Method for modifying vanadium slag before tapping from molten iron converter for vanadium extraction

Abstract

The present invention discloses a method for modifying vanadium slag before tapping in a molten iron converter for vanadium extraction, belonging to the field of metallurgy. To address the problems in existing converter vanadium extraction processes, the present invention provides a method for modifying vanadium slag before tapping in a molten iron converter for vanadium extraction, comprising: adding different amounts of a slag conditioning agent according to the silicon content in the molten iron after oxygen blowing in the vanadium extraction converter is completed; when the silicon content of the molten iron is less than 0.18wt%, no slag conditioning agent is added; when the silicon content of the molten iron is between 0.18wt% and 0.21wt%, 1.5 to 2.5 kg / ton of semi-steel of slag conditioning agent is added; when the silicon content of the molten iron is greater than 0.21wt%, 2.5 to 3 kg / ton of semi-steel of slag conditioning agent is added; the slag conditioning agent is composed of a carbonaceous material, an aluminum-containing slag-forming material, and a binder. By adding a specially prepared slag conditioning agent and strictly controlling the slag conditioning agent addition index, the present invention can effectively reduce the oxidizability of the vanadium slag, increase the slag viscosity, reduce the fluidity, reduce the amount of slag entrainment during tapping, and reduce the loss of vanadium slag.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for modifying vanadium slag before tapping vanadium from a molten iron converter. Background Art

[0002] When the silicon content of vanadium-titanium molten iron is high (silicon content is greater than 0.18%), the slag at the end of vanadium extraction becomes very thin. The vanadium slag at the end of vanadium extraction has good fluidity. When the semi-steel tapping speed is relatively fast, it will inevitably cause serious slag curling, resulting in serious loss of vanadium slag during the semi-steel tapping process. Other conventional methods of increasing slag viscosity, such as adding lime and silica, cannot be used because they will reduce the grade of vanadium slag. Therefore, it is necessary to reduce the oxidizability of vanadium slag from the perspective of reducing the oxidizability of vanadium slag so that the slag is "dried" to increase the slag viscosity, reduce fluidity, reduce slag curling during semi-steel tapping, and reduce vanadium slag loss.

[0003] CN104673964A discloses a method for modifying high-silicon vanadium-chromium slag in a converter, comprising the following steps: a. calculating the amount of a slag-adjusting agent based on the content of vanadium and chromium elements in vanadium-chromium-containing molten iron before extracting vanadium and chromium in the converter; if the sum of the weight percentages of vanadium and chromium in the molten iron is greater than or equal to 1%, the amount of the slag-adjusting agent is 3.5-6.5 kg / tFe; if the sum of the weight percentages of vanadium and chromium in the molten iron is greater than 0.5% and less than 1%, the amount of the slag-adjusting agent is 2.5-5.5 kg / tFe; b. adding the slag-adjusting agent according to the amount calculated in step a 3-5 minutes after the start of converter treatment of the vanadium-chromium-containing molten iron; c. obtaining vanadium-chromium slag and semi-steel after the converter treatment; the slag-adjusting agent comprising the following components in weight percentage: Al2O3 15%-45%, MgO 0-45%, TiO2 0-5%, CaO 0-3%, S <0.02%, H2O <2%, and the remainder being FeO. However, in actual production, the vanadium and chromium contents have little effect on the slag state. Therefore, it is difficult to change the slag-making effect by adjusting the amount of slag regulator according to the vanadium and chromium contents.

[0004] CN104694700A discloses a slag-based conditioning agent for extracting vanadium and chromium from high-silicon hot metal converters. The conditioning agent's raw material composition, by weight, is SiO2 0-20%, MnO 5-25%, Na2O 0-5%, CaO 2-5%, S <0.02%, H2O <2%, with the balance being iron oxides. The conditioning agent is suitable for producing vanadium-chromium slag when the hot metal silicon content is greater than 0.25wt%. However, in actual production, when the silicon content of the hot metal is greater than 0.2%, the vanadium slag becomes very thin, and this method cannot be used to condition the vanadium slag for hot metal with a silicon content of ≤0.25wt%. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for modifying vanadium slag before tapping in a converter for vanadium extraction, which can effectively reduce the oxidizability of the slag, increase the viscosity of the slag, reduce the fluidity, reduce the slag rolling during semi-steel tapping, and reduce the loss of vanadium slag.

[0006] The present invention provides a method for modifying vanadium slag before tapping in a molten iron converter for vanadium extraction, which comprises the following steps:

[0007] After oxygen blowing is completed in the vanadium-extracting converter, different amounts of slag-adjusting agents are added according to the silicon content in the molten iron. When the silicon content in the molten iron is less than 0.18wt%, no slag-adjusting agent is added; when the silicon content in the molten iron is 0.18-0.21wt%, 1.5-2.5 kg / ton of semi-steel of slag-adjusting agent is added; when the silicon content in the molten iron is greater than 0.21wt%, 2.5-3.5 kg / ton of semi-steel of slag-adjusting agent is added.

[0008] The slag conditioning agent is composed of a carbonaceous material, an aluminum-containing slag-forming material and a binder, wherein the carbonaceous material accounts for 80% of the total mass, the aluminum-containing slag-forming material accounts for 12-17% of the total mass, and the binder accounts for 3-8% of the total mass; the slag conditioning agent contains the following components in percentage by mass: C 65-80%, metallic Al ≥3%, CaO ≤3%, H2O ≤2%, S ≤0.40%, P <0.20%, and organic matter (organic matter is tar and other substances) 5-10%.

[0009] Wherein, in the above method for modifying vanadium slag before tapping vanadium from molten iron converter, the particle size of the slag regulating agent is 30 to 50 mm.

[0010] Wherein, in the above method for modifying vanadium slag before tapping vanadium from molten iron converter, the carbonaceous material is at least one of graphite carbon, coke powder, anthracite or petroleum coke, and its fixed carbon content is ≥85%.

[0011] Wherein, in the above-mentioned method for modifying vanadium slag before tapping vanadium from molten iron converter, the content of metallic aluminum in the aluminum-containing slag-forming material is ≥30wt%, and the rest is Al2O3.

[0012] Wherein, in the above-mentioned method for modifying vanadium slag before tapping vanadium from a molten iron converter, the binder is asphalt or starch.

[0013] Preferably, in the above method for modifying vanadium slag before tapping vanadium from a molten iron converter, the binder is asphalt.

[0014] Beneficial effects of the present invention:

[0015] The present invention provides an effective method for modifying vanadium slag before vanadium extraction and tapping in a converter. By adding a specially prepared slag conditioning agent and controlling the amount of the slag conditioning agent added in a more targeted manner according to the silicon content of molten iron, the oxidizability of the vanadium slag is successfully reduced, the slag viscosity is increased, the fluidity is reduced, the slag curling during semi-steel tapping is reduced, and the loss of vanadium slag is reduced, thereby achieving significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the SiO2-FeO phase diagram.

[0017] Figure 2 This is the phase diagram of FeO-V2O3 system. DETAILED DESCRIPTION

[0018] Based on the SiO2-FeO and FeO-V2O3 phase diagrams, the inventors observed the effect of changes in FeO content on the phase range. In regions with high FeO content, a large amount of liquid phase is present in the system, indicating that high FeO content results in a lower melting point and better fluidity for the slag. As the FeO content decreases, the liquid phase region decreases significantly and the solid phase region increases significantly, indicating that the slag's melting point increases, viscosity increases, and fluidity decreases.

[0019] Figure 1 Specifically, when the FeO content is high, the silicate phase formed by SiO2 and FeO, such as 2FeO·SiO2, has a lower melting point (1177°C), which helps maintain the fluidity of the slag. However, when the FeO content decreases, these low-melting-point silicate phases decrease, and more SiO2 may exist in the solid phase, causing the melting point of the slag to increase to 1205°C or even higher. This change makes the slag easier to solidify at a lower temperature, increases the cohesiveness of the slag, and reduces loss during the tapping process.

[0020] Figure 2 Specifically, when the FeO content is high, compounds formed by V2O3 and FeO, such as FeO·V2O3, have lower melting points. As the FeO content decreases, these low-melting-point compounds decrease, resulting in more V2O3 remaining in the solid phase. This change allows the slag to solidify more easily at lower temperatures, increasing its viscosity and cohesiveness and reducing loss during tapping.

[0021] During the converter vanadium extraction process, changes in FeO content affect the ratio of the complex with silica, thereby affecting the viscosity and melting point of the slag. Therefore, the inventors envisioned changing the physical properties of the slag by controlling the FeO content.

[0022] The present invention first designs a special slag conditioning agent, which is composed of 80% carbonaceous material, 12-17% aluminum-containing slag-forming material and 3-8% binder. The carbonaceous material and metallic aluminum material are deoxidized to reduce the FeO content in the slag, thereby changing the ratio of the FeO to silica composition, thereby affecting the melting point and viscosity of the slag and destroying the fluidity of the slag. Among them, the use of metallic aluminum can further ensure the slag conditioning effect.

[0023] At the same time, the present invention deeply analyzes the relationship between the silicon content in the molten iron and the properties of the slag, and accurately controls the amount of slag adjusting agent added: when the silicon content of the molten iron is less than 0.18wt%, no slag adjusting agent is added; when the silicon content of the molten iron is 0.18-0.21wt%, 1.5-2.5 kg / ton of semi-steel of slag adjusting agent is added; when the silicon content of the molten iron is greater than 0.21wt%, 2.5-3.5 kg / ton of semi-steel of slag adjusting agent is added; thereby optimizing the physical properties of the slag, reducing the oxidizability of the slag, increasing the viscosity of the vanadium slag and reducing the fluidity, reducing the "slagging" in the semi-steel tapping process, and thus improving the vanadium recovery rate.

[0024] The present invention is further described in detail below through examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0025] In the embodiment, the slag conditioning agent used is prepared by the following method: 80% carbonaceous material, 15% aluminum-containing slag-forming material and 5% binder are evenly mixed; wherein, the carbonaceous material is graphite carbon, and its fixed carbon content is ≥85%; the aluminum-containing slag-forming material contains 30-40% metallic aluminum, and the rest is Al2O3; the binder is asphalt; and the particle size of the slag conditioning agent is 50 mm.

[0026] Example 1

[0027] A certain plant's 200-ton vanadium-extraction converter produced 210 tons of semi-steel. After oxygen blowing, the molten iron contained 0.20% Si. Adding 400 kg of the aforementioned slag-conditioning agent increased the vanadium yield to 82.3%, the V₂O₅ content in the vanadium slag to 18.26%, and the TFe content in the vanadium slag to 27.2%.

[0028] Example 2

[0029] A 200-ton vanadium-extraction converter at a certain plant produced 215 tons of semi-steel. After oxygen blowing, the molten iron contained 0.25% Si. Adding 540 kg of the aforementioned slag conditioning agent resulted in a vanadium yield of 81.43%, a vanadium slag grade of 17.85% V₂O₅, and a TFe content of 26.5%.

[0030] Example 3

[0031] A 200-ton vanadium-extraction converter at a certain plant produced 208 tons of semi-steel. After oxygen blowing was completed, the molten iron contained 0.30% Si. Adding 580 kg of the aforementioned slag-conditioning agent resulted in a vanadium yield of 83.5%, a vanadium slag grade of 19.02% V₂O₅, and a TFe content of 27.5%.

[0032] Comparative Example 1

[0033] A certain plant's 200t vanadium-extracting converter produced 210t of semi-steel. After oxygen blowing, the molten iron contained 0.21% Si. No slag conditioning materials were added before or during blowing, resulting in a very thin slag during and after the blowing process. The vanadium yield was only 76.3%, the vanadium slag contained only 13.02% V₂O₅, and the TFe content was as high as 33.5%.

[0034] Comparative Example 2

[0035] A certain plant's 200-ton vanadium-extraction converter produced 215 tons of semi-steel steel. After oxygen blowing, the molten iron contained 0.19% Si. Adding 560 kg of the aforementioned slag-conditioning agent increased the vanadium yield to 82%, while the vanadium slag had a V₂O₅₅% grade of 14.3% (adding too much slag-conditioning agent would have lowered the vanadium slag grade). The TFe content in the vanadium slag was 26.8%.

[0036] According to experiments, when the silicon content of molten iron is 0.18-0.21wt%, adding a slag conditioning agent of up to 2.5 kg / ton of semi-steel can achieve a good slag conditioning effect. Continuing to increase the dosage will lead to a decrease in vanadium recovery rate and vanadium slag grade, and waste resources.

[0037] Comparative Example 3

[0038] A certain plant's 200-ton vanadium-extraction converter produced 210 tons of semi-steel. After oxygen blowing, the molten iron contained 0.23% Si. Adding 420 kg of the aforementioned slag-conditioning agent increased the vanadium yield to 77%, the V₂O₅ content in the vanadium slag to 14.2%, and the TFe content to 32%.

[0039] According to experiments, when the silicon content of molten iron is greater than 0.21wt%, if the amount of slag adjustment agent added is insufficient, the slag adjustment effect is poor and the recovery rate of vanadium resources is improved to a certain extent, but it is very limited.

[0040] From the above, it can be seen that the present invention significantly reduces the oxidizability of vanadium slag, increases slag viscosity, reduces fluidity, reduces slag rolling during semi-steel tapping, reduces vanadium slag loss, improves vanadium recovery rate and vanadium extraction efficiency by adding a special slag conditioning agent and strictly controlling the slag conditioning agent addition indicators, and has significant economic and social benefits.

Claims

1. A method for modifying vanadium slag before tapping from a molten iron converter, characterized by: The following steps are involved: After the oxygen blowing is completed in the vanadium-extracting converter, different amounts of slag-adjusting agents are added according to the silicon content in the molten iron. When the silicon content in the molten iron is less than 0.18 wt%, no slag-adjusting agent is added. When the silicon content in the molten iron is 0.18-0.21 wt%, 1.5-2.5 kg / ton of semi-steel of slag-adjusting agent is added. When the silicon content in the molten iron is greater than 0.21 wt%, 2.5-3 kg / ton of semi-steel of slag-adjusting agent is added. The slag conditioning agent is composed of a carbonaceous material, an aluminum-containing slag-forming material and a binder, wherein the carbonaceous material accounts for 80% of the total mass, the aluminum-containing slag-forming material accounts for 12-17% of the total mass, and the binder accounts for 3-8% of the total mass; the slag conditioning agent contains the following components in percentage by mass: C 65-80%, metallic Al ≥3%, CaO ≤3%, H2O ≤2%, S ≤0.40%, P <0.20%, and organic matter 5-10%; the metallic aluminum content in the aluminum-containing slag-forming material is ≥30wt%, and the rest is Al2O3.

2. The method for modifying vanadium slag before tapping from a molten iron converter according to claim 1, characterized in that: The particle size of the slag conditioning agent is 30-50 mm.

3. The method for modifying vanadium slag before tapping from a molten iron converter according to claim 1, characterized in that: The carbonaceous material is at least one of graphite carbon, coke powder, anthracite or petroleum coke, and its fixed carbon content is ≥85%.

4. The method for modifying vanadium slag before tapping from a molten iron converter according to any one of claims 1 to 3, characterized in that: The binder is asphalt or starch.

5. The method for modifying vanadium slag before tapping from a molten iron converter according to claim 4, characterized in that: The binder is asphalt.

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