A method for extracting vanadium from molten iron by oxidation

Abstract

The present invention provides a method for oxidizing vanadium from molten iron, the method comprising the following steps: top-bottom combined blowing is performed on vanadium-containing molten iron, sodium salt is added during the top-bottom combined blowing process to form sodium vanadium slag; during the top-bottom combined blowing process, the gas used for top blowing is a first mixed gas, and the gas used for bottom blowing is a second mixed gas; the first mixed gas includes carbon dioxide and oxygen; the second mixed gas includes carbon dioxide and oxygen. In the process of vanadium extraction from molten iron, the present invention uses top blowing of a mixed gas of carbon dioxide and oxygen, and bottom blowing of a mixed gas of carbon dioxide and oxygen, and utilizes the weak oxidizing property of carbon dioxide to replace part of oxygen to participate in the reaction, thereby achieving the effect of extracting vanadium and retaining carbon without adding a coolant.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and relates to a method for extracting vanadium, and in particular to a method for extracting vanadium by oxidizing molten iron. Background Art

[0002] As an important metal resource, vanadium has good stability and fatigue resistance and is widely used in the steel industry, electronics industry, chemical industry, medicine, aerospace and other fields. Vanadium is dispersed in nature and there is no vanadium material that can be mined alone. 88% of the world's vanadium is obtained from vanadium-titanium magnetite. Vanadium-containing molten iron is usually obtained through blast furnaces or other iron-making processes. Oxygen is blown into the converter to oxidize and enrich the vanadium in the metal into the slag phase.

[0003] In the process of vanadium extraction in the converter, the oxidation of silicon, manganese, vanadium and carbon in the molten iron will generate a lot of heat, causing the temperature in the furnace to rise sharply, and it is easy to exceed the carbon-vanadium conversion temperature in a short time, thereby restricting the oxidation of vanadium and accelerating the reaction consumption of carbon, resulting in a too short vanadium extraction cycle and reduced vanadium production. The existing technology often adds an appropriate amount of coolant during the reaction process to adjust the rising trend of the molten pool temperature so that the vanadium is in a low-temperature oxidation zone, thereby achieving the purpose of vanadium extraction and carbon preservation.

[0004] CN104060015A discloses a vanadium extraction process of high silicon vanadium-containing hot metal in a converter, wherein the high silicon vanadium-containing hot metal is blown in a converter, and a coolant is added during the blowing process, the amount of the coolant is 30-37 kg / t high silicon vanadium-containing hot metal, and the coolant contains 40-50% Fe2O3, 40-50% FeO and 10-20% SiO2. The vanadium slag obtained by this technical solution has a high grade, and the carbon content of the obtained semi-steel is relatively high, and the temperature of the semi-steel can meet the subsequent steelmaking requirements. However, the amount of coolant used in this method is high, there is unnecessary waste, and the refining cost is increased.

[0005] CN104073587A discloses a method for vanadium extraction in a converter, wherein the first batch of coolant is added to the converter molten pool at the beginning of or before the top gun oxygen blowing stage, and the second batch of coolant is added to the converter molten pool at 100-140s of vanadium extraction blowing; wherein the coolant comprises at least one of cold pressed blocks, pig iron blocks, iron oxide scale and pelletized ore, and the cold pressed blocks are spherical blocks formed by pressing converter dust removal ash and / or iron oxide scale with a binder. By adding coolant in steps, the amount of coolant used in the blowing process can be reduced, but the process control and process safety requirements are high.

[0006] CN104831091A discloses a method for extracting vanadium from a double-blown converter, in which a coolant is added before blowing, a mixed gas of oxygen and carbon dioxide is blown into the molten iron through an oxygen lance, and carbon monoxide or a mixed gas of carbon monoxide and nitrogen is blown into the molten iron through the furnace bottom. The redox equilibrium relationship between carbon, carbon monoxide and carbon dioxide is utilized to optimize resource utilization and reduce production costs. Although the amount of coolant used is reduced to a certain extent, the adverse effects of impurity elements in the coolant on the quality of vanadium slag cannot be avoided.

[0007] Therefore, it is necessary to provide a method for extracting vanadium from molten iron, which can achieve the purpose of extracting vanadium and retaining carbon without adding a coolant during the process. Summary of the invention

[0008] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for extracting vanadium by oxidizing molten iron, which does not require the addition of a coolant during the vanadium extraction process and can still achieve the purpose of extracting vanadium and retaining carbon.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] The present invention provides a method for extracting vanadium by oxidizing molten iron, the method comprising the following steps:

[0011] The vanadium-containing molten iron is subjected to top-bottom combined blowing, and sodium salt is added during the top-bottom combined blowing process to form sodium vanadium slag;

[0012] In the top-bottom combined blowing process, the gas used for top blowing is the first mixed gas, and the gas used for bottom blowing is the second mixed gas;

[0013] The first mixed gas includes carbon dioxide and oxygen;

[0014] The second mixed gas includes carbon dioxide and oxygen.

[0015] In the process of vanadium extraction from molten iron, the present invention uses top blowing of a mixed gas of carbon dioxide and oxygen and bottom blowing of a mixed gas of carbon dioxide and oxygen, utilizes the weak oxidizing property of carbon dioxide to replace part of oxygen to participate in the reaction, and oxidizes vanadium in the vanadium-containing molten iron into a slag phase; the reaction of carbon dioxide with the vanadium-containing molten iron is an endothermic reaction as a whole, which can effectively reduce the temperature of the fire point zone and delay the temperature rise, and achieves the effect of vanadium extraction and carbon preservation without adding a coolant; and the bottom blowing of the mixed gas enhances the stirring effect, so that the reaction is more sufficient and complete, thereby obtaining high-grade sodium vanadium slag.

[0016] Preferably, the mass fraction of vanadium element in the vanadium-containing molten iron is 0.3-1.2wt%, for example, it can be 0.3wt%, 0.5wt%, 0.7wt%, 0.9wt%, 1.1wt% or 1.2wt%, but is not limited to the listed values, and other unlisted values ​​in the numerical range are also applicable.

[0017] Preferably, the mass fraction of carbon element in the vanadium-containing molten iron is 3.5-4.8wt%, for example, it can be 3.5wt%, 3.8wt%, 4.1wt%, 4.3wt%, 4.5wt% or 4.8wt%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] Preferably, the sodium salt comprises any one or a combination of at least two of sodium carbonate, sodium oxide or sodium sulfate. Typical but non-limiting combinations include a combination of sodium carbonate and sodium oxide, a combination of sodium oxide and sodium sulfate, a combination of sodium carbonate and sodium sulfate, or a combination of sodium carbonate, sodium oxide and sodium sulfate.

[0019] Preferably, the molar ratio of the sodium element in the sodium salt to the vanadium element in the vanadium-containing molten iron is (1.5-2.5):1, for example, it can be 1.5:1, 1.7:1, 1.9:1, 2.1:1, 2.3:1 or 2.5:1, but is not limited to the exemplified values, and other values ​​not exemplified within the numerical range are also applicable.

[0020] Preferably, the sodium salt is added all at once when 1 / 3-3 / 5 of the top blowing is completed, for example, it can be 1 / 3, 2 / 5, 7 / 15, 1 / 2, 8 / 15 or 3 / 5, but is not limited to the exemplified values, and other values ​​within the numerical range not exemplified are also applicable.

[0021] The sodium salt of the present invention is added all at once when 1 / 3-3 / 5 of the top blowing is completed. If it is added too early, the vanadium element in the vanadium-containing molten iron has not been completely oxidized into the slag phase, resulting in increased sodium salt consumption; if it is added too late, the vanadium conversion rate will be low before the end of the blowing.

[0022] Preferably, the volume content of carbon dioxide in the first mixed gas is 10-30 vol%, for example, it can be 10 vol%, 15 vol%, 20 vol%, 25 vol% or 30 vol%, but is not limited to the exemplified values, and other values ​​not exemplified within the numerical range are also applicable.

[0023] Preferably, the volume content of carbon dioxide in the second mixed gas is 10-50 vol%, for example, it can be 10 vol%, 15 vol%, 20 vol%, 25 vol%, 30 vol%, 35 vol%, 40 vol%, 45 vol% or 50 vol%, but is not limited to the exemplified values, and other values ​​not exemplified within the numerical range are also applicable.

[0024] When the volume content of carbon dioxide in the first mixed gas in the present invention is 10-30 vol%, it is beneficial to reduce the temperature of the fire point area, delay the temperature rise in the furnace, and make the vanadium element oxidized first, and the carbon element is retained, thereby achieving the purpose of extracting vanadium and retaining carbon. At the same time, the bottom blowing mixed gas strengthens the stirring effect and makes the oxidation reaction more complete.

[0025] When the volume content of carbon dioxide in the first mixed gas is lower than 10 vol%, the temperature in the furnace rises sharply, which will restrict the oxidation of vanadium, accelerate the reaction consumption of carbon, reduce the vanadium extraction output, and cause serious carbon oxidation loss; when the volume content of carbon dioxide in the first mixed gas is higher than 30 vol%, the vanadium in the vanadium-containing molten iron is not fully oxidized and cannot completely enter the slag phase, resulting in a low output of sodium vanadium slag.

[0026] Preferably, during the top blowing, the gas supply intensity of the first mixed gas is 2.0-3.5m 3 / (min·t Fe ), for example, it can be 2.0m 3 / (min·t Fe )、2.2m 3 / (min·t Fe ), 2.5m 3 / (min·t Fe )、2.8m 3 / (min·t Fe )、3.0m 3 / (min·t Fe )、3.3m 3 / (min·t Fe ) or 3.5m 3 / (min·t Fe ), but are not limited to the exemplified values, and other values ​​not exemplified within the numerical range are also applicable.

[0027] Preferably, during the top blowing, the Mach number of the first mixed gas is 1.8-2.5, for example, it can be 1.8, 2.0, 2.2, 2.4 or 2.5, but is not limited to the exemplified values, and other values ​​within the numerical range not exemplified are also applicable.

[0028] During the top blowing of the present invention, the first mixed gas is sprayed in from the nozzle of the top blowing oxygen lance.

[0029] Exemplarily, during top blowing, the intake pressure of the first mixed gas is 0.2-1.2 MPa; during bottom blowing, the intake pressure of the second mixed gas is 0.3-1.5 MPa.

[0030] Preferably, the top blowing time is 5-15 min, for example, 5 min, 7 min, 9 min, 11 min, 13 min or 15 min, but is not limited to the exemplified values, and other values ​​not exemplified within the numerical range are also applicable.

[0031] Preferably, during the bottom blowing, the supply intensity of the second mixed gas is 0.1-1m 3 / (min·t Fe ), for example, it can be 0.1m 3 / (min·t Fe )、0.3m 3 / (min·t Fe )、0.5m 3 / (min·t Fe )、0.8m 3 / (min·t Fe ) or 1m 3 / (min·t Fe ), but are not limited to the exemplified values, and other values ​​not exemplified within the numerical range are also applicable.

[0032] Preferably, the bottom blowing time is 5-10 min, for example, 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but is not limited to the exemplified values, and other values ​​not exemplified within the numerical range are also applicable.

[0033] Preferably, the temperature of the top and bottom combined blowing is 1300-1400°C, for example, 1300°C, 1330°C, 1350°C, 1380°C or 1400°C, but is not limited to the exemplified values, and other values ​​within the numerical range not exemplified are also applicable.

[0034] The reaction vessel for oxidizing molten iron to extract vanadium in the present invention is not specifically limited, and may be, for example, a converter, a ladle or other devices. The capacity of the reaction vessel is not specifically limited either, and may be specifically selected and adjusted according to actual needs.

[0035] Preferably, the source of the carbon dioxide in the first mixed gas includes any one of carbon dioxide recovered and separated from steel plant gas, carbon dioxide recovered and treated from other industrial furnace waste gases, or carbon dioxide in nature, or a combination of at least two of them. Typical but non-limiting combinations include a combination of carbon dioxide recovered and separated from steel plant gas and carbon dioxide recovered and treated from other industrial furnace waste gases, a combination of carbon dioxide recovered and separated from steel plant gas and carbon dioxide in nature, and a combination of carbon dioxide recovered and treated from other industrial furnace waste gases and carbon dioxide in nature.

[0036] Preferably, the source of the carbon dioxide in the second mixed gas includes any one of carbon dioxide recovered and separated from steel plant gas, carbon dioxide recovered and treated from other industrial furnace waste gases, or carbon dioxide in nature, or a combination of at least two of them. Typical but non-limiting combinations include a combination of carbon dioxide recovered and separated from steel plant gas and carbon dioxide recovered and treated from other industrial furnace waste gases, a combination of carbon dioxide recovered and separated from steel plant gas and carbon dioxide in nature, and a combination of carbon dioxide recovered and treated from other industrial furnace waste gases and carbon dioxide in nature.

[0037] As a preferred technical solution of the method of the present invention, the method comprises the following steps:

[0038] (1) top-bottom re-blowing of vanadium-containing molten iron at 1300-1400° C., wherein the mass fraction of vanadium element in the vanadium-containing molten iron is 0.3-1.2wt%, and the mass fraction of carbon element is 3.5-4.8wt%;

[0039] The gas used for top blowing is a mixture of carbon dioxide and oxygen, with a volume content of carbon dioxide of 10-30 vol%, and a gas supply intensity of 2.0-3.5 m 3 / (min·t Fe ) and a Mach number of 1.8-2.5 for top blowing for 5-15 minutes; the gas used for bottom blowing is a mixture of carbon dioxide and oxygen, the volume content of carbon dioxide is 10-50vol%, and the gas supply intensity is 0.1-1m 3 / (min·t Fe ) Bottom blowing for 5-10 minutes;

[0040] (2) The sodium salt is added at one time when 1 / 3-3 / 5 of the top blowing is completed, and sodium vanadium slag is formed until the top and bottom blowing is completed; the sodium salt comprises any one of sodium carbonate, sodium oxide or sodium sulfate, or a combination of at least two of them; the molar ratio of the sodium element in the sodium salt to the vanadium element in the vanadium-containing molten iron is (1.5-2.5):1.

[0041] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] In the process of vanadium extraction from molten iron, the present invention top blows a mixture of carbon dioxide and oxygen and bottom blows a mixture of carbon dioxide and oxygen, utilizes the weak oxidizing property of carbon dioxide to replace part of oxygen to participate in the reaction, and achieves the effect of vanadium extraction and carbon preservation without adding a coolant. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0045] In order to illustrate the technical solution of the present invention, the converter capacity used in the following specific implementation manner is 120t. This is for the convenience of explaining the technical solution here and should not be regarded as a further limitation to the technical solution.

[0046] Example 1

[0047] This embodiment provides a method for extracting vanadium from molten iron by oxidation, the method comprising the following steps:

[0048] (1) At 1350°C, the vanadium-containing molten iron was subjected to top and bottom combined blowing. The gas used for top blowing was a mixture of carbon dioxide and oxygen, with a volume content of carbon dioxide of 15 vol% and a gas supply intensity of 3.0 m 3 / (min·t Fe ) and a Mach number of 2.0 flow rate for 12 minutes; the gas used for bottom blowing is a mixture of carbon dioxide and oxygen, with a volume content of carbon dioxide of 20 vol%, and a flow rate of 0.7 m 3 / (min·t Fe ) with a gas supply intensity of 8 minutes; top blowing and bottom blowing are started at the same time;

[0049] (2) Sodium carbonate is added once when the top blowing is half completed to form sodium vanadium slag until the top and bottom blowing is completed. The molar ratio of sodium element in the sodium carbonate to vanadium element in the vanadium-containing molten iron is 2:1.

[0050] Example 2

[0051] This embodiment provides a method for extracting vanadium from molten iron by oxidation, the method comprising the following steps:

[0052] (1) At 1300°C, the vanadium-containing molten iron was subjected to top-bottom combined blowing. The gas used for top blowing was a mixture of carbon dioxide and oxygen, with a volume content of carbon dioxide of 10 vol% and a gas supply intensity of 3.5 m 3 / (min·t Fe ) and a Mach number of 2.1 for top blowing for 15 minutes; the gas used for bottom blowing is a mixture of carbon dioxide and oxygen, with a volume content of carbon dioxide of 10 vol%, and a flow rate of 1m 3 / (min·t Fe ) with a gas supply intensity of 10 minutes; top blowing and bottom blowing are started at the same time;

[0053] (2) Sodium oxide is added once when 1 / 3 of the top blowing is completed to form sodium vanadium slag until the top and bottom blowing is completed. The molar ratio of sodium element in the sodium oxide to vanadium element in the vanadium-containing molten iron is 2.5:1.

[0054] Example 3

[0055] This embodiment provides a method for extracting vanadium from molten iron by oxidation, the method comprising the following steps:

[0056] (1) At 1400°C, the vanadium-containing molten iron was subjected to top and bottom combined blowing. The gas used for top blowing was a mixture of carbon dioxide and oxygen, with a volume content of carbon dioxide of 30 vol% and a gas supply intensity of 2.5 m 3 / (min·t Fe ) and a Mach number of 1.8 flow rate for 5 minutes; the gas used for bottom blowing is a mixture of carbon dioxide and oxygen, the volume content of carbon dioxide is 50vol%, and the volume content of 0.5m 3 / (min·t Fe ) with a gas supply intensity of 500 g / min; top blowing and bottom blowing are started simultaneously;

[0057] (2) Sodium sulfate is added once when 3 / 5 of the top blowing is completed to form sodium vanadium slag until the top and bottom blowing is completed. The molar ratio of sodium element in the sodium sulfate to vanadium element in the vanadium-containing molten iron is 1.5:1.

[0058] Example 4

[0059] This embodiment provides a method for extracting vanadium from molten iron by oxidation, which is the same as that of Embodiment 1 except that the content of carbon dioxide in the top-blown mixed gas in step (1) is 5 vol%.

[0060] Example 5

[0061] This embodiment provides a method for extracting vanadium from molten iron by oxidation, which is the same as that of Embodiment 1 except that the content of carbon dioxide in the top-blown mixed gas in step (1) is 35 vol%.

[0062] Example 6

[0063] This embodiment provides a method for extracting vanadium from molten iron by oxidation. Except that sodium carbonate is added all at once when 1 / 5 of the top blowing is completed in step (2), the rest is the same as that of embodiment 1.

[0064] Example 7

[0065] This embodiment provides a method for extracting vanadium from molten iron by oxidation. Except that in step (2), sodium carbonate is added all at once when 4 / 5 of the top blowing is completed, the rest is the same as that of embodiment 1.

[0066] Comparative Example 1

[0067] This comparative example provides a method for extracting vanadium from molten iron by oxidation, which is the same as Example 1 except that the bottom blowing gas in step (1) is carbon dioxide.

[0068] Comparative Example 2

[0069] This comparative example provides a method for extracting vanadium from molten iron by oxidation, which is the same as Example 1 except that the bottom blowing gas in step (1) is oxygen.

[0070] Comparative Example 3

[0071] This comparative example provides a method for extracting vanadium from molten iron by oxidation, which is the same as Example 1 except that the carbon dioxide in the bottom-blown mixed gas in step (1) is replaced by nitrogen of an equal volume content.

[0072] Comparative Example 4

[0073] This comparative example provides a method for extracting vanadium from molten iron by oxidation, which is the same as Example 1 except that the oxygen in the bottom-blown mixed gas in step (1) is replaced by nitrogen of equal volume content.

[0074] Performance Testing

[0075] For the methods provided in Examples 1-7 and Comparative Examples 1-4, the carbon content and vanadium content in vanadium-containing molten iron and semi-steel were compared, and the carbon burnout rate, vanadium oxidation rate, vanadium slag sodiumization rate and vanadium yield were tested, wherein:

[0076]

[0077]

[0078] The results are shown in Table 1.

[0079] Table 1

[0080]

[0081]

[0082] As shown in Table 1, in the method provided by the present invention, the carbon burnout rate is below 20%, the vanadium oxidation rate is above 91%, and the sodiumization rate of vanadium slag can reach about 95%, so that high-grade sodiumized vanadium slag can be obtained, with a higher vanadium yield.

[0083] By comparing Examples 4 and 5 with Example 1, it can be seen that when the volume content of carbon dioxide in the top-blown mixed gas is lower than 10 vol%, the temperature in the furnace rises sharply, which will restrict the oxidation of vanadium, accelerate the reaction consumption of carbon, reduce the vanadium extraction output, and cause serious iron oxidation loss; when the volume content of carbon dioxide in the top-blown mixed gas is higher than 30 vol%, the vanadium in the molten iron is not fully oxidized and cannot completely enter the slag phase, resulting in a low yield of sodium vanadium.

[0084] From the comparison between Examples 6 and 7 and Example 1, it can be seen that the sodium salt is added all at once when 1 / 3-3 / 5 of the top blowing is completed, which is beneficial to converting the oxidized vanadium into sodium vanadium. If it is added too early, the vanadium element in the vanadium-containing molten iron has not been completely oxidized into the slag phase, resulting in increased sodium salt consumption; if it is added too late, the vanadium yield will be reduced before the end of the blowing.

[0085] Comparison of Comparative Examples 1 and 2 with Example 1 shows that when the bottom blowing gas is only carbon dioxide, the vanadium in the molten iron is not completely oxidized, resulting in a reduced vanadium oxidation rate and severe vanadium loss; when the bottom blowing gas is only oxygen, the heating rate in the furnace is accelerated, the carbon burnout rate increases, and the vanadium yield is also reduced.

[0086] From the comparison between Comparative Examples 3 and 4 and Example 1, it can be seen that when the bottom blowing gas is a mixture of nitrogen and oxygen, the temperature rise in the furnace is aggravated, vanadium oxidation is restricted, carbon oxidation is serious, and the carbon content in the semi-steel is reduced; when the bottom blowing gas is a mixture of carbon dioxide and nitrogen, the vanadium in the molten iron is not completely oxidized, resulting in a decrease in the vanadium oxidation rate and serious vanadium loss.

[0087] In the process of vanadium extraction from molten iron, the present invention uses top blowing of a mixed gas of carbon dioxide and oxygen and bottom blowing of a mixed gas of carbon dioxide and oxygen, and utilizes the weak oxidizing property of carbon dioxide to replace part of the oxygen to participate in the reaction, which is beneficial to delaying the temperature rise of the molten iron in the furnace, increasing the vanadium oxidation rate, and reducing the carbon burn-off rate, thereby obtaining high-grade sodium vanadium, and achieving the effect of vanadium extraction and carbon preservation without adding a coolant.

[0088] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for extracting vanadium from molten iron by oxidation without adding solid coolant, characterized in that: The method comprises the following steps: The vanadium-containing molten iron is subjected to top-bottom combined blowing, and sodium salt is added during the top-bottom combined blowing process to form sodium vanadium slag; The molar ratio of the sodium element in the sodium salt to the vanadium element in the vanadium-containing molten iron is (1.5-2.5): 1; The sodium salt is added at one time when 1 / 3-3 / 5 of the top blowing is completed; in the top-bottom combined blowing process, the gas used for top blowing is the first mixed gas, and the gas used for bottom blowing is the second mixed gas; The first mixed gas includes carbon dioxide and oxygen; The volume content of carbon dioxide in the first mixed gas is 10-30 vol%; The second mixed gas includes carbon dioxide and oxygen; The volume content of carbon dioxide in the second mixed gas is 10-50 vol%.

2. The method according to claim 1, characterized in that The mass fraction of vanadium element in the vanadium-containing molten iron is 0.3-1.2wt%.

3. The method according to claim 1, characterized in that The mass fraction of carbon element in the vanadium-containing molten iron is 3.5-4.8wt%.

4. The method according to claim 1, characterized in that The sodium salt includes any one of sodium carbonate, sodium oxide or sodium sulfate, or a combination of at least two of them.

5. The method according to claim 1, characterized in that: During the top blowing, the gas supply intensity of the first mixed gas is 2.0-3.5m 3 / (min·t Fe ).

6. The method according to claim 1, characterized in that During the top blowing, the Mach number of the first mixed gas is 1.8-2.

5.

7. The method according to claim 1, characterized in that The blowing time of the top blowing is 5-15 minutes.

8. The method according to claim 1, characterized in that During the bottom blowing, the gas supply intensity of the second mixed gas is 0.1-1m 3 / (min·t Fe ).

9. The method according to claim 1, characterized in that: The bottom blowing time is 5-10 minutes.

10. The method according to claim 1, characterized in that The bottom blowing and the top blowing are started simultaneously.

11. The method according to claim 1, characterized in that: The temperature of the top and bottom combined blowing is 1300-1400°C.

12. The method according to claim 1, characterized in that The source of the carbon dioxide in the first mixed gas includes any one or a combination of at least two of the carbon dioxide recovered from steel plant gas, carbon dioxide recovered from other industrial furnace waste gases, or carbon dioxide in nature.

13. The method according to claim 1, characterized in that The source of the carbon dioxide in the second mixed gas includes any one or a combination of at least two of the carbon dioxide recovered from steel plant gas, carbon dioxide recovered from other industrial furnace waste gases, or carbon dioxide in nature.

14. The method according to claim 1, characterized in that The method comprises the following steps: (1) top-bottom combined blowing is performed on vanadium-containing molten iron at 1300-1400° C., wherein the mass fraction of vanadium element in the vanadium-containing molten iron is 0.3-1.2wt%, and the mass fraction of carbon element is 3.5-4.8wt%; The gas used for top blowing is a mixture of carbon dioxide and oxygen, with a volume content of carbon dioxide of 10-30 vol%, and a gas supply intensity of 2.0-3.5 m 3 / (min·t Fe ) and a Mach number of 1.8-2.5 for top blowing for 5-15 minutes; the gas used for bottom blowing is a mixture of carbon dioxide and oxygen, the volume content of carbon dioxide is 10-50vol%, and the gas supply intensity is 0.1-1m 3 / (min·t Fe ) Bottom blowing for 5-10 minutes; (2) Sodium salt is added once when 1 / 3-3 / 5 of the top blowing is completed, and sodium vanadium slag is formed until the top and bottom blowing is completed; the sodium salt comprises any one of sodium carbonate, sodium oxide or sodium sulfate, or a combination of at least two of them; the molar ratio of sodium element in the sodium salt to vanadium element in the vanadium-containing molten iron is (1.5-2.5):1.

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