A method for smelting low-vanadium alloys using vanadium-containing molten steel slag from steelmaking

Abstract

This invention discloses a method for smelting low-vanadium alloys using vanadium-containing steel slag from steelmaking. The method includes the following steps: Step 1: Using desulfurized steel slag, scraped iron, semi-steel ladle, and slag obtained from magnetic separation iron melting as raw materials, and mixing them with a reducing agent, the low-vanadium alloy is smelted in an electric furnace; Step 2: After smelting in Step 1, slag and iron are separated, and the molten steel is discharged through an eccentric hole and smelted in a ladle; Step 3: The molten slag in the electric furnace is continuously smelted for reduction, with nitrogen blowing and stirring at the bottom; Step 4: After all the slag in the electric furnace is melted, a slag sample from the No. 1 electric furnace is taken for spectral analysis of FeO, V2O5, SiO2, and CaO; Step 5: Lime is added to adjust the slag basicity to 1.3-1.5, and when FeO ≤ 3.0%, the furnace temperature is raised to 1650℃, while silicon slag is added to make the silicon content reach 1.0-1.3%; Step 6: After tapping, desulfurization is performed in a refining furnace to adjust the alloy composition. The method of this invention for refining vanadium steel alloys saves on the power consumption of slag melting, shortens the smelting time, and increases the vanadium yield to 90%.

Description

Technical Field

[0001] This invention relates to the field of metallurgical slag application technology, and in particular to a method for smelting low-vanadium alloys using liquid vanadium-containing steel slag from steelmaking. Background Technology

[0002] my country is rich in vanadium resources, ranking among the world's largest holders of vanadium reserves. However, vanadium is also subject to significant waste, making the refining and recycling of vanadium still of considerable economic value. In proven vanadium mines, vanadium is primarily found in vanadium-titanium magnetite. Recycling mainly involves smelting vanadium-containing iron slag and steel slag to form ferrovanadium alloys. Currently, the extraction of vanadium from vanadium-containing steel slag primarily employs the submerged arc furnace method. This method involves cold slag batching, pre-reduction in a rotary kiln, and then melting and reducing in a submerged arc furnace. This process is characterized by a long smelting cycle (approximately 12 hours per furnace, yielding only 30-40 tons of ferrovanadium from 100 tons of raw material), high power consumption, and is uneconomical and inefficient. Summary of the Invention

[0003] This invention provides a method for smelting low-vanadium alloys using vanadium-containing slag from steelmaking processes, thereby reducing costs and increasing vanadium recovery rates.

[0004] A method for smelting low-vanadium alloys using vanadium-containing steel slag from steelmaking processes, characterized by comprising the following steps:

[0005] Step 1: Using desulfurized steel slag, scrap iron, semi-steel ladle, and slag obtained from melting magnetically separated iron as raw materials, and mixing them with reducing agents, low-vanadium alloys are smelted in an electric furnace.

[0006] Step 2: After smelting in Step 1, molten steel and electric furnace slag are obtained. The molten steel is discharged through the eccentric hole and continues to be smelted and its composition is adjusted in the ladle. Finally, it is continuously cast into steel billets. The electric furnace slag can be directly reduced in the electric furnace or discharged from the furnace door to obtain vanadium-containing steel slag (FeO 20-30%, V2O5 1-2%).

[0007] Step 3: The molten slag in the electric furnace is continuously smelted and reduced, with nitrogen blowing and stirring at the bottom;

[0008] Step 4: After all the slag in the electric furnace has been melted and cleared, take a slag sample from electric furnace #1 for spectral analysis of FeO, V2O5, SiO2, and CaO.

[0009] Step 5: Add lime to adjust the slag alkalinity to 1.3-1.5. When FeO ≤ 3.0%, raise the furnace temperature to 1650℃ for smelting. At the same time, add silicon slag to make the silicon content reach 1.0-1.3%.

[0010] Step 6: After tapping the steel, the alloy composition can be adjusted by desulfurization in the refining furnace according to the composition requirements.

[0011] Furthermore, the reducing agent in step one includes semi-coke, carbon blocks, carbon powder, silicon slag, ferrosilicon, and silicon carbide.

[0012] Furthermore, the V2O5 content in the raw materials of step one is more than 1%, and the magnetic iron content is more than 70%.

[0013] Furthermore, in step three, the nitrogen blowing melting period uses level 7, the temperature range of 1500-1600℃ uses level 4-7, and the temperature range of 1600-1650℃ uses level 1-2.

[0014] Furthermore, in step three, if the amount of molten slag is small, a mixture of cold electric furnace slag, silicon slag, and semi-coke in a ratio of 82%:9%:9% can be added to ensure the total amount of material fed into the furnace.

[0015] Furthermore, in step four, when analyzing the FeO content in the slag, if the FeO content is too high, an appropriate amount of semi-coke or carbon blocks can be added from the high-level silo to continue the reduction. If necessary, the carbon lance at the furnace door can be inserted into the molten steel to inject carbon powder.

[0016] Furthermore, in the smelting stage of step five, nitrogen blowing and stirring are carried out at the bottom of the furnace, and the temperature does not exceed 1670℃.

[0017] Furthermore, in step five, the smelting time is as follows: after the slag turns yellowish-white and remains so for 30 to 60 minutes, the power is turned off and the nitrogen blowing is stopped.

[0018] The beneficial effects of this invention are as follows: The method of refining vanadium steel alloys using this invention saves on the melting power consumption of slag, saving an average of 800 kWh per ton of slag and significantly shortening the smelting cycle. Secondly, the reduction reaction is dominated by a liquid-solid reaction, resulting in a faster reaction rate and shorter smelting time. Nitrogen blowing and stirring at the bottom of the electric furnace accelerates the CO reaction, increasing the vanadium yield to approximately 90%, and resulting in low residual vanadium content in the slag. The finished product can also be further refined in a refining furnace to adjust its composition and meet user needs. This invention not only solves the problem of treating solid waste from slag in steel smelting but also recovers V₂O₅ and FeO from the slag. Detailed Implementation

[0019] This invention provides a method for smelting low-vanadium alloys using vanadium-containing molten steel slag from steelmaking processes, comprising the following steps:

[0020] Step 1: Using desulfurized steel slag, scrap iron, semi-steel ladle, and slag obtained from melting magnetically separated iron as raw materials, and mixing them with reducing agents, low-vanadium alloys are smelted in an electric furnace.

[0021] Step 2: After smelting in Step 1, molten steel and electric furnace slag are obtained. The molten steel is discharged through the eccentric hole and continues to be smelted and its composition is adjusted in the ladle. Finally, it is continuously cast into steel billets. The electric furnace slag can be directly reduced in the electric furnace or discharged from the furnace door to obtain vanadium-containing steel slag (FeO 20-30%, V2O5 1-2%).

[0022] Step 3: The molten slag in the electric furnace is continuously smelted and reduced, with nitrogen blowing and stirring at the bottom;

[0023] Step 4: After all the slag in the electric furnace has been melted and cleared, take a slag sample from electric furnace #1 for spectral analysis of FeO, V2O5, SiO2, and CaO.

[0024] Step 5: Add lime to adjust the slag alkalinity to 1.3-1.5. When FeO ≤ 3.0%, raise the furnace temperature to 1650℃ for smelting. At the same time, add silicon slag to make the silicon content reach 1.0-1.3%.

[0025] Step 6: After tapping the steel, the alloy composition can be adjusted by desulfurization in the refining furnace according to the composition requirements.

[0026] In this invention, the reducing agent in step one includes semi-coke, carbon blocks, carbon powder, silicon slag, ferrosilicon, and silicon carbide.

[0027] In this invention, the V2O5 content in the raw materials of step one is more than 1%, and the magnetic iron content is more than 70%.

[0028] In this invention, nitrogen is blown from the bottom in step three. The melting period uses level 7, the temperature range of 1500-1600℃ uses level 4-7, and the temperature range of 1600-1650℃ uses level 1-2.

[0029] In this invention, if the amount of molten slag is small in step three, a mixture of cold electric furnace slag, silicon slag, and semi-coke in a ratio of 82%:9%:9% can be added to ensure the total amount of material fed into the furnace.

[0030] In this invention, when analyzing the FeO content in the slag in step four, if the FeO content is too high, an appropriate amount of semi-coke or carbon blocks can be added from the high-level silo to continue the reduction. If necessary, carbon lances can be inserted into the furnace door to inject carbon powder into the molten steel.

[0031] In this invention, the smelting stage in step five is carried out by bottom nitrogen blowing and stirring, with a temperature not exceeding 1670°C.

[0032] In this invention, the smelting time in step five is as follows: after the slag turns yellowish-white and remains so for 30 to 60 minutes, the power is turned off and the nitrogen blowing is stopped.

[0033] In this invention, the key is to carry out the reduction reaction in steps. FeO is reduced at a low temperature (1500-1600℃). When the FeO content is less than 1%, the alkalinity of the slag is adjusted to 1.3-1.5. Then, the temperature is raised to about 1650℃ and silicon is added to reduce V2O5, so that the vanadium recovery rate reaches the maximum.

[0034] The present invention will be further illustrated below with reference to the embodiments. The embodiments are only used to help understand the present invention and are not intended to limit the present invention.

[0035] Example

[0036] In this embodiment, vanadium steel alloy was refined using 95 tons of raw materials.

[0037] Raw material source and composition: Waste slag steel from Panzhihua Iron and Steel Group. The raw material composition includes 10 tons of semi-steel tank, 20 tons of desulfurized slag steel, 15 tons of screened / unscreened iron, 40 tons of magnetically separated iron, and 10 tons of scraped slag iron. The MFe content is ≥70%. The mass composition ratio of the mixed raw materials is: V 1%~3%, C 2%~4%, P≤0.6%, S≤0.2%.

[0038] Process flow: Raw material batching → EBT electric furnace smelting → Molten electric furnace slag → Direct reduction in electric furnace → Low vanadium alloy → Desulfurization and alloy composition adjustment in refining furnace → Casting machine / mold casting.

[0039] The refining of vanadium alloys from the above raw materials using an electric furnace includes the following steps:

[0040] (1) The prepared raw materials are added to the EBT electric furnace in one go through the disk batching.

[0041] (2) After melting for about 1 hour, the furnace temperature is raised to 1630-1670℃ to obtain about 60 tons of molten steel and about 30 tons of electric furnace slag. After melting in the electric furnace, the slag is discharged in a concentrated manner. The molten electric furnace slag is collected by the slag pot at the furnace door and then transported to an idle electric furnace by a ladle car or ladle car for reduction to produce low vanadium alloys, or the slag after tapping is left directly in the furnace for further reduction. The V2O5 content in the electric furnace slag is 1.5%-2.5%, and TFe is 28%-30%. Nitrogen blowing is used at level 7 during the melting period, level 4-7 at 1500-1600℃, and level 1-2 at 1600-1650℃. The power supply should be kept as continuous as possible to avoid large boiling in the furnace and shorten the melting period.

[0042] (3) Continue smelting directly using molten electric furnace slag, keeping the electrodes buried in the slag and ensuring that the electrodes can start arcing and conduct electricity. At the same time, continuously add 3 tons of carbon blocks (8-10% of the total slag) around the electrodes. Control the amount of electric furnace slag added and the rate of carbon block addition according to the electric furnace volume to avoid slag overflow. During this period, all oxygen-containing gases (oxygen, compressed air) are turned off, and nitrogen is blown from the bottom. After the furnace charge is completely melted, take the No. 1 electric furnace slag sample to analyze the FeO, V2O5, SiO2, and CaO content, and perform spectral analysis on the No. 1 steel sample. If the FeO in the slag is too high, calculate based on the FeO content and add an appropriate amount of semi-coke from the high-level silo to continue reduction.

[0043] (4) Based on the analysis results of No. 1 slag and No. 1 steel sample, lime is added to adjust the slag basicity to 1.3-1.5. When FeO ≤ 3.0%, the temperature can be raised to 1650℃ for smelting operation. About 2 tons of silicon slag (ferrosilicon / silicon carbide can be added) are added through the alloy silo or horizontal continuous feeding section to adjust the silicon content to 1.0-1.3%. At this stage, nitrogen stirring is carried out by bottom blowing, and the temperature is controlled not to exceed 1670℃ to reduce furnace lining erosion. After the slag turns yellowish-white and is maintained for 30-60 minutes, the power is turned off and the bottom blowing is turned off. After standing for 10 minutes, the steel can be tapped. If composition adjustment is required, the ladle is hoisted to the refining furnace to remove sulfur and adjust the alloy composition. Finally, it is cast / molded using a cast iron casting machine.

[0044] Using this method, 8.6 tons of low-vanadium alloy (V≥3.0%) and 21.4 tons of reducing slag (which can be used as a slag-reducing agent, covering agent, and raw material for cement clinker) can be smelted from 30 tons of electric furnace slag (V2O5 1.8%~2.0%, TFe 28%~30%). This method not only solves the problem of solid waste treatment, but also recovers V2O5 and FeO from the slag.

Claims

1. A method for smelting low-vanadium alloys using vanadium-containing steel slag from steelmaking processes, characterized in that, Includes the following steps: Step 1: Using desulfurized steel slag, scrap iron, semi-steel ladle, and slag obtained from melting magnetically separated iron as raw materials, and mixing them with reducing agents, low vanadium alloys are smelted in an electric furnace. The reducing agents include semi-coke, carbon blocks, carbon powder, silicon slag, ferrosilicon, and silicon carbide. The V2O5 content in the raw materials of Step 1 is more than 1%, and the magnetic iron content is more than 70%. Step 2: After smelting in Step 1, molten steel and electric furnace slag are obtained. The molten steel is discharged through an eccentric hole and continues to be smelted and its composition adjusted in the ladle. Finally, it is continuously cast into steel billets. The electric furnace slag is directly reduced in the electric furnace or discharged from the furnace door to obtain vanadium-containing steel slag with 20-30% FeO and 1-2% V2O5. Step 3: The molten slag in the electric furnace is continuously smelted and reduced. Nitrogen blowing is used to stir the bottom. If the amount of molten slag is small, a mixture of cold electric furnace slag, silicon slag and semi-coke in a ratio of 82%:9%:9% is added to ensure the total amount of material fed into the furnace. Step 4: After all the slag in the electric furnace has been melted and cleared, take a slag sample from electric furnace #1 for spectral analysis of FeO, V2O5, SiO2, and CaO. Step 5: Add lime to adjust the slag alkalinity to 1.3-1.

5. When FeO ≤ 3.0%, raise the furnace temperature to 1650℃ for smelting. At the same time, add silicon slag to make the silicon content reach 1.0-1.3%. Step 6: After tapping the steel, desulfurize and adjust the alloy composition in the refining furnace according to the composition requirements.

2. The method for smelting low-vanadium alloys using vanadium-containing steel slag from steelmaking as described in claim 1, characterized in that: In step three, the nitrogen blowing melting period uses level 7, the temperature range of 1500-1600℃ uses level 4-7, and the temperature range of 1600-1650℃ uses level 1-2.

3. The method for smelting low-vanadium alloys using vanadium-containing steel slag from steelmaking as described in claim 1, characterized in that: When analyzing the FeO content in the slag in step four, if the FeO content is too high, add an appropriate amount of semi-coke or carbon blocks from the high-level silo to continue the reduction. If necessary, insert the carbon lance at the furnace door into the molten steel to inject carbon powder.

4. The method for smelting low-vanadium alloys using vanadium-containing steel slag from steelmaking as described in claim 1, characterized in that, The smelting stage in step five is carried out by bottom nitrogen blowing and stirring, with a temperature not exceeding 1670℃.

5. The method for smelting low-vanadium alloys using vanadium-containing steel slag from steelmaking as described in claim 1, characterized in that: In step five, the smelting time is as follows: after the slag turns yellowish-white and remains so for 30 to 60 minutes, the power is turned off and the nitrogen blowing is stopped.