A method for protecting a converter by using steel plant waste resources to smelt low-carbon steel

Abstract

This invention discloses a method for using waste resources from steel plants for slag splashing protection in converters after low-carbon steel smelting. This method improves the converter slag splashing protection process under low-carbon steel smelting conditions by controlling the amount of final slag, adjusting the final slag system, and optimizing the slag splashing process parameters. This enhances the effectiveness of slag splashing protection under low-carbon steel smelting conditions and provides a reference for the maintenance of converter linings after low-carbon steel smelting. This invention uses blast furnace dust, waste refractory materials from the tundish, and converter tail slag as slag conditioning materials, enabling the efficient recycling and utilization of these waste resources.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel smelting technology, specifically relating to a method for using waste resources from steel plants to protect the furnace after slag splashing during converter smelting of low-carbon steel. Background Technology

[0002] The converter slag splashing protection technology mainly involves using high-pressure nitrogen gas to splash the remaining high-melting-point slag after converter smelting onto the converter lining surface, thereby reducing the consumption of original refractory materials. When the carbon content at the end of converter smelting is ≤0.05wt%, the oxygen content of the molten steel rapidly increases from ≤500ppm to 600-900ppm, while the FeO content of the final converter slag increases from 14.0-17.0wt% to 19.0-21.0wt%, the slag basicity (R=CaO wt% / SiO2wt%) decreases from 3.1-3.4 to 2.6-2.8, and the MgO content in the slag decreases from 10.0-13.0 wt% to 8.0-9.0wt%. The increase in the content of low-melting-point substance FeO and the decrease in the content of high-melting-point substances CaO and MgO in the slag result in the final converter slag exhibiting reduced viscosity, increased fluidity, easy slag layer detachment after splashing, and a thin slag layer, making it difficult to effectively isolate the molten steel and protect the original furnace lining. Therefore, when the carbon content at the end of converter smelting is low, the final slag and slag splashing processes must be adjusted to protect the converter lining. Summary of the Invention

[0003] The purpose of this invention is to provide a method for using waste resources from steel plants to protect the furnace after slag splashing during converter smelting of low-carbon steel.

[0004] The objective of this invention is achieved by providing a method for using scrap resources from steel plants to protect the furnace after slag splashing during converter smelting of low-carbon steel, which is implemented through the following steps:

[0005] 1) Converter slag removal: When the endpoint C > 0.05%, the slag removal time is 25-40 seconds; when the endpoint C ≤ 0.05%, the slag removal time is 35-50 seconds.

[0006] 2) Final slag adjustment: After the converter has finished dumping the initial slag, for heats with a final slag concentration (C) > 0.05%, the converter is tilted directly to the tapping position for tapping. After tapping, the remaining slag in the furnace is directly splashed to protect the furnace.

[0007] For heats with a final concentration C ≤ 0.05%, when the converter is tilted to the vertical position, add 150-250 kg / heat of blast furnace dust and 80-150 kg / heat of scrap refractory material from the hopper, then tilt the converter to the tapping position for tapping. After tapping, tilt the converter to the vertical position, add 200-400 kg / heat of tail slag, tilt the converter forward 60-75°, then tilt it backward 60-75°, and finally tilt the converter to the vertical position to complete the slag adjustment.

[0008] 3) Nitrogen splashing furnace protection operation: Convert oxygen in the oxygen lance to nitrogen, and adjust the nitrogen pressure to 1.10-1.30 MPa and the flow rate to 515-530 Nm³. 3 / min, nitrogen supply time: 150-240s; when the endpoint C>0.05%, the oxygen lance position is controlled in high-low mode, and when the endpoint C≤0.05%, the oxygen lance position is controlled in low-high-low mode; after slag splashing is completed, the converter is tilted to a horizontal position to observe the slag splashing situation and take samples for analysis.

[0009] This invention utilizes waste resources from steel plants, such as blast furnace dust, converter tail slag, and waste refractory materials from intermediate ladles, as slag conditioning materials for the final slag of the converter. It also optimizes the process control of slag splashing and furnace protection in the converter to improve the slag splashing and furnace protection effect when the carbon content at the end of the converter is low.

[0010] The beneficial effects of this invention are as follows:

[0011] 1) This invention improves the converter slag splashing furnace protection process under low carbon steel smelting conditions by controlling the amount of converter final slag, adjusting the converter final slag system, and optimizing the slag splashing process parameters. It improves the effect of slag splashing furnace protection under low carbon steel smelting conditions and provides feasible measures for the maintenance of converter furnace lining after low carbon steel smelting.

[0012] 2) This invention uses blast furnace dust, waste refractory materials from tundishes, and converter steel tailings as slag conditioning materials, enabling these waste resources to be efficiently recycled and utilized.

[0013] 3) The method of the present invention is simple, reliable, and easy to promote and apply. Detailed Implementation

[0014] The present invention will be further described below with reference to embodiments, but this is not intended to limit the present invention in any way. Any modifications or substitutions made based on the teachings of the present invention shall fall within the protection scope of the present invention.

[0015] This invention discloses a method for using waste resources from steel plants to protect the furnace after slag splashing during converter smelting of low-carbon steel, which is implemented through the following steps:

[0016] 1) Converter slag removal: When the endpoint C > 0.05%, the slag removal time is 25-40 seconds; when the endpoint C ≤ 0.05%, the slag removal time is 35-50 seconds.

[0017] 2) Final slag adjustment: After the converter has finished dumping the initial slag, for heats with a final slag concentration (C) > 0.05%, the converter is tilted directly to the tapping position for tapping. After tapping, the remaining slag in the furnace is directly splashed to protect the furnace.

[0018] For heats with a final concentration C ≤ 0.05%, when the converter is tilted to the vertical position, add 150-250 kg / heat of blast furnace dust and 80-150 kg / heat of scrap refractory material from the hopper, then tilt the converter to the tapping position for tapping. After tapping, tilt the converter to the vertical position, add 200-400 kg / heat of tail slag, tilt the converter forward 60-75°, then tilt it backward 60-75°, and finally tilt the converter to the vertical position to complete the slag adjustment.

[0019] 3) Nitrogen splashing furnace protection operation: Convert oxygen in the oxygen lance to nitrogen, and adjust the nitrogen pressure to 1.10-1.30 MPa and the flow rate to 515-530 Nm³. 3 / min, nitrogen supply time: 150-240s; when the endpoint C>0.05%, the oxygen lance position is controlled in high-low mode, and when the endpoint C≤0.05%, the oxygen lance position is controlled in low-high-low mode; after slag splashing is completed, the converter is tilted to a horizontal position to observe the slag splashing situation and take samples for analysis.

[0020] The chemical composition of the blast furnace dust, by weight percentage, is as follows: C 13.4-15.7%, FeO 14.3-17.2%, Zn 1.2-3.1%, MgO 2.0-3.6%, CaO 2.7-7.5%, SiO2 3.7-6.3%, TiO2 0.8-3.4%, Pb 0.6-3.5%, Na2O 0.4-1.8%, K2O 0.6-2.1%, Al2O3 1.2-2.8%, with the remainder being unavoidable inclusions; the particle size is 1-3 mm.

[0021] The chemical composition of the waste refractory material in the continuous casting tundish is as follows (weight percentage): MgO 70.0%-79.4%, SiO2 5.3%-8.5%, Al2O3 5.2%-8.4%, with the remainder being unavoidable inclusions; the particle size is 1-3 mm.

[0022] The chemical composition of the steel tailings by weight percentage is: FeO 17.4-22.3%, MgO 7.5-9.2%, SiO2 10.6-14.7%, CaO 32.3-39.8%, with the remainder being unavoidable inclusions; the slag basicity R is 2.71-3.75, and the particle size is 1-3 mm.

[0023] Example 1

[0024] A method for using scrap resources from steel plants to protect the furnace by splashing slag after smelting low-carbon steel in a converter is implemented according to the following steps:

[0025] 1. Before tapping, the auxiliary lance measures the converter blowing endpoint C to be 0.04%. After tilting the converter to the position of dumping the slag, the converter is left to stand for 42 seconds. During this process, the slag flows into the slag collection jar.

[0026] The chemical composition of the slag by weight percentage is: FeO 20.2%, MgO 8.3%, SiO2 13.4%, CaO 36.8%, with the remainder being unavoidable inclusions; the slag basicity R is 2.75.

[0027] 2. After completing step 1, tilt the converter to the vertical position, add 192 kg of blast furnace dust and 122 kg of scrap refractory material from the hopper, and then tilt the converter to the tapping position for tapping. After tapping, tilt the converter to the vertical position and add 275 kg of steel tail slag from the hopper. Tilt the converter forward 68° - tilt to the vertical position 0° - tilt the converter backward 68° - tilt to the vertical position 0°.

[0028] The chemical composition (by weight percentage) of the blast furnace dust is C 14.6%, FeO 16.8%, Zn 2.5%, MgO 2.8%, CaO 6.2%, SiO2 5.7%, TiO2 2.2%, Pb 1.1%, Na2O 1.2%, K2O 1.1%, Al2O3 2.1%, with the remainder being unavoidable inclusions; the chemical composition (by weight percentage) of the scrap refractory material from the continuous casting tundish is MgO 76.2%, SiO2 7.7%, Al2O3 7.3%, with the remainder being unavoidable inclusions; the chemical composition (by weight percentage) of the steel tailings is FeO 20.2%, MgO 8.3%, SiO2 13.4%, CaO 36.8%, with the remainder being unavoidable inclusions; the slag basicity R is 2.75.

[0029] 3. After completing step 2, begin the slag splashing and furnace protection operation: Convert the oxygen in the oxygen lance to nitrogen, and adjust the nitrogen pressure to 1.12 MPa and the flow rate to 518 Nm³ / min. After opening the nitrogen supply valve, first place the oxygen lance at its lowest position of 0.9m and supply gas for 47 seconds; then quickly raise the oxygen lance position to 2m and supply gas for 109 seconds; finally, gradually lower the oxygen lance from the 2m position to the lowest control position of 0.9m, with the gas supply taking 212 seconds; shut off the nitrogen supply, raise the oxygen lance to the waiting position, and the slag splashing is complete. After tilting the converter to a horizontal position, take a sample of the final slag for testing. The final slag test results are: FeO 15.3%, CaO 39.7%, SiO₂ 12.6%, MgO 10.8%, and slag basicity R is 3.15. After slag adjustment and splashing, the FeO content in the final converter slag decreased from 20.2% to 15.3%, while the MgO content increased from 8.3% to 10.8%, and the slag basicity R increased from 2.75 to 3.15. This indicates that changing the converter slag composition after low-carbon steel smelting improved the slag splashing effect and met the requirements for converter slag splashing and furnace protection.

[0030] Example 2

[0031] 1. The endpoint C of the converter blowing test was determined to be 0.03% using the auxiliary lance. After tilting the converter to the position for pouring the slag, the converter was left to stand for 37 seconds, during which the slag flowed into the slag collection hopper. The chemical composition of the slag by weight percentage was FeO 21.3%, MgO 7.9%, SiO 212.6%, CaO 36.3%, with the remainder being unavoidable inclusions; the slag basicity R was 2.88.

[0032] 2. After completing step 1, tilt the converter to the vertical position, add 228 kg of blast furnace dust and 137 kg of scrap refractory material from the hopper, and then tilt the converter to the tapping position for tapping. After tapping, tilt the converter to the vertical position and add 352 kg of steel tail slag from the hopper. Tilt the converter forward 73° - tilt to the vertical position 0° - tilt the converter backward 73° - tilt to the vertical position 0°.

[0033] The chemical composition of the blast furnace dust by weight percentage is C 14.6%, FeO 16.8%, Zn 2.5%, MgO 2.8%, CaO 6.2%, SiO2 5.7%, TiO2 2.2%, Pb 1.1%, Na2O 1.2%, K2O 1.1%, Al2O3 2.1%, with the remainder being unavoidable inclusions;

[0034] The chemical composition (by weight percentage) of the scrap refractory material from the continuous casting tundish is MgO 76.2%, SiO2 7.7%, Al2O 37.3%, with the remainder being unavoidable inclusions; the chemical composition (by weight percentage) of the steel tailings is FeO 20.2%, MgO 8.3%, SiO2 13.4%, CaO 36.8%, with a slag basicity R of 2.75, and the remainder being unavoidable inclusions.

[0035] 3. After completing step 2, begin the slag splashing furnace protection operation: convert the oxygen in the oxygen lance to nitrogen, and adjust the nitrogen pressure to 1.20 MPa and the flow rate to 523 Nm³. 3 / min. After opening the nitrogen supply valve, first place the oxygen lance at the lowest position of 0.9m and supply gas for 55s; then quickly raise the oxygen lance to 2m and supply gas for 147s; finally, gradually lower the oxygen lance from the 2m position to the lowest control position of 0.9m, with the gas supply taking 223s; shut off the nitrogen, raise the oxygen lance to the waiting position, and slag splashing is complete. After tilting the converter to the horizontal position, take a sample of the final slag for testing. The final slag test results are: FeO 15.1%, CaO 38.6%, SiO2 11.7%, MgO 11.3%, and slag basicity R is 3.30. After slag adjustment and splashing, the FeO content in the final converter slag decreased from 21.3% to 15.1%, while the MgO content increased from 7.9% to 11.3%, and the slag basicity R increased from 2.88 to 3.30. This indicates that the composition of the converter slag after low-carbon steel smelting was altered, improving the slag splashing effect and meeting the requirements for converter slag splashing for furnace protection.

[0036] Example 3

[0037] 1. Before tapping steel, the auxiliary lance at a certain plant measured the final slag concentration (C) of the converter blowing process to be 0.07%. After tilting the converter to the position for dumping the slag, the converter was left to stand for 28 seconds, during which time the slag flowed into the slag collection hopper. The chemical composition of the slag, by weight percentage, was FeO 14.7%, MgO 11.7%, SiO2 12.5%, CaO 42.1%, with the remainder being unavoidable inclusions; the slag basicity (R) was 3.36.

[0038] 2. After completing step 1, tilt the converter to the tapping position to tap the steel;

[0039] 3. After tapping, the remaining slag in the furnace is directly splashed for furnace protection: the oxygen in the oxygen lance is converted to nitrogen, and the nitrogen pressure is adjusted to 1.24 MPa and the flow rate to 528 Nm³. 3 / min. After opening the nitrogen supply valve, the oxygen lance is first placed at the highest position of 2.0m, and then gradually lowered from 2.0m to the lowest control position of 0.9m, with nitrogen supply lasting 212s. The nitrogen supply is then shut off, and the oxygen lance is raised to the waiting position, completing the slag splashing. After tilting the converter to a horizontal position, a final slag sample is taken for testing. The final slag test results are: FeO 14.5%, MgO 11.8%, SiO2 12.5%, CaO 42.1%, with the remainder being unavoidable inclusions; the slag basicity R is 3.36, meeting the requirements for converter slag splashing and furnace protection. In this embodiment, the converter endpoint C is 0.07%, the final slag composition is FeO 14.7%, MgO 11.7%, SiO2 12.5%, CaO 42.1%, with the remainder being unavoidable inclusions, and the slag basicity R is 3.36. The final slag composition indicators already meet the requirements for slag splashing and furnace protection, and there is no need to adjust the final slag using waste resources.

Claims

1. A method for using scrap resources from steel plants to protect the furnace after slag splashing during converter smelting of low-carbon steel, characterized in that, Follow these steps to achieve the following: 1) Converter slag removal: When the endpoint C > 0.05%, the slag removal time is 25-40 seconds; when the endpoint C ≤ 0.05%, the slag removal time is 35-50 seconds. 2) Final slag adjustment: After the converter has finished dumping the initial slag, for heats with a final slag concentration (C) > 0.05%, the converter is tilted directly to the tapping position for tapping. After tapping, the remaining slag in the furnace is directly splashed to protect the furnace. When the converter is tilted to the vertical position for heats with a final C ≤ 0.05%, add 150~250kg / heat of blast furnace dust and 80~150kg / heat of scrap refractory material from the hopper before tilting the converter to the tapping position for tapping. After tapping, the converter is tilted to a vertical position and 200-400 kg / furnace of tail slag is added. Then the converter is tilted forward 60-75°, then tilted backward 60-75°, and finally tilted to a vertical position to complete the slag adjustment. 3) Nitrogen splashing furnace protection operation: Convert oxygen in the oxygen lance to nitrogen, and adjust the nitrogen pressure to 1.10~1.30MPa and the flow rate to 515~530Nm. 3 / min, nitrogen supply time: 150~240s; when the endpoint C>0.05%, the oxygen lance position is controlled in high-low mode, and when the endpoint C≤0.05%, the oxygen lance position is controlled in low-high-low mode; after slag splashing is completed, the converter is tilted to a horizontal position to observe the slag splashing situation and take samples for analysis.

2. The method for using steel plant waste resources for slag splashing and furnace protection after converter smelting of low-carbon steel, as described in claim 1, is characterized in that... The chemical composition (by weight percentage) of the blast furnace dust is as follows: C 13.4~15.7%, FeO 14.3~17.2%, Zn 1.2~3.1%, MgO 2.0~3.6%, CaO 2.7~7.5%, SiO2 3.7~6.3%, TiO2 0.8~3.4%, Pb 0.6~3.5%, Na2O 0.4~1.8%, K2O 0.6~2.1%, Al2O3 1.2~2.8%, with the remainder being unavoidable inclusions; the particle size is 1~3 mm.

3. The method for using steel plant waste resources for slag splashing and furnace protection after converter smelting of low-carbon steel according to claim 1, characterized in that, The chemical composition by weight percentage of the waste intermediate packaging refractory material is as follows: MgO 70.0%~79.4%, SiO2 5.3%~8.5%, Al2O3 5.2%~8.4%, with the remainder being unavoidable inclusions; the particle size is 1~3mm.

4. The method for using steel plant waste resources for slag splashing and furnace protection after converter smelting of low-carbon steel according to claim 1, characterized in that, The chemical composition of the steel tailings by weight percentage is: FeO 17.4~22.3%, MgO 7.5~9.2%, SiO2 10.6~14.7%, CaO 32.3~39.8%, with the remainder being unavoidable inclusions; the slag basicity R is 2.71~3.75, and the particle size is 1~3mm.