Method for segmental reduction and vanadium enrichment of electric furnace smelting and separation pre-reduced iron concentrate pellets

Abstract

The present application belongs to the technical field of steel metallurgy, and discloses a method for sub-section reduction and vanadium enrichment of electric furnace melting and separation pre-reduced iron concentrate pellets. The method comprises the following steps: (1) pure melting and separation stage: 40% to 60% of the total amount of pre-reduced iron concentrate pellets is added into an electric furnace for melting and separation to obtain molten iron and molten slag; (2) tapping stage: part of the molten iron is discharged; (3) carbon addition and over-reduction stage: a first carbonaceous reducing agent is added into the remaining molten slag; (4) supplementary material over-reduction stage: the remaining pre-reduced iron concentrate pellets are mixed with a second carbonaceous reducing agent and added into the electric furnace, and reduction is continued to the end point, and then molten iron and slag are discharged to obtain molten iron containing vanadium. Through four-stage coordinated control, the vanadium content of the obtained molten iron containing vanadium is increased to about 1.5 times of that of the original one-time melting and separation process.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and specifically discloses a method for staged reduction and enrichment of vanadium in pre-reduced iron concentrate pellets obtained by electric furnace melting. Background Technology

[0002] The smelting reduction of pre-reduced iron concentrate pellets is an important non-blast furnace ironmaking route for obtaining molten iron, especially for vanadium-containing iron concentrates, where efficient resource utilization is beneficial to improving the overall economic value of the process. In the comprehensive utilization process of vanadium-titanium magnetite, the vanadium-titanium magnetite is usually first pre-reduced in a rotary kiln or rotary hearth furnace to obtain pre-reduced pellets with a certain metallization rate. Then, the pre-reduced pellets are sent to an electric furnace for smelting treatment to obtain vanadium-containing molten iron and titanium-containing slag, thereby achieving the initial separation of valuable elements such as iron, vanadium, and titanium.

[0003] In existing technologies, electric arc furnace (EAF) smelting processes mostly adopt a "one-time smelting-deep reduction-full tapping" model, meaning that smelting and reduction are completed in one go after the material is added to the EAF, with tapping being the final operation point. This model generally suffers from low vanadium content in molten iron during actual production, resulting in insufficient vanadium enrichment and increased difficulty and cost in subsequent vanadium extraction. The main reason is that the pre-reduced pellets still contain a certain amount of FeO, which enters the slag during EAF smelting, leading to a high FeO content in the slag. Furthermore, vanadium oxide (V₂O₅) has high chemical reactivity at high temperatures and easily interacts with FeO at the slag-metal interface. This results in most vanadium existing as V₂O₅ in the slag phase rather than being reduced into the molten iron, ultimately resulting in a vanadium content in the molten iron typically only 0.2% to 0.5%, with a large amount of vanadium lost with the slag.

[0004] To address the aforementioned issues, some improved processes attempt to add pre-reduced iron concentrate pellets to the electric furnace in batches to achieve staged reduction. For example, the electric-coal smelting reduction process disclosed in CN102925610A, although adding materials in batches and using staged heating reduction, lacks an intermediate tapping step. Vanadium already reduced into the molten iron is re-oxidized during subsequent high-temperature processes due to the equilibrium reaction between slag and gold, re-entering the slag phase. This results in the vanadium content in the molten iron remaining limited by the initial vanadium grade of the raw material, preventing further vanadium enrichment. Furthermore, the amount of reducing agent added in the two feeding stages lacks a clear quantitative relationship; it is usually estimated based on experience or added in a fixed proportion with the material, making precise carbon formulation difficult based on the actual amount of material to be reduced. While the HIsmelt smelting reduction process offers some energy savings, its vanadium enrichment effect is also unsatisfactory, and equipment corrosion is a significant problem, making it difficult to meet the stability requirements of industrial production.

[0005] Some technologies have attempted to enhance vanadium reduction by increasing the amount of reducing agent. However, since the reducing agent is added in large quantities at the beginning of the melting process, it can easily cause local over-reduction in the molten pool, resulting in excessive slag viscosity and poor fluidity, which affects the slag-iron separation effect. At the same time, excessive reducing agent is prone to undergo the Bourdon reaction with CO2 in the furnace gas at high temperatures, resulting in ineffective consumption of the reducing agent. The actual proportion of carbon participating in the reduction reaction is limited, and the improvement in vanadium reduction efficiency is not significant.

[0006] In summary, the existing electric furnace smelting process lacks precise stage-by-stage control of the smelting process, especially lacking quantitative ratios for the amount of reducing agent used in the two charging operations. This results in unstable vanadium reduction rate and large fluctuations in vanadium content in the molten iron, making it difficult to achieve stable preparation of high-vanadium molten iron.

[0007] Therefore, there is an urgent need in this field to develop an electric furnace smelting process that can achieve vanadium enrichment. By optimizing the feeding method and the quantitative ratio of reducing agent, the vanadium content in molten iron can be effectively increased, the difficulty of subsequent vanadium extraction can be reduced, and the vanadium recovery efficiency can be improved. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a method for preparing high-vanadium-content molten iron through a four-stage synergistic control process involving "melting and separation, tapping, carbon addition and over-reduction, and replenishment and over-reduction." The specific technical solution is as follows: A method for staged reduction enrichment of vanadium in pre-reduced iron concentrate pellets obtained by electric furnace melting, the method comprising the following stages: (1) Pure smelting stage: 40% to 60% (preferably 50%) of the total weight of the pre-reduced iron concentrate pellets are added to the electric furnace for smelting treatment to initially separate the slag and iron and obtain molten iron and slag; (2) Tapping stage: Open the tapping port at the bottom of the electric furnace to discharge part of the molten iron obtained in step (1), and keep the remaining molten iron and slag in the electric furnace; (3) Carbon addition and reduction stage: Add the first carbonaceous reducing agent to the remaining molten iron and slag in step (2); (4) Feeding and reduction stage: After the feeding in step (3) is completed, immediately add all the remaining pre-reduced iron concentrate pellets and the mixture of the second carbonaceous reducing agent and slag conditioner into the electric furnace, continue the reduction to the end point, and after the slag and iron are separated, iron and slag are discharged to obtain vanadium-containing molten iron.

[0009] Furthermore, the metallization rate of the pre-reduced iron concentrate pellets in step (1) is 90%~95% (preferably 93%), and the melting treatment temperature is 1550~1650℃ (preferably 1600℃).

[0010] Furthermore, the amount of molten iron discharged in step (2) is 80% to 90% (preferably 90%) of the total molten iron, and the tapping temperature is 1450 to 1550°C (preferably 1500°C).

[0011] Furthermore, in step (3), the first carbonaceous reducing agent is one or more of coke, metallurgical coke or semi-coke (preferably coke); the amount added is based on fixed carbon and is 1.2 to 1.5 times the sum of the number of FeO moles and five times the number of V2O5 moles in the remaining slag after iron tapping in step (2).

[0012] Furthermore, the type of the second carbonaceous reducing agent in step (4) is the same as that of the first carbonaceous reducing agent in step (3); the amount added is determined by the following formula based on a fixed amount of carbon: M2 = M1 × (m2 / m1) Where M1 is the amount of the first carbonaceous reducing agent added, calculated as fixed carbon, in mol; m1 is the mass of the pre-reduced iron concentrate pellets added in step (1), in tons; m2 is the mass of all remaining pre-reduced iron concentrate pellets mentioned in step (4), in tons; and M2 is the amount of the second carbonaceous reducing agent added, calculated as fixed carbon, in mol. That is, when m 1= When m2, M 1= M2.

[0013] Furthermore, the temperature of the carbon addition and reduction stage in step (3) is 1550~1650℃ (preferably 1600℃); the temperature of the continued reduction to the endpoint in step (4) is 1550~1650℃ (preferably 1600℃).

[0014] Furthermore, in step (3), the first carbonaceous reducing agent is added by injection; the slag conditioner in step (4) is fluorite.

[0015] Furthermore, the pre-reduced iron concentrate pellets are vanadium-containing pre-reduced pellets obtained by pre-reducing vanadium-titanium magnetite.

[0016] By adopting the above technical solution, the present invention has at least the following advantages and beneficial effects: (1) This invention breaks through the single mode of the existing technology of "one-time smelting-deep reduction-full iron tapping" by controlling the four stages of "pure smelting → tapping iron → carbon addition over-reduction → feed over-reduction". In the pure smelting stage, 40% to 60% of the total amount of pre-reduced iron concentrate pellets are added to the electric furnace to achieve preliminary separation of slag and iron and obtain molten iron. Then, the iron is collected separately through intermediate tapping (the discharge amount is 80% to 90% of the total molten iron), which avoids the vanadium being oxidized again by the balance reaction between slag and gold in the subsequent high-temperature over-reduction process and re-entering the slag phase. The remaining molten iron and slag enter the carbon addition over-reduction and feed over-reduction stages, so that the vanadium reduced later is fully enriched in the final high-vanadium molten iron. Its vanadium content can reach 0.8% to 0.95%, which is about 1.5 times that of the original one-time smelting process (0.55%), which is significantly better than the existing process level.

[0017] (2) By setting a carbon-adding over-reduction stage after tapping, the present invention significantly reduces the oxidizing properties of the slag under the condition that most of the reduced metallic iron has been eliminated, creating more favorable thermodynamic conditions for the deep reduction of vanadium oxides; at the same time, based on the measured content of FeO and V2O5 in the remaining slag after tapping, the first carbonaceous reducing agent is precisely added at 1.2 to 1.5 times the theoretical amount, avoiding insufficient or excessive reducing agent, thus significantly improving the vanadium reduction rate.

[0018] (3) In the feeding and over-reduction stage, the remaining pre-reduced iron concentrate pellets are mixed with the second carbonaceous reducing agent and then added. The amount of the second carbonaceous reducing agent added is determined according to the proportion of the added pellets to the first added pellets. This achieves a quantitative ratio of the amount of reducing agent added in the two feeding stages, so that the supply of reducing agent for each batch of material matches the amount of material to be reduced. This overcomes the problem of inaccurate carbon matching caused by the lack of quantitative relationship between the amount of reducing agent added in the two feeding stages and the reliance on experience for estimation in the traditional method, and improves the utilization rate of reducing agent.

[0019] (4) The present invention uses a coordinated metering method to accurately calculate the first reducing agent based on the measured values ​​of FeO and V2O5 in the remaining slag, and adjust the second reducing agent according to the feeding ratio. This method ensures that the supply of reducing agent in the entire melting process is precisely matched with the actual carbon demand at each stage, avoiding insufficient or excessive reducing agent and greatly improving process stability.

[0020] (5) The method of the present invention does not change the existing electric furnace main equipment. It can achieve efficient enrichment of vanadium by optimizing the feeding method and the quantitative ratio of reducing agent. The equipment investment cost is low, the operation is simple, and it is easy to promote and apply in industrial applications. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples.

[0022] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0023] Example 1 (Base Example) Taking a 6.3 MVA electric furnace as an example, the specific implementation steps are as follows: It is estimated that a total of 20 tons of pre-reduced iron concentrate pellets will be added to the furnace, with a metallization rate of 93% (metallic iron content / total iron content). The mass fractions of metallic iron (MFe), total iron (TFe), FeO, and V2O5 in the pellets are 60.45%, 65.00%, 5.85%, and 0.9%, respectively. Phase 1: Pure Melting Stage Ten tons of the aforementioned pre-reduced iron concentrate pellets are added, and the furnace temperature is raised to 1600℃ by electric arc heating. The temperature is held for 30 minutes for pure smelting treatment, which melts the pellets into molten iron and initially separates them from the slag, yielding molten iron and slag. No reducing agent is added at this stage, producing approximately 6 tons of molten iron. Phase Two: Iron Production Phase Open the tapping spout, the tapping temperature is 1500℃, and after about 5 tons of molten iron produced in the first stage are discharged, close the tapping spout (this part of the molten iron is collected separately and is not combined with the vanadium-containing molten iron obtained in the fourth stage. The same applies to the following examples, and will not be repeated). The remaining molten iron and slag are left in the furnace. Third stage: Carbon addition and reduction stage The remaining slag from the second stage was sampled and tested. The results showed 8125 mol of FeO and 439.56 mol of V₂O₅. Therefore, 12387.36 mol of reducing agent (based on fixed carbon) needs to be added (calculated as follows: Let 'a' represent the number of FeO moles in the slag and 'b' represent the number of V₂O₅ moles; then the total number of moles of carbonaceous reducing agent added is 1.2 * (a + 5b)). Based on a coke fixed carbon content of 85%, 174.88 kg of coke needs to be added. This coke is injected into the lower part of the slag layer in the furnace via a blowing rate of 50 kg / min. The furnace temperature is maintained at 1600℃.

[0024] Phase 4: Replenishment and Reduction Phase The remaining 10 tons of pre-reduced iron concentrate pellets were mixed evenly with 174.88 kg of coke and 600 kg of fluorite to obtain mixture A. After the third stage of feeding was completed, mixture A was immediately added evenly into the furnace at a rate of 4 tons / hour, while maintaining an hourly power supply of about 6 MWh and maintaining the furnace temperature at 1600℃ until the reaction was completed (the FeO content in the slag was measured to be ≤2.0%, the same as in the following examples and comparative examples, and will not be repeated). After slag and iron separation, iron and slag were discharged to obtain vanadium-containing molten iron.

[0025] The vanadium-containing molten iron produced using this method has a V content of 0.88%. In contrast, the traditional process (without mid-process tapping) produces molten iron with a V content of only 0.55%. The V content of the molten iron produced by this technology is significantly increased, creating favorable conditions for subsequent vanadium extraction.

[0026] Example 2 (Changing the iron output) Taking a 6.3 MVA electric furnace as an example, the specific implementation steps are as follows: It is estimated that a total of 20 tons of pre-reduced iron concentrate pellets will be added to the furnace, with a metallization rate of 93% (metallic iron content / total iron content). The mass fractions of metallic iron (MFe), total iron (TFe), FeO, and V2O5 in the pellets are 60.45%, 65.00%, 5.85%, and 0.9%, respectively. Phase 1: Pure Melting Stage Ten tons of the aforementioned pre-reduced iron concentrate pellets are added, and the furnace temperature is raised to 1600℃ by electric arc heating. The temperature is held for 30 minutes for pure smelting treatment, which melts the pellets into molten iron and initially separates them from the slag, yielding molten iron and slag. No reducing agent is added at this stage, producing approximately 6 tons of molten iron. Phase Two: Iron Production Phase Open the tapping spout, the tapping temperature is 1500℃, and after about 5.4 tons of molten iron produced in the first stage are discharged, close the tapping spout, and leave the remaining molten iron and slag in the furnace; Third stage: Carbon addition and reduction stage The remaining slag from the second stage was sampled and tested. The results showed 8150 mol of FeO and 441.20 mol of V₂O₅. Therefore, 12427.2 mol of reducing agent (based on fixed carbon) needs to be added (calculated as follows: Let 'a' represent the number of FeO moles in the slag and 'b' represent the number of V₂O₅ moles; then the total number of moles of carbonaceous reducing agent added is 1.2 * (a + 5b)). Based on a coke fixed carbon content of 85%, 175.44 kg of coke needs to be added. This coke is injected into the lower part of the slag layer in the furnace via a blowing rate of 50 kg / min. The furnace temperature is maintained at 1600℃.

[0027] Phase 4: Replenishment and Reduction Phase The remaining 10 tons of pre-reduced iron concentrate pellets were mixed evenly with 175.44 kg of coke and 600 kg of fluorite to obtain mixture A. After the third stage of feeding was completed, mixture A was immediately added evenly into the furnace at a rate of 4 tons / hour, while maintaining an hourly power supply of about 6 MWh and maintaining the furnace temperature at 1600℃ until the reaction was completed. After the slag and iron were separated, the iron and slag were discharged to obtain vanadium-containing molten iron.

[0028] The vanadium-containing molten iron produced using this method has a V content of 0.94%.

[0029] Example 3 (Changing the amount of reducing agent) Taking a 6.3 MVA electric furnace as an example, the specific implementation steps are as follows: It is estimated that a total of 20 tons of pre-reduced iron concentrate pellets will be added to the furnace, with a metallization rate of 93% (metallic iron content / total iron content). The mass fractions of metallic iron (MFe), total iron (TFe), FeO, and V2O5 in the pellets are 60.45%, 65.00%, 5.85%, and 0.9%, respectively. Phase 1: Pure Melting Stage Ten tons of the aforementioned pre-reduced iron concentrate pellets are added, and the furnace temperature is raised to 1600℃ by electric arc heating. The temperature is held for 30 minutes for pure smelting treatment, which melts the pellets into molten iron and initially separates them from the slag, yielding molten iron and slag. No reducing agent is added at this stage, producing approximately 6 tons of molten iron. Phase Two: Iron Production Phase Open the tapping spout, the tapping temperature is 1500℃, and after about 5 tons of molten iron produced in the first stage are discharged, close the tapping spout, and leave the remaining molten iron and slag in the furnace. Third stage: Carbon addition and reduction stage The remaining slag from the second stage was sampled and tested. The results showed 8100 mol of FeO and 438.00 mol of V₂O₅. Therefore, 15435.0 mol of reducing agent (based on fixed carbon) needs to be added (calculated as follows: let 'a' be the number of FeO moles and 'b' be the number of V₂O₅ moles in the slag, then the total number of moles of carbonaceous reducing agent added is 1.5 * (a + 5b)). Based on a fixed carbon content of 85% for coke, 217.91 kg of coke needs to be added. This coke is injected into the lower part of the slag layer in the furnace via a blowing rate of 50 kg / min. The furnace temperature is maintained at 1600℃.

[0030] Phase 4: Feeding and Reduction Phase The remaining 10 tons of pre-reduced iron concentrate pellets were mixed evenly with 217.91 kg of coke and 600 kg of fluorite to obtain mixture A. After the third stage of feeding was completed, mixture A was immediately added evenly into the furnace at a rate of 4 tons / hour, while maintaining an hourly power supply of about 6 MWh and maintaining the furnace temperature at 1600℃ until the reaction was completed. After the slag and iron were separated, the iron and slag were discharged to obtain vanadium-containing molten iron.

[0031] The vanadium-containing molten iron produced using this method has a V content of 0.95%.

[0032] Example 4 (Changing the type of reducing agent) Taking a 6.3 MVA electric furnace as an example, the specific implementation steps are as follows: It is estimated that a total of 20 tons of pre-reduced iron concentrate pellets will be added to the furnace, with a metallization rate of 93% (metallic iron content / total iron content). The mass fractions of metallic iron (MFe), total iron (TFe), FeO, and V2O5 in the pellets are 60.45%, 65.00%, 5.85%, and 0.9%, respectively. Phase 1: Pure Melting Stage Ten tons of the aforementioned pre-reduced iron concentrate pellets are added, and the furnace temperature is raised to 1600℃ by electric arc heating. The temperature is held for 30 minutes for pure smelting treatment, which melts the pellets into molten iron and initially separates them from the slag, yielding molten iron and slag. No reducing agent is added at this stage, producing approximately 6 tons of molten iron. Phase Two: Iron Production Phase Open the tapping spout, the tapping temperature is 1500℃, and after about 5 tons of molten iron produced in the first stage are discharged, close the tapping spout, and leave the remaining molten iron and slag in the furnace. Third stage: Carbon addition and reduction stage The remaining slag from the second stage was sampled and tested. The results showed 8135 mol of FeO and 440.50 mol of V₂O₅. Therefore, 12405.0 mol of reducing agent (based on fixed carbon) needs to be added (calculated as follows: let 'a' be the number of FeO moles and 'b' be the number of V₂O₅ moles in the slag, then the total number of moles of carbonaceous reducing agent added is 1.2 * (a + 5b)). Based on a fixed carbon content of 82% for semi-coke, 181.54 kg of semi-coke needs to be added. This semi-coke is injected into the lower part of the slag layer in the furnace via injection (injection rate of 50 kg / min). The furnace temperature is maintained at 1600℃.

[0033] Phase 4: Feeding and Reduction Phase The remaining 10 tons of pre-reduced iron concentrate pellets were mixed evenly with 181.54 kg of semi-coke and 600 kg of fluorite to obtain mixture A. After the third stage of feeding was completed, mixture A was immediately added evenly into the furnace at a rate of 4 tons / hour, while maintaining an hourly power supply of about 6 MWh and maintaining the furnace temperature at 1600℃ until the reaction was completed. After the slag and iron were separated, the iron and slag were discharged to obtain vanadium-containing molten iron.

[0034] The vanadium-containing molten iron produced using this method has a V content of 0.82%.

[0035] Comparative Example Traditional process (without using the technique of tapping iron midway) This comparative example provides a smelting method that uses traditional centralized charging and no molten iron discharge operation. Taking a 6.3 MVA electric furnace as an example, the specific implementation steps are as follows: (1) Raw materials and ingredients: It is estimated that a total of 20 tons of pre-reduced iron concentrate pellets will be added to the furnace, with a metallization rate of 93% (metallic iron content / total iron content). The mass fractions of metallic iron (MFe), total iron (TFe), FeO, and V2O5 in the pellets are 60.45%, 65.00%, 5.85%, and 0.9%, respectively. The above 20 tons of pre-reduced iron concentrate pellets were mixed evenly with 349.76 kg of coke (the total amount of reducing agent was the same as in Example 1) and 600 kg of fluorite to obtain a mixture.

[0036] (2) Feeding and operation: The mixture was added to the furnace in a single, centralized feeding process. After feeding, the furnace was energized and heated for smelting. Throughout the smelting process, the hourly power supply was maintained at approximately 6 MWh, and the furnace temperature was maintained at 1600°C until the reaction was complete. After the slag and iron were separated, the iron and slag were tapped to obtain vanadium-containing molten iron.

[0037] The vanadium-containing molten iron produced using this method has a V content of 0.55%.

[0038] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0039] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for staged reduction enrichment of vanadium in pre-reduced iron concentrate pellets obtained by electric furnace melting, characterized in that, The method Includes the following stages: (1) Pure smelting stage: 40% to 60% of the total weight of pre-reduced iron concentrate pellets are added to an electric furnace for smelting treatment to initially separate slag and iron and obtain molten iron and slag; (2) Tapping stage: Open the tapping port at the bottom of the electric furnace to discharge part of the molten iron obtained in step (1), and keep the remaining molten iron and slag in the electric furnace; (3) Carbon addition and reduction stage: Add the first carbonaceous reducing agent to the remaining molten iron and slag in step (2); (4) Feeding and reduction stage: After the feeding in step (3) is completed, immediately add all the remaining pre-reduced iron concentrate pellets and the mixture of the second carbonaceous reducing agent and slag conditioner into the electric furnace, continue the reduction to the end point, and after the slag and iron are separated, iron and slag are discharged to obtain vanadium-containing molten iron.

2. The method according to claim 1, characterized in that, The metallization rate of the pre-reduced iron concentrate pellets in step (1) is 90%~95%, and the melting treatment temperature is 1550~1650℃.

3. The method according to claim 1, characterized in that, The amount of molten iron discharged in step (2) is 80% to 90% of the total molten iron, and the tapping temperature is 1450 to 1550℃.

4. The method according to claim 1, characterized in that, In step (3), the first carbonaceous reducing agent is one or more of coke, metallurgical coke, or semi-coke.

5. The method according to claim 4, characterized in that, In step (3), the amount of the first carbonaceous reducing agent added is based on fixed carbon and is 1.2 to 1.5 times the sum of the number of FeO moles and five times the number of V2O5 moles in the remaining slag after iron tapping in step (2).

6. The method according to claim 4, characterized in that, The type of the second carbonaceous reducing agent in step (4) is the same as that of the first carbonaceous reducing agent in step (3).

7. The method according to claim 6, characterized in that, The amount of the second carbonaceous reducing agent added in step (4), based on fixed carbon, is determined by the following formula: M2 = M1 × (m2 / m1) Wherein, M1 is the amount of the first carbonaceous reducing agent added in fixed carbon, in mol; m1 is the mass of the pre-reduced iron concentrate pellets added in step (1), in tons; m2 is the mass of all remaining pre-reduced iron concentrate pellets mentioned in step (4), in tons; and M2 is the amount of the second carbonaceous reducing agent added in fixed carbon, in mol.

8. The method according to claim 1, characterized in that, The temperature of the carbon addition and reduction stage in step (3) is 1550~1650℃; the temperature of the continued reduction to the endpoint in step (4) is 1550~1650℃.

9. The method according to claim 1, characterized in that, In step (3), the first carbonaceous reducing agent is added by injection; in step (4), the slag conditioner is fluorite.

10. The method according to claim 1, characterized in that, The pre-reduced iron concentrate pellets are vanadium-containing pre-reduced pellets obtained by pre-reducing vanadium-titanium magnetite.