Integrated slagging agent for hot metal pretreatment based on bayer process red mud and method for its preparation

Abstract

The present application relates to the technical field of steelmaking auxiliary materials, in particular to a molten iron pretreatment integrated slagging agent based on Bayer process red mud and a preparation method thereof. The slagging agent is composed of activated red mud, dephosphorization component, desulfurization component, fluxing agent, anticaking agent and binder. The dephosphorization component is a mixture of manganese dioxide and iron red, the desulfurization component is a mixture of calcium carbide and magnesium oxide, the fluxing agent is a mixture of calcium fluoride and sodium carbonate, the anticaking agent is magnesium carbonate, and the binder is carboxymethyl cellulose. The preparation method comprises the following steps: calcining the Bayer process red mud at 600-700 DEG C and crushing to obtain activated red mud; mixing and grinding the auxiliary materials, and then mixing with the activated red mud and binder, granulating, drying and activating at high temperature in stages to obtain the finished product. Through the synergistic compatibility of multifunctional components, the present application realizes the integrated pretreatment of simultaneous desiliconization, dephosphorization and desulfurization of molten iron, shortens the treatment time by more than 50%, reduces the raw material cost of the slagging agent by more than 30%, and realizes the resource utilization of red mud solid waste.

Description

Technical Field

[0001] This invention relates to the field of steelmaking auxiliary materials technology, specifically to an integrated slag-forming agent for molten iron pretreatment based on Bayer process red mud and its preparation method. Background Technology

[0002] In the steelmaking process, hot metal pretreatment is a crucial step in producing high-quality clean steel. Hot metal typically contains harmful impurities such as silicon, phosphorus, and sulfur. If these elements are not effectively removed before steelmaking, they will severely affect the mechanical properties, corrosion resistance, and processing performance of the steel. Therefore, before the hot metal enters the converter or electric arc furnace for steelmaking, a pretreatment process is necessary to reduce the content of these impurities to the target range.

[0003] Currently, the industrial practice commonly employs a "single-function slag-forming agent added in stages" approach for pretreatment of molten iron. Specifically, a lime-iron oxide desilication agent is added sequentially to the molten iron to remove silicon, followed by a lime-fluoride dephosphorization agent to remove phosphorus, and then a magnesium-based or calcium carbide-based desulfurization agent to remove sulfur. This approach has several significant drawbacks: First, the process is lengthy, requiring sequential processing, typically taking 30-40 minutes, and necessitating multiple stirring operations, resulting in low production efficiency. Second, energy consumption is high, with multiple additions and stirring increasing equipment occupancy time and energy consumption. Third, the slag system is complex, with different slag phase compositions generated at each stage, making slag treatment difficult. Fourth, raw material costs are high, as each single-function slag-forming agent is purchased and stored separately, increasing overall production costs.

[0004] Bayer process red mud is a highly alkaline solid waste generated during the alumina production process using the Bayer process in the alumina industry. my country's annual Bayer process red mud emissions exceed 100 million tons, with a massive accumulated stockpile, consuming vast amounts of land resources and posing environmental pollution and safety hazards. The main chemical components of Bayer process red mud are CaO (typically 28%–40%), Fe₂O₃ (typically 16%–25%), Al₂O₃, and SiO₂, among others. Theoretically, its compositional characteristics suggest potential for slag formation in molten iron pretreatment: CaO can serve as an alkaline component for dephosphorization and desulfurization, while Fe₂O₃ can act as an oxidizing component for desiliconization and dephosphorization. However, current research on the application of red mud in molten iron pretreatment is still in its early stages. Previous studies have only simply mixed red mud with auxiliary materials such as CaO for use as a single-function dephosphorizing agent, without systematically analyzing and quantifying the synergistic mechanism among multiple components such as CaO, Fe2O3, Al2O3, and SiO2 in red mud. This has failed to fully leverage the natural advantages of the multi-component coupling in red mud. Furthermore, the direct use of raw red mud powder suffers from low activity, poor formability, and uneven dispersion in slag, making it difficult to meet the industrial requirements for the comprehensive performance of slag-forming agents in hot metal pretreatment.

[0005] Furthermore, existing technologies have not yet proposed a systematic approach for preparing composite slag-forming agents that can simultaneously achieve desiliconization, dephosphorization, and desulfurization using red mud. Since the removal of silicon and phosphorus from molten iron requires oxidizing conditions, while the removal of sulfur requires reducing conditions, and these thermodynamic requirements differ, industrial practice has long favored separating desiliconization / dephosphorization processes from desulfurization processes. How to coordinate the functions of oxidative and reductive removal in a single slag-forming agent and achieve simultaneous multi-objective treatment is a pressing technical problem that needs to be solved in this field.

[0006] In summary, existing hot metal pretreatment technologies suffer from problems such as complex processes, long processing times, high energy consumption, and high production costs. Meanwhile, Bayer red mud, as a major industrial solid waste, has not had its multi-component synergistic potential fully explored and utilized, and there is a lack of efficient composite slag-forming agents that can achieve integrated hot metal pretreatment. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides an integrated slag-forming agent for molten iron pretreatment based on Bayer process red mud and its preparation method. Using Bayer process red mud as the main raw material, it has multiple functions including desilication, dephosphorization, and desulfurization, which simplifies the molten iron pretreatment process, reduces production costs, and realizes the resource utilization of solid waste.

[0008] To achieve the above objectives, the present invention employs the following technical solution: The integrated slag-forming agent for molten iron pretreatment based on Bayer process red mud comprises, by weight, 60-80 parts activated red mud; 10-20 parts dephosphorizing component; 5-15 parts desulfurizing component; 8-15 parts flux; 2-5 parts anti-caking agent; and 0.5-1.5 parts binder. The activated red mud is obtained by calcining Bayer process red mud at 600-700℃ for 1.5-2.5 hours and then pulverizing it. The dephosphorizing component is a mixture of manganese dioxide and iron oxide. The desulfurizing component is a mixture of calcium carbide and magnesium oxide. The flux is a mixture of calcium fluoride and sodium carbonate. The anti-caking agent is magnesium carbonate. The binder is carboxymethyl cellulose.

[0009] Furthermore, the activated red mud has a particle size of 100-140 mesh and a calcination temperature of 650-700℃.

[0010] Furthermore, the weight ratio of manganese dioxide to iron oxide red in the dephosphorization component is 1:(0.5~0.8).

[0011] Furthermore, the weight ratio of calcium carbide to magnesium oxide in the desulfurization component is 1:(0.2~0.5).

[0012] Furthermore, the weight ratio of the dephosphorization component to the desulfurization component is 1:(0.7~1).

[0013] Furthermore, the weight ratio of calcium fluoride to sodium carbonate in the flux is 1:(1~2).

[0014] Furthermore, the particle size of the dephosphorization component, desulfurization component, flux, and anti-caking agent is 150-200 mesh.

[0015] Furthermore, the slag-forming agent is composed of particles with a particle size of 3-5 mm.

[0016] The preparation method of the above-mentioned integrated slag-forming agent for molten iron pretreatment based on Bayer process red mud includes the following steps: 1) Calcine Bayer red mud at 600~700℃ for 1.5~2.5h, cool it and then pulverize it to 100~140 mesh to obtain activated red mud.

[0017] 2) Mix the dephosphorization component, desulfurization component, flux, and anti-caking agent, and grind them together to 150-200 mesh to obtain the auxiliary material; the dephosphorization component is a mixture of manganese dioxide and iron oxide red, with a weight ratio of 1:(0.5-0.8); the desulfurization component is a mixture of calcium carbide and magnesium oxide, with a weight ratio of 1:(0.2-0.5); the flux is a mixture of calcium fluoride and sodium carbonate, with a weight ratio of 1:(1-2); the anti-caking agent is magnesium carbonate.

[0018] 3) By weight, mix 60-80 parts of the activated red mud obtained in step 1), the auxiliary materials and binder obtained in step 2); wherein, the dephosphorization component is 10-20 parts, the desulfurization component is 5-15 parts, the flux is 8-15 parts, the anti-caking agent is 2-5 parts, and the binder is 0.5-1.5 parts, and the weight ratio of the dephosphorization component to the desulfurization component is 1:(0.7-1.0); the mixing conditions are: rotation speed 250-350 r / min, time 20-30 min, temperature ≤45℃.

[0019] 4) Granulate the mixture obtained in step 3) to obtain particles with a particle size of 3~5mm.

[0020] 5) Dry the particles obtained in step 4) at 80~100℃.

[0021] 6) The dried particles from step 5) are preheated at 100-200℃ for 1-2 hours, and then kept at 300-400℃ for 2-3 hours to obtain the integrated slag-forming agent for molten iron pretreatment based on Bayer red mud.

[0022] Further, in step 1), the calcination temperature is 650~700℃ and the particle size is 120~140 mesh; in step 3), the mixing speed is 300~350 r / min and the temperature is 35~42℃; in step 5), the drying temperature is 90~100℃; in step 6), the preheating temperature is 150~200℃ and the holding temperature is 350~400℃.

[0023] Compared with existing methods, the beneficial effects of the present invention are: 1. Process integration and significantly improved production efficiency Existing hot metal pretreatment processes require the sequential addition of desilication, dephosphorization, and desulfurization agents in three steps, taking a total of 30-40 minutes. This process is complex, requires extensive equipment, and is energy-intensive. This invention utilizes a multi-functional compound of "activated red mud base material + dephosphorization component + desulfurization component + flux + anti-caking agent" to achieve integrated desilication, dephosphorization, and desulfurization in a single process, combining multiple steps into one. Example data shows that the processing time can be reduced to 18-22 minutes, more than 52% shorter than the traditional step-by-step process; energy consumption per ton of hot metal is reduced by 15-20 kWh, significantly improving production efficiency and reducing energy consumption.

[0024] 2. Significantly improved removal efficiency and outstanding synergistic effect. On the one hand, after Bayer red mud is roasted at 600~700℃, free CaO is fully released and alkali activity is greatly improved, providing sufficient alkaline components for dephosphorization and desulfurization reactions; on the other hand, the roasting temperature is controlled below 700℃ to avoid Fe2O3 sintering deactivation and retain its ability to oxidize, desiliconize and dephosphorize.

[0025] On the other hand, MnO2 in the dephosphorization component decomposes and releases oxygen at high temperatures, forming a gradient oxidation system with Fe2O3 in red mud and iron oxide. This makes the oxidative desilication and dephosphorization reactions more stable and efficient, avoiding incomplete reactions or over-oxidation problems caused by fluctuations in the activity of a single oxidant. In the desulfurization component, calcium carbide (CaC2) reacts directly with sulfur in molten iron to generate CaS, while the addition of MgO not only increases the activity of sulfur and promotes the forward desulfurization process, but also adjusts the slag phase alkalinity, synergistically enhancing dephosphorization. Crucially, the dephosphorization reaction is an exothermic process, and the heat released rapidly increases the slag-iron interface temperature in the initial stage, creating favorable thermodynamic conditions for the subsequent endothermic desulfurization reaction. Thus, synergistic oxidative dephosphorization and reductive desulfurization are achieved in the same slag system, overcoming the traditional technical limitation that these two processes need to be handled in separate steps.

[0026] The measured results of the embodiments verified the above-mentioned synergistic effect: for molten iron with initial [Si] of 0.55%~0.70%, [P] of 0.09%~0.13%, and [S] of 0.05%~0.08%, the desiliconization rate can reach 85.5%~91.4%, the dephosphorization rate can reach 86.7%~91.5%, and the desulfurization rate can reach 70.0%~83.8%, and the final impurity content of the molten iron meets the requirements for high-quality steel smelting.

[0027] 3. Significant benefits from solid waste resource utilization and environmental impact. This invention uses Bayer process red mud as the main raw material, consuming 0.5-0.7 tons of red mud per ton of slagging agent. It provides a reliable method for large-scale red mud disposal, effectively reducing the land occupation and environmental pollution risks associated with red mud stockpiling, and realizing the green metallurgical concept of "treating waste with waste." Simultaneously, the fluoride content in the slagging agent formula is reduced by more than 35% compared to traditional dephosphorizing agents, lowering the emission of harmful fluorides. The Fe2O3 content in the final dephosphorizing slag can reach over 18%, which can be recycled as an iron-containing raw material, further improving the resource recycling rate.

[0028] 4. Costs are significantly reduced. Regarding raw material costs, the slag-forming agent of this invention uses industrial solid waste red mud as a base material, and all auxiliary materials used are conventional industrial raw materials. The overall raw material cost is reduced by more than 30% compared to traditional single-function slag-forming agent combinations. In terms of process costs, the integrated treatment eliminates the equipment operating costs of multiple feeding and stirring operations, resulting in a simultaneous decrease in labor and maintenance costs. Comprehensive calculations show that the pretreatment cost per ton of molten iron is significantly lower than existing step-by-step processes, demonstrating outstanding economic benefits.

[0029] 5. Excellent slag-forming performance and strong process adaptability. The combined use of fluxes CaF2 and Na2CO3 can effectively lower the melting point of the slag system and promote the rapid entry of desilication products Ca2SiO3 and dephosphorization products Ca3(PO4)2 into the slag phase. Na2CO3 can also react with SiO2 to generate low-melting-point Na2SiO3, reducing CaO consumption and accelerating slag formation. The anti-caking agent MgCO3 decomposes at high temperatures to produce MgO and CO2 micropores, which not only improves desulfurization activity but also regulates the slag layer's expansibility, effectively preventing slag agglomeration and improving slag removal operating conditions.

[0030] After granulation, the slag-forming agent has a particle size of 3-5mm, high strength, and no component segregation. It is suitable for existing KR stirring, blowing, and other molten iron pretreatment equipment without the need for production line modification. The preparation method has a maximum temperature of only 700℃, eliminating the need for high-temperature sintering. The process has low energy consumption, is simple to operate, and is easy to promote industrially. Detailed Implementation

[0031] This invention discloses an integrated slagging agent for molten iron pretreatment based on Bayer process red mud and its preparation method. Those skilled in the art can refer to the content of 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, and 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.

[0032] This invention provides an integrated slag-forming agent for molten iron pretreatment based on Bayer process red mud and its preparation method. Through red mud activation, composite functional component design and process optimization, it achieves integrated pretreatment of molten iron for simultaneous desiliconization, dephosphorization and desulfurization.

[0033] (I) Raw material composition design 1. Pretreatment of red mud base material Bayer process red mud is calcined at 600-700℃ to release free CaO, enhancing CaO activity and providing an alkaline environment for dephosphorization and desulfurization of molten iron. Fe2O3 in the red mud can assist in the oxidation of [Si] in molten iron to form SiO2 and [P] to form P2O5.

[0034] 2. Auxiliary material design To enable the composite slag-forming agent to possess both dephosphorization and desulfurization functions, two functional components are added to the base material. The first is a dephosphorization component, a mixture of manganese dioxide (MnO2) and iron oxide red, with a mass ratio of 1:(0.5~0.8). MnO2 undergoes a decomposition reaction above 1100℃ (2MnO2=2MnO+O2), releasing oxygen and enhancing dephosphorization; iron oxide red and Fe2O3 in red mud form a gradient oxidation system with a buffering effect, avoiding fluctuations in the activity of a single oxidant. The second is a desulfurization component, a mixture of calcium carbide (CaC2) and magnesium oxide (MgO), with a mass ratio of 1:(0.2~0.5). CaC2 reacts with [S] in molten iron to generate CaS and C, and MgO can increase the activity of [S], promoting the desulfurization reaction. At the same time, MgO can adjust the slag phase basicity, synergistically promoting dephosphorization. In the initial stage, the dephosphorization reaction releases a large amount of heat, creating favorable thermodynamic conditions for the subsequent desulfurization reaction. The two functional components are compounded at a mass ratio of 1:(0.7~1.0) to ensure a balance between oxidation efficiency and desulfurization efficiency.

[0035] To facilitate the reaction by rapidly melting the composite slag-forming agent into slag, a flux is required. The flux used in this invention is a mixture of calcium fluoride (CaF2) and sodium carbonate (Na2CO3), with a mass ratio of 1:(1~2). CaF2 lowers the melting point of the slag system, promoting the entry of desilication product Ca2SiO3 and dephosphorization product Ca3(PO4)2 into the slag phase; Na2CO3 reacts with SiO2 to generate low-melting-point Na2SiO3, reducing CaO consumption.

[0036] To prevent the composite slag-forming agent from caking during use, magnesium carbonate (MgCO3) is added to the auxiliary materials at a rate of 3% to 5% of the pretreated base material mass. MgCO3 decomposes at high temperatures to generate MgO, which can both improve desulfurization activity and regulate slag phase expansion, thus preventing slag layer caking.

[0037] To prevent component segregation between the base material and auxiliary materials during transportation or use, the slagging agent needs to be granulated. To improve particle strength and prevent pulverization, carboxymethyl cellulose, a binder, is added to the mixture, with the addition amount controlled at 0.5%~1.5% of the total material weight. To ensure uniform mixing of the auxiliary materials with the base material in subsequent processes, the prepared auxiliary materials are ground to 150~200 mesh.

[0038] (II) Preparation steps and methods 1. Preprocessing control The red mud is roasted at a temperature controlled between 600 and 700°C. Below 600°C, the release of free CaO is insufficient (≤18%), while above 700°C, Fe2O3 sinters and its activity decreases. The roasted red mud blocks are then ground into 100-140 mesh powder, ensuring uniform mixing with other components, with 100-140 mesh particles accounting for ≥90%.

[0039] 2. Mixed processing The pretreated red mud base material and auxiliary materials are added to a mixer at a mass ratio of 1:(0.3~0.6) for mixing. The mixing speed is 250~350 r / min, and the time is 20~30 min, ensuring that the dispersion deviation of the composite functional components is ≤3%. The mixing temperature is controlled at ≤45℃ to prevent the pyrolysis of carboxymethyl cellulose.

[0040] 3. Molding and curing treatment The mixed materials are granulated to a particle size of 3-5mm, suitable for industrial blowing or top-feeding equipment. The granules are then dried at a temperature controlled at 80-100℃ to ensure the particle strength meets transportation requirements.

[0041] 4. High-temperature activation treatment The solidified material is preheated at 100-200℃ for 1-2 hours to prevent high-temperature cracking; then the temperature is raised to 300-400℃ and held for 2-3 hours to slowly decompose the organic matter in the binder. At the same time, heating increases the lattice defects inside the material particles, thereby improving the activity of the material and obtaining the slagging agent.

[0042] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0043] Example 1: Adaptation to low-carbon steel molten steel pretreatment This embodiment addresses the requirement for simultaneous desiliconization, dephosphorization, and desulfurization of low-carbon molten iron. The initial composition of the molten iron is 0.55% [Si], 0.09% [P], and 0.05% [S]. The specific preparation and application steps are as follows: (1) Raw material pretreatment and proportioning By weight, take 60 parts of activated red mud, 14 parts of dephosphorization component, 11.2 parts of desulfurization component, 10 parts of flux, 3.8 parts of anti-caking agent, and 1 part of binder, for a total of 100 parts by weight.

[0044] Bayer process red mud was used as the raw material for preparing activated red mud base material. This Bayer process red mud is derived from solid waste discharged from the alumina Bayer process. Its main chemical components, by mass percentage, are: CaO 32% and Fe2O3 20%. The Bayer process red mud was calcined at 650℃ for 2.5h to release free CaO. After cooling, it was crushed and passed through a 120-mesh sieve. The material passing through the sieve was used as the activated red mud base material.

[0045] The auxiliary materials are prepared in the following proportions: the dephosphorizing component is a mixture of MnO2 and iron oxide red, with a mass ratio of 1:0.6; the desulfurizing component is a mixture of calcium carbide and MgO, with a mass ratio of 1:0.3; the combined mass ratio of the dephosphorizing component and the desulfurizing component is 1:0.8; the flux is a mixture of CaF2 and Na2CO3, with a mass ratio of 1:1.5; the anti-caking agent is MgCO3, and its dosage is as shown in the above weight parts. The binder is carboxymethyl cellulose, and its dosage is as shown in the above weight parts. After mixing all the auxiliary materials, grind them to 180 mesh.

[0046] (2) Mixing and molding Add the base material and auxiliary materials to the mixer, control the speed at 300 r / min and the temperature at 35℃, and mix for 25 minutes. Use a pelletizer to process the mixture into 4 mm particles, and dry them at 90℃ for 3 hours to ensure that the particle strength meets the transportation requirements.

[0047] (3) High temperature activation The dried granules are preheated at 150℃ for 1.5 hours, then heated to 350℃ and held for 2.5 hours to complete the activation treatment, resulting in the composite slag-forming agent. Each ton of slag-forming agent consumes approximately 0.6 tons of red mud.

[0048] (4) Application of molten iron pretreatment The composite slag-forming agent prepared in this embodiment was added to the KR stirring device at 3.0% of the mass of molten iron, with a stirring speed of 120 r / min, a treatment time of 18 min, and a treatment temperature of 1350℃.

[0049] (5) Implementation results The final composition of the molten iron is [Si]≤0.08%, [P]≤0.012%, and [S]≤0.015%, with a desiliconization rate of 85.5%, a dephosphorization rate of 86.7%, and a desulfurization rate of 70.0%. The pretreatment time is reduced by 52% compared to the traditional step-by-step process, saving 18 kWh of energy per ton of molten iron. The raw material cost of the slag-forming agent is reduced by 32% compared to a single agent combination, the fluoride usage is reduced by 36%, and the Fe2O3 content in the dephosphorized slag is 20%, making it recyclable.

[0050] Example 2: Adaptation to low alloy steel molten steel pretreatment This embodiment addresses the high-quality pretreatment requirements for low-alloy steel molten iron, with an initial composition of 0.62% [Si], 0.11% [P], and 0.06% [S]. The specific preparation and application steps are as follows: (1) Raw material pretreatment and proportioning By weight, take 62 parts of activated red mud, 13.5 parts of dephosphorization component, 12.15 parts of desulfurization component, 8.85 parts of flux, 3 parts of anti-caking agent, and 0.5 parts of binder, for a total of 100 parts by weight.

[0051] Bayer process red mud was used as the raw material for preparing activated red mud base material. This Bayer process red mud is derived from solid waste discharged from the alumina Bayer process. Its main chemical components, by mass percentage, are: CaO 35% and Fe2O3 22%. The Bayer process red mud was calcined at 680℃ for 2 hours to release free CaO. After cooling, it was crushed and passed through a 130-mesh sieve. The material passing through the sieve was used as the activated red mud base material.

[0052] The auxiliary materials are prepared in the following proportions: the dephosphorizing component is a mixture of MnO2 and iron oxide red, with a mass ratio of 1:0.7; the desulfurizing component is a mixture of calcium carbide and MgO, with a mass ratio of 1:0.4; the combined mass ratio of the dephosphorizing component and the desulfurizing component is 1:0.9; the flux is a mixture of CaF2 and Na2CO3, with a mass ratio of 1:1.8; the anti-caking agent is MgCO3, and its dosage is as shown in the above weight parts. The binder is carboxymethyl cellulose, and its dosage is as shown in the above weight parts. After mixing all the auxiliary materials, grind them to 190 mesh.

[0053] (2) Mixing and molding The base material and auxiliary materials are fed into a mixer, and the speed is controlled at 320 r / min and the temperature at 40℃, and the mixture is mixed for 28 min. The mixture is then processed into granules with a particle size of 5 mm using a pellet mill, and dried at 95℃ for 2.5 h to ensure the granule formability and strength.

[0054] (3) High temperature activation The dried granules are preheated at 180℃ for 1.2 hours, then heated to 380℃ and held for 2.2 hours to complete the activation treatment, resulting in the composite slag-forming agent. Each ton of slag-forming agent consumes approximately 0.65 tons of red mud.

[0055] (4) Application of molten iron pretreatment The composite slag-forming agent prepared in this embodiment was added to the injection equipment at 3.5% of the molten iron mass, with an injection pressure of 0.6 MPa, a treatment time of 20 min, and a treatment temperature of 1380℃.

[0056] (5) Implementation results The final composition of the molten iron is [Si]≤0.07%, [P]≤0.010%, and [S]≤0.012%, with a desiliconization rate of 88.7%, a dephosphorization rate of 90.9%, and a desulfurization rate of 80.0%. The pretreatment time is reduced by 55% compared to the traditional step-by-step process, saving 19 kWh of energy per ton of molten iron. The raw material cost of the slag-forming agent is reduced by 35% compared to a single agent combination, the fluoride usage is reduced by 38%, and the Fe2O3 content in the dephosphorized slag is 22%, meeting the requirements for green metallurgical recycling.

[0057] Example 3: Pretreatment of high-sulfur and high-phosphorus molten iron This embodiment addresses the need for deep pretreatment of high-sulfur and high-phosphorus molten iron, with an initial composition of 0.70% [Si], 0.13% [P], and 0.08% [S]. The specific preparation and application steps are as follows: (1) Raw material pretreatment and proportioning By weight, take 63 parts of activated red mud, 12.5 parts of dephosphorization component, 12.5 parts of desulfurization component, 8 parts of flux, 2.5 parts of anti-caking agent, and 1.5 parts of binder, totaling 100 parts by weight.

[0058] Bayer process red mud was used as the raw material for preparing activated red mud base material. This Bayer process red mud is derived from solid waste discharged from the alumina Bayer process. Its main chemical components, by mass percentage, are: CaO 38% and Fe2O3 25%. The Bayer process red mud was calcined at 700℃ for 1.5h to release free CaO. After cooling, it was crushed and passed through a 140-mesh sieve. The material passing through the sieve was used as the activated red mud base material.

[0059] The auxiliary materials are prepared in the following proportions: the dephosphorizing component is a mixture of MnO2 and iron oxide red, with a mass ratio of 1:0.8; the desulfurizing component is a mixture of calcium carbide and MgO, with a mass ratio of 1:0.5; the combined mass ratio of the dephosphorizing component and the desulfurizing component is 1:1.0; the flux is a mixture of CaF2 and Na2CO3, with a mass ratio of 1:2.0; the anti-caking agent is MgCO3, and its dosage is as shown in the above weight parts. The binder is carboxymethyl cellulose, and its dosage is as shown in the above weight parts. After mixing all the auxiliary materials, grind them to 200 mesh.

[0060] (2) Mixing and molding Add the base material and auxiliary materials to the mixer, control the speed at 350 r / min and the temperature at 42℃, and mix for 30 min. Use a pelletizer to process the mixture into granules with a particle size of 3 mm, and dry them at 100℃ for 2 h to ensure particle uniformity.

[0061] (3) High temperature activation The dried granules are preheated at 200℃ for 1 hour, then heated to 400℃ and held for 2 hours to complete the activation treatment, thus obtaining the composite slag-forming agent. Each ton of slag-forming agent consumes approximately 0.7 tons of red mud.

[0062] (4) Application of molten iron pretreatment The KR stirring and injection combined process was adopted. The composite slag-forming agent prepared in this embodiment was added at 4.0% of the mass of molten iron. The stirring speed was 130 r / min, the injection pressure was 0.7 MPa, the treatment time was 22 min, and the treatment temperature was 1400℃.

[0063] (5) Implementation results The final composition of the molten iron was [Si]≤0.06%, [P]≤0.011%, and [S]≤0.013%, with a desiliconization rate of 91.4%, a dephosphorization rate of 91.5%, and a desulfurization rate of 83.8%. The pretreatment time was reduced by 58% compared to the traditional step-by-step process, saving 20 kWh of energy per ton of molten iron. The raw material cost of the slag-forming agent was reduced by 33% compared to a single agent combination, and the fluoride usage was reduced by 37%. The Fe2O3 content in the dephosphorized slag was 23%, achieving the dual goals of solid waste resource utilization and deep pretreatment.

[0064] 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. An integrated slag-forming agent for molten iron pretreatment based on Bayer process red mud, characterized in that, The raw material composition, by weight, includes: 60-80 parts of activated red mud; 10-20 parts of dephosphorization component; 5-15 parts of desulfurization components; 8-15 parts flux; 2-5 parts of anti-caking agent; 0.5 to 1.5 parts of adhesive; The activated red mud is obtained by calcining Bayer process red mud at 600-700℃ for 1.5-2.5 hours and then pulverizing it; The dephosphorization component is a mixture of manganese dioxide and iron oxide red; The desulfurization component is a mixture of calcium carbide and magnesium oxide; The flux is a mixture of calcium fluoride and sodium carbonate; The anti-caking agent is magnesium carbonate; The adhesive is carboxymethyl cellulose.

2. The integrated slag-forming agent for molten iron pretreatment based on Bayer red mud according to claim 1, characterized in that, The activated red mud has a particle size of 100-140 mesh and a calcination temperature of 650-700℃.

3. The integrated slag-forming agent for molten iron pretreatment based on Bayer red mud according to claim 1, characterized in that, The weight ratio of manganese dioxide to iron oxide red in the dephosphorization component is 1:(0.5~0.8).

4. The integrated slag-forming agent for molten iron pretreatment based on Bayer red mud according to claim 1, characterized in that, The weight ratio of calcium carbide to magnesium oxide in the desulfurization component is 1:(0.2~0.5).

5. The integrated slag-forming agent for molten iron pretreatment based on Bayer red mud according to claim 1, characterized in that, The weight ratio of the dephosphorization component to the desulfurization component is 1:(0.7~1).

6. The integrated slag-forming agent for molten iron pretreatment based on Bayer red mud according to claim 1, characterized in that, The weight ratio of calcium fluoride to sodium carbonate in the flux is 1:(1~2).

7. The integrated slag-forming agent for molten iron pretreatment based on Bayer red mud according to claim 1, characterized in that, The particle size of the dephosphorization component, desulfurization component, flux, and anti-caking agent is 150-200 mesh.

8. The integrated slag-forming agent for molten iron pretreatment based on Bayer red mud according to claim 1, characterized in that, The slag-forming agent is composed of particles with a diameter of 3-5 mm.

9. A method for preparing an integrated slag-forming agent for molten iron pretreatment based on Bayer red mud as described in any one of claims 1-8, characterized in that, Includes the following steps: 1) Calcine Bayer red mud at 600~700℃ for 1.5~2.5h, cool it and then pulverize it to 100~140 mesh to obtain activated red mud; 2) Mix the dephosphorization component, desulfurization component, flux, and anti-caking agent, and grind them together to 150-200 mesh to obtain the auxiliary material; 3) By weight, mix 60-80 parts of the activated red mud obtained in step 1), the auxiliary materials and binder obtained in step 2); The mixing conditions are: rotation speed 250~350 r / min, time 20~30 min, temperature ≤45℃; 4) Granulate the mixture obtained in step 3) to obtain particles with a particle size of 3~5mm; 5) Dry the granules obtained in step 4) at 80~100℃; 6) The dried particles from step 5) are preheated at 100-200℃ for 1-2 hours, and then kept at 300-400℃ for 2-3 hours to obtain the integrated slag-forming agent for molten iron pretreatment based on Bayer red mud.

10. The preparation method of an integrated slagging agent for molten iron pretreatment based on Bayer red mud according to claim 9, characterized in that, In step 1), the roasting temperature is 650~700℃, and the particle size is 120~140 mesh; In step 3), the mixing speed is 300~350 r / min and the temperature is 35~42℃; The drying temperature in step 5) is 90~100℃; In step 6), the preheating temperature is 150~200℃ and the heat preservation temperature is 350~400℃.