Red mud-based converter composite coolant and staged addition temperature control method thereof

Abstract

The present application relates to converter steelmaking auxiliary material technical field, specifically to a kind of red mud-based converter composite coolant and its stage adding temperature control method.The composite coolant is composed of modified bayer process red mud 40~60 parts, low melting point cooling component 25~40 parts and stable slag lining component 10~20 parts;Low melting point cooling component is mixed by Fe3O4≥85% iron oxide scale and FeCO3≥90% siderite according to 2~3:1;Stable slag lining component is mixed by MgO≥35%, active ≥90% light-burned dolomite and purity ≥92% active Al2O3 according to 3~4:1.Modified red mud is obtained by drying at 105~110℃, calcination at 550~650℃, 1200~1500Gs magnetic separation.The stage adding temperature control method is: top adding granular agent 0.3%~0.6% in early blowing, mid-term blowing powder 0.8%~1.5%, top adding granular agent 0.2%~0.5% in later period, and synergistically adjusting oxygen lance position and oxygen supply intensity.The present application has the advantages of high temperature control precision, effective removal of alkali metal in red mud, prolonging the service life of furnace lining, reducing the cost of coolant, reducing spatter, etc.

Description

Technical Field

[0001] This invention relates to the field of auxiliary materials technology for converter steelmaking, specifically to a red mud-based converter composite coolant and its staged addition and temperature control method. Background Technology

[0002] In converter steelmaking, coolant needs to be added to the furnace to balance the excess heat generated during blowing and to accurately control the final temperature. Currently, commonly used coolants in converter smelting mainly include iron ore, scrap steel, iron oxide scale, and sinter. However, traditional coolants have significant shortcomings in practical applications: when iron ore is used as a coolant, its decomposition endothermic reaction is delayed, often resulting in a 3-5 minute delay in temperature control, affecting the accuracy of the final temperature hit; the cooling efficiency of scrap steel is only 60%-70% of that of iron ore, and it requires pretreatment such as crushing and sorting, resulting in higher costs; when iron oxide scale is used alone, its large specific surface area and violent reaction can easily cause large fluctuations in furnace temperature, and even trigger splashing. In addition, the above-mentioned coolants have a single function, only serving a cooling purpose, and cannot simultaneously address slag system optimization and furnace lining protection during the smelting process. Often, additional slag conditioners such as fluorite and lightly calcined dolomite are required, increasing the complexity of the process and the consumption of auxiliary materials.

[0003] Bayer process red mud is a solid waste generated during the production of alumina from bauxite. Its main chemical components are Fe2O3, SiO2, Al2O3, CaO, Na2O, and TiO2. my country discharges over 100 million tons of Bayer process red mud annually, resulting in a massive accumulated stockpile. The stockpiling of red mud not only occupies large amounts of land, but its high alkalinity (typically 3%–10% Na2O content) also easily leads to soil alkalization and groundwater pollution. Furthermore, after drying, it becomes particulate dust, seriously harming the ecological environment. Therefore, achieving large-scale, high-value-added resource utilization of red mud has significant environmental and economic value.

[0004] In recent years, there have been attempts to apply red mud as a coolant in converters. For example, Chinese patent CN101914654B discloses "A Red Mud Steelmaking Coolant and Its Manufacturing Process," which uses red mud with an iron content ≥47% (by weight) after magnetic separation, adds bentonite and sodium silicate, and then granulates and dries it to obtain red mud spheres as a coolant. This scheme has achieved the initial application of red mud in converter cooling, but the following problems still exist: First, low-temperature drying (200~400℃) alone cannot effectively remove alkali metals (Na2O) from the red mud. High-alkali components can easily cause "alkali embrittlement" defects in molten steel and aggravate furnace lining erosion after entering the converter with the coolant; Second, the coolant composition is singular, relying only on the cooling and slag-forming capacity of the red mud itself, lacking active control over slag viscosity, melting point, and lining performance; Third, differentiated addition processes are not designed for the dynamic temperature requirements of different blowing stages in the converter, resulting in limited temperature control accuracy.

[0005] Chinese patent CN103352099B further proposes a method for producing converter coolant using Bayer process red mud. This method employs wet magnetic separation to increase the total iron content of the red mud and adds water glass and sodium fluorosilicate as binders. The coolant is obtained after pelletizing and drying. While this technology improves the iron grade in the red mud, it still fails to solve the problem of alkali metal removal. Furthermore, the added binders only improve pellet strength and do not provide auxiliary cooling or slag stabilization / lining functions. In addition, this scheme also does not address the staged and precise addition of the coolant.

[0006] In summary, existing converter coolants prepared from red mud generally suffer from problems such as high alkali metal residues, limited functionality, poor temperature control precision, and a lack of synergistic addition methods with the smelting process. They struggle to simultaneously achieve multiple objectives, including solid waste disposal, precise temperature control, slag stabilization and lining protection, and cost control. Therefore, developing a composite coolant that can effectively remove alkali metals from red mud, combines cooling and slag system regulation functions, and is compatible with the phased smelting process of converters, along with its application method, is a pressing technical problem to be solved in this field. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a red mud-based converter composite coolant and its staged addition and temperature control method, which simultaneously achieves multiple effects such as bulk red mud disposal, precise temperature control, slag stabilization and furnace protection, reduction of steelmaking auxiliary material costs, and reduction of smelting splashing.

[0008] To achieve the above objectives, the present invention employs the following technical solution: A red mud-based converter composite coolant, comprising the following components in parts by weight: 40-60 parts modified Bayer process red mud; 25-40 parts low-melting-point cooling component, wherein the low-melting-point cooling component is a mixture of iron oxide scale and siderite in a mass ratio of 2:1-3:1; the iron oxide scale has an Fe3O4 content ≥85wt%, and the siderite has an FeCO3 content ≥90wt%; 10-20 parts slag stabilizing and lining component, wherein the slag stabilizing and lining component is a mixture of light-burned dolomite and active Al2O3 in a mass ratio of 3:1-4:1; the light-burned dolomite has an MgO content ≥35wt% and an activity ≥90wt%; and the active Al2O3 has a purity ≥92wt%.

[0009] Furthermore, the modified Bayer red mud is prepared by drying Bayer red mud at 105~110℃, calcining and modifying it at 550~650℃, and then wet magnetic separation at 1200~1500Gs. The Na2O content of the modified Bayer red mud is ≤1.2wt%.

[0010] Furthermore, the composite coolant includes two dosage forms: granules and powder. The granules have a particle size of 2-4 mm and a compressive strength ≥5 MPa; the powder has a mesh size of 100 and a bulk density of 0.8-1.2 g / cm³. 3 Free water ≤1.0wt%.

[0011] Preferably, the modified Bayer red mud comprises 40 parts, the low-melting-point cooling component comprises 40 parts, and the slag stabilizing lining component comprises 20 parts.

[0012] Preferably, the modified Bayer red mud comprises 60 parts, the low-melting-point cooling component comprises 25 parts, and the slag stabilizing lining component comprises 10 parts; the mass ratio of iron oxide scale to siderite is 2:1, 2.5:1, or 3:1; and the mass ratio of lightly calcined dolomite to active Al2O3 is 3:1, 3.5:1, or 4:1.

[0013] The preparation method of the above-mentioned red mud-based converter composite coolant is characterized by comprising the following steps: (1) Preparation of modified red mud: Bayer process red mud is dried and dehydrated at 105~110℃, calcined and modified at 550~650℃, and wet magnetic separation at 1200~1500Gs to remove impurities, thereby obtaining modified Bayer process red mud. (2) Raw material pretreatment: Modified Bayer red mud, iron oxide scale, siderite, lightly calcined dolomite and active Al2O3 are crushed and sieved respectively to make the particle size of modified Bayer red mud 80~120 mesh, iron oxide scale 100~140 mesh, siderite 120~160 mesh, lightly calcined dolomite 80~120 mesh and active Al2O3 100~140 mesh; (3) Mixing: Under the protection of inert gas, weigh each raw material according to the weight parts described in claim 1, and mix them at a speed of 200~300r / min for 15~25min under the condition of ambient temperature ≤40℃ to obtain a mixture. (4) Molding: The mixture is made into granules with a particle size of 2-4 mm and a compressive strength of ≥5 MPa, or ground into powder with a fineness of 100 mesh; (5) Packaging: Vacuum-sealed moisture-proof packaging of the prepared granules or powders.

[0014] A staged addition and temperature control method based on the above-mentioned red mud-based converter composite coolant, used in the converter smelting process, includes the following steps: (1) Early stage of blowing: Within 5 to 10 minutes after the start of converter blowing, granules are added into the furnace through the top of the furnace, with the amount added being 0.3% to 0.6% of the mass of molten iron; (2) Mid-stage of blowing: Within 10 to 20 minutes after the start of converter blowing, powder is added into the furnace by injection, with the amount added being 0.8% to 1.5% of the mass of molten iron; (3) Later stage of blowing: Within 20 to 28 minutes after the start of converter blowing, granules are added into the furnace again through the top of the furnace, and the amount added is 0.2% to 0.5% of the mass of molten iron.

[0015] Furthermore, the method also includes: controlling the oxygen lance position to 1.8~2.5m and the oxygen supply intensity to 2.5~3.5Nm during the early and late stages of blowing. 3 / (min·t); During the middle stage of blowing, the oxygen lance position is controlled at 1.2~1.8m, and the oxygen supply intensity is 3.5~4.5Nm. 3 / (min·t).

[0016] Technical principle explanation: (1) Modification mechanism of Bayer process red mud: 105-110℃ completely removes free water from the red mud; 550-650℃ medium-temperature roasting dehydrates the goethite and limonite in the red mud, transforming them into highly active magnetite, and decomposes and volatilizes bound sodium salts upon heating; when the roasting temperature is below 550℃, the sodium salts decompose incompletely, and when it is above 650℃, the red mud particles sinter densely, and the activity decreases significantly upon cooling and heat absorption; 1200-1500Gs wet magnetic separation relies on the difference in magnetic properties of the materials to separate non-magnetic silica-alumina alkaline slag, and when the magnetic field strength is below 1200Gs, the impurity removal efficiency is insufficient, and when it is above 1500Gs, the energy consumption for mineral processing increases by 32%, resulting in poor economic efficiency. After modification, the Na2O in the red mud is ≤1.2wt%, solving the alkali damage problem from the source.

[0017] (2) Mechanism of action of low melting point cooling components: Fe3O4 in iron oxide scale decomposes and absorbs heat at high temperature step by step, while FeCO3 in siderite decomposes and absorbs heat in advance in the medium temperature range of 850-1150℃. The two form a medium temperature + high temperature stepped heat absorption system to make up for the heat absorption lag defect of iron ore. When Fe3O4 < 85wt% and FeCO3 < 90wt%, the proportion of inert impurities increases and the cooling efficiency decreases by more than 20%.

[0018] (3) Mechanism of action of slag stabilizing and protective lining components: High-pollution fluorite raw materials are discarded, and lightly calcined dolomite decomposes at high temperature to generate active CaO and MgO. MgO adheres to the inner wall of the furnace lining to form a protective layer to slow down melting loss; active Al2O3 precisely controls the viscosity of slag to prevent slag from drying out in the middle and late stages of smelting; if the MgO of lightly calcined dolomite is less than 35wt% and the activity is insufficient, the protective lining will fail; when the purity of active Al2O3 is less than 92wt%, impurities will destroy the stability of the slag system.

[0019] (4) Inert low temperature mixing mechanism: Siderite is easily oxidized and deteriorated when exposed to air at room temperature, and loses its decomposition and heat absorption capacity. Oxidation of the iron oxide scale will reduce the effective iron content. Low temperature ≤40℃ + inert gas closed mixing ensures the stability of the physical and chemical properties of the raw materials.

[0020] (5) The mechanism of phased addition process: the temperature rises slowly in the early stage of blowing, and the granules melt slowly and the temperature is steadily controlled; in the middle stage, carbon and oxygen react violently and the heat release reaches the peak. The fine powder has a large specific surface area and absorbs heat quickly and instantaneously, suppressing overheating and splashing; in the later stage, the heat load drops and a small number of particles are used to finely adjust the final temperature; the oxygen lance position and oxygen supply intensity are matched with the heat surplus change law in the furnace at each stage.

[0021] Compared with existing methods, the beneficial effects of the present invention are: 1. Excellent temperature control accuracy: The stepped heat absorption formula + segmented addition + oxygen lance linkage control can control the final temperature deviation within ±10℃ and the furnace temperature fluctuation throughout the process ≤±30℃. Compared with traditional iron ore cooling, the temperature control accuracy is improved by 65%, and the cooling efficiency is improved by 15% to 20% compared with single iron ore, eliminating the disadvantage of the 3 to 5 minute heat absorption lag of traditional coolants.

[0022] 2. Effectively eliminates red mud alkali damage and extends furnace lining life: roasting + wet magnetic separation dual dealkali removal, modified red mud Na2O≤1.2wt%; slag stabilizing components form slag in situ to protect the furnace, reducing the furnace lining erosion rate by 12%~18%, and eliminating steel alkali embrittlement defects.

[0023] 3. Large-scale red mud utilization and significant reduction in production costs: The main raw material for coolant is waste red mud, and the comprehensive selling price of the finished product is 450-600 yuan / t, which is significantly advantageous compared to iron ore (700-800 yuan / t) and scrap steel (2100-2500 yuan / t); A steel enterprise with an annual output of 10 million tons of steel can utilize 10 million tons of red mud per year: 10 million tons × (25-40 kg / t) = 250,000-400,000 tons, reducing the cost of coolant per ton of steel by 25%-35%.

[0024] 4. Simplified slag-making process and environmental protection and emission reduction: The coolant has built-in slag-stabilizing components, so there is no need to add fluorite during smelting. The amount of slag-making auxiliary materials added per ton of steel is reduced by about 2kg, and the emissions of fluoride and yellow smoke from smelting flue gas are reduced by more than 40%.

[0025] 5. Stable smelting conditions: Mid-term powder injection rapidly controls temperature, reducing the frequency of smelting splashes by more than 50%, thus improving the on-site working environment.

[0026] 6. Good storage and transportation stability: The granular products have a compressive strength of ≥5MPa, and the product strength decreases by <3% after 6 months of vacuum sealing storage. They are not easy to absorb moisture and turn into powder, and generate less dust. Detailed Implementation

[0027] This invention discloses a red mud-based converter composite coolant and its staged addition and temperature control method. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0028] This invention provides a red mud-based converter composite coolant and its staged addition and temperature control method, as detailed below: 1. Composite coolant formulation: Based on mass percentage, the composite coolant mainly consists of three parts: 40% to 60% modified Bayer red mud, 25% to 40% low-melting-point cooling components, and 10% to 20% slag stabilizing and lining components.

[0029] The preparation process of modified Bayer red mud includes three key steps: first, drying at 105~110℃ to completely remove moisture; then, calcination modification treatment at a high temperature of 550~650℃; and finally, effective removal of impurities through a wet magnetic separation process of 1200~1500Gs, thereby obtaining modified red mud raw materials that meet the requirements.

[0030] The low-melting-point cooling component is prepared by mixing iron oxide scale (requiring a Fe3O4 content of not less than 85%) and siderite (requiring a FeCO3 content of not less than 90%) in a mass ratio of 2:1 to 3:1. The slag stabilizing lining component is prepared by compounding lightly calcined dolomite (with an MgO content ≥35% and an activity index ≥90%) and active Al2O3 (purity ≥92%) in a mass ratio of 3:1 to 4:1 to ensure the stability and effectiveness of the final component performance.

[0031] 2. Preparation method: Each raw material component needs to be pre-treated and sieved separately. Specifically, modified red mud requires a particle size of 80-120 mesh, iron oxide scale 100-140 mesh, siderite 120-160 mesh, lightly calcined dolomite 80-120 mesh, and activated Al₂O₃ 100-140 mesh. Subsequently, under an inert gas atmosphere, maintaining an ambient temperature not exceeding 40℃, the materials are added to a mixing device according to the predetermined formula ratio and mixed at a speed of 200-300 r / min for 15-25 minutes to ensure homogeneity.

[0032] The mixture can be further processed into two dosage forms as needed: one is to produce granular products with a particle size of 2-4 mm and a compressive strength of not less than 5 MPa; the other is to grind it into a powder with a fineness of 100 mesh. The final product must be vacuum-sealed to ensure its quality and storage stability.

[0033] 3. Application process: The use of this coolant must be closely integrated with the three stages of the converter blowing process and their furnace temperature variation characteristics, implementing precise, phased addition. In the early blowing stage (approximately 5-10 minutes), granular agent is added through the furnace top at a rate of 0.3% to 0.6% of the molten iron mass to achieve initial temperature control. In the middle blowing stage (approximately 10-20 minutes), powdered agent is added via injection at a rate of 0.8% to 1.5% to enhance the cooling effect. In the later blowing stage (approximately 20-28 minutes), granular agent is again added through the furnace top at a rate of 0.2% to 0.5% for fine-tuning the furnace temperature. Throughout the process, the oxygen lance position and oxygen supply intensity must be coordinated. Specifically, in the early and later blowing stages, the oxygen lance position should be controlled at 1.8-2.5m and the oxygen supply intensity at 2.5-3.5Nm. 3 / (min·t), during the mid-stage of blowing, the oxygen lance position is controlled at 1.2~1.8m and the oxygen supply intensity is 3.5~4.5Nm. 3 / (min·t), thereby achieving precise and stable control of the converter furnace temperature, ensuring the smooth and efficient operation of the smelting process.

[0034] Example 1 (suitable for low carbon steel, target endpoint C: 0.08%, temperature: 1540±10℃) The composite coolant consists of the following components in parts by weight: a total of 100 parts by weight, 50 parts of modified Bayer red mud; 35 parts of low-melting-point cooling component, which is a mixture of iron oxide scale with a Fe3O4 content of 87% and siderite with a FeCO3 content of 92% in a mass ratio of 2.5:1; and 15 parts of slag stabilizing lining component, which is a mixture of lightly calcined dolomite with a MgO content of 38% and an activity of 92% and active Al2O3 with a purity of 93% in a mass ratio of 3.5:1.

[0035] Among them, the modified Bayer process red mud is prepared by drying Bayer process red mud at 108℃, calcining at 600℃ for modification, and then wet magnetic separation at 1350Gs.

[0036] The preparation method of the composite coolant is as follows: (1) Preparation of modified red mud: Bayer process red mud was dried and dehydrated at 108℃, calcined and modified at 600℃, and then wet magnetically separated at 1350Gs to remove impurities, in order to obtain modified Bayer process red mud.

[0037] (2) Raw material pretreatment: Modified Bayer red mud, iron oxide scale, siderite, lightly calcined dolomite and active Al2O3 are crushed and sieved respectively to make the particle size of modified Bayer red mud 100 mesh, iron oxide scale 120 mesh, siderite 140 mesh, lightly calcined dolomite 100 mesh and active Al2O3 120 mesh.

[0038] (3) Mixing: Under nitrogen protection, weigh each raw material according to the above weight parts, mix at an ambient temperature of 35℃ and a rotation speed of 250r / min for 20min to obtain a mixture.

[0039] (4) Molding: The mixture is made into granules with a particle size of 3 mm and a compressive strength of 5.5 MPa.

[0040] (5) Packaging: The prepared granules are vacuum-sealed for moisture protection.

[0041] The staged addition and temperature control method is as follows: Early stage of blowing: Within 7 minutes after the start of converter blowing, the above-mentioned granular agent is added into the furnace through the top of the furnace, and the amount added is 0.5% of the mass of molten iron.

[0042] Mid-stage of blowing: Within 15 minutes after the start of converter blowing, 100-mesh powder made from the same formula is added into the furnace by injection, with the amount added being 1.2% of the mass of molten iron.

[0043] Late stage of blowing: Within 24 minutes after the start of converter blowing, the granular agent is added into the furnace again through the top of the furnace, and the amount added is 0.3% of the mass of molten iron.

[0044] Simultaneously, the oxygen lance position and oxygen supply intensity are adjusted in a coordinated manner: in the early and late stages of blowing, the oxygen lance position is controlled at 2.0m, and the oxygen supply intensity is controlled at 3.0Nm. 3 / (min·t); During the middle stage of blowing, the oxygen lance position is controlled at 1.5m, and the oxygen supply intensity is 4.0Nm. 3 / (min·t).

[0045] The final temperature measured after smelting was 1542℃, with a P content of 0.012% and a S content of 0.018% in the molten steel. The final temperature deviation was within ±10℃, and the furnace temperature fluctuation throughout the process was ≤±28℃. 35kg of red mud was disposed of per ton of steel, reducing the coolant cost per ton of steel by 30% compared to iron ore, and reducing the splashing frequency by more than 52%.

[0046] Example 2 (suitable for high carbon steel, target endpoint C: 0.6%, temperature: 1500±10℃) This embodiment provides a red mud-based converter composite coolant and its staged addition and temperature control method, which is applied to the smelting of high carbon steel in a 120-ton converter.

[0047] The composite coolant consists of the following components in parts by weight: a total of 100 parts by weight, 60 parts of modified Bayer red mud; 25 parts of low-melting-point cooling component, which is a mixture of iron oxide scale with 86% Fe3O4 content and siderite with 91% FeCO3 content in a mass ratio of 3:1; and 15 parts of slag stabilizing lining component, which is a mixture of lightly calcined dolomite with 37% MgO content and 91% activity and active Al2O3 with 93% purity in a mass ratio of 4:1.

[0048] Among them, the modified Bayer process red mud is prepared by drying Bayer process red mud at 105℃, calcining at 550℃ for modification, and then wet magnetic separation at 1200Gs.

[0049] The preparation method of the composite coolant is as follows: (1) Preparation of modified red mud: Bayer process red mud was dried and dehydrated at 105℃, calcined and modified at 550℃, and then subjected to wet magnetic separation at 1200Gs to remove impurities, in order to obtain modified Bayer process red mud.

[0050] (2) Raw material pretreatment: Modified Bayer red mud, iron oxide scale, siderite, lightly calcined dolomite and active Al2O3 are crushed and sieved respectively to make the particle size of modified Bayer red mud 80 mesh, iron oxide scale 100 mesh, siderite 120 mesh, lightly calcined dolomite 80 mesh and active Al2O3 100 mesh.

[0051] (3) Mixing: Under nitrogen protection, weigh each raw material according to the above weight parts, mix at an ambient temperature of 30℃ and a rotation speed of 200r / min for 15min to obtain a mixture.

[0052] (4) Molding: Grind the mixture into a powder with a fineness of 100 mesh.

[0053] (5) Packaging: The prepared powder is vacuum-sealed for moisture protection.

[0054] The staged addition and temperature control method is as follows: Early stage of blowing: Within 5 minutes after the start of converter blowing, granules with a particle size of 2mm and a compressive strength of 5.2MPa, made with the same formula, are added into the furnace through the top of the furnace. The amount added is 0.3% of the mass of molten iron.

[0055] Mid-stage of blowing: Within 10 minutes after the start of converter blowing, the above-mentioned powder is added into the furnace by injection, with the amount added being 0.8% of the mass of molten iron.

[0056] Late stage of blowing: Within 20 minutes after the start of converter blowing, the granular agent is added into the furnace again through the top of the furnace, and the amount added is 0.2% of the mass of molten iron.

[0057] Simultaneously, the oxygen lance position and oxygen supply intensity are adjusted in a coordinated manner: in the early and late stages of blowing, the oxygen lance position is controlled at 1.8m, and the oxygen supply intensity is controlled at 2.5Nm. 3 / (min·t); During the middle stage of blowing, the oxygen lance position is controlled at 1.2m, and the oxygen supply intensity is 3.5Nm. 3 / (min·t).

[0058] The final temperature measured after smelting was 1502℃, with a P content of 0.011% and a S content of 0.015% in the molten steel. The final temperature deviation was within ±10℃, and the furnace temperature fluctuation throughout the process was ≤±25℃. 40kg of red mud was disposed of per ton of steel, reducing the coolant cost per ton of steel by 35% compared to iron ore, and reducing the splashing frequency by more than 55%.

[0059] Example 3 (Suitable for alloy structural steel, target endpoint C: 0.2%, temperature: 1530±10℃) This embodiment provides a red mud-based converter composite coolant and its staged addition and temperature control method, which is applied to the smelting of alloy structural steel in a 200-ton converter.

[0060] The composite coolant consists of the following components in parts by weight: a total of 100 parts by weight, 40 parts of modified Bayer process red mud; 40 parts of low-melting-point cooling component, which is a mixture of iron oxide scale with 88% Fe3O4 content and siderite with 93% FeCO3 content in a mass ratio of 2:1; and 20 parts of slag stabilizing lining component, which is a mixture of lightly calcined dolomite with 40% MgO content and 93% activity and active Al2O3 with 94% purity in a mass ratio of 3:1.

[0061] Among them, the modified Bayer process red mud is prepared by drying Bayer process red mud at 110℃, calcining at 650℃ for modification, and then wet magnetic separation at 1500Gs.

[0062] The preparation method of the composite coolant is as follows: 1) Preparation of modified red mud: Bayer process red mud was successively dried and dehydrated at 110℃, calcined and modified at 650℃, and removed by wet magnetic separation at 1500Gs to obtain modified Bayer process red mud.

[0063] 2) Raw material pretreatment: Modified Bayer process red mud, iron oxide scale, siderite, lightly calcined dolomite and active Al2O3 are crushed and sieved respectively to make the particle size of modified Bayer process red mud 120 mesh, iron oxide scale 140 mesh, siderite 160 mesh, lightly calcined dolomite 120 mesh and active Al2O3 140 mesh.

[0064] 3) Mixing: Under argon protection, weigh each raw material according to the above weight proportions, mix at an ambient temperature of 38℃ and a rotation speed of 300r / min for 25min to obtain a mixture.

[0065] 4) Molding: The mixture is made into granules with a particle size of 4 mm and a compressive strength of 6.0 MPa.

[0066] 5) Packaging: The prepared granules are vacuum-sealed for moisture protection.

[0067] The staged addition and temperature control method is as follows: Early stage of blowing: Within 10 minutes after the start of converter blowing, the above-mentioned granular agent is added into the furnace through the top of the furnace, and the amount added is 0.6% of the mass of molten iron.

[0068] Mid-stage of blowing: Within 20 minutes after the start of converter blowing, 100-mesh powder made from the same formula is added to the furnace by injection, with the amount added being 1.5% of the mass of molten iron.

[0069] Late stage of blowing: Within 28 minutes after the start of converter blowing, the granular agent is added into the furnace again through the top of the furnace, and the amount added is 0.5% of the mass of molten iron.

[0070] Simultaneously, the oxygen lance position and oxygen supply intensity are adjusted in a coordinated manner: in the early and late stages of blowing, the oxygen lance position is controlled at 2.5m and the oxygen supply intensity at 3.5Nm. 3 / (min·t); During the middle stage of blowing, the oxygen lance position is controlled at 1.8m, and the oxygen supply intensity is 4.5Nm. 3 / (min·t).

[0071] The final temperature measured after smelting was 1531℃, with a P content of 0.014% and a S content of 0.019% in the molten steel. The final temperature deviation was within ±10℃, and the furnace temperature fluctuation throughout the process was ≤±30℃. 25kg of red mud was disposed of per ton of steel, reducing the coolant cost per ton of steel by 25% compared to iron ore, and reducing the splashing frequency by more than 50%.

[0072] Example 4 (Effect verification under different formulations and parameters) Following the steps of Example 1, multiple sets of experiments were conducted by changing only the proportions of each component and the addition parameters in the composite coolant. In Experiment 1, the composite coolant formulation was: 45 parts modified Bayer process red mud, 30 parts low-melting-point cooling component (iron oxide scale to siderite mass ratio 2.2:1), and 12 parts slag stabilizing and lining component (lightly calcined dolomite to activated Al2O3 mass ratio 3.2:1); the staged addition amounts were 0.4% in the early stage, 1.0% in the middle stage, and 0.3% in the later stage; the oxygen lance position was 1.9m in the early and later stages and 1.4m in the middle stage; the oxygen supply intensity was 2.8Nm in the early and later stages. 3 / (min·t), medium term is 3.8 Nm 3 / (min·t). The final smelting temperature was 1538℃, with a furnace temperature fluctuation of ±25℃ throughout the process, and the splashing frequency was reduced by 52%.

[0073] In Experiment 2, the composite coolant formulation was as follows: 55 parts modified Bayer process red mud, 35 parts low-melting-point cooling component (iron oxide scale to siderite mass ratio 2.8:1), and 18 parts slag stabilizing and lining component (lightly calcined dolomite to activated Al2O3 mass ratio 3.8:1). The staged addition rates were 0.5% in the early stage, 1.3% in the middle stage, and 0.4% in the late stage. The oxygen lance position was 2.2m in the early and late stages and 1.6m in the middle stage, with an oxygen supply intensity of 3.2 Nm in the early and late stages. 3 / (min·t), the intermediate value is 4.2 Nm 3 / (min·t). The final smelting temperature was 1541℃, with a furnace temperature fluctuation of ±22℃ throughout the process, and the splashing frequency was reduced by 55%.

[0074] In Experiment 3, the composite coolant formulation was as follows: 50 parts modified Bayer process red mud, 32 parts low-melting-point cooling component (iron oxide scale to siderite mass ratio 2.5:1), and 16 parts slag stabilizing and lining component (lightly calcined dolomite to activated Al2O3 mass ratio 3.5:1). The staged addition rates were 0.45% in the early stage, 1.1% in the middle stage, and 0.35% in the late stage. The oxygen lance position was 2.0m in the early and late stages and 1.5m in the middle stage, with an oxygen supply intensity of 3.0 Nm in both the early and late stages. 3 / (min·t), the intermediate value is 4.0 Nm 3 / (min·t). The final smelting temperature was 1536℃, with a furnace temperature fluctuation of ±28℃ throughout the process, and the splashing frequency was reduced by 50%.

[0075] In all the above experiments, the endpoint temperature could be controlled within ±10℃ of the target deviation, the furnace temperature fluctuation throughout the process was ≤±30℃, and the splashing frequency was reduced by more than 50% compared with the traditional process. This shows that the technical solution of the present invention has good process adaptability and stability under different formulations and parameters.

[0076] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A red mud-based converter composite coolant, characterized in that, The composite coolant is composed of the following components in parts by weight: 40-60 parts of modified Bayer process red mud; The low-melting-point cooling component comprises 25-40 parts, wherein the low-melting-point cooling component is a mixture of iron oxide scale and siderite in a mass ratio of 2:1 to 3:1; the Fe3O4 content of the iron oxide scale is ≥85wt%, and the FeCO3 content of the siderite is ≥90wt%. The slag stabilizing lining component consists of 10-20 parts, wherein the slag stabilizing lining component is a mixture of lightly calcined dolomite and active Al2O3 in a mass ratio of 3:1 to 4:1; the MgO content of the lightly calcined dolomite is ≥35wt%, and the activity is ≥90wt%; the purity of the active Al2O3 is ≥92wt%.

2. The red mud-based converter composite coolant according to claim 1, characterized in that, The modified Bayer red mud is prepared by drying Bayer red mud at 105~110℃, calcining and modifying it at 550~650℃, and then wet magnetic separation at 1200~1500Gs. The Na2O content of the modified Bayer red mud is ≤1.2wt%.

3. The red mud-based converter composite coolant according to claim 1, characterized in that, The composite coolant includes two dosage forms: granules and powder. The particle size of the granules is 2~4mm, and the compressive strength is ≥5MPa; The powder has a mesh size of 100 and a bulk density of 0.8–1.2 g / cm³. 3 Free water ≤1.0wt%.

4. A method for preparing a red mud-based converter composite coolant as described in any one of claims 1-3, characterized in that, Includes the following steps: 1) Preparation of modified red mud: Bayer process red mud is successively dried and dehydrated at 105~110℃, calcined and modified at 550~650℃, and removed by wet magnetic separation at 1200~1500Gs to obtain modified Bayer process red mud. 2) Raw material pretreatment: Modified Bayer process red mud, iron oxide scale, siderite, lightly calcined dolomite and active Al2O3 are crushed and sieved respectively to make the particle size of modified Bayer process red mud 80~120 mesh, iron oxide scale 100~140 mesh, siderite 120~160 mesh, lightly calcined dolomite 80~120 mesh and active Al2O3 100~140 mesh; 3) Mixing: Under the protection of inert gas, weigh each raw material according to the weight parts described in claim 1, and mix them at a speed of 200~300 r / min for 15~25 min under the condition of ambient temperature ≤40℃ to obtain a mixture. 4) Molding: The mixture is made into granules with a particle size of 2-4 mm and a compressive strength of ≥5 MPa, or ground into powder with a fineness of 100 mesh. 5) Packaging: Vacuum-sealed moisture-proof packaging of the prepared granules or powders.

5. A method for staged addition and temperature control of the red mud-based converter composite coolant according to any one of claims 1-3, characterized in that, This method is used in converter smelting processes and includes the following steps: 1) Early stage of blowing: Within 5 to 10 minutes after the start of converter blowing, add granular agent into the furnace through the top of the furnace, with the amount added being 0.3% to 0.6% of the mass of molten iron; 2) Mid-stage of blowing: Within 10 to 20 minutes after the start of converter blowing, powder is added into the furnace by injection, with the amount added being 0.8% to 1.5% of the molten iron mass; 3) Late stage of blowing: Within 20 to 28 minutes after the start of converter blowing, granules are added into the furnace again through the top of the furnace, with the amount added being 0.2% to 0.5% of the mass of molten iron.

6. The staged addition and temperature control method according to claim 5, characterized in that, The method further includes: controlling the oxygen lance position to 1.8~2.5m and the oxygen supply intensity to 2.5~3.5Nm during the early and late stages of blowing. 3 / (min·t); During the middle stage of blowing, the oxygen lance position is controlled at 1.2~1.8m, and the oxygen supply intensity is 3.5~4.5Nm. 3 / (min·t).