A red mud-based composite balling agent, a preparation method and application thereof

Abstract

This invention belongs to the technical field of metallurgical auxiliary materials and solid waste resource utilization, and specifically relates to a red mud-based composite pelletizing agent, its preparation method, and its application. The raw material components of the red mud-based composite pelletizing agent, by mass percentage, are: red mud: 40%-65%, iron oxide scale: 15%-35%, lime: 10%-25%, and binder: 2%-8%; wherein the mass ratio of iron oxide scale to lime is 0.6:1 to 3.5:1. This invention achieves improved slag fluidity and optimized dephosphorization kinetics during the pre-dephosphorization process of titanium-containing molten iron, as well as the synergistic high-value utilization of red mud and iron oxide scale in the iron and steel metallurgical field.

Description

Technical Field

[0001] This invention belongs to the technical field of metallurgical auxiliary materials and solid waste resource utilization, and particularly relates to a red mud-based composite pelletizing agent, its preparation method and application. Background Technology

[0002] Pretreatment and dephosphorization of molten iron is a crucial step in producing high-quality steel. Pre-dephosphorization of titanium-containing molten iron (Ti content 0.1-0.5%) faces dual constraints from thermodynamics and kinetics: Thermodynamically, titanium and phosphorus have similar oxidation potentials, and under conventional dephosphorization conditions, titanium oxidizes preferentially, leading to a decrease in molten iron yield and the formation of high-melting-point TiO2 (1840℃) and complex titanates, increasing slag viscosity and reducing the phosphorus distribution ratio. Kinetically, the temperature of titanium-containing molten iron is relatively low (1300-1350℃), lime dissolves slowly, and the slag fluidity is poor. These problems are particularly pronounced when the Ti content exceeds 0.4%, causing a sharp decline in the efficiency of conventional dephosphorizing agents, accompanied by severe titanium loss and phosphorus reversion.

[0003] Traditional lime-based and soda ash-based dephosphorizing agents struggle to balance dephosphorization efficiency with titanium resource protection. While special processes like ORP and NRP can achieve dephosphorization, they involve large equipment investments, complex operations, and fail to consider the characteristics of titanium-containing molten iron. Red mud, a major solid waste from the aluminum industry, faces significant environmental pressure from traditional stockpiling methods. Its utilization as a steel resource is a crucial way to broaden disposal channels; however, direct application faces multiple technological obstacles. Although industrial solid wastes, such as red mud and iron oxide scale, have been attempted as dephosphorizing agents, direct feeding into the furnace presents numerous challenges: high moisture content (30-40%) affects heat balance; fine particle size and large specific surface area lead to severe dust pollution during transportation and use; direct addition to high-temperature molten pools easily causes splashing and compositional fluctuations; and its dephosphorization efficiency is limited when used alone.

[0004] Current technologies lack systematic and synergistic optimization for titanium-containing molten iron systems. Existing studies have mostly focused on the utilization of single solid waste or conventional molten iron dephosphorization, failing to address the fundamental contradiction between slag system deterioration and insufficient dephosphorization kinetics under high titanium conditions. Summary of the Invention

[0005] In view of the above problems, this application provides a red mud-based composite pelletizing agent, its preparation method, and its application. This invention solves at least one of the following problems in the pre-dephosphorization of titanium-containing molten iron: poor slag fluidity, insufficient dephosphorization kinetics, and difficulties in the synergistic resource utilization of red mud and industrial solid wastes such as iron oxide scale in the iron and steel metallurgical field.

[0006] On the one hand, the present invention provides a red mud-based composite pelletizing agent, wherein the raw material components of the red mud-based composite pelletizing agent are, by mass percentage: red mud: 40%-65%, iron oxide scale: 15%-35%, lime: 10%-25%, and binder: 2%-8%; wherein the mass ratio of iron oxide scale to lime is 0.6:1 to 3.5:1.

[0007] Preferably, the red mud is derived from solid waste from the aluminum industry, with a moisture content of ≤5% and a particle size of ≤200 mesh.

[0008] For example, the total iron content of the iron oxide scale is ≥65%; the moisture content is ≤3%; and the particle size is ≤100 mesh.

[0009] Preferably, the lime has a CaO content ≥ 85% and a particle size ≤ 150 mesh.

[0010] Specifically, the binder is one or more of bentonite, water glass, or dextrin.

[0011] On the other hand, the present invention also provides a method for preparing the red mud-based composite pelletizing agent, comprising the following steps: (1) Pretreatment: Prepare raw materials red mud, iron oxide scale, lime and binder. Dry, crush and screen the red mud and iron oxide scale respectively, and crush and screen the lime to obtain raw materials; (2) Ingredients and mixing: Weigh the pretreated raw materials according to the predetermined ratio and mix them to obtain a mixture; (3) Pelletizing: The mixture is fed into a pelletizing machine and atomized water is sprayed to form pellets, thus obtaining green pellets; (4) Drying: Dry the green pellets to obtain the red mud-based composite pelletizing agent.

[0012] Specifically, the pretreatment in step (1) includes: drying the raw material red mud to a moisture content of ≤5%, crushing and sieving to a particle size of ≤200 mesh; drying the raw material iron oxide scale to a moisture content of ≤3%, crushing and sieving to a particle size of ≤100 mesh, and controlling its total iron content to ≥65%; crushing and sieving the raw material lime to a particle size of ≤150 mesh, and controlling its CaO content to ≥85%.

[0013] Furthermore, the green pellets obtained in step (3) have a particle size of 10mm-30mm.

[0014] Furthermore, the drying temperature in step (4) is 80℃-150℃, and the drying time is 2h-6h.

[0015] On the other hand, the present invention also provides an application of the red mud-based composite pelletizing agent, which is used for pre-dephosphorization of titanium-containing molten iron.

[0016] Preferably, the titanium content of the titanium-containing molten iron is greater than 0.4% by mass percentage.

[0017] Specifically, the red mud-based composite pelletizing agent is added to the titanium-containing molten iron at a rate of 30-60 kg / t of molten iron and stirred. After the reaction is completed, the phosphorus-containing slag is removed.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention constructs a ternary synergistic system of red mud, iron oxide scale, and lime. It utilizes the functional coupling between the basic slag system provided by red mud from the aluminum industry, the oxidizing component (FeO) provided by iron oxide scale, and the high-alkalinity component (CaO) provided by lime. This eliminates the need for chemical purification or homogenization of the red mud, which has fluctuating composition. By controlling the specific mass ratio of iron oxide scale to lime (0.6:1 to 3.5:1), the oxidation potential and alkalinity of the system are balanced, improving the slag fluidity under high-titanium conditions and achieving a dephosphorization rate of over 85%. For high-titanium molten iron with a titanium content greater than 0.4%, the dephosphorization rate remains stable at over 86%, solving the technical problem of pre-dephosphorization of high-titanium molten iron. Simultaneously, it establishes a technical approach for the direct synergistic resource utilization of red mud from the aluminum industry and iron oxide scale from the steel industry, realizing high-value-added utilization of solid waste and demonstrating good economic and environmental benefits.

[0019] 2. The red mud used in this invention comes from solid waste from the aluminum industry, the iron oxide scale comes from solid waste from the iron and steel industry, and the lime is a conventional metallurgical auxiliary material. The raw materials are widely available and inexpensive. The preparation method adopts conventional batching, mixing, pelletizing and drying processes, without the need for high-temperature roasting or complex chemical treatment. The process flow is short, the equipment investment is low, and it is easy to realize industrial production. Attached Figure Description

[0020] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a flow chart of the preparation process of the red mud-based composite pelletizing agent of the present invention; Figure 2 This is a SEM image of the slag after reaction in Application Example 1 of the present invention; Figure 3 Here is a SEM image of the slag after reaction in Comparative Application Example 1 of this invention; Figure 4 This is a SEM image of the slag after reaction in Comparative Application Example 2 of the present invention. Detailed Implementation

[0021] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0023] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] Pretreatment and dephosphorization of molten iron is a crucial step in producing high-quality steel. Pre-dephosphorization of titanium-containing molten iron faces dual constraints from thermodynamics and kinetics: Thermodynamically, titanium and phosphorus have similar oxidation potentials, and under conventional dephosphorization conditions, titanium preferentially oxidizes, generating high-melting-point TiO2 and complex titanates, leading to a significant increase in slag viscosity and a decrease in phosphorus distribution. Kinetically, the temperature of titanium-containing molten iron is relatively low (1300-1350℃), lime dissolves slowly, and the slag fluidity is poor. These problems are particularly pronounced when the Ti content exceeds 0.4%, leading to a decrease in the efficiency of conventional dephosphorizing agents.

[0026] Red mud, a solid waste from the aluminum industry (generated by the Bayer process or sintering process), faces significant environmental pressure due to its large output, strong alkalinity, and complex composition (CaO content fluctuating from 10-25%, Fe2O3 content from 20-45%), and the traditional method of disposal primarily involving stockpiling. Although red mud has applications in building materials and soil remediation, large-scale disposal in the iron and steel metallurgy sector still faces technical obstacles: on the one hand, the composition of red mud fluctuates significantly depending on the source of bauxite and the production process, and when directly used in furnaces, the uncertainty of its alkalinity and iron content can easily lead to unstable performance of dephosphorizing agents; on the other hand, existing technologies often require complex chemical purification or homogenization treatment of red mud to fix its chemical composition, which does not conform to the original intention of "direct utilization and short-process disposal" of solid waste, resulting in poor economic efficiency and operability.

[0027] On one hand, embodiments of the present invention provide a red mud-based composite pelletizing agent, wherein the raw material components of the red mud-based composite pelletizing agent are, by mass percentage: red mud: 40%-65%, iron oxide scale: 15%-35%, lime: 10%-25%, and binder: 2%-8%; wherein the mass ratio of iron oxide scale to lime is 0.6:1 to 3.5:1.

[0028] This invention constructs a ternary synergistic system of red mud, iron oxide scale, and lime, and utilizes the functional coupling of each component in the dephosphorization process to regulate the slag composition and reaction kinetics conditions of titanium-containing molten iron pre-dephosphorization. This achieves highly efficient pre-dephosphorization of titanium-containing molten iron (especially high-titanium molten iron with a titanium content greater than 0.4%), with a dephosphorization rate of over 85%. At the same time, it realizes the synergistic high-value utilization of two industrial solid wastes, red mud and iron oxide scale.

[0029] Specifically, in this invention, the raw material components of the red mud-based composite pelletizing agent function as follows: Red mud: The content is limited to 40%-65% to ensure that the pelletizing agent has sufficient alkaline components (CaO, SiO2, etc.) and iron oxides (Fe2O3) to participate in the dephosphorization reaction and slag formation, while realizing the large-scale disposal of red mud, a solid waste from the aluminum industry; to avoid excessive content leading to a relative deficiency of key functional components such as iron oxide scale and lime, which would affect the dephosphorization efficiency.

[0030] Iron oxide scale: with a limited content of 15%-35%, it is used in conjunction with lime to regulate the redox potential of the system, provide the oxygen source required for the dephosphorization reaction, and improve the fluidity of the high-titanium slag system through the synergistic effect of FeO and CaO.

[0031] Lime: The content is limited to 10%-25% to give the pelleting agent appropriate alkalinity so as to fix phosphorus oxides to form calcium phosphate phase and maintain the thermodynamic driving force of dephosphorization reaction.

[0032] Binder: The content is limited to 2%-8%. Under the premise of ensuring that the green balls have the cold strength required for transportation and addition processes and avoiding dust pollution, the excessive content should be prevented from introducing too many impurities that would affect the cleanliness of the molten iron.

[0033] The mass ratio of iron oxide scale to lime is 0.6:1 to 3.5:1: This gives the pelletizing agent both suitable oxidizing properties and alkalinity. During the pre-dephosphorization process of titanium-containing molten iron, FeO lowers the melting point of the slag system and alleviates the increase in slag phase viscosity caused by high-melting-point TiO2. CaO stabilizes the dephosphorization products. The two work together to maintain the slag system fluidity and dephosphorization reaction kinetics.

[0034] Preferably, the red mud is derived from solid waste from the aluminum industry, with a moisture content ≤5% and a particle size ≤200 mesh. The red mud originates from industrial waste generated during the Bayer process or sintering process for alumina production. After pretreatment through drying, crushing, and screening, its moisture content is controlled to ≤5% and its particle size ≤200 mesh. This ensures stable dry-basis quality of the red mud during the batching stage, preventing moisture fluctuations from causing proportioning deviations. Simultaneously, the fine particle size facilitates uniform micro-scale dispersion of the red mud with other components such as iron oxide scale and lime during mixing, resulting in homogeneous components within the pelletizing agent. This allows for the synergistic release and stable function of each functional component (alkaline component, oxidizing component, and calcareous component) during the pre-dephosphorization reaction, reducing fluctuations in dephosphorization efficiency caused by local component segregation.

[0035] For example, the iron oxide scale has a total iron content ≥65%, a moisture content ≤3%, and a particle size ≤100 mesh. The iron oxide scale is iron scale produced during the hot rolling or forging process in steel mills, and its main components are FeO and Fe3O4. After drying, crushing, and screening pretreatment, iron oxide scale raw material with a total iron content ≥65%, a moisture content ≤3%, and a particle size ≤100 mesh is obtained. This ensures that the iron oxide scale provides sufficient FeO component, controls moisture for stable batching calculations, and has a suitable particle size to maintain the uniformity of mixing with other components and maintain the stability of the pelletizing agent's oxidation capacity.

[0036] Preferably, the lime has a CaO content ≥ 85% and a particle size ≤ 150 mesh. The lime is metallurgical activated lime; controlling the CaO content in the lime ensures high reactivity and a suitable dissolution rate at the pre-dephosphorization temperature (1300-1400℃), providing sufficient CaO for the dephosphorization reaction. 2+ To stabilize the calcium phosphate phase, while particle size control helps to ensure uniform mixing with other solid waste components.

[0037] Specifically, the binder is one or more of bentonite, water glass, or dextrin.

[0038] On the other hand, embodiments of the present invention also provide a method for preparing the aforementioned red mud-based composite pelletizing agent, such as... Figure 1 As shown, it includes the following steps: (1) Pretreatment: Prepare raw materials red mud, iron oxide scale, lime and binder. Dry, crush and screen the red mud and iron oxide scale respectively, and crush and screen the lime to obtain raw materials; (2) Ingredients and mixing: Weigh the pretreated raw materials according to the predetermined ratio and mix them to obtain a mixture; (3) Pelletizing: The mixture is fed into a pelletizing machine and atomized water is sprayed to form pellets, thus obtaining green pellets; (4) Drying: Dry the green pellets to obtain the red mud-based composite pelletizing agent.

[0039] Specifically, the pretreatment in step (1) includes: drying the raw material red mud to a moisture content ≤5%, crushing and sieving to a particle size ≤200 mesh; drying the raw material iron oxide scale to a moisture content ≤3%, crushing and sieving to a particle size ≤100 mesh, and controlling its total iron content ≥65%; crushing and sieving the raw material lime to a particle size ≤150 mesh, and controlling its CaO content ≥85%. Through the above pretreatment, the red mud and iron oxide scale obtain stable dry basis quality to avoid moisture fluctuations leading to proportion deviations, and at the same time, each raw material reaches a specific fineness, achieving uniform dispersion at the microscale during subsequent mixing, thereby making the internal components of the pelletizing agent uniform and reducing the fluctuation of dephosphorization efficiency caused by local component segregation.

[0040] Furthermore, the green pellets obtained in step (3) have a particle size of 10mm-30mm. Controlling the particle size range of the pelletizing agent can ensure that it has an appropriate settling rate and reaction interface area in the molten iron pool. If the particle size is too small, it will easily cause dust to fly around, while if it is too large, it will reduce the reaction efficiency. The above range can balance the convenience of operation and the requirements of reaction kinetics.

[0041] Furthermore, the drying temperature in step (4) is 80℃-150℃, and the drying time is 2h-6h. The above drying conditions can remove the physical moisture in the green pellets, reduce the moisture content of the pelletizing agent to meet the requirements for storage, transportation and furnace loading, and at the same time reduce the risk of oxidation of the active components of the raw materials (such as FeO) or premature failure of the binder due to excessively high temperatures, thus maintaining the chemical stability of the product.

[0042] On the other hand, embodiments of the present invention also provide an application of the red mud-based composite pelletizing agent, which is used for pre-dephosphorization of titanium-containing molten iron.

[0043] Preferably, the titanium content of the titanium-containing molten iron is greater than 0.4% by mass percentage.

[0044] The pelletizing agent of this invention is particularly suitable for high-titanium molten iron with a titanium content greater than 0.4%, and can still maintain a dephosphorization rate of over 86% under these conditions.

[0045] Specifically, the red mud-based composite pelletizing agent is added to the titanium-containing molten iron at a rate of 30-60 kg / t of molten iron and stirred. After the reaction is complete, the phosphorus-containing slag is removed. The temperature of the titanium-containing molten iron is 1300-1400℃.

[0046] By quantifying process parameters, the pelletizing agent can fully react with the molten iron, achieving effective phosphorus oxidation and slag-iron separation under specific thermodynamic and kinetic conditions, and maintaining the chemical equilibrium of the dephosphorization reaction.

[0047] In some embodiments, the red mud-based composite pelletizing agent is added to titanium-containing molten iron at a temperature of 1300-1400℃, with an addition amount of 30-60 kg / t of molten iron. After stirring and reacting for 12-20 minutes, the phosphorus-containing slag is removed. The stirring is mechanical stirring at a speed of 80-90 rpm.

[0048] Mechanical stirring enhances mass transfer in the molten pool, promotes contact between the pelletizing agent and the molten iron, accelerates the dephosphorization reaction kinetics, and controls the stirring intensity to avoid excessive oxidation or splashing of the molten iron.

[0049] This invention addresses the technical challenge of a sharp increase in slag viscosity and severe deterioration of dephosphorization kinetics caused by the excessive formation of TiO2 in high-titanium molten iron. By using a specific mass ratio of iron oxide scale to lime (0.6:1 to 3.5:1), sufficient FeO and CaO components are provided to form a low-melting-point composite slag system, reducing the viscosity of the high-titanium slag and maintaining the oxidation potential and kinetic conditions required for the dephosphorization reaction. This achieves a dephosphorization rate of over 86% in high-titanium molten iron with a Ti content greater than 0.4%, solving the technical problem of difficult pre-dephosphorization of high-titanium molten iron.

[0050] The red mud-based composite pelletizing agent of the present invention, its preparation method, and its application are described below with reference to specific embodiments.

[0051] Example 1 This embodiment provides a red mud-based composite pelletizing agent and its preparation method.

[0052] The raw material composition of the red mud-based composite pelletizing agent is as follows by mass percentage: red mud 50%, iron oxide scale 25%, lime 20%, and binder (bentonite) 5%. Among them, the mass ratio of iron oxide scale to lime is 1.25:1.

[0053] The preparation method is as follows: (1) Ingredients: Weigh out the dried, crushed and pretreated red mud (moisture content ≤5%, particle size ≤200 mesh), iron oxide scale (total iron content ≥65%, moisture content ≤3%, particle size ≤100 mesh), lime (CaO content ≥85%, particle size ≤150 mesh) and binder according to the above proportions; (2) Mixing: Place the weighed red mud, iron oxide scale, lime and bentonite into a mixer and mix for 30 minutes to obtain a mixture; (3) Pelletizing: The mixture is fed into a disc pelletizer and atomized water is sprayed to pelletize, and the particle size of the green pellets is controlled at 15-20 mm. (4) Drying: Dry the raw pellets in a drying oven at 120°C for 4 hours to obtain the finished pelleting agent.

[0054] Example 2 This embodiment provides a red mud-based composite pelletizing agent and its preparation method.

[0055] The raw material composition of the red mud-based composite pelletizing agent is as follows by mass percentage: red mud 52%, iron oxide scale 24%, lime 24%, and binder (water glass) 5%. The mass ratio of the iron oxide scale to the lime is 1.0:1.

[0056] The preparation method is basically the same as that in Example 1, except that the drying temperature in step (4) is 100°C and the drying time is 5 hours.

[0057] Example 3 This embodiment provides a red mud-based composite pelletizing agent and its preparation method.

[0058] The raw material composition of the red mud-based composite pelletizing agent is as follows by mass percentage: red mud 42%, iron oxide scale 33%, lime 22%, and binder (dextrin) 3%. The mass ratio of the iron oxide scale to the lime is 1.5:1.

[0059] The preparation method is basically the same as that in Example 1, except that the drying temperature in step (4) is 140°C and the drying time is 2.5 hours.

[0060] Example 4 This embodiment provides a red mud-based composite pelletizing agent and its preparation method.

[0061] The raw material composition of the red mud-based composite pelletizing agent is as follows by mass percentage: red mud 55%, iron oxide scale 20%, lime 25%, and binder (bentonite) 5%. The mass ratio of the iron oxide scale to the lime is 0.8:1.

[0062] The preparation method is the same as in Example 1.

[0063] Example 5 This embodiment provides a red mud-based composite pelletizing agent and its preparation method.

[0064] The raw material composition of the red mud-based composite pelletizing agent is as follows by mass percentage: red mud 45%, iron oxide scale 35%, lime 11%, and binder (water glass) 9%. The mass ratio of the iron oxide scale to the lime is 3.2:1.

[0065] The preparation method is the same as in Example 1.

[0066] Application Example 1 The red mud-based composite pelletizing agent prepared in Example 1 was applied to the pre-dephosphorization treatment of titanium-containing molten iron. The composition of the titanium-containing molten iron included: Ti 0.25%, Si 0.40%, C 4.2%, P 0.12%, and an initial temperature of 1350℃. The pelletizing agent was added at a rate of 45 kg / t of molten iron.

[0067] Mechanical stirring was used at a speed of 80 rpm for a reaction time of 15 minutes. After the reaction, the phosphorus-containing slag was removed and samples were taken for analysis. As shown in Table 1, the average phosphorus content of the dephosphorized molten iron was 0.015%, and the dephosphorization rate reached 87.5%.

[0068] Application Example 2 The red mud-based composite pelletizing agent prepared in Example 2 was applied to the pre-dephosphorization treatment of titanium-containing molten iron. The composition of the titanium-containing molten iron was basically the same as that in Application Example 1, and the initial temperature was 1330℃. The pelletizing agent was added at a rate of 55 kg / t of molten iron.

[0069] The reaction was carried out using top-blown nitrogen stirring for 18 minutes. As shown in Table 1, the dephosphorization rate reached 89.2%.

[0070] Application Example 3 The red mud-based composite pelletizing agent prepared in Example 3 was applied to the pre-dephosphorization treatment of titanium-containing molten iron. The composition of the titanium-containing molten iron was basically the same as that in Application Example 1, and the initial temperature was 1380℃. The pelletizing agent was added at a rate of 35 kg / t of molten iron.

[0071] Mechanical stirring was used, and the reaction time was 12 minutes. As shown in Table 1, the dephosphorization rate reached 85.5%.

[0072] Application Example 4 The red mud-based composite pelletizing agent prepared in Example 1 was applied to the pre-dephosphorization treatment of high-titanium molten iron. The titanium-containing molten iron had a titanium content of 0.45%, Si of 0.35%, C of 4.1%, and P of 0.11%, and an initial temperature of 1340℃. The pelletizing agent was added at a rate of 50 kg / t of molten iron.

[0073] Mechanical stirring was used at a speed of 85 rpm for a reaction time of 18 minutes. As shown in Table 1, the average phosphorus content of the dephosphorized molten iron was 0.014%, and the dephosphorization rate reached 87.3%. This indicates that even under high titanium conditions (greater than 0.4%), the pelletizing agent of this invention can still maintain good slag fluidity through the synergistic effect of iron oxide scale and lime, achieving efficient dephosphorization.

[0074] Application Example 5 The red mud-based composite pelletizing agent prepared in Example 2 was applied to the pre-dephosphorization treatment of high-titanium molten iron. The titanium-containing molten iron had a titanium content of 0.52%, Si 0.30%, C 4.3%, and P 0.13%, and an initial temperature of 1320℃. The pelletizing agent was added at a rate of 58 kg / t of molten iron.

[0075] The reaction was carried out using top-blown nitrogen stirring for 20 minutes. As shown in Table 1, the average phosphorus content of the dephosphorized molten iron was 0.017%, and the dephosphorization rate reached 86.9%. This further verifies the applicability of this invention for pre-dephosphorizing high-titanium molten iron.

[0076] Application Example 6 The red mud-based composite pelletizing agent (iron oxide scale: lime = 0.8:1) prepared in Example 4 was applied to the pre-dephosphorization treatment of titanium-containing molten iron. The titanium-containing molten iron contained the following components: Ti 0.25%, Si 0.40%, C 4.2%, P 0.12%, and an initial temperature of 1350℃. The pelletizing agent was added at a rate of 45 kg / t of molten iron.

[0077] Mechanical stirring was used at a speed of 80 rpm for a reaction time of 15 minutes. After the reaction, the phosphorus-containing slag was removed and samples were taken for analysis. The results, as shown in Table 1, indicate that the dephosphorization rate reached 86.8%.

[0078] Application Example 7 The red mud-based composite pelletizing agent (iron oxide scale: lime = 3.2:1) prepared in Example 5 was applied to the pre-dephosphorization treatment of titanium-containing molten iron. The composition of the titanium-containing molten iron was basically the same as that in Application Example 1, and the initial temperature was 1350℃. The pelletizing agent was added at a rate of 45 kg / t of molten iron.

[0079] Mechanical stirring was used at a speed of 80 rpm for a reaction time of 15 minutes. As shown in Table 1, the dephosphorization rate reached 86.2%.

[0080] Application Example 8 The red mud-based composite pelletizing agent (iron oxide scale: lime = 0.8:1) prepared in Example 4 was applied to the pre-dephosphorization treatment of high-titanium molten iron. The titanium-containing molten iron had a titanium content of 0.48%, Si of 0.32%, C of 4.1%, and P of 0.12%, and an initial temperature of 1340℃. The pelletizing agent was added at a rate of 52 kg / t of molten iron.

[0081] Mechanical stirring was used at a speed of 85 rpm for a reaction time of 18 minutes. As shown in Table 1, the dephosphorization rate reached 86.1%.

[0082] Comparative Example 1 This comparative example is basically the same as Example 1, except that the raw material composition by mass percentage is: red mud 50%, iron oxide scale 10%, lime 35%, and binder 5%. The mass ratio of the iron oxide scale to the lime is 0.29:1.

[0083] Comparative Example 2 This comparative example is basically the same as Example 1, except that the raw material composition by mass percentage is: red mud 50%, iron oxide scale 40%, lime 5%, and binder 5%. The mass ratio of the iron oxide scale to the lime is 8:1.

[0084] Comparative Example 3 This comparative example provides a dephosphorizing agent whose raw material composition by mass percentage is: 75% red mud, 20% lime, and 5% binder. The system does not contain iron oxide scale.

[0085] Comparative Example 4 This comparative example is basically the same as Example 1, except that the raw material composition by mass percentage is: 80% red mud, 10% iron oxide scale, 8% lime, and 2% binder. The red mud content exceeds the 40-65% range specified in this invention.

[0086] Comparative Application Example 1 The pelletizing agent prepared in Comparative Example 1 was applied to the pre-dephosphorization treatment of titanium-containing molten iron (Ti 0.25%, P 0.12%, composition the same as in Application Example 1) at a dosage of 45 kg / t of molten iron, with other process conditions the same as in Application Example 1. As shown in Table 1, the dephosphorization rate was only 72.3%.

[0087] The results show that due to the low mass ratio of iron oxide scale to lime (0.29:1), the system's oxidizing power is insufficient, slag formation is slow, and the dephosphorization reaction kinetics deteriorate, resulting in a significantly lower dephosphorization efficiency than in the embodiments of the present invention.

[0088] Comparative Application Example 2 The pelletizing agent prepared in Comparative Example 2 was applied to the pre-dephosphorization treatment of titanium-containing molten iron (Ti 0.25%, P 0.12%, composition the same as in Application Example 1) at a dosage of 45 kg / t of molten iron, with other process conditions the same as in Application Example 1. As shown in Table 1, the dephosphorization rate was only 68.5%.

[0089] The results showed that due to the excessively high mass ratio of iron oxide scale to lime (8:1), the slag system was not sufficiently basic and could not effectively fix phosphorus oxides to form a stable calcium phosphate phase. Furthermore, the excessively high proportion of iron oxide scale resulted in an overly thin slag system and a significant decrease in the dephosphorization rate.

[0090] Comparative Application Example 3 The dephosphorizing agent (without iron oxide scale) prepared in Comparative Example 3 was applied to the pre-dephosphorizing treatment of titanium-containing molten iron (Ti 0.25%, P 0.12%, composition the same as in Application Example 1), with an addition amount of 45 kg / t of molten iron. The remaining process conditions were the same as in Application Example 1. As shown in Table 1, the dephosphorization rate was only 65.8%.

[0091] The results show that without the FeO component provided by the iron oxide scale, the alkaline components in the red mud cannot effectively play a dephosphorization role. The ternary synergistic system lacks the key oxidizing component, and the dephosphorization effect is far lower than that of the present invention.

[0092] Comparative Application Example 4 The pelletizing agent prepared in Comparative Example 1 (low iron oxide scale, mass ratio 0.29:1) was applied to the pre-dephosphorization treatment of high-titanium molten iron (Ti 0.45%, P 0.11%, composition the same as Application Example 4), with an addition amount of 50 kg / t of molten iron. Other process conditions were the same as in Application Example 4. As shown in Table 1, the dephosphorization rate was only 61.5%.

[0093] The results show that under insufficient oxidizing conditions, titanium in high-titanium molten iron preferentially oxidizes, generating a large amount of high-melting-point TiO2, which further increases the slag viscosity, worsens the dephosphorization kinetics, and leads to a sharp decline in dephosphorization efficiency. This demonstrates the importance of this invention in maintaining good slag fluidity while providing sufficient oxidizing power by controlling the specific mass ratio of iron oxide scale to lime (0.6:1 to 3.5:1).

[0094] Comparative Application Example 5 The pelletizing agent prepared from Comparative Example 4 (80% red mud) was applied to the pre-dephosphorization treatment of titanium-containing molten iron (Ti 0.25%, P 0.12%, composition the same as in Application Example 1), with an addition amount of 45 kg / t of molten iron. The results, as shown in Table 1, showed a dephosphorization rate of 70.2%.

[0095] Due to the excessive red mud content and the relative deficiency of key functional components such as iron oxide scale and lime, the oxidizing power and alkalinity of the system are imbalanced, thus limiting the dephosphorization efficiency.

[0096] Table 1

[0097] The results from the above application examples and comparative application examples show that: The dephosphorization rates of Application Examples 1-8 (iron oxide scale to lime mass ratio in the range of 0.6:1 to 3.5:1) all reached over 86%, while the dephosphorization rates of Comparative Application Example 1 (ratio 0.29:1), Comparative Application Example 2 (ratio 8:1), and Comparative Application Example 3 (without iron oxide scale) were only 72.3%, 68.5%, and 65.8%, respectively. This indicates that when the mass ratio of iron oxide scale to lime is within the range of 0.6:1 to 3.5:1 defined in this invention, a slag system with suitable oxidizing properties and alkalinity can be formed, achieving efficient dephosphorization.

[0098] When the mass ratio of iron oxide scale to lime is less than 0.6:1 (as in Comparative Application Example 1), the system's oxidizing power is insufficient, and the FeO supply is inadequate to effectively oxidize phosphorus. Simultaneously, it cannot effectively reduce the melting point and viscosity of the slag system, leading to slow slag formation and deteriorating dephosphorization reaction kinetics. When this ratio is greater than 3.5:1 (as in Comparative Application Example 2), the slag system's basicity is insufficient, failing to effectively fix phosphorus oxides to form a stable calcium phosphate phase. Furthermore, an excessively high FeO ratio results in an overly thin and fluid slag system, which is detrimental to the stable transport of phosphorus at the slag-iron interface. Therefore, a specific ratio range of 0.6:1 to 3.5:1 is crucial for balancing oxidizing power and basicity and maintaining efficient dephosphorization. This ratio range allows the pelletizing agent to be adapted to the compositionally fluctuating red mud from the aluminum industry, eliminating the need for chemical homogenization treatment and maintaining good dephosphorization kinetics through the synergistic effect of FeO and CaO.

[0099] like Figure 2 As shown in the SEM image of the slag after the reaction in Example 1, the slag layer structure is dense and uniform. Phosphorus is mainly enriched in the 2CaO·SiO2-3CaO·P2O5 solid solution phase (point A), with uniform distribution and no obvious unmelted particles. This indicates that under the specific ratio of iron oxide scale to lime in this invention, the dephosphorization reaction proceeds fully, the generated calcium phosphate phase exists stably in the slag, and the slag system has good fluidity, consistent with the result of a dephosphorization rate of 87.5%.

[0100] like Figure 3 As shown, the SEM image of the slag after the reaction of Application Example 1 (iron oxide scale to lime mass ratio 0.29:1) shows that the slag layer structure is loose, with a large number of unmelted particles. The phosphorus element is dispersed and not significantly enriched in the 2CaO·SiO2-3CaO·P2O5 solid solution phase (point A). This is consistent with the result of a dephosphorization rate of 72.3%, indicating that due to insufficient oxidizing power, the red mud and lime failed to fully melt to form a homogeneous slag system, resulting in poor dephosphorization reaction kinetics.

[0101] like Figure 4 As shown, the SEM image of the slag after the reaction in Application Example 2 (iron oxide scale to lime mass ratio 8:1) reveals that a large number of high-melting-point phases (point D) exist in the slag layer, hindering the slag-iron interface reaction, and some phosphorus remains in the molten iron. This is consistent with the dephosphorization rate of 68.5%, indicating that an excessively high proportion of iron oxide scale leads to insufficient basicity, which cannot effectively stabilize phosphorus oxides. At the same time, the increase in high-melting-point phases in the slag system hinders the dephosphorization reaction.

[0102] The dephosphorization rates of Application Examples 4, 5, and 8 (titanium content 0.45%-0.52%) reached 87.3%, 86.9%, and 86.1%, respectively, comparable to the effects of Application Examples 1-3 and 6-7 (conventional titanium-containing molten iron), demonstrating the good adaptability of the pelletizing agent of this invention to high-titanium molten iron. In contrast, the dephosphorization rate of Comparative Application Example 4 (using a pelletizing agent at a ratio of 0.29:1 to treat molten iron with a titanium content of 0.45%) decreased to 61.5%. This indicates that when treating high-titanium molten iron, if the proportion of iron oxide scale is insufficient, the high-melting-point TiO2 generated by the preferential oxidation of titanium will severely deteriorate the slag fluidity, leading to a sharp deterioration in the dephosphorization reaction kinetics. This invention, by optimizing the specific ratio of iron oxide scale to lime, can provide sufficient FeO to reduce the viscosity of high-titanium slag and maintain the kinetic conditions required for the dephosphorization reaction, thereby solving the technical problem of difficult pre-dephosphorization of high-titanium molten iron.

[0103] In summary, this invention constructs a ternary synergistic system of red mud, iron oxide scale, and lime. It utilizes the functional coupling between the basic slag system provided by red mud from the aluminum industry, the oxidizing component (FeO) provided by iron oxide scale, and the high-alkalinity component (CaO) provided by lime. By adjusting the specific mass ratio of iron oxide scale to lime (0.6:1 to 3.5:1), the oxidation potential and alkalinity of the system are balanced, improving the slag fluidity under high-titanium conditions and achieving a dephosphorization rate of over 85%. For high-titanium molten iron with a titanium content greater than 0.4%, the dephosphorization rate remains stable at over 86%, solving the technical problem of pre-dephosphorization of high-titanium molten iron. Simultaneously, it establishes a technical approach for the direct synergistic resource utilization of red mud from the aluminum industry and iron oxide scale from the steel industry.

[0104] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A red mud-based composite pelletizing agent, characterized in that, The raw material components of the red mud-based composite pelletizing agent, by mass percentage, are: red mud: 40%-65%, iron oxide scale: 15%-35%, lime: 10%-25%, and binder: 2%-8%; wherein the mass ratio of iron oxide scale to lime is 0.6:1 to 3.5:

1.

2. The red mud-based composite pelletizing agent according to claim 1, characterized in that, The red mud is derived from solid waste from the aluminum industry, with a moisture content of ≤5% and a particle size of ≤200 mesh.

3. The red mud-based composite pelletizing agent according to claim 1, characterized in that, The iron oxide scale has a total iron content of ≥65%, a moisture content of ≤3%, and a particle size of ≤100 mesh.

4. The red mud-based composite pelletizing agent according to claim 1, characterized in that, The lime has a CaO content ≥ 85% and a particle size ≤ 150 mesh.

5. The red mud-based composite pelletizing agent according to claim 1, characterized in that, The binder includes one or more of bentonite, water glass, or dextrin.

6. A method for preparing a red mud-based composite pelletizing agent as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Pretreatment: Prepare raw materials red mud, iron oxide scale, lime and binder. Dry, crush and screen the red mud and iron oxide scale respectively, and crush and screen the lime to obtain raw materials; (2) Ingredients and mixing: Weigh the pretreated raw materials according to the predetermined ratio and mix them to obtain a mixture; (3) Pelletizing: The mixture is fed into a pelletizing machine and atomized water is sprayed to form pellets, thus obtaining green pellets; (4) Drying: Dry the green pellets to obtain the red mud-based composite pelletizing agent.

7. The preparation method according to claim 6, characterized in that, The green pellets in step (3) have a particle size of 10mm-30mm.

8. The preparation method according to claim 6, characterized in that, The drying temperature in step (4) is 80℃-150℃, and the drying time is 2h-6h.

9. The application of a red mud-based composite pelletizing agent as described in any one of claims 1-5, characterized in that, The red mud-based composite pelletizing agent is used for pre-dephosphorization of titanium-containing molten iron.

10. The application according to claim 9, characterized in that, Add the red mud-based composite pelletizing agent to the titanium-containing molten iron at a rate of 30-60 kg / t of molten iron and stir. After the reaction is complete, remove the phosphorus-containing slag.

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