast furnaces according to claim 1, characterized in that, The waste activated carbon has a particle size of 0.5~3mm and a specific surface area ≥800 m². 2 / kg, fixed carbon content ≥65%, sulfur content ≤1.2%; the water content of the cold-rolled sludge is 25%~35%, the oil content is 15%~25%, the fixed carbon content is ≥18%, the ash content is ≤30%, and the metal impurity content is ≤5%.

6. The method for preparing composite injection material for co-processing hazardous waste in blast furnaces according to claim 1, characterized in that, The mass ratio of the waste activated carbon to the cold-rolled sludge is (2~3):1; the pressure of the low-pressure saturated steam is 0.25~0.35MPa.

7. The method for preparing composite injection material for co-processing hazardous waste in blast furnaces according to claim 1, characterized in that, The anthracite, steel slag modified biochar, and mixture A are mixed at mass ratios of 83%~89%, 10%~15%, and 1%~2%, respectively; the powder is ground to a particle size ≤100 mesh.

8. The method for preparing composite injection material for co-processing hazardous waste in blast furnaces according to claim 1, characterized in that, The length of the crushed Miscanthus plants is 3-5 mm; the drying temperature is 110-130℃, the time is 10-20 min, and the moisture content of the dried Miscanthus plants is 10%-15%; the extrusion pressure is 15-18 MPa; the biomass fuel rod is cylindrical, with a diameter of 2-3 cm and a length of 7-9 cm.

9. A composite injection material for co-processing hazardous waste in blast furnaces, prepared by the method according to any one of claims 1 to 9.

10. The composite injection material for co-processing hazardous waste in blast furnaces according to claim 9, characterized in that, The composite sprayed material has a calorific value ≥25MJ / kg, a sulfur content ≤0.5%, and an alkali metal content ≤1.5%.