Method for efficiently dephosphorizing converter slag by using electric furnace slag

Abstract

The invention provides a method for efficiently dephosphorizing converter slag by using electric furnace slag, which comprises the following steps: discharging the electric furnace slag after electric furnace smelting is finished, sampling and analyzing main chemical components of the electric furnace slag, and calculating the amount of active lime needing to be supplemented and added; the discharged electric furnace slag is conveyed to a converter area through a special slag tank with a heat preservation function, and the hot-state electric furnace slag is poured into a converter through a traveling crane; the method comprises the following steps: firstly adding scrap steel into a converter, then adding molten iron, supplying oxygen for blowing, finally adding active lime, adjusting the alkalinity of slag to 2.5-4.5, blowing to the end point, and tapping. According to the method, the low-phosphorus characteristic of the electric furnace slag is combined, the electric furnace slag has good interface reaction performance and dephosphorization capacity in the thermal state and is directly returned to the converter smelting process, lime consumption is reduced, efficient dephosphorization of the converter slag is achieved, efficient dephosphorization and resource utilization of the electric furnace slag are achieved, and the method has the advantages of saving energy, reducing emission, reducing cost, improving efficiency and recycling resources.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel smelting technology and relates to an efficient dephosphorization method for converter slag. Background Technology

[0002] In the steel smelting industry, the proportion of electric arc furnace (EAF) steelmaking is gradually increasing, and most enterprises will have a coexistence of EAF and converter steelmaking. Because the molten iron used in converter steelmaking has a high phosphorus content, the converter slag also has a high phosphorus content, approximately 3-5% phosphorus pentoxide. Due to the high phosphorus content, the proportion of converter slag recycled within steel enterprises is limited, resulting in low resource utilization efficiency and value. Furthermore, the free calcium oxide in the steel slag has a certain impact on the quality of cement, building materials, and other products. The main raw material for electric arc furnace (EAF) steelmaking is scrap steel, and the amount of molten iron used in smelting is much lower than that of converter steelmaking. In some EAF steelmaking processes, all scrap steel is used for smelting. Therefore, the phosphorus content in the raw materials of EAF steelmaking is much lower than that of converter steelmaking. The phosphorus content of the slag produced by EAF steelmaking is also lower than that of converter slag. For example, in EAF steelmaking where the weight ratio of molten iron in the main raw material is about 50%, the phosphorus content in the final molten steel is about 0.01%, corresponding to a phosphorus pentoxide content of about 1-1.5% in the EAF slag, while the binary basicity of wCaO / wSiO2 is about 4.0 and TFe is about 25%. Theoretically, this type of EAF slag still has a strong dephosphorization capacity.

[0003] The current solutions for recycling high-phosphorus converter slag in the converter smelting process mainly have the following problems: 1) It requires dephosphorization through reduction gasification, which has a low dephosphorization rate, high cost, and increases carbon emissions; 2) The process is complex, which increases the difficulty of production and affects production efficiency. Summary of the Invention

[0004] To address the problems described in the background art, such as low dephosphorization rate, high cost, increased carbon emissions, complex process flow, increased production difficulty, and reduced production efficiency of high-phosphorus converter steel slag during converter smelting, this invention provides a method for efficient dephosphorization of converter slag using electric furnace slag.

[0005] The method of the present invention includes: After the electric furnace smelting is completed, the slag is discharged, and samples are taken to analyze its main chemical components and calculate the amount of quicklime that needs to be added. A special slag bin with heat preservation function is used to transport the discharged electric furnace slag to the converter area, and a crane is used to pour the hot electric furnace slag into the converter; First, scrap steel is added to the converter, then molten iron is added, oxygen is supplied for blowing, and finally, quicklime is added to adjust the slag basicity to between 2.5 and 4.5. The steel is then blown to the end point and tapped.

[0006] Preferably, the method for calculating the amount of quicklime to be added is as follows: , In the formula, W CaO To supplement the amount of activated lime; R 目标 The target binary basicity of the final slag from converter smelting; SiO 2总 Total SiO2 content, including SiO2 from electric furnace slag and molten iron; CaO 初始 This refers to the initial CaO content, i.e., the CaO content in the electric furnace slag; CaO 石灰 This refers to the effective CaO content in lime. p For lime utilization rate, 0 < p <1 refers to the proportion of CaO that participates in the reaction during steelmaking out of the total amount consumed; FeO 实际 FeO content in electric furnace slag; FeO 目标 The target FeO content in the final slag of converter smelting; the latter half of the formula (1-0.1*(FeO) 实际 -FeO 目标 ) / 5), is a correction coefficient summarized by combining activity theory and empirical data.

[0007] Preferably, the temperature of the hot electric furnace slag poured into the converter is ≥1300℃.

[0008] Preferably, in the oxygen-supplying blowing process, the oxygen supply intensity is 2.5-3.0 Nm. 3 / (min·t).

[0009] Preferably, the chemical composition of the molten iron is required by weight ratio as follows: C 4-5%, Si 0.2-0.4%, Mn 0.2-0.3%, P 0.1-0.2%, with the remainder being Fe.

[0010] Compared with the prior art, the present invention has the following advantages: (1) Significantly improve dephosphorization efficiency: By taking advantage of the characteristics of hot electric furnace slag itself, such as high alkalinity, suitable TFe content and low phosphorus content, it is directly used as part of the slag-forming material in the converter smelting process, which effectively improves the phosphorus distribution capacity and dephosphorization efficiency of the slag. (2) Reduced consumption and cost of auxiliary materials: By utilizing the alkalinity and physical heat of electric furnace slag, the amount of active lime added is greatly reduced, thereby reducing the cost of auxiliary materials and energy consumption; (3) Achieve heat recovery and energy conservation and emission reduction: Hot electric furnace slag is transported to the converter through a special slag pot with heat preservation function, making full use of its sensible heat, reducing heat loss in the converter smelting process, reducing overall energy consumption, and conforming to the direction of green smelting; (4) Promote the resource utilization of solid waste: Electric furnace slag is used as a dephosphorization material and recycled in converter smelting, realizing the high-value recycling of solid waste in the steel plant and reducing the pressure of environmental disposal; (5) Simplified process flow: It eliminates the complicated steps of traditional gasification dephosphorization or slag treatment, and the operation process is simple and easy to implement in production without affecting the smelting rhythm and efficiency.

[0011] In summary, this invention combines the low phosphorus characteristics of electric furnace slag with its good interfacial reaction performance and dephosphorization capacity under hot conditions, allowing it to be directly returned to the converter smelting process, reducing lime consumption, achieving efficient dephosphorization of converter slag, realizing efficient dephosphorization and resource utilization of electric furnace slag, and combining the advantages of energy saving and emission reduction, cost reduction and efficiency improvement and resource recycling. Attached Figure Description

[0012] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0013] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0014] A method for efficient dephosphorization of converter slag using electric arc furnace slag, the flowchart of which is shown below. Figure 1 As shown, the specific steps are as follows.

[0015] First, after the electric furnace smelting is completed, the slag is discharged, and samples are taken to analyze its main chemical components, and the amount of quicklime that needs to be added is calculated.

[0016] Specifically, the calculation method for the amount of quicklime that needs to be added is as follows: , In the formula, W CaO To supplement the amount of activated lime; R 目标 The target binary basicity of the final slag from converter smelting; SiO 2总 Total SiO2 content, including SiO2 from electric furnace slag and molten iron; CaO 初始 This refers to the initial CaO content, i.e., the CaO content in the electric furnace slag; CaO 石灰 This refers to the effective CaO content in lime. p For lime utilization rate, 0 < p <1 refers to the proportion of CaO that participates in the reaction during steelmaking out of the total amount consumed; FeO 实际 FeO content in electric furnace slag; FeO 目标 The target FeO content in the final slag of converter smelting; the latter half of the formula (1-0.1*(FeO) 实际 -FeO 目标 ) / 5), is a correction coefficient summarized by combining activity theory and empirical data.

[0017] The discharged electric furnace slag is then transported to the converter area using a dedicated slag hopper with heat preservation function, and the hot electric furnace slag is poured into the converter by a crane. Specifically, the temperature of the hot electric furnace slag poured into the converter is ≥1300℃.

[0018] First, scrap steel is added to the converter, then molten iron is added, oxygen is supplied for blowing, and finally, quicklime is added to adjust the slag basicity to between 2.5 and 4.5. The steel is then blown to the end point and tapped.

[0019] Specifically, in oxygen-powered blowing processes, the oxygen supply intensity is 2.5-3.0 Nm. 3 / (min·t).

[0020] Specifically, the chemical composition of molten iron, by weight, should be: C 4-5%, Si 0.2-0.4%, Mn 0.2-0.3%, P 0.1-0.2%.

[0021] Example 1 This embodiment uses the method of the present invention to return the hot electric furnace slag to the converter for recycling.

[0022] Electric furnace capacity: 110 tons.

[0023] After the electric furnace smelting is completed, the electric furnace slag is discharged. The electric furnace slag discharge is 11.2 tons. The main chemical components are analyzed by sampling. The main components are: P2O5 1.1%, CaO 44.6%, SiO2 10.8%, FeO 2 1.4%.

[0024] The discharged electric furnace slag is transported to the converter area using a special slag hopper with heat preservation function. The hot electric furnace slag is then poured into the converter by a crane at a converter temperature of 1410℃.

[0025] In the converter, 38 tons of scrap steel are first charged, followed by 122 tons of molten iron. The composition of the molten iron in the converter (wt%) is: C 4.6%, Si 0.28%, Mn 0.20%, P 0.12%, with the remainder being Fe. Oxygen blowing is used, and finally, quicklime is added. The target basicity R of the final slag is set to 3.0, and the steel is tapped at the end of the blowing process.

[0026] Specifically, the total SiO2 content of the electric arc furnace slag and molten iron is 1.87 tons, the initial CaO content in the electric arc furnace slag is 5.0 tons, the FeO content in the electric arc furnace slag is 21.4%, and the target FeO content of the final converter slag is set at 20%. Based on the formula, 0.66 tons of lime need to be added; the oxygen supply intensity is 2.8 Nm. 3 / (min·t); The final phosphorus content in the molten steel is 0.010%.

[0027] Example 2 This embodiment uses the method of the present invention to return the hot electric furnace slag to the converter for recycling.

[0028] Electric furnace capacity: 110 tons.

[0029] After the electric furnace smelting is completed, the electric furnace slag is discharged. The discharge of electric furnace slag is 10.9 tons. The main chemical components are analyzed by sampling. The main components are: P2O5 1.2%, CaO 45.2%, SiO2 11.3%, FeO 24.8%.

[0030] The discharged electric furnace slag is transported to the converter area using a special slag hopper with heat preservation function. The hot electric furnace slag is then poured into the converter by a crane at a converter temperature of 1400℃.

[0031] In the converter, 35 tons of scrap steel are first charged, followed by 125 tons of molten iron. The composition of the molten iron (wt%) is: C 4.2%, Si 0.35%, Mn 0.25%, P 0.15%, with the remainder being Fe. Oxygen blowing is used, and finally, quicklime is added. The target basicity R of the final slag is set to 3.5, and the steel is tapped at the end of the blowing process.

[0032] Specifically, the total SiO2 content of the electric arc furnace slag and molten iron is 2.08 tons, the initial CaO content in the electric arc furnace slag is 4.92 tons, the FeO content in the electric arc furnace slag is 24.8%, and the target FeO content of the final converter slag is set at 20%. Based on the formula, 2.5 tons of lime need to be added; the oxygen supply intensity is 3.0 Nm³. 3 / (min·t); The final phosphorus content in the molten steel is 0.014%.

[0033] Example 3 This embodiment uses the method of the present invention to return the hot electric furnace slag to the converter for recycling.

[0034] Electric furnace capacity: 110 tons.

[0035] After the electric furnace smelting is completed, the electric furnace slag is discharged. The electric furnace slag discharge is 9.6 tons. The main chemical components are analyzed by sampling. The main components are: P2O5 1.0%, CaO 42.5%, SiO2 11.8%, FeO 18.5%.

[0036] The discharged electric furnace slag is transported to the converter area using a special slag hopper with heat preservation function. The hot electric furnace slag is then poured into the converter by a crane at a converter temperature of 1420℃.

[0037] In the converter, 32 tons of scrap steel are first charged, followed by 128 tons of molten iron. The composition of the molten iron in the converter (wt%) is: C 4.5%, Si 0.34%, Mn 0.25%, P 0.14%, with the remainder being Fe. Oxygen blowing is used, and finally, quicklime is added. The target basicity R of the final slag is set to 4.0, and the steel is tapped at the end of the blowing process.

[0038] Specifically, the total SiO2 content of the electric arc furnace slag and molten iron is 1.98 tons, the initial CaO content in the electric arc furnace slag is 4.1 tons, the FeO content in the electric arc furnace slag is 18.5%, and the target FeO content of the final converter slag is set at 20%. Based on the formula, 4.05 tons of lime need to be added; the oxygen supply intensity is 3.0 Nm³. 3 / (min·t); The final phosphorus content in the molten steel is 0.008%.

[0039] Comparative Example This comparative example uses conventional converter smelting.

[0040] Converter volume: 150 tons.

[0041] First, 130t of molten iron is added, followed by 30t of scrap steel. The composition of the molten iron (wt%) is: C 4.3%, Si 0.37%, Mn 0.28%, P 0.16%, with the remainder being Fe.

[0042] Oxygen blowing was used for refining, with a final addition of 12 tons of lime (CaO 95%) and 1.5 tons of fluorite (CaF2 85%), achieving an oxygen blowing intensity of 3.2 Nm. 3 / (min·t), blown to the end point and tapped, the final phosphorus content of the molten steel is 0.018%.

[0043] From the above Examples 1-3 and Comparative Examples, it can be seen that: by utilizing the characteristics of hot electric furnace slag itself—high alkalinity, suitable TFe content, and low phosphorus content—this invention directly uses it as part of the slag-forming material during converter smelting, which greatly reduces the amount of active lime added compared to conventional converter smelting. Through the determination results of the final phosphorus content of molten steel, it can be seen that the final phosphorus content of molten steel of this invention is lower than that of molten steel of conventional converter smelting, thus verifying that this invention effectively improves the phosphorus distribution capacity and dephosphorization efficiency of slag.

[0044] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings and specific examples. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A method for efficient dephosphorization of converter slag using electric arc furnace slag, characterized in that, Includes the following steps: After the electric furnace smelting is completed, the slag is discharged, and samples are taken to analyze its main chemical components and calculate the amount of quicklime that needs to be added. A special slag bin with heat preservation function is used to transport the discharged electric furnace slag to the converter area, and a crane is used to pour the hot electric furnace slag into the converter; First, scrap steel is added to the converter, then molten iron is added, oxygen is supplied for blowing, and finally, quicklime is added to adjust the slag basicity to between 2.5 and 4.

5. The steel is then blown to the end point and tapped.

2. The method for efficient dephosphorization of converter slag using electric furnace slag according to claim 1, characterized in that: The method for calculating the amount of quicklime that needs to be added is as follows: ， In the formula, W CaO To supplement the amount of activated lime; R 目标 The target binary basicity of the final slag from converter smelting; SiO 2总 Total SiO2 content, including SiO2 from electric furnace slag and molten iron; CaO 初始 This refers to the initial CaO content, i.e., the CaO content in the electric furnace slag; CaO 石灰 This refers to the effective CaO content in lime. p For lime utilization rate, 0 < p <1; FeO 实际 FeO content in electric furnace slag; FeO 目标 The target FeO content is the final slag content in converter smelting.

3. The method for efficient dephosphorization of converter slag using electric furnace slag according to claim 2, characterized in that: The temperature of the hot electric furnace slag poured into the converter is ≥1300℃.

4. The method for efficient dephosphorization of converter slag using electric furnace slag according to claim 3, characterized in that: In the oxygen-supply blowing process, the oxygen supply intensity is 2.5-3.0 Nm. 3 / (min·t).

5. A method for efficient dephosphorization of converter slag using electric furnace slag according to claim 3, characterized in that: The chemical composition of the molten iron, by weight, is required to be: C 4-5%, Si 0.2-0.4%, Mn 0.2-0.3%, P 0.1-0.2%, with the remainder being Fe.

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