A smelting method for converter semi-steel temperature raising and fluxing by using aluminum electrolytic cell waste brick

Abstract

This invention discloses a smelting method for using waste bricks from aluminum electrolytic cells as a heating and fluxing agent in converter semi-steel smelting. The method involves adding waste brick particles from aluminum electrolytic cells with a SiC mass fraction ≥60% to the converter before or during the early blowing stage. The amount of waste bricks added, the oxygen lance height, the oxygen supply intensity, and the addition method are precisely controlled according to the initial carbon content. The waste bricks used are primarily composed of silicon carbide (SiC), supplemented with small amounts of Si3N4, Na2SiO3, and NaF. The exothermic oxidation of these bricks provides chemical heat to the molten pool, and the reaction product SiO2 effectively improves slag fluidity. This invention effectively consumes the waste bricks from aluminum electrolytic cells while solving problems such as insufficient heat and poor fluidity in semi-steel smelting. Using this method, the consumption of heating agent can be reduced by 1-5 kg ​​per ton of steel, flux consumption by 1-3 kg, slag formation time shortened by more than 10%, and dephosphorization rate increased by more than 2%, achieving high-value-added resource utilization of industrial solid hazardous waste and optimization of semi-steel smelting processes.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgical technology and resource recycling, especially in the field of converter steelmaking process, and specifically relates to a smelting method for using waste bricks from aluminum electrolysis cells to heat up and assist melting of converter semi-steel. Background Technology

[0002] During the electrolytic aluminum production process, the lining of the aluminum electrolytic cell will gradually be damaged under high temperature and strong corrosion environment. Regular overhaul and replacement will generate a large amount of waste bricks from the aluminum electrolytic cell. Smelting 1 ton of aluminum will generate about 0.50-0.75 kg of waste bricks. At present, it is extremely difficult to achieve the harmless disposal of these bricks.

[0003] Waste bricks from aluminum electrolysis cells are primarily waste lining materials composed of SiC and Si3N4, but also contain soluble fluorides such as Na3AlF6, NaF, and CaF2, and soluble cyanides such as NaCN and Na4(Fe(CN)6). Fluorides are hazardous substances, and cyanides are toxic, making them the dominant environmental contributors. Currently, there are two main methods for treating waste bricks from aluminum electrolysis cells: wet and pyrometallurgical processes. Wet processes primarily rely on water leaching to remove fluorides and achieve harmless treatment of the waste bricks. Pyrometallurgical processes mainly achieve harmless treatment by diluting the waste bricks. However, these methods generate fluorides, metallurgical wastewater solutions, and gases, resulting in high treatment costs and failing to achieve resource utilization of high-value components such as SiC in the waste bricks, thus exhibiting poor economic viability.

[0004] On the other hand, steelmaking processes using semi-steel smelted in twin-converter furnaces as raw materials are widely used due to their advantages such as reduced raw material consumption and faster production pace. After vanadium extraction or dephosphorization in the twin-converter furnace, the silicon content of the semi-steel is close to zero, resulting in insufficient SiO2 and other acidic oxides in the slag during the initial smelting stage. This leads to excessively high slag basicity, poor fluidity, difficulty in slag formation, easy sticking to the lance, and splashing. Simultaneously, the significantly reduced exothermic reaction due to silicon oxidation results in insufficient chemical heat in the molten pool and lower smelting temperatures. Currently, adding sludge balls, bauxite, ferrosilicon, coke foam, and low-manganese ore can supplement heat and improve slag formation, but this increases smelting costs, limiting the development of semi-steel smelting processes and further reductions in the silicon content of molten iron.

[0005] Therefore, if waste bricks from aluminum electrolytic cells can be applied to the converter semi-steel smelting process, the exothermic reaction of SiC oxidation can be used to increase the temperature of the molten pool, and the generated SiO2 can be used to improve the fluidity of the slag. This will not only enable the harmless treatment of waste bricks from aluminum electrolytic cells but also realize the resource utilization of silicon carbide and silicon nitride, and provide an effective method for raising the temperature and aiding melting in semi-steel smelting. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a smelting method for using waste bricks from aluminum electrolysis cells as a heating and fluxing material in converter semi-steel smelting. This invention utilizes the exothermic oxidation reaction of SiC under oxygen blowing conditions to raise the temperature of the molten pool. Simultaneously, the reaction product SiO2 effectively replenishes the acidic components of the slag, improves slag fluidity, and prevents sticking and splashing, thereby achieving resource utilization of aluminum electrolysis solid waste and optimization of the semi-steel smelting process.

[0007] The objective of this invention is achieved through the following technical solution: A smelting method for using waste bricks from aluminum electrolysis cells to boost the temperature of semi-steel in a converter includes the following steps: Before or at the beginning of the blowing process, waste brick particles from aluminum electrolysis cells are added to a converter that has already been mixed with semi-steel; the chemical composition of the semi-steel, by mass percentage, includes: C: 2.4%-3.8%, Si: ≤0.05%, with the remainder being Fe and unavoidable impurities; The amount of waste brick particles added to the aluminum electrolysis cell and the oxygen lance operation procedure are controlled according to the initial carbon content of the semi-steel. When the carbon content of the semi-steel is 2.4%-3.2%, the amount of waste brick particles added to the aluminum electrolysis cell is 0.5%-1.5% of the weight of the semi-steel; during smelting (0-2 min), the oxygen lance is operated at a low position, and the oxygen supply intensity is 3.3-4.5 Nm. 3 / (t·min); During blowing [2-4 min), raise the oxygen lance position by 0.2-0.4 m and adjust the oxygen supply intensity to 3.0-4.0 Nm. 3 / (t·min); During blowing [4-10min), lower the oxygen lance position by 0.1-0.3m and adjust the oxygen supply intensity to 3.2-4.2Nm. 3 / (t·min), during the re-drying process, raise the lance position by 0.2-0.4m; during smelting [10min - 30s before the end point), lower the oxygen lance position by 0.1m and adjust the oxygen supply intensity to 3.3-4.5Nm. 3 / (t·min); The flow rate remains constant before the blowing end point, and the gun position is lowered for more than 30 seconds; When the carbon content of the semi-steel is 3.2%-3.8%, the amount of waste brick particles added to the aluminum electrolysis cell is 0.2%-1.0% of the weight of the semi-steel; during smelting (0-2 min), the oxygen lance is operated at the reference position, and the oxygen supply intensity is 3.2-4.2 Nm. 3 / (t·min); During blowing [2-4 min), raise the oxygen lance position by 0.1-0.3 m and adjust the oxygen supply intensity to 3.0-4.0 Nm. 3 / (t·min); During blowing [4-11 min), lower the oxygen lance position by 0.1-0.3 m and adjust the oxygen supply intensity to 3.3-4.5 Nm. 3 / (t·min), during the re-drying process, raise the lance position by 0.2-0.4m; during smelting [11min - 30s before the end point), lower the oxygen lance position by 0.1m and adjust the oxygen supply intensity to 3.3-4.5Nm. 3 / (t·min); The flow rate remains constant before the blowing end point, and the gun position is lowered for more than 30 seconds.

[0008] Preferably, the mass fraction of SiC in the waste brick particles from the aluminum electrolysis cell is ≥60%.

[0009] Preferably, by mass percentage, the waste brick particles from the aluminum electrolysis cell also contain Si3N4: 8%-20%, Na2SiO3: 6%-20%, and NaF≤2%.

[0010] Preferably, the waste brick particles from the aluminum electrolysis cell are those discarded during the aluminum electrolysis process.

[0011] Preferably, the waste brick particles from the aluminum electrolysis cell are waste lining material generated during maintenance.

[0012] Preferably, in the waste brick particles from the aluminum electrolysis cell, more than 90% of the particles are distributed in the particle size range of 5-50 mm by mass percentage.

[0013] Preferably, the processing of the waste brick particles from the aluminum electrolysis cell includes: The waste bricks from aluminum electrolysis cells are initially coarsely crushed using a jaw crusher, and then finely crushed using a hammer crusher or impact crusher to achieve the preset particle size.

[0014] Preferably, the waste brick particles from the aluminum electrolysis cell are added to the converter in one go along with the waste steel through the waste steel hopper.

[0015] Preferably, the waste brick particles from the aluminum electrolysis cell are transported to the high-level silo in the steelmaking workshop by a belt conveyor, and added to the converter in 1-2 batches via a vibrating feed chute within 3 minutes after the start of oxygen blowing.

[0016] Preferably, the nominal capacity of the converter is 30-400 tons.

[0017] The present invention has the following beneficial effects: In the smelting method of using waste bricks from aluminum electrolysis cells for heating and fluxing in converter semi-steel, the waste bricks from aluminum electrolysis cells are used as a metallurgical auxiliary material with functions of heating, slag formation, and carbon supplementation in converter semi-steel smelting. The core of this invention lies in addressing the problems of insufficient heat and difficulty in slag formation and poor slag fluidity caused by the lack of acidic oxides such as SiO2 during semi-steel smelting. This is achieved by utilizing the high SiC content in the waste bricks from aluminum electrolysis cells. According to thermodynamic calculations, the oxidation reaction is SiC + 3 / 2O2 → SiO2 + CO, with a theoretical heat release of up to 19200 kJ / kg (based on SiC), which can replace purchased ferrosilicon and provide supplementary heat to the molten pool. Simultaneously, the SiO2 generated by this reaction effectively replenishes the acidic components of the slag, effectively reducing the melting point and viscosity of high-alkalinity slag, solving the problems of lance sticking, splashing, and low dephosphorization efficiency, thus realizing the resource utilization of waste bricks from aluminum electrolysis cells and optimizing the smelting process. Therefore, this invention dynamically adjusts the amount of waste bricks added to the aluminum electrolytic cell and the oxygen lance operation based on the carbon content of the semi-steel. When the carbon content is in the range of 2.4%-3.2%, the heat is insufficient. Therefore, the amount of waste bricks added to the aluminum electrolytic cell is controlled to be 1.0%-1.5% of the weight of the semi-steel, and a low lance position is used in the early stage of smelting, with an oxygen lance operating at 3.8-4.5 Nm. 3 An oxygen supply intensity of / (t·min) promotes the rapid oxidation of SiC in the waste bricks of the aluminum electrolysis cell, achieving rapid temperature rise of the molten pool; during the middle stage of smelting, after the temperature rise meets the requirements, the oxygen lance position is raised by 0.1-0.3 meters, and the oxygen supply intensity is 3.2-3.8 Nm. 3 / (t·min), to promote slag formation and conversion; maintain the lance position and oxygen supply intensity of the middle stage of smelting in the later stage of smelting until the blowing end, in order to stabilize the later reaction. When the carbon content is in the range of 3.2%-3.8%, the self-chemical heat is relatively sufficient, and the focus is on promoting the initial slag formation. The amount of waste bricks added to the aluminum electrolysis cell is controlled at 0.5%-1.0% of the weight of half steel. High lance position operation is adopted in the early stage of smelting, and the oxygen supply intensity is controlled at 3.2-3.8 Nm. 3 / (t·min), prioritize its slag-forming function to improve the initial slag fluidity and create conditions for efficient dephosphorization; during the middle stage of smelting, lower the oxygen lance position by 0.1-0.3 meters and adjust the oxygen supply intensity to 3.5-4.2 Nm. 3 / (t·min), entering the strong decarburization stage; in the later stage of smelting, the oxygen lance position is adjusted to the lance height in the early stage of smelting, and the oxygen supply intensity is adjusted to 3.0-3.6 Nm. 3 / (t·min) is used for precise control of the endpoint. This dynamic and coordinated control ensures the accuracy of heat replenishment, the rationality of slag formation path, and guarantees sufficient heat, slag formation efficiency, and endpoint hit rate in the smelting process.

[0018] Furthermore, by mass percentage, the waste bricks from aluminum electrolysis cells utilized in this invention mainly comprise: SiC ≥ 60%, Si3N4: 13-16%, Na2SiO3: 14-17%, and NaF ≤ 2%. From these components and their behavior during the smelting process, it can be seen that SiC and Si3N4 undergo an oxidation reaction under oxygen blowing conditions, providing the heat of oxidation and the source of SiO2, which is the material basis for improving thermal balance and slag structure. Na2SiO3 is a low-melting-point silicate, and NaF is a powerful slagging agent. Both play a role in the early stages of blowing, producing a synergistic effect with the SiO2 generated by oxidation, further reducing the slag melting point and viscosity. In the early stages of blowing, this allows for the rapid formation of highly fluid and active slag, significantly shortening the slag formation time. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0020] Conversely, this invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined in the claims. Furthermore, to provide a better understanding of the invention, certain specific details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0021] The present invention discloses a smelting method for using waste bricks from aluminum electrolysis cells to heat up and assist melting in the production of semi-steel in a converter, comprising the following steps: First, the waste bricks from aluminum electrolytic cells undergo pretreatment. These waste bricks originate from the lining waste generated during the scrapping and / or maintenance of electrolytic cells in the aluminum electrolysis process. They are initially coarsely crushed using a jaw crusher, followed by fine crushing using a hammer crusher or impact crusher. Screening controls the particle size distribution of the waste bricks to be over 90% within the range of 5-50mm to meet the converter feeding requirements. Before or at the initial stage of blowing, the waste brick particles are added to the converter already containing semi-steel. During the converter blowing process, the waste bricks undergo an exothermic oxidation reaction, providing supplementary heat to the molten pool. The generated SiO2 acts as a slag-forming component, improving the slag's fluidity, while the generated CO gas increases the gas volume and calorific value. By mass percentage, the main components of the waste bricks from aluminum electrolytic cells include: SiC ≥ 60%, Si3N4: 8%-20%, Na2SiO3: 6%-20%, and NaF ≤ 2%. The semi-steel, after vanadium extraction or dephosphorization in a twin-cell converter, is added to the converter. The chemical composition of the semi-steel, by mass percentage, includes: C: 2.4%-3.8%, Si≤0.05%, with the remainder being Fe and unavoidable impurities. The amount of waste bricks added to the aluminum electrolysis cell is controlled according to the initial carbon content of the semi-steel: When the carbon content of the semi-steel is 2.4%-3.2%, the amount of waste brick particles added to the aluminum electrolysis cell is 0.5%-1.5% of the weight of the semi-steel; when the carbon content of the semi-steel is 3.2%-3.8%, the amount of waste brick particles added to the aluminum electrolysis cell is 0.2%-1.0% of the weight of the semi-steel. The waste brick particles can be added to the converter at one time along with the scrap steel in the scrap steel hopper; or they can be transported to the high-level silo in the steelmaking workshop by belt conveyor and added to the converter in 1-2 batches via a vibrating feed chute within 3 minutes after the start of oxygen blowing. Throughout the blowing process, different oxygen lance operating procedures are implemented based on the initial carbon content of the semi-steel: When the carbon content of the semi-steel is 2.4%-3.2%, during smelting (0-2 min), a low-lance position operation is adopted, and the oxygen supply intensity is 3.3-4.5 Nm. 3 / (t·min), which is beneficial for the rapid reaction and exothermic temperature rise of waste brick particles in aluminum electrolysis cells; during blowing [2-4min), the oxygen lance position is raised by 0.2-0.4m, and the oxygen supply intensity is adjusted to 3.0-4.0Nm. 3 / (t·min), to promote slag melting and improve dephosphorization efficiency; during blowing [4-10min), lower the oxygen lance position by 0.1-0.3m and adjust the oxygen supply intensity to 3.2-4.2Nm. 3 / (t·min), strengthen the stirring of the molten pool to improve decarburization efficiency; during the drying process, the lance position needs to be raised by 0.2-0.4m to promote slag formation; during smelting [10min-30s before the end point], lower the oxygen lance position by 0.1m and adjust the oxygen supply intensity to 3.3-4.5Nm. 3 / (t·min), strengthen the stirring of the molten pool to further dephosphorize and decarbonize; keep the flow rate unchanged before the blowing end point, reduce the lance position by more than 30s to reduce slag iron loss; When the carbon content of the semi-steel is 3.2%-3.8%, the amount of waste brick particles added to the aluminum electrolysis cell is 0.2%-1.0% of the weight of the semi-steel. During smelting (0-2 min), the reference lance position is used to facilitate the reaction of the waste brick particles in the aluminum electrolysis cell to generate SiO2 flux. During blowing (2-4 min), the oxygen lance position is raised by 0.1-0.3 m, and the oxygen supply intensity is adjusted to 3.0-4.0 Nm. 3 / (t·min), to promote slag melting and improve dephosphorization efficiency; during blowing [4-11min), lower the oxygen lance position by 0.1-0.3m and adjust the oxygen supply intensity to 3.3-4.5Nm. 3 / (t·min), strengthen the stirring of the molten pool to improve decarburization efficiency; during the drying process, the lance position needs to be raised by 0.2-0.4m to promote slag formation; during smelting [11min - 30s before the end point), lower the oxygen lance position by 0.1m and adjust the oxygen supply intensity to 3.3-4.5Nm.3 / (t·min), strengthen the stirring of the molten pool to further dephosphorize and decarbonize; keep the flow rate unchanged before the blowing end point, reduce the lance position by more than 30s to reduce slag iron loss.

[0022] The above-mentioned solution of the present invention is applicable to converters with a nominal capacity of 30-400 tons.

[0023] Example 1 For a converter with a nominal capacity of 50t, the semi-steel after vanadium extraction, by mass percentage, has the following main chemical composition: C: 3.60%, Si: 0.01%, P: 0.10%, with the remainder being Fe and unavoidable impurities. The temperature is 1320℃. The specific steps of the method described in this invention are as follows: First, prepare waste bricks from aluminum electrolysis cells. The chemical composition, by mass percentage, includes: SiC: 68.05%, Si3N4: 14.10%, Na2SiO3: 13.55%, NaF: 1.52%, with the remainder being other impurities. Use a jaw crusher for coarse crushing, and then use a hammer crusher or impact crusher for fine crushing. Screen out the waste bricks from aluminum electrolysis cells to 5-50mm for later use. Based on the carbon content of the semi-steel being 3.60%, the amount of waste bricks added is determined to be 0.9% of the weight of the semi-steel, i.e., 450 kg. This waste brick is then added to the converter along with the waste steel through the waste steel hopper before oxygen blowing begins. During smelting (0-2 min), the oxygen lance position is controlled at 1.0 m, and the oxygen supply intensity is 3.3 Nm. 3 / (t·min), which is beneficial for the reaction of waste bricks in the aluminum electrolysis cell to generate SiO2 flux; during blowing [2-4min), the oxygen lance position is raised to 1.2m, and the oxygen supply intensity is adjusted to 3.2Nm. 3 / (t·min), to promote slag melting and improve dephosphorization efficiency; during blowing [4-11min), the oxygen lance position is lowered to 0.8m and the oxygen supply intensity is adjusted to 3.5Nm. 3 / (t·min), strengthen the stirring of the molten pool to improve decarburization efficiency; if back-drying occurs, raise the lance position to 1.0m to promote slag formation; during smelting [11min - 30s before the end point), lower the oxygen lance position to 0.9m and adjust the oxygen supply intensity to 3.4Nm. 3 / (t·min), strengthen the stirring of the molten pool to further dephosphorize and decarbonize; keep the flow rate unchanged before the end of blowing, lower the lance position to 0.8m and keep it for more than 30s to reduce slag iron loss, and then raise the lance to stop oxygen supply.

[0024] When this invention was applied to vanadium-extracted semi-steel in a 50t converter, the tapping temperature was 1660℃. The consumption of heating agent was reduced by 2kg per ton of steel, and the consumption of flux was reduced by 1.5kg. The slag fluidity was improved. Compared with the process without adding waste bricks from aluminum electrolysis cells, the slag formation time was shortened by 10.5%, and the dephosphorization rate was increased by 3.5%.

[0025] Example 2 For a converter with a nominal capacity of 120t, the dephosphorized semi-steel, by mass percentage, has the following main chemical composition: C: 2.60%, Si: 0.01%, P: 0.035%, with the remainder being Fe and unavoidable impurities, at a temperature of 1350℃. The specific steps using the method described in this invention are as follows: First, prepare waste bricks from aluminum electrolysis cells. The chemical composition, by mass percentage, includes: SiC: 70.20%, Si3N4: 12.80%, Na2SiO3: 12.52%, NaF: 1.45%, with the remainder being other impurities. Use a jaw crusher for coarse crushing, and then use a hammer crusher or impact crusher for fine crushing. Screen out the waste bricks from aluminum electrolysis cells to 5-50mm for later use. Based on the carbon content of the semi-steel being 2.60%, the amount of waste bricks added was determined to be 1.3% of the weight of the semi-steel, i.e., 1560 kg. The waste bricks were first transported to the high-level silo in the steelmaking workshop via a belt conveyor. One minute after the oxygen blowing started, 780 kg of waste bricks from the aluminum electrolysis cell were added to the converter via a vibrating feed chute. One minute later, another 780 kg of waste bricks from the aluminum electrolysis cell were added to the converter in the same way. During smelting (0-2 min), the oxygen lance position is controlled at 1.4 m, and the oxygen supply intensity is 4.2 Nm. 3 / (t·min), which is beneficial for the rapid reaction and exothermic temperature rise of waste bricks in aluminum electrolysis cells; during blowing [2-4min), the oxygen lance position is raised to 1.6m, and the oxygen supply intensity is adjusted to 3.5Nm. 3 / (t·min), to promote slag melting and improve dephosphorization efficiency; during blowing [4-10min), the oxygen lance position is lowered to 1.4m and the oxygen supply intensity is adjusted to 3.8Nm. 3 / (t·min), strengthen the stirring of the molten pool to improve decarburization efficiency; if back-drying occurs, raise the lance position to 1.6m to promote slag formation; during smelting [10min - 30s before the end point), lower the oxygen lance position to 1.5m and adjust the oxygen supply intensity to 4.0Nm. 3 / (t·min), strengthen the stirring of the molten pool to further dephosphorize and decarbonize; keep the flow rate unchanged before the end of blowing, lower the lance position to 1.4m and keep it for more than 30s to reduce slag iron loss, and then raise the lance to stop oxygen supply.

[0026] When this invention was applied to the dephosphorized semi-steel produced in a 120t converter, the tapping temperature was 1650℃. The consumption of heating agent was reduced by 2.5kg per ton of steel, and the consumption of flux was reduced by 1kg. The slag fluidity was improved. Compared with the process without the addition of waste bricks from aluminum electrolysis cells, the slag formation time was shortened by 12%, and the dephosphorization rate was increased by 4.2%.

[0027] Example 3 For a converter with a nominal capacity of 300t, the dephosphorized semi-steel, by mass percentage, has the following main chemical composition: C: 3.20%, Si: 0.02%, P: 0.045%, with the remainder being Fe and unavoidable impurities, at a temperature of 1330℃. The specific steps using the method described in this invention are as follows: First, prepare waste bricks from aluminum electrolysis cells. The chemical composition, by mass percentage, includes: SiC: 65.80%, Si3N4: 16.50%, Na2SiO3: 14.23%, NaF: 1.80%, with the remainder being other impurities. Use a jaw crusher for coarse crushing, and then use a hammer crusher or impact crusher for fine crushing. Screen out the waste bricks from aluminum electrolysis cells to 5-50mm for later use. Based on the carbon content of the semi-steel being 3.20%, the amount of waste bricks added is determined to be 1.0% of the weight of the semi-steel, i.e., 3000 kg. First, the waste bricks are transported to the high-level silo in the steelmaking workshop via a belt conveyor. One minute after the oxygen blowing begins, 1500 kg of waste bricks from the aluminum electrolysis cell are added to the converter via a vibrating feed chute. One minute later, another 1500 kg of waste bricks from the aluminum electrolysis cell are added to the converter in the same way. During smelting (0-2 min), the oxygen lance position is controlled at 2.0 m, and the oxygen supply intensity is 3.8 Nm. 3 / (t·min), which is beneficial for the reaction of waste bricks in the aluminum electrolysis cell to generate SiO2 flux; during blowing [2-4min), the oxygen lance position is raised to 2.2m, and the oxygen supply intensity is adjusted to 3.5Nm. 3 / (t·min), to promote slag melting and improve dephosphorization efficiency; during blowing [4-11min), the oxygen lance position is lowered to 2.0m, and the oxygen supply intensity is adjusted to 4.0Nm. 3 / (t·min), strengthen the stirring of the molten pool to improve decarburization efficiency; if back-drying occurs, raise the lance position to 2.2m to promote slag formation; during smelting [11min - 30s before the end point), lower the oxygen lance position to 2.1m and adjust the oxygen supply intensity to 4.2Nm. 3 / (t·min), strengthen the stirring of the molten pool to further dephosphorize and decarbonize; keep the flow rate unchanged before the end of blowing, lower the lance position to 2.0m and keep it for more than 30s to reduce slag iron loss, and then raise the lance to stop oxygen supply.

[0028] When this invention was applied to dephosphorized semi-steel produced in a 300t converter, the tapping temperature was 1640℃. The consumption of heating agent was reduced by 2kg per ton of steel, and the consumption of flux was reduced by 2kg. The slag fluidity was improved. Compared with the process without the addition of waste bricks from aluminum electrolysis cells, the slag formation time was shortened by 11%, and the dephosphorization rate was increased by 4.7%.

[0029] As can be seen from the results of the embodiments of this invention, the method of this invention has both technical and economic benefits as well as environmental benefits. In terms of technical and economic benefits, this method provides a solution to the problems of insufficient heat and difficulty in slag formation in semi-steel smelting. It utilizes the exothermic oxidation of SiC in waste bricks from aluminum electrolysis cells to compensate for the chemical heat deficit caused by the extremely low silicon content of semi-steel; the generated SiO2 replenishes the acidic oxides in the slag, improving the slag's fluidity. Using the smelting method of this invention, the consumption of heating agent can be reduced by 1-5 kg ​​per ton of steel, and the consumption of fluxing agent can be reduced by 1-3 kg; at the same time, due to the improved slag performance, it is expected to shorten the slag formation time by more than 10%, increase the dephosphorization rate by more than 2%, reduce splashing and lance sticking, increase the scrap steel ratio in semi-steel smelting, and improve metal recovery and operating efficiency. In terms of environmental benefits, this invention opens up a high-value-added approach for the direct resource utilization of waste bricks from aluminum electrolysis cells, an industrial solid hazardous waste that does not require complex pretreatment. Its raw material processing and feeding methods are fully compatible with existing steelmaking processes, making it easy to implement and promote on a large scale in steel enterprises, thus achieving a balance between economic and environmental benefits.

[0030] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A smelting method for using waste bricks from aluminum electrolysis cells to heat-boost and assist in the melting of semi-steel in a converter, characterized in that, Includes the following steps: Before or at the beginning of the blowing process, waste brick particles from aluminum electrolysis cells are added to the converter that has already been mixed with semi-steel. The chemical composition of the semi-steel, by mass percentage, includes: C: 2.4%-3.8%, Si: ≤0.05%, with the remainder being Fe and unavoidable impurities; The amount of waste brick particles added to the aluminum electrolysis cell and the oxygen lance operation procedure are controlled according to the initial carbon content of the semi-steel. When the carbon content of the semi-steel is 2.4%-3.2%, the amount of waste brick particles added to the aluminum electrolysis cell is 0.5%-1.5% of the weight of the semi-steel; during smelting (0-2 min), the oxygen lance is operated at a low position, and the oxygen supply intensity is 3.3-4.5 Nm. 3 / (t·min); During blowing [2-4 min), raise the oxygen lance position by 0.2-0.4 m and adjust the oxygen supply intensity to 3.0-4.0 Nm. 3 / (t·min); During blowing [4-10min), lower the oxygen lance position by 0.1-0.3m and adjust the oxygen supply intensity to 3.2-4.2Nm. 3 / (t·min), during the re-drying process, raise the lance position by 0.2-0.4m; during smelting [10min - 30s before the end point), lower the oxygen lance position by 0.1m and adjust the oxygen supply intensity to 3.3-4.5Nm. 3 / (t·min); The flow rate remains constant before the blowing end point, and the gun position is lowered for more than 30 seconds; When the carbon content of the semi-steel is 3.2%-3.8%, the amount of waste brick particles added to the aluminum electrolysis cell is 0.2%-1.0% of the weight of the semi-steel; during smelting (0-2 min), the oxygen lance is operated at the reference position, and the oxygen supply intensity is 3.2-4.2 Nm. 3 / (t·min); During blowing [2-4 min), raise the oxygen lance position by 0.1-0.3 m and adjust the oxygen supply intensity to 3.0-4.0 Nm. 3 / (t·min); During blowing [4-11 min), lower the oxygen lance position by 0.1-0.3 m and adjust the oxygen supply intensity to 3.3-4.5 Nm. 3 / (t·min), during the re-drying process, raise the lance position by 0.2-0.4m; during smelting [11min - 30s before the end point), lower the oxygen lance position by 0.1m and adjust the oxygen supply intensity to 3.3-4.5Nm. 3 / (t·min); The flow rate remains constant before the blowing end point, and the gun position is lowered for more than 30 seconds.

2. The smelting method for using waste bricks from aluminum electrolysis cells as a heating aid in converter semi-steel production according to claim 1, characterized in that, The mass fraction of SiC in the waste brick particles from the aluminum electrolysis cell is ≥60%.

3. A smelting method for using waste bricks from aluminum electrolysis cells as a heating aid in converter semi-steel production according to claim 1 or 2, characterized in that, By mass percentage, the waste brick particles from the aluminum electrolysis cell also contain Si3N4: 8%-20%, Na2SiO3: 6%-20%, and NaF≤2%.

4. The smelting method for using waste bricks from aluminum electrolytic cells as a heating aid in converter semi-steelmaking according to claim 1, characterized in that, The waste brick particles from the aluminum electrolysis cell are from the scrapped electrolysis cells during the aluminum electrolysis process.

5. A smelting method for using waste bricks from aluminum electrolysis cells as a heating aid in converter semi-steel production according to claim 1, characterized in that, The waste brick particles from the aluminum electrolysis cell are derived from the cell lining waste generated during maintenance.

6. A smelting method for using waste bricks from aluminum electrolysis cells as a heating aid in converter semi-steel production according to claim 1, characterized in that, Of the waste brick particles from the aluminum electrolysis cell, more than 90% by mass are distributed in the particle size range of 5-50 mm.

7. A smelting method for using waste bricks from aluminum electrolytic cells as a heating aid in the melting of semi-steel in a converter, according to any one of claims 4-6, characterized in that... The processing of the waste brick particles from the aluminum electrolysis cell includes: The waste bricks from aluminum electrolysis cells are initially coarsely crushed using a jaw crusher, and then finely crushed using a hammer crusher or impact crusher to achieve the preset particle size.

8. A smelting method for using waste bricks from aluminum electrolysis cells as a heating aid in converter semi-steel production according to claim 1, characterized in that, The waste brick particles from the aluminum electrolysis cell are added to the converter in one go, along with the waste steel, through the waste steel hopper.

9. A smelting method for using waste bricks from aluminum electrolysis cells as a heating aid in converter semi-steel production according to claim 1, characterized in that, The waste brick particles from the aluminum electrolysis cell are transported to the high-level silo in the steelmaking workshop by a belt conveyor. Within 3 minutes after the start of oxygen blowing, they are added to the converter in 1-2 batches via a vibrating feed chute.

10. A smelting method for using waste bricks from aluminum electrolysis cells as a heating aid in converter semi-steel production according to claim 1, characterized in that, The nominal capacity of the converter is 30-400 tons.