Method for enhancing stirring intensity in vanadium extraction

Abstract

This invention relates to a method for enhancing the stirring intensity during vanadium extraction, belonging to the field of steel pretreatment. The method includes the following three steps: first, vanadium-containing molten iron is added to a converter; then, a top-and-bottom blowing process is used for smelting; coolant is added according to the composition and temperature at the smelting endpoint; finally, semi-steel is removed from the lance at the smelting endpoint. The top-blown gas is an oxygen-nitrogen mixture, and the total flow rate of the oxygen-nitrogen mixture is 31,000~35,000 Nm³. 3 / h; the oxygen consumption per ton of iron, the top blowing lance position, and the nitrogen consumption per ton of iron are controlled in segments according to the blowing period; the bottom blowing gas is nitrogen, and the nitrogen supply intensity is controlled in segments according to the blowing period. This invention significantly enhances the stirring intensity of the molten pool without significantly increasing the temperature rise rate through the synergistic effect of the high-flow-rate oxygen-nitrogen mixed gas from the top and the variable-flow-rate nitrogen from the bottom, thereby shortening the mixing time and enhancing the slag-metal reaction, further increasing the vanadium oxidation amount and further reducing the TFe content in the vanadium slag.

Description

Technical Field

[0001] This invention belongs to the field of steel pretreatment, and specifically relates to a method for enhancing the stirring intensity of vanadium extraction. Background Technology

[0002] Converter vanadium extraction is one of the main methods for extracting vanadium from vanadium-containing molten iron. Its purpose is to oxidize vanadium in the molten iron as much as possible while minimizing carbon oxidation, thereby improving vanadium recovery rate and the quality of semi-steel. Current converter vanadium extraction methods mostly employ a combination of top-blowing oxygen and constant bottom-blowing flow rates. This process suffers from problems such as insufficient vanadium oxidation and high total iron (TFe) content in vanadium slag.

[0003] To address the aforementioned issues, several improvements have been proposed in existing technologies. For example, Chinese patent "A Method for Vanadium Extraction Using Top-blown Oxygen-Nitrogen Mixed Gas" (application number: 202510537901.2) discloses a converter vanadium extraction method using a mixed oxygen-nitrogen gas, which achieves "vanadium removal and carbon retention" by mixing nitrogen into the top oxygen. Furthermore, Chinese patent "A Method for Reducing Residual Vanadium at the End of Vanadium Extraction in a Converter" (application number: 202310866746.X) proposes improvements from a process flow perspective, employing a multi-furnace combined production mode. This involves adding vanadium-extraction coolant in stages during non-slag-discharging furnace cycles to control the molten pool temperature, thereby reducing the residual vanadium content at the end of vanadium extraction. At the equipment level, Chinese patent "Oxygen Lance Nozzle and Vanadium Extraction Converter for a 120-ton Vanadium Extraction Converter" (application number: 202423105717.0) optimizes the structure of the oxygen lance nozzle, designing the nozzle as a Venturi tube shape and enlarging the throat and outlet diameters. This aims to shorten smelting time and improve production efficiency by increasing oxygen flow. Regarding the bottom blowing process, the Chinese patent "A method for vanadium extraction in a top-bottom combined blowing converter" (application number: 201711223813.7) uses carbon monoxide for bottom blowing during the blowing stage. By filling the material space with carbon monoxide, the oxidation reaction of carbon is inhibited, thereby reducing heat release and coolant consumption.

[0004] However, the above methods mostly focus on temperature control in a single stage, modification of static nozzle size, or direct replacement of bottom blowing gas type. There is still room for improvement in dynamic control of gas flow under complex blowing conditions and in-depth synergistic optimization of top and bottom blowing modes. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention optimizes the gas flow rate, gas type, and oxygen and nitrogen supply intensity during the blowing process, and proposes a method to enhance the stirring intensity during vanadium extraction.

[0006] The blowing period of this invention refers to the entire blowing process from the start of blowing to the end of vanadium extraction; the top blowing lance position refers to the vertical distance between the end face of the oxygen lance nozzle and the surface of the molten pool before the start of blowing.

[0007] The specific solution of the present invention is as follows: A method for enhancing the stirring intensity of vanadium extraction includes the following three steps: first, vanadium-containing molten iron is added to a converter; then, a top-and-bottom blowing process is used for smelting; coolant is added according to the composition and target temperature at the smelting endpoint; finally, semi-steel is extracted from the lance at the smelting endpoint. The method is characterized in that the top-blown gas is an oxygen-nitrogen mixture, and the total flow rate of the oxygen-nitrogen mixture is 31000~35000 Nm³. 3 / h; the oxygen consumption per ton of iron, the top blowing lance position, and the nitrogen consumption per ton of iron are controlled in segments according to the blowing period; the bottom blowing process includes: the bottom blowing gas is nitrogen, and the nitrogen supply intensity is controlled in segments according to the blowing period.

[0008] This invention utilizes the synergistic effect of top-blown high-flow-rate oxygen-nitrogen mixed gas and bottom-blown variable-flow-rate nitrogen gas. Taking advantage of nitrogen's non-participation in the violently exothermic reaction, it increases the kinetic energy input to the molten pool without significantly increasing the temperature rise rate. High-intensity oxygen and nitrogen supply enhances molten pool stirring, significantly increasing the stirring rate, thereby shortening the mixing time and enhancing the slag-metal reaction. This further increases vanadium oxidation and reduces the TFe content in the vanadium slag. Ultimately, while achieving deep vanadium removal, it achieves comprehensive optimization of efficient carbon retention, high vanadium slag grade, and low slag-iron loss, resulting in a dual improvement in vanadium extraction efficiency and economic benefits.

[0009] Preferably, the oxygen consumption per ton of iron is controlled in segments according to the blowing period, including: 0~0.5min: 1.9~2.1 Nm³. 3 / (t) min), 0.5~2 min: 1.8~1.9 Nm 3 / (t) (min), 2~4min: 1.7~1.8Nm 3 / (t) (min), 4min ~ blowing endpoint: 1.6~1.7Nm 3 / (t) min).

[0010] More preferably, the oxygen consumption per ton of iron is controlled in stages according to the blowing period, including: 0~0.5min: 1.95~2.05Nm 3 / (t) min), 0.5~2min: 1.85~1.9Nm 3 / (t) (min), 2~4min: 1.75~1.8Nm 3 / (t) (min), 4min ~ blowing endpoint: 1.65~1.7Nm 3 / (t) min).

[0011] Preferably, the nitrogen consumption per ton of iron is controlled in stages according to the blowing period, including: 0~0.5min: 0.4~0.5Nm 3 / (t) min), 0.5~2 min: 0.5~0.6 Nm 3 / (t) (min), 2~4min: 0.7~0.9Nm 3 / (t) (min), 4min ~ blowing endpoint: 0.9~1.1Nm 3 / (t) min).

[0012] More preferably, the nitrogen consumption per ton of iron is controlled in stages according to the blowing period, including: 0~0.5min: 0.45~0.5Nm 3 / (t) min), 0.5~2min: 0.55~0.6Nm 3 / (t) (min), 2~4min: 0.8~0.9Nm 3 / (t) (min), 4min ~ blowing endpoint: 1.0~1.1Nm 3 / (t) min).

[0013] Preferably, the top blowing lance position is controlled in segments according to the blowing period, including: 0~2min: the top blowing lance position is 1.65~1.8mm from the molten pool surface; 2~4min: the top blowing lance position is 1.9~2.2m from the molten pool surface; 4min~blowing end point: the top blowing lance position is 1.7~1.9m from the molten pool surface.

[0014] More preferably, the top blowing lance position is controlled in segments according to the blowing period, including: 0~2min: the top blowing lance position is 1.7~1.8m from the molten pool surface; 2~4min: the top blowing lance position is 1.9~2.0m from the molten pool surface; 4min~blowing end point: the top blowing lance position is 1.7~1.8m from the molten pool surface.

[0015] Preferably, the nitrogen supply intensity is controlled in stages according to the blowing period, including: 0~2min: nitrogen supply intensity of 0.083~0.1Nm. 3 / (t) (min), 2min ~ blowing endpoint: nitrogen supply intensity is 0.079~0.085 Nm 3 / (t) min).

[0016] More preferably, the blowing endpoint is 5-12 minutes.

[0017] Preferably, the semi-steel is removed from the lance at the end of the blowing process, wherein when the blowing process reaches the end, the composition of the semi-steel satisfies the following conditions: carbon (C) content ≥ 3.0 wt%, vanadium (V) content ≤ 0.030 wt%.

[0018] Preferably, the target temperature at the end of the blowing process is 1360~1420℃.

[0019] Preferably, the main components of vanadium-containing molten iron include: C content of 3.5 to 4.5 wt%, silicon (Si) content of 0.07 to 0.3 wt%, V content of 0.18 to 0.35 wt%, and the remainder being iron and its unavoidable impurities.

[0020] Preferably, the coolant is one or both of cold-pressed blocks or cast iron blocks.

[0021] More preferably, the cold-pressed briquettes are made from vanadium extraction dust, ironmaking dust, and iron oxide scale, and the TFe content of the cold-pressed briquettes is ≥50wt%.

[0022] More preferably, the dosage of cold-pressed briquettes is 20-70 kg per ton of vanadium-containing molten iron.

[0023] More preferably, the dosage of pig iron blocks added is 30-95 kg per ton of vanadium-containing molten iron.

[0024] The beneficial effects of this invention are as follows: (1) Significantly reduced vanadium content in semi-steel and iron loss in final slag: By enhancing the stirring intensity of the top-blown jet through oxygen-nitrogen mixed blowing and optimizing the overall stirring dynamics of the molten pool through stepped variable-flow bottom blowing, the selective oxidation of vanadium was significantly promoted, while the excessive oxidation of iron was effectively suppressed. The results of the examples and comparative examples show that the method of the present invention can reduce the vanadium content in semi-steel to below 0.028 wt% and the TFe content in final slag to below 28 wt%.

[0025] (2) Improve the quality of vanadium slag: The V2O5 content in the vanadium slag obtained by the method of the present invention is significantly increased, the impurity content is reduced, and the grade and added value of vanadium slag are improved.

[0026] (3) Stable process and good economy: The stepped bottom blowing flow mode (high in the early stage and moderately reduced in the middle and late stages) ensures the vanadium extraction effect, while being more energy-efficient than the full-process high flow mode, and the permeable bricks have a longer lifespan, which is conducive to maintaining the stability of the process.

[0027] (4) While improving the vanadium oxidation rate, the present invention can also effectively reduce the carbon oxidation rate. By adjusting the gas composition in stages, the combination of vanadium and oxygen is prioritized in the key stage of enhancing vanadium oxidation, thus avoiding excessive oxidation of carbon. Detailed Implementation

[0028] The specific embodiments listed in this invention are merely examples, and the invention is not limited to the specific embodiments described below. For those skilled in the art, any equivalent modifications and substitutions to the embodiments described below are also within the scope of this invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of this invention should be covered within its scope. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. All reagents or instruments whose manufacturers are not specified are commercially available conventional products. To better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In other embodiments, methods, means, equipment, and steps well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. Unless otherwise specified, all units used in this specification are International Standard Units (SI), and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors unavoidable in industrial production.

[0030] Unless otherwise specified, the main components of the cold-pressed blocks in the examples and comparative examples are shown in Table 1, with the balance being loss on ignition or impurities.

[0031] Table 1 Main components of cold-pressed blocks

[0032] Example 1 This embodiment provides a method for enhancing the stirring intensity during vanadium extraction, taking a 200t vanadium extraction converter in a steel plant as the implementation object, including the following steps: S1. 200t of vanadium-containing molten iron with a C content of 4.3wt%, a Si content of 0.167wt%, and a V content of 0.336wt% (the remainder being iron and impurities) was added to the converter, and the temperature of the vanadium-containing molten iron entering the furnace was measured to be 1320℃.

[0033] S2. A top-and-bottom combined blowing process is used to smelt vanadium-containing molten iron, wherein... Top-blowing technology includes: The top-blown gas is an oxygen-nitrogen mixture, with a total flow rate of 35,000 Nm³. 3 / h; The oxygen consumption per ton of iron is controlled in stages according to the blowing period, of which: 0~0.5min: 2.0Nm³ 3 / (t) min), 0.5~2 min: 1.85 Nm 3 / (t) (min), 2~4min: 1.75Nm 3 / (t) min), 4~6.5 min: 1.65 Nm 3 / (t) min); The position of the top blowing lance is controlled in segments according to the blowing time period. Specifically, from 0 to 2 min: the top blowing lance is 1.7 m away from the molten pool surface; from 2 to 4 min: the top blowing lance is 2.0 m away from the molten pool surface; and from 4 to 6.5 min: the top blowing lance is 1.7 m away from the molten pool surface. Nitrogen consumption per ton of iron is controlled in stages according to the blowing period, of which: 0~0.5min: 0.5Nm 3 / (t) min), 0.5~2 min: 0.6 Nm 3 / (t) min), 2~4 min: 0.8 Nm 3 / (t) min), 4~6.5 min: 1.0 Nm 3 / (t) min).

[0034] Bottom blowing technology includes: The bottom-blown gas is nitrogen; The nitrogen supply intensity is controlled in stages according to the blowing period. Specifically, the nitrogen supply intensity is 0.085 Nm for the first 0-2 minutes. 3 / (t) (min). 2~6.5min: nitrogen supply intensity is 0.080 Nm 3 / (t) min).

[0035] Meanwhile, 4815 kg of cold-pressed briquettes and 13.4 t of pig iron blocks are added during the blowing process to keep the temperature of the vanadium-containing molten iron at 1350~1360℃.

[0036] S3, 6.5 min later (blowing ends), the lance is lifted out and the semi-steel is taken out. The temperature of the semi-steel at the end of the blowing process is measured to be 1366℃. In the semi-steel composition, the C content is 3.3wt%, the V content is 0.026wt%, and the mass fraction is not higher than 0.028wt%. In the vanadium slag composition, the V2O5 content is 18.40wt%, the TFe content is 28wt%, and the mass fraction is not higher than 30.0wt%.

[0037] Comparative Example 1 This comparative example provides a method for vanadium extraction using a top-blown oxygen converter, taking a 200t vanadium extraction converter in a steel plant as the implementation example, including the following steps: S1. 200t of vanadium-containing molten iron with a C content of 4.1wt%, a V content of 0.329wt%, and a Si content of 0.155wt% (the remainder being iron and impurities) was added to the converter, and the temperature of the vanadium-containing molten iron entering the furnace was measured to be 1320℃.

[0038] S2. A top-and-bottom blowing process is used to smelt vanadium-containing molten iron, wherein, Top-blowing technology includes: The top-blown gas is oxygen, and the total oxygen flow rate is 25000 Nm³. 3 / h; The oxygen consumption per ton of iron is controlled in stages according to the blowing period, of which: 0~0.5min: 1.9Nm 3 / (t) min), 0.5~6 min: 2.2 Nm 3 / (t) min); The position of the top blowing lance is controlled in segments according to the blowing time period. Specifically, from 0 to 2 minutes, the top blowing lance is 1.7m away from the molten pool surface; from 2 to 4 minutes, the top blowing lance is 2.0m away from the molten pool surface; and from 4 to 6 minutes, the top blowing lance is 1.7m away from the molten pool surface.

[0039] The bottom-blowing process includes: the bottom-blowing gas is nitrogen, and the nitrogen supply intensity is 0.075 Nm. 3 / (t) min).

[0040] Meanwhile, 5326 kg of cold-pressed briquettes and 12.1 t of pig iron blocks are added during the blowing process to keep the temperature of the vanadium-containing molten iron at 1360~1380℃.

[0041] S3, End of blowing (6 min), remove the lance and the semi-steel is measured to be 1378℃ at the end of blowing; the semi-steel composition is C content of 3.2wt% and V content of 0.033wt%; the vanadium slag composition is V2O5 content of 16.35wt% and TFe content of 35.10wt%.

[0042] Comparative Example 2 This comparative example provides a method for vanadium extraction in a converter using top-blown oxygen-nitrogen mixed gas and bottom-blown nitrogen gas. The difference between this method and the previous example lies in the bottom-blowing process. Taking a 200t vanadium extraction converter in a steel plant as the implementation example, the method includes the following steps: S1, same as in Example 1, omitted here.

[0043] S2. A top-and-bottom combined blowing process is used to smelt vanadium-containing molten iron, wherein... The top-blowing process is the same as in Example 1, and is omitted here.

[0044] Bottom blowing technology includes: The bottom-blown gas is nitrogen; The nitrogen supply intensity is controlled in stages according to the blowing period. Specifically, from 0 to 2 minutes, the nitrogen supply intensity is 0.075 Nm. 3 / (t) (min), 2~6.5min: nitrogen supply intensity is 0.080 Nm 3 / (t) min).

[0045] Meanwhile, 5012 kg of cold-pressed briquettes and 13.6 t of pig iron blocks are added during the blowing process to keep the temperature of the vanadium-containing molten iron at 1360~1370℃.

[0046] S3, 6.5 min later (blowing ends), the lance is lifted out and the semi-steel is taken out. The temperature of the semi-steel at the end of the blowing process is measured to be 1370℃. The semi-steel composition is C content of 3.5wt% and V content of 0.0030wt%. The vanadium slag composition is V2O5 content of 17.1wt% and TFe content of 31.1wt%.

[0047] Comparative Example 3 This comparative example provides a method for vanadium extraction in a converter using top-blown oxygen-nitrogen mixed gas and bottom-blown nitrogen gas. The difference between this method and the previous example lies in the top-blowing process. Taking a 200t vanadium extraction converter in a steel plant as the implementation example, the method includes the following steps: S1, same as in Example 1, omitted here.

[0048] S2. A top-and-bottom combined blowing process is used to smelt vanadium-containing molten iron, wherein... Top-blowing technology includes: The top-blown gas is an oxygen-nitrogen mixture, with a total flow rate of 35,000 Nm³. 3 / h; The oxygen consumption per ton of steel is controlled in segments according to the blowing period, of which: 0~0.5min: 1.65Nm 3 / (t) min), 0.5~2 min: 1.75 Nm 3 / (t) (min), 2~4min: 1.85Nm 3 / (t) min), 4~6.5 min: 2.0 Nm 3 / (t) min); The position of the top blowing lance is controlled in segments according to the blowing time period. Specifically, from 0 to 2 min, the top blowing lance is 1.7 m away from the molten pool surface; from 2 to 4 min, the top blowing lance is 2.0 m away from the molten pool surface; and from 4 to 6.5 min, the top blowing lance is 1.7 m away from the molten pool surface.

[0049] Nitrogen consumption per ton of steel is controlled in stages according to the blowing period, of which: 0~0.5min: 1.0Nm³3 / (t) min), 0.5~2 min: 0.8 Nm 3 / (t) (min), 2~4min: 0.6Nm 3 / (t) min), 4~6.5 min: 0.5 Nm 3 / (t) min).

[0050] The bottom blowing process is the same as in Example 1. (Omitted here.)

[0051] Meanwhile, 5315 kg of cold-pressed briquettes and 15.6 t of pig iron blocks are added during the blowing process to keep the temperature of the vanadium-containing molten iron at 1360~1390℃.

[0052] After 6.5 minutes (s3), the semi-steel was removed from the lance, and the temperature of the semi-steel at the end of the blowing process was measured to be 1375℃. The semi-steel composition contained 3.6wt% C and 0.0030wt% V. The vanadium slag composition contained 17.1wt% V2O5 and 31.5wt% T.Fe.

[0053] The above implementation and comparison results show that the application of this method can achieve vanadium reduction and carbon preservation, as well as reduce vanadium slag TFe, effectively utilize vanadium resources and reduce steel material consumption, thus contributing to the improvement of the comprehensive utilization level of vanadium and iron resources.

[0054] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A method for enhancing the stirring intensity of vanadium extraction, comprising the following three steps: first, adding vanadium-containing molten iron into a converter; then, employing a top-and-bottom combined blowing process for smelting; adding a coolant according to the final composition and target temperature of the smelting endpoint; and finally, removing semi-steel from the lance at the smelting endpoint, characterized in that... The top-blown gas is an oxygen-nitrogen mixture, and the total flow rate of the oxygen-nitrogen mixture is 31,000~35,000 Nm³. 3 / h; the oxygen consumption per ton of iron, the top blowing lance position, and the nitrogen consumption per ton of iron are controlled in segments according to the blowing period; the bottom blowing process includes: the bottom blowing gas is nitrogen, and the nitrogen supply intensity is controlled in segments according to the blowing period.

2. The method for enhancing the stirring intensity during vanadium extraction according to claim 1, characterized in that, The oxygen consumption per ton of iron is controlled in segments according to the blowing period, including: 0~0.5min: 1.9~2.1Nm³. 3 / (t) min), 0.5~2 min: 1.8~1.9 Nm 3 / (t) (min), 2~4min: 1.7~1.8Nm 3 / (t) (min), 4min ~ blowing endpoint: 1.6~1.7Nm 3 / (t) The nitrogen consumption per ton of iron is controlled in segments according to the blowing period, including: 0~0.5min: 0.4~0.5Nm. 3 / (t) min), 0.5~2 min: 0.5~0.6 Nm 3 / (t) (min), 2~4min: 0.7~0.9Nm 3 / (t) (min), 4min ~ blowing endpoint: 0.9~1.1Nm 3 / (t) min).

3. The method for enhancing the stirring intensity during vanadium extraction according to claim 1, characterized in that, The top blowing lance position is controlled in segments according to the blowing period, including: 0~2min: the top blowing lance position is 1.65~1.8mm from the molten pool surface; 2~4min: the top blowing lance position is 1.9~2.2m from the molten pool surface; 4min~blowing end point: the top blowing lance position is 1.7~1.9m from the molten pool surface.

4. The method for enhancing the stirring intensity during vanadium extraction according to claim 1, characterized in that, The nitrogen supply intensity is controlled in segments according to the blowing period, including: 0~2min: nitrogen supply intensity is 0.083~0.1Nm. 3 / (t) (min), 2min ~ blowing endpoint: nitrogen supply intensity is 0.079~0.085 Nm 3 / (t) min).

5. The method for enhancing the stirring intensity during vanadium extraction according to claim 1, characterized in that, The blowing endpoint is 5~12 minutes; the blowing endpoint for removing the semi-steel includes: when the blowing reaches the endpoint, the composition of the semi-steel satisfies: C content ≥ 3.0 wt%, V content ≤ 0.030 wt%.

6. The method for enhancing the stirring intensity during vanadium extraction according to claim 1, characterized in that, The target temperature at the end of the blowing process is 1360~1420℃.

7. The method for enhancing the stirring intensity during vanadium extraction according to claim 1, characterized in that, The main components of the vanadium-containing molten iron include: C content of 3.5-4.5 wt%, Si content of 0.07-0.3 wt%, V content of 0.18-0.35 wt%, and the remainder being iron and its unavoidable impurities.

8. The method for enhancing the stirring intensity during vanadium extraction according to claim 1, characterized in that, The coolant is one or both of cold-pressed blocks or cast iron blocks.

9. The method for enhancing the stirring intensity during vanadium extraction according to claim 8, characterized in that, The cold-pressed block is made of vanadium extraction dust, ironmaking dust and iron oxide scale, and the TFe content of the cold-pressed block is ≥50wt%.

10. The method for enhancing the stirring intensity of vanadium extraction according to claim 8, characterized in that, The dosage of the cold-pressed block is 20-70 kg per ton of vanadium-containing molten iron; the dosage of the pig iron block is 30-95 kg per ton of vanadium-containing molten iron.

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