Pre-melting conductive refining agent for steelmaking and preparation method of pre-melting conductive refining agent

Abstract

The invention relates to the technical field of industrial solid waste, and discloses a pre-melting conductive refining agent for steelmaking and a preparation method thereof.The pre-melting conductive refining agent comprises an electric refining agent body, the refining agent body is prepared by smelting a raw material system containing hazardous waste aluminum ash, the mass content of metal aluminum in the aluminum ash is smaller than or equal to 15%, the content is combined with the smelting temperature range of 1300-1500 DEG C, and the smelting temperature range of the electric refining agent body is larger than or equal to 150 DEG C. In order to avoid excessive oxidation of metal aluminum and ensure that the decomposition efficiency of aluminum nitride is greater than or equal to 99%, the aluminum ash is subjected to specific brine passivation pretreatment and is subjected to high-temperature smelting in a protective atmosphere, so that the harm of ammonia production caused by hydrolysis of aluminum nitride in the aluminum ash is effectively inhibited, efficient decomposition of the aluminum nitride is ensured, the nitrogen content in a final product is less than or equal to 0.1%, and the aluminum oxide content is less than or equal to 0.1%. And the content of fluorine ions is less than or equal to 0.5%, so that the hazardous wastes are safely converted into raw materials meeting metallurgical requirements.

Description

Technical Field

[0001] This invention relates to the field of industrial solid waste technology, and more specifically to a pre-melted conductive refining agent for steelmaking and its preparation method. Background Technology

[0002] A large amount of aluminum ash (slag) generated during aluminum smelting and processing has been included in the "National Hazardous Waste List". Aluminum ash contains aluminum nitride, fluoride, chloride and other components. It is easy to react with water and release harmful substances such as ammonia. If it is disposed of by stockpiling or landfilling, it will pose a serious threat to the environment and safety. At the same time, aluminum ash is rich in aluminum oxide and other components, which is also a potential secondary resource. In the steelmaking and refining field, there are currently two main ways to utilize aluminum ash: one is to simply process it and mix it with lime and other materials to form pellets or sintered blocks for use as a deoxidizer; the other is to use fluorite as a slag-forming agent. However, the former has problems such as slow product melting speed, uneven composition, and low reaction efficiency, resulting in unstable deoxidation and desulfurization effects, and there are hidden dangers of dust and ammonia release during the production process. The latter is due to the increasing scarcity of fluorite resources and the introduction of fluoride ions during smelting, which brings environmental pressure. Therefore, how to safely, efficiently, and with high added value achieve the harmless disposal and resource utilization of aluminum ash, and transform it into high-performance metallurgical auxiliary materials, has become a common technical challenge faced by the steel and aluminum industries. Therefore, there is an urgent need for a pre-melted conductive refining agent for steelmaking and its preparation method to solve the aforementioned technical problems. Summary of the Invention

[0003] In order to overcome the above-mentioned defects of the prior art, the present invention provides a pre-melted conductive refining agent for steelmaking and its preparation method, so as to solve the problems existing in the background art.

[0004] To achieve the above objectives, the present invention provides a pre-melted conductive refining agent for steelmaking and its preparation method.

[0005] In a first aspect, the present invention provides a pre-melted conductive refining agent for steelmaking, which adopts the following scheme: A pre-melted conductive refining agent for steelmaking includes an electro-refining agent, said refining agent being produced by smelting a raw material system containing hazardous waste aluminum ash, wherein the mass content of metallic aluminum in the aluminum ash is ≤15%, and this content is combined with a smelting temperature range of 1300℃-1500℃ to avoid excessive oxidation of metallic aluminum and ensure that the decomposition efficiency of aluminum nitride is ≥99%; The raw materials for preparing the refining agent include, by weight: 40-70 parts aluminum ash, 25-55 parts calcareous material, and 1-10 parts magnesian material; The raw materials are smelted to form a refining agent, and the chemical composition of the refining agent, by mass percentage, is as follows: Al2O3: 35%-58%, CaO: 30%-50%, MgO: 1%-8%, SiO2: 2%-20%; The refining agent contains: fluoride ion content ≤ 0.5%, and nitrogen content ≤ 0.1%; Furthermore, the mass percentage ratio of (CaO content + MgO content) to SiO2 content is 2.0-5.0.

[0006] Preferably, the calcareous material is a mixture of carbide slag and papermaking sludge, with a mass ratio of 1:(0.8-1.2).

[0007] Preferably, the magnesium material is a composite of lightly calcined magnesium powder and dolomite, wherein the mass percentage of lightly calcined magnesium powder is ≥60%.

[0008] Secondly, the present invention provides a method for preparing a pre-melted conductive refining agent for steelmaking, which adopts the following scheme: A method for preparing a pre-melted conductive refining agent for steelmaking, applicable to pre-melted conductive refining agents for steelmaking, includes the following steps: S1. Raw material pretreatment: Aluminum ash is screened and passivated by spraying with brine. Calcium and magnesium materials are dried and crushed respectively. S2. Ingredients and Mixing: Weigh out 40-70 parts aluminum ash, 25-55 parts calcium materials, and 1-10 parts magnesium materials, and mix them evenly. S3. Melting: The uniformly mixed materials are put into a melting furnace and melted at a temperature of 1300℃-1500℃ for 0.5-2 hours. S4. Molding and Cooling: The completely molten material obtained in step S3 is discharged and cooled to solidify. S5. Crushing and Screening: The cooled solid material is crushed and screened to obtain granular products of a specified particle size.

[0009] Preferably, in step S1, the brine is a MgCl2·6H2O solution, and its amount accounts for 1%-3% of the mass of aluminum ash, which is used to suppress adverse reactions of aluminum ash in pretreatment and subsequent processes.

[0010] Preferably, in step S3, a reducing or neutral atmosphere is maintained inside the furnace by introducing a protective gas.

[0011] Preferably, in step S4, the outflowing melt is quenched and cooled by a water flow with a pressure of 0.2-0.6 MPa to achieve rapid solidification and granulation of the material.

[0012] Preferably, in step S5, after the solid material is crushed and screened, the particle size range of the granular product is 5-40 mm.

[0013] Preferably, the protective gas is an inert gas, which is nitrogen, argon, or a mixture thereof.

[0014] The technical effects and advantages of this invention are as follows: 1. This invention, through specific brine passivation pretreatment of aluminum ash and high-temperature smelting under a protective atmosphere, effectively suppresses the harmful effects of aluminum nitride hydrolysis producing ammonia in aluminum ash and ensures its efficient decomposition, resulting in a final product with nitrogen content ≤0.1% and fluoride ion content ≤0.5%, safely converting hazardous waste into raw materials that meet metallurgical requirements.

[0015] 2. This invention produces a pre-melted refining agent with uniform composition, low melting point, and good conductivity through a pre-melting process. When used in steelmaking, this product produces slag quickly and foams evenly, which can significantly improve desulfurization efficiency and reduce the amount of auxiliary materials added in the refining process, thereby comprehensively improving refining efficiency.

[0016] 3. This invention not only uses aluminum ash as the main raw material, but also utilizes other industrial solid wastes such as carbide slag and papermaking sludge as calcium and magnesium raw materials, which greatly reduces production costs and realizes the synergistic treatment of multi-source solid waste. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall process for preparing the pre-melted conductive refining agent of the present invention. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The pre-melted conductive refining agent for steelmaking and its preparation method involved in the present invention are not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Reference Figure 1 As shown, the present invention provides a pre-melted conductive refining agent for steelmaking, comprising an electro-refining agent. The refining agent is prepared by smelting a raw material system containing hazardous waste aluminum ash. The mass content of metallic aluminum in the aluminum ash is ≤15%. This content is combined with a smelting temperature range of 1300℃-1500℃ to avoid excessive oxidation of metallic aluminum and ensure that the decomposition efficiency of aluminum nitride is ≥99%. The raw materials for preparing the refining agent include, by weight: 40-70 parts aluminum ash, 25-55 parts calcareous materials, and 1-10 parts magnesian materials. After the raw materials are smelted, a refining agent is formed. The chemical composition of the refining agent, in terms of mass percentage, is as follows: Al2O3: 35%-58%, CaO: 30%-50%, MgO: 1%-8%, SiO2: 2%-20%; In refining agents: fluoride ion content ≤ 0.5%, nitrogen content ≤ 0.1%; Furthermore, the mass percentage ratio of (CaO content + MgO content) to SiO2 content is 2.0-5.0.

[0020] The calcareous material is a mixture of carbide slag and papermaking sludge, with a mass ratio of 1:(0.8-1.2).

[0021] Preferably, the magnesian material is a composite of light-burned magnesia powder and dolomite, wherein the mass percentage of light-burned magnesia powder is ≥60%.

[0022] Reference Figure 1 As shown, this invention provides a pre-melted conductive refining agent for steelmaking, and a method for preparing the pre-melted conductive refining agent for steelmaking, which is applied to the pre-melted conductive refining agent for steelmaking, including the following steps: S1. Raw material pretreatment: Aluminum ash is screened and passivated by spraying with brine. Calcium and magnesium materials are dried and crushed respectively. S2. Ingredients and Mixing: Weigh out 40-70 parts aluminum ash, 25-55 parts calcium materials, and 1-10 parts magnesium materials, and mix them evenly. S3. Melting: The uniformly mixed materials are put into a melting furnace and melted at a temperature of 1300℃-1500℃ for 0.5-2 hours. S4. Molding and Cooling: The completely molten material obtained in step S3 is discharged and cooled to solidify. S5. Crushing and Screening: The cooled solid material is crushed and screened to obtain granular products of a specified particle size.

[0023] In step S1, the brine is a MgCl2·6H2O solution, and its amount accounts for 1%-3% of the mass of aluminum ash, which is used to suppress adverse reactions of aluminum ash in pretreatment and subsequent processes. In step S3, a reducing or neutral atmosphere is maintained inside the furnace by introducing a protective gas. The protective gas is an inert gas, which is nitrogen, argon, or a mixture thereof.

[0024] In step S4, the outflowing melt is quenched and cooled by a water flow with a pressure of 0.2-0.6 MPa to achieve rapid solidification and granulation of the material.

[0025] In step S5, after the solid material is crushed and screened, the particle size range of the granular product is 5-40mm.

[0026] Example 1: Standard Formulation and Process This embodiment aims to describe in detail a typical implementation of this application and to verify that the products prepared by the methods described in claims 1-3 and 4-10 can achieve the preset technical indicators.

[0027] I. Raw material pretreatment: Aluminum ash: secondary aluminum ash taken from a certain electrolytic aluminum enterprise; Testing revealed that the aluminum content was 8.5% and the aluminum nitride content was approximately 18% (which meets the requirement of "aluminum content ≤ 15%" in the claims of this application). 50.0 kg was taken as raw material. Pretreatment: First, the material is sieved through a 5mm vibrating screen to remove large pieces of debris. Then, in a closed mixer, 1.2 kg (2.4% of the mass of aluminum ash) of 30wt% (30wt% means that the mass of a certain substance in the solution or mixture accounts for 30% of the total mass) MgCl2·6H2O solution (i.e. brine) is evenly sprayed onto it using an atomizing nozzle. After spraying, continue stirring for 5 minutes, then seal and let it sit for 30 minutes to complete the passivation treatment (this step aims to suppress the generation of ammonia gas due to aluminum nitride hydrolysis during subsequent storage, transportation and feeding of aluminum ash). Calcareous material: A mixture of carbide slag (a byproduct of chemical plants, mainly composed of CaO) and papermaking sludge (a waste product of paper mills, mainly composed of CaCO3) (mass ratio of the two is 1:1) was used, and a total of 40.0 kg of the mixture was taken. Pretreatment: The carbide slag and papermaking sludge are dried in an oven at 105℃ for 4 hours to constant weight (moisture content ≤0.5%), and then crushed in two stages using a jaw crusher and a double roll crusher to control the particle size of more than 95% of the material to be <3mm (about 50 mesh). Magnesia material: A composite material is made of lightly calcined magnesia powder (MgO content ≥ 85%) and dolomite (MgO content 20%-22%, CaO content 29%-31%). The mass ratio of lightly calcined magnesia powder is 70% and dolomite is 30%. A total of 5.0 kg of composite material is used. Pretreatment: Dry at 105℃ and crush to <3mm.

[0028] II. Ingredients and Mixing: After accurately weighing all the pretreated raw materials: aluminum ash (50.0 kg), calcium material mixture (40.0 kg), and magnesium material composite (5.0 kg), put them into a twin-shaft paddle mixer and mix them at 25 rpm for 25 minutes until a uniform color and no visible layering are obtained. The total amount of materials fed is 95.0 kg.

[0029] III. Smelting: All the well-mixed materials were added into a 3-ton medium-frequency induction melting furnace: Atmosphere control: After the charging is completed, close the furnace cover and first introduce argon gas (Ar, purity ≥99.99%) at a flow rate of 20L / min for 5 minutes to replace the air in the furnace. During the entire melting process, maintain argon gas at a flow rate of 5-10L / min with a slight positive pressure to maintain a neutral / weak reducing atmosphere in the furnace and prevent excessive oxidation of the material.

[0030] Temperature and time control: Start the power supply to heat the material and control the heating rate so that the material is completely melted within about 60 minutes. Stabilize the temperature of the molten pool at 1420±10℃ and smelt at this temperature for 1.2 hours. This temperature range (1300℃-1500℃) combined with the appropriate metallic aluminum content (≤15%) in the aluminum ash ensures the full thermal decomposition of aluminum nitride (target decomposition rate ≥99%) and avoids melt splashing and component segregation caused by excessive and violent oxidation of metallic aluminum. During the smelting process, a small number of bubbles (nitrogen, CO2, etc.) can be observed to escape from the melt in the early stage, and it gradually calms down and becomes homogenized in the later stage.

[0031] IV. Cooling and Molding: After smelting, the furnace is tilted to allow the homogeneous melt to flow out continuously and stably through a high-temperature resistant corundum flow channel. Water quenching granulation: A high-pressure water quenching device is set up about 1.5 meters directly below the flow channel. Clean industrial water with a pressure of 0.5MPa and a temperature of room temperature is used to impact the melt stream at a specific angle, breaking it up and rapidly cooling it to form glassy or fine crystalline particles. Collection: The water-quenched wet granules enter the dewatering screen, and after most of the water is separated, wet granules with a moisture content of about 8-10% are obtained.

[0032] V. Crushing and Screening: The wet granular material is conveyed to a rotary drying kiln and dried with hot air at 150°C for 1.5 hours to reduce the moisture content to ≤0.5%. The dried granules are lightly crushed using a double-roll crusher to separate the adhering granules. Finally, the crushed material is fed into a three-layer vibrating screen for grading. Regular particles with a particle size of 10-30mm are collected as the final product and packaged in a moisture-proof manner. Large pieces on the screen are returned to the crushing plant, while fine powder under the screen can be returned to the batching system for reuse.

[0033] VI. Product Performance Testing and Analysis: Random samples were taken from the products prepared using the above process, and their chemical composition and physical properties were tested according to national standards. The results are as follows: Chemical composition (mass percentage, wt%): Al2O3: 46.3%; CaO: 39.8%; MgO: 5.1%; SiO2: 8.0%; The alkalinity R is calculated using the following formula: ; The calculated alkalinity R in this embodiment is not within the range of 2.0-5.0 defined in this application, indicating that the formulation needs further adjustment. To meet the requirements, the formulation should be adjusted to increase the SiO2 content or decrease (CaO+MgO) (for example, if SiO2 is increased to 10.0%, then R=4.49, which meets the requirements). Fluoride ion content: 0.32%; Nitrogen content: 0.062% (indirectly proving that aluminum nitride decomposition efficiency is ≥99% at 1420℃); Other impurities are approximately 0.4% (mainly including Fe2O3, TiO2, Na2O, K2O, and P2O5, etc.).

[0034] Physical properties: The electrical conductivity of the melt at 1500℃ was measured to be 1520 S / cm using a high-temperature conductivity meter, proving that it has good electrical conductivity and is suitable for forming a conductive slag layer in refining equipment such as LF furnaces, with stable arc ignition. Melting point (hemispherical point): approximately 1350℃, lower than the typical temperature of molten steel, which is conducive to rapid melting and slag formation.

[0035] Conclusion: This embodiment demonstrates a complete process flow. The product obtained meets the invention requirements in all key indicators except alkalinity. By fine-tuning the raw material ratio (such as appropriately increasing silicon-containing raw materials or reducing calcium-containing raw materials), the alkalinity R value can be easily made to fall into the ideal range of 2.0-5.0, thereby obtaining a fully compliant product. The steps of brine passivation, argon protection, and specific temperature melting in the process are all effectively implemented.

[0036] In this embodiment of the application, it should be noted that if the step of spraying brine passivation is omitted in the aluminum ash pretreatment step, although the final product composition may meet the standards, the aluminum nitride (AlN) in the aluminum ash is prone to react with moisture in the air during the mixing and feeding process, releasing ammonia gas, causing serious production environment and safety problems. Therefore, the passivation step is the key to achieving safe and environmentally friendly disposal of hazardous waste aluminum ash. This application embodiment uses high-temperature melting to form a uniform pre-melted phase structure among the components, which is fundamentally different from the simple mechanical mixing-brickling process described in the background art. Unmelted mixtures melt slowly and have uneven composition during steelmaking, resulting in conductivity, slag formation rate and desulfurization efficiency that are far lower than the pre-melted products of this invention. For example, under the same conditions, the melt conductivity of unmelted briquette products is usually less than 1000 S / cm, and the desulfurization efficiency is low. The applicant's research found that when the aluminum content in the raw material aluminum ash exceeds 15% (e.g., reaches 20% or more), the intense oxidation and exothermic reaction of the aluminum during the smelting process will cause the molten pool to become out of control, which will inhibit the full decomposition of aluminum nitride. As a result, the nitrogen content of the final product is difficult to control below 0.1%, which fails to meet the requirements for high-quality steel smelting. Therefore, limiting the aluminum content in the aluminum ash to ≤15% is a key condition that works in synergy with the smelting temperature to ensure the efficient removal of harmful elements.

[0037] Example 2: Adjusting the formula to meet all the requirements of this application This embodiment optimizes the formulation of Example 1 to ensure all indicators, especially alkalinity; I. Raw materials and proportions: Aluminum ash (9% metallic aluminum content): 55.0 kg Calcareous material (carbide slag: papermaking mud = 1:1): 35.0 kg Magnesia-based material (70% lightly calcined magnesia powder + 30% dolomite): 5.0 kg New addition: Low-grade silica powder (SiO2>90%): 2.0kg (for fine-tuning SiO2 content and alkalinity) II. Process: Completely identical to Example 1; III. Product Performance Testing: Al2O3: 48.5%; CaO: 36.2%; MgO: 4.8%; SiO2: 9.2%; The alkalinity R is calculated using the following formula: ; Fluoride ion content: 0.29%; Nitrogen content: 0.058%; Other impurities are approximately 0.95%; Electrical conductivity of melt at 1500℃: 1550 S / cm; Conclusion: This embodiment successfully prepared a pre-melted conductive refining agent whose chemical composition fully complies with all the limitations of the claims of this application by finely adjusting the raw material ratio (slightly increasing the proportion of aluminum ash and introducing a small amount of silica), verifying the feasibility and implementability of the claims.

[0038] Example 3: Verification of Industrial Application Effects Test product: a pre-melted conductive refining agent produced in industrial batches using the same process and formula as in Example 2; Test steel plant and equipment: Fushun Shenglong Special Steel Manufacturing Co., Ltd., 60-ton LF furnace; Test steel grade: 8620RH (gear steel); Instructions for use: During the tapping process of the electric furnace, add the product of this invention into the ladle along with the steel flow, at a rate of 5 kg / ton of steel (i.e., 300 kg / furnace). Comparison benchmark: The commercial pre-melted refining slag (mainly composed of calcium aluminate) used in the original process of this steel plant; Test results (average of 3 consecutive furnaces):

[0039] The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments of this disclosure. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other. The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A pre-melted conductive refining agent for steelmaking, comprising an electro-refining agent, characterized in that, The refining agent is prepared by smelting a raw material system containing hazardous waste aluminum ash. The aluminum ash contains ≤15% by mass of metallic aluminum. This content, combined with a smelting temperature range of 1300℃-1500℃, is used to avoid excessive oxidation of metallic aluminum and ensure that the decomposition efficiency of aluminum nitride is ≥99%. The raw materials for preparing the refining agent include, by weight: 40-70 parts aluminum ash, 25-55 parts calcareous material, and 1-10 parts magnesian material; The raw materials are smelted to form a refining agent, and the chemical composition of the refining agent, by mass percentage, is as follows: Al2O3: 35%-58%, CaO: 30%-50%, MgO: 1%-8%, SiO2: 2%-20%; The refining agent contains: fluoride ion content ≤ 0.5%, and nitrogen content ≤ 0.1%; Furthermore, the mass percentage ratio of (CaO content + MgO content) to SiO2 content is 2.0-5.

0.

2. The pre-melted conductive refining agent for steelmaking according to claim 1, characterized in that: The calcareous material is a mixture of carbide slag and papermaking mud, with a mass ratio of 1:(0.8-1.2).

3. The pre-melted conductive refining agent for steelmaking according to claim 1, characterized in that: The magnesium material is a composite of lightly calcined magnesium powder and dolomite, wherein the mass percentage of lightly calcined magnesium powder is ≥60%.

4. A method for preparing a pre-melted conductive refining agent for steelmaking, applied in any one of the pre-melted conductive refining agents for steelmaking according to claims 1-3, characterized in that, Includes the following steps: S1. Raw material pretreatment: Aluminum ash is screened and passivated by spraying with brine. Calcium and magnesium materials are dried and crushed respectively. S2. Ingredients and Mixing: Weigh out 40-70 parts aluminum ash, 25-55 parts calcium materials, and 1-10 parts magnesium materials, and mix them evenly. S3. Melting: The uniformly mixed materials are put into a melting furnace and melted at a temperature of 1300℃-1500℃ for 0.5-2 hours. S4. Molding and Cooling: The completely molten material obtained in step S3 is discharged and cooled to solidify. S5. Crushing and Screening: The cooled solid material is crushed and screened to obtain granular products of a specified particle size.

5. The method for preparing the pre-melted conductive refining agent for steelmaking according to claim 4, characterized in that: In step S1, the brine is a MgCl2·6H2O solution, and its amount accounts for 1%-3% of the mass of aluminum ash, which is used to suppress adverse reactions of aluminum ash in pretreatment and subsequent processes.

6. The pre-melted conductive refining agent for steelmaking according to claim 4, characterized in that: In step S3, a reducing or neutral atmosphere is maintained inside the furnace by introducing a protective gas.

7. The method for preparing the pre-melted conductive refining agent for steelmaking according to claim 4, characterized in that: In step S4, the outflowing melt is quenched and cooled by a water flow with a pressure of 0.2-0.6 MPa to achieve rapid solidification and granulation of the material.

8. The method for preparing the pre-melted conductive refining agent for steelmaking according to claim 6, characterized in that: In step S5, after the solid material is crushed and screened, the particle size range of the granular product is 5-40mm.

9. The method for preparing the pre-melted conductive refining agent for steelmaking according to claim 6, characterized in that: The protective gas is an inert gas.

10. The method for preparing the pre-melted conductive refining agent for steelmaking according to claim 9, characterized in that: The inert gas is nitrogen, argon, or a mixture thereof.

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